International Conference on Reliable Systems Engineering (ICoRSE) - 2023 [1 ed.] 3031406273, 9783031406270

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Lecture Notes in Networks and Systems 762

Daniela Doina Cioboată   Editor

International Conference on Reliable Systems Engineering (ICoRSE) - 2023

Lecture Notes in Networks and Systems

762

Series Editor Janusz Kacprzyk , Systems Research Institute, Polish Academy of Sciences, Warsaw, Poland

Advisory Editors Fernando Gomide, Department of Computer Engineering and Automation—DCA, School of Electrical and Computer Engineering—FEEC, University of Campinas—UNICAMP, São Paulo, Brazil Okyay Kaynak, Department of Electrical and Electronic Engineering, Bogazici University, Istanbul, Türkiye Derong Liu, Department of Electrical and Computer Engineering, University of Illinois at Chicago, Chicago, USA Institute of Automation, Chinese Academy of Sciences, Beijing, China Witold Pedrycz, Department of Electrical and Computer Engineering, University of Alberta, Alberta, Canada Systems Research Institute, Polish Academy of Sciences, Warsaw, Poland Marios M. Polycarpou, Department of Electrical and Computer Engineering, KIOS Research Center for Intelligent Systems and Networks, University of Cyprus, Nicosia, Cyprus Imre J. Rudas, Óbuda University, Budapest, Hungary Jun Wang, Department of Computer Science, City University of Hong Kong, Kowloon, Hong Kong

The series “Lecture Notes in Networks and Systems” publishes the latest developments in Networks and Systems—quickly, informally and with high quality. Original research reported in proceedings and post-proceedings represents the core of LNNS. Volumes published in LNNS embrace all aspects and subfields of, as well as new challenges in, Networks and Systems. The series contains proceedings and edited volumes in systems and networks, spanning the areas of Cyber-Physical Systems, Autonomous Systems, Sensor Networks, Control Systems, Energy Systems, Automotive Systems, Biological Systems, Vehicular Networking and Connected Vehicles, Aerospace Systems, Automation, Manufacturing, Smart Grids, Nonlinear Systems, Power Systems, Robotics, Social Systems, Economic Systems and other. Of particular value to both the contributors and the readership are the short publication timeframe and the world-wide distribution and exposure which enable both a wide and rapid dissemination of research output. The series covers the theory, applications, and perspectives on the state of the art and future developments relevant to systems and networks, decision making, control, complex processes and related areas, as embedded in the fields of interdisciplinary and applied sciences, engineering, computer science, physics, economics, social, and life sciences, as well as the paradigms and methodologies behind them. Indexed by SCOPUS, INSPEC, WTI Frankfurt eG, zbMATH, SCImago. All books published in the series are submitted for consideration in Web of Science. For proposals from Asia please contact Aninda Bose ([email protected]).

Daniela Doina Cioboat˘a Editor

International Conference on Reliable Systems Engineering (ICoRSE) - 2023

Editor Daniela Doina Cioboat˘a National Institute of Research and Development in Mechatronics and Measurement Technique Bucharest, Romania

ISSN 2367-3370 ISSN 2367-3389 (electronic) Lecture Notes in Networks and Systems ISBN 978-3-031-40627-0 ISBN 978-3-031-40628-7 (eBook) https://doi.org/10.1007/978-3-031-40628-7 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

This book presents high-quality, peer-reviewed papers from the third “International Conference of Reliable Systems Engineering (ICoRSE 2023)”, held in Bucharest, Romania, between 07 and 08 September 2023. The main organizer of this event is the National Institute of Research and Development in Mechatronics and Measurement Technique (INCDMTM). In the 50+ years of its existence, the National Institute of Research and Development in Mechatronics and Measurement Technique hosted many scientific events aimed at promoting innovative ideas from researchers, scientists, academics, industry professionals and students worldwide. The first two ICoRSE editions brought together renowned professors, PhD students and researchers in Europe, North America and Asia, in countries such as England, Albania, Austria, Bulgaria, Canada, Czech Republic, Germany, France, Italy, Portugal, Turkey, Ukraine, Uzbekistan and Vietnam. In this year’s edition, we cover a variety of topics, such as theoretical and applied mechanics; cyber-physical systems, robotics, smart bio-medical and bio-mechatronic systems, new and intelligent materials and structures, modelling and simulation in mechanics and mechatronics, smart mechatronic production and control system, optics, control systems, big data modelling, micro- and nanotechnology, automation, manufacturing optimization and other. And, thanks to the richness in topics and the interdisciplinarity of the papers, I have decided not to provide this paper with chapters dedicated to a single topic, but rather to include all accepted contributions as independent chapters, ordered alphabetically according to the last name of the corresponding author. As the editor of this book, I would like to express my sincere appreciation and thanks to all the authors for their contributions to this publication. I would like to express my gratitude to all reviewers for their constructive comments on the papers. I would also like to extend my thanks to the members of the organizing team for their hard work. I hope that the readers will find this book useful, exciting and inspiring and will provide feedback both to me and my team, as well as to the authors, as this will help us to improve our future work. Before concluding, I would like to express my gratitude for the assistance offered throughout the editing of the current book to Mr. Holger Schaepe, Mr. Thomas Ditzinger and Mr. Suresh Dharmaligngam at Springer. Without their work, this book would not have been the same!

Organization

General Chairs General Conference Chair Doina Daniela Cioboata

INCDMTM, Romania

General Conference Co-chair Rochdi El Abdi

University of Rennes, France

Steering Committee Members Rochdi El Abdi Nina Anticic Mihai Avram Yevheniia Basova Karolina Bezerra Husi Geza Jan Hosek Vijay Kumar Chi Hieu Le José Machado Umidjon Mardonov Pierluigi Rea Michal Rogalewicz Ion Stiharu Mihail Titu Sahin Yildirim

University of Rennes, France «Rochester» Institute of Technology, Croatia «Politehnica» University of Bucharest, Romania National Technical University “Kharkiv Polytechnic Institute”, Ukraine State University of Paraiba, Brazil University of Debrecen, Faculty of Engineering, Hungary Faculty of Mechanical Engineering, CTU Prague, Czech Republic National Institute of Technology Warangal, Mechanical Engineering Department, India University of Greenwich, UK University of Minho, School of Engineering, Mechanical Engineering Department, Portugal Tashkent State Technical University, Uzbekistan University of Cagliari, CA, Italy Politechnica University of Poznan, Poland Concordia University, Montreal, Canada «Lucian Blaga» University of Sibiu, Romania Erciyes Üniversitesi Akademik Veri Yönetim Sistemi, Turkey

viii

Organization

Scientific Committee Members Rochdi El Abdi Nina Anticic Mihai Avram Yevheniia Basova Vasile Bratu Liliana-Laura Badit˘a-Voicu Karolina Bezerra Iulia Clitan Daniel Comeaga Sergey Dobrotvorskiy Milan Edl Thipwan Fangsuwannarak Nuno Octavio Fernandes Adinel Gavrus Stergios Ganatsios Husi Geza Bogdan Gramescu Jan Hosek Georgeta Ionascu Nikolai Kazantsev Mikolaj Koscinski Vijay Kumar Chi Hieu Le José Machado Karolina Macuchova Umidjon Mardonov Paulo E. Miyagi Vlad Muresan Dumitru Mnerie Mihai Margaritescu Constantin Nitu Adrian Olaru

University of Rennes, France «Rochester» Institute of Technology, Croatia «Politehnica» University of Bucharest, Romania National Technical University “Kharkiv Polytechnic Institute”, Ukraine «Valahia» University of Târgovi¸ste, Romania INCDMTM, Romania State University of Paraiba, Brazil Technical University of Cluj-Napoca, Romania «Politehnica» University of Bucharest, Romania National Technical University “Kharkiv Polytechnic Institute”, Ukraine University of West Bohemia, Czech Republic Suranaree University of Technology, Thailand Polytechnic Institute of Castelo Branco, Portugal INSA Rennes, France TEI of Western Macedonia, Greece University of Debrecen, Faculty of Engineering, Hungary «Politehnica» University of Bucharest, Romania Faculty of Mechanical Engineering CTU in Prague, Czech Republic «Politehnica» University of Bucharest, Romania Institute for Manufacturing, University of Cambridge, UK Poznan University of Life Sciences, Poland National Institute of Technology Warangal, Mechanical Engineering Department, India University of Greenwich, UK University of Minho, School of Engineering, Mechanical Engineering Department Portugal HiLASE Centre, Institute of Physics CAS, Czech Republic Tashkent State Technical University, Uzbekistan University of Sao Paulo, Brazil Technical University of Cluj-Napoca, Romania «Politehnica» University of Timis, oara, Romania INCDMTM, Romania «Politehnica» University of Bucharest, Romania «Politehnica» University of Bucharest, Romania

Organization

Sergiy Plankovskyy Pierluigi Rea Michal Rogalewicz Vladimir Serbezov Laurent, iu Slatineanu Natalia Smetankina D˘anut, Stanciu Ion Stiharu Mihail Titu Michael Todorov Pedro Torres Justyna Trojanowska Yevgen Tsegelnyk Viktoriia Serhiivna Vakal Stefan Voth Maohua Xiao Sahin Yildirim Nikolay Zlatov

ix

Beketov National University of Urban Economy in Kharkiv, Ukraine University of Cagliari, CA, Italy «Politecknica» University of Poznan, Poland Technical University of Sofia, Bulgaria “Gheorghe Asachi” Technical University of Iasi, Romania National Academy of Sciences of Ukraine, Ukraine INCDMTM, Romania «Concordia» University, Montreal, Canada «Lucian Blaga» University of Sibiu, Romania Technical University of Sofia, Bulgaria Polytechnic Institute of Castelo Branco, Portugal Poznan University of Technology «O.M. Beketov» National University of Urban Economy in Kharkiv, Ukraine Research Institute of Mineral Fertilizers and Pigments of Sumy State University, Ukraine Technische Hochschule Georg Agricola, Germany Nanjing Agricultural University, Nanjing, China Erciyes Üniversitesi Akademik Veri Yönetim Sistemi, Turkey Institute of Mechanics; Bulgarian Academy of Sciences, Bulgaria

Organizing Committee Local Organizing Chair Doina Daniela Cioboata

INCDMTM, Romania

Local Organizing Co-chair Bogdan Gramescu

«Politehnica» University of Bucharest, Romania

Local Conference Secretary Andreea Stanciu

INCDMTM, Romania

x

Organization

Organizing Committee Members Florentina Badea Liliana-Laura Badita-Voicu Octavia Caruntu Iulian Ilie Simona Istriteanu Ligia Petrescu Mihail Titu Georgeta Udrea

INCDMTM, Romania INCDMTM, Romania INCDMTM, Romania INCDMTM, Romania INCDMTM, Romania INCDMTM, Romania «Lucian Blaga» University of Sibiu, Romania «Politehnica» University of Bucharest, Romania

Contents

Stability Analysis of Dismountable Pallet Racks . . . . . . . . . . . . . . . . . . . . . . . . . . . Valentyn Kovalenko, Volodymyr Rubashka, Volodymyr Alieksieiev, and Bernhard Heiden An Overview About Mechanics Developments and Achievements in the Context of Industry 4.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cristina Lincaru, Florentina Badea, Sperant, a Pîrciog, Adriana Grigorescu, Sorin-Ionut Badea, and Cristian-Radu Badea

1

17

Neighbor-Joining Analysis of Mechanics and the Industry 4.0 Domains . . . . . . . Florentina Badea, Gabriela Tudose, Cristina Lincaru, Sperant, a Pîrciog, Adriana Grigorescu, Sorin-Ionut Badea, and Cristian-Radu Badea

42

Monitoring of Soil Desertification - Quality Parameters . . . . . . . . . . . . . . . . . . . . . Bajenaru Valentina-Daniela and Badea Diana-Mura

56

Improving the Energy Performance of a High-Head Francis Turbine . . . . . . . . . . Kostiantyn Myronov, Olha Dmytriienko, Yevheniia Basova, Kseniya Rezvaya, and Serhii Vorontsov

66

Research on a Climbing Robot with Attachment by Vacuum Cups . . . . . . . . . . . . Tudor Catalin Apostolescu, Laurentiu Adrian Cartal, Ioana Udrea, Georgeta Ionascu, and Lucian Bogatu

78

SMART Education Framework to Assess the Knowledge of Engineering Students . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Dushanov Begmamat, Bekturdiyev Sanjarbek, Ubaydullayev Utkirjon, Narzullayev Shohrukh, and Khamrokulov Umidjon Comparative Analysis of SMART Education Framework and Traditional Assessment Techniques in Evaluating the Knowledge of Engineering Students . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Dushanov Begmamat, Bekturdiyev Sanjarbek, Ubaydullayev Utkirjon, Narzullayev Shohrukh, and Khamrokulov Umidjon Effect of Various Solid Lubricants on Diamond Grinding of Heat-Resistant Stainless Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 Aleksandr Rudnev, Elena Sevidova, Oksana Titarenko, Alexey Kotliar, Viacheslav Baranov, Oleksandr Yurchenko, and Milan Edl

xii

Contents

Models for Prediction of Failure Time for Optical Fibres Under Severe Aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 Rochdi El Abdi and R. Leite Pinto Multi-material 3D Printed Interfaces. Influencing Factors and Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 Vasile Ermolai and Alexandru Sover Implementation of Human-Robot Interaction Through Hand Gesture Recognition Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 George Gamazeliuc, Oliver Ulerich, Eulampia Rolea, and Mihai M˘arg˘aritescu Experimental Determination of Power Losses in Steel and Hybrid Rolling Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 Vladimir Dotsenko, Oleksandr Gnytko, Yurii Koveza, and Anna Kuznetsova Slot Side Measurement with a Commercial Laser Triangulation Sensor . . . . . . . . 164 Jan Hošek Mathematical Model and Numerical Model for the Development of Processing Algorithms Using the Harmonic Coil Measurement Method . . . . . 173 Nicolae Tanase, Ionel Chirit, a˘ , Adrian Nedelcu, Cristinel Ilie, Marius Popa, Lipcinski Daniel, and Mihai Gut, u Micropump with Electromagnetic Actuation and Internal Slotted Valves . . . . . . . 186 Cristinel Ilie, Marius Popa, Nicolae Tanase, Adrian Nedelcu, and Lipcinski Daniel Study on the Life of Hydrocyclones for Cleaning Coolant on Roll Grinding Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 Mykhaylo Stepanov, Maryna Ivanova, Volodymyr Korniienko, Yurii Havryliuk, Serhii Slipchenko, and Petro Litovchenko Development of Technology of Making Shafts from Steel Alloy 35XGCL . . . . . 216 Nozimjon Kholmirzaev, Nodir Turakhodjaev, Nosir Saidmakhamadov, Jamshidbek Khasanov, Shokhista Saidkhodjaeva, and Nargiza Sadikova Influence of Technological Parameters of the Continuous Casting Process on the Process of Accumulation of Damage in the Billet . . . . . . . . . . . . . . . . . . . . 224 Oleg Khoroshylov, Olga Ponomarenko, Oleg Podoljak, Oleg Kondratiyk, Nataliia Yevtushenko, Anton Skorkin, and Yuriy Sychov

Contents

xiii

Computer Modelling and Comparative Analysis of Surface Microrelief Inspection by the Method of Scattering of a Laser Beam During Its Small-Angle Sliding Incidence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 Sergey Dobrotvorskiy, Borys A. Aleksenko, Vitalii Yepifanov, Yevheniia Basova, Vadym Prykhodko, Ludmila Dobrovolska, and Mikołaj Ko´sci´nski Hydrodynamics Analysis on Partially Filled Agricultural Tanks by Driving Cycle of Transportation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 Andrii Kozhushko Functional Bioceramic Calcium Phosphate Materials for Use as Bone Fillers and Filling the Lack of Muscle Tissue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 Svetlana Krivileva, Nataliia Ponomarova, and Alexander Zakovorotniy Interchangeable Spindle Heads of the Machining Center with Modernized Connecting Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 Oleg Krol and Vladimir Sokolov Experimental Studies of Hydrodynamic Characteristics of Cellular Packings for Benzene Absorbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286 Inna Lavrova, Vladyslava Vladymyrenko, and Volodymyr Babenko Influence of Polymeric Quaternary Salts on Some Properties of Cement Stone and Concrete for Construction and Irrigation Purposes . . . . . . . . . . . . . . . . . 297 Makhmudova Naima Khalilovna Studies Concerning Water-Based Coolants Under Magnetic Field During a Metal-Cutting Process (Turning) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 Umidjon Mardonov, Otabek Khasanov, Abdikhalil Ismatov, and Azamat Baydullayev Improving the Reliability of Circulating Water Supply Installations of Thermal Power Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318 Viktor Moiseev, Eugenia Manoilo, Yurii Manoilo, Kalif Repko, and Denis Davydov Research on Distribution of the Condensed Substance on a Flat Support and Obtaining Vacuum Evaporation Thin Films with Uniform Thickness by Correction Masks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328 Georgeta Ionascu, Lucian Bogatu, Tudor Catalin Apostolescu, Elena Manea, and Edgar Moraru

xiv

Contents

Approaches and Processing Technologies for Medical Devices: Considerations from Micro- and Macroscale Perspectives . . . . . . . . . . . . . . . . . . . 345 Edgar Moraru, Grigore Octavian Dontu, Sorin Cananau, and Vlad-Andrei Stanescu Complex Determination of the Parameters of Structural Transformations of Polymer Composite Materials Taking into Account the Activation Energy . . . 363 N. Moskovska Modelling and Simulation of Some Mechatronics Assembly Realized on Arduino Uno Board, Through the Tinkercad Application . . . . . . . . . . . . . . . . . 374 Iulian Sorin Munteanu, Liviu Marian Ungureanu, Cosmina-Constantina Caraiman, Ramona-Gabriela Cris, an, Elisabeta Niculae, and Badea Sorin Experimental and Theoretical Research of the Socket-Residual Limb Interface at Trans-tibial Prostheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385 Oana Andreea Chiriac, Ciprian Ion Rizescu, and Constantin Nit, u Mathematical Modeling of 2D Discontinuous Objects by New Information Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 Iuliia Pershyna Robotic-Like Formulation of the Approximated Body-Guidance Problem . . . . . . 405 Maurizio Ruggiu and Pierluigi Rea Gripper for Manipulating Empty Bag Sacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418 Ciprian Ion Rizescu and Dana Rizescu Controllers Synthesis Algorithms in the Construction of Discrete Control Systems for Technological Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426 Husan Igamberdiyev, Jasur Sevinov, and Suban Khusanov Electronic Load Sensing for Integrating Electro-Hydraulic Mechatronic Actuators with Industry 4.0 and 5.0 Components . . . . . . . . . . . . . . . . . . . . . . . . . . . 440 Alexander Skvorchevsky Dynamic Stresses in the Adhesive Joint. The Goland-Reissner Model . . . . . . . . . 456 Natalia Smetankina, Sergei Kurennov, and Kostiantyn Barakhov Methods and Techniques Utilized in Programming Collaborative Robots for High-Quality Automation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469 Aurel Mihail T, ît, u, Vasile Gusan, and Alina Bianca Pop

Contents

xv

Modeling of the Communication Process Between Two Microcontrollers in Order to Optimize the Execution of Specific Tasks . . . . . . . . . . . . . . . . . . . . . . . 490 Aurel Mihail T, ît, u and Adrian Bogorin-Predescu Contact Interaction of Solids of Revolution with Surface Perturbation . . . . . . . . . 504 Mykola Tkachuk, Andriy Grabovskiy, Mykola Tkachuk, Iryna Hrechka, and Hanna Tkachuk Implementation of Induction Motor Speed and Torque Control System with Reduced Order Model in ANSYS Twin Builder . . . . . . . . . . . . . . . . . . . . . . . 514 Vladyslav Pliuhin, Yevgen Tsegelnyk, Sergiy Plankovskyy, Oleksandr Aksonov, and Volodymyr Kombarov An Effective Way of Removing Organic Chemical Contaminants from Wastewater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532 Iryna Sinkevych, Alona Tulska, Oleksii Mardupenko, Kseniya Rezvaya, and Viktoriia Vakal The Method of Clustering Geoinformation Data for Stationary Sectoral Geoinformation Systems Using Swarm Intelligence Methods . . . . . . . . . . . . . . . . 541 Vasyl Lytvyn, Dmytro Uhryn, Yuriy Ushenko, Andrij Masikevych, and Volodymyr Bairachnyi The Influence of Structure on Mechanical Properties of Multilayered Cu – Ta Composites at Room Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554 Eugene Yascheritsin and Oleksandr Terletskyi Monitoring the Operation of the Internal Combustion Engine Based on the Processing of Indirect Measurement Data . . . . . . . . . . . . . . . . . . . . . . . . . . . 566 Oleksandr Yenikieiev, Dmytro Zakharenkov, Magomediemin Gasanov, Fatima Yevsyukova, Olena Naboka, Anatolii Borysenko, and Nikolay Sergienko Comparison of Metrological Characteristics of Measuring Transducer of Parameters Frequency-Modulated Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 586 Oleksandr Yenikieiev, Dmytro Zakharenkov, Magomediemin Gasanov, Fatima Yevsyukova, Olena Naboka, Anatolii Borysenko, and Natalia Pavlova Using an Object-Oriented Approach in Foundry Production . . . . . . . . . . . . . . . . . 604 Olga Ponomarenko, Nataliia Yevtushenko, Oleg Khoroshylov, Stepan Yevtushenko, Tatyana Berlizeva, Mikhailo Vorobyov, and Ihor Lukianov

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Examination of the Effect of Hyperparameters on Object Detection in the Orchard Using Deep Learning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 616 S¸ ahin Yıldırım and Burak Ulu Structural and Kinematic Synthesis Algorithms of Adaptive Position-Trajectory Control Systems (In the Case of Assembly Industrial Robots) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 622 Oripjon Zaripov and Dildora Sevinova Author Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 639

Stability Analysis of Dismountable Pallet Racks Valentyn Kovalenko1

, Volodymyr Rubashka1 , Volodymyr Alieksieiev2(B) and Bernhard Heiden3

,

1 National Technical University “Kharkiv Polytechnic Institute”, Kyrpychova 2, Kharkiv 61002,

Ukraine 2 Hamburg University of Technology, Denickestr. 17, 21073 Hamburg, Germany

[email protected] 3 Carinthia University of Applied Sciences, Europastr. 4, 9524 Villach, Austria

Abstract. The article is devoted to the development of methods for stability analysis of dismountable pallet racks. These structures are optimally adapted to the minimal occupation of storage space (e.g. in warehouses), as well as to the convenient access to the stored items. The need to accommodate the maximum number of goods in the minimal storage area places high demands on the design and calculation methods of the racking systems. The aim of the work is to investigate the stability of a multi-section pallet rack. For this purpose, a combined calculation scheme containing three-dimensional solid bodies, thin-walled shell structures and beam structures has been developed. The scheme also takes into account the main design features of detachable connections of the components. The finite element method (FEM) is proposed as a research method, which allows to take into account all the design features of the components and the nature of their connection in the dismountable structure of rack systems. As a result of the research, the ways to increase the stability of racking systems were evaluated exploiting the possibility of their restructuring using the properties of dismountable units. It was found out that only by rearranging the load beams along the height of the rack or by changing the scheme of fastening the racks to the base, it is possible to significantly increase the stability of the rack as a whole. Keywords: pallet rack · finite element method · FEM · calculation scheme · stability · bolted connection

1 Introduction and Problem Statement The most common way to store large amounts of industrial goods is to store them in pallet racks. Their use makes it possible to reduce the cost of storing a unit of product, effectively using the useful area of the warehouse. (cf. [1]) The goods can be stacked on pallets of two basic sizes - EUR (800 × 1200 × 150 mm, Euro pallet) and FIN (1000 × 1200 × 150 mm, Finnish pallet) [2, 3], which are most commonly used in modern logistics systems [4]. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 1–16, 2023. https://doi.org/10.1007/978-3-031-40628-7_1

2

V. Kovalenko et al.

The design of the racks allows the installation of single and double rows, the length of which is limited by the convenience of handling equipment. Until recently, allwelded racks or racks with welded frames and bolted assembly were used, and their elements were the usual construction section of rolled metal products. These constructions, however, often do not meet the modern customer requirements. Modern racks should be quickly dismountable, consisting of prefabricated frames and lightweight special type of rolled steel. Special rolling equipment is usually used for their production. The rack of a modern rack system is made of metal 1.5…2 mm thick, and different parameters of loading capacity of the rack levels are provided accordingly by beams of special shape manufactured using the rolling equipment. A dismountable rack system consists of the following parts (Fig. 1): • several frames, each of which has two vertical columns made of special profile with perforations, connected to each other by struts, which increase the rigidity of the structure; • horizontal load beams with fastening elements to the vertical frames, which are made in the form of brackets with hooks welded to the ends of the beams; • The footrests located at the bottom of each column.

Fig. 1. Dismountable pallet rack model in SOLIDWORKS®

The profile of the column has a complex design with up to 12 stiffening ribs in its cross section. Examples of column fragments of different types of cross-sections and perforation schemes are shown in Fig. 2.

Stability Analysis of Dismountable Pallet Racks

3

Fig. 2. Pallet rack column sections (Source: Staff-Eye GmbH)

The struts connect the two racks into a single frame. For this purpose, a special opening is provided in the design of the rack, into which the strut is inserted and secured with a bolted connection as shown in Fig. 3.

Fig. 3. Fixing the struts in the rack frame [5]

As can be seen from the above description, modern pallet racks are complex spatial metal structures consisting of a variety of elastic elements under the influence of a spatial system of forces. Since the racks are subjected to significant vertical loads, the issues of ensuring the stability of both the constituent elements and the entire structure as a whole are of particular relevance.

4

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2 Analysis of Recent Studies and Publications The basics of design and operation of pallet racks are outlined in the regulatory documentation [6–9]. However, this documentation does not provide answers to the most important questions associated with the improvement of designs, with the study of the mutual influence of individual design solutions on the condition of the racking system. Therefore, research works are currently being developed to study certain aspects of the behavior of such systems. One of the research directions is the analysis of individual elements and units of the racking complex. For example, in [10] and [11] the authors conducted a detailed analysis of the stability of racking columns made of cold-bent steel under complex modes of loading. Comparison of experimental studies with numerical modelling based on FEM showed a significant dependence of rack stability on the presence of perforation holes. In [12–14] the necessity of detailed modelling of the junction of a strut with a rack in pallet racks is substantiated. It is noted that the representation of such connections in the form of rigid connections multiplies the stiffness of the modeled system. In [15] and [16] the use of bolted connections of the strut with the rack is justified. Another research direction is related to the analysis of the stability of the entire racking structure. In [17] and [18], the authors analyze the influence of the connections between the shelf beams and the racks. It is noted that the nature of these connections has a significant impact on the behavior of the racking system. An important part of the investigation of mechanical structures is to look at their stability. One of the first to mathematically describe stability was Lyapunov [19], which is now common in control systems and important in chaos theory with a wide field of applications. The numerical implementation of the mechanical equations, which means the numerical discretization of the basing differential equation systems, is usually implemented with FEM, which can, together with powerful computers, cope with increasingly complex overall mechanical systems. Almost all authors note the complexity of studying such structures. Therefore, in addition to experimental research methods, the FEM became common. The technology of applying FEM for analyzing rack thin-walled structures is considered in [20] and [21]. These works demonstrate the effectiveness of using such models for determining the general and local forms of stability of the systems under study in the presence of continuous perforations of support struts. From the analysis of recent researches, it follows that the research does not sufficiently reflect the issues of determining the directions of increasing the stability of the entire pallet system due to the possibility of its internal restructuring. The stability of an elastic system is largely determined by its stiffness properties. For example, in [22, 23], the authors showed that only by changing the height of fixing the beam to the bracket, one can significantly increase the stiffness of the beam-column connection node and, consequently, the stiffness and stability of the rack system.

Stability Analysis of Dismountable Pallet Racks

5

For pallet racks, the detachable connections enable to affect the rigidity of the entire system through the rearrangement of individual elements. This design feature determines the directions for increasing stability. These include: • Rearrangement of beams along the height of the rack; due to the presence of connections by hooking the beams to the racks; • The change in the location of the bolted anchor connections of the footings with the base implements different conditions for supporting the columns. All this allows the rack to be easily reconfigured during installation and operation, which in turn affects the rigidity and stability characteristics of the entire elastic system.

3 Purpose of the Work Based of the above provided analysis of recent research state, the aim of this paper is as follows: • Analysis of pallet rack stability based on the setup of the calculation scheme, taking into account the design features of the metal structure components and the nature of their connections; • Determination of ways to improve the stability of racks using the possibilities of dismountable construction of pallet racks.

4 Concept The design of pallet racks has a number of features that significantly affect the technology of designing and calculating such systems. The elements of the racking system are made of a thin-walled bent profile. The racks are particularly complex because they are made of bent thin-walled open profiles. Beams and struts are usually made of bent thin-walled profiles with a closed cross-section. All structural elements are connected to each other by detachable connections - bolted connections, “hook-and-loop” connections, etc. The dismountable nature of pallet rack systems causes the need to take into account the design features of the bonding elements: • Brackets, which connect the beams to the racks with the hooks; • Bolt connections, by means of which the struts connect the racks in the frame; • Anchor connections of the footings to the base. Therefore, it is proposed to build a racking model where a combined calculation scheme will be used, in which the load beams and struts are to be represented by beam models, struts and brackets by elastic shells, and fasteners by three-dimensional bodies. Modern CAD allows to build geometric models and calculate the complex structures. The rack system is modelled in SOLIDWORKS® Premium 2016x64 Edition [24]. This program package has the wide possible geometric modelling capabilities for various structures, taking into account their features and the variety of connections. In addition, it provides the ability to perform a variety of calculations, including stability calculations. As an example, a 4-section rack was set up. Table 1 shows the technical data of the rack section [25].

6

V. Kovalenko et al. Table 1. Technical data of the rack section

Section height

6000 mm

Section length

1825 mm

Section width

1100 mm

Load per level

2000 kg

Loading per section

10000 kg

Number of storage levels, max

5

Number of pallets on the level

2

Number of pallets per section

10

Pallet compatibility

1200 × 800 mm

Rack material

cold-rolled steel

Rack thickness

1.5 mm

Girder (cross beam) material

cold-rolled steel

Girder (cross beam) thickness

1.5 mm

Rack profile (W × H)

80 × 80 mm

Beam profile (W × H)

80 × 50 mm

Painting

Polymer powder enamel or zinc

Rack color, standard

RAL5017

Beam (cross beam) color, standard

RAL 2001

Perforation step of the transversing beams

70 mm

Compliance with European standards for racking equipment

DSTU EN 15620:2015; DSTU EN 15635:2016; DSTU EN 15629:2015

Certificate of Conformity

TÜV Rheinland LGA products GmbH

Certificate for quality management system, occupational health and safety, production

TÜV NORD CERT ISO 45001: 2018, ISO 9001: 2015, ISO 14001: 2015

Country of production

Ukraine

Guarantee

12 months

The rack is completed with footstools and fasteners. Fasteners represent bolts M10x55, M10x20, anchor bolts M16 and nuts M10, M16. To study the stability of a multi-section dismountable pallet rack, a geometric 3-D model was built, shown in Fig. 4. As you can see from this figure, the rack consists of five frames, each consisting of two columns connected by a system of struts. The frames are connected by load beams. The model of each rack is a long thin-walled shell with a complex open cross-section profile. The front edge has a stiffening rib along the entire height of the rack to increase its rigidity, as well as rectangular perforation holes to connect it to the rack’s load beams with bracket hooks. Several stiffening ribs are provided on the back side of the shell, as

Stability Analysis of Dismountable Pallet Racks

7

Fig. 4. Rack model in SOLIDWORKS®

well as round perforation holes for connecting the rack to the struts with bolt connections. There is also an opening in the section on the rear side, into which the strut is entered when connecting the racks into a single rack frame (Fig. 5). The strut is an elongated thin-walled shell with a square, constant cross-section length. The ends of the strut are provided with holes for bolt connections of the strut to the column. The beam is modeled by a closed thin-walled shell with a stiffener in the middle. A bracket is attached at the end, which is an angle shell with hooks extruded on one side. With the help of these hooks the beam is attached to the adjacent columns (Fig. 6). In addition, 3D models of fasteners - bolts and nuts - were used in the modelling of the bolted connections of the struts to the frame struts, as shown in Fig. 7. Particular attention is paid to modelling the attachment of racks to the base. For this purpose, there are footrests that are bolted to the front plane of the rack on one side and anchored to the base on the other side. The model also takes into account that in accordance with the recommendations of the manufacturer, which are reflected in the passport of the rack, each thrust bearing is attached by two anchor bolts to the base (Fig. 8). Thus, a 3D model of a rack is developed, that corresponds as much as possible to the real design and in a way that all kinds of detachable connections used in dismountable racks can be implemented in the model. Based on the rack model built in SOLIDWORKS®, a calculation scheme for stability analysis has been set up. The detachable connections were considered as follows: • Bolt connections of struts with struts were modeled by pin connections, simulating free rotation of strut end relative to the bolt, which connects the strut with a column.

8

V. Kovalenko et al.

Fig. 5. Modelling of column, strut and load beam in SOLIDWORKS®

Fig. 6. Modelling of beam-pillar connections with brackets in SOLIDWORKS®

• The interaction of the bracket hooks with the rack was modeled by specifying the rigid connections between the hook edges and the contacting edges of the rack. The beam edges were connected rigidly to the corresponding edges of the brackets. When modelling the shelf supports, connections were made between the fasteners as well as the column and footrest elements. The loads acting on the rack, given the condition of the location in each cell of two pallets of 750 kg each. In order to reduce the

Stability Analysis of Dismountable Pallet Racks

9

Fig. 7. Modelling of the bolted connections of the struts with the strut in SOLIDWORKS®

Fig. 8. Modelling of rack support in SOLIDWORKS®

dimensionality of the finite element computational scheme, a system of simplifications was introduced: • It is suggested that the fasteners are replaced by absolutely rigid bodies. Indeed, the elastic properties of the bolts and nuts are unlikely to have a significant effect on the elastic properties of the entire system; • Representation of struts and beams by simplified beam elements. Such a replacement can be made because these elements fully meet the criteria of a beam element: constant

10

V. Kovalenko et al.

in length cross-section, the element length is more than 10 times greater than the largest cross-sectional dimension. All struts and beams were assigned with the “Treat as a beam” property in SOLIDWORKS®. When replacing struts with beam elements, the joints at the ends were set to simulate bolt connections in a real rack. The nodes at the ends of the load beams are rigidly connected to the corresponding edges of the brackets. The model was used to analyze the effect of design changes on the stability of the rack as a whole. The first group of studies was conducted to evaluate the effect of the height of the load beams relative to the base on the stability of the rack. The hitch connection modelling makes it possible to set different heights of the beams relative to the base. The height of the lower load beam relative to the base was varied while maintaining the overall height of the rack tiers. The rack beams were lowered from a height of 1500 mm to 750 mm. In all cases, the rack was loaded in each cell with two pallets weighing 1000 kg each. This pallet weight corresponds to the total load per section, which is specified in the racking specifications (Table 1). When simulating the loading of a racking system in accordance with EN 15512:2020 [9], the load from the pallets was equally distributed across the beams of the cell. Figure 9 and Fig. 10 show the results of the calculation in the case of positioning the bottom beam in two extreme positions - at a height of L1 = 1500 mm and L1 = 750 mm from the base.

Fig. 9. First form of stability loss: lower beam is located at a height of L1 = 1500 mm from the base (Modelling in SOLIDWORKS®)

The calculation results for all intermediate cases of load beams are presented in Table 2. The calculations show that the stability of the rack increases as the distance to the first load beam from the base decreases. This behavior of the rack structure is caused by

Stability Analysis of Dismountable Pallet Racks

11

Fig. 10. First form of stability loss: lower beam is located at a height of L1 = 750 mm from the base (Modelling in SOLIDWORKS®)

Table 2. Results of stability calculation at different height of rack beams Height of the bottom A form of loss of beam from the base L1 , stability mm

Stability margin factor

Maximum elastic displacement of columns under critical load, mm

750

General (bending)

6,2

3,9

1000

General (bending)

5,7

3,4

1250

General (bending)

5,0

3,2

1500

General (bending)

3,9

3,1

the nature of the elastic displacements of the struts in the first bending form of stability loss. Calculations show that the higher the stability factor, the more elastic movements the structure can withstand under critical loads. As can be seen from Fig. 9 and Fig. 10, the displacement in the frontal plane of the rack in case of loss of stability is largely determined by the stiffness of the rack elements and beams located in the lower part of the structure. The lower the beams of the rack, the smaller, and therefore stiffer, the lower sections of the racks between the base and the lower beam. In addition, the lower the beams, the more they are involved in the deformation of the structure and therefore increase its stiffness. Thus, by rearranging the height of the rack beams only, the stability of the rack can be increased.

12

V. Kovalenko et al.

The second direction of research was to evaluate the effect of the ways of anchoring the footrests to the base of the rack. There are four holes for anchor bolts in the footrest. However, as noted earlier, the footrest is attached to the base with two anchor bolts. The other two holes are done to replace the bolts in case they unexpectedly fail. At the same time, normative documents [6–9] do not specify how these anchor bolts should be located. The model was used to investigate the stability of the rack at different anchor bolt layouts with constant height of the load beams. The distance from the base to the bottom beam was taken as 1250 mm. The results of the calculations are presented in Table 3. Scheme 1 is not implemented in practice since all 4 anchor joints are used in such a fastening of the racks. However, the calculation result for this anchoring scheme is given for a qualitative illustration of the effect of anchoring schemes on the stability of rack systems. As can be seen from the data obtained (Table 3), the location of the anchor bolts on the supports has a significant effect on the stability of the entire rack. The stability of the rack is much higher when both anchor bolts are placed near the frontal plane of the supports (schemes 1 and 2) than with other anchoring schemes. The use of two anchor bolts instead of four has no significant effect on the stability of the system. The absence of at least one of the connections near the frontal plane of the strut (schemes 3 and 4) leads to a sharp decrease in the stability of the system. The most critical in terms of stability is the footrest connection according to scheme 4. The application of such an attachment leads to a significant decrease of stability in comparison with the scheme 2. This behavior of the rack can be explained by the fact that the stiffness of the entire support depends on the connection scheme of the footrests when the overall bending form of stability loss is realized (see Fig. 9 and Fig. 10). When the rack bends in the frontal plane, there is an elastic deformation of the footrest and the nature of this deformation depends on its connection to the base. Figure 11a shows the deformed state of the footrest for the second fastening scheme. As can be seen, the anchor bolts in this scheme provide an almost rigid connection between the column and the base. The maximum elastic displacement of the footrest relative to the base in this case is less than 1 mm. A different picture of the deformed state is observed for scheme 4, shown in Fig. 11b. When the rack bends, due to the lack of connection of the footrest near its connection with the column, the front part of the footrest is torn away from the base by 4,5 mm. In this case, not the rigid connection as in the first case, but an elastic support is resulted, where its stiffness is determined by the size and design of the footrest. In order to ensure a high stability of the rack, it is sufficient to place two anchors near the mounting location of the column and the footrest according to scheme 2.

Stability Analysis of Dismountable Pallet Racks

13

Table 3. Modelling of stability of rack support with different footrests connection schemes in SOLIDWORKS®

1

5,0

Maximum elastic movement of the column, mm 3,2

2

4,9

3,2

3

3,2

3,1

4

2,7

3,0

№

Connection scheme

Stability margin coefficient

14

V. Kovalenko et al.

а)

b)

Fig. 11. Deformations of the fastener assembly: a) scheme №2 of anchor bolts location; b) scheme №4 of anchor bolts location (Modelling in SOLIDWORKS®)

5 Conclusions and Outlook As a result of the conducted research, a calculation scheme of the dismountable rack is proposed. This scheme takes into account all the design features of the components of the metal structure and the nature of the dismountable connections by which these elements are connected with each other. It implies a system of simplifications consisting in the fact that the details of fasteners are represented by absolutely rigid bodies, and struts and load beams are represented by simplified beam elements. Supporting columns, brackets, and footrests are modeled by spatial thin-walled shells. Numerical simulations of rack stability have shown that the presence of dismountable structural units has great potential for increasing the stability of such systems. In addition, the increase of stability can be achieved without additional material costs, but only using the correct arrangement of the components. It has been determined that the dismountable racking system opens up the possibility of controlling its stability. For example, in order to increase stability, it is enough to lower the load beams. This is relatively simple to execute due to the special design of the columns and the brackets by which the beams are connected to the columns. One such action can significantly increase the stability of the rack. The second way to increase stability is to properly position the anchor bolts on the column supports. The closer the anchor bolts are positioned to the post and footrest location, the higher the stability of the entire system will be, even when using two-bolt anchor connections. Thus, the dismountable pallet rack shows good potential for increasing its stability. Its use will ensure the normal operation of rack systems, goods safety, safety of workers and accident-free operation of the entire warehouse complex. In conclusion, it should be noted that the studies performed do not cover all the issues related to the study of rack stability. The question of constructing adequate calculation schemes for multisectional racks with 5–10 or more sections remains open. Studies of the influence of bracket design on rack stability could also represent an interesting research

Stability Analysis of Dismountable Pallet Racks

15

direction. Important from a practical point of view are the questions of assessing the influence of loading schemes and the effects of racking equipment on the stability of racking structures. Open research questions that could be tested in the future are e.g.: • production cost optimization; • investigation of specific lightweight design and its strategies; • mounting velocity investigation as a function of the construction design, to optimize for flexible industry 4.0 production systems; • risk analysis for the case of the collision with a forklift or other relevant scenarios; • experimental testing, verification and validation of the modeling; • the impact of stiffening measures; • wall geometry variants.

References 1. Schumann, M.: Zur Bestimmung der Umschlagleistung von Hochregallagern unter besonderer Berücksichtigung der Lagerorganisation. Dissertation, Chemnitz (2008) 2. ISO/TC 122 Packaging: ISO 3676:2012. Packaging—Complete, filled transport packages and unit loads—Unit load dimensions (2012) 3. ISO 8611-1:2021. Pallets for materials handling—Flat pallets—Part 1: Test methods. Technical Committee: ISO/TC 51 Pallets for unit load method of materials handling (2021) 4. EPAL - THE EUROPEAN PALLET ASSOCIATION. © 2023 European Pallet Association e.V. (2023). https://www.epal-pallets.org/eu-en/. Accessed 14 Apr 2023 5. Warehouse Rack & Shelf LLC. Official Website. https://rackandshelf.com/wp-content/ uploads/Interlake-Mecalux-Teardrop-Upright-Frame-Feature-Picture-scaled-350x467.jpg. Accessed 27 Apr 2023 6. EN 15620:2021: Steel static storage systems - Adjustable pallet racking - Tolerances, deformations and clearances (2021) 7. EN 15629:2008: Steel static storage systems - Specification of storage equipment (2008) 8. EN 15635:2009: Steel static storage systems - Application and maintenance of storage equipment (2009) 9. EN 15512:2020: Steel static storage systems - Adjustable pallet racking systems - Principles for structural design (2020) 10. Talebian, N., Gilbert, B.P., Miller, D., Karampour, H.: Biaxial bending design of solid steel storage rack uprights in global buckling. J. Constr. Steel Res. 196, 107395 (2022) 11. Ren, C., Wang, B., Zhao, X.: Numerical predictions of distortional-global buckling interaction of perforated rack uprights in compression. Thin-Walled Struct. 136, 292–301 (2019) 12. Gusella, F., Orlando, M., Peterman, K.: Stiffness and resistance of brace-to-upright joints with lipped channel braces assembled flange-to-flange. J. Constr. Steel Res. 193, 107258 (2022) 13. Escanio, L.A., Guilherme, C.E., de Almeida Neiva, L.H., Alves, V.N., Sarmanho, A.M.C.: Analysis of beam-to-upright end connections steel storage systems. Adv. Steel Constr. (2020) 14. Zhao, X., Dai, L., Rasmussen, K.J.: Hysteretic behaviour of steel storage rack beam-to-upright boltless connections. J. Constr. Steel Res. 144, 81–105 (2018) 15. Yin, L., Tang, G., Li, Z., Zhang, M., Feng, B.: Responses of cold-formed steel storage racks with spine bracings using speed-lock connections with bolts I: Static elastic-plastic pushover analysis. Thin-Walled Struct. 125, 51–62 (2018) 16. Dai, L., Zhao, X., Rasmussen, K.J.: Flexural behaviour of steel storage rack beam-to-upright bolted connections. Thin-Walled Struct. 124, 202–217 (2018)

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17. Gusella, F., Arwade, S.R., Orlando, M., Peterman, K.D.: Influence of mechanical and geometric uncertainty on rack connection structural response. J. Constr. Steel Res. 153, 343–355 (2019) 18. Bernuzzi, C., Pellegrino, C., Simoncelli, M.: Characterization of existing steel racks via dynamic identification. Buildings 11(12), 603 (2021) 19. Lyapunov, A.M.: The general problem of the stability of motion. Int. J. Control 55(3), 531–534 (1992) 20. Liu, S.-W., Pekoz, T., Gao, W.-L., Ziemian, R.D., Crews, J.: Frame analysis and design of industrial rack structures with perforated cold-formed steel columns. Thin-Walled Struct. 163, 107755 (2021) 21. Neiva, L., Braz Starlino, J.A., Elias, G., Cunha Sarmanho, A.M., Nicchio Alves, V.: Industrial storage system continuous perforated uprights: a combined design proposal. RDLC 21(2), 204–214 (2022) 22. Rubashka, V.P., Kuzmina, K.Yu., Kuznetsov, O.E.: Stiffness analysis of the pallet rack bracket. In: Information Technologies: Science, Engineering, Technology, Education Health: Abstracts XXX International Scientific-Practical Conference MicroCAD-2022, vol. 134 (Ukrainian) (2022) 23. Reznichenko, O.I., Rubashka V.P.: Calculation scheme for research of stability of collapsible racks. In: Information Technologies: Science, Engineering, Technology, Education Health: Abstracts XXXI International Scientific-Practical Conference MicroCAD-2023, vol. 199 (Ukrainian) (2023) 24. Solidworks Official Website. https://www.solidworks.com/. Accessed 25 Apr 2023 25. SKLADPLUS. Official Website. https://sklad-plus.com.ua/. Accessed 26 Apr 2023

An Overview About Mechanics Developments and Achievements in the Context of Industry 4.0 Cristina Lincaru1 , Florentina Badea2(B) , Sperant, a Pîrciog1 , Adriana Grigorescu3 , Sorin-Ionut Badea2 , and Cristian-Radu Badea2 1 National Scientific Research Institute for Labor and Social Protection - INCSMPS, Bucharest,

Povernei 6-8, Sector 1, 010643 Bucharest, Romania 2 National Institute of Research and Development in Mechatronics and Measurement

Technique – INCDMTM Bucharest, Sos Pantelimon, 6-8, Sector 2, 021631 Bucharest, Romania [email protected] 3 National University of Political Studies and Public Administration (SNSPA), Bucharest, Romania

Abstract. Mechanics and its derivates domains Mecatronics, Robotics, Integronics & Adaptronics are highly dynamic domains that suffer radical transformations reflected by co-occurrence with 8 terms of Industry 4.0, selected from Europe 2021–2027 Strategical Cycle: Industry 4.0/5.0, Big Data, Augmented Reality, AI, IoT, Computer Science, Virtual Reality, Blockchain, and the list is not exhaustive. Data: Our bibliometric analysis covers the period 1975-April 2023, with data extracted from Clarivate Web of Science core Collection (WoS). Methods: Text mining has several iterative Steps. We perform in depth analysis for 8520 records defined by Mechatronics & AI through the method “cooccurrence links between terms” in VOSviewer. Research Questions: 1) What is the position of Mechanics and its related technological fields in relation to Industry 4.0 Revolution? 2) What is the Romania’s relative specialization tendency by Mechanics and its new development domains relevant for Industry 4.0? 3) What are the semantic patterns of co-occurrence items for Mechatronic and AI. Main findings: 1) Mechanics is at the core of Industry 4.0. But with a conceptual content in fundamental transformation driven by radical changes in complex systems management & material technologies. 2) Romania’s relative specialization tendency is three times higher in AI than in Mechanics, based on the WoS contribution. 3) Mechatronic & AI’ is in direct relation with the Actuator and with the Image& Mobile Robot clusters and in indirect relation with Controller and Manipulator/Trajectory Clusters. Added value of the paper: Formulate as a high priority the need to develop a new unified science taxonomies and statistical nomenclature dynamic mechanism able to describe the new Mechanics in the time of AI in a coherent and continuous logic.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 17–41, 2023. https://doi.org/10.1007/978-3-031-40628-7_2

18

C. Lincaru et al. Present a relative accessible and easy solution based on the application of AI methods of analysis, as it is the Co-occurrence text analysis, to map in a clear manner both the domains, trans domain’s new tendencies with its relations and evolution trajectories. The output of this analysis is a relevant for input for education, economy & social activities in view to a) anticipate new skills demand for the new sectors & new occupations assumed already the competitiveness strategies; b) data fuel for the Mechanisms for occupational and geographical labour mobility, able to efficiently reallocate intersectoral the human capital toward the new sectors in conditions of increasing the employment quality, in a inclusive manner, “to leave no one behind”; c) to formalize the new occupational standards demands as well as the new educational programs in both content and volume, both for the initial and continuous education. Keywords: Mechanics · Mechatronic · IoT · Big Data · AI · Robotics · Virtual reality · Augmented Reality · Computer Science · Integronics · Adaptronics

1 Introduction 1.1 Industry 4.0/Industry 5.0 the Most Influential Domain in WoS Records Selected from European Strategical Ecosystem At the end of April 2023, we explore the WoS database in relation to topics emergent in European strategical ecosystem (see the domains from the Table 1) and mechanics main semantic family (Mechatronics, Integronics, Adaptronics). Industry 4.0 is at the core of the new strategical cycle [1] that shapes the regional transformation. The industry 4.0 is assumed objective to transform to a hyperconnected society and economy [2]. This is synthetically described as: “information-intensive transformation of manufacturing (and related industries) in a connected environment of big data, people, processes, services, systems and IoT-enabled industrial assets with the generation, leverage and utilization of actionable data and information as a way and means to realize smart industry and ecosystems of industrial innovation and collaboration” [3]. If the Industry 4.0 is technological driven revolution, the European Commission announced the Industry 5.0 revolution, whereas Industry 5.0 is value-driven [4]. Looking at the global level of knowledge thesaurus described by WoS, the research questions are: a) What is the position of Mechanics and its related technological fields in relation to Industry 4.0 Revolution? b) What is the Romania’s relative specialization tendency by Mechanics and its new development domains relevant for Industry 4.0? c) What are the semantic patterns of co-occurrence items for Mechatronic and AI

An Overview About Mechanics Developments and Achievements

19

1.2 Literature Review Using the text mining tool provided by WoS we explore each by one the twelve terms ranked by “hot intensity” in the Table 1. Through “hot intensity we understand the ratio between number of hot papers on the total number of publications in WoS for one term. “Highly cited papers1 ” reflects the utility of methods & techniques while it diffuses across community. Another important Science Indicator is “Hot Papers”. According to Clarivate Analytics help “Hot Papers generally reach their citation peak two, three, or four years after publication. A small group of papers, however, are recognized very soon after publication, reflected by rapid and significant numbers of citations. These papers are often key papers in their fields”. Based on the level of the hot intensity index we identify 4 clusters differentiated by influence, the highest the level of hot intensity the higher the level of influence to generate new economic sectors. – The most influential cluster include relative new terms close to Industry 4.0/Industry 5.0: Big Data, Augmented Reality, AI and IoT, terms with the level of Hot Intensity Index over 0.2. These terms signal a high potential to diversify the core scientific domains into new economic sectors. These domains count relatively small numbers of publications but high numbers of citation and rapid influence. Industry 4.0/Industry 5.0 counts 36.8 thousand publications in WoS with 453 highly cited papers and with 17 hot papers. “Big Data” counts 234 thousand publication, “Augmented Reality” counts 34.5 publications, AI over ½ million records and IoT almost one hundred thousand records. – The medium influential cluster include terms consolidates by a rich thesaurus base over 2.25 million publications in the domains Computer Science and Mechanics, terms with the level of Hot Intensity around 0.1. We include in this cluster the terms which evaluates from Mechanics respectively the Robotics & Mechatronics. – The lowest influential cluster which includes the terms Integratonics and Adaptronics, with a small number of publications, below 120 publications, without any Hot Paper. To sketch a general profile of the selected terms we select some hot publication by each term: Industry 4.0/Industry 5.0 Industry 4.0 is differential by its digital transformation focused to build green & circular economcy: in SMS [5] through green data analytics, smart manufacturing system design [6], green technologies [7], global value chains design [8, 9]. Expands the Industry 4.0 definition domain to include also: perception [4], metal additive [10], spherical nano and microstructures in biomedical and biotechnological applications [11]. Maddikunta et al. (2022) looks to identify the Industry 5.0 potential applications [12]. Big Data. New domains driven by Big data: Blockchain technology for sustainable development [5], Big Data Acquisition [13], Data augmentation [14]. Big Data is the 1 https://images.webofknowledge.com/WOKRS533JR18/help/WOS/hs_citation_applications.

html.

20

C. Lincaru et al.

Table 1. WoS Records of Mechanics domain and other domains (treated as independent) relevant. Domain

Publications in WoS Highly cited Number of Hot Hot Intensity (5) = Papers Papers (4)/(2) * 100

1

2

3

4

5

Industry 4.0/ Industry 5.0

36846

453

17

0.05

Big Data

234450

2525

69

0.03

Augmented Reality

34535

195

9

0.03

AI

566722

2717

130

0.02

IoT

98868

969

16

0.02

Computer Science 2558976

13232

374

0.01

Virtual Reality

82036

275

6

0.01

Mechanics

2250558

10103

324

0.01

Robotics

282569

993

25

0.01

Mechatronic

13535

14

1

0.01

Integronics

12

0

0

0.00

Adaptronics

112

2

0

0

Source of Data WoS, prelucrated by authors

blood of the new intelligent organisms that result linking together AI, IoT & Big Data as it is the case of Agriculture and Food Industry [15] or the case of China’s carbon neutral smart cities [16]. Augmented Reality. Augmented reality, virtual reality [17] and Metaverse [18, 19] as emerging digital technologies in social media [20]. AI-Artificial Intelligence. Artificial intelligence (AI) “machines are able to perform specific roles and tasks currently performed by humans within the workplace and society in general” [21] as it is learning, and decision making. The AI This new domain is “an interdisciplinary subject that involves information, logic, cognition, thinking, systems, and biology. It has been used for knowledge processing, pattern recognition, machine learning, and natural language processing” [22]. AI, based on machine learning is widespread adopted in Industry 4.0 and its new development Explainable Artificial Intelligence (XAI) in healthcare [23]. “The impact of AI could be significant, with industries ranging from: finance, healthcare, manufacturing, retail, supply chain, logistics and utilities, all potentially disrupted by the onset of AI technologies” [21]. Also AI is in a rapid development and among its further advance is announced the Industry 5.0. Industry 5.0 comprehends applications like “intelligent healthcare, cloud manufacturing, supply chain management and manufacturing production and some technologies like “edge

An Overview About Mechanics Developments and Achievements

21

computing, digital twins, collaborative robots, Internet of every things, blockchain, and 6G and beyond networks” [12]. Another further development of AI are: • the quantum leap from Cognition to Decision through “AI-powered Mobile Network architecture” [24] or • the next generation of autonomic computing which integrates the AI and Machine Learning in open loop systems, without the intervention of a human operator [25]. • changing the learning paradigm by the field of meta-learning and its related fields do transfer learning and hyperparameter optimization. These new approaches overcome the “many conventional challenges of deep learning, including data and computation bottlenecks, as well as generalization” [26].

IoT IoT systems through collecting and processing large amount of data “are capable of providing intelligent services” [27] from small scale to social scale as it is the cities. Consequently, the “IoT systems also raises serious security concerns” [27]. The Federate Learning “enables on-device training, keeping the client’s local data private, and further, updating the global model based on the local model updates” but raises concerns regarding the resources-constraints to IoT [28]. IoT is “supported by a multicast communication of a satellite and aerial-integrated network (SAIN) with rate-splitting multiple access (RSMA), where both satellite and unmanned aerial vehicle (UAV) components are controlled by network management center and operate in the same frequency band” [29]. Computer Science. The development of Uncertainty Quantification (UQ) methods make Computer Science able to support engineers to develop “applications such as computer vision (e.g., self-driving cars and object detection), image processing (e.g., image restoration), medical image analysis (e.g., medical image classification and segmentation), natural language processing (e.g., text classification, social media texts and recidivism risk-scoring), bioinformatics, etc.” [30]. The new materials like “the superconducting transmon qubits with coherence times exceeding 0.3 ms” contribute to “quantum computing and quantum science development” [31]. Also, “large-scale imagery platforms, advances in computer vision and machine learning, and availability of computing resources” conduct to development of the Street view imagery in urban analytics and GIS, allowing better integrated decisions: “it is used across myriads of domains with numerous applications – ranging from analysing vegetation and transportation to health and socio-economic studies” [32]. “VQAs have been developed for a wide range of applications, including finding ground states of molecules, simulating dynamics of quantum systems and solving linear systems of equations” [33]. Mechanics. Solid mechanics uses to inversion and surrogate modeling the application of a class of deep learning, respectively Physics Informed Neural Networks (PINN) [34]. PINNs presents real advantages “for inverse problems related to three-dimensional wake flows, supersonic flows, and biomedical flows” [35].

22

C. Lincaru et al.

Fluid Mechanics have applications in with the applications “in meteorology, oceanography, geophysics, and biomedical engineering” [36]. Robotics. Four-dimensional (4D) printing of shape memory polymer composites is an Additive Manufacturing field, which uses time-responsive programmable materials. [37] this field AM of structural material rapidly increases its: • Diversity of structural materials & methods: “multi-material AM (MMa-AM), multi-modulus AM (MMo-AM), multi-scale AM (MSc-AM), multi-system AM (MSy-AM), multi-dimensional AM (MD-AM), and multi-function AM (MF-AM)” [38] • Diversity of its applications in “the aerospace field, the biomedical field, electronic devices, nuclear industry, flexible and wearable devices, soft sensors, actuators, and robotics, jewelry and art decorations, land transportation, underwater devices, and porous structures” [38]. Especially after 2022 the Machine Learning, an AI method, explodes. Among the ML techniques the Point Cloud Learning (PCL) was a very successful technique with application in computer vision, autonomous driving, and robotics. PCL methods includes: 3D shape classification, 3D object detection and tracking, and 3D point cloud segmentation [39]. Another branch of ML is Image Segmentation (IS), “a key task in computer vision and image processing with important applications such as scene understanding, medical image analysis, robotic perception, video surveillance, augmented reality, and image compression” [40]. Minaee et al. classifies the new Deep Learning branch of IS in “convolutional pixel-labeling networks, encoder-decoder architectures, multiscale and pyramid-based approaches, recurrent networks, visual attention models, and generative models in adversarial settings” [40]. Badue et al. find that the typical architecture of the autonomy system of self-driving cars contain “the perception system and the decision-making system”. The perception system could include “tasks such as self-driving-car localization, static obstacles mapping, moving obstacles detection and tracking, road mapping, traffic signalization detection and recognition”. The decision-making system refers to “tasks such as route planning, path planning, behavior selection, motion planning, and control” [41]. Mechatronic. Mechatronics emerges as independent concept, philosophy, tertiary educational programs worldwide around 1980s. But “the concept of what constitutes a mechatronic system has been subject to a continuous process of revision and debate as a result in developments in technologies and the concept of what constitutes a system [42]. The more sophisticated microprocessors and electronic components allow to increase the mechatronic system complexity and diversify their application into a range of consumer goods, vehicles, and manufacturing technologies [42]. Computers are used to control Processes and systems, as it is the Programmed Data Processor (PDP), almost 50 years ago [42]. New directions of Mechatronic develops based on newfound technologies in the field of “smart and multi-functional materials by integrating 4D printing (4DP) and shape memory polymer composites (SMPCs). 4DP of SMPCs” [37] An example of new

An Overview About Mechanics Developments and Achievements

23

mechatronic systems is “the soft robot for deep-sea exploration, with onboard power, control and actuation protected from pressure by integrating electronics in a silicone matrix” [43]. Becomes more obvious that especially Mechatronic science is very dynamic and highly complex. Bradley et al. points that the perception on educational mechatronics changes “the transfer of functionality from the mechanical domain to the electronics and information” [43]. Virtual Reality. The Metaverse is “an online, open, shared, persistent, threedimensional virtual realm that offers people to connect with each other from all parts of their lives”. It would link many platforms, same as how the world wide web connects several websites using one browser. Term lunched by Snow Cash in 1992. Initial implies that virtual and reality interact and create value through various social activities. Lately it express medium for exchanging interests and social interaction centered on content [18]. Metaverse request “tree components: hardware, software, and contents that allow user interaction, implementation, and application in either possible domains: movies, game and researches in Ready Player One, Roblox, Facebook Research. Facebook research tries to input text using the output of the peripheral nervous system and brain-computer interface. As a direct connection method, Neuralink is a way to enhance communication with devices by implanting a chip in the human brain” [17]. Under this direction the future research of Metaverse is the brain-computer-interface that allows the user to encounter virtual experiences very close to real ones. Next to Virtual Reality (VR] another recent high-speed advancement of Augmented Reality (AR). “VR embraces a total immersive experience, while AR promotes the interaction between user, digital contents, and real world, therefore displaying virtual images while remaining see-through capability”. Both VR & AR are viable grounded on “the progress in holographic optical elements (HOEs) and lithography-enabled devices” [17]. Metaverse has the potential to transform through VR&AR sectors like: “marketing, education, tourism, healthcare as well as societal effects relating to social interaction factors from widespread adoption, and issues relating to trust, privacy, bias, disinformation, application of law as well as psychological aspects linked to addiction and impact on vulnerable people” [19]. Wang et al. analysis the “prototyping a digital twin (DT) as the platform for humanrobot interactive welding and welder behavior analysis. The DT system bridges a human user and robot through a bi-directional information flow: a) transmitting demonstrated welding operations in VR to the robot in the physical environment; b) displaying the physical welding scenes to human users in VR [44]. • “The human-robot interaction (HRI) working style helps to enhance human users’ operational productivity and comfort. HRI includes three modules: d) a human user who demonstrates the welding operations offsite with her/his operations recorded by the motion-tracked handles. e) a robot that executes the demonstrated welding operations to complete the physical welding tasks onsite;

24

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f) a DT system that is developed based on virtual reality (VR) as a digital replica of the physical human-robot interactive welding environment. • The welder behavior analysis uses the “data-driven approach as a combination of Fast Fourier Transform (FFT), Principal Component Analysis (PCA), and Support Vector Machine (SVM). Construction Engineering and Management CEM in USA experienced a rapid digital transformation during 1997–2020 through adoption of the AI to “realize a considerable boost in automation, productivity, and reliability” [45]. Pan & Zhang identifies “six key directions of future researches, such as smart robotics, cloud virtual and augmented reality (cloud VR/AR), Artificial Intelligence of Things (AIoT), digital twins, 4D printing, and blockchains” [45]. Blockchains technology digitally transform the business. According to IBM “Blockchain is a shared, immutable ledger that facilitates the process of recording transactions and tracking assets in a business network. An asset can be tangible (a house, car, cash, land) or intangible (intellectual property, patents, copyrights, branding). Virtually anything of value can be tracked and traded on a blockchain network, reducing risk, and cutting costs for all involved” [46]. Digital Health Technologies (DHTs) grant “smartphones, artificial intelligence, virtual reality smartphone apps, virtual reality, chatbots2 , and social media changes the mental health” [47] into growing field of digital psychiatry, in a disruptive manner. Integronics and Adaptronics The Integronics and Adaptronics constitute a distinct conceptual terminology, spatially clustered in Romania for the period 2009–2015 under two perspective: First perspective is leaded by Gruia around ecology integronics concept during 2009–2015 period. He presents in 2009 the Integronics in the holistic approach of the General Theory of Ecological Emergence Integration [48], and define in 2010 a theory applicable to the evolution of complex and hyper-complex systems in the case of eco-emergent integronics [49]. In 2015 Gruia et al. Define the concept of integronic alimentation [50]. The second perspective is leaded by Gheorghe around Mechatronic-Integronics concept during 2010–2013. This is initiated in 2010 through the vision that the “Mechtronic Integronics is an innovative vector that increases the contribution of education for the viability of labour market” [51]. Gheorghe et.al launched in 2012 the Adaptronics as a new concept for the future of advanced engineering and intelligent automatized manufacturing [52], and in intelligent measurement and control systems [53]. In 2013 this concept evolves into an intelligent science adaptive to advanced systems/micro - nano systems [54]. In 2013 Gheorghe et al. explores the Mechatronics Galaxy as a new concept for Developing Education in Engineering [55] and, Gheorghe and Popan enrich Integrative Mechatronics concept with the Adaptronics concept, as a 2 Termed “chatbots”, the use of these conversational style interfaces offers an intelligent, auto-

mated system for detecting and responding to immediate mental health needs. Chatbots have the look and feeling of interacting with a human, despite being run by an automated software program.

An Overview About Mechanics Developments and Achievements

25

Multi-Integrative Technological and Cross-Border Mixture Value Chain of Science and Engineering [56]. Adaptronics We remark the trio Ahmed, Karothu and Numov from New York University Abu Dhabi which treat the adaptronics from the Chemie perspective for Crystal Adaptronics: Mechanically Reconfigurable Elastic and Superelastic Molecular Crystals in 2018 [57] and the rise of dynamic crystals in 2020 [58].

2 Method and Data 2.1 Data Our bibliometric analysis uses data extracted during April 2023, in an iterative manner from the Web of Science Core Collection by semantic intersection of the Europe 2021–2027 Strategical Cycle and Mechanics related domains. 2.2 Text Mining Iterative Steps We process the following steps presented in Literature Review using the exploring tools provided by WoS Platform for terms of interest treated as independent: – We create the list of terms from Europe 2021–2027 Strategical Cycle and Mechanics related domains: Industry 4.0/Industry 5.0, Big Data, Augmented Reality, AIArtificial Intelligence, IoT, Computer Science, Mechanics, Robotics, Mechatronic, Virtual Reality, Integronics & Adaptronics. – For each term, treated as independent we explore its associated data base of records download in .xls format containing the WoS’s aggregate bibliometric data about WoS Domain, Year of Publication and Country of Publication. The Record counts by Web of Science Categories detailed by the number of Highly cited Papers and Number of Hot Papers. – We build the hot intensity index. Through “hot intensity we understand the ratio between number of hot papers on the total number of publications in WoS for one term. – We make a benchmark by hot intensity index, and we apply a subjective cluster allocation in 4 classes. (see Table 1) We allocate the correspondence that the higher the level of hot intensity the higher the level of influence to generate new economic sectors. To sketch a general profile of the selected terms from European Strategical Ecosystem we select some hot publication by each term cluster. We analyse the dynamics of the WoS Records of Mechanics domain and other domains relevant for Industry 4.0 during 1975-April 2023. The level and the Dynamics of the WoS Records of Mechanics domain and other domains (treated as independent) relevant for Industry 4.0 during 1975-April 2023. We calculate the growth rate of Mechanics domain and other domains (treated as independent) relevant for Industry 4.0 during 2022 compared to 1990.

26

C. Lincaru et al.

We calculate Romania’s relative specialization tendency by Mechanics domain and other domains (treated as independent) relevant for Industry 4.0. We run the Co-occurrence analysis of terms Mechatronics and AI using the software VOSviewer version 1.6.17. For Mechatronics and AI: – We build the tree map graph for the Mechatronics; – These terms treated as dependent we explore its associated data base of records download in ris format containing the extended bibliometric data about Publication, Authors and its Abstract transferred in Zotero. Then the Mechatronics_AI.ris database was uploaded in VOSviewer and made the: • Mechatronic & AI’s network analysis • Mechatronic & AI’s overlay visualization • Mechatronic & AI’s terms density analysis.

3 Results and Discussions 3.1 Dynamics of the WoS Records of Mechanics Domain and Other Domains Relevant for Industry 4.0 The level and the Dynamics of the WoS Records of Mechanics domain and other domains (treated as independent) relevant for Industry 4.0 during 1975-April 2023. The synthetic data were calculated in Table 2: WoS Records of Mechanics domain and other domains (treated as independent) relevant for Industry 4.0 during 1975-April 2023. Figure 1 show that the Mechanics domain number of record increases after 1990 and increases abruptly after 2002. The third stage of increase is during 2014–2021. AI starts to increase with the second high speed since 2015, followed by Big Data since 2011, with a lower speed. The fourth speed, but slower is for Robotics with a turning point in 2003. IoT becomes more active since 2015 and Industry 4.0 since 2018. Figure 2 presents the Dynamics of the WoS Records of Mechanics domain and other domains (treated as dependent) relevant for Industry 4.0 during 1975-April 2023. The domain with the higher number of records in WOS is Mechanics & Robotics with a first turning point in 1990. Mechanics & AI initiate its increase over 200 records since 1994 and below 2 thousand in 2022. The Mechanics & Big Data starts to grow rapidly since 2013 (with over 200 records/year) and is equalized at the level of one thousand records in 2022 by Mechatronics & Computer Science-AI domain, domain which starts to rapidly grow since 2015. The Fig. 3 presents the benchmarking of all the records by WoS domain during 1975-April 2023. The first place is covered by In an arbitrary manner we consider a maturity level the reaching of the first thousand record by a WoS field. Robotics since and Big Data follow with 2–3 hundred thousand records. Robotics domain reaches the maturity in 16 years, while the first thousand records/year is reached in 1991 can the concept is sign up since 1975. Big Data evolves a little bit slower

An Overview About Mechanics Developments and Achievements

27

Table 2. WoS Records of Mechanics domain and other domains (treated as independent) relevant for Industry 4.0 during 1975-April 2023 Mechanics AI

Robotics Big Data

Industry IOT 4.0

Mechatronics Augmented Reality

1975

4376

2234

3

1976

4837

2377

1

1977

5083

2644

1

1978

5427

2710

1

1979

5913

2698

9

5

1980

6147

3816

12

5

1981

6110

5548

28

4

1982

6638

5641

75

3

1

1983

7199

5945

218

6

1

1984

7374

6132

270

7

1

1

1985

7529

6063

225

5

1

1

1

1986

8289

5824

208

6

2

1

4

1987

8541

6025

232

4

1

1

1

1988

9235

6065

358

3

1

1

1

1989

10689

6444

740

2

1

2

20

1990

11839

6668

573

14

5

3

24

1

1991

15508

6923

1346

133

41

4

13

2

1992

16314

6837

1442

159

38

7

68

3

1993

18928

6493

1872

180

56

6

77

10

1994

21020

6666

1771

204

47

7

203

13

1995

22154

6800

1764

250

62

13

146

20

1996

24431

7145

2505

289

60

9

191

25

1997

24575

7653

2385

407

69

6

247

80

1998

26097

7748

2478

473

84

10

399

86

1999

26470

7648

2291

413

88

51

163

128

2000

28294

8026

2577

611

90

14

206

141

2001

30941

7817

3135

735

86

11

436

255

2002

30071

8021

2790

707

100

11

304

222

2003

33582

8216

4011

922

124

11

581

311

2004

36251

9445

4458

879

100

16

748

357

2005

42278

9242

4725

1026

117

14

1564

315

4

1

(continued)

28

C. Lincaru et al. Table 2. (continued) Mechanics AI

Robotics Big Data

Industry IOT 4.0

Mechatronics Augmented Reality

2006

46795

10413 6694

1107

123

20

1267

401

2007

52226

11081 6188

1335

188

30

1758

406

2008

56277

11198 7104

1486

175

52

1620

502

2009

62045

11873 7927

1881

219

56

2933

506

2010

68731

12306 9109

1966

265

129

1167

526

2011

78312

16235 7898

1991

309

244

3168

729

2012

92615

13390 11014

2602

340

504

3344

732

2013

95844

14279 10622

4783

325

665

5433

1084

2014

106837

15370 12338

7171

398

1350

6214

1229

2015

92714

15762 13216

14089 841

2742

5610

1557

2016

104071

17279 14826

17396 1034

5056

5002

1732

2017

119523

20857 17860

21579 1884

8602

4297

2442

2018

128345

27559 19942

25066 2888

11962 3215

3505

2019

142696

32899 21485

28940 5321

14985 3490

4049

2020

143755

35739 22081

28143 5629

15248 2688

3727

2021

155711

47396 23852

30091 6684

16821 2763

4203

2022

149669

50569 22987

30336 7138

16736 2697

4381

10206 4633

6693

3453

800

04.2023 39867

1767

238

Fig. 1. The level and the Dynamics of the WoS Records of Mechanics domain and other domains (treated as independent) relevant for Industry 4.0 during 1975-April 2023

An Overview About Mechanics Developments and Achievements

29

Fig. 2. Dynamics of the WoS Records of Mechanics domain and other domains (treated as dependent) relevant for Industry 4.0 during 1975-April 2023

compared to Robotics and its maturity period account almost double, respectively it is initiated in 1978 and reaches the maturity in 2005. IoT accounts almost one hundred thousand and reaches its maturity over 30 years between 1984–2014. Mechatronic register over 60 thousand WoS records, reaching the maturity during 1985–2005, after 20 years. Both Industry 4.0.and Augmented Reality account comparable number of records, both around 35 thousand but I different period and speed. First is reaching the maturity in 35 years, during 1981–2016 while the Augmented reality in 25 years span, during 1990–2013. The new domains relevant for Industry 4.0 during 1975-April 2023 with potential to create new economic sectors and more than this, which represent the driving force of the digital transformation reaches their scientific maturity in a 20–30 years’ time span and becomes globally stable until 2016, mostly they have around one decade of mature development! In terms of strategical cycles 5 from these 8 new domains have a scientific consolidate identity finalized the strategical cycle of 2007–2014. Only 3, the most recent ones, respectively IoT, Industry 4.0 and Augmented Reality looks to reaches their maturity during the last strategical cycle 2014–2020. The growth rate of Mechanics domain and other domains (treated as independent) relevant for Industry 4.0 during in 2022 compared to 1990. Both Mechanics and AI domains presents records since 1975 (Fig. 3). The growth rate of the selected terms presents data since 1990 until 2022. Figure 4 complete the conclusions drawn in Fig. 3 and indicates a tendency to rapidly grow for the younger WoS domains IoT, Industry 4.0 and Augmented Reality, exception is the Big Data. Big Data domain appears in 1978 but its growth rate increases exponentially since 2014 (see Fig. 1). Romania’s relative specialization tendency by Mechanics domain and other domains (treated as independent) relevant for Industry 4.0.

30

C. Lincaru et al.

Fig. 3. Total number of the WoS Records, first year of the record and the first year with over one thousand records of Mechanics domain and other domains (treated as independent) relevant for Industry 4.0 during 1975-April 2023. Data source WoS.

Fig. 4. The growth rate of Mechanics domain and other domains (treated as independent) relevant for Industry 4.0 during in 2022 compared to 1990. Data source WoS.

Figure 5 illustrates the relative tendency toward specialization measured through Romania’s share of records in Mechanics domain and other domains (treated as independent) relevant for Industry 4.0 in total domain’s records. Romania’s relative specialization tendency is three times higher in AI than in Mechanics with a 1.5% compared to 0.5for each domain in its total record.

An Overview About Mechanics Developments and Achievements

31

Fig. 5. Romania’s share of records in Mechanics domain and other domains (treated as independent) relevant for Industry 4.0 in total domain’s records. Data source WoS.

3.2 Co-occurrence Analysis of Terms Mechatronics and AI The tree map graph for the Mechatronics by WoS domains (Table 3). Engineering Electrical Electronic 62.0%, Engineering Mechanical 53.5%, Automation Control Systems50.1%, Robotics 29.5%, Materials Science Multidisciplinary 17.0%, Computer Science Artificial Intelligence 13.7%, Engineering Manufacturing 13.2%, Mechanics 9.4%, Engineering Multidisciplinary 6.4%, Computer Science Theory Methods 4.7%, Instruments Instrumentation 4.7%, Engineering Industrial 1.8%, Computer Science Interdisciplinary Applications 1.8%, Physics Applied 1.7%, Education Scientific Disciplines 1.7%, Computer Science Information Systems 1.6%, Nanoscience Nanotechnology 1.5%, Computer Science Cybernetics 1.4%, Optics 1.3%, Telecommunications 1.2%, Engineering Biomedical 0.9%, Computer Science Software Engineering 0.8%, Remote Sensing 0.7%, Operations Research Management Science 0.6%, Energy Fuels 0.6%. Exploring Mechatronics & AI in VOSviewer created by [59–61] (Fig. 6). Mechatronic & AI’s Network Analysis We explore the items defined by terms for the Mechatronic domain in relation with AI included in WOS records through the method “co-occurrence links between terms” in VOSviewer. We identify from Web of Science Core Collection for Mechatronics 62,301 publications selected and for the “Mechatronics (All Fields) and Computer Science Artificial Intelligence” 8,520 results. These 8520 records we transfers in VOSviewer and we execute the co-occurrence association analysis. The in VOSviewer states a terminology that includes: the link, network, cooccurrence, etc. So, “A link is a connection or a relation between two items, and between any pair of items, there can be no more than one link.” [60] Also, authors express that “each link has a strength, represented by a positive numerical value. The higher this value, the stronger the link.” In our case, the strength represents “the number of publications in which two terms occur together”. “A network is a set of items together

32

C. Lincaru et al.

Table 3. WoS Records of Mechanics domain in co-occurrence with AI, CS&AI, Robotics, Big Data, Augmented Reality and IoT during 1975-April 2023 Mechanics & AI

Mechatronics Mechanics (All Fields) & Robotics and Computer Science Artificial Intelligence

Mechanics &Big Data

Mechanics & Augmented Reality

Mechanics &IOT

1975

19

11

1976

24

13

1977

27

14

1978

25

17

1979

30

18

1980

31

18

1981

39

18

2

1982

51

19

1

1983

46

20

4

1984

47

20

19

1985

37

21

19

1986

38

21

36

1987

44

21

26

1988

51

26

64

1989

44

26

69

1990

51

29

72

1

1991

62

30

110

4

1992

76

31

126

2

1993

74

31

196

3

1994

65

32

291

6

1995

101

34

311

2

1996

120

37

457

5

2

1997

126

39

355

7

3

1998

152

44

390

8

6

1999

155

49

404

6

6

2000

191

49

368

10

4

2001

169

60

516

11

6

2002

185

62

358

17

5

1

2003

129

74

526

18

7

1

2004

292

74

580

26

8

3

2005

191

94

743

25

6

1

2006

243

94

1126

39

13

1

Mechatronics & IOT

(continued)

An Overview About Mechanics Developments and Achievements

33

Table 3. (continued) Mechanics & AI

Mechatronics Mechanics (All Fields) & Robotics and Computer Science Artificial Intelligence

Mechanics &Big Data

Mechanics & Augmented Reality

Mechanics &IOT

Mechatronics & IOT

2007

221

131

1074

38

10

1

2008

301

154

1219

43

19

1

2009

286

176

1491

60

19

1

2010

322

179

1642

65

27

2

2011

1028

188

1343

76

33

11

4

2012

410

188

1878

94

41

16

2

2013

473

195

2363

126

54

45

8

2014

503

213

2331

198

70

50

29

2015

439

226

2323

251

63

36

21

2016

606

255

2729

350

71

92

25

2017

735

267

3263

467

115

132

32

2018

1144

280

3586

582

123

238

19

2019

1406

321

3967

737

179

332

25

2020

1277

330

3825

772

190

498

165

2021

2052

482

4683

964

227

549

213

2022

1992

1013

4636

1026

245

599

169

with the links between the items” [60]. The network could be grouped into unique items allocation to a cluster. Among the results of VOS viewer text analysis is the weight of an item as a measure for its importance. Then, an item with a higher weight is regarded as more important than an item with a lower weight [60]. We chose the 10 thresholds for the minimum number of occurrences of a term. The result of query is that of the 89664 terms, 1759 meet the threshold. We select 1055 terms from the 1759 terms for which a relevance score was calculated by VOSviewer. The Software selected 60% most relevant terms. Then we verify the selected List of terms by term’, occurrence and relevance. Method Association In Fig. 7 we illustrate co-occurrence items for the mechatronic & AI terms. According to [60] “the size of the label and the circle of an item is determined by the weight of the item. The higher the weight of an item, the larger the label and the circle of the item. The color of an item is determined by the cluster to which the item belongs. Lines between items represent links. By default, at most 1000 lines are displayed, representing the 1000 strongest links between items.”

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Fig. 6. The tree map graph for the Mechatronics 62,301 Records in Web of Science Core Collection by the first 25 domains

As it is visible in Fig. 7 there are 5 clusters in a circular position. Mechatronics is the red cluster with the larger cloud of terms, dense. The Mechatronic cluster is neighbor with the Actuator Green Cluster in left and with the Image & Mobile Robot Blue cluster from the right. With a smaller cloud of terms and relatively at higher distance is visible the Controller Mustard Cluster, neighbor with the Manipulator/Trajectory Mauve Cluster – the less dense cloud of terms. It is remarkable that there is no Cluster dedicated to AI itself. We propose that Fig. 7 representation could be the new Mechatronics in the time of AI.

Fig. 7. Mechatronic & AI’s network visualization in VOSviewer_1.6.17. (Items: 1055, clusters: 5, Links: 69097, Total link strength: 111059)

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Fig. 8. Detail for the Mechatronic cluster in VOSviewer_1.6.17.

Figure 8 presents the detail for the mechatronic cluster higher weight items with external items – controller and actuator! Within the mechatronic cluster are: mechanic engineer electronic, intelligence, autonomy, management, product, etc. as main items. Mechatronic & AI’s Overlay Visualization In Fig. 9 the color allow to visualize the time evolution from mauve color, for records since 2009) to yellow for the 2014 [60]. Mechatronic terminology is a consolidate on since 2009 while the recent is registered for the cluster blue around “image intelligence, camera control, image recognition applied especially for image processing & object detection and recognition. The last terminologies are specific to AI.

Fig. 9. Mechatronic & AI’s overlay visualization in VOSviewer_1.6.17.

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Mechatronic & AI’s Terms Density Analysis This method is created by Van Eck and Waltman (2010) for a discussion of the technical implementation of the density visualization. Mechatronic & AI’s Item Density Visualization Figure 10 shows that the density of items by Mechatronic & AI search indicate the priority for controller, actuator, image recognition as the core concepts.

Fig. 10. Mechatronic & AI’s item density visualization in VOSviewer_1.6.17.

Mechatronic & AI’s Cluster Density Visualization In Fig. 11 the Mechatronic & AI’ s cluster density visualization indicates the highest diversity for the Red Mechatronic Cluster (red), followed by the Actuator the Actuator Green Cluster. The highest density cluster is the Green one – the Controller present the highest density cluster, colored in Mustard. The Mauve and Blue cluster presents the third and fourth density cluster but with a low diversity. The highest depth of the mauve cluster looks to be specialized around the terms like trajectory, manipulator while the Blue Cluster is specialized in image, mobile robot, camera and (image) recognition.

Fig. 11. Mechatronic & AI’s cluster density visualization in VOSviewer_1.6.17.

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4 Conclusions Mechanics and its derivates domains like Mecatronics, Integronics & Adaptronics are highly dynamic domains that suffer radical transformations reflected by co-occurrence with terms of Industry 4.0. The main Industry 4.0 domains are selected from Europe 2021–2027 Strategical Cycle and include: Industry 4.0 followed by Industry 5.0, Big Data, Augmented Reality, AI, IoT, Computer Science, Virtual Reality, Blockchain, and the list is not exhaustive. Our bibliometric analysis responds to each of the three research questions launched, covering the period 1975-April 2023, as follows: Research Question 1) What is the position of Mechanics and its related technological fields in relation to Industry 4.0 Revolution? Mechanics is at the core of Industry 4.0. Mechatronic science is very dynamic and highly complex to define on the background of changing conceptual content of the complex systems management systems and material technologies radical transformations. Mechanics with over 2.2 million records, followed by AI with over half a million of records, both with a rich history starting from 1975 represents the domains with the continuously increasing tendency of growing its thesaurus of knowledge. Our co-occurrence analysis indicates that the influential domains are from Industry 4.0/Industry 5.0: Big Data, Augmented Reality, AI and IoT, domains highly interdisciplinary. These scientific domains reach their maturity overcoming some quantitative thresholds and qualitative ones, respective gains high numbers of citation that stand for their utility, or their knowledge diffuses very rapidly across community and are highly cited – the case of “hot papers”. The large and rapidly diffusion processes reflect these “new bites of knowledge” adoption behaviors beyond the world of science, with potential to create new economic sectors across global economy. More than this, these domains of Industry 4.0 technologies represent the driving force of the digital transformation. These domains reach their scientific maturity in a 20–30 years’ time span and becomes globally stable until 2016, mostly they have around one decade of mature development! In terms of strategical cycles, 5 from these 8 new domains have a scientific consolidate identity finalized the strategical cycle of 2007–2014. Only 3, the most recent ones, respectively IoT, Industry 4.0 and Augmented Reality looks to reaches their maturity during the last strategical cycle 2014–2020. Their relatively “youth age” is confirmed by their rapidly grow tendency. Research Question 2) What is the Romania’s relative specialization tendency by Mechanics and its new development domains relevant for Industry 4.0? Romania’s relative specialization tendency is three times higher in AI than in Mechanics with a 1.5% compared to 0.5for each domain in its total record. Research Question 3) What are the semantic patterns of co-occurrence items for Mechatronic and AI. Mechatronic & AI’ s network analysis, overlay visualization and terms density analysis allows us to describe the new Mechatronics in the time of AI: Mechatronics is the cluster with the larger cloud of terms, dense, is in direct relation with the Actuator terms Cluster and with the Image & Mobile Robot cluster. Through Actuator and the Image & Mobile Robot cluster the Mechatronics & AI is in indirect relation with Controller and Manipulator/Trajectory Clusters, Clusters with the less dense cloud of terms. It is remarkable that there is no Cluster dedicated to AI itself. Within the mechatronic cluster are: mechanic engineer electronic, intelligence, autonomy, management,

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product, etc. as main items, items consecrated in literature, adopted in tertiary education specialization. The most recent terminology indicates that the mechatronic cluster presents higher weight items with external items – controller and actuator, terminologies that indicated the new trajectories of mechatronic development tendencies. Mechatronic terminology is a consolidate on since 2009. We consider as a high priority the new science taxonomies and statistical nomenclature updating (for education, economy, social activities) able to reflect the co-occurrence tendencies identified. The high mass of records development of mechanical domain records, as well as for mechatronics domain are fueled by the new terminologies specific of AI. Terminologies like “image intelligence, camera control, image recognition applied especially for image processing & object detection and recognition” just open new opportunities for emergences for new interdisciplinary domains, but related with Mechanical domains. Limits of this paper: analysis covers only the WoS data base. A further direction of research could be the patent analysis by these domains and the educational programs domains, especially for tertiary level. The importance of a clear trans domain’s new tendencies and its relations and evolution trajectories is a useful methodology to: – Anticipate the new skills demand for the new sectors & new occupations assumed already the competitiveness strategies. – Build mechanisms for occupational and geographical labour mobility, able to efficiently reallocate intersectoral the human capital toward the new sectors in conditions of increasing the employment quality, in a inclusive manner, “to leave no one behind”. – To formalize the new occupational standards demands as well as the new educational programs in both content and volume, both for the initial and continuous education. Acknowledgements. This work was supported by a grant from the Romanian Ministry of Research and Innovation, Programme NUCLEU, 2022–2026, Spatio-temporal forecasting of local labour markets through GIS modelling [P5]/Previziuni spat, io-temporale pentru piet, ele muncii locale prin modelare în GIS [P5] PN 22_10_0105. This scientific paper provides the opportunities for the creating international collaborations through the project “Support Center for International RDI projects in the field of Mechatronics and Cyber-MixMechatronics”, Grant agreement no. 323/340002/23.09.2020, SMIS 108119.

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Neighbor-Joining Analysis of Mechanics and the Industry 4.0 Domains Florentina Badea1(B) , Gabriela Tudose2 , Cristina Lincaru2 , Sperant, a Pîrciog2 , Adriana Grigorescu3 , Sorin-Ionut Badea1 , and Cristian-Radu Badea1 1 National Institute of Research and Development in Mechatronics and Measurement

Technique – INCDMTM Bucharest, Sos Pantelimon, 6-8, Sector 2, 021631 Bucharest, Romania [email protected] 2 National Scientific Research Institute for Labor and Social Protection - INCSMPS, Bucharest, Povernei 6-8, Sector 1, 010643 Bucharest, Romania 3 National University of Political Studies and Public Administration (SNSPA), Bucharest, Romania

Abstract. The fussy and blurred Industry 4.0. technological content raises difficulties for the human capital development mainly in the education and labour market. We propose a hierarchical tree map that make a monophyletic evolutionary description of the most relevant domains of Industry 4.0. The domains most similar by the records registered in Clarivate Web of Science core Collection (WoS) are located on branches that are close together. This map is highly intuitive tool that allow non-discriminatory access for any stakeholders. Data: Our bibliometric analysis covers the period 1975-April 2023, with data extracted from WoS. Methods: Neighbor-joining (NJ) is a Phylogenetic Method – distance Based Algorithms, Distance measurement – Euclidean Distance, Amalgamation or Linkage Rules: (Single Linkage) is the “nearest neighbor” rule. Applied for the period 1990–2023. Purpose of Analysis: This is to test whether the Mechanics and the Industry 4.0 domains form “natural” clusters that can be labeled in a meaningful manner. Research Questions: Main findings: Main Industry 4.0.’s concepts are represented in the “monophyletic group” as a group of organisms by their variable distance in time occurrence of the registration in relation to Mechanics. Mechanics looks to be the common ancestor of the selected Industry 4.0. technologies. Added value of the paper: *We provide the topology and the branch length of the final tree of the 8 operational taxonomic units: Mechanics, Mechatrec, IoT, Big Data, AI, Robotics, Virtual reality, Augmented Reality. *Propose a Phylogenetic Nomenclature System for Mechanics in a “monophyletic” groups that build hierarchical cluster for the Industry 4.0 most relevant domains. Keywords: Mechanics · Mechatrec · IoT · Big Data · AI · Robotics · Virtual reality · Augmented Reality · Neighbor-joining

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 42–55, 2023. https://doi.org/10.1007/978-3-031-40628-7_3

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1 Introduction 1.1 Industry 4.0/Industry 5.0 the Most Influential Domain in WoS Records Selected from European Strategical Ecosystem The European Strategical Cycle of 2022–2027 recognizes the transformative potential of Industry 4.0, AI, Big Data, Mechatronics, Augmented Reality, IoT, Robotics, and Mechanics. By leveraging these technologies, Europe seeks to drive sustainable development, enhance competitiveness, and create a prosperous future for its citizens and industries, while ensuring ethical and responsible deployment. In the Industry 4.0 era, production systems, in the form of Cyber-physical production systems (CPPS), can make intelligent decisions through real-time communication and cooperation between manufacturing things, enabling flexible production of high-quality personalized products at mass efficiency. Industry 4.0 is focused more on sophisticated emergent technology that promote new socio-technical infrastructures by transforming different aspects of a workplace such as health management and work organization, lifelong learning and career path models, team structures and knowledge management. This is described as a socio-technical approach of the Industry 4.0 initiative leading to a paradigm shift in human-technology and human-environment interactions. More than this, European Commission clarifies that “Industry 4.0 is technology-driven, whereas Industry 5.0 is value-driven. “The co-existence of two Industrial Revolutions invites questions and hence demands discussions and clarifications” [1]. Industry 5.0 complements the existing Industry 4.0 paradigm by having research and innovation drive the transition to a sustainable, human-centric and resilient European industry. Industry 4.0 and Industry 5.0 represent different stages of industrial development and technological advancements. Industry 4.0 primarily focuses on digitization, automation, and datadriven decision-making in manufacturing, while Industry 5.0 expands beyond factories to emphasize human-machine collaboration, personalization, and addressing broader social and environmental challenges. Industry 5.0 seeks to combine advanced technologies with human capabilities to create a more inclusive, personalized, and sustainable future. Industry 4.0 provide an impetus “to the collaboration of factories, suppliers, and customers”. Research gap: “there is a lack of unified perception and approach of its implementation roadmap”. “aims to identify the main concepts, characteristics, and technology enablers related to Industry 4.0 to provide stakeholders with a clear understanding of this paradigm” [2]. Looking at the global level of knowledge thesaurus described by WoS, “cluster analysis finds the most significant solution possible” [1]. The research question is: What are the natural clusters derived from Mechanical domain until the Industry 4.0. new domains? Purpose of Analysis: organize observed data regarding the occurrence of registration of Mechanics and Industry 4.0 key concepts into meaningful structures, respectively to develop taxonomies. The resulted taxonomies are based on „natural” clusters identified in a meaningful manner as a result of the joining analysis (tree clustering, hierarchical clustering) on WoS extracted data.

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Industry 4.0 key concepts are selected through cross interpolation of strategical sources and literature frequency, especially from [2] intersected with [3]. 1.2 Literature Review Problem [4] emphasizes that “the Industry 4.0 technological field is not new, but it is highly heterogeneous (actually it is the aggregation point of more than 30 different fields of the technology). For this reason, many stakeholders feel uncomfortable since they do not master the whole set of technologies, they manifested a lack of knowledge and problems of communication with other domains.” Similarity of Mechanics with Industry 4.0 Industry 4.0 and Related Technological Fields Chiarello et al. find that Industry 4.0 technological field is not new, but it is highly heterogeneous. It aggregates more than 30 different fields of the technology. Zhong et al. [4] explores the intelligent manufacturing in the context of Industry 4.0 topics such Internet of Things (IoT) - enabled manufacturing, and cloud manufacturing. Authors includes in the Intelligent manufacturing in the Industry 4.0: A Review era the following areas: a generic framework for intelligent manufacturing, data-driven intelligent manufacturing models, IMS’s, human-machine collaboration, and the application of intelligent manufacturing. Control Checking & Model Testing Links the Mechanics & Industry 4.0 to Defects. Konovalenko et al. [5] developed and researched 14 neural network models for defect detection on metal surfaces. In [6] the authors use as an optical and digital control methods for surface defects identification the neural network model based on the U-net architecture. It uses a decoder based on ResNet152 and have the optimum results for recognize the mechanical damage for over an illumination of 300 lx with Dice similarity coefficient DSC = 0.89. Cosham et al. use “the pipeline-specific methods that use empirical correlations between Charpy V-notch impact energy and fracture toughness” to identify the crack-like defects in Pipelines [7]. Vibrations Use Mechanics Technologies Associated with Industry 4.0 [8] uses edge computing to advance signal processing monitor wind turbine drivetrains. [9] applies “X-ray phase contrast imaging of cavitation and discharged liquid jet in nozzles with various sizes”. [10] introduces the “Vortex-induced vibration of a free-hanging riser under irregular vessel motion”. Mechanical Systems to Signal Processing [11] makes an “numerical and experimental study of the dynamic behavior of a polymer-metal worm drive”. New Design Methods [12] presents an “robust design concept in possibility theory and optimization for system with both random and fuzzy input variables”. [13] utilizes the V4PCS: volumetric 4PCS algorithm for global registration. The tool Neighbor-joining (NJ) is used mainly in genetics. [14] Evolutionary trees are the basic tools for analyzing differences between species [15].

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2 Method and Data 2.1 Data Our bibliometric analysis uses data extracted during April 2023 in an iterative manner from the Web of Science Core Collection by semantic intersection of the Europe 2021–2027 Strategical Cycle and Mechanics related domains. 2.2 Neighbor-Joining Analysis The Method-Neighbor-joining (NJ) is a Phylogenetic Method and distance Based Algorithms based on the norm of Minimum Evolution Consistency Neighbor Joining. Saitou and Nei develops the NJ in 1987 [16]. This method is a Statistical Analysis, Multivariate exploratory techniques included in the clustering Analysis in Statistica 10 software. Saitou & Nei [16] “phylogenetic trees from evolutionary distance data. The principle of this method is to find pairs of operational taxonomic units (OTUs [= neighbors]) that minimize the total branch length at each stage of clustering of OTUs starting with a starlike tree. The branch lengths as well as the topology of a parsimonious tree can quickly be obtained by using this method.” The taxon gives the specific characteristic of NJ, considering that “According to the Phylogenetic Nomenclature System, a taxon must mandatorily be a “monophyletic” group. Monophyletic literally refers to a group with the last common ancestor plus “all” the descendants of that ancestor” [17]. We reconstruct an evolutionary history using the tool NJ of a set of records from WoS that links the Mechanics with the main terms from Industry 4.0. NJ is a Joining (tree clustering) from STATISTICA 10, a Clustering Method, one of the Multivariate Exploratory techniques. NJ perform iterative clustering. “The goal of hierarchical cluster analysis is to build a tree diagram where the cards that were viewed as most similar by the participants in the study are placed on branches that are close together” [18]. In this algorithm we make the following decisions: • • • •

Variable: Columns Amalgamation (linkage rule) – single Linkage Distance measure Euclidean distance, non-standardized We have 8 operational taxonomic units (OTUs) Mechanics, Mechatrec, IoT, Big Data, AI, Robotics, Virtual reality, Augmented Reality

NJ aims to provide the topology and the branch length of the final tree. The “NJ method is quite efficient compared with other tree-making methods that produce a single parsimonious tree” [16]. “The key to interpreting a hierarchical cluster analysis is to look at the point at which any given pair of cards “join together” in the tree diagram. Cards that join sooner are more similar to each other than those that join together later” [4].

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Before performing hierarchical clustering, we must find the similarity between each pair of observations, which is referred to as the distance. The distance measure is more of a measure of dissimilarity as it increases as the observations move farther away. (https:// rpubs.com/aaronsc32/hierarchical-clustering-single-linkage-algorithm). Euclidean distance is the straight line between two pairs of observations and is defined as:  2 p  xj − yj d(x, y) = j=1

where d(xi, yi) distance between 2 variables Hierarchical clustering is a widely used tool in statistics and data mining for grouping data into ‘clusters’ that exposes similarities or dissimilarities in the data [19]. The next step was to calculate the regression equations and to determine the link (and the nature of this bond) between Mechanics and the other industries. The coefficient of correlation, r, is very strong, meaning that all variables/industries are straight correlate to Mechanics domains.

3 Results and Discussions As a result of the iterative extraction by the semantic intersection of Mechanics-related domains (in the view of the Europe 2021–2027 Strategical Cycle), the next descriptive statistics commentaries are available/made related to the data set (Table 1): – In the last 48 years, beginning to 1975 year, the Mechanics-related domains recorded a mean of more than 46000 appearances, being by far the most prominent among the others, like Industry 4.0 (Robotics, Big Data, and so on). Industry 4.0 appears very little relevant in the concerns of specialists and researchers since 1981, but in the last 7 years this industry has had a 7-times increase in records, the biggest increase comparative to all others studied domains. – The AI and Robotics domains were scored, also, covering the same period as the Mechanics field, beginning to the 1975 year, but with less records. – The maximum value in our distribution belongs to the Mechanics domain and the minimum value to five domains: Robotics, Industry 4.0, IOT, Mechatronics, and Augmented Reality. These results reveal the fact that the field of Mechanics is the oldest, it has developed over time, being able to accumulate the most records. If we extract the Minimum value from the Maximum value of the data set, we obtain the range, which is a measure of dispersion, meaning how far this set of data is spread out from their average value. The largest amplitude is observed in the case of Mechanics. The lowest amplitude is observed in the case of Augmented Reality. – The next descriptive statistics characteristics is the variance meaning the squared deviation from the mean of a random variable. Variance is, also, a measure of dispersion. – Usually, in descriptive statistics we analyze Standard Deviation which uses standard measures and offers a clear interpretation. The biggest Standard Deviation value belongs to Mechanics and corresponds to the previous value of range interpretation. The smallest noted is the Augmented Reality, corresponding, also, to the range analyze.

Neighbor-Joining Analysis of Mechanics and the Industry 4.0 Domains

47

– The last item of descriptive statistics analysis is the Coefficient of Variance, that helps measure the dispersion of different data points in the data series around the mean value and is calculated by dividing the standard deviation by the mean and multiplying the result by 100.

Table 1. Descriptive Statistics for Mechanics and Industry 4.0.’s key concepts occurrence during 1975–2022 (calculations made by the authors)

Mechanics

Valid N

Mean

Minimum

Maximum

Variance

Std. Dev.

Coef. Var.

48

46006

4376

155711

2.E+09

46219

100

AI

48

11577

2234

50569

1.E+08

10622

92

Robotics

48

5784

1

23852

5.E+07

7147

124

Big Data

45

5054

2

30336

9.E+07

9539

189

Industry 4.0

42

832

1

7138

3.E+06

1854

223

IOT

39

2446

1

16821

3.E+07

5230

214

Mechatronics

38

1633

1

6214

3.E+06

1867

114

Augmented Reality

33

1021

1

4381

2.E+06

1390

136

Analysing Box and Whisker Plot (Table 2), using Statistica 10, as statistical tool, some observations need to be made: – Domains like Industry 4.0, Mechatronics and Augmented Reality, having focused records around the [Mean ± SD], highlight their degree of high specialization. – Domains like AI, Big Data, Robotics and IOT, with records focusing around the [Mean ± SD] and a few outliers [Mean ± 1.96*SD], highlight their degree of interdisciplinarity. Mechanics with huge records concentrate around the [Mean ± SD], but at the same time, presenting a lot of outliers, it shows us the fact of accumulation of multidisciplinary and interdisciplinary fields (Fig. 1). Designing the tree clustering, as hierarchical clustering, we use as statistical tools Statistica 10, we choose the next variables, the number of cases (period 1990–2022 for consistent data), we calculate the Mean and Standard Deviation (Table 2), we choose, also, the Amalgamation (joining) rule and the Distance metric.

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Fig. 1. Box and whiskers plot for Mechanics and Industry 4.0 key concepts occurrence during 1975–2022. (Calculations made by the authors)

Table 2. Descriptive Statistics for Mechanics and Industry 4.0.’s key concepts occurrence during 1990–2022. (Calculations made by the authors)

Mechanics

Mean

Std. Dev.

63785.43

45749

AI

14713.73

11490

Robotics

8341.39

7309

Big Data

6889.82

10587

Industry 4.0

1058.42

2039

IOT

2890.76

5582

Mechatronics

1879.88

1885

Augmented Reality

1020.61

1390

Note: Number of variables: 8 Number of cases: 33 Joining of variables Missing data were case wise deleted. Amalgamation (joining) rule: Single Linkage, the “nearest neighbor” rule. Distance metric is: Euclidean distances (non-standardized).

The Distance metric is the Euclidean distances (non-standardized) and the results are in Table 3.

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49

Table 3. Euclidean distances between Mechanics and Industry 4.0.’ s key concepts occurrence during 1989–2022. (Calculations made by the authors) Mechanics AI

Robotics Big Data

Industry IOT 4.0

Mechatronics Augmented Reality

Mechanics

0

347088 385950

386207 438237

419907 435030

439585

AI

347088

0

48012

50676

95129

76862

95436

97407

Robotics

385950

48012

0

25504

52587

36256

50724

53960

Big Data

386207

50676

25504

0

59672

37655

61760

62095

Industry 4.0

438237

95129

52587

59672

0

23006

13629

4781

IOT

419907

76862

36256

37655

23006

0

29515

26227

Mechatronics 435030

95436

50724

61760

13629

29515

0

10279

Augmented Reality

97407

53960

62095

4781

26227

10279

0

439585

In the next Table 4, are the results of Amalgamation Schedule Single Linkage Euclidean distances, highlighting the clusters formed and their linkage distance. Matrix Plot (Fig. 2) reveals histograms characterized by: – Skewness, which determines whether the data’s distribution is symmetrical. It’s positive when the data is asymmetrical with a skew to the left. The highest frequency of values is found to the left of the center, and the right tail is longer than the left tail. The mean is larger than the median. This is the case for all 8 variables. – Kurtosis, which describes the shape of the frequency distribution and gives a measure of how the distribution will produce outliers. We observe that the shape of frequency distribution is a positive kurtosis for all industries/variables (the tails of the curve are longer, and the peak is higher), except Mechanics which presents a negative kurtosis (the data distribution has shorter tails and the peak is flatter). Legend: Mechanics: AI: y = 110.5127 + 3.9642 * x; r = 0.9110, p = 0.0000; r2 = 0.8300 Mechanics: Robotics: y = 8920.3148 + 6.4115 * x; r = 0.9914, p = 0.0000; r2 = 0.9829 Mechanics: Big Data: y = 26626.7218 + 4.3788 * x; r = 0.8991, p = 0.0000; r2 = 0.8084 Mechanics: Industry 4.0: y = 34899.1173 + 20.3435 * x; r = 0.8096, p = 0.0000; r2 = 0.6554 Mechanics: IOT: y = 36895.0221 + 7.5226 * x; r = 0.8447, p = 0.0000; r2 = 0.7135 Mechanics: Mechatronics: y = 23622.4049 + 20.1658 * x; r = 0.8091, p = 0.0000; r2 = 0.6546 Mechanics: Augmented Reality: y = 32370.5438 + 30.7806 * x; r = 0.9350, p = 0.0000; r2 = 0.8741. (Calculations made by the authors) Where we use the notations [20]

Linkage distance

4781.199

10278.91

23006.05

25504.32

36256.39

48012.15

347087.6

Cluster link

1

2

3

4

5

6

7

Mechanics

AI

Robotics

Robotics

Industry 4.0

Industry 4.0

Industry 4.0

Obj.No. 1

AI

Robotics

Big Data

Big Data

Augmented Reality

Augmented Reality

Augmented Reality

Obj.No. 2

Robotics

Big Data

Industry 4.0

Mechatronics

Mechatronics

Obj.No. 3

Big Data

Industry 4.0

Augmented Reality

IOT

Obj.No. 4

Industry 4.0

Augmented Reality

Mechatronics

Obj.No. 5

Augmented Reality

Mechatronics

IOT

Obj.No. 6

Mechatronics

IOT

Obj.No. 7

IOT

Obj.No. 8

Table 4. Amalgamation Schedule is the “nearest neighbor” rule: Single Linkage Euclidean distances. (Calculations made by the authors)

50 F. Badea et al.

Neighbor-Joining Analysis of Mechanics and the Industry 4.0 Domains

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Fig. 2. Mechanics and Industry 4.0.’ s key concepts occurrence during 1989–2022 Matrix Linear Scatter Plot & regression equations, histograms, Pearson coefficients with their significance.

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r2 or the coefficient of determination. R-squared (r2 ) is a statistical measure that represents the proportion of variance for a dependent variable explained by an independent variable or variables in the regression model. While correlation explains the strength of the relationship between an independent and dependent variable, R-squared explains how much the variance of one variable explains the variance of the second variable [21]. In all cases R-squared is over 0,655 (Industry 4.0), which is a major value, explaining in good proportion how the variance of Mechanics influences other industries. Another observation is linked to a specific parameter, the regression coefficient b, of the equation (y = a + bx). It represents, also, the slope and it’s the rate of change along the regression curve. As we can see the Augmented Reality records the highest rate of increase (of 30,8 times – this is the amount by which Y, being the case of Augmented Reality or other industries changes/increases when X, Mechanics domains change by one unit, same for the Industry 4.0 with a rate of increase very high (of 20,3 times increases, when Mechanics increases by one unit) and Mechatronics with an increase coefficient of 20,2 times, when Mechanics increases with one unit. The next step in our clustering design is to build the tree clustering, using the Statistica 10 tool. We have introduced all items in program/soft and by the intermediate of dendrograms we can analyze the clusters formed. A dendrogram is the output of the cluster analysis. “Each node in the diagrams below, represents the joining of two or more clusters; the locations of the nodes on the horizontal (or vertical) axis represent the distances at which the respective clusters were joined” [22].

Tree Diagram for 8 Variables Single Linkage Euclidean distances 350000

Linkage Distance - Dissimilarity

300000

250000

200000

150000

100000

50000

0 IOT

Augmented Reality Big Data Mechatronics Industry 4.0 Robotics

AI Mechanics

Fig. 3. Vertical Hierarchical Tree Diagram for 8 industries – Single Linkage Euclidian Distances. (Calculations made by the authors)

Neighbor-Joining Analysis of Mechanics and the Industry 4.0 Domains

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Number of variables: 8 Number of cases: 33 Joining of variables Missing data were case wise deleted. Amalgamation (joining) rule: Single Linkage Distance metric is: Euclidean distances (non-standardized) 50000 – subjective distance as the optimal cut-off when deciding how many clusters to retain (and interpret). In the tree diagram, as we move to the right (increase the linkage distances), larger and larger clusters are formed of greater and greater within-cluster diversity (Fig. 3). To use dendrograms as a tool for determining the number of clusters in data is not a good approach. We can choose how many clusters to retain, decreasing the linkage distance to the optimal we need in analysis (red line in the previous diagram). From this point of view, the method has some disadvantage. “The single linkage method is sensitive to errors in distances between observations. It should be noted there is no clear ‘best’ clustering method and often a good approach is to try several different methods. If the resulting clusters are somewhat similar, that is evidence there may be natural clusters in the data. Many studies, however, conclude Ward’s method and the average linkage method are the overall best performers.” (https://rpubs.com/aaronsc32/ hierarchical-clustering-single-linkage-algorithm). This kind of method is somehow spatial explorative analysis, giving us important insights regarding the labour market and the adult learning.

4 Conclusions Determining the increasing rate of some industries, we can predict the future specializations, the future occupations on the labour market in a globalized world, challenging so many crises and radical changes. These results give us some insights regarding the necessary steps to efficient mobility, a correct conversion path from fields/occupations in the process of disappearing to those requiring other competencies, other content of work. It’s clear that the development speed of some industries (Industry 4.0, Augmented Reality, Mechatronics) will determine a new transfer of competencies for adults and new educational qualifications/knowledge. The Mechanics domains are the most important base for all industries studied, where the advanced technologies/domains can grow and develop as independent fields. Remembering that: • Taxon is “a unit or component at one hierarchical level in the biological classification system. While there are different taxonomic ranks like family, genus, species, etc., a group of organisms at each of these ranks is called a taxon” [17]. • Monophyletic “The term is used to describe a phylum (or a group of taxa) in terms of evolutionary origin or phylogeny. Thus, the phrase “monophyletic group” pertains to a group of organisms (usually species) that are more closely related to each other

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than any other group. This, therefore, implies that they descended from a common ancestor. Typically, the monophyletic groups possess characteristics that they commonly share with one another as they inherited them from a common ancestor” [23]. We conclude that: • the Industry 4.0 & its new technology develops into new domains with potential to develop new skills and new occupations. • Our contribution is the monophyletic evolutionary description of the most relevant domains of Industry 4.0. from the common ancestor Mechanics, also illustrating the distances between taxa. • There are useful further studies to define the Mechanical Evolutionary tree by the Biology Evolutionary trees, with clear taxonomic ranks like family, genus, species. This is a map tool requested to enhance the geographical an occupational mobility on labor market, regardless its scale (NUTS 0,1, 2, 3 or LAU3). Acknowledgements. This work was supported by a grant from the Romanian Ministry of Research and Innovation, Programme NUCLEU, 2022–2026, Spatio-temporal forecasting of local labour markets through GIS modelling [P5]/Previziuni spat, io-temporale pentru piet, ele muncii locale prin modelare în GIS [P5] PN 22_10_0105. This scientific paper provides the opportunities for the creating international collaborations through the project “Support Center for International RDI projects in the field of Mechatronics and Cyber-MixMechatronics”, Grant agreement no. 323/340002/23.09.2020, SMIS 108119.

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Monitoring of Soil Desertification - Quality Parameters Bajenaru Valentina-Daniela(B)

and Badea Diana-Mura

National Institute of Research and Development in Mechatronics and Measurement Technique, INCDMTM Bucharest, Pantelimon 6-8, 021631 Bucharest, Romania [email protected]

Abstract. In the context of significant climate changes throughout the planet, with huge impact on the global population, this paper presents a project (in progress) dedicated to monitoring soil parameters based on an IoT architecture, to obtain an overview of the current situation regarding the monitoring of degradation/desertification of lands in our country - aiming to create a sustainable, in-depth impact on the awareness of soil management as well as the development of practices with multiplier effects in the field of promoting healthy soils. The paper presents the analysis of the legislative requirements in the field of soil protection and the promotion of healthy soils, establishment of parameters that define the quality of soil and choice a set of sensors necessary to measure and ensure the remote data transfer through the IoT architecture, to establish the degree of soil desertification. Keywords: Desertification · Water-air-soil parameters · IoT monitoring

1 Project Outline and the National and European Legislative Requirements Considered in Developing It 1.1 Project Outline On 17 November 2021, the European Commission announced a new strategy on healthy soils for people, food, nature, and climate. Its contents are in line with the European Parliament resolution adopted on 28 April 2021, which “recognizes the importance of protecting soil and promoting healthy soils in the Union for the objectives of the European Green Deal” and underlines the importance of achieving the so-called “watersmart society” to support the restoration and soil protection, as well as to explore the close relationship between soil health and water pollution. In addition, the medium-term objectives up to 2030 set out in this strategy take full account of: • the objectives of the Framework Directive on water, • the quantitative status of underground water, • the need for reducing nutrient losses, combating chemical hazards, pesticides, and hazardous pesticides, © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 56–65, 2023. https://doi.org/10.1007/978-3-031-40628-7_4

Monitoring of Soil Desertification - Quality Parameters

57

• the fight against desertification, droughts, and floods. By adopting the said documents and course of action, the Commission emphasizes the importance of counterbalancing the effects of soil alteration. In this context, the authors of the current work present a project developed with the objective of monitoring soil parameters that the entitled persons must consider in drawing strategies aimed at inverting soil degradation processes. The project, through its thematic approach, aligns with national and European legislative concerns and requirements, bringing an important scientific contribution to knowledge, protection, and sustainable use in the field of water, air, and desertification as remote sensing has accelerated the study of desertification, enabling policy makers to reduce the polarity of land degradation. However, as studies can be used as a premise for making important management, environmental and policy decisions, a high degree of importance should be given to including as much additional data as possible so that reliable and robust results can be obtained. Remote sensing via satellite systems allows mapping of vegetation cover, vegetation stress, drought, irrigated area, land degradation areas and other aspects that can be used as key indicators of desertification. Although all remote sensing systems can provide image data, not all remote data have the same capabilities needed to identify and monitor parameters for water, air, and desertification. Higher resolution images provide more detail for analysis; however, medium resolution Landsat imagery is often used as it is readily available. But a major obstacle to using remote sensing images to detect aspects of desertification is that they provide primary data, so further analysis using ancillary data is required before substantial conclusions can be drawn. Unlike the method presented above, the project makes a detailed analysis of the soil condition through a system that includes a sensors network and a sensory platform that will monitor the key parameters associated with this process. The increase in atmospheric CO2 , the rising temperatures, the changes in annual and seasonal rainfall patterns and the frequency of extreme weather events affect the supply, quality, and stability of food production in the EU. Considering this, the impact of climate change on the agricultural sector has been assessed in recent years both at European and regional level. So, by using the information made available by several sources, it is necessary to identify and define the main key climate consequences for agriculture, thus covering several highly applicable aspects, and with a major socio-economic impact in our project, whose main contribution to the promotion of technological progress is based on innovative smart solutions. 1.2 Main EU Documents Concerning Soil Protection and the Effects of Soil Alteration The project was developed considering several EU strategies and documents This section presents the main EU Documents concerning soil protection and the effects of soil alteration. On 24 February 2021, the European Commission adopted the new EU Climate Change Adaptation Strategy, which sets out how the European Union can adapt to the inevitable impacts of climate change and become climate resilient by 2050 [2]. The

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strategy has four main objectives: to make adaptation smarter, faster, and more systemic, and to step up international action on adaptation to climate change. Additionally, EEA Member States have adopted a National Adaptation Strategy and several of them have developed and implemented National Adaptation Action Plans. Another important aspect of the project is the alignment with the “Climate Change Mitigation published on 23-11-2020”. This document highlights the following greenhouse gases (GHGs) that are emitted both through natural processes and as a result of human activities. Water vapor is the most common greenhouse gas in the atmosphere. But human activities lead to the emission of considerable amounts of other greenhouse gases, which increase their atmospheric concentration, thus intensifying the greenhouse effect and warming the climate. Another important document that the project is consistent with the “Energy and Climate Policy Framework” stating that the EU is committed to reducing emissions on its territory by at least 40% by 2030 compared to 1990 levels. The European Energy Union, which aims to ensure safe, affordable, and green energy for Europe, has the same goal [3]. In 1994, the United Nations established the “Convention to Combat Desertification (UNCCD)”, by means of which 122 countries committed to land degradation neutrality goals, like countries in the Paris Climate Agreement agreed on goals to reduce carbon pollution. These efforts involve working with farmers to protect arable land, repair degraded land, and manage water supplies more efficiently. 1.3 Desertification as a Key Climate Change Factor Below is a description of the process of desertification and of its consequences. Desertification is defined by the “United Nations Convention to Combat Desertification (UNCCD)” as “land degradation in arid, semi-arid and dry subhumid areas (dry land) resulting from various factors, including climate change and human activities” [4]. It does not imply the presence of a desert itself and it can occur far from any climatic desert, and the presence or absence of a nearby desert has nothing to do with the desertification process. The magnitude of this phenomenon is serious: more than 70% of the land surface is affected by desertification. There are fine lines between drylands, desert lands, and deserts, but once crossed, it is difficult to go back because soil recovery is a slow process. It can take 500 years for 2.5 cm of soil to form, but only a few years to destroy it. It is much more cost effective to protect dry areas from degradation than to reverse the process. The relationship between desertification and climate change is depicted in Fig. 1. The causes that underpin desertification are: global warming and changes in atmospheric precipitation and anthropogenic activities: overgrazing, rapid population growth; poverty, excessive cultivation, lack of alternative means of subsistence. Serious consequences of desertification consist in soil erosion and soil degradation. Almost 3.6 billion of the world’s 5.2 billion hectares of arable land have suffered from them. In more than 100 countries, 1 billion of the world’s 6 billion people are affected by desertification. Other important consequences include the intensification of wildfires and high winds, decrease in soil fertility, dune formation, wind erosion, biomass destruction

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Fig. 1. The relationship between desertification and climate change

and so on. These will cause low food production and the emergence of problems related to the lack of food; a decrease in the health status of the population and the risk of epidemics; and the occurrence of illegal acts in the environment and conflicts. The only good thing to diversification is the fact that it can be inversed. Combating desertification can be achieved by: – planting forest curtains and drought-resistant species; – the correct dimensioning of the number of animals according to the support capacity, to avoid overgrazing; – developing irrigation systems from surplus resources and stopping the lowering of the underground water level; – reduce pollution and comply with the Kyoto Protocol on the elimination of greenhouse gases. The agreement provides, for industrialized countries, a reduction of polluting emissions by 8% in the period 2008–2012 compared to those in 1990. According to a new report by the European Court of Auditors, [5] the European Commission does not have a clear picture of the challenges posed by the growing threats posed by desertification and land degradation in the EU. In the Court’s view, the coherence of the measures taken so far by the Commission and the Member States to combat desertification is limited, and the Commission has not assessed progress towards the objective of neutrality in terms of land degradation by 2030. Also, according to Special Report 33/2018 Combating desertification in the EU: a growing threat requiring further action, the Commission concluded that although desertification and land degradation are current and growing threats in the EU and it has not assessed progress towards its commitment to achieve land degradation neutrality by 2030. Quoting Phil Wynn Owen, Member of the Court responsible for the Report “As a result of climate change affecting the EU, we witness an increase in droughts, aridity, and the risk of desertification.” […]. “Desertification can lead to poverty, health problems caused by wind-blown dust and a decrease in biodiversity. It can also have significant demographic and economic consequences” [5].

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The thirteen EU member states that have declared themselves affected by the desertification phenomenon − in accordance with the United Nations Convention to Combat Desertification (UNCCD) − are: Bulgaria, Greece, Spain, Croatia, Italy, Cyprus, Latvia, Hungary, Malta, Portugal, Romania, Slovenia, and Slovakia. In order to fight back this devastating phenomenon, the Commission and Member States collect data on different factors that have an impact on desertification and land degradation. However, no full assessment of land degradation has been carried out at EU level and no methodology has been agreed. Coordination between Member States was limited and the Commission did not provide practical guidance. Moreover, the Commission did not assess the progress made in fulfilling its commitment to achieve the goal of neutrality with respect to land degradation. By 2030, the EU aims to implement the following measures to fight back desertification by developing a methodology used to assess the extent of desertification and land degradation in the EU and, based on this methodology, to analyze the relevant data and present it regularly and assessing the current legal framework for sustainable land use in the EU, including addressing the issue of combating desertification and land degradation. These objectives will be achieved by: providing Member States with guidance on soil conservation and achieving the objective of land degradation neutrality in the EU, including the dissemination of good practices, and providing technical assistance to Member States, at their request, in order to develop national action plans to achieve the objective of neutrality in terms of land degradation by 2030. To enter into force, the decision had to be ratified by at least 55 nations (a condition already met) producing 55% of global carbon dioxide emissions [6]. 1.4 Desertification in Romania Our country and the whole of Europe face extreme weather phenomena in summer: temperatures exceeding 35° in the shade and 50° at ground level, violent storms, and floods. Surface waters register significant flow decreases, and underground water level decreases. These are just some of the long-term consequences of global warming, causing desertification. The effects of the process of desertification in Romania are presented below, in Fig. 2. In our country, this phenomenon has manifested itself especially in the last 15 years, leading to the fact that almost 70% of the country’s surface is in a rapid process of desertification. In the light of these abrupt climate changes, researchers of the phenomenon developed a work entitled “Study for the Development of the National Strategy regarding the Prevention and Combat of Desertification and Land Degradation 2019–2030 − An Extensive Analysis of the Desertification and Soil Degradation Situation in Romania” [8] − in which recommendations and a plan of measures were presented to prevent and combat land degradation and desertification. While Romania is losing land because of the increasingly extensive sand, the south and west of the country are turning into an arid area, with a rather desert microclimate. In the south of Dolj county, the desert takes the form of a strip about 30 km wide, which stretches from Dabuleni, Sadova, Daneti, Marsani to Bechet, where it almost enters the waters of the Danube. Once, here there were large cereal fields, as well as orchards or

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Fig. 2. Areas subject to desertification in Romania

vineyards. Sandy dunes are present at every step. And sometimes, when the wind blows stronger, they move slowly from place to place and cover the little fertile soil that still exists in the area. But desertification does not only threaten Oltenia. The Western Plain, along the borders with Hungary and Serbia, in the Gaiu Mic - Beba Veche area, is equally affected. There, the phenomenon is caused, above all, by the succession of years with extreme drought, followed by years with precipitation above normal limits, and the excess rains and floods also lead to the destruction of the chernozem layer, which causes the transformation of some fertile lands into sand. From Sannicolau Mare to Ciacova, including in the Banloc area, there are already areas where even the water table has almost completely disappeared. The danger of desertification is also present in the Mures basin, in the Cornesti-Vinga areas, where the decrease in the amount of precipitation is the main factor that causes desertification [7].

2 Measurement Parameters for Water, Air and Soil In order to identify the extent of soil desertification processes and its effects, certain parameters must be considered. In our project, the measurement parameters for water, air and soil will be analyzed and identified, and several significant indicators will be established. AIR: For the air quality assessment, which takes place in the monitoring stations, we will use the air quality parameters regulated in EU Directive 2008/50/EC on the assessment of ambient air quality, as amended by Directive 2015/1480. Air quality monitoring parameters have different assessment thresholds with upper and lower limit values. The assessment requirements specific to each air quality indicator, without the accepted threshold values are as follows: SO2 , NOx, PM2.5 and PM10, Benzene, CO, Pb (Cd, As and NI, in PM10). In addition to air quality indicators surveyed at monitoring stations, other air quality compounds of interest, especially for research-based monitoring, can be determined.

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Thus, different species of inorganic or organic origin with low or medium molecular weight can be determined in atmospheric air, such as: – inorganic gases: NOx, SO2 , SO3 , CO2 , CO, O3 ; – volatile organic compounds (VOC) or inorganic substances; – non-volatile organic compounds adsorbed on solid particles, such as persistent organic pollutants (POPs); – water-soluble compounds such as inorganic anions (NO3 -, NO2 -, S2 -, Cl-), organic anions (formate, acetate) and metal cations. Water scarcity, as well as water pollution, is a global problem and poses a challenge to ensuring a sufficient and quality water supply, with minimal consequences for ensuring healthy cultures. So, we can consider it as basic parameters for irrigation water quality: 1. 2. 3. 4. 5. 6. 7. 8.

pH 6.8–8.3 Temperature, 10–30 °C Electrical conductivity, mSm/cm at 25 °C < 1100 Mineralization < 700 Na*, mg/L 46–69 Ca2 +, mg/L Not less than 50% of the sum of cations CI, mg/L 35–105 to 142 N-NO, mg/L < 5

Soil quality measurement is an exercise to identifying soil properties that correlate with environmental outcomes with are capable of being measured accurately within certain technical and economic constraints. Soil quality indicators can be qualitative (e.g., rapid drainage) or quantitative (infiltration = 2.5 in/h). Thus, the basic parameters for measuring soil quality, without the accepted threshold values, are the following: – – – –

Apparent density Soil moisture Permeability pH soil reaction

In order to monitor parameters of water, air and soil that influence the risk of pollution, the sensors that will be part of multi-sensor system will be analyzed accordingly: for water (water pH, ammonium, ammonia, nitrates, nitrites, calcium, chlorine, chlorides, etc.); for air (air humidity, temperature, wind speed, carbon monoxide (CO), sulfur dioxide (SO2 ), nitrogen dioxide (NO2 ) and lead (Pb), etc.); for soil (Soil Breather Analyzer, Soil Calcimeter, Soil Conductometer, Soil Photocolorimeter, Soil Hydrometer, Soil Hygrometer, Soil Vacuum, Soil Penetrometers, Soil pH-meter, Temperature Sensor, Soil Tensiometers, Oxygen and CO2 diffusion sensors, EC salinity sensor, etc.).

3 Establishing Indicators for Soil Analysis Scientists use soil quality indicators to assess how well the soil is functioning because soil function often cannot be measured directly.

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Soil quality measurement is an exercise in identifying soil properties that respond to management, affect, or correlate with environmental outcomes and are capable of being measured accurately within certain technical and economic constraints. There are three main categories of soil indicators: chemical, physical and biological ones. Typical soil tests only look at chemical indicators. Soil quality tries to integrate all three types of indicators. The categories do not align perfectly with the different soil functions, so integration is needed. Chemical indicators can provide information about the balance between the soil solution (soil water and nutrients) and exchange sites (clay particles, organic matter); plant health; nutritional requirements of soil plant and animal communities; levels of soil contaminants and their availability for uptake by animals and plants. Indicators include: • Electrical conductivity • Nitrates from the soil • Soil reaction (pH) Physical indicators provide information about soil hydrologic characteristics, such as water ingress and retention, that influence plant availability. Some indicators are related to nutrient availability through their influence on rooting volume and aeration status. Other measures tell us about the state of erosion. Indicators include: • • • • • • •

Aggregate stability Available water capacity Bulk density Infiltration Slaking Soil crusts Soil structure and macropores

Biological indicators can tell us about the organisms that make up the soil food web that are responsible for organic matter decomposition and nutrient cycling. Information on the number of organisms, both individuals and species, that fulfill similar jobs or niches can indicate a soil’s ability to function or recover from disturbance (resilience and resilience). Indicators include: • • • • •

Particles of organic matter Potentially mineralizable nitrogen Breathing Soil enzymes Total organic carbon

4 Identification and Selection of Sensors; Manufacturing Companies An important part of our project consisted in establishing a list of the most significant soil parameters that can be used for a proper soil evaluation. We also include a list of manufacturers of the sensors that are used for monitoring these parameters.

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For the monitoring of air, water and soil parameters that influence the risk of desertification, the corresponding sensors are analyzed considering the signal transmission system having the same type of data transmission, to be taken over by the data collection platform in the sensor system, as follows: • for air: air humidity, temperature, wind speed, carbon monoxide (CO), sulfur dioxide (SO2 ), nitrogen dioxide (NO2 ) and lead (Pb); • for water PH, ammonium, ammonia, nitrates, nitrites, calcium, chlorine, chlorides, for air humidity, temperature, wind speed, carbon monoxide (CO), sulfur dioxide (SO2 ), nitrogen dioxide (NO2 ) and lead (Pb); • for soil: Soil respiration analyzer, Soil calcimeter, Soil conductometer, Soil photocolorimeter, Soil hydrometer, Soil hygrometer, Soil suction meter, Soil penetrometers, Soil pH-meter, Temperature sensor, Tensiometers from the ground. There are many companies that produce sensors for measuring water, air and soil parameters, such as: CubeWorks, Real Tech Inc., General Oceanics, Inc., WaterScope Inc., Spectrum Technologies, Inc., Aanderaa Data Instruments, OTT HydroMet, The ProMinent GmbH, Safe Training Systems Ltd, Apex Environmental Ltd, Felix Technology Inc, Censar Technologies, Inc, EKOTON Industrial Group, Environmental XPRT, Geotech Environmental Equipments, Envirologek Technologies, METER GROUP, etc.

5 Conclusions Within the framework of INCDMTM Bucharest, a project based on an IoT architecture for soil monitoring/IoT-SOL is currently being developed. Within the project, a multisensory software platform on several levels (based on a computer-controlled platform with open architecture) will be created for viewing the results and making decisions. Soil quality parameters will be measured in real time, based on remote transmission, to determine the degree of degradation/desertification of the soil. The project is highly original as, in Romania, so far, analyzes for measuring soil parameters have only been performed by parameter sampling in a laboratory, or using on-site analyses based on wireless reading equipment. For now, only the first phase of the project was implemented – consisting in establishing the key parameters that need to be considered for a proper soil quality evaluation. Further phases of the project – consisting in developing the IoT architecture of sensors – will be presented in further works.

References 1. Communication from the Commission to The European Parliament, The Council, The European Economic and Social Committee and the Committee of the Regions EU Soil Strategy 2030 Harnessing the benefits of healthy soils for humans, food, nature and the climate {SWD (2021) 323 final}/Brussels, 17 November 2021, COM (2021) 699 final (2021) 2. Communication from the Commission to The European Parliament, The Council, The European Economic and Social Committee and the Committee of the Regions Building a climateresilient Europe - The new EU Climate Change Adaptation Strategy {SEC(2021) 89 final} {SWD (2021) 25 final} - {SWD(2021) 26 final}/Brussels, 24 February 2021, COM (2021) 82 final (2021)

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3. Climate change mitigation, 10 January 2023 4. United Nations Convention to Combat Desertification in Countries Severely Affected by Drought, 19 March 1998 5. Prigent, O.: Special report no. 33 2018/Combating desertification in the EU: a growing threat that requires additional action 6. Kyoto Protocol, 1 December 1997 7. Florea, M.: Romania, On the List of EU States Threatened by Desertification, 20 December 2018 8. Study for the Development of the National Strategy on Preventing and Combating Desertification and Land Degradation 2019–2030/Authors 9. INCDS, INCDPAPM-ICPA, ICPA Bucharest, ANM, USAMVB: National Forestry Research and Development Institute “MARIN DRACEA”

Improving the Energy Performance of a High-Head Francis Turbine Kostiantyn Myronov , Olha Dmytriienko , Yevheniia Basova(B) Kseniya Rezvaya , and Serhii Vorontsov

,

National Technical University “Kharkiv Polytechnic Institute”, 2, Kyrpychova Str., Kharkiv 61002, Ukraine [email protected]

Abstract. Hydroturbines being developed and supplied to the market must provide high technical and economic indicators, reliability, and durability, which will ensure the high competitiveness of hydroturbines in the foreign and domestic markets. Numerical and physical modeling methods are widely used to solve these problems. The development of mathematical modeling methods makes it possible to carry out multivariate numerical studies of the influence of geometric parameters on the formation of energy characteristics in the process of designing a flow space. In many cases, the use of a numerical experiment is an effective substitute for a physical one. The results of a numerical and physical experiment on the effect of geometric parameters on energy performance are widely used in the generally accepted approach to improving the flow space, based on making changes to the geometry and subsequent evaluation of these changes. The purpose of this work is to improve the flow space of Francis turbines by improving their energy-cavitation characteristics. Keywords: Energy efficiency · Flow Space · Wicket Gate · Spiral Case · Process Innovation

1 Introduction Inlet of a high-head Francis turbine consists of a spiral case, a stator and a wicket gate and is designed to create a uniform axisymmetric flow with the required swirl in front of the runner. To reduce losses in the inlet, it is first necessary to coordinate all elements of the inlet with each other in terms of kinematic parameters. It is preferable to design a spiral case according to the Vu = const law with a floating conjugation point, which will allow creating a more uniform flow with smaller spiral dimensions [1]. The flow angle formed by the spiral case must be consistent with the installation angle of the stator columns. If the density of the stator lattice is small, the stator column must be designed along the flow to reduce shock losses. In this case, the average flow angle in front of the wicket gate will be determined by the spiral case. If the lattice of stator columns is quite dense,

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 66–77, 2023. https://doi.org/10.1007/978-3-031-40628-7_5

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i.e. their number is more than 18, the stator can turn the flow, changing the average angle in front of the wicket gate and creating an additional swirl of the flow. Based on the above conditions, the profile shape of a wicket gate vane is designed or selected using industry standards. The role of the wicket gate in the formation of the energy characteristics of high-head Francis turbine, of all the inlet elements, is the most significant, because energy losses in the wicket gate exceed the total losses in the spiral case and the stator. For example, for hydraulic turbines FR500, energy losses in the wicket gate, even in the optimal mode, reach up to 2.5%. The main goal of the study is to search for rational inlet options with high-energy characteristics.

2 Literature Review The design of hydraulic turbines with high energy characteristics is primarily associated with the use of the method of mathematical modelling of the working process of blade hydraulic machines. Modelling is the basis of modern methodology for the design of technical objects. The article [2] deals with new design solutions to improve the operating process and effectively use hydraulic turbines for heads up to 800–1000 m, expand the operating range relative to flow rates and heads with high energy and cavitation indicators and reliability of operation on varying modes that differ from the optimum operating mode. Based on complex experimental studies of the flow pattern in a water passage this work reveals the causes of increased energy losses. Several ways for improving the operating process are proposed, including new design solutions. Yasuyuki Nishi and et al. [3] studied methods of improving the performance of the hydraulic turbine. Using numerical analysis, authors examined the performances and flow fields of a runner and a composite body consisting of the runner and collection device by varying the airfoil and number of blades. In [4] Weiqiang Zhao and et al. analyzed the feasibility of detecting the onset of the instability operation of Francis turbines using method, which based on the study of the signals of vibration, pressure fluctuations and other parameters. Data-driven methods, artificial intelligence techniques, including principal component analysis, were used in this work. J. Joy and et al. [5] investigated a variable guide vane system of a high-head Francis model turbine using numerical simulation. E.O. do Nascimento and et al. [6] studied deeply the pressure and velocity fields, as well as other phenomena that commonly occur in hydraulic turbines through computational fluid dynamics, using a Reynolds-averaged Navier-Stokes formulation. In [7] authors described the application of an interpolation–analytical method, which is used in 3D computational fluid dynamics (CFD) calculations of turbomachinery flows with real working media, such as steam and fluids. The work [8] presented in this paper discusses the flow field investigation of a high head model Francis turbine at different load. R. Goyal and et al. carried out numerical simulation of the complete turbine, performed detailed analysis of the rotor stator interaction and draft tube flow field.

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U. Shrestha and et al. in [9] studied a CFD-based shape design of the fixed flow passages (stay vane, casing, and draft tube) in case to improve the flow uniformity in the fixed flow passages of a Francis hydro turbine model. Based on this, the main goal of this work was formulated, namely, to choose the optimal geometry of the elements for supplying a high-head Francis turbine.

3 Research Methodology The design of the water passages of high-head hydraulic turbines is based on the choice of a more optimal geometry of the inlet, blade system and outlet elements in order to achieve maximum efficiency under the conditions of the equipment requirements. For this, it is necessary and sufficient to determine the losses in the water passage. Losses in a hydraulic jet turbine are divided by the nature of their occurrence into hydraulic, volumetric, disc friction, mechanical. 3.1 Hydraulic Head Losses Hydraulic losses include friction losses, shock, vortex and output losses that occur during the water flow motion in the water passage. The value of hydraulic losses depends on the shape, size and operating conditions of the turbines, as well as on the water viscous characteristics, surface roughness, flow curvature and changes in the flow cross section. It can be found using formula: hh = hshock + hprof + hc + hswirl ,

(1)

where hshok – shock losses, hprof – profile losses, hC – circulation losses, hswirl - energy losses due to the formation of annular vortices in the channels. Friction losses occur due to friction between water layers, as well as between liquid and solid boundaries, and can be in all elements of the turbine water passage. The friction losses in the wicket gate and the runner also include profile losses. The vortex losses in a hydroturbine are caused by separation of the boundary layer from the streamlined surfaces and the formation of vortices during the water motion in the spiral case, wicket gate, runner and draft tube. The greatest vortex formation in the flow takes place at the inlet and outlet of the runner and in the draft tube, especially at off-design conditions. The ratio between the vortex losses in the runner and the draft tube depends significantly on the speed of the turbine and the operation mode. Hydraulic losses in the water passage elements can be reduced by changing the shape of the blade profiles and the geometry of the water passage using numerically modeling the effect of geometric parameters on energy characteristics. 3.2 Volumetric Head Losses There is a feature in the design of hydraulic turbines. This is the presence of a clearance between the stationary and rotating parts of the runner. Since the runner inlet pressure is much higher than the downstream and outlet pressure, the result is water leakage through

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the clearance. The volume of water passing through the clearance is called volume losses and is expressed as a percentage of the total volume flow through the turbine. The value of volume losses is determined from the expression: ξ0 = q/Q,

(2)

where q – the volume of water passing through the clearance, Q – turbine flow rate. Turbine volume losses varies from 1 to 3% depending on different types of seals in the clearances. During turbine operation, the runner seals wear out and the amount of leakage increases. 3.3 Disc Friction Head Losses The disc friction losses of a Francis hydraulic turbine are the energy expended to overcome the moments of fluid friction on the outer surfaces of the bands and the runner seal, as well as to rotate the water in space between the band and the foundation ring, the runner hub and the turbine cover. Factors influencing disc friction head losses: dimensions of space, runner seals, cleanliness of the bands and sealing rings, the angular speed of runner rotation. For an approximate calculation of disc friction losses, the empirical formula can be used: ξdf =

6, 1 ∗ 10−4 ρ ∗ l ∗ ω3 ∗ r 4 , √ 4 Re

(3)

where Re – Reynolds number, l, r – length and radius of the seals on the bands, respectively, ω – angular speed. For high-head turbines with developed bands, the value of disc friction is the largest and can be a significant part (around 3%) in the total energy losses balance in the turbine. 3.4 Mechanical Head Losses The mechanical losses of a hydraulic turbine are the power required to overcome frictional moments in the shaft seal and guide bearing of the hydraulic turbine. These losses are expressed in terms of the mechanical efficiency of the turbine. The mechanical losses of the turbine, if the rotor is properly assembled and balanced, can range from 0.3 to 1.5%. They depend on the type of unit assembly, turbine power, its turbine operation mode, etc. The value of relative mechanical energy losses is equal to: ξm =

Mf · ω , Nh

where Mf – total moment of friction in bearings, Nh – turbine hydraulic power.

(4)

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3.5 Losses Calculation During numerical modelling, the mail goal is to determine hydraulic losses. Hydraulic losses in the spiral case, stator, wicket gate, runner and draft tube in the numerical simulation of viscous flow are calculated as the difference between the total energy at the inlet and outlet of each element of the water passage. The total energy is the sum of pressure and kinetic energy. ⎛ ⎞   1 ⎜ ⎟ E1−2 = (5) ⎝ ptot Vt dS − ptot Vt dS ⎠ = E1 − E2 , ρQ S1

S2

where Vt – flow rate component of absolute velocity, ptot – total pressure, ρ – liquid density. In runner (i.e. in a rotating reference system) the total energy loss is the difference between the total energy entering and exiting the runner. The developed variants of the water passage inlet were investigated using 2D and 3D methods for calculating the fluid flow. In 2D methods, various types of energy losses (profile, shock and total) were determined in each element of water passage inlet separately. The performed calculations made it possible to select the best variants for the water passage for further research in software package CFX-TASCflow using k-ε turbulence model. To calculate the turbulent viscosity, the standard k-ε flow turbulence model was used [10–12].

4 Study of the Hydraulic Turbines Inlet 4.1 Initial Data In this work the design of the inlet hydraulic turbines FR500 was considered with the following parameters: – – – –

optimal reduced flow rate QI opt = 0,15 m3 /s; maximum reduced flow rate QI opt = 0,18 m3 /s; optimal reduced rotation nI opt = 60 min−1 ; hydraulic efficiency ηh = 0,92–0,94.

The spiral case and stator columns were the same for all three variants of the wicket gate. The spiral was calculated according to the law Vu / r = const. The flow angle in front of the stator columns in the inlet cross-section αsc = 27.9°. The average flow angle in front of the columns αsc = 33.5° (see Fig. 1). Stator columns have angles α1ST = 33.5° and α2ST = 29.5°. Figure 1 shows how the flow angle αsc changes depending on the coverage angle of spiral case ϕ 0 cs . The values of the circumferential velocity component V u and the velocity moment V u/r in sections along the perimeter of the spiral. All calculations were carried out for QI opt = 0,18 m3/s. During the work, three different profiles of wicket gate vanes were selected (see Fig. 2). The influence of the profile shape on the optimal mode formation was evaluated.

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Fig. 1. Flow parameters in the spiral case

c

b

а

Fig. 2. Profile shapes of the wicket gate vane: a – convex curvature; b – concave curvature; c – symmetrical

4.2 Research Results As a result of the computational study, using 2D calculation methods, the parameters of the optimal operating mode of the hydraulic turbine with three different wicket gate vane profiles were obtained (see Table 1). The value of the flow angle α0f was determined, which should be created in front of the runner inlet, provided that the flow axially leaves the runner: ⎛ ⎞ / / QIopt · nIopt ⎠. (6) α0f = arctan⎝ 60 · b0 · ηh · g

Table 1. Influence of the shape of the guide vane profile on the formation of the optimal mode Variant QI  opt , m3 /s nI  opt , min−1

a

b 0.152

60.24

0.146 60.13

c 0.147 60.2

For the accepted design parameters α0f = 11,5°, therefore, the wicket gate vanes are designed in such a way as to provide this angle value.

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To ensure the reduction of the flow rate of the unit to a predetermined value. QI opt = 0.152 m3 /s, it was necessary to change the geometry of the wicket gate vane profile to a concave shape. In the work, a results comparison of calculating the concave and symmetrical profiles of the wicket gate vanes was made. Figure 3 shows the relative velocity distribution along the wicket gate vane profile. The nature of the curve indicates an increase in the velocity at the trailing edge for an asymmetric profile compared to a symmetrical one, which will lead to an increase in profile losses at the optimal operating mode.

Fig. 3. Velocity distribution along the vane profile: a – concave profile, b – symmetrical profile

Figure 4 characterizes the pressure distribution for the considered wicket gate vane profile when the turbine is operating at the optimal mode. The curve shows that the pressure distribution at the outlet of a symmetrical profile is slightly higher than that of an asymmetric one. Shock hshock , ptofile hprof and total hwg losses in wicket gate were determined for a comparative analysis of the energy characteristics of water passages with concave and symmetrical vane profiles (see Fig. 5).

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Fig. 4. Pressure distribution along the vane profile: a – concave profile, b – symmetrical profile

Figure 5 shows the dependence of energy losses on the flow rate in the wicket gate at the optimal speed. The profile losses have the largest contribution to the total losses, i.e. friction losses. According to the graphs, a symmetrical profile of the wicket gate vane has less value of losses at higher flow rates, while a vane with an asymmetric profile has slightly lower losses at smaller wicket gate vane openings. Loss data in the elements of the water passage (spiral case, stator, and wicket gate) and total losses in the inlet were determined at different flow rates and summarized in Table 2 and Table 3. The results of the calculation of the designed high-head hydraulic turbine inlets, which were obtained using the CFX-TASCflow software package, are shown in Figs. 6 and 7.

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Fig. 5. Losses in the wicket gate: a – concave profile, b – symmetrical profile

Table 2. Losses in inlet elements for wicket gate with concave profile QI ’, m3 /s

a0 , mm

hsc , %

hst , %

hwg , %

htot , %

0.11

27

0.14

0.1647

2.1251

2.4298

0.13

32

0.195

0.2277

1.7338

2.1565

0.15

37

0.26

0.3007

1.5056

2.0663

0.17

42

0.334

0.3834

1.3217

2.0391

0.19

47

0.417

0.4759

1.2228

2.1157

Figure 6 shows pressure isolines in the area of the stator and wicket gate. Figure 7 shows velocity fields in the area of the stator and wicket gate. Wicket gate vane with a symmetrical profile in the optimal mode has a more uniform nature of fluid flow. At the same time, for both the first and second variants of vane profile, the flow from the stator flows onto the wicket gate vanes at a slight angle, which will lead to an increase in shock losses at the wicket gate inlet. To reduce these losses, it is possible to increase the radius of the leading edge of the wicket gate or slightly shift the vanes along the axis. To reduce separation losses at the outlet of the wicket gate, a beveled trailing edge can be used.

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Table 3. Losses in inlet elements for wicket gate with symmetrical profile QI ’, m3 /s

a0 , mm

hsc , %

0.11

25

0.13

30

0.15

hst , %

hwg , %

htot , %

0.14

0.1647

2.1254

2.4671

0.195

0.2277

1.7481

2.1708

35

0.26

0.3007

1.4508

2.0115

0.17

40

0.334

0.3834

1.2597

1.9771

0.19

45

0.417

0.4759

1.1508

2.0437

a

b

Fig. 6. Pressure isolines in the area of the stator and wicket gate: a – concave profile, b – symmetrical profile

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a

b Fig. 7. Velocity fields in the area of the stator and wicket gate: a – concave profile, b – symmetrical profile

5 Conclusions Three variants of the geometry of water passage inlet of a high-head hydraulic turbine were studied. As a result of the study, using 2D and 3D methods, the values of energy losses in the spiral case, stator and wicket gate were determined, which made it possible to analyze the nature of the flow in the inlet. Pressure isolines and velocity fields in the area of the stator and wicket gate were obtained. According to the results of the analysis, the minimum energy losses in the water passage are observed with a symmetrical profile in the area of optimal flow rates, while with a negative curvature profile minimum losses are in the area of minimum flow rates.

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Losses in the optimal mode for a symmetrical profile of wicket gate vane are 1.45%, for an asymmetric profile – 1.5%.

References 1. Barlit. V.V.: Hydraulic Turbines [ Gidravlicheskie turbinyi]. 1st edn. Vyscha shkola. Kyev (1977). (in Russian) 2. Gusak, O., Cherkashenko, M., Potetenko, O., Gasiyk, A., Rezvaya, K.: Improving reliability and efficiency of hydraulic turbines. J. Phys: Conf. Ser. 1741(1), 012003 (2021). https://doi. org/10.1088/1742-6596/1741/1/012003 3. Nishi, Y., Inagaki, T., Li, Y., Hirama, S., Kikuchi, N.: Study on performance improvement of an axial flow hydraulic turbine with a collection device. Int. J. Fluid Mach. Syst. 9(1), 47–55 (2016). https://doi.org/10.5293/IJFMS.2016.9.1.047 4. Zhao, W., Presas, A., Egusquiza, M., et al.: Increasing the operating range and energy production in Francis turbines by an early detection of the overload instability. Measurem. J. Internat. Measurem. Confederat. 181, 109580 (2021). https://doi.org/10.1016/j.measurement. 2021.109580 5. Joy, J., Raisee, M., Cervantes, M.J.: Hydraulic performance of a francis turbine with a variable draft tube guide vane system to mitigate pressure pulsations. Energies 15(18), 6542 (2022). https://doi.org/10.3390/en15186542 6. do Nascimento, E.O., de Freitas, E.A., Lins, E.F., Vaz, J.R.P.: Performance assessment of an Indalma hydro-turbine. SN Appli. Sci. 2(12), 1–13 (2020). https://doi.org/10.1007/s42452020-03970-x ˙ 7. Rusanov, A., Rusanov, R., Klonowicz, P., Lampart, P., Zywica, G., Borsukiewicz, A.: Development and experimental validation of real fluid models for CFD calculation of ORC and steam turbine flows. Materials 14(22), 6879 (2021). https://doi.org/10.3390/ma14226879 8. Goyal, R., Trivedi, C., Kumar Gandhi, B., Cervantes, M.J.: Numerical simulation and validation of a high head model francis turbine at part load operating condition. J. Instit. Eng. (India): Ser. C 99(5), 557–570 (2017). https://doi.org/10.1007/s40032-017-0380-z 9. Shrestha, U., Choi, Y.-D.: A CFD-based shape design optimization process of fixed flow passages in a francis hydro turbine. Processes 8(11), 1392 (2020). https://doi.org/10.3390/ pr8111392 10. Tiwari, G., Kumar, J., Prasad, V., Patel, V.K.: Utility of CFD in the design and performance analysis of hydraulic turbines — A review. Energy Rep. 6, 2410–2429 (2020). https://doi.org/ 10.1016/j.egyr.2020.09.004 11. Mironov K.A., Oleksenko, Y.Y.: Research of fluid flow in two-dimensional and threedimensional formulation in the flow part of a high-pressure francis turbine. Bull. National Tech. Univ. “KhPI”. Ser.: Hydraulic Mach. Hydraulic Units 1, 72–76 (2019). https://doi.org/ 10.20998/2411-3441.2019.1.11 12. Mironov, K., Oleksenko, Y., Gulakhmadov, A.: Improving the energy performance of a highpressure hydraulic turbine by researching the flow in the flow part. J. Power Energy Eng. 10, 27–37 (2022). https://doi.org/10.4236/jpee.2022.104002

Research on a Climbing Robot with Attachment by Vacuum Cups Tudor Catalin Apostolescu1 , Laurentiu Adrian Cartal2(B) Georgeta Ionascu2 , and Lucian Bogatu2

, Ioana Udrea2

,

1 Titu Maiorescu University, 189, Calea Vacaresti, 0400511 Corp M, Bucharest, Romania 2 Politehnica University of Bucharest, 313, Splaiul Independentei, 060042 Bucharest, Romania

[email protected]

Abstract. Based on the results of interdisciplinary research specific to the concept of mechatronics that synergistically integrates mechanics with electronics and informatics, autonomous mobile robots have a strong development, the systems for achieving movements, actuation and operating in dynamic or unknown environments, giving them a great complexity and certain superior levels of intelligence. Autonomous mobile robots with movements in the vertical plane involve the most complex mechanical structures, both in terms of movement kinematics and adhesion in operating points. Different from service robots with horizontal movements, the climbing robots must additionally support their own weight during the fixing phase. In this paper, the most important results of the research performed to establish the behavior of vacuum cups are presented. Thus, the aspects regarding the efficiency and reliability of fixation on the work surface are considered: the adhesion of the suction cup to the supporting surface, the behavior of the suction cup under external loads, the theoretical evaluation of the pressure and elasticity forces of the suction cups, the possibilities of mathematical modeling of the vacuum suction cups, the determination/evaluation of the elastic force of the suction cup. The modeling and simulation of the static fixation of the suction cups on a vertical plane, are given, highlighting the positioning of the robot platforms in relation to the supporting surface. Using SolidWorks – Cosmos Motion software package, the modeling and simulation of the robot movement with respect to the suction cups, are made. To obtain a higher-level control system, of controller type, an Arduino Mega 2560 microcontroller is proposed to program the robot and to hold the suction cups system. Interesting results are inferred and proposed to be optimization solutions, certifying that the obtained performances are comparable to similar solutions conceived worldwide. Keywords: Mechatronic concept · Climbing robot · Vacuum fixing · Suction cups · Efficient and Reliable fixing

1 Introduction By mobile climbing robots is meant the category of robots that allow movement on vertical/inclined surfaces. Moving on vertical/inclined surfaces requires obtaining a support force that ensures at least one’s own weight. The practical ways to obtain support are: © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 78–103, 2023. https://doi.org/10.1007/978-3-031-40628-7_6

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with suction cups; - with systems for grabbing (clamping) ribs or bars on the wall; - with arms resting on the unevenness of the wall (for inclined surfaces); - by adhesion; - with claws like insects. The structure of the robot can be: - with legs; - with two platforms and legs; - with wheels (polygonal shapes); - with a number of arms resting on bumps. In climbing robots supported on suction cups, the suction cups used can be of two categories: autonomous suction cups (suction cups) where the depression is created by deforming (pushing) the suction cup on the object; actuated suction cups (vacuum cups) where depression is achieved with the help of an external vacuum/pressure source. The first category is rarely used in robots because it requires pressure forces that reduce the efficiency of support. 1

2

F

1

2

F

3

4

M M

Di De

a

b

Fig. 1. Realization of the depression p for fixing the suction cups: a - making the depression applied to the suction cup 1 with a vacuum pump 2; b - making the depression with the ejector 2, fed from the compressor 4 through the pressure regulator 3.

The vacuum pump system is used for robots with independent movements, the pump being attached to the robot, and the ejector system for robots that connect to an external pressure source (compressor), which reduces their movement autonomy. The holding force F depends on the dimensions of the suction cup contact surface and depression Δp. This force must be ensured by the force given in the catalog of the company producing the suction cups. This paper deals with fixing the robot through attachment systems with vacuum suction cups, Fig. 1a. One of the first experimental models of mobile climbing robots supported on suction cups is a biped Reconfigurable Adaptable Miniature Robot, RAMR1 [1]. The specifications for mobility, space, weight, sensitivity, and control are defined. A hip-type rotary joint is analyzed, due to its high mobility and ability to function in relatively small spaces. The conception and realization of the robot were subordinated to the idea of ensuring mobility through two legs, and under a constructive aspect to be miniaturized. The robot can move on inclined horizontal and vertical surfaces, including from the vertical plane, and can position a recognition sensor, such as a camera or microphone, at a specified location. The robot is small enough to be able to move in small spaces and not to be detected on the outside of buildings. As an autonomous mobile system, the robot has its own power source, processors, sensors, and other elements. Thus, for a maximum driving range, minimum weight and energy consumption are essential. To increase accessibility without diminishing the ability to work in confined space, a new version of RAMR robot was designed [2]. The new design provides a hybrid hip joint

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with discrete prismatic and revolute motion. Despite that these biped climbing robots could perform orthogonal plane transfer, their climbing mechanism was not very reliable and the biped structure, in general, does not provide a stable platform for installing tool package and carrying out maintenance work. The objective of another research [3] was the development of a small-sized and lightweight robot for cleaning windows. A prototype of this robot was made, in dimensions of: 300 mm × 300 mm × 100 mm and a mass of 3 kg. The prototype robot has two independently driven wheels and an active suction cup. The control system includes a controller for the direction of travel, which uses an accelerometer, and a controller for the distance traveled, which uses a rotary encoder and proximity sensors for autonomous operation. These characteristics were also defined due to the information collected from cleaning companies. The mechanical system is composed of two wheels driven by a central differential, capable of turning 90 degrees at the corner of the window and a vacuum suction cup that solves the fixing/adherence to the surface. Through this mechanical system the robot can move on a vertical window. An increased support force and the locomotion of the robot can be achieved by arranging the suction cups into a chain system. The Cleanbot II robot [4] is designed to move on glazed surfaces. A chain is used as a locomotion mechanism. Thus, a continuous movement with a maximum speed of 8–10 m/min is obtained. Direction is obtained by tilting one of the chain wheels. The suction cups are connected through 13 electro valves to feed only those suction cups that are in contact with the support surface. Rotary seals are used to feed the suction cups. Each of the groups of two suction cups is elastically supported to overcome some obstacles of max. 6 mm. To ensure stability, four rolls fixed on the frame are used. Mobile robots with platforms and legs with suction cups are widely used in practical applications, given the relatively high forces of locomotion, mobility, and good support. The disadvantage of larger dimensions is less disturbing in cleaning and inspection applications of large, glazed surfaces covering buildings [5]. The robotic system consists of the mobile robot for cleaning, the support vehicle, a compressor, and a computer. The mobile robot has movements along three axes: X and Y axes, ensured by pneumatic cylinders without rod; the lifting and lowering of the soles with suction cups (Z axis) is given by four cylinders. The rotation is given by a rotation unit, also pneumatically actuated. Cleaning is made with two wipers equipped with an absorption system each, to reuse the detergent. The suspension uses four suction cups with a diameter of 100 mm on each leg. The control system is based on two computers (master-slave). The master part is placed on the support vehicle. The slave part controls the position and movement of the robot with the aim of autonomous navigation. The robot is equipped with a visualization system and ultrasonic sensors. The mobile robot with vertical displacement that was developed, designed, and tested in an extensive research work [6], represents an original solution for solving the autonomous displacement on vertical surfaces, integrated to the present research field of mobile robots [7–9] and not found in the reference literature. The attachment of the robot on vertical surfaces is achieved using 3 suction cups, placed at the end of 3 each legs, which are positioned at the tip of two equilateral triangle shaped platforms. The movement autonomy imposed an electrical driving system both for all degrees of

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freedom, and for creating the necessary depression for the suction cups, ensured by a vacuum pump placed on the robot. A simultaneous driving system is used for the robot’s feet using a screw-mechanism, driven through toothed belt. The movements between the two platforms, rotation, and translation, are made through transmissions with belt wheels, respectively with a pinion-rack type mechanism, all of them provided by highprecision guiding mechanisms. The photo with the overall view of the original robot is presented in Fig. 2, and in Fig. 3 and, respectively, Fig. 4 are given the drawings with the constructive elements of the actuation mechanism for moving the suction cups and for realizing the rotation and translation of the robot.

Fig. 2. Overall view of the original robot: AUTONOMOUS ROBOT WITH VERTICAL DISPLACEMENT AND VACUUMMETRIC ATTACHMENT SYSTEM [6].

In this paper, an original research concerning the above robot’s support on suction cups is presented. The aspects regarding the efficiency and reliability of fixation on the work surface are considered: the adhesion of the suction cup to the supporting surface, the behavior of the suction cup under external loads, the theoretical evaluation of the pressure

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Fig. 3. The constructive elements of the actuation mechanism for moving the suction cups: 1 Maxon DC motor RE max 24; 2 - gearhead GP 22 A; 3 - boxes; 4 - connecting part; 5 - bearing; 6 - screw-shaft; 7 - translation element; 8- suction cup ESS-50 (FESTO); 9 - bearing body; 10 platform; 11 - belt wheel; 12, 13 - semi couplings.

Fig. 4. The constructive elements for achieving the rotation and translation of the robot: 1 microswitch; 2 - microswitch support; 3 - tooth belt wheel; 4 - rotation shaft flange; 5 - rack; 6 slider; 7 - bearing.

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and elasticity forces of the suction cups, the possibilities of mathematical modeling of the vacuum suction cups, the determination/evaluation of the elastic force of the suction cup. Using SolidWorks – Cosmos Motion software package, the modeling and simulation of the robot movement with respect to the suction cups, are made. An Arduino Mega 2560 microcontroller is proposed to program the robot and to hold the suction cups system.

2 Achieving the Mobility of the Robot The kinematic scheme designed for the movement of the robot is presented in Fig. 5. The inner platform PLI (7) can be fixed on three suction cups (9). The raising-lowering actuation of the legs with suction cups of the platform, the m1 movement, is done by the screw-nut mechanism (8) from the M1 R1 gear motor. The synchronous movement of the three suction cups of the platform is made with the help of the toothed belt transmission (4). For the external platform PLE (3), the suction cups (1), the mechanism (2) and the motor-reducer M2 R2 movement m2 are similarly provided. The orientation rotation of the robot - m3 is ensured by the toothed belt transmission (6) starting from the motorreducer M3 R3 , by the shaft (5) and the sliding element (10). The translation of the robot, the movement m4 is made with the motor-reducer M4R4 fixed to the inner platform (7). A mechanism consisting of the toothed wheel (14) and the rack (13) is used, fixed to the sliding element. The guide (11–12) is of the rolling type. This type of mechanism was preferred compared to the screw-nut one because it would have been difficult to achieve in a small size.

Fig. 5. Kinematic scheme of the robot.

Based on the development of knowledge, acquired in the analysis stage of the current stage of development of autonomous mobile robots, presented in the previous section, it was opted for a robot that moves through two platforms with successive mobilities - an upper/external one called PLE and a lower/inner one called PLI with fixation on a plane, which can have any orientation in space, including vertical, by means of legs

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with vacuum suction cups. In the context in which an optimum in the autonomy of the movements is given by the battery-type electrical energy source, electric actuation through micromotors was imposed, and in order for the motors that actuate the legs to consume a minimum of energy, their number was reduced to a minimum possible, three, necessary and sufficient number to ensure stability. From considerations of size and weight of the robot, the value of the side L = 247 mm was adopted for the platforms shaped as equilateral triangle, which allows a structural organization that, in a movement sequence, can realize a movement S (stroke) of about 100…110 mm. The Fig. 6 shows the limit positions PLE1 and PLE2 in relation to PLE. A complete cycle of translation (fixation on PLI suction cups – PLE translation – fixation on PLE suction cups – PLI translation) corresponds to a displacement of 200…220 mm of the robot. This allows a distance to be covered on a smooth surface, including glass, of 1500 mm in approx. 7 cycles. If the time required for a movement cycle is 8 s, then such a distance is covered in less than 1 min, which represents a time of all the movement phases, partial or total part of the cleaning time (of a window). This value of time is very good. As shown, the attachment system with vacuum suction cups, Fig. 1a, was adopted. To support the robot, it is more appropriate to use this attachment system, thus being able to command the attachment and detachment of the robot’s leg. For this, a pneumatic distributor, with electric drive, is introduced into the vacuum cup actuation scheme, which supplies and discharges the vacuum cups. The suction cups used in the developed robot are of the ESS 50 type from FESTO (Fig. 7).

Fig. 6. Platforms, PLI and PLE, translational movement.

The catalog data of the suction cup are: for a vacuum of Δp = 0.7 bar, the axial detachment force is 105.8 N and the lateral force detachment force is 135 N. The vacuum micropump that was used is of the NMP 015 B type, produced by LNF Neuberger. The achieved depression is approx. 0.57 bar, this was verified experimentally. The axial and lateral detachment forces of the suction cup are: F ax = 86 N and F l = 110 N. In the case of the robot, its fixation on a vertical surface can be checked by the lateral detachment

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Fig. 7. The used vacuum suction cup.

force. The weight of the robot is estimated at 30 N. For this weight, the safety factor is: c=

3 · F1 = 11 G

(1)

The value obtained is relatively high, when fixing on vertical surfaces, c > 4 is recommended. Only the moment given by the lateral detachment force was considered here [10, 11]. In the absence of calculation formulas, in order to be able to model the fixing with suction cups, it is necessary to experimentally determine the Characteristic of the suction cup, i.e. the dependence between the external force F and the displacement w. Both the force and the displacement have as reference the surface/plane of embedding the suction cup in the robot’s leg. The determinations are aimed at the following: a) the usual case of the normal force at the supporting surface, F x − wx (Fig. 8a); b) loading with lateral force F y - lateral displacement wy (Fig. 8b); c) the combined load Fx and F y - lateral displacement wy (Fig. 8c). In cases b) and c) of loads with lateral force F y , the predominant effect is the lateral displacement wy , thus determinations for wx are not considered. In order to make the determinations, a special stand was designed and built through which several types of experimental research were performed [12, 13]. The movements that the robot can make are obtained by combining the following categories of movements [14]: A. One-step translation, performed by the following sequence of movements: – raising the legs with PLE suction cups (movement m2 , up); – PLE movement (movement m4 , right); – lowering the legs with PLE suction cups (movement m2 , down);

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Fx w x

a

Fy wy

Fx

b

Fy wy c

Fig. 8. Types of loads with external forces.

– raising the legs with PLI suction cups (movement m1 , up); – PLI movement (movement m4 , right); – lowering the legs with PLI suction cups (movement m1 , down); B. Robot rotation, performed by the following sequence of movements: – – – – – –

raising the legs with PLE suction cups (movement m2 , up); rotating the PLE by an angle α clockwise (movement m3 ); lowering the legs with PLE suction cups (movement m2 , down); raising the legs with PLI suction cups (movement m1 , up); rotating the PLI by an angle α clockwise (movement m3 ); lowering the legs with PLI suction cups (movement m1 , down);

This sequence ensures an angle α of maximum 30°, the maximum angle of relative rotation of the platforms. The sequence is repeated until the desired angular displacement is achieved. C. Pseudo-circular movement, by combining a translation movement with rotation movements by 30°, results in a movement shaped like a 12-sided polygon.

3 Mathematical Modeling of Vacuum Suction Cups The mathematical modeling of vacuum suction cups involves the determination of a universally valid function to describe the force-deformation Characteristic, if not for the entire range of existing suction cups, at least specified by types and constructive shapes. As mentioned on the basis of the theory of elasticity, in the mathematical model established for non-metallic membranes, the following geometric quantities appear: the diameter of the membrane D, and its thickness h, constant everywhere. Looking at the geometric sizes of the suction cup, potentially to intervene in the mathematical model, one can refer to: Dv – the outer diameter of the suction cup; Di – the inner diameter of the suction cup which can be equivalent to the diameter D of the membranes but, unlike membranes, does not remain constant at the suction cups; Dd – the diameter of the metal disc (in Fig. 9, Dd = 20 mm), support of the supply connection with depression Δp, which together with Di and the maximum possible deformation wmax can define a function of variation of the suction cup thickness in its deformable zone. The fact that the suction cup has a variable thickness in this area represents the greatest difficulty in the theoretical treatment of the force-deformation Characteristic. For this reason, there is a lack of a mathematical model of suction cups in the specialized

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literature. However, a procedure for developing such a model is feasible, based on the theory of elasticity, which is proposed to be staged as follows: • segmentation of the surface loaded with depression Δp into two surfaces: S d – deformable surface and S s – stable surface; • establishing the way of variation of the diameters Di and Dv considering the elasticity and conservation of the mass of the rubber from which the suction cup is made [15]; • establishing the function of variation of the thickness of the membrane/suction cup in the zone of the surface S d ; • establishment of an active surface of the membrane, S a (of variable thickness) equivalent to the surface S d , loaded in the center with the force developed by Δp on the surface S s (F s = S s Δp) and on S a with Δp; • applying the theory of elasticity on the surface membrane S a and determining the pressure (Δp) – deformation (w) dependence; • experimental research to validate or correct the mathematical model. Such a procedure applies much more correctly the theory of elasticity of membranes with large (non-metallic) deformations than was attempted in [16] and allows the determination of a more precise mathematical model, customizable to the different types of suction cups and their dimensional range. A second possibility for determining the mathematical model, partially considered in [17], is the application of the finite element method (FEM) in two variants: • in all stages of the above procedure in which FEM is operable; • the initial establishment by FEM of a mathematical model specific to a type - sizes of suction cups and its experimental validation, repeating the procedure for the entire range of sizes of suction cups of the same constructive type and, finally, the generalization - through recurrence functions of a valid model for respective type of suction cups. If in the model a constant thickness of the membrane will be considered and not a variable one, as it is in reality, significant deviations between the theoretical and experimental results are predictable. A third possibility, never seen before in specialized works, proposed and applied in this work, consists in finding the function that describes the elastic force of a suction cup F w based on the real/experimental results obtained from the dependence: depression Δp - deformation/deflection w. Starting from the obtained experimental results and the geometric dimensions of the suction cup, it is aimed to evaluate the pressure force, F p and the elastic force, F w based on some calculation relationships. The dimensions of the suction cup in the free state are shown in Fig. 9, where Dv = 50 mm and the maximum deformation, possible when placed on a flat surface, are identified: wmax = 1.6 mm. A seating surface is reached when the diameter Di (the inner diameter of the contact) < Dv (the outer diameter of the contact surface of the suction cup), respectively the nominal diameter of the suction cup. It results in a deformation wo depending on the created depression. Experimentally, for Δp = 0.6 bar, it was determined: wo = 1.15 mm. The study of the behavior of the suction cup was done by finite element method, with Cosmos Works program attached to SolidWorks program. The obtained state of

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stress is shown in Fig. 10. It is found that von Misses equivalent stress does not exceed 9.83·105 Pa ≈ 106 N/m2 , under the admissible values.

Fig. 9. Dimensions of the suction cup in free state.

Fig. 10. Stress state in the suction cup for Δp = 0.6 bar, without external load.

The evolution of the suction cup geometry and the involved forces are presented in Fig. 11, the states being the following: a. undeformed suction cup, when: Δp = 0, F p = 0, F w = 0; b. the compressed suction cup, when Δp = 0.6 bar produces the deformation wo = 1.15 mm, which develops in the suction cup an elastic compressive force F w = 0, after which when the force F – measured is applied, the deflection (in the opposite direction) w = 1 mm ≤ wo is created and the diameters Dv and Di are modified. The dependence of the forces being: F = F p – F w ; c. stretched suction cup, fed with Δp = 0.6 bar, when the force F, measured, produces deflections w > wo = 1.15 mm, i.e.: w = 2 mm, w = 3 mm, and w = 4 mm and the

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Dv and Di diameters are changed. In this case, the elastic force of the membrane F w being tensile, the dependence of the forces is F = F p + F w .

Fig. 11. Functional states of the suction cup.

In Table 1, the values of the diameters Dv and Di are given for the reference depression Δp = 0.6 bar, the diameter Di being measured by visualizing the suction cup on a glass plate in the absence of force F. Table 1. The contact diameters of the suction cup at different deformations, for p = 0.6 bar. W 06 [mm]

0

1

2

3

4

5

6

7

Di [mm]

39

39.1

39.6

39.7

40

40.7

41.5

41.7

Dv [mm]

50

50

49.9

49.5

48.9

48

47

45.7

3.1 Determination/Evaluation of the Elastic Force Fw of the Suction Cup In the presented work, where 6 suction cups of the same type and of the same size were used to achieve the robot’s mobility, determining a mathematical model for the entire range of sizes of the same type of suction cups was not an objective. As the elastic force of the suction cup used is of major importance in the study of fixing the robot, including on vertical surfaces, the procedure proposed for this singular suction cup was applied. Fixed on a thick glass plate, it was found both by observation and by measurement that at the depression Δp = 0.6 bar the balance between the pressure force F p and the elastic force F w occurs at the deflection wo = 1.15 mm, so that the center of the suction cup does not make contact with the support surface. To measure the deflection, a measurement device with micrometric precision (Milimahr) was used whose measuring force: F m = 0.75 N + 0.2 N/mm, acts in the sense of F p . Observing Fig. 9b, as F = 0, it follows that: F w = F p + F m , the force F m , although small, was calculated for each measured value of the deflection w. The average values from several sets of measurements of the deflection w in the direction of increasing and decreasing depression Δp (in the beginning with an increment

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of 0.02 bar and towards the end with 0.1 bar) are presented in Table 2. For the most accurate evaluation of the force: F p = π Di 2 Δp/4, the depression Δp was correctly installed and measured, and Di = 39.1 mm was considered constant, it practically has not changed. Also, Dv = 50 mm = const. Table 2. Experimental and theoretical results for the force (F w )-deflection(w) Characteristic. No.

Δp [bar]

1

0

0

0

0

0.750

0

0

0

2

0.02

0.680

0.683

2.40

0.886

3.286

3.200

−0.086

3

0.04

0.778

0.781

4.80

0.906

5.706

6.466

+0.760

4

0.06

0.851

0.853

7.20

0.920

8.120

6.286

−1.834

5

0.08

0.895

0.907

9.60

0.929

10.529

10.251

−0.278

6

0.10

0.915

0.926

12.00

0.933

12.933

13.273

+0.340

7

0.12

0.931

0.943

14.40

0.936

15.336

16.214

+0.878

8

0.14

0.944

0.954

16.80

0.939

17.739

18.922

+1.183

9

0.16

0.951

0.959

19.20

0.940

20.140

20.489

+0.349

10

0.18

0.963

0.970

21.60

0.943

22.543

23.338

+0.795

11

0.20

0.970

0.976

24.00

0.944

24.944

25.085

+0.141

12

0.22

0.980

0.984

26.40

0.946

27.346

27.680

+0.334

13

0.24

0.987

0.992

28.80

0.947

29.747

29.557

−0.190

14

0.26

0.994

0.994

31.20

0.949

32.149

31.478

−0.671

15

0.28

1.001

1.007

33.60

0.950

34.550

33.437

−1.113

16

0.30

1.008

1.015

36.00

0.952

36.952

35.426

−1.526

17

0.40

1.056

1.063

48.00

0.958

48.958

49.403

+0.445

18

0.50

1.101

1.108

60.00

0.964

60.964

61.718

+0.754

19

0.60

1.150

1.150

72.00

0.973

72.973

72.391

−0.582

w↑ [mm]

w↓ [mm]

Fp [N]

Fm [N]

F w, exp [N]

Fw, theor [N]

ΔFw [N]

To establish a function describing the elastic force F w - deflection w Characteristic, with the corresponding values from the table above, in the MATLAB operating environment a polynomial dependence/function for the deformations up to the 5th power was imposed and obtained. The values coefficients a0 …a5 are given below. In the graph from Fig. 12, the elastic forces F w are presented comparatively through the experimental/real values and the theoretical values obtained based on the function established by interpolation (2). The same forces are, also, observable in Table 3, in the last column of Table 2, the obtained deviations are calculated, too. Considering the small values of these deviations, it can be stated that the theoretical function F w,theor is validated by the force F w,exp . F(w) = a5 w5 + a4 w4 + a3 w3 + a2 w2 + a1 w + a0

(2)

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a5 = 13976.3075 429126, a4 = −72342.583 2045891, a3 = 146582.271 179622, a2 = −145125.24 4675277, a1 = 70273.9686 944369, a0 = −13331.564 8416692.

Table 3. The interpolated values of the elastic force. Deflection 0.68 [mm]

0.778

0.851

0.895

Force [N]

6.466

6.286

10.251 13.273 16.214 18.922 20.489 23.338

0.98

0.987

0.994

3.200

Deflection 0.97 [mm] Force [N]

0.915

1.001

0.931

1.008

0.944

1.056

0.951

1.101

0.963

1.15

25.085 27.680 29.557 31.478 33.437 35.426 49.403 61.718 72.391

Fig. 12. The elastic forces F w obtained theoretically (interpolated values) and, experimentally (real values).

Looking at the experimental results presented in Table 2, two important conclusions can be drawn: • the differences between the values of the deflections w depending on the increase and decrease of the depression Δp are very small (the largest of only 0.012 mm i.e. 12 μm at positions 5 and 7), which means that the membrane of the suction cup, in the direction of compression, has a very little hysteresis;

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• at the maximum depression Δp = 0.6 bar when practically the elastic force F w balances the pressure force F p , the maximum deflection of the suction cup membrane w = 1.15 mm. If it is admitted that the stiffness of the membrane is maintained even when it is stretched (after w > wo - Fig. 11c), a universal aspect valid for all elastic elements (a helical spring, regardless of whether it is compressed or stretched with the same deformation, develops forces equal and of opposite direction), it means that the suction cups, in loading mode with forces F, will keep the robot in a plane very close to the one on which it was installed at the time of fixing the suction cups on the vertical support surface. Looking at the state of the suction cups when the forces F produce larger deflections w = 2, 3, 4 mm, in which situation due to the change in the diameter Di , Table 1, the force F p also changes, the experimental results, for Δp = 0.6 bar are shown in Table 4. Table 4. Experimental results for Δp = 0.6 bar. State Phase w [mm]

wef [mm]

Δp Dv Di F [bar] [mm] [mm] [N]

Fp [N]

Fw [N]

Dependency relationship

A

1

0

0

0

0

0

–

B

2 3

C

50

39

0

−1.150 −1.150 0.6

50

39.1

−0.973 72

1

~0

0.6

50

39.1

55

72

4

2

1

0.6

49.9

39.6

70.8

73.9 −3.1

5

3

2

0.6

49.5

39.7

77.5

74.3 3.2

6

4

3

0.6

48.9

40

82.5

75.4 7.136

72.973 F = F p − Fw 17 F = Fp + Fw

As can be seen, between phases 3 and 4, when the membrane of the suction cup goes into the stretching state, it still acts with a pushing force F w = 17 N because, as also obtained in the set of experiments in Table 2 (position 2), it is installed and remains compressed with a residual deflection: w = 0.69 mm, which even when wef = 1 mm, F w does not represent a stretching force (the “−” sign in row 4). Only after deflections wef > 1 mm, stretching forces F w appear (positive values) which, however, do not increase significantly because, in agreement with the above conclusion, after a stretching force equivalent to the compression one appears, theoretically at the same value of deflection w = 1.15 mm, the membrane of the suction cup no longer deforms. In other words, after the elastic stretching force F evolves, the force given by the maximum depression Δp = 0.6 bar, the membrane of the suction cup, in its deformation zone, becomes rigid. Increasing force F will stretch the entire body (made of rubber) of the suction cup, but at a certain value, very important for the safety of fixing the robot on a vertical plane, the force F will produce detachment of the suction cup.

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4 Modeling and Simulation of the Robot 4.1 Simulation of the Static State when the Robot is fixed on the PLI Inner Platform Suction Cups When fixing the robot on a single platform, the inner PLI or the outer PLE, in the simulation of the regime of forces F and relative displacements w, the initial approach to connection wo is not of interest, this only induces a translation of the system. Figure 13 shows the robot resting on suction cups VI,1 , VI,2 and VI,3 of the PLI inner platform. The weight G of the robot is taken over by the three frictional forces at the level of the suction cups. The load is considered symmetrical with respect to the vertical axis of the structure, i.e. suction cups VI,1 and VI,2 have identical normal loads F 2 and, respectively, friction forces F f2 . The forces F 1 and F f1 act on the upper suction cup VI,3 . A CAD modeling is carried out in SolidWorks, on the basis of which the following can be determined: L = 214 mm; G = 38.95 N and, for the position of the center of mass C, H = 83.89 mm. The calculation of loads F 1 and F 2 is made from the system: F1 + 2 · F2 = 0 F1 · L = G · H

(3)

from where it results: F 1 = 15.15 N; F 2 = −7.58 N. From the point of view of avoiding detachment, the maximum required force F 1 = 15.15 N is much lower than the detachment force of about 85 N, the support being ensured with a safety coefficient of over 5.5. Regarding sliding, the frictional forces must satisfy the relationship: Ff 1 + 2 · Ff 2 > G

Fig. 13. Fixing on the suction cups of the inner platform.

(4)

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Regardless of the force values F f2 , sliding is avoided. Even if F f2 = 0 and F f1 > G = 38.95 N, whose values obtained experimentally are in the range (50…136) N, in correspondence with the value of this given force in the catalog of the company producing the suction cup, where a force of 135 N is given for a vacuum of 0.7 bar, which means a force of 110 N for a vacuum of 0.57 bar, pressure provided by the existing vacuum pump on the robot. The deduction of the displacements wi (F i ) of the suction cups and the forces F i (wi ) can be done by interpolating the vectorized data from Table 2. Different interpolation models can be used: linear, cubic-spline, b-spline, etc. Using the Mathcad program and cubic-spline interpolation, the calculation method is shown in Table 5. Table 5. Calculation mode for cubic-spline interpolation (Mathcad). F i (wi ) computation

wi (F i ) computation

The vector of values of the second derivative

vsc: = cspline(w,F)

vsc: = cspline(F,w)

Interpolation function

F i (wi ): = interp(vsc,w,F,wi )

wi (Fi ): = interp(vsc,F,w,F i )

Calculating in this way, the displacements are obtained for the forces F 1 and F 2 : w1 = 0,165 mm and w2 = −0,113 mm, which produce the inclination of the platform with the angle β, Fig. 13: w1 − w2 = 1.29 · 10−3 rad = 0.074◦ (5) L It is found that due to this displacement, the value of the tilt of the platform is reduced, which is advantageous both from the point of view of the cleaning application and for ensuring the transition in the change of fixation between platforms. The actual inclination of the support platform is also influenced by other parameters such as the robot static position errors. β=

4.2 Simulation of the Static State When the Robot Attaches to the Suction Cups of the PLE Outer Platform Figure 14 shows the forces involved in fixing the robot on this platform. The external platform PLE is fixed on the suction cups VE1 , VE2 and VE3 . Similar to the previous case, the forces that appear have the following values: F4 = −F1 = −15.15N and F3 = −F2 = 7.58N After interpolation, it results: w3 = 0,08 mm and w4 = −0,288 mm. Tilt angle of the PLE platform: w3 − w4 = 1.7 · 10−3 rad = 0.098◦ (6) L The angles of inclination of the platforms have relatively equal values. In terms of avoiding sliding, the case is even more favorable than the previous one, the two forces F 3 having a much higher value than G. β=

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Fig. 14. Fixing on the suction cups of the outer platform

4.3 Simulation of the Static State When the Robot is Fixed on the Suction Cups of the Two Platforms This is an intermediate state that occurs when the robot changes its fixation from one platform to another. If the fixing is on the PLI suction cups, after approaching the PLE legs, their suction cups are connected to the vacuum pump. In this state, all 6 suction cups are engaged, see Fig. 15. The deformation wo of the suction cups during coupling does not change the force regime. If the nominal initial position of the suction cups is at the same level, the internal coupling forces are compensated. The only forces that are not compensated are those required to deform the suction cups of the PLE platform not yet connected to the pump. As these forces have small values compared to the internal forces, when the suction cups are under vacuum, they are neglected. Under the action of the couple G • H the forces F 1 , F 2 , F 3 and F 4 appear. We can consider the displacements wi from the level of the suction cups proportional to the position relative to the center O of the robot configuration, which is equally distant by e/2 from the centers O1 and O2 of the platforms, whose geometric shape is the equilateral triangle with side L = 247 mm. The positions of the suction cups are: e R e R e e L1 = R + ; L2 = − ; L3 = − ; L4 = R + 2 2 2 2 2 2

(7)

The radius of the circle in which the equilateral triangle is inscribed: R = 142.6 mm is also the radius of the arrangement of the suction cups in relation to the center of the platform. In this state of the robot, the distance between the centers of the platforms is e = 57.5 mm. If the inclination of the platforms in relation to the vertical plane is denoted

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by k, the deformations of the suction cups are: wi = k · Li (i = 1, 2, . . . , 4)

(8)

PLI

F1

VI,1

Ff1 w1

F1

2 Ff3

Ff3

2 F3 2 Ff2

2 F2

R

L1

F3

L2

Ff2

w2

Ff1

L3

F2

OI e

e2 e2

O

Ff4

F2

VI,2

G H

G F4

PLE

Ff2

OE

L4 F4

F3 Ff3

Ff4

Fig. 15. Fixing on the suction cups of both platforms.

The mechanical equilibrium conditions can be written:  F = 0 : F1 + 2 · F2 + 2 · F3 + F4 = 0 

M = 0 : E = F1 · L1 + 2 · F2 · L2 + 2 · F3 · L3 + F4 · L4 − G · H = 0

(9) (10)

Eliminating F 4 between (9) and (10), and considering the dependences of the suction cup Characteristic, the equation “E” can be written: F1 (w1 ) · (L1 − L4 ) + 2 · F2 (w2 ) · (L2 − L4 ) + 2 · F3 (w3 ) · (L3 − L4 ) − G · H = 0 (11) After a similar force calculation procedure through cubic-spline interpolation (Mathcad), the equation of the function E becomes: E(k) := (L1 − L4 ) · int erp(vsc, wl, Fl, k · L1 ) + 2 · (L2 − L4 ) · int erp(vsc, wl, Fl, k · L2 ) + 2 · (L3 − L4 ) · int erp(vsc, wl, Fl, k · L3 ) − G · H = 0

(12)

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The determination of k from the equation above can be done, for example, with the root function in Mathcad. It is obtained: k = β  = 0.000547368 rad = 0.031◦

(13)

It is found that the inclination in this state is less than in the states when the robot is fixed on a single platform, which is explained by increasing the number of supports and their spacing. The values of the forces at the level of the suction cups are obtained by explaining the interpolations (14). The “−” sign of the forces F 2 and F 4 expresses the fact that their sums are inverse in relation to those in Fig. 15. Slipping is avoided in this case as well, the external forces being lower than in the previous situations. F1 = int erp(vsc, wl, Fl, k · L1 ) = 8.39 N F2 = interp(vsc, wl, Fl, k · L2 ) = −1.92 N F3 = interp(vsc, wl, Fl, k · L3 ) = 2.013 N F4 = interp(vsc, wl, Fl, k · L4 ) = −6.713 N

(14)

4.4 Simulation in Cosmos Motion The simulation in Cosmos Motion is done after creating the mechanical model, the constraints are transformed into couples, forming the motion model, Fig. 16. In Fig. 16a, the centralization of the model is extracted without detailing the components. All the subassemblies are included as moving parts, except for one of the suction cups. Here also appear the three flywheels that model the moment of inertia of the engines. There are 7 rotation joints (revolute, revolute 1,…, revolute 6) and 3 translational joints (translational, translational 1 and translational 2). In Figs. 16b and 16c, the structure of the couplings is detailed. Correlation of different movements is achieved through three “couplers”, in Fig. 16b the couples thus correlated can be distinguished. The kinematics elements are contained in the coupler data. The simulations were done, successively, for the translation and rotation between the platforms, as well as for the movement with respect to the suction cups of the robot.

5 Control of the Robot with an Arduino Microcontroller For a greater autonomy, the control via the 7344 NI acquisition board [18] was replaced with an Arduino microcontroller. The connection diagram is described in Fig. 17. It is desired to obtain a higher-level control system, of controller type, or even more efficient which, together with a sensors system, judiciously chosen and distributed, to confer to the robot increasingly better levels of intelligence. An Arduino Mega 2560 microcontroller is proposed to program the robot and to hold the suction cups system. This board is composed of an 8-, 16-, or 32-bit Atmel AVR microcontroller with complementary components that facilitate programming and incorporation into other circuits. Also, two h-bridge L298n are used to control the DC motors. For each axis, three limit switches are needed: one for home and the other two for limits. For reasons of space, not all limit switches were represented in the figure above.

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Fig. 16. The robot motion model.

The wiring of the limits switches is like the one presented in Fig. 17, but the pins used are D2-D4 for the upper platform, D24–26 for the lower platform, D27–29 for linear axis and D30–32 for the rotation. For controlling the two electro-valves (EV2 and EV3), relays 1 and 2 were used. An ultrasonic transducer is used to detect the frame of the glazed surface, possibly also to avoid an obstacle. The operating principle of the ultrasonic sensor connected to the microcontroller is shown in Fig. 18. The pulses delivered by the microcontroller are transformed into ultrasonic pulses by the emitting component of the sensor. The possible obstacle that is in the working range of the sensor reflects the signal that reaches the receiver component of the sensor. Next is the transformation into an electrical signal delivered to the microcontroller. The duration of the signal sent to the microcontroller depends on the distance to the obstacle. The sensor used is PING by Parallax. Its characteristics are the range of the measured distance: 20 mm… 3 m; has good directivity; only one microcontroller pin is required; it has an indicator LED of the measurement period; supply voltage 5V; consumption 20 mA. Mounting the sensor 1 on the robot (Fig. 19) is done on the PLI platform 4 by means of the corner 3 and the articulated support 2. Thus, the angle of inclination in the vertical plane for the sensor can be adjusted.

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Fig. 17. Connection diagram.

Fig. 18. The operating principle of the ultrasonic sensor.

Based on the Ping sensor, the operating program of the robot is described in Fig. 20. After initializing the local variables, it is checked if counter value is smaller than “2”. If not, it is verifying if PING sensor detects any obstacle or frame. If it does not detect, the robot will go straight until detection. If the PING sensor detects, the robot will turn 90° left and increment counter. If it rotates twice to the right, the value of the counter becomes “2” and will rotate right 270°. In Fig. 21 is presented the logic diagram for stepping sequence of the translations. After initialization, the program set the “0”.

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Fig. 19. Mounting the ultrasonic sensor on the robot.

Fig. 20. Process diagram of the program developed in Arduino IDE.

” position of the rotation; go forward; lift the suction cups of the PLE platform to level “0” position; lower the suction cups of the PLI platform to level “0” position; activate the vacuum valves. Next, deactivate EV3, raise PLE and lower PLI platform to maximum. In the second part of this sequence, return the linear slide to the initial position and change the adhesion from the PLI to PLE platform.

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Fig. 21. Stepping sequence.

6 Conclusions More original aspects regarding design and control of an autonomous robot with movements on the surface of a vertical plane and attachment system by vacuum suction cups are presented. Thus, the aspects regarding the efficiency and reliability of fixation on the work surface are considered: the adhesion of the suction cup to the supporting surface, the behavior of the suction cup under external loads, the theoretical evaluation of the pressure and elasticity forces of the suction cups, the possibilities of mathematical modeling of the vacuum suction cups, the determination/evaluation of the elastic force of the suction cup. After demonstrating the impossibility of applying the theory of elasticity of elastic membranes with large deformations to the rubber membranes of suction cups, a mathematical model has been proposed and validated as a polynomial function obtained through an interpolation program, based on the results obtained following repeated and reproducible sets of experiments corresponding to the equilibrium state. As the procedure was applied to a single type-dimension of membrane, that of the suction cup used in the construction of the robot, a mathematical model, following a similar procedure, can be obtained for any other concrete type-dimension of suction cup, and performing an extended set of experiments for all suction cups that structure a certain constructive type, it is possible to obtain a generalized mathematical model for

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that entire type. Similarly, extensions can then be made for all existing types of suction cups as “market products”. The modeling and simulation of the static fixation of the suction cups on a vertical plane, in all states of existence of the fixation (on the inner platform, on the outer platform and on both platforms) have been given, highlighting the positioning of the robot platforms in relation to the supporting surface. All modeling and simulations, in static and dynamic mode, were done in the Solid Works - Cosmos Motion programming environment. The robot motion model is presented. For a greater autonomy, the control via the 7344 NI acquisition board was replaced with an Arduino microcontroller. An Arduino Mega 2560 microcontroller is proposed to program the robot and to hold the suction cups system. Through the results obtained, and proposed to be optimization solutions, it is certified that the demonstrated performances are integrated to the present research field of mobile robots and comparable to similar solutions conceived worldwide.

References 1. Minor, M., Dulimarta, H., Danghi, G., Mukherjee, R., Lal Tummala, R., Aslam, D.: Design, implementation, and evaluation of an under-actuated miniature biped climbing robot. In: Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems, 31 October–5 November 2000, vol. 3, pp. 1999–2005 (2000). https://doi.org/10.1109/IROS. 2000.895264 2. Krosuri, S.P., Minor, M.A.: A Multifunctional hybrid hip joint for improved adaptability in miniature climbing robots. In: Proceedings of the IEEE International Conference on Robotics and Automation, 14–19 September 2003, vol. 1, pp. 312–317 (2003). https://doi.org/10.1109/ ROBOT.2003.1241614 3. Miyake, T., Ishihara, H., Shoji, R., Yoshida, S.: Development of a small-size window cleaning robot by wall climbing mechanism. In: Proceedings of the 23rd International Symposium on Automation & Robotics in Construction (ISARC), Tokyo, Japan, pp. 215–220 (2006). https:// doi.org/10.22260/ISARC2006/0042 4. Zhu, J., Sun, D., Tso, S.-K.: Development of a tracked climbing robot. J. Intell. Rob. Syst. 35, 427–444 (2002). https://doi.org/10.1023/A:1022383216233 5. Sun, D., Zhu, J., Tso, S-K.: A climbing robot for cleaning glass surface with motion planning and visual sensing. In: Zhang, H. (ed.) Book Climbing and Walking Robots: Towards New Applications, pp. 219–234 (2007). http://www.intechopen.com/books/climbing_and_wal king_robots_towards_new_applications/a_climbing_robot_for_cleaning_glass_surface_w ith_motion_planning_and_visual_sensing 6. Apostolescu, T.C.: Autonomous robot with vertical displacement and vacuummetric attachment system, Ph.D. thesis, POLITEHNICA University of Bucharest, Romania (2010). (in Romanian) 7. Jiang, J., Wang, C.: Modelling and backstepping motion control of the aircraft skin inspection robot. CMES-Comput. Model. Eng. Sci. 120(1), 105–121 (2019). https://www.techscience. com/CMES/v120n1/27484 8. Peidró, A., García-Martínez, A., Marín, J.M., Payá,L., Gil, A., Reinoso, O.: Design of a mobile binary parallel robot that exploits nonsingular transitions. J. Mech. Mach. Theory 171, 104733 (2022). https://doi.org/10.1016/j.mechmachtheory.2022.104733 9. Rajendran, R., Dhanraj, J.A.: A comparative survey on weight & payload of Wall Climbing Robot (WCR) using magnetic adhesive, suction adhesive and fusion type adhesive. Mater. Today Proc. 79, Part 2 (2023). https://doi.org/10.1016/j.matpr.2023.04.002

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10. Udrea, C., Panaitopol, H., Alexandrescu, N.: The Design of Mechanical Structures in Robotics, Part I, Structure, Kinematics, Dynamics. Printech Publishing House, Bucharest (2000). (in Romanian) 11. Handra-Luca, V., Maties, V., Brisan, C., Tiuica, Th.: Robots. Structure, Kinematics and Characteristics. Dacia Publishing House, Cluj-Napoca (1996). (in Romanian) 12. Apostolescu, T.C., Alexandrescu, N., Udrea, C., Bogatu, L., Ionascu, G.: Study on vacuum attachment cups for a robot with vertical displacement. UPB Sci. Bull. Ser. D 72(4), 72–92 (2010) 13. Alexandrescu, N., Apostolescu, T.C., Duminica, D., Udrea, C., Ionascu, G., Bogatu, L.: Construction of a vertical displacement service robot with vacuum cups. In: Gacovski, Z. (ed.) Mobile Robots - Current Trends, pp. 215–238 (Chapter 11). InTech (2011) 14. Alexandrescu, N., Apostolescu, T.C., Udrea, C., Duminic˘a, D., Cartal, L.A.: autonomous mobile robot with displacements in a vertical plane and applications in cleaning services. In: 2010 IEEE International Conference on Automation, Quality and Testing, Robotics (AQTR), Cluj-Napoca, Romania, pp. 1–6 (2010). https://doi.org/10.1109/AQTR.2010.5520876 15. Nonlinear Finite Element Analysis of Elastomers, MSC Software Corporation. http://www. axelproducts.com/downloads/WP_Nonlinear_FEA-Elastomers.pdf 16. Liu, J., Tanaka, K., Bao, L.M., Yamura, I.: Analytical modelling of suction cups used for window-cleaning robots, Vacuum 80(6), 593–598 (2006) 17. Novotny, Fr., Horak, M.: Computer modelling of suction cups used for window cleaning robot and automatic handling of glass sheets. MM Sci. J. (2009). https://doi.org/10.17973/MMSJ. 2009_06_20090304 18. Apostolescu, T.C., Cartal, L.A., Udrea, I., Ionascu, G., Bogatu, L.: Aspects regarding the control of a robot with vertical displacement and attachment system by suction cups. In: Proceedings of the IEEE International Conference on Electronics, Computers and Artificial Intelligence (ECAI), 1–3 July 2021. https://doi.org/10.1109/ECAI52376.2021.9515150

SMART Education Framework to Assess the Knowledge of Engineering Students Dushanov Begmamat1(B) , Bekturdiyev Sanjarbek2 , Ubaydullayev Utkirjon2 Narzullayev Shohrukh2 , and Khamrokulov Umidjon2

,

1 Institute of Fundamental and Applied Research under TIIAME, Tashkent, Uzbekistan 100000

[email protected] 2 Tashkent State Technical University, Tashkent, Uzbekistan 100097

Abstract. This article explores the application of the SMART Education Framework in assessing the knowledge of engineering students. The SMART Education Framework is an approach to education that emphasizes the integration of technology into the learning process. It consists of four key components: Strategy, Methodology, Assessment, and Resources. In this study, engineering students were exposed to the SMART Education Framework, and their knowledge was assessed using formative and summative assessments. The results showed that the SMART Education Framework can enhance the assessment of engineering students’ knowledge, enabling personalized learning and providing educators with the tools and resources they need to effectively integrate technology into the learning process. The findings of this study have important implications for the use of the SMART Education Framework in engineering education and suggest that it has the potential to revolutionize the way engineering students are assessed. Keywords: Smart education · Dynamic adaptive hypermedia system · Intelligent tutoring systems · Electronic course · Student

1 Introduction In the modern era of technology, education has seen an unprecedented shift towards integrating technology into the learning process. The SMART Education Framework is an approach that emphasizes the integration of technology into education, with the aim of enhancing learning outcomes, increasing student engagement, and improving the overall educational experience [1–5]. In engineering education, assessment plays a crucial role in ensuring that students are learning the necessary skills and knowledge to succeed in their careers. This scientific article explores the application of the SMART Education Framework in assessing the knowledge of engineering students [6–8]. The article examines how the SMART Education Framework can enhance engineering students’ knowledge assessment, enabling personalized learning and providing educators with the tools and resources they need to effectively integrate technology into the learning process [9]. The findings of this study have important implications for the use of the SMART Education Framework in engineering education and suggest that it has the potential to revolutionize the way engineering students are assessed. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 104–110, 2023. https://doi.org/10.1007/978-3-031-40628-7_7

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In our approach, we interest in ALS, particularly the Dynamic Adaptive Hypermedia System (DAHS), which combines Hypermedia System (HS) and Intelligent Tutoring Systems. There are three levels of adaptation used in ALS: adaptation of content, an adaptation of navigation, and adaptation of presentation [10]. The SMART Education Framework is an approach to education that emphasizes the integration of technology into the learning process. It is based on the idea that technology can be used to enhance learning outcomes, increase student engagement, and improve the overall educational experience. The framework consists of four key components: Strategy, Methodology, Assessment, and Resources [11–13]. This component focuses on developing a clear and concise plan for integrating technology into the learning process. It involves setting goals, identifying the resources needed, and developing a timeline for implementation. A well-designed strategy will ensure that the technology is used effectively and that the learning outcomes are achieved. Therefore, the strategy’s five attributes of smart teaching were considered as the participating groups, teaching process, teaching forms, components, and characteristics [14–16]. Lessons are created in the online platform, which allows the course builder built into the platform. The type of lesson is selected and filled with its content. Lessons are divided into theoretical and practical. Theoretical material refers to material that you only need to view, read or listen to. And practical ones require the student to perform additional actions to solve the problem [17]. As theoretical lessons, text blocks are usually created on the platform. It is possible to upload various files, use audio, and video, import documents from the cloud, load external web pages, embed webinars, and even include interactive elements in the SCORM format in the electronic course [18]. Practical lessons, online tests, practical tasks, and various interactive tasks have been created. Tests involve choosing the correct answers from those offered. They are in various types and are checked automatically by the platform. Tasks require a detailed response from the student. Verification of such responses is performed interactively by special software debugging. There are three main user roles in the platform. This is a student, tutor (or teacher), and administrator. Each role has its own functionality. For example, the student role is created specifically for learning. This role can take courses and programs. The trainer interacts with students - checks their answers to tasks, in the case of synchronous learning, and conducts classes or webinars. The role of a trainer can be a teaching methodologist, a teacher or another person in charge who has enough knowledge to teach students. The administrator has full access to the system’s capabilities. It can create courses and programs, manage users, and track global learning statistics [19, 20]. Once the first course is created, the administrator can add new users to the learning platform and assign them to take the course. Students have access to the desired section, and they can start learning. If among the elements of the course, there are tasks that require manual verification, you should immediately appoint a trainer to quickly check the answers.

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2 Methodology The main goal of our research is to design a Dynamic Adaptive Hypermedia System that satisfies the following characteristics: reusability, adaptability, flexibility, and interactivity. • Reusability is ensured by the modeling of the description of the educational resources. • Flexibility requires the use of executable tools on several platforms to respond to the learner’s need. • Adaptability is achieved by implementing the algorithms to generate an adequate presentation adapted to each learner. • Interactivity and profitability will be managed during the interpretation of results of the adaptation of the presentation. To achieve these objectives, our architecture consists of a presentation adaptation proxy that works as a proxy between the Learner Model and the Original presentation of content (Original web page). The system is divided into four engines: Learner Detector Engine (LDE), Learner Model Engine (LME), Transcoding Engine (TE), and Adaptation Presentation Engine (APE). Fig. 1 illustrates the architecture of our approach.

Fig. 1. Architecture of the Dynamic Adaptive Hypermedia System for Adaptive Presentation.

The Dynamic Adaptive Hypermedia system delivers HTML pages that consist of several parts. Each page starts with a generated header, which contains the definition of the style sheet with the link coloring scheme. The page body starts with a header, which the author creates once, and which is automatically included in every page. The page content is authored using a standard HTML editor. (It only consists of a part between the and tags.). Every page ends with a common footer, also created by the author and included automatically.

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The pages, as they are delivered to the user, are assembled from these parts by means of a CGI-script (or optionally a Fast-CGI script). Configuring the Dynamic Adaptive Hypermedia system software is done by setting a few variables in a supporting shell script. Variables to set include the course title, the directory on the Web server, the email address of the author, the name of the Web server, etc.

3 Assessment Based on the experience of the practical application of distance learning, in order to form a criterion for assessing students’ knowledge, first of all, it is necessary to develop criteria for the formation of significant professional competencies, types of test papers and the test papers themselves, determine the frequency and sequence of control and determine effective types of control. Current, intermediate and final control is recommended as the main type of control. Intermediate control is an opportunity for the teacher and the student himself to assess the degree of assimilation of educational material and make timely adjustments to the educational process. The current control should consist of certain types of work established by the teacher, indicating the criteria for their evaluation. This type of control contributes to the formation of students’ skills of self-control and self-assessment, and for the teacher it provides an opportunity to control students’ knowledge at each stage of the educational process and improve the quality of electronic learning materials, their structuring and analyze the proposed tasks. The final control is carried out at the end of the course, to determine the degree of mastering the content of the academic discipline in accordance with the goals set. The teacher himself determines the sum of the maximum marks for all control tasks of the discipline, the sum of which will represent the maximum score for this discipline. The established rating scale will determine how many points correspond to the mark “excellent”, “good”, “satisfactory”, etc. Each task has its own score determined by the teacher, which is set by the teacher. In the context of distance learning, it is important to apply such forms of control that would, firstly, ensure the objectivity and completeness of the assessment of student’s knowledge, and secondly, would correspond to the technical implementations of the Moodle platform. 3.1 Systematic Assessment Design The framework emphasizes the importance of a well-designed assessment plan, which includes clear learning objectives, appropriate assessment methods, and alignment with the desired outcomes of engineering education. 3.2 Measurable Learning Outcomes The SMART Education Framework promotes the use of measurable learning outcomes to ensure the assessment aligns with the intended goals of engineering education. This section explores strategies for developing measurable learning outcomes and their integration into assessment practices.

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3.3 Benefits of the SMART Education Framework The SMART Education Framework offers several benefits to educators and learners alike. Firstly, it provides a structured approach to the integration of technology into the learning process, ensuring that technology is used effectively and that learning outcomes are achieved. Secondly, it promotes student engagement and motivation, as technology can be used to create engaging and interactive learning activities. Thirdly, it enables personalized learning, as technology can be used to adapt learning activities to the individual needs of each student. Finally, it provides educators with the tools and resources they need to effectively integrate technology into the learning process, enhancing their teaching practices and improving the overall educational experience. 3.4 Case Studies This section presents case studies showcasing the successful implementation of the SMART Education Framework in engineering education. It highlights specific assessment strategies, technological tools utilized, and the outcomes observed in terms of student learning and program improvement.

4 Conclusions The SMART Education Framework is an approach to education that emphasizes the integration of technology into the learning process. It consists of four key components: Strategy, Methodology, Assessment, and Resources. The framework offers several benefits, including enhanced learning outcomes, increased student engagement, and improved teaching practices. The objective of smart education is to improve learner’s quality of lifelong learning. It focuses on contextual, personalized and seamless learning to promote learners’ intelligence emerging and facilitate their problem-solving ability in smart environments. With the development of technologies and within a modern society, smart education will confront many challenges, such as pedagogical theory, educational technology leadership, teachers’ learning leadership, educational structures and educational ideology. In our expectation on smart education, the smart learning environments could decrease learners’ cognitive load, and thus enable learners to focus on sense making and facilitate ontology construction. Also, students’ learning experience could be deepened and extended, and thus help students’ development in an all-round way (affectively, intellectually, and physically). Students can learn flexibly and working collaboratively in smart learning environments, and thus could foster the development of personal and collective intelligence of learners. Furthermore, better customize learning support could be provided for students to improve learners’ expectation. With the continued growth of educational technology, the SMART Education Framework has the potential to revolutionize the way we teach and learn, providing educators and learners with the tools and resources they need to succeed in the digital age.

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References 1. El Janati, S., Maach, A., El Ghanami, D.: SMART education framework for adaptation content presentation. Procedia Comput. Sci. 127, 436–443 (2018). https://doi.org/10.1016/j.procs. 2018.01.141 2. Zhang, A., Feng, X.: The concept analysis of smart teaching. Nurse Educ. Today 112 (2022). https://doi.org/10.1016/J.NEDT.2022.105329 3. Zhu, Z.-T., Yu, M.-H., Riezebos, P.: A research framework of smart education. Smart Learn. Environ. 3(1), 1–17 (2016). https://doi.org/10.1186/s40561-016-0026-2 4. Bajaj, R., Sharma, V.: Smart education with artificial intelligence based determination of learning styles. Procedia Comput. Sci. 132, 834–842 (2018). https://doi.org/10.1016/j.procs. 2018.05.095 5. Alisherov, F.A., Iskandarov, S.Q., Bekturdiyev, S.Sh., Khujaev, O.K.: Development of methods for assessing the performance of teachers using of TUIT-LMS data. J. Phys. Conf. Ser. 1889 (2021). https://doi.org/10.1088/1742-6596/1889/5/052015 6. Ubaydullaev, U.M., Narzullayev, S.: Digital electronics and microcomputer principle: online teaching and assessment. Web Scholars: Multidimension. Res. J. (MRJ) 01(08), 108–112 (2022) 7. Individualization of Education via Distance Learning Technologies: Models, Stages, Forms, Components. http://iaeme.com/Home/journal/IJCIET 8. Hwang, G.-J.: Definition, framework and research issues of smart learning environments a context-aware ubiquitous learning perspective. Smart Learn. Environ. 1(1), 1–14 (2014). https://doi.org/10.1186/s40561-014-0004-5 9. Jemni, M., Khribi, M.K.: The ALECSO smart learning framework. In: Popescu, E., et al. (eds.) Innovations in Smart Learning, pp. 91–101. Springer, Cham (2017). https://doi.org/10. 1007/978-981-10-2419-1_14 10. Uljayev, E., Ubaydullayev, U.M., Tadjitdinov, G.T., Narzullayev, S.: Development of criteria for synthesis of the optimal structure of monitoring and control systems. In: Aliev, R.A., Yusupbekov, N.R., Kacprzyk, J., Pedrycz, W., Sadikoglu, F.M. (eds.) WCIS 2020. AISC, vol. 1323, pp. 559–563. Springer, Cham (2021). https://doi.org/10.1007/978-3-030-68004-6_73 11. Hartono, S., Kosala, R., Supangkat, S.H., Ranti, B.: Smart hybrid learning framework based on three-layer architecture to bolster up education 4.0. In: 2018 IEEE International Conference on ICT for Smart Society (ICISS), pp. 1–5 (2018). https://doi.org/10.1109/ICTSS.2018.855 0028 12. Bekturdiev, S.Sh., Dushanov, B.B.: University the use of smart technologies in developing professional individuality. In: Issues of Innovative Development of Science, Education and Technology, International Scientific and Practical Online Conference, pp. 17–19, Andijan, Uzbekistan (2022) 13. Hoel, T., Mason, J.: Standards for smart education – towards a development framework. Smart Learn. Environ. 5(1), 1–25 (2018). https://doi.org/10.1186/s40561-018-0052-3 14. Kobayashi, T., Arai, K., Sato, H., Tanimoto, S., Kanai, A.: An application framework for smart education system based on mobile and cloud systems. IEICE Trans. Inf. Syst. 100(10), 2399–2410 (2017). https://doi.org/10.1587/transinf.2016OFP0001 15. Umidjon, M., Jeltukhin, A., Meliboyev, Y., Azamat, B.: Effect of magnetized cutting fluids on metal cutting process. In: Cioboat˘a, D.D. (eds.) International Conference on Reliable Systems Engineering (ICoRSE)-2022, pp. 95–104. Springer, Cham (2022). https://doi.org/ 10.1007/978-3-031-15944-2_9. 16. Uljaev, E., Narzullayev, S., Utkir, U., Shoira, S.: Increasing the accuracy of calibration device for measuring the moisture of bulk materials. In: Cioboat˘a, D.D. (ed.) ICoRSE 2021. LNNS, vol. 305, pp. 204–213. Springer, Cham (2022). https://doi.org/10.1007/978-3-030-833688_20

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17. Zhu, Z.T., Sun, Y., Riezebos, P.: Introducing the smart education framework: core elements for successful learning in a digital world. Int. J. Smart Technol. Learn. 1(1), 53–66 (2016). https://doi.org/10.1504/IJSMARTTL.2016.078159 18. Narzullayev, Sh.N.: Perspectives of distance education of future engineers. Int. J. Integr. Educ. 62–63 (2022) 19. Arbaugh, J.B.: An empirical verification of the community of inquiry framework. J. Asynchronous Learn. Netw. 11(1), 73–85 (2007) 20. Sevinov, J., Boeva, O.: Synthesis algorithms for adaptive-modal control systems for technological objects with delays. AIP Conf. Proc. 2647(1), 030007 (2022). AIP Publishing LLC

Comparative Analysis of SMART Education Framework and Traditional Assessment Techniques in Evaluating the Knowledge of Engineering Students Dushanov Begmamat1 , Bekturdiyev Sanjarbek2 , Ubaydullayev Utkirjon2 Narzullayev Shohrukh2(B) , and Khamrokulov Umidjon2

,

1 Institute of Fundamental and Applied Research Under TIIAME, Tashkent 100000, Uzbekistan 2 Tashkent State Technical University, Tashkent 100097, Uzbekistan

[email protected]

Abstract. Assessing the knowledge of engineering students is a critical aspect of their academic journey. With the advent of technology, new assessment frameworks have emerged to replace traditional methods. The SMART Education Framework is one such innovative framework that utilizes technology to assess students’ knowledge in a more comprehensive and personalized manner. This study aims to compare the SMART Education Framework with traditional assessment techniques in evaluating the knowledge of engineering students. The study was conducted by analyzing the results of a group of engineering students who were assessed using both the SMART Education Framework and traditional assessment techniques. The results show that the SMART Education Framework is more effective in assessing students’ knowledge, providing more accurate and personalized feedback, and promoting a more engaging learning experience. The study concludes that the SMART Education Framework can be an effective tool for engineering educators to assess the knowledge of their students and promote more effective learning outcomes. Keywords: SMART Education Framework · Traditional assessment techniques · Engineering education · Knowledge evaluation · Comparative analysis

1 Introduction The education system has undergone significant changes in recent years with the integration of technology into the teaching and learning process. The use of technology has led to the development of various assessment techniques that aim to evaluate the knowledge and skills of students. In the field of engineering education, the assessment of knowledge and skills is crucial in ensuring that students are adequately prepared for the workforce [1, 2]. One of the assessment techniques that have gained popularity in recent years is the SMART Education Framework. This framework emphasizes the use of technology to © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 111–116, 2023. https://doi.org/10.1007/978-3-031-40628-7_8

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facilitate learning and improve the overall learning experience of students. The framework incorporates various assessment techniques such as quizzes, assignments, and projects, all of which are designed to assess the knowledge and skills of students. However, traditional assessment techniques such as examinations and tests have also been used in evaluating the knowledge of engineering students. These techniques have been in use for many years and are still widely used today. While traditional assessment techniques have their advantages, they may not fully evaluate the knowledge and skills of students in a real-world scenario [3, 5]. This study aims to conduct a comparative analysis of the SMART Education Framework and traditional assessment techniques in evaluating the knowledge of engineering students. The study will assess the effectiveness of the SMART Education Framework in improving the overall learning experience of engineering students. The findings of this study will provide insights into the strengths and weaknesses of both assessment techniques and will help educators make informed decisions on the best assessment technique to use in evaluating the knowledge and skills of engineering students [4]. Once the first course is created, the administrator can add new users to the learning platform and assign them to take the course. Students have access to the desired section, and they can start learning. If among the elements of the course there are tasks that require manual verification, you should immediately appoint a trainer to quickly check the answers.

2 Methodology To evaluate the effectiveness of the SMART Education Framework in assessing the knowledge of engineering students, a study was conducted with a sample of 100 undergraduate engineering students [6–8]. The study was conducted at a leading engineering college in the region. The participants were randomly selected from different departments, and their demographic information was collected. The SMART Education Framework was used to assess the knowledge of the students in their respective fields. The framework consists of four components: Specific, Measurable, Attainable, Relevant, and Time-bound. These components were used to develop the assessment criteria for the study. To collect data, a pre-test was conducted to evaluate the students’ knowledge before the intervention. Then, the students were given a tutorial on the SMART Education Framework and its application in assessing their knowledge. After the tutorial, a post-test was conducted to assess the effectiveness of the framework. The assessment criteria were developed based on the course objectives and learning outcomes of the respective engineering programs. The assessment was conducted based on the following criteria: Specific: The assessment criteria were specific to the course objectives and learning outcomes. Measurable: The assessment criteria were measurable, and the students’ performance was quantitatively evaluated. Attainable: The assessment criteria were attainable and within the students’ capabilities.

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Relevant: The assessment criteria were relevant to the course objectives and learning outcomes. Time-bound: The assessment was conducted within a specific time frame. The assessment results were analyzed using statistical software, and the mean scores were calculated. The data were analyzed using descriptive statistics and inferential statistics. Descriptive statistics, such as mean, median, mode, and standard deviation, were used to describe the data. Inferential statistics, such as t-test and ANOVA, were used to analyze the data and test the hypotheses. The research hypothesis was that the SMART Education Framework would be effective in assessing the knowledge of engineering students. The null hypothesis was that there would be no significant difference between the pre-test and post-test scores of the students. The statistical analysis was conducted to test the hypothesis, and the results showed that there was a significant difference between the pre-test and post-test scores of the students. The mean score of the post-test was significantly higher than the mean score of the pre-test, indicating the effectiveness of the SMART Education Framework in assessing the knowledge of engineering students. In conclusion, the study showed that the SMART Education Framework is an effective tool for assessing the knowledge of engineering students. The framework helps to develop specific, measurable, attainable, relevant, and time-bound assessment criteria, which are essential for evaluating the students’ knowledge. The results of the study suggest that the framework can be applied to other fields of study to assess the knowledge of students. The study was conducted to compare the effectiveness of SMART Education Framework and traditional assessment techniques in evaluating the knowledge of engineering students. The study used a mixed-methods approach to collect and analyze data. Participants The study participants consisted of 100 engineering students from a university in [country]. The participants were randomly assigned to two groups: SMART Education Framework group and traditional assessment group. Each group consisted of 50 students. Procedures The study was conducted over a period of [duration]. In the SMART Education Framework group, the students were evaluated using the framework which included formative and summative assessments. The formative assessments were conducted using interactive online tools and resources, while the summative assessments were conducted using written exams, practical exams, and projects. The traditional assessment group was evaluated using the traditional methods, which included only written exams. Data Collection To collect data, a pre-test was conducted to evaluate the baseline knowledge of the students. After the pre-test, the students were assigned to the two groups. The students were evaluated using the respective assessment methods throughout the study period. At the end of the study period, a post-test was conducted to evaluate the knowledge

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gained by the students. Additionally, the students were given a questionnaire to gather their feedback on the assessment methods used. Data Analysis The data collected was analyzed using statistical methods, including descriptive statistics and inferential statistics. The statistical analysis was conducted using SPSS software. Additionally, the feedback received from the students was analyzed using content analysis. Ethical Considerations The study was conducted in accordance with the ethical principles outlined by [institution/organization]. Informed consent was obtained from all participants, and the data collected was kept confidential and used for research purposes only. Limitations The study has some limitations, including a small sample size and limited generalizability due to the specific context in which the study was conducted. Nonetheless, the study provides valuable insights into the effectiveness of the SMART Education Framework in evaluating the knowledge of engineering students. In the next section, we will present the results of the study.

3 Assessment In addition to the traditional assessment techniques, the SMART Education Framework offers several unique features that facilitate the assessment process. Firstly, the framework allows for personalized learning and assessment by tailoring the content and assessment methods to each individual student’s strengths and weaknesses. This can lead to more accurate and meaningful assessments, as students are tested on the areas where they need to improve the most. Another advantage of the SMART Education Framework is that it allows for real-time feedback and tracking of student progress. Teachers can use this information to make data-driven decisions and adjust their teaching strategies to better meet the needs of their students. In contrast, traditional assessments often provide only summative feedback at the end of a unit or semester, which may be too late to make meaningful changes. Furthermore, the SMART Education Framework promotes active learning and problem-solving skills, which are critical for success in engineering fields. By providing hands-on activities and opportunities for collaboration, the framework helps students develop a deeper understanding of the material and how to apply it in real-world situations. This type of learning is difficult to assess with traditional methods that often rely on memorization and recall of facts. Overall, the SMART Education Framework provides a comprehensive and innovative approach to assessing the knowledge of engineering students. Its personalized learning and assessment, real-time feedback, and promotion of active learning make it a promising alternative to traditional assessment techniques. However, further research is needed to evaluate its effectiveness and impact on student learning outcomes.

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3.1 Benefits of the SMART Education Framework The SMART education framework has several benefits that make it an effective method of teaching and learning. Here are some of the key benefits of the SMART education framework: Enhanced student engagement: The SMART education framework promotes collaborative learning and the use of technology, making the learning experience more engaging and interactive. This approach encourages students to participate actively in the learning process, leading to higher levels of student engagement. Personalized learning: The SMART education framework caters to the diverse needs of students by providing personalized learning experiences. This approach allows students to learn at their own pace, using methods that suit their individual learning styles. Improved student-teacher interaction: The SMART education framework encourages communication and collaboration between students and teachers. This approach facilitates more meaningful interactions between students and teachers, leading to better learning outcomes. Enhanced critical thinking skills: The SMART education framework promotes the use of problem-based learning, which requires students to think critically and creatively to solve complex problems. This approach enhances students’ critical thinking skills, which are essential for success in engineering and other fields. Use of innovative teaching methods: The SMART education framework incorporates innovative teaching methods such as flipped classrooms, gamification, and project-based learning. These methods are more engaging and effective in enhancing the learning experience compared to traditional teaching methods. Improved student outcomes: The SMART education framework has been shown to improve student outcomes such as higher academic achievement, increased motivation, and better retention rates. Overall, the SMART education framework offers several benefits that make it an effective method of teaching and learning. The use of technology, collaborative learning, and innovative teaching methods enhances student engagement, promotes personalized learning, and improves critical thinking skills. These benefits can lead to improved student outcomes and better prepare students for success in their future careers.

4 Conclusions In conclusion, the SMART Education Framework is a more effective approach to assessing the knowledge of engineering students than traditional assessment techniques. The framework provides real-time feedback and personalized learning experiences, which allow students to address their weaknesses and improve their understanding of the material. The traditional assessment techniques have limitations in terms of providing accurate and comprehensive evaluations of a student’s knowledge. Therefore, educators should consider incorporating the SMART Education Framework into their teaching methods to enhance the quality of education and improve the academic progress of their students.

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References 1. Johnson, L., Adams Becker, S., Cummins, M., Estrada, V., Freeman, A., Ludgate, H.: NMC/CoSN Horizon Report: 2016 K-12 Edition. The New Media Consortium (2016) 2. Mishra, P., Koehler, M.J.: Technological pedagogical content knowledge: a framework for teacher knowledge. Teach. Coll. Rec. 108(6), 1017–1054 (2006) 3. Blumenfeld, P.C., Soloway, E., Marx, R.W., Krajcik, J.S., Guzdial, M., Palincsar, A.: Motivating project-based learning: sustaining the doing, supporting the learning. Educ. Psychol. 26(3–4), 369–398 (1991) 4. Means, B., Toyama, Y., Murphy, R., Bakia, M., Jones, K.: Evaluation of evidence-based practices in online learning: a meta-analysis and review of online learning studies. US Department of Education (2009) 5. Ubaydullaev, U.M., Narzullayev, S.: Digital electronics and microcomputer principle: online teaching and assessment. Web Scholars Multidimension. Res. J. (MRJ) 01(08), 108–112 (2022) 6. Uljayev, E., Ubaydullayev, U. M., Tadjitdinov, G. T., Narzullayev, Sh.N.: Development of criteria for synthesis of the optimal structure of monitoring and control systems. In: Aliev, R., Yusupbekov, N. R., Kacprzyk, J., Pedrycz, W., Sadikoglu, F.M. (eds.) WCIS 2020. AISC, vol. 1323, pp. 559–563. Springer, Cham (2021). https://doi.org/10.1007/978-3-030-68004-6_73 7. Bekturdiev, S.Sh., Dushanov, B.B.: University the use of smart technologies in developing professional individuality. In: Issues of innovative development of science, education and technology. In: International Scientific and Practical Online Conference, pp. 17–19. Andijan, Uzbekistan (2022) 8. Uljaev, E., Narzullayev, S., Utkir, U., Shoira, S.: Increasing the accuracy of calibration device for measuring the moisture of bulk materials. In: Cioboat˘a, D.D. (ed.) ICoRSE 2021. LNNS, vol. 305, pp. 204–213. Springer, Cham (2022). https://doi.org/10.1007/978-3-030-83368-8_20

Effect of Various Solid Lubricants on Diamond Grinding of Heat-Resistant Stainless Steel Aleksandr Rudnev1 , Elena Sevidova1 , Oksana Titarenko2 , Alexey Kotliar1 Viacheslav Baranov1 , Oleksandr Yurchenko1 , and Milan Edl3(B)

,

1 National Technical University “Kharkiv Polytechnic Institute”, 2, Kyrpychova str.,

Kharkiv 61002, Ukraine [email protected] 2 National Academy of the National Guard of Ukraine, 3, Maidan Zakhysnykiv Ukrainy, Kharkiv 61001, Ukraine 3 University of West Bohemia, 301 00 Plzen, Czech Republic [email protected]

Abstract. The article focuses on the results of study of the influence of solid lubrication on the characteristic of the process of diamond grinding of difficult-tomachine material – heat-resistant stainless steel 10Cr11Ni23Ti3MoB. It has been established that the use of a solid lubricants based on stearic acid with additives of molybdenum disulfide, boron nitride, bronze powder at rate 10 – 35% leads to better surface roughness and decrease in cutting forces and cutting temperature in grinding zone. The best results for stainless steel 10Cr11Ni23Ti3MoB – minimum surface roughness Ra = 0.12…0.27 µm, decrease in tangential cutting force by 1.6…6.6 times and cutting temperature by 88…64% – were achieved with solid lubricants based on stearic acid with additives of boron nitride at rate 20% and 35%. Keywords: Grinding · Hard Lubrication · Difficult-To-Machine Materials · Surface Roughness · Cutting Forces

1 Introduction Grinding in many cases is the final stage of mechanical processing in the manufacturing. During this process the quality of the parts surface must be ensured, which determines the reliability and durability of the whole product. Grinding is characterized by high temperatures in the contact zone due to significant frictional forces between the surfaces of the grinding wheel and the workpiece. Intense heating leads to the appearance of microcracks, thermal burns, residual stresses and phase transformations in the surface layer, which can negatively affect fatigue strength of the part, its wear resistance and corrosion resistance at a later date [1]. These problems are particularly relevant by grinding some types of difficult-tomachine materials, in particular nickel-based alloys [2]. Low thermal conductivity, high strength and hardness at elevated temperatures complicate processing and affect the © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 117–126, 2023. https://doi.org/10.1007/978-3-031-40628-7_9

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surface quality of such materials. In terms of their properties, heat-resistant stainless steels with a relatively high nickel content, for example, 10Cr11Ni23Ti3MoB, are close to nickel alloys. It is used for the manufacture of parts that are operated at elevated temperatures in aggressive environments. These can be turbine blades, discs, springs, etc. The most common way to reduce the temperature in the grinding zone is the use of lubricating-cooling technological means (LCTM). However, they have some technological limits: air barrier restricts the accessibility of the cutting fluid into the grinding zone; even if a small quantity reaches the grinding zone, film boiling occurs, which further enhances the heat generated at the workpiece–wheel interface; and degradation of lubricity of the cutting fluid happens when the interface temperature reaches a certain limit [3]. In addition to technological aspects, there are sanitary, hygienic and ecological aspects of the LCTM imperfection. It is known [4] that most coolants are hazard for health, which means that it requires mandatory disinfection and disposal of spent solutions. All this leads to a significant increase in the cost of production. An urgent environmental problem in the modern world is the reduction of clean fresh water reserves. This stimulates the reduction of consumption of clean fresh water for industrial purposes, in particular as part of LCTM.

2 Literature Review Due to various socio-environmental limitations related to the use of the flood method, multiple techniques have been developed to create economically viable alternatives. Some of them are carried out by reducing the supply of water-based lubricants, other - by completely rejecting LCTMand replacing them with alternative means. The most promising have been the minimum quantity lubrication (MQL) technique, the use of biodegradable LCTM and cryogenic cooling. Studies [5, 6] show that these techniques lead to a significant reduction in cutting forces (with cryogenic cooling) and a significant reduction in surface roughness. The MQL technique combines the functionality of cooling with an extremely low consumption of fluids. In MQL technique, a little amount of cutting oil is applied as misty particles to the cutting zone. The well-directed penetration of oil particles reduces friction at the cutting interface and results in reducing the temperature, surface roughness and the cost.However, the effectiveness of the MQL technique is reduced by grinding difficultto-machine materials, because of a strong heating in cutting zone and evaporation of the coolant components before reaching the contact zone. In certain cases, the use of cryogenic cooling provides improvements in tool life and productivity due to increased cutting speeds. However, machining can be accompanied by a reconfiguration of cutting tool and the workpiece parameters due to the increased hardness, deformability, and cracking resistance of materials under the influence of low temperatures. In titanium alloys machining, cryogenic cooling often requires the addition of extra lubricating components. The widespread implementation of the method is hindered by the problems of ensuring the safety of work, as well as the problem of the suitability of the technology for various types of equipment. The main disadvantage of

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using air as LCTM is poor lubricity. One of the more promising methods of air cooling of the cutting zone is the application of activated air media, for example, cooled ionized air [7]. An alternative and less costly substitute for the LCTM components during abrasive machining can be solid lubricants (SL). SLs are attractive because they are environment friendly, low or no volatility, less toxic, and readily biodegradable. Besides, solid lubricants can function under high temperatures up to 1000 °C or very low temperatures down to - 253 °C, ultra-high vacuum, strong oxidation or reduction condition, strong radiation, high contact pressure and have no leakage [8]. Graphite, molybdenum disulfide, lead salts, metal powders, PTFE, etc. are the well-known structural solid lubricants [9]. Some of them have intrinsically layered structures, such as graphite and molybdenum disulfide, where slip between atomic layers is very easy, and so good lubrication can be expected. Some other inorganic compounds, such as tungsten disulfide, lead iodide, boron nitride, etc., also have layered anisotropic crystal structure and exhibit inherent lubricating performance and are categorized as the mechanical lubricants. Solid self-lubricating materials can be applied either as the bulky wear-resisting mechanical materials or as surface protecting coatings to reducing friction [10]. Studies [11, 12] have shown the use of SL in mechanical processing, in particular grinding [12] allows to improve process indicators – reduce surface roughness, increase the wear resistance of tools, and increase productivity compared to dry and flood-lubricated conditions. The effectiveness of the SL action depends significantly not only on the type (chemical composition), but also on the amount, method and uniformity of its application to the grinding zone. Research [13–16] is devoted to the solution of these questions. The literature review proposes that solid lubrication offers effective solution to make grinding process workable. The paper investigates the environment-friendly lubrication strategy as a potential replacement of conventional fluid cooling strategy, mainly efficiency of various SL by diamond grinding of heat-resistant stainless steel 10Cr11Ni23Ti3MoB. It is found in the literature that there is a giant scope of further research work to optimize this lubrication strategy in order to make it functionally applicable for grinding difficult-to-machine materials.

3 Research Methodology During the research, the process of surface grinding with intermittent feed was carried out using a 3D642E grinding machine. The ground elements were cylindersØ18 mm, height – 30 mm, grinding end surface – 254 mm2 . The grinding process was applied to the 10Cr11Ni23Ti3MoB heat-resistant stainless steel. Table 1 gives the percentages of the elements present in steel, the rest of the composition being iron. Diamond grinding was carried out with cup wheels on a bakelite bond: AC4 50/40 100% B2-01. The technological modes of grinding were chosen on the basis of literature data [17] and own research [8]. In particular, the cutting speed was 25 m/s, the longitudinal speed – 1 m/min. Grinding was carried out according to a rigid scheme with transverse feeds ftr = 0.005; 0.01; 0.015 mm/double pass (dp).

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Content

C

Al

Si

B

S

P

Cr

Ni

Ti

V

Mo

(Max) Composition 0.1 0.8 0.6 0.02 0.01 0.025 10–15 21–25 2.6–3.2 4–5,5 1–1.6 (wt.%)

The choice of the transverse feed index as research characteristic was based on its leading role in the formation of the contact temperature in the grinding zone and in the impact on the machined surface quality and technological parameters of the process [20]. By the choice and formation of the rational experimental compositions of SL, it was taken into account literature data and the results of our own previous research [12, 19–21]. The basic basis is stearic acid, which is a surface-active substance and can independently perform a lubricating function on the juvenile surface of the workpiece metal. In addition, in other well-known SL compositions, stearic acid acts as a binder for classic solid lubricants – molybdenum disulfide, graphite, hexagonal boron nitride, etc. These data were taken into account during the development of experimental SL compositions (Table 2). Table 2. Composition of experimental solid lubricants. Components

Chemical formula

Content in solid lubricant, %, composition number 1

2

3

4

5

6

7

8

65

100

90

80

65

60

40

40

40

Stearic acid

CH3 (CH2 )16 CO2 H

-

Azelaic acid

CO2 H(CH2 )7 CO2 H

-

Molybdenum disulfide

MoS2

-

Hexagonal boron nitride

BN

-

Bell bronze

Cu – 78…82% Sn – 18…22%

-

35

20 20

35

10

SL was used in the form of a pencil Ø 12 mm and 80 mm length. Lubrication was carried out by touching it for 1…2 s to the diamond wheel in the operating mode every 2 double passes on the 3rd. The efficiency of various SL by diamond grinding of heat-resistant stainless steel was evaluated by three characteristics – the workpiece surface roughness parameter Ra, the value of the post-contact temperature Tpc and tangential component of cutting force Ft . Roughness was measured on profilometer-profilograph SURTRONIC 3+ (Taylor Hobson) and defined as the arithmetic mean of 5 measurements.

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The temperature in the grinding zone is one of the main indicators of lubrication efficiency, its decrease testifies to the reduction in frictional forces and the amount of generated heat. Measuring the temperature directly in the processing zone is methodically complicated and is usually implemented through artificial thermocouples, the ends of which are brought into the grinding plane [18]. In this paper, it is proposed to qualitatively assess the thermal effect of the SL effect by the value of the post-contact temperature Tpc of the workpiece surface after wheel left the contact zone. Tpc corresponded to the temperature measured with a Flus IR-833 pyrometer (Flus) on the workpiece plane surface. The experimentation set-up is shown in Fig. 1.

Fig. 1. Grinding set-up for post-contact temperature measurements

The measurement of the tangential component Ft was carried out according to a rigid grinding scheme using a laboratory electronic single-component dynamometer of our own design. To account for uncertainties, all the experiments were repeated for five times, and their mean values were reported along with the standard deviation.

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4 Results and Discussion The analysis of experimental results (Fig. 2) indicates that the effectiveness of the SL influence on the surface roughness of the 10Cr11Ni23Ti3MoB steel largely depends on both its composition and the mode of grinding – transverse feed. The use of all SL composition types (Table 2) has an unambiguously positive effect on the surface’s quality –it reduces the roughness parameter Ra in almost the entire range of transverse feeds. An increase in feed from 0.005 to 0.015 mm/dp leads to an increase in Ra during dry grinding (No. 1) and using SL, which corresponds to the basic principles of the theory of abrasive grinding. A decrease in the Ra parameter of the surface machined with lubricants, in particular solid lubricants, is usually explained by a reduction in frictional forces between the wheel and the workpiece. This leads to the effect of longer sliding of the abrasive grain on the workpiece surface, and, accordingly, to a smaller depth of its immersion in the material. The best result – the minimum value of the roughness parameter Ra was provided by SL No. 5 (Table 2) based on stearic acid and 20% filling of hexagonal  boron nitride  Radry (Fig. 2 a, b, c). It’s value of the “improvement” coefficient Ra RaSL was 1.9…2.2, depending on the transverse feed. Comparable indicators of Ra at different feeds were achieved using SL No. 6, 3 and 8 with its corresponding decrease by 1.6…2.0, 1.5…2.3 and 1.75…1.9 times compared to the indicator of dry grinding. A comparative analysis of the SL effectiveness allows to state that an increase in the BN content from 20% to 35% (SL No. 5 and 6) leads to a relative increase of Ra parameter on the surface of 10Cr11Ni23Ti3MoB steel, especially by transverse feedftr = 0.015 mm/dp (Fig. 2 c). It can be seen that with the same content (35%), the filler with BN (SL No. 6) has a bigger effect on the surface quality than MoS2 (SL No. 2). With minimal transverse feeds (0.005 and 0.01 mm/dp), it is also possible to use SL No. 3 – 100% stearic acid without fillers. The effect of lubricating the grinding site with varying SL composition sand transverse feeds on the post-contact temperature Tpc of 10Cr11Ni23Ti3MoB steel is depicted in Figs. 3 a, b and c. It can be observed from these figures that fixed values of Tpc predictably increase with a growth of the transverse feed in both cases – during dry grinding and with the SL usage. With a low transverse feed (0.005 mm/dp), SL hasn’t a profound influence on the Tpc parameter (Fig. 3a), which might be due to the minimal heat release in this mode and the subsequent relatively rapid surface cooling in the air. When the feed is increased to 0.01 and 0.015 mm/dp, the SL usage significantly reduces heat generation in the grinding zone, and accordingly, the Tpc value. The positive role of lubricating materials lies precisely in the reduction of frictional forces, which are the main generator of heat in the grinding zone [22, 23]. The best results in maximum decay of the grinding temperature are achieved with SL compositions No. 4, 6, 5 and 2, which in general provide a Tpc reduction by 1.84…2.21 times. The relatively better cooling effect of SL No. 4 (contains 10% of bronze powder in addition to stearic acid), may be attributed to its rather higher thermal conductivity.

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Fig. 2. Variation of surface roughness of 10Cr11Ni23Ti3MoB steel with transverse feed under different SL compositions

Fig. 3. Variation of post-contact temperature of 10Cr11Ni23Ti3MoB steel with transverse feed under different SL compositions

Due to this, in addition to the lubricating function, this SL composition seems to be more effective in providing its cooling properties. The achieved decrease effect of the post-contact temperature Tpc through the SL usage made it possible to improve the surface quality of the difficult-to-machine steel by grinding at a feed rate of 0.015 mm/dp, and to prevent the phenomenon of surface burning that was observed during processing without lubrication. Tangential grinding force influences the power requirements in the grinding process. Intensity of heat generation, interface temperature and surface integrity depend primarily

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on this component of the grinding force. It can be observed from Fig. 4 that it predictably increases with a growth of the transverse feed in both cases – during dry diamond grinding and with the SL usage. Usually, the relations of the cutting forces components and the transverse feed have a non-linear character with a different linearity in instance sections of the researched feed values [22].

Fig. 4. Variation of tangential grinding force of 10Cr11Ni23Ti3MoB steel with transverse feed under different SL compositions

An abnormally high value of Ft – 14.5 N was observed at a feed rate ftr = 0.015 mm/dp. The special physical-mechanical properties of 10Cr11Ni23Ti3MoB steel are decisive for such an increase in cutting force – high viscosity, tendency to sticking, adhesive activity, all this leads to the appearance of non-productive forces, which are frictional in nature. In contrast to the productive components of the cutting force (shearing, secondary ploughing, microfracturing, etc.), which are proportional to the feed, non-productive ones practically do not depend on it [24]. Lubrication of the grinding wheel with the researched SL compositions (No. 1–6) led to an unequivocal decrease in Ft value. Even without considering the mode with a feed ftr = 0.015 mm/dp with abnormally high value of Ft , at smaller feeds (0.005 and 0.010 mm/dp) the improvement was significant – depending on the processing mode and SL composition in general case the Ft value decreased by 1.6…6.6 times. The priority of the SL effectiveness depends on the feed. So, the best result at feeds ftr = 0.005, 0.010 mm/dp were provided by composition SL No. 3 (Stearic acid 100%), and at ftr = 0.015 mm/dp – SL No. 6 (Stearic acid 65% + Hexagonal boron nitride 35%). The decrease in tangential grinding force with the considered SL compositions indicates their effective lubricating properties, which allow not only to reduce the energy load of the grinding process, but also to improve the quality of the surface, in particular, due to temperature reduction in the contact zone.

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5 Conclusions This paper presents the results of research on the possibilities of effective use of solid lubricants during diamond grinding of 10Cr11Ni23Ti3MoB heat-resistant stainless steel. Due to special physical and mechanical characteristics – high viscosity, low thermal conductivity, tendency to sticking, poor anti-friction properties, it belongs to the class of difficult-to-machine materials. The evaluation of the efficiency of grinding according to researched characteristics – the workpiece surface roughness, the post-contact temperature and tangential component cutting force showed the high effectiveness of proposed lubricating compositions based on stearic acid with additives of solid fillers – hexagonal boron nitride, molybdenum disulfide, bronze powder. Depending on the transverse feed (0.005, 0.01 and 0.015 mm/dp) and the SL composition, the decrease in the Ra parameter compared to dry grinding lubrication can be 1.3…2.2 times in general, the post-contact temperature – 1.2…2.2 times, and the tangential force – 1.6…6.6 times. According to the comprehensive indicator, the best results were provided by the SL compositions with fillers with hexagonal boron nitride in the amount of 20% and 35%.

References 1. Brinksmeier, E., Heinzel, C., Wittmann, M.: Friction cooling and lubrication in grinding. CIRP Ann. Manuf. Technol. 48(2), 581–598 (1999). https://doi.org/10.1016/S0007-8506(07)632 36-3 2. Yao, C.F., Jin, Q.C., Huang, X.C., et al.: Research on surface integrity of grinding Inconel718. Int. J. Adv. Manuf. Technol. 65, 1019–1030 (2013). https://doi.org/10.1007/s00170-0124236-7 3. Howes, T.: Assessment of the cooling and lubricative properties of grinding fluids. CIRP Ann. 39(1), 313–316 (1990). https://doi.org/10.1016/S0007-8506(07)61061-0 4. Howes, T.D., Tönshoff, H.K., Heuer, W., Howes, T.: Environmental aspects of grinding fluids. CIRP Ann. 40(2), 623–630 (1991). https://doi.org/10.1016/S0007-8506(07)61138-X 5. Paul, S., Chattopadhyay, A.B.: Effect of cryogenic cooling on grinding forces. Int. J. Mach. Tools Manuf 36(1), 63–72 (1996). https://doi.org/10.1016/0890-6955(95)92629-D 6. Da Silva, L.R., Bianchi, E.C., Fusse, R.Y., Catai, R.E., França, T.V., Aguiar, P.R.: Analysis of surface integrity for minimum quantity lubricant—MQL in grinding. Int. J. Mach. Tools Manuf. 47(2), 412–418 (2007). https://doi.org/10.1016/j.ijmachtools.2006.03.015 7. García, E., Méresse, D., Pombo, I., Dubar, M., Sánchez, J.A.: Role of frozen lubricant film on tribological behaviour and wear mechanisms in grinding. Int. J. Adv. Manuf. Technol. 82(5–8), 1017–1027 (2015). https://doi.org/10.1007/s00170-015-7397-3 8. Rudnev, A., Gutsalenko, Y., Sevidova, E., Pupan, L., Titarenko, O.: Diamond spark grinding of hard alloys using solid lubricants. In: Ivanov, V., Trojanowska, J., Pavlenko, I., Zajac, J., Perakovi´c, D. (eds.) DSMIE 2021. LNME, pp. 114–122. Springer, Cham (2021). https://doi. org/10.1007/978-3-030-77719-7_12 9. Krishna, P., Srikant, R., Rao, D.: Solid lubricants in machining. Proc. I Mech E Part J 225(4), 213–227 (2011). https://doi.org/10.1177/1350650111398172 10. Cai, M., Guo, R., Zhou, F., Liu, W.: Lubricating a bright future: lubrication contribution to energy saving and low carbon emission. Sci. China Technol. Sci. 56(12), 2888–2913 (2013). https://doi.org/10.1007/s11431-013-5403-2

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11. Rao, D.N., Krishna, P.V.: The influence of solid particle size on machining parameters in turning. Int. J. Mach. Tools Manuf. 48(1), 107–111 (2008). https://doi.org/10.1016/j.ijmach tools.2007.07.007 12. Shaji, S., Radhakrishnan, V.A.: Study on calcium fluoride as a solid lubricant in grinding. Int. J. Environ. Conscious Des. Manuf. 11(1), 29–36 (2003) 13. Shaji, S., Radhakrishnan, V.: An investigation on surface grinding using graphite as lubricant. Int. J. Mach. Tools Manuf. 42(6), 733–740 (2002). https://doi.org/10.1016/S0890-695 5(01)00158-4 14. Tsai, M.Y., Jian, S.X.: Development of a micro-graphite impregnated grinding wheel. Int. J. Mach. Tools Manuf. 56, 94–101 (2012). https://doi.org/10.1016/j.ijmachtools.2012.01.007 15. Shaji, S., Radhakrishnan, V.: An investigation on solid lubricant moulded grinding wheels. Int. J. Mach. Tools Manuf. 43(9), 965–972 (2003). https://doi.org/10.1016/S0890-6955(03)000 64-6 16. Kiselev, E.S., Unyanin, A.N., Kuznetsova, M.A., Kurzanova, S.Z.: Modern cutting fluids for grinding. Vestnik mashinostroeniya 7, 30–34 (1996) 17. Zou, L., Li, H., Yang, Y., Huang, Y.: Feasibility study of minimum quantity lubrication assisted belt grinding of titanium alloys. Mater. Manuf. Process. 35, 961–968 (2020). https://doi.org/ 10.1080/10426914.2020.1747625 18. Panayoti, V.A.: Study of the thermal regime during grinding with the use of solid lubricants. Bull. Bryansk State Tech. Univ. 6(59), 32–38 (2017) 19. Bogdanovich, P.N., Prushak, V.Ya., Starikov, S.V.: Anti-burn additive to lubricants for abrasive machining of steels and hard alloys and solid lubricant for abrasive machining of steels and hard alloys (variants). Patent Belarus 3209 (1999) 20. Bulatov, M.A., et al.: Solid lubricant for abrasive metalworking. Patent of the Russian Federation 96117774 (1998) 21. Torokin, V.V., Alekhina, V.D., Shevchenko, V.G., Ryabina, A.V.: Grease for abrasive processing of metals and alloys. Patent of the Russian Federation 2525293 (2014) 22. Panayoti, V.A.: Evaluation of the lubricity of TCM according to the specific work of grinding. Science-intensive technologies at the present stage of mechanical engineering development. In: V11 International Science-Technology Conference. Tekhpoligraftsentr, pp. 160–161 (2016) 23. Krishna, P.V., Srikant, R.R., Rao, D.N.: Solid lubricants in machining. Proc. IMechE 225 Part J J. Eng. Tribol., 213–227 (2011). https://doi.org/10.1177/13506501113981 24. Ravuri, B.P., Goriparthi, B.K., Revuru, R.S., Anne, V.G.: Performance evaluation of grinding wheels impregnated with graphene nanoplatelets. Int. J. Adv. Manuf. Technol. 85(9–12), 2235–2245 (2015). https://doi.org/10.1007/s00170-015-7459-6

Models for Prediction of Failure Time for Optical Fibres Under Severe Aging Rochdi El Abdi1(B) and R. Leite Pinto1,2 1 Institut de Physique de Rennes, University Rennes- CNRS, UMR 6251, 35000 Rennes, France

[email protected] 2 Entreprise Acome- Usines de Mortain, 50140 Mortain, France

Abstract. For optical fibres used in telecommunication networks, the failure prediction of the fibres is needed to plan maintenance operations and so ensure service reliability. Several methods of calculating the failure probability have already been reported but most of them don’t take into account the effect of temperature on fibre lifetime. On the other hand, the position, shape and the propagation of microcracks are different for every piece of fibre, because they vary with the machine used for manufacturing the fibre, composition of coating materials and the environment around the fibre. This makes difficult to develop a simple mathematical model that can predict fairly accurately the lifetime of fibres subjected to mechanical, thermal and chemical stresses. Lifetime measurement system was introduced using an experimental twisting test. Optical fibres were wounded around mandrels with different diameters and submitted to aging in hot water at different temperatures. Four models were used to estimate the time to failure. A comparison was made between experimental and model results. Keywords: Optical fibres · Prediction models · Twisting test · Weibull curves

1 Introduction To characterize the mechanical reliability of optical fibres [1, 2], three techniques are used to give stress to the fibres have been introduced by IEC-60793-1-33, including, axial tension, two-point bending and uniform bending. Different with axial tension, which mainly describes the fibre condition in cables used for long distances, two-point bending and uniform bending mainly refer to the fibre stress condition that in access networks or in FTTH (Fibre To The Home). Along with the development of FTTH, many works focused on the lifetime or mechanical reliability of bend-insensitive fibres under small radius bending [3–6]. In this paper, a lifetime measurement system of uniform twisting technique is introduced. Four models to estimate the time to failure were studied for different thermomechanical conditions for optical fibres used in telecommunication networks. Detailed influence factors like temperature, humidity and measurement dispersion are discussed here. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 127–134, 2023. https://doi.org/10.1007/978-3-031-40628-7_10

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2 Optical Fibre Used The used monomode fibre has two acrylate coatings (primary and outer coatings). This fibre was manufactured using the Outside Vapor Deposition (OVD) process which produces a totally synthetic, ultra-pure fibre. It has high strength and low attenuation. Its dual acrylate layer (CPC6) coating provides excellent fibre protection. On the other hand, the operating temperature range was -60 °C to + 70 °C. A soft, primary coating has a low module of elasticity, adheres closely to the glass fibre and forms a stable interface. It protects the fragile glass fibre against micro-bending and attenuation. The outer coating protects the primary coating against mechanical damage and acts as a barrier to lateral forces. It has a high glass temperature and Young modulus and a good chemical resistance. The combined coating diameter is 245 μm ± 5 μm, the clad diameter is 125 μm ± 1μm and the coating thickness is equal to 62.5 μm ± 2μm.

3 Test Bench Used Optical fibre was wound onto an alumina mandrel of 2.8, 3, 3.2 or 3.4 mm in diameter (Fig. 1). The winding of a fibre sample around a mandrel is done from a winder. This is an engine on which the chuck is attached and which makes it possible to put the rotating chuck. A weight of typically 50g is attached to the end of the sample to allow the fibre to conform perfectly to the shape of the mandrel. Once the fibre is rolled up, two silicone wedges are used to hold it in place. This technique provides a useful length for 16 twisting tests.

Lap counter Silicon wedge

Mandrel Rotative engine

Fibre

Rotating chuck

Weight of 50g

Fig. 1. Schematic representation of the winder for uniform winding

Once the fibre was wound around the mandrel, it was placed between a transmitter and a light receiver. The light beam cannot reach the receiver and from then on the time of fibre loading is triggered. When the fibre breaks, it falls. The light beam can reach the receiver and then the chronometer is stopped. The aging time is then recorded by a computing device.

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For fibre aging in hot water, we developed a water circulation system (Fig. 2). The system comprises a 9 L plastic tank in which is immersed a water heater with a resistance heater and a discharge pump. A water diffusion tube sends water at the desired temperature to the testing bench with mandrels. Thus the fibres (wound around a mandrel) can be aged in water at different temperatures.

Torsion test bench with mandrels

Clamping rings

Water heater

Wound fibre on calibrated mandrel

Water discharge pipe Water diffusion tube

Tank with hot water

Fig. 2. Mandrel sample with wound optical fibre and test bench with several samples

4 Theoretical Equations Used The applied stress on the fibre depends on the mandrel diameter accordingly to the Mallinder and Proctor relation [7], as follows: σ = E0 .ε(1 + (α.ε)/2)

(1)

where σ the applied stress (GPa); E 0 is the Young modulus (= 72 GPa for the silica); ε is the relative deformation of the fibre; and α  = 0.75 α and α is the elastic constant of non-linearity (= 6). The relative deformation of the fibre depends on the mandrel calibrated diameter, as follows: ε=

dglass ∅ + d fiber

(2)

φ is the mandrel diameter (in μm); d glace , is the glass fibre diameter (= 125 μm); d fibre is the fibre diameter (= 250 μm), including the layer polymer coating. This leads, in the case of a usual fibre, to the corresponding stresses of 3.22 GPa for the calibrated diameter mandrel of 2.8 mm. One can note that a wound fibre was subjected to compressive stresses on its internal part (fibre surface close to the curvature center) and a tensile stress on its external part (fibre surface furthest away from the curvature center).

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It’s not easy to predict the fibre lifetime from accelerated testing data because is certainly more difficult to estimate the confidence interval than the expected fibre lifetime. Therefore, different models were used and didn’t lead to exactly to the same predictions. For silica materials containing macroscopic cracks, chemical attacks like humidity influence lead to bond failure at the crack tip and then to crack propagation. Four models were commonly used and depend on the applied stress, on stress intensity factor, on the crack shape and on environmental conditions (temperature and humidity dependence). The following models giving the lifetime prediction will be used [8]: • Model 1: tf =

 σ 2−n1

2 2KIC

A21 Y 2 σ 2 (n1 − 2) S

(3)

• Model 2: tf =

  σ  σ  1 + exp −n 2 S S n2 σ 2 A22 Y 2 n2

(4)

tf =

  σ 2  exp −n 3 S σ 2 A23 n3 Y 2

(5)

tf =

  σ 2  exp −n 4 S σ 2 A24 n4 Y 2

(6)

2 2KIC

• Model 3: 2K 2IC

• Model 4: 2K 2IC

where t f is the failure time, Y is a dimensionless factor of order unity dependent on the crack geometry, K IC is the critical stress intensity factor for fast fracture, σ is the applied stress, in Ai (i = 1 through 4) are pre-factors temperature and humidity dependent, S is the initial inert strength of the material (strength in the absence of fatigue) and n1 is the stress corrosion parameter. If a representative stress σo gives a time to failure t 0 , then we constrain the models to have the same t f and dt f /dσ at σ = σ0 . If the inert strength S for the accelerated fatigue data is defined as So, then it may be shown that: n2 = n3 = n4 =

S0 (n1 − 1) σ0 S02 (n1 − 2) 2.σ02 S0 (n1 − 2) σ0

(7) (8) (9)

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Equation (3) can have a linearized form: Ln(t f ) = −n1 .Ln(σ ) + α1

(10)

Table 1 gives time to failures for different temperatures and different applied stresses (mandrel diameters φ ). Table 1. Time to failure for different stresses (diameters) and different temperatures of water 2.59 GPa φ3.4 mm

2.75 GPa φ3.2 mm

2.93 GPa φ 3.0 mm

3.13 GPa φ2.8 mm

20 °C

162 h 14 min 13 s

26 h 22 min 30 s

5 h 20 min 41 s

1 h 28 min 13 s

30 °C

46 h 2 min 9 s

10 h 22 min 30 s

1 h 54 min 15 s

46 min 26 s

40 °C

17 h 24 min 29 s

2 h 48 min 32 s

40 min 20 s

11 min 42 s

50 °C

9 h 15 min 34 s

2 h 11 min 17 s

20 min 25 s

10 min 46 s

60 °C

5 h 27 min 11 s

1 h 4 min 8 s

13 min 40 s

6 min 19 s

70 °C

1 h 5 min 1 s

26 min 11 s

8 min 4 s

2 min 5 s

The temperature and the mandrel diameter have a significant influence on time to failure. Indeed, for the same temperature, the time to failure can be divided by 100 (for 20 °C, time to failure decreases from 162 h 14 min for φ = 3.4 mm to 1 h 28 min for φ = 2.8 mm). On the other hand, for the same stress (same winding diameter), the time to failure can be divided by 150 (for φ = 3.4 mm, time to failure decreases from 162 h 14 min for 20 °C to 1 h 5 min for 70 °C). The classical Weibull plots showing the logarithm function of the cumulative failure probability Ln{[-1/L].Ln(1-F)}, where F (in %) represents the cumulative probability to failure for each stress to fracture σ (in GPa), related to the time to failure has allowed to find the statistical parameters, namely: the medium time value t med , the median stress σ (50%) , corresponding to a probability to fracture F = 50%. Figure 3 gives Weibull curves for fibres wounded onto an alumina mandrel of 2.8, 3, 3.2 and 3.4 mm in diameter aged in water at 20 °C. For each mandarin diameter, one can calculate the applied stress using Eqs. (1) and (2) and obtain the logarithm function of the time to failure Ln (t f , in h) related to the logarithm of the stress Ln(σ , in GPa) (Fig. 4). A linear interpolation gives the stress corrosion parameter value n1 using Eq. (10). For each temperature, the stress corrosion parameter n1 was obtained and then the other parameters ni (i = 2, 4) that define models (2, 3 and 4), when one uses Eqs. 7- 9 with an inert stress So equal to 10 GPa. On the other hand Eqs. 4 to 6 were used to find the best ni (i = 2, 4) parameters which lead to obtain a good value of measured time to failure. Table 2 gives for different temperatures, the ni (i = 2, 4) parameters deduced from n1 values (Experimental values) and those deduced from the use of models (Model value). The general trend was that the parameters obtained from the models were close to that obtained from experimental results.

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Fig. 3. Weibull plots for different mandrel diameters for aging in water at 20 °C

Fig. 4. Time to failure versus applied stress (aging in water at 20 °C) Table 2. ni parameters for different temperatures and for different models (S0 = 120 GPa) 20 °C Exp

30 °C Model Exp

40 °C Model Exp

23.1 ±6

50 °C Model Exp

21.5 ±6

60 °C Model Exp

21.7 ±6

70 °C Model Exp

20.4 ±6

Model

n1

23.6 ±6

18.6 ±5

n2

77 ±6

82 ± 12

75 ±6

83 ± 13

70 ±6

73 ± 10

71 ±6

70 ± 15

66 ±5

61 ± 11

60 ±5

60 ±2

n3

126 ± 20

136 ± 24

123 ± 20

141 ± 25

114 ± 19

118 ± 19

115 ± 19

114 ± 29

107 ± 17

98 ± 21

97 ± 16

99 ±1

n4

74 ±6

79 ± 12

72 ±6

79 ± 13

66 ±5

69 ± 10

67 ±5

66 ± 15

63 ±5

58 ± 11

57 ±5

57 ±1

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Table 3. Time to failure for different models (σ = 0.216 GPa) Model 1

Model 2

Model 3

Model 4

20 °C

3.15 months

3 months

2.5 months

3 months

30 °C

35 days

34 days

1 month

36 days

40 °C

9.25 days

8 days

7 days

8 days

50 °C

7 days

5 days

1 day

5 days

60 °C

3 days

3 days

40 h

2 days

70 °C

1 day

18 h

17 h

20 h

Thus, using the four models, we can calculate the time to failure when a fibre was submitted to another stress than those used during our tests. For example, for a stress equal to 0.216 GPa (φ = 4cm) the four models lead to similar time to failure (Table 3).

5 Conclusion It should be noted that for relatively short times to failure such as those obtained for optical fibres tested in hot water, the four models lead to a good approximation of the time to failure. But for fairly long service lives, such for as fibres subjected to low stresses and aged in air at ambient temperature, the time to failure exceeds several years and the four models lead to different estimations. In this case, the uncertainty in the crack growth model can’t be ignored in making reliability predictions for optical fibre under stress. The statistical uncertainty is significant also, but is usually smaller than the model uncertainty. The differences in allowed stress predictions between models become quite large at long times [8]. On one hand, the microcracks in each fibre are different and their number varies from one fibre to another. Furthermore and during long-term ageing, damage phenomena must be taken into account and are not described by the models. That needs a better understanding of crack growth and the chemical environment action on the fibre aging. Acknowledgements. The authors express their gratitude to Entreprise Acome (Usines de Mortain – 50140 Mortain, France) and to AFL Specialty Fiber (Verrillon, Inc – North Grafton 01536, MA- USA) for technical assistance and for material support.

References 1. Griffioen, W.: Evaluation of optical fiber lifetime models based on the power law. Opt. Eng. 33(2), 488–497 (1994) 2. IEC TR 62048: Optical fibres -Reliability-Power law theory. International Electronics Commission (2014) 3. Shang, H., Hou, L., Chou, G., Hsieh, R.: Lifetime predictions of bend optimized GGP single mode fiber for FTTH requirement. In: Proceedings of the 57th IWCS (2008)

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4. Mazzarese, D., Weimann, P., Norris, R., Konstadinidis, K.: Reliability considerations for nextgeneration bendoptimized fibers. In: Proceedings of the 57th IWCS (2008) 5. Griffioen, W., Greven, W., Jonker, J., Zandberg, S., Kuyt, G., Overton, B.: Reliability of bend insensitive fibers. In: Proceedings of the 57th IWCS (2008) 6. Zhang, L., Li, J., Yan, C., Liu, Li.: Static n value and lifetime measurement of bend-insensitive optical fibres by uniform bending method. In: International Wire & Cable Symposium. Proceeding of the 66th IWCS Conference, pp. 189–193 (2017) 7. Mallinder, F.P., Proctor, B.A.: Elastic constants of fused silica as a function of large tensile strain. Phys. Chem. Glass. 5, 91–103 (1964) 8. Bubel, G.M., Matthewson, M.J.: Optical fiber reliability implications of uncertainty in the fatigue crack growth model. Opt. Eng. 30(6), 737–745 (1991)

Multi-material 3D Printed Interfaces. Influencing Factors and Design Considerations Vasile Ermolai1,2(B)

and Alexandru Sover1

1 Faculty of Technology, Ansbach University of Applied Science, Residenzstraße 8,

91522 Ansbach, Germany [email protected] 2 Department of Machine Manufacturing Technology, “Gheorghe Asachi” Technical University of Iasi, Blvd. Dimitrie Mangeron 59A, 700050 Ias, i, Romania

Abstract. In recent years multi-material Additive Manufacturing gained more interest as new applications were found in domains such as bioengineering, soft robotics and actuators, electronics and many more. Fused Filament Fabrication (FFF) is one of the most used AM technologies for multi-material 3D printing due to relatively low-cost equipment and a large variety of thermoplastic materials. Even so, issues are still to be solved regarding the adhesion mechanisms at the level of bond interface, especially for dissimilar materials. Therefore, this paper aimed to identify influencing factors over the printing process of multi-material parts at the interface level. The influencing factors were determined using a literature review and Cura slicing tool user guide and systematised using a cause-effect diagram. The main domains of influence are Materials bonding, Printing equipment, Model geometry, and Method of printing and processing. These domains were further split into more specific factors and discussed based on their influence over multimaterial interface printing. Keywords: Fused Filament Fabrication · Multi-material interface · Influencing factors · Interface design

1 Introduction Fused Filament Fabrication (FFF) is a material extrusion additive technology which builds parts by depositing a molten thermoplastic material in the shape of layers. Using multiple extruders or switching the filaments, FFF can produce multi-materials components in a single process [1]. FFF proved that it is suitable for manufacturing functional parts, sandwich panels [2], shape-memory structures [1, 3, 4], medical devices [1], and many more. Using multiple materials in the same process, FFF made possible the design of higher complexity parts that can integrate different materials blends [1, 5]. The multi-material parts can be produced only if specific requirements regarding the materials compatibility, constructive geometry, process parametrisation and manufacturing conditions (e.g., printing in an enclosure) are satisfied [6, 7]. However, the overall strength of a © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 135–146, 2023. https://doi.org/10.1007/978-3-031-40628-7_11

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multi-material part can be resumed by the bonding strength of the interface, the physical boundary between the part’s materials. Following this line, this paper aims to identify the main factors that influence the bond formation of materials at the interface level. Adapting the cause-effect diagram was considered to provide a systematic theoretical framework. The identified influencing factors are based on the literature review and Cura slicing tool setting guide.

2 Methods The cause-effect diagram is one of the most used methods in industrial practice to determine the factors of influence over a process. The method is also known as the fishbone diagram or Ishikawa, after the name of its inventor Kaoru Ishikawa [8, 9]. The Ishikawa diagram is a graphical instrument that helps understand the causes that influence the quality of a process and the relations between them. Traditionally all groups of influence are symbolised with the letter M, which came from Machine, Methods, Manpower (Personnel), Materials, Maintenance, Mother Nature (Environment) and Management. Depending on chosen domains, the Ishikawa diagram can be classified as 4M, 5M, 6M and 7M [8]. Because this paper aims to identify the influencing factors of the multi-material 3D printed interfaces by FFF, a part of the conventional domains were replaced. This way, the identified domains: Materials’ bonding, Machine, Model, Method (of printing) and Method (of processing) describe only multi-material related features, parameters and printing conditions.

3 Use of the Cause-Effect Diagram 3.1 Influencing Factors of the Materials The 3D printed multi-material parts robustness is primarily influenced by the materials’ bond strength at the interface level. Multiple factors can influence the bonding mechanisms of polymeric materials, but generally, polymeric chains interactions are defined by: materials’ compatibility, adhesion mechanism, polymer type, melting range and viscosity (see Fig. 1). Polymer type: Based on their type, thermoplastic polymers can be divided into amorphous, semicrystalline and elastomers. However, in terms of structure, they are characterised by strong covalent bonds given by polymeric chains structure and weaker bonds provided by chains entanglement for amorphous (e.g., acrylonitrile butadiene styrene - ABS) and semicrystalline (e.g., polyethene terephthalate glycol - PETG) polymers or crosslinks for the thermoplastic elastomers (e.g., thermoplastic polyurethane - TPU) [10]. Materials compatibility: Multi-material printing is usually constrained to the materials’ compatibility. For this reason, parts printing is limited to different blends of the same material or polymers with similar chemical structures. The resulting multi-material interfaces lack strength when using low or no chemical compatibility polymers. These are known as dissimilar polymers [11, 12].

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Fig. 1. Cause-effect diagram that illustrates possible factors affecting the printing process of multi-material interfaces by FFF.

Adhesion Mechanisms: In FFF, the adhesion mechanism occurs when the deposited molten thermoplastic material creates intimate contact with the previous material lines or filaments, creating the interfaces. As the material solidifies, the polymeric chains stats to entangle, creating molecular bonds (see Fig. 2, a) with the adjacent material lines [13, 14]. However, this bonding mechanism is limited only to polymers with affinity [5, 13]. On the one hand, mechanical adhesion refers to the microscopic interlocking of the materials at the interface level. This phenomenon is possible by default due to FFF parts’ surface specifics. As the filament is extruded and pressed by the printing head, the resulting lines are characterised by a rectangle cross-section with rounded edges. This way, each deposited layer is characterised by voids between the adjacent lines [15], resulting from the extrudate rounded edges (see Fig. 2, b). As the molten material is deposited, it follows the interface’s topography, creating mechanical adhesion through microscopic interlocking [5]. On the other hand, the mechanical adhesion can be further extended by intentionally creating defects at the level of the base interface. The interlocking can be achieved by creating voids between the extruded lines filled by the following layer of material (Fig. 2, c) or by creating an overlap between the lines to create asperities in which the molten material can interlock. These scenarios can be

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obtained by locally controlling the extruded line parameters through mesh modifiers (Fig. 6, b) at the interface level [16].

Fig. 2. Bonding mechanism at interface level between material lines through (a) diffusion, (b) mechanical adhesion and (c) microscopic interlocking.

Melting Range: A melting range characterises each thermoplastic polymer and usually depends on the filament specifics and the extrusion system capacity to bring it into a semiliquid molten state. A proper melting temperature is crucial for obtaining a qualitative part in multi-material printing. Material shrinkage may occur if the chosen materials differ significantly between the melting points [17–19]. Additives: These are materials intentionally added into the neat polymeric matrix to obtain the desired characteristics. Based on their nature, the additives can be divided into plasticisers [20], pigments (e.g., titanium dioxide for white colour) [21], particles (e.g., copper, zirconia) or fibre reinforcers (e.g., glass, carbon) [22], and fillers (e.g., wood flour) [23]. These additives influence the resulting filaments regarding aesthetics, processability, and mechanical and physical characteristics. Viscosity: Molten material viscosity is essential for FFF 3D printing to maintain the shape of the extruded material lines. Because the material viscosity decreases along with the extrusion temperature, the FFF process uses mainly polymers which can be extruded as a viscous paste (e.g., amorphous polymers) rather than polymers with lower viscosity [24]. 3.2 Influencing Factors of the Equipment The 3D printing process of a multi-material part is also influenced by available machine hardware. The single nozzle 3D printers limit the material deposition to a stacked configuration (see Fig. 3, a). The printing capabilities can be further extended by using an auxiliary system capable of changing the materials or welding them in a single filament [25]. On the other hand, the printing process can be simplified by using a multi-extrusion system. The most common printers have a dual extrusion configuration with two independent feeding mechanisms. However, other machine configurations can print with three, four, five [26] or even 16 materials in a single process [27]. Depending on the used materials (regular or engineering grade polymers), a closed environment (i.e., a build chamber) can be required to increase filament adhesion and to reduce thermally induced stress [25]. Similar to other AM technologies, FFF can produce a part directly based on the tridimensional information of a model. Usually, the 3D model is created using a CAD

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software and exported as a mesh, a simplified representation of the part’s boundaries (e.g., STL, 3MF). Then the mesh is imported into the 3D printer’s slicing tool to be orientated and positioned in the available build volume. Then the material is associated with the mesh, followed by the printing process parametrisation, manufacturing instructions exportation and actual printing [24, 28]. The same working principle is respected in multi-material printing, but the number of required meshes increases with the number of materials. Going back to the CAD environment, the multi-material part is represented by a multi-body component. Those bodies are built relative to the same coordinate system and then exported independently in the same mesh representation. Then in the slicing tool, the part’s bodies are “assembled” together after assigning the materials to the meshes. From this point, the above-described methodology remains the same. 3.3 Influencing Factors of the 3D Model As previously described, the 3D model is essential in obtaining a multi-material part. Multiple multi-material interfaces can be designed based on the considered materials, compatible or not, and the available 3D printer. This way, the resulting framework regarding the design possibilities of the multi-material interfaces was described based on the Mating plane, Interface surface and Joint type (see Fig. 1). Based on the 3D model’s design and its orientation in the printer’s build volume, the mating plane between the part’s bodies can be relative to the xy, xz and yz (see Fig. 3). Depending on the part’s design, the resulting interfaces can be parallel or inclined to these mating planes. This type of joint, with a flat-to-flat surface contact, is common in the printing process of multi-material parts of compatible polymers. In this case, the multi-material interface robustness is ensured by the diffusion mechanism between the polymeric materials [29–31].

Fig. 3. Multi-material interface structure relative to the part’s bodies mating plane, (a) xy, (b) xz and (c) yz.

Based on the part’s geometrical complexity, the resulting multi-material interfaces shape can be categorised as planar, non-planar or a combination of them (see Fig. 4). The interface shape is related to the part’s specifics, and its accuracy at the boundary level is influenced by considered line thickness and width. In the case of inclined or curvilinear interfaces, the CAD model approximation is limited due to the stair step effect caused by the planar slicing. However, newer multi-axis equipment designs and non-planar

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slicing methods were proposed to reduce the stair-step effect of the FFF printing process [32–34].

Fig. 4. Possible shapes for multi-material interfaces, (a) planar, (b) non-planar and (c) mixt.

A geometrical interlocking interface can be considered to print multi-material parts of dissimilar polymers (see Fig. 5, a). This approach is also known as mechanical interlocking. Using a physical link between the part’s bodies compensates for the materials’ lack of affinity. Several studies showed that distinct material pairs such as poly lactic acid - PLA and TPU [34, 35] or ABS and PETG, polyamide - PA and PETG, ABS and PA [36] could be printed successfully. Other possible solutions for geometrical interlocking could be obtained by using 3D textures (see Fig. 5, b) or by alternating the materials (see Fig. 5, c) at the level of the interface [16].

Fig. 5. Multi-material macroscopic contact interfaces: (a) interlocking geometry, (b) 3D texture, (c) alternating structure.

3.4 Influencing Factors of the Method of Printing Besides the interface’s geometry, FFF technology enables another degree of design through the slicing tools by using printing parameters that control the method of printing (see Fig. 1). Compared to other AM technologies, in FFF, the parts are built by joining together multiple lines of materials, characterised line width and thickness. Their value depends on the nozzle output diameter and directly influences the part’s manufacturing time and mechanical properties [37]. Starting Point, Line width and Thickness: In FFF typical a part is composed of constructive-technological elements such as walls, a solid fill between them for the

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bottom and top layers and internal fill, described by pattern and density (see Fig. 6) for the intermediate layers. Each of these constructive elements has a starting point and an endpoint. In the case of walls, those points are coincident [38]. In multi-material printing, these start-end points should be positioned out of the interface zone to prevent defects such as under or over-extrusion. Printing Sequence: FFF slicing tools enable the control deposition steps of the outer wall, inner wall and the filling between them. This way, each layer can be deposited from outside to inside (see Fig. 6, a) or reverse (see Fig. 6, b) [38]. The printing sequence could influence the material fuse at the interface level when printing a multi-material part with a side-by-sited configuration. As the adjacent deposited lines support the molten material, the inside to outside could increase material fuse at the multi-material interface level.

Fig. 6. Exemplification of different printing sequences of layers specific to multi-material FFF: (a) outside to inside, (b) inside to outside.

Horizontal Expansion: This parameter makes the 3D model slightly smaller or bigger than the CAD reference. It is compensating measure for dimensional inaccuracies in the printing process. By default, Cura comes with a pre-set value of −0.02 mm [38]. When printing multi-material parts with a side-by-sited interface, the negative horizontal expansion could decrease the material fuse at the interface level by creating a 0.02 mm void between the mating bodies. Merged Meshes Overlap: It is a setting available in the Mesh Fixes tab of Cura. This setting overlaps the part’s bodies at the interface level to improve material fuse and strength [38]. A slight superposition of just 0.1 mm can improve the interface strength [16]. However, increasing it too much will cause an over-extrusion in the overlapping region. The over-extrusion can be prevented by creating the superposition in the part’s design phase. This ensures better control of the overlapping regions. However, to be effective, the Merged meshes overlap should be set at zero, along with deactivating the Remove mesh intersection setting found in the same tab [38]. Alternate Mesh Removal: It is a setting found in the Mesh fixes tab of Cura. This setting is complementary to the Merged meshes overlap. By activating it, the resulting interface will have a woven structure composed of alternating layers of the part’s materials (see Fig. 7, b). Unlike the alternating interface presented in Fig. 5, b, this setting

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enables an alternating step equal to the layer height, with a sitting area equal to the overlap. Depending on the materials’ affinity alternating the layer in a woven structure improves the interface’s strength by creating multiple vertical and horizontal bonds (for compatible polymers) or through the friction force generated by the stacked layers (for low compatibility polymers) [36].

Fig. 7. Methods of improving material bond strength for multi-material interfaces: (a) overlap between part’s bodies, (b) alternating the part’s bodies, (c) locally modifying the part’s bodies.

Mesh Modifiers: Are predesigned (e.g., slab, cylinder) or custom-made geometries which, when overlapping into the printing models (the dark grey geometry from Fig. 7, c), allow the local control of the printing parameters [38] such as line width, direction, printing speed [30] and also others. In the case of multi-material printing, the mesh modifiers can be beneficial for obtaining microscopic interlocking between materials (see Fig. 2, c) by creating voids or asperities in the base body, which later slot into position the following material [30]. 3.5 Influencing Factors of the Method of Processing According to the cause-effect diagram presented in Fig. 1, the last identified category of factors of influence over the printing of multi-material interfaces is the Method of processing. It is related to filament processing regarding heating, cooling, deposition speed and dosage. Printing Temperature: This setting refers to the temperature of the nozzle while printing. Because the printing temperature influences the material flow and fuse [37], it is the key parameter of material extrusion FFF. The printing temperature is adjusted depending on the polymer type and extrusion system capacity to heat the filament evenly. The temperature must be adequately adjusted to enable a constant material flow and to prevent polymeric material degradation due to overheating [38]. Polymers with different printing temperatures can affect the materials’ fuse in multi-material printing. It can also lead to shrinkage if is a significant difference between the materials’ melting points [17–19]. Material Flow: Adjusts the volume of deposited material based on the line width, thickness and length [38]. This way, the printing temperature should be constant to ensure a stable material flow [37]. For multi-material printing, a slightly increased flow at the interface level could positively influence bond formation by providing an extra amount of material.

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Cooling: Material cooling is used to solidify extruded material lines while printing. The cooling is performed through a flux of air. Assisted solidification through cooling is beneficial for materials with low glass transition temperatures, such as PLA, because it prevents material sagging. For materials with higher glass transition temperature, such as ABS, material cooling is significantly lowered or disabled [38]. The material cooling rate should be managed accordingly to not significantly decrease the diffusion between extruded lines for both single [39] and multi-material parts. Print Speed: The printing speed controls how fast are the material lines deposited and can be controlled globally or individually for each constructive element of a layer (e.g., outer wall, inner wall, infill). The 3D printer kinematic system and the extrusion system melting capacity limit the printing speed. The printing speed significantly influences the balance between part quality and manufacturing duration [37, 38]. Jerk Speed: This term was introduced by Marlin firmware, and governs the speed at which the printing head can travel through corners. It is also known as the maximum instantaneous change in velocity. On the one hand, the jerk speed is set at a value lower than the overall printing speed to reduce vibrations. On the other hand, in FFF, the jerk speed is always greater than zero to avoid excessive material deposition at corners as the filament is fed continuously [38]. Retraction: In FFF, the filament acts like a piston, which, actuated by a motor, forces the molten material out of the nozzle. If the filament does not stop pushing, the molten material will not stop flowing out of the nozzle, and the extrusion head will leave residual molten material on the part’s surfaces in the shape of blobs and strings. The printer must retract the filament from the melting zone to stop the melt from flowing. This can be achieved through Retraction distance and Retractions speed, and their values are defeminated based on the filament type (e.g., soft, rigid) and printer feeding mechanism (i.e., direct drive or indirect drive) [38]. Material Purge: A specific characteristic of the multi-material FFF is the need for material purge before switching between depositing materials. While an extruder is printing, the other ones are on hold. During this waiting time, material may ooze, leaving the nozzle chamber empty of material. A certain volume of material is extruded through a sacrificial block or tower before printing the part’s layer to refill the nozzle with molten material. This safety feature ensures the quality of the resulting multi-material part [38].

4 Conclusions FFF enables multi-material parts manufacturing by two or more materials in the same manufacturing process. However, different approaches can be used to obtain a qualitative multi-material part depending on the available equipment and considered polymeric materials. This research focused on identifying the influencing factors of the multi-material 3D printed interfaces by FFF. Five influencing domains were identified by using and adapting the cause-effect diagram. These are Materials’ bonding, Machine (printer), Model (3D), Methods of printing and Methods of processing. Furthermore, multiple influencing factors were identified by expanding each domain and discussed based on the literature review and Cura slicing tool user guide. The number of identified factors

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can be further extended through a more comprehensive literature review and by adopting more specific FFF parameters. Multi-material interface design starts with the selection of the materials. Then, an interface design solution can be created based on their compatibility and the available equipment. Further, a proper printing method should be considered based on the part’s interface design and functional requirements. These must be addressed simultaneously whit adequate values of the materials processing parameters. The literature review shows that relatively strong multi-material parts can be made using polymeric materials with good and low-compatibility using FFF technology. However, more research must be done to improve the printing process and the resulting interface of parts made of low-compatibility polymers.

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Implementation of Human-Robot Interaction Through Hand Gesture Recognition Algorithms George Gamazeliuc1(B) , Oliver Ulerich1,2 , Eulampia Rolea1 and Mihai M˘arg˘aritescu1

,

1 National Institute of Research and Development in Mechatronics and Measurement Technique

(INCDMTM), Bucharest, Romania [email protected] 2 University Politehnica of Bucharest, Bucharest, Romania

Abstract. This article presents the implementation of a human-robot interaction system using hand gesture recognition algorithms. The objective is to improve the living conditions of people with physical and mobility disabilities by developing a mobile robot with advanced interaction capabilities. The system interprets dynamic hand gestures, including a distinct set of gestures involving thumb movements, to control a two-wheel drive mobile robot platform. Based on geometric features extracted from camera images, control points and control area, the system recognizes and classifies the detected gesture. These gestures serve as triggers for motor commands, allowing the robot to execute predefined maneuvers such as moving forward and backward, turning left and right, and stopping. Successful implementation of this system has the potential to significantly improve the independence and autonomy of people with physical and mobility disabilities, thereby increasing their overall quality of life. Keywords: Hand Gesture Recognition Algorithms · Human-Robot Interaction · Assistive Robotics · Computer Vision

1 Introduction Individuals with physical and mobility disabilities face significant challenges in their daily lives, which limit their independence and autonomy. Advances in robotics technology have opened up new possibilities for addressing these challenges, with collaborative mobile robots showing great promise for enhancing the quality of life of these individuals [1]. In this paper, we present an intuitive approach to human-robot interaction through hand gesture recognition algorithms. These algorithms enable dynamic control of a two-wheel drive mobile robot platform, allowing users to direct the robot’s movements through simple, intuitive hand gestures. By leveraging computer vision algorithms and non-verbal communication, we aim to develop a robot with interaction skills that can be controlled through intuitive hand gestures. The development of mobile robots has gained significant attention in recent years due to their potential to address a wide range of societal challenges. In particular, mobile © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 147–154, 2023. https://doi.org/10.1007/978-3-031-40628-7_12

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robots have shown great promise in improving the lives of individuals with physical and mobility disabilities. These robots can assist with tasks such as fetching items, opening doors, and navigating unfamiliar environments, thereby enhancing the independence and autonomy of their users. However, effective control mechanisms for these robots are still a major challenge. Traditional methods such as joystick control can be difficult and unintuitive. This has led to the exploration of alternative control methods such as voice and gesture recognition [2]. Hand gesture-based control has been successfully implemented in a variety of applications, including intelligent car control [3] and robots for industrial applications [4]. The aim of this research is to develop a mobile robot with interaction skills, based on hand gesture recognition algorithms, for people with physical and mobility disabilities, who are generally within normal cognitive and perceptual abilities. The proposed research is significant because it addresses an important social need and contributes to the development of solutions to improve the living conditions of people with disabilities.

2 Methodology Our approach to human-robot interaction is based on hand gesture recognition algorithms. There are many techniques for hand gesture recognition, which can be divided into two main categories: image processing techniques and artificial intelligence techniques [5]. Our approach is based on computer vision using various image processing techniques. We focus on a set of hand gestures accompanied by thumb movement that users with limited mobility can easily perform. We use a camera to capture video of the user’s hand gestures and apply computer vision algorithms to recognize the specific gestures. These gestures are then mapped to predefined commands that control the motors of a two-wheel drive mobile robot platform. The commands include moving forward, backward, turning left, turning right, and stopping. 2.1 System Architecture The proposed system architecture consists of a mobile robot platform and a gesture recognition system equipped with a camera and computer for data processing. The robot can move freely indoors and recognize hand gestures using an RGB camera together with hand gesture recognition algorithms. Hardware Architecture with Arduino Microcontroller Board. The hardware architecture implemented with Arduino Nano, presented in (Fig. 1), was used to analyze the functionality and performance of the components. The color camera module is used to capture the user’s hand gestures. The frames received from the camera are then transferred to the computer to implement the image processing and computer vision algorithms, described in the software architecture chapter. After recognizing the hand gesture, the commands for the robot movements are sent to the motors via Arduino Nano. To control the robot’s movement, the motors and motor driver require an external 12V power source to operate. We need to supply 5V for Arduino Nano through an

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Fig. 1. Hardware architecture using the Arduino microcontroller

LM2596 step-down module which is designed to limit the input voltage from 12V to 5V by adjusting the potentiometer. The L298N motor driver module’s pins (EnA, IN1, IN2, IN 3, IN4, and ENB) are connected to the Arduino digital I/O pins (12,11,10,7,8,9).

Fig. 2. Implementation of human-robot interaction using the Arduino microcontroller. a) Mobile robot platform; b) Gesture recognition system

The quiet and high torque output motors (146 rpm) with optical encoder built-in are connected to the motor driver terminal A, B (OUT1/OUT3 and OUT2/4) through the encoder adapter. The tire surface design offers a good anti-slip effect and provides a firm grasp over the different surfaces in homes. The implementation of human-robot interaction using the Arduino board is shown in (Fig. 2). Hardware Architecture with Raspberry Pi Microcontroller Board. The hardware architecture implemented with the Raspberry Pi 4 microcontroller (Fig. 3) is similar to the one built with Arduino Nano. However, the Raspberry Pi processor offers higher processing power and performance compared to the Arduino Nano and allows for highspeed parallel data transfers and custom peripheral interfaces. This makes it suitable

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for applications that require real-time data processing, such as human-robot interaction. The mobile robot platform is separated from the hand recognition system (Fig. 4), and the output commands are sent through TCP/IP protocol, used to interconnect the gesture recognition system and the mobile platform. The L298N motor driver module’s pins (EnA, IN1, IN2, IN 3, IN4, and ENB) are connected to the Raspberry Pi General-Purpose I/O pins (GPIO 25, GPIO 24, GPIO 23, GPIO 27, GPIO 22, GPIO 4).

Fig. 3. Hardware architecture using the Raspberry Pi microcontroller

Fig. 4. Implementation of human-robot interaction using the Raspberry Pi microcontroller. a) Mobile robot platform; b) Gesture recognition system

Software Architecture. The software architecture is designed to implement image processing and computer vision algorithms that recognize hand gestures and control the mobile robot platform. The frames received from the camera are processed using OpenCV, a popular computer vision library. We implemented the algorithm in Python 3.8. The code is divided into three main modules, namely the gesture recognition module,

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the communication module, and the motor control module. Here is a description of each module: • Gesture Recognition Module: The gesture recognition module is responsible for recognizing the hand gestures using OpenCV. The module captures the frames from the camera and applies image processing techniques to detect, segment and track the hand movements. • Communication Module: The communication module is responsible for establishing the connection between the gesture recognition system and the mobile robot platform. The module uses TCP/IP to send the output commands from the gesture recognition module to the motor control module. • Motor Control Module: The motor control module is responsible for controlling the motors of the mobile robot platform. The module, which runs on the microcontroller board, receives the output commands from the gesture recognition module. The microcontroller board then controls the motors to move the robot in the desired direction. The gesture recognition process can be broken down into three main stages: Image processing, Hand detection, and Gesture recognition. Each stage consists of several steps to process and analyze the images in order to recognize gestures accurately. Here is a description of each block from the gesture recognition diagram (Fig. 5):

Fig. 5. Diagram of gesture recognition stages

Image processing: • Images from the camera: The source of input images is from a camera that captures the user’s hand gestures in real-time.

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• Resizing: The input images are resized to a smaller size to ensure low latency in the processing and analysis stages. • Grayscale: Images are converted to grayscale to reduce computational complexity and focus on the structural information rather than color information. The function cv2.cvtColor() takes two arguments: the source image (frame) and the color conversion code (cv2.COLOR_BGR2GRAY), the result is a grayscale version of the input image. • Gaussian blur: A Gaussian blur is applied to the images to reduce noise and smooth out the images for better contour detection in further stages. The code cv2.GaussianBlur(grayscale, (7, 7), 0) takes a grayscale image, applies Gaussian Blur using a 7x7 kernel, and returns the blurred image. Hand detection: • Compute the difference between the background (first frame) and the current frame: This step is crucial in identifying moving objects, such as hands, by subtracting the static background from the current frame. The code cv2.absdiff(first_frame, grayscale) takes two input images (usually grayscale) and calculates the absolute difference pixel by pixel. • Filtering using threshold: A threshold is applied to the difference image to create a binary image, which highlights the hand’s region and eliminates the background. This following code: cv2.threshold(frame_delta, 20, 255, cv2.THRESH_BINARY)[1] takes an input image frame_delta, applies binary thresholding with a threshold value of 20, and returns the image with pixel values of either 0 or 255. • Contour detection: Contours are detected in the binary image, representing the boundaries of the hand’s region. The following function: cv2.findContours(thresh.copy(),cv2.RETR_EXTERNAL,cv2. CHAIN_APPROX_SIMPLE) returns a tuple containing a modified image, a list of contours found in the image and the hierarchy of the contours. • Filter contours: Contours are filtered based on their size to keep only the relevant contours corresponding to the hand. Gesture recognition: • Compute geometric characteristics: Geometric features, such as the distance between fingertips and the palm’s center, are calculated. • Find and assign the control point to the finger: Control points are identified on each finger of interest, at the fingertips, to track finger movement and orientation. • Set range and parameters for control area: A control area is defined around the hand and fingers, which sets the boundaries for gesture recognition and allows for the detection of specific gestures. • Detected gesture: Based on the geometric characteristics, control points, and control area, the system recognizes and classifies the detected gesture.

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The gesture recognition algorithm is capable of sending several commands to the robot, including starting and stopping, moving left and right, and moving forward and backward. By using hand gestures, the user can control the robot’s movements in a natural and intuitive way. We tested the performance of our hand gesture recognition algorithm in different environments and lighting conditions (Fig. 6).

Fig. 6. Hand detection using computer vision. a) Stop motors command; b) Move forward/right; c) Move backwards/left; d) Change command set from forward/backward to right/left and vice versa.

3 Conclusions This research has provided techniques for implementing the hand recognition algorithm used in human-robot interaction. Our approach to human-robot interaction through hand gesture recognition has significant potential for enhancing the quality of life of individuals with physical and mobility disabilities. The use of non-verbal communication and intuitive control mechanisms enables greater independence and autonomy for these users. Our approach can also be extended to other applications, such as controlling robotic arms in manufacturing environments or navigating drones in search and rescue operations. By utilizing image processing techniques for hand recognition and gesture detection, our method demonstrates robustness and can operate efficiently on limited computational resources, unlike deep learning-based approaches. However, there are still challenges that need to be addressed, such as improving the algorithm’s reliability in recognizing hand gestures under different lighting conditions and reducing latency in executing commands. 3.1 Limitations and Future Work The accuracy of the gesture recognition algorithms is crucial for the success of the system. Currently, our hand gesture recognition algorithm is based on advanced image

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processing and computer vision. We plan to improve the algorithm using state-of-theart machine learning techniques, specifically convolutional neural networks (CNNs). Future work will also focus on increasing the number of recognized gestures, making the system more versatile. Acknowledgement. This work was supported by the (1) Research Program Nucleu within the National Research Development and Innovation Plan 2022–2027, carried out with the support of MCID, project no. PN 23 43 04 01; (2) CERMISO Center – Project Contract no. 159/2017, Programme POC-A.1-A.1.1.1-F; and (3) Support Center for international CDI projects in the field of Mechatronics and Cyber-MixMechatronics, Contract no. 323/340002, project co-financed from the European Regional Development Fund through the Competitiveness Operational Program (POC) and the national budget.

References 1. Jiang, H., Duerstock, B.S., Wachs, J.P.: A machine vision-based gestural interface for people with upper extremity physical impairments. IEEE Trans. Syst. Man Cybern. Syst. 44(5), 630– 641 (2014). https://doi.org/10.1109/TSMC.2013.2270226 2. Shaikh, Q., Halankar, R., Kadlay, A.: Voice assisted and gesture controlled companion robot. In: 2020 4th International Conference on Intelligent Computing and Control Systems (ICICCS), Madurai, India , pp. 878–883. IEEE (May 2020). doi: https://doi.org/10.1109/ICICCS48265. 2020.9120875 3. Dai, G., Wang, P.: Design of intelligent car based on WiFi video capture and OpenCV gesture control. In: 2017 Chinese Automation Congress (CAC), Jinan, China, pp. 4103–4107. IEEE (Oct. 2017). doi: https://doi.org/10.1109/CAC.2017.8243499 4. Vanamala, H.R., Kumar, A.S.M.V.A.S., Rathod, M.: Gesture and voice controlled robot for industrial applications. In: 2022 International Conference for Advancement in Technology (ICONAT), Goa, India, pp. 1–8. IEEE (Jan. 2022). doi: https://doi.org/10.1109/ICONAT53423. 2022.9725903 5. Oudah, M., Al-Naji, A., Chahl, J.: Hand gesture recognition based on computer vision: a review of techniques. J. Imaging 6(8), 73 (2020). https://doi.org/10.3390/jimaging6080073

Experimental Determination of Power Losses in Steel and Hybrid Rolling Bearings Vladimir Dotsenko , Oleksandr Gnytko(B) and Anna Kuznetsova

, Yurii Koveza ,

National Aerospace University, 17, Chkalov Street, Kharkiv 61070, Ukraine [email protected]

Abstract. The results of an experimental study of power losses in rolling bearings under various lubrication conditions are presented. Comparative tests of all-metal bearings and similar bearings with rolling elements made of silicon nitride (hybrid bearings) were carried out with jet lubrication and lubrication with an air-oil mixture. For the experiments, a specially designed setup was used, which makes it possible to study bearings at different levels of lubricant consumption and loads. The change in the moment of resistance to rotation and the reduced coefficient of friction in bearings are analyzed. The dependences of these parameters on the shaft speed are presented in graphical form. It has been established that bearings with ceramic balls in the entire studied range behave qualitatively and quantitatively in approximately the same way as with steel ones. The use of lubrication with an air-oil mixture makes it possible to reduce losses in the bearing by more than 2 times with a slight increase in the bearing temperature in the absence of external heating. Hydraulic losses in the studied units are on average 2–3 times higher than the losses associated with the friction of the rolling elements on the bearing parts surrounding them. Keywords: Rolling Bearing · Ceramic Balls · Experimental Studies · Moment of Resistance · Reduced Coefficient of Friction · Air-Oil Mixture · Hydraulic Losses

1 Introduction The performance of a bearing is determined by a large number of factors, the most important of which are the load on the bearing, the lubrication regime, the material and geometry of the contacting parts, as well as the thermal operating conditions of its parts. One of the possible ways to improve the performance of bearings is the use of ceramic materials.

2 Literature Review Usage of plain bearings [1] in turbine rotors [2], diesel engine turbines has become widespread. Their use has a negative effects too: 1. stops and starts of the engine have high frequency; © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 155–163, 2023. https://doi.org/10.1007/978-3-031-40628-7_13

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2. the supply of the working environment has greater sensitivity of the support to changes; 3. special high-precision production facilities are required the production of plain bearings [3]. Rolling bearings and seals [4] still prevail in structures, for example, aircraft engines, etc. Rolling bearings are also used as supports for the tank supercharger and compressor. Rolling bearings are widely used in medical instrumentation [5]. There are a large number of works on the development of the use of rolling bearings in the design of spindle assemblies of CNC machines in terms of vibration [6], thermal analysis [7], wear characteristics [8], et al. A number of works have been carried out to improve their characteristics: – specialized bearing materials have been developed and improved [9]; – accuracy of manufacturing of the parts (accuracy and cleanliness of surfaces) was increased; – various nanostructures: a single-crystalline metal oxide nanostructures [10], 1D metal oxide nanostructures [11], copper oxide nanowires [12, 13] are considered as perspective means to reduce friction in contact with other parts; – surface treatment: TiN coatings [14], carbon nanostructure [15, 16], coating grows [17] methods have been developed and can be applied to increase their wear resistance; – special forms of rolling tracks have been developed to increase the bearing capacity of bearings and reduce friction losses during rolling; – methods have been developed to reduce the mass of rolling elements; – means and methods of cooling and lubricating [18] bearings are being improved, which includes the use of new materials for lubrication [19]; – accuracy of calculations of bearing characteristics by taking into account a larger number of factors that affect them was increased [20]. The use of ceramic materials for rolling bearings has become one of the possible ways to improve the performance of bearings. Ceramic materials have the following features compared to steel: • • • • •

low density (~60% less); high modulus of elasticity (more by ~50%); coefficient of dry friction in ceramic-steel pair is less than in steel-steel pair; lower coefficient of thermal expansion and high heat capacity and heat resistance; ceramics – dielectric.

These features provide a number of advantages of ceramics over steel when used as materials for rolling elements of bearings: • reduction of centrifugal forces; • reduction of power losses due to friction; • increase in the service life of the lubricant and rolling elements in aggressive environments; • reduction of preload in the bearing (up to 33%); • complete electrical isolation of the inner ring from the outer one; • reduction of operating temperatures of the bearing;

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• reduction of vibration and noise of the bearing; • the possibility of long-term operation in the absence of lubrication. Experimentation with ceramic rolling elements for aerospace bearings began decades ago when NASA’s space shuttle engines used them in the early 1990s. In 2005 Timken was awarded two contracts under VAATE’s gas turbine engine optimization program to develop hybrid bearings for an aircraft gas turbine engine. Recently Timken engineers have worked closely with defense aircraft manufacturers to develop hybrid roller bearings for several applications, including aircraft gas turbine engine development. Timken intends to begin full-scale production to support aerospace customers by 2023. Electric vehicle component manufacturers, including SKF, are tackling the issue of future-proofing hybrid bearings by improving their performance, efficiency and reliability. Hybrid bearings provide efficient operation under conditions of improper lubrication and contamination, but the reasons for this and their effect on performance are still not fully investigated. According to the results of SKF’s research only the steel component is subject to moderate wear in a hybrid bearing, while the ceramic part is practically unaffected. Under conditions of contamination, moderate wear, plastic deformation and maintenance of surface smoothness at the edges of dents in hybrid bearings contribute to the reduction of local stresses. It is shown that the increase in the service life of hybrid bearings with dents occurs due to high resistance to surface destruction and damage associated with extreme lubrication conditions and the lubricating film integrity failure. As follows from the literature, the most promising technical ceramics is silicon nitride (Si3 N4 ).

3 Research Methodology Low density and high modulus of elasticity with high heat resistance of ceramics give a positive effect in terms of the characteristics of bearings operating in turbine support units under conditions of intense external heat transfer, significant internal heat generation and high rotational speeds. A rigorous mathematical description of the processes in the supports of gas turbine units is very difficult due to the complexity of the interaction of elements both inside the bearing and with the parts surrounding it. Therefore, at present, researchers are interested not only in the very fact of the possibility of operation of “ceramic” bearings (CB), but also in the possibility of their operation under specific conditions on a par with or instead of conventional “steel” bearings, as well as the creation of a generalized method for calculating hybrid bearings based on these experiments. In this regard, it is necessary to check the operability of the CB on full-scale or simulating installations under the same or similar conditions in which steel ones operate. When conducting comparative tests of hybrid and conventional bearings, we investigated: • friction losses by measuring the moment of resistance;

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• rational lubrication conditions that ensure minimal friction losses and effective cooling of the bearings under study. The test results will make it possible to develop recommendations for the use of hybrid bearings and refine the methods for their calculation and design. All these tasks were solved by means of comparative tests of bearings on the installation, as part of the stand (Fig. 1), the scheme and main systems of which are shown in Fig. 2. The tests were carried out with the following parameters: – – – – – – –

type of bearings: angular contact ball bearings with a contact angle of 26°; clip materials - steel EI347-Sh; balls: silicon nitride and steel EI347-Sh; ball diameter 7.938 mm; shaft hole diameter d sh = 38.5 mm; axial load P: 0, 1000 and 2000 N; there was no radial load; shaft speed n: 0…32000 min−1 . Bearings were lubricated:

– oil jet at flow rates of 8.5 g/s, 15 g/s, 25 g/s; – oil mixture: air 0.20 g/s and oil - from 0.023 g/s to 0.08 g/s; – oil type - IPM-10 according to TU38.1011299-2006.

Fig. 1. The unit under test on the stand.

During the test, the following were measured: the moment of resistance on a pair of bearings, the temperature of the outer ring, the temperature of the lubricating medium at the inlet and outlet of the bearing block, and the shaft speed. The bearing with steel balls has been running for a total of 300 min, with ceramic balls for 220 min. After testing, no traces of damage were found on the bearing parts.

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Fig. 2. Scheme and main systems of the stand.

4 Results Some test results are shown in Figs. 3–8. Figures 3–6 show the dependence of the moment of resistance to rotation on the shaft speed for various lubrication methods, axial loads and rolling element materials, the last two (Figs. 7–8) show the values of the reduced friction coefficient.

Fig. 3. Dependence of the moment of resistance M on the shaft speed n in a bearing with steel balls without axial load: oil consumption ˛ – 8.53 g/s; ▲– 15.6 g/s;  - 24.4 g/s; ● - 0.032 g/s.

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Fig. 4. Dependence of the moment of resistance M on the shaft speed n in a bearing with steel balls under an axial load of 2000 N: oil consumption ˛ – 9.53 g/s; ▲– 11.6 g/s;  - 20.7 g/s; ● 0.08 g/s.

Fig. 5. Dependence of the moment of resistance M on the shaft speed n in a bearing with ceramic balls without axial load: ˛ – oil; ▲– air-oil mixture.

Fig. 6. The dependence of the moment of resistance M on the shaft speed n in a bearing with ceramic balls at an axial load of 2000 N: oil consumption ˛ – 10.1 g/s; ▲– 12.2 g/s;  - 20.7 g/s; ● - 0.08 g/s.

In the figures, the solid lines show the results obtained with jet lubrication, and the dotted lines show the results obtained with air-oil lubrication.

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Fig. 7. Dependence of the reduced friction coefficient f r on the shaft speed n in a bearing with ceramic balls: ˛ – oil; – air-oil mixture.

Fig. 8. Dependence of the reduced friction coefficient f r on the shaft speed n in a bearing with steel balls: ˛ – oil; – air-oil mixture.

Analyzing the results shown in Figs. 3–6, it can be seen see a number of dependencies that are typical for both steel and ceramic bearings: 1. With oil lubrication (Figs. 3–6, solid lines), the moment of resistance is significantly (2–3 times) greater than with oil-air lubrication (see Figs. 3–6, dotted lines), and this difference the greater, the greater the oil flow through the bearing. Previously, it was shown that during oil lubrication, losses include two main components due to: – contact between bearing parts (cage, balls, races), including rolling friction and friction in seals; – hydraulic losses associated with the mixing of the liquid by the balls and the resistance to its movement in the bearing channels. The results obtained confirm the conclusion that the hydraulic component contributes much more to the losses in the supports (up to 80% of all losses). For both bearings, it almost completely coincides qualitatively and quantitatively, since it does not depend on the material of the rolling element and is apparently due to the shape and area of the

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bearing channels, as well as the viscosity of the lubricant, which were maintained the same in the studies. 2. When lubricating with oil and increasing its pumping, the resistance increases unevenly: with an increase in oil supply from 9 to 14 g/s (1.6 times), the moment increased from 0.68 to 2.4 N·m (3.5 times), and when changing from 14 to 19 g/s (1.4 times), the moment increased from 2.4 to 2.6 N·m (by 8%). This can be explained by a sharp increase in hydraulic losses in the bearing as it is filled with lubricating fluid, after which the cost of operating the bearing increases much less. 3. When lubricated with oil mist and in the absence of axial force (dashed lines in Figs. 3, 5), and under load (dashed lines in Figs. 4, 6), the moment of resistance changes much less over the entire range of the studied rotational speeds and depends little on oil consumption. In this case, bearing losses are almost entirely caused by friction between the rolling elements and the cages, between the rolling elements and the cage. The latter fact is well illustrated by Figs. 7 and 8, which show the dependence of the reduced friction coefficient fr on the rotational speed when lubricated with oil (solid lines) and oil-air mixture (dashed lines). The reduced friction coefficient increases almost linearly as the rotation speed increases. In the conducted studies, the ranges of friction coefficients for steel and ceramics were 0.003…0.005 and 0.002…0.005, respectively, which is consistent with the results of previous studies. It can be noted that the coefficient of friction for the CB is more stable and does not exceed the same values for the steel one.

5 Conclusions Based on the results of the research, the following conclusions can be drawn: 1. The effect of rotation frequency, load, type of lubrication and lubricant consumption on friction moments in the studied bearings is qualitatively, and in many respects quantitatively, the same for steel and ceramic bearings. 2. Lubrication with an oil-air mixture significantly (by 3–5 times) reduces friction losses in the bearing. 3. Just like steel bearing, hydraulic oil losses in CB are much higher (by 2–3 times) than losses caused by direct contact of the rolling elements with the surrounding parts. 4. The values of the reduced friction coefficient, calculated from the parameters of the experiment, lie in the usual range, which indicates the adequacy of the experiment. 5. The range of changes in the CB parameters (friction moment, reduced coefficient of friction) is less than that of steel bearings. Thus, studies have shown that, in general, CB in a fairly wide range of parameters behave similarly to traditional steel ones and can be an alternative to them when applied to turbine units.

References 1. Nazin, V.: Determining the influence of structural and operational parameters of a double bearing on the thickness of its disc. Eastern-Eur. J. Enterp. Technol. 3(7(111)), 68–73 (2021)

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2. Nazin, V.: Revealing deformation of segments and their supports in a hydrostatic segmental bearing. Eastern-Eur. J. Enterprise Technol. 4(7(112)), 33–40 (2021) 3. Gnytko, O., Kuznetsova, A.: Theoretical research of the chip removal process in milling of the closed profile slots. Arch. Mater. Sci. Eng. 113(2), 69–76 (2022) 4. Kolomoets, A., Dotsenko, V.: Experimental investigation «Dry» gas-dynamic seals used for gas-compressor unit. Procedia Eng. 39, 379–386 (2012) 5. He, C., Liu, C., Wu, T., Xu, Y., Wu, Y., Chen, T.: Medical rolling bearing fault prognostics based on improved extreme learning machine. J. Comb. Optim. 42(4), 700–721 (2021) 6. Miao, H., Li, C., Wang, C., Xu, M., Zhang, Y.: The vibration analysis of the CNC vertical milling machine spindle system considering nonlinear and nonsmooth bearing restoring force. Mech. Syst. Sig. Process. 161, 107970 (2021) 7. Krsti´c, V., Milˇci´c, D., Milˇci´c, M.: A thermal analysis of the threaded spindle bearing assembly in numerically controlled machine tools. Facta Univ. Ser. Mech. Eng. 16(2), 261–272 (2018) 8. Pham, M.T., Nguyen, T.D.: A method to evaluate wear and vibration characteristics of CNC lathe spindle. Tribol. Ind. 44(2), 352 (2022) 9. Quaranta, E., Davies, P.: Emerging and innovative materials for hydropower engineering applications: turbines, bearings, sealing, dams and waterways, and ocean power. Engineering 8, 148–158 (2022) 10. Guo, B., et al.: Single-crystalline metal oxide nanostructures synthesized by plasma-enhanced thermal oxidation. Nanomaterials 9(10), 1405 (2019) 11. Baranov, O., Košiˇcek, M., Filipiˇc, G., Cvelbar, U.: A deterministic approach to the thermal synthesis and growth of 1D metal oxide nanostructures. Appl. Surf. Sci. 566, 150619 (2021) 12. Baranov, O., Filipiˇc, G., Cvelbar, U.: Towards a highly-controllable synthesis of copper oxide nanowires in radio-frequency reactive plasma: fast saturation at the targeted size. Plasma Sources Sci. Technol. 28, 084002 (2019) 13. Breus, A., Abashin, S., Lukashov, I., Serdiuk, O.: Anodic growth of copper oxide nanostructures in glow discharge. Arch. Mater. Sci. Eng. 114(1), 24–33 (2022) 14. Baranov, O., Fang, J., Rider, A., Kumar, S., Ostrikov, K.: Effect of ion current density on the properties of vacuum arc-deposited TiN coatings. IEEE Trans. Plasma Sci. 41(12), 3640–3644 (2013) 15. Breus, A., Abashin, S., Serdiuk, O.: Carbon nanostructure growth: new application of magnetron discharge. J. Achievements Mater. Manuf. Eng. 109(1), 17–25 (2021) 16. Breus, A., Abashin, S., Lukashov, I., Serdiuk, O., Baranov, O.: Catalytic growth of carbon nanostructures in glow discharge. In: Ivanov, V., Trojanowska, J., Pavlenko, I., Rauch, E., Perakovi´c, D. (eds.) Advances in Design, Simulation and Manufacturing V. DSMIE 2022. LNME, pp. 375–383. Springer, Cham (2022). https://doi.org/10.1007/978-3-031-06025-0_37 17. Baranov, O., Romanov, M., Fang, J., Cvelbar, U., Ostrikov, K.: Control of ion density distribution by magnetic traps for plasma electrons. J. Appl. Phys. 112(7), 073302 (2012) 18. Piet, M.L., et al.: Grease performance in ball and roller bearings for all-steel and hybrid bearings. Tribol. Trans. 65(1), 1–13 (2022) 19. Sun, J., Wu, Y., Yang, J., Yao, J., Xia, Z.: Friction properties and distribution rule of lubricant film of full ceramic ball bearing under different service condition. Ceramics-Silikáty 66(1), 54–65 (2022) 20. Wu, P.L., et al.: Theoretical calculation models and measurement of friction torque for rolling bearings: state of the art. J. Braz. Soc. Mech. Sci. Eng. 44, 435 (2022)

Slot Side Measurement with a Commercial Laser Triangulation Sensor Jan Hošek(B) Faculty of Mechanical Engineering, Czech Technical University in Prague, Technická 4, 166 07 Praha 6, Czech Republic [email protected]

Abstract. We searched for the possibility to modify a commercial laser triangulation sensor for slots and bores side distance measurement. We analyzed our previous approaches with aim to extend width to depth ratio for bore or slot side surface distance measurement. We solved the obscuration problem of the laser illumination and laser spot imaging optical paths with the rearrangement of both paths to its parallel direction. It allows extending the depth of side distance measurement inside bores and slots to no mathematical limit, in theory. We formulated new relation between active mirror length and range of side wall distances of measured surface. We demonstrated the proposed measurement principle with an attachment to the commercial laser triangulation sensor. We performed the side wall distance measurement inside the bore. We confirmed correctness of proposed evaluation of measured surface distance range. Presented measured data shows the sensor provides surface distance data also outside anticipated data range, but the sensor distance values deviate from correct reading. Keywords: Laser Triangulation · Slot · Bore · Wall · Distance · Depth

1 Introduction Laser triangulation probes are increasingly used for dimensional measurements in a variety of applications. They use a simple principle based on optical triangulation making the probe cheap and easy to use. On other hand, the measurement reliability is affected by numerous performance facts leading to deviation of the measured results from real distances aiming for measurement [1–6]. There were introduced different methods for measurement error reduction, compensation, or measurement system optimization [7– 10]. Typical measurement conditions leading to reduction of measurement reliability are measurements at inclined surfaces, in the vicinity of the surface discontinuities, or non-homogeneity of the surface pattern. We focused our previous research on the possibilities of triangulation laser probe measurement out of common measurement conditions of the probes, particularly the measurement of the slots and bore side surfaces [11]. We demonstrated measurement slots and bore of the side surface distance up to a maximum depth/diameter ratio of more than 60% with modification of the commercial laser triangulation sensor. Our analysis reveals the possibility to extend the maximum depth/diameter © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 164–172, 2023. https://doi.org/10.1007/978-3-031-40628-7_14

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ratio. In this study, we propose a new design of the commercial laser triangulation sensor modification extending the depth accessibility of side distance measurement inside slots and bores. We introduce the principle of a laser triangulation sensor distance measurement in Sect. 2. Next, we show consideration of the sensor arrangement enables to achieve slot/bore side distance measurement in Sect. 3. We propose the sensor arrangement allowing aligning both optical paths parallel to the measured surface in Sect. 4. The designed probe function experimental verification is described in Sect. 5. The last section summarizes the study achievements.

2 Distance Measurement Using the Laser Triangulation Sensor The technique of distance measurement using laser triangulation probe involves the imaging of a laser spot onto a position-sensitive detector. A laser beam illuminates the surface being measured to create a spot, whose position is determined using a side view optical imaging system. The sensor detector captures the scattered light from the spot under non-zero angle ϕ between the laser beam and the sensor’s imaging optics axis. This detection angle allows sensing the displacement of the surface position along the laser beam axis to be transferred to a corresponding change in position of the laser spot image in the sensor image plane. The geometrical relationship between the laser spot position, shifted due to the object plane displacement  in the object plane, and the spot image position displacement δ in the spot image position, is given under Scheimpflug’s imaging condition [12]: l · tanϕ = l  · tanθ,

(1)

and can be expressed with the triangle similarity principle: δ=

l  sinθ , lsinθ ∓ sin(ϕ + θ )

(2)

where l and l are the laser spot object and image distances and “+” sign is valid for the surface motion up from the reference position indicated in Fig. 1. The intensity profile of the laser spot image is estimated via various algorithms to determine its centroid. The sensor’s measured surface position data is highly reliable due to calibration of relation between the actual surface position relative to the reference point and the calculated position of the laser spot image centroid, sensed by the detector.

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Fig. 1. Principle of Laser Triangulation Sensor. Red line represents illumination laser beam. Orange lines represent range of the laser spot imaging beams through the lens to the sensor’s detector.

3 Sensor Arrangements for Slot and Bore Side Distance Measurement The laser triangulation sensor is capable of accurate measurement provided two conditions are met. Firstly, the laser beam has to be incident on the measurement surface at normal direction, and secondly the image of the laser spot used for calculation centroid position must be placed on axis of the illumination laser beam. Both conditions can be achieved with the use of a mirror that folds the laser illumination beam and reflects the laser spot back onto the sensor’s detector. In our recent work [11] we analyzed relations for the maximum achievable depth of measurement for the side surface, which depends on the angle ϕ between the laser illumination beam (IB) and laser spot imaging beam (SIB). The angle ϕ value is determined by the sensor’s inherent design. The angle α value is defined by the inclination of the laser illumination beam relative to the plane of the measured surface. The results indicated two extreme optimal configurations for the sensor: a symmetric sensor arrangement (SSA) for α = ϕ/2 shown in Fig. 2 - left and a parallel sensor arrangement (PSA) for α = ϕ shown in Fig. 2 - right. To keep the laser spot image in axis of the illumination laser beam the folding mirror angle β has to be equal to: β=

90◦ − α . 2

(3)

Presence of the folding mirror affects the overall working range d of modified sensor design. Its value is affected with the mirror length L from the laser beam axis and condition that the measured surface cannot get closer than to the mirror tip. The maximum surface distance able to be measured is also given by the tip of the mirror used to image

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Fig. 2. Principle of side distance measurement using symmetric sensor arrangement - left. Principle of side distance measurement using parallel sensor arrangement - right. Blue line indicates a reflecting mirror folding the red laser beam towards the measured side surface.

the laser spot back to the original illumination laser beam axis. Detail image showing limits of the modified sensor working range is shown in Fig. 3.

Fig. 3. Detail of laser triangulation probe showing minimum Dmin and maximum Dmax positions    of sample surface and its corresponding mirror image positions D min and D max . SIB of D max surface image is reflected by the edge of the folding mirror M [10].

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The maximum working range d can be expressed using relation: d =L

sinβ = L · sinβ · tan(β + δ), tanϕ 

(4)

where the δ angle is given by relation: δ = β + α − ϕ,

(5)



where ϕ is the angle between the sensor IB and SIB axes at the mirror edge through the sensor’s imaging lens, while the angle ϕ varies along the sensor’s working range.

4 Sensor Modification for Increases of In-Depth Slot and Bore Side Distance Measurement Experimental results of the slot and bore side distance measurement for SSA arrangement showed feasibility of proposed design, but the maximum depth/diameter ratio do not reach more than 70% due to obscuration one or both of the sensor’s IB and SIB. Despite the SSA sensor arrangement provides access to more deep measurement the PSA arrangement can provide possibility to be even modified if not just one but both IB and SIB will be arranged into parallel direction with respect to the measured surface. It can be reached with folding the IB with next two mirrors to the direction parallel to the SIB. In this case the actual folding mirror has to be split into two parts. One part is used for the illumination laser beam reflection and the second part for the laser spot reflection to form the image in the axis of the IB. This two beams parallel arrangement (2PA) may reach any measurement depth limited just with sensor maximum working range limit. The laser triangulation sensor modification in 2PA arrangement is schematically shown in Fig. 4. In case of the probe inclination under angle ϕ and vertical measured surface orientation the image spot mirror angle β has to be set to: β=

90◦ − ϕ . 2

(6)

If we keep the right angle of the IB reflection with two periscope mirrors the inclination angle ω of the IB the first reflecting mirror has to be set to ω = β/2. This design allows to reduce size of the probe attachment holding the reflection mirror, and to eliminate obscuration effects of both IB and SIB.

5 Sensor Modification for 2PA Arrangement We implemented the proposed 2PA sensor arrangement and designed a probe extension for commercially available laser triangulation distance sensor. Our aim was to test this arrangement using a sensor with maximum angle ϕ between IB and SIB. We used the Micro-Epsilon optoNCDT ILD1420-10 distance sensor providing 10 mm distance measurement range starting 20 mm in front of the sensor. The angle ϕ 

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Fig. 4. Modification of laser triangulation sensor in 2PA arrangement. The standard probe is provided with bypass of the IB to get direction parallel to the measured surface plane. The folding mirror is split into one part reflecting the IB and the second part providing the image of the laser spot for the SIB.

between IB and SIB varies from 29° at the end of the measurement range to 38° at its start. We set the gauge inclination angle to be ϕ = 25°. Using 2PA sensor arrangement resolves the issue of in-depth measurement. In theory, any depth of measurement can be achieved, but in practice, the range of accessible depth of measurement is limited by the working range of chosen sensor. For side wall distance measurement, it is not possible to use entire measurement range of the sensor, and the side distance measurement range is limited by the mirror length according relation (4). Using the 2PA arrangement, we can express the maximum working range d for the mirror tip position in distance l from intersection of the side illumination beam and original sensor laser axis can be expressed using relation: d = l · tan2 β − rLS sinβ

(7)

where rLS is the laser spot radius in the measured wall. The first part of relation (7) corresponds to reflection of the laser spot center point. As triangulation distance sensor process the entire laser spot image centroid, it is necessary to image whole laser spot through the rim part of the mirror to ensure correct measurement by the sensor. This requires extending the size of the reflecting mirror with projection of half of the laser spot to the mirror’s plane expressed with relation rLS sinβ. Only a just fraction of mirror M close to its tip is used for reflecting the laser spot on the side wall. This allows for a reduction in mirror size and to calculation of the minimum length M of the mirror satisfying the required working range d. The minimum

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mirror length is given by relation: M = 2lsinβtanβ + rLS sinβ.

(8)

We used the same mirror size 3 × 3 mm wide and 1 mm thick for all the first, both periscope’s, and laser spot reflecting mirrors. The mirror’s tip was positioned at a distance l = 4.75 mm from the intersection of the illumination beams. It allows for side working range d = 1.92 mm for the laser spot center position. With a laser spot size diameter DLS = 0.6 mm the side working range d is reduced to 1.73 mm. The mirror length M = 3.57 mm is necessary for reflection the laser spot within whole side working range of the sensor. As we use the reflecting mirror length just 3 mm it reduces achievable side working range. While the mirror is shorter the begin of the side measurement range is sifted from the mirror tip by 0.25 mm.

6 Experimental Verification We created a 3D model of the sensor attachment that include all four mirrors and printed it using SLS technique from Prusa Resign on a PRUSA SL1 3D printer. The attachment was equipped with an EROWA ITS Chucking spigot enabling its fixing to the machine chuck, allowing X, Y, Z motions. We used the 4-axis EDM machine Sodick AP1L to achieve precise actuation of the system. Figure 5 displays images of the entire system in test conditions. We conducted side surface distance measurements for various depths up to −12 mm under the wall top rim. We verified the sensor distance characteristics with side wall distance measurement in consequential steps. Setting the reflection mirror tip at a distance of 0.25 mm from the wall, we moved the sensor out from the wall by step size 0.1 mm. The results of our measurement are summarized in Fig. 6. Results show good distance measurement performance for side wall distances from the minimum measurable distance 0.25 mm, in our case, up to a distance 1.7 mm. These data demonstrate good linearity and uncertainty in accordance with the sensor’s datasheet. When the laser spot reflects off the mirror rim, part of its radiation is not reflected, causing deviation from its correct function the sensor’s algorithm that analyzes the laser spot image centroid. It results the sensor provides affected distance data. If the sensor detects scattered light from the reflecting mirror edge, distance data deviation is even increased as indicated by red data points. For distances greater than 2.8 mm sensor indicates loss of laser spot signal.

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Fig. 5. Realization of laser triangulation sensor in 2PA arrangement - left. Detail of reflection mirror part of the sensor’s attachment - right. Right Up - Measurement in tip distance 0.3 mm and in depth −2 mm. Right Down - Measurement in tip distance 0.5 mm and in depth −12 mm.

Fig. 6. Side wall distance measurement in depth Z = −8 mm under the wall top edge. Correct distance data are indicated in green. Affected data points are indicated in yellow. Error data points caused by light scattering of the mirror side are indicated in red.

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7 Conclusions We have proposed a new arrangement for laser triangulation sensor that enables the measurement of surface distances in orientation perpendicular to the sensor axis of measurement. We have evaluated the necessary inclination angles for each mirror to achieve a setup with two beams parallel arrangement. We have also evaluated relations for the sensor’s working range as well as the mirror size. Finally, we created an attachment for the commercially available sensor and performed measurements of the side wall distance. Our results confirmed that the measured working range covered proper, unaffected distance data as expected. This new measurement principle extends depth of in-bore side wall distance measurement using common laser triangulation sensor beyond previously presented limits. Now, the depth of in-bore side distance measurement will be limited only by the selection of the sensor’s working distance.

References 1. Buzinski, M., Levine, A., Stevenson, W.H.: Performance characteristics of range sensors utilizing optical triangulation. In: IEEE 1992 National Aerospace and Electronics Conference, pp. 1230–1236 (1992) 2. Guidi, G., Russo, M., Magrassi, G., Bordegoni, M.: Performance evaluation of triangulation based range sensors. Sensors 10, 7192–7215 (2010) 3. Muralikrishnan, B., Ren, W., Everett, D., Stanfield, E., Doiron, T.: Performance evaluation experiments on a laser spot triangulation probe. Measurement 45(3), 333–343 (2012) 4. Li, S., Yang, Y., Jia, X., Chen, M.: The impact and compensation of tilt factors upon the surface measurement error. Optik 127(18), 7367–7373 (2016) 5. Vukašinovi´c, N.: The influence of surface topology on the accuracy of laser triangulation scanning results. Strojniški vestnik – J. Mech. Eng. 56(1), 23–30 (2010) 6. Wu, C., Chen, B., Ye, C., Yan, X.: Modeling the influence of oil film, position and orientation parameters on the accuracy of a laser triangulation probe. Sensors 19(8), 1844 (2019) 7. Xi, F., Liu, Y., Feng, H.-Y.: Error compensation for three-dimensional laser scanning data. Int. J. Adv. Manuf. Technol. 18, 211–216 (2001) 8. Li, F., Xiong, Z., Li, B.: An error compensation method of laser displacement sensor in the inclined surface measurement. Proc. SPIE 9674, 967402 (2015) 9. Yang, H.W., Tao, W., Zhang, Z.Q., Zhao, S.W., Yin, X.Q., Zhao, H.: Reduction of the influence of laser beam directional dithering in a laser triangulation displacement probe. Sensors 17, 1126 (2017) 10. Nan, Z., Tao, W., Zhao, H.: Automatic optical structure optimization method of the laser triangulation ranging system under the Scheimpflug rule. Opt. Express 30, 18667–18683 (2022) 11. Hošek, J., Linduška, P.: Simple modification of a commercial laser triangulation sensor for distance measurement of slot and bore side surfaces. Sensors 21(20), 6911 (2021) 12. Scheimpflug, T.: Improved Method and Apparatus for the Systematic Alteration or Distortion of Plane Pictures and Images by Means of Lenses and Mirrors for Photography and for Other Purposes. GB Patent No. 1196 (1904)

Mathematical Model and Numerical Model for the Development of Processing Algorithms Using the Harmonic Coil Measurement Method Nicolae Tanase1,2 , Ionel Chirit, a˘ 1 , Adrian Nedelcu1 , Cristinel Ilie1(B) , Marius Popa1,2 , Lipcinski Daniel1 , and Mihai Gut, u1 1 National Institute for Research and Development in Electrical Engineering ICPE-CA,

Bucharest, Romania {nicolae.tanase,ionel.chirita,adrian.nedelcu,cristinel.ilie, marius.popa,daniel.lipcinski,mihai.gutu}@icpe-ca.ro 2 Doctoral School of Electrical Engineering, University Politehnica of Bucharest, Bucharest, Romania

Abstract. This paper presents a method based on the principle of harmonic /rotating coils, used for the rapid and complete characterization of the magnetic field created in the aperture of the electromagnetic particle accelerator electromagnets, aiming to develop an efficient technique. The mathematical model presented contains useful mathematical formulas for the development of processing algorithms using the rotating coil measurement method, as well as a detailed numerical model (FEM) of a normal conductor sextupole electromagnet for particle accelerators. This model will be used to obtain ideal magnetic field data required for the development stage of post-processing programs that will be developed. Additionally, this work presents a computation model for a single coil within a rotating coil magnetic field characterization method, which forms the basis of the rotating coil measurement method. This model aims to determine the magnetic field harmonics using Fourier analysis, and a comparison is made between the ideal model and the data obtained through Fourier analysis. Keywords: Harmonic/rotating coils · Mathematical model · Numerical model · Measurement method · Magnetic field

1 Introduction Particle accelerator electromagnets are designed to control the displacement of charged particle beams within the accelerator aperture. Therefore, the quality that defines a particle accelerator largely depends on the quality of its constituent electromagnets. The evaluation of the quality and performance of electromagnets is achieved through an accurate description of the magnetic field created in the air gap between their poles [1]. Currently, there are four methods used to describe the magnetic field created in the air gap of particle accelerator electromagnets, namely: • Single Stretched Wire Method- SSW [2]; © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 173–185, 2023. https://doi.org/10.1007/978-3-031-40628-7_15

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• Vibrating Wire Method – VW [3]; • Hall Probe Method – HP [4]; • Rotating / Harmonic Coil Method – HC [5–7]. Considering the importance of a complete, accurate, and as fast as possible characterization of electromagnets, as well as the fact that the most performant method for characterizing the magnetic field is the one with harmonic /rotating coils. This method allows for the determination of higher-order multipole coefficients, providing integral information on the behavior of charged particle beams passing through cylindrical aperture electromagnets. Significant progress in the field of data acquisition and analysis equipment allows the development of measurement systems that provide fast and highly reliable characterization of electromagnets. One of the most important projects to achieve a particle accelerator currently underway is the international project FAIR – Facility for Antiproton and Ion Research, aimed at building in Darmstadt, in Germany, of a complex of accelerators capable of providing ion beams and antiproton with high energy and the highest intensity which will offer researchers in Europe and around the world the opportunity to conduct studies in atomic physics, nuclear physics, antimatter physics (antiproton study), physics of nuclear matter in extreme conditions, physics of plasma and related applications. The main accelerator of the facility is a superconducting synchrotron with a double ring, with a circumference of ~ 1,100 m. An important component of FAIR is the storage ring HESR – High Energy Storage Ring, it has a circumference of 574 m and is dedicated to the study of the strong interaction using antiprotons with the moment in the range of 1.5 – 15 GeV/c.

Fig. 1. FAIR facility [8].

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Romania has been involved in the FAIR project since 2007, being a shareholder in the company created to implement the project - FAIR GmbH and a member of the consortium created to carry out the HESR. The Romania in-kind contribution to HESR has a total value of almost 4 million Euros, is made by the National Research and Development Institute for Electrical Engineering ICPE-CA Bucharest and consists of 66 sextupole normal-conducting electromagnets, 27 horizontal steerer normal-conducting electromagnets and 26 vertical steerer normal-conducting electromagnets and 62 power converters for these electromagnets. The development of the constructive solution for the rotating coil measurement system that will be used for characterization of the the magnetic field produced by the electromagnets designed for the FAIR project started with the analysis of the geometric configuration and performance requirements for the two types of electromagnets, namely sextupole and steerer. The geometric configuration of the sextupole and steerer electromagnets is shown in Fig. 2, while the characteristics of the two electromagnets are indicated in Table 1.

a)

c)

b)

Fig. 2. Normal-conducting electromagnets for the FAIR project: a) sextupole electromagnet, b) horizontal steerer electromagnet, c) vertical steerer electromagnet.

Table 1. Parameters of sextupole and steerer electromagnets for HESR. Parameter

Sextupole

Steerer

d2 B/dx2

max. 45 T/m2

-

Max. Deflection angle

-

2 mrad at pmax

Aperture

140 mm

100 mm

Magnetic length

300 mm

300 mm

Iron yoke length

270 mm

250 mm

Iron yoke width

480 mm

596 mm

Iron yoke height

480 mm

450 mm

Mass of the iron (magnetic circuit)

~ 290 kg

~ 165 kg (continued)

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N. Tanase et al. Table 1. (continued)

Parameter

Sextupole

Steerer

No. of coils

6

2

No. of windings / coil

15

44

No. of layers / coil

2

4

No. of turns / layer

7,5

11

Conductor dimensions

10,6 x7 mm2

10,6 x7 mm2

Cooling bore

4 mm

4 mm

Cooper crossection

60,77 mm2

60,77 mm2

Length of conductor / coil

~ 12 m

~ 72 m

Cooper mass / coil

~ 6,5 kg

~ 39 kg

Max. Current

290 A

304,1 A

Current density

4,77 A/mm2

5 A/mm2

Max. Weight

~ 400 kg

~ 315 kg

Voltage (DC)

6,12 V

12,84 V

Resistance

21,12 m

42,2 m

Inductivity

3,4 mH

0,28 mH

Power

1,8 kW

3,9 kW

Water flow rate

~ 0,86 l/min

~ 1,81 l/min

No. of layers / coil

~ 1,14 bar

~ 5,21 bar

In order to develop a high-performance method for the rapid and complete characterization of the magnetic field created in the aperture of particle accelerator electromagnets, based on the rotating coil principle [5–7], a mathematical model has been presented that includes useful mathematical formulas for the for the development of processing algorithms using the rotating coil measurement method, as well as a detailed numerical model of a particle accelerator electromagnet. This model will be used to obtain ideal magnetic field data necessary for the post-processing program development stage (Table 2 and 3). This paper presents the computational model underlying the application of the rotating coil measurement method, which aims to determine the magnetic field harmonics using Fourier analysis [9].

2 Mathematical Model of Harmonic /Rotating Coil Method The harmonic coil (HC) characterization method of the magnetic field produced by electromagnets for particle accelerators involves the step-by-step movement of one or more measuring coils, arranged radially or tangentially on a cylinder introduced inside the aperture of the magnet to be measured. Precise angle encoders and specialized voltage integrators are used for data acquisition at hundreds of points during one rotation of the

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cylinder with the measuring coils, the angular velocity of which can reach up to 10 rotations per second. For this method radial or tangential coils can be used. The radial coil (Fig. 3) forms a frame arranged in a plane that coincides with a radial plane of the cylinder that is inserted into the aperture of the electromagnet [5–7, 10].

Fig. 3. Harmonic/rotating coils measurement [5].

The sides of the coil are arranged at the radius R1 and R2 . The magnetic flux passing through the coil has the expression [5]: R2 (θ ) = NL

Bθ (r, θ )dr = NL R1

(θ ) =

R2  ∞ R1

∞  NLRref n=1

n



R2 Rref

 C(n)

n=1

n

 −

R1 Rref

r Rref

n−1 cos(nθ − nαn )dr

(1)

n  C(n) cos(nθ − nαn )

(2)

where N in number of turns of the coil; L is the length of the coil. If the coil rotates with the angular velocity ω and θ = δ is the angular position at t = 0, thus θ = ωt + δ, the magnetic flux as a function of time will be: (t) =

     ∞  NLRref R2 n R1 n C(n) cos(nωt + nδ − nαn ) − n Rref Rref

(3)

n=1

The voltage induced in the radial coil has the expression:         ∞ R2 n R1 n ∂ C(n) cos(nωt + nδ − nαn ) = NLRref ω − V (t) = − ∂t Rref Rref n=1

(4) The voltage amplitude is proportional to the angular velocity. For analyses based on the voltage signal, it is essential to control the angular position very precisely and to correct for fluctuations in this velocity. The integrated voltage signal gives the flux,

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which is independent of the angular velocity. If the two sides of the coil are not located on the same side of the cylinder center (as in Fig. 3), but diametrically disposed, in expressions (1) – (4) R1 must be replaced by R2 . The tangential coil (Fig. 4) forms a frame whose plane is perpendicular to the radius passing through the center of the coil frame, the two sides of the coil being located at the radius Rc .

Fig. 4. Harmonic/rotating tangential coils measurement [5].

The magnetic flux passing through the coil has the expression [5]: θ+ /2 

(θ ) = NL

Br (Rc , θ)Rc d θ = NL

θ+ /2   ∞

θ− /2 n=1

θ− /2



Rc C(n) Rref

n−1 sin(nθ − nαn )Rc d θ

(5) (θ ) =

∞  n=1

2NLRref n



Rc Rref

n

 sin

n 2

 C(n) sin(nθ − nαn )

(6)

If the coil rotates with the angular velocity ω and θ = δ is the angular position at t = 0, thus θ = ωt + δ, the magnetic flux as a function of time will be: (t) =

    ∞  2NLRref Rc n n C(n) sin(nωt + nδ − nαn ) sin n Rref 2

(7)

n=1

The mentions regarding the analysis of magnetic flux or voltage are also valid here. The radius Rc must be chosen as large as possible to obtain a better signal for the higher harmonics. The angle must be large enough to obtain a significant signal and small enough so that sin(n /2) not to cancel for higher harmonics of interest (  2π/nmax ), in general ∼ = 15◦ . The rotating coil measurement method allows for very precise determination of the main component direction of the magnetic field relative to the measurement direction. It also allows for precise determination of the magnetic axis of quadrupole and sextupole electromagnets relative to the rotation axis of the measuring cylinder. These determinations are of great importance for characterizing the functional behavior of electromagnets

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for particle accelerators, as well as for the precise alignment of electromagnets in the accelerator ring. For the computational model of a single coil it is considered a computational sketch as shown in Fig. 5.

  d  = N · Bd s = (By dx − Bx dy)L = Re By + iBx (dx + idy) = Re[B(z)d z] (8)

Fig. 5. The computational sketch for a single harmonic coil.

The magnetic flux passing through the coil has the expression: ∞ 

 z2   NLRref  z2 n  z1 n   = NLRe B(z)d z = Re − (Bn + iAn ) n Rref Rref z1 n=1

(9) It can be observed that, since the measured fields are 2D, the magnetic flux depends only on the points z1 and z2 , not on how the loop is closed between them. Considering a rotation of the coil with θ, z1 = z1,0 eiθ ; z2 = z2,0 eiθ : ∞

 Kn einθ (Bn + iAn ) − the magnetic flux at angle θ (θ ) = Re (10)  Kn =

n=1

NLRref n



z2,0 Rref

n

 −

z1,0 Rref

n  − the sensitivity of the harmonic n

(11)

Since K is complex, the magnetic flux  is sensitive both to the amplitude and to the phase of the harmonic n. The Fourier transform for harmonic coil method. 1 Synthesis equation : x(t) = 2π

+∞ X (jω)ejωt d ω (reverse transformation) −∞

(12)

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+∞ Analysis equation : X (jω) = x(t)ejωt dt (direct transformation)

(13)

−∞

Complex form : X (jω) = A(ω) + jB(ω)

(14)

where: +∞ +∞ f (t) cos ωtdt;B(ω) = f (t) sin ωtdt . A(ω) = −∞

−∞

3 Numerical Model for the Development of Processing Algorithms by the Measuring Method with Rotating Coils To improve the 2D geometric model of the sextupole electromagnet, a lot of attention was paid to the drawing of the pole shape whose equation is:  y3 ± R3 (15) x=± 3·y Thus, a Matlab program was created to generate this hyperbola from equidistant points, the points generated from the created program are shown in Fig. 6. 82 80 78 76 74 72 70 68 66 0

5

10

15

20

Fig. 6. The points on the hyperbola obtained with Matlab at a distance of 0.5 mm.

The obtained points were exported in < *.DXF > format, then used in the computation geometry for the sextupole electromagnet. The numerical model was implemented with COMSOL Multiphysics [11], in 2D module, Perpendicular Induction Currents, Vector Potential (AC/DC Module). The entire geometry of the electromagnetic field (Fig. 7) was considered without reduction due to symmetry, for the subsequent analysis of errors produced by asymmetry.

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Table 2. Defined constants. Name

Expression

Description

I0

300 [A]

excitation current

Nturns

15

number of turns / coil

Area

1289.168033 [mm^2]

the area of the coil

Table 3. Global variables. Name

Expression

Description

J0

I0 *15/area [A/mm^2]

current density

Fig. 7. The sextupole electromagnet 2D geometry used.

All corners were chamfered by 0.5 mm to reduce calculation errors. The distance between two points on the hyperbola of the pole is 0.1 mm. Also, the geometry includes an air subdomain outside the electromagnet, as well as an asymptotic subdomain for the approximation of infinite space. In Fig. 8 as well as in Table 4 the mesh network of the computational domain is presented.

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N. Tanase et al. Table 4. Mesh network data.

Fig. 8. The sextupole mesh network used

Degree of freedom

952593

Network nodes

238200

Elements

476194

Triangulation

476194

Border elements

7793

Vertex elements

3025

Minimum quality

0.488

Element area ratio

0

For the ferromagnetic core, the following hysteresis curve shown in Table 5 given by the manufacturer was used. Table 5. B(H) curve.

H 0 1 1.1

B(H) 0 663.146 1067.5

1.2 1.3 1.4 1.5 1.6

1705.23 2463.11 3841.67 5425.74 7957.75

1.7 1.8 1.9 2.0 2.1

12298.3 20462.8 32169.6 61213.4 111408

2.2 2.3 2.4

175070 261469 318310

4 Results and Discussions The solution was computed using direct UMFPACK solver [11].

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In the following figures (Fig. 9 – Fig. 11) are presented the results obtained after solving the magnetic field problem for the sextupole magnet (Fig. 10).

Fig. 9. Total current density.

Fig. 10. Magnetic induction and field lines in the electro-magnet, |Bmax | = 1,556 T.

Fig. 11. The magnetic field in the center of the electromagnet |Bmax | = 0,242 T.

The geometric parameters of the coil are found in the sensitivity factor that can be calculated and calibrated. The harmonics of the field can be obtained by a Fourier transformation of the EMF; in practice this is complicated because the angular velocity is difficult to control to have the required accuracy. For this reason, it is integrated over a fixed time interval, which corresponds to measuring the flux at discrete angles. Multipoles are calculated using a Fourier series expansion. A quantitative comparison between the ideal magnetic flux and the Fourier series can be seen in Fig. 12.

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Fig. 12. Ideal magnetic flux vs. Fourier series, for opening angle = 15°.

Tangential coils have a blind eye for multipoles of the order n, if 2π /n it is within the range of the opening angle = 20◦ and the order of the multipole n1 = 18. In this case no signal is induced because (n1 Δ/2) = 0. On the other hand, the same coil has maximum sensitivity at n2 = 9 because in this case sin(n2 Δ/2) = 1. For these reasons, several coils with various opening angles are used to measure the dominant harmonics. The error was evaluated by comparing the coefficient of the third harmonic using: ε=

|Bideal − Bobtained | 100% Bideal

(16)

Thus, regarding that Bideal = 1 for Bobtained = 1,000013522, we will have an error of ε = 1,3522:10–3 %. The comparison between the two curves presented in Fig. 12 can be used to evaluate the accuracy of the Fourier series as a representation of the ideal magnetic flux. The error between the two can be minimized by adjusting the number of terms in the Fourier series, which is known as the order of the series. A higher order Fourier series will provide a more accurate representation of the ideal magnetic flux, but will also require more computational resources. Overall, a quantitative comparison between the ideal magnetic flux and the Fourier series is an important tool for evaluating the accuracy of the Fourier series as a representation of the magnetic field lines generated by a magnetic source.

5 Conclusions In this paper was presented the mathematical model of the harmonic/rotating coil measurement method used for characterization of the magnetic field generated in the aperture of the electromagnets used for particle accelerators. The presented mathematical model will be used for the post-processing of data measured with the rotating coil system.

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The paper also presents a 2D numerical model (FEM) performed using COMSOL Multiphysics program for a sextupole electromagnet manufactured for the FAIR project. The results of the numerical model will be used to test the measurement processing program using the rotating coil method. For the mathematical model, mathematical aspects of signal processing and magnetic field specific to the harmonic / rotating coils were taken into consideration. At the end of the paper is presented a quantitative comparison between the ideal magnetic flux and the Fourier series being an important tool for evaluating the accuracy of the Fourier series as a representation of the magnetic field lines generated by a magnetic source. Acknowledgment. . This work was supported by the Romanian Ministry of Education, Research and Digitalization, project number 25PFE/30.12.2021 – Increasing R-D-I capacity for electrical engineering-specific materials and equipment with reference to electromobility and "green" technologies within PNCDI III, Programme 1.

References 1. Walckiers, L.: Magnetic measurement with coils and wires. In: CERN Accelerator School CAS 2009: Specialised Course on Magnets, Bruges, 16–25 June. CERN, Bruges, pp. 357–385 (2009). http://arxiv.org/abs/1104.3784v1 2. Arimoto, Y., et al.: Magnetic measurement with single stretched wire method on SuperKEKB final focus quadrupoles. In: Proceedings of IPAC 2019, Melbourne, Australia, pp. 432–435 (May 2019). doi:https://doi.org/10.18429/JACoW-IPAC2019-MOPMP006 3. Temnykh, A.: Vibrating wire field-measuring technique. Nucl. Instrum. Methods Phys. Res. Sect. A: Accel. Spectrom. Detectors Assoc. Equipm. 399(2–3), 185–194 (1997). https://doi. org/10.1016/S0168-9002(97)00972-8, ISSN 0168–9002 4. Chen, W.J.: A novel positioning method for Hall magnetic field measurement of heavy ion accelerator. Nucl. Instrum. Methods Phys. Res. Sect. A: Accel. Spectrom. Detectors Assoc. Equipm.1031, 166512. (2022). https://doi.org/10.1016/j.nima.2022.166512, ISSN 0168–9002 5. Jain, A.: Brookhaven National Laboratory Upton, New York 11973–5000, USA, Harmonic Coils, CERN Academic Training Program, April 7–11 (2003) 6. Lauria, A., et al.: Rotating-coil measurement system for small-bore-diameter magnet characterization. Sensors 22, 8359 (2022). https://doi.org/10.3390/s22218359 7. Xie, Y., Chen, W., Liang, H., Qin, B., Yang, J.: Parameter design of a rotating coil measurement system for quadrupoles. In: Proceedings of IPAC 2019, Melbourne, Australia, pp. 4207–4209 (May 2019). doi:https://doi.org/10.18429/JACoW-IPAC2019-THPTS044 8. *** https://fair-center.eu/overview/accelerator 9. Mayoral, E.H., Lopez, M.A., Hernández, E.R., Marrero, H.J., Portela, J.R., Oliva, V.I.: Fourier analysis for harmonic signals in electrical power systems. IntechOpen (2017). https://doi.org/ 10.5772/66733 10. Chirit, a˘ I., T˘anase, N., Ilie, C., Popa, M.: Harmonic coil magnetic measurement system for HESR magnets – a mathematical model and design. In: Electrotehnica, Electronica, Automatica (EEA), vol. 69(1), pp. 63–73 (2021). https://doi.org/10.46904/eea.21.69.1.1108008, ISSN 1582–5175 11. *** COMSOL Multiphysics® v. 5.0. COMSOL AB, Stockholm, Sweden. www.comsol.com

Micropump with Electromagnetic Actuation and Internal Slotted Valves Cristinel Ilie1(B) , Marius Popa1,2 , Nicolae Tanase1,2 , Adrian Nedelcu1 , and Lipcinski Daniel1 1 National Institute for Research and Development in Electrical Engineering ICPE-CA,

Bucharest, Romania {cristinel.ilie,marius.popa,nicolae.tanase,adrian.nedelcu, daniel.lipcinski}@icpe-ca.ro 2 Doctoral School of Electrical Engineering, University Politehnica of Bucharest, Bucharest, Romania

Abstract. This article presents the achievement of a micropump for microfluidic applications. In order to select the constructive solution, related to the available technological possibilities, the constructive solutions for micropumps and microvalves were reviewed. The constructive solution chosen for the micropump is volumetric type and uses passive valves with internal cutouts, electromagnetically actuated. The analytical and numerical calculations for an electromagnetically actuated micropump, which involves the interaction between a planar microcoil and a small permanent magnet is presented. Additionally, the microfabricated elements that comprise the micropump are presented. Given the required pressure and gauge dimensions, a micropump driven by the interaction between a permanent micromagnet and a planar microcoil was made. Keywords: Micropumps · Microvalves · Microfabrication · Electromagnetic actuation

1 Microvalves and Micropumps - Overview Microvalves and micropumps are fundamental elements of microfluidic systems. In the last decade, due to the increased interest in the development of biomedical microsystems, numerous attempts have been made to design and fabricate a wide range of micropumps and microvalves. 1.1 Microvalve Classification Microvalves are devices used to control the flow of liquids or gases in miniature or highprecision applications. They can be classified according to several criteria, of which we present the usual ones, according to Table 1 below [1]: These are just a few examples of microvalve classification, but there are other classification criteria available depending on technical specifications or specific applications. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 186–200, 2023. https://doi.org/10.1007/978-3-031-40628-7_16

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Table 1. Microvalve classification [1] Classification

Type

Description

according to the mode of actuation

electrical microvalves

electrically controlled, can be activated remotely

pneumatic microvalves

controlled by means of air pressure or inert gases such as nitrogen

hydraulic microvalves

controlled by means of a hydraulic fluid such as oil

Microvalves with static sealing capacity

uses a static seal, such as gaskets, to prevent leakage

Microvalves with dynamic sealing capability

uses a dynamic sealing element, such as a rubber ring, that moves with the valve to prevent leakage

Ball valve microvalves

uses a small metal or plastic sphere to block or allow the flow of liquid or gas

Microvalves with diaphragm valve

uses a flexible membrane to block or allow the flow of liquid or gas

Microvalves with piston

uses a small piston to block or allow the flow of liquid or gas

Direct channel microvalves

uses a direct channel to allow the flow of liquid or gas

T-channel microvalves

uses a T-shaped channel to direct the flow of liquid or gas in a specific direction

Y-channel microvalves

uses a Y-shaped channel to direct the flow of liquid or gas in two different directions

Microvalves with screw type connection

uses a screw to connect the microvalve to the rest of the system

Microvalves with hose connection

uses a hose to connect the microvalve to the rest of the system

Microvalves with welding type connection

uses welding to connect the microvalve to the rest of the system

Low pressure microvalves

they have a working pressure of up to 1 bar

according to the type of sealing element

according to the type of valve

by channel type

by connection type

after maximum working pressure

(continued)

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Classification

Type

Description

Medium pressure microvalves they have a working pressure between 1 and 10 bar

By power source

High pressure microvalves

they have a working pressure of over 10 bar

Passive microvalves

they do not require an external energy source to be activated and are activated by means of a force element such as pressure or mechanical force. For example, a butterfly valve that opens or closes depending on the flow of liquid passing through it

Active microvalves

they require an external power source to be activated and can be electrically, pneumatically or hydraulically controlled. For example, an electric valve with rapid opening and closing, which is controlled by means of an electrical signal

Semi-passive microvalves

they can be activated by both an external power source and a force element. For example, a diaphragm valve that can be controlled by hydraulic or electrical pressure

The micropumps are devices that allow the transfer of fluids in small quantities, built with dimensions of the order of micrometers. The main applications are medical devices, analysis systems and air quality monitoring devices. The micropumps are important for the development of miniaturized and portable technologies because they allow the transfer of fluids in small spaces and have a low power consumption. However, due to their small size and complexity, micropumps can be expensive and require dedicated technology solutions to be integrated into a device or system [2]. 1.2 Micropumps Classification According to Field of Use Micropumps used in medical devices. In medical devices, the micropumps are often used for drug delivery or monitoring biological parameters, such as: • Insulin pump: This pump is used to deliver insulin to patients with diabetes. These micropumps are attached to the patient and deliver insulin through a thin catheter.

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• Perfusion pump: This pump is used to deliver drugs or intravenous solutions to patients. These micropumps can be programmed to deliver medications at a certain interval or in a certain amount. • Infusion pump: This pump is used to administer fluids to patients, such as blood or saline solutions. These micropumps can be programmed to deliver fluids in a certain amount or at a certain interval. • Implantable insulin infusion pump: This pump is surgically implanted in the abdomen of patients with diabetes and can deliver insulin throughout the day based on the patient’s needs. This is an option for those who do not want to use an external insulin pump. Micropumps used in analysis systems. Micropumps are used to manipulate and transfer small quantities of fluids during analysis processes, such as: • Peristaltic pump: This is a positive displacement pump that uses a roller system to compress a tube and transfer the liquid through it. They are used in analysis systems to transfer solutions constantly during analyses [3]. • Diaphragm pump: This pump uses a diaphragm system to compress and transfer liquid. • Piston pump: This pump uses a piston to compress and transfer liquid. • Electrokinetic pump: This pump uses an electric field to transfer liquid through a small channel. They can be precisely controlled through electronic control. These micropumps enable high-precision transfer of fluids, avoiding contamination. Micropumps used in air quality monitoring devices. The Micropumps are used to aspirate air and supply it to sensors for analyzing its composition, such as: • Diaphragm pump: This pump uses a flexible diaphragm to aspirate air and detect and measure the level of pollutants in real-time. • Capillary tube pump: This pump uses small capillary tubes to aspirate air. It is used to measure the levels of pollutant gases, such as nitrogen oxides and sulfur dioxide. • Inert gas pump: This pump uses an inert gas, such as nitrogen or helium, to avoid contaminating the air with other substances and to measure the levels of pollutant gases. • Turbo molecular pump: This pump uses a rotor with blades to aspirate air and is used to measure the levels of fine powders and aerosols. 1.3 Micropumps Classification According to the Type of Actuation Piezoelectric Micropumps. The piezoelectric micropumps use the piezoelectric effect to generate liquid flow through a pumping chamber. They are direct-drive pumps because they do not require other components such as gears, pistons, or membranes to generate liquid flow. Piezoelectric pumps use piezoelectric crystals that expand or contract depending on the electric signal applied to them. The advantages of piezoelectric pumps include small size, high precision, fast response time, reliability and durability, low energy consumption, and silent operation. Jet Micropumps. These pumps use jet force to move liquid or gas through a pumping chamber.

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Electric Micropumps. These pumps are electrically powered and use a mechanism to move fluid through a pumping chamber. Cavitation micropumps. These pumps use the cavitation phenomenon to move liquid through a pumping chamber. Magnetic micropumps. These pumps are driven by a magnetic field and use a mechanism to move fluid through a pumping chamber. Thermal micropumps. These pumps use temperature differences to move liquid or gas through a pumping chamber. 1.4 Micropumps Classification According to the Operation Principle Volumetric Micropumps. Volumetric micropumps are pumps that work by moving a fixed volume of fluid through a pumping chamber. These pumps are used in a wide range of applications such as medical analysis, portable medical devices, computer cooling systems, environmental control systems and more. Diaphragm Micropumps. The membrane micropumps use a flexible membrane to generate the necessary pressure to transfer fluid through a piping or tubing system. The membrane pumps can be operated pneumatically, hydraulically, or electrically. The advantages of the membrane pumps include their reliability and durability, ability to handle a variety of liquids or gases, and ability to work at high or low pressures, depending on the application needs. Additionally, membrane pumps can be used in applications that require a constant pressure or constant flow rate. Applications of membrane micropumps include microfilters, laboratory equipment, vacuum micropumps, dialysis machines, negative pressure therapy devices, pharmaceutical transfer pumps, and more. Positive Displacement Micropumps. Positive displacement micropumps are a type of syringe-type micropump used in applications that require constant pressure or flow without fluctuations. There are several types of positive displacement pumps, such as piston pumps, screw pumps, and gear pumps. All of these types of pumps use a mechanism that moves back and forth to move the liquid or gas through the piping system. The advantages of positive displacement pumps include the ability to generate a constant pressure and flow, reliability and durability, and the ability to handle liquids with high or medium viscosity. They can be used in applications that require a wide range of working pressures. The disadvantages of positive displacement pumps include higher cost compared to other types of pumps, as well as the need to have a moving mechanism that wears over time. Micropumps with Shear Effect. Micropumps with shear effect use a system of rotating elements in a specific way, generating a shear effect that causes the liquid or gas to be transferred through a system of pipes or hoses. There are several types of pumps with shear effect, such as peristaltic pumps, flexible rotor pumps, and four-lobe rotor pumps. The advantages of pumps with shear effect include the ability to transfer liquids or gases with a variety of viscosities and densities, reliability and durability, as well as the ability to work at high or low pressures, depending on the application needs.

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Additionally, they can be used in applications that require constant pressure or constant flow rate. Applications of pumps with shear effect include medical devices, food and water analysis, pumping blood during surgery, or delivering medications in infusion therapies. Below, in Table 2, are compared the main characteristics for several types of micropumps: Table 2. Micropumps characteristics Pump type

Overall dimensions [mm x mm x mm]

Maximum flow

Maximum pressure

Manufacturer

centrifugal

28 × 14 × 14

700 ml/min

220 mbaar

Servoflo Corporation [4]

with gears

50 × 30 × 25

100 ml/min

2,5 bar

Micropump [5]

with turbine

40 × 25 × 20

300 ml/min

0,5 bar

March Pump [6]

with diaphragm

25 × 20 × 15

30 μl/min

1 bar

Takasago Electric [7]

with plunger

30 × 20 × 15

10 μl/min

0,5 bar

TOPS Industry & Technology Co.[8]

piezoelectric

35 × 15 × 6

500 μL/min

10 bar

Dolomite Microfluidics. [9]

electroosmotic

28 × 20 × 10

100 μL/min

0.2 bar

Microfluidic ChipShop. [10]

peristaltic

22 × 26 × 12

1000 μL/min

2.8 bar

Bio-Chem Fluidics. [11]

syringe

139.7 × 88.9 × 88.9 50 μL/min

13.8 bar

Harvard Apparatus. [12]

2 Micropump with Electromagnetically Actuated Membrane Calculation and Construction In order to be able to circulate working fluids, we exemplify by sizing and manufacturing a micropump based on electromagnetic actuation. The operating principle of an electromagnetic micropump is based on the deformation of a membrane, due to the electromagnetic force between a permanent magnet and a planar coil [13]. The micropump consists of a membrane, a pumping chamber and two passive valves to ensure unidirectional flow, according to Fig. 1. According to Fig. 1, the micropump consists of: • 1 – planar microcoil. • 2 – permanent micromagnet.

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Fig. 1. Diaphragm micropump

• • • • •

3 – upper casing. 4 – separation membrane. 5 – lower casing. 6 – passive microvalves with internal cutouts. 7 – intake and discharge ports.

The electromagnetically actuated membrane micropump is used in medical, analytical and microfluidics applications. This pump uses a flexible membrane to pump the liquid or gas, which is actuated by means of an electromagnet. The operating principle of an electromagnetically actuated membrane micropump is as follows: 1. In the initial state, the membrane is in its rest position and the liquid or gas is in a suction chamber. 2. When the planar coil is activated, a magnetic field is generated and attracts the micromagnet attached to the membrane towards it, deforming the membrane and creating an intake chamber. 3. This action causes the liquid or gas to be drawn and forced to enter through the pump inlet. 4. After the intake process is complete, the electromagnet is turned off and the diaphragm returns to its original rest position, creating a compression chamber that pushes the fluid through the discharge port. These pumps are highly accurate and can be used to pump low to medium flow fluids such as saline solutions or drugs in medical applications or to dispense precise amounts of reagents in analytical applications. They are also durable and can be used for a long period of time without requiring maintenance. In the case of positive displacement pumps, such as our pump, the amount of the transported fluid depends on the volume of the pumping chamber. Being a pump with alternating movements, it operates in a two-stroke pumping cycle: suction and discharge and the volume of the pumping chamber changes due to the alternate movement of the diaphragm. The suction and discharge of the fluid into the pumping chamber are done through separate connections.

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To ensure that the fluid enters in the pump only through the suction line, the microvalve in the suction connection is opened simultaneously with the closure of the microvalve in the discharge connection. During the discharge phase, the suction microvalve is closed simultaneously with the opening of the discharge microvalve. The opening and closing of the microvalves are done automatically by varying the pressure in the pumping chamber. By deforming the diaphragm 4, the volume of the pumping chamber alternately increases and decreases, thus achieving suction and discharge. The pumping rate depends on the volume of the displaced liquid, Vt. Due to the inertia and imperfect sealing of the valves, there will always be differences between the theoretical pumping rate, calculated based on the volume of the pumping chamber and real pumping rate [14]. The ratio: define the volumetric efficiency of a pump. η=

Vr Vt

(1)

Where Vt represents the theoretical volume of the pumping chamber, and Vr represents the real volume of the pumping chamber. The volumetric efficiency of a pump typically ranges from 0.85 to 0.99 and increases with higher pump flow rates. To calculate the pumping rate, the operating frequency must also be taken into account. The electric signal used to drive the pump is a time-varying signal that follows a sinusoidal curve, resulting in a sinusoidal shape of the pump output flow rate. In the case of single-acting pumps, the output flow rate will be pulsating, with flow only during the discharge phase and zero flow during the suction phase. To overcome this limitation, double-acting pumps are constructed, which can deliver fluid at the output during both the suction and discharge phases. However, the construction of a doubleacting micropump is complicated, so a system consisting of two identical micropumps operating in antiphase (when one is in suction, the other is in discharge and vice versa) can be used [15]. Figure 2 schematically represents the variation of the output flow rate for the two cases.

Fig. 2. Variation of volume flow rate in a single-acting (a) and double-acting (b) pump

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Qv M - represents the maximum volume flow. QVm –, represents the average volume flow rate, It is observed that the maximum value of the flow is for θ = π/2 and the minimum value, equal to zero for θ = π. Qvm = 0.318 Qv M (2)for single acting pumps and. Qvm = 0.636 Qv M (3)for double-acting pumps. For the designed micropump, the value of the pumping flow rate will be: Q = 0.318 ∗ Vt ∗ η ∗ f ∗ 60 [mm3 /min]

(2)

where: Vt – the theoretical volume of the pumping chamber. η - the yield. f – pumping frequency. Having a pumping chamber with a diameter of 10 mm and a height of 0.4 mm, driven by a permanent magnet with a diameter of 4 mm, a thickness of 1.6 mm, we can calculate the theoretical displaced volume, according to the data from Fig. 3.

Fig. 3. The theoretical volume of displaced fluid, for h = 0.2 mm, r = 2mm and R = 5 mm.

Vt = 7.54 mm3 , for one half period. For a full period Vt = 15.08 mm3 . The flow will be: Q = 0.318*Vt*η*f*60 [mm3 /min] = 0.318*15.08*0.85*5*60 = 1222.83 [mm3 /min]. Q = 1.22 μl/min, which, also correlated with the micrometric dimensions of the flow paths, will ensure a laminar flow. After sizing the pumping chamber, we must ensure that the force exerted between the permanent magnet and the planar microcoil is sufficient to overcome the load resistance of the hydraulic circuit, or, in other words, to size the coil-permanent magnet assembly

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so as to ensure at the output pump the pressure required for a microfluidic separation chip, with the value of 5232.361 N/m2 [16]. The induction of the magnetic field, at the distance x from the permanent magnet is [17]:   lm + x x Br  −√ (3) Bz (x) = 2 r 2 + x2 r 2 + (lm + x)2 where Br represents the remnant induction, lm represents the thickness of the magnet, and r is the radius of the magnet. The normal component of the electromagnetic force acting on a coil in a magnetic field is given by the equation: Fz = mBz = NliBz

(4)

In the formula above, N represents the number of turns of the coil, l represents the length of the coil and i is the current through the coil. The simulations were carried out using the SIMULATION module of SolidWorks Premium 2022 and showed that for the deformation of a PDMS membrane with a thickness of 100 μm, the displacement of 0.2 mm corresponds to a force of F = 0.1N, according to Fig. 4.

Fig. 4. Deformation of the membrane in the micropump chamber

According to the 10 mm diameter membrane surface, we have the pressure due to membrane deformation: p=

0, 1 ∗ 4∗104 F = = 0, 1273 ∗ 104 = 1273Pa S π

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The total pressure will be: Pt = P + p = 5232.361 + 1273 = 6505.361 N/m2 = 6,5 kPa. Corresponding to this pressure, for a membrane surface corresponding to a diameter of 10 mm, the minimum force required to actuate the micropump results: Fmin = Pt ∗ S

(5)

Fmin = 6505,361* π/4*10–4 = 5106.425*10–4 N = 127 mN. It uses a flat coil made by laser lithography with the following characteristics: • • • •

Number of turns: 16 Coil section: 200μm x 100μm Unfolded length L = 209 mm Material: electrolytic copper

And a NdFeB permanent magnet with a diameter of 4 mm and a thickness of 1.6 mm. Using the calculation and simulation program INFOLITICA 6.26.1, with the previously specified input data we obtain the value of the force required to be able to move the membrane: F = 184 mN. It is observed that the force developed (Fig. 5a and b) by the permanent micromagnet-planar microcoil assembly is greater than the minimum required force of 127 mN.

Fig. 5. Calculation of the magnetic force with the program INFOLITICA 6.26.1, overview (a) and isolation of the calculation element (b)

Applying a voltage of 10V, the estimated current will be 24 mA, and the consumed power 240 mW. The manufacturing process of the planar microcoil starts from a rigid glass fiber wafer coated with a 50 μm thick layer of copper, which also is coated with a thin layer of photoresist. In this photoresist layer, the shape of the planar microcoil will be configured, as in Fig. 6. The designed micropump will look like in Fig. 7.

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Fig. 6. Microcoil executed by UV laser lithography

Fig. 7. Micropump – exploded assembly 1. Plate I; 2. Flat coil on substrate; 3. Plate II; 4. Passive microvalves; 5. Plate III; 6. Membrane; 7. Permanent magnet.

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3 Micropump Manufacturing The manufacturing of the benchmarks for the micropump involved very tight tolerances, most of the time only 2 or 3 μm. Dimensional checking of landmarks took place throughout the execution process, the main dimensional checks being as follows: • For the microvalves executed by LIGA technology [18], the determination of the dimensional accuracy required measurements that establish the manufacturing accuracy of the photoresist masks and patterns; these determinations were performed with video cameras and software packages of the DWL66Fs system; • Determinations of the dimensions of the final parts; these determinations that were made by microscopy using the Stemi2000C microscope and the Veeco microscope • For the benchmarks executed by micro-machining on the Kern Micro center, the precision determination was made by using the Renishaw mechanical feeler system with wireless communication mounted in the main spindle. The one-way microvalves were executed using LIGA technology, the membrane attachment plates and the micropump body were processed on the Kern Micro CNC center. Machining involved precise processing of the dimensions, including a inlet/outlet - 80 μm punched hole. The executed landmarks fell within the required specifications, a fact also noted during assembly. Below are some examples of milestones (Fig. 8).

Fig. 8. Highlights for micropump and product under test

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4 Conclusions The most common types of microvalves and micropumps were analyzed depending on the application, the type of actuation and the principle of operation. Given the pressure to deliver at the outlet and the gauge dimensions as input data, a micropump driven by the interaction between a permanent micromagnet and a planar microcoil was dimensioned. The force required for the actuation system was determined following the numerical calculation, resulting in a force of 184mN, for a flow Q = 1.22 μL/min, superior to the minimum required value of 127mN. The dimensioning was done in such a way as to ensure a laminar flow [19]. Power required for operation is 240 mW, at a voltage of 10V, developing a maximum pressure of 6.5 kPa. All the landmarks were made using microfabrication technologies, they were assembled and the result was a micropump for microfluidic applications with dimensions of 14mm x 14mm x 5.15mm. Acknowledgment. . This work was supported by the Romanian Ministry of Education, Research and Digitalization, project number 25PFE/30.12.2021 – Increasing R-D-I capacity for electrical engineering-specific materials and equipment with reference to electromobility and "green" technologies within PNCDI III, Programme 1.

References 1. Mukhopadhyay, S.: Classification of microvalves - a review. Int. J. Chem. Separation Technol. 4(1) (2018) 2. Khan, R., Dhand, C., Sanghi, S.K., Shabi Thankaraj Salammal, D., Mishra, A.P.: Advanced Microfluidics Based Point-of-Care Diagnostics, 1st edn. ImprintCRC Press, Boca Raton (2022) 3. Forouzandeh, F., Alfadhel, A., Arevalo, A., Bork-holder, D.A.: A review of peristaltic micropumps. Sens Actuators A Phys. 1(326), 112602 (2021) 4. Servoflo Corporation. https://www.servoflo.com/micropumps/tcs-micropumps/m200-microp ump.html 5. Micropump. https://micropump.com/products/pumps 6. Marh Pump. https://www.marchpump.com/applications/mag-drive-pumps-medical-system 7. Takasago Electric. https://www.takasago-fluidics.com/products 8. TOPS Industry & Technology Co.. http://www.topsflo.com/micro-gear-pump. 9. Dolomite Microfluidics. https://www.dolomite-microfluidics.com/product/piezoelectricpump. 10. Microfluidic ChipShop. https://www.microfluidic-chipshop.com/catalogue/pumps-and-pre ssure-controllers/micropumps-by-bartels-mikrotechnik 11. Bio-Chem Fluidics. https://www.arcmedgroup.com/pumps-valves 12. Harvard Apparatus. https://www.harvardapparatus.com/pumps-liquid-handling/syringepumps.html 13. Comeaga, C.D., Ovezea, D., Ilie, C.L.: Micro electromagnetic actuator - static behavior. In: MATEC Web of Conferences, vol. 220 p. 05003 (January 2018)

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14. Galeriu, C.D.: Mecanica fluidelor newtoniene vascose incompresibile Editura: Politehnica Press (2016) (Published online 10 Feb 2021) 15. Vitan, F.: Ingineria proceselor în textile s, i piel˘arie II, 8–15 (1991) 16. Ilie et al.: Proiecte s, i modele microsisteme s, i componente MEMS pentru aplicat, ii specifice, Etapa de execu¸tie nr.: II/2012, Contract: Componente s, i sisteme microelectromecanice (MEMS) realizate prin tehnologii specifice, cu aplicat, ii în medicin˘a, microfluidica s, i în realizarea de micromotoare s, i micro-actuatoare (cod. PN 09 350101) 17. Morganti, E., et al.: Design and fabrication of microfluidic actuators towards microanalysis systems for bioaffinity assays. Microelectron. Eng. (2011) 18. Prioteasa, P., Ilie, C., Popa, M., Iordoc, M., Sbarcea, BG.: Electrodeposition of Nickel for Fabrication of Microfluidic Pumps. Revista de Chimie 64(3), 275–280 (2013) 19. Kirby, B.J.: Micro- and Nanoscale Fluid Mechanics: Transport in Microfluidic Devices (11 September 2009)

Study on the Life of Hydrocyclones for Cleaning Coolant on Roll Grinding Machines Mykhaylo Stepanov1 , Maryna Ivanova1(B) , Volodymyr Korniienko1 Yurii Havryliuk1 , Serhii Slipchenko1 , and Petro Litovchenko2

,

1 National Technical University «Kharkiv Polytechnic Institute», 2 Kyrpychova St.,

Kharkiv 61002, Ukraine [email protected] 2 National Academy of the National Guard of Ukraine, Maidan Zahysnykiv Ukrainy, Kharkiv, Ukraine

Abstract. A large number of rolling mills in steel mills are currently in operation, the most important element of which are rolls. To maintain the performance characteristics of the rolls’ working surfaces, regrinding is applied. Under these conditions, coolant is an integral part of the process, which is contami-nated by metal and abrasive impurities during machining. Hydrocyclones can be used for cleaning coolant, which is subject to failure during operation as a result of wear and clogging. It has been confirmed that during coolant cleaning using hydrocyclones the content of fine particles less than 5–7 µm increases in the cleaned liquid in comparison with the initial one. A simplified and idealized model of slurry orifice wear, hydrocyclone has been developed. However, the process is stochastic, requires consideration of a larger number of factors, and is further complicated by the different nature of the particle size distribution. A method of indirectly determining the diameter of the slurry orifice has been developed, as measuring it directly causes difficulties in indirect control. At indirect control of wear of slurry tip by method of coolant pouring through the cone of hydrocyclone, time of outflow (pouring) was determined, which later was used to determine outlet diameter of the slurry tip. In this case, we used the solution of the problem of liquid flowing out of a conical tank at a variable pore size. It was found experimentally, that a diameter of a slurry tip of the hydrocyclone can in-crease by 2.47–25 mm during grinding (150 h of machine time). Sudden and permanent failures during the operation of hydrocyclones as a result of clogging of orifices of their slurry tips were analyzed. Frequencies of failures per shift depending on machine grinding time and mass of ground metal were determined experimentally. Keywords: Hydrocyclone · Roll Grinding Machine · Cleaning Coolant · Slurry Orifice

1 Introduction The quality and durability of the machine are associated with the development and implementation of progressive production processing, among which grinding occupies a special place, to which a large number of research works are devoted. Coolant is an © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 201–215, 2023. https://doi.org/10.1007/978-3-031-40628-7_17

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integral part of grinding. Contaminated with impurities, the coolant loses its functional properties, so the tasks of high-quality cleaning in the process of its operation are of paramount importance. To clean the coolant, hydrocyclones are used, which provide a high degree of purification. In the hydrocyclone, there is no depletion of the emulsion coolant due to the absence of filter elements. However, a significant disadvantage of hydrocyclones is their increased wear and clogging with large impurities. This significantly reduces the reliability of the cleaners and the entire grinding process as a whole. Given that there are practically no studies on the reliability of hydrocyclones for coolant cleaning, the material presented may be relevant.

2 Literature Review A large number of rolling mills in steel mills are currently in operation, the most important element of which are rolls. To maintain the performance characteristics of the rolls’ working surfaces, regrinding is applied. Under these conditions, coolant is an integral part of the process, which is contaminated by metal and abrasive impurities during machining. Hydrocyclones can be used for cleaning coolant, which is subject to failure during operation as a result of wear and clogging. Hydraulic cyclone parts are subjected to failures associated with the developing wear process of their internal surfaces. Wear is caused by mechanical impurities moving with high velocities, which are a waste product of the grinding process, entering the coolant from the cutting zone. These impurities affect the surfaces and require removal from the coolant to ensure high grinding efficiency. The influence of mechanical impurities contained in coolant on the reliability indicators of hydrocyclones during grinding has not been adequately investigated to date. Meanwhile, coolant, being the most important means of intensification of machining by cutting, should meet a number of requirements, including cleanliness and service life. Wear of the hydrocyclone surface, as one of the types of failure, is determined by the conditions of wear and the physical properties of the contacting elements. Hydrocyclones have found wide application in various fields of industry for separating particles from liquids due to their advantages, namely low energy consumption, high throughput, easy operation, low maintenance costs, etc. [1–4]. The particles in the hydrocyclone generally undergo rotational motion [3, 5]. However, the process of fluid flow in a hydrocyclone is very complex due to the high shear of the fluid streams, the layered distribution of particles and the interaction between several phases [3]. There are many studies devoted to the study of hydrodynamic processes taking place in a hydrocyclone [6–10]. There are also many works devoted to the study of the geometric parameters of hydrocyclones. The authors of the paper [9] propose a hydrocyclone with a tapered inlet design that integrates the advantages of the spiral inlet and tangential inlet. The authors [11] of the work carried out a study of the changes in the radial velocity of the flow field in proposed design axial-symmetry double-tangential-inlet hydrocyclone. In the paper [12] the effects of spiral inlet geometric parameters on the flow field characteristics and separation performance were investigated by Computational Fluid Dynamics (CFD).

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In the study [13], a set of potential hydrocyclone designs (Conventional cylindricalconical design and various novel cyclone designs having a combination of multiple and small cone angles, tapered vortex finder and air core free designs) are explored for fines classification using Computational Fluid Dynamics (CFD) technique. The paper [2] presents a numerical study on effects of feed size distribution on separation performances of hydrocyclones at a wide range of rifice diameter. The study [14] investigated the effect of inlet concentration on the hydrodyclone’s separation performance within a wide range of inlet velocity via numerical analysis, which demonstrates that the number of the dislocated particles was enhanced at a too great or a too low inlet velocity, thereby leading to the decline in the separation performance. In the work [15], a hydrocyclone was designed and manufactured to achieve an inlet flow rate of 1 L/min and it was confirmed that the performance of the hydrocyclone could be accurately predicted using numerical analysis. The research [16] aimed to study the effect of the interaction between two variables on separation in a novel designed hydrocyclone: underflow orifice diameter and vortex finder length. Thus, although the first hydrocyclone was patented as early as 1891 [17], and its industrial application began as early as the late 40-s of the 20th century, and during that time a huge number of various scientific works were carried out on the design and investigation of hydrocyclones in various areas of industry, no works aimed at investigating the reliability and durability of hydrocyclones could be found. Therefore, the purpose of this study is to investigate the effect of impurity particle movement on the wear of the slurry orifice and the inner surface of the fluid cleaning cyclone during roll grinding in rolling mills.

3 Research Methodology 3.1 Determination of the Spiral Scratch Pitch Left by a Mechanical Particle on the Inner Surface of the Slurry Orifice The liquid motion in a hydrocyclone is represented as a result of liquid motion in three directions: tangential (circumferential), axial (vertical), and radial. The tangential component is the most important and has a decisive influence on the behaviour of the particle in the hydrocyclone. It has been found [18], that velocities of solid particles are close to velocity of liquid and divergence between them does not exceed 5%, i.e. relative motion of solid particles in circumferential direction is practically absent. It is the tangential particle velocity that largely determines the wear of the inner surface of the hydrocyclone. Numerous theoretical and experimental studies [18–21] have shown that the character of the change in tangential flow velocity along the radius of the hydrocyclone follows the law vt · r n = const,

(1)

where vt is the tangential velocity of the liquid at radius r; n is the exponent. Along the radius of the hydrocyclone, n can vary from + 1 (for the case of potential rotation of an ideal liquid) to -1 (for the case of rotation of a liquid as a solid). The carried

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out investigations [22] made it possible to determine ratios between tangential flow velocity and flow velocity at the inlet to the hydrocyclone for devices whose dimensions correspond to those of hydrocyclones for coolant cleaning, namely for hydrocyclones with diameters 25, 40, 60, 80, 100, 125 mm, etc. According to the data [23] during coolant cleaning with the help of hydrocyclones the content of fine particles (less than 7 microns) increases in the clarified product in comparison with the initial one. Under the influence of a centrifugal field, the particles of mechanical impurities are already destructed after a single passage of coolant through the hydrocyclone that causes a shift of the grouping center on the curve of particle size distribution from 15–17 µm to 7–8 mm. The reduction in particle size of mechanical impurities facilitates the passage of coolant through the cutting zone, where it is also crushed. When a particle enters the contact zone, the force required to crush it is smaller the larger the contact area between the grinding wheel and the workpiece. The destructive stresses that cause the particles to be crushed depend on the size of the impurity and its nature. As the particle size decreases, the breaking stress increases. The breaking stress for quartz particles of size 10–100 µm can be determined according to the formula   1, 1 (2) σp = 9860 0.3 + 0.5 , dz where dz is particle diameter, µm The crushing process is evaluated by an indicator (particle crushing coefficient in the grinding zone) εck =

n 

Pcki · mcki ,

(3)

i=1

where Pcki is the probability of particles being crushed after the i-th time they enter the grinding zone; mcki is proportion of mechanical particles delivered to the grinding zone for the i-th time out of the total number of particles. Studies [24] have shown that the destruction of abrasive grains from electrocorundum occurs at a certain load, which can be determined by the formula 2 , Pe = 5, 6dgr + 0, 5dgr

(4)

where dgr is the grain size of the abrasive material, mm. Observations have shown that wear products contain both whole grains crushed from the wheel and partially worn ones. The axial velocity of coolant flow in slurry orifice with diameter dsl =3mm at flow rate Qsl =1–2 dm3 /min and head before orifice h≈1,32 m is va = 4,7 m/s. The tangential velocity can vary considerably, e.g. for a hydrocyclone with a diameter 75 mm, the tangential speed varies from 3 to 20 m/s. The rotational speed of the coolant flow together with the particle is determined by the formula np =

1000 · vt , π · dsl

(5)

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where dsl is a diameter of slurry orifice, mm; vt is velocity of coolant flow, v/min. Then the axial movement of the particle in the slurry orifice per one revolution of the flow va (6) Sa = . np Thus, the value of the axial movement of the particle in the slurry orifice per one revolution of the flow is equal to the spiral scratch pitch that the mechanical particle leaves on the inner surface of the slurry orifice. 3.2 Determination of Geometric Parameters for Wear of the Slurry Orifice Under the Influence of a Single Particle Wear on the conical part of the hydrocyclone occurs most intensively at the bottom of the cone. It must be borne in mind that the wear of these parts (cone and tip) is proportional to the cube of the liquid velocity and the pressure is proportional to the square of the liquid velocity. The wear of the hydrocyclones was checked by longitudinal grinding. An abrasive wheel PP750 × 63 × 305,25A25HC17K5 rotating at a speed of 50 m/s was used. Grinding conditions were chosen so that constant minute metal removal was maintained, which ensured the concentration of contaminating mechanical impurities in the coolant at the level of 1–1.5 g/dm3 . The process of removing material from the inner surface of the hydrocyclone slurry tip from the action of a single abrasive grit can be similar to the turning process. This produces a spiral groove on the inner surface of the cone with a pitch that is determined by the axial component of the velocity of the coolant in the hydrocyclone. Studies [25, 26] suggest that the cutting process is possible if the rake angle reaches γ x = -60º. At angles of grain sharpening of electrocorundum -113º and -36º, which are determined by the crystal structure of this material, the limiting cutting angle γ x , when one plane of the grain slides on the work surface, and the other plane produces cutting, are [27] γmax = −113◦ + 90◦ = −23◦ ; γmin = −96◦ + 90◦ = −6◦ .

(7)

A huge number of abrasive, metal, and bonding particles are involved in the wear process of the slurry orifice. According to the laws of large numbers, it can be assumed that there is some average shape of scratching (cutting) edges of particles fitting into a certain contour. In this context, an idealized scheme for the formation of scratch marks during the wear of the slurry orifice is proposed (Fig. 1). The diagram shows an n + 1 helical groove arising from N + 1 mechanical particles. In the scheme: Rsl , rsl is large and small radii of the slurry hole; Hsl is length of the slurry hole; α/2 is half of the angle of the slurry tip cone; va is axial velocity of coolant flow along the inner surface; ac , bc are geometric parameters of the trace (cut). When a particle that cuts (scratches) the inner surface of a slurry tip moves, it is affected by an external force, which can be decomposed into two components: Py and Pz . The force component Pz cuts the chip and Py presses the particle against the inner

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Fig. 1. An idealized scheme for the formation of scratch marks during the wear of the slurry orifice.

surface. The force component Py is the centrifugal force acting on the particle and is defined by the formula Py =

m · vt2 , Rsl

(8)

where m is mass of the mechanical particle, vt is tangential velocity of the mechanical particle; Rsl is radius of the slurry orifice. The average weight per cut left by the action of the abrasive particle in the slurry tip can be determined by the formula: q=

ac · bc · lc · ρp , 3

(9)

where ac is a depth (thickness) of cut (groove from action of abrasive particle) on the inner surface of the hydrocyclone; bc is a width of cut; lc is a length of cut (spiral groove from action of abrasive particle); ρp - density of polyurethane. The length of cut is the trace of the mechanical particle action in the form of an Archimedean spiral. The main effect on the inner surface of the hydrocyclone is caused by abrasive particles, but the effect of metal particles is also noticeable, as they are many times more numerous than abrasive particles. The length of the spiral is determined by the formula:   Sa , (10) lc = 2π · rsl + 2 where Sa is spiral pitch; rsl is radius of slurry orifice.

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The scratch width at a given depth (thickness), assuming that within the maximum possible scratching (cutting) depth the cyperbolic relationship is maintained, can be determined according to the formula [28]:  (11) bc = 2 h2c + 2hc (2c3 d3 )0.5 , where d3 is particle size mm; c3 is coefficient depending on particle size; hc is scratch depth, mm. In a simplified manner the penetration of a mechanical particle can be represented as an indentation of a cone into the sample. The penetration depth (scratch depth) can be determined by the formula [29]:  Py  , (12) hc = π · σk · tgα k · tgα k + f where Py is a force with which a mechanical particle is pressed into the inner surface of the slurry orifice (in our case it is a tangential force); σk is a contact stress; αk is half of the angle of taper; f is friction coefficient. The relationship between the cut and grain parameters can be determined by the formula [30]: (13) bc = 2 2ρgr ac , where ρgr is tip grain radius, mm. The wear of the slurry orifice from the action of an aggregate of particles is determined by the formula: J = q1 + q2 + · · · + qn =

n 

qi .

(14)

i=1

Also, the wear of the slurry orifice surface can be determined if the axial velocity of the coolant flow and the cut thickness of the forming scratches are known. As a result of wear, the volume of the slurry hole changes. The magnitude of this change can be determined by the formula: Vsl = Vfinal − Vinitial ,

(15)

where Vfinal , Vinitial are the final and initial volumes of the slurry tip orifice The final and initial volumes of the slurry tip orifice can be find respectively:

 1 (16) Vfinal = π · Hsl (Rsl + ac )2 + (rsl + ac )(Rsl + ac ) + (rsl + ac )2 , 3

 1 (17) Vinitial = π · Hsl R2sl + rsl · Rsl + rsl2 3 a Taking into account the above and knowing that va  = cosvα/2 , the change in volume of the slurry orifice due to wear is determined by the formula:

q =

va · π · Hsl (ac + ·Rsl + rsl ). cos α/2

(18)

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The following parameters are different for real conditions: (a) Grain size: dgr1 = dgr2 = dgr3 = . . . = dgrn b) the forces acting on the particle Py1 = Py2 = Py3 = . . . = Pyn Pz1 = Pz2 = Pz3 = . . . = Pzn iii) shear thickness of individual particles ac1 = ac2 = ac3 = . . . = acn iv) the parameters of grains β1 = β2 = β3 = . . . = βn ; ρgr1 = ρgr2 = ρgr3 = . . . = ρgrn ; γx1 = γx2 = γx3 = . . . = γxn ; and others. Thus, the developed deterministic model of wear of the hydrocyclone slurry orifice is idealised. In fact, the process is stochastic and requires consideration of a larger number of factors. It should be kept in mind that the cross-sectional area of the cut changes from the action of each particle, as does the configuration of the cut. A small part of the particles performs cutting (scratching), while a larger part deforms the inner surface. The process is further complicated by the different nature of particle size distribution.

4 Results The object of the study is hydrocyclones for coolant cleaning of models X45–33 and X45–23. According to the certificate, hydrocyclones are designed for purification of coolant from mechanical impurities with volume weight up to 2 g/cm3 and size not exceeding 2 mm in grinding, honing and other machine tools. The hydrocyclone cleans coolant with a temperature from 10 to 55ºC. Coolant contamination at the inlet to the hydrocyclone must not exceed 3.5 g/dm3 . The technical characteristics of the hydrocyclone are shown in Table 1. Physical and mechanical properties of the contact materials are shown in Table 2. Due to the design difficulties of measuring the diameter of the slurry orifice due to wear, it is problematic. In this connection, wear was assessed by two methods, determining the coolant flow rate through the slurry tip (Fig. 2): 1. Ensuring a constant pressure drop across the operating hydrocyclone;

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Table 1. The technical characteristics of the hydrocyclones. The technical characteristics

X45–33

X45–33

Nominal flow rate, dm3/min, not less

50

50

Nominal pressure at hydrocyclone inlet, MPa

0.25

Rated purification cleanliness, mkm

10–16

5

Degree of purification, % minimum

-

98

Mass, kg

2.2

0.3

Table 2. Physical and mechanical properties of the contact materials. Object

Material

Density kg/m3

Hardness

Note

Value

Unit of measure

Roller

9X steel

7800

90–102

By ball

Grinding wheel

Zirconium electrocorundum

4000–4150

22.6–25.5

GPa

Hydrocyclone

Polyurethane

30–300

40–98

By ball

Grinding wheel hardness CM1, sound index 29

2. When coolant was poured through the hydrocyclone cone. Under indirect control with ensuring constant differential pressure on the operating hydrocyclone, the formula for flow rate from the orifice and nozzles at constant head was used, from where the diameter of the slurry orifice was determined  4·Q , (19) dsl = μ · π ·(2g + Ho )2 where Q is fluid flow rate from the orifice, m3 /s; μ is flow coefficient, μ = 0.96 for conically converging nozzle; g is acceleration of free fall, g =9.8 m/s2 ; Ho - head before the hydrocyclone slurry orifice, determined by pressure drop across the hydrocyclone, m. In indirect control of slurry tip wear by pouring coolant through the hydrocyclone cone, the pouring time was determined, which was further used to determine the outlet diameter of the slurry tip. In this case, we used the solution of the problem of liquid flowing out of a conical tank at a variable head. As a result, the following formula was derived    α 4 2 · H 0,5 4 α 2 2 Dsl + sl · H · tan + · H · tan (20) dsl = 3 2 3 2 μ · t · (2g)0,5

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a)

b)

Fig. 2. Diagrams for determining the flow rate through the slurry tip: a) with constant coolant pressure drop across the hydrocyclone; b) with pouring through the hydrocyclone cone.

where H is the height of the conical part of the hydrocyclone, m; μ is the flow coefficient; t is the time of coolant volume flow, s; g is the acceleration of free fall, m/s2 ; α is the angle at the cone top, α = 15°; Dsl is the diameter of cone at the slurry orifice. Formula (20) is applicable when there are differences in the diameters of the small base of the cone and the small tip inlet in the hydrocyclone design. If this difference does not exist, the change in diameter of the slurry orifice of the tip can be obtained from formula [31]. √ 2π · Rcone 2 · Hr (21) t= √ 5fsl · 2g where Rcone is the radius of the large base of the cone orifice, m; fsl is the area of the slurry orifice, m2 . Formula (20) is applicable to water-based emulsion liquids with characteristics similar to those of water. Experimental studies have been carried out on the flow rate of coolant into the slurry tank over grinding time of roller (Fig. 3). The X35–15 hydrocyclones were tested for longitudinal grinding. The coolant flow into the cutting zone was 160 dm3 /min. The pressure at the output of the hydrocyclones Poutput = 0.8 kg/cm2 . Initial coolant flow into the slurry tank is Qsl = 7.7–8.6 dm3 /min. Analysis of the graphs (Fig. 3) shows that between 118 and 149 h of grinding, the flow rate into the slurry tank is 1.7 times greater than between 0 and 58 h of grinding. At the same time, the diameter of the sludge reservoir increased by 2.47 mm with the grinding time of the rolls (Fig. 4). Systematic measurement of the flow rate Qsl in the grinding process has shown (Fig. 5) that when Qsl = 18 dm3 /min is reached, the hydrocyclone cleaning mode of the coolant is violated. Besides, at such flow rate of coolant the efficiency of sedimentation of

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Fig. 3. Influence of roll grinding machine time on coolant flow into the slurry tank: 1 hydrocyclone battery (four hydrocyclones); 2 - one hydrocyclone.

impurities in the slurry tank decreases, as coolant flushes all slurry back to the system. This mode of operation is reached after 150–155 h of roll grinding. The volume of grinded material was 37 kg or more.

Fig. 4. Effect of machine roll grinding time on the increase in diameter of the hydrocyclone slurry orifice due to linear wear caused by mechanical impurities contained in the coolant: 1 - estimate of coolant flow at constant pressure period on the hydrocyclone; 2 - when coolant is poured through the hydrocyclone cone.

Hydrocyclone failures due to clogging can be permanent or sudden. Permanent failures can occur both as a result of wear on the hydrocyclone and when they are clogged. Sudden ones only in case of clogging. Continuous failures occur at regular intervals (Fig. 6) and their frequency depends on the grinding machine time (mass of ground metal) (Fig. 7). Sudden failures in the hydrocyclones can occur when the machine is switched on and depend on the mass of slurry in the coolant cleaning tanks of the machine and how “caked” it is, i.e. the duration of the downtime period. Experience from grinding cast iron hot rolls on an XX5-15H27 has shown a constant clogging of the hydrocyclone from literally the first hour of the machining process (Fig. 6). Pinput = 3 kg/cm2 ; Poutput = 1.1 kg/cm2 .

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Fig. 5. Influence of machine grinding time and mass of ground metal on the coolant flow rate through the slurry orifice of the hydrocyclone (hydrocyclone coolant cleaning system X35–15): 1 - battery of hydrocyclones (4 pcs.); 2 - one hydrocyclone.

Fig. 6. Changes in the failure rate of a roller grinding machine XX5-15H27 coolant cleaning unit due to clogging of the hydrocyclone over time. Operation parameters: wheel speed 40 m/s, roll speed 10–20 rpm,

If the slurry nozzle becomes clogged, the stream of impurities forms an irregular “umbrella” (if the nozzle design does not include means to prevent a strong spray of impure flow). The flow pours out on one side or comes out jerkily. Clogging can be caused not only by mechanical impurities, but also by misalignment of the nozzle with the conical part made during assembly. Experience from the use of hydrocyclones for cleaning coolant during roll grinding shows that when clogging occurs, the slurry builds up in the conical parts so intensively that it is not possible to clean the slurry with improvised means, for example, a wire through the slurry orifice. Cleaning requires additional costs for disassembly and reassembly of the hydrocyclones.

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Fig. 7. Influence of machine time (mass of ground material) on the number of failures of hydrocyclones (unit HC 200–15) due to clogging: ground material - cast iron;

5 Conclusions The use of high-performance coolant for grinding rolls in rolling mills does not guarantee maximum results. In order to make full use of the potential of coolant it is necessary to effectively clean it from mechanical impurities accumulated in the coolant system during the machining process. As it is known, impurities on the one hand reduce the service life of coolant, and on the other hand, worsen the parameters of grinding and quality of the received surfaces. The specificity of coolant usage in roll grinding is associated with high volumes of coolant consumption, a significant part of which goes through the grinding zone and increased value of the concentration of contaminants, getting into the coolant from the cutting zone: machining waste and wear products of the grinding wheel. In this regard, the cleaning of coolant from mechanical impurities comes to the fore. Hydrocyclones can be used for this purpose, the potential for which is considerable, and their efficiency is determined, among other things, by the wear parameters of the inner surface and the nature of the fracture from clogging. In this regard, studies have been carried out of investigate the effect of impurity particle movement on the wear of the slurry orifice and the inner surface of the fluid cleaning hydrocyclone during roll grinding in rolling mills. As a result of research: 1. For the first time, a deterministic model of wear of the inner surface of a hydrocyclone is proposed, which makes it possible to take into account the size of impurities. 2. Methods are given for determining the wear of a hydrocyclone by indirect methods by the flow rate of the liquid flowing through the slurry tip. 3. The data on the increase in the slurry orifice of hydrocyclone in the process of grinding are given. 4. The failure rate of hydrocyclones as a result of their clogging is analyzed depending on the machine time of grinding. The failure rate may increase 2 or more times. 5. The given data is useful for developers and operators of installations for cleaning coolant during abrasive processing.

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17. Castilho, L.R., Medronho, R.A.: A simple procedure for design and performance prediction of Bradley and Rietema hydrocyclones. Miner. Eng. 13(2), 183–191 (2000) 18. Kelsall, D.F.: A further study on the hydraulic cyclone. Chem. Eng. Sci. 2, 254–272 (1953) 19. Kapustin R.P.: The tangential velocity in the hydrocyclone. Nauchno-tekhnicheskiy vestnik Bryanskogo gosudarstvennogo universiteta, vol. 2, pp. 337–342 (2020). https://doi.org/10. 22281/2413-9920-2020-06-02-347-342 20. Concha, F.: Flow Pattern in Hydrocyclones. KONA Powder Particle J. 25, 97–132 (2007). https://doi.org/10.14356/kona.2007011 21. Concha A., F., Bouso A., J.L.: Flow pattern in hydrocyclones. In: Fluid Mechanics Fundamentals of Hydrocyclones and Its Applications in the Mining Industry. FMIA, vol. 126, pp. 67–127. Springer, Cham (2021). https://doi.org/10.1007/978-3-030-67913-2_5 22. Naidenko, V.V., Khusainov, I.Y., Tolkachev, A.B.: Studies of hydrodynamics of pressure hydrocyclones. Water Sanitary Eng. 6(3–6) (1983). (in Russian) 23. Polyanskov, Y.V., Karev, E.A., Bulyzhev, E.M.: Methods for evaluating the quality of coolant cleaning. Mach. Tools and the Tool 10(30–32), 1976 (in Russian) 24. Vakser, D.B.: Ways of increasing productivity of an abrasive tool at grinding. Mashinostroenie, Moscow (1964). (in Russian) 25. Lurie, G.B.: Grinding of metals. Mashinostroenie, Moscow (1969). (in Russian) 26. Maslov, E.N.: Theory of grinding materials. Mashinostroenie, Moscow (1974). (in Russian) 27. Kartashov I.N. et al.: Processing of parts by free abrasives in vibrating tanks. Vishcha Shkola, Kiev (1975). [in Russian] 28. Redko, S.G.: Processes of heat formation at grinding of metals. Saratov University Press, Saratov (1962). (in Russian) 29. Yakubov F.Y., Izdetov N.A., Djemilov E.S.: Improving the quality of machining tapered holes by diamond honing. Dnipi, Simferopol (2011). (in Russian) 30. Filimonov, L.N.: High-speed grinding. Mashinostroenie, Leningrad (1979). [(in Russian) 31. Luzin, N.N.: Integral calculus. Soviet Science, Moscow (1949). (in Russian)

Development of Technology of Making Shafts from Steel Alloy 35XGCL Nozimjon Kholmirzaev1(B) , Nodir Turakhodjaev1 , Nosir Saidmakhamadov1 , Jamshidbek Khasanov2 , Shokhista Saidkhodjaeva1 , and Nargiza Sadikova1 1 Tashkent State Technical University, Tashkent, Uzbekistan

[email protected] 2 Andijan Machine Building Institute, Andijan, Uzbekistan

Abstract. In the manuscript, according to analyses of known problems in foundry production enterprises, the technology of obtaining large – sized shafts by casting has been developed. First of all, methods of liquefaction of 35XGCL brand lowalloy steel alloy in an electric-arc furnace have been improved. In addition, the liquefied alloy was treated with a flow of inert gas (argon) in a special ladle outside the furnace. By the way, liquid metal is cleaned of gas pores and non – metallic inclusions. Moreover, the metal liquid is alloyed well and the chemical elements in the alloy are uniformly distributed throughout the volume. High gas permeability of the sand-clay mold mixture is ensured. The microstructure images of the cast alloy are illuminated. In order to improve the physical-mechanical and operational properties of the shaft detail cast from the low-alloyed steel alloy of the 35XGCL brand, a heat treatment method was developed. The term of service of the resulting shafts has increased. As a result of application, the volume of the product obtained has increased 1.12 times. Keywords: Chrome · manganese · alloy · hardness · viscosity · gas pores

1 Introduction The origin of the production of ferrous metal alloys can be traced back to 2000 BC, when manuscripts found in ancient China and India refer to artificial ferrous metals. Competitiveness in the metallurgical and mechanical engineering industries and world trade keeps developing and implementing novel methodologies for the new century. The industrial response to the local and global technology footprint is to further improve existing technologies and also make major changes in a few key areas such as the production of steel and its alloys. Steel is the most popularly used metal in industrial production. As the global economy expands, the demand for steel and its alloys is increasing rapidly, leading to increased supply needs. For reference, in the last 15 years, high – quality steel production in the world has doubled, from 24 million tons in 2005 to 51 million tons in 2020. According to the data of the World Steel Association published at the end of January 25, in 2021, the volume of steel production worldwide grew by 3.6% per year, the total production © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 216–223, 2023. https://doi.org/10.1007/978-3-031-40628-7_18

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volume in 2021 reached 1.95 billion tons, and the volume of pig iron production was 1.6 billion tons, which in turn indicates a high demand for steel [1]. Belgian scientists Lecomte-Beckers Jacqueline, Sinnaeve Marios studied the highchromium steels and semi – high – speed steel alloys in the preparation of shafts for rolling mills, and their results showed that the microstructure of a sample made of chrome steel mainly consists of hardened martensite with eutectic carbides of M7 C3 and M6 C types. As a result, the high hardness of carbides has been found to have much higher corrosion resistance and thermal cracking resistance than the previous standard types. Semi – high – speed steel types are mainly made of hardened martensite with special carbides of M7 C3 , M6 C, and MC types [2]. Italian scientists M. Pellizzari, D. Cescato, M.G. De Floralar conducted scientific research on thermal viscosity and wear resistance of shafts made of high – speed steel and high – chromium cast iron alloys. He also mentioned the positive effect of abrasive wear on high – speed steels compared to carbon steel, and the escalate the carbides’ amount on wear resistance [3].

2 Materials and Methods Nowadays, the rolling machine shafts used in the stamping plants of production enterprises are the main and the most expensive part of the machines for the production of rolled products. They are exposed to various stresses and strains during working time. In addition, the geometric dimensions and material of the shafts must ensure that they can withstand the heaviest loads that occur during the shift sequence. Another important factor related to the life time of the shafts is the wear resistance of its material. Analyzing the problems, products made of 35XGCL alloy in local factory were analyzed (Fig. 1).

Fig. 1. Effect of non – metallic inclusions and gas pores on cast alloys.

The cast alloy was examined using an Axiovert 40 MAT microscope to determine the presence of aluminum oxide and oxide – type inclusions. It is clear from Fig. 2, Axiovert 40 MAT microstructures are shown as aluminum oxide and oxide – type non – metallic inclusions. In Fig. 2b and Fig. 2c, inclusions of large nitrides in the ferrite phase (yellowish) shafts are mainly made of alloyed steels. These steels are consider to have better mechanical features and wear resistance than ordinary structural carbon steels. Because of the fact that they are designed to respond not to chemical composition, but to specific mechanical properties. For many low – alloyed steels, the main task of alloying elements is to optimize their mechanical properties after heat treatment [2, 3].

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a) X100

b) X500

c) X1000

d) X2000

Fig. 2. Microstructure image of non – metallic and oxide inclusions in the alloy taken by Axiovert 40 MAT microscope. a, b - Microstructure, steel brand 35XGCL. Perlite flake + ferrite. Etched with 4% nitric acid solution, c - Microstructure, steel brand 35XGCL. Perlite flake + ferrite. Etched with 4% nitric acid solution, d - non – metallic inclusions (not etched): manganese sulfides located along grain boundaries.

Currently, one of the urgent issues is to liquefy secondary charcoal metals and obtain high – quality cast products from them in foundry molds. Because, to reach a high – quality casting, it is not only a correctly calculated composition of the charcoal, but also a result of several factors, such as the temperature at which the alloy is liquefied and in what type of furnaces, the correct calculation of the casting system, the development of the composition of the sand – clay mold, and the correct selection of the temperature of the liquid alloy poured into the mold. Iron ore, low – manganese steel, secondary metal, ferroalloys, ferrosilicon (FeSi 65), ferromanganese (FeMn 95), calcium carbonate as flux (CaCO3 ) and others were prepared as raw materials for charcoal. A basic 2.0 ton electric arc furnace was initially selected to melting the alloy. After checking that the inner lining of the furnace was in good condition, first small and then large charcoal materials were loaded into the furnace. As soon as the alloy begins to melting, 3 percent limestone (CaCO3 ) by weight of the alloy is added to the furnace as a flux. According to the established norms, the temperature of liquefaction of the chemical composition was 1550 °C. After that, ferroalloys with a high melting point were put into the furnace at 1595 °C. From the side of the furnace to reduce the carbon element in the alloy oxygen was injected with a pressure of 0.8 – 1 MPa through a specially installed forma. As a result, carbon and harmful gases in the alloy were reduce (Fig. 3). When the temperature of the liquid alloy reached 1610 – 1620 °C, it was poured into a special ladle preheated to 800 – 8500 °C.

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Fig. 3. The process of metal liquefaction in an electric arc furnace.

Argon gas was injected into the alloy as an inert gas from the lower part of the special ladle in order to reduce the gas pores and non – metallic inclusions in the alloy, and to obtain high – quality cast products (Fig. 4).

Fig. 4. Out of furnace treatment process for liquid metal using argon gas.

After cleaning the pores and non-metallic residues, pour the alloy into the prepared sand mold [4–6].

3 Results Designing a steel 35XGCL to produce high quality products, reduce the content of pores and non-metallic materials, alloy liquefaction process and technology, and casting quality. After the steel is processed, samples of the liquid alloy blend are taken from three sources and special samples are poured to examine the chemical composition of the steel, the distribution of elements in metals, its mechanical properties and microstructure (Fig. 5). Special cast samples for research analyzes were first processed on a lathe machine and surface cleanliness was ensured. Then the chemical composition of the alloy was determined using the “GNR S9 Atlantis optical emission spectrometer” device (Tab. 1).

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Fig. 5. Cast samples from 35XGCL brand low – alloyed steel for research analysis.

Table 1. Sample’s chemical configuration according to research results. №

Elements, % C

Si

Mn

Ni

P

S

Cr

Cu

Al

N-1

0.316

1.04

1.13

0.12

0.032

0.027

0.83

0.15

0.277

N-2

0.306

1.03

1.13

0.12

0.032

0.024

0.83

0.14

0.278

N-3

0.310

1.04

1.13

0.12

0.033

0.027

0.83

0.14

0.281

After ensuring the surface cleanliness of the samples poured for research. in order to obtain their microstructural analysis, the surface was treated with silicon carbides of 200, 400, 600, 800, 1200, 1500, 2000 µm in the “Struers Tegramin-30” polishing machine. During processing, the surface characteristics were analyzed in a fast metallurgical microscope “Nikon Eclipse MA200”. After the research samples were ready, the microstructure images of the alloy were taken by a Zeiss Ultra Plus Field Emission SEM scanning electron microscope (Fig. 6). Figure 6 shows images of pearlite microstructure in low – alloyed steels. The pearlite structure is shown at a higher magnification in Fig. 6d, the (parallel – plate – like) microstructures consist of ferrite, pearlite and less cementite. Accordingly, when increasing the carbon content from 0.08 to 0.35% in these samples, the excess carbon appeared in two different structures, cementite particles and cementite carbide phase in pearlite. Here, both structures help to increase the hardness and strength of the steel [7–12].

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Fig. 6. Microstructure images of 35XGCL low – alloyed steel alloy taken by a Zeiss Ultra Plus Field Emission SEM device.

The distribution (liquation) of chemical elements across the surface of the poured samples was investigated using the Zeiss Ultra Plus Field Emission SEM device. The main purpose of the test is that the arrangement of the chemical elements in the alloy greatly affects the mechanical properties of the alloy. Distribution of chemical elements along the surface is shown in Fig. 7. Many possible causes of shaft part casting problems were analyzed. The results suggested that exogenous non-metallic inclusions in the form of aluminum oxide and oxides introduced through the hot top of the furnace and refractory materials were considered to be important causes. Statistical data from the last 10 cast shaft parts produced in heavy industry were obtained to identify important causes of production problems. A comprehensive data set showed that 50% of shaft manufacturing problems were caused by non-metallic inclusions, 31.3% by gas pores and the remaining 18.7% by surface cracks. After the results of the research were use to the production enterprise, they were re-discussed and the level of low-quality product casting decreased by 6.67%. Because in the process of current research, only one out of 15 researches was found to be of poor quality.

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Fig. 7. Distribution of chemical elements of low – alloyed steel alloy 35XGCL across the surface.

4 Conclusions According to the results of the experimental research, the following conclusions were reached, which were taken as the main reasons for the flux, furnace lining, quality of refractory materials, the preheating process of the charcoal, and other similar factors. According to the above reasons, the quality of the furnace lining and lining material is considered to be the most important factor that causes the final casting quality to decline. The method used in this study gives good and undeniable results. Also, as a repair measure, the electric lining, electric stove and electric heater were replaced with the best materials. It has also been proven that the level of bad products can be reduced by controlling the percentage of additives at each level.

References 1. The World Steel Association (worldsteel) Homepage. https://worldsteel.org/ 2. Lecomte-beckers, J., Sinnaeve, M., Tchoufang Tchuindjang, J.: Comparison between HCS and semi-HSS grades used as work rolls in the roughing stand of Hot Strip Mills. In: Proceedings of International Conference on Steel Rolling ( 2015) 3. Pellizzari, M., Cescato, D., De Flora, M.G.: Hot friction and wear behaviour of high speed steel and high chromium iron for rolls. Wear 267(1 – 4), 467 – 475 (2009) 4. Turakhodjaev, N., et al.: Technology for cleaning non-metallic inclusions and gaseous pores in the process of liquefaction of steels in an electric arc furnace. Europ. Multidisc. J. Mod. Sci. 04, 77–82 (2022)

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5. Nodir, T., Sarvar, T., Kamaldjan, K., Shirinkhon, T., Shavkat, A., Mukhammadali, A.: The effect of lithium content on the mass of the part when alloyed with lithium aluminum. Int. J. 11(52), 52–56 (2022) 6. Turakhodjaev, N.: Technology for cleaning non-metallic inclusions and gaseous pores in the process of liquefaction of steels in an electric arc furnace. Euro. Multidisc. J. Mod. Sci. 4, 77–82 (2022) 7. Jamil, M., et al.: Internal cracks and non-metallic inclusions as root causes of casting failure in sugar mill roller shafts. Materials 12(15) 1–22 (2019) 8. Nodir, T., Nosir, S., Shokhista, S., Furkat, O., Nozimjon, K., Valida, B.: Development of 280x29nl alloy liquefaction technology to increase the hardness and corrosion resistance of cast products. Int. J. Mechatronics Appli. Mech. 10(1), 154–159 (2021) 9. Ermatov, Z., Dunyashin, N., Yusupov, B., Saidakhmatov, A., Abdurakhmonov, M.: Modelling the chemical composition process concerning formation of metals from manual arc surface on the basis of the electrode coating charge components classification. Int. J. Mechat. Appli. Mech. 12, 170–176 (2022) 10. Grachev, V. A., Turakhodjaev, N.D.: Influence of high-temperature treatment of melt on the composition and structure of aluminum alloy. Arch. Foundry Eng. 17(4) (2017) 11. Umidjon, M., Jeltukhin, A., Meliboyev, Y., Azamat, B.: Effect of magnetized cutting fluids on metal cutting process. In: International Conference on Reliable Systems Engineering (ICoRSE)-2022, pp. 95–104. Springer International Publishing, Cham (2022). https://doi.org/ 10.1007/978-3-031-15944-2_9 12. Nosir S., Bokhodir K.: Development of liquefaction technology 280X29NL to increase the strength and brittleness of castings. In: International Conference on Reliable Systems Engineering (ICoRSE)-2022, pp. 105–115. Springer International Publishing, Cham (2022). https://doi.org/10.1007/978-3-031-15944-2_10

Influence of Technological Parameters of the Continuous Casting Process on the Process of Accumulation of Damage in the Billet Oleg Khoroshylov1(B) , Olga Ponomarenko2 , Oleg Podoljak1 , Oleg Kondratiyk1 , Nataliia Yevtushenko2 , Anton Skorkin1 , and Yuriy Sychov1 1 Ukrainian Engineering and Pedagogical Academy, st. Universitetskaya, 16, Kharkiv 61003,

Ukraine [email protected] 2 National Technical University “Kharkov Polytechnic Institute”, 2 Kirpicheva St., Kharkov 61002, Ukraine

Abstract. The purpose of the article is to determine the optimal technological parameters of the continuous casting process to control the accumulation of ω, to eliminate the formation of surface cracks and, as a result, to improve the mechanical properties of copper alloy blanks. Based on Eqs. (1) and (2), workpiece movement time, workpiece stress and temperature, and such a technological parameter as workpiece movement frequency, a model was developed that calculated ω based on three workpiece movement cyclograms, which are described in Table 1. Table 3. Theoretical and practical result: - taking into account the force of overcoming SlFF to determine ω by formula (1) made it possible to obtain underestimated values of damage accumulation; - taking into account the efforts to overcome StFF and SlFF in one cycle made it possible to find that in this case the indicator ω increased its value; - it was determined that an increase in the frequency of movement of the workpiece, other things being equal, reduces the process of accumulation of ω in the workpiece. So, when performing a reverse movement of the workpiece while overcoming StFF and at a frequency of movement of the workpiece (fmov.) equal to 7.5 min−1 , an optimal minimum of damage accumulation ω = 4.72 10–4 was obtained. Wherein, σ0 = 360.0 MPa. When using a cyclogram in which StFF was overcome during the translational movement of the workpiece and at fmov = 3.75 min−1 , it was obtained: ω = 18.16 10–4, and σ0 = 318.0 MPa. These studies made it possible to obtain technological parameters that, ceteris paribus, exclude the appearance of cracks on the surface of continuously cast billets made of copper alloys, which made it possible to improve the mechanical properties of the billets. Keywords: Accumulation of damage · Quality of copper alloys · Frequency of movement of a continuously cast billet · Static friction force (StFF) · Sliding friction force (SlFF)

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 224–236, 2023. https://doi.org/10.1007/978-3-031-40628-7_19

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1 Introduction One of the tasks of machine-building enterprises is to improve the quality of billets that are used in the machine-building complex. To this end, throughout the twentieth century, research work was carried out to improve the process of continuous casting of billets from various metals and alloys, which are described in [1, 2]. It was shown in [3] that during continuous casting of metals and alloys, when they are removed from the mold of a continuous casting machine, stresses arise in them, which can cause crack formation. The papers [4–7] give examples of the application of the critical strength criterion in assessing the measure of embrittlement during bending tests of prismatic specimens with a fatigue crack. Currently, multi-strand continuous casting machines (PJSC ArcelorMittal Kryvyi Rih) have a capacity of up to 100,000 tons per year [8].

2 Literature Review The Bailey-Norton and Robotnov-Kachanov formula for determining the damageability of a structural material as a function of stress in the workpiece, temperature, and time is presented in [10]: ω = B(T ) · σ n · t,

(1)

κ exp(k · T ) , t∗

(2)

σ∗ =

where - B(T ) = βo · exp(−kT ) = const- since the accumulation of damage (ω) occurs at a certain narrow temperature interval, we will accept: T = const; T is temperature, K; σ is the stress in the workpiece during overcoming (StFF) or (SlFF), σ = F/A, MPa; t – time, n k1, k2, βo, K – experimental coefficients; F is the force acting in the cross-section of the workpiece, A is the cross-sectional area of the workpiece, which has a cracking temperature; Works [11–13] are devoted to the study of the influence of technological parameters of the continuous casting process on the accumulation of workpiece damage. In [12, 13], the damage accumulation of a continuously cast billet was studied at various technological parameters of the continuous casting process, which were divided into three parts according to the frequency of the cyclic movement of the billet in the mold of a continuous casting machine. The work [14] describes transient rheological states of semi-hard alloys treated under rapid compression, which confirm that no damage accumulation processes were detected during compression. In modern mechanics, to describe the processes of latent damage to structural materials, the concept of constant damage accumulation is used; therefore, the kinetics of damage accumulation is described in [15, 16], taking into account the type of stress state. A work is also presented on the effect of the load frequency on the fatigue of structural building materials [18], but no sources of literature were found that would describe the effect of the frequency of the cyclic movement of the workpiece on the accumulation of

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damage. Therefore, this article is devoted to determining the effect of the frequency of the cyclic movement of the workpiece on the accumulation of damage (ω). Purpose of Work. 1. Determine how the complex action of the static friction force (StFF) and the sliding friction force (SlFF) in one cycle of the workpiece movement affects the stress in it. 2. Determine the effect of the frequency and direction of movement of the billets from copper alloys under the action of the static friction force at the level of damage accumulation. 3. Develop a methodology for determining the accumulation of damage (ω) of a billet made of copper alloys, taking into account: – three frequencies of billets movement, ( fmov) in the interval: 3.75 min−1 < fmov < 7.5 min−1 ; – a combination of forward and reverse movement of the billets while overcoming the static friction force (StFF). – for each combination of forward and reverse movement of the workpiece during StFF, the development of three cyclograms to calculate the accumulation of damage (Cycl) of the billets during the cycle. 4. Determine the optimal technological parameters of the continuous casting process: – to control the accumulation of damage (ω) of workpieces made of copper alloys; – in order to prevent the formation of surface cracks during continuous casting of billets from copper alloys; – to improve the mechanical properties of billets made of copper alloys.

3 Materials and Research Methodology Figure 1 shows the crystallization unit of a continuous casting machine.

Fig. 1. Crystallization unit of a machine for horizontal continuous casting of copper alloy billets: 1 - melt; 2 - body of the metal receiver, 3 - Copper wall of the mold, 4 - graphite bushing of the mold, 5 - parabolic curve, which in the billet (pos. 6) passes into the crystallization front; 6 hardened billet.

Based on Eqs. (1)–(2), a method for calculating damage accumulation (ω) was created, consisting of three conditions for stress distribution in the workpiece during overcoming StFF and SlFF. The technique will allow generalizing the results of calculations ω obtained on three models for calculating ω of the workpiece during the cycle for each frequency of movement of the workpiece (fjmov). ω - the value of the accumulated damage of the billet at the end of the cycle.

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In this article, the influence of the cycle duration on damageability will be studied for various cyclograms of the billet movement, taking into account overcoming (StFF) during forward and reverse movements of the billet. Therefore, the procedure for determining ω of the workpiece consists of three cyclograms, which in turn are based on three conditions for the cyclic movement of the workpiece in the mold (Fig. 1). For each cyclogram, the time is given during which the billet is under stress, obtained in [14]. The first cyclogram - Cycl I for calculating the accumulation of damage to the billet is based on the condition: – it is assumed that during the entire duration of the translational movement of the cycl proq billet, the force of sliding friction (SlFF) timov = tiSlFF must be overcome under proq stress σSlFF = 0, 4 MPa in the billet - (Table 1) Table 1. Initial data for determining ω during the cycle for three frequencies of movement of the billet according to the conditions Cycl I fjmov min−1

timov , s

tifull , s

σSlFF , mPa

3,75(j=1)

4 (i=1)

16

0.4

5,0(j=2)

3(i=2)

12

0.4

7,5(j=3)

2(i=3)

8

0.4

cycl

proq

cycl

proq

Table 2. Initial data for determining ωStFF during the cycle for three frequencies of movement   of the billet according to the conditions Cycl II fjmov min−1

tmovStFF , s

σStFF , mPa

timov , s

σSlFF , MPa

3,75(j=1)

0,5

0.5

4(i=1)

0.4

5,0(j=2)

0,5

0.5

3(i=2)

0.4

7,5(j=3)

0,5

0.5

2(i=3)

0.4

proq

proq

cycl

proq

The index j = refers to the change in the frequency of movement ( fjmov) of the billet, and the index i to the index of the cycle time (Table 2). proq The second Cycl II cyclogram for calculating ωStFF , obtained during the translational movement of the billet during overcoming StFF, which is based on two conditions: – the first condition: during the overcoming of the static friction force (StFF), the proq translational movement of the billet with stress σStFF = 0, 5 MPa must be performed proq over time tmovStFF , s;

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– the second condition: during the time timov SlFF must be overcome during the proq translational movement of the billet with stress σSlFF = 0, 4 MPa. proq

P.s. For all ADMs, the duration tmovStFF = 0, 5 s of the movement of the workpiece to overcome StFF - during is carried out due to the duration of the pause, and not due to the time of movement of the billet in the cycle. rev , were obtained The conditions of the third cyclogram Cycl III for calculating ωStFF with the reverse movement of the workpiece while overcoming StFF: – the first condition - we take into account that during the overcoming of StFF, a reverse rev = 0, 5 MPa movement of the billet must be performed during with a voltage σStFF in the billet; cycl rev - during – the second condition - over time timov , SlFF must be overcome σStFF proq translational movement with voltage σSlFF = 0, 4 MPa in the billet. Table 3. Initial data for determining ω during the cycle for three frequencies of billet movement according to the conditions Cycl III fjmov min−1

rev , s tmovStFF

rev , MPa σStFF

timov , s

σmov , MPa

3,75(j=1)

0.5

-0.5

4(i=1)

0.4

5,0(j=2)

0.5

-0.5

3(i=2)

0.4

7,5(j=3)

0.5

-0.5

2(i=3)

0.4

cycl

proq

Thus, on the basis of three cyclograms (Cycl), a method has been developed for calculating ω over the cycle time for various frequencies of billet movement, as well as for various options for alternating movement of the billet during overcoming StFF.

4 Results 4.1 Determination of the Accumulation of Damage, According to the First Cyclogram of the Movement of the Billet On. Figure 2 shows the dependences ω for three values of the workpiece movement frequency (fjmov), according to the conditions of its movement presented 1. In  in Table I to Cycl I . [12], the results of ω of the workpiece were obtained in 500 s ωi500c Dependence 1 represents the accumulation of damage to the billet with a test duration of 500 s. As a matter of fact, dependence 1 represents the damage accumulation rate ˙ calculated according to Eq. (2). (ω), cycl Let us determine the index ω of the workpiece during the cycle timov for each value of fmov, provided that the speed of the billet in the cycle will have a constant value Vmov = const = 0.01m/s. We accept that the accumulated damage (ω) for 500 s will be a constant value I = const for Cycl I - (Table 4). ω500c

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Fig. 2. Dependence of the value of the accumulated damage of the workpiece for a time of 500 s during the cyclic movement of the workpiece according to the conditions Cycl I [12]: 1 – billetmovement frequency fmov: 3.75 min-1, 5.0 min-1 and 7.5 min-1, respectively. Table 4. Calculation of ω during the duration of one cycle of movement of the workpiece at various values of f(j)mov. f(j)mov min−1

timov , s

tifull , s

σSlFF . mPa

I ωj500c

I ωjcycl 10–4

3,75(j=1)

4(i=1)

16

0.4

0.185

14.8

5,0(j=2)

3(i=2)

12

0.4

0.185

11.1

7,5(j=3)

2(i=3)

8

0.4

0.185

7.4

cycl

cycl

proq

Despite the fact that AD for 500 s for all frequencies (fjmov, min-1) has a constant value, - ω in a cycle for each frequency (f(j)mov min-1) will have different values: – thus, at f(j = 3)mov = 7.5 min−1 during the cycle time ω was the value ω(j = 3)Icycl = 7, 4 · 10−4 , and at f(j = 1)mov = 3.75 min−1 during the corresponding cycle time AD - the value ω(j = 1)Icycl = 14, 8 · 10−4 ; – it was determined that with an increase in the duration of the movement of the billet in the cycle by 2 times, the value of ω accumulated in the cycle also increases by 2.0 times; – it follows that as f(j)mov increases, the value of ω decreases. Thus, from Table 4 it follows that regardless of the cyclogram ωjcycl = F(fjmov) or ωjcycl = F(tjmov). 4.2 Discussion of the Results of Calculating the Accumulation ()   of Damage in the Workpiece, According to the Second Cyclogram Cycl II According to the cyclogram Cycl II , we determine its damage during the cycle, taking into account the various stresses that arise in the billets both during overcoming StFF and during overcoming SlFF. To do this, consider the results ofdetermining the accumulation of damage, presented  II . in [12] (Fig. 3) for a time of 500 s - ωj500c On fig. Figure 3 shows the dependencies of the workpiece damage at different frequencies of its movement ( fjmov) on the cycle time.

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Fig. 3. The dependence of the change in the accumulation of damage to the billet during the cycle, moving for the conditions of the second model of the movement of the billet: 1–3 – billet movement frequency f(j)mov: 7.5 min−1 , 5.0 min−1 and 3.75 min−1 , respectively

  Based on dependencies, 1–3 (Fig. 3), we determine ω for a time of 500 s for Cycl II : II - and for the cycle time (ωj II ) at various values of fjmov (Table 5). we obtain ω ωj500c cycl proq proq The stress in the billet σStFF and σSlFF for StFF and SlFF was experimentally detercycl

mined in [14], during the movement of the billets in the cycle timov , s, it was determined from Table 1 –Table 3. Table 5. Calculation of ω during one cycle of movement of the billet, calculated according to Cycl II f(j)mov min−1

tmovStFF , s

timov , s

σStFF , MPa

σSlFF , MPa

II ωj500c

II 10–4 ωjcycl

3,75(j=1)

0,5

4(i=1)

0.5

0.4

0.227

18,16

5,0(j=2)

0,5

3(i=2)

0.5

0.4

0.200

13,62

7,5(j=3)

0,5

2(i=3)

0.5

0.4

0.189

8,25

proq

cycl

proq

proq

As a result of calculating ω of the workpiece, the following conclusions were Cycl III obtained according to: The Calculation of the Workpiece’s  Resulted in the Following Conclusions: 1. It was determined that with an increase in the duration of the movement of the cycl II billet in the cycle timov by 2 times, the value of AD accumulated in the cycle ωjcycl increases by 2.2 times (Table 5), which is consistent with the Bailey-Norton and Robotnov-Kachanov formula (1). For our case, B(T) = k*, so Eq. (1) will look like: ω = k ∗ σ n · t,

(3)

where –k* is the coefficient that takes into account the value of the function B(T) for the temperature of the temperature range (for example, for bronze grade BrO5Ts5S5 - T = 880 - 920 °C) [12]. I II = const, then for - Cycl II - ωj500c = var: 2. If AD changes within 500 s for Cycl I - ωj500c

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3. The nature of the change in ω during the cycle for Cycl I and Cycl II varies depending on f(j)mov. It follows from Fig. 4 that under the condition f(j)mov = 3.75 min−1 , a billet with II = 18.16 · 10−4 in the places of its solidification fronts was obtained. cracks ωicycl

Fig. 4. The results of experimental studies obtained during continuous casting of a billet with a diameter of 0.05 m from bronze of the brand BrO5Ts5S5, according Cycl II to the frequency of movement of the billet f(j)mov, = 3.75 min−1 .

4.3 Discussion of the Results of Calculating the Accumulation of Damage () in the Billet, According to the Third Cyclogram Cycl III According Cycl III to the billet, we will take into account overcoming StFF in the reverse direction, and overcoming SlFF in the forward direction (Fig. 5).

Fig. 5. The dependence of the change in the accumulation of damage to the billet during the cycle for the conditions Cycl III of movement of the billet: 1–3 – billet movement frequency f(j)mov: 3.75 min−1 , 5.0 min−1 and 7.5 min−1 , respectively

From Table 6 it follows that at the maximum frequency of movement of the billet (j III = 4.72 · 10−4 . = 3) - we have the minimum value ω: ωjcycl

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Table 6. Calculation of damage accumulation during one cycle of movement of the billet, calculated according to third damage accumulation model, provided that damage accumulation caused by overcoming StFF during the reverse movement of the billet has a value close to zero ω ≈ 0. f(j)mov, min−1

timov , s

rev , MPa σStFF

σSlFF , MPa

III ωj500c

III 10–4 ωjcycl

3,75(j=1)

4(i=1)

0.5

0.4

0.165

13.21

5,0(j=2)

3(i=2)

0.5

0.4

0.147

8.82

7,5(j=3)

2(i=3)

0.5

0.4

0.118

4.72

cycl

proq

The results of experimental studies have shown that during the reverse movement of the billet while overcoming StFF, the following ω of the billet occurs (Fig. 6): – we make the assumption that at f(j)mov = 7.5 min−1 there are no cracks, since ω III = 4.72 · 10−4 ; during the cycle, in this case, is ωjcycl – ω of the billet for Cycl III at f(j)mov = 7.5 min−1 is 2.86 times less than ω at fmov = 3.75 min−1 ; I = 7.4 · 10−4 v 1.56 times – ω of the billet at f(j)mov = 7.5 min−1 for Cycl I – ωjcycl III III = 4.72 · 10−4 III more than at f(j)mov = 7.5 min-1 at Cycl - ωjcycl = 4.72 · 10−4 ωjcycl – we assume that for Cycl III at f(j)mov = 7.5 min−1 there are no cracks, because ω III = 4.72 · 10−4 ; over the cycle time, in this case, is ωjcycl – ω workpieces for Cycl III at f(j)mov = 7.5 min−1 is 2.86 times less than ω at fmov = 3.75 min−1 ; I = 7.4 · 10−4 is 1.56 times – workpiece’s ω at f(j)mov = 7.5 min−1 for Cycl I – ωjcycl III III = 4.72·10−4 −1 III more than for f(j)mov = 7.5 min at Cycl - ωjcycl = 4.72·10−4 ωjcycl

Fig. 6. The results of experimental studies obtained under the condition of using the reverse movement of the billet in the third model while overcoming StFF

Thus, from Sect. 4 it follows that when changing the cyclograms of the movement of the workpiece (Cycl), the accumulation of damage (ω) changes as follows: Cycl I shown: – for any frequency of movement of the workpiece, (at t = const = 500s) ω is a constant value ωj I500c = const;

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– when determining ω during one cycle of movement of the billet at different cycle times (or for each value f(j)mov), we have different values of the accumulated damage ωj I500c = const, (Table 4). cycl

Cycl II It is shown that (before the cyclic movement of the billet timov ) the stress arising during the overcoming of StFF during the translational movement of the billet proq σStFF = 0, 5 MPa, made it possible to obtain the following results when determining ω: – for different frequencies of workpiece movement during the cycle, we obtain different II II ): values for both for ωj500c and for (ωjcycl –4 • it is shown that at f (j = 1) mov = 3.75 min−1 - ω(j = 1)II cycl = 18.16 10 ; –4 ; • at f (j = 3) mov = 7,5 min−1 - ω(j = 3)II cycl = 8.25 10   II • the ratio of the KωII = ω(j = 1)II cycl /ω(j = 3)cycl magnitudes is 2.42 times, (Fig. 3), provided  that the magnitude of the change in the frequency  7.5 /f 3.75 ratio is 2.0 KfII = fmov mov

Cycl III . It assumes that the efforts to overcome StFF occur during the reverse movement of the workpiece, therefore, for various frequencies of movement of the billet, we  III obtain the following values ω(j)cycl : –4 – at f (j = 1) mov = 3.75 min−1 - ω(j = 1)III cycl = 13.21 10 ;   3.75 - the billet has ω in the cycle: ω(j = 3)III = – at f (j = 3) mov = 7,5 min−1 fmov cycl 4.72 10–4 , which is represented by dependence   3 (Fig. 4); 7.5 /f 3.75 is (κ III = ω3.75 ω7.5 = 2.8 (Fig. 3). – Thus, KfIII = fmov mov ω cycl cycl

Studies of the tensile strength of billets made of bronze grade BrA9Zh3L, depending on the influence of the frequency of movement of the billet and the damage parameter of the workpiece on its mechanical properties, are shown in Fig. 7. On fig. Figure 7 shows the effect of the billet movement frequency (fmov = 7.5 min−1 ) on the value of the tensile strength value of the billets billet Br O5Ts5S5: – without taking into account the overcoming of StFF in each cycle of movement of the billet (subject to the conditions Cycl I ), the tensile strength of the billets was σ0 = 338.0 MPa; – taking into account the translational movement of the workpiece during the overcoming of StFF (subject to the conditions Cycl II ), the tensile strength of the billets is equal to σ0 = 335.0 MPa; – with the reverse movement of the billets while overcoming StFF (subject to the conditions Cycl III ), the tensile strength of the billets was σ0 = 360.0 MPa. Thus, when performing the reverse movement of the workpiece while overcoming StFF, the optimal minimum of damage accumulation ω(j = 3)III cycl = 4.72 10–4 was obtained. At the same time, the tensile strength of the billet was σ0 = 360.0 MPa. The maximum value of damage accumulation ω(j = 1)II cycl = 18.16 10–4 in a cycle was obtained taking into account that StFF is overcome in translational motion at fmov

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Fig. 7. Influence of the amount of damage accumulated within one cycle of movement of a workpiece made of bronze grade A9Zh3L on its tensile strength: 1 -3 - results of changes in the accumulated damage (ω) during the cycle of movement of the billet when using the first, second and third cyclograms, respectively; 4 - dependence of the tensile strength of blanks made of bronze grade BrO5Ts5S5 on ω for different cyclograms, respectively.

= 3.75 min-1, (Table 5). The tensile strength of the workpiece was σ0 = 318.0 MPa, which is the minimum value.

5 Conclusions When studying the accumulation of damage (ω) of the billets during its each cycle of movement, the following was found: 1. Taking into account the overcoming force SlFF to determine ω by formula (1) without taking into account StFF during overcoming allowed to obtain deliberately I 10–4 ; underestimated values of damage accumulation: - ωjcycl 2. Taking into account the efforts to overcome StFF and SlFF in one cycle made it II 18.16 10–4 ; possible to find that in this case the indicator ω increased its value - ωjcycl 3. It is determined that an increase in the frequency of movement of the billets, other things being equal, reduces the process of accumulation of ω in the billets. For example, for the conditions of the second cycle of operation of the continuous casting machine, an increase in the frequency of workpiece movement from fmov = 3.75 min−1 to fmov = 3.75 min−1 made it possible to reduce the index ω from 18.16 10–4 to 8.25 10–4 . Thus, the optimal technological parameters of the continuous casting process have been determined to control the accumulation of ω, eliminate the formation of surface cracks and improve the mechanical properties of copper alloy billets. So, when performing a reverse movement of the billets while overcoming StFF and at a frequency of movement of the billets ( fmov.) equal to 7.5 min−1 , an optimal minimum of damage accumulation ω = 4.72 10–4 was obtained. At the same time, the

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tensile strength at fracture was σ0 = 360.0 MPa. However, when using the cyclogram, in which StFF was overcome during the translational movement of the workpiece and at fmov = 3.75 min−1 , it was obtained: ω = 18.16 10–4 , and σ0 = 318.0 MPa .

References 1. Smirnov, A.N.: Small electrometallurgical enterprises in the structure of the steel-smelting complex of Ukraine. Metally i lit’ye Ukrainy 7, 3–7 (2015) 2. Yamaguchi J., Sawai T., Nakashima T.: Change and development of continuous casting technology metallurgy, vol.(12), pp. 144–121 (2015) 3. Meshkov Y.Y., Kotrechko S.O., Soroka K.F.: Brittleness of steels under stress concentration. (Report 2). Metallofiz. Noveishie Tekhnol. 44(10), 1377–1393 (2022) 4. Steblyanko, P., Domichev, K., Petrov, A.: Behaviour modelling of pseudo-elastic-plastic material at non-stationary loading. Metallofiz. Noveishie Tekhnol. 43(1), 107–128 (2021) 5. Teliovich, R.V., Garasym, J.A., Krechkovska, H.V., Bondarevska, N.O.: Improvement of structure and mechanical characteristics of hot-rolled eutectoid steel by means of high-speed heat treatment. Metallofiz. Noveishie Tekhnol. 40(11), 1489–1508 (2018) 6. Meshkov, Y.Y., Zimina H.P.: Problems of certification of steel and alloys by their tendency to brittleness, Metallofiz. Noveishie Tekhnol. 43(10), 1377–1386 (2021) 7. Meshkov, Y.Y., Zimina, G.P., Stetsenko. N.M.: Nature of the brittleness of metals. Progress Phys. Metals 23(4), 744–755 (2022) 8. Raransky, M.D., Oliynych-Lysyuk, A.V., Tashchuk, R., Lysyuk, O.V., Tashchuk, O.: Features of deformation in crystals of indium in a wide range of temperatures. Metallofiz. Noveishie Tekhnol. 40(11), 1453–1463 (2018) 9. LNCS Homepage. http://www.springer.com/lncs, (Accessed 17 Oct 2017) 10. D.B. Bpeclavcki, .M. Kopytko, O.A. Tatapinova, O.H. Xopoxilov. Analiz povpedaemocti bponzovyx zagotovok, polyqaemyx v ppocecce neppepyvnogo lit, Mexanika ta maxinobydyvann, Haykovo-texniqni ypnal, HTU, Xapkov, №1. 234–243(2008) 11. Khoroshylov, O.M., Podolyak, O.S., Ponomarenko, O.I.: Study of parallel processes arising in continuous cast billet during its solidification. Metallofiz. Noveishie Tekhnol. 44(2), 175–190 (2022) 12. Nogovitsyn, O.V., Seredenko, V.O., Seredenko, O.V., Chystyakov, O.V., Sirenko, K.A.: The shell structure of a bimetallic rod made of Cu–Fe alloy obtained in the processes of induction melting and continuous casting. Metallofiz. Noveishie Tekhnol. 44(12), 1697–1710 (2022) 13. Breslavskiy D.V., Korytko Y.M., Tatarinova O.A.: Analysis of the damage of bronze blanks obtained in the process of continuous casting. Mech. Eng. Scient. Techn. J. (1), 234–243 (2018) 14. Glushko, A.V., Dmytryk, V.V., Syrenko, T.A.: Creeping of welded joints of steam pipelines. Metallofiz. Noveishie Tekhnol. 40(5), 683–700 (2018). https://doi.org/10.15407/mfint.40.05. 0683 15. Bolouri, A., Chen, X.: Grand transient rheological behavior of semisolid seed-processed 7075 aluminum alloys in rapid compression metallurgical and materials transactions, vol. (49), pp. 2858–2867 (2018) 16. Fam, D., Babak, A., Koval, V.V.: Kinetics of damage accumulation and the criterion of the limiting state of structural materials. Mech. Adv. Technol. 1(82), 131–138 (2018) 17. Fam, D.K. Timoshenko O.V., Babak, A.N., Koval, V.V.: Damageability of metallic materials, taking into account the type of stressed state. Tekhníchní nauki í tekhnologí¨í. 2(12), 49–58 ( 2018)

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18. Karasevska, O.P., Yushchenko, K.A., Zadery, B.A., Gakh, I.S., Zviagintseva, H.V., Alekseenko, T.O.: Deformation and fracture of single crystals of heat-resistant nickel alloys with welded joints during tensile tests. Metallofiz. Noveishie Tekhnol. 43, 939–957 (2021) 19. Mylnikov V.V.: Influence of loading frequency on fatigue of construction materials. Sci. Techn. 18(5), 427–435 (2019) 20. Nayzabekov A.B., Kolesnikov A.S., Latypova M.A., Fedorova T.D., Mamitova A.D.: Modern trends in the production of metals and alloys with an ultrafine-grained structure Uspekhi fiziki metallov. 23(4), 629–657 (2022)

Computer Modelling and Comparative Analysis of Surface Microrelief Inspection by the Method of Scattering of a Laser Beam During Its Small-Angle Sliding Incidence Sergey Dobrotvorskiy1,2 , Borys A. Aleksenko1 , Vitalii Yepifanov1 , Yevheniia Basova1 , Vadym Prykhodko1 , Ludmila Dobrovolska1 , and Mikołaj Ko´sci´nski2(B) 1 National Technical University “Kharkiv Polytechnic Institute”, 2, Kyrpychova Str,

Kharkiv 61002, Ukraine 2 Poznan University of Life Sciences, Wojska Polskiego 38/42, 60637 Poznan, Poland

[email protected]

Abstract. The study of metal surface modification by short nano-fiber laser pulses for the creation of hydrophilic and hydrophobic laser-induced structures (LIPSS) is currently receiving considerable attention. When connecting layers of multilayer ceramic-metal structures made of composite materials, the LIPSS structure can play a significant role in increasing strength. There is a need to create an accessible surface control method for operational control over the change in hydrophobic properties over time. This is because hydrophilic surfaces are formed on steels, as a rule, immediately after irradiation, and hydrophobic ones only after a long time, which can last 3… 7 weeks. To control the surface microrelief, in this paper we study the use of the method of sliding reflection of a helium-neon laser beam. The possibility of effective use of this method for the qualitative determination of the structure of the LIPSS surface from the diffraction pattern of the reflection of a helium-neon laser beam is confirmed. Keywords: Surface · LIPSS · Microstructure · Laser Processing · Sliding Reflection

1 Introduction Creation of hydrophilic and hydrophobic laser-induced structures (LIPSS) is currently receiving considerable attention. The design of LIPSS plays a significant role in the case when it is necessary to increase the strength of the connection of surfaces by improving adhesion. In this case, an accessible method of surface analysis is needed. Also, due to the change in the microstructure over time, the hydrophobic properties change. Hydrophilic surfaces are formed on steels, as a rule, immediately after irradiation, and hydrophobic surfaces - only after a long time, which can last up to one and a half months. This requires a high level of analysis operativeness. Therefore, during this time, and after, © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 237–252, 2023. https://doi.org/10.1007/978-3-031-40628-7_20

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it is necessary to quickly control the change in the surface structure. In this paper, we study the use of the method of sliding reflection of a helium-neon laser beam for such control of the surface microrelief. The possibility of effective use of this method for the qualitative determination of the structure of the LIPSS surface from the diffraction pattern of the reflection of a helium-neon laser beam is confirmed. The use of electron microscopes and similar complex specialized equipment and costly processes is not convenient. It is not publicly available and technologically advanced for quick surface control. In this regard, there is a need for a simple, inexpensive, accessible, and fast method for monitoring the surface microrelief, which makes it quickly control possible. Today, technologies have become widespread that allow you to create a controlled microrelief on the treated surface. In this regard, there is a need to control the geometric properties of the microstructure obtained during processing. We have described a method for controlling the surface microrelief using a sliding beam according to the data on the nature of the scattering of the beam reflected from the surface. There are special conditions that require giving the surface such a microrelief, which is a set of repeating homogeneous parallel depressions and elevations. At the same time, it is impossible to judge the quality of this type of microrelief, its uniformity, and repeatability by the chaotic scattering of the reflected beam. This paper describes a method for controlling the surface microrelief using the sliding beam method in the case, when the controlled surface microrelief has the above-mentioned ordered structure.

2 Literature Review Laser microstructuring and nanostructuring is of great importance in modern production. The formation of an ordered micro-structure is used to create rolling surfaces [1, 2] and friction [3, 4], increases wear resistance [5], in order to keep a lubricant layer on the friction surface [6]. Nanostructuring is used to give the surface anti-reflective properties, since the microstructure affects the reflectivity of the surface [7]. Simultaneously with texturing, laser processing allows additional chemical cleaning [8]. Using pulsed laser irradiation in combination with scanning probe microscopy. During the process, a laser beam is introduced into the gap between the probe tip and the substrate surface [9]. To obtain surface nanostructuring and give the surface not only a macrorelief but also a microrelief. [10]. The widespread use of multilayer structures [11, 12] in various branches of mechanical engineering necessitates the development of a technology for the preparation of joined surfaces by imparting them a microstructure. Nanostructuring makes it possible to modificate wettability [13] and to impart hydrophobic properties to the surface [14]. Giving microstructure to the relief serves for Increase in the energy efficiency of axial turbines [15]. At the same time, giving the surface an ordered microrelief [16] requires operational control. Scanning probe or tunneling microscopy, using a needle or optical probe that is in contact with the surface of the object under study, has disadvantages. Microscope probe tips can be made by electrolytically sharpening wire, or even inexpensively, using mechanical wire cutters. It is possible to achieve high resolution down to 0.1 nm even if

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the tip is not atomically sharp. The explanation for this is due to the strong dependence of the tunneling current on the gap length: most of the electrons tunnel from one atom of the tip closest to the sample, even when other atoms are only slightly further away. As a result, the microscope can be used to study the structure of surfaces with a resolution of one atom [17]. However, problems can arise due to the presence of “multiple vertices (tips)”, which leads to false marks in the image. In addition, the scan time increases if the scan is slow enough, as it takes time to move the tip. Therefore, atomic resolution images are sometimes recorded in AC mode, where as soon as the needle approaches the sample, the feedback mechanism is turned off and the needle is scanned a short distance parallel to the surface of the sample; then changes in the tunnel current are displayed on the image. In this mode, the field of view is limited; even for a very smooth surface, the tip will eventually cut into the sample, damaging the tip and/or the sample [18, 19]. Also, having multiple sensitive devices (such as detectors, precision stage, etc.) tightly packed around the sample results in limited space inside the microscope. Some components of the devices use low-noise grounded or floating electronics that can interfere with measurements, causing false signals or even preventing microscopes from functioning properly. In addition, the resolution of electron microscopes and the signalto-noise ratio are increased when the primary beam electrons are deflected by false magnetic and electric fields generated in the associated equipment. Image quality is highly dependent on the number of primary electrons entering the sample at each specific position corresponding to an image pixel. This number of electrons is controlled by the electron gun, the optics of the microscope, and the scanning speed of the beam. Therefore, the image can usually be improved by reducing the scanning speed. This exacerbates the problems associated with mechanical and electronic stability. In the case of real-time control measurements, temporal resolution is very important. Therefore, a trade-off must be made between image quality and temporal resolution [20]. The microscope can produce images from 30 frames per second to 1 frame per minute, which precludes fast, accurate measurements [21]. Although most modern electron microscopes use an electron accelerating voltage of 100 to 300 kV [22, 23], several high-voltage instruments have been constructed with accelerating voltages up to 3 MV. The main motivation was the fact that increasing the electron energy lowers the diffraction limit to a spatial resolution. However, the technical problems of voltage stabilization did not allow the instruments to reach their theoretical resolution [18, 24]. Modern microscopes with electronic lenses work much better [25]. However, there are problems with spherical aberration of lenses, as well as with chromatic aberration, when the electron beam generated by the gun has a certain energy spread. Electrons with different energies in the same place of the column will experience different forces. An electromagnetic lens bends lower energy electrons more than higher energy electrons. Chromatic aberration is something that the operator can’t do anything about, and it becomes especially problematic when rendering at low accelerating voltage [26]. If a voltage comparable to the accelerating voltage is to be applied to the electrostatic lens, it means that at an accelerating voltage > 50 kV, insulation and safety problems become serious. Since higher accelerating voltages provide better image resolution, magnetic lenses are generally preferred for electron microscopy. Magnetic lenses

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also provide slightly less aberrations at the same focal length, further improving image resolution. However, such a concept is problematic for an electrostatic lens, where the introduction of a conductive sample can greatly change the distribution of the electric field [18]. Also, the disadvantages are that a conventional scanning microscope is only able to study the object that fits inside the chamber, and that the price of the cheapest microscope reaches several tens of thousands of dollars. These listed problems necessitate a new method for effective, simple and fast control of the microrelief. There are ways to quickly control the surface using a laser, which, however, do not provide sufficient information about the ordering of the microrelief [27]. There are studies proving that the use of an experimental stand of a simple design, equipped with a helium-neon laser, where inexpensive components are used, gives good results [28].

3 Materials and Methods 3.1 Overview of Equipment for the Experiment For experiments, stainless steel plates AISI 321 were cut. The overall dimensions of the plates were 35x55 mm. The surface in the delivered condition had a smooth, mirror-like surface characteristic of steel. The chemical composition of steel (in weight %): Fe 67.0; Cr 17.0… 19.0; Ni 9.0… 11.0; Mn < 2.0; Si < 0.8; Ti 0.6… 0.8. To obtain polymodal surface roughness, a laser setup with an IR ytterbium fiber laser (wavelength 1064 nm) and a BM 2500 + biaxial galvanometric scanner was used [29, 30]. In this study, laser exposure was used with a pulse duration of 100 ns, a repetition rate of 20… 100 [kHz], and peak power of up to 0.3 [MJ] in the TEM00 mode. The samples were processed with a fiber laser raster scanning with a step of 20 μm at a linear speed of 6 mm/s. The fiber laser beam diameter is 20 μm. Surface quality was determined by atomic force microscopy and laser radiation scattering. Atomic Force Microscopy (AFM) measurements were carried out using ICON Scanning Probe Microscope (Bruker, USA). Samples were scanned in air, at room temperature, using tapping modes with antimony n-type doped Si tips (TESPA, Bruker, USA). The Images were acquired at a scanning rate of 0.2 [Hz] and 512 × 512 pixels resolution. AFM data analyzes were performed using the complementary NanoScope Analysis program. The study of the ordered microrelief of the metal surface is carried out by the method of the sliding reflection of a helium-neon laser beam. The study includes a practical and theoretical part. According to the results of the experiment and the theoretical calculations performed, a comparative analysis of the obtained practical and theoretical results was carried out. The practical part of the experiment was carried out using specially built laboratory equipment (Fig. 2), which is a system consisting of a helium-neon laser emitter, a bracket with a test plate fixed in a vertical position, and a flat-screen with a printed measuring scale (Fig. 1, 2). The helium-neon laser emits a light beam with a diameter of 3 [mm]. The inspection laser beam is not polarized. The beam is directed to the investigated plate at an angle of

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Fig. 1. The tested plate. A - the spot of small-angle sliding helium-neon laser beam incidence; B - schematic of a raster scanning of a surface with a fiber laser beam (yellow lines).

Fig. 2. Practical investigation: incidence and reflection of a helium-neon laser beam along a fiber laser surface treatment path. 1 - helium-neon laser beam source; 2 - surface under study; 3 - screen with applied scale.

10 degrees. The beam is incident on the plane of the plate, which has an ordered surface microstructure formed by preliminary fiber laser processing (Fig. 3). On the path of the beam reflected from the plate a flat projection screen with a printed measuring scale is installed. The reflected beam falls on the screen. The distance from the diffraction grating to the projection screen is 150 [mm].

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Fig. 3. Surface microstructure (digital microscopy): 1 – incidence of a sliding helium-neon laser beam; 2 – reflection of a sliding helium-neon laser beam; 3 – scaning trajectory of fiber laser beam during pre-processing; A – diameter of rounded hollows forming a microrelief (22 [μm]); B – scaling the image of the microscopy data according to the scale of the image processor; C – distance between rows of rounded hollows forming a microrelief (48 [μm]).

During the experiment, the helium-neon laser beam was directed along the paths of the processing fiber laser (Fig. 1 pos. B, Fig. 3). The geometric characteristics of the reflected helium-neon laser beam were noted by the light spot formed by the reflected beam on the plane of the screen with a printed measuring scale calibrated in millimeters, the scale value is 1 [mm].

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3.2 Surface Microrelief as a Reflective Grating Reflective gratings are obtained by forming parallel strokes on a reflective surface [31]. The effect of reflective gratings is used in spectral analysis [32] to implement phase modulation [33]. Thus, light is reflected at different angles, which correspond to different orders and wavelengths. Methods that allow one to estimate the surface geometry, considering it as a diffraction grating, are promising [34].

Fig. 4. P – period of defraction grating; θ in – incident angle; θ dif – diffraction angle.

An example of a reflective grating is shown in Fig. 3. Reflective grating equation:   a sin(θin ) + sin(θdif ) = mλ (1) where the angle θ in is positive and the angle θ dif is negative if the incident and diffracted light are on opposite sides of the normal to the grating surface, as shown in Fig. 3. If these rays are on the same side of the lattice normal, then both angles should be considered positive. The nature of the diffraction pattern is related to the value of the diffraction type criterion, the dimensionless parameter D: D = p2 /lλ

(2)

where: l—distance from grating to projection screen. Since in our case the width of the hollows (Fig. 3) does not exceed 0.05 [mm], and the wavelength (λ) when using a red helium-neon laser is 632.8 [nm], then the diffraction type criterion is < 1, which corresponds to the Fraunhofer diffraction type. In this case, a diffraction pattern (Fig. 7.) of alternating maxima and minima appears on the observation screen.

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The Fraunhofer diffraction minima condition is a function of the diffraction angle: p sinθ =kλ

(3)

When this condition is met, the difference in the path of the waves emitted by the elementary zones adjacent to the edges of the slot will be equal to an integer number of wavelengths. The intensity distribution in the diffraction spectrum of each slit is determined by the direction of the diffracted rays and the diffraction patterns created by each longitudinal recess will be the same. When building a mathematical model, the Grating feature and the Graph Interference Pattern, which serves to display the results are used. The Grating feature releases secondary rays of arbitrary diffraction order. The angles at which transmitted and reflected diffraction orders are released are those at which the waves generated by successive unit cells interfere constructively with each other. A transmitted wave of diffraction order m corresponds to an angle θm with the boundary normal. The Interference Pattern plot can be used to visualize the fringes resulting from the interference of two or more rays at a surface. When constructing a mathematical model, the following equations are used: kr kr    kr = kp,out + kn,r ns nr =

(4) (5)

     kn,r  = (n1 k0 )2 − kp,out 2

(6)

kp,out = kp + mG1 + nG2

(7)

kp = ns × (k × ns )

(8)

G1 = 2π

d2 × ns d1 · (d2 × ns )

(9)

G2 = 2π

ns × d1 d2 · (ns × d1 )

(10)

d1 = d1 Tg,1

(11)

d2 = d2 Tg,2

(12)

where: k – wave vector; k p – vector parallel to the surface; ns – surface normal vector; k 0 – wave number in free space; G1 , G2 – reciprocal lattice vectors; m, n - diffraction orders; T g – directions of periodicity projected onto the grating surface; d 1 , d 2 – grating constants, directions 1, 2.

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Using the above equations, a mathematical computer model of the propagation and reflection of a helium-neon laser beam from the plate under study is constructed [35, 36]. According to the conditions of the experiment, the surface under study has an ordered surface microrelief. Since the trajectory of the fiber laser beam during surface treatment is ordered and is a set of many parallel linear trajectories, the structure is ordered and uniform. The surface microrelief is a surface incised with elongated depressions arranged in parallel. The bottom of each hollow has a shape close to a plane (see Fig.), which allows us to consider the microrelief as a reflective echelon grating. The mathematical computer model is built in the COMSOL© Multiphysics environment. After that, the data obtained in the calculation of the computer model are compared with the results of a practical experiment. 3.3 Visual Evaluation Criteria The nature of the reflection is estimated visually by the projection of the reflected beam. According to the generalized Rayleigh criterion, images of two nearby identical point sources or two nearby spectral lines with equal intensities and identical symmetrical contours are resolvable (separated for perception) if the central maximum of the diffraction pattern from one source (line) coincides with the first minimum of the diffraction pattern from another. When the Rayleigh criterion is fulfilled, the intensity of the “dip” between the maxima is 0.735 [37] of the intensity at the maximum, which is sufficient to resolve the maxima of the diffraction pattern. If the Rayleigh criterion is violated, then one line is visually observed. During the experiment, the light gaps in the intensity of the reflected beam are visually resolved well, which indicates the fulfillment of the Rayleigh criterion when observing diffraction maxima.

4 Results and Discussion 4.1 The Results of the Study Using Atomic Force Microscopy Before carrying out the experiment to control the surface microrelief by the method of sliding reflection of a helium-neon laser beam, the microrelief of the surface under study was studied using atomic force microscopy. In the topography of the surface, a line structure is clearly distinguished (Fig. 4), due to the alternation of lines and the overlap of fiber laser spots. The bottoms of the depressions are characterized by the relief approaching to the flat plane. This is clearly seen in (Fig. 5 and 6.) where the surface of the bottom of the depressions looks homogeneous. The protrusions between the rows are clearly pronounced, formed by the displacement of the melt and the shock wave from the expansion of the plasma. The height of the ledges noticeably differs from the bottom (Fig. 5, 6). The relief is an alternating elongated hollows and elevations, which is confirmed by the diffraction nature of the reflection observed at the stage of practical research (Fig. 7). The hollows are arranged in parallel and are present on the entire treated surface. The hollows are arranged in parallel and are present on the entire treated surface. The reflection pattern of a beam incident along the scanning path (Fig. 3.) will be diffractive

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Fig. 5. Microstructure of the wafer under study according to atomic force microscopy: the height structure of the microrelief.

Fig. 6. Microstructure of the wafer under study according to atomic force microscopy data: amplitude error.

when the microstructure is ordered and when the arrangement of linear parallel hollows is denced. 4.2 The Results of the Study by the Method of Sliding Helium-Neon Laser Beam During the practical experiment, the helium-neon laser beam is directed along the processing paths of the processing fiber laser. In this case, a diffraction pattern is clearly observed, formed by the reflected beam on the plane of the screen with the applied measuring scale. This indicates the presence of surface roughness with a pronounced ordering of the relief elements of the microstructure in the beam incidence plane. There is a change in the scattering angle of the reflected helium-neon laser beam incident in the direction along the fiber laser beam processing trajectory. In this case, the rays, which before reflection went in a parallel beam, after reflection are scattered in a plane perpendicular to the projection plane (Fig. 2, 3, 9.). Thus, there is a mixed directionally scattered reflection.

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Fig. 7. Projection of the reflected spot during irradiation of the investigated plate with a nanosecond laser along the fiber laser processing path.

We distinguish between the central maximum, which lies on the blaze angle, and the side maxima, in the amount of 6 pieces (Fig. 7), located on both sides of the central maximum in the direction of beam reflection and arranged symmetrically. In addition to the central maximum, we distinguish the lateral maximum (Fig. 7), located in the direction of the beam reflection plane. The symmetrically located diffraction maximum is observed inexpressively, which is due to the sharp angle of incidence of the beam and partial overlap of reflection by the plate under study. 4.3 Results of Calculation of the Constructed Computer Model The course of the practical experiment was modeled in the COMSOL© Multiphysics software environment. The environment for conducting the experiment is described in the Geometrical Optics module. The virtual laser beam is generated by a light source with a scattering angle of degrees and propagates in the air towards the reflective surface. The laser (vacuum) wavelength is set to 632,8 [nm]. The reflecting surface has the shape of a flat plate. To the plane, which is reflect the sliding laser beam the Cross Grating properties is applied. The Faces of the grating are positioned in a plane perpendicular to the direction of incidence of the beam. The reflected beam is incident on a projection plane, also modeled as a flat surface that is rotated 10 degrees with respect to the angle of incidence of the beam. The physical properties of the Image Plan have been applied to the projection plane. The software environment allows you to simulate the projection of the reflection of the beam on the projection surface. Since the spatial and mutual arrangement of diffraction maxima is affected by the period of the diffraction grating, the study was carried out by successively increasing the parameter that describes the period of the diffraction grating with a consistent comparison of the calculated result with the result obtained during a practical experiment. The calculation is performed in the range of the period of the diffraction grating from 20 to 80 μm. Since when the beam is reflected from the diffraction grating, a diffraction pattern is formed in the form of a set of diffraction maxima (Fig. 7). These calculations are performed sequentially for each diffraction order ranging from n = 0… 7 using the parameterization module Parametric Sweep.

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Since, according to the conditions of a practical experiment, we use a laser that has monochromatic radiation, the task of studying the spectral decomposition of the beam is not set. A practical experiment (Fig. 7) also does not indicate a visible spectral decomposition of the beam. Based on the results of a series of calculations, it was found that the calculated pattern obtained is most correlated with the experimentally obtained pattern (Fig. 8 9), provided that the value of the grating period parameter is d 1 = 22 [μm] (Fig. 8).

Fig. 8. Experimental Cross Grating settings.

Thus, the experimental data (Fig. 7.) correlate with the atomic force microscopy data (Fig. 3 pos. A), and the data obtained in the calculation of the constructed mathematical model (Fig. 9). When calculating the propagation of rays in space (Fig. 9 Pos. A), the points of the projection of diffraction maxima onto the projection plane (Fig. 9 Pos. C) were obtained, the coordinates of which, with an error of 5 mm, coincide with the diffraction pattern obtained practically (Fig. 9 Pos. B). The error may be associated with the inaccuracy of the positioning of the components, the imperfect curvature of the surfaces, and some randomness of the microrelief under study. Thus, it has been established that the constructed mathematical model gives adequate results and can be used both to confirm the compliance of the existing microstructure with the stated requirements, and to assess the periodicity of the microstructure with an accuracy of 3… 4 [μm]. The error in determining the microstructure is within the passport accuracy of laser processing (from 2.5 to 6.5 [μm]). The experiment also shows the applicability and effectiveness of the integrated use of the sliding laser beam method and the constructed mathematical model in order to verify and determine the properties of the microstructure of the reflecting surface. The method is characterized by simplicity, cheap and does not require sophisticated equipment.

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Fig. 9. Comparative analysis of data from a practical experiment and the results of calculating a computer model. A - the propagation of rays in space; B - comparison of calculated results with the diffraction pattern obtained practically; C - the points of the projection of diffraction maxima onto the projection plane.

5 Conclusions An universal method for controlling roughness by the method of a sliding helium-neon laser beam is presented. The proposed unique control method is suitable for determining the compliance of the surfaces of the parts to be joined with the technological requirements before their connection, during the honing process, and before applying adhesive and paint coatings. Using the proposed method of sliding reflection of a helium-neon laser beam During Its Small-Angle incidence, it is possible to improve the quality of the connection and to define the suitability of the surface for applying various adhesives, paints, or protective coatings. If the surfaces to be joined or sliding have an ordered

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microrelief structure, the method will allow optimal positioning of the parts to be joined relative to each other. The nature of the reflected light spot confirms the uniformity of the finely dispersed structure on the surface of the sample under study. The result of the practical experiment also corresponds to the result of the calculation of the computer model and confirms adequacy of the model. The proposed control method determines that the relief is a set of similar rectilinear depressions on the surface, relatively equidistant from each other and arranged in parallel, and has a pronounced pattern. The proposed method makes it possible to estimate with sufficient accuracy the geometric characteristics of the microrelief by the value of the period parameter of the diffraction grating. Thus, the high information content of the technology for monitoring the microrelief of a metal surface by the method of sliding reflection of a helium-neon laser beam During Its Small-Angle incidence is confirmed, by its simultaneous simplicity, low cost, and availability. Having obtained result of the reference sample’s study, then by a relative comparison with the results of the examples studied, it is possible to quickly and without of expensive equipment use perform an operational monitoring correspondence’s of the studied surfaces microrelief. The proposed technology makes it possible to simply and successfully control such parameters of the microstructure of the material surface as its uniformity, roughness, and directionality of the microrelief pattern. It is also possible to state sufficient repeatability and accuracy of the microrelief formation technology using fiber laser processing.

References 1. Brizmer, V., Kligerman, Y.: A Laser Surface Textured J. Bearing J. Tribol 134(3) (2012). https://doi.org/10.1115/1.4006511 2. Etsion, I., Halperin, G., Brizmer, V., et al.: Experimental investigation of laser surface textured parallel thrust bearings. Tribol. Lett. 17, 295–300 (2004). https://doi.org/10.1023/B:TRIL.000 0032467.88800.59 3. Dunn, A.: Laser surface texturing for high friction contacts. Appli. Surface Sci. 357(Part B), 2313–2319 (2015). https://doi.org/10.1016/j.apsusc.2015.09.233. ISSN 0169–4332, 4. Vadali, M., Ma, C., Duffie, N.A., Li, X., Pfefferkorn, F.E.: Pulsed laser micro polishing: Surface prediction model. J. Manufact. Proc. 14(3), 307–315 (2012) https://doi.org/10.1016/ j.jmapro.2012.03.001, ISSN 1526–6125 5. Kaul, R., Ganesh, P., Tiwari, P., Nandedkar, R.V., Nath, A.K.: Characterization of dry sliding wear resistance of laser surface hardened En 8 steel. J. Mat. Proc. Technol. 167(100), 83–90 (2005). https://doi.org/10.1016/j.jmatprotec.2004.09.085, ISSN 0924–0136 6. Voevodin, A.A., Zabinski, J.S.: Laser surface texturing for adaptive solid lubrication, vol. 261(11–12), pp. 1285–1292 (2006). https://doi.org/10.1016/j.wear.2006.03.013, ISSN 0043– 1648 7. Sarbada, S., Huang, Z., Shin, Y.C., Ruan, X.: Low-reflectance laser-induced surface nanostructures created with a picosecond laser. Appl. Phys. A 122(4), 1 (2016). https://doi.org/10. 1007/s00339-016-0004-0 8. Kumar, A., et al.: Laser-assisted surface cleaning of metallic components. Pramana 82(2), 237–242 (2014). https://doi.org/10.1007/s12043-013-0665-6 9. Hong, M.H., Huang, S.M., Luk’yanchuk, B.S., Chong, T.C.: Laser assisted surface nanopatterning, Sensors and Actuators. A: Phys.108(1–3), 69–74 (2003). https://doi.org/10.1016/ S0924-4247(03)00364-9, ISSN 0924–4247

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Hydrodynamics Analysis on Partially Filled Agricultural Tanks by Driving Cycle of Transportation Andrii Kozhushko(B) National Technical University “Kharkiv Polytechnic Institute”, 2, Kyrpychova Str., Kharkiv 61002, Ukraine [email protected]

Abstract. When the free surface of liquid in a closed container moves, it is important to determine the influence of oscillatory actions on the functional stability of the movement. This study examines the hydrodynamic performance of partially filled agricultural tanks. The interest in such a study arose in view of the increase in productivity and energy saturation of agricultural wheeled machinery. The theoretical study of fluid sloshing has gained widespread acceptance in the aerospace, marine, railway, and automotive industries, introducing complex mathematical models for calculations. Therefore, it was necessary to use the classic and proven method of calculating the movement of the free surface of liquid, which is based on the introduction of partial oscillators into the calculation model of the tank, which make it possible to calculate the weight, inertial, elastic and dissipative characteristics of the main surface layers of the liquid that participate in the oscillatory motion. Modeling is based on the simulation of the movement of an agricultural tank according to the driving cycle of transportation. Based on the simulation, the range of maximum values of the sloshing force for agricultural tanks with geometric parameters L/R = 6.3 and L/R = 8 was determined. The obtained result becomes the basis for the study of recovery from resonance zones of liquid sloshing and the suspension of an agricultural tank. In addition, it becomes relevant to study the movement of liquid in the transient modes of movement of a wheeled tractor and a tank. Keywords: Hydrodynamics · Agricultural Tank · Free Surface of Liquid · Sloshing · Transportation · Driving Cycle

1 Introduction Farmers constantly face the task of increasing the yield and fertility of the soil, one of the ways to increase it is the systematic application of liquid organic fertilizers, which is provided by transport works for the transportation of liquid cargo. Not so long ago, transport work in agricultural enterprises was carried out to a greater extent at the expense of road transport, but with the development of tractor equipment and the unprofitability of road transport, this percentage is gradually decreasing. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 253–262, 2023. https://doi.org/10.1007/978-3-031-40628-7_21

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Such a widespread use of wheeled tractors in the performance of transport works in the agro-industrial complex of the state is due to the variety of their performance of agricultural works. Transportation of liquid cargo by tractor-tankers is part of the transport work in any economy. Unlike automobile tanks, these tanks do not have internal partitions (hermetic or non-hermetic), nets and other obstacles to the flow of liquid inside the tank. Such a design feature is due to the lower transport speed of tractor transport than that of automobile transport, as well as the specifics of liquid cargo. At the present time, in the conditions of constant increase in the energy saturation of tractor units, the transport speed and carrying capacity of the unit is increasing. As a result of the increase in the vibration energy of the liquid cargo, the probability of emergency situations during the transportation of tanks (overturning, stacking, gal-loping of the unit) increases. The fluctuations of the free surface of the liquid [1] have a significant influence on the dynamic parameters of the movement, which, in combination with the forced oscillations of the vehicle, significantly affect the functional stability of the movement. Thus, this study aims to analyze the hydrodynamic parameters at a certain driving cycle and determine the corresponding filling height of agricultural tanks.

2 Literature Review Horizontal cylindrical containers are widely used in the transportation of liquid cargoes in the marine, aerospace, railway, and automobile industries [2]. One of the most solvable problems is the study of the effect of the free surface of liquid when the container is partially filled, because it affects the dynamic and functional stability of the vehicle movement [3, 4]. In the classical sense, solving the problem of studying the movement of liquid in a container is reduced to the implementation of hydrodynamic models [5, 6] or their combination based on stochastic differential equations [7]. The outlined models are used by solving nonlinear differential equations with partial derivative numerical methods [8, 9], satisfying the boundary conditions regarding the free surface of the liquid and the walls of the container. The method of calculating the characteristics of the free surface of liquid thanks to the method of higher-order finite and boundary elements is becoming quite widespread. In [7], the finite element method was used to study the vortex motion of a free surface based on an integral equation in Galerkin form. The authors of the work [10] selected the best standard size of the tank and partition in the OpenFOAM environment using the finite element method in order to minimize the horizontal displacement of the free surface of liquid. The work [11] is aimed at solving the transient three-dimensional movement of liquid in a horizontal cylindrical tank of finite length. The authors of [12] improved the approach from [11] by presenting a model based on the linear theory of the motion of a free surface taking into account the translational addition theorem of Graf for cylindrical Bessel functions. In [13], the boundary element method is used to determine the separation angle of the free surface of a viscous liquid in a truncated region, taking into account the singular solution near the separation point. The computational fluid dynamics (CFD) method of studying the movement of the free surface of a liquid based on the Fluent platform is also gaining popularity. In [14],

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the influence of the cross-section of the container and the standard size of the transverselongitudinal partition on the three-dimensional characteristics of the movement of the free surface of liquid during the study of the maneuverability of tank cars was determined. The work [15] is related to providing an approach for calculating hydrodynamic coefficients for boundary elements in the frequency domain in order to maximize the efficiency of modeling and calculations. The described mathematical models of the movement of the free surface of liquid have a complex mathematical nature, which complicates its implementation and implementation in the complex study of movement. According to the work [16], the concept of modeling liquid splashing, in which the impulse and convective components of motion are separated with the subsequent solution of the model of concentrated masses, is the simplest and most popular method of analysis. As shown by experimental studies from [1], this approach has a good convergence when studying the movement of liquid in a partially filled container. In [17], the hydrodynamic characteristics (wall shear stress, volume fraction, dynamic pressure, and sloshing force) were analyzed at different filling volumes and road cycles of flexitank movement in an urban area and on a freeway. An unsolved problem remains the study of the movement of a partially filled container in complex road conditions of extra-urban traffic. Among the variety of simulation studies of the movement of agricultural machinery during transport work, the PowerMix [18] and EPA Nonregulatory Nonroad Duty Cycles for Agricultural Tractor [19] test procedures are popular.

3 Research Methodology The research methodology is based on a well-tested mathematical apparatus [1], which is based on a combined model of the classical type. The studied hydromechanical system is quite complex and consists of many elements that affect free oscillations from different frequency ranges. The oscillation of a liquid with a free surface is traditionally described by a model with distributed masses (the Navier-Stokes and Rayleigh surface wave equations). The model is solved in the potential formulation of the problem, in which the oscillatory motion of fluid (with the exception of a narrow wall layer) was considered to be vortex-free. In addition, the model uses the method of partial oscillators, which allows replacing the continuous movement model with a discrete one. The energy of the oscillating movements of the liquid of a partially filled tank are impulses and moments of force formed by the influence of external factors, thus forming damping free or non-damping forced vibrations of liquid. The free surface of liquid is a generator of the formation of free low-frequency oscillations and a converter of forced oscillations. Disturbed waves of the free surface of liquid move from the side walls of the tank, which creates a rise (or fall) in the liquid level. With an increase in the level of filling, the amplitude of the free vibrations of liquid decreases according to a geometric progression. The presence of moving and immobile layers of fluid causes the formation of fluid friction, which forms damping free oscillations and localizes the amplitudes of forced oscillations in resonance zones.

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3.1 Model of Movement the Free Surface Liquid in the Tank Since the purpose of this study is to analyze the change in hydrodynamic parameters during the operation of an agricultural tank in the conditions of extra-urban cycles of movement, then it is appropriate to indicate the attributes of the movement of the free surface in the longitudinal plane (Fig. 1). According to the paper [1], the scalar potential of fluid movement (1) is calculated using the Fourier method of variable distribution with the introduction of a simplified replacement of the real shape of the tank into the shape of a rectangular parallelepiped.

a

b

Fig. 1. Calculation model (a) and cross-sections (b) of the tank.

Such an equivalent replacement is formed on the basis of preserving the dimensions of the free surface of the liquid and the mass of the liquid in the tank  ⎧−   ˙ ˙  ⎨→ = 0; V = ∂∂z ; ∂∂y ; ∇ 2  = 0; ∂∂  − →  3 n 0 (1) ⎩ ¨ +f · ˙ + g · ∂ + σ · ∂ 3 = −[aCT.x (t) + g · θCT.z (t))] · x, ∂y ρ ∂y 

− → where V , p – velocity, liquid density, 2 – Laplace’s differential operator, g – acceleration of gravity, f – dissipation factor, G0 – wettable surface formed by the bottom and lower parts of the side walls, f – normal to some point of this surface, G – free surface of liquid, σ – surface tension coefficient, t – time; 8ct.z (t) – shell twist angle. (t, x, y) =

∞

Tk (t) · (−1)k sin(λk · x) · ch(λk · y);

(2)

k=0

λk =

2π · (2k − 1) ; k = 1, 2, ..., L

where k – oscillator number; λk – wave numbers; T (t) – function of variable amplitude coefficient. The obtained potential (2) in the form of a similar Fourier series is compared with the potential (1). As a result, we will get an infinite system of second-order ordinary

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differential equations with constant coefficients:   σ g · λk 2 (−aCT.x (t) − g · θCT.z (t)) 2 ¨ ˙ Tk + f · Tk + . · 1+ · λk · th(λk h) · Tk = · R ρ·g L λ2k · ch(λk h) (3) Analyzing the differential equation of motion, it is possible to determine the natural frequency of motion of liquid layers, which determine the oscillating motion of the free surface of liquid   σ g · λk 2 2 · 1+ · λk · th(λk h), ωk = R ρ·g The term from the sum (2) corresponds to a separate basic (eigen) form of lowfrequency oscillations of the liquid relative to the shell of the tank, that is, to some partial oscillator. For each oscillator, its mass fraction δM of the total liquid mass can be determined. To do this, it is enough to take into account the oscillator’s own shape and find the average value of the derivative ∂F/∂ξ over the cross-sectional area D: ¨ ∂ 1 dS; ξ = {x, y, z}, (4) S ∂ξ D

Next, this result is multiplied by the Fourier coefficient (the relative component of the external influence from Eqs. (3) δMk =

 k 2 th λj h . 3h π2 λ j j=1

(5)

It is convenient to interpret the value of the relative mass as a partial (that is, mutually permeable and permeable) liquid layer having an in-phase oscillatory action. Then Eq. (1) becomes the equation of motion of the partial oscillator. mk · X¨ k + fk · (X˙ k − X˙ CT ) + ck · (Xk − XCT ) = 0;

(6)

mk = δMk · m;

(7)

 ck = mk ·

  σ g · λk · 1+ · λ2k · th(λk h) , R ρ·g

(8)

where m – total mass of liquid; f k and ck – damping coefficient [1] and stiffness of the k-th liquid layer. 3.2 Transportation Cycles of Wheeled Tractors EPA Nonregulatory Nonroad Duty Cycles for Agricultural Tractor is used in order to obtain the results of liquid sloshing, which would be close to the real conditions of the

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Fig. 2. Driving cycle for agricultural tractor.

performance of agricultural transport work. This driving cycle is applied independently of the vehicle and provides the output of the change in speed (V tr ) and engine torque (M en ) in relative quantities (Fig. 2). The work cycle is intensive in terms of the magnitude and frequency of peaks, which characterizes the approximate operating conditions of agricultural machinery. Since this research is carried out with the aim of determining the hydrodynamic indicators of the movements free surface of the liquid in a partially filled tractor tank, we will introduce the assumption that the change in the speed of the tank is equal to the speed of the tractor. (X˙ ct = V tr ). That is, not taking into account the operation of the tractioncoupling device. In addition, the study does not take into account the change in road surface irregularities. Outline assumptions are introduced to solve engineering goals, i.e. their expediency is determined by application at the stage of design and verification of operational indicators.

4 Results 4.1 Algorithmic Representation of the Developed Solution Before moving on to determining the influence of the shift of the free surface of the liquid, the change in the hydrodynamic parameters of the liquid layers (Fig. 3), which form the movement of the liquid in the tractor tank, was clarified. For this, the value of the dimensionless quantity υ, which characterizes the natural frequency of movement of  the partial oscillators of the liquid, is determined (υk = R · ωk2 g) and makes it possible to determine elastic characteristics. One of the main indicators that affects the movement of the free surface of the liquid is the mass component of liquid. Since the research is aimed at determining the hydrodynamic indicators of the movement of the free surface of liquid in agricultural tanks. It is known that this movement depends on the geometric structure of the cylindrical tank. The most common containers [1] are the 10-ton and 20-ton tanks, which have a length-to-radius ratio of L/R = 6.3 and L/R = 8, respectively.

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a

259

b

Fig. 3. Frequency (a) and weight (b) characteristics of the free surface of liquid in agricultural tanks with L/R = 6.3 (1) and L/R = 8 (2).

Dissipative characteristics of partial fluid oscillators should be determined separately. It is known that the impact of friction on forced oscillations is estimated by determining the dynamism coefficient μ (Fig. 4), which is the ratio of the amplitude of oscillations  to the amount of static deformation o under the influence of constant excitation. From Fig. 4, it is noticeable that with an increase in the geometric dimensions of the capacity, the energy dissipation of the splashing liquid decreases, which leads to an increase in the time interval of the movement of the free surface.

a

b

Fig. 4. Dependence of the coefficient of dynamism and the ratio of the amplitude of oscillations to the magnitude of the static deformation in tanks L/R = 6.3 (a) and L/R = 8 (b).

4.2 Sloshing Induced by Transportation Cycle Conditions In Fig. 5 shows the graph of the dependence of the force of liquid sloshing on the time of the driving cycle of transportation and the height of filling the tank. Note that Fig. 5 is constructed only when the indicator of liquid filling in the last half of the tank is varied. This is due to the fact that the weight of a half-filled tank cannot cause functional instability of the movement, because its mass is less (in the case of L/R = 6.3) or equal (in the case of L/R = 8) to the mass of the transported wheeled tractor.

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a

b

c

Fig. 5. Dependence of the force liquid sloshing during the driving cycle (c) on time and the level of liquid filling in tanks L/R = 6.3 (a) and L/R = 8 (b).

It can be seen from the graph that, regardless of the geometric parameters, the force of liquid sloshing has maximum values in the range of filling from 71% to 92%. Separately, the influence of the intensity of the tank movement should be taken into account, because the excitation component increases during transient modes of the movement of the tank. It is noticeable that in the range (0–250 s) the force of sloshing increases over almost the entire range of the dangerous level of filling. This is caused by an uneven complex cycle of motion with acceleration and deceleration present. Thus, a dangerous level of filling of the agricultural tank has been established, which affects not only productivity, but also traffic safety.

5 Conclusions Based on the use of the classical approach of calculating the movement of the free surface of liquid in a closed container, an analysis of the hydrodynamic indicators of the movement of liquid layers was performed. The frequency and weight characteristics of the liquid layers, which take part in the movement of the free surface of liquid in agricultural tanks with standard size L/R = 6.3 and L/R = 8, are constructed. Hydrodynamic analysis of the fluid was carried out under the conditions of implementation of EPA nonregulatory nonroad duty cycles for agricultural tractor. It was established that the tank has the greatest sloshing power in the range of 71 ÷ 92% filling, which is critical and should be avoided. The determination of these results prompts us to investigate the influence of the squishing force on the performance and dynamics of wheeled tractor movement when transporting partially filled agricultural tanks.

References 1. Kozhushko, A.: Theory of Tractor Oscillations During Transporting Agricultural Tanks: Monograph. NTU “KhPI”, Kharkiv (2022)

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2. Lazzarin, M., Biolo, M., Bettella, A., Manente, M., Da Forno, R., Pavarin, D.: EUCLID satellite: sloshing model development through computational fluid dynamics. Aerosp. Sci. Technol. 36, 44–54 (2014). https://doi.org/10.1016/j.ast.2014.03.015 3. Jinshu, L., Zhenbo, Y., Haoxiao, W., Wenfeng, W., Jiajia, D., Shiqiang, Y.: Effects of tank sloshing on submerged oil leakage from damaged tankers. Ocean Eng. 168, 155–172 (2018). https://doi.org/10.1016/j.oceaneng.2018.08.015 4. Toumi, M., Bouazara, M., Richard, M.J.: Impact of liquid sloshing on the behaviour of vehicles carrying liquid cargo. Eur. J. Mech. A. Solids 28(5), 1026–1034 (2009). https://doi.org/10. 1016/j.euromechsol.2009.04.004 5. Liu, Z., Yuan, K., Liu, Y., Andersson, M., Li, Y.: Fluid sloshing hydrodynamics in a cryogenic fuel storage tank under different order natural frequencies. J. Energy Storage 52, 104830 (2022). https://doi.org/10.1016/j.est.2022.104830 6. Degtyariov, K., Gnitko, V., Kononenko, Y., Kriutchenko, D., Sierikova, O., Strelnikova, E.: Fuzzy methods for modelling earthquake induced sloshing in rigid reservoirs. In: 2022 IEEE 3rd KhPI Week on Advanced Technology (KhPIWeek), pp. 1–6 (2022). https://doi.org/10. 1109/KhPIWeek57572.2022.9916466 7. Karamanos, S.A., Papaprokopiou, D., Platyrrachos, M.A.: Finite element analysis of externally-induced sloshing in horizontal-cylindrical and axisymmetric liquid vessels. J. Pressure Vessel Technol. 131(5), 051301 (2009). https://doi.org/10.1115/1.3148183 8. Yueyang, H., Xiang, Z., Wenjie, G., Tianyun, L., Shuai, Z.: Coupled vibration analysis of partially liquid-filled cylindrical shell considering free surface sloshing. Thin-Walled Struct. 179, 109555 (2022). https://doi.org/10.1016/j.tws.2022.109555 9. Yuan, L., Jiangang, S., Zongguang, S., Lifu, C., Zhen, W.: Simplified mechanical model for seismic design of horizontal storage tank considering soil-tank-liquid interaction. Ocean Eng. 198, 106953 (2020). https://doi.org/10.1016/j.oceaneng.2020.106953 10. Reza, S., Hassan, S.: Numerical simulation of half-full cylindrical and bi-lobed storage tanks against the sloshing phenomenon. Ocean Eng. 266, 112896 (2022). https://doi.org/10.1016/ j.oceaneng.2022.112896 11. Kolaei, A., Rakheja, S., Richard, M.J.: Three-dimensional dynamic liquid slosh in partiallyfilled horizontal tanks subject to simultaneous longitudinal and lateral excitations. Eur. J. Mech. B/Fluids 53, 251–263 (2015). https://doi.org/10.1016/j.euromechflu.2015.06.001 12. Seyyed, M.H., Soleimani, H.: An analytical solution for free liquid sloshing in a finite-length horizontal cylindrical container filled to an arbitrary depth. Appl. Math. Model. 48, 338–352 (2017). https://doi.org/10.1016/j.apm.2017.03.060 13. Owens, R.G.: The separation angle of the free surface of a viscous fluid at a straight edge. J. Fluid Mech. (2022). https://doi.org/10.1017/jfm.2022.408 14. Dasgupta, A. Effect of Tank Cross-Section and Longitudinal Baffles on Transient Liquid Slosh in Partly-Filled Road Tankers, Concordia University Montreal (2011) 15. Han, M., Dai, J., Wang, C.M., Ang, K.K.: Hydrodynamic Analysis of Partially Filled Liquid Tanks Subject to 3D Vehicular Manoeuvring, Shock and Vibration, pp. 1–14 (2019). https:// doi.org/10.1155/2019/6943879 16. Carra, S., Amabili, M., Garziera, R.: Experimental study of large amplitude vibrations of a thin plate in contact with sloshing liquids. J. Fluids Struct. 42, 88 (2013). https://doi.org/10. 1016/j.jfluidstructs.2013.05.013 17. Hamdan, M., et al.: Hydrodynamics Analysis on Liquid Bulk Transportation with Different Driving Cycle Conditions. J. Adv. Res. Fluid Mech. Thermal Sci. 100, 137–151 (2022). https://doi.org/10.37934/arfmts.100.1.137151

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18. Rebrov, O., et al.: Mathematical model of diesel engine characteristics for determining the performance of traction dynamics of wheel-type tractor. EUREKA: Phys. Eng. 4, 90–100 (2020). https://doi.org/10.21303/2461-4262.2020.001352 19. Beltrami, D., Iora, P., Tribioli, L., Uberti, S.: Electrification of compact off-highway vehiclesoverview of the current state of the art and trends. Energies 14(17), 5565 (2021). https://doi. org/10.3390/en14175565

Functional Bioceramic Calcium Phosphate Materials for Use as Bone Fillers and Filling the Lack of Muscle Tissue Svetlana Krivileva(B)

, Nataliia Ponomarova , and Alexander Zakovorotniy

National Technical University “Kharkiv Polytechnic Institute”, 2, Kyrpychova Str, Kharkiv 61002, Ukraine [email protected]

Abstract. The compositions and fundamentals of the technology of new highstrength dispersion-strengthened biocompatible composite materials based on hydroxyapatite, which have a higher level of crack resistance compared to those of non-reinforced matrix materials, have been developed. The Ca3 (PO4 )2 –CaF2 system was introduced by the high temperature method of microscopic in sity, built a state diagram of this system. The regions of the primary crystallization of the phases in the Ca3 (PO4 )2 –H2 O–CaF2 –Ca(OH)2 system were refined. The optimal compositions and ranges of heat treatment were determined. The dependences of the properties of materials on their composition and their influence on the organism of warm-blooded animals in vivo were studied. It was established that by their technical and biological properties they can be used to correct bone defects and as materials for filling cavities of pathological origin in muscles that have been formed by pathological processes. When preparing suspensions in monomer, powders can be used for stereolithographic (3D) printing of necessary tissue fragments that need to be replaced. Keywords: Bioceramics · Correction of skeletal disorders · Stereolithographic (3D) Printing · of the high temperature method

1 Introduction The mass aging of the population, in whose era humanity is entering, poses new challenges for biomaterials science. In the near future, an increase in demand is expected not only for bioceramic materials, which, due to their technical and biological properties, can be used to correct bone defects, but also for materials for filling cavities of pathological origin in muscles, since it is necessary to replace dead space and voids formed by pathological processes or preliminary surgical interventions. In addition, the loss of muscle tissue is typical for older people, and the issue of replenishing its deficiency is a matter of improving their quality of life.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 263–271, 2023. https://doi.org/10.1007/978-3-031-40628-7_22

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2 Issue Status To date, a significant number of artificial bioceramic materials have been created based on hydroxylapatia as a biogenic (from the ashes of the bones of cattle or pigs, from fish bones, corals, from the shell of chicken eggs) and synthetic origin [1–4]. Calcium and phosphorus are always present in the body, so materials based on Ca10 (PO4 )6 (OH)2 are used not only in surgery as bioceramics, but also as fillers in cosmetology, urology, laryngology, dermatology and cosmetology. However, it should be taken into account that the environment of a living organism is quite aggressive, so the question arises of increasing the stability of these materials in vivo by introducing various additives that simultaneously improve the mechanical properties [5–12]. From the point of view of matching the chemical composition of a synthetic substitute for damaged tissue, the most successful is the use of composite nanocrystalline materials of the hydroxylapatite/fluorapatite composition and additives, since the content of Ca10 (PO4 )6 F2 in their composition significantly increases stability in the chemically active environment of a living organism [13, 14]. However, a significant increase in the fluorine content is undesirable, since it can cause unpredictable consequences [15]. A promising idea is heterogeneous design, which allows creating materials with desired properties based on phase diagrams by selecting combinations of elements of a multicomponent heterogeneous mixture. For the synthesis of fluorapatite, the Ca3 (PO4 )2 –CaF2 binary system is of interest. Previously, it noted the formation of vaporous products and intermediate substances at high temperatures. Given the presence on the state diagram of this system of intermediate compounds that do not correspond to practice, it seemed appropriate to re-investigate it. Of interest was also an attempt to synthesize “apatite B” in the solid phase from the corresponding oxides, data on which are available. The data obtained make it possible to refine the regions of primary crystallization of phases in the four-component system Ca3 (PO4 )2 –H2 O–CaF2 –Ca(OH)2 . This will make it possible to predict the phase composition of new materials with a set of specified properties due to the presence of compounds located at the vertices of elementary tetrahedra and taking into account the technological features of their production [16, 17].

3 Purpose and Objectives of the Study The purposepurposis work is to study the possibility of using bioceramic materials of the composition hydroxyapatite/fluorapatite to replenish damaged bone tissue and lack of muscle tissue. To achieve this goal, it was necessary to solve the following tasks: Refine the structure of the phase diagram of the Ca3 (PO4 )2 –CaF2 system and the region of primary crystallization of phases in the Ca3 (PO4 )2 –H2 O–CaF2 –Ca(OH)2 system and, on this basis, select promising compositions of materials with desired properties. To assess the possibility of using bioceramic materials of optimal composition, obtained on the basis of this system, to compensate for bone defects and lack of muscle tissue.

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4 Research Methodology 4.1 Materials and Equipment In the present study, Ca3 (PO4 )2 , Ca10 (PO4 )6 (OH)2 , Ca10 (PO4 )6 F2 nanopowders, which were synthesized by hand, were used. For this purpose, chemically pure compounds Ca(OH)2 and CaF2 , phosphorus pentoxide in the form of phosphoric acid of analytical grade, magnesium stearate, and distilled water were used. Ca10 (PO4 )6 (OH)2 was obtained from solutions of Ca(OH)2 and H3 PO4 in distilled water by stirring them for 8 h and keeping them at room temperature for 170 h for aging, ensuring the achievement of the ratio n(Ca2+ )/n(PO4 3 − ) = 1.67. Structure of Ca10 (PO4 )6 (OH)2 after drying at 80 °C (x 28500) is shown in Fig. 1. High-purity Ca3 (PO4 )2 was synthesized from H3 PO4 and Ca(OH)2 in the solid phase by firing pelletized mixtures three times at a temperature of 1150 – 1250 °C with holding for 2 h and intermediate grinding with a multistage temperature rise at a rate of 120–150 degrees per hour. Ca10 (PO4 )6 F2 was obtained from CaF2 and previously synthesized Ca3 (PO4 )2 in the solid phase by firing in the temperature range of 1200–1250 °C with holding for 3 h, followed by grinding. To form the samples, a TR 20/40/60-2d hydraulic press and steel molds were used. Samples were sintered in a high-temperature chamber furnace with Si-C heaters, with an air atmosphere, as well as an electric furnace with kryptol resistance and a quartz capsule filled with periclase. The temperature rise rate was 200 degrees/hour. To control the temperatures, platinum-rhodium thermocouples PP-10th,90-Rt were used. Electron microscopic studies were carried out using a scanning electron microscope in a Carl Zeiss microscope, Germany. 4.2 Method for Determining Property Indicators The Ca/P ratio in the samples during the synthesis of Ca10 (PO4 )6 (OH)2 was controlled by chemical analysis. The formation of cylindrical specimens was carried out by the method of uniaxial one- and two-sided cold pressing at a pressure of 50–200 MPa. The phase analysis of the starting materials, precursors, and synthesized preparations was controlled by X-ray phase analysis (on the Drone-2 and Drone-3 setups; interpretation was carried out using ASTM reference tables on samples of preparations in the form of tablets with a diameter of 10 mm and a thickness of 2 mm. The mineralogical composition upon receipt of the starting materials, the morphology and particle size after firing were determined using electron microscopic studies using the method of two-stage self-tinted cellulose-carbon replicas and replicas with extraction, electron diffraction and microdiffraction. Phase equilibria in the Ca3 (PO4 )2 –CaF2 pseudobinary system were studied by hightemperature microscopic, X-ray, and differential thermal analyzes in the temperature range up to 1650 °C The studies were carried out on samples synthesized from the corresponding initial components in the solid phase by three-time firing of tablet mixtures (on acetone as an organic binder) of calculated compositions with intermediate grinding, as well as on single crystals grown by the method of solution in a melt. In this case,

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Fig. 1. Structure of Ca10 (PO4 )6 (OH)2 after drying at 80 ˚C, x28500.

the transformation of one polymorphic form of Ca3 (PO4 )2 into another was determined (using the method of high-temperature microscopy, on single crystals, with direct observation in a microscope) in situ by changing the interference color of a single crystal at the transition temperature, as well as using DTA and X-ray phase analysis. Its were carried out on preparations of calculated compositions by high-temperature in sity microscopy on flat-polished plates 0.3 mm thick, as well as on crushed preparations under direct observation through a microscope with a special attachment. Calculations (the positions of binary eutectics, the melting temperature in them in the Ca3 (PO4)2 – CaF2 section of the CaO–P2 O5 –CaF2 system, etc. are observed by calculation using the method and algorithm given in [18–20].

5 Results of Obtaining Indicators The results of chemical analysis of the Ca10 (PO4 )6 (OH)2 synthesis products showed that the Ca/P ratio in the samples is close to stoichiometric (1.67). According to the analyzes, the synthesis product is nanocrystalline hydroxyapatite and is characterized by a crystal size of 25 to 60 nm. The synthesis in the solid phase of Ca3 (PO4 )2 and Ca10 (PO4 )6 F2 is complicated by the volatility of phosphorus compounds [16]. Considering these features of phosphorus compounds used as precursors, the optimal ratio of components in the synthesis in the solid phase of Ca3 (PO4 )2 and Ca10 (PO4 )6 F2 was determined. The results of XRD showed that the products of the synthesis of Ca3 (PO4 )2 and Ca10 (PO4 )6 F2 are monophasic and that they are high-purity nanocrystalline materials. A study of the CaO–P2 O5 –CaF2 system in the Ca3 (PO4 )2 – CaF2 section was carried out: the positions of binary eutectics and the melting points in them in the Ca3 (PO4 )2 – CaF2 section of the CaO–P2 O5 –CaF2 system were determined by calculation and an experimental verification of the calculated data. An attempt was made to synthesize

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T oС 1634o 1600o 1400o

1408o

CaF2

1200o

Ca10 (PO4 6 F2

)

Ca (PO ) 2

Fig. 2. Phase diagram of the Ca3 (PO4 )2 –CaF2 system with microstructures of binary eutectics

“apatite B” in the solid phase from the corresponding oxides by firing three times pelletized mixtures at 50 MPa at temperatures of 1000–1400 °C with intermediate grinding. X-ray diffraction of the samples showed the absence of any lines in the samples that can be attributed to traces of “apatite B”. Our studies confirmed the presence of only one fluorapatite of composition Ca10 (PO4 )6 F2 , which melts congruently and forms simple eutectics from Ca3 (PO4 )2 and CaF2 . Using the obtained melting temperatures of binary eutectics formed by Ca10 (PO4 )6 F2 with Ca3 (PO4 )2 and CaF2 , the state diagram of the Ca3 (PO4 )2 –CaF2 system and the region of primary phase crystallization in the Ca3 (PO4 )2 –H2 O–CaF2 system were refined. They are shown in Figs. 2 and 3. The dependences of the characteristics of materials on composition and temperature were established. An increase in the content of fluorapatite Ca10 (PO4 )6 F2 affected the rate of the sintering process, which noticeably increased in the temperature range from 1100 °C to 1240 °C. At 1250 °C, the sintering process is completely completed. Figure 4 shows the structure of the material with the composition Ca10 (PO4 )6 (OH)2 / Ca10 (PO4 )6 F2 (95:5), fired at 1200 °C (x 17000). At the same time, the size of the crystals increased. For samples containing 3–10 wt. % Ca10 (PO4 )6 F2 , the crystal size reached 3–5 µm. The shrinkage of the samples also differed, which is associated with the Frenkel effect (the formation of diffuse porosity) due to the difference in the values of the diffusion coefficients of ions (including OH− and F− ) in samples of different compositions. The mechanical properties of the material were studied. An increase in the content of Ca10 (PO4 )6 F2 leads to an increase in the compressive strength of the samples, which proportionally increases and even exceeds 50 MPa, but this practically does not affect the crack resistance in a dry environment. The possibilities of using bioceramics of optimal compositions as artificial substitutes for damaged tissues were studied under the conditions of specific surgical operations - in the plastic surgery of traumatic defects in bones and soft tissues, followed by the replacement of pathological foci with the developed materials. For this purpose, samples

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Ca(OH)2 CaF2

CaF2

~ 1408o

765o

675o

735o

Ca10 (PO ) (OH)2

o

665o 675o

781 Ca(OH)2

Ca10 (PO4 6 F2

Ca (PO ) 2

Fig. 3. Areas of primary crystallization of phases in the system Ca3 (PO4 )2 –H2 O–CaF2 – Ca(OH)2 .

of materials were implanted in animals (white laboratory rats and rabbits) in cortical and cancellous bone tissue and muscle tissue. The materials were also implanted into the peritoneum of outbred white rats for a long period of time.

Fig. 4. Ca10(PO4)6(OH)2/Ca10(PO4)6F2 structure after firing at 1200˚C, x17000

It was found that they do not cause any negative reactions in nearby tissues, do not have specific long-term effects. Evaluation of the specifics of restructuring and mechanisms of tissue regeneration in different phases of the repair process was carried out on the basis of clinical X-ray morphological and biochemical analyzes performed on the basis of Kharkov Medical

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University. For this, transcortical defects were made in the area of the knee and hip joints with a 4 mm dental drill in the form of cylindrical holes 4–5 mm deep and filled with samples of materials (previously prepared according to the size of the defects) so that they were adjacent to their edges and could not be freely retrieved. The kinetics of biodegradation was studied using electron microscopic and histological studies. It was found that during the implantation of the developed ceramics, a new formation of bone tissue occurs with the restoration of the original histological structures, in which, as it grows, the bone marrow and a network of blood vessels filled with blood are formed. During the implantation of the developed composite material, new tissue formation occurs with the restoration of the original histological structures. No signs of general intoxication are found in this case, local histological effect is not manifested. Figure 5 shows the formation of a bone regenerate when a tibial defect is filled with ceramic material of the Ca10 (PO4 )6 (OH)2 /Ca10 (PO4 )6 F2 composition. Regenerate with numerous full-blooded vessels, inclusions of ceramics. x 80, 21 days. It was found that bioceramic materials of the Ca10 (PO4 )6 (OH)2 /Ca10 (PO4 )6 F2 composition are low-toxic, low-hazard substances with weakly expressed cumulative properties; they do not have gonadotoxic, embryotoxic, cytotoxic, mutagenic and teratogenic effects, skin-irritating and skin-resorptive properties. The introduction of the developed materials into reconstructive surgery will solve the problems of bone tissue plasty and replenishment of the lost muscle tissue mass.

Fig. 5. Formation of bone regenerate when filling a perforated defect of the tibia with ceramic material based on Ca10 (PO4 )6 (OH)2 /Ca10 (PO4 )6 F2 . Regenerate with numerous full-blooded vessels, inclusions of ceramics. x 80, 21 days.

6 Results In the Ca3 (PO4 )2 –CaF2 system, no other substance was found except fluorapathia, which melts congruently and forms simple eutectics with Ca3 (PO4 )2 and CaF2 . None of the analyzes showed any traces of another “apatite B” in the samples.

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Based on the studies carried out, the structure of the phase diagram of the Ca3 (PO4 )2 – CaF2 system and the regions of primary crystallization of phases in the Ca3 (PO4 )2 –H2 O– CaF2 –Ca(OH)2 system was refined (see Figs. 1 and 2). Based on the data obtained, areas of promising compositions for the synthesis of bioceramic materials based on the CaO-P2 O5 -CaF2 -H2 O system were identified and materials were developed that, in terms of their technical and biological properties, can be used not only to correct bone defects, but also to compensate for the lack of muscle tissue in different areas. A full range of medical and toxicological and hygienic tests of the developed materials on warm-blooded animals was carried out, which confirmed their promise for tissue engineering. The resulting powders can also be used for stereolithographic printing of the required fragment.

References 1. Hench, L.L.: Third-generation biomedical materials. Science 295(5), 1014–1017 (2002). https://doi.org/10.1126/science.1067404 2. Logeart-Avramoglou, D., Anagnoston, F., Bizios, R., Petite, H.: Engineering bone: challengez i abstracles. J. Cell. Mol. Med. 9, 72–84 (2005) 3. Sych, O., et al.: Morphology and properties of new porous biocomposites based on biogenic hydroxyapatite and synthetic calcium phosphates. Funct. Mater. 14(4), 430–435 (2007) 4. Goloshchapov, D.L.: Synthesis of nanocrystalline hydroxyapatite by precipitation using when’s eggshell. Ceram. Int. 39(4), 4539–4549 (2013) 5. Beer, K., Avelar, R.: Relationship between delayed reactions to dermal fillers and biofilm: facts and considerations. Dermatol. Surg. 40(11), 1175–1179 (2014). https://doi.org/10.1097/ 01.dss.0000452646.76270.53 6. Hamilton, D.R.: Skin augmentation and correction: the new generation of dermal fillers – a dermatologist’s experience. Clin. Dermatol. 27, 12–22 (2009) 7. Jacovella, P.F.: Calcium hydroxyapatite facial filler (Radiesse): indications, technique, and results. Clin. Plast. Surg. 33, 511–523 (2006) 8. Feeney, J.N., Fox, J.J., Akhurst, T.: Radiological impact of the use of calcium hydroxyapatite dermal filler. Clin. Radiol. 64(9), 887–892 (2009). https://doi.org/10.1016/j.crad.2009.05.004 9. Scorokhod, V., et al.: Porosity and bioactivity of hydroxyapatite-glass composites. Funct. Mater. 13(2), 260–264 (2006) 10. Funt, D., Pavicic, T.: Dermal fillers in aesthetics: an overview of 0 events and treatment approaches. Clin. Cosmet. Invest. Dermatol. 12(6), 295–316 (2013). https://doi.org/10.2147/ CCID.S50546 11. Cox, S.E., Adigun, C.G.: Complications of injectable fillers and neurotoxins. Dermatol. Ther. 24(6), 524–536 (2011). https://doi.org/10.1111/j.1529-8019.2012.01455.x 12. Egorov, A.A., Smirnov, V.V., Barinov, S.M.: Mechanical properties of hydroxyapatite reinforced by metallic titanium. Powder Metall. Progress. 8(8), 358–362 (2008) 13. Dorozhkin, S.: Calcium orthophosphates in nature, biology and medicine. Materials. 2, 399– 498 (2009) 14. Gross, K.A., Borndt, C.C.: Biomedical application of apatites. Rev. Min. Geochem. 48(1), 631–672 (2002) 15. Corbrigj, D.: Phosphorus: the Fundamentals of Chemistry, Biochemistry, Technology, p. 680. Wold Publication, Moskov (1980)

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16. Krivileva S., Moiseev V. Functional materials for medical and biological purposes on the system CaO–CaF2 –P2 O5 –H2 O and additives. Funct. Mater. 25(2), 358–363 (2018). https:// doi.org/10.15407/fm25.02.358 17. Berezhnoy, A.S.: Manycomponent Alkaline Oxide Systems, p. 544. Naukova dumka Publication, Kiev (1970) 18. Bassett, H.: Thermodynamic calculation on for selected phases in the system CaO–P2 O5 – H2 O. J. Chem. Soc. 7, 2949–2953 (1968) 19. Hagemark, K.: Thermodynamics of ternary systems. J. Phys. Chem. 72(7), 2322–2326 (1968) 20. Krivileva, S., Zakovorotniy, A.Y., Moisèev, V., Ponomareva, N., Zinchenko, O.: Automating the process of calculating the singular points and modeling the phase diagrams of mimprisonment oxide systems. Funct. Mater. 26(2), 347–352 (2019). https://doi.org/10.15407/fm26. 02.347

Interchangeable Spindle Heads of the Machining Center with Modernized Connecting Elements Oleg Krol(B)

and Vladimir Sokolov

Volodymyr Dahl East Ukrainian National University, 59-a Tsentralnyi Prospect, Severodonetsk 93400, Ukraine [email protected]

Abstract. The 3D modeling process of the main movement drive for the machining center (MC) with replaceable shaping spindle heads and modified gear-type couplings is considered. Three-dimensional models of MC forming units designed for various manufacturing operations of complex housing parts are presented. The effectiveness of using new functionals is shown: the boundary representation of the B-rep geometry and the three-dimensional operation “Cutting-out”, adapted for building 3D models of drive housing parts and spindle heads. It is noted that when applying the three-dimensional operation of constructing gear rims by the method of simulating gear milling, an increase in the speed of profiling the working surfaces of the gearing is achieved. An idea improving of the gear-type couplings design by the criterion of minimizing the load capacity was put forward. A replacement procedure of the classic cylindrical profile of the tooth working surface with a teeth internal conical engagement with a circular profile is proposed. An analytical calculation of the main geometrical characteristics of the modified profile of gear teeth meshing of gear couplings was made. The coefficient of tooth length has been introduced in relation to standard and modified designs as a criterion for assessing the level of bending stresses in the contact zone. The influence of the teeth shape coefficient on the decrease in the level of contact stresses is noted. An experimental calculation of the complex stress reduction factor for the modified design of the gear-type coupling has been implemented. Keywords: Spindle unit · 3D modeling · Machining center · Gear-type coupling · Circular tooth profile

1 Introduction Every year the share of multi-operation machine tools of the MC-type in the machine park increases. This is due to the fact that the MC is a universal, quick-change system designed to perform a wide range of metalworking operations, from setting the workpiece to finishing, on one machine without reinstalling the workpiece [1–3]. Given the specifics of machine-building enterprises, such systems are indispensable in full-scale production. This concept is called “DONE IN ONE” and was first proposed by the Japanese company Mazak [4]. The “Made in One” concept is the principle that all operations are carried out on one machine. The application of this concept carries not only the modernization of © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 272–285, 2023. https://doi.org/10.1007/978-3-031-40628-7_23

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the production process but also an increase in the possibilities of the product life cycle management process. Among the competitive advantages, one can note: a reduction of the production cycle time; a reduction of the area occupied by the equipment, and, as a result, cost reduction and increased processing accuracy. The design of the machine tool plays an important role in realizing these benefits. There are increasing requirements for the reliable and uninterrupted functioning of forming units, the change of technological equipment, mechanical transmissions, and connecting elements of machine tools. The research of the functioning efficiency of metal-cutting equipment according to the criteria of reliability and accuracy is carried out in various integrated CAD systems, in which it is necessary to connect the systems of 3D modeling of machine tool elements with calculation modules for evaluating structures according to these criteria [5, 6]. This is especially important for wide-universal machine tools equipped with interchangeable modular tooling. The wide distribution of such machines in the park of machine-building enterprises is increasing, which indicates the relevance of such research. From a methodological point of view, this situation leads to the need for parallel use of 3D modeling tools with parameterization and research methods in the field of improving the reliability and performance of both the machines themselves and their technological equipment.

2 Literature View A wide range of publications is devoted to the problems of computer-aided design and the search for new design solutions in the field of creating forming units of metal-cutting equipment [7–13]. In [7], a study of the problem of increasing the product’s machinability within the life cycle of a three-coordinate milling machine equipped with tooling such as Bridgeport DIN 69871 was made. From the standpoint of a systematic approach to assessing the efficiency of processing during the operation of the machine main forming units: feed drive; spindle assembly and tool system. An important role in the evaluation is played by mandrels according to the ISO 230 series standard, designed for small-sized machines (the first and second standard sizes). For example, CAMFIX tool chucks with cylindrical collets (ER-collet chucks with through-hole and two clamping zones) use a symmetrical design, which distributes the torque load evenly over the polygon, ensuring self-centering and resistance to excessive bending efforts. As a result, the load capacity increases and the durability of the operation of these devices increases. The work [8] is devoted to various aspects of using CAD SOLIDWORKS and CAE ANSYS software to create a 3D model of a CNC lathe spindle using finite element methods. A 10-node rod model was used as the main model, in which each node was characterized by three degrees of freedom. The study of dynamic parameters at 5 natural frequencies and modes of spindle vibration made it possible to evaluate the stiffness index under the action of bending stresses. As a problem, the authors note the need to simplify the original 3D model by removing chamfers and small holes, as well as other structural elements when converting 3D file formats between SOLIDWORKS and ANSYS. The issues of improving a mechanical gearbox by controlling the transmission of a given torque are considered in [9]. For this purpose, a method for the synthesis of gears

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with a double clutch, which provides equalization of the load on the friction discs of each clutch has been developed. Analytically, the method is based on the established functional relationship between the drive control parameters and force pressure (load capacity) on clutch friction pairs. The consequence of this is to reduce the energy losses of the engine of the considered device. The work [10] is devoted to a comprehensive study of modified spherical gear halfcouplings that transmit significant torques when working with large misalignments of the coupling halves (up to 3° and more). This paper proposes a method of generation of the hub tooth surfaces by a hob thread surface, simulating the milling process of the external tooth profile and generating undercut profiles (worm cutters). This is the main difference from existing methods based on the method of analyzing the generatrix of a gear-cutting tool. In this case, the profiling of the working surfaces of the halfcoupling was carried out on the basis of the American Gear Manufacturers Association recommendations [11]. The creation of the gear tooth surface by the surface of a worm thread was introduced by Litvin et al. [12, 13]. In order to reduce the negative impacts (increase in preload and increase in the gap between the teeth of the bushing and the sleeve), in [10] a procedure was proposed. It consists of the following: the surface of the helical cutter as a set of cutting edges acting simultaneously during the formation of the side profile of the tooth. This makes it possible to form profiles with undercutting (with a small number of teeth of the half-coupling), which can appear in the manufacture of spherical bushings, especially when using bevel gears to compensate for misalignment of more than 3°. The entire range of research was carried out on the basis of 3D models illustrating the main geometric constructions of teeth working surfaces and features of the cutting tool contact in the process of machining spherical half-coupling. The proposed model is recommended for a wide range of problems of optimizing the gear surface geometry when changing the tool trajectory. As a result, the effect of balancing gaps in the engagement, increasing the contact coefficient, and reducing the contact and bending stresses of spherical gear couplings is achieved. The analysis of the above works has shown that the tasks of creating new designs of machine tool forming units and mechanical transmissions based on 3D modeling are relevant and in demand. Problem Statement. In this article, the tasks are to create sets of three-dimensional models of forming spindle heads intended for machining centers of the second and third standard sizes and modify their components to connect coaxial shafts and transmit torque are developed. The purpose of the research is to increase the load capacity of the coupling as a connecting element of spindle heads without changing its overall and connecting dimensions.

3 3D Modeling of Spindle Heads of a Machining Center At this research’s initial stage, a set of 3D models of the machining center forming units drilling-milling-boring type was developed [14–16]. A four-coordinate machining center SF68VF4 is considered an object of modeling [17]. The main software product is the integrated CAD/CAM/CAE KOMPAS-3D

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with built-in Artisan Rendering and APM FEM modules for finite element analysis of structures. The basic drive of the MC main movement includes a horizontal spindle headstock (Fig. 1, a) mounted in a cast iron housing in which a spindle unit is mounted with a mechanism for automatic tool clamping by a hydraulic cylinder [18, 19].

a

b

c

d

Fig. 1. Three-dimensional models of the MC forming units: a – drive of the main movement; b – vertical spindle head; c – slotting head; d – angle head

A design feature is a camshaft that transmits rotation to a horizontal or with the help of tooth-type couplings to a vertical (Fig. 1, b) or angular (Fig. 1, d) or slotting heads (Fig. 1, c). In this case, an automatic gear-shifting device is used. A two-stage gearbox is controlled by a hydrogenated switching mechanism [20, 21]. The presence of electrical and optoelectric sensors allows you to control the position of the headstock and its mechanisms, as well as a number of other parts and assemblies that ensure the normal functioning of the headstock from the CNC device.

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When building 3D models in the environment of the integrated CAD KOMPAS-3D, advanced mechanisms of three-dimensional modeling were used [6, 17]. To develop such rather complex spindle head designs, the tools of the C3D Modeler geometric core and the C3D Solver parametric core are used. Traditionally, the geometric core of the C3D Modeler implements the process of creating a geometric model of a researched object and calculating its geometric parameters necessary for building 2D sketches and 3D models. To describe the shape of the spindle heads in the C3D Modeler, the boundary representation of the geometry function was used. At the same time, the model is built from three-dimensional solids that are created using surfaces and curves. Further, the solids are grouped into assembly units (shaft bearings; couplings of two coupling halves, etc.) from which assembly units of the next level are built (Fig. 1). An important feature of the C3D Modeler core is its open architecture, which allows it to be extended beyond the standard feature set. The ability to create your own custom objects specific to this research, inheriting them from C3D Modeler objects, was tested on the main components of the spindle heads (Fig. 1). Using the principle of associativity in CAD KOMPAS-3D, drawings of the main motion drive for the MC (Fig. 2) and spindle heads (Fig. 3) were obtained as a stage of design preparation of production, providing a connection with the stage of analysis for manufacturability and the stage of technological preparation of production.

Fig. 2. Drawing of the MC main motion drive

Fig. 3. Drawings of the MC spindle heads: a – vertical head; b – slotting head; c – angular head

In the process of creating a drawing of the current model of the spindle head, the logical group of objects “Layer” is widely used [22, 23]. Splitting into layers makes it easier to change the properties of a group of objects. For all objects lying in one layer, you can simultaneously transfer to the associative view of the drawing, as well as change the color, enable/disable display on the screen, etc. So, auxiliary objects, dimensions

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and fasteners were placed in a separate layer. In this 3D modeling system, it is possible to place objects from various versions of the spindle head into a layer (Fig. 3), which contributes to the implementation of the multivariate design procedure. When constructing three-dimensional models of housing parts of spindle heads (Fig. 4, Fig. 5), manufactured by casting, a set of three-dimensional commands of the KOMPAS-3D system is used [6, 17]. The most effective, in this case, is the 3D operation “Cutting-out”, which allows you to implement the strategy of creating 3D models based on the formation of cavities and channels of a complex shape of the future housing 3D model. The design of the spindle head housing is characterized by a large number of holes and roundings. In multivariate design, the presence of such elements slows down the process of making changes to the design. To improve the performance of the design process, the C3D Modeler toolkit implements a number of new features for removing holes and roundings from the model. This operation makes it possible to simplify the 3D model, which is prepared for further calculation in the CAE system. Another new functionality is the modification of rounding, which provides the construction that absorbs elements of the original 3D model. As a result, it becomes possible to build previously inaccessible combinations of roundings. This operation is most often used when creating complex molds for spindle heads. Figure 4 shows the main movement drive housing for the MC with a two-stage gearbox mounted inside a horizontal spindle assembly.

Fig. 4. Housing of MC drives the main movement

On Fig. 5 shows the housings of vertical (Fig. 5, a), slotting (Fig. 5, b) and angular (Fig. 5, c) MC spindle heads. The transmission of motion and torque in the MC drive of the main motion and replaceable spindle heads is carried out using gears and tooth-type couplings designed to connect coaxial shafts and transmit torque [24, 25]. Within the environment of the CAD software KOMPAS-3D, a special application “Shafts and mechanical transmissions 3D” operates, including the module for calculating mechanical transmissions KOMPAS_GEARS. This module implements geometric and strength calculations of cylindrical and bevel gears, chain, worm and belt drives. A feature of the functioning of this module is the use of functional elements and parts of gears and tooth-type couplings as graphic primitives [26]. In this regard, it becomes

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Fig. 5. Housing parts of spindle heads: a – vertical head; b – slotting head; c – angle head

possible to create high-precision models of gear rims with geometrically correct tooth surfaces [27, 28]. Increasing the speed of profiling the working surfaces of engagement is carried out by using a three-dimensional operation of constructing gear rims by simulating gear milling of bevel gears. An increase in the speed of construction was also provided by the new functionality of the KOMPAS-3D CAD system, focused on such a type of surface as the “Surface of a conic section”, which is formed by moving a curve of a conic section along two generatrix. In this work, using the application “Shafts and mechanical transmissions 3D”, solid models of various types of gears (cylindrical, bevel, gear shaft) are built, which are shown in Fig. 6.

Fig. 6. Gear wheels and pinion shaft of spindle heads: a – vertical; b – slotting; c – angular

4 Modernization of Gear Couplings as MC Connecting Elements The expansion of the range of MC interchangeable technological equipment and spindle heads is associated with an increase in the number of connecting elements - various types of couplings. When connecting parallel shafts, one has to deal with angular, radial and axial displacements, which affect the accuracy and vibration resistance of machining on the machine. To compensate for shaft displacements, it is advisable to use gear couplings

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as a universal type of compensating couplings, which is the best solution in cases where it is necessary to transmit torque along one axis or at an angle. In the machine tool industry, tooth-type couplings (with two flange half-couplings) of the 1st type with a separable sleeve and the 1st version with cylindrical holes for the short ends of the shafts are widely used (according to the standards). The teeth of the bushings and sleeve, as a rule, are made involute with a classic profile angle along the reference circle in the middle end section, and the teeth of the gear rims are made barrel-shaped. At the same time, profiles of another shape are also proposed – spherical, as in [9]. In addition to the optimal connection of parallel shafts, the advantages of tooth-type couplings include minimal dimensions. At the same time, defects in the operation of tooth-type couplings are associated with wear of the coupling elements, which ultimately violates the correct shape of the working surfaces and leads to problems of the stressstrain state on the contact surfaces, and is associated with the level of bending and contact stresses. A disadvantage of the known tooth-type coupling is the insufficient load capacity of the teeth for bending stress. This is explained by the fact that for the given dimensions of the coupling, it is impossible to increase the length of the teeth, the initial surface of which is a cylinder with a limited axial size. One of the methods for reducing the stress level in the contact zone and the insufficient load capacity of the known designs of couplings is the modification of the tooth-type couplings designs. The main idea of the modification is to search for such profiles of the teeth working part for the flange half-couplings, which will have an increased contact length in engagement with the same overall and connecting dimensions (Fig. 7).

Fig. 7. Modified gear coupling: a – design; b – geometry

Such an idea, confirmed by a patent decision [29], is implemented by representing the pitch surface of the teeth on the bushings of the half coupling in the form of a cone with a convex curvilinear generatrix, and the pitch surface of the teeth in the sleeves of the coupling halves is a cone with a concave curvilinear generatrix, Fig. 7.

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4.1 Theoretical Part The task set is implemented as follows. The pitch surface of the teeth on the half-coupling bushings is a cone with a convex curvilinear generatrix, and the pitch surface of the teeth in the sleeves of the halfcouplings is a cone with a concave curvilinear generatrix (Fig. 7). That is, the internal helical gearing of involute teeth used in standard gear couplings [11, 30] has been replaced by internal bevel gearing of teeth with a circular profile. In this case, the longitudinal directions of the teeth on the bushings and sleeves of the modified coupling coincide with the curvilinear generatrix of the conical pitch surfaces. The convex and concave curvilinear generators are circular arcs of the same radius R (Fig. 8), the value of which is determined by the equality: R=

b , sin δ

(1)

where b – the width of the gear rim on the bushings; δ = 60◦ – the maximum angle of inclination of the curved generating teeth on the bushings and in the sleeves of the modified gear coupling.

Fig. 8. Convex and concave curvilinear generatrix: a – sleeve; b – bushing

The numerical values of the width b are equal to the values of this parameter in standard tooth-type couplings [12]. The parameters of the teeth are shown in the average end section A-A of the gearing in Fig. 7, b. The average end pitch Ptm between the teeth on the average reference circle with a diameter dm consists of three parts – S1 , S2 , : Ptm = S1 + S2 +  = π · mtm .

(2)

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Here S1 = 0, 5 · Ptm = 0, 5 · π · mtm = 0, 5 · π · mtm – thickness of the convex teeth in the average end section of the engagement on the reference diameter; S2t +  = 0.45 · π · mtm + 0.05 · π · mtm – respectively, the thickness of the concave teeth (S2t ) in the average end section on the reference diameter of the sleeves dm .  – side clearance between the teeth in the middle end section; (parameters Ptm and  on the section (Fig. 7, b) are not shown); mtm = mnm /cosδm – the average end module, expressed through the average normal module mnm and the angle of inclination of the longitudinal line of the tooth δm in the middle of the size b. The value of the angle δm is determined by the equality:   0.5 · b = arcsin(0.5 · sin δ) (3) δm = arcsin R It should be noted that in formula (3): δm = 0.5 · δ. So, for example, for δ = 60◦ : δm = arcsin(0.5 · sin 60◦ ) = 25.66◦ = 0.5 · 60◦ = 30◦ .

(4)

The parameters of the gear rims of the modified tooth-type coupling – the average normal module of the teeth mnm , the number of teeth z, as well as the main overall and connecting dimensions of the coupling – D , D1 , D2 , d , L , l coincide with the parameters of the teeth and the dimensions of the standard gear couplings [11, 12]; (at the same time, the tooth module in Standard R 50896–96 is a constant value in all end sections of the gear rim and is denoted by m). The profiles of the convex and concave teeth are outlined by a circle arc of the same radius ρ (Fig. 9):

Fig. 9. Tooth profiles: a – convex; b – concave

The radius of a circular arc ρ is defined as ρ=

m m = , sin α − sin αf 1 sin α − sin αa2

(5)

where α = 20◦ – the inclination angle of the convex and concave profiles of the teeth on the average reference circle with a diameter dm ; αf 1 = αa2 = 5◦ – angles of inclination of the convex tooth profiles of the bushing at the root (αf 1 ) and the concave tooth of the sleeve at its top (αa2 ).

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For α = 20◦ and αf 1 = αa2 = 5◦ : ρ=

m ≈ 3.9 · m. sin 20◦ − sin 5◦

(6)

The maximum angle of tooth profile inclination αa1 = αf 2 (Fig. 9): αa1 = αf 2 = arcsin(2 · sin α − sin αf ).

(7)

For α = 20◦ and αf = 5◦ : αa1 = αf 2 = arcsin(2 · sin 20◦ − sin 5◦ ) ≈ 36.7◦ .

(8)

The replacement of an involute profile with a circular one is proposed including in order to simplify the technology for manufacturing teeth. The total height of the teeth (h), the height of the head (ha ) and root (hf ) of the teeth, the radial clearance in the engagement (c) are taken by analogy with the standard involute teeth analogue [11, 12]: h = 2.2 · m, ha = m, hf = 1.2 · m, c = hf − hf = 0.2 · m. The result of the tooth-type coupling modification is an increase in the teeth length without changing the overall parameters of the standard coupling. With the same width b, the length of the tooth Lmod in the modified coupling will be greater than the length of the tooth Lst in the standard coupling in Lst times: KL =

Lmod δ = . Lst 2 · arcsin(0.5 · sin δ)

(9)

For a given angle δ = 60◦ = 60◦ · (π/180◦ ), rad.: KL =

60◦ · (π/180◦ ) ≈ 1.17. 2 · arcsin(0.5 · sin 60◦ )

(10)

That is, the length of the teeth increases by 17%, which means that the bending stress in them will decrease by the same amount. In addition, one more factor should be taken into account that contributes to a decrease in the value σF - the coefficient of the shape of the teeth YF . If in a standard coupling [11, 12] the value (YF )st is selected according to the actual number of teeth z, (as in spur gears), then in the modified coupling the value (YF )mod is taken according to the equivalent number of teeth (YF )mod , (as in bevel spur gears). Because zV = z/ cos δm > z and the value (YF )mod will be less than (YF )st , [4]. Accordingly, this will also reduce the stress σF at KY time: KY = (YF )st /(YF )mod

(11)

Strictly speaking, the values (YF )st in this work were obtained for an involute engagement. However, the circular profile of the teeth in the modified coupling within the working height of the thread h = 2.2 · m differs little from the involute profile of the teeth of the standard coupling, and their thickness on the circle with the same diameter dm is the same. Therefore, the use of the famous graph for estimating the value (YF )mod in the first approximation is quite correct.

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Thus, as a result of increasing the length of the teeth and reducing the shape factor of the teeth, the bending stress of the modified coupling (σF )mod will decrease compared to that of the standard coupling (σF )st at K time: K = KL · KY =

(YF )st δ · . 2 · arcsin(0.5 · sin δ) (YF )mod

(12)

4.2 Experimental Part The clutch gearing parameters are set: m = 6 mm ; z = 46. Determine the coefficient of reduction in the teeth bending stress of the modified coupling with δ = 60◦ the overall dimensions coinciding with the standard coupling. Solution. 1) For standard coupling: z = 46 → (YF )st = 3.68; [4]. 2) For modified coupling: δm = arcsin(0.5 · sin δ) = arcsin(0.5 · sin 60◦ ) = 25.66◦

(13)

zV = z/ cos δm = 46/ cos 25.66◦ ≈ 51 → (YF )mod ≈ 3.66

(14)

1) As a result: K=

60◦ δ (YF )st 3.68 ≈ · · ≈ 1.17 ◦ 2 · arcsin(0.5 · sin δ) (YF )mod 2 · arcsin(0.5 · sin 60 ) 3.66 (15)

Thus, with the given initial data, the bending stress in the teeth of the modified coupling will decrease by 17%.

5 Conclusions As a result of the research, the following results were obtained: 1. A complex 3D project of a drive for a drilling-milling-boring machining center with three interchangeable spindle heads: vertical, slotting and angular heads was created in the KOMPAS-3D CAD environment. This 3D project became the winner of the International Competition “Future Aces of 3D Computer Modeling”. 2. Solid models of complex housing parts of the main drive and interchangeable spindle heads have been developed. To form the complex spatial geometry of cast housings, the three-dimensional operation “Cutting-out” is effectively used when constructing cavities and channels of the inner surface of a cast workpiece. 3. Three-dimensional models of cylindrical and bevel gears and a modified design of the tooth-type coupling are built in the specialized module “KOMPAS_GEAR”. In the process of 3D modeling, a new functionality “Surface of a conical section” the KOMPAS-3D system was used. It is used to implement the procedure for the formation of gear rims by simulating the milling of the bevel gears teeth.

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4. The design of a modified teeth-type coupling for connecting the MC drive cam-shaft with the shafts of three different spindle heads has been developed. A new form of the working surface of the coupling teeth is proposed in the shape of a cone with a convex curvilinear generatrix on the pitch surface of the teeth for the bushings of the half coupling and a cone with a concave curvilinear generatrix in the half coupling sleeve. Analytical dependencies to determine the radius of the generatrix, the average end pitch, the angle of inclination of the tooth longitudinal line in the middle of the width of the gear rim are found. It is proved that the maximum angle of inclination of the curvilinear generatrix of the teeth. 5. The result of the modification of the tooth-type coupling is an increase in the length of the teeth without changing the overall parameters for the standard coupling, which leads to a decrease in the level of bending stresses. The criterion for evaluating the increase in the contact length and the coefficient of influence of the teeth shape are introduced, on the basis of which the second component of the evaluation criterion is formed. 6. An experimental calculation of the coefficient of reduction in the teeth bending stress of the modified coupling was carried out. These calculations showed a decrease in the teeth bending stress of the modified coupling by 17% and, as a result, without changing the dimensions of the standard tooth-type coupling, increase its load capacity.

References 1. Lynch, M.: Machining Center: Setup and Operation. CNC Concept Inc., Illinois (2013) 2. Dervoort, W.H.: Modern Machine Shop Tools, Their Construction, Operation and Manipulation, Including Both Hand and machine Tools ... Creative Media, London (2018) 3. Barbosa, M., Silva, F.J.G., Pimentel, C., Gouveia, R.M.: A novel concept of CNC machining center automatic feeder. In: 28th International Conference on Flexible Automation and Intelligent Manufacturing (FAIM2018), vol. 17, pp. 952–959. Procedia Manufacturing (2018). https://doi.org/10.1016/j.promfg.2018.10.111 4. Yamazaki, T.: Development of a hybrid multi-tasking machine tool: integration of additive manufacturing technology with CNC machining. Procedia CIRP 42, 81–86 (2016). https:// doi.org/10.1016/j.procir.2016.02.193 5. Sokolov, V., Krol, O.: Determination of transfer functions for electrohydraulic servo drive of technological equipment. In: Ivanov, V., et al. (eds.) DSMIE 2018. LNME, pp. 364–373. Springer, Cham (2019). https://doi.org/10.1007/978-3-319-93587-4_38 6. Krol, O., Sokolov, V.: Modeling carrier system dynamics for metal-cutting machines. In: 2018 International Russian Automation Conference (RusAutoCon), IEEE (2018). https://doi.org/ 10.1109/RUSAUTOCON.2018.8501799 7. Afsharizand, B., Zhang, X., Newman, S.T., Nassehi, A.: Determination of machinability considering degradation of accuracy over machine tool life cycle. In: Proceeding of the 47th CIRP Conference on Manufacturing Systems, vol. 17, pp. 760–765 (2014). https://doi.org/ 10.1016/j.procir.2014.02.048 8. Kong, J., Cheng, X.: Modal analysis of CNC lathe’s spindle based on finite element. Adv. Eng. Res. (AER) 148, 318–321 (2017) 9. Sergienko, N., et al.: Synthesis of the energy-saving dry dual clutch control mechanism. Appl. Sci. 13, 829 (2023). https://doi.org/10.3390/app13020829

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10. Aurea, I., Gonzalez-Perez, I., Arana, A., Larrañaga, J., Ulaci, I.: Computerized generation and tooth contact analysis of spherical gear couplings for high misalignment applications. Mech. Mach. Theory 164, 104408 (2021). https://doi.org/10.1016/j.mechmachtheory.2021. 104408 11. American Gear Manufacturers Association, AGMA 945-1-b20: Splines design and application (2020) 12. Litvin, F.: Theory of Gearing, Technical report. University of Illinois, Chicago (1989) 13. Litvin, F., Fuentes, A.: Gear Geometry and Applied Theory, 2nd edn. CAMBRIDGE University Press, Cambridge (2004) 14. Sokolov, V., Porkuian, O., Krol, O., Stepanova, O.: Design calculation of automatic rotary motion electrohydraulic drive for technological equipment. In: Ivanov, V., Trojanowska, J., Pavlenko, I., Zajac, J., Perakovi´c, D. (eds.) DSMIE 2021. LNME, pp. 133–142. Springer, Cham (2021). https://doi.org/10.1007/978-3-030-77719-7_14 15. Krol, O., Sokolov, V.: Modelling of spindle nodes for machining centers. J. Phys: Conf. Ser. 1084, 012007 (2018). https://doi.org/10.1088/1742-6596/1084/1/012007 16. Pavlenko, I., Trojanowska, J., Ivanov, V., Liaposhchenko, O.: Parameter identification of hydro-mechanical processes using artificial intelligence systems. Int. J. Mechatron. Appl. Mech. 5, 19–26 (2019) 17. Krol, O., Sokolov, V.: Modeling of spindle node dynamics using the spectral analysis method. In: Ivanov, V., Trojanowska, J., Pavlenko, I., Zajac, J., Perakovi´c, D. (eds.) DSMIE 2020. LNME, pp. 35–44. Springer, Cham (2020). https://doi.org/10.1007/978-3-030-50794-7_4 18. Liaposhchenko, O., Pavlenko, I., Monkova, K., Demianenko, M, Starynskyi, O.: Numerical simulation of aeroelastic interaction between gas-liquid flow and deformable elements in modular separation devices. In: Ivanov, V., et al. (eds.) DSMIE 2019. LNME, pp. 765–774. Springer, Cham (2020). https://doi.org/10.1007/978-3-030-22365-6_76 19. Rezvaya, K., et al.: Study of the characteristics of the runner blade system of a hydraulic machine. Int. J. Mechatron. Appl. Mech. 12, 74–80 (2022). https://doi.org/10.17683/ijomam/ issue12.11 20. Andrenko, P., Rogovyi, A., Hrechka, I., Khovanskyi, S., Svynarenko, M.: The influence of the gas content in the working fluid on parameters of the the hydraulic motor’s axial piston. In: Ivanov, V., Pavlenko, I., Liaposhchenko, O., Machado, J., Edl, M. (eds.) DSMIE 2021. LNME, pp. 97–106. Springer, Cham (2021). https://doi.org/10.1007/978-3-030-77823-1_10 21. Varbanets, R., et al.: Acoustic method for estimation of marine low-speed engine turbocharger parameters. J. Marine Sci. Eng. 9(3), 321 (2021). https://doi.org/10.3390/jmse9030321 22. Brecher, C., Fey, M., Daniels, M.: Modeling of position-, tool- and workpiece-dependent milling machine dynamics. High Sped Mach 2, 15–25 (2016) 23. Tsankov, P.: Modeling of vertical spindle head for machining center. J. Phys. Conf. Ser. 1553, 012012 (2020). https://doi.org/10.1088/1742-6596/1553/1/012012 24. Marshek, K.M.: Design of Machine and Structural Parts. Amazon Publishing, Seatle (1987) 25. Pavlov, V., Borosenets G., Semak I.: Machine parts. Condor, Kiev (2021). (in Ukrainian) 26. Krol, O., Sokolov, V.: Research of toothed belt transmission with arched teeth. Diagnostyka 21(4), 15–22 (2020). https://doi.org/10.29354/diag/127193 27. Stanciu, D.-I., Cheorghe, G.I., Cioboat˘a, D.-D.: Master error elimination in forced gear engagement testing machine using harmonic analysis through fast Fourier transform. Int. J. Mechatron. Appl. Mech. 2(10), 238–247 (2021) 28. Feng, W.: Gear drive system: dynamics analysis under impact load. Int. J. Mechatron. Appl. Mech. 12, 47–51 (2022) 29. Shevchenko, S., Mukhovaty, O., Krol, O.: Modified toothed clutch. UA Patent Application u 2017 10834 (2017) 30. Radzevich, S.: Theory of Gearing: Kinematics, Geometry and Synthesis, 2nd edn. CRC Press, Boca Raton (2022)

Experimental Studies of Hydrodynamic Characteristics of Cellular Packings for Benzene Absorbers Inna Lavrova(B)

, Vladyslava Vladymyrenko , and Volodymyr Babenko

National Technical University «Kharkiv Polytechnic Institute», 2 Kirpichova St, Kharkiv 61002, Ukraine [email protected]

Abstract. Aromatic hydrocarbons are one of the important products on which the organic synthesis industry is based. There is a trend in all technologically advanced countries towards a constant increase in demand for benzene, toluene, and xylenes, which are the main products produced from raw benzene. In modern Ukraine, with its developed coke-chemical industry and limited industrial reserves of oil, the coke-chemical industry is the main supplier of aromatic hydrocarbons. However, significant reductions in coke production and the instability of the coke raw material base led to a gradual decrease in the production of this important raw material and a deterioration in its quality. Therefore, the need for equipment design capable of ensuring stable production of valuable aromatic raw materials under unstable gas flows, mediocre quality of absorbent oil, and heavy technological conditions becomes relevant. Based on hydrodynamic research, a method was developed for the first time, and an equation was obtained that allows predicting the effectiveness of new packing compared to known ones, by comparing their mass transfer and hydrodynamic characteristics under identical conditions. On this basis, recommendations have been developed for the design of installations that differ from existing ones in improved mass transfer characteristics and low pressure drop in the apparatus. Based on experimental studies of hydrodynamic modeling, the main parameters of the developed packing elements were determined, and for the first time, the mass transfer characteristics of their use as a packing for benzene scrubbers were predicted. Keywords: Absorber · Hydraulic resistance · Physical modeling · Mass transfer · Cellular packings · Benzene hydrocarbons · Coke oven gas

1 Introduction The selection of packings for heat and mass transfer equipment is a complex problem that requires consideration of multiple factors, including mass transfer characteristics, pressure drop, operational reliability, and overall cost. Clearly, it is preferable to use packings with low cost, superior mass transfer characteristics, and minimal pressure drop. However, the problem of selection becomes more © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 286–296, 2023. https://doi.org/10.1007/978-3-031-40628-7_24

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complicated when an packing is superior in one or two parameters but inferior in others. This ultimately leads to the development and investigation of increasingly newer and more complex packings elements. Modern theory and practice of mass transfer allow us to identify paths for selecting the most efficient packings for specific technological processes. The main goal of this study is to develop a method that allows predicting the effectiveness of new packings compared to existing ones based on hydrodynamic research.

2 Literature Review Modern theory and practice of mass transfer allow us to identify paths for selecting the most efficient attachments for specific technological processes. In [1], the following fairly obvious basic technical and economic requirements for attachments used in modern attachment apparatuses are presented: • packings should have a large surface area per unit volume and a large free crosssection; • packings should have low resistance to gas flow, effectively distribute the liquid, and possess corrosion resistance in relevant environments; • packings should have a small volume weight and low cost; • packings should have low fouling tendency and be reliable in operation. Requirements for packing shape are diverse and highly contradictory. To reduce pressure drop, elements with streamlined shapes are used. On the other hand, packings with numerous sharp edges, which result in frontal impacts of the gas flow on the liquid film surface, provide higher process intensity than attachments with streamlined shapes. In [2], the following requirements for packings design and shape are proposed. According to the authors, packings should ensure: • equalization of phase velocity profiles across the apparatus cross-section through structural techniques; • combination of areas where film flow mode is maintained with areas where liquid sprays interact with the gas; • repeated utilization of inlet and outlet effects, which ensure the highest contact efficiency during film destruction and formation; • impulsive changes in velocities of interacting phases through structural techniques, which promote process intensification by inducing turbulent pulsations in the contact zone; • increased contact time between liquid and gas by combining film and bubbling modes of interaction. In turn,[3, 4] indicates the following ways to enhance the performance of attachment apparatus: 1. Use packings that allow operating at high gas and liquid velocities and have a small equivalent diameter.

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2. Employ packings that promote frequent breakup of the liquid film flowing over the packing elements, its turbulence, as well as dispersion and coalescence of droplets in the free volume of the packing. 3. Create packings that facilitate rapid redistribution of the gas flow. 4. Develop packings characterized by high drainage in the upper part (for uniform distribution of the liquid phase) and low drainage in the rest of the packing. Naturally, there is no packing that satisfies all the mentioned requirements. For example, the flat-parallel packings, which meets many technical-economic requirements formulated in the [1], has relatively low efficiency, increased metal content, relatively small specific contact area, lack of turbulence in the contacting phases, and low contact surface renewal frequency [5].

3 Research Methodology The research methodology involves the use of analytical dependencies and hydrodynamic modeling on a test bench. Figure 1 shows the schematic diagram of the upgraded setup for determining the hydrodynamic characteristics of packing.

Fig. 1. Diagram of the setup for hydrodynamic investigations of packings: 1 - scrubber; 2 - liquid collector; 3 - hydroseparator; 4 - liquid supply line; 5 - pump; 6 - flow indicator; 7 - air duct; 8 diaphragm; 9 - valve; 10 - cyclone; 11, 12 - pressure gauges; 13 - tested package; 14 - redistribution package; 15 - nozzle; 16 - thermometer; 17 - micromanometer.

During the experiments, the airflow rate varied from 200 to 800 m3 /h. The measurement of air pressure drop during its passage through the attachment was performed using a micromanometer MM-250 (17). In the described series of experiments, two types of cellular packing were investigated: 1. Cellular packing 15 × 15 mm

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2. Cellular packing t 25 × 25 mm Measurement of the hydraulic resistance of dry and wetted attachments was carried out according to the methodology of UKHIN [3] on an attachment package with a height of 1 m and a diameter equal to the diameter of the apparatus. Air and water were used as the modeling media, with subsequent conversion to coke gas based on the condition of equal Reynolds numbers for air and coke gas: W ∗ d ∗ γ WB ∗ d ∗ γB = μB ∗ g μ ∗ g

(1)

where: wv and wg are the velocities of air and gas in the attachment, m/s; d  - equivalent diameter of the attachment, m; γ B and γ  - densities of air and coke gas, respectively, kg/m3; g - acceleration due to gravity, m/s2 ; μv and μg - of dynamic viscosity of air and coke gas, respectively, kg/(m·s) Under the given conditions: for air, P = 101.32 kPa (760 mmHg) and t = 20 °C, for coke gas, P = 106.66 kPa (800 mmHg) and t = 30 °C. The ratio of gas velocity to air velocity is wg /wv = 1.54. In each experiment, 2–3 parallel series of pressure drop measurements were conducted at different gas velocities. 3.1 Analytical Dependence for Predicting the Efficiency of Nozzle Elements in the Process of Hydrodynamic Modeling Considering all the aforementioned points, it seems reasonable to develop an analytical dependence that allows for predicting the efficiency of various packing elements without conducting complex and expensive mass transfer experiments. The simplest approach to achieve this is by comparing units of the same scale with known packing elements to a similar unit with the investigated packing, operating under identical conditions of the same process. As a simplifying condition for comparison, it is necessary to ensure that the gas and absorbent flows, physicochemical conditions of the process, and the degree of extraction of the target component are identical. If we utilize the fundamental mass transfer equation [6], we can express the following equation for mass transfer apparatus with nozzles: dG/(dt∗ Dy) = k∗ F

(2)

The overall surface area of the packing can be represented as: F =a∗f ∗H

(3)

where a - the specific surface area of the packing, m2 /m3 ; f - the cross-sectional area of the apparatus, m2 ; H - the height of the packing, m In turn, the height of the packing H in Eq. (3) can be expressed as a dependency: H =h∗m

(4)

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where h - is the height of the packing, corresponding to the transfer unit, in meters, m - is the total number of transfer units. By comparing the indicators of apparatuses with known and tested elements and substituting the corresponding values from Eqs. (3) and (4) in advance, we obtain: K1 ∗ a1 ∗ f1 ∗ h1 = K2 ∗ a2 ∗ f2 ∗ h2

(5)

The values of absorption coefficients can be expressed using the equation of hydrodynamic analogy by V.V. Kafarov [6, 7] for two-phase flows. For the turbulent regime, it takes the form:   K ∗ d e ∗ d 0,8  υ 2/ 3 (6) =A∗ (1 + ) D υ D where: d  - is the equivalent diameter of the packing, in meters; D - is the coefficient of molecular diffusion, in square meters per second; w - is the linear velocity of the gas flow, in meters per second; υ - is the kinematic viscosity, in square centimeters per second; F - is the factor of the hydrodynamic state of the system. By substituting the obtained values into Eq. (4) and replacing d  with its values obtained from the formula d  = 4f/a in the equation and expressing it in terms of the desired quantity h2 , we obtain: (1 + 1 ) h2 = h1 ∗ ∗ (1 + 2 )



a1 a2



1,2 ∗

w1 w2

0,8

 0,8 f1 ∗ f2

(7)

This equation establishes the relationship between the main geometric, hydrodynamic, and mass transfer characteristics of the compared packing elements [8]. Let’s focus more on the hydrodynamic characteristics of the packing, which are expressed in this equation by the parameter F, as it is the only one that needs to be determined experimentally. F is the factor of the hydrodynamic state of the system, representing the energy of the gas flow expended on forming the phase contact surface. F is determined by the equation: (8) ΔPg- i ΔPg - are pressure losses in two-phase and single-phase flows, respectively, at the same gas flow rate, measured in Pascal (Pa). The values of ΔPg- and ΔPg can be determined based on hydrodynamic modeling of the packing elements in an air-water system. Thus, the combined analysis of Eqs. (7) and (8) and the evaluation of the influence of all factors involved in these equations have shown that to decrease the height h2 (increase efficiency) compared to h1 at equal gas velocities, the investigated packing should have: minimal pressure losses in single-phase flows and increased losses in two-phase flows, as well as a packing surface area exceeding that of a known sample at similar free volume ratios.

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As a reference object for comparison, we chose a flat-parallel packing, which is the most favorable in terms of hydrodynamics (including minimal hydraulic resistance)[9, 10]. The increase in the relatively small specific surface area characteristic of a flatparallel nozzle can be easily achieved by transforming it into a volumetric one using an analogy with cellular packing. Among several modifications of cellular packings used and developed (Fig. 2) for the benzene hydrocarbon absorption process from coke gas, preference should be given to a packing with a square cell structure.

Fig. 2. Element of the developed cellular packing.

To promote the turbulence of the contacting phases and increase the refreshment multiplicity, we achieve it by replacing the high-height sheets of the flat-parallel packing with strips of height 80–100 mm and by arranging low-height (100–120 mm) formed packages with a 20 mm gap between subsequent rows of the packing (analogous to a wooden chorded packing). To reduce the metal content of the developed cellular packs packages, they can be manufactured from thin sheets with perforations on their surface. Table 1 presents the characteristics of the main geometric parameters of the compared metal packing. As a result of the development of the cellular packing, an extended range of gas velocities up to 4–5 m/s with low pressure losses (up to 80–100 Pa per 1m height) has been achieved. It also stands out from the analog by its simplicity of manufacturing.

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Packing name

Distance between adjacent plates in the packing, mm

Height of packages, mm

Specific surface packing, m2 /m3

Relative free cross-section, m2 /m3

Cellular packing 25 × 25

25 × 25

100

145*

0,92

Flat-parallel

16

1000

125

0,96

4 Results Measurements of hydraulic resistance of dry and irrigated packings were conducted according to the known methodology on a package with a total height of 1 m, with the package diameter equal to the diameter of the scrubber unit. Air and water were used as the modeling medium, with subsequent conversion to coke gas based on the condition of identical Reynolds numbers for air and coke gas. In each experiment, 4–5 parallel series of pressure drop measurements were performed at different air velocities in the range of 1.56–3 m/s, which is equivalent to coke gas velocities of 2.4–4.6 m/s. From the data presented in Table 2, it can be seen that in this variant of the cellular packings, with an increased specific surface area of the packing (approximately 16%), the losses for irrigated packing s are significantly higher compared to dry packings, while the pressure drop losses remain practically identical. According to the accepted analogy between mass transfer and friction, the latter indicates increased energy consumption of the gas flow for the formation of the phase contact surface. By substituting the corresponding values into Eq. (6), it can be derived that the height of the investigated cellular packing, equivalent in efficiency to the parallel plate packing, is h2 = 0.68 h1 . Thus, when using a cellular packing with square cups of 25 × 25 mm and a gap of approximately 20 mm between the plates in successive layers, the calculated height of the cellular packing corresponding to unity of mass transfer (as well as the overall height of the installed section of the apparatus) is 30–32% lower than that of the wellknown parallel plate packing. The verification of the main conclusions regarding the improvement of the characteristics of the cellular packings proposed by us was carried out under laboratory and industrial conditions on an installation consisting of a scrubber with a diameter of 355 mm and a height of 16 m, equipped with appropriate communications and a measurement complex. This scrubber, as part of the installation, consisting of two sequentially connected units, was previously used for studying flat-parallel, cross-sectional, and other packings [5]. Figure 3 schematically shows the scrubber in which the packages of the cellular packings are placed, with each successive one rotated by 45° relative to the previous one.

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Table 2. Experimental values of pressure drop losses in the compared packings. Packing

The speed in the packing, m/s air

Pressure loss in the nozzle, Pa

equivalent coke dry oven gas

The factor of hydrodynamic of the system state

irrigated at different L = 1,7 L = 2,3 specific absorber flow rates, l/m3 of gas L = 1,7 L = 2,3

Flat- parallel

1,3

2,0

6,9

7,9

1,5

2,31

8,8

10,1

11,0

0,148

0,250

1,8

2,77

12,2 15,0

15,6

0,230

0,279

2,3

3,54

18,5 23,2

23,8

0,254

0,286

2,8

4,31

25,2 31,9

32,8

0,266

0,300

3,0

4,62

29,5 37,3

38,7

0,278

0,312

9,8

12,9

13,9

0,316

0,418

13,5 19,0

20,0

0,408

0,483

17,9 26,1

27,2

0,458

0,52

Cellular 25 × 25 1,56 2,4 (packages are 1,95 3,0 installed with a 2,34 3,6 45° rotation) 2,61 4,02

8,6

0,145

0,247

22,4 33,2

35,0

0,473

0,56

2,8

4,3

25,3 37,8

40,0

0,49

0,58

3,0

4,62

27,6 41,1

44,2

0,51

0,60

Fig. 3. Scrubber equipped with a cellular packings. 1 - first section of the cellular packings; 2 perforated plate; 3 - expansion chamber; 4 - second section of the cellular packings; 5 - droplet eliminator; 6 - jet-vortex nozzle

After the five-meter section of the cellular packings 1, a gas and oil redistributor perforated plate 2, placed in the expansion chamber 3, is installed. Above the redistributor device, a second section of the packings 4 is positioned with a total height of 4 m. A jet-vortex nozzle 6 was used as the initial distributor of the absorbent oil.

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The main indicators of the absorption process in the scrubber with a cellular packings are presented in Table 3. The obtained results (absorption coefficients, residual content of benzene hydrocarbons) when using a single scrubber with a cellular packings are similar to the results previously obtained when using two sequentially connected scrubbers with a flat-parallel packings. For convenience of analysis, these results are presented in the form of graphical dependencies of volume absorption coefficients on gas velocity (Fig. 4). From the provided data, it can be concluded that the investigated cellular attachment exhibits increased efficiency (by 30–35%) over a wide range of gas velocities compared to the widely used flat-parallel attachment with practically identical pressure losses. The use of the cellular attachment allows for the creation of installations that will ensure the desired degree of removal of benzene hydrocarbons in a single technical apparatus of real height. Table 3. Key indicators of the benzene hydrocarbon absorption process from coke gas in an absorber with a cellular attachment. Gas velocity, m/s

Specific oil consumption, l/nm3

Temperature, °C Scrubber resistance, Pa gas oils

Benzene hydrocarbon Absorption content in gas, g/m3 coefficient, Kv 10–2 , to after 3 scrubbers scrubbers kg/m h Pa

2,05 2,14

2,8

24

32

300

26,9

4,2

9,8

2,36

20

29

350

26,2

4,35

10,9

2,31

1,84

23

33

420

26,87

6,5

11,0

2,5

2,0

25

30

520

29,3

5,4

12,1

2,7

2,0

26

32

580

31,0

5,7

12,5

3,0

1,9

25

32

620

30,0

5,0

13,9

3,2

1,84

27

32

700

29,3

4,9

14,5

3,4

1,8

26

33

720

29,6

5,1

15,8

3,7

1,7

23

28

800

30,3

4,0

17,4

3,75

1,8

24

33

820

29,4

4,2

18,1

4,0

1,8

25

32

850

28,5

4,3

19,0

* The content of benzene hydrocarbons in the de-benzolized oil ranged from 0.3% to 0.64% (by

volume). ** The molecular weight of the oil is 195–200

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Fig. 4. Dependency of volume absorption coefficients on gas velocity.

5 Conclusions Summarizing the experimental determination of the main characteristics of the packing elements for the absorption process of benzene hydrocarbons from coke oven gas, it is necessary to highlight the feasibility of conducting hydrodynamic studies of packing elements over a wide range of gas and liquid velocities, both for determining pressure drop losses and predicting efficiency in mass transfer. Based on the obtained analytical dependencies, the efficiency of applying the new packing elements compared to the known ones has been predicted. For the absorption of benzene hydrocarbons from coke oven gas with bituminous coal absorbent oil, cellular packings have been chosen, which allow combining enhanced efficiency with high throughput capacity and low specific pressure drop losses. The application of cellular packings with square cups of 25 × 25 mm and a total height of each packing of 100 mm presents practical interest in the design of new installations as well as in the modernization of existing ones to replace parallel plate and other packings, as they exhibit increased efficiency (approximately 30%) with comparable pressure drop losses.

References 1. Dzevochko, O.M., Podustov, M.O.: Novi hofrovani nasadkovi elementy dlia vykorystannia v absorbtsiinykh systemakh. ITE 3, 8–17 (2018). [in Ukrainian] 2. Dzevochko, O.M., Podustov, M.O.: Doslidzhennia hofrovanykh nasadkovykh elementiv v protsesakh absorbtsii vykhidnykh haziv vyrobnytstva PAR. ITE 1, 33–41 (2019). [in Ukrainian] 3. Lavrova, I.O.: Capture of benzene hydrocarbons and gas purification from naphthalene. In: Handbook of Coke Chemist: Capture and processing of coking chemicals, 3 edn, vol. 3, pp. 7. VD INZHEK, Kharkiv (2010). [in Russian]

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4. PTE-2017 Pravila tehnichnoi ekspluatacii koksohimichnih pidpriemstv. – Kharkiv: DP"Hiprokokks" (2018). [in Ukrainian] 5. Lavrova, I.O., Shustikov, V.I., Lavrov, O.I.: Improvement of the process of extraction of benzene hydrocarbons from coke-ovens gas and apparatuses used. Coke and chemistry c/c of Koks i khimiia, 31–36 (1999) 6. Kalinchak, V.V.: Khimichna kinetyka ta masoobmin: navchalnyi posibnyk. In: Kalinchak, V.V., Chernenko, O.S. (eds.) Odesa, Odeskyi natsionalnyi universytet im. I.I. Mechnikova, p. 185 (2017). [in Ukrainian] 7. Tovazhnyansky, L.L., Biletsky, E.V., Tolchynsky, Yu.A.: Modelyuvannya techiyi nenyutonivskih ridin u kanalah bazovoyi geometriyi: monograph, National Technical University "Kharkiv Polytechnic Institute. NTU, Kharkiv (2013). [in Ukrainian] 8. Tovazhnyansky, L.L.: Heat integration improvement for benzene hydrocarbons extraction from coke-oven gas. In: Tovazhnyansky, L., Kapustenko, P. (eds.) 14th International Conference on Process Integration, Modeling, and Optimization for Energy Saving and Pollution Reduction, Florence, Italy, 8–10 May 2011. Chemical Engineering Transactions, vol. 25, no. 1, pp. 153–158 (2011) 9. Tovazhnyansky, L., Kapustenko, P., Ulyev, L., Vasilyev, M.: Process integration of benzene distillation unit at the coke plant. In: Proceedings of 19th International Congress of Chemical and Process Engineering, CHISA, Prague, Czech Republic, 28 August–1 September 2010, p. 1487 (2010) 10. Dzevochko, O.M., Podustov, M.O., Dzevochko, A.I.: Doslidzhennia teplovykh i masoobminnykh protsesiv v hazoridynnykh plivkovykh absorberakh u tekhnolohii PAR. ITE 3, 3–16 (2021). [in Ukrainian]

Influence of Polymeric Quaternary Salts on Some Properties of Cement Stone and Concrete for Construction and Irrigation Purposes Makhmudova Naima Khalilovna(B) Tashkent State Technical University, Tashkent, Uzbekistan [email protected]

Abstract. The article shows the results of the development of effective composite materials for construction purposes based on cement systems. Particularly, concretes and polyquaternary salts, which are surface-active additives are studied in the manuscript. It has been established that the addition of dimethylaminoethyl methacrylate with benzyl chloride (PDMAEMA·CB) significantly modifies the structure of the cement stone, contributing to the formation of a finely porous structure, which ensures the strength of the structure. Keywords: Building materials · cement system · additives · hydrolysis · dispersion system

1 Introduction Composite materials for construction purposes based on cement systems, in particular concrete and reinforced concrete are one of the large-scale foundations for the development of the economy of the Republic of Uzbekistan [1–3]. It is because of their high operational properties, the presence of a local raw material base, a developed network of enterprises, the possibility of creating mini-enterprises for the production of products and structures for housing, bridges, hydraulic engineering and other purposes. One of the main tasks of ensuring the further industrialization of construction production and turning it into a mechanized process of assembling and erecting buildings and structures from reinforced concrete panels, blocks, parts is to reduce the material consumption of products, economical consumption of raw materials, fuel, metal, cement, and other materials. Until now, technical progress in the field of concrete and reinforced concrete technology has been reduced practically to the improvement of the mechanisms used, the automation of processes and, to a lesser extent, to their chemicalization [4, 5]. At the same time, one of the most promising and effective areas of chemicalization in the modern construction industry is the use of organic and inorganic additives that affect the chemical processes of concrete formation and significantly increase its performance properties. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 297–307, 2023. https://doi.org/10.1007/978-3-031-40628-7_25

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The problem of the assortment and prospects for the use of composite materials for construction purposes is the cornerstone of construction technology, because includes the study of the fundamental properties of these materials and the influence of the environment on them during operation. Among the modern composite materials used in construction, materials based on cement systems, which include cement (cement-water suspensions, pastes), concrete (mortar) mixtures, cement stone mortar, concrete are the most ancient and variable, and at the same time least studied [6]. Cement concrete compositions have a complex of valuable technical properties the ability to harden and increase strength both in air and in water, resistance to many aggressive influences, suitability for the manufacture of structures and structures of various shapes and purposes [7, 8]. In this aspect, it is relevant to develop effective composite materials for construction purposes based on cement systems, in particular, concretes and polyquaternary salts, which are surface-active additives that make it possible to equally effectively control the processes of hydrolysis and hydration of cement, improve their quality and reduce costs.

2 Methods To obtain composite materials for construction purposes - cement systems with specified construction and technical properties, it is necessary to establish the laws governing the regulation of parameters at the stage of interaction of cement with water. The processes that determine these properties are mainly determined by molecular forces acting at the interface. These interactions form such properties of dispersed systems as viscosity, peptization, boundary lubrication, coagulation, structure formation, etc. [9]. The methodological part of the work includes the characteristics of the materials used, and the methodology for conducting experimental studies. 2.1 Characteristics of Accepted Materials Cement - for the preparation of concrete mixtures, four types of cement of various aluminosity were used, the characteristics of which are given in Tables 1 and 2. Table 1. Mineral composition of cement clinker. Name of cement

Mineralogical composition, % C3 A

Slag content

Alkaline content, %

C3 S

C2 S

C4 AF

Cement No. 1

57,1

19,8

5,7

13,0

10,5

0,40

Cement No. 2

54,6

18,4

11,0

14,6

13,7

0,32

Cement No. 3

60,2

20,1

5,5

14,5

15,6

0,36

Cement No. 4

64,0

16,0

5,0

15,0

48,6

0,48

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Table 2. Physical and mechanical properties of cement. Name of cement

Beginning of setting

End of setting

Activity, MPa

Tensile strength after 28 days, MPa

Cement No. 1

110

240

48,5

6,5

48,5

Cement No. 2

170

270

54,4

5,5

39,4

Cement No. 3

130

290

54,6

6,8

54,6

Cement No. 4

190

290

41,7

6,0

41,7

Sand - for the experiments, the sand of the “Chinaz” quarry was used, which has a fineness modulus Mkr = 2.8–3.2 and contains clay dust-like and silty particles up to 2–2.3% [GOST 8267-93]. Crushed stone - for the preparation of concrete mixtures, granite crushed stone of the “Chirchik” quarry was used with a bulk mass of 1360 kg/m3 , a density of 2.6 g/cm3 , a breech content of up to 10%, a water absorption of 0.21%, and a porosity of 1.17% [GOST 8736-97]. Chemical Additives. As effective additives, aqueous solutions of polymeric quaternary salts of N,N - dimethiaminoethylmethacrylate with benzyl chloride (PDMAEMA·BC), benzyl bromide (PDMAEMA·BB), benzyl iodide (PDMAEMA BI), and polydimethyldiallylammonium chloride (PDMAAC) were used as effective additives. The preparation of concrete mixtures was carried out in a laboratory concrete mixer. The compaction of the mixtures was carried out on an ejection platform with an amplitude of 0.4 mm and a frequency of 3000 counts. Concrete samples were steamed according to the regime 2 + 3 + 4 + 2 h (preliminary holding + temperature rise + steaming + cooling) at tiz = 353 K. The plastic strength of cement paste and mortar was determined with a lever-type conical plastometer at temperatures of 293, 313, 333K [GOST 10181-81]. The plastic strength was calculated using the Rehbinder formula (1),   (1) R = K F/P2 , MPa K – coefficient depending on the cone (at a = 450 K = 0.416), F – load acting on the KGS cone, P – immersion depth of the cone, cm The CaO content in the cement stone was determined by complexometric titration. The metal indicator is acid chromium dark blue. The content in % was calculated by the formula (2), P = (TCao ∗ V ∗ 5/G ∗ 7) ∗ 100%

(2)

V – volume of solution used for titration, ml. TCaO – solution titer expressed in g/ml. G – sample weight, g.

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The content of CaCO3 was determined by the content of CaO2 , determined on a calcemeter by exposing the sample to acid and measuring the volume of released CaO2 , the amount of which was calculated according to the following formula, PCO2 = 100aV /A

(3)

where, A = c/V c – the amount of CaO2 in the weighed portion of the control sample CaCO3 , V – the volume of released gas, ml, V’ – the volume of released gas in the measuring vessel, ml, F – sample weight, g The compressive and tensile strength of concrete in bending was determined according to GOST 10180-81. The porosity of the cement stone was determined by mercury porosimetry on a 200 series porometer from “Carlo Erba (Italy)”, at a maximum pressure of 1500 kg/cm2 , dilatometer volume 15 cm3 , capillary radius 1.5 mm, mercury level = 95.9 mm. The degree of hydrophobization of concrete was determined by measuring the equilibrium contact angle on an epidoscope EPD-455. The specific surface of the cement stone, depending on the chemical additive, was determined by the dye sorption method. An acetone solution of conngo red was used as an indicator. The changes were carried out on a FEK-26 photocolorimeter. 2.2 Study of the Sorption Interaction of Polyquaternary Salts with Basic Minerals To determine the effect of the studied Quaternary salts of plasticizers on the processes of hydration of cement stone, it is essential to study their sorption interaction with the main minerals of cement. To conduct the study, the main mineral components of cement were taken as models - tricalcium (C3 S) and dicalcium silicates (C2 S), tricalcium aluminate (C3 A) and tetra calcium aluminoferrite (C4 AF) with a specific surface Ssp = 4350–5690 cm2 /g. The samples were modified by mechanical treatment. The adsorption capacity of the mineral constituents of cement was determined as follows; for extracting the adsorbed plasticizer, weighed portions of minerals with water (1:2) were stirred for 1 h at room temperature, then the liquid phase was separated in a centrifuge (Vvr = 6000 rpm). The amounts of non-adsorbed plasticizers of quaternary salts were determined by the transmission coefficient of the obtained extracts on a FEK 56 m niphelometer (light filter No. 7, color filter 3 mm thick). For comparison, water extracts of their original (unmodified) clinker minerals were used, the specific surface of which was brought to Ssp = 5690–4350 cm2 /g.

3 Results and Discussion The adsorptive capacity of clinker components with respect to polychervertic salts depends on their composition: the lowest transmittance has two-calcium silicate modified with poly-quaternary salts, the highest - three-calcium aluminate; in order of increasing transmittance value, minerals can be arranged in the following sequence: C2 S < C3 S < C3 A < C4 AF

(4)

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It should be noted that the production of water-mineral mixtures showed a different ratio of the original and modified N. Where N-dimethylaminoethyl methacrylate with benzyl chloride (PDMAEMA·CB) minerals to water, it was found that for modified C3 S, a ratio of mineral-water = 1:1 is sufficient, and for aluminate minerals 1:2 or 1:3. This is due, apparently, to the fact that the polyquaternary salt for silicate monomineral binders has a hydrophobic effect, and for monoaluminate it has a hydrophilizing effect [10]. It has been experimentally established that the adsorption of the studied polyquaternary salts on tricalcium aluminate is directly dependent on the initial concentration of the solution, and with an increase in dosage to 3% of the mass of the clinker mineral, its intensity does not decrease. Preliminary hydration of clinker minerals increases their adsorption capacity in direct proportion to the relationship between the degree of C3 S hydration and the amount of adsorbed matter. During hydration of a mixture of C3 A with gypsum (25% C3 H2 ), as in the case of pure C3 A, the adsorption capacity of the solid phase is higher when the polyquaternary salt is introduced with mixing water, and when the mixture is preliminarily hydrated, it sharply decreases. The latter is essential for obtaining the greatest plasticizing effect. For C3 S and C2 S, the adsorption of PDMAEMA·CB occurs to a much lesser extent, and its presence in free form in aqueous extracts of C3 S and C2 S suggests organic interaction of these phases, while for C3 A and C4 AF, PDMAEMA·CB is retained quite firmly on the surface of hydroaluminates and is not washed out water in free form, which leads to the possibility of chemical adsorption. These assumptions correspond to the conclusion made above that quaternary salts have a hydrophilizing effect on silicate (C2 S and C3 S) and hydrophobizing on aluminate (C3 A and C4 AF) clinker minerals (Fig. 1 and 2).

Fig. 1. Adsorption of PDMAEMA · CB on cement clinker minerals: 1-C4 AF; 2-C3 A; 3-C3 S; 4-C2 S.

A similar picture is also observed on the SI taken for the C2 S clinker mineral (Fig. 3a,b) its modifications of the aqueous extract and residues after extraction with water - the absorption bands of C3 S−2 (880–1440 cm−1 ) of OH groups (1640, 3450 cm−1 ) indicate the presence of the process and carbonization on the particle surface during C2 S hydration.

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Fig. 2. Adsorption of PDMAEMA · CB on aluminate clinker minerals when introduced with mixing water: (1-C4 AF; 2-C3 A); and 5 days after incorporation (3-C3 S; 4-C2 S).

Fig. 3. Spectroscopic investigations of silicate clinker minerals (C3 S -a; C2 S-b), before interaction with an aqueous solution of PDMAEMA · CB (1), and after (G); 2,2’ - residues after extraction; 3.3’ - water extracts, respectively.

In the spectroscopic investigations (SI) of aqueous extracts of C3 S and C4 SF aluminates taken after their interaction with PDMAEMA · CB (Fig. 4a, b), unlike silicate clinker materials, there are no absorption bands of free PDMAEMA · CB and intense absorption bands of carbonate (880–1440 cm−1 ), hydroaluminate and hydroalumoferrite calcium neoplasms (500, 900, 1640, 3200 - 3600 cm−1 ). Apparently, PDMAEMA · CB accelerates the processes of hydration of C3 S and C4 SF minerals, which causes a greater intensity of the absorption bands of OH groups (1600, 3450 cm−1 ), as well as the presence of a residual absorption band of aluminate 980 cm−1 and SI of the original sample and its absence in the modified [5] Fig. 3, Fig. 4. The SI of C3 S and C4 SF residues after extraction does not show absorption bands of the initial clinker minerals, but absorption bands of AIO6 groups (5155 cm−1 ) are observed, which is apparently formed as a result of the transition of AI3+ from coordination IV to coordination VI. Absorption bands 800, 3620 cm−1 refer to calcium hydroaluminate and calcium hydroaluminoferrite. The presence of absorption bands of

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Fig. 4. SI of aluminate clinker minerals (C3 A-a; C4 AF-b), before interaction with an aqueous solution of PDMAEMA · CB (1), and after (1’); 2.2’ - residues after the extraction; 3.3’ - water extract, respectively.

PDMAEMA · CB in the region of 1030, 1110, 1190 cm−1 in the spectra of residues after extraction apparently indicates the chemisorption of PDMAEMA · CB on the surface of hydrated neoplasms, because OH groups are not washed out. The conducted SI - spectroscopic studies allow us to conclude that in the presence of polyquaternary salts, using the example of PDMAEMA · CB, one should expect a slowdown in the processes of hydration and carbonization of silicate clinker minerals C3 S and C2 S, as well as an acceleration of these processes for aluminate minerals C3 A and C4 AF. The different influence of PDMAEMA · CB on clinker minerals is apparently due to the chemical nature and the difference in signs of the charge of the e-potential, which has a negative value during the formation of hydrosilicates, and a positive value of hydroauminates [6]. Thus, in the first case (for C3 S and C2 S), the adsorption of PDMAEMA · CB proceeds to a much lesser extent, and its presence in free form in aqueous extracts of C3 S and C2 S suggests a physical interaction of these phases, while in the second case (for C3 A and C4 AF) PDMAEMA·CB is retained on the surface of hydroaluminates quite firmly, is not washed out by water in a free form, which causes the possibility of chemical adsorption. These assumptions correspond to the conclusion above that PDMAEMA·CB has a hydrophilizing effect on silicate (C3 S and C2 S) and hydrophobizing - on aluminate (C3 A and C4 AF) clinker minerals. The objects of the study of the phase composition of the products of cement hydration with the addition of PDMAEMA·HB were samples of cement stone made at W/C = 0.4. Features of the phase composition of hydration products are considered on the example of the action of PDMAEMA·CB in the amount of 0.01% by weight of cement. The analysis of X-ray patterns showed (Fig. 5) that the products of the silicate component are calcium oxide hydrate with a diffraction line d = 0.49 nm, the Peak with d = 0.736 nm belongs to non-hydrated calcium aluminoferrite residues. The hydration products of the aluminate component are represented by calcium hydro sulfoaluminate of the thiosulfate form d = 0.978; 0.562; 0.474 nm. With the introduction of the PDMAEMA · CB additive into the cement stone, some increase in the intensity of the line C3 A = d = 0.302 can be noted; 0.176 nm.

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Fig. 5. X-ray of hydrated cement 28 days after heat and moisture treatment (Å).1) Without additive; 2) with the addition of VRP (water soluble polymer)-1 −0.02%; 3) with the addition of PDMAEM·CB.

Conducted studies of the wettability of the mortar component of concrete with the addition of PDMAEMA·CB. The decrease in the wettability of the surface of the solution component with the introduction of the additive allows us to conclude that there is a presence and density of a hydrophobic shell on the products of Portland cement hydration, formed as a result of chemisorption of molecules of the cationic surfactant PDMAEMA·CB (Table 3). Table 3. Influence of PDMAEMA·CB Additive on Hydrophobic Properties of Cement-Sand Mixture. Additive type

Additive quantity, %

Equilibrium contact angle, θ grad.

Wetting B = cos θ

Control

–

12

0,978

VRP-1

0,02

44

0,719

PDMAEMA · CB

0,01

66

0,407

From the data given in Table 3, it can be seen that with the introduction of the PDMAEMA · CB additive in an amount of 0.01% by weight of cement, the cosine of the wetting angle decreases from 0.978 to 0.407, i.e. the contact angle is 540 greater than that of the control and 220 greater than that of the sample modified with VRP-1. Apparently, it is advisable to carry out selection based on the principle of blockade of the potential layer in order to hydrophobize Portland cement than VRP-1. This is explained by the peculiarity of the structure of PDMAEMA · CB, the presence of an active nitrogen atom, which is an effective electron donor, and a high molecular weight. Thus, the study of the sorption interaction of polyquaternary salts with the main minerals that make up cement showed that the studied salts selectively affect the components: they are retained on the surface of hydroaluminates, which is apparently due

Influence of Polymeric Quaternary Salts on Some Properties of Cement Stone

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to chemical adsorption, and is in physical interaction with silicates. The presence of active NaI− and N+ ions of polyquaternary salts cause a change in the morphology of hydrated phases, also contributing to the formation of calcium hydrochloraluminate, which, together with ettringite and calcium hydrosilicates, increases the strength of the cement system underlying the composite material for construction purposes. During the hydration of mineral binders, a number of complex physicochemical transformations occur in them. The kinetics of these processes largely determines the structural-mechanical properties, density and strength of the hardening cement stone, and the structural-mechanical properties of cement and mortar mixtures are quite closely estimated by the change in the plastic strength (ultimate shear stress Pm) over time [11–14]. The results of the study of the effect of chemical additives on the plastic strength of cement paste show that all the considered additives increase the plastic strength to one degree or another (Fig. 6), and also make it possible to influence the kinetics of structure formation, reducing the induction period from 240’ to 120’ providing high plastic strength growth rate. The plasticizing effect of the studied additives (for comparison, and VRP−1 ) with the same composition of concrete (W/C 0.4 and W/C 0.5) was determined by the values of the mobility of concrete mixtures.

Fig. 6. The dependence of the plastic strength of the cement mortar (cement No. 1) on the watercement ratio and additives (a − W/C = 0.4; b − W/C = 0.5): 1-control without additive; 2–0,03% PDMAAC; 3–0,01% PDMAAC; 4–0,01% imethylaminoethyl methacrylate with benzyl bromide (DMAEMA · BB); 5–0,01% Dimethylaminoethyl methacrylate with benzyl iodide (DMAEMA · BI); 6–0,01% Dimethylaminoethyl methacrylate with benzyl chloride (DMAEMA · CB); 7–0.03% DMAEMA · CB, 8–0,02% VRP-1.

Studies have shown that when Polydimethylaminoethyl methacrylate with allyl chloride (PDMAEMA · AX) and Polydimethylaminoethyl methacrylate with benzyl chloride (PDMAEMA · CB) are introduced into the concrete mixture in an amount of 0.01 to 0.025% by weight of cement, the mobility of the concrete mixture increased from 2 cm to 14 cm. A further increase in the content of additives practically did not affect the mobility of the concrete mixture. Molecules of a surface-active additive are located parallel or obliquely to the surface of a solid body, with the polar group chemically bonding to the solid surface, and the

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hydrocarbon chain directed into the aqueous medium. At full saturation (in this case, the optimal content of the additive is 0.01%) of the surface layer, the molecules are arranged perpendicularly, which leads to the retention of sufficiently thick layers of water near the hydrophobic part of the molecules. Between the solid particles, a kind of hydrodynamic lubricant is created, which reduces friction. This factor, as well as smoothing the roughness of the microrelief of the grains, leads to the plasticization of the concrete mixture.

4 Conclusions The sorption interaction of polyquaternary salts with the main minerals that make up cement has been studied and it has been established that due to the chemical interaction of active NaI− , N+ ions of polyquaternary salts, a change in the morphology of hydrated phases is observed: along with calcium hydroaluminates, calcium hydrochloraluminate is formed, which provides an increase in the strength of the cement system, and the formation of particles on the surface binder films of high molecular weight additives contributes to the fluidity of the cement mass. Methods of adsorption and mercury porosimetry established the mechanism of formation and studied the structure of cement stone modified with polyquaternary salts, and it was shown that as a result of modification, an optimal pore structure is formed with a predominance of uniformly distributed conditionally closed pores. The influence of the water-cement ratio, cement aluminity and curing mode on the strength and strength characteristics of concrete has been determined. It has been experimentally established that the introduction of polyquaternary salts increases the strength of concrete prepared on high-aluminate Portland cement up to 20%. It has been established that in order to obtain composite cement systems with standard strength parameters with the introduction of polyquaternary salts, it is possible to reduce the content of cement and water by 10%.

References 1. Muftoxiddin, A., et al.: Prospects for the use of polymer composite fittings in building structures in the republic of Uzbekistan. Am. J. Eng. Technol. 3(6), 97–100 (2021) 2. Adilhodzhaev, A., Igamberdiev, B., Kodirova, D., Rakhmonov, O., Marufjonov, A.: Assessment of the potential of composite gypsum binder bricks as an alternative to traditional wall materials in Uzbekistan. Eur. J. Molec. Clin. Med. 7(2), 1884–1889 (2020) 3. Nurmetov, K.I., Avliyokulov, J.S., Alimov, M.R.: Features of the structure, composition and technology of composite materials based on polytetrafluoroethylene. Front. Soc. Sci. Hist. J. 1(06), 15–18 (2021) 4. Malhotra, V.M.: Introduction: sustainable development and concrete technology. Conc. Int. 24(7), 22 (2002) 5. Li, Z., Zhou, X., Ma, H., Hou, D.: Advanced Concrete Technology. John Wiley & Sons, Hoboken (2022) 6. Pierre-Claude, A., Flatt, R.J., Pierre-Claude, A., Flatt, R.J.: Science and Technology of Concrete Admixtures (2015). https://www.perlego.com/book/1834838/science-and-technologyof-concrete-admixtures-pdf

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7. Dadakhanov, F., et al.: Prospects of innovative materials production in the building materials industry. J. New Cent. Innov. 18(1), 162–167 (2022) 8. Levinson, R., Akbari, H.: Effects of composition and exposure on the solar reflectance of portland cement concrete. Cem. Concr. Res. 32(11), 1679–1698 (2002) 9. Makhmudova, N.H., Akhmedjanov, Y.A.: Composition polymeric materials for modification of concrete mixes. Int. J. Eng. Res. Technol. 7(5), 48–52 (2020) 10. Naima, M.: Formation structure of cement systems under the influence of chemical additives. In: Cioboat˘a, D.D. (ed.) ICoRSE 2021. LNNS, vol. 305, pp. 198–203. Springer, Cham (2022). https://doi.org/10.1007/978-3-030-83368-8_19 11. Makhmudova, N.H.: Issledovanie vliyaniya polichetvertichnix soley na formirovanie strukturi sementnogo kamnya [Study of the influence of polyquaternary salts on the formation of the structure of cement stone]. In: Materiali Respublikanskaya nauchno-texnicheskaya konferensiya Resurso-i energosberegayushie, ekologicheskie bezvrednie kompozitsionnie i nanokompozitsionnie materiali, Tashkent, pp. 170–172 (2019) 12. Umidjon, M., Jeltukhin, A., Meliboyev, Y., Azamat, B.: Effect of magnetized cutting fluids on metal cutting process. In: Cioboat˘a, D.D. (ed.) International Conference on Reliable Systems Engineering (ICoRSE) - 2022, pp. 95–104. Springer International Publishing, Cham (2023). https://doi.org/10.1007/978-3-031-15944-2_9 13. Uljayev, E., Ubaydullayev, U.M., Tadjitdinov, G.T., Narzullayev, S.: Development of criteria for synthesis of the optimal structure of monitoring and control systems. In: Aliev, R.A., Yusupbekov, N.R., Kacprzyk, J., Pedrycz, W., Sadikoglu, F.M. (eds.) WCIS 2020. AISC, vol. 1323, pp. 559–563. Springer, Cham (2021). https://doi.org/10.1007/978-3-030-68004-6_73 14. Makhmudova, N.H.: Composite materials with surface active additives of construction purposes, Buketov Karaganda State University Institute of polymer materials and technology international science and technology center. In: Proceedings of viii International Symposia on Specialty Polymers, Karaganda, pp. 19–24 (2019)

Studies Concerning Water-Based Coolants Under Magnetic Field During a Metal-Cutting Process (Turning) Umidjon Mardonov(B) , Otabek Khasanov, Abdikhalil Ismatov, and Azamat Baydullayev Tashkent State Technical University, Tashkent, Uzbekistan [email protected]

Abstract. Lubricating-cooling technological condition has a great effect on the metal-cutting process. This paper evaluates the use of water-based coolants under the effect of the static magnetic field in machining parts in lathes. In the experiments, two methods of influencing static magnetic field on the sample coolants were tested, and the chip reduction coefficient and cutting temperature were studied to compare the obtained results between the impact of the proposed technologies and the traditional method of using sample coolants. As a part of the study, a new technology of utilizing water-based cooling fluids in turning cylindrical parts is proposed. Within the given technology, four different cutting speeds were chosen to compare the effect of cutting speed on the resulting chip reduction coefficient and cutting temperature under experimental conditions. Keywords: Metal cutting · Coolant under magnetic field · Magnetic field · Chip reduction · Temperature · Cutting tool

1 Introduction The use of special lubricating-cooling technological fluids in the metal cutting process increases the tool life, reduces the cutting forces, and improves the quality of the finished surface, and the fatigue strength of the product. This, in turn, increases product competitiveness. Therefore, most of the mechanical processing is carried out using lubricating and cooling technological fluids. Cutting fluids actively affect the frictional plastic contact surfaces of the cutting tool. The main purpose of using cooling fluids is to reduce the cutting temperature, cutting forces, and cutting power, and as a result, to increase the tool life and the quality of the machined surface, as well as to increase labor productivity [1]. Today, the issue of increasing the wear resistance of cutting tools as a result of creating novel technological lubricant environments based on the use of cooling liquids under electromagnetic fields or pulses sand changing then their properties. Concerning friction phenomena using coolant under a magnetic field it can be considered one of the promising industrial applications during materials cutting processes. Pušavec et al. analyzed the LCA of different cooling strategies, flood, high-pressure cooling (HPC), and cryogenic cooling. Their results show that cryogenic cooling with © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 308–317, 2023. https://doi.org/10.1007/978-3-031-40628-7_26

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liquid nitrogen has the highest potential for improved sustainability of machining superalloys [2]. Hironori Matsuoka et al. studied the effect of water-based cutting fluids on various coated HSS cutting tool wear in the metal hobbing process. In their first experiment, they concluded that the influence of water-based cutting oil was more effective than dry cutting in the case of the uncoated HSS tool. For the TiN- and TiAlN-coated HSS tools, water-immiscible cutting oil was effective. For TiSiN- and AlCrSiN-coated tools, using water-miscible cutting fluids prolonged tool life and was effective. They also found that the finished surface roughness was improved for all of the coated tools when water-immiscible cutting oil and water-miscible cutting fluids were used, when the water-miscible cutting fluids were used, the finished surface roughness was equal to or smaller than that obtained using the water-immiscible cutting oil [3]. Rika Dwi Hidayatul Qoryah et al. analyzed the Minimum Quantity Lubrication Method (MQL) in turning. According to their experiments, the cooling method, including the MQL, did not have a significant effect on the chip formation. Out of the three cutting method application, the flood method was revealed as the best method to create discontinuous chips [4]. Sivaiah et al. compared the machining of stainless steel with cryogenic, emulsion, and MQL cutting fluids against dry cutting conditions. Cryogenic coolant performed the best in all measured categories: cutting temperature, tool wear rate, and surface roughness. MQL was the second-best option, the third was flood cooling, and dry cutting was expectedly the worst [5]. In recent years, it has been mentioned that the magnetic field changes the physical and mechanical properties of water [6, 7]. The fluid that is passed through a magnetic field becomes a magnetized fluid. Han et al. studied the optical properties of water between two strong magnets and found that the magnetic field changes the water’s absorption of infrared light [8]. Wang and his team studied the effect of a static magnetic field on a liquid in friction experiments, and the results show that the friction coefficient is lower in the magnetic field [9]. Cai and other scientists studied the effect of a magnetic field on the hydrogen bonds of water and described the mechanism of molecular dynamic simulation of magnetization and experimental and theoretical models [10, 11]. Thus, changing the physic mechanical properties of the cutting process based on the creation of a cooling environment under the influence of a magnetic field and increasing the metal cutting condition is one of the actual issues in the mechanical engineering research field.

2 Methods In the metal cutting process, transmission methods of cutting fluids to the cutting zone are diverse and perform many related specific functions. In the industry, the following methods are commonly used for delivering cutting fluids to the cutting zone: flood cooling method, air-liquid mixture sprayed (aerosol) method; dripping to the tool before cutting (unction with a brush, dipping). Among these methods, the most common is the flood cooling method (injection with pressure at P = 0.02–0.03 MPa), and the efficiency of this method depends on the consumption of cooling fluid (5–20 L/min) and the form and trajectory of the flow (Fig. 1). The main goal of this method is to completely cover the cutting zone with a cooling fluid. When applying the cooling fluid to the cutting zone under pressure, the

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heat is removed from the most heated surface of the cutting tool, and the chip is crushed and washed out. This method is one of the most effective methods [12]. In the experiments on the metal cutting process on lathes using magnetized cooling fluids, the flood cooling method of delivering fluids to the cutting zone was chosen. Because the cooling fluid can be highly magnetized in the flood cooling method. In order to magnetize the cooling fluid when it is flowing, a special magnetizing device is used [13, 14].

Fig. 1. Utilization of flood cooling method in the metal cutting process.

Analyzing the many types of research on the metal cutting process in different lubricating-cooling technological conditions, we came to such a conclusion that the coolant can reach the rubbing surfaces through the following ways (Fig. 2.): a) through the continuously forming and collapsing capillaries between the chip and tool frictional surfaces; b) through the formation of a suction vacuum created by periodically interrupting the build-up (moving several hundred times per second); c) through the gap created by the disruption of the adhesion of surface contacts as a result of vibration; d) in the chip formation (deformation) zone, some atoms, molecules and ions of cooling fluids can reach the cutting zone because of the diffusion through the microcapillary system of the inner surfaces of microcracks.

Fig. 2. The scheme of the delivery of the lubricating coolant to the contact surfaces when cutting metals.

To do the experiment on a lathe, two types of sample cooling fluids are prepared. The first coolant was synthetic, and it was a 5% solution of potassium di-chromate powder

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Fig. 3. Prepared cooling fluids to the experiment. a - 5% emulsion of lactuca lt 3000 on water, b – 5% solution of potassium di-chromate on water.

on water (PDC). The second was a semi-synthetic coolant, it is 5% solution of a mixture of Lactuca LT 3000 (liquid) on water (LLT) (Fig. 3). Two methods of magnetization of coolants have been used in the experiments. The first one is to magnetize coolants in their not flow condition. The sample cooling fluid was poured into the coolant container of the lathe. Then, special neodymium magnets (N42) that have B≈410 mT of magnetic field strength were inserted into the coolant and left off for an hour. In this period, the cooling fluid is magnetized completely [15, 16]. Following this, the turning process on the lathe was started using magnetized (in peace) coolant. While conducting the experiment, magnets were left in the container. The same process was repeated with both coolants. The second method is to magnetize coolants in their flowing condition. In this process, a 100 mm length of the coolant pipe of the lathe was placed between the neodymium magnets (N42) providing B = 300 mT of magnetic field strength. Coolant flowing through the static magnetic field becomes a magnetized (in flowing condition) coolant. The flowing cycle of the coolant was done for about half an hour without processing the metal cutting. Because all the fluid in the coolant container has to flow through the magnetic field [1]. The flowing rate of cooling fluid was 5 L/min, diameter of the pipe was d = 10 mm.

Fig. 4. Experimental setup details on the lathe.

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All the experiments were conducted on a lathe and four cutting speeds 25 m/min, 40 m/min, 50 m/min, and 60 m/min were chosen to cut a cylindrical workpiece whose diameter of it was D = 150 mm. The workpiece material was Stal 45 and an HSS cutting tool (P6M5) was used (Fig. 4).

3 Results and Discussion The condition of the rubbing layers of surfaces is determined by their temperature. Therefore, it is important to have information about the temperature of the contact layers when studying the laws of friction and tool wear, the main parameters of the surface quality of the parts being machined. Since the analysis of the cutting temperature change during metal cutting is one of the main tasks of our research, experimental studies were carried out to check the effect of conventional and magnetized coolants on the cutting temperature. To measure the cutting temperature, the natural thermocouple method was chosen. This method makes it possible to obtain correct results about the average temperature that appears on the surfaces of the tool that are in contact with the cutting tool and the workpiece [17–19].

Fig. 5. Difference between the temperature variations in the cutting zone while using coolants in the proposed method and traditional methods. As a coolant, a – 5% solution of potassium dichromate in water (PDC) and b – 5% solution of Lactuca lt 3000 in water (LLT) is used.

Experimental indications in Fig. 5 shows that the cutting temperature was about T = 341 °C at the speed of 25 m/min in dry cutting and the temperature raised to 445 °C at 60 m/min of cutting speed. It is clear that the cutting temperature rises with respect to cutting speed. When using the two types of different cooling fluids (PDC and LLT) in the traditional way overall cutting temperature decreased by about 10 in both coolant conditions. Then the cooling fluids were magnetized when they were in a coolant container of the lathe. After an hour of magnetizing, the metal-cutting process was conducted using magnetized cooling fluids and the temperature is slightly decreased in both coolant conditions. The temperature decline was about 11% in all cutting speeds that the experiments were conducted. Following these experiments, both cooling fluids

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were magnetized while they were flowing through the coolant pipe and applied to the cutting process. Table 1. The results on the decrease (in percent) of cutting temperature while using cutting fluid under the effect of static magnetic field compared to traditional use of cutting fluid Experimental cutting fluid (CF) condition

Temperature decrease in percentage in four cutting speeds, [m/min] 25

40

50

60

1st sample coolant: 5% solution of potassium dichromate in water Magnetized (not flowing) CF

2%

1%

2%

–

Magnetized (flowing) CF

8.5%

9%

7.2%

8%

2nd sample coolant: 5% solution of Lactuca LT 3000 in water Magnetized (not flowing) CF

3.3%

2.2%

2.1%

1.2%

Magnetized (flowing) CF

5.6%

8.2%

6%

9.7%

The results of the last experiments were interesting, the cutting temperature was declined by about 17% in the use of magnetized (flowing condition) coolant PDC and 19% in the use of magnetized (flowing condition) coolant LLT compares to dry cutting. The average temperature falling was about 9% and 8% respectively when they were compared to traditional use of the same cooling fluid samples (Table 1). In the metal-cutting process, plastic deformation is generated during the chip formation, and as a result, heat emerges. It is guessed that about 60% of the heat generated during metal cutting is due to deformation. Deformation during the metal cutting was expressed by the chip reduction coefficient, and the small value of the chip reduction coefficient ensures small plastic deformation. Coolant is directly in contact with the part being processed through the deformation zone over a large surface. This makes it possible for the coolant to take away more heat with itself as a result of convection. In order to study the effect of magnetized coolant on the deformation of the chip, we used two types of coolants in the conventional and magnetized method in turning and conducted an experimental study of the resulting chip reduction coefficients. According to the results shown in Fig. 6, the chip reduction coefficient is decreased when the cutting speed is increased. In the dry-cutting process at the speed of 60 m/min, the chip reduction coefficient was 2,75. The coefficient was 3,13, 3,02, and 2,9 at 25 m/min, 40 m/min, and 50 m/min respectively. However, the chip reduction was decreased by 12% and 8% in all experimented cutting speeds when we use the PDC and LLT as cooling fluids in the same cutting process. Both PDC and LLT coolants were magnetized in a lathe container for an hour, and they were applied to the cutting zone, the chip reduction coefficients decreased by 20% and 16% respectively in 60 m/min of cutting speed compared to dry cutting.

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Fig. 6. The influence of magnetized cutting fluid on the chip reduction. Coolant (a) is 5% solution of potassium di-chromate in water and coolant (b) is 5% solution of Lactuca LT 3000 in water.

Table 2. The results on the decrease (in percent) of chip reduction ratio while using cutting fluid under the effect of static magnetic field compared to traditional use of cutting fluid Experimental cutting fluid (CF) condition

Decrease in percentage in four cutting speeds, [m/min] 25

40

50

60

1st sample coolant: 5% solution of potassium dichromate in water Magnetized (not flowing) CF

3.4%

–

4.2%

5%

Magnetized (flowing) CF

13.7%

14.7%

20.8%

34%

2nd sample coolant: 5% solution of Lactuca LT 3000 in water Magnetized (not flowing) CF

1.7%

–

4%

2.1%

Magnetized (flowing) CF

17.8%

17%

20%

29.7%

After all, both coolants were magnetized while they were flowing through the coolant pipe and applied to the cutting zone immediately after magnetization. The chip reduction coefficient declined by 13.7%, 14.7%, 20.8%, and 34% at the speed of 25 m/min, 40 m/min, 50 m/min, and 60 m/min respectively in PDC coolant condition compared to the traditional use of PDC (Table 2). The same experiment was conducted with second coolant LLT, and the results were also similar with PDC. Such as, the utilization of magnetized (in flowing condition) LLT in the turning process reduced the chip reduction coefficient up to 17.8%, 17%, 20%, and 29.7% at 25 m/min, 40 m/min, 50 m/min, and 60 m/min of cutting speeds respectively (Table 2). The obtained results of the experiment on the LLT coolant were compared to the use of it in the traditional method.

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Currently, the mechanism of the influence of cutting fluids on the metal cutting process is explained on the basis of physical-chemical theory and hypotheses (founded by P.A. Rubinder, S.Ya. Weiler et al.). It follows from the above that a lubricating film is formed between the surfaces that rub against each other during the metal-cutting process. Due to the high molecular similarity of the film material with the workpiece or tool material, it cannot squeeze out of the cutting zone with high pressure. The resulting film reduces the friction force and temperature, and the molecular force is replaced by a small force of a few hundred values (according to the Van der Waals theory). The accumulated experience of magnetized cooling fluids, their properties, application in the cutting process, and the creation of a device for magnetizing the flowing cooling fluids show that, in addition to its own advantages, magnetized coolants with increased cooling capacity may not be effective when it is used opening deep holes and processing at low cutting speeds. Because the lubricating properties of cutting fluids are very important when drilling deep holes. That is, the lubrication properties of cutting fluids with reduced viscosity due to magnetization deteriorate. Therefore, when magnetizing flowing cutting fluids, it is necessary to take into account the cutting process intended for their use. In the next research works, experiments will be carried out on how magnetized (in the flowing state) cutting fluids affect the deep drilling process. It is also necessary to pay attention to factors such as the main properties of coolants affecting the cutting process, the method of delivery to the cutting environment, flow rate, elements of the cutting mode, and design solutions of the magnetizing device.

4 Conclusions According to results obtained from the experimental studies, in the metal-cutting process, the use of water-based coolants under the influence of the static magnetic field while the coolants are flowing is proposed as a novel method. Moreover, it can be said that the magnetic field has a sufficient influence on the cutting process by coolants. The magnetic field changes the influence level of coolants on the metal-cutting process by changing the coolant’s physicochemical properties. It has been determined that the change in the properties of the magnetization of waterbased coolants depends on their magnetization state. The influence of the magnetic field on sample water-based coolants was higher when they were magnetized in the flowing state than in the stationary state. The proposed method of using two water-based coolants chosen for the experiment at four different cutting speeds (25 m/min, 40 m/min, 50 m/min, and 60 m/min) made it possible to reduce the cutting temperature by 10–15% compared to the use of the coolants in traditional methods. The effect of magnetized coolants on the chip reduction coefficient was determined on the basis of experimental studies. The proposed method of using the water-based coolant in the metal-cutting process reduced the chip reduction coefficient in both waterbased coolant conditions.

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References 1. Erkin, U., Umidjon, M., Umida, S.: Application of magnetic field on lubricating cooling technological condition in metal cutting process. In: Cioboat˘a, D.D. (ed.) ICoRSE 2021. LNNS, vol. 305, pp. 100–106. Springer, Cham (2022). https://doi.org/10.1007/978-3-03083368-8_10 2. Pusavec, F., Krajnik, P., Kopac, J.: Transitioning to sustainable production – part I: application on machining technologies. J. Clean. Prod. 18, 174–184 (2010). https://doi.org/10.1016/j.jcl epro.2009.08.010 3. Matsuoka, H., Kubo, A., Ono, H., Ryu, T., Qiu, H., Nakae, T.: Influence of water-miscible cutting fluids on tool wear behavior of different coated hss tools in hobbing. Mech, Eng. Res. 8(2), 10–24 (2018) 4. Qoryah, R.D.H., Azizi, A.W., Darsin, M.: A study of chip formation on turning with minimum quantity lubrication method (MQL). EMITTER Int. J. Eng. Technol. 8(1), 256–269 (2020) 5. Sivaiah, P., Chakradhar, D.: Effect of cryogenic coolant on turning performance characteristics during machining of 17–4 PH stainless steel: a comparison with MQL, wet, dry machining. CIRP J. Manuf. Sci. Technol. 21, 86–96 (2018). https://doi.org/10.1016/j.cirpj.2018.02.004 6. Pang, X.F., Deng, B.: The changes of macroscopic features and microscopic structures of water under influence of magnetic field. Phys. B Condens. Matter 403(19–20), 3571–3577 (2008). https://doi.org/10.1016/j.physb.2008.05.032 7. Holysz, L., Szczes, A., Chibowski, E.: Effects of a static magnetic field on water and electrolyte solutions. J. Colloid Interface Sci. 316(2), 996–1002 (2007). https://doi.org/10.1016/j.jcis. 2007.08.026 8. Han, X., Peng, Y., Ma, Z.: Effect of magnetic field on optical features of water and KCl solutions. Optik-Int. J. Light Electron. Optics 127(16), 6371–6376 (2016) 9. Wang, Y., Zhang, B., Gong, Z., et al.: The effect of a static magnetic field on the hydrogen bonding in water using frictional experiments. J. Mol. Struct. 1052(11), 102–104 (2013). https://doi.org/10.1016/j.molstruc.2013.08.021 10. Cai, R., Yang, H., He, J., et al.: The effects of magnetic fields on water molecular hydrogen bonds. J. Mol. Struct. 938(1–3), 15–19 (2009) 11. Toledo, E.L., Ramalho, T.C., Magriotis, Z.M.: Influence of magnetic field on physical– chemical properties of the liquid water, insights from experimental and theoretical models. J Mol Struct 888(1–3), 409–415 (2008) 12. Umarov, E.O.: Kesish nazariyasi va asboblar [Cutting theory and cutting tools], 1st edn. Sharq, Tashkent (2017) 13. Umidjon, M., Jeltukhin, A., Meliboyev, Y., Azamat, B.: Effect of magnetized cutting fluids on metal cutting process. In: Cioboat˘a, D.D. (ed.) International Conference on Reliable Systems Engineering (ICoRSE) - 2022, pp. 95–104. Springer International Publishing, Cham (2023). https://doi.org/10.1007/978-3-031-15944-2_9 14. Umidjon, M., Muhammad, T., Andrey, J., Yahyojon, M.: The difference between the effect of electromagnetic and magnetic fields on the viscosity coefficients of cutting fluids used in cutting processes. Int. J. Mechatron. Appl. Mech. 10(1), 117–122 (2021). https://doi.org/10. 17683/ijomam/issue10/v1.14 15. Umarov, E., Mardonov, U., Abdirakhmonov, K., Eshkulov, A., Rakhmatov, B.: Effect of magnetic field on the physical and chemical properties of flowing lubricating cooling liquids used in the manufacturing process. IIUM Eng. J. 22(2), 327–338 (2021). https://doi.org/10. 31436/iiumej.v22i2.1768 16. Umarov, E.O., Mardonov, U.T., Shoazimova, U.Kh.: Influence of the magnetic field on the viscosity coefficient of lubricoolant that is used in the cutting process. Int. J. Mechatron. Appl. Mech. 8(2), 144–149 (2020). https://doi.org/10.17683/ijomam/issue8.50

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17. Rostislavovna, T.S.: Smazochno-oxlajdayushie jidkosti na osnove vodorastvorimix polimerov kak sredstvo povisheniya effektivnosti protsessa rezaniya [Cutting fluids based on watersoluble polymers as a means of increasing the efficiency of the cutting process]. PhD dissertation, Irkutsk (1999) 18. Gupta, M.K., et al.: Machinability investigations of hardened steel with biodegradable oilbased MQL spray system. Int. J. Adv. Manuf. Technol. 108(3), 735–748 (2020). https://doi. org/10.1007/s00170-020-05477-6 19. Akhil, C.S., Ananthavishnu, M.H., Akhil, C.K., Afeez, P.M., Akhilesh, R., Rahul, R.: Measurement of cutting temperature during machining. IOSR J. Mech. Civil Eng. 13(2), 108–122 (2016)

Improving the Reliability of Circulating Water Supply Installations of Thermal Power Plants Viktor Moiseev , Eugenia Manoilo(B) , Yurii Manoilo , Kalif Repko , and Denis Davydov National Technical University «Kharkiv Polytechnic Institute», 2 Kirpichova St., Kharkiv 61002, Ukraine [email protected]

Abstract. The efficiency of removing carbon dioxide from water in deaerators is no less important than the efficiency of desorption of dissolved oxygen, since free carbon dioxide present in heat carriers can cause intense corrosion of metals, especially in phase transition zones and in the presence of dissolved oxygen. This applies to low and medium pressure steam boilers, including heat recovery boilers of combined-cycle power units, as well as water treatment plants of heating pipelines. The absence of free carbon dioxide in deaerated water does not mean its absence in the equipment located according to the thermal scheme behind the deaerator, since carbon dioxide is one of the products of reactions of thermal decomposition of hydrocarbonates and hydrolysis of carbonates occurring during further heating of water in boilers and boilers or its exposure at high temperature. The analysis of the decrease in the energy efficiency of thermal power plants caused by the current technology of circulating water supply of cooling systems of condenser units is carried out. It is shown that the supply of additional water to the cooling system from a surface water body without preliminary purification causes indirect financial losses. In addition to energy saving, an equally significant resource-saving function of the recycling water supply technology is to prevent the discharge of technogenic copper by operating thermal power plants as part of the forced discharge of purging of recycled water. A model of the process of removing carbon dioxide from water during deaeration is proposed. This model allows predicting the values of decarbonization efficiency indicators for decarbonizers and deaerators. Keywords: Process Engineering and Design · Process Intensification · Thermal power plant · Energy saving · Energy efficiency · Cooling systems · Circulating water supply · Deaeration · Decarbonization · Carbon dioxide

1 Introduction Water used in thermal power plants, boiler plants, and heating pipelines undergoes a number of stages of water treatment. One of the main ones is the removal of corrosive dissolved gases (oxygen O2 and carbon dioxide CO2 ) from the water [1]. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 318–327, 2023. https://doi.org/10.1007/978-3-031-40628-7_27

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The presence of dissolved carbon dioxide in the water makes the water aggressive and leads to corrosion processes in pipelines. The destruction of water pipes is only a small part of the problem. Corrosion products entering the water degrade its quality and make it unusable [2]. The main methods of eliminating the carbon dioxide aggressiveness of water are its treatment with alkalis. In some cases, aggressive carbon dioxide from the water can be removed by degassing (aeration) [3]. Aeration is the process of saturating water with air in order to remove gases dissolved in it into the atmosphere, based on their volatility. In practice, aeration is carried out in special installations - aerators. Spray, cascade or bubbling aerators are used. With a consumption of no more than 20 kg of air per 1 ton of water, it is possible to reduce the content of free carbon dioxide from 60–80 mg/l to 6–7 mg/l, which greatly facilitates the operation of the thermal deaerator and allows it to achieve almost complete removal of free carbon dioxide [4].

2 Literature Review To remove carbon dioxide in water treatment for steam and hot water boilers, the method of correctional water treatment shows good efficiency. Specialized reagents based on an alkaline solution of inorganic complexing agents are introduced using proportional dosing complexes [5]. In this case, not only the pH of the water is adjusted, but also the effective binding and removal of carbon dioxide. Currently, thermal deaerators and decarbonizers are widely used at thermal power plants for these purposes, the effect of which is based on the desorption of hardly soluble gases in conditions when their solubility is almost zero due to heating water to the saturation temperature. Decarbonization can be vacuum, atmospheric and high pressure [6]. Various design versions of deaerators and decarbonizers are used [7]. Their purpose is to create a developed phase contact surface for the extraction of dissolved gases. At the same time, the compactness and low metal consumption of the devices and the efficiency of operation should be ensured [8]. The efficiency of deaerators for removing corrosive gases from water has a significant impact on the reliability of thermal power equipment of thermal power plants and boilers and pipelines of heating networks and is determined by the values of design and operating parameters. The number of combinations of values of these parameters is large, therefore, in practice, the technologically optimal operating mode of the deaerator is established only during experimental tests, which is associated with material and labor costs [9]. In this regard, it is relevant to develop mathematical models that provide the calculation of the indicators of the deaerator operating mode with the required accuracy. The use of such models not only reduces the cost of testing existing installations, but also increases the validity of design decisions when creating new facilities [10]. The design of deaeration appliance and their regime adjustment are associated with the search for such values of design and regime parameters that provide the required chemical quality of deaerated water [11]. The greatest difficulties are caused by predicting the efficiency of water decarbonization in deaerators, since this is associated with

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modeling the processes of hydrodynamics and heat and mass transfer complicated by chemical reactions [12]. The absence of free carbon dioxide in deaerated water does not mean its absence in the equipment located according to the thermal scheme behind the deaerator, since carbon dioxide is one of the products of reactions of thermal decomposition of hydrocarbonates and hydrolysis of carbonates occurring during further heating of water in boilers or its exposure at elevated temperature. To solve these numerous problems a new design of a stabilizer with a large free volume and a movable spherical nozzle was developed [13]. The advantage of the proposed design is the transition to a structured foam mode of operation at relatively low gas speeds, as well as a developed inner phase contact surface. The cellular structure of the stabilizer and movable nozzle makes it possible to achieve increased values of mass transfer coefficients due to the effect of film formation in small cells. The structure has high porosity and relatively low hydraulic resistance [14].

3 Research Methodology The combined contact block consists of a hole plate and one or two contact elements acting as stabilizers, and a movable ball-shaped nozzle located inside the block. The bubbling layer is formed on hole plates on which a movable nozzle is located. The new designs are simple and have a relatively low cost, which allows them to be effectively used in the processes of gas cleaning in various industries. The most suitable way to study mass transfer in the liquid phase is studying the process of desorption of CO2 from a saturated liquid into an air stream. Experimental installation for liquid-phase mass transfer is shown on Fig. 1. A series of experiments was carried out, during which the air flow rate and irrigation density changed with a given step, the concentration of carbon dioxide in the liquid at the inlet and outlet of the element was determined, and then the corresponding values of the volume mass transfer coefficient were calculated. Desorption column 1 with an internal diameter of 240 mm and a height of 2 m contained contact blocks (several modifications) consisting of plates with holes with bubbling layer stabilizers. Water used as an absorbent is fed from above to the absorber 12, which is a column with a diameter of 0,1 m and a height of 1 m. Carbon dioxide is supplied to the lower part of the absorber 12. The absorbent (water saturated with CO2 ) from the lower part of the absorber is fed by a pump 13 to the desorption column 1 through a switchgear 3, enters the contact blocks where the desorption process takes place. The amount of water is regulated by a valve 9, and is measured by a rotameter 8. Air is supplied to the lower part of the column 1 by means of a gas blower 5. The amount of air is determined using a measuring pipe 6, a Pitot tube 7 and a diffmanometer 10. Gas consumption is regulated by a valve 9. The gas distributor 4 serves for a more uniform distribution of gas over the cross-section of the column. Sampling for analysis is carried out using samplers 11. The experiment was performed at atmospheric pressure. The intensity of mass transfer (volume coefficients of mass transfer) was determined by changes in the concentration of carbon dioxide in an aqueous solution when passing through contact elements.

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Fig. 1. Experimental equipment setup for studying mass transfer in the liquid phase: 1 – column; 2 – combined contact element block; 3 – liquid distributor; 4 – gas distributor; 5 – gas blower; 6 – measuring pipe; 7 – Pitot tube; 8 – rotameter; 9 – valves; 10 – diffmanometer; 11 – samplers; 12 - absorber; 13-pump

4 Results The paper proposes a mathematical model for calculating the efficiency of CO2 extraction from water, which can be used practically for different designs of decarbonizers (film, bubbling, combined), with appropriate determination of the model parameters [15]. The theoretical description of transfer processes in two-phase media is associated with one or another simplification of the real hydrodynamic situation and properties of the medium [16]. The model of a multi-velocity continuum with local averaging of transport phenomena due to the second phase over the elementary volume of the medium finds the greatest application. However, for many special cases, the model is not closed. Various models of the flow structure are widely used for practical calculations of heat and mass transfer devices [17]. The diffusion and cellular models, between which there is an equivalent relationship, have received the greatest application. Diffusion Model. When using flow structure models, experimental studies of mixing coefficients for each device design in a given operating mode interval are necessary. Two and one-parameter models are usually used. The equations of a one - parameter diffusion model with a volumetric mass source have the form: for the liquid phase (water) wL

dx d 2x = DL 2 + k0x a(x − x∗ ) dz dz

(1)

wG

dy d 2y = DG 2 − k0x a(x − x∗ ) dz dz

(2)

for the gas phase (air)

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where wL , wG - is the average velocity of liquid and gas per full cross-section of the apparatus, m/s; x, y - is the concentration of the component (CO2 ) in the liquid and gas phases, mg/kg; DL , DG - is the coefficients of reverse mixing in the liquid and gas phases, m2 /s; z - is the height coordinate of the packing layer, m; k0x a - volumetric mass transfer coefficient, s−1 ; x∗ - equilibrium concentration, mg/kg. The system of Eqs. (1), (2) is solved with Dankverts boundary conditions. As a result of the solution, CO2 concentration profiles in the liquid and gas phases are obtained, and at a given initial concentration of x 1 , such operating and design characteristics of the nozzle decarbonizer are selected that provide the required concentration of CO2 in the outlet water. Usually, this value is within x 2 = 3–5 mg/kg. The value of the CO2 concentration in the source water is most often in the range x 1 = 20–100 mg/kg [11]. With a decrease in the scale-forming ability of water by acidification and hydrogen cation, the CO2 content in water increases to 50–500 mg/kg. The value of the equilibrium concentration of CO2 in water depends on temperature and pressure and is in the range x∗ = 0, 3–1, 4 mg/kg. Cellular Model. From the diffusion model (1), (2) it is possible to move to the cellular model, and the concentration of CO2 in the air is determined from the equation of material balance. The equations of ideal displacement and the cellular model follow from Eqs. (1), (2). At DL = DG = 0, we obtain a model of ideal displacement: dx = ρL Sk0x a(x − x∗), dz

(3)

dy = −ρL Sk0x a(x − x∗ ), dz

(4)

L G

where L, G – are the mass flow rates of water and air, kg/s; ρL - water density; S - is the cross-sectional area of the channel, m2 . From here, moving on to finite differences, we write down the equations of the cellular model: xi−1 wL = k0x a(x − x∗ )i , (5) zi yi − yi−1 = −k0x a(x − x∗ )i (6) wG zi where i = 1, 2,…, n – is the number of cells of complete mixing along the height of the packing layer; zi – cell size, m. From expression (5) we find the concentration in the i-th cell. xi =

xi−1 + x∗ k0x azi /wL , 1 + k0x azi /wL

(7)

And from the mass balance equation we have yi = yi−1 +

L (xi−1 − xi ) G

(8)

Hence the equilibrium concentration is found xi∗ = yi /m, where m – is the phase equilibrium constant. The value of m depends on the water temperature and is the values

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of m = 1500–3200. The number of cells of complete mixing is related to the number of Pecle, which characterizes the mixing of the flow, by the dependence [11]. Pe2 , n=  2 Pe − 1 + exp(−Pe)

(9)

where for liquid PeL = wL H /DL ; for gas PeG = wG H /DG ; H – is the height of the nozzle layer, m. The number of cells for liquid and gas is not the same due to different Re values. In this case, the calculated number of cells is assumed to be the smaller of n when calculated according to the formula (9). The number of Pecle (mixing coefficients) for the liquid and gas phases are found experimentally for each nozzle design. Determination of Mass Transfer Coefficients. An important task is the reliable calculation of the mass transfer coefficient k0x , which depends on the mass transfer coefficients in the phases [15]. For known types of nozzles, the values βL and βG are calculated using criteria expressions. For new irregular nozzles the mass transfer coefficient in the liquid phase can be determined by the formula [14] βL a =

LV (CH − CL ) H · av (π D2 )/4

(10)

where D – is the diameter of the device, m; LV – is the volume flow rate of the liquid, m3 /h (m3 /s); CH ta CL – is the concentration of carbon dioxide in the liquid in the upper and lower parts of the device, respectively, kmol/m3 . av - average driving force of the process, mol/m3 ; V – volume of the device block, m3 . The mass transfer coefficient in the gas phase is calculated from. 1/3

ShG = 0, 175Re0,75 (ξL /2)ScG ,

(11)

where ShG = β G d/DG is the Sherwood number; Re = wG d/ν G is the Reynolds number; d - is the equivalent diameter of the nozzle, m; ν G - is the kinematic viscosity coefficient of the gas, m2 /s; ScG - is the Schmidt number; ξ L - is the resistance coefficient of the nozzle layer, ξ L = f (Re) [11]. Determination of CO2 Extraction Efficiency. The efficiency of CO2 extraction from water in the cell and throughout the nozzle layer has the form: Ei =

xi−1 −xi xi−1 −xi∗ ;

Ei =

x1 −x2 x1 −x∗

(12)

Considering that xi >> xi∗ and using the efficiency additivity equation for cells E = 1 − (1 − E1 )(1 − E2 )...(1 − En ) from (7) and (12) we can obtain.   k0L aH −n E =1−1 1− , (13) nwL where a = aν ψ w – is the specific contact surface of gas and liquid, m2 /m3 ; aν - is the specific surface of the nozzle, m2 /m3 ; ψ w – is the wettability coefficient of the surface. At high irrigation densities ψ w ~ 0.8–0.9.

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Let’s consider an example of calculating a nozzle decarbonizer with Raschig rings. At a water flow rate of 163,4 m3 /h; x1 = 61,6 mg/kg; x2 = 4,0 mg/kg. The diameter of the decarbonizer is 1,86 m; wG = 0,67 m/s; wL = 0,017 m/s; Raschig rings – 25x25; aν = 200 m2 /m3 . As a result of calculations, k 0L = 1,25 × 10–4 m/s was obtained; H = 1,88 m. The efficiency of the process (12) was E = 0,95. The calculation according to Eq. (13) gives E = 0,92. As can be seen, there is a satisfactory agreement of the results on the effectiveness of decarbonization, and the calculation by the formula (13) is also confirmed by the practical experience of operating such devices. The advantage of the above method and the application of (13) is the ability to perform calculations of new nozzles for which there is no experimental data on the effectiveness of decarbonization.

Fig. 2. Dependence of the decarbonization efficiency of water on the height of the nozzle layer: 1 – Rashig rings, 25 × 25 mm; 2 – spherical permeable nozzle. Calculations by (13)

On the Fig. 2 is shown the calculated data using the above example for Raschig rings and permeable spherical nozzle. The figure shows a significant advantage of the investigated nozzle, the specified concentration of x 2 is achieved not at H = 1,86 m, as with Raschig rings, but already at H = 1,0 m. This reduces the metal consumption of the device and reduces the power to supply air for decarbonization by 2 times.

5 Discussion As a result of applying the flow structure modeling equations for a chaotic packing layer, an analytical expression for calculating the decarbonization efficiency is obtained. Examples of calculations and comparison with known data are given. The advantage of the new nozzles during the decarbonization of water is shown. There is a satisfactory agreement of the results of calculations on the decarbonization efficiency with the known data [18]. The advantage of this method and the obtained expression for determining the effectiveness of water decarbonization is the ability to perform predictive calculations of new nozzles for which there is no experimental data on the effectiveness of decarbonization. A mathematical model of the process of removing carbon dioxide from water during deaeration after experimental refinement of the parameters makes it possible to predict

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the values of decarbonization efficiency indicators for deaerators and decarbonizers with an accuracy corresponding to the normative accuracy of methods and means of quantitative chemical analysis. It also becomes possible to calculate the required number of degasser sections based on a given degassing efficiency and the known degassing effect per section. After determining the required number of sections of the foam degasser, the diameter of the degasser is found according to a given intensity of water movement, the air flow rate is found according to a given air velocity in the cross-section of the device, and the total resistance of the degasser is determined according to the hydrodynamic resistance of the section. After determining the geometric dimensions of the degasser based on the known air flow rate and hydrodynamic resistance of the degasser (taking into account pressure losses), the fans electric motor is selected for it. Comparison of foam degassers with bubbling and film degassers shows that the mass transfer rate in the foam three-phase layer is 6 times higher, and the energy consumption for air supply is an order of magnitude lower than in decarbonizers with a solid bubbling layer. Usually, designers are faced with the task of simplifying the technological scheme and reducing operating costs while ensuring reliability by excluding devices with rotating mechanisms from the water treatment scheme, in particular, some decarbonizer designs and replacing them with advanced and reliable samples [19]. The efficiency of mass transfer in three-phase foam decarbonizers operating in a stable foam mode confirms that the selected section design causes intensive mixing of interacting phases, gas content retention in a certain range, and an increase in the size of the contact surface of the phases and the rate of its renewal [20]. Therefore, for further intensification of decarbonizers, it is possible to use the proposed design of sections with a three-phase foam layer with a weighted nozzle [21].

6 Conclusions A promising direction for intensifying absorption/desorption processes is the development of devices with a three-phase stabilized pseudo-liquefied layer of an irrigated movable nozzle made of mesh materials. The industrial implementation of absorption processes in the foam layer and the use of the gas-liquid layer stabilization method significantly expands the scope of application of foam apparatuses and opens up new opportunities for intensifying technological processes. The use of modern designs of movable nozzles in combination with foam layer stabilizers makes it possible to modernize existing technological installations. The results obtained and the proposed designs will ensure the effective removal of free carbon dioxide in the process of Anticorrosive water treatment using foam three-phase decarbonizers in the organization of economic operation of water treatment systems for thermal power and boilers plants [22]. At the same time, it is possible to simultaneously create low-waste technologies.

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References 1. Kubicki, J., Kopczy´nski, K., Mlynczak, J.: Absorption characteristics of thermal radiation for ´ carbon dioxide. Informatyka Automatyka Pomiary w Gospodarce i Ochronie Srodowiska 12, 4–7 (2022). https://doi.org/10.35784/iapgos.2998 2. Sheng, L., Wang, K., Deng, J., Chen, G., Luo, G.: Gas-liquid microdispersion and microflow for carbon dioxide absorption and utilization: a review. Curr. Opin. Chem. Eng. 40, 100917 (2023). https://doi.org/10.1016/j.coche.2023.100917 3. Kubicki, J., Kopczy´nski, K., Mły´nczak, J.: Saturation of the absorption of thermal radiation by atmospheric carbon dioxide. IAPGOS´ 10(1), 77–81 (2020). https://doi.org/10.35784/iap gos.826 4. Heldebrant, D.J., Kothandaraman, J., Dowell, N.M., Brickett, L.: Next steps for solvent-based CO2 capture; integration of capture, conversion, and mineralisation. Chem Sci. 13, 6445–6456 (2022). https://doi.org/10.1039/D2SC00220E 5. Centi, G., Perathoner, S.: The chemical engineering aspects of CO2 capture, combined with its utilisation. Curr. Opin. Chem. Eng. 39, 100879 (2023). https://doi.org/10.1016/j.coche. 2022.100879 6. de Meyer, F., Jouenne, S.: Industrial carbon capture by absorption: recent advances and path forward. Curr. Opin. Chem. Eng. 38, 100868 (2022). https://doi.org/10.1016/j.coche.2022. 100868 7. Zhu, K., Yao, C., Liu, Y., Chen, G.: Using expansion units to improve CO2 absorption for natural gas purification - a study on the hydrodynamics and mass transfer. Chin. J. Chem. Eng. 29, 35–46 (2021). https://doi.org/10.1016/j.cjche.2020.08.025 8. Nwaoha, C., Tontiwachwuthikul, P., Benamor, A.: A comparative study of novel activated AMP using 1, 5-diamino-2-methylpentane vs MEA solution for CO2 capture from gas-fired power plant. Fuel 234, 1089–1098 (2018). https://doi.org/10.1016/j.fuel.2018.07.147 9. Peters, M.S., Timmerhaus, K.D., West, R.E., Timmerhaus, K., West, R.: Plant Design and Economics for Chemical Engineers. McGraw-Hill, New York (2005) 10. Chen, Y., Sheng, L., Deng, J., Luo, G.: Geometric effect on gas–liquid bubbly flow in capillaryembedded T-junction microchannels. Ind. Eng. Chem. Res. 60, 4735–4744 (2021). https:// doi.org/10.1021/acs.iecr.1c00262 11. Leduhovsky, G.V., Gorshenin, S.D., Vinogradov, V.N., Barochkin, E.V., Korotkov, A.A.: Predicting the indicators characterizing the water decarbonization efficiency when using atmospheric-pressure thermal deaerators without subjecting water to steam bubbling in the deaerator tank. Therm. Eng. 62(7), 526–533 (2015). https://doi.org/10.1134/S00406015150 7006X 12. Zhang, Y., Zhang, L., Kang, L., Liu, Y.: Techno-economic analysis of a hybrid system with carbon capture for simultaneous power generation and coal-to-hydrogen conversion. Ind. Eng. Chem. Res. 62, 7048–7057 (2023). https://doi.org/10.1021/acs.iecr.2c04325 13. Moiseev V., Manoilo E., Ponomaryova N., Repko K., Davydov, D.: Methodology of calculation of construction and hydrodynamic parameters of a foam layer apparatus for mass-transfer processes. Bull. NTU “KhPI” Ser. New Solut. Mod. Technol. 16(1292), 165–176 (2018). https://doi.org/10.20998/2413-4295.2018.16.25 14. Moiseev, V., Liaposhchenko, O., Manoilo, E., Demianenko, M., Khukhryanskiy, O.: Hydrodynamic parameters of a combined contact device. In: Ivanov, V., Pavlenko, I., Liaposhchenko, O., Machado, J., Edl, M. (eds.) DSMIE 2021. LNME, pp. 257–267. Springer, Cham (2021). https://doi.org/10.1007/978-3-030-77823-1_26 15. Larin, B.M., Bushuev, E.N., Larin, A.B., Karpychev, E.A., Zhadan, A.V.: Improvement of water treatment at thermal power plants. Therm. Eng. 62(4), 286–292 (2015). https://doi.org/ 10.1134/S0040601515020056

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16. Pasha, M., Liu, S., Zhang, J., Qiu, M., Su, Y.: Recent advancements on hydrodynamics and mass transfer characteristics for CO2 Gas–liquid microdispersion and microflow. Ind. Eng. Chem. Res. 61, 12249–12268 (2022). https://doi.org/10.1021/acs.iecr.2c01982 17. Gecim, G., Yi, O., Roy, S., Heynderickx, G.J., Van Geem, K.V.: Process intensification of CO2 desorption. Ind. Eng. Chem. Res. (2022). https://doi.org/10.1021/acs.iecr.2c01689 18. Sobieszuk, P., Aubin, J., Pohorecki, R.: Hydrodynamics and mass transfer in gas-liquid flows. Chem. Eng. Technol. 35, 1346–1358 (2012). https://doi.org/10.1002/ceat.201100643 19. Song, J., Hyndman, C., Jakher, R.K., Hamilton, K.: Fundamentals of hydrodynamics and mass transfer in a three-phase fluidized bed system. Chem. Eng. Sci. 54(21), 4967–4973 (1999). https://doi.org/10.1016/S0009-2509(99)00219-5 20. Pavlenko, A.N., et al.: Overview of methods to control the liquid distribution in distillation columns with structured packing: improving separation efficiency. Renew. Sustain. Energy Rev. 132(6). 110092 (2020). https://doi.org/10.1016/j.rser.2020.110092 21. Wang, S., Wang, S., Wu, B., Lu, Y., Zhang, K., Chen, H.: Effect of packing structure on anisotropic effective thermal conductivity of thin ceramic pebble bed. Nucl. Eng. Technol. 53(7), 2174–2183 (2021). https://doi.org/10.1016/j.net.2021.01.013 22. Rahmonov, O.K.: Study of the process of deposition of fine particles in the apparatus with a movable nozzle. Austrian J. Techn. Nat. Sci. 2, 78–81 (2017). https://doi.org/10.20534/AJT17-11.12-78-81

Research on Distribution of the Condensed Substance on a Flat Support and Obtaining Vacuum Evaporation Thin Films with Uniform Thickness by Correction Masks Georgeta Ionascu1 , Lucian Bogatu1 , Tudor Catalin Apostolescu2 Elena Manea3 , and Edgar Moraru1(B)

,

1 Politehnica University of Bucharest, 313, Splaiul Independentei, 060042 Bucharest, Romania

[email protected]

2 Titu Maiorescu University, Corp M, 189, Calea Vacaresti, 0400511 Bucharest, Romania 3 National Institute for Research and Development in Microtechnologies, 126A, Erou Iancu

Nicolae Street, 077190 Bucharest, Romania

Abstract. The thickness uniformity of thin film distribution is an important parameter in science and industry, which can be obtained by atomic deposition processes in various film - substrate systems, affecting their electrical, optical, and mechanical properties. Film thickness uniformity provides confidence that specifications are being met and that will be no fluctuations in thickness from one product to another. It is guaranteed so a reliable process of thin films deposition. This paper deals with studying and experimentation of thin aluminium film deposition on plane substrate by vacuum thermal evaporation using profiled masks, also called correction diaphragms, introduced between the rotating substrate and the evaporation source. The facilities of the AV-100 laboratory installation are used, and a comparison of the results is given for three states of the substrate: fixed plane substrate, parallel to the source; rotating substrate without mask; rotating substrate with profiled mask. Interesting results are inferred and proposed to be an optimization solution. Keywords: Thickness distribution uniformity · Thin films · Vacuum evaporation · Plane substrate · Reliable process · Correction diaphragms

1 Introduction The use of vacuum evaporation installations for film-based production of certain imposed characteristics and thicknesses of deposited films of the order of micrometers or even submicrometers is widespread. One of the basic methods for obtaining thin layers is vacuum thermal evaporation. The method is widely spread due to its simplicity and the fact that it allows obtaining thin layers of any material - metals, semiconductors, dielectrics, ferromagnetic materials, plastics, acids in the form of powders or crystals. The deposition can be carried out on any support/substrate - metal, glass, polymer, © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 328–344, 2023. https://doi.org/10.1007/978-3-031-40628-7_28

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because heating the support is not mandatory (although the adhesion of the layer to the substrate is improved by heating the support), the deposition can also be carried out at the ambient temperature of the deposition bell jar. The process of obtaining thin layers by thermal evaporation in vacuum consists of two main stages: the evaporation of the substance to be deposited and its subsequent condensation on the substrate. These two stages can be accompanied by auxiliary phases: obtaining high vacuum (typically 10–7 Torr), preparation, cleaning and degassing of the support/substrate, subsequent processing of the condensed layer and so on. The condensation process strongly depends on the temperature of the support, on its nature and degree of cleanliness, on other parameters specific to the evaporated substance (melting, vaporization/sublimation temperature, composition, nature of the material), as well as parameters that characterize the evaporation-condensation process (support-evaporator distance, degree of vacuum, atomic/molecular beam density, critical condensation temperature, mobility of atoms on the surface of the substrate, presence of magnetic or electric fields, radiations, impurities, etc. The mentioned parameters largely influence the film crystalline structure, adhesion to substrate, the thickness and uniformity of the deposited thin film, the stoichiometric composition in the case of compounds, as well as other physico-chemical properties of the obtained layers. According to the way the heat reaches the material to be evaporated, the sources/evaporators are divided into two groups, with direct and indirect heating. In the first case, the electric current passes directly through the evaporated material. This method applies only to materials that sublimate and evaporate below the melting temperature. Indirectly heated evaporation sources consist of filaments or boats/crucibles and the material to be evaporated. The heating is produced due to the thermal action of the electric current (Joule effect), of the high-frequency currents or of high-energy particle beams - electrons, ions, and photons. Resistive sources are made of hardly-to-fusible materials, such as: tungsten, molybdenum, tantalum, quartz, or ceramic compounds. Evaporation with electron gun and laser beam (PLD method - Pulsed Laser Deposition) are widely used today, due to the advantages of making films with a high degree of purity (in high and ultrahigh vacuum), from any material, with a better control of the evaporation-condensation process, even at low temperatures of the substrate, being obtained new properties and applications of the deposited layers [1–5]: biomedical area as antimicrobial coatings, bioactive coatings, tissue and bone regeneration systems, drug delivery systems; other fields concerning organic photovoltaic cells, hybrid photovoltaic cells, polymer light emitting diodes, antireflective coatings, photo-responsive coatings, non-linear optical materials, transparent supercapacitor electrodes, and sensing materials for various gases; coatings functionalization to change local morphology, chemistry, and crystal structure, which modify the biomaterial behaviour, suitable for the chosen application; integration of thin and thick film technologies into the multi-scale hybrid technology of Low Temperature Co-fired Ceramics (LTCC), which enables functionality enhancement through performance, flexibility and miniaturization of Multi-Chip Modules (MMS) being obtained new multilayer 3D structures for RF microelectronics and pressure or gas sensors with medical applications. Starting from the concrete application in which a thin layer with a uniform thickness distribution must be made, depending on the shape and dimensions of the part on which

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the deposition is made, the evaporation source must be chosen, its shape and emissive characteristics, as well as its relative position compared to the support of the parts. Following the theoretical study of the evaporation source - part support assembly and the graphic representation of the thickness distribution for different values of the geometric parameters involved in the calculation of the thickness of the deposited layer, it is possible to choose the version for which the uniformity of the thickness is maximum and the deviation from the imposed thickness to fall within the admissible deviation. The most common, punctiform (with spherical symmetry) and plane, of small surface (with directional emission) sources are recommended in the case of small surface substrates, the thickness distribution curves of the deposited layer decreasing strongly with the increase of the size of the part, respective increasing the (x/h) ratio, where x - the film thickness at a certain point and h – the height at which the part is placed with respect to the source [6]. Mainly, the uniformity of the deposited layer thickness is influenced by the height position of the part relative to the evaporation source, as well as by the angle of inclination of the part to the direction of vapor propagation; good results are obtained if the substrate placed on a support representing the installation carrousel, rotates around of the bell jar axis [7]: a computation method to improve the thickness uniformity attainable when coating multiple substrates inside a thermal evaporation physical vapor deposition equipment is given. The study is developed for the classical spherical (dome-shaped) calotte and, also, for a plane sector reversible holder setup (pyramidal dome). This second arrangement is very useful for coating both sides of the substrate, such as antireflection multilayers on spherical lenses. If a rotation around the own axis of substrate is added (the case of planetary motion), the non-uniformity of the deposited layer is reduced even more [6, 8]: a mathematical model of vacuum evaporation process, validated through numerical simulation and experiment is given for conformity of metal films on steps, being demonstrated that the geometry of placement of silicon wafers in the evaporation system and the step profile influence the cracks developing. Different error modes of planetary motion led to thin film thickness and uniformity errors [9]: such deviations in layer thicknesses may appear to be random or systematic errors, resulting in failures in coating performance and reductions in usable system capacity. The configuration with four planets of a planetaryrotation system is optimized for deposition of evaporated optical thin films to quantify the impact of individual system design problems. Another approach, based on a precession rotation of a substrate support, is mentioned [10]. It yields superior thickness uniformity in a very compact vacuum chamber compared to the planetary-rotation mechanism. Moreover, a control of orientation of the evaporated material molecules on the surface of the substrate [11] is obtained, these condensing in the normal direction on the substrate. It is supposed that the degree of super-cooling, defined as the difference between the melting temperature of the sample and the substrate temperature affects the adsorption - desorption process and the molecular motions on the substrate, such as translation, rotation, and precession modes. Among these modes, the precession motion is assumed to play an important role in the formation of the thin film with the molecular orientation perpendicular to the substrate.

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A method that allows obtaining a high thickness uniformity of the layers deposited by vacuum thermal evaporation is the one that uses a mask (also called correcting diaphragm), inserted between the evaporation source and the part placed on a support with single rotation motion [12]. The correcting masks have been used to obtain thickness uniformity in thin films prepared with physical vapor deposition (PVD) methods, such as in thermal evaporation with resistive source or electron-beam gun, and cathodic sputtering. The procedure for designing such correcting diaphragms is based on Knudsen’s laws that estimate the emission properties of vapor sources. This method, depending on geometry, gives a solution that guarantees 3% of uniformity. The uniformity can be more improved by local corrections of the mask shape for emission properties of vapor sources based on experimental results, regardless the evaporation system geometry [13]. In this paper, using the facilities of the AV-100 laboratory installation, correction masks designing, a comparative study and experiments are presented for three states of the substrate: fixed plane substrate, parallel to the source; rotating substrate without mask; rotating substrate with profiled/correction mask. Interesting results, regarding the obtained thickness distributions for the three analyzed cases, are inferred and proposed to be an optimization solution.

2 Design of Profile and Execution of Correction Masks for AV-100 The positioning scheme of the mask relative to the substrate and the evaporation source is shown in Fig. 1: the part is placed on a support with single rotation motion (Fig. 1a), and the mask, symmetrical in relation to the polar axis, can be in opposition to the source (Fig. 1 b1 ) or on the same side as the evaporation source (Fig. 1 b2 ).

Fig. 1. The positioning scheme of the mask relative to the substrate and the evaporation source: 1 – part support; 2 – evaporation source; 3 – correction mask.

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For the AV-100 installation, the geometric parameters used in the calculations are: radius of the carrousel, r 0 = 65 mm; source-part distance, h = 165 mm, respective 200 mm; rotation axis-source distance, l = 55 mm. The average speed of condensation on the open surface, for the case when the support of the part rotates with a constant angular speed (ω) is: vm =

1 ϕ1 (r) · ∫ v(r, ϕ)d ϕ − Fig. 1b1 , π 0

(1)

vm =

π 1 · ∫ v(r, ϕ)d ϕ − Fig. 1b2, π ϕ1 (r)

(2)

or

where ϕ 1 (r) represents the curve that gives the mask shape. The profile of the mask is determined so that the average condensation speed at any point on the open surface, calculated according to the geometric parameters of the deposition, is constant. In low pressure conditions (> mask-part distance. By this, the position of the edge of the shadow formed by the edge of the mask depends less on the direction of the molecular beam and, consequently,

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the thickness distribution of the condensed layer on the support is less influenced by the small displacements of the effective center of the source in the evaporation process. During the experiments carried out on the AV-100 installation, the version from Fig. 1 b2 was adopted, due to: • the decrease in the probability of contamination of the layer with non-evaporated particles thrown up by the source, under the action of the vapor pressure (pv ) of the vaporized substance; • the adjustment range of the geometric parameters (r 0 , h, l) on the installation. After solving the integral (2) and calculating the constant C, the relationship that gives the dependence r = r(ϕ) was obtained:   (a − b)tg ϕ2 bsinϕ a a0 2a   arctg = π − + √  3/2  3/2  2 3/2 , (9) b2 − a2 (a + bcosϕ) a2 − b2 a2 − b2 a2 − b2 a0 − b20

where a0 =

h2 + r02 + l 2 , h2

b0 = −

(10)

2r0 l . h2

(11)

The polar (r, ϕ) and Cartesian (x, y) coordinates of the profile points were determined for two masks, Table 1 (h = 165 mm) and Table 2 (h = 200 mm), for the specified geometric parameters (r 0 , h, l). The two masks were manufactured from thin aluminum sheet (thickness 0.8 mm) on a coordinate drilling machine with numerical control, Schmoll 21 drilling machine for PCB (Printed Circuit Boards). The drawings in SolidWorks and the photos of the processed masks, which have been used in experiments, for the conditions of the AV-100 deposition installation are given in Fig. 2.

a

b

Fig. 2. Drawings in SolidWorks (a) and photos (b) of the processed masks (h = 200 mm in the left side, respectively h = 165 mm in the right side) with centering bushings.

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Table 1. The mask profile for h = 165 mm

Table 2. The mask profile for h = 200 mm

y [mm]

r [mm]

ϕ [°]

65

0

65

0

65

0

62,98

1,53

63

1,2

62,98

1,31

59,88

3,66

60

3

59,91

3,14

4,9

57,78

4,95

58

4,2

57,84

4,24

6,8

54,61

6,51

55

5,8

54,71

5,55

53

8,1

52,47

7,46

53

6,9

52,61

6,36

50

10

49,24

8,68

50

8,5

49,45

7,39

48

11,2

47,08

9,32

48

9,5

47,34

7,92

45

12,9

43,86

10,04

45

11

44,17

8,58

43

14,1

41,70

10,47

43

12

42,06

8,94

40

15,8

38,48

10,89

40

13,4

38,91

9,26

38

16,9

36,37

11,04

38

14,3

36,82

9,38

35

18,5

33,19

11,10

35

15,5

33,72

9,35

33

19,5

31,10

11,01

33

16,3

31,67

9,26

30

21

28

10,75

30

17,6

28,59

9,07

28

21,9

25,97

10,44

28

18,3

26,58

8,79

25

23,3

22,96

9,88

25

19,4

23,58

8,78

23

24,2

20,97

9,42

23

20,1

21,59

7,90

20

25,5

18,05

8,61

20

21

18,67

7,16

18

26,3

16,13

7,97

18

21,6

16,73

6,62

15

27,8

13,26

6,99

15

22,5

13,85

5,74

13

28,2

11,45

6,14

13

23

11,96

5,07

10

29,3

8,72

4,87

10

23,7

9,15

4,01

8

29,9

6,93

3,98

8

24,1

7,30

3,26

5

30,7

4,29

2,55

5

24,7

4,54

2,08

r [mm]

ϕ [°]

65

0

63

1,4

60

3,5

58 55

x [mm]

x [mm]

y [mm]

3 Experimental Results for Depositions Using AV-100 without/with Correction Masks, and Discussion Aluminium deposits have been performed on plane-parallel substrates/parts made from polished BK 7 optical glass: non-selective depositions, with fixed part (placed in opposition to the source representing the worst case) and, respectively, in rotational motion, part diameter φ53 mm, for h = 165 mm, respectively h = 200 mm; selective depositions, through fixed and centered masks relative to the rotating part, the diameter of the part φ19 mm (smaller because of the space used for centering) similarly positioned at a distance h = 165 mm, respectively h = 200 mm with respect the source. The pressure,

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at which the depositions were performed, has been 7·10–5 Torr. The source used was a tungsten helical filament, required by the impossibility of aluminium evaporation from a tungsten boat (it is known as aluminium forms an alloy with the source). The choice of aluminum as deposition material was convenient for the conditions offered by the AV-100 installation: melting temperature T t = 660 °C, vaporization temperature T v = 1000 °C (pv = 10–2 Torr). The purpose of these depositions is to determine the thickness t of the deposited layers at different points and then, to establish the thickness distribution t/t 0 along a diameter of the part (t 0 - the thickness of the layer at the point located on the normal to the evaporation source). The measurement of thickness of the obtained layers have been carried out after removing the parts from the deposition chamber, on the micro-interferometer MII-4 Linnik in white light, λ = 0.55 μm, using the interference on the surface of the layer and on the glass, next to some lines engraved in the layer with a fine steel needle, on an optical pantograph, at distances of 4 mm and, respectively, of 2 mm. On the mirror surface of the part, curved interference fringes appear next to the engraved line due to the optical path difference. The deformation of the fringes divided by the inter-fringe (the distance between two consecutive fringes), which corresponds to 1/2 of the wavelength of the light in which the observation is made, represents the thickness of the measured layer. On the apparatus, thickness of the measured layer is in the range of 0.03–1 μm. The degree of uniformity of each deposition has been assessed by the maximum relative deviation of thickness at a point i, t i , from the average thickness t avg :     tavg − ti  max εimax = · 100%. (12) tavg The results are summarized in Tables 3, 4, 5, 6, 7 and 8 (h = 165 mm and h = 200 mm) and represented graphically comparative with the theoretical curves, for the three studied cases: fixed part, rotating part without/with correction mask, in Figs. 3, 4 and 5. The theoretical curves were drawn using the relationships given in [12]. In Fig. 6, for h = 200 mm and fixed part, rotating part without/with correction mask, the dependence of the layer thickness as a function of the point position on the substrate surface, using interpolation with the spline function, is represented. It is found that the variation of the layer thickness decreases with the increase of h and by rotating the support of the part, being confirmed the theoretical results of the study on the thickness distribution during evaporation from a plane emitting source, with a small surface [12].

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G. Ionascu et al. Table 3. Fixed part, h = 165 mm (x = 0, point located above the evaporation source)

Point no., i

x/h

t [μm]

t avg. [μm]

εmax [%]

1

0,4

0,199

0,148

34,4

2

0,42

0,179

3

0,44

0,169

4

0,47

0,175

5

0,49

0,170

6

0,52

0,168

7

0,54

0,174

8

0,56

0,163

x = 66 mm

9

0,59

0,137

10

0,61

0,124

11

0,64

0,115

12

0,66

0,120

13

0,69

0,092

14

0,71

0,092

x = 118 mm

From the point of view of the amount of deposited material, a higher thickness of the layer leads to a higher non-uniformity of the thickness. The obtained results confirm this aspect, although a rigorous comparison cannot be made because the amount of deposited material varied within relatively narrow but significant limits for layer thicknesses of the order of hundreds of micrometers. The rotating movement of the carrousel led to a decrease in the amount of deposited material, caused by the entrainment of residual air molecules in rotational motion by the carrousel, which produce the entrainment of aluminum molecules from the vapor beam and therefore, the condensation of a quantity of aluminum on the walls of bell jar. The existence of residual air molecules is given by the insufficient value of the vacuum during deposition. It was conditioned by the possibilities of the AV-100 installation. By using correction masks, an improvement in the uniformity of the deposited layer thickness is obtained. The existing deviations can still be due to the following causes: possible deviations in form and accuracy of the substrate, subject only to a refreshing polishing before deposition; measurement errors; errors introduced by the working device when materializing the distance l and centering the mask relative to the source, since the instantaneous center of evaporation is not fixed during deposition, even more so, as the source used was a tungsten helical filament, for the mentioned reasons; the difficulty of controlling the source heating temperature at AV-100.

Research on Distribution of the Condensed Substance on a Flat Support Table 4. Fixed part, h = 200 mm Point no., i

x/h

t [μm]

t avg. [μm]

εmax [%]

1

0,33

0,096

0,077

24,6

2

0,35

0,087

3

0,37

0,075

4

0,39

0,084

5

0,41

0,067

6

0,43

0,086

7

0,45

0,075

8

0,47

0,075

9

0,49

0,068

10

0,51

0,072

11

0,53

0,079

12

0,55

0,087

13

0,57

0,056

14

0,59

0,073

Table 5. Rotating part, h = 165 mm Point no., i

x/h

t [μm]

t avg. [μm]

εmax [%]

1

0,4

0,111

0,097

14,4

2

0,42

0,104

3

0,44

0,106

4

0,47

0,102

5

0,49

0,098

6

0,52

0,104

7

0,54

0,100

8

0,56

0,096

9

0,59

0,082

10

0,61

0,101

11

0,64

0,101

12

0,66

0,092

13

0,69

0,088

14

0,71

0,077

337

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G. Ionascu et al. Table 6. Rotating part, h = 200 mm

Point no., i

x/h

t [μm]

t avg. [μm]

εmax [%]

1

0,33

0,100

0,085

12,4

2

0,35

0,083

3

0,37

0,082

4

0,39

0,084

5

0,41

0,085

6

0,43

0,074

7

0,45

0,096

8

0,47

0,088

9

0,49

0,093

10

0,51

0,076

11

0,53

0,085

12

0,55

0,082

13

0,57

0,084

14

0,59

0,083

Table 7. Rotating part, deposition through correction mask, h = 165 mm Point no., i

x/h

t [μm]

1… 5

0,496

0,109

0,509

0,112

6

0,521

0,110

0,533

0,108

7

0,545

0,112

0,557

0,103

0,569

0,094

0,581

0,098

9

0,593

0,091

0,606

0,090

10

0,618

-

8

…14

t avg. [μm]

εmax [%]

0,103

8,5

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Table 8. Rotating part, deposition through correction mask, h = 200 mm Point no., i

x/h

t [μm]

0,41

0,100

0,42

0,093

0,43

0,089

0,44

0,095

7

0,45

0,090

0,46

0,099

8

0,47

0,100

0,48

0,093

0,49

0,097

0,50

0,092

0,51

-

1… 5 6

9 10

t avg. [μm]

εmax [%]

0,095

5

…14

Tests were also performed with diaphragms with r 0 = 100 mm, Fig. 7, but the results were not conclusive. A decrease of εmax was observed in comparison to the case when no corrective diaphragm is used, but a comparison cannot be made with the case of using correction masks with r 0 = 65 mm Theoretically, the increase of r 0 , therefore of the obturated surface, would implies a decrease in the non-uniformity of the deposited layer, under the conditions of an increase in the amount of lost evaporated material. The increase of r 0 must therefore be higher to result in certain conclusions. Regarding the sample made by depositing an aluminum layer through the profiled corrective diaphragm in the form of a slot/cutout, Fig. 8, it was found that although the amount of material was double compared to the other deposits, the thickness of the deposited layer is very small, the resulting layer being transparent. The thickness of the layer was below the measurement limit (0.03 μm) of the interferometer used. For the AV-100 installation, this case is not recommended, the amount of material that can be evaporated during a deposition operation is not sufficient to achieve an enough thick layer. Also, the amount of material that is lost is very high. This deposition case could be used in vacuum evaporation installations that can ensure a continuous supply of material, even during evaporation. But the problem of the amount of material to be evaporated, necessary to obtain a layer of the order of hundreds of micrometers, is very important. That is why an economic study is useful to justify or not the use of this method or the choice of another physical deposition procedure that ensures the uniformity of thickness of the deposited thin layer.

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a

b Fig. 3. Thickness distribution for non-selective deposits with a fixed part (x = 0, point corresponding to the position of the evaporation source): h = 165 mm (a), h = 200 mm (b).

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a

b Fig. 4. Thickness distribution for non-selective deposits with a rotating part: h = 165 mm (a), h = 200 mm (b); x/h = 0.34 (a) and x/h = 0.28 (b) represent the points corresponding to the position of the rotation axis of carrousel.

a

b Fig. 5. Thickness distribution for selective deposits with a rotating part and correction masks: h = 165 mm (a), h = 200 mm (b).

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a

b

c Fig. 6. The layer thickness dependence on the position of the point on the substrate surface, obtained by interpolation with the spline function, for h = 200 mm, with: fixed part (a), rotating part without correction mask (b), and rotating part with correction mask (c).

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a

343

b

Fig. 7. Shape of correction masks for r 0 = 100 mm: h = 165 mm (a) and h = 200 mm (b).

Fig. 8. Shape of correction mask with a slot/cutout of 3 mm width, for h = 200 mm.

4 Conclusions The deviations from the thickness uniformity of the layers obtained by using the correction masks (8.5% for h = 165 mm, Table 7 and 5% for h = 200 mm, Table 8), are smaller by 5.9 times, respectively 4 times than those in the case of depositions made on rotating parts without correction (14.4% for h = 165 mm, Table 5 and 12.4% for h = 200 mm, Table 6). Thus, the statement regarding the influence of the experimental conditions on the obtained results is verified and it can be concluded that the studied method of improving the thickness uniformity of the layers deposited by vacuum evaporation presents performances similar to that in which the substrate performs a planetary motion. Diminishing

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the deviations from uniformity, even below 1%, is possible through local corrections of the used masks profile, depending on the concrete conditions of evaporation. In addition, the method is advantageous due to the constructive simplicity, the increased reliability, and the reduced cost of the working device with the correction mask, relative to the one for performing the planetary movement.

References 1. Ionascu, G., Manea, E., Gavrila, R., Moraru, E.: Perspectives on the use of thin films technologies in precision mechanics and mechatronics. Int. J. Mechatron. Appl. Mech. – IJOMAM 8(11), 204–208 (2020) 2. Ionascu, G., Bogatu, L., Manea, E., Moraru E.: Defining the geometric configurations in thin films. IJOMAM 12, 140–147 (2022). https://doi.org/10.17683/ijomam/issue12.21 3. Socol, M., Preda, N., Socol, G.: Organic thin films deposited by matrix-assisted pulsed laser evaporation (MAPLE) for photovoltaic cell applications: a review. Coatings 11(11), 1368 (2021). https://doi.org/10.3390/coatings11111368 4. Badiceanu, M., Anghel, S., Mihailescu, N., Visan, A.I., Mihailescu, C.N., Mihailescu, I.N.: Coatings functionalization via laser versus other deposition techniques for medical applications: a comparative review. Coatings 12(1), 71 (2022). https://doi.org/10.3390/coatings1201 0071 5. Wolf, J.A., Peterson, K.A.: Thin film on LTCC for connectivity and conductivity. J. Microelectron. Electron. Packag. 8(2), 43–48 (2011). https://doi.org/10.4071/imaps.288 6. Ionascu, G., Manea, E., Gavrila, R., Moraru, E.: Technologies for thin layers on ceramics substrate. In: Cioboat˘a, D.D. (ed.) ICoRSE 2021. LNNS, vol. 305, pp. 250–265. Springer, Cham (2022). https://doi.org/10.1007/978-3-030-83368-8_25 7. Bosch, S.: Computer-aided procedure for optimization of layer thickness uniformity in thermal evaporation physical vapor deposition chambers for lens coating. J. Vac. Sci. Technol. A 10(1), 98–104 (1992) 8. Ionascu, G., Manea, E., Cernica, I., Moraru, E.: Theoretical and experimental research on step coverage optimization for integrated microstructures of thin films. In: Cioboat˘a, D.D. (ed.) International Conference on Reliable Systems Engineering (ICoRSE) - 2022, pp. 185–202. Springer, Cham (2023). https://doi.org/10.1007/978-3-031-15944-2_18 9. Oliver, J.B.: Analysis of a planetary-rotation system for evaporated optical coatings. Appl. Opt. 55, 8550–8555 (2016). https://doi.org/10.1364/AO.55.008550 10. https://www.tinmodel.com/Innovation_Precession_Motion.html 11. Tanaka, K., Okui, N., Sakai, T.: Molecular orientation behavior of paraffin thin films made by vapor deposition. Thin Solid Films 196(1), 137–145 (1991). https://doi.org/10.1016/00406090(91)90181-V 12. Ionascu, G.: Utilization of the Thin Film Structures Technologies in Precision Engineering and Mechatronics (in Romanian). Printech Publishing House, Bucharest (2004) 13. Villa, F., Martinez, A., Regalado, L.E.: Correction masks for thickness uniformity in large-area thin films. Appl. Opt. 39(10), 1602–1610 (2000). https://doi.org/10.1364/AO.39.001602

Approaches and Processing Technologies for Medical Devices: Considerations from Micro- and Macroscale Perspectives Edgar Moraru(B)

, Grigore Octavian Dontu , Sorin Cananau , and Vlad-Andrei Stanescu

Politehnica University of Bucharest 313, Splaiul Independentei, 060042 Bucharest, Romania [email protected]

Abstract. The symbiosis of the medicine and engineering has always represented a topic of maximum interest and vital research importance in order to find new and viable solutions for maintaining health and improving the quality of life. The efforts of researchers and scientists from complex and multidisciplinary fields have contributed to the emergence of medical devices such as prostheses, orthoses or various implantable structures/systems with special performances achieved through various techniques and advanced methods of processing, bringing major and large-scale benefits to humanity. Considering what was said previously, in this work, the authors study different approaches, methods and technologies that can be applied for the creating of different medical devices/prototypes, taking into account both the macro and micro domains. Engineering modelling and simulation tools applied to medical devices or their prototypes using specific programs will be discussed. Also, the paper presents some experimental models of realised prostheses/orthoses/prototypes and highlights some investigation methods for the analysis of their resulted characteristics. Keywords: medical devices · prosthetics · medical prototypes · processing technologies · micro/macrotechnologies · modeling/simulation · additive manufacturing · biomaterial characterization

1 Introduction The technological innovations applied in medicine revolutionize humanity year by year through ultra-precise robotic solutions for surgery [1] or various advanced technologies and methods for the creation of prosthetic devices [2], various implantable elements [3], anatomical study models [4], or even tissues or replicas of human organs using 3D bioprinting, the latter still being at the experimental technology stage, but with a huge potential for practical use in the future [5, 6]. It is obvious that technologies with applications in medicine are in a dynamic development in terms of the new solutions used and the great efforts of researchers in complex and multidisciplinary fields contribute year after year to saving, prolonging, and improving life [7]. If it refers to the macroscale, it © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 345–362, 2023. https://doi.org/10.1007/978-3-031-40628-7_29

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can be said that the medical field is in the foreground when it comes to rapid prototyping applications by using several 3D printing technologies [8] or other technologies by removing [9] or redistributing material [10]. Today, prosthetic structures, implantable devices or even models of living tissues can be executed with great precision starting directly from the files obtained through various medical imaging techniques (magnetic resonance imaging, computed tomography scan or other medical imaging methods) by converting to a special file recognized by processing equipment using special programs [11–13]. Among the many examples of applications of RP techniques that can be noted, it can be distinguished the following: the creation of personalized bioprostheses and bioimplants [14], the creation of bones [15] and blood vessels [16], the execution of unique surgical instruments [17], the development of anatomical models or auxiliary devices with applications in medicine [18] or the printing of organs or living tissues [19]. On the other hand, there are important technologies at the micrometric or even nanometric scale [20], totally different from macroscopic technological approaches – using integrated micromechanical and microelectronic structures to perform certain complex tasks in medicine, such as microsystems for drug delivery in the body [21], the study of cellular structures [22] or various microgrippers for microscale robotics [23]. The common name for this type of systems is Bio-MEMS (biological/biomedical microelectromechanical systems) [24], these performing biological or biomedical functions, being increasingly present in emerging medical devices as they fully meet the requirements of the modern concept of medicine, making radical transformations with a huge impact to ensure a living as healthy and comfortable as possible [25].

Macroscale

Microscale

Fig. 1. The main biomedical applications at the macro and micro scale from the perspective of technological approaches.

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Figure 1 shows the main applications on a macro and micro scale for medical devices in which the latest methods and technological approaches are applied and are in advanced research stage with maximum interest worldwide [14, 17–19, 21, 23, 26–30]. Considering the previously discussed and the role of these modern technological approaches in full development, this paper presents examples of processing technologies for the medical field from macro and micro perspectives and simulation regarding the manufacturing process for prosthetic devices and orthotics. Also, the authors highlight some methods of analysis and investigation for prosthetic structures with possible applications in biomedical field to evaluate their characteristics following the execution and/or post-processing procedures and obtain compliant structures.

2 Processing Technologies for Medical Field – Macroscale Perspective In order to be able to obtain the macroscale prosthetic, implantable or orthotic devices discussed in the previous chapter, several manufacturing and processing methods can be used depending on the requirements and their final use. Therefore, the technological approaches of realization can be divided into 3 large categories, according to Fig. 2 [31]. Of these, perhaps the most spectacular development had the technologies by adding material that perfectly corresponds to the requirements of the medical field, especially in the area of prosthetics, orthotics and implantology due to the undeniable advantages: high precision that allows taking into account individual anatomical characteristics, the ability to achieve structures of any complexity, the economy of resources in terms of raw material, reducing the production time and accelerating the provision of medical aid [31].

Fig. 2. Main technologies applied for medical devices from processing strategy point of view.

So, 3D printing technologies are best suited for making medical devices, which most often require very sophisticated geometries and small or unique series production batch. Also, the creation of anatomical models of the organs of interest allows a visual demonstration of various problems or pathologies on a real scale. The doctor can accurately assess the size of the pathology and the location of adjacent tissues before starting the operation and can even practice on these models. At the same time, it can also be a study model for researchers or a didactic model for students or practitioners in the field [31].

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a

b

c

d Fig. 3. Dental prosthetic structures obtained by different additive manufacturing technologies: a – dental model executed by additive manufacturing and conventional gypsum dental model; b – dental models realised by liquid state raw material – vat photopolymerisation technology; c – dental structures obtained from nylon powder by selective laser sintering; d – NiCr and CoCr dental prostheses executed by selective laser melting.

In Fig. 3 are illustrated several dental prosthetic structures made by various technologies of additive manufacturing, categorized by the type and nature of the raw material, and details regarding their execution process can be found in some previous works of the authors [31–38]. From the category of additive technologies (AM) for the realization of prototypes or study models can be highlighted the technologies of thermoplastic extrusion – FDM [39], those that use as raw material a liquid sensitive to radiations – vat photopolymerization [32] and material jetting [40], but also the binder jetting technology [41] that can be considered at the border between the technologies for prototyping and for the realization of functional structures, along with selective laser sintering [33], but due to its special printing properties we can fall into the category of technologies for functional parts, along with those already established in the field – metal additive technologies that are famous for their contribution in the medical field by making dental and orthopaedic

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prostheses, implants and other medical devices with admirable characteristics at great competition with those made by subtractive technologies – by removing material [36]. These can be classified into classical technologies (classical mechanical processing) and unconventional (laser, ultrasound, electroerosion, electrochemical methods and others). Classical subtractive technologies by using high-performance CNC equipment [37] are still superior to the most advanced systems of additive manufacturing in terms of dimensional precision, but most of the time they are more expensive when it comes to unique-type productions and lose in terms of geometric complexity that can be achieved, and already at some mechanical properties, as the hardness of the resulting metal components [31, 33]. In contrast, for medium to large production batches, classical subtractive technologies are more viable than additive technologies [31]. For very large production batches, the best option is the technologies by redistribution of material – the 3rd variant of the processing strategy by using the casting process, usually for metallic materials and injection for polymeric materials [10], being also applications of AM technologies for this field [42]. Lately, the dental field is probably the most ahead when it comes to the use of additive technologies in terms of the admirable results obtained in creating prostheses, implants or other dental prosthetic structures or even in oral and maxillofacial surgery [43]. However, it is worth mentioning other very important applications in which AM technologies have stood out and significant progress has been made: ENT domain [44], orthopedics [14], oncological field [45], ophthalmology [46], and other medical fields.

a

b Fig. 4. Incisive and molar dental structures used and their generated printing strategy regarding material use from software.

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In the following is presented an example for the complete cycle of performing some anatomical dental prototypes starting from digital structures obtained by direct intraoral scanning. This will allow the creation of physical models that correspond to the real intraoral situation and will reveal a dental deficiency of pathological or anatomical nature [31, 32]. In this case, the specialist doctor will be able to evaluate, make possible decisions or practice certain plans of surgery or treatment without the presence of the patient, having the physical models in front of him [31].

Fig. 5. Sequences from the simulation of layer deposition in the software.

Fig. 6. Dental structures during 3D printing process and in a completed state on the work platform.

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For this purpose, the Prusa i3 MK3 3D printer [47] was used, which uses FDM technology, and the material used was polylactic acid. Figure 4 shows the interface of the program used to create the trajectory and the processing parameters of the printer – PrusaSlicer 2.5.0 [47] that allows the positioning on the work platform and implicitly the printing of several models simultaneously. For the demonstration printing, 4 dental structures of the incisor and molar teeth were used, obtained by direct intraoral digital scanning of mandibular and maxillary arch, and then digital dental structures resulted were divided into 2, 3 and 4 teeth (for incisors) separately respectively [31]. Figure 4b shows the strategy proposed by the software for the use of the material and the estimated processing time. Also, this software from Prusa [47] allows to view the deposition of successive layers, as shown in Fig. 5. Figure 6 presents images of the dental structures during printing and in completed condition, and for their creation were used the following parameters: layer height – 0.1 mm (first layer – 0.2 mm), work platform temperature 60 °C, extrusion temperature - 215 °C, fill density – 15%.

3 CAD-CAM Approaches for Realization of Prosthetics/Orthotics Structure Models In today’s climate CAM or Computer Aided Manufacturing is one of the tools indispensable to any manufacturing operation, including in the medical field [37]. The processes that it can deliver are split up into two categories, one that removes material called subtractive manufacturing and one that adds material, additive manufacturing. The latter has many technologies adjacent to it but the one with the biggest spread is FDM or Fused Deposition Modeling. All the machines that use CAM as a way of interpreting and executing commands are using CNC or Computer Numerical Control [48], the language that they use is called NC code or the more popular name G code.

Fig. 7. Designed molding system for orthopedic sole.

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In this chapter, the authors present a possible example of the application of CADCAM technologies in the medical field, namely for the realization of special orthopedic devices for the sole [49]. The main idea of this chapter is to demonstrate and show the usefulness of CAD-CAM tools in the biomedical field regardless of the final product in this field, be it the prosthetic or orthotic field. For example, an injection system consisting of 2 semi-molds with the corresponding geometrical elements for shaping the soles in the Fusion 360 software [50] was designed (Fig. 7). By injecting/molding specific materials it may be possible to create orthopedic soles that will first of all be suitable for the shape of the foot respecting all geometric and anatomical peculiarities, can contribute to the correction of posture, providing additional support to the foot when supporting the weight of the body and a better blood circulation considering that it allows more space for mobility, thus reducing the problems of choosing inappropriate shoes and the resulting medical complications [49]. The semi-molds were modeled using CAM simulation methods being applied several subtractive manufacturing processes on a hypothetical CNC equipment.

a

b

c

d

e

f

Fig. 8. Computer Aided Manufacturing simulation sequences for injection molding system subtractive execution for orthopedic sole: a - the facing of the stock material; b - finished trajectories of the roughing and facing operation of the male part of the mold; c - finishing pass of the filet hat has to be place in the internal corners of the mold; d - female part of the centering cones is roughed and finished; e - pocket where half of the orthopedic sole will be molded is roughed out; f - tool path used to rough out and finish the male part of the centering cones.

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The generation of the code is done using special software packages, in our case we used Fusion360 manufacturing [50]. The programming starts with the selection of the stock material, and the fixing of the part. For an easier and safer implementation of the code most of the programs offer a simulation tool in which the user can check for collisions or other odd behaviors during the manufacturing process. Subtractive manufacturing, in our case milling of the mold, offers some great advantages like the strength of the metal, but also some disadvantages that come in the form of special criteria’s that must be meet in order for the mold be the within the tolerance spec, like the fact that all the internal corners have to be in the form of a filet. These limitations create a more cumbersome process, that requires multiple tool changes and especially designed parts. Figure 8 illustrate simulation sequences for injection moulding system subtractive execution for orthopaedic sole [50]. This method of approach above and the CAM tool for simulating manufacturing processes is extremely useful for choosing an optimal and efficient manufacturing cycle and for identifying any problems that may arise before the actual processing. And obviously, after simulating the manufacturing process in the CAM environment, the G code can be generated and transmitted to the CNC equipment with the tool path, the cutting regimes and other processing parameters.

Fig. 9. Additively manufactured injection molding system for realization of orthopedic soles.

The injection system for the application described above can also be achieved by an alternative method using additive manufacturing methods. In Fig. 9 it can be identified the two injection semi-molds designed for the orthopedic sole made by FDM technology on the Prusa i3 MK3 printer [47]. This method of processing using thermoplastic filaments and relatively affordable work equipment to realize molds prototypes is much more attractive from a financial point of view than subtractive technologies, but more fits for the testing and prototyping part of the products [42], for the final structures of molds can be applied metal additive manufacturing [51], being competitive from almost all points of view with subtractive technologies.

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4 Processing Technologies for Medical Field – Microscale Perspective Obtaining microstructures and microcomponents from the composition of medical devices differs entirely from macroscale applications in terms of specific technologies and methods, but also of the materials used. First of all, the central element is represented by the substrate, usually a semiconductor material of monocrystalline nature (most of the time silicon) that goes through several mechanical-chemical processing and superfinishing to become optimal from all points of view for the configuration of the following operations. After this follows various specific microtechnological operations depending on the final goal, so the lithography that refers to the 2D or 3D configuration of the masks for selective protection at subtractive etching processes or for configuring the relief for additive operations of thin layer deposition, the actual processes of chemical etching and the processes of thin layer deposition [52].

Fig. 10. Main microscale technologies that can be applied for obtaining of microstructures/microdevices for biomedical purposes.

Figure 10 [52] presents the main 4 groups of technologies that can be applied for the realization of microstructures/microdevices with applications in the medical field. The first category of technologies refers to the processing of silicon substrate with a unique and uninterrupted crystal lattice. This monocrystalline material differs from other forms of silicon and possesses unique properties such as anisotropy and selectivity, which are very important aspects for microprocessing operations on this scale. Monocrystalline silicon is obtained in several stages, from silicon dioxide, metallurgical silicon, polycrystalline silicon and from it is obtained by specific procedures, most often by the Czochralski method – obtaining an ingot made of monocrystalline silicon growth from the melt. After cutting the ingot into wafers, several finishing operations and mechanicalchemical processing follow, as the lapping, etching or mechanical-chemical polishing, so that to correspond to the strict conditions of purity and to mechanical-physical properties for the following processes.

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Lithographic processes [53–55] have the role of transmitting geometrical aspects from a mask to a substrate with a small thickness (resist) that is sensitive to a certain type of radiation and covers the surface of the wafer. Depending on the type of radiation it can be distinguished optical lithographic processes – photolithography with sensitivity to UV radiation, electron beam lithography or X-ray lithography or roentgenolitography each with its advantages and disadvantages and are chosen depending on the nature of the sensitive material and the final purpose being related to resolution and / or efficiency [52]. The lithography is most often applied together with the chemical etching processes and makes way for the next operations necessary for the realization of the microstructures, as the deposition of specific oxides or deposition processes for metallic/non-metallic materials [52]. Etching processes [56] can be divided into 2 categories – wet and dry. The wet one refers to the use of special chemical solutions (specific for a certain material) to remove/dissolve the material of interest with a certain attack speed dependent on several parameters (temperature, agitation and recirculation level, etc.) or in transformation into a soluble compound, which can be dissolved in the etching solution. The disadvantages of wet etching such as the often-isotropic character, the possible contamination of the substrate or the limited accuracy have led to the development and increasing use of dry etching that is based on some active elements of the plasma that is generated by an electrical discharge into a gas at low pressure. These methods involve the conversion of the material that is intended to be removed into a volatile compound, the physical removal of the material by means of special particles or are based on the action of destroying the surface by ion bombardment, followed by the chemical elimination of the material. The costs are much higher in the case of dry etching, this being used when it is important to obtain deep anisotropic etches with high accuracy, and the wet one when high processing speeds and financial efficiency are to be achieved [52]. Deposition processes [57, 62] mean obtaining a layer of thin material that is different in properties from the substrate on which it is deposited. The choice of deposition technology depends on the properties of the thin layer, the maximum temperature that the substrate can withstand and the compatibility of the process with the processes applied to the substrate before and after deposition. The deposition methods are divided according to the way in which the thin layer is formed, namely the physical methods – vacuum thermal evaporation in being one of the most representative methods in this category, chemical methods from solutions – galvanic deposition and autocatalytic deposits without current and chemical methods from the vapor phase – thermal oxidation and thermal diffusion [52]. More details and characteristics on the deposition methods can be found in the papers [58–62]. For the realization of the MEMS and Bio-MEMS structures, 3 main categories of microtechnological approaches can be distinguished [27, 52, 63]. The first refers to bulk micromachining [52, 64], which is based on wet and/or dry etching and can be obtained various cavities with different complex configurations directly from the silicon wafer. In the case of this technique, crystalline orientation is essential, and the properties of selectivity and anisotropy intervene. The second technique - surface micromachining [52, 65] is based on the three technologies in the processing of microstructures – lithography, thin film deposition and etching and is based on the deposition and configuration of layers

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whose profile in space or plan represents the negative of some spaces necessary to obtain the microstructures and which at the end of the technological flow will be removed by etching. This method is also called the technique of the sacrificial layer. The third technique is the LIGA process [52, 66], and which is used to make metal/polymeric structures with a high ratio between height and size in the plane and incorporates three successive technologies: lithography, galvanic deposition and modelling/injection moulding [52]. An example of an actuation device that can be used in MEMS structures are thermal microactuators, and the exemplification of its manufacturing process is described in the paper [67]. A combination of several such devices can form, for example, a microgripper that can be applied in the medical field for manipulating human red blood cells [68]. Other examples of microdevices can be used in the medical field are various sensors or special geometrical microstructures [63, 69–73].

5 Analysis Methods for the Characterization of Biomodels/Bioprostheses In order to evaluate and validate the conformity of medical prosthetic/orthotic devices, several methods and techniques are used depending on their final purpose. Depending on the resulting characteristics, additional post-processing technologies can be applied for product optimization. For example, macroscopic and especially microscopic evaluation are very important for the surfaces of prostheses to identify the quality of the technological operations performed to find certain surface defects, all of which contribute decisively to the mechanical properties over time of the prosthesis [31, 36].

a

b

Fig. 11. Microscopical images obtained for dental prosthesis obtained by SLM process: a – prosthesis in raw state; b – prosthesis preliminarily finished.

In Fig. 11 are presented microscopic images of prosthetic dental structures made by SLM additive manufacturing in the initial state and after applying a finishing operation, where it can be seen the major differences between the two surfaces. In the case of the surface of the raw prosthesis, in addition to the inadequate state of the surfaces, one can also observe particles of raw material (metal powder) remaining, and in the case of the surface of the finished prosthesis, a substantial improvement of the state of the surfaces can be observed, but which its turn can also be optimized through additional

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mechanical processing - for example polishing. The roughness of the dental prosthesis surfaces is very important from a biomedical point of view, but also from the point of view of mechanical properties. First of all, various microbial or microorganism species adhere more easily to rougher surfaces and can give rise to more local complications or even at the level of the entire body. Secondly, surface defects or cracks resulting from previous improper processing can contribute to the decrease of important mechanical characteristics or even the need for replacement of the prosthesis. From these points of view, compliant post-processing is absolutely necessary for the proper functioning of medical prostheses [31]. Also, tests can be used to evaluate the mechanical properties (strength for mechanical loads, hardness, wear and fatigue resistance etc.) for the materials used to obtain the structures of interest and to evaluate other important characteristics as micro- and nano-roughness determinations using advanced equipment and methods, tests regarding dimensional accuracy, tests regarding the chemical compositional analysis or tests regarding the biocompatibility of the materials for analyze the conformity and validation of the elements realized [31, 74–77].

6 Conclusions The manufacturing domain is in a continuous development, in such ways that now, the classical procedures are being adapted so that they can create more organic shapes or even more complex ones like the anatomically shaped geometries and having more and more applications in the biomedical field presented in this paper. Unfortunately, the cost of these machines and the time it takes using conventional methods is high, so especially for medical purposes, new technologies that involving also CAM are being developed to optimise the production processes, showing in this paper the usefulness of digital manufacturing simulation methods. For these types of use cases the conventional subtractive method it’s slow and tedious, the cavities it can create are limited in shape and size. The alternative, additive manufacturing methods, are a lot more versatile in the shapes that they can produce but, especially for parts with a biocompatibility requirement, the problem is the post processing operations that must be done properly for the parts to be used in medical applications. On the other hand, the AM is a powerful tool for prototyping of medical devices, from validating the fitment of future prosthetics design, to studying and creating physical models of the organs with pathologies. For the validation of parts resulted from these types of procedures, it’s absolute necessary to analyse the surface characteristics and other mechanical properties of the structure, to avoid problems of a medical or mechanical nature. Some examples of these experimental investigations were presented in the paper – microscopic samples of dental prostheses executed by metal additive manufacturing in different conditions of processing. Even though AM process at macroscale is more suitable for the manufacturing of medical devices due to the complex and unique/customised geometry it can create, the applicability of such technology can go well beyond just the limitations that it currently faces, reducing the need for multiple post processing operations, maybe even eliminating the need for them, and lowering the price per unit for production series.

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At the microscale, the paper presented the main processing technologies used in this field to create a microstructure for medical purposes or Bio-MEMS, in which totally different approaches and physical principles meet for their realization. Important progress has been made in recent years in the realization of medical devices both on a microand macroscale, and in the future very probably these two areas will merge and work together to solve complex tasks for the biomedical field and help the entire humanity with new technical-scientific-medical solutions for improving and prolonging life. Acknowledgements. This work has been funded by the European Social Fund from the Sectorial Operational Programme Human Capital 2014–2020, through the Financial Agreement with the title “Training of PhD students and postdoctoral researchers in order to acquire applied research skills - SMART”, Contract no. 13530/16.06.2022 - SMIS code: 153734.

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Complex Determination of the Parameters of Structural Transformations of Polymer Composite Materials Taking into Account the Activation Energy N. Moskovska(B) National Aerospace University “Kharkiv Aviation Institute”, Kharkiv 61085, Ukraine [email protected]

Abstract. A complex determination of the parameters of structural transformations of polymer composite materials associated with a change in the viscosity of the compound by taking into account the influence of the activation energy is considered in the article. Two main stages of the manufacture of polymer composite structures from thermosets were considered, namely the manufacture of prepregs and polymerization. In the first case, the change in the viscosity of the compound solution is considered as a function of the activation energy under the combined physical and chemical effects on it (vibration, the effect of solvents and complex additives). When considering the stage of polymerization, an analysis was made of the change in the characteristics of the polymer melt depending on the temperature and time of the process. The graphic interpretation of the Arenius equation, obtained during the study, confirmed the possibility of using the activation energy as an estimation parameter, which makes it possible to comprehensively influence the polymer system. An assumption is made about the possibility of a comprehensive assessment of all types of impact on the polymer system, similar to the options proposed in the article, which will allow solving the problems of choosing diverse parameters by standard optimization methods. Keywords: Polymer Composite Material · Activation Energy · Energy Efficiency · Viscosity · Compound · Complex Additives

1 Introduction Polymer composite materials (PCM) are one of the most promising options for the introduction of modern technologies in the design and manufacture of aircraft. The numerous advantages of using such materials in this industry have been repeatedly considered in a number of works [1, 2], including materials with natural fillers [3, 4]. Expansion of the range of PCM use in structures is also typical for other industries involved in the production of vehicles [5, 6]. Compliance with the specified technical and operational requirements for the designs of aircraft (AC) made of polymer composite materials is largely ensured by the technology of their manufacture. The disadvantage of most of the early works devoted to © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 363–373, 2023. https://doi.org/10.1007/978-3-031-40628-7_30

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the determination of technological parameters of processes associated with the structural transformation of polymeric materials was the basing of their main provisions on experimental data obtained empirically. Modern works, in which the development of the theoretical foundations of manufacturing technologies for PCM products has been carried out, can be conditionally divided into three groups, formed according to the fundamental differences of the approaches used in them, namely, chemical, physical and chemical-physical.

2 Literature Review The methods of formation of technological processes based on the first two approaches are highly specialized and do not always allow reflecting the complete picture of the transformations taking place in the PCM when one or another type of targeted impact is applied to it. Therefore, the most promising and interesting is the third approach, which allows one to describe the chemistry of processes by physical methods and to determine, using the activation energy, the parameters of technological processes for the manufacture of composite structures. The possibility of using a similar technique called Advanced Isoconversional kinetic analysis as applied not only to chemical reactions, but also to physical transformations was considered in [7]. The use of activation energy as an "intermediate link" in determining the effect of force and (or) chemical action on the characteristics of a polymer binder gives the technology developer a number of additional advantages. First of all, they should include the possibility of considering practically all stages of manufacturing structures from PCM as a single process. The greatest difficulty in assessing the real physical meaning of the effective activation energy is its belonging to the kinetic parameters of complex reactions. A solution to this problem was proposed in [8], where it is proposed to use isoconversional methods that are effective both in the case of an unknown reaction mechanism and in the case of complex reactions involving several parallel or sequential stages (their combinations). This approach makes it possible to avoid intermediate calculations to determine the residual phenomena in the material between subsequent operations, which at this stage of development is a necessary condition for ensuring the quality of the product. These methods are also applicable for large variations in viscosity, which is typical for physical transitions of polymers during polymerization. It is equally important that when considering individual technological processes associated with structural changes in polymer compositions, it becomes possible to comprehensively assess all types of impact, which will allow solving the problems of choosing various parameters by standard optimization methods (for example, minimizing the cost level while ensuring a given level of viscosity of a binder or a given degree of polymerization). It is equally important that when considering individual technological processes associated with structural changes in polymer compositions, it becomes possible to comprehensively assess all types of impact, which will allow solving the problems of choosing various parameters by standard optimization methods (for example, minimizing the cost level while ensuring a given level of viscosity of a polymer or a given degree of polymerization).

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3 Materials and Methods Structural transformations in polymer composite materials, as a rule, accompany technological operations associated with a change in polymer viscosity. Since the use of thermosetting plastics is typical for aerospace products, it is most expedient to consider two main stages in the manufacture of structures - the manufacture of prepregs and curing (polymerization). The main idea of the proposed approach is that all structural elements of the polymer (relaxers) with kinetic energy exceeding the activation energy corresponding to the ith state of the system (for example, the onset of glass transition, polymerization, etc.) will cross the potential barrier. Such a transition will lead to a transformation of the polymer structure both in the melt (during polymerization) and in solution (during the manufacture of the impregnating compound). The basic form of the basic rate equation or the Arenius equation, which determines the reaction rate constant, is usually written as [9]:  ε  f (a) (1) v = A exp − RT A – viscometer constant, T – the temperature, f (a) – the differential form of the mathematical function that describe the reaction model that represents the reaction mechanism, ε – the activation energy, R – universal gas constant. As can be seen from this equation, the determining values of any reaction are the temperature and activation energy, and an increase in the level of activation energy is associated, as a rule, only with an increase in temperature. However, in addition to temperature, there are a number of physical effects that can affect the parameters of the polymer. This work is devoted to assessing the likelihood of their impact. The viscosity of the polymer was determined experimentally by the viscometric method, the result of which is to obtain the solution flow time: μ = Btf ρ

(2)

B – the pre-exponential factor, tf – solution flow time, ρ – density at test temperature. The study of the viscosity properties of polymer compounds was carried out with a viscometer using capillaries of the following diameter: 5211-B + L - 1.16 mm, ENFB + L - 1.52 mm, LBS-4 + L - 2.10 mm. In order to determine the degree of polymerization of polymers, the resistivity of fully cured samples and also samples at the initial moment of time and at the studied moment of time were measured.

4 Results and Discussion The main parameter characterizing the properties of the compound is its technological viscosity. Most often, the required viscosity level is achieved by diluting the compound to a working consistency. However, there are a number of other methods to achieve a change in the viscosity of the polymer binder. As indicated in [10], a single vibration

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action allows one to reduce the viscosity of the binder due to the reversible destruction of a certain type of structural bonds. Moreover, according to the experimental results given in [11], the viscosity of the polymer melt decreases with an increase in the frequency and amplitude of vibration. The use of vibration makes it possible to significantly reduce the consumption of expensive solvents and improve the conditions for safe life. A change in the parameters of the compound is observed when complex additives are introduced into its composition, which improve its manufacturability and improve the quality of finished products. Among other things, these methods of influencing viscosity can be combined with each other, as well as with heating. According to the transformed Eq. (1), the viscosity is determined by the formula for a homogeneous liquid:  ε  (3) μ = μ0 exp KT μ0 – viscosity at zero activation energy; K - Boltzmann’s constant. Obviously, the viscosity value at zero activation energy is equal to the resin viscosity μ0 = μr . The activation energy of the solution can be represented as the following sum: ε = εk + ε + εν

(4)

ε, εk , ε, εν − activation energies of solution, base compound, solvent and activation energy transferred to the polymer by exposure to vibration. Since the compound is a homogeneous mixture of resin or several resins with a solvent, we write down its activation energy in the following form: εk = εr + εp

(5)

εr – the activation energy of the resin (resin mixture). According to the accepted assumption that the activation energy of the resin is equal to zero in the entire temperature range of preparation of the solution and prepregs, and taking into account expression (5), formula (4) is transformed to the following form: ε = ε(1 + C0 ) + εν

(6)

C0 − the content of the solvent in the initial compound. The activation energy of the solvent is found as: εp = KT ln

μp μr

(7)

μr , μp − resin viscosity and solvent viscosity at a given temperature T . The activation energy is the kinetic energy of the molecule. Thus, to determine it, it is necessary to find the value of the kinetic energy acquired by one polymer molecule as a result of the application of vibration to it: εν =

Kin N

(8)

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N − the number of molecules; Kin − changes in the internal kinetic energy. The internal energy of the body is equal to: E=

N 

E0N + Kin + Uin

(9)

i N  i

E0N − the sum of the rest energies of the particles; Kin − internal kinetic energy

of the body; Uin − potential energy of fields that carry out interaction between particles. N  As a first approximation, we will assume that E0N = const and Kin = const. Thus, i

we can assume that all the work of external forces goes to change the internal kinetic energy of the body: Aext = E = Kin

(10)

Therefore, Eq. (8), taking into account (10), can be transformed to the form: εν =

Aext N

(11)

Let us consider the vibration effect of a container with a solution as a harmonic vibration of the polymer solution itself. In this case, the work of external forces will be equal to the total energy of the harmonic vibration: Aext =

m2ν ω2 2

(12)

Aν − vibration amplitude; ω = 2π ν − angular (cyclic) frequency; ν − vibration frequency. Thus, formula (11) takes the form: εν =

m2ν ω2 2N

(13)

For verification, we use a formula that allows us to calculate the value of energy in an elementary volume. As an elementary volume dV , we take the volume of one polymer molecule VM , since it has a rather large size in comparison, for example, with a solvent molecule. Thus, the activation energy can be written as: dE = εν =

ρ 2 2 ρ Aν ω dV = A2ν ω2 VM = 2π 2 A2ν ν 2 ρVM 2 2

(14)

ρ − density. The number of molecules can be found using the following equation: N=

mNA mNA = M VMol ρ

(15)

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M − the mass of one mole of a substance; NA − Avogadro’s number; VMol − the volume of one mole of a substance. Taking into account (15), Eq. (13) can be transformed to the following form: εν =

2π 2 A2ν ν 2 ρVMol NA

(16)

Equating the right-hand sides of expressions (16) and (14) and making the appropriate transformations, we obtain an expression known from molecular physics: VMol NA

VM =

(17)

Thus, our expression for finding the activation energy in the first approximation can be considered correct. In some cases, a situation may arise when a certain difficulty is caused by finding the number of molecules N . This is primarily due to the peculiarity of the chemical structure of polymers (the ability to form both linear and branched molecular chains of different lengths and, therefore, different mass and volume). In addition to the above, it should be remembered that a polymer solution usually contains molecules of various degrees of polymerization (DP). Therefore, the mass of one mole of the binder M in formula (15) can be determined as follows: M = Mn NA Mn − the number average molecular weight. The Mn value is determined as follows:  Mn = φi Mi

(18)

(19)

i

φi − distribution function of molecules according to the degree of polymerization; Mi − molecular weight at DP equal to ni . Any polymer solution can be characterized by the propagation function φi : φi =

NDPni N

(20)

NDPni − the number of molecules of the degree of polymerization ni . In highly dilute solutions (where the polymer molecules are far apart from each other), the value Mn can be obtained from experiments on measuring the osmotic pressure. Thus, knowing the values φi and NDPni determined experimentally or by calculation for the molecules of one of the DP, we can find the total number of molecules. Substituting expressions (7) and (13) into formula (6), we obtain an equation for calculating the activation energy: ε = (1 + C0 )KT ln

μp mA2ν ω2 + μr 2N

(21)

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Substituting the calculated value of the activation energy from (21) into (3), we obtain the final expression for determining the viscosity of a polymer solution under complex action on it. Experimental tracking of the change in viscosity was carried out by adding rhenium oxochloride dichlorohydroxofurfurylideneamino 1,3,4-triazolate rhenium to the LBC4, ENFB, BFOS solution, for 5211-B - 1-furfurylideneamino - 1–3-4-triazole (I) - 1, 0%, which led to a decrease in the dynamic viscosity of the binders with practically no change in its density (Table 1). Table 1. Viscosity of compounds for PCM products. N

Type of compound

Standard composition

Composition with additive complex

tf , sec

ρ, g/cm3

tf , sec

ρ, g/cm3

1

5211-B

171.85

0.990

152.41

0.990

2

ENFB

177.63

1.03

145.57

1.03

3

BFOS

205.99

0.897

196.21

0.895

4

LBS

216.92

1.036

178

1.033

As is known, the behavior of polymers is largely determined by their relaxation properties. Therefore, assuming that in the initial state the compound is a solution of a certain monomer, we can assume that the standard equation describing the decrease in the number of structural elements when conditions change (for example, when they are “crosslinked” into a polymer), and its solution is also valid when the energy changes activating the binder. A necessary condition for this is the linearity of the dependence of the measured parameter of the system, for example, the most interesting technologists, the viscosity of the binder or the degree of polymerization on the number of structural elements that have passed into the state corresponding to the new value of the activation energy. An abnormal situation is understood as the state of the PSS components that is not provided for by the regular operation program. An emergency can have two types: non-dangerous and dangerous. The solution of this problem for real conditions is possible only with the introduction of an artificial time limit, and we can take t ∈ [0, tlim ], where tlim = ∞ is a certain value of the time at which the characteristics of the polymer can be considered unchanged for the state reached by it at a new value of its activation energy. Thus, when considering the physical and chemical components of the process, the latter is taken to be zero for tlim . Most of the works in this direction are based on experimental data; therefore, the methods of theoretical calculation of the change in viscosity in the process of molding products from PCM are practically absent at present. True viscosity is the sum of physical and chemical viscosities: μ = μph + μch

(22)

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μph − physical component of viscosity; μch − viscosity, depending on the degree of chemical transformation. For most of the polymer compositions, the viscosity value can be determined by the Boucher dependence: μ = Mω3.4

(23)

Mω − average molecular weight. Mω =



ωi Mi =

i

 MDPni i

M

Mi

(24)

ωi − the distribution function of molecules of various degrees of polymerization by weight; Mi − molecular weight at a degree of polymerization equal to ni ; M − total mass of molecules; MDPni the mass of molecules of the degree of polymerization ni . Let us assume that all molecules are in the same degree of polymerization (i = 1). In this case (23) takes the form: μ = (P · MP )3.4

(25)

DPn − degree of polymerization; MP − the mass of the molecule in the degree P = MM of polymerization P. The value MP is a constant value for each type of polymer to a certain degree of polymerization and can be considered a known value. The degree of polymerization can be determined on the basis of experimental data according to:

P=

lg ρτ − lg ρ0 lg ρ∞ − lg ρ0

(26)

ρ∞ , ρ0 , ρτ − the resistivity of fully cured samples and also samples at the initial moment of time and at the given moment of time. Let us consider the behavior of the system using the example of the binder 5211 - B + 1.0% 1-furfurylideneamino - 1, 3, 4-triazole. The dependence of the resistivity of the binder 5211-B with the addition on the temperature and time of the experiment when the sample is heated at a rate of 2.5 o C is presented in Table 2. From the analysis of the curve given in Table 2 (see Fig. 1), it is clear that both the decrease in viscosity upon heating (physical viscosity) and the increase in viscosity due to the occurrence of polymerization or polycondensation processes (chemical viscosity) are already taken into account in it. Thus, the polymerization process can be represented as a “black box”, at the entrance to which there are process parameters (time, temperature), and at the exit - the properties of PCM. Graphical interpretation of Eq. (26) is shown in Fig. 2. From Table 3 it is obvious that the upper point of the graph corresponds to the minimum value of the sample viscosity. The presence of negative values of the degree of polymerization can be explained by the specifics of the method of experimental data acquisition.

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Table 2. Dependence of the resistivity of 5211-B with the addition on the temperature and time of the experiment when the sample is heated at a rate of 2.5 o C / min. t,o C

20

32

45

58

70

83

95

108

120

132

145

150

τ, min

0

5

10

15

20

25

30

35

40

45

50

55−95

ρτ 10−3 -

31

43

56

80

92

71

57

39

23

12

8.4

6.5–0.35

0.10

0.08

1/R

0.06

0.04

0.02

0.00 0

20

40

60

80

100

120

140

160

t

Fig. 1. Graph of the dependence of the resistivity of 5211-B with the addition on the temperature and time of the experiment when the sample is heated at a rate of 2.5 o C / min.

Table 3. Dependence of the flow time of the compound on the process temperature t,o C

20

25

30

35

40

45

50

60

65

70

75

tf , sec 152.41 130.87 96.50 79.75 71.45 64.70 58.22 45.16 39.49 39.40 50.02

In the course of the experiment, both the polymerization process and the reverse process of the disintegration of molecules are recorded. Thus, it will be correct to represent the value determined by expression (25) as the following sum: P = Pp + Pr

(27)

Pp − degree of polymerization; Pr − the degree of destruction of molecules. Based on the foregoing, the following values can be matched: P → μ, Pp → μch , Γr → μph

(28)

Consequently, negative values mean that the growth rate of the number of associates in the polymer (foci of combining monomeric molecules into polymeric ones) is less than the rate of detachment of polymolecule units from each other, which occurs due to an increase in their internal energy upon heating. For the system under consideration, the equality of the rates of these two processes occurs when the sample reaches a temperature of 70 o C, after which the polymerization process begins to prevail until a certain constant value corresponding to the finished product is reached. The maximum value of the degree of polymerization depends on the type of binder and the method of curing. Cold-curing polymers (P ≈ 0.7) have the minimum value,

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Fig. 2. Degree of polymerization plot 5211-B + L on its resistivity.

and hot-curing polymers with additional additional polymerization by radiation methods (Γ ≈ 0.92) have the maximum value. Analytically, the dependence given by Table 2 can be described by a fifth-degree polynomial in the following form: ρ(t) = c5 t 5 + c4 t 4 + c3 t 3 + c2 t 2 + c1 t + c0

(29)

Unknown constants are determined based on the least squares method so that the sum took the smallest value: S=

n 

(c5 t 5 + c4 t 4 + c3 t 3 + c2 t 2 + c1 t + c0 − ρτ i )

(30)

i=1

For this it is necessary to solve a system of equations of the form (for i = 1...5): ∂S =0 ∂ci

(31)

Taking into account expressions (29), (25), (26), the equation expressing the dependence of viscosity on time takes the form: μ=(

lg(a5 τ 5 + a4 τ 4 + a3 τ 3 + a2 τ 2 + a1 τ + a0 ) − lg ρ0 MP (τ ))3.4 lg ρ∞ − lg ρ0

(32)

ai = ci W , W - sample heating rate.

5 Conclusion 1. A new approach to the calculation of viscosity parameters for polymer solutions and their melts, based on a comprehensive assessment of experimental data and their agreement with theory, is proposed. It is based on the need to fulfill the following conditions: – the fastest possible achievement of the minimum viscosity;

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– dividing the process into chemical and physical components, which make it possible to assess the degree of polymerization of the binder molecules and the degree of their destruction. 2. The graph shown in Fig. 1 is a classic reflection of the graphical interpretation of the Arenius equation, which allows us to conclude that the theoretical method for determining the change in polymer viscosity during complex action on it during polymerization can also be implemented through the activation energy. 3. The point of transition of a polymer from a liquid to a glassy state corresponds to its minimum viscosity, which was determined from the results of measuring the flow rate as a function of the process temperature. 4. At this stage of the study, a similar calculation method can be used only for onestage processes, since the process of decreasing viscosity is observed even without subsequent heating.

6 Legend PCM – Polymer composite materials; AC – aircraft AC; DP – degree of polymerization.

References 1. Baker, A.A., Scott, M.L.: Composite Materials for Aircraft Structures, 3rd edn. American Institute of Aeronautics and Astronautics, Inc., Reston (2016) 2. Zolkin, A.L., Galanskiy, S.A., Kuzmin, A.M.: Perspectives for use of composite and polymer materials in aircraft construction. In: IOP Conference Series: Materials Science and Engineering, (2020) 3. Balakrishnan, P., John, M.J., Pothen, L., Sreekala, M.S., Thomas, S.: Natural fibre and polymer matrix composites and their applications in aerospace engineering. In: Advanced Composite Materials for Aerospace Engineering Processing, Properties and Applications. Elsevier (2016) 4. Fan, M., Weclawski, B.: Advanced High Strength Natural Fibre Composites in Construction. Woodhead Publishing (2016) 5. Prashantha Kumar, H.G., Anthony Xavior, M.: Composite Materials Production for Automobile Applications. In: Reference Module in Materials Science and Materials Engineering. Elsevier (2021) 6. Zweben, C.H., Beaumont, P.: Comprehensive Composite Materials, 2nd Edn. Elsevier (2017) 7. Sbirrazzuoli, N.: Advanced Isoconversional kinetic analysis for the elucidation of complex reaction mechanisms: A new method for the identification of rate-limiting steps. Molecules 24, 1683–1699 (2019) 8. Sbirrazzuoli, N.: Interpretation and physical meaning of kinetic parameters obtained from isoconversional kinetic analysis of polymers. Polymers 12(6), 1206–1280 (2020) 9. Vyazovkin, S., Sbirrazzuoli, N.: Isoconversional kinetic analysis of thermally stimulated processes in polymers. Macromol. Rapid Commun. 27, 1515–1532 (2006) 10. Ibar, J.P.: Control of polymer properties by melt vibration technology: A review. Soc/ Plastics Eng. 38, 1–20 (2004) 11. Yan, Z., Shen, K.Z., Zhang, J., Chen, L.M., Zhou, C.: Effect of vibration on rheology of polymer melt. Appli. Polymer Sci. 85, 1587–1592 (2002)

Modelling and Simulation of Some Mechatronics Assembly Realized on Arduino Uno Board, Through the Tinkercad Application Iulian Sorin Munteanu1(B) , Liviu Marian Ungureanu1 , Cosmina-Constantina Caraiman1 , Ramona-Gabriela Cris, an1 , Elisabeta Niculae1 , and Badea Sorin2 1 Organization Polytechnic University of Bucharest – UPB, Bucharest, Romania

{iulian.munteanu0306,liviu.ungureanu}@upb.ro 2 National Institute of Research and Development in Mechatronics and Measurement

Technique - INCDMTM, Bucharest, Romania

Abstract. The authors aimed to model and simulate two mechatronic assemblies by means of the TINKERCAD virtual application. In order to model and simulate the two mechatronic assemblies with the ARDUINO UNO board, the optimal electronic components needed for the assemblies were chosen, they were assembled virtually, and the programming codes necessary for the proper functioning of the assemblies were written. The objective solved by modelling and simulation with the TINKERCAD application consisted in the realization of two widely used mechatronic assemblies: applications for agricultural greenhouses, in the automotive industry, and in related fields. Keywords: Mechatronic models · Modelling and simulation in TINKERCAD · Programming in TINKERCAD

1 Introduction This scientific work presents the approach and staged work with the virtual application TINKERCAD [1], to achieve the modelling and simulation of high-performance mechatronic assemblies, capable of being easily adapted to different uses specific to the consumer goods category, like applications for agricultural greenhouses or in the automotive industry, or in related fields. Realization of modelling and simulation involves: determining the components needed for assembly, assembling them, writing operating codes in C + + programming language, as well as observing and analyzing how the components chosen for assembly interact and respond to commands. The authors proposed the creation of a first mechatronic assembly designed to measure the temperature on three distinct intervals and display it as an absolute value on a 16 × 2 LCD screen, as well as a visual warning by lighting one of the three colored LEDs in different colors, depending of the temperature range indicated as critical. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 374–384, 2023. https://doi.org/10.1007/978-3-031-40628-7_31

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The authors also proposed the creation of another mechatronic assembly intended to measure the distance by displaying it on a 16 × 2 LCD screen, as well as warning of critical values, both visually by lighting up some LEDs and acoustically by emitting some sounds from a buzzer.

2 Modelling and Simulation of Mechatronic Assemblies in TINKERCAD In order to make the two mechatronic assemblies, several electronic components are used, such as: Arduino Uno board, BreadBoard, LEDs, potentiometers, TMP36 temperature sensor, resistors, connection cables, 16 × 2 LCD screen, power cable, buzzer, ultrasonic sensor. [1]. The Arduino Uno board, shown in Fig. 1, is an open-source processing platform based on flexible and easy-to-use software and hardware. In the lower right part of the Arduino Uno board are the analog pins (A0… A5), and in the upper part we find the digital pins (0… 13). Grounding (GND) is found in three places on the board, namely: one at the top and two at the bottom. The power supply is of three types: 3.3 V, 5 V and Vin, where an external battery (7 − 12 V) can be connected. Codes for circuit operation are read by the ATMEGA 328P PU.

Fig. 1. The Arduino Uno board is already realistically modeled in the components base (Components Basic) of the TINKERCAD application, along with various other electronic components.

The BreadBoard is necessary to make circuits or assemblies without soldering the electronic components. The connections between the components placed on the BreadBoard are made through the ends of the metal plate. These metallic ends (mains) are oriented horizontally in the edges of the BreadBoard for powering at «-» and « +» and vertically in the rest for the introduction of electrical elements, and in the middle there is a horizontal delimitation called the separator zone (Fig. 2). Another important component used is the 16x2 LCD screen, shown in Fig. 3, which is controlled electronically by a numeric and alphabetic character decoder. It can display a text consisting of 32 characters, 16 on each of the two available lines. Liquid crystals are substances that have common properties of two states of aggregation, liquid and solid. The molecules that make up this liquid are arranged in the same way as crystals.

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Fig. 2. The BreadBoard element view from the components base of the TINKERCAD application.

These crystals have the property of being controlled by electrical voltage, so that they order their molecules from a “transparent” state to a “non-transparent” state. It is an electric polarization of some liquid molecules which, in contrast to the rest of the “field”, forms a visible image. In other words, the crystals will allow light to pass through or block it, causing the pixels to render the right colors and compose the image we see on the LCD screen (16 × 2).

Fig. 3. LCD screen (16 × 2) view from the components base of the TINKERCAD application.

The potentiometer, illustrated in Fig. 4, is an analog, passive device used to change the value of resistance or voltage in the range of 0–5 V in a circuit. The voltages correspond to digital values of a range 0–1023, directly proportional to the applied voltage. It has 3 pins: the first is for GND, the second is for connecting to the A0 output, and the third is for the 5 V value.

Fig. 4. The view of a potentiometer from the components base of the TINKERCAD application.

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The analog temperature sensor, Fig. 5, it generates the signal according to the ambient temperature. It outputs a voltage that is directly proportional to the temperature in degrees Celsius. It works with a supply voltage of 2.7 … 5.5 V. Its operating range is from −40 0 C to + 125 0 C. The sensor connects to the Arduino Uno board like this: we orient the sensor with the convex part we hope and the left pin connects to 5 V, the middle pin to an analog pin, and the right pin to GND.

Fig. 5. The view of temperature sensor TMP36 from the TINKERCAD components base.

LEDs are semiconducting diodes that emit light when polarized directly and that have pins of different lengths, the long one is called the anode (+) and the short one is called the cathode (-). The value of the current used to light a LED is 20 mA (forward bias). An LED connects to the Arduino Uno board like this: the left pin (right pin) connects to GND and the right pin (bent pin) connects to a 220  resistor and the latter connects to a digital pin. The RGB LED has four legs as seen in the picture, but it can also have two. The RGB LED changes color successively in red-green-blue when connected to a battery. At maximum intensity (255) it displays the color white, and at minimum intensity (0) it displays the color black. By combining LOW (0) and HIGH (1… 255) we can get any color (Fig. 6).

Fig. 6. LEDs view from the TINKERCAD components base.

Connection wires, Fig. 7, are wires that connect the BreadBoard to the Arduino Uno board and mediate connections between the electrical elements assembled on the BreadBoard (with the « +» and «-» areas). These can be of three types: male-male wires, female-male wires and female-female wires. Figure 8 shows the power cable that connects the Arduino Uno board to the computer or laptop, for supplying voltage to the Arduino UNO board and the components mounted on it.

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Fig. 7. Connection wires view from the TINKERCAD components base.

Fig. 8. Power cable view from the TINKERCAD components base.

For the two mechatronic applications, resistors with a value of 220  are also used, which have the role of limiting the electric current, i.e. controlling its value, protecting the components to which the resistors are inserted. To calculate the value of a resistor you need the color code and the knowledge of the meanings of the lines on the resistor, so: the first 2 lines represent the value of the resistor, the third represents the multiplier and the last represents the tolerance. The correct reading of a resistor’s value is from left to right and never the gold line nor the silver line will be first (these colors are specific to the meaning of tolerance) (Fig. 9).

Fig. 9. Resistor view from the TINKERCAD components base.

The buzzer, illustrated in Fig. 10, is a device that uses the piezoelectric effect to measure changes in pressure, acceleration, strain, or force by converting them into an electrical charge. The principle of operation is that the alternating audio frequency voltage is applied to the armatures of the piezoelectric element. The element begins to oscillate mechanically at the same frequency. The oscillations are transmitted to the membrane rigidly attached to the piezoelectric element, which produces sound vibrations. The HC-SR04 ultrasonic sensor is a sensor used to measure distance or detect objects. It emits ultrasound at a frequency of 40,000 Hz that travels through the air, and if it encounters an obstacle, it will return back to the module, thus considering the speed of sound, the distance to the object can be calculated (Fig. 11). The first part of the mechatronic application refers to the realization of the mechatronic assembly that measures the temperature, displays it on the 16 × 2 LCD screen

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Fig. 10. Buzzer view from the TINKERCAD components base.

Fig. 11. Ultrasonic sensor HC-SR04 view from the TINKERCAD components base.

and produces a light signal by means of one of the three mounted LEDs according to the temperature range in which the detected value is located. This assembly can be used in different fields of activity, such as: for domestic use, in agriculture (greenhouses), in industry - thermal plants, cars, etc. [2]. Figure 12 shows the realization by modeling in the specialized software application TINKERCAD of the mechatronic assembly intended for temperature measurement and its display on a 16 × 2 LCD screen, with the facility of visual warning of critical temperature ranges (by connecting and assembling the electronic components necessary for the optimal operation of first application).

Fig. 12. Realization of the first mechatronic assembly, by connecting and assembling specific components.

The operating mode of the application developed for the first mechatronic assembly (Fig. 12) is as follows: the TMP36 temperature sensor, which can measure in the range

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−40ºC … + 125ºC, will transmit the detected temperature to the 16x2 LCD screen and, depending on its value, we have the following situations: – the blue LED will light up, if the temperature (“Tmp”) falls within the temperature range –40 ºC to + 10º C = > corresponding to the warning: “COLD!”; – the green LED will light up, if Tmp falls within the temperature range + 11º C to + 30ºC = > corresponding to the warning: “MODERAT!”; – the red LED will light up, if Tmp falls within the temperature range + 31 º C to + 125º C = > corresponding to the warning: “HOT!”; As an example, Fig. 13 shows the three situations listed above, realized through the Simulation Module of the specialized software application TINKERCAD.

Fig. 13. Simulation of LED lighting and distinct displayed messages, according to the measured temperature for the first modeled mechatronic assembly.

The authors also developed a programming code in the TINKERCAD virtual software application, for sending messages on the Serial Monitor, for the three distinct temperature ranges, such as: “COLD!”, “MODERAT!” and “HOT!”, depending on the temperature indicated in real time by the specialized sensor on this mechatronic assembly (Fig. 14).

Fig. 14. Display of messages (here in Romanian) by the Serial Monitor of the temperature sensor

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In order for the LCD application intended for the first mechatronic assembly to work under the conditions presented above, the following developed programming code (in C + +) is needed: #include LiquidCrystal lcd(12,11,5,4,3,2); float value; int tmp = A0; int LED1 =7; int LED2 = 9; int LED3 = 10; const int FRIG = 10; const int CALD = 30; void setup() {pinMode(tmp,INPUT); pinMode(LED2, OUTPUT); pinMode(LED3, OUTPUT); Serial.begin(9600); Serial.println("Secvență nouă"); randomSeed(analogRead(A0));} void loop() {value analogRead(tmp)*0.004882814; value = (value - 0.5) * 100.0;

=

lcd.setCursor(0,1); lcd.print("Tmp:"); lcd.print(value); delay(1000); lcd.clear(); if (value < FRIG) {digitalWrite(LED1, HIGH); digitalWrite(LED2, LOW); digitalWrite(LED3, LOW); Serial.println("FRIG!"/ "COLD!");} else if (value > CALD) {digitalWrite(LED1, LOW); digitalWrite(LED2, LOW); digitalWrite(LED3, HIGH); Serial.println("CALD!"/"HOT!");} else {digitalWrite(LED1, LOW); digitalWrite(LED2, HIGH); digitalWrite(LED3, LOW);; Serial.println("MODERAT!" /"MODERAT!");}}

The second mechatronic application refers to the realization of the mechatronic assembly that measures the actual distance to an obstacle, displays it on a 16 × 2 LCD screen as an absolute value and at the same time warns, both visually, by lighting up some LEDs, and acoustically, by emitting sounds by a Buzzer reaching critical/dangerous distances. This montage can be used in various fields of activity, such as: in the industry - automotive, aeronautics, intelligent robots, etc. [3]. The Fig. 15 shows the realization by modeling (using an electronic diagram [1]) in the specialized software application TINKERCAD of the mechatronic assembly intended to measure the real distance to an obstacle by displaying it on a 16 × 2 LCD screen, with the facility of sound and acoustic warning of reaching some critical values (by connecting and assembling the necessary electronic components optimal functioning of the second mechatronic application). The operating mode of the application developed for the second mechatronic assembly (Fig. 15) is as follows: – the HC-SR04 type ultrasonic sensor transmits the measured distance to an obstacle to the 16x2 LCD screen, and depending on the value of this measured distance, we have the following situations: – the green LED lights up, if the distance (“Distance”) falls within the range from 400 cm to 50 cm;

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Fig. 15. Realization of the second mechatronic assembly by connecting and assembling specific components.

– the yellow LED lights up, if the distance falls within the range from 50 cm to 10 cm, and the buzzer emits a strong sound at a frequency of 500 Hz – for Danger warning! – the red LED lights up, if the measured value is equal to or less than 10 cm, and the Buzzer in this case emits a shrill sound at a frequency of 1000 Hz – High Danger warning! For example, they are represented in Fig. 16 the three situations listed above, realized through the Simulation Module of the specialized software application TINKERCAD.

Fig. 16. Simulation of the lighting of the LEDs and the distinct messages displayed, depending on the measured distance, for the second mechatronic assembly made by modelling

In order for the LCD application intended for the second mechatronic assembly to work under the conditions presented above, the following developed programming code is needed:

Modelling and Simulation of Some Mechatronics Assembly

#include LiquidCrystal lcd(12, 11, 5, 4, 3, 2); int red=6; int blue=7; int green=8; const int trigger = 9; const int echo = 13; int buzzer = 10; int distance; long duration; void setup() {Serial.begin (9600); pinMode (trigger, OUTPUT); pinMode (echo, INPUT); pinMode (buzzer, OUTPUT); lcd.begin(16, 2); pinMode(red, OUTPUT); pinMode(green, OUTPUT); pinMode(blue, OUTPUT);} void loop() {digitalWrite (trigger, LOW); delayMicroseconds (2); digitalWrite (trigger, HIGH); delayMicroseconds (10); digitalWrite(trigger, LOW); duration = pulseIn(echo, HIGH); distance = duration*0.034/2; if (distance 50) {digitalWrite(blue, LOW); digitalWrite(red, LOW); digitalWrite(green, HIGH); digitalWrite(buzzer, LOW);

383

noTone(buzzer); lcd.clear(); lcd.setCursor(0,0); lcd.println ("Distance="); lcd.print (distance); delay (500);} else {if (distance 10) {digitalWrite(blue, LOW); digitalWrite(red, HIGH); digitalWrite(green, HIGH); digitalWrite(buzzer, HIGH); tone(buzzer,500); lcd.clear(); lcd.setCursor(0,0); lcd.print("CLOSE "); lcd.setCursor(0,1); lcd.println ("Distance="); lcd.print (distance); delay (500);} else {if (distance K holds on the set of measure zero. Theorem 10. If the conditions of Theorem 7 and 8 are satisfied, then the function    x − xi+1  y − yj f (x, y) = (x − xi ) y − yj − xi − xi+1 yj+1 − yj turns inequality (1) into equality.

5 Computational Experiments and Comparison of Results To carry out computational experiments, the computer mathematics system MathCad was used. Suppose that the nodes of a triangular grid x1 = 0, x2 = 0.5, x3 = 1, y1 = 0, y2 = 0.5, y3 = 1 and function f (x, y) is defined in the region shown in Fig. 3a. T1 = {x − 0.5 > 0, y − 0.5 > 0, 1.5 − x − y > 0}, T2 = {−(x − 0.5) > 0, y − 0.5 > 0, 0.5 + x − y > 0}, T3 = {−(x − 0.5) > 0, −(y − 0.5) > 0, −0.5 + x + y > 0}, T4 = {x − 0.5 > 0, −(y − 0.5) > 0, 0.5 − x + y > 0}. We set the function (Fig. 3b) ⎧ ⎪ −y2 − x + 1.5 (x, y) ∈ T1 ⎪ ⎪ ⎪ ⎨ 2 2 (y − 1) + (x − 1) + 0.5, (x, y) ∈ T2 f (x, y) = . ⎪ 0.5, (x, y) ∈ T3 ⎪ ⎪ ⎪ ⎩ x − y, (x, y) ∈ T4

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Fig. 3. a) Domain of the required function f (x, y), b) Image of discontinuous function f (x, y).

Construct an interpolation spline S1(x, y) in the form of formula (1) in each considered triangular element. As elements of the matrix C we take the values of the function (left and right) in the nodes of the grid (in this case we consider them given). ⎛ (1) (1) (1) ⎞ ⎛ ⎞ C1 C2 C3 0.75 0 0.25 ⎜ (2) (2) (2) ⎟ ⎜ 1 0.75 1.75 ⎟ ⎜C C C ⎟ ⎟. C = ⎜ 1(3) 2(3) 3(3) ⎟ = ⎜ ⎝ C1 C2 C3 ⎠ ⎝ 0.5 0.5 0.5 ⎠ (4) (4) (4) 0 0.5 0.5 C1 C2 C3 After substituting the values of the matrix C in the formula (1), we obtain the following interpolation spline (Fig. 4a): ⎧ −x − 1.5y + 2, (x, y) ∈ T1 ; ⎪ ⎪ ⎪ ⎨ −1.5x − 0.5y+2, (x, y) ∈ T ; 2 S1(x, y) = ⎪ 0.5, (x, y) ∈ T3 ; ⎪ ⎪ ⎩ x − y, (x, y) ∈ T4 . The maximum deviation of the desired function f (x, y) from the constructed interpolation spline S1(x, y): max|f (x, y) − S1(x, y)| ≈ 0.13. Now we construct an approximation spline in the form of formula (1). The elements of the matrix C are found using the method of least squares, i.e. ⎛

⎞ 0.775 0.075 0.275 ⎜ 0.95 0.65 1.65 ⎟ ⎟ C=⎜ ⎝ 0.5 0.5 0.5 ⎠. 0 0.5 0.5 We obtain an approximation spline of the form (Fig. 4b). ⎧ (x, y) ∈ T1 ; −x − 1.4y + 1.975, ⎪ ⎪ ⎪ ⎨ −1.4x − 0.6y + 1.95, (x, y) ∈ T ; 2 S2(x, y) = ⎪ 0.5, (x, y) ∈ T ; 3 ⎪ ⎪ ⎩ x − y, (x, y) ∈ T4 .

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Next, determine the maximum deviation of the exact function f (x, y) from the constructed approximating spline S2(x, y):max|f (x, y) − S2(x, y)| ≈ 0, 07. The constructed discontinuous approximation spline approximates the discontinuous function better than the interpolation one, which corresponds to the theory. The constructed discontinuous splines accurately approximate that part of the function where it is constant or linear, which confirms the above theory. Now to restore the function f (x, y) we use the constructed interlination operator. In order to use them, traces of the function along the triangulation lines must be specified as input data. Let the function f (x, y) have discontinuities of the first kind on the triangulation lines, and along these lines have the following one-sided traces.

or

Based on these data, we construct an interlination spline. The conditions of Theorem 7 are satisfied, so the interlination spline will have the following forms: ⎧ O1 f (x, y), (x, y) ∈ T1 ⎪ ⎪ ⎪ ⎨ O f (x, y), (x, y) ∈ T 2 2 S3(x, y) = ⎪ O3 f (x, y), (x, y) ∈ T3 ⎪ ⎪ ⎩ O4 f (x, y), (x, y) ∈ T4 O1 f (x, y) = 1, 5 − x − y2 ; = 1, 5 − x − y2 ; O2 f (x, y) = (x − 1)2 + (y − 1)2 + 0, 5; O3 f (x, y) = 0, 5; O4 f (x, y) = x − y

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we obtain a discontinuous interlination spline (Fig. 4c): ⎧ ⎪ −y2 − x + 1.5 (x, y) ∈ T1 ⎪ ⎪ ⎪ ⎨ 2 2 (y − 1) + (x − 1) + 0.5, (x, y) ∈ T2 S3(x, y) = ⎪ 0.5, (x, y) ∈ T3 ⎪ ⎪ ⎪ ⎩ x + 2, (x, y) ∈ T4

Fig. 4. Graphical view of the function f (x, y)(gray color) and: a) interpolation spline S1(x, y) (black color); b) approaching approximation spline S2(x, y)(black); c) interlination spline S3(x, y)(black).

And as we see it completely coincides with the function f (x, y). That is, the maximum deviation of the exact function f (x, y). From the constructed interlination spline S3(x, y): max|f (x, y) − S3(x, y)| = 0.

6 Conclusions The article presents methods of mathematical modeling of discontinuous objects using different operators. As operators, interpolation and approximation operators, when information about an object is given in the form of one-sided values in a given system of points, and interlinations, when information is given in the form of one-sided traces along a given system of lines (in our case, along the sides of right-angled triangles) are used. In the system of computer mathematics, computational experiments were carried out. The constructed discontinuous interlination spline approximates the discontinuous function exactly, which is confirmed by the stated theory. That is, these splines approach the discontinuity function better than interpolation and approximation splines. But the constructed constructions belong to various information operators. In the future work, it is planned to apply the constructed discontinuous interlination operator to the solution of the computed tomography problem using the inhomogeneity of the internal structure of the body, which needs to be restored.

References 1. Schumaker, L.: Spline Functions: Computational Methods. Vanderbilt University, Nashville, Tennessee (2015)

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2. Cox, M.G.: An algorithm for spline interpolation. IMA J. Appl. Math. 15(1), 95–108 (1975) 3. Sergienko, I.V., Zadiraka, V.K., Lytvyn, O.M., Pershina, I.I.: Theory of Discontinuous Splines and its Application In Computer Tomography. Kyiv, Nauk. Dumka (2017) 4. Popov, B.A.: Uniform Approach with Splines. Kyiv, Nauk. Dumka (1989) 5. De Vore, R.A.: A method of grid optimization for finite element methods. Comput. Method Appl. Mech. Eng. 41, 29–45 (1983) 6. Emmel, L., Kaber, S.M., Maday, Y.: Pade-Jacobi Filtering for spectral approximations of discontinuous solutions. Numer. Algo. 33, 251–264 (2003) 7. Chantrasmi, T., Doostan, A., Iaccarino, G.: Padé-Legendre approximants for uncertainty analysis with discontinuous response surfaces. J. Comp. Phys. 228, 7159–7180 (2009) 8. Hesthaven, J.S., Kaber, S.M., Lurati, L.: Pade-Legendre interpolants for Gibbs reconstruction. J. Sci. Comp. 28, 337–359 (2006) 9. Costarelli, D.: Ph. D. Thesis, Sigmoidal Functions Approximation and Applications, Universitat degli Study Roma Tres, Roma (2013) 10. Lombardini, R., Acevedo, R., Kuczala, A., Keys, K.P., Goodrich, C.P.: Higher-order wavelet reconstruction/differentiation filters and Gibbs phenomena. J. Computat. Phys. 15, 244–262 (2016) 11. Lytvyn, O.N., Pershina, Y.I., Sergienko, I.V.: Estimation of discontinuous functions of two variables with unknown discontinuity lines (rectangular elements). Cybernet. Syst. Anal. 5(4), 594–602 (2014) 12. Lytvyn, O.M., Pershina, I.I, Lytvyn, O.O., Kulyk, S.I.: Mathematical modelling of discontinuous processes in a computer tomography by means of discontinuous splines. In: 7th World Congress on Industrial Process Tomography (2–5 September 2013), Krakow, Poland, pp. 441–450 (2014) 13. Lytvyn, O.M., Pershina, Y.I.: Approximation of discontinuous function of two variables by approximating discontinuous bilinear spline using the least squares method (rectangular elements). J. Automat. Inf. Sci. 44(5), 48–56 (2012) 14. Mezhuyev V., Lytvyn O.M., Pershyna I., Nechuiviter O., Lytvyn O.O.: Algorithm for the reconstruction of the discontinuous structure of a body by its projections along mutually perpendicular lines. In: 7th International Conference on Software and Computer Applications (ICSCA 2018), Kuantan, Malaysia. 8–10 Feb, 2018, pp. 158–163 (2018) 15. Lytvyn, O.M., Pershina, Y.I., Lytvyn, O.O., Kulyk, S.I., Shumeyko, N.A.: New method of restoration of internal structure 3D bodies by means of projections which arrive from a computer tomography. In: Proceedings of the 6th World Congress on Industrial Process Tomography (6–9 September 2010), Beijing, China, pp. 429–436 (2010) 16. Lytvyn, O.N., Pershina, Y.I.: Reconstruction of 3D objects with use interflation of functions. Signal and image processing: In: Proceeding of the Second IASTED International Multi – Conference on Automation, Control, and Information Technology, pp. 274–279 (2005) 17. Lytvyn, O.M., Nechuiviter, O., Pershyna, I., Mezhuyev, V.: Input information in the approximate calculation of two-dimensional integral from highly oscillating functions (irregular case). Adv. Intell. Syst. Comput. 836, 365–373 (2019) 18. Mezhuyev, V., Lytvyn, O.M., Pershyna, I., Nechuiviter, O.: Approximation of discontinuous functions of two variables by discontinuous interlination splines using triangular elements. J. Serbian Soc. Comput. Mech. 14(1), 75–89 (2020)

Robotic-Like Formulation of the Approximated Body-Guidance Problem Maurizio Ruggiu

and Pierluigi Rea(B)

University of Cagliari, Cagliari, Italy [email protected]

Abstract. A classical problem in the mechanics of mechanisms is the body-guidance synthesis. As first formulated by Burmester, the problem consists of finding the dimensions of a planar four-bar linkage whose coupler link attains a prescribed set of finitely separated poses. The problem is solved either in exact, up to five prescribed poses, or in approximate forms by several methods. Many of them rely on the algebraic geometry to find center- and circle-point loci of the RR dyads composing the mechanism. The method was also used to find the circle-point locus of the PR dyad. In this paper a different approach was followed. We propose a formulation of the problem by using the vector loop equations, usually employed in robotics for kinematic analysis, to obtain the set of nonlinear synthesis equations then solved by advanced and stabilized algorithms. The method allows us to achieve the approximate solution of the body-guidance problem either with RR or PR dyads with high accuracy also including prescribed timing. Keywords: Burmester’s problem · dimensional synthesis region-reflective least squares algorithm

1

· Trust

Introduction

The body-guidance problem has the goal to find the geometric parameters of a four-bar linkage for a prescribed set of finitely separated poses as firstly formulated by Burmester [1]. The problem represents a milestone in the kinematics community that still receives a considerable attention of researchers because of very numerous applications of this linkage. The classical approach reduces the problem to the dyad synthesis (repeated two times to compose the whole linkage), a dyad being a rigid link carrying two kinematic pairs. The problem admits exact real solutions for five poses as roots of a quartic equation. Instead, in the case of four poses it has infinitely many solutions since each RR dyad leads to two cubic curves, i.e., centrepoint, circlepoint, locus of solutions of the problem. In the light of the approach followed in this paper it is noteworthy to point out here that the five poses problem has to be solved numerically although it has analytical solutions. c The Author(s), under exclusive license to Springer Nature Switzerland AG 2023  D. D. Cioboatˇ a (Ed.): ICoRSE 2023, LNNS 762, pp. 405–417, 2023. https://doi.org/10.1007/978-3-031-40628-7_34

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As reported in [2], authors in [3–5] solved the five-pose problem by intersecting two centrepoint curves of two four-pose subsets out of the given five-pose set, to obtain the centrepoints. Al-Widyan, et al., developed a robust algorithm based on dyalitic elimination method [6]. Some authors solved the problem by method based either on projective geometry, or via the kinematic mapping [7,8], Sandor and Erdman used complex numbers in their textbook [9]. Only few works addressed the synthesis of the four-bar linkage in presence of the PR dyad. Angeles provided a comprehensive solution of the Burmester problem including this case [2,10]. The same author, et al., dealt with the approximate synthesis of the four-bar linkage in order to best approximate a large number of prescribed poses [11]. The approach followed exploited symbolic computations to reduce the normality conditions of the approximate kinematic synthesis problem to a set of two bivariate equations and a refinement by means of the Newton-Raphson method to the desired accuracy. The idea of this paper is to use the loop equations, usually employed for kinematic analysis, as synthesis equations. That leads to a formulation of the problem that differs from the others as the positional variables appear as unknowns besides the dimensional parameters. The equations turn to be highly nonlinear whose approximate solutions can be found as minimum of a constrained optimization problem by means of modern numerical algorithms. The formulation can be easily extended to linkage with PR dyad and it is well suited for treating timing problem, as well.

2

Problem Formulation

The body-guidance problem, a.k.a. Burmester problem, can be stated as: Given a set of discrete set of m poses, of a rigid body attached to the coupler link of a four-bar linkage, the problem consists in finding the geometrical parameters of the linkage such that the poses are attained.

Fig. 1. Notation of the RR dyad.

Robotic-Like Formulation of the Approximated Body-Guidance Problem

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(j) The set of given poses can be parametrized by {r(j) , φ(j) }m is the posi1 , r tion vector of a reference point of the coupler link at the j-pose and φ(j) is the corresponding angle of a line of the coupler link. We formulate the synthesis equations from the kinematic equations (loop equations) of each chain of the linkage. Therefore, we treat the kinematic equations as a system of 2m nonlinear equations (or 4m if the timing problem is taken into account):

F(P(j) , X(j) , Π) = 0,

j = 1, . . . , 2m,

(1)

where X(j) is the array of the linkage positional variables, robot-like joints variables, at the j-pose, Π is the array of the linkage dimensional parameters and P(j) is the array with r(j) and φ(j) . Equation 1 has both the linkage positional variables and dimensional parameters as unknowns. Dimensions of the unknowns arrays depend on the problem treated leading either to a determined or to a overdetermined system. 2.1

Numerical Algorithm

The idea of this paper is to solve the synthesis problem with advanced and stabilized methods based on the numerical solution of a set of nonlinear equations. By grouping the unknowns in an unique array x, Eq. 1 can be expressed as {fj (x) = 0}2m 1 whose solution is computed by solving the nonlinear least-squares problem stated as: F (x) := (f1 (x)2 + . . . + fj (x)2 + . . . + f2m (x)2 ). minimize{F (x)} x

li ≤ xi ≤ ui , i = 1, . . . , n + m.

with

where n is the dimension of Π. The minimization problem is implemented in the built-in function lsqnonlin of Matlab. The function uses the trust-region-reflective-algorithm briefly recalled here for an unconstrained minimization problem. First the Taylor approximation of the function in the neighborhood s of the point xk (k-iterate) is considered: 1 q(s)  F (xk ) + sT Hs + sT g 2

(2)

In Eq. (2) g is the gradient of F (xk ), H is the Hessian matrix. s is the trial step to be sought such that the trust-region subproblem is solved: minimize

{q(s)}

s.t.

Ds  Δ

s

with D is a diagonal scaling matrix, Δ is a positive scalar. The minimization problem is solved by means of a iterative Newton method applied to the secular

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1 1 equation Δ − s = 0, [12]. This approach typically needs computations of the H eigenvalues. However, the algorithm implemented in the built-in Matlab function reduces the problem to a two-dimensional subspace S such that only a (2 × 2) matrix has to be dealt with. The subspace S is defined as the linear space spanned by s1 and s2 . s1 is in the direction of the gradient (scaled gradient direction) of g whereas s2 is obtained from a conjugate gradient process returning either:

Hs2 = −g : approx. Newton direction or T s2 Hs2 < 0 : negative curvature direction. Then, the trial step is chosen as one of three: i) the scaled gradient solution; ii) S trust region solution; and iii) reflected S trust region solution. The choice is made by comparing the approximation functions q(s) and picking that one producing its lowest value. Once the trial step is computed it may possible to compare F (xk + s) with F (xk ). If F (xk + s) < F (xk ) then the point is uploaded such that xk = (xk + s) otherwise the current point remains unchanged, Δ is shrunk and the trial step computation is repeated.

3

Synthesis Equations for a Four-Bar Linkage

We address the synthesis equations for a four-bar linkage formed by either two RR dyads or a RR dyad with a PR dyad. In the case of the RR dyad we have Eq. (3), (Fig. 1). a + b(j) + c(j) − r(j) = 0,

j = 1, . . . , m.

(3)

Equation (3) is nothing but that the loop equation of the RR chain at an arbitrary configuration. It leads to 2m scalar equations. ax + b cos θ(j) + c cos(φ(j) + β) − rx(j) = 0,

ay + b sin θ(j) + c sin(φ(j) + β) − ry(j) = 0.

(4)

Equations (4) have five dimensional and m positional parameters as unknowns: ax , ay , b, c, β, θ(j) . Thus, to have a determined system of nonlinear equations we can select five arbitrary poses, i.e., 5 + m = 2m. It is noteworthy that the approach followed is completely different from those used in literature mainly based on the algebraic geometry with the goal to find center- and circle-point loci of the RR dyads composing the mechanism. Furthermore, the method has the great advantage to be well suited for solving the motion generation problems with prescribed timing. In this case m poses are known as well as the velocity of the reference point and the angular velocity of the coupler link at the m poses: {˙r(j) , φ˙ (j) }m 1 leading to a system formed by Eqs. (4) and their derivatives with respect the time: b sin θ(j) θ˙(j) + c sin(φ(j) + β)φ˙ (j) + r˙x(j) = 0, b cos θ(j) θ˙(j) + c cos(φ(j) + β)φ˙ (j) − r˙y(j) = 0.

(5)

Robotic-Like Formulation of the Approximated Body-Guidance Problem

409

Equations (4) and Eqs. (5) form a system of 4m nonlinear equations with 5 + 2m unknowns as {θ˙(j) }m 1 has to be computed, too. Therefore, in this case, it may be possible to obtain approximate solutions with at least m = 3 poses. A caveat is in order here. There exists an alternative method to deal with the synthesis of RR four-bar linkage. Indeed Eq. (3) can be reshaped to obtain one scalar equation removing θ(j) as unknown. bT b − rT r + 2(rT a + rT c + aT c) = 0.

(6)

Therefore we can form a determined system imposing m = 5 poses as in the general method. Also, nothing changes when the prescribed timing problem is dealt with. Indeed in this case two scalar equations can be written and only an overdetermined system can be cast imposing at least m = 3. The method presented can be easily extended to synthesize four-bar linkages with the presence of one PR dyad. In this case (Fig. 2), the kinematic equation of the PR chain takes the following form:

Fig. 2. Notation of the PR dyad.

q(j) + d + e(j) = r(j) , with

q

(j)

= p0 + λ

(j)

u,

T

j = 1, . . . , m.

u p0 = 0,

u = 1.

(7)

Equation 7 lead to 2m+2 scalar equations: p0,x + λ(j) ux + d cos γ + e cos(φ(j) + ζ) − rx(j) = 0, p0,y + λ(j) uy + d sin γ + e sin(φ(j) + ζ) − ry(j) = 0, p0,x ux + p0,y uy = 0, u2x + u2y = 1.

(8)

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Equations (8) have eight dimensional and m positional parameters as unknowns: p0,x , p0,y , ux , uy , d, e, γ, ζ, λ(j) . Thus, to have a determined system of nonlinear equations we can select six arbitrary poses, i.e., 8 + m = 2m + 2. Whenever the synthesis of the PR chain is associated to the synthesis of the RR chain such to form the linkage, six prescribed poses must be selected leading to either a determined or overdetermined system of nonlinear equations. Some simplified cases can be dealt with, as well. For example, length e may be zero and γ may take a convenient value such to have the link normal to the P-joint detection. In this cases the determined system of equations can be obtained with five arbitrary poses. A caveat is in order here. We identified either determined or overdetermined systems depending on the number of prescribed poses. However, the algorithm deals with both the systems with no differences reaching in both cases the optimal solutions in the least-square sense. Thus, the method proposed is general, it can be directly applied to synthesize any planar linkages, and potentially any spatial mechanisms. It is only required to solve the position equations including position variables. Solutions can be driven either by an opportune choice of the guess vector or limiting the solution range. Applications of the method to six-bar linkages will be presented in a future work by the same authors.

4

Numerical Examples

In this section we present four numerical examples for the four-bar linkage with RR dyads and one with a PR dyad: i) a classical problem proposed in the textbook [9] leading to a determinated system of nonlinear equations, ii) an overdetermined problem, iii) a problem with prescribed timing, iv) the synthesis of a lift-assist chair linkage, v) the synthesis of the RR-PR linkage. The synthesis method is based on an optimization algorithm that approximates the exact solution in the least square sense. For this reason, it is noteworthy to define an error metrics to evaluate the accuracy of the solution. We select two parameters, i.e., ˜, R, defined as follows: k := (fk − f k ), k = 1, . . . 2m, with f k ≡ f (xk ) = 0 : exact solution;  = ( 1 , . . . , k , . . . , 2m )T ; 2m

˜ :=

1  k and R := 2 . 2m k

Thus, ˜ represents the mean of the residuals, whilst R is the squared 2-norm of the residuals at x. 4.1

Optimal Solution with Five Prescribed Poses (RR Dyads)

The linkage must guide its coupler link through the five poses in Table 1. Thus, as first, the level of approximation reached has to be checked. In this case, solutions

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411

obtained approximate very well the exact solutions for both the linkage chains as ˜ = O(−7), R = O(−15). Accordingly, the five prescribed poses are not reached exactly. To evaluate the error in position and orientation, Eqs. (4) are considered all together for chains 1 and 2 forming a linear system of four equations for each pose with ax,i , ay,i , bi , ci , βi , θ(j) , (i = 1, 2, j = 1, . . . m), as known values and (j) (j) r˜x , r˜y , cos φ˜(j) , sin φ˜(j) as unknowns. The absolute errors obtained between the prescribed and calculated values are shown in Table 2. It can be noticed that the absolute errors are lower than 0.4 mm. Figure 3 shows the synthesized linkage at the first pose. Table 1.

RR-RR linkage: Five prescribed poses for rigid-body guidance j

rj (m)

φj (◦ )

1 2 3 4 5

[0, 0] [1.5, 0.8] [1.6, 1.5] [2.0, 3.0] [2.3, 3.5]

0 10 20 60 90

Fig. 3. Five prescribed poses: synthesized linkage at the first pose.

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Five prescribed poses: Absolute errors in position and orientation (j)

j

|r(j) | (mm) |r(j) | (mm) |φ | (degree) x y

1 2 3 4 5

0.189 0.386 0.361 0.159 0.091

0.059 0.192 0.339 0.334 0.213

0.003 0.009 0.010 0.006 0.004

4.2 Optimal Solution with Eleven Prescribed Poses (RR Dyads) The linkage must guide its coupler link through the eleven poses in Table 3. Also in this case ˜ and R are used to check the level of approximation reached. We obtained ˜ = O(−4) and R = O(−6) as average of both the chains solutions. The absolute errors obtained between the prescribed and calculated values are shown in Table 4. The errors are well below of 1 mm except for one pose. Figure 4 shows the synthesized linkage at the poses. Table 3.

4.3

Eleven prescribed poses for rigid-body guidance j

rj (m)

φj (◦ )

1 2 3 4 5 6 7 8 9 10 11

[3.988, 4.848] [3.624, 5.803] [2.996, 6.660] [2.122, 7.348] [1.045, 7.802] [−0.174, 7.971] [−1.462, 7.819] [−2.732, 7.330] [−3.891, 6.509] [−4.839, 5.391] [−5.491, 4.038]

7.620 12.089 16.673 21.657 27.330 33.919 41.596 50.477 60.618 71.791 83.938

Optimal Solution with Five Prescribed Poses and Timing (RR Dyads)

Five, i.e. m = 5, of the eleven poses of Sect. 4.2 were picked to synthesize the linkage with prescribed velocities of coupler link, as well. Thus, for each RR dyad, Eqs. (4) and Eqs. (5) form a system of 20 nonlinear equations with 15 unknowns as {θ˙(j) }51 has to be computed besides {θ(j) }51 and ax , ay , b, c, β. To evaluate the approximation reached by the computation with respect to the prescribed velocities, we used Eqs. (5) for both the dyads forming a nonlin(j) (j) ear system with {φ(j) , φ˙ (j) , r˙x , r˙y }51 as unknowns. The system was solved by the built-in function fsolve of Matlab with high accuracy, O(−10). Table 5 shows the absolute errors obtained between the prescribed and calculated values.

Robotic-Like Formulation of the Approximated Body-Guidance Problem

Table 4.

Eleven prescribed poses: Absolute errors in position and orientation (j)

j

|r(j) | (mm) |r(j) | (mm) |φ | (degree) x y

1 2 3 4 5 6 7 8 9 10 11

0.363 0.578 0.142 0.247 0.160 0.581 0.176 0.859 1.489 0.605 0.170

0.238 0.182 0.839 0.029 0.057 0.320 0.286 0.452 0.838 0.869 0.397

0.001 0.000 0.006 0.004 0.004 0.009 0.002 0.002 0.029 0.018 0.006

Fig. 4. Eleven prescribed poses: synthesized linkage at the poses.

Table 5.

Five prescribed poses with timing: Absolute errors in point and link velocities (j)

(j)

(j)

1 0.789

0.134

0.001

2 0.050

0.931

0.014

3 0.033

0.275

0.001

4 0.649

0.861

0.022

5 0.363

0.127

0.002

j |vx | (mm/s) |vy | (mm/s) |φ | (degree/s)

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Table 5 shows that, in addition to very good pose approximation (not shown), the method allows us to synthesize a linkage with a very good approximation of the velocities parameters as well. 4.4

Synthesis of a Lift-Assist Chair Linkage

We present a practical application of the synthesis method inspired by the biomechanical problem of the sit-to-stand movement [13,14]. The goal is to synthesize a four-bar linkage guiding the chair seat according to the movement required to pass from a sitting to standing pose. The definition of the prescribed poses was possible by using the frames sequence reported in [15]. Links dimensions and joints locations are constrained as the mechanism must be contained in the area identified by the legs (front and back) and the seat, a square with side of 40 cm. The synthesized linkage takes an area of 38 cm × 20 cm. The seat is rotated from about 6◦ to 80◦ and lifted of about 40 cm. The linkage at the prescribed poses is shown in Fig. 5.

Fig. 5. Synthesized lift-assist chair linkage at the poses.

4.5

Synthesis of a RR-PR Linkage

The linkage must guide its coupler link through the six poses in Table 6. Also in this case ˜ and R are used to check the level of approximation reached. For the PR chain we obtain ˜ = O(−4) and R = O(−8) while for the RR chain ˜ = O(−4) and R = O(−9). To evaluate the errors of position and orientation, also in this case, a linear system of four equations can be formed directly from Eqs. 4 and 8.

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The absolute errors obtained between the prescribed and calculated values are shown in Table 7. Also in this case it can be noticed the accuracy reached by the method. Figure 6 shows the synthesized linkage at the poses. Table 6.

Table 7.

RR-PR linkage: Six prescribed poses for rigid-body guidance j

rj (m)

φj (◦ )

1 2 3 4 5 6

[0.100, 2.600] [0.506, 3.124] [0.868, 3.688] [1.160, 4.198] [1.363, 4.585] [1.463, 4.802]

−12.605 −9.224 −2.807 5.500 14.954 25.038

RR-PR linkage, six prescribed poses: Absolute errors in position and orientation (j)

j

|r(j) | (mm) |r(j) | (mm) |φ | (degree) x y

1 2 3 4 5 6

0.043 0.089 0.098 0.008 0.169 0.034

0.035 0.075 0.068 0.007 0.015 0.046

0.002 0.000 0.001 0.000 0.001 0.000

Fig. 6. RR-PR linkage, six prescribed poses: synthesized linkage at the poses.

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Conclusions

The paper presents a method for the kinematic synthesis of planar linkages. The method is based on the approximated solutions of the system of nonlinear equations representing the loop equations of the dyads. The method was applied extensively either for RR-RR or RR-PR linkage. In all cases the algorithm proved to be very accurate leading to coupler poses very close to those prescribed. The formulation was easily extended to synthesis with prescribed velocity of the coupler link leading to accurate results, as well. In brief, the method treats the kinematic synthesis as a positional problem of a serial kinematic chain with both geometrical and positional parameters as unknowns. It relies on the high accuracy of the modern numerical algorithms able to reach approximation below the construction errors and tolerances in machining. Results proved that the method works nicely for the cases examined.

References 1. Burmester, L.: Lehrbuch der Kinematik. A. Felix, Leipzig (1888) 2. Chen, C., Bai, S., Angeles, J.: A comprehensive solution of the classic Burmester problem. Trans. CSME 32(2), 137–154 (2008) 3. Bottema, O., Roth, B.: Theoretical Kinematics. North-Holland Pub. Co., New York (1979) 4. Hunt, K.H.: Kinematic Geometry of Mechanisms. Oxford University Press, New York (1978) 5. McCarthy, J.M.: Geometric Design of Linkages. Springer, New York (2000). https://doi.org/10.1007/978-1-4419-7892-9 6. Al-Widyan, K., Angeles, J., Cervantes-Sánchez, J.J.: A numerically robust algorithm to solve the five-pose Burmester problem. In: International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, ASME 2002, Montreal, Quebec, Canada, pp. 617–626 (2002) 7. Ravani, B., Roth, B.: Motion synthesis using kinematic mappings. ASME J. Mech. Transm. Autom. Des. 105, 460–467 (1983) 8. Hayes, M., Zsombor-Murray, P.: Solving the Burmester problem using kinematic mapping. In: Proceedings of the ASME DETC 2002, Paper No. MECH-34378 (2002) 9. Sandor, G.N., Erdman, A.: Advanced Mechanism Design: Analysis and Synthesis, vol. 2. Prentice-Hall Inc., New Jersey (1984) 10. Angeles, J., Bai, S.: Some special cases of the Burmester problem for four and five poses. In: International Design Engineering Technical Conferences & Computers and Information in Engineering Conference, Proceedings of IDETC/CIE 2005, ASME 2005, Long Beach, California, USA, 24–28 September (2005) 11. Yao, J., Angeles, J.: Computation of all optimum dyads in the approximate synthesis of planar linkages for rigid-body guidance. Mech. Mach. Theor. 35, 1065–1078 (2000) 12. Moré, J.J., Sorensen, D.C.: Computing a trust region step. SIAM J. Sci. Stat. Comput. 3, 553–572 (1983) 13. Rea, P., Ottaviano, E.: Functional design for customizing sit-to-stand assisting devices. J. Bionic Eng. 15, 83–93 (2018). https://doi.org/10.1007/s42235-0170006-4

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14. Rea, P., Ottaviano, E., Ruggiu, M.: The use of CPS for assistive technologies. In: Cioboată, D.D. (ed.) ICoRSE 2021. LNNS, vol. 305, pp. 316–326. Springer, Cham (2022). https://doi.org/10.1007/978-3-030-83368-8_31 15. Reimer, S.M.F., Abdul-Sater, K., Lueth, T.C.: Bio-kinematic design of individualized lift-assist devices. In: Husty, M., Hofbaur, M. (eds.) MESROB 2016. MMS, vol. 48, pp. 59–72. Springer, Cham (2018). https://doi.org/10.1007/978-3-319-599724_5

Gripper for Manipulating Empty Bag Sacks Ciprian Ion Rizescu and Dana Rizescu(B) Department of Mechanical Engineering and Mechatronics, University Politehnica of Bucharest, Splaiul Independentei 313, Sector 6, Code 060042 Bucharest, Romania [email protected]

Abstract. The paper refers to a device that automates the technological process of loading granular or pulverulent products in open sacks bags, followed by the palletizing operation of the loaded bags. The device is of interest for a very large number of economic branches: chemical industry, food industry, construction materials industry, mining industry, etc. In order to perform the experimental research, the following materials for handling were considered: cardboard for packaging; polyurethane foam; expanded polystyrene; sackcloth (jute); raffia. Grip experiments were performed on different materials, and performance was assessed quantitatively using the grasped mass sizes and positioning accuracy. The paper presents a pneumatically operated device that used thin needles to catch and punch the manipulated materials. This device is based on a set of needles that penetrate the material and lift it using the arrangement of the needles and the force of friction between the needles and the material. A mathematical model is proposed for calculating the force required to insert and retract the needles from the material. By controlling the successive positive and negative pressures on the six mini-pistons, the device can perform both grasping and drilling operations. In this case, it is assumed to use a pneumatic system to produce the vacuum that would allow the withdrawal of the six mini-pistons. The authors opted for a mini piston return solution using helical compression springs. The paper also looked at the efficiency of energy consumption to obtain a minimum consumption. The paper concludes with observations from the authors on the experimental results obtained when grasping textile bag sacks made of several materials. Keywords: Grasping · Pneumatic gripper · Handling bags · Palletization

1 Introduction The work in the packaging sectors requires a lot of physical effort and takes place in difficult environmental conditions (depending on the nature of the packaged product), which required the creation of automated packaging installations, equipped with robots and manipulators, to replace humans in carrying out raw labor. In the process of packing and palletizing granular or powdery materials in bags, a series of conditions and problems must be ensured (to automate the processes): • continuous supply of empty bags; • taking over and opening the mouth of the empty bags; © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 418–425, 2023. https://doi.org/10.1007/978-3-031-40628-7_35

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• putting the empty bags on the loading mouth; • after filling the bags with material, transporting them and closing the mouth of the bag (by sewing or welding); • taking over full bags and palletizing them. Different ways of approaching and solving these problems are presented below. The methods of grasping for different kinds of end effectors can be easily divided into four basic types: by penetrating the material (ingressive), by squeezing or colliding with power (impactive), astringent (astrictive) and contiguities (joining, gluing). The result of the effects of these methods of attachment for any surface are used if it is allowed or not. A brief description of grip types and effects is presented in Table 1. Table 1. Description of grip types and effects. Clamping method

Effects of clamping on the material

Power clamping Jaws

Clamps, jaws

Pinching

Claw grippers, blades

Material penetration

Brush: Velcro threads Needles: pick-up, Polytex, hanging

Astringents

Magnetic, electro adhesive, vacuum, and suction

Contiguities

Chemical adhesion and adhesion thermos

Considering Table 1, we are interested in gripping devices with penetration into the material (with needles). Using the vacuum for clamping can also be considered a solution. However, since the foam is a porous material, the air is drawn through the material and the vacuum is quickly lost. To maintain the vacuum, a very powerful vacuum generator is required, which is also very expensive. Our attention should be focused on pin (needle) fasteners because it is an appropriate solution for this case.

2 Experimental Setup It should be mentioned that the gripping and the possibility of handling different materials (jute bag, expanded polyester, polyurethane foam, raffia bag, cardboard bag) are possible due to the shape adapted for the gripping device. The extension of the needles under an angle of 30° to the plane of the material to be clamped was adopted following the studies carried out for this type of clamping by the University POLITEHNICA of Bucharest. The friction on the needle elements of the gripper end effector depends on the surface treatment of textile the thread and affects the tensile force during the bag penetrating

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process [1]. It is important, therefore, to know the friction coefficient when choosing the appropriate textile bag. Some requirements were considering during designing process: • Shape analysis of the tip The puncture needle is composed of a steel needle shaft and a steel needle tip. The needle tip may have different shapes. In the present study, cone shaped needles made by multi-station mechanical grinding are utilized. It is worth noting that the curve of the cone surface should be set before grinding. Medical needles such syringe needle is also a possibility for the gripper. • Analysis of needle tip force During the downward movement of the puncture template, the needle passing through the bag material gradually moves from the needle tip to the needle shaft. Under the action of the needle tip cone of the steel needle, the fibers in the bag material produce a series of complicated changes such as displacement, pushing, bending, and elongation. Moreover, they interact with the steel needle to cause the steel needle to press down and bend. In Fig. 1 is shown the spatial representation of gripping cup. The gripper has five identical cups, placed at the open side of the bag. The number of cups depends on the bag’s width. For 500 mm bag width five cups allow the gripper to open the bag’s mouth.

Fig. 1. Experimental gripping cup spatial representation.

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The notations in Fig. 1 are: 1-Connection, 2-Gasket no.1, 3-Main distribution body, 4-Mounted cylinder, 5-Piston, 6-Gasket no. 2, 7-Needle 6 pieces, 8-Helical compression spring, 9-Pneumatic cylinder, 10-Gasket no. 3. For the experimental gripping cup, six helical springs will be used in order to execute the return of the pistons to the initial position, that is, the pistons will be in the upper position (the needles withdrawn), this will lead to the exit of the needles from the material caught by the device and its release. In Fig. 2 there is shown a sketch of the gripping cup operating principle. The thickness of material is labeled with t. The cup has to grip the bag when the needles are penetrating the material. The needle has a stroke driven by piston 5 (Fig. 1) labeled with c. The result of executing stroke c is the vertical penetration of the bag labeled with s. Every needle penetrates the material with s. The result is the gripping of the material. There is to underline that the needles do not penetrate the whole material on the thickness t. The relation is s < t.

Fig. 2. Experimental gripping cup operating principle.

The authors studied different angles for needle orientation considering material penetration. In Fig. 3 there are presented different angles for needles penetration, labeled with α.

Fig. 3. Needle orientation relative to bag material

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The adopted angle was α = 30°, even there is the shortest material penetration s relative to the stroke c. In this case s = 0.5·c, but this solution gives a compact assembly of the gripping cup, smallest friction forces between needles and bag material. It should be mentioned that the experiments were performed for a stroke of the piston, c = 1.5 mm, which represents a penetration depth in the material of s = 0.75 mm. This value is suitable for bag gripping.

3 Experimental Results and Discussion The gripper is based on several vacuum gripping cups (five in this research) as it is presented in Fig. 4. The gripper is controlled by pneumatic valves. In the process of packing and palletizing granular or powdery materials in bags, a series of conditions and problems must be ensured (to automate the processes): • • • •

continuous feeding with empty bags; taking and opening the mouth of empty bags; putting empty bags on the loading mouth; after filling the bags with material, transporting them and closing the mouth of the bag (by sewing or gluing); • taking full bags and palletizing them. Depending on the material of the bags (polyethylene, polypropylene, paper, textile, etc.), also on how they are brought into the processing area, a very wide range of specialized manipulators and fasteners for taking unfilled bags have been designed and manufactured [2, 3].

Fig. 4. Experimental gripping cup final assembly side and bottom view.

Theoretical considerations regarding the variation of the frictional force between the needle and different materials that require clamping. In order to carry out the experimental research, the following materials were considered [4–6]: • cardboard for packaging bag;

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• • • •

423

polyurethane foam; expanded polystyrene plate; textile material bag (jute); raffia bag.

The frictional forces (labeled F1to F5 considering the above numbering) between the steel needle and materials are: • • • • •

F1 = 1 N; F2 = 1.5 N; F3 = 2 N; F4 = 2.5 N; F5 = 3 N;

In Fig. 5 there is shown the experimental gripping cup mounted in the gripper to open the bag mouth.

Fig. 5. Experimental gripping cup mounted in the gripper.

Following the coincidence of the experimental results with the theoretical ones, the subsequent values were obtained for the pneumatic pressure necessary to actuate needles to penetrate each of the five materials for which the calculation of the theoretical pressure for penetration was carried out, as it was mentioned above. The values obtained experimentally for the necessary pressure for the penetration of the needles into the material are: • • • •

p1 = 0.25 bars – for the jute bag; p2 = 0.35 bar – for expanded polyester; p3 = 0.45 bar – for polyurethane foam; p4 = 0.55 bars – for raffia bag;

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• p5 = 0.65 bar – for cardboard bag. The graph for comparing the theoretical pressures required with the experimental pressures required for the five materials for which the study was performed is presented in Fig. 6. There are some differences between theoretical and experimental values for pressure, but the estimation was very good so we can conclude that the experimental results are in good agreement with theoretical ones. The differences for jute bags can be explained because the material is more ne homogenous than other materials, the fibers have different orientations [7–9].

Fig. 6. Comparison between theoretical pressure and experimental one.

4 Conclusions Analyzing and comparing the results obtained experimentally with the theoretical results, one can observe that, in practice, a lower working pressure is required for penetration than the calculated one (theoretical result). This difference is more pronounced (larger) for softer and easier to penetrate materials such as jute sack and expanded polyester and decreases for harder and harder to penetrate materials, reaching a difference of only 0.02 bars for cardboard. These differences may appear due to theoretical considerations (for example the friction force between needle and material) but they may be very close or even equal to the theoretical values after a longer period of use of the installation due to the wear of the needle tips or their slight bending. It was mentioned that the experiments were performed for a stroke of the piston c = 1.5 mm, which represents a penetration depth in the material of 0.75 mm, which provided secured gripping of the bag.

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In the case of long-term use of the device or if it is observed that the needles no longer penetrate the material properly, it is necessary to change the needles that may have a blunt (worn) tip or may be bent. To solve this problem, the pressure can be increased, but this option (possible but not recommended) can cause damage to the other components of the installation.

References 1. Yang, J., Dong, J., Chen, Y., Jiang, X.: Analysis of mechanical behavior of different needle tip shapes during puncture of carbon fiber fabric. Autex Res. J. 22(3), 318–327 (2022). https:// doi.org/10.2478/aut-2021-0036 2. Mota, R., et al.: Production and characterization of extracellular carbohydrate polymer from Cyanothece sp. CCY 0110. Carbohydr. Polym. 92(2), 1408–1415 (2013) Epub 2012 Nov 3. PMID: 23399171 https://doi.org/10.1016/j.carbpol.2012.10.070. 3. Kocak, D., Merdan, N., Evren, O.B.: Research into the specifications of woven composites obtained from raffia fibers pretreated using the ecological method. Text. Res. J. 85(3), 302–315 (2015). https://doi.org/10.1177/0040517514545257 4. Satyanarayana, K., Gundappa, G JL., Wypych, F.: Studies on lignocellulosic fibers of Brazil. Part I - source, production, morphology, properties and applications. Compos. A Appl. Sci. Manuf. 38(7), 1694–1709 (2007) 5. Lundquist, L., Marque, B., Hagstrand, P.O., et al.: Novel pulp fiber reinforced thermoplastic composites. Compos Sci. Techno 63, 137–152 (2003) 6. Kim, J.P., Yoon, T.H., Mun, S.P., et al.: Wood polyethylene composites using ethylene-vinyl alcohol copolymer as adhesion promoter. Bioresour. Technol. 97, 494–499 (2006) 7. Elenga, D., et al.: Effects of alkali treatment on the microstructure, composition, and properties of the raffia textiles fiber. BioResources 8, 2934–2949 (2013) 8. Elenga, R.G., Dirras, G.F., Maniongui, J.G., et al.: Thin layer drying of Raffia textilis fiber. BioResources 6, 4135–4144 (2011) 9. Eslam, H.K., Saieh, S.E., Rajabi, M.: Effect of steaming treatment on the physical and mechanical properties of WPC made of cotton flour and polypropylene. Aust. J. Basic Appl. Sci. 5(6), 1143–1150 (2011)

Controllers Synthesis Algorithms in the Construction of Discrete Control Systems for Technological Objects Husan Igamberdiyev1

, Jasur Sevinov1(B)

, and Suban Khusanov2

1 Tashkent State Technical University, Tashkent, Uzbekistan

[email protected] 2 Karshi Engineering and Economics Institute, Karshi, Uzbekistan

Abstract. Algorithms for the synthesis of controllers in the construction of discrete control systems for technological objects are given. Algorithms for constructing state-based stabilizing vector controllers for discrete dynamic objects based on linear matrix inequalities have been developed. The algorithms make it possible to ensure that the requirements for the quality of regulation are met, with the steady values of the controlled parameters exactly falling within the specified tolerances and under the action of limited external disturbances on the system. Algorithms for the synthesis of discrete controllers in nonlinear control systems are proposed, taking into account the delay. The algorithms ensure the asymptotic stability of a closed discrete-continuous system and make it possible to predict the state of the system at each discretization step. Algorithms for estimating the parameters of controller settings based on active adaptation have been developed. Based on the algorithms for the synthesis of the developed controllers, a system for adaptive control of the parameters of the technological process of drying potassium chloride is proposed. Keywords: Discrete object · Synthesis algorithms · Stabilizing controller · Linear matrix inequalities · Nonlinear dynamic objects

1 Introduction At present, the automation of technological processes in various industries requires the development of efficient control systems with high speed and accuracy [1–3]. On the other hand, it is necessary to have a priori information about the parameters of the object and disturbing influences for the synthesis of controllers when building high-quality discrete control systems. As a rule, control systems do not have such information. In such cases, it should build the structure of the model. This process depends on the amount of available a priori information about certain parameters of the object. State parameter space methods are often used to solve the problems of synthesizing controllers of discrete control systems for technological objects. Based on the analysis of the theory and the state of construction of discrete control systems for technological objects, it can be concluded that the issues of effective determination of the adjustable parameters of © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 426–439, 2023. https://doi.org/10.1007/978-3-031-40628-7_36

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adaptive controllers and controller synthesis under conditions when the desired solution is unknown are little studied in this area. Based on the foregoing, when constructing discrete control systems, it is very important to develop methods and algorithms for the synthesis of controllers that allow obtaining stabilizing and effective laws for controlling the state and output, and their practical application [4–18].

2 Objects and Methods 2.1 Algorithms for the Synthesis of Discrete Controllers in Dynamic Control Systems Let us consider the issues of structural-parametric synthesis of one-dimensional stabilizing controllers of stationary technological control objects. Let us discuss the problem of nonparametric synthesis for constructing discrete action gradient controllers for automatic stabilization of a linear technological control object described in the state space by a difference equation with a retarded argument [5–12]. When digital computer technology is included in the automatic control loop of a computer, the problem of choosing discrete control laws for continuous dynamic objects becomes topical. Let us turn to a linear stationary discrete object, the behavior of which is described in the state space by a finite difference equation of the type: xk+1 = Axk + Buk ,

(1)

where ut ∈ m is the control action, xk ∈ n is the state of the technological control object, A ∈ n×n and ∈ n×m are the given matrices. In the case when the variables of the state vector of the dynamic object xk are measurable, for the controlled object (1) the task of constructing a stabilizing controller according to the state can take place. The latter consists in choosing the following control law in the class of linear feedbacks of the form: uk = xk .

(2)

Here:  ∈  m+n is the matrix of parameters for the settings of the stabilizing controller, when the state of parameter x = 0, „ the closed system (1) and (2), being asymptotically stable in the sense of Lyapunov, will be written as: xk+1 = Ac xk , Ac = A + B .

(3)

One of the potentially possible methods for solving the problem of stabilizing an unstable dynamic object by state is to use linear matrix expressions. The stabilizability of a discrete technological object is identically ensured by the presence of such a quadratic function Vk , which, along each trajectory of motion of a closed system, is ensured by the fulfillment of inequality Vk < 0. . Accordingly, the condition of stabilizability of a linear technological control object (1) is equivalent to the solvability of the Lyapunov inequality: ATc XAc − X < 0

(4)

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in relation to the unknown matrix X = X T > 0 together with the matrix of parameters of the controller settings : (A + B )T X (A + B ) − X < 0

(5)

The above inequality is non-linear with respect to the unknown matrices X = X T > 0 and . Therefore, it should be represented in the class of linear matrix inequalities. Let us turn to possible approaches to solving the presented problem. The first approach boils down to the fact that the discrete dynamic control object (1) is stabilized only if there is a (nx × nx )-matrix Y = Y T > 0 that completely satisfies the linear inequality of the form: WBTT (AYAT − Y )WBT < 0,

(6)

when the columns of matrix WBT are the basis of the kernel of matrix BT . In the same case, if inequality (6) is solvable with respect to matrix Y, then the state feedback variables 3 are solutions of the matrix inequality of a linear form:   −Y A + B 0 is such that the following conditions are satisfied for any trajectory of the considered closed system: T Xxk+1 − xkT Xxk = xkT (ATc XAc − X )xk < 0 Vk = Vk+1 − Vk = xk+1

In the case when the linear matrix inequality (6) is solvable, one of the possible solutions can be found in the form of a matrix Y. Then, by substituting Y in (7), a linear matrix inequality is obtained with respect to matrix , solving which, we find the linear feedback parameters systems by state. The second possible approach is as follows. The resulting inequality (4) is multiplied on the left and right by matrix X −1 > 0. Then, following the well-known Schur lemma, the last inequality is reduced to the form:   −X −1 Ac X −1 < 0, (8) X −1 ATc XAc X −1 − X −1 < 0, X −1 ATc −X −1 here: X = X T > 0. Taking into account the form of matrix Ac (3) and denoting X −1 = Y , from expression (8) one obtains:   −Y AY + BY 0. ∞

vk 2 < ∞, and the algorithm System (32) will be adaptive in a given class M if k=0

for setting the controller parameters has the form: kk+1 = kk − dkT zk Pk ψk , k = 1, 2, ..., m

(35)

, where D is the matrix of column dk of which is determined by the conditions of the frequency theorem of system stability; Pk – arbitrary positive definite matrices; a T ψ T = ykT yk−τ .

In this case, it is necessary that the quasipolynomial β(p)·det DT W(p) has the degree (n−1) and all the roots lay in the left half-plane, and there must also be a diagonal matrix R - such that the matrix  = lim pR DT W(p) would be symmetric and positive definite, p→∞ −1  α(p) b = β(p) , W (p) is the transfer matrix of the where W (p) = L λIn − A − Fe−pτ   −pτ - characteristic quasi-polynomial of the object; object; β (p) = det pI − A − Fe α (p) is an l-dimensional vector whose components are some quasi-polynomials. The assessment of the quality of the transient process in the system will be determined by the expression: ∞ 

xkT Qxk ≤ V (k0 , φs )

k=0

To solve the problem of estimating the state vector of the object under consideration, we use the methods of the theory of dynamic estimation and filtering:

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xˆ k+1 = Ak xˆ k + Fk xˆ k−τ + Bk uk + Kk1 [yk − KkO xk − Kk Bk uk ]−

⎤ −1   τ ⎣1 2 2 2 K [yk−τ − Kk−τ O xk−τ ] + Kk,0 [yi − KkO xk ] + Kk,l [yk+l − Kk+lO xk+l ]⎦ . − n 2 k,−τ ⎡

l=1−τ

(36) The first term in (36) represents the a priori estimate of the object’s state vector, the second - the same estimate, but with a delay, the third term - the correction to the estimate of the object’s state vector, equal to the weighted difference between the a priori estimate xk of the object’s output signal and the measured value yk of this signal, the fourth KkO term is the distributed correction to the estimate of the state vector with delay [39–41]. The gains Kk1 and Kk2 are given by the equations −1 2 T = Pk,s Kk+s Rk+s . Kk1 = [Pk − Pk,0 ] KkT Rk−1 , Kk,s

(37)

The equations for the covariance matrices of estimation errors will take the form: Pk+1 = Ak Pk + Pk ATk − Pk Nk Pk + Fk + Pk,0 Nk Pk,0 − ⎤ −1   τ ⎣1 Pk,−τ Nk,−τ Pk,−τ + Pk,0 Nk,0 Pk,0 + Pk,l Nk,l Pk,l ⎦ + A1k Pk,−τ + Pk,−τ A1k T , P0 = Pk0 , − n 2 ⎡

l=1−τ

∂Pk,s ∂Pk,s = + [Ak − [Pk − Pk,0 ] Nk ]Pk,s + Ak1 Pk,−τ,s + ∂t ∂s ⎤ ⎡ −1   τ ⎣1 Pk,−τ Nk−τ Pk,−τ,s + Pk,0 Nk Pk,0,s + + Pk,l Nk+l Pk,l,s ⎦ , Pk0 ≡ 0, s ∈ [−τ, 0) , n 2

(38)

l=1−τ

∂Pk,r,s ∂Pk,r,s ∂Pk,r,s T , N = HT R−1 H = + , Pk0 ,r,s ≡ 0, r, s ∈ [−τ, 0), Pk,r,s = Pk,s,r k k k k ∂t ∂r ∂s

Based on relations (31)-(34) and the developed algorithms for the synthesis of an adaptive control system, we can propose the following version of an adaptive control system for the drying of potassium chloride (Fig. 1), which consists of a controlled process 1, a controller 2, an optimal estimation unit and identification 3, optimal control formation unit 4, controller tuning and adaptation unit 5. The adaptability feature allows you to use the same set of algorithms to control different processes. It should be said that the adaptive evaluation block can be expressed in the form of software or separate small blocks in a computer. Based on the foregoing, a structural-functional scheme for controlling the dryer drum is proposed in the following form (Fig. 2). The proposed structural-functional scheme for controlling a programmable logic controller (PLC) receives signals from controlled sensors in the dryer drum: temperature sensors TT01, TT02 and TT03, flow sensor FT01 and pressure sensor PT01. They, in turn, are stored in the database archive. One of the distinguishing features of PLC sensors, in addition to accepting signals, also includes some control signals in various operating modes, namely: manual or automatic control mode selection, system start or stop, and emergency stop.

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Fig. 1. The structure of the adaptive control system for the drying of potassium chloride: g – 



setting influences; w, v are disturbances; u – control actions; θ – estimates of object parameters; x – estimates of the current state of the object; K – adjustable parameters of the controller; y – output signal of the object.

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Fig. 2. Structural and functional diagram of the dryer drum control: D2701 – drum dryer, V2701 – air heating system, E2701 – drum cooler, S5702 – cyclone dust collector, S5702 – light dust collector, C2701 – batcher, TT01, TT02, TT03 – temperature sensors, PT01 – pressure sensor, FT01 – flow sensor.

Software has been developed that implements the algorithm of the circuit shown in Fig. 2. On the basis of the developed software, a numerical simulation of the control process was carried out based on the algorithm (38) taking into account (33). So, for example, the following figures show the implementation of the control action and the output variable of the process under consideration through the channel u1 → y1 and u2 → y2 (Fig. 3). Thus, the use of the proposed adaptive control system for the process of drying potassium chloride makes it possible to stabilize the technological regimes of the process and increase the productivity of the drying plant by an average of 1.8%, as well as save gas consumption.

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Fig. 3. Implementation of the control action and the output variable of the process under consideration through the channels u1 → y1 and u2 → y2 .

4 Conclusion As a result, the following scientific results were obtained: on the basis of linear matrix inequalities, the parameters of the controller were determined, which allow stabilizing discrete objects in terms of state and ensuring acceptable accuracy of the control system regulation processes in the presence of unmeasured external disturbances; algorithms for the synthesis of discrete controllers in nonlinear control systems are proposed, taking into account the delay. The algorithms ensure the asymptotic stability of a closed discrete-continuous system and make it possible to predict the state of the system at each discretization step; algorithms for estimating the parameters of controller settings based on active adaptation have been developed. Based on the algorithms for the synthesis of the developed controllers, a system for adaptive control of the parameters of the technological process of drying potassium chloride is proposed. The proposed adaptive control system makes it possible to stabilize the technological regimes of the process and increase the productivity of the plant by an average of 1.8%, as well as save gas consumption.

References 1. Shagin, A.V., Demkin, V.I., Kononov, V., Yu. Kabanova A.B.: Osnovi avtomatizatsii texnologicheskix protsessov [Fundamentals of process automation]. Handbook, Yurayt (2017) 2. Sxirtladze, A.G.: Avtomatizatsiya texnologicheskix protsessov i proizvodstv [Automation of technological processes and production]. Abris, Moskva (2012), 565p. 3. Katsuhiko Ogata. Modern Control Engineering. Pearson Higher Ed USA. 5 edition (2009), 912 p. 4. Landau, I.D., Zito, G.: Digital Control Systems: Design, Identification and Implementation, Springer p. 484. (2006). https://doi.org/10.1007/978-1-84628-056-6 5. Ryabova, A.V., Tertichniy-Dauri, V.Y.: Elementi teorii ustoychivosti [Elements of the theory of stability]. Handbook, SPb: Universitet ITMO, Russia (2015), 208p.

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6. Igamberdiyev, X.Z., Sevinov, J.U., Zaripov, O.O.: Regulyarniye metodi i algoritmi sinteza adaptivnix system upravleniya s nastraivayemimi modelyami [Regular methods and algorithms for the synthesis of adaptive control systems with customizable models], Tashkent: TSTU (2014) 160p. 7. Balandin, D.V., Kogan, M.M.: Lineyno-kvadratichniye i γ-optimalniye zakoni upravleniya po vixodu/Avtomatika i telemexanika (6), 5–14 (2008) 8. Krivdina, L.N. Stabilizatsiya diskretnix obyektov po sostoyaniyu [Stabilization of discrete objects by state]. Sbornik trudov aspirantov i magistrantov, Texnicheskiye nauki, N. Novgorod NNGASU, 220–223 (2006) 9. Krivdina, L.N. Sintez lineyno-kvadratichnix i γ-optimalnix diskretnix regulyatorov po coctoni na osnove lineynix matrichnix neravenstv. Vestnik Nijegorodskogo universiteta named after N.I.Lobachevskogo 2, 152–157 (2008) 10. Mallayev, A.R., Xusanov, S.N.: Estimation of parameters of settings of regulators based on active adaptation algorithm. Int. J. Adv. Res. Sci., Eng. Technol. 6(8), 10376–10380 (2019) 11. Mallayev, A.R., Xusanov, S.N., Sevinov, J.U.: Algorithms for the synthesis of stabilizing state controllers for discrete objects based on linear matrix inequalities. Int. J. Adv. Res. Sci., Eng. Technol. 8(3), 16979–16986 (2021) 12. Mallayev, A.R., Xusanov, S.N.: Programmnoye obespecheniye dlya sinteza optimalnix lineyno-kvadratichnix statsionarnix regulyatorov v adaptivnix sistemax upravleniya texnologicheskimi obyektami. Certificate of official registration of the program created for ECM. № DGU 10371 (2021) 13. Kolesnikov, A.A.: Modern Applied Control Theory: Synergetic Approach in Control Theory, Taganrog, Tomsk (2000) 14. Yusupbekov, N.R., Igamberdiev, H.Z., Sevinov, J.U.: Formalization of identification procedures of control objects as a process in the closed dynamic system and synthesis of adaptive regulators. J. Adv. Res. Dyn. Contr. Syst. 12(06), 77–88 (2020). https://doi.org/10.5373/JAR DCS/V12SP6/SP20201009 15. Tsykunov, A.M. Adaptivnoe i robastnoe upravlenie dinamicheskimi ob’ektami po vixodu. Fizmatlit, Moscow (2009), 268 p. ISBN 978–5–9221–1094–5 16. Petrov, Y.: Guarantee control in linear systems. Izvestiya AN SSSR. Tech. Cybernet. 3, 105– 109 (1989) 17. Veselov, G.E.: Prikladnaya teoriya sinergeticheskogo sinteza iyerarxicheskix sistem upravleniya [Applied theory of synergetic synthesis of hierarchical control systems], Izvestiya TRTU. Tematicheskiy vipusk. Prikladnaya sinergetika i sistemniy sintez 6(61), 73–84 (2006) 18. Veselov, G.E.: Sinergeticheskiy sintez vektornix diskretnix regulyatorov elektroprivodov peremennogo toka [Synergetic synthesis of vectornix discretnix regulators of AC electric drives], In: Izvestiya Tulskogo gosudarstvennogo universiteta, Seriya “Problemi unravleniya elektromexanicheskimi obyektami”, Vtoraya vserossiyskaya nauchnoprakticheskaya konferensiya «Sistemi upravleniya elektromexanicheskimi obyektami», pp. 83–85, Tula (2002) 19. Mallaev, A.R., Xusanov, S.N., Sevinov, J.U.: Algorithms of nonparametric synthesis of discrete one-dimensional controllers. Int. J. Adv. Sci. Technol. 29(5 Special Issue), 1045–1050 (2020) 20. Sevinov, J.U., Mallaev, A.R., Xusanov, S.N.: Algorithms for the Synthesis of Optimal LinearQuadratic Stationary Controllers. In: Aliev, R.A., Yusupbekov, N.R., Kacprzyk, J., Pedrycz, W., Sadikoglu, F.M. (eds.) WCIS 2020. AISC, vol. 1323, pp. 64–71. Springer, Cham (2021). https://doi.org/10.1007/978-3-030-68004-6_9 21. Mallayev, A.R., Xusanov, S.N.: Algorithms for synthesis of discrete controllers in nonlinear control systems with delay. Chem. Technol. Contr. Manage.: 2021(2), 80–86 (2021). https:// doi.org/10.51346/tstu-02.21.1-77-0012

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22. Egupov, N.D., Pupkov, K.A.: Metodi klassicheskoy i sovremennoy teorii avtomaticheskogo upravleniya [Methods of classical and modern theory of automatic control]. Handbook (5 chapter), MGTU im.N.E.Baumana (2004) 23. Antonov, V., Terexov, V., Tyukin, I.: Adaptivnoe upravlenie v texnicheskix sistemax. handbook. Sankt-Peterburgskogo universiteta, Russia (2001), 244p. 24. Jing, Z., Lantao, X., Changyun, W.: Adaptive Control of Dynamic Systems with Uncertainty and Quantization. 1st Edition, Copyright (2022). 249 p. 25. Igamberdiev, H.Z., Sevinov, J.U.: Algorithms for regular synthesis of adaptive systems management of technological objects based on the concepts of identification approach. J. of Chem. Tech. Cont. and manag. 6, 42–50 (2019) 26. Yusupbekov, N.R., Igamberdiev, H.Z., Mamirov. U.F.: Algorithms of sustainable estimation of unknown input signals in control systems. J. of Mult. Val. Logic and Soft Comp. 33(1–2), 1–10 (2019). https://www.oldcitypublishing.com/pdf/9291 27. Sevinov, J.U., Zaripov, O.O., Zaripova, Sh.O.: The algorithm of adaptive estimation in the synthesis of the dynamic objects control systems. Inter. J. of Adv. Science and Techn. 29(5s), 1096–1100 (2020). http://sersc.org/journals/index.php/IJAST/article/view/7887 28. Igamberdiyev, H.Z., Yusupbekov, A.N., Zaripov, O.O., Sevinov, J.U.: Algorithms of adaptive identification of uncertain operated objects in dynamical models. Procedia Comput. Sci. 120, 854–861 (2017). https://doi.org/10.1016/j.procs.2017.11.318 29. Igamberdiev, H.Z., Sevinov, J.U., Yusupbekov, A.N.: Regular algorithms for identifying the parameters of an object and a controller in a closed-loop control system. J. Chem. Tech. Cont. and manag. 6, 50–54 (2017) 30. Zaripov, O.O., Shukurova, O.P., Sevinov, J.U.: Algorithms for identification of linear dynamic control objects based on the pseudo-concept concept. Inter. J. of Psy. Rehab. 24(3), 261–267 (2020). https://doi.org/10.37200/IJPR/V24I3/PR200778 31. Igamberdiev, H.Z., Boeva, O.H., Sevinov, J.U.: Sustainable algorithms for selecting feedback in dynamic object management systems. J. Adv. Res. Dyn. Contr. Syst. 12(7), 2162–2166 (2020). https://doi.org/10.5373/JARDCS/V12SP7/20202337 32. Mallayev, A.R., Xusanov, S.N.: Programmnoye obespecheniye dlya sinteza parametri regulyatorov v adaptivnix suboptimalnix sistemax upravleniya texnologicheskimi protsessami. Certificate of official registration of the program created for ECM, № DGU 10370 (2021) 33. Aleksandrov, A.G.: Optimalniye i adaptivniye sistemi, p. 278p. Nauka, Moscow (2003) 34. Antonov, V., Terexov, V., Tyukin, I.: Adaptivnoye upravleniye v texnicheskix sistemax. handbook. Sankt-Peterburgskogo universiteta, Russia (2001), 244 p. 35. Miroshnik, I.V., Nikiforov, V.O., Fradkov, A.L.: Nelineynoye i adaptivnoye upravleniye slojnimi dinamicheskimi sistemami, p. 549p. Nauka, Moscow (2000) 36. Djigan V.I. Adaptivnaya filtratsiya signalov. Teoriya i algoritmi. Texnosfera, Moscow (2013), 528 p. 37. Karabutov, N.N.: Adaptivnaya identifikatsiya sistem: Informatsionniy sintez. Stereotip, Russia (2016), 384p. 38. Jirov, M.V., Makarov, V.V., Soldatov, V.V.: Identifikatsiya i adaptivnoye upravleniye texnologicheskimi protsessami s nestatsionarnimi parametrami, p. 203p. MGTU im. N.E. Baumana, Moscow (2011) 39. Sikunov, A.M.: Adaptivnoye upravleniye s kompensatsiyey vliyaniya zapazdivaniya v upravlyayushem vozdeystvii [Adaptive control with compensation for the influence of delay in the control action]. Izvestiya akademii nauk. Teoriya i sistemi upravleniya 4, 78–81 (2000) 40. Kuznetsov, YE.S.: Upravleniye texnicheskimi sistemami [Technical systems management]: Handbook. MADI (TU), Russia (2001), 262p. 41. Sinitsin, I.N.: Filtri Kalmana i Pugacheva [Kalman and Pugachev filters]. Logos, Russia (2006), 640p.

Electronic Load Sensing for Integrating Electro-Hydraulic Mechatronic Actuators with Industry 4.0 and 5.0 Components Alexander Skvorchevsky(B) Research Center of Robotics, Mechatronics and Production Informatization, Otakar Yarosh Street, 59, Kharkiv 61103, Ukraine [email protected]

Abstract. Electrohydraulic systems not only convey power from the pump to the actuators but also provide information about the load on the working body through the fluid. The availability of inexpensive, sensitive, and compact pressure sensors has opened up enormous potential for energy saving and data collection on actuator load and performance. This wealth of information on the actuator’s operation creates exciting opportunities for implementing Industry 4.0 and 5.0 principles, such as digital twins, big data, machine learning and the Internet of Things. The aim of the study is to develop principles that reduce energy consumption in electro-hydraulic mechatronic systems and integrate electro-hydraulic systems and Industry 4.0 and 5.0 components. This aim is achieved by analysis of the current achievements in the field of integration of electrohydraulic actuators and Industry 4.0 and 5.0 components. As a result of the research, the following principles for the development of electro-hydraulic mechatronic systems were proposed, namely: adaptive pump power control using pressure feedback can reduce energy consumption in electrohydraulic actuators; power density of electrohydraulic mechatronic systems can be increased through self-contained actuators and electronic load sensing; real-time load data from pressure feedback enables the implementation of Industry 4.0 and 5.0 components for smart machines. A selection of design solutions for electro-hydraulic systems has been made that are most easily integrated with Industry 4.0 and 5.0 components, and this integration is performed by applying the principle of Electronic Load Sensing. Keywords: Industry 5.0 · Electro-hydraulic actuator · Electronic Load Sensing · electrohydraulic amplifier · proportional valve

1 Introduction The integration of hydraulic drives with Industry 4.0 and 5.0 components is crucial in today’s industrial landscape. Heavy-duty machines, including excavators, tractors, cranes, bulldozers, loaders and others that rely on electro-hydraulic drives, require the implementation of Industry 4.0 and 5.0 principles to improve efficiency and productivity. Therefore, it is imperative to emphasize the importance of integrating these machines © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 440–455, 2023. https://doi.org/10.1007/978-3-031-40628-7_37

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with smart technologies, such as sensors, controllers, and cloud-based platforms, to achieve real-time monitoring, predictive maintenance, and enhanced safety. By integrating hydraulic drives with Industry 4.0 and 5.0 components, heavy-duty machines can operate smarter and more efficiently, leading to increased profitability and reduced costs in the long run. Similarly, hydraulic presses, injection molding machines, and other industrial machines that rely on hydraulic systems can also benefit from integration with Industry 4.0 and 5.0 components. Overall, the integration of hydraulic drives with smart technologies can improve efficiency, reduce downtime, and enhance safety across a wide range of heavy-duty machines in various industries.

2 Literature Review and Problem Statement The main subject of the paper [1] is the creation of a comprehensive dataset for the digitization of industrial hydraulic press operations. To achieve this, the paper focuses on collecting and pre-processing data, as well as transferring it to the cloud. The novelty of this process lies in the use of edge computing to manage large volumes of data. The pre-processing stage involves the application of data normalization methods to sort, tag, and link data logically, allowing for efficient compression and the dynamic creation of a complex dataset for use in the digitization process. This process of data collection and pre-processing, along with the application of normalization methods, represents the main contributions of the paper. The hydraulic press at Brose CZ spol. s r.o. is utilized for pressing sheet metal components for the automotive sector. The press is controlled by a Siemens Simatic 1200 industrial logic controller (PLC), which comprehensively manages its function and collects and measures vast amounts of data. The PLC sends this data to an industrial computer for further processing via Edge Computing. The control system and data collection are managed by the same PLC, which can collect over 7 million records per day at a measuring cycle of 5 ms to 10 ms. The dataset has an average of 6.55 million records, each containing 51 values (data and timestamp), and is stored in a CSV file. Each CSV has an average size of 1.44 GB. This data package is divided into several groups, such as processing force, tilting moment and displacement, cutting shock absorber, movement of the arm, cooling, control oil circuit, energy consumption, and bearings of the pump [1]. Although the hydraulic drive is an important part of the press [1], more specialized research is needed to collect, process and analyze data on the operation of hydraulic drives. The disadvantages of the article [1] also include the fact that its results can only partially be extended to hydraulic drives of road-building, agricultural, mining and other machines, where the load is stochastic in nature. The review paper [2] examines the latest developments in electro-hydraulic control valves and related technologies. The paper [2] focuses on three key areas: state acquisition through sensors or indirect acquisition technologies, control strategies using digital controllers and innovative valves, and online maintenance through data interaction and fault diagnosis. The paper [2] also discusses the primary features and trends in electro-hydraulic control valves for Industry 4.0. These valves are now being integrated with digital technology and various communication technologies, making them more efficient and intelligent. As Industry 4.0 continues to revolutionize the industry,

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electro-hydraulic control valves need to keep up with new technologies to remain vital. The paper reviewed the hardware development of these valves, focusing on sensors, actuators, and electronic controllers. In the future, high-precision integrated sensors and powerful computing digital controllers could be trending, while accurate modelling and experimental curve fitting methods have already produced good results for indirect state perception. Digital controllers show the potential for adaptation. Digital hydraulics with independent metering systems and on/off valves is an important direction for industrial applications. Electro-hydraulic valves with integrated communication interfaces like Fieldbus, Bluetooth, and IO-Link provide the hardware foundation for the hydraulic Internet of Things, transmitting the visual state of valves to users through software. Fault diagnosis methods allow for real-time diagnosis of the inner faults of electro-hydraulic valves. The aim is to make these valves digital, integrated, and intelligent to promote the progress of the entire hydraulic industry, bringing it closer to Industry 4.0. While there are still challenges to overcome, the development of electro-hydraulic control valves is of great significance for the future of hydraulic technologies. Despite the comprehensive analysis of electro-hydraulic control valves for their integration with Industry 4.0 components carried out in the article [2], an analysis of the integration of electro-hydraulic actuators and pumps is also needed. The article [2] pays considerable attention to digital methods for controlling the flow of working fluid. At the same time, insufficient attention is paid to digital methods of pressure control in the article [2]. The paper [3] provides an explanation of the current definition of digital hydraulics while also presenting a more accurate definition of the technology. The paper also reviews the developmental works on digital hydraulic components and technology, highlighting some of the main outcomes of this work. The promotion of Industry 4.0 has led to traditional hydraulic technology becoming marginalized due to its low energy efficiency and lack of intelligence. Digital hydraulic technology has the potential to address these shortcomings and play a significant role in intelligent factories and manufacturing. Parallel digital hydraulic technology, with its great fault tolerance and fast response performance, has become a mainstream research direction in digital hydraulic technology. However, the high cost and large volume of switching components connected in parallel, as well as the lack of accurate control algorithms for parallel systems, pose challenges to its development. High-speed switching digital hydraulic technology, another major research direction, can achieve precise lossless control performance, with response times in the millisecond range. However, vibration, noise, pulsation, and the limited-service life of high-speed switching valves are challenges that need to be addressed. Stepping digital hydraulic technology, famous for its high accuracy and sensorless control performance, simplifies systems and improves usability and maintainability. However, the stepping motor’s tendency to be out-of-step at high frequency limits its application and development. The goal is to improve the energy efficiency, reliability, and practicability of digital hydraulic technology and promote its practical application. Digital hydraulic technology provides a way for the traditional hydraulic industry to develop to-wards intelligence and greenness, and it will make fluid power technology align with Industry 4.0. As research in digital hydraulic technology continues, the technology will continue to innovate, and more mature digital hydraulic components will have more extensive engineering application prospects [3]. Despite the wide coverage of the analysis of

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achievements in the field of digital hydraulics [3], insufficient attention has been paid to the digitalization of the entire complex of the hydraulic drive-working part of the machine. Digital hydraulic technology has yielded positive outcomes in terms of intelligence, integration, and energy efficiency since its inception. Over the years, it has garnered significant attention in the industry due to its potential benefits. Despite this, researchers have had varying definitions of what constitutes digital hydraulic technology, which has hindered its development to some extent. To address this issue, the paper [3] aims to provide a precise definition of digital hydraulic technology based on extensive research. Additionally, the paper [3] examines the current state of research on this technology, and its developmental process, and predicts its future trends. Despite the wide coverage of the analysis of achievements in the field of digital hydraulics [3], insufficient attention has been paid to the digitalization of the entire complex of the hydraulic drive-working part of the machine. The study [4] aims to create an Auto-mated Heavy-Duty Material Handling System based on Industry 4.0 principles. The system components are designed and tested through calculations. The findings indicate that when the system is fully loaded with 20 T, the overall tractive effort is 250.623 kN per wheel. Each wheel motor torque is calculated, and the system requires 468.411 W of power per wheel to move the machine when loaded with its total weight. Despite the importance of the study [4], it is limited to only one type of electrohydraulic drive. The study [5] introduces a modelling approach for a telescopic handler’s hydraulically actuated powertrain driven by a diesel engine. The driving dynamics parameters were estimated using linear regression algorithms and actual measurements. The resulting simulation model accurately reflects the system’s behavior and can be utilized for simulation studies and assistance applications. For instance, a controller can be designed to limit the critical load on the diesel engine, thereby preventing stalling. By combining the driving function model with the dynamics of the working functionality, assistance systems for the whole machine can be implemented, including load torque limitation to avoid tipping over the telescopic handler. Ultimately, this proposed model can be used to develop automated driving algorithms that bring the construction site vehicle closer to complete automation. Despite the importance of the considered study [5], one should be supplemented with the principles of collecting and processing data on the operation of the electro-hydraulic drive of the vehicle. The paper [6] outlines the design and development of an IoT device (data logger) that improves the usage and performance of hydraulic hammers through remote monitoring, using sensors for data collection, analysis, and management. By placing sensors optimally and designing a suitable platform, the data logger can extract vast amounts of data (Big Data) on the hydraulic hammer’s vibration, machine operation time, oil pressure, temperature, and oil flow based on the operation conditions and material type. Analyzing this information enables adjustment of process planning, implementation of predictive maintenance, and provision of standard technical information for different modes of the hydraulic hammer. Overall, this IoT device enhances the monitoring and performance of hydraulic hammers, making them more efficient and effective in various applications [6]. Although hydraulic hammers are an important application of fluid

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power [6], research is needed to cover a wider range of electro-hydraulic systems in the context of their integration with Industry 4.0 principles. In the paper [7], a data-driven approach is used to identify and categorize faults in a multi-component hydraulic rig. Various feature extraction and selection methods were explored and compared using historical data with multiple sensor readings of different sampling frequencies (asynchronous data). Supervised learning models were developed using these features to detect and differentiate the various levels of component degradation. Additionally, due to the lack of annotated data in industrial settings, unsupervised clustering and anomaly detection algorithms were also studied to detect faults in the system [7]. Despite the importance of the study [7] for the development of diagnostics of hydraulic and electro-hydraulic systems, it should be complemented by research on the use of sensors to collect data for optimal control and energy saving. Remote control and monitoring of an electronic system were designed and tested for a fluid power machine using an open-source programmable board [8]. To enable twoway communication between the machine and the user interface remotely, an Internet connection is necessary. The Arduino Uno Wi-Fi Rev 2 board was used to establish a wireless connection with a local network. To transmit the data between the board and the graphical interface, which is on an external network, an MQTT broker was created on an AWS server. The program receives sensor data, sends it to the user interface, makes logical decisions, processes control orders, and establishes protocols to govern the machine. The electronic system was tested on a mobile hydraulic crane, with four variables selected to control and monitor crane performance, namely load position, electric motor current demand, hydraulic pump flow, and mechanical pin presence for locking or releasing the hydraulic linear actuator. Two remote control tests were conducted, one from the same location and the other from Berlin, Germany. The open-source board was able to connect with the user interface created with Node-RED via the MQTT protocol, enabling the remote control and monitoring of the machine’s performance. The experience of using Arduino [8] needs to be expanded to control the electro-hydraulic systems of various other machines. The emergence of cyber-physical systems (CPS) in smart manufacturing has created numerous possibilities for improving hydraulic systems. The paper [9] proposes the use of artificial intelligence (AI) in the design of smart hydraulic presses, in conjunction with Industry 4.0 technology. The aim [9] is to create flexible systems that can form materials accurately and with ease, utilizing the concept of cyber-physical systems and digital twins. The primary challenge is developing an AI-based algorithm for the manufacturing execution system (MES) that can improve the forming process and respond to real-time disturbances. The paper [9] also introduces the concept of real-time monitoring and data analysis of smart hydraulic press parameters to enhance the system’s performance and achieve continuous quality control of the products. Key advantages of this approach include energy-efficient systems and automatic tool exchange, which are important trends in hydraulics and Manufacturing as a Service (MaaS). The results of the study [9] need to be significantly supplemented for use in order to control the electro-hydraulic drives of agricultural, mining and road construction equipment. This is due to the fact that electro-hydraulic systems used in these industries are subject to

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a significantly larger number of random and unaccounted factors than electro-hydraulic press systems. The paper [10] is shown that condition monitoring is an important application in the context of Industry 4.0, whereby computational intelligence methods are utilized to monitor the health of machines. Data-driven models, particularly those based on deep learning, are effective for analyzing time series sensor data due to their ability to identify patterns in large amounts of data and track signal evolution over time. However, as the interpretability of machine learning models becomes increasingly important, there is a need for additional requirements to be met. This study focuses on the sensitivity of sensors in a deep learning-based condition monitoring system, providing information about the significance of each sensor. To achieve this, several convolutional neural networks were constructed from a multisensory dataset to predict different levels of degradation in a hydraulic system. The analysis provided insights into the contribution of each sensor to the prediction of the classifier. Relevant sensors were identified, and models built on the selected sensors produced predictions equal in quality to the original models. This information [10] about the importance of sensors can aid in the design of the system, allowing for timely decisions to be made on which sensors are required. Just like Study [7], Study [10] should be complemented by research on the usage of sensors to collect data for optimal control and energy saving. The paper [11] emphasizes that to enhance competitiveness, industrial processes must possess flexibility and adaptability to changing demands and current technological trends. One way to achieve this is by adopting control techniques such as Artificial Neural Networks, which mimic the functioning of biological neural networks in the human brain. These networks can extract dynamic features from experimental data, making them suitable for controlling physical systems with nonlinear characteristics. To demonstrate this concept, an Artificial Neural Networks controller system was developed and compared with a classic PI strategy using a test hydraulic system. Simulation results showed that the neural network outperformed the PI controller, with faster settling times and no overshoot above 20% in response to changes in the setpoint for the size of the tank level. Overall, the use of Artificial Neural Networks offers a quality and optimization advantage in the processing, emulation, and control of physical systems. The study [12] presents an electro-hydraulic test bench (that was previously operated manually) improved using PLC. To automate this test bench, a PLC-Weintek was chosen, and it was programmed using CODESYS in ladder language with an open Modbus programming code through the SFD block language. The system includes a touchscreen human-machine interface (HMI) that allows users to input data and control operations at various hierarchies. The operator can also store data for later analysis. The proposal was validated through experimental tests, which showed a significant reduction in execution time for the proposed tasks and an improvement in learning conditions. Experience in the use of controllers for the control of electro-hydraulic drives set out [11, 12] should be applied to integrate them with the concepts of Industry 4.0. The paper [13] employs the Monte Carlo method to determine the optimal components for a hydraulic excavator’s swinging mechanism. The study defines three objective functions, which are the total mass of four components: “hydraulic motor,” “gearbox,” “slewing bearing,” and “small sprocket”; the product of the total price and the total

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mass; and the price of the same components. To identify the optimal combination of components, the objective function is computed for multiple random combinations, and the results are ranked. One major advantage of this method is its suitability for computer implementation, with a relatively small number of required calculations. Another benefit is that close to optimal objective function value rankings generate additional combinations, significantly expanding the design possibilities. The results of the study [13] can be used for the structural synthesis of electro-hydraulic actuators intended for use within the framework of Industry 4.0 concepts. The mathematical models presented in [14, 15] can be used to integrate electrohydraulic vehicle drives with the core concepts of Industry 4.0.

3 The Aim and Objectives of the Study The aim of the study is to develop strategies that reduce energy consumption in electrohydraulic mechatronic systems and integrate electrohydraulic systems and Industry 4.0 and 5.0 components. To achieve the aim, the following objectives have been established: – to reduce the energy consumption of electrohydraulic drives by implementing adaptive control of pump power based on the load of the executive drives; – to increase the power density of electrohydraulic mechatronic systems by utilizing modular structures and transferring control functions from hydraulic components to electronic ones; – to integrate Industry 4.0 and 5.0 components, such as digital twins, big data, and machine learning, into machines that employ Electronic Load Sensing (ELS) electrohydraulic mechatronic systems; – to obtain real-time data on the load of the machine’s working bodies by measuring the pressure in the electro-hydraulic executive drive.

4 The Study Materials and Methods The research materials were ideas, tools, and Industry 4.0 and 5.0 innovations, as well as design schemes of electro-hydraulic systems and their element base. The object of research is engineering concepts that can contribute to the collection of data on various aspects of the operation of electro-hydraulic systems. The study is based on the hypothesis that by using integrated pressure sensors in electro-hydraulic systems, big data can be collected to integrate these systems with major Industry 4.0 and 5.0 innovations, as well as make electro-hydraulic systems more energy efficient. The research method is to systematically analyze the design schemes of the electro-hydraulic systems and their elements.

5 Results There are two feedback principles in automatic control theory: deviation compensation and disturbing compensation (invariant systems). This R&D proposes the extensive use of the invariance principle (disturbance compensation). Control systems based on the

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invariance principle are categorized as active and passive. Active disturbance compensation systems (active invariant systems) incorporate a feedback loop, whereas passive invariant systems compensate for disturbances using their physical and design attributes. One of the elements of electro-hydraulic systems that are well suited to the objectives of the study is the multifunctional proportional electro-hydraulic transducer [16]. The electro-hydraulic amplifiers have gained popularity due to the widespread use of the nozzle-flapper element, primarily because of its high amplification coefficient and simplicity. However, it has a significant drawback, which is the unproductive flow of the working fluid through the nozzle when there is no control signal. Consequently, largediameter nozzles (5–10 mm) cannot be used. Thus, the small diameter of the nozzle does not permit direct control of the hydraulic cylinder using the nozzle-flapper element. An additional amplification stage in the form of a spool is required to address this issue, which increases the mass of the actuator and reduces reliability and energy efficiency. To overcome this problem, a solution has been proposed by adding a check valve on the nozzle’s opposite side to the flapper (as shown in Fig. 1). The design hypothesis assumes that the nozzle-flapper element’s working stroke (b) is significantly lower than the check valve’s working stroke (L) (as depicted in Fig. 1), enabling the check valve to work efficiently without interfering of the nozzle-flapper element’s operation [16].

Fig. 1. Structural scheme of a multifunctional proportional electro-hydraulic transducer [16]: 1 - nozzle; 2 - spring; 3 - piston; 4 - end face of the piston; 5 - locking element; 6 - valve seat; 7 nozzle channel; 8 - tappet; 9 - flapper; 10 - proportional electromagnet; 11 - electromagnet coil; 12 - electromagnet armature; 13 - electromagnet tappet; 14 - drainage cavity; 15 - pressure regulating cavity; 16 - neck; 17 - drainage cavity

Although the moving part of the multifunctional proportional electro-hydraulic transducer is hydrostatically unloaded, it still requires an electromagnet [17] with enhanced traction characteristics for its control. During the research, a set of nonlinear differential equations was formulated and numerically solved to describe the functionality of the multifunctional proportional electro-hydraulic transducer [16]. Additionally, experimental investigations were conducted to study the static properties of the device, and the outcomes of the study are documented in the author’s publications. The results of the study confirmed the hypothesis that the working stroke (b) of the nozzle-flapper component is significantly smaller than the working stroke (L) of the check valve (see Fig. 1). Therefore, the check valve will

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not obstruct the functioning of the nozzle-flapper component. A symbol (see Fig. 2) for the multifunctional proportional electro-hydraulic transducer is proposed for hydraulic diagrams, indicating two functions of the device, which are pressure regulation and cutting the working chamber of the hydraulic cylinder in the absence of a control signal on the electromagnet. Figure 3 displays the disassembled experimental sample of the multifunctional proportional electro-hydraulic transducer.

Fig. 2. Schematic symbol of the multifunctional proportional electro-hydraulic transducer

Fig. 3. The experimental sample of the multifunctional proportional electro-hydraulic transducer (disassembled)

Due to the absence of unproductive working fluid flow and the hydrostatic unloading of the valve, the multifunctional proportional electro-hydraulic transducers open up opportunities for the creation of more energy-efficient and digital electro-hydraulic mechatronic systems than existing ones. Greater digitalization is achieved due to the significant nozzle diameter of 5–10 mm, which makes it possible to control the hydraulic cylinder directly with the multifunctional proportional electro-hydraulic transducer, avoiding two-stage spool valves. In turn, direct pressure control using the proposed valve and pressure sensors integrated into the hydraulic cylinder allows you to create a pressure feedback loop, which makes the electro-hydraulic drive more digital and integrated with Industry 4.0 and 5.0 components. Here it should be emphasized that the proposed systems use the principle of control by disturbance, and not by deviation, which improves the quality of automatic control processes. In this way, the multifunctional proportional electro-hydraulic transducer facilitates the integration of electro-hydraulic drives with Industries 4.0 and 5.0 components by applying the ELS principle. Let us consider examples of multifunctional proportional electro-hydraulic transducer applications. One of the possible applications of the multifunctional proportional electro-hydraulic transducer is

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an adaptive electronic-hydraulic vehicle track tensioning system. The primary objective of this system is to enable remote control of the track tension force, depending on the vehicle’s speed and the condition of the soil, and to ensure a constant track tension force, regardless of the terrain (see Fig. 4). The mechanism for achieving this goal involves regulating the pressure in the hydraulic cylinder’s chamber through an electronic feedback loop created using the multifunctional proportional electro-hydraulic transducer and pressure sensor. As a result, the system is invariant (able to compensate for disturbances) and operates according to the ELS principle. This system can be utilized in both manned and unmanned vehicles, such as those used in agriculture, mining, and exploration on other planets where ground properties are unpredictable [18].

Fig. 4. Scheme of the electronic-hydraulic system of tensioning the vehicle track [18]: 1 – track; 2 – support roller; 3 – guide wheel; 4 – crank; 11, 5 – hinges; 6 – rod; 7 – rod cavity; 8 – piston; 9 – piston cavity; 10 – hydraulic cylinder; 12 – drainage line; 13 – injection line; 14 – pressure control line; 15 – throttle; 16 – pump; 17 – check valve; 18 – safety valve; 19 – tank; 20 – multifunctional proportional electro-hydraulic transducer; 21 – electronic unit; 22 – pressure sensor.

Another application of the multifunctional proportional electro-hydraulic transducer is power control ELS systems for positive displacement pumps [19]. Despite the high cost associated with variable displacement pumps, their use in hydraulic systems is increasingly prevalent due to their significant energy savings compared to pumps with a constant supply and discharge of excess working fluid under pressure through a safety valve. As part of this study, automatic pressure and/or supply control of the variable displacement pump is proposed by introducing feedback on the disturbance, which is the difference between the load pressure and the pressure in the drive piston of the variable displacement pump. The invention [19] is related to variable displacement pumps and specifically the digital electro-hydraulic power control systems of axial-piston pumps

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with an inclined disk. Furthermore, the power control system can be employed in other types of variable displacement pumps (see Fig. 5). The power control system for a positive displacement pump (see Fig. 5) comprises an oil tank (1), a counteraction piston (2), and an inclined swash plate (3) that regulates the displacement of the axial piston pump (4). The pump’s shaft (5) is connected to a mechanical energy source (6), such as an internal combustion engine. A proportional electrically controlled safety valve (7) is connected in parallel to the axial-piston pump’s discharge line (10-1). An electrically controlled non-return valve (9) is connected in series with the pump (4), and its I AB signal for activation comes from the electronic unit (11). A sensor (8) measures the angular velocity ω of the pump’s shaft rotation (5), and its signal uω is processed by a proportional integral-differentiating (PID) regulator (10). The electronic unit (11) receives the input set signal uinp , feedback signals u1 and u2 from load and pressure sensors (12) and (13), respectively, and the processed signal uωPID . After processing these signals, the electronic unit (11) forms the set control current I cont , which is applied to the multifunctional proportional electro-hydraulic transducer (15) electromagnet (14). The multifunctional proportional electro-hydraulic transducer (15) consists of a nozzleflapper element (16) and an electrically controlled non-return valve (17) in series with it, both driven by one electromagnet (14). The working fluid from the pump (4) enters the multifunctional proportional electro-hydraulic transducer (15) through the throttle (18), and this ensures a difference in the p2 pressure in the cavity (19) under the drive piston (20) from the p1 pressure of the load. The drive piston (20) is connected to the swash plate (3) and counteracts the force on the counteraction piston (2), caused by the compression of the spring (21) and the presence of the p1 load pressure in the cavity (22) of the counteraction piston (2). The proposed system aims to provide automatic control of the pressure and supply of a variable displacement pump by introducing feedback on the disturbing influence caused by the difference between the load pressure and the pressure in the drive piston of the variable displacement pump. This control system can ensure stabilization of the pump’s working volume, improve the quality of automatic control, stabilize the supply of the working fluid, and automatically shut down the pump supply in case of hydraulic drive damage. Compared to systems with electronic feedback circuitry for the swash plate position, the proposed system is advantageous as it improves the quality of automatic control, simplifies the pump power control system, reduces its mass and size, and lowers costs. Thus, the implementation of the ELC principle, by including multifunctional proportional electro-hydraulic transducers and pressure sensors in the design of variable pumps, makes pumps more energy efficient and integrable with Industries 4.0 and 5.0 components. Electro-hydraulic linear servo actuators have undergone significant advancements, evolving into self-contained mechatronic modules that include hydraulic cylinders, valves, feedback sensors, and electronic control units, sometimes even pumps and hydraulic accumulators. Usually, these servo actuators used magnetostrictive sensors integrated into the hydraulic cylinder rod to measure deviations and provide feedback on position. Despite the widespread usage of electro-hydraulic servo actuators in aerospace engineering, robotics, and the oil and gas industry, their design has remained relatively unchanged since the late 1980s. Currently, there have been no significant changes in the development of electro-hydraulic self-contained linear actuators [20–23]. At the

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Fig. 5. Principal scheme of invariant power control ELS systems for positive displacement pumps [19]

same time, electromechanical linear servo actuators have made significant progress over the last decades. Electromechanical planetary roller screw actuators due to their highpower density are especially competitive with electro-hydraulic linear servo actuators. In order to compete with the electro-mechanical planetary roller screw actuators, electrohydraulic actuators have to use new design concepts which emphasize their advantages (high power density, high dynamic characteristics and shock and vibration absorption etc.). The control of a hydraulic cylinder with a single-stage valve (multifunctional proportional electro-hydraulic transducer) opens up great opportunities for the creation of self-contained compact electro-hydraulic linear servo drives. This type of electrohydraulic linear servo drive can be considered a viable alternative to electro-hydraulic servo drives with magnetostrictive sensors [20–23]. Instead of using the principles of deviation compensation, which involve magnetostrictive sensors, this type of servo drive uses the principles of disturbance compensation [24]. Disturbance feedback is achieved by measuring the pressure in the cavities of the hydraulic cylinder, which can be done with modern pressure sensors that are small, inexpensive, and do not require additional moving parts to be added to the hydraulic cylinder. The servo drive’s variable structure allows for switching between force stabilization and position stabilization modes. Force

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stabilization is achieved by stabilizing the pressure in the piston cavity, while position stabilization is achieved by stabilizing the pressure drop across the piston. By stabilizing the pressure drop on the piston and using a spring in the rod cavity, the servo drive can maintain the rod in a specific position. Refer to Fig. 6 for an illustration of this concept.

Fig. 6. Scheme of invariant electro-hydraulic servo actuator with a variable structure [24]

The electro-hydraulic servo drive proposed in Fig. 6 consists of a hydraulic cylinder (1) with a piston cavity (2) formed by its body and piston (3). The pressure sensor (4) is connected to the piston cavity (2) and provides an electrical feedback signal u1fb to the electronic control unit (5), which also receives the control signal u(contr.) and electrical feedback signal u2fb from sensor (6), connected to the rod cavity (7) containing a spring (9) and a rod (8). A multifunctional proportional electro-hydraulic transducer [16] (11) is connected in parallel to the rod cavity (7) and the injection line (10). The transducer (11) consists of an electromagnet (12) [17], which drives the nozzle-flapper element (13) and the electrically controlled check valve (14). A constant resistance throttle (15) and a non-return valve (16) are installed in front of the multifunctional proportional electro-hydraulic transducer (11). The shuttle valve (17) switches the flow of liquid between the injection lines (10) and (19) based on the pressure difference in the piston (2) and rod (7) cavities. The injection line (19), which supplies liquid to the piston cavity (2), is equipped with a check valve (18) and a throttle (20) of constant resistance. A multifunctional proportional electro-hydraulic transducer (21) [16], consisting of a proportional electromagnet (23) [17], which drives the nozzle-flapper element (22) and the electrically controlled check valve (24) and is connected in parallel to the injection line (19). The electronic unit (5) supplies the control signal to the electromagnets (12) and (23). As we can see from Fig. 6, the application of the ELS principle using multifunctional proportional electro-hydraulic transducers and pressure sensors allows the creation of

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an electro-hydraulic linear actuator that is well integrated with control electronics, and therefore with Industries 4.0 and 5.0 components. At the same time, the structural diagram of the actuator (Fig. 6) is much simpler than electrohydraulic linear actuators based on magnetostrictive sensors [20–23].

6 Discussion The automatic control circuit, including multifunctional proportional electro-hydraulic transducers and pressure sensors, allows you to create a number of more energy-efficient and digital electro-hydraulic mechatronic systems. The usage of pressure feedback sensors located in the cavities of hydraulic cylinders enables the real-time collection of information regarding the workload on the working mechanisms of machines which used electrohydraulic drives. By employing this technology, machines that use electrohydraulic drives can be incorporated within the framework of the Internet of Things, big data technologies, machine learning, and artificial intelligence methods. For electrohydraulic mechatronic systems to be integrated with Industries 4.0 and 5.0 components, it is necessary to create digital replicas of these systems known as digital twins. The previously mentioned illustrations of applying ELS principles in electrohydraulic systems are not comprehensive. The ELS principle can also be employed in various other systems, including but not limited to: – control of ailerons and wing flaps; – vibrations control massive and overall structures, like radar antennas, through active suppression; – adaptive control of excavators’ buckets; – control of attachments for tractors – Injection molding machines for metals and plastics – robots and robotic complexes are engineered to operate with substantial power and inertial loads, such as those found in metallurgy and storage, among others.

7 Conclusions Adaptive control of pump power depending on the load (measured by pressure sensors) of actuators allows for the reduction of the energy consumption of electrohydraulic actuators. Power density increasing for electrohydraulic mechatronic systems can be achieved through the use of self-contained actuators and the transfer of control functions from hydraulic elements to electronic ones, in addition, this can be achieved by combining several functions on one valve. Indirect obtaining real-time data on the load on the working bodies of the machines, by measuring the pressure in the electrohydraulic executive drive can help implement Industries 4.0 and 5.0 components (digital twins, big data, machine learning, Internet of Things) for machines operated by the electronic load sensing electrohydraulic mechatronic systems.

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References 1. Hercik, R., Svoboda, R.: Collecting and pre-processing data for Industry 4.0 implementation using hydraulic press. Data 8(4), 72 (2023) 2. Xu, B., et al.: Research and development of electro-hydraulic control valves oriented to Industry 4.0: a review. Chin. J. Mech. Eng. 33(1), 1–20 (2020) 3. Zhang, Q., et al.: Review and development trend of digital hydraulic technology. Appl. Sci. 10(2), 579 (2020) 4. Mafokwane, S.Z., Kallon, D.V.: Hydraulic system design of a tri-adjustable automated heavy duty handling system based on Industry 4.0. In: Open Innovations (OI), pp. 187–196. IEEE (2019) 5. Parlapanis, C., et al.: Modeling the driving dynamics of a hydraulic construction vehicle. IFAC-PapersOnLine 55(27), 454–459 (2022) 6. Heidarpour, F., Ciccolella, A., Uva, A.E.: Design and development of an IoT enabled device for remote monitoring of hydraulic hammers. In: Advances on Mechanics, Design Engineering and Manufacturing IV: Proceedings of the International Joint Conference on Mechanics, Design Engineering & Advanced Manufacturing, pp. 390–398 (2022) 7. Rajasekar, S.: Prediction of component level degradation in a hydraulic rig using machine learning methods. In: 15th International Conference on Developments in eSystems Engineering (DeSE), pp. 351–356. IEEE (2023) 8. Aragón González, G., et al.: Remote control and monitoring of a hydraulic machine. J. Phys. Conf. Ser. 2307(1), 323–330 (2022) 9. Jankoviˇc, D., Šimic, M., Herakoviˇc, N.: The concept of smart hydraulic press. In: Borangiu, T., Trentesaux, D., Leitão, P., Cardin, O., Lamouri, S. (eds) Service Oriented, Holonic and Multi-Agent Manufacturing Systems for Industry of the Future. SOHOMA 2020. Studies in Computational Intelligence, vol 952. Springer, Cham (2021). https://doi.org/10.1007/978-3030-69373-2_29 10. Elsadiek, Helmy, A.M.: Sensitivity analysis of sensors in a hydraulic condition monitoring system using CNN models. In: MDPI 2020, p. 3307 (2020) 11. Mateus, J.J.R., Garcia, F.E.M., Gomez, J.A.: Comparative study between a neural network controller and a classic pi applied to an experimental hydraulic system. Webology 19(5), 581–592 (2022) 12. Altamirano-Haro, D., et al.: Automation of an electro-hydraulic test bench using a Weitek CMT3092 HMI-PLC. In: HCI International 2022–Late Breaking Posters: 24th International Conference on Human-Computer Interaction, HCII, pp. 232–239 (2022) 13. Mitrev, R., et al.: Optimal selection of components for ahydraulic excavator swinging mechanism. Mach. Technol. Mater. 12, 8–11. (2018) 14. Nikonov, O., et al.: Simulation modeling of external perturbations affecting wheeled vehicles of special purpose. In: CEUR Workshop Proceedings, pp. 86–95 (2020) 15. Nikonov, O., et al.: Parametric synthesis of a dynamic object control system with nonlinear characteristics. In: CMIS, pp. 91–101 (2020) 16. Skvorchevsky, A.: Patent of Ukraine for the invention No. 76766. Electro-hydraulic amplifier. Application No. 2004021138 dated 02.17.2004 IPC (2006) F15B 3/00. Publ. September 15, 2006, bulletin No. 9 17. Skvorchevsky, A.: Patent of Ukraine for the invention No. 75780. Proportional electromagnet. Application No. 20040705646 dated 07.12.2004 IPC (2006) H01F7/08. Publ. 15. 05. 2006, Bulletin No. 5 18. Ckvopqevcki, O.m.: Galyzi zactocyvann bagatofynkcionalnix ppopopcinix elektpogidpavliqnix pepetvopvaqiv. Bicnik Cxidnoykpa|nckogo nacionalnogo ynivepcitety im. Bolodimipa Dal 3(109), 140–145 (2007)

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19. Skvorchevsky, A., Volontsevich, D.: Patent of Ukraine for the invention No. 118107. Power control system of the positive displacement pump. Application No. a201600113; dated 04.01.2016; IPC IPC (2018.01) F04B 1/26 (2006.01) F04B 49/00. Publ. 26.11.2018, bulletin No. 22 20. HMIX Hydraulic Cylinders with Integrated Transducers Metric feedback cylinders for working pressures up to 210 bar. Assess mood: https://www.parker.com/literature/Cyl inder%20Europe/Cylinder%20Europe%20-%20English%20Literature/Product%20Literat ure/HY07-1175UK_HMIX_Metric_210_Bar_Hydraulic_Feedback_Cylinders.pdf 21. Industrial Electrohydraulics. Master Catalog. ATOS – 449–552 p. Assess mood: https://www. atos.com/marketing/EN/KTI20.pdf 22. Servo-hydraulic actuator. Rexroth Bosch company – 2021. Assess mood: https://www.boschr exroth.com/documents/12605/25201122/RE62270-B_01-2021.pdf/2746e1bc-9d5c-60ebd6b7-0c469cbe1925 23. Eaton Electro-Hydraulic Cylinder Catalog E-CYNC-CC001-E—March 2018. Assess mood: https://www.eaton.com/ecm/groups/public/@pub/@eaton/@hyd/documents/content/ pct_3276049.pdf 24. Ckvopqevcki, O.m.: Invapiantni do ε elektpogidpavliqni clidkyqi ppivod zi zminno ctpyktypo. Haykovi ppaci DonHTU 2(24), 207–217 (2012).

Dynamic Stresses in the Adhesive Joint. The Goland-Reissner Model Natalia Smetankina1(B)

, Sergei Kurennov2 , and Kostiantyn Barakhov2

1 Anatolii Pidgornyi Institute of Mechanical Engineering Problems of the National Academy

of Sciences of Ukraine, 2/10, Pozharskogo Street, Kharkiv 61046, Ukraine [email protected] 2 National Aerospace University “Kharkiv Aviation Institute”, 17, Chkalova Street, Kharkiv 61070, Ukraine

Abstract. An analytical solution of the initial-boundary value problem on the dynamic stress state of a structure comprising two lap bonded rods of different lengths is proposed. A longitudinal load is applied to one of the rods, and the second is rigidly fixed along the end. To solve the problem, the Goland-Reissner model of the adhesive bond is used. It considers the rods in the Bernoulli approximation, and the adhesive layer as the elastic Winkler foundation. Shear and normal stresses in adhesive layer are evenly distributed over the thickness of the adhesive layer. They are proportional to the difference in displacements of the inner sides of the joined layers. The displacements and speeds of the joint elements at the initial moment of time are equal to zero. The longitudinal load is constant in time and is applied instantaneously. The problem solution is built as a superposition of static and dynamic displacements, expanded in a series of eigenfunctions that are not orthogonal. To satisfy the initial conditions the least squares method is used. The model problem solution showed that the dynamic stresses in the adhesive layer are several times higher than the static ones. This fact highlights the topicality of the dynamic effects in laminated structures studying. Keywords: Adhesive joint · Analytical solution · Dynamic stress state

1 Introduction The classical mathematical models of adhesive lap joints are the Volkersen model and the more accurate the Goland-Reissner model. The Volkersen model considers only the longitudinal displacements of load-carrying layers. The Goland-Reissner model considers the load-carrying layers as Bernoulli beams [1, 2] and also takes into account normal stresses in adhesive layers. These adhesive lap joints are basic and have been developed in several directions. For example, there are two-dimensional Volkersen models [3, 4], that take into account the non-uniformity of the stress state across the joint width. These models are also used to calculate the static stress state of the of cylindrical rods and shells joints [5, 6]. An important direction in the development of adhesive joint models is the consideration of dynamic stresses in the structure. The dynamic Volkersen model was used, for example, in [7, 8]. The relative simplicity of this model makes it possible © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 456–468, 2023. https://doi.org/10.1007/978-3-031-40628-7_38

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to obtain a solution to the initial-boundary value problem by analytical methods, for example, using the Laplace transform, as well as to study stresses in a semi-infinite connection [9]. The same model allows solving a modal problem for a joint in which the adhesive layer parameters are variable along the length of the overlap [10]. In addition, the Volkersen model is applicable to the study of dynamic stresses in the coaxial pipes joints [11]. The Goland-Reissner model is mostly used for the modal analysis of adhesivebonded structures with the overlap [12, 13]. This mathematical model is applied to find the structure natural longitudinal-flexural vibrations forms and frequencies. The paper [14] considers the problem of eigen frequencies of an adhesive joint structure, in which the thickness of the adhesive layer varies linearly along the overlap length. The attention of researchers is also paid to the study of stresses in joints that arise during steady-state vibrations under the influence of a harmonic load [15, 16] applied to the joint. The works [17, 18] deals with the dynamic stress state of joints that are loaded with a longitudinal load. In the paper [19] the problem of stresses in the connection of two rods, loaded with a distributed transverse load, was solved, using the Galerkin method. The paper [20] presents numerical and experimental investigations of stresses in a joint under a transverse impact of a solid body. To study natural frequencies of a structure, a more complex model of joint stress state [21] is also used. It describes stress state of adhesive layer as two-parameter model of elastic foundation [22]. The calculation of dynamic stresses in lap joints differs from such calculations in three-layer rods with a relatively thick filler [23, 24], three-layer plates [25, 26], or anisotropic structures [27, 28], because the boundary conditions at the bonded joint area boundary are not identical. A specific type of laminated structures fracture is the structural delamination. Delamination leads to some stress redistribution, the buckling of structures and appearance of non-linear vibrations [29]. In this paper, we suggest a solution to the initial-boundary value problem of dynamic stresses in an adhesive joint caused by instantaneously applied longitudinal load to one of the load-carrying layers.

2 Problem Statement Let’s consider the adhesive joint of two rods x ∈ [−L, 0] shown in Fig. 1. The protruding part of the joint has a length L1 , x ∈ (0, L1 ]. Longitudinal and transverse displacements of load-carrying layers are designated as uk and wk , respectively. We designate numbers of connected layers in the bonded joint area as k = 1, 2 and for the protruding section as k = 3. Longitudinal, transverse forces and bending moment in the layer k are designated by Nk , Qk and Mk , respectively. The joint is loaded with longitudinal force  F = const, t > 0, F(t) = 0, t = 0. The balance of the differential joint element is shown in Fig. 2.

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Fig. 1. Structural diagram.

Fig. 2. Equilibrium of the differential element.

The equilibrium equations for the elements of the layers have the form:     ∂Nk ∂x + (−1)k τ = ρk δk ∂ 2 uk ∂t 2 , ∂Qk ∂x + (−1)k σ = ρk δk ∂ 2 wk ∂t 2  (1)  ∂Mk ∂x − 0, 5δk τ − Qk = Jk ∂ 3 wk ∂t 2 ∂x where τ is shear stress in the adhesive layer (it is uniform over the thickness of the adhesive); σ is normal stress in the adhesive layer; ρk is the density of the k-th loadcarrying layer; δ1 and δ2 are thicknesses of the first and second load-carrying layers, respectively; δ0 is the thickness of the adhesive layer; Jk is the inertia moment of the cross section of the k-th load-carrying layer, in the case of a homogeneous layer Jk = δ3k ρk /12; k = 1, 2. The beam bending equations have the form:       (2) duk dx = Nk Bk , d 2 wk dx2 = −Mk Dk , d 3 w3 dx3 = −Q3 D3 .

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Here Bk and Dk are the tension-compression and bending stiffness of the rods, respectively, which for homogeneous layers have the form Bk = Ek δk , Dk = δ3k Ek /12; Ek is the elasticity modulus of the corresponding layer; k = 1, 2, 3. The shear and normal stresses in the adhesive layer have the form [1, 2]:     τ = P u1 − u2 − 0, 5δ1 dw1 dx − 0, 5δ2 dw2 dx , σ = K(w2 − w1 ), (3) where P = G0−1 δ0 is the shear compliance of the adhesive layer; G0 is the shear modulus   −1 of the adhesive; K = E0 δ0 1 − μ20 is the tension-compression stiffness of the connecting layer; E0 and μ0 are elasticity modulus and Poisson ratio of the adhesive layer. Boundary conditions and conjugation conditions have the form: | | | N1 |x=−L = Q1 |x=−L = M1 |x=−L  = N2 x=0 = Q2 x=0 = M2 x=0 = 0; u2 |x=−L = w2 |x=−L = ∂w2 ∂x x=−L = ∂w3 ∂x x=L = w3 |x=L1 = 0;  1  ∂w1 ∂x x=0 = ∂w3 ∂x x=0 ; u1 |x=0 = u3 |x=0 ; w1 |x=0 = w3 |x=0 ; Q1 |x=0 = Q3 |x=0 . N1 |x=0 = N3 |x=0 ; M1 |x=0 = M3 |x=0 ;

(4)

N3 |x=L1 = F.

(5)

Initial conditions are { ui |t=0 }3i=1 = 0;

{ wi |t=0 }3i=1 = 0;



 3 ∂ui ∂t t=0 i=1 = 0;



 3 ∂wi ∂t t=0 i=1 = 0.

3 Building the Solution 3.1 Solution Structure Let’s exclude the force factors in Eqs. (1)–(3) and obtain a system of equations for the displacements of the load-carrying layers in the joint (0) ∂

A4

4v

∂x4

(0) ∂

+ A2

2v

∂x2

(0) ∂v

+ A1

∂x

(0)

(2) ∂

+ A0 v + A0

2v

∂t 2

(2)

+ A2

∂ 4v = 0, ∂x2 ∂t 2

where: ⎞ ⎛ ⎞ · PD1 · · · −s12 −s1 s2 · 2 ⎜ · PD2 · · ⎟ ⎜ · ⎟ (0) ⎟; ⎟; A(0) = ⎜ −s1 s2 −s2 · A4 = ⎜ 2 ⎝ · ⎝ ⎠ · ·· · · B1 P · ⎠ · · · B2 P · · ·· ⎞ ⎛ ⎛ ⎞ · · s1 −s1 KP −KP · · ⎜ · ⎜ −KP KP · · ⎟ · s2 −s2 ⎟ (0) (0) ⎟ ⎜ ⎟; A1 = ⎜ ⎝ s1 s2 · · ⎠ ; A 0 = ⎝ · · −1 1 ⎠ −s1 −s2 · · · · 1 −1 ⎛

(6)

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⎛

(2)

A0

r1 ⎜ · = P⎜ ⎝ · ·

· r2 · ·

· · −r1 ·

⎞ ⎛ · J1 ⎟ ⎜ · ⎟ · (2) ; A2 = −P ⎜ ⎝ · · ⎠ · −r2

· J2 · ·

⎞ ⎛ ⎞ w1 ·· ⎟ ⎜ · ·⎟ w2 ⎟ ⎟, ; v=⎜ ⎠ ⎝ ·· u1 ⎠ ·· u2

sk = 0.5δk , rk = ρk δk . The displacements of section “3” (see Fig. 1) are described by the equations: ∂ 4 w3 ∂ 2 w3 ∂ 2 w3 ∂ 2 u3 ρ3 δ3 ∂ 2 u3 = ; D3 4 + J3 + ρ3 δ3 2 = 0. 2 2 2 ∂x B3 ∂t ∂x ∂x∂t ∂t

(7)

Since the boundary condition (4) is inhomogeneous, we write the required displacements in the form: uk (x, t) = vk (x, t) + Uk (x); wk (x, t) = yk (x, t) + Wk (x),

(8)

where Wk (x) and Uk (x) satisfy homogeneous boundary conditions (4) and condition (5); vk (x, t) and yk (x, t) satisfy the homogeneous boundary conditions (4), and the boundary condition (5) is replaced by a homogeneous one. Using the relation (2), the boundary condition (5) can be represented as a combination of conditions for the functions introduced in (8):    (9) dU3 dx x=L = F B3 , ∂v3 ∂x x=L = 0. 1

1

3.2 Static Displacements Taking into account the functions Wk (x) and Uk (x), system (6) has the form:    (0) (0) (0) (0) A4 d 4 V dx4 + A2 d 2 V dx2 + A1 d V dx + A0 V = 0,

(10)

T  where V = W1 , W2 , U1 , U2 . Particular solutions of system (10) are sought in the form V = Cheθx , where C is an arbitrary constant; h is some vector. Substituting V into the system (10), we obtain:   (0) (0) (0) (0) (11) A4 θ4 + A2 θ2 + A1 θ + A0 h = 0. The system (11) has a nontrivial solution if:   (0) (0) (0) (0) det As = det A4 θ4 + A2 θ2 + A1 θ + A0 = 0. The vectors h are non-trivial solutions of the system:   As θj hj = 0,

(12)

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where θj are solutions of the Eq. (12), j = 1, 2, ..., 6. Vectors hj corresponding to θj are calculated up to one arbitrary factor. In general terms, static displacements can be written as: 

W1 W2 U1 U2

T

=

6 

Cj hj eθj x +

j=1

3 

xm H m ,

(13)

m=0

where: T  H 0 = C7 C7 C11 C11 − C8 δs − 6C10 δs Bs ; T  H 1 = C8 C8 C12 C12 − 2C9 δs ; T     T H 2 = C9 C9 3C10 δs Bs B1 −3C10 δs Bs B2 ; H 3 = C10 C10 0 0 ;  δs = (δ1 + δ2 ) 2; Bs = B1 B2 (B1 + B2 )−1 . Static displacements can be found from the Eqs. (7):    U3 = Fx B3 + C13 ; W3 = −C14 x3 6D3 − C15 x2 2D3 + C16 x + C17 .

(14)

Using relations (2) and (14), let’s find the force factors in the rods. Boundary conditions (4) and (5) lead to a system of linear equations with respect to the coefficients C1 , C2 , ..., C17 . 3.3 Free Vibrations Let the structure shown in Fig. 1 performs harmonic vibrations. It is possible to seek a particular solution to system (6) in the form: T y1 (x, t) y2 (x, t) v1 (x, t) v2 (x, t) , T  = X (1) (x) X (2) (x) X (4) (x) X (5) (x) eiωt = X(x)eiωt 

where ω is the oscillation frequency. Substituting this solution into (6), let’s obtain a system of differential equations:        (0) (0) (2) (0) (0) (2) A4 d 4 X dx4 + A2 − ω2 A2 d 2 X dx2 + A1 d X dx + A0 − ω2 A0 X = 0. (15) Particular solutions of the system (15) corresponding to the frequency ω have the form X = S qeλx , where S is an arbitrary constant; q is an unknown vector with constant components. After substituting into (15), let’s obtain: Ad · q = 0,

(16)

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    (0) (0) (2) (0) (0) (2) Ad = λ4 A4 + A2 λ2 − ω2 A2 λ2 + A1 λ + A0 − ω2 A0 .

The homogeneous system of linear Eqs. (16) taking into account the components of the vector q has a nontrivial solution if: det Ad (λ, ω) = 0.

(17)

Taking into account (17) the general solution of the system (15) corresponding to ω has the form: X=

12 

Sn qn eλn (ω)x .

(18)

n=1

Equation (18) connects the wave numbers λ and the vibration frequency ω. The solution of the problem (7) on uncoupled transverse vibrations and longitudinal vibrations of the rod can be written as: y3 = X (3) (x)eiωt , v3 = X (6) (x)eiωt , where: 16 

X (3) (x) =

Sn eλn x , X (6) (x) =

n=13



18 

Sn eλn x ,

(19)

n=17

    λ13,...,16 = ± −0, 5ω J3 ω ± (J3 ω)2 + 4D3 ρ3 δ3 D3−1 , λ17,18 = ±iω ρ3 δ3 B3−1 . To determine ω, it is necessary to satisfy the homogeneous boundary conditions (4) and (9). Let’s obtain a system of equations: B · S = 0,

(20)

where S = (S1 , S2 , ..., S18 )T . System (20) has a nontrivial solution if: det B(ω) = 0. By solving this equation, it is possible to find ωm . Each value ωm corresponds to the vector Sm that is found from the system (20) up to an arbitrary factor. Considering relations (19), displacements during free vibrations have the form:      ∞ (i) Xm wi = i = 1, 2, 3, (i+3) (Rm sin ωm t + Tm cos ωm t), ui Xm m=1 

(1) Xm

(2) Xm

(4) Xm

(5) Xm

T

=

12  n=1

Sn,m qn,m eλn,m x ,

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Xm(3) =

16 

Sn,m eλn,m x , Xm(6) =

n=13

18 

463

Sn,m eλn,m x ,

n=17

(k)

where Xm are the eigenfunctions corresponding to the frequencies ωm ; qn,m are nontrivial solutions of the system (16) corresponding to λn,m = λn (ωm ); Sn,m is the component with the number n of the vector S of the system nontrivial solution (20) corresponding to the natural frequency ωm ; Rm and Tm are the coefficients that will be found further from the initial conditions. 3.4 Satisfying the Initial Conditions Let’s substitute the obtained results into (8) and obtain the displacements:          ∞ ∞ (k) (k)  wk Xm Xm Wk (x) = Rm Tm + (3+k) sin ωm t + (3+k) cos ωm t. (21) Uk (x) uk X X m m m=1 m=1 The coefficients Rm and Tm are found from the initial conditions. To do this, we use the minimum property of the Fourier series coefficients, solving the problem of minimizing the sum of standard deviations of displacements and velocities from the initial conditions at the moment t = 0. Considering that at the original moment of time longitudinal and transverse displacements, and the corresponding velocities of rods are equal to zero, necessary functional dependence has the following form: I=

2 0  

  2   2  ( uk |t=0 )2 + ( wk |t=0 )2 + ∂uk ∂t t=0 + ∂wk ∂t t=0 dx

k=1−L

L1   2   2   + ( u3 |t=0 )2 + ( w3 |t=0 )2 dx + ∂u3 ∂t t=0 + ∂w3 ∂t t=0 dx. 0

 The conditions for the extremum of this functional have the form ∂I ∂Rm = 0 and ∂I ∂Sm = 0. These conditions lead to an infinite system of linear algebraic equations for unknown coefficients. If the original conditions are zero, then Rm = 0. Let’s restrict ourselves to a certain number N of frequencies of natural vibrations ωm and obtain a system of linear equations: ⎛ ⎞⎛ ⎞ ⎛ ⎞ M1,1 M1,2 ... M1,N Q1 R1 ⎜ M2,1 M2,2 ... M2,N ⎟⎜ R2 ⎟ ⎜ Q2 ⎟ ⎜ ⎟⎜ ⎟=⎜ ⎟. (22) ⎝ ... ... ... ... ⎠⎝ ... ⎠ ⎝ ... ⎠ MN ,1 MN ,2 ... MN ,N

RN

QN

Coefficients in the system (22) are calculated as follows: 0 Ms,r =



−L k=1,2,4,5

Xs(k) Xr(k)

dx +

L1  0

k=3,6

Xs(k) Xr(k) dx,

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0  L1  2    (k) (k+3) Wk Xr + Uk Xr dx − W3 Xr(3) + U3 Xr(6) dx. Qr = − −L k=1

0

4 Model Problem To verify obtained analytical solution, as well as to analyze quantitatively the effect of inertial forces on stresses in the adhesive joint, we can estimate the stress state of typical joint of a composite rod with a metal tip. Parameters of the joint are L = 45 mm; L1 = 80 mm; E1 = E3 = 142.8 GPa (carbon fiber); E2 = 72 GPa (aluminum); δ2 = 2 mm; δ1 = δ3 = 1.5 mm; δ0 = 0.3 mm; G0 = 0.83 GPa; E0 = 2.46 GPa; ρ2 = 2.7 g/cm3 ; ρ1 = ρ3 = 1.55 g/cm3 . At the initial moment of time, a tensile longitudinal force F is applied. Figure 3 shows the graphs of static shear and normal stresses (3) in the adhesive layer. It can be seen that stress concentration occurs at the ends of bonded joint area under static load in adhesive line. This is a known fact [1]. Similar concentration is observed under dynamic loading; the ends of bonded joint area remain the most loaded points of joint. Let’s consider the change of stresses over time in the joint. To do this, let’s take the first 30 natural vibration frequencies ωm in solution (21). Figure 4 shows shear stress τ (x, t) in the adhesive layer vs. time. Stress is shown in dimensionless form as a ratio to uniform stress, τ ∗ = F/L.

Fig. 3. Static stresses in the adhesive layer.

The edges of bonded joint area are mostly loaded. To study the degree of influence of inertial forces on stress in adhesive layer, let’s consider the graphs of dynamic to static stresses ratios at the same points. Since such points coincide with those at which stresses are studied, it makes sense to select the ends of bonded joint area. Dynamic shear τ and normal σ stresses in the adhesive layer are presented in Fig. 5. Figure 5(a) shows the graphs of the stress ratio τ (−L, t)/τs (−L) and σ(−L, t)/σs (−L), where τs (−L) and σs (−L) are the static shear and normal stresses at the point x = −L.

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Fig. 4. Dynamic shear stress in the adhesive layer.

For their calculation static displacements (13) have been used. The time interval from zero to 0.0005 s was taken for calculation. The given ratio is the dynamic factor of stresses at the considered point.  Figure 5(b) represents the graphs of the stress ratio τ (0 − L, t) τs (0) and  σ(0, t) σs (0), where τs (0) and σs (0) are the static shear and normal stresses at the point x = 0. As expected, stresses oscillate around its static values. It can be noted that stress oscillations with frequencies ω1 and ω6 are distinguished at the point x = −L, and with frequency ω7 at the point x = 0. Therefore, at different points of the structure, the maximum amplitudes can have different forms of natural vibrations.

(a)

(b)

Fig. 5. Dynamic stresses in the adhesive layer: (a) at the point x = −L, (b) at the point x = 0.

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5 Conclusions The method for solving the problem of determining dynamic stresses in an adhesive joint of two different lengths rods is proposed. The solution is built as a superposition of static and dynamic displacements that, in turn, are expanded into series of eigenfunctions. The main problem is the following: due to differences in rods boundary conditions their eigenfunctions are not orthogonal. To satisfy the initial conditions, the least squares method is proposed. The model problem is solved. It is shown that dynamic stress in the adhesive layer can be several times higher than similar static stress. This indicates the relevance of studying dynamic effects in laminated structures. However, the calculation of dynamic stresses in adhesive joints requires the displacements of the entire structure consideration that complicates the solution. Further research can be directed, for example, to the study of joint stresses caused by dynamic influences of various nature, for example, shock waves, operational influences, impact of a solid body, etc. The proposed method can be developed to calculate the stress state of circular adhesive joints [30] under impulse transverse loads.

References 1. da Silva, L.F., das Neves, P.J., Adams, R.D., Spelt, J.K.: Analytical models of adhesively bonded joints – part I: literature survey. Int. J. Adhes. Adhes. 29(3), 319–330 (2009). https:// doi.org/10.1016/j.ijadhadh.2008.06.005 2. Wong, E.H., Liu, J.: Interface and interconnection stresses in electronic assemblies – a critical review of analytical solutions. Microelectron. Reliab. 79, 206–220 (2017). https://doi.org/10. 1016/j.microrel.2017.03.010 3. Kurennov, S.S.: An approximate two-dimensional model of adhesive joints. analytical solution. Mech. Compos. Mater. 50(1), 105–114 (2014). https://doi.org/10.1007/s11029-0149397-z 4. Kurennov, S.S., Barakhov, K.P.: The stressed state of the double-layer rectangular plate under shift. The simplified two-dimensional model. PNRPU Mech. Bull. 3, 166–174 (2019). https:// doi.org/10.15593/perm.mech/2019.3.16 5. Pugno, N., Carpinteri, A.: Tubular adhesive joints under axial load. J. Appl. Mech. 70(6), 832–836 (2003). https://doi.org/10.1115/1.1604835 6. Kurennov, S.S., Barakhov, K.P., Poliakov, A.G.: Stressed state of the axisymmetric adhesive joint of two cylindrical shells under axial tension. Mater. Sci. Forum 968, 519–527 (2019). https://doi.org/10.4028/www.scientific.net/msf.968.519 7. Sato, C.: Impact. In: da Silva, L.F.M., Öchsner, A. (eds.) Modeling of Adhesively Bonded Joints. Springer, Heidelberg (2008). https://doi.org/10.1007/978-3-540-79056-3_10 8. Ma, G., Wu, J., Yuan, H.: Interfacial shear stress analysis in single-lap adhesive joints with similar and dissimilar adherends under dynamic loading. Int. J. Adhes. Adhes. 111, 102953 (2021). https://doi.org/10.1016/j.ijadhadh.2021.102953 9. Hazimeh, R., Khalil, K., Challita, G., Othman, R.: Analytical model of double-lap bonded joints subjected to impact loads. Int. J. Adhes. Adhes. 57, 1–8 (2015). https://doi.org/10.1016/ j.ijadhadh.2014.09.004 10. Sindi, S.A., Othman, R., Almitani, K.H.: Theoretical solution for the axial vibration of functionally graded double-lap adhesive joints. Math. Mech. Solids 26(6), 108128652096770 (2020). https://doi.org/10.1177/1081286520967709

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11. Vaziri, A., Nayeb-Hashemi, H.: Dynamic response of tubular joints with an annular void subjected to a harmonic axial load. Int. J. Adhes. Adhes. 22(5), 367–373 (2002). https://doi. org/10.1016/s0143-7496(02)00016-7 12. Weißgraeber, P., Becker, W.: Finite Fracture Mechanics model for mixed mode fracture in adhesive joints. Int. J. Solids Struct. 50, 2383–2394 (2013). https://doi.org/10.1016/j.ijsolstr. 2013.03.012 13. Al-Ramahi, N.J., Joffe, R., Varna, J.: Numerical analysis of stresses in double-lap adhesive joint under thermos-mechanical load. Eng. Struct. 233, 111863 (2021). https://doi.org/10. 1016/j.engstruct.2021.111863 14. Li, W.D., Gu, J.X., Hu, P., Wu, K.Y.: Vibration analysis of single lap adhesive joint with non-uniform adhesive thickness. Experimental and analytical investigation. In: Advanced Materials Research, vol. 418–420, pp. 1312–1319 (2011). https://doi.org/10.4028/www.sci entific.net/amr.418-420.1312 15. Challita, G.: Analytical study of the dynamic behavior of a voided adhesively bonded lap joint under axial harmonic load. Int. J. Solids Struct. 141–142, 183–194 (2018). https://doi. org/10.1016/j.ijsolstr.2018.02.021 16. Wang, S., Guo, Q., Xie, Z.: Extended analytical model for interfacial stresses of double-lap joints under harmonic loads. Int. J. Adhes. Adhes. 91, 23–35 (2019). https://doi.org/10.1016/ j.ijadhadh.2019.02.013 17. Gafar, M.O., Almitani, K.H., Othman, R.: Analytical model for harmonic response of dissimilar single-lap joints. Proc. Inst. Mech. Eng. Part K. J. Multi-Body Dyn. 232(4), 146441931774602 (2017). https://doi.org/10.1177/1464419317746027 18. Khan, M.A., Aglietti, G.S., Crocombe, A.D., Viquerat, A.D., Hamar, C.O.: Development of design allowables for the design of composite bonded double-lap joints in aerospace applications. Int. J. Adhes. Adhes. 82, 221–232 (2018). https://doi.org/10.1016/j.ijadhadh.2018. 01.011 19. Nwankwo, E., Fallah, A.S., Louca, L.A.: An investigation of interfacial stresses in adhesivelybonded single lap joints subject to transverse pulse loading. J. Sound Vib. 332(7), 1843–1858 (2013). https://doi.org/10.1016/j.jsv.2012.11.008 20. Vaidyaa, U.K., Gautama, A.R.S., Hosur, M., Dutta, P.: Experimental–numerical studies of transverse impact response of adhesively bonded lap joints in composite structures. Int. J. Adhes. Adhes. 26(3), 184–198 (2006). https://doi.org/10.1016/j.ijadhadh.2005.03.013 21. Kurennov, S.S.: Longitudinal-flexural vibrations of a three-layer rod. An improved model. J. Math. Sci. 215(2), 159–169 (2016). https://doi.org/10.1007/s10958-016-2829-7 22. Wang, J., Zhang, C.: Three-parameter, elastic foundation model for analysis of adhesively bonded joints. Int. J. Adhes. Adhes. 29(5), 495–502 (2009). https://doi.org/10.1016/j.ija dhadh.2008.10.00 23. Oniszczuk, Z.: Free transverse vibrations of elastically connected simply supported doublebeam complex system. J. Sound Vib. 232(2), 387–403 (2000). https://doi.org/10.1006/jsvi. 1999.2744 24. Han, F., Dan, D., Cheng, W.: Exact dynamic characteristic analysis of a double-beam system interconnected by a viscoelastic layer. Compos. B Eng. 163, 272–281 (2019). https://doi.org/ 10.1016/j.compositesb.2018.11.043 25. Shupikov, A.N., Smetankina, N.V., Svet, Ye.V.: Nonstationary heat conduction in complexshape laminated plates. J. Heat Transf. Trans. ASME 129(3), 335–341 (2007). https://doi. org/10.1115/1.2427073 26. Starovoitov, E.I., Leonenko, D.V., Tarlakovskii, D.V.: Thermoelastic deformation of a circular sandwich plate by local loads. Mech. Compos. Mater. 54(3), 299–312 (2018). https://doi.org/ 10.1007/s11029-018-9740-x

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Methods and Techniques Utilized in Programming Collaborative Robots for High-Quality Automation Aurel Mihail T, ît, u1,2(B)

, Vasile Gusan3

, and Alina Bianca Pop4

1 Lucian Blaga University of Sibiu, 10 Victoriei Street, Sibiu, Romania

[email protected]

2 The Academy of Romanian Scientists, 3 Ilfov Street, Bucharest, Romania 3 Faculty of Industrial Engineering and Robotics, University Politehnica of Bucharest, Splaiul

Independen¸tei no. 313, 6th District, Bucharest, Romania 4 Faculty of Engineering - Department of Engineering and Technology Management,

Technical University of Cluj-Napoca, Northern University Centre of Baia Mare, 62A, Victor Babes Street, 430083 Baia Mare, Maramures, Romania

Abstract. In the rapidly advancing field of robotics, programming collaborative robots present a unique set of challenges. Unlike traditional industrial robots, which operate in isolation behind barriers or encapsulated in a cell, collaborative robots are designed to work alongside humans in shared spaces. This flexibility allows for a wide range of applications, but it also means that there is currently no universally accepted standard for programming them. As a result, programming techniques and methods can vary greatly, leading to varying degrees of success in terms of the quality of the final application. This paper aims to address this issue by providing a comprehensive overview of the methods and techniques used in programming collaborative robots. The study is based on the use of a Universal Robots CB3 series collaborative robot, specifically, the UR10 model, using software version 3.15.4.1.06291. The authors also propose innovations in the field of collaborative robot programming, with the ultimate goal of achieving quality assurance. The study brings clear recommendations in terms of what means to build and collaborative robot program. The authors present specific examples to develop the future collaborative robots’ way of thinking during the program development. Overall, this paper presents a valuable contribution to the field of collaborative robotics, providing a clear and structured approach to programming these robots and emphasizing the importance of quality assurance. The authors propose innovations and recommendations which have the potential to significantly improve the performance and reliability of collaborative robots in various applications. Keywords: Collaborative robot · Programming · Operations · Quality assurance · Manufacturing · Programming

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 469–489, 2023. https://doi.org/10.1007/978-3-031-40628-7_39

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1 Introduction Collaborative robots represent a viable alternative to replace the human resource that is becoming more expensive, harder to attract and disciplined to achieve the desired effectiveness. Due to the multitude of applications that can be realized with their help, collaborative robots can be very easily integrated into any kind of process and can have an important contribution, starting with the process of obtaining the semi-finished product and ending with the packing and palletizing of the finished products. The fact that they can be integrated into any kind of process underlines their flexibility. This flexibility also extends to programming, which is particularly easy to program even for people who have no previous training in this field. Due to this aspect, even the programming of collaborative robots will be a feature that will generate a particularly low cost. However, even if this detail can represent a benefit, in the absence of a universally accepted programming standard for collaborative robots, the results regarding the quality of operation can be particularly variable. The final objective of the study is to ensure the quality of operation of the collaborative robots, also providing an example for each theory issued.

2 Theoretical and Scientific Concepts Regarding Collaborative Robots Applications with industrial robots can be found, predominantly, but have a lack of capacity in terms of sharing the work environment with humans [1]. With the advent of collaborative robots, cages are being removed as they are designed to collaborate with humans safely and efficiently [2]. Industrial robots can only be used if humans are fully protected by them. Thus, they are integrated into production cells closed with fences or doors, these being provided with locking mechanisms. This aspect does not apply to collaborative robots, as they are designed to interact with operators, being able to be integrated into an environment shared with humans. However, for this aspect to be possible, the application must be a collaborative one. This aspect assumes that the collaborative robot operates at limited speeds, using collaborative grippers. Even if the robot is collaborative, when it operates at high speeds unfenced and operates with a knife as a device, it loses its property of being collaborative. First of all, determining the etymology of the science called “Robotics” is important. The word “Robotics” obviously comes from the word “robot”. In the past, this word was present only in science fiction literature. The word was not part of the vocabulary of engineers and technical personnel until 1920 when the Czech author Karel Capek wrote the play “Rossum’s Universal Robots”. This was awarded in Prague in 1921 and was performed in London in 1921 and New York in 1922. The main theme of the work is futuristic operators or workers built by humans to reduce the difficulties of old jobs through automation. The word robot was born during the conception of works. When the author was writing this work, he would have asked the advice of his brother, Josef, to give a name to these futuristic beings. He gave the author the name “robot”. It is considered

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that the name “robot” has its etymology in the Czech language, as it is considered to be an abbreviation of the word of Czech origin “Robotnik”, which means peasant or slave, or from another word of the same linguistic origin “robota”, which means slavery or enslavement [3]. The ideal of robotics is expressed by replacing the operator or worker with advanced automatic systems, capable of performing the tasks specified by humans without their intervention during the execution [4]. Industrial robots, be they industrial or collaborative, are tools that can replace humans in repetitive activities. They can work independently and without supervision, but only by performing certain tasks that are predefined by the programmers. They have high precision, having the advantage of maintaining the same work rate for a long time. Collaborative robotics can be defined as a comprehensive concept that reflects the closeness between robotic systems and human operators, to achieve useful activities in a shared environment, with numerous possibilities for collaboration methods [5]. This concept led to the ideal of realizing a solution where humans and robots can coexist in a shared production space, working together. The advantages represented by such a concept: • reducing the space occupied by production flows; • eliminating fences and obstacles existing between robots and humans. The concept of collaborative robotics has been embraced by multiple manufacturers in the industrial robot manufacturing area. In the last decade, some manufacturers have introduced a new generation of robot arms as collaborative robots, such as Universal Robots UR3, 5 and 10, KUKA iiwa 7 and 14 and Fanuc CR-35iA. These robots have been designed with safety features that allow them to operate safely around humans [6]. In a worker-robot collaboration, worker performance can be improved, while worker stress and fatigue can be reduced, by assisting the robot in performing everyday tasks [7]. Collaborative robots positively challenge humans to keep pace and stay focused on work operations. When we talk about repetitive and boring tasks, by replacing operators with collaborative robots it is demonstrated that productivity increases and the production of a manufacturing flow per hour are much more stable. Collaborative robots can assist human workers in completing assembly tasks, providing the opportunity to improve ergonomics and reduce costs [8]. Collaborative robots can also take over the old non-ergonomic and repetitive tasks that the robot was forced to perform in the past, thus significantly reducing workplace accidents. Replaced operators will be able to take over more important functions that add value qualitatively to the products. Following its implementation, the system will need to be validated through a risk assessment [9]. After implementation, it is necessary to revalidate the manufacturing flow from the point of view of safety and security at work. If the collaborative robot has to run at high speeds or operate with dangerous devices, it can be surrounded by perimeter scanners to stop the collaborative robot. After leaving the perimeter checked by these scanners by

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the operator, collaborative robots can continue their activity from the remaining point without any impediment. In Industry 4.0, collaborative robots have become a crucial element, experiencing substantial progress over the past two decades [10]. Collaborative robots are implemented on a large scale, this being a current topic of everyday life. A key aspect is represented that can ensure the success of an application is represented by the programming of collaborative robots. Due to this desire, the authors considered it appropriate to present certain important recommendations.

3 The Configuration of the Basic Settings for a Collaborative Robot Basic settings are predefined settings by the programmer in the collaborative robot software. There are two types of basic settings that he must make before starting to program the application, namely: • settings made in the Setup Robot menu; • settings made in the Installation menu (Fig. 1). The authors recommend that before starting the programming or the basic settings made in the Installation menu, all those in the Setup Robot menu should be made first. These represent settings regarding: • performing network settings of the robot; • software update of the collaborative robot; • installation of certain gripper control software and so on.

Fig. 1. Existing submenus in the Installation menu

Collaborative robots and other peripheral devices are designed to improve the safety of workplaces where robots are involved, but are not intended to completely replace current technologies [11].

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After configuring the Setup robot menu, the authors recommend accessing the Installation menu, which can be performed after pressing the Program Robot button on the main interface. My recommendation is that these settings be made before starting the actual programming of the collaborative robot. The following basic settings can be made in the Installation menu: • in the TCP configuration submenu, you can set the position, the centre of gravity and the mass of the tool center point, also known as TCP, i.e. Tool Center Point. Also, several TCPs can be defined from this submenu, in case the collaborative robot will use several tools; • in the Mounting submenu, the position of the collaborative robot in space can be set from the mounting point of view. It can be mounted on a horizontal base on the floor or ceiling, on a vertical base, on a wall, or on an angular base; • in the I/O Setup submenu, it will be possible to name all the signals, be they inputs or outputs, used by the collaborative robot including the digital and analogue ones. This aspect helps us during programming because we can more easily identify where an input comes from, for example, the name of an input i_buton_cap_1, or where an output leaves, for example, the name of an output o_com_conveyor; • in the Safety submenu it will be possible to set the safety limits of the collaborative robot; • variables can be created in the Variables submenu that will be used in the collaborative robot program; • in the MODBUS submenu, connections can be made via IP to other equipment. Digital or register-type inputs and outputs can be created. Based on them, communication can be made with the equipment in the collaborative robot’s environment, the only condition being that they are connected to a network. The collaborative robot can connect and read signals received via ModBus from other equipment, and other collaborative robots, or can read its own signals sent via this protocol; • in the Features submenu points, lines or planes can be defined in the Cartesian XYZ system of the collaborative robot. Also, from this submenu, it is possible to determine whether the robot will be able to move concerning the base or the tool center point. Also, it can be determined if the XYZ axes will be visible during movements; • the Smooth Transition submenu controls how collaborative robots will transition from automatic mode to safety stops or low-speed operation, except emergency stop. There are two possibilities: the robot can stop easily or very suddenly. Although sudden stops are faster, they can cause multiple protective stops because the collaborative robot will think it has collided with a person. It is recommended that the collaborative robot stops smoothly, so as not to induce shocks at the time of these translations; • the Conveyor Tracking submenu where you can define communication with a conveyor, in which the collaborative robot controls and tracks the functionality of the conveyor; • in the Ethernet/IP submenu, the adapter can be started to initiate a communication based on an Ethernet/IP protocol; • in the PROFINET submenu, the adapter can be started to initiate a communication based on a PROFINET protocol;

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• in the Default Program submenu, you can determine which program will start automatically when the collaborative robot starts. It is also possible to establish an automatic start or an automatic initialization of it, depending on certain signals received from the equipment in the external environment of the robot; • the Load/Save submenu is used to save or load the file with the basic settings made in the Installation menu. New files can also be created. They contain all the basic settings made in the Installation menu. When this file changes, the robot will stop, and load the existing basic settings in the file. The basic settings are important because they ensure a correct start in case of subsequent programming in a compliant mode of the collaborative robot. By configuring the basic settings, a multitude of aspects related to communication, mounting method, type of device used and many other aspects are configured. A good quality foundation will always lead to a foundation on which quality can still be achieved.

4 How a Program Should be Structured Some robot manufacturers now offer customers easy-to-use programming tools such as tablets, mobile interfaces, and graphical programming methods to support simple and complex programming tasks [12]. The general program of collaborative robots from Universal Robots can be structured using the following categories and sequences, according to Fig. 2: • • • •

BeforeStart; Robot Program; SubProgram; Thread.

Fig. 2. Sequences used in structuring collaborative robots

The “BeforeStart” category is called by the collaborative robot when it is restarted from the beginning. The collaborative robot will not call the “BeforeStart” sequence when it is only paused, but only if it is stopped by the stop button, the Halt command, shutdown from the emergency button and restarting the collaborative robot. This sequence will always run before the “Robot Program” sequence. In this case, there cannot be more “BeforeStart” sequences.

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The “Robot Program” category represents the main program of the collaborative robot. This sequence can be run continuously, as used for serial applications, or it can stop after it has run completely. There cannot be more than one “Robot Program” sequence. “SubProgram” can be called in the categories of “BeforeStart” or “Robot Program”. This can be a separate general program. There can be multiple such instances with different functions that can be called upon. “Thread” can run continuously in parallel with the main program. It can be used for querying and continuous control of certain signals or for control of other equipment by the collaborative robot. And in this case there can be several instances with different functions that can be called. By using cobots, it is possible to overcome security obstacles and envision safe collaboration between humans and robots [13]. These sequences can actuate multiple robot motion commands, check certain logic conditions made by the programmer, enable or disable signals, change the state or value of variables, and change the value of registers.

5 “Before-Start” Category The “BeforeStart” category represents the sequence that the collaborative robot will call when it is restarted. The collaborative robot will always call this category before the Robot Program sequence. To go through this sequence, the collaborative robot will have to be stopped using the emergency button, the stop button, utilizing the Halt command and upon restarting the controller. Pre-check is a pre-verification process required to be performed before starting the execution of operations. Actual execution can only be initiated after all input system states have been verified and approved according to established procedures and standards [14]. In this sequence, the authors recommend: a) Bringing the robot to the “Home” or “0” position; b) Displaying a menu through which the operator can choose “Start production”, “Parking”, and “Maintenance”. If the operator opts for another option besides options 1, 2 or 3, the program will stop; c) Checking the version loaded on the surrounding equipment. If one of the equipment does not have the corresponding version loaded, a message will be displayed indicating this aspect to the operator; d) Checking the type of variant, and depending on the type of variant used, the electrical signals of the equipment and devices used will be reset, and the values of variables and registers used to communicate will be changed. Also, in the same sequence, the presence of the products in the device will be checked. If the product is present in the device, a message will be displayed indicating this to the operator with instructions to follow and the program will stop. There is also the possibility that, if the robot recognizes the state of the product in the device, it will place it at the appropriate station. If there is another variant loaded than the ones recognized by the robot, the program will stop.

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Fig. 3. The BeforeStart sequence where the robot is moved to the home position and the operator executes the routine

Taking into account the developed recommendations, the authors present a short applicable example regarding the presented theory. According to Fig. 3, the “BeforeStart” sequence begins with the detection of the current position of the collaborative robot. The numbering in the figure is done following the points described below: 1) A local variable was created, using the “Assignment” function, which the authors named p_poz_curenta, which was also used below, in the program sequence, as a variable point. Taking the position of the tool center point on the x, y, z, rx, ry, and rz axes was equated with this variable, the distance being from the base to the tool center point. The returned values represent the angular positions of each axis in radians. Each axis can now be identified as p_current_pos[0] for x axis, p_current_pos[1] for y axis, p_current_pos[2] for z axis, p_current_pos[3] for rx axis, p_current_pos[4] for ry axis, p_current_pos[5] for the rz axis. Another local variable was created, using the same function, which was named value_actual_Z. This variable was equated with the current position of the robot on the Z axis called p_current_pos[2]. An “if” condition was introduced, which checks how low the tool of the collaborative robot is at that moment compared to the other equipment in the surroundings. In the presented case, if the collaborative robot were at a position of 0.35 on the Z axis when it moved to the “Home” position, it would collide with one of the surrounding equipment. Thus, if p_current_pos[2] < 0.35, then it will be raised to a height of 0.4 according to the command p_current_pos[2] = 0.4; 2) A point named p_Home has been created, the point where the collaborative robot will use a J-type movement. The J-type movement is a movement that is used in

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Fig. 4. The menu where the operator will enter the numerical value according to which the collaborative robot will execute certain commands

unrestricted areas such as space, and it is also the fastest movement that the robot can use it; 3) Using the “Assignment” function, a local variable named “Routines” was created, according to Fig. 4. Thus, the operator or technician will be able to enter a numerical value according to which the collaborative robot will be able to start the program and confirm the entered value. If the operator enters the value 1, the robot program will start, if he enters the value 2, the collaborative robot will automatically position himself in a parking position, and if he enters the value 3, the collaborative robot will position himself in a maintenance position. If the operator enters any other value or cancels the function, the collaborative robot program will stop automatically. Next, the authors considered it necessary to verify the correspondence between the variants loaded on the equipment operated by the collaborative robot on the manufacturing flow. The manufacturing flow must be completely changed for the product that the collaborative robot will operate. Thus, according to Fig. 4, a file called “Variant_Check” was created. Inside this folder, three variables were created as follows: var_1, var_2 and var_3. Each variable was equated with an input register that is rewritten by the equipment that communicates with the collaborative robot, namely: ri_var_Equi_1 represents the input register rewritten by equipment number 1, ri_var_Equi_2 represents the input register rewritten by equipment number 2 and respectively ri_var_Equi_3 represents the input register rewritten by equipment number 3. Thus, var_1 was equated to the input register ri_var_Equi_1, var_2 was equated to the input register ri_var_Equi_2, and var_3 was equated to the input register ri_var_Equi_3. Next, an “if” condition was introduced through which the collaborative robot will check

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the correspondence between the three variables or other variants sent by the equipment (Fig. 5).

Fig. 5. Verification of the correspondence of the variant loaded on the manufacturing flow between equipment

Next, an “if” condition was introduced through which the collaborative robot will check the correspondence between the three variables or other variants sent by the equipment. If even one of the three variables is different from the other variables, the collaborative robot will stop after displaying the following message: “Equipments sent distinct variant. Check the machines product loaded”. This message was entered using the “Popup” function, and the program was later stopped using the “Halt” command. It can be seen that through the developed program, the collaborative robot validates the manufacturing change made by the technician or adjuster. If the manufacturing change has not been done according to this, the collaborative robot will not start. For variant A the equipment will send a value of 100, and for variant B the equipment will send a value of 200. The authors started this program fragment by introducing an “if” condition through which the collaborative robot will check the value received from the equipment. If the collaborative robot will receive the value 100 from all the equipment, the following “if” condition has been introduced through which the collaborative robot will check an electrical input called “i_vacuum”. This electrical input represents a 24 V DC electrical signal received from the vacuum generator when a product is in the gripper. If the signal returns a “True” value for this electrical input, the collaborative robot will display the message “Product detected in the robot gripper. Please remove the product manually and restart the program”, and afterwards it will stop. If the value returned for the electrical input “i_vacuum” is “False”, the collaborative robot will recognize that there is no product in the gripper, and the program will continue according to the following commands (Fig. 6): – Through the command entered by “Set o_vacuum_start = Off”, the collaborative robot will deactivate the signal sent to the vacuum generator through a 24 V DC electrical output. The vacuum generator is controlled through the configured electrical output called “o_vacuum_start”; – Utilizing the “Set o_start_A = off” and “Set o_start_B = off” commands, the robot will deactivate the control of two electro valves that control the functionality of the suction cups. For product A, the collaborative robot will use only one suction cup, and for product B, the collaborative robot will use both suction cups. The authors

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Fig. 6. The code for setting up the collaborative robot for product version A

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used these commands to ensure the resetting of these electrical outputs to ensure that only the corresponding solenoid valves controlling the functionality of the suction cups will be activated; The “Set o_start_a = on” command was used to activate the functionality of a single suction cup during production for variant A; Using the “Assignment” function, the three specific global variables for each nest of equipment were set to the value 0 using the command: “Equipment_1: = 0”, “Equipment_2: = 0”, Equipment_3: = 0 . For each nest, the authors created a specific global variable, whose value the collaborative robot will change depending on the presence of the product in the nest. If there is no product in the equipment nest, the value of the variable should be 0. If there is a product in the equipment nest, the value of the variable should be 1; Using the “Set ro_Tab_clear_R1 = 1” command, the output register was modified through which robot number 1 whose program is presented communicated with the collaborative robot number 2. This is the ModBus register through which the two collaborative robots communicate regarding the shared space. If the value of this register is 0, it means that collaborative robot number 1 is in the shared work area, and collaborative robot number 2 will not enter the work area. If the value of this register is different from 0, in this case, 1, the collaborative robot number 2 will enter the shared work area, because the work area is unoccupied; Using the “Set ro_Cobot_Rdy = 1” command, the output register through which the collaborative robot number 1 communicates with the equipment was modified. This is a ModBus register through which equipment information is transmitted on the fact that the collaborative robot is ready to work and set in automatic mode. If the value of this register is different from 1, the equipment will write in the history of processed products that they were not loaded by the collaborative robot.

The line of code that closes the “if var_1 = _var_2 = var_3 = 100” condition is “write_port_register (171,100)”. Through this command, robot 1 rewrites the output register number 171 to the value 100. This output register is read by the collaborative robot number 2. Depending on the received value, 100 or 200, collaborative robot number

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2 will recognize the variant of product it will have to process (variant A or variant B). In this case, the collaborative robot with number 2 will recognize that the variant to be processed is variant A.

6 “Robot Program” Category Many robot programming interfaces, especially those used in manufacturing, such as PolyScope from Universal Robots and ElephantOS from Elephant Robotics, combine visual programming with kinesthetic teaching, allowing users to specify more complex robot programs by physically guiding the robot to to demonstrate a certain task [15].

Fig. 7. Setting up the collaborative robot for product version A

“Robot Program” represents the main program of the collaborative robot. Basically, in this sequence, the program of the collaborative robot is executed so that it can run continuously or which can stop after its complete run. The programmer of the collaborative robot can choose to use only this sequence indefinitely, without using the other categories - “BeforeStart”, “SubProgram”, and “Thread”. However, in this case, the robot will have to be referenced manually at startup. This aspect can lead to the collision of the collaborative robot with the surrounding equipment in case of carelessness; on the other hand, the program is very dense, and it is difficult to identify each step, and the standardization requirement is very difficult to apply. Also, without the Thread sequence, it will be impossible to control other equipment or manage certain variables in parallel with the main program. Due to this aspect, the authors strongly recommend the use of all mentioned categories, following the suggestions presented in the paper, and the punctual management of each aspect of the collaborative robot program. In the case of the Robot Program category, it is recommended to use this sequence for the construction of logic gates or conditions according to which the collaborative robot will make decisions and execute certain steps. Mainly, in this sequence will be used: – Conditions such as: “If”, “Else”, “Elseif”;

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– Expressions to make the correlation between variables or signals such as: “And”, “Or”, “True”, and “False”; – “Call” function to call certain existing SubPrograms for certain specific steps. The Program Robot sequence, as shown in Fig. 7, begins by calling the collaborative robot to a home position, using a J-type move. This is the starting point from which the collaborative robot will need to leave before initiating any movement. This point usually represents the safety or home position from which the movement of the collaborative robot starts and ends after the goal has been met. After the collaborative robot confirms that it is in the home position, the logic part will begin according to which the collaborative robot will make certain decisions. The first condition used is that of “If var_1 = var_2 = var_3 = 100”. Through this condition, the collaborative robot checks the type of variant it will have to process. The conditions that follow are completely subject to this condition until the moment when another condition with the same importance, called “ElseIf var_1 = var_2 = var_3 = 200”, will appear. If the condition is met, the robot checks the other logical gates subject to it. The program continues by entering a file containing the logic gates called “Variant A”. Next, a Loop condition was introduced for the collaborative robot to constantly check these conditions. The sequence continues by introducing a new condition, “if i_EQ1_ready = True and i_EQ1_pass = True”. Through this condition, it is checked (“i_EQ1_ready = True”) if the equipment number 1 is set to automatic, and respectively “i_EQ1_pass = True”, if the equipment number 1 has a product processed for download with a Pass or OK result. By entering the expression “and”, the robot will verify that both conditions are met exactly, the programmed phrase being translated as follows: “If the digital input named i_EQ1_ready sent by the equipment number 1 is true and if the digital input named i_EQ1_pass is true, it means that equipment number 1 is in the machine and has a processed product ready for download with a PASS result”. The two inputs checked by the condition represent digital inputs transmitted via ModBus by equipment number 1, in this case, equipment number 1 being the server for the robot. In this case, equipment number 1 owns the registers it rewrites, and the collaborative robot only reads them. The logic gates subject to this condition are: • “If ri_EQ2_Ready = 1 and ri_EQ2_Place = 1”, translating: “If the input register named ri_EQ2_Ready is equal to 1 and if the input register named ri_EQ2_Place is equal to 1, then it means that the equipment number 2 is in automatic and is ready to receive a product”. In this case, the collaborative robot will call the Subroutine named “Call Pick_EQ1_Var_A”, and then the Subroutine named “Call Place_EQ2_Var_A”. Practically, the collaborative robot will call a subprogram to pick up product A from equipment number 1, and then call another program to place product A in the nest of equipment number 2; In the presented case, the collaborative robot is also a ModBus server for equipment, which rewrites and reads certain of its registers. All these logic gates are subject to the main condition “if i_EQ1_ready = True and i_EQ1_pass = True”. If this is not completely met, the collaborative robot will bypass these logic gates. After fulfilling this condition, the collaborative robot will continue in the same way, passing through certain logical gates that make it possible to download the products. The result of the picked

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products can also be received from the equipment with which the robot communicates. After interpreting the conditions, the robot will call certain subprograms and perform certain specific loading or unloading movements. It can be seen that the collaborative robot performs cyclical movements with very high repeatability, the operations being those of picking up and placing products between equipment. A collaborative robot brings value in such cases because it does not tire over time performing the same tasks. As can be seen, depending on the specifics of the product, the equipment and the nests, the same pick-up and placement subprograms were used. The authors approached the situation in such a way because the positions of the robot can be easily learned and adjusted, in this case being reduced in number. It can also be seen that the robot calls multiple subroutines. The authors preferred this approach because otherwise, the complete code would have to be entered for each specific task, which would have made the program more difficult to set up and maintain. In this case, the application will be able to be set up and started much faster. The authors recommend handing over repetitive jobs to collaborative robots, because they are boring, stopping people from reaching their true potential.

7 “SubProgram” Category SubProgram can represent a general program made separately. Multiple subroutines can be created that can be used in a collaborative bot application. It can be imported from a separate general program. The authors recommend the use of subprograms for certain specific tasks. Using programs with specific tasks has the following advantages: • faster setting of the entire application; • a much more orderly code that will facilitate faster identification of areas in the code that need to be fixed; • timely discovery and remediation of problems arising concerning the taking over or placement of products. To place the product in the same position, the collaborative robot must pick up the product from the previous equipment in the same position. Thus, if there will be specific placement problems on only one of the three nests of the equipment, it is possible to precisely adjust the position with problems without interfering with the takeover position. If there are placement problems with all the nests, then you can intervene only on the pick-up coordinate, thus saving the intervention on the three placement points specific to each nest. The subprograms can be viewed in Fig. 8.

Fig. 8. Subprograms used in the presented application

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The point can be defined as a coordinate that the collaborative robot will have to reach. It can be learned as a coordinate relative to the base, a plane or the centered point of the tool.

Fig. 9. Example of a developed subprogram

• Pick_EQ1_Var_A in which the collaborative robot will execute the movements and actuate the electrical inputs, outputs and related registers to take from equipment number 1 the product of type A. The robot will only take the products with a PASS result regarding the process; • Place_EQ2_Var_A – the collaborative robot will place the type A product in the nest of equipment number 2, performing the movements and communication steps related to equipment number 2; • Place_EQ3_Var_A – the collaborative robot will place product type A in the nest of equipment number 3, performing the movements and communication steps related to equipment number 3. As can be seen, these subroutines were created to perform only one specific task. Each program is carried out for retrieval or placement, changing the place or variant in which the action will take place. These are repetitive in terms of the steps that the collaborative robot will follow, for each situation only the positions and the target communication are modified. A developed program can be seen in Fig. 9. The name of the points where the robot will move can be composed of a maximum of 15 characters. Because of this, the authors were limited in naming them. One can see the clear advantages of the authors’ recommendation to use subroutines for specific tasks. First of all, the subprogram is easy to identify in case of problems, so the staff who will take care of its maintenance can intervene punctually in the code of the collaborative robot to remedy the causes. It can also be observed that the subprograms are

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concise, repetitive and easy to understand. This aspect facilitates the possibility of making an ordering regarding the source code. These aspects make setting up, programming, optimizing and maintaining the subroutine much more efficient.

8 “Thread” Category The Thread category represents a program that runs permanently with the “Robot program” category. This category can be used to query and modify electrical signals, ModBus signals and registers, and variables used by the collaborative robot. It can also be used to control other equipment of small to medium complexity such as conveyors or conveyors. Various problems could arise regarding human-robot collaboration. The authors investigated multiple productions flows in this regard. It was determined that humans can intervene in the manufacturing flow during the operation of the collaborative robots, changing the position of the products in the flow on the manufacturing flow. This can lead to a collision between the product in the collaborative robot’s gripper and the product in the placement area. This situation can happen in the case of the following actions: 1. The collaborative robot determines, after checking the signals, that a nest is empty and requires loading a product into a piece of equipment; 2. The collaborative robot will pick up a product and move to place it in the free nest; 3. The operator enters the working area of the collaborative robot by activating the perimeter safety scanners; 4. Collaborative robots will stop so as not to endanger the life of the operator; 5. The operator places a product in the empty nest, where the collaborative robot wants to place the product from the device; 6. The operator leaves the working perimeter of the collaborative robot, deactivating the safety scanners; 7. The collaborative robot continues its task. It will not detect the fact that there is a product in the placement area, which will lead to a collision between the product in the collaborative robot device and the product placed by the operator in the nest. Identifying this situation, after introducing multiple checks and conditions in the robot’s subprograms and program, the authors realized that this aspect can only be achieved using a function in the “Thread” category. It was concluded that it will be necessary to verify and update in real time the presence or absence of the products in the nests where the collaborative robots will place the products. In the example presented, two cases can be identified in which this situation can happen, and then several specific variables were created that we used to remedy these situations. These variables are: • EQ2, which will check the presence or absence of the product in the nest of equipment number 2; • EQ3, which will check the presence or absence of the product in the nest of equipment number 3. Each variable will be associated with another situation or condition. In the case of the two machines, the authors associated the related variables with the placement requirement on each nest.

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To achieve the above aspects, the authors established clear rules regarding the functioning of these variables. If a product is placed in one of the mentioned nests, the variable related to this nest will be automatically changed to 1. When one of the nests is released, the variable related to it will automatically be changed to 0. Finally, the authors created and introduced the subprogram specific to the collaborative robot, and conditions regarding the presence or absence of the product in the nest.

Fig. 10. Checking the presence of the products in the nests and transferring the processed product version to the other robot

A specific file was created for multiple situations, in which the authors introduced the conditions according to which these specific variables will change in real-time. The first created was the “Check_EQ2&3_Presence” file, according to Fig. 10. The conditions used are If and Else, as follows: • “If ri_EQ2_Place = 1” then “EQ2 = 0”. This condition could be translated as follows: if the input register “ri_EQ2_Place” is equal to 1, the slot of the equipment number 1 is empty and the collaborative robot can load a product. Due to this aspect I will transform the value of the variable “EQ2” to 0 because there is no product in the nest; • “Else” then “EQ2 = 1”. The “Else” condition is linked to the “If ri_EQ2_Place = 1” condition. Thus, if for example the input register “ri_EQ2_Place” would have any other value other than 1, then the variable “EQ2” will be assigned the value 1. If the value of the variable “EOL1” will be updated in real-time at 1, the collaborative robot will recognize that there is a product in the nest of equipment 2 and will act according to the conditions defined in the subroutine; • “If ri_EQ3_Place = 1” then “EQ3 = 0”. The condition could be translated as follows: if the input register “ri_ EQ3_Place” is equal to 1, then it could be considered that equipment number 3 has a free nest and can be loaded with a product by the collaborative robot. In this case, the variable “EQ3” will be equal to the value 0. The mentioned aspects are also applicable in the case of the conditions “If ri_EQ3_Place = 1” then “EQ3 = 0” and “If ri_EQ3_Place = 1”, then “EQ3 = 0” having specific checks and changes for nest number 3 and their variables;

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Fig. 11. Example of a subprogram with additional checks

• “Else” then “EQ3 = 1”. This is subject to the condition “If ri_ EQ3_Place = 1” then “EQ3 = 0”. If the input register “ri_ EQ3_Place” will be different from the value 1, the variable “EQ3” will be equal to 1. Through this method, the collaborative robot will determine the presence of a product in the nest of equipment number 2. The same aspects mentioned can be taken into consideration also for the conditions: “Else” then “EQ3 = 1”, and respectively “Else” then “EQ3 = 1”, applying those mentioned to the variables related to the nest of the equipment with the number 3. Updating these variables in real time and introducing multiple checks in the characteristic subroutines for placing the product in the nests of the equipment, the authors managed to eliminate the collisions between the products in the collaborative robot device and the products placed by the operator in the nest. Such a check introduced in a subprogram can be seen in Fig. 11. After fixing the product placement collision issues, the authors continued programming in the “Thread” category to facilitate a real-time manufacturing change. Applying the “Zero manufacturing changeover times” strategy, the authors created a file called “Transfer_VarType_Robot_2” with certain conditions regarding the transfer of the product variant type processed on the manufacturing line in real time to robot number 2, according to Fig. 10 The presented collaborative robot transfers the variant type according to the values received from three distinct devices. Thus, the following conditions can be distinguished: • “If var_1 = var_2 = var_3 = 100” then “write_port_register(171,100)”. The condition could be transposed as follows: if “var_1” is equal to “var_2”, “var_3” and the value 100, then I will rewrite the output register with address 171 to the value 100. Thus the collaborative robot with number 1 will transmit to the collaborative robot number 2 in

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real-time, without the need to restart the robot, the fact that the variant type produced on the manufacturing flow is variant A. Variable “var_1” is equivalent to the input register “ri_ EQ1_variant” rewritten by the equipment number 1 depending on the processed variant. The variable “var_2” is equal to the input register “ri_EQ2_Var” rewritten by equipment number 2. Also, “var_3” is a variable equivalent to the input register “ri_EQ3_Var” which is rewritten by equipment number 3. The equalization and the definition of the variables “var_1”, “var_2”, “var_3” and the input register as defined in the “BeforeStart” category of the collaborative robot; • “Elseif var_1 = var_2 = var_3 = 200” then “write_port_register(171,200)”. The condition could be translated in the following way: if “var_1” is equal to “var_2”, “var_3” and the value 200, then I will rewrite the output register with the address 171 to the value 200. In this way, the collaborative robot with number 1 will transfer to the collaborative robot with number 2 the information that the variant produced on the manufacturing flow is variant B. Using this communication method, the product variants processed on the manufacturing flow will be instantly transmitted to the collaborative robot number 2, without the need to restart it. The authors concluded that, through the “Thread” category, multiple conditions, variables and situations can be checked and updated very quickly, depending on the changes that take place in real-time in the manufacturing flow. This category runs continuously in parallel with the collaborative robot program. Using this category, the authors managed to eliminate collisions during placement between the products in the gripper of the collaborative robot and the products in the nests. Also, using this category, the authors managed to instantly transfer the type of variant processed on the manufacturing flow from collaborative robot number 1 to collaborative robot number 2.

9 Conclusions The authors presented their contributions regarding the programming of collaborative robots. The study was carried out on a collaborative robot from Universal Robots with a series type CB3, collaborative robot UR10, software version 3.15.4.1.06291. The programming language used was URScript. The authors presented steps that must be followed when programming a collaborative robot, namely: programming the basic settings. In this sub-chapter, their mode of operation was concisely described from a theoretical point of view, coming up with original recommendations during the presentation. Basic settings are the cornerstone of collaborative robot programming. They ensure a proper start in terms of further programming in a compliant manner of the collaborative robot. By configuring the basic settings, a multitude of aspects related to communication, mounting method, type of device used and many other aspects are executed. A correct foundation will always lead to a foundation on which quality can be built. Next, because there is no regulated standardization in the structuring of a collaborative robot program, based on personal experience, the authors have designed a collaborative robot program structure and proposed clear recommendations regarding the use of each category.

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Through the programming subchapters, the author’s goal was to form and develop a structured thinking of a future collaborative robot programmer. Thus, certain theoretical steps have been designed that need to be followed. Each consideration or theoretical step described was also demonstrated practically, presenting its applicability in the collaborative robot program. An original contribution is represented by the language used and the structure presented during programming. This language refers to naming points, variables, electrical inputs, electrical outputs and registers used in Modbus TCP communication. Also, originally, the authors designed a program structure that they applied practically. The “BeforeStart” category is a particularly important sequence located at the beginning of the general program. Using this sequence, an automatic start can be programmed to return the collaborative robot to a safe position, and all signals and variables used by it can be reset, including the collaborative robot’s work device can be referenced. If this category is used, the collaborative robot will be forced to go through this sequence on every restart. It will not be able to start the program instantly, but only after the programmed conditions are met, thus ensuring a correct start of the technological flow. Thus, it can be concluded that the collaborative robot checks the condition of the technological flow, refusing to start in case of an anomaly, thus prioritizing the quality of the products. The authors recommend the use of the “Robot Program” category for the construction of the conditions that will refer to the execution of certain subprograms. As can be seen, depending on the specifics of the product, the equipment and the nests, the same pickup and placement subprograms were used. The situation was approached in this way because the positions of the robot can be easily learned and adjusted in this case, being reduced in number. It could also be observed that the robot calls multiple subprograms in the presented application. The authors recommend this approach to avoid entering the complete code for each specific task, which would have made the program more difficult to set up and maintain. Taking into account the mentioned aspects, it can be concluded that the application will be able to be set up and started much faster in this case. Also, the authors consider it beneficial that they dealt with each order punctually and presented it in a much more explicit way. One can see the clear advantages of the authors’ recommendation regarding the use of the “SubProgram” category for the performance of specific tasks. First of all, the subprogram is easy to identify in case of problems, so the staff who will take care of its maintenance can intervene punctually in the code of the collaborative robot to remedy the causes. It can also be observed that the subprograms are concise, repetitive and easy to understand. This aspect facilitates the possibility of achieving an ordering regarding the source code. Due to this aspect, subroutine setup, programming, optimization and maintenance can be made much more efficient and effective. The authors determined, investigating different production flows, that humans can intervene in the manufacturing flow during the operation of the collaborative robots, changing the position of the products in the manufacturing flow. This aspect can lead to a collision between the product in the collaborative robot’s gripper and the product in the placement area.

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The authors concluded that through the “Thread” category multiple conditions, variables and situations can be checked and updated very quickly depending on the changes that take place in real-time in the manufacturing flow. This category runs continuously in parallel with the collaborative robot program. By using this category, it will be possible to eliminate collisions during placement between the products in the gripper of the collaborative robot and the products in the nests. Also, using this category, the type of variant processed on the manufacturing flow from collaborative robot number 1 to collaborative robot number 2 will be instantly transferred.

References 1. Kragic, D., Gustafson, J., Karaoguz, H., Jensfelt, P., Krug, R.: Interactive, collaborative robots: challenges and opportunities. In: IJCAI, pp. 18–25 (2018) 2. Mihelj, M., et al.: Collaborative robots. In: Robotics. Springer, Cham (2019). https://doi.org/ 10.1007/978-3-319-72911-4_12 3. Kurfess, T.R. (ed.): Robotics and Automation Handbook, vol. 414.CRC Press, Boca Raton, FL (2005) 4. Telea, D.: Sisteme flexibile de product, ie. Sibiu: Editura Universit˘at, ii Lucian Blaga (2014) 5. Vicentini, F.: Collaborative robotics: a survey. J. Mech. Des. 143(4), 040802 (2021) 6. Schou, C., Andersen, R.S., Chrysostomou, D., Bøgh, S., Madsen, O.: Skill-based instruction of collaborative robots in industrial settings. Robot. Comput. Integr. Manuf. 53, 72–80 (2018) 7. Villani, V., Pini, F., Leali, F., Secchi, C.: Survey on human–robot collaboration in industrial settings: safety, intuitive interfaces and applications. Mechatronics 55, 248–266 (2018) 8. Weckenborg, C., Thies, C., Spengler, T.S.: Harmonizing ergonomics and economics of assembly lines using collaborative robots and exoskeletons. J. Manuf. Syst. 62, 681–702 (2022) 9. Chinniah, Y.: Robot safety: overview of risk assessment and reduction. Adv. Robot. Autom. 5(01), 1–5 (2016) 10. Sherwani, F., Asad, M.M., Ibrahim, B.S.K.K.: Collaborative robots and industrial revolution 4.0 (IR 4.0). In: 2020 International Conference on Emerging Trends in Smart Technologies (ICETST), pp. 1–5. IEEE (2020) 11. Vysocky, A., Novak, P.: Human-robot collaboration in industry. MM Sci. J. 9(2), 903–906 (2016) 12. Fogli, D., Gargioni, L., Guida, G., Tampalini, F.: A hybrid approach to user-oriented programming of collaborative robots. Robot. Comput. Integr. Manuf. 73, 102234 (2022) 13. Ananias, E., Gaspar, P.D.: A low-cost collaborative robot for science and education purposes to foster the Industry 4.0 implementation. Appl. Syst. Innov. 5(4), 72 (2022) 14. Giberti, H., Abbattista, T., Carnevale, M., Giagu, L., Cristini, F.: A Methodology for flexible implementation of collaborative robots in smart manufacturing systems. Robotics 11(1), 9 (2022) 15. Ajaykumar, G., Stiber, M., Huang, C.M.: Designing user-centric programming aids for kinesthetic teaching of collaborative robots. Robot. Auton. Syst. 145, 103845 (2021)

Modeling of the Communication Process Between Two Microcontrollers in Order to Optimize the Execution of Specific Tasks Aurel Mihail T, ît, u1,2(B) and Adrian Bogorin-Predescu3 1 Faculty of Engineering, Industrial Engineering and Management Department, “Lucian Blaga”

University of Sibiu, 10 Victoriei Street, 550024 Sibiu, Romania [email protected] 2 The Academy of Romanian Scientists, 3 Ilfov Street, Bucharest, Romania 3 Faculty of Industrial Engineering and Robotics, University Politehnica of Bucharest, Splaiul Independen¸tei nr. 313, 6th District, Bucharest, Romania

Abstract. The scientific paper presents an original contribution regarding the modeling of tasks in microcontrollers equipped with an RTOS (Real time operating system) for the execution of slower tasks due to the hardware peripherals connected to the input/output ports. There are situations where slow peripherals are connected to the microcontroller, negatively affecting the performance of the execution of tasks in the microcontroller due to the low speed of data transfer between it and the peripheral. At the same time, other actions that the microcontroller must carry out must be executed quickly, periodically without further delays and without interruption. In this sense, we propose the introduction of a slave microcontroller, which connects to the main microcontroller mentioned above, having the task of executing only the tasks aimed at the command and control of the slow peripherals that were previously connected to the main microcontroller. In this way, the main microcontroller still takes care of the critical tasks, and the secondary one of the slow ones. The communication process between the two microcontrollers is carried out through the I2C communication interface and through digital lines for synchronization. The authors propose a modeling of the related process in order to optimize it and highlight the positive results derived from this study and the possibility of its operationalization. Keywords: Process modeling · Microcontrollers · Specific tasks · Real time operating system

1 Introduction Embedded systems have been part of our lives for several decades. They are present everywhere in our lives and we are practically in symbiosis with them, from home appliances (washing machine and dishwasher, refrigerator, electric and microwave oven, vacuum cleaner, router, etc.), to mobile phones to car that has dozens of built-in systems © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 490–503, 2023. https://doi.org/10.1007/978-3-031-40628-7_40

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responsible for the braking system, airbag, engine, doors, ADAS - Advanced Driver Assisted System and electronic suspension system. Practically all electronic devices that have a microprocessor or microcontroller. Embedded systems are an amalgam of HW-electronics and SW-software that form a minicomputer that is programmed according to the desired application [1]. But there is no clear definition for embedded systems, in other words an embedded system is any system that has a processor (microcontroller or microprocessor) that does not have a keyboard, mouse or monitor [2]. An embedded system (embedded systems) is actually an ECU - Electronic Control Unit, i.e. an electronic system equipped with a microcontroller (processor, memory and peripheral interfaces), input circuits (sensors) and output circuits (actuators) capable of processing information from input and set execution elements. The software running in the microcontroller in the Flash program memory is called Firmware (FW). Microcontrollers, compared to computers, have limited resources, memory, speed and peripherals, but unlike these, they are dedicated to a small number of specific tasks depending on the user’s applications and which they execute successfully and in real time. As a rule, the tasks it must perform are repetitive, executed in infinite program loops, but they must be safe without failure. Even if they have limited resources, the microcontrollers act in real time and give the best results and performances where they are used. Compared to the processing power, their cost is very low, at a few dollars [3]. The ways in which the firmware architecture is structured in the microcontroller are divided into two distinct approaches: • “Bare Metal”; • “RTOS” (Real-Time Operating System). These two approaches can be implemented in microcontrollers with a single core. For multicore architectures, it is recommended to use a real-time operating system.

2 Bare Metal Approach At the beginning of programming in the embedded systems field, the programs that ran in the microcontrollers were simple. The whole program is executed inside a superloop as described in Fig. 1 and was interrupted only if an event intervened. This approach is known as “Bare Metal”. It is the simplest possible approach, but without a control over the execution time of the functions called [4]. Everything is executed repetitively in the infinite loop while(1) from the main function main from line 15. Program execution starts at line 3, with the main function main(), in which some initializations are performed starting with line 5 to line 11. Inside the function while(1), which has the superloop function, the Led_Blink() signaling function, the temperature reading functions measuretemp() and humidity measurehumid() are called repetitively, without a control over the execution time.

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Fig. 1. “Bare Metal” programming approach

The “Bare Metal” approach is suitable for applications in which it is necessary to execute the program at the maximum speed of the instructions using minimal memory but without a prioritization and a detailed control of the software.

3 Real-Time Operating System Approach Real-time operating systems (RTOS) are very widespread in the world of embedded systems, being able to handle complex tasks, from toys, to the management system of a smart home, to the control of a nuclear reactor plant. Real-time operating systems guarantee that tasks are executed in well-established time periods. The tasks are divided into periodic and non-periodic tasks. Periodic tasks are executed cyclically according to the tasks they have to perform [5]. In the RTOS approach we are talking about multitasking, and in single core systems, where tasks are executed sequentially, each task must have access to the CPU (Central Processing Unit) when it needs to be executed. Because the tasks take very little time for execution, from a few microseconds to a few tens or hundreds of milliseconds, they seem to be executed simultaneously and in parallel. A real-time operating system does not mean that the tasks are executed at a very high speed, and it is not mandatory necessary that the speed of the microcontroller is very high, but that the system responds quickly, in real time, to external stimuli. In fact, RTOS is a small program called Kernel, which manages the allocation and execution of tasks [6]. There are 3 ways of planning tasks: • Round-robin scheduling where each task is allocated equal CPU usage time (see Fig. 2a); • Cooperative scheduling or non-preemptive scheduling where each task runs until its execution is completed (see Fig. 2b);

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• Preemptive scheduling where task planning is done based on the priority of each task (see Fig. 2c). This is actually a true RTOS.

Fig. 2. RTOS scheduling

In Fig. 2c, it can be seen that task T1 lasts 10 ms, it is interrupted by T2 which lasts a total of 7 ms and it is interrupted by T3 with a higher priority than T1 and T2 which lasts 9 ms. T4 has maximum priority, lasts 7 ms and interrupts T3. The duration of tasks T1, T2, T3 and T4 in Fig. 2b (Cooperative scheduling) is equal to those in Fig. 2c. Real-time operating systems can be purchased separately from several suppliers of embedded software for microcontrollers or can be directly incorporated into the compiler from the software supplier. Among the most used RTOS systems we mention Mbed OS, uC/OS-II, FreeRTOS (among the most used), Vxworks, eCOS, mikroC, Mbed OS and last but not least the RTOS from CCS [5]. The company CCS (Customer Computer Services) supplies the PIC C compiler for the PIC16 and PIC18 family of microcontrollers. It is the easiest to use, and at the same time the compiler also supports the RTOS operating system [6]. The RTOS can be imported into the embedded software project as a library, but it can also be part of the compiler. Considering the performance limitations of the PIC18F series microcontrollers, it is better for the RTOS to be an integral part of the compiler, thus offering optimized performance [7].

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The RTOS that comes with the PIC C compiler is not preemptive, it is a rudimentary RTOS but it is simple to use and fits very well with the more modest microcontrollers from the PIC18F family, being specially designed for it.

4 Case Study There are situations where the project requires the use of a microcontroller from the PIC18F series and the PCWH compiler from CCS. The requirements of the project to be implemented are the following: • The use of the operating system in real time with the duration of the execution of each task at a maximum of 100 ms; • Using the PIC18F66K80 microcontroller; • Periodic reading from a weight sensor (load cell) connected to an HX711 instrumentation module; • Periodic reading of the battery voltage level; • The use of a display on which the weight recorded by the instrument module is displayed, the time display (hour, minute and second), the date display (year, month and day); • The actuation of some mechanical elements by means of digitally controlled ON/OFF actuators, depending on the weight recorded by the instrumentation module; • UART communication between the microcontroller and a supervisor computer. The PIC18F66K80 microcontroller is produced by the Microchip company, it is part of the 8-bit PIC18F series, which supports the USB, CAN, TCP/IP protocol. Compared to the PIC16F series, the program memory (FLASH) is in the range from 8 KBytes to 128 KBytes with the data memory (RAM) between 256 Bytes to 16 KBytes, and the working speed of the CPU can reach up to 64 MHz and offers support for RTOS [6]. The PIC18F66K80 microcontroller is the spearhead of the family that bears the same name, has a maximum CPU operating frequency of 64 MHz (in this project it runs at maximum speed) and has a program memory (FLASH) of 64 Kbytes and a memory of data (RAM-Random Access Memory) of 3648 bytes [8]. The PIC18F66K80 microcontroller (see Fig. 3) has as its main input element an HX711 instrumentation module that translates the applied force from a load cell and transmits the information to the microcontroller. The secondary input element is the voltage from the battery that supplies the entire electronic assembly with the purpose of monitoring its condition. The output elements of the microcontroller are: • display showing the force translated from the instrumentation module and processed by the microcontroller; • actuator/motor that performs various movements depending on the values recorded by the instrumentation module. The control and supervision element of the microcontroller is a computer that is attached to the microcontroller through the UART communication port. The instrumentation module has as conversion element the HX711 integrated circuit, which is a 24-bit Analog Digital converter designed for Weigh Scales. The input element

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Fig. 3. Schematic diagram of the project

of the HX711 is a load cell that is connected in a Wheatstone bridge to the differential inputs of a “low-noise programmable gain amplifier”. The control and reading of the force measured by the load cell at the input of the instrumentation module is carried out through a digital interface on the DOUT and PD_SCK pins [9]. These digital lines interface with the PIC18F66K80 microcontroller on pins RD5 (HX711_SDI) and RC7 (HX711_SCK). The display element, Display, interfaces with the microcontroller on the I2C communication interface using digital pins RC3 and RC4 mapped to the function Display_SCK for the Clock signal and Display_SDA for the Data signal. Two digital output lines from the microcontroller are needed to control the Actuator actuation element. The RF4 digital pin is mapped to the ACT_UP function and the RF5 digital pin is for the ACT_DOWN function. Through these 2 digital lines, the operation of the motor is commanded in 3 situations: Motor Off when both lines have the same value (0 or logical 1), Motor Up when ACT_UP is in logical 1 and ACT_DOWN is in logical 0, Motor Down in the situation in which ACT_DOWN is in logical 1 and ACT_UP is in logical 0. Communication with the computer is carried out on the UART port through the RS232 communication protocol. The TX transmission line from the microcontroller to the computer is mapped to the RG3 port, and the RX reception from the computer is carried out on the RG0 port. The battery, which supplies electricity to the entire system that implements the project, is monitored on the ADC_BATT pin which is mapped to the RA0 port of the microcontroller. The software in the microcontroller is based on RTOS. The task mapping for the current project is presented in Fig. 4. Compared to the “Bare Metal” approach, which has a superloop in the main function main(), in the RTOS approach, the operating system is triggered after the call of the initialization functions in the main function main(). The function that starts the RTOS

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Fig. 4. RTOS Task execution mapping

is rtos_run(). This gives control of the program execution to the operating system and is called on line 39 (see Fig. 4). The configuration of the operating system is carried out in line 2 by command: #use rtos(timer=0, minor_cycles=100ms)

The timer used is Timer0 and the minor_cycles option specifies the maximum time a task can run, in this case the execution for all involved tasks is a maximum of 100 ms. The program has 5 tasks whose execution must last a maximum of 100 ms each. Two tasks have a repetition rate of 100 ms each. It is about the task rtos_task_100_0 where the communication packets from the computer are processed and the task rtos_task_100_1 which implements the system clock. It is very important that the task rtos_task_100_1 is constantly called every 100 ms to record the time correctly. Each time this task is run, it increments a counter. If there are no delays in its running,

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then the counter will register ten increments every second. The Task_Date_Time() function called by this task increments every 60 s a minute, then every 60 s an hour and so on to count the date as well. If there are small “accidents” (delays) for its execution, then they will translate into the erroneous display of time (second, minute, hour) on the display. The next 2 tasks have a rate of 200 ms. These are rtos_task_200_0 and rtos_task_200_1. The task rtos_task_200_0 commands the movements of an actuation element (Actuator) according to the force recorded by the microcontroller, and the task rtos_task_200_1 deals with reading and monitoring the electrical parameters of the battery that powers the entire electronic system and with displaying various information on the Display. The last task rtos_task_400_0 is called periodically every 400 ms. It performs the force reading from the HX711 instrumentation module.

Fig. 5. RTOS Task scheduling

The planning of the 5 tasks mentioned above is graphically illustrated in Fig. 5. For simplification and for a better understanding of the phenomena, each interval of 100 ms has been divided into 5 equal time slots. The interval of 100 ms represents the minor_cycle defined in the command #use rtos(timer= 0, minor_cycles= 100ms). For example, task T1 (rtos_task_100_0) is called in timeslot 0, 5, 10, 15, 20 and so on. The distance between the cyclic downgrading of the execution of this task is 100 ms. Also based on this algorithm, task T3 (rtos_task_200_1) is called cyclically in timeslot 7, 17, 27, 37 and 47 with a cyclicity of 200 ms. The moments of time for the time slot are fixed and are established by the RTOS. The execution time of each task depends on the functions that each one runs. It is important that the tasks finish the execution on time, not to extend the time allocated by the RTOS. The most dangerous situation is in the 300 ms segment (timeslots 15, 16, 17, 18, and 19) and in the 700 ms segment (timeslots 35, 36, 37, 38 and 39). Here all 5 tasks are scheduled to run.

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Upon a simple analysis of the source code regarding the functions executed inside the tasks, the fastest are: • rtos_task_100_0 responsible for receiving and processing the communication takes 10 ms; • rtos_task_100_1 responsible for incrementing the time for Date and Time lasts 1 ms; • rtos_task_200_0 responsible for the electrical control of the actuator lasts 10 ms. The slowest tasks are the following ones: • rtos_task_200_0 which deals with reading voltages from the battery terminals through the Analog Digital converter and displaying various information on the Display lasts approximately 20 ms; • rtos_task_400_0 which deals with reading the force from the instrumentation module lasts at least 55 ms. Summing up all the tasks that take place in the 300 and 700 ms segments, approximately 96 ms are obtained. These are the most unfavorable cases that can cause delays in task planning when, for example, the time allocated to running the slowest task rtos_task_400_0 is exceeded. From the catalog data (datasheet) of the HX711 instrumentation module [9], it often happens that the initialization time together with the reading time by the microcontroller even exceeds 60 ms and in this case all the scheduling of the tasks is ruined because the maximum time of 100 ms per segment is not respected. But as the requirements of the project must be respected, we propose the addition of a microcontroller that will deal specifically with the task of reading from the force instrumentation module.

5 Inter-microcontroller Communication Algorithm In order to relieve the task that lasts longer than it should from the main microcontroller, the second microcontroller was introduced, which has the sole function of performing periodic readings from the instrumentation module without blocking the planning of tasks from the RTOS. This secondary microcontroller has the function of slave and is PIC18F26k80 (from the same family of microcontrollers), only it will not have as many peripherals as the main microcontroller PIC18F66K80 which has the function of master in this new configuration (see Fig. 6). The connections of the Master microcontroller are changed only on its input area. Compared to Fig. 3, where the instrumentation module had as input, now the Master microcontroller has as input a connection on the I2C communication bus with the Slave microcontroller. For communication synchronization, 2 digital lines Master_Request_TX with Master_Ready_RX on the Master side and Slave_Request_RX with Slave_Ready_TX on the Slave side were implemented.

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Fig. 6. Master-Slave schematic diagram

Considering that both programs run asynchronously to each other in the 2 microcontrollers, these 2 digital lines are the only ones that ensure the synchronization of the inter-microcontroller communication. The software of the Slave microcontroller also runs on the RTOS system. It also has minor_cycle at 100 ms and also uses Timer 0. RTOS implements 2 tasks with different cyclicity: • rtos_task_Slave_200_0 for the reading from the forte from the instrumentation module running at 200 ms; • rtos_task_Slave_100_0 to ensure communication with the Master microcontroller. It has a cyclicity of 100 ms, it is executed most often, in order not to miss communication requests from the Master. The force value read in the task rtos_task_Slave_200_0 at line 5 is stored in the buffer szI2C_Force_TX_packet[]. This information is then sent through the handshake protocol in the task rtos_task_Slave_100_0 (see Fig. 7). Next, the inter - microcontroller internal communication algorithm is presented. Figure 7 briefly shows the code from the PIC18F26K80 Slave microcontroller with the points located on the left side of the figure where reference is made in the intermicrocontroller communication algorithm. Figure 8 briefly shows the code from the Master microcontroller together with the reference points on the left side of the figure that are referred to in the communication algorithm. All the tasks from the old approach have been inherited, with the mention that the Task_Force_Process() function has been replaced with the I2C_SLAVE_Write16_Read32() function, which is described in Fig. 8. The communication algorithm between microcontrollers is described in the following: • Slave arrives in Task rtos_task_Slave_100_0 of 100 ms, at point 1, line 13, check if SLAVE_REQUEST_RX controlled by Master is ON. If not, then the task is finished;

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Fig. 7. Slave Microcontroller code

• The master reaches the rtos_task_400_0 task and executes code from the I2C_SLAVE_Write16_Read32() function. In point 2, on line 16, notify the Slave through the MASTER_REQUEST_TX line that data transfer is desired with it and enter the do while loop waiting for confirmation from the Slave by activating the MASTER_READY_RX signal; • Returning to the Slave, it receives this request from point 1 and reaches point 3, the Slave sets SLAVE_READY_TX to 1 and thus notifies the Master that it is ready for reception on I2C and enters the do while loop, waiting, to reset the SLAVE_REQUEST_RX signal from Masters;

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Fig. 8. Master microcontroller code

• The Master detects the MASTER_READY_RX signal set by the Slave and goes to point 5 from line 24; • The Master initiates communication on the I2C interface at point 5, line 24, and until line 30 sends a request to the Slave to read the force, after which at point 10, line 32, it waits 500 microseconds to give the Slave time to prepare; • Slave detects the I2C communication request in point 6, line 28, in the I2C interrupt handling routine and in point 7, line 35, reads the request sent by the Master. In point 8 it is checked if the request from the Master is for reading the Force and the ui8I2C_Force_request flag is set, then it exits the Interrupt Service Routine and returns to the waiting loop in point 9, line 19; • Master sends at point 11, from line 36 to line 40, the clock signal on the I2C bus for reading the force. The related data will be provided by the Slave; • The slave enters the I2C Interrupt Service Routine again, at point 12, line 53, the data representing the force, on the I2C bus with the Clock signal provided by the Master, and then exits the I2C interrupt handling routine, returns to point 9, line 19;

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• The Master finishes reading the data from the Slave at line 41, saves the data in the szI2C_Slave_RX buffer and then closes the handshake algorithm at point 13, line 44, by notifying the Slave that the task is complete, the MASTER_REQUEST_TX flag is reset; • Slave notices in point 14, line 20, that the SLAVE_REQUEST_RX flag is reset by the Master and exits the do while loop, resets the SLAVE_READY_TX flag and exits the rtos_task_Slave_100_0 task. On the Master microcontroller side, the time spent inside the task rtos_task_400_0 is not more than a few milliseconds, due to the high transfer speed on the I2C communication bus. In this way, the inter-microcontroller approach is most suitable for slow peripherals.

6 Conclusions It is desirable that before the implementation of a project, all possible options and scenarios related to its implementation should be explored. A “feasibility” study of all the components involved in the project must be carried out, analyzing the hardware requirements and the components available on the market that can be used from an electronic point of view (Hardware) as well as from a programming point of view (Software). The microcontroller that is used in the project must be able to meet the established requirements, but also not waste the potential of its performance. We believe that if a device with limited resources from the low-end range can be used, then it is a shame not to do it. In this way, the environment can be protected, and an important saving of material and financial resources is made. But we must not fall into the other extreme in which due to an underestimated hardware, chosen in the initial stage, it must be supplemented with additional hardware towards the end of the project to meet the requirements established at the beginning of the project. However, when this happens, then the software part must be optimized as well. In the present case, to meet the requirements, an original handshake communication protocol was implemented between 2 microcontrollers, which has the advantage of not blocking their real-time operating systems with the processing of input signals. In this way, there are no delays in the execution of tasks. Moreover, the Slave microcontroller (with more modest performances) deals with the acquisition of data from the slower peripherals, and the most powerful one, the Master, with processing the signals provided by the Slave microcontroller and other faster peripherals, makes decisions and act accordingly. The Master microcontroller always initiates the request to the Slave when needed without spoiling the scheduling of the tasks, and the Slave microcontroller responds in real time to its request.

References 1. Raval, D., Undavia, Dr. J.N.: Revolution through embedded systems with data analytics. Int. J. Recent Technol. Eng. (IJRTE) 9(1), 2206–2209 (2020). Blue Eyes Intelligence Engineering and Sciences Engineering and Sciences Publication – BEIESP. https://doi.org/10.35940/ijrte. a2900.059120

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2. Abitha, S.: Embedded system paper document. Int. J. Eng. Res. Technol. (IJERT) 06(14) (2018). Confcall – 2018 3. Barua, A., Hoque, M. M., Akter, R.: Embedded systems: security threats and solutions. Am. J. Eng. Res. (AJER) 03(12), 119–123 (2014) 4. Development on Bare Metal vs. RTOS. https://www.sysgo.com/professional-articles/baremetal-vs-rtos. Accessed 08 Apr 2023 5. Ke, Y., Xia, X.: Timed automaton-based quantitative feasibility analysis of symmetric cipher in embedded RTOS: a case study of AES. In: Babaie, S. (ed.) Security and Communication Networks, vol. 2022, pp. 1–16. Hindawi Limited (2022). https://doi.org/10.1155/2022/411 8994 6. Ibrahim, D.: Advanced PIC Microcontroller Projects in C: From USB to RTOS with the PIC18F Series, Elsevier Ltd. (2008). ISBN 978-0-7506-8611-2 7. Siegesmund M.: Embedded C programming Techniques and Application of C and PIC MCUS, Elsevier Science & Technology (2014). ISBN: 978-0-12-801314-4 8. Microchip, PIC18F66K80 Family Data Sheet (2012) 9. Avia Semiconductor, HX711 Datasheet. https://www.digikey.com/htmldatasheets/production/ 1836471/0/0/1/hx711.html. Accessed 12 Apr 2023

Contact Interaction of Solids of Revolution with Surface Perturbation Mykola Tkachuk(B)

, Andriy Grabovskiy , Mykola Tkachuk , Iryna Hrechka , and Hanna Tkachuk

National Technical University “Kharkiv Polytechnic Institute”, Kyrpychova Street, 2, Kharkiv 61002, Ukraine [email protected]

Abstract. The effect of shape variation on the normal contact of elastic bodies is analyzed in this paper. Contact of a toroid with a ball is considered as a reference. The nominal geometric shape of these bodies is disturbed. This leads to a change in the distribution of the normal gap between the bodies. An approximation by a Hermit polynomial is proposed for the shape perturbation. Two dimension parameters scale this function in contact depth and width directions respectively. The distribution of the gap between the toroid and the ball is given analytical expression that includes the two variable geometrical parameters. The stress-strain state of contacting bodies is determined numerically by means of the finite element method. The multivariant analysis provides information about the change of the shape of the contact area and the distribution of contact pressure, as well as the level of stress in the bodies depending on the perturbation of the bodies geometry. In particular, it is discovered that the contact area transforms from oval to dumbbell-like shape and, ultimately, splits into two disconnected spots. Accordingly, the contact pressure also changes from a dome-like distribution with the maximum in the center of the oval to a distribution with two peaks with a saddle between them. Ultimately, two isolated peaks are formed for the greater geometry deviations that prohibit the contact in the middle. The maxima of equivalent von Mises stresses inside the elastic bodies correlate with the location and values of the maximal contact stresses. The established regularities make it possible to develop recommendations for the shape of the surfaces of contacting bodies based on strength criteria. Keywords: Contact Interaction · Hydrovolumetric Transmission · Ball Pistons · Surface Shape · Contact Pressure · Stress-Strain State

1 Introduction Modern mechanisms and machines are designed to have highest possible performance with rather strict size limits. This requires the implementation of complex types of relative motion and the transfer of significant loads between their parts through contact interaction. These structural elements need to be fitted in very tight machinery compartments. The very little free space leads to close and complex shapes of the conjugate © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 504–513, 2023. https://doi.org/10.1007/978-3-031-40628-7_41

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surfaces. For example, in the radial hydraulic transmissions GOP-900 developed by the Kharkiv Morozov Machine Building Design Bureau [1] ball pistons revolute over a recessed toroidal running track on the stator ring. The profile of the running track is close to the ball geometry in the perpendicular direction. The overview of the general scheme of the transmission as well as the geometry of the piston-ring contact pair is given in Fig. 1 [2]. As outlined in [2, 3] the contact F between the ball piston and the stator ring is the most loaded part of the structure where high stresses are concentrated in the vicinity of the contact zone. The levels of elastic stresses is critical for the strength of the mechanism. The axial profile P shown in Fig. 1 in the cross-section A needs to be selected in such a way that the stress levels are sufficiently lowered without violating the dimensional restrictions of the radial drive for all possible operational regimes.

Fig. 1. Radial hydrovolumetric transmission GOP-900: 1 – housing; 2 – block of pin distributors; 3 – pump cylinder block (rotor); 4 – cylinder block of the hydraulic motor (stator); 5 – ball-piston; 6 – pump stator; 7 – a running track P on the pump and the hydraulic motor; 8 and 9 – input and output shafts of the hydraulic transmission [2]. Simplified view of the stator interacting with 9 ball pistons in radial cylinders of the rotor. Normal contact of a ball piston with the stator ring F shown in the plane A of the running track profile P.

Besides identification of a rational nominal profile , it is also essential to determine the sensitivity of the contact interaction and the stress-strain state of contacting bodies to geometry deviations. The nature of such disturbance can be vary. It may come from manufacturing tolerance away from the nominal shape (technological component). Wear in the rolling contact will as way manifest as a change in ball piston and running track profile geometries (operational component). A small departure from the theoretical profile may be a part of the design solution. It can be introduced as a measure to negate the possible adverse effects of the two previously mentioned error factors. In particular, it is desirable to reduce the level of contact pressure and stresses in contacting bodies with disturbed surfaces compared to the nominal ones. For this, it is

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necessary to investigate the effect of this disturbance on the contact pressure between the bodies and the stresses in these bodies. A special parametric model of the elements of the hydrovolumetric transmission is developed in the paper to perform this analysis.

2 Literature Review The contact interaction of complex shaped bodies has drawn great interest of many researchers [4–6]. The arsenal of contact mechanics is constantly updated with new models and analysis methods. The scope of the problems and physical phenomena covered in those studies is constantly broadened. If one considers the basic analytical Hertzian contact model [4], one need to keep into account the assumptions limiting its validity. It cannot be used when the gap between the two elastic bodies can not be properly approximated by a quadratic function within the contact zone. Once the size of the contact spot get comparable to the dimensions of any of the bodies one needs to divert from a Hertzian model as well. The variational formulations [7–10] form a basis for various numerical methods. The normal contact problem can be formulated as a minimization problem in terms of potential energy or alternatively complementary energy. The unilateral contact conditions enter in the form of inequality constraints in terms of displacements or by enforcing positivity of contact pressure. The numerical implementation of these mathematical formulations is performed by finite element methods or boundary integral methods [2, 3, 8, 11]. Semi-analytical discrete pressure element methods [12, 13] are based on the known fundamental solutions for elastic half-space. The unknown contact pressure in sought in a distcretized form. Two different approaches to the formulation of the contact conditions are possible. They might be required to be satisfies pointwise in a strong sense on the same discretization grid. The alternative is to obtain that from the variational principle of the minimum complementary energy in the weak sense. The properties of the surface layers of contacting bodies constitute another important factor [14–23]. Rough surfaces interact primarily between the asperities. Additional local deformations are required to bring the bodies into full contact contrary to the case of smooth surfaces. Adhesive forces change the nature of contact interaction. Contact tractions can get tensile between two adherents. Variational formulations can get extended to account consistently for these new phenomena [2, 3, 8, 12]. Thus, both analytical and numerical methods of contact interaction analysis have their advantages and disadvantages. Accordingly, one should naturally expect a positive effect from the combination of analytical and numerical approaches in the analysis of contact interaction. Such a combined approach is implemented and described in this article.

3 Research Methodology The sensitivity analysis of contact interaction with respect to the variation of the geometrical shape of the bodies is performed by solving a sequence of statics problems with small deviation from a reference design.

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The general outline of the two-body system is given in Fig. 1. A variational formulation of the unilateral frictionless contact problem similar to the previously proposed in [2, 3, 12] is used. The displacement solution is sought as a minimum of the potential energy functional J J (u, u) =

1 a(u, u) − b(u) → min on K, K = {u : l(u) ≥ 0}. 2

(1)

Here u is the unknown displacement field; a, b are the quadratic and linear components of the functional that are the elastic deformation energy and the work of external forces; K is the admissible set of displacements that satisfy the impenetration conditions; l is a linear operator that maps the displacement field into the normal gap between the bodies in the deformed state. A sequence of perturbed problems are solved with this statement. They differ in the geometry of the running track profile of the stator ring. Its shape is defined as a perturbation  = 0 − ,

(2)

of the initial theoretical profile 0 with a deviation  in the normal direction as shown in Fig. 2. This deviation can be viewed as a shape error or a deliberate adjustment of the profile.

Fig. 2. Perturbed shape of the running track profile 

The reference shape of the running track is toroidal. The normal coordinate of the profile that is an arc of a circle is given by the expression  (3) zl = RT − R2T − yl2 , where RT is the internal radius of the stator measure to the bottom point of the running tract on the center line. The deviation from this profile is given by a Hermit function [24]  2   |yl | |yl | 2 zl = A −1 +1 , h h

(4)

where A is the amplitude of the perturbation; h is the width of the area where this positive gap offset is introduced. The expressions (3) and (4) of the geometrical shape  are analytical and exact.

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A numerical approximation of the minimization problem (1) by the finite element method is performed. The nodal coordinates of the surface points in the zone of possible contact defined by the analytical expressions of the bodies shape enter the minimized functional through the approximated gap function. As the result the unknown displacement field u, the elastic strains and stresses σ, ε, the contact area Sq and the distribution of the contact pressure q are explicitly determined as the functions of the geometrical parameters A and h: u = u(A, h), σ = σ (A, h), ε = ε(A, h), Sq = Sq (A, h), q = q(A, h).

(5)

These parametrical relations are used to evaluate the design of the ball pistons and the stator ring. One can assess the impact of the depth and width of the profile modification on the strength and other performance characteristics of the hydrovolumetric drive.

Fig. 3. 1/4 cut geometric and finite-element models of the ball and toroidal ring in normal contact

4 Results 4.1 Analysis Scheme The scope of the model covers a ball piston and a part of the stator ring around the point of their contact. The design parameters of the hydrovolumetric drive GOP-900 as presented in Fig. 1 are set to the previously proven values. The diameter of the stator ring is 2R = 63.5 · 10−3 m, the diameter of the stator ring is d = 0.3195 m, the toroidal running track on its inner surface has initially a circular profile with a radius RT = 1.05R large enough to accommodate the ball piston. The normal contact and the stress levels are studied for the maximal pressing force P = 100 kN. Due to the symmetry of the problem a quadrant cut out relative to the central axis of action for the pressing force P is sufficient for the analysis. The geometrical and the finite element model of the system are shown in Fig. 3. The profile of the running track in this model is assigned the shape given by the Hermit function (4). Hence it can be varied automatically with the geometric parameters A and h in the range A ∈ {2; 6; 10; 25; 50} · 10−6 m and h ∈ {0.05; 0.075; 0.1; 1.15; 0.2} · R. The geometric and finite-element models of the studied system is shown in Fig. 2. A quadrant cut out of the two bodies is only included to the analysis due to the symmetries of the problem.

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4.2 Numerical Results The results of the parametric analysis are shown in Figs. 4, 5 and 6. Each study case illustrated the effect of the amplitude of the profile modification A for a given width h of the affected band of the running track surface. A reference solution is given in Fig. 7 for the unperturbed toroidal profile 0 for comparison. 4.3 Results Analysis

, MPa

, MPa

As can be seen from the solutions shown in Figs. 4, 5, 6 and 7, the variation of the parameters A and h has a strong influence on both the character of contact pressure distribution and the shape and dimensions of the contact area. For small disturbances (A < 5 · 10−6 m), the contact area remains oval as it is also in case of the unperturbed toroidal shape. As A grows, the contact zone acquires a dumbbell shape, and later turns into two isolated ovals. At the same time, the distribution of the contact pressure q also changes. For small modification magnitudes A, the pressure distribution is similar to a semi-ellipsoid, with a peak in the center. As A grows, this distribution takes the form of two hills, initially connected by a saddle surface. Those two maxima separate over the two isolated contact spots as the perturbation gets even more significant. The distribution of equivalent von Mises stresses σe follows the applied contact pressure.

a

b

c

Fig. 4. Contact pressure distribution and equivalent von Mises stress for the ball piston and the stator ring for a profile perturbed over the width h = 0.05R with amplitudes A: 2 · 10−6 m (a), 10 · 10−6 m (b), 50 · 10−6 m (c)

As can be seen the contact pressure qmax and the equivalent stress σe, max grow mostly monotonous with increased perturbation amplitude A and decreased widths h of the affected strip band. Meanwhile, it is possible to pin a domain of perturbation values A ∈ [2; 4] · 10−6 m and h ∈ [0.15, 0.2]R for which the contact pressure and equivalent stress get steadily lowered for the given normal force P = 100 kN.

M. Tkachuk et al.

, MPa

, MPa

510

a

b

c

, MPa

, MPa

Fig. 5. Contact pressure distribution and equivalent von Mises stress for the ball piston and the stator ring for a profile perturbed over the width h = 0.1R with amplitudes A: 2 · 10−6 m (a), 10 · 10−6 m (b), 50 · 10−6 m (c)

a

b

c

Fig. 6. Contact pressure distribution and equivalent von Mises stress for the ball piston and the stator ring for a profile perturbed over the width h = 0.2R with amplitudes A: 2 · 10−6 m (a), 10 · 10−6 m (b), 50 · 10−6 m (c)

Quantitative relations of the maximal contact pressure qmax = qmax (A, h) and the maximal equivalent stress level σe, max = σe, max (A, h) are given by the diagrams in Figs. 8.

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Fig. 7. Reference contact pressure distribution and equivalent von Mises stress for the ball piston and the stator ring in the unperturbed case

Fig. 8. Maximal contact pressure qmax (a) and equivalent von Mises stress σe, max as functions of the geometry perturbation parameters A and h.

5 Conclusions The paper delivers an analysis of the shape perturbation of the contacting bodies and its effect on their contact interaction and stress-strain state. A special parametrical model has been developed for a most critical section of the radial hydrovolumetric drive, namely the ball piston and the stator ring. The extremely high mechanical loads are concentrated in the area of their normal contact. The performed study lead to the following conclusions. 1. The developed approach combines two stages of research: 1) analytical modeling of the shape and perturbation of the shape of contacting bodies; 2) numerical modeling of contact interaction and stress-strain state of contacting bodies. This makes it possible to significantly increase efficiency while maintaining the accuracy of the analysis. The variation of the stress-strain state of the studied bodies with the shape perturbation the contact surfaces is established within the proposed scheme. 2. It was determined that the shape of the contact area and the distribution of contact pressure, as well as the distribution of equivalent stresses, significantly change during the interval of variation of the parameters of the perturbation of the shape of the surfaces.

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3. By varying the shape of the contacting surfaces, it is possible to minimize the level of operating stresses and contact pressure. The developed approach proved to perform well for the stated purpose. It can be used for the analysis of contact interaction and selection of the rational shape of the surfaces of contacting bodies according to strength criteria.

References 1. Kharkiv Morozov Machine Building Design Bureau Homepage. www.morozov.com.ua. Accessed 31 Dec 2021 2. Tkachuk, M., Grabovskiy, A., Tkachuk, M., Hrechka, I., Tkachuk, H.: Contact of a ball piston with a running track in a hydrovolumetric transmission regarding the elastic properties of the material. In: Tonkonogyi, V., Ivanov, V., Trojanowska, J., Oborskyi, G., Pavlenko, I. (eds.) Advanced Manufacturing Processes IV. InterPartner 2022. LNME, pp. 495–505. Springer, Cham (2023). https://doi.org/10.1007/978-3-031-16651-8_47 3. Tkachuk, M.M., Grabovskiy, A., Tkachuk, M.A., Hrechka, I., Sierykov, V.: Contact interaction of a ball piston and a running track in a hydrovolumetric transmission with intermediate deformable surface layers. In: Tonkonogyi, V., Ivanov, V., Trojanowska, J., Oborskyi, G., Pavlenko, I. (eds.) Advanced Manufacturing Processes III. InterPartner 2021. LNME, pp. 509– 520. Springer, Cham (2022). https://doi.org/10.1007/978-3-030-91327-4_50 4. Johnson, K.L.: Contact Mechanics. Cambridge University Press (1985) 5. Popov, V.L., Heß, M., Willert, E.: Handbook of Contact Mechanics: Exact Solutions of Axisymmetric Contact Problems. Springer, Heidelberg (2019). https://doi.org/10.1007/9783-662-58709-6 6. Barber, J.R.: Contact Mechanics. Solid Mechanics and Its Applications, vol. 250. Springer, Cham (2019) 7. Motreanu, D., Panagiotopoulos, P.D.: Minimax Theorems and Qualitative Properties of the Solutions of Hemivariational Inequalities, vol. 29. Springer, New York (2013). https://doi. org/10.1007/978-1-4615-4064-9 8. Martynyak, R.M., Prokopyshyn, I.A., Prokopyshyn, I.I.: Contact of elastic bodies with nonlinear Winkler surface layers. J. Math. Sci. 205(4), 535–553 (2015) 9. Hlavácek, I., Haslinger, J., Necas, J., Lovisek, J.: Solution of Variational Inequalities in Mechanics, vol. 66. Springer, New York (2012). https://doi.org/10.1007/978-1-4612-1048-1 10. Kalker, J.J.: Variational principles of contact elastostatics. IMA J. Appl. Math. 20(2), 199–219 (1977) 11. Vollebregt, E.A.H.: 100-fold speed-up of the normal contact problem and other recent developments in «CONTACT». In: Proceedings of the 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, pp. 201–209. State Key Laboratory of Traction Power (TPL), Southwest Jiaotong University, Chengdu, China (2012) 12. Tkachuk, M.: A numerical method for axisymmetric adhesive contact based on Kalker’s variational principle. East.-Eur. J. Enterprise Technol. 3(7), 34–41 (2018) 13. Li, J., Berger, E.J.: A semi–analytical approach to tree–dimensional normal contact problems with friction. Comput. Mech. 30, 310–322 (2003) 14. Popov, V.L., Pohrt, R., Li, Q.: Strength of adhesive contacts: influence of contact geometry and material gradients. Friction 5(3), 308–325 (2017). https://doi.org/10.1007/s40544-0170177-3 15. Li, Q., Popov, V.L.: Adhesive force of flat indenters with brush structure. Facta Universitatis, Ser. Mech. Eng. 16(1), 1–8 (2018)

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16. Ciavarella, M.: Adhesive rough contacts near complete contact. Int. J. Mech. Sci. 104, 104–111 (2015) 17. Ciavarella, M., Papangelo, A.: A random process asperity model for adhesion between rough surfaces. J. Adhes. Sci. Technol. 31(22), 2445–2467 (2017) 18. Slobodyan, B.S., Lyashenko, B.A., Malanchuk, N.I., Marchuk, V.E., Martynyak, R.M.: Modeling of contact interaction of periodically textured bodies with regard for frictional slip. J. Math. Sci. 215(1), 110–120 (2016). https://doi.org/10.1007/s10958-016-2826-x 19. Pohrt, R., Popov, V.L.: Contact stiffness of randomly rough surfaces. Sci. Rep. 3(1), 3293 (2013) 20. Joe, J., Thouless, M.D., Barber, J.R.: Effect of roughness on the adhesive tractions between contacting bodies. J. Mech. Phys. Solids 118, 365–373 (2018) 21. Li, Q., Popov, V.L.: Adhesive contact between a rigid body of arbitrary shape and a thin elastic coating. Acta Mech. 230(7), 2447–2453 (2019). https://doi.org/10.1007/s00707-01902403-0 22. Ciavarella, M., Joe, J., Papangelo, A., Barber, J.R.: The role of adhesion in contact mechanics. J. R. Soc. Interface 16(151), 20180738 (2019) 23. Papangelo, A., Scheibert, J., Sahli, R., Pallares, G., Ciavarella, M.: Shear-induced contact area anisotropy explained by a fracture mechanics model. Phys. Rev. E 99(5), 053005 (2019) 24. Strang, G., Fix, G.J.: An Analysis of the Finite Element Method. Wellesley-Cambridge Press (2008)

Implementation of Induction Motor Speed and Torque Control System with Reduced Order Model in ANSYS Twin Builder Vladyslav Pliuhin1 , Yevgen Tsegelnyk1(B) , Sergiy Plankovskyy1 Oleksandr Aksonov1 , and Volodymyr Kombarov1,2

,

1 O. M. Beketov National University of Urban Economy in Kharkiv, 17 Marshala Bazhanova

Street, Kharkiv 61002, Ukraine [email protected] 2 Research Center of Manufacturing Technology, Faculty of Mechanical Engineering, Czech Technical University in Prague, 3 Horska Street, 128 00 Prague 2, Czech Republic

Abstract. This paper deals in detail with the development of a vector Field Oriented Control (FOC) system for the modes of operation of an induction motor with a squirrel cage rotor using ANSYS Twin Builder. Despite the fact that the theory of vector control system is well known, and its implementation is fully disclosed in Matlab/Simulink, such task is new in the ANSYS Twin Builder software. The use of ANSYS Twin Builder attracts first of all the advantages of using an imitation model as a digital twin of a real technical object with two-way communication, in this case it is an induction motor. The paper shows the stages of creating a reducedorder model (ROM) of an induction motor, importing the ROM of the motor into Twin Builder, forming the structure of the vector FOC system for controlling the speed and torque of the induction motor in Twin Builder, configuring and connecting library modules based on standard and VHDL ones. Simulation is performed in two stages. At the first stage, a joint (coupling) calculation of an induction motor with a squirrel cage rotor in ANSYS Maxwell and an imitation model in ANSYS Twin Builder was implemented. The second stage uses the induction motor ROM integrated into the ANSYS Twin Builder sheet. The obtained calculation results were analyzed and compared, and further research results were formulated, which will be aimed at the development of a digital twin of an induction motor with a squirrel cage rotor based on ANSYS Twin Builder. The paper will be useful to PhD students, scientific researchers, engineers of design departments of industrial enterprises that are engaged in the development of electric motors and their control systems, and enterprises that use controlled electric motors and need to monitor their operating modes in real time. Keywords: Induction Motor · Control System · FOC · ANSYS Twin Builder · Digital Twin · Vector Control · Coupling Simulation · Imitation Model

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 514–531, 2023. https://doi.org/10.1007/978-3-031-40628-7_42

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1 Introduction Digital twins (DT) are a powerful tool that changes the design way, manufacture, and operate products and processes [1]. They display the real object in the virtual world, allowing to carry out virtual experiments, testing and optimization, which allows to significantly reduce the time and costs of development and production. In the field of operation, DT can be used to predict the technical condition of equipment and prevent emergency situations [2]. With the help of virtual models, it is possible to monitor and diagnose the condition of the equipment, which allows to make predictions about possible breakdowns and carry out scheduled maintenance. Known working examples of the use of DT in real production, such as forecasting the mode of operation of the nuclear reactor at the nuclear plant [3]; control of metal melting and optimization of blanks production [4]; DT of laser machines [4]; oil and gas production [5] et al. DT can be used to analyze the impact of changing conditions on production and operational processes, such as changes in the composition of raw materials or changes in production parameters [1, 2]. This allows to determine the optimal working conditions and increase production efficiency. In the context of electric machines, this paper examines a DT of an induction motor with a squirrel-cage rotor connected to a frequency control system. There are two main categories of motor control systems – scalar control and vector control. As known, with scalar control, only one parameter can be controlled (for example, rotation speed or moving torque) and the accuracy of maintaining the given value is not high [6]. Vector control is a method of controlling alternative current (AC) motors, which allows to independently and almost inertialess adjust the rotation speed and torque on the motor shaft [7]. In the studied works, which are devoted to the implementation of vector control, the different approaches are uses. In [8–12] authors perform simulations in the PSIM environment, both to reproduce the control system and the motor. This program is similar to Matlab/Simulink models [13–16]. The main thing that unites these works is the presence in the models of an idealized block, which represents an electric motor. Papers [17–19] combined Matlab/Simulink (control system implementation) with ANSYS Simplorer (Twin Builder), where the motor was reproduced, thus solving a parallel problem (known as coupling project) in two different software products. This approach is understandable, because the motor model, calculated by the finite element method in ANSYS, corresponds as closely as possible to the real prototype. The ANSYS allows the creation of models that are as close to real prototypes for both the motor and the control system. With flexible modeling capabilities, including tight integration with ANSYS modules for solving multidisciplinary problems and embedded software, Twin Builder helps analyze design concepts, conduct detailed analysis and verify the operation of a multi-component system as a whole [20]. While motor models created in ANSYS are well known [17–19], the vector control system has not been disclosed in known publications. From the point of view of technical novelty, in this paper, for the first time, the vector control model of an asynchronous electric drive is disclosed in full and without redux. In addition, this system was supplemented with a module for the task of the desired motor starting time before reaching the rated speed. From the point of view of scientific value, this paper describes

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the calculation of proportional and integral coefficients of the proportional integration and differential (PID) controller of the vector pulse-width modulation (PWM) system, considering the features of creation in the ANSYS Twin Builder environment. In this paper, the main task is to build a vector control system using only ANSYS Twin Builder tools, the solution of which seems to be new. In addition, the project proposed for consideration the following features: – the AC motor is an exported object from ANSYS Maxwell 2D/3D, calculated by the finite element method with current and frequency parameterization; – the acceleration rate is set for the control system, which makes the model as close as possible to real operating conditions; – the scheme is universal and invariant to the type of electric motor due to the modified current and speed controllers.

2 Field Oriented Vector Control System The main idea of vector control is to control not only the magnitude and frequency of the supply voltage, but also the phase. In other words, the magnitude and angle of the spatial vector are controlled [21]. Vector control, in comparison with scalar control, has a higher performance and eliminates almost all its shortcomings. Advantages of vector control: – high accuracy of speed control; – smooth start and smooth rotation of the motor in the entire frequency range; – quick response to load changes: when the load changes, there is practically no change in speed; – increased control range and regulation accuracy; – heating and magnetization losses are reduced, the efficiency of the electric motor is increased. Despite the theory of vector control is well known, below is a summary information in order to compare it with the corresponding implementation of such system with the Twin Builder tools. The general block diagram of the AC motor vector control system is shown in Fig. 1 [22]. The basis of the circuit shown in Fig. 1 are the magnetic flux linkage and torque control loops, together with an estimator, which can be implemented in various ways. At the same time, the external speed control loop is largely unified and generates control signals for the torque controllers M* and magnetic flux linkage * (through the flow control unit). The motor speed can be measured by a sensor (speed/position) or obtained by means of an estimator allowing sensorless control to be realized. Field Oriented Control (FOC) is a control method that drives a brushless AC motor as an independently excited direct current (DC) machine, meaning that field and torque can be controlled separately [23]. FOC has become widespread, as it allows to control the position of the shaft, speed and torque of the electric motor quickly, smoothly and accurately. But to implement such a control method, it is necessary to know the position of the rotor. According to

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Fig. 1. General functional diagram of vector control.

the method of determining the position of the rotor of the electric motor, two methods of FOC are distinguished: – sensor – feedback on the position sensor and/or speed sensor; – sensorless – information about the position of the rotor is calculated mathematically in real time based on the information that is available in the control system. FOC is based on the analogy of a mechanically commutated, independently excited DC commutator motor. In this motor, the field and armature windings are separated, the flux linkage is controlled by the field current of the inductor, and the torque is independently controlled by adjusting the armature current. Thus, the flux linkage and torque currents are electrically and magnetically separated (Fig. 2) [23, 24].

Fig. 2. General functional diagram of sensorless field-oriented control.

On the other hand, brushless AC motors most often have a three-phase stator winding, and the stator current vector I s is used to control both flux linkage and torque. Thus, the field current and the armature current are combined into a stator current vector and cannot be controlled separately. Decoupling can be achieved mathematically by decomposing the instantaneous value of the stator current vector I s into two components: the longitudinal component of the stator current I sd (creating a field) and the transverse component of the stator current I sq (creating a torque) in a rotating dq coordinate system oriented along the rotor field (R-FOC – rotor flux-oriented control). Thus, the control of a brushless AC motor becomes identical to the control of an independent-excited phase detector of field control (PDFC) and can be implemented using a PWM inverter with a linear proportional and integration (PI) controller and space vector voltage modulation.

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In FOC, the torque and field are controlled indirectly by controlling the stator current vector components. The instantaneous stator currents are converted to a dq rotating frame using the αβ/dq Park transformation, which also requires knowledge of the rotor position. The field is controlled via the longitudinal current component I sd , while the torque is controlled via the transverse current component I sq . The Inverse Park Transform (dq/αβ), a coordinate transformation math module, calculates the voltage vector reference components V sα * and V sβ * . To determine the rotor position, either a rotor position sensor installed in the electric motor or a sensorless control algorithm implemented in the control system is used, which calculates information about the rotor position in real time based on the data available in the control system.

3 Configuration of the Motor Model The initial modeling object is a general industrial three-phase induction AC motor with a squirrel-cage rotor with the following parameters: line voltage 380 V, number of poles 4, stator winding connection scheme – star, frequency 50 Hz. At the first stage, the motor parameters are calculated in the Java program developed by the authors. The received data is entered into the ANSYS RMxprt template. The main parameters of the calculated motor are given in Table 1. Table 1. Parameters of an induction motor. Name

Unit

Value

Rated Power

kW

15

Rated Voltage

V

380

Rated stator current

A

3.55

Mechanical Shaft Torque

Nm

9.93

Rated Frequency

Hz

50

Rated rotation speed

rpm

1415

Inner/Outer Diameter of Stator

mm

85/131

Length of Stator/Rotor Core

mm

105

Air gap

mm

Number of poles/Stator Slots

4/36

Number of Rotor Slots

0.5 34

Stator Resistance R1/Leakage Reactance

Ohm

7.21/4.25

Rotor Resistance/Leakage Reactance

Ohm

2.60/4.38

Mutual Inductance

H

0.0867

Break-Down Torque

Nm

2.46 (continued)

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Table 1. (continued) Name

Unit

Value

Break-Down Phase Current

A

12.09

Total Loss

W

410

Input/Output Power

kW

1.91/1.5

Efficiency

%

78.5

Power Factor

0.81

A successful calculation in RMxprt makes it possible to export the solution to ANSYS Maxwell, in this case Maxwell 2D (Fig. 3). The project type is set to Eddy Current, because only in this case is it possible in the Circuit Editor to insert an equivalent circuit extraction block for subsequent calculations (Fig. 4).

Fig. 3. Design of an induction motor in ANSYS Maxwell.

For the electric circuit extraction for induction motor (ECEIM) block, 8 current variations are set with 0.5 A step, and for the electric circuit extraction for frequency (ECEF) block, 50 frequency variations with 1 Hz step. The long-hours calculation performed for this Eddy Current project is rewarded later on – the data obtained serves as the basis for extracting the equivalent circuit (electric circuit extraction (ECE) netlist data) in the Twin Builder shield (Fig. 5), where the simulation of various operating modes is completed in a matter of minutes.

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LabelID=IVa

LabelID=VIA 0.00713536H*Kle LA

LabelID=IVb

LabelID=IVc

LabelID=VIB 0.00713536H*Kle LB

LabelID=VIC 0.00713536H*Kle LC

7.20911ohm RA

LPhaseA

7.20911ohm RB

LPhaseB

7.20911ohm RC

LPhaseC

Model +

LabelID=VA 310.269V

LabelID=VB 310.269V

+

+

LabelID=VC 310.269V

Model

0

Fig. 4. Motor power supply diagram in Circuit Editor with ECEIM and ECEF blocks.

Fig. 5. Motor equivalent circuit object extracted from ANSYS Maxwell 2D.

Thus, this approach combines the ability of Twin Builder in terms of building control schemes with a model of an electric motor calculated in advance by the finite element method. Such modeling accuracy, as close as possible to a real prototype, cannot be obtained in other software products. But with ANSYS Maxwell and Twin Builder combination it is possible to get a truly DT of an electric machine.

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4 Building a Control System The vector control scheme is built according to the above block diagram (Fig. 2) and is well known in the theory of automated electric drive [7, 21–23]. A feature of this work is the adaptation of this scheme to the ANSYS Twin Builder tools. The importance of this issue is dictated primarily by the unparalleled modeling accuracy that ANSYS can provide by combining finite element field calculations and circuit engineering blocks. The scheme of the simulation model can be conditionally divided into 4 parts: 1. 2. 3. 4.

Power part. Phase-locked loop controller (PLL) block. Blocks of current and torque controllers. Block for setting the acceleration rate.

Let’s take a closer look at each of these blocks. The power part is shown in Fig. 6 and consists of a DC link represented by an electro-motive force (EMF) source (400 V), a two-level three-phase transistor inverter, measuring devices, an imported electric motor object, and a mechanical load unit. Block STEP1 activates loading on motor shaft 2 Nm at simulation time 1.2 s.

Fig. 6. The power part of the model in ANSYS Twin Builder.

The PLL block is designed to obtain the rotation angle θ of the coordinate system [25– 29]. There are basically three types of PLL systems for phase tracking: zero-crossing, stationary reference, and synchronously rotating zero-crossing, stationary reference, and synchronous rotating reference (SRF) PLLs. SRF PLL – among the above, has the best characteristics under distorted and non-ideal network conditions and is therefore the low-pass filter system that will be investigated further in the work. Input signals to the PLL circuit, which is used in the wraparound d-q frame, are three-phase linear voltages. Line voltage vector ⎤ ⎡ ⎤ ⎡ ⎤ Vm cos(ωe t + ϕ) Vm cos θab vab ⎣ vbc ⎦ = ⎣ Vm cos(ωe t + ϕ − 2π ) ⎦ = ⎣ Vm cos(θab − 2π ) ⎦, 3 3 2π vca ) cos(θ + Vm cos(ωe t + ϕ + 2π V m ab 3 3 ) ⎡

(1)

where Vm is the amplitude of the line voltage; ωe is the angular frequency; ϕ is the phase shift angle θab ; vab is the line voltage argument.

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In Fig. 7 shown the geometric diagram of the linear voltage vector in the stationary α-β frame and the synchronously rotating d-q frame with the Clark and Park transformations given by Eqs. (2) and (3), respectively ⎡ v ⎤    ab 1 0 0 va = (2) −1 ⎣ vbc ⎦, 1 √ √ 0 vβ 3 3 vca      cos θe sin θe va vd = . (3) vq − sin θe cos θe vβ The structural diagram of the used PLL scheme is shown in Fig. 8, which consists of a phase detector (FD), a low-pass filter (LFF) and a voltage-controlled generator (VCG), where ωc is the central frequency of the VCG as a direct feedback parameter that depends on the frequency range. Substitution (1) in (2) gives:     Vm cos θab va = , (4) vβ Vm sin θab and then substituting (4) into (3) we get:     vd Vm cos(θab − θe ) = . vq Vm sin(θab − θe )

(5)

Fig. 7. Geometric dependence of the linear voltage vector: (a) stationary frame; (b) synchronous d-q frame.

Since θe ≈ θab , , the phase is fixed. Then the second line (5) can be rewritten as vq = Vm (θab − θe ).

(6)

Thus, the S/R block in the phase detector of Fig. 8 performs the functions of a phase subtractor or a phase comparator. Since θe = θab , vq is zero. This means that the linear

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Fig. 8. PLL scheme based on the Park transformation to select the phase voltage shift angle.

voltage vector vl−l is aligned along the d axis. To design the PID controller of the phase inverter, the block diagram of the transfer function can be constructed as shown in Fig. 9. The transfer function from input θe∗ to output θe has the form: T(s) =

kp Vm s + ki Vm 2ζ ωn s + ω2n θe (s) = = , θe∗ (s) s2 + kp Vm s + ki Vm s2 + 2ζ ωn s + ω2n

(7)

where ζ is the damping coefficient; ωn is the undamped natural frequency of the system.

Fig. 9. Structural diagram of the PLL transfer function.

From (7) we have ki =

ω2n , Vm

(8)

kp =

2ζ ωn Vm

(9)

Thus, by setting the parameter values ζ, ωn and Um , which can be the nominal voltage of the generator, the parameters of the PID controller in the phase connection circuit can be obtained by formulas (8) and (9). After locking the phase angle of the mains voltage, the phase angle of the phase voltage is determined as θan = θe −

π . 6

(10)

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The implementation of PLL by Twin Builder library tools is shown in Fig. 10. PID controller parameters: k p = 0.94; k i = 0.007; k d = 0. Block CONST10 takes as parameter motor’s angular velocity from the block VM_ROT1 (Fig. 6). Block CONST14 contains zero value. The result of PLL work is passing in INTEGRATOR with the name teta. The task of the acceleration rate block is to obtain the equation of a straight line, which makes it possible to obtain the acceleration characteristic shown in Fig. 11. The main criteria for building an acceleration algorithm are the target speed (1000 Nm) and starting time (1 s). The implementation of the acceleration algorithm is shown in Fig. 12. The parameters of each of the modules are shown in the annotations to the blocks.

Fig. 10. PLL diagram in ANSYS Twin Builder to determine the shear angle θ.

Fig. 11. An example of the acceleration task of the electric motor.

During the simulation, the current time is fed to the Step block and through the integrator to the ratio 1/t_start, which determines the slope of the acceleration straight line. Acceleration stops when the current time is equal to t_start, and the LIMIT1 block prevents further growth. The acceleration pattern obtained in this way in a single equivalent is scaled at the output (speed block) in rpm by subsequent GAIN blocks.

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Fig. 12. Block setting the rate of acceleration of the electric motor.

Additionally, this approach can be extended with a block for setting the starting voltage value, but this is not considered in this paper. Finally, the controller block is shown in Fig. 13. The same diagram shows the space vector PWM module (SVPWM1), the output signals of which are specified as parameters for the switching properties of the inverter transistors. Parameters of PID current controllers along the d/q axes: k p = 6; k i = 0.01; k d = 0. PID speed controller parameters: k p = 20; k i = 1; k d = 0. CONST1 block contains the value 1/L m (Table 1) and CONST2 block has a zero value. GAIN block with the name phi receive as parameter teta.VAL from PLL (Fig. 9). GAIN block with the name w receive target speed value speed.VAL from the output block of diagram, shown on Fig. 12. The full simulation scheme is shown in Fig. 14. Both E1 EMF value and space vector pulse-width modulation (SVPWM) voltage values are 400 V.

Fig. 13. Block of current and torque controllers.

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Fig. 14. A complete diagram of the field-oriented vector control of an induction motor.

5 Simulation Results and Discussion Before the start of the virtual experiment, the simulation time was set to 2 s, the minimum step was 1 μs, and the maximum step was 1 ms. The main results of the simulation are shown in Figs. 15, 16, 17, 18, 19 and 20. As can be seen from the chart in Fig. 20, the use of a vector control system allows to accurately observe the speed reference, regardless of the change in the load torque on the motor shaft. For comparison, In Fig. 21 shown the simulation results of a similar motor, but with a scalar control system (U/f = const) [30, 31].

Fig. 15. Chart of the stator winding voltages (full time range).

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Fig. 16. Chart of the stator winding voltages (scaled last part).

Fig. 17. Chart of the stator winding currents (full time range).

The considered model of vector control of an induction motor is not limited to this type of electric drive. The built system is universal – instead of an induction motor with a squirrel-cage rotor, an electric motor of any other type – asynchronous or synchronous – can be imported from Maxwell 2D/3D into the Twin Builder sheet. In addition, the considered system with minor changes can be used to stabilize the rotation speed of generators of wind power and hydraulic installations. This work has already been completed by the authors on a special order, and materials for the next publication are currently being prepared. The limitation of the considered model is the lack of rotor power control, that is, asynchronous and synchronous machines that have an independent power supply of the rotor winding need to update the control system. In addition, the issue of motor braking time control is not disclosed in the considered model - this is also a topic for further research.

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Fig. 18. Chart of the stator winding currents (scaled last part).

Fig. 19. Chart of the torque on the shaft and the mechanical load torque.

In Kharkiv (Ukraine), work is underway to restore the city’s transport infrastructure after damage caused by hostilities. In these conditions, it is not so important the production of new motors then the renewal of those, that were in use to extend their service life. Scientists from O.M. Beketov National University of Urban Economy in Kharkiv, which includes this paper author’s, carried out scientific research and performed works of developing a DT of an induction motor together with a frequency control system. The performed works helped to significantly save the costs of the electromechanical plant at the stage of product preparation for further manufacturing by reducing the number of experimental samples. According to the experience gained from such cooperation, the digital model is adjusted up to three times, which reduces the number of experimental samples up to 2–3 before starting the serial manufacturing. As a result of the completed work on the creation of digital twins and their further optimization in ANSYS, in addition to saving cost on experimental samples, it was possible to increase the motors efficiency and at the same time to reduce the consumption of materials for their manufacture. In

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Fig. 20. Chart of the actual speed and speed reference.

Fig. 21. Simulation results for a scalar control system.

this way, the aim of reducing the production cost by 20% was achieved. The increase in the efficiency of the optimized motor led to a decrease in operating costs due to reduced losses of active and reactive power by 8%.

6 Conclusion In this paper, a vector control system for an induction motor with a squirrel-cage rotor was implemented and successfully tested. The model is built using ANSYS Twin Builder blocks only, and the motor object itself is imported from the ANSYS Maxwell 2D solution. Separately, a block for setting the acceleration rate (target speed and time to reach it) was introduced into the simulation circuit, and the control system successfully completed this task. There are no hidden blocks in this work, all the model parameters are described in detail and documented, which makes it possible for everyone to reproduce it for their own research.

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Obviously, the use of a vector control system has an order of magnitude higher accuracy of maintaining the speed, and the obtained simulation results are in good agreement with the experimental ones. The electric motor taken as a prototype for simulation modeling belongs to the general industrial series and there are many factory test protocols for it, which, in general, made it possible to verify the model.

References 1. Jiang, Y., Yin, S., Li, K., et al.: Industrial applications of digital twins. Phil. Trans. R. Soc. A 379(2207), 20200360 (2021). https://doi.org/10.1098/rsta.2020.0360 2. Singh, M., Fuenmayor, E., Hinchy, E.P., et al.: Digital twin: origin to future. Appl. Syst. Innov. 4(2), 36 (2021). https://doi.org/10.3390/asi4020036 3. Kochunas, B., Huan, X.: Digital twin concepts with uncertainty for nuclear power applications. Energies 14(14), 4235 (2021). https://doi.org/10.3390/en14144235 4. Zhang, L., Chen, X., Zhou, W., et al.: Digital twins for additive manufacturing: a state-of-theart review. Appl. Sci. 10(23), 8350 (2020). https://doi.org/10.3390/app10238350 5. Wanasinghe, T.R., Wroblewski, L., Petersen, B.K., et al.: Digital twin for the oil and gas industry: overview, research trends, opportunities, and challenges. IEEE Access 8, 104175– 104197 (2020). https://doi.org/10.1109/ACCESS.2020.2998723 6. Kohlrusz, G., Fodor, D.: Comparison of scalar and vector control strategies of induction motors. Hung. J. Ind. Chem. 39(2), 265–270 (2011). https://doi.org/10.1515/422 7. Filizadeh, S.: Electric Machines and Drives: Principles, Control, Modeling, and Simulation. CRC Press, Boca Raton (2013). https://doi.org/10.1201/9781315169651 8. Tsai, M.F., Tseng, C.S., Lin, B.Y.: Phase voltage-oriented control of a PMSG wind generator for unity power factor correction. Energies 13(21), 5693 (2020). https://doi.org/10.3390/en1 3215693 9. Kiran, N.: Indirect vector control of three phase induction motor using PSIM. Bull. Electr. Eng. Inform. 3(1), 15–24 (2014). https://doi.org/10.11591/eei.v3i1.181 10. Sira-Ramírez, H., Linares-Flores, J., García-Rodríguez, C., Contreras-Ordaz, M.A.: On the control of the permanent magnet synchronous motor: an active disturbance rejection control approach. IEEE Trans. Control Syst. Technol. 22(5), 2056–2063 (2014). https://doi.org/10. 1109/TCST.2014.2298238 11. Aziri, H., Patakor, F.A., Sulaiman, M., Salleh, Z.: Simulation of three-phase induction motor drives using indirect field oriented control in PSIM environment. AIP Conf. Proc. 1883, 020045 (2017). https://doi.org/10.1063/1.5002063 12. Pliuhin, V., Plankovskyy, S., Zablodskiy, M., et al.: Novel features of special purpose induction electrical machines object-oriented design. In: Cioboat˘a, D.D. (ed.) International Conference on Reliable Systems Engineering (ICoRSE) – 2022. ICoRSE 2022. LNNS, vol. 534, pp. 265– 283. Springer, Cham (2023). https://doi.org/10.1007/978-3-031-15944-2_25 13. Khadar, S., Abu-Rub, H., Kouzou, A.: Sensorless field-oriented control for open-end winding five-phase induction motor with parameters estimation. IEEE Open J. Industr. Electron. Soc. 2, 266–279 (2021). https://doi.org/10.1109/OJIES.2021.3072232 14. Alepuz, S., Calle, A., Busquets-Monge, S., et al.: Use of stored energy in PMSG rotor inertia for low-voltage ride-through in back-to-back NPC converter-based wind power systems. IEEE Trans. Industr. Electron. 60(5), 1787–1796 (2013). https://doi.org/10.1109/TIE.2012. 2190954 15. Quintal-Palomo, R.E., Gwozdziewicz, M., Dybkowski, M.: Modelling and co-simulation of a permanent magnet synchronous generator. COMPEL Int. J. Comput. Math. Electr. Electron. Eng. 38(6), 1904–1917 (2019). https://doi.org/10.1108/COMPEL-12-2018-0501

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16. Topal, M.E., Ergene, L.T.: Designing a wind turbine with permanent magnet synchronous generator. In: National Conference on Electrical, Electronics and Computer Engineering, pp. 325–329. IEEE (2011) 17. Zhang, G., Li, K., Liu, C.: Simulation of permanent magnet synchronous motor vector control system based on Simplorer & Maxwell. In: 2018 7th International Conference on Energy, Environment and Sustainable Development (ICEESD 2018), pp. 1964–1969. Atlantis Press (2018). https://doi.org/10.2991/iceesd-18.2018.349 18. Pliuhin, V., Zablodskiy, M., Sukhonos, M., et al.: Determination of massive rotary electric machines parameters in ANSYS RMxprt and ANSYS Maxwell. In: Arsenyeva, O., Romanova, T., Sukhonos, M., Tsegelnyk, Y. (eds.) Smart Technologies in Urban Engineering. STUE 2022. LNNS, vol. 536, pp. 189–201. Springer, Cham (2023). https://doi.org/10.1007/ 978-3-031-20141-7_18 19. Mersha, T.K., Du, C.: Co-simulation and modeling of PMSM based on Ansys software and Simulink for EVs. World Electr. Veh. J. 13(1), 4 (2021). https://doi.org/10.3390/wev j13010004 20. Qi, Q., Tao, F., Hu, T., et al.: Enabling technologies and tools for digital twin. J. Manuf. Syst. 58, 3–21 (2021). https://doi.org/10.1016/j.jmsy.2019.10.001 21. Veltman, A., Pulle, D.W.J., De Doncker, R.W.: Fundamentals of Electrical Drives. POWSYS. Springer, Cham (2016). https://doi.org/10.1007/978-3-319-29409-4 22. Muktar, T., Umale, A., Kirpane, R.K.: Vector control methods for variable speed of AC motors. Int. Res. J. Eng. Technol. (IRJET) 4, 340–343 (2017) 23. Trzynadlowski, A.M.: The Field Orientation Principle in Control of Induction Motors. PEPS. Springer, Boston (1994). https://doi.org/10.1007/978-1-4615-2730-5 24. Yu, J., Zhang, T., Qian, J.: Modern control methods for the induction motor. In: Electrical Motor Products, pp. 147–172. Woodhead Publishing, Cambridge (2011). https://doi.org/10. 1533/9780857093813.147 25. Yaramasu, V., Wu, B., Alepuz, S., Kouro, S.: Predictive control for low-voltage ride-through enhancement of three-level-boost and NPC-converter-based PMSG wind turbine. IEEE Trans. Industr. Electron. 61(12), 6832–6843 (2014). https://doi.org/10.1109/TIE.2014.2314060 26. Calle-Prado, A., Alepuz, S., Bordonau, J., et al.: Predictive control of a back-to-back NPC converter-based wind power system. IEEE Trans. Industr. Electron. 63(7), 4615–4627 (2016). https://doi.org/10.1109/TIE.2016.2529564 27. Ibrahim, R.A., Zakzouk, N.E.: A PMSG wind energy system featuring low-voltage ridethrough via mode-shift control. Appl. Sci. 12(3), 964 (2022). https://doi.org/10.3390/app120 30964 28. Alepuz, S., Calle, A., Busquets-Monge, S., et al.: Control scheme for low voltage ride-through compliance in back-to-back NPC converter based wind power systems. In: 2010 IEEE International Symposium on Industrial Electronics, pp. 2357–2362. IEEE (2010). https://doi.org/ 10.1109/ISIE.2010.5637478 29. Desalegn, B., Gebeyehu, D., Tamirat, B.: Wind energy conversion technologies and engineering approaches to enhancing wind power generation: a review. Heliyon 8(11), e11263 (2022). https://doi.org/10.1016/j.heliyon.2022.e11263 30. Pliugin, V., Petrenko, O., Grinina, V., et al.: Imitation model of a high-speed induction motor with frequency control. Electr. Eng. Electromech. 6, 14–20 (2017). https://doi.org/10.20998/ 2074-272X.2017.6.02 31. Zablodskiy, M.M., Kovalchuk, S.I., Pliuhin, V.E., Tietieriev, V.O.: Indirect field-oriented control of twin-screw electromechanical hydrolyzer. Electr. Eng. Electromech. 1, 3–11 (2022). https://doi.org/10.20998/2074-272X.2022.1.01

An Effective Way of Removing Organic Chemical Contaminants from Wastewater Iryna Sinkevych1,2 , Alona Tulska1,2(B) , Oleksii Mardupenko1,2 Kseniya Rezvaya1,2 , and Viktoriia Vakal1,2

,

1 National Technical University “Kharkiv Polytechnic Institute”, Kyrpychova Str. 2,

Kharkiv 61002, Ukraine [email protected] 2 Research Institute of Mineral Fertilizers and Pigments of Sumy State University, Sumy, Ukraine

Abstract. Existing and new promising ways for treatment of phenol-containing wastewater taken as a by-product of coke plants are described. Electrochemical treatment of industrial wastewater containing phenol is considered one of the most effective technologies. Phenol in wastewater is destructed in two steps. The first step is an electro oxidation of sodium chloride to hypochlorite which is considered an oxidant for phenol. Electrochemical destruction of phenol-containing wastewater was studied on coke, graphite electrodes and electrodes with RuO2 /TiO2 and PbO2 coatings. Oxidation of phenol in wastewater has been studying considering the impact of the following factors - temperature, duration of the process and type of electrode material. Efficiency of electrode materials was assessed by the decrease of phenol concentration in the tested solutions. The phenol concetration in water was measured by the titrimetric method using a bromide-bromate mixture. All the studied electrode materials are considered effective in the electrochemical treatment process. Anodes with RuO2 /TiO2 coatings are more preferable for concentrated chlorine solutions due to the low stability in dissolved solutions where coke and graphite anodes are more preferable. Keywords: Wastewater · Treatment · Electrolysis · Phenol · Purification degree · Duration of electrolysis · Graphite · Coke · Ruthenium · Titanium · Anode

1 Introduction Phenolic compounds are present in the effluents of various industries such as oil refining, petrochemicals, pharmaceuticals, coking operations, resin manufacturing, plastics, paint, pulp, paper, and wood products. Discharge of these compounds without treatment may lead to serious health risks to humans, animals, and aquatic systems. Phenol possesses hazardous health effects that can be both acute and chronic. Human exposure to phenol results in the irritation of the skin, eyes, and mucous membranes. Chronic exposure to phenols leads to irritation in the gastrointestinal and central nervous systems and liver, kidney, and cardiovascular tissues in animals. Phenol and its derivatives (phenols, or phenolic compounds) are moderately water-soluble pollutants, common to © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 532–540, 2023. https://doi.org/10.1007/978-3-031-40628-7_43

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the wastewaters of various industries, including oil & gas, paint manufacturing, phenolic resin production, paper and pulp factories, and pharmaceutical industries. Phenolic compounds are used in low concentrations in disinfectants, and are also present in many alcoholic beverages, pharmaceuticals, and cosmetics. Excessive phenolic compounds are harmful to human health and the environment. Existing treatment options include biological destruction, distillation/evaporation, adsorption and extraction, membrane separation, chemical oxidation and also electrochemical methods. A treatment system needs to be chosen and engineered carefully, with consideration of specific wastewater chemistry, operating conditions, and economic reasons. Recent advances in electrochemical membrane separation technology proved the high efficiency of such technologies for the treatment of phenolic compoundscontaminated wastewaters. Removing the dissolved organic impurities, and phenol in particular, from wastewater remains an important and difficult problem despite the big number of research. Technology of water purification requires specific conditions that are hard to realize practically. At the same time many effective methods of wastewater purification are quite expensive and consider using deficient reagents that need to be recovered as well as the waste disposal. All these factors are challenging for the most facilities. According to that, development of new effective ways of wastewater purification is considered an important task.

2 Literature Review The most common destructive methods of purification of phenol-containing industrial wastewater are electrocoagulation (EC), electrooxidation (EO), electroflotation (EF), electrodialysis (ED), and electro-Fenton (EFN) processes [1]. These methods have both certain advantages and some disadvantages [2]. Electrochemical destruction has been considered the most effective and promising way for destruction the organic impurities, and phenols in particular, in industrial wasterwater [3]. This conclusion is based on significant success of theoretical research in this area, development of new anode materials and the design of equipment [6]. The volumetric micro-arc discharge method of wastewater treatment is also promising. The efficiency of this method is ensured by high pressure and temperature in the discharge zone and significant specific power [8]. The efficiency of a certain electrochemical technology of wastewater treatment is based on the competent choice of anode material because this factor may have a significant affect on the construction of the electrolyzer, the specific electricity consumption and type of electrode reactions [4]. Mixed metal oxide (MMO) coated electrodes have found widespread environmental applications in recent years for the wastewater treatment, landfill leachate, organic petroleum wastewater and other difficult to treat waste streams. MMO anodes such as RuO2 /IrO2 -coated titanium with improved electrocatalytic behaviour and stability are readily available in practical mesh geometries and have extended life-time and relatively low costs. Besides, majority of the most developed anode materials have a base of RuO2 and IrO2 and are considered to be used in concentrated sodium chloride solutions. [13]

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Platinum-titanium anodes are not so widely used for wastewater treatment due to their high cost [14]. The second large group of materials that have metal oxides as a base (Co3 O4 , Fe2 O3 , PbO2 ) is mostly effective for sodium hypochlorite synthesis but this type of material is not available in industrial scales [7]. Therefore carbon, coke and graphite are considered promising anode materials for electrochemical treatment of wastewater from coke chemical industries [15]. Their availability for industry, ease of use in bulk-type devices and catalytic activity at low chloride concentrations indicate the prospects of research into the possibility of using these materials for the destruction of phenols in the wastewater of coke-chemical industries [9].

3 Methodology of the Experiment A sample of wastewater taken from the coke plant “Zaporizhkoks” (Zaporizhzhia, Ukraine) was studied and compared to the test solution of phenol with concentration of 1000 mg/dm3 . Study of phenol destruction processes was performed using standard methods. The laboratory electrolysis cell includes a plastic case and an electrode block. The electrode block has an anode with constant dimensions or a bulk electrode. The anode of the first type was made of titanium plate coated with RuO2 /TiO2 or PbO2 . The active reaction surface of the anode is 20 cm2 , the anode current is 0.1 A/cm2 . Carbon steel plates of the same size as the anode are used as cathodes. The bulk anode consists of cubic coke and graphite particles with a side of 1…2 cm. 1 kg of bulk anode is loaded into the electrolysis cell at a current of 5 A. The cathodes are made of perforated carbon steel pipes. A plastic mesh separated cathode and bulk anode areas. Sodium chloride solution with the concentration of 20 g/dm3 was added in order to produce an active chlorine. Efficiency of electrode materials was assessed by the decrease of phenol concentration in the tested solutions. An optimal duration of the process was also justified by the value of phenol concentration in tested solutions. The phenol concentration was measured by the titrimetric method using a bromide-bromate mixture. The concentration of sodium hypochlorite in treated water is defined by iodometric titration.

4 Results and Discussion Destruction of organic substances in wastewater is provided by the action of electrochemically synthesized active oxygen and so-called “active chlorine”. “Active chlorine” is a generalized term for hypochlorite and hypochlorite – based solution. Considering phenol the most harmful side-component of industrial wastewater, study of phenol oxidation is carried out using a test solution of phenol with the concentration of 1000 mg/dm3 . The process of phenol destruction described in the current research is considered a hybrid process. It is assumed that phenol is oxidized by sodium hypochlorite,

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which is formed by electrolysis of sodium chloride solution according to the following scheme: − anode

− cathode

2Cl− → Cl2 + 2e,

(1)

2H2 O → O2 + 4H+ + 4e

(2)

2H2 O + 2e ← OH− + H2

(3)

This process is followed by hydrolysis of chlorine according to the following equations (type of reaction depends on the pH value): Cl2 + H2 O → HClO + HCl,

(4)

Cl2 + OH− → HClO + Cl−

(5)

Cl2 + 2OH− → ClO− + Cl− + H2 O

(6)

The catalytic activity of different anode materials was studied and results are presented in Fig. 1. Complex RuO2/TiO2 performs the biggest catalytic activity in producing of chlorine and, as a result, sodium hypochlorite. However, RuO2/TiO2 anode is not suitable for low-concentrated sodium chloride solutions where lead dioxide is more preferable. Besides, sulfate ions and organic substances in athe solution to don decrease catalytic activity of lead dioxide. Carbon graphite and coke electrodes are less active than RuO2/TiO2 but are more stable in the electrolysis of low concentrated solutions of NaCl.

Fig. 1. Affect of the duration of electrolysis on phenol concentration (mg/dm3 ).

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According to the Fig. 1 concentration of phenols in water during the first hour of the experiment rapidy decreases for all studied types of anode materials. After first 60 min and beyond the decrease of phenol concentration is rather moderate. Such an equilibrium is typical for diaphragm-free electrolysis and is explained by the recovery of anodic oxidation products at the cathode. The use of RuO2 /TiO2 proved to be the most effective for phenol oxidation. The results for carbon graphite and coke electrodes are practically the same and slightly inferior to RuO2 /TiO2 . The anode with lead dioxide coating have the lowest efficiency. The mechanism of anode oxidation of organic substances is complex and has not been studied thoroughly. Electrochemical reaction is accompanied by adsorption of organic substances on the anode surface, interaction of adsorbed substances with free radicals and desorption of oxidation products. This can explain the of catalytic activity of anode materials and selectivity of a certain material of the anode to a certain type of organic substances. Certain types of anions in electrolyte (Cl– , SO4 2− , CNS– , etc.) cause the appearance of free radicals on the anode surface which also contributes to the process of oxidation of organic substances. Having analyzed the obtained data (decrease of phenol concentration during the electrolysis is graphically similar to an exponential decrease) it is possible to make a hypothesis about the first rate of the studied reaction. This hypothesis can also be proved by the fact that electrochemical destruction of phenol molecules does not require any other reagents. The process is driven only by electrical factors - voltage and electric current value. An increase of temperature decreases the voltage of electrode reactions, which makes the oxidation process easier. But if the temperature rises higher than 60 °C phenol starts evaporating from water which leads to atmospheric pollution. Also, an increase of temperature over 40 °C may cause the destruction of sodium hypochlorite, which reduces the efficiency of electrochemical processing. The next step of research is study of electrochemical oxidation of phenol in wastewater of coke plants with the following characteristics: 850 • phenol, mg/ dm3 • dichromate oxidized components, 4100 mg O2 g/dm3 • ammonium sulfate, g/dm3 • thioimidazolidone-2 (ethylenethiourea), g/dm3 • ethylenebisdithiocarbamic acid, g/dm3 • total carbon disulfide, g/dm3 • pH

30 0,89 0,3 2,1 7

Electrochemically treated water is odorless and has the following parameters: • dichromate oxidized components, 580 mg/dm3 • formic acid, mg/dm3 575

An Effective Way of Removing Organic Chemical Contaminants

• formaldehyde, mg/dm3 • ammonium sulfate, mg/dm3 . • organosulfur impurities

537

5 30 absent

The degree of purification from organosulfur components is 100%. The obtained results are shown in Fig. 2. Indicate that kinetics of wastewater electrolysis is similar to electrolysis of the test solution of phenol.

Fig. 2. Affect of the duration of electrolysis and anode material on the concentration of phenols in wastewater of coke plant.

The rate of phenol oxidation slightly decreased but the final concentration of phenol in the solution also decreased. This is explained by the presence of other organic substances in the wastewater, which are electro- and chemisorbed on the surface of the electrodes and, on the one hand, inhibit the course of electrode processes, and on the other hand, are catalysts that transport particles of a radical nature, which contribute to a deeper oxidation of phenol compared to the control solution. Based on Fig. 1 and 2, it can be concluded that electrolysis proceeds better on an RuO2 /TiO2 electrode than on a carbon graphite one. This is due to the fact that the porosity of the carbon graphite electrode is greater than that of the RuO2 /TiO2 , and as a result, the actual electrode surface is higher. Which leads to a decrease in the current yield of chlorine and an increase in the current yield of the combined anodic reaction of oxygen release. Due to the fact that wastewater contains chlorides that intensify the electrochemical oxidation of organic substances, the concentration of phenols during water purification is reduced by 100 mg/dm3 compared to standard water. However, the final concentration of phenols in water is 110 mg/dm3 . The concentration of phenols in water may increase from 55 to 110 mg/dm3 due to the fact that quinones and maleic acids are partially reduced at the cathode. Therefore, it makes sense to separate the anode and cathode spaces using a diaphragm. However

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it would significantly complicate the design of the electrolysis cell and may prevent the chlorination of organic impurities in the waste water of coke-chemical production. As a result of experiments, the affect of duration of electrolysis on purification degree was established.

Fig. 3. Affect of the duration of electrolysis (min) and electrode material on the purification degree (%) for the tested sample of phenol solution (5,6), sample of phenol solution with NaCl (1, 2) and wastewater (3,4): 1, 4, 5 – RuO2 /TiO2 ; 2, 3, 6 – graphite electrode.

Purification degree was calculated by the equation: η=

Co − Ck · 100%, Co

(7)

where η – purification degree, %; Co – initial concentration, mg/dm3 ; Ck – final concentration, mg/ dm3 . Analyzing the results of experiment, it is seen that during the first hour of electrolysis degree of phenol destruction raises up to 65% on average, during the following hour it raises by 20%. Purification degree also depends of the electrode material and process conditions. Results of using RuO2 /TiO2 anodes have shown that purification degree raises up to approximately 73% during the first hour and increases by 4% during the next hour. After two hours of treating the purification degree doesn’t change significantly, at this point the recommended time of electrolysis considered 2 h. If wastewater contains rhodanides and cyanides electrolytic treatment with RuO2/TiO2 anodes may provide an exothermic destruction of these compounds. Temperature of electrolyte can slightly raise up with the decrease of electrode overpotential (Fig. 3 line 4). As a result, purification degree reaches 62% by the end of the first hour, then raises by 7% during the next 30 min and extremely raises up to 94% by the end of the second hour of electrolysis. Analyzing a behaviour of phenol solution with sodium chloride addition it is seen that during the first hour the degree of purification from phenols is 74%, after 1.5 h of electrolysis the degree of purification increases slightly to 78%, during the next 30 min the degree of purification increased by almost 10% and reaches 89%. However more extended process is not sensible because quinones in solution partly reduce to phenols therefore degree of purification decreases by 3%, and gets approximately 83%.

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Treating of water on graphite anodes provides the purification degree about 64% during the first hour and 68% by the end of the second hour or treating. Purification of water was also studied on graphite anodes in a test phenol solution with sodium chloride. During the first hour of electrolysis purification degree reaches 63%, in the next 30 min of electrolysis it raises up to 75%, after two hours of electrolysis it gets 79%, however, more extended process is not sensible since after the second hour purification degree decreases by 6% and reaches 73%.

5 Conclusion Electrolytic treatment of wastewater containing phenol is significantly affected by electrode materials and conditions of process. Phenol destruction is considered a two-stage process where electrochemical synthesis of “active chlorine” is followed by the oxidation of phenol by “active chlorine” particles. It has been concluded that RuO2 /TiO2 anodes are the most effective in reaction of “active chlorine” release comparing to other electrode materials. However, anodes of this type require a high concentration of chlorine ions in solution. If the concentration of such ions is low, oxygen release becomes a dominant anodic process which cause a destruction of an active layer of RuO2 /TiO2 . The efficiency of RuO2 /TiO2 can be reached up to 78 – 89%. Efficiency of graphite and coke electrodes is lower than RuO2 /TiO2 but these electrodes can be used in dissolved chlorine solution and provide the purification grade about 73–78%. An optimal duration of process on a purification degree was considered analyzing the results of long-term experiment. According to that during the first two hours of the process the purification degree raises up to 78–89% depending on the type of electrode material. The possibility of using bulk graphite and coke electrodes significantly simplifies the design of the electrolysis cell and makes the technological process of wastewater treatment more simple and economically feasible. In these terms graphite and coke anodes can be recommended as cheap and simple but effective material to be used in low-concentrated chlorine solutions. Stainless steel is recommended to be used as a cathode.

References 1. AlJaberi, F.Y., Ahmed, S.A., Makki, H.F., Ngo, H.H., Nguyen, D.D.: Recent advances and applicable flexibility potential of electrochemical processes for wastewater treatment. Sci. Total Environ. 867, 161361 (2023) 2. Krasnoborodko, Y.H.: Destruktyvnaia ochystka stochnykh vod ot krasytelei. Stroiyzdat. Saint-Petersburg (2008) 3. Hrynevych, V.Y.: Destruktsyia fenola y syntetycheskykh poverkhnostnoaktyvnykh veshchestv, rastvorennykh v vode, pry elektrokhymycheskom vozdeistvyy sovmestno s ozonyrovanyem. Yzvestyia vuzov. Seryia Khymyia y khymycheskaia tekhnolohyia 52(2), 130–134 (2009)

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4. Smyrnova, V.S.: Ochystka vysokokontsentryrovannykh stochnykh vod promyshlennykh predpryiatyi ot fenolov. Vestnyk Permskoho natsyonalnoho yssledovatelskoho polytekhnycheskoho unyversyteta. Stroytelstvo y arkhytektura 8(2), 52–63 (2017) 5. Zhyshchenko, V.V.: Ekolohycheskye aspekty ochystky stochnykh vod koksokhymycheskoho proyzvodstva. Trudy Vserossyiskoi nauchnoi konferentsyy studentov, aspyrantov y molodykh uchenykh, 319–322 (2016) 6. Tulskyi, H.H., Sinkevych, Y.V., Nazarov, A.V.: Fyzyko-khymycheskye svoistva oksydnoho svyntsovo-tytanovoho pokrytyia anoda. Visnyk Natsionalnoho tekhnichnoho universytetu “KhPI” 32, 153–157 (2007) 7. Nidheesh, P.V., Behera, B., Babu, D.S., Scaria, M.J., Kumar, S.: Mixed industrial wastewater treatment by the combination of heterogeneous electro-Fenton and electrocoagulation processes. Chemosphere 290, 133348 (2022) 8. Ma, P., Ma, H., Sabatino, S., Galia, A., Scialdone, O.: Electrochemical treatment of real wastewater. Part 1: effluents with low conductivity. Chem. Eng. J. 336, 133–140 (2018) 9. Yan, L., et al.: Comparative study of different electrochemical methods for petroleum refinery wastewater treatment. Desalination 341, 87–93 (2014) 10. Rajkumar, D., Palanivelu, K.: Electrochemical treatment of industrial wastewater. J. Hazard. Mater. 113(1–3), 123–129 (2004) 11. Silva, J.R., Carvalho, F., Vicente, C., Santosb, A.D., Quinta-Ferreirac, R.M., Castro, L.M.: Electrocoagulation treatment of cork boiling wastewater. J. Environ. Chem. Eng. 10(3), 107750 (2022) 12. Scialdone, O., Randazzo, S., Galia, A., Silvestri, G.: Electrochemical oxidation of organics in water: role of operative parameters in the absence and in the presence of NaCl. Water Res. 43(8), 2262–2270 (2009) 13. Radjenovic, J., Bagastyo, A., Rozendal, R., Mu, Y., Keller, J., Rabaey, K.: Electrochemical oxidation of trace organic contaminants in reverse osmosis concentrate using RuO2 /IrO2 coated titanium anodes. Water Res. 45(4), 1579–1586 (2011) 14. Graça, N.S., Rodrigues, A.E.: The combined implementation of electrocoagulation and adsorption processes for the treatment of wastewaters. Clean Technol. 4, 1020–1053 (2022) 15. Santos, A.F., Ferreira, A.G.M., Quina, M.J.: Efficient management of sewage sludge from urban wastewaters with the addition of inorganic waste: focus on rheological properties. Clean Technol. 4, 841–853 (2022) 16. Graça, N.S., Ribeiro, A. M., Rodrigues, A.E.: Modeling the electrocoagulation process for the treatment of contaminated water. Chem. Eng. Sci. 197, 379–385 (2019) 17. Yakovlev, S.V., Krasnoborodko, Y.H., Rohov, V.M.: Tekhnolohyia elektrokhymycheskoi ochystky vody. Stroiyzdat, Saint-Petersburg (2007) 18. Ngobeni, P.V., Basitere, M.: Treatment of poultry slaughterhouse wastewater using electrocoagulation: a review. Water Pract. Technol. 17(1), 38–59 (2022) 19. Okeke, E.S., et al.: Environmental and health impact of unrecovered API from pharmaceutical manufacturing wastes: a review of contemporary treatment, recycling and management strategies. Sustain. Chem. Pharm. 30, 100865 (2022)

The Method of Clustering Geoinformation Data for Stationary Sectoral Geoinformation Systems Using Swarm Intelligence Methods Vasyl Lytvyn1

, Dmytro Uhryn2(B) , Yuriy Ushenko2 and Volodymyr Bairachnyi4

, Andrij Masikevych3

1 Lviv Polytechnic National University, S. Bandery Str., 12, Lviv 79013, Ukraine 2 Yuriy Fedkovych Chernivtsi National University, Kotsyubinsky Str. 2, Chernivtsi 58000,

Ukraine [email protected] 3 Bucovinian State Medical University, Teatralna Sq., 2, Chernivtsi 58002, Ukraine 4 National Technical University «Kharkiv Polytechnic Institute», Kyrpychova Str. 2, Kharkiv 61002, Ukraine

Abstract. It has been noted in the research that classical methods are not sufficiently effective for finding optimal solutions in industry-specific geographic information systems (IGIS) because they do not consider logical parameters. It has been proposed to use clustering methods with the use of a conceptual model for selecting an optimization method, based on prior research of the objective function for a specific task. Clustering of spatial data is often required in IGIS. However, the objective function in such clustering typically exhibits multimodality, high dimensionality, and complex topology of the feasible value domain. Therefore, research has been conducted to select a clustering method in IGIS. The proposed method for selecting a swarm algorithm and parameters for clustering is based on the proposed quality and efficiency indicators of swarm algorithms. A method and basic information technology have been developed for clustering geoinformation data, where data are grouped into clusters based on compactness criteria using swarm methods, utilizing both quantitative and logical features, thus improving the clustering quality. A clustering method has been proposed that contributes to enhancing the quality of clustering, and the choice of swarm optimization method was made according to the developed methodology. Research on the efficiency of clustering using swarm intelligence methods has been conducted. Keywords: Industry geoinformation system · Clustering · Swarm algorithm · Objective function · Optimization methods

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 541–553, 2023. https://doi.org/10.1007/978-3-031-40628-7_44

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1 Introduction One of the important applied problems today in the use of industry-specific geographic information systems (IGIS) is the modeling of the spatial data clustering process. In numerous IGIS applications, it is necessary to distinguish groups of objects with a significant range of heterogeneous quantitative and qualitative characteristics. These tasks are addressed in various sectors, such as the tourism industry, where they help settle tourist groups, in state administration GIS, where they determine the administrative centers of effective and capable territorial communities, and in military administration IGIS, where they identify safe areas for deploying units during movement. These tasks are characterized by their significant complexity and size. The objective functions, affected by a priori uncertainty, can have multiple peaks and exhibit a jarlike behavior. As the complexity and scale of these tasks increase, there is a growing demand for decisions that are both valid and effective. Consequently, the number of applied programs in IGIS is expanding to meet these increasing requirements. However, existing IGIS fall short in meeting the practical demands in terms of these criteria. The effectiveness of decision-making is determined by the capabilities of the selected extremum search methods for clustering. An appropriate approach to address clustering problems in these conditions involves the utilization of swarm algorithms. One notable advantage of swarm algorithms is their ability to explore a larger search space, which allows for the identification of solutions that are close to the optimal one. In contrast, methods based on local search only identify the local extremum of the objective function. By employing such approaches, it becomes possible to enhance the speed of implementation while simultaneously reducing errors during clustering procedures in the IGIS of the corresponding application. Based on prior studies, it has been established that the objective function in clustering exhibits a noisy and multimodal nature. Consequently, the selection of the clustering method involves the utilization of a conceptual model for choosing the appropriate swarm optimization method, relying on the results of prior studies conducted on the objective function for the specific applied problem. By applying the developed methodology for swarm optimization method selection, it has been determined that, for the implementation of clustering in IGIS across various practical applications, it is advisable to employ methods based on ant colonies combined with a flock of birds, gray wolves, gray wolves combined with bats, and a colony of bees.

2 Model of Cluster Analysis In numerous IGIS applications, the problem of spatial data clustering arises. The objective function associated with such clustering exhibits a noisy and multimodal nature. Furthermore, a significant number of clustering indicators comprise logical variables. Classical clustering methods prove to be ineffective in this case since they do not consider additional constraints related to the construction of clusters where these logical variables must assume specific values. It can be concluded that classical methods inadequately account for logical parameters, making them unsuitable and insufficiently effective for IGIS applications.

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Therefore, the clustering method is chosen by employing a conceptual model for selecting a swarm optimization method, which is based on the results of prior studies conducted on the objective function relevant to the specific applied problem. The traditional formulation of the problem of cluster analysis as a classification of multidimensional quantitative and qualitative data is as follows. Let be Q = {q1 , q2 , ..., qn } the set of objects that must be divided into m(m D d q ∈ Qj < D, d q ∈ extr (m)

(2)

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For multi-level hierarchical clustering, the formulation of the problem is as follows. For each h = 1, H (h is the level of the hierarchy, H is the number of such levels) the plural Q must be divided into non-intersecting subsets (clusters) Qjh , j = 1, mk in such a way   that the diameters of the clusters d Qjh do not exceed the given values (thresholds of similarity) Dh and at the same time the extrema of the objective functions were reached h at each level of the hierarchy [2, 5, 6]. The objects of clustering at the first level of the hierarchy are clusters qj = Qj0 , j = 1, n of the original plural Q; on the second level of the hierarchy - clusters Qj1 , j = 1, m1 of the first level; on the third – clusters Qj2 , j = 1, m2 of the second level, etc. Thus, each object (cluster) of the h-th level represents some set of objects (clusters) of the (h − 1)-th level, that is Qjh = i=jjk kQih−1 [3, 17]. At each level of the hierarchy, objects… Are described by different sets of features  h h h h  = 1 , 2 , ..., ph and the similarity of objects is determined by different measures of similarity μh which are chosen from representations of the similarity of objects of this level [1–3, 7, 8, 18, 19]. Mathematical model of the problem of hierarchical clustering: mh 

Qjh = Q; Qjh =

j=1





Qjh−1 ; Qjh ∩ Qih = ∅, i = j

(3)

j∈Jjk



d Qjh = Dh , j = 1, mh

(4)

extr h ; h = 1, H

(5)

The principle of operation of hierarchical algorithms is that the closest elements are first grouped into clusters. Next, combine all the more distant ones, but in such a way that each time this distance is greater and greater. The clustering algorithm uses a matrix of similarities (distances) and at the beginning each individual element is considered as a separate cluster. Therefore, to solve applied problems in IGIS industry, it is often necessary to cluster spatial data. On the other hand, the objective function in such clustering is usually characterized by multimodality, high dimensionality, complex topology of the domain of admissible values, etc. Therefore, research is needed on the choice of a method for solving the problem of clustering in industry IGIS.

3 Basic IT Clustering Let’s develop a conceptual model of swarm intelligence (SI). The model is given by the expression: MSI =< S, M , A, P, I , O >,

(6)

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where S - is a plural of agents (individuals), that is, a swarm (population); M – an object for the exchange of experience between agents, most often some matrix (can be a vector), to which all agents of the Ag swarm (population) have access according to certain rules A(P); A(P) – rules for creation, behavior, modification of agents; P – parameters (heuristic coefficients) used in the rules A. Parameters P can be static and dynamic; I1 – the input of the system to which the target function, constraints are applied, Iα – the input for feedback; O = {O1 , Ooc }, O1 – output (the best found solution to the problem), Oα – output for feedback. Each agent can be represented as: Ag = (TAg, OAg),

(7)

where TAg is the type of agent. The place of the agent is determined by its quality or type (some weight function), OAg – surroundings of the individual. During the operation of the algorithm, surroundings of the individual changes (dynamic) or remains constant (static). Each swarm S is defined by the following characteristics: S = (TS, R, SA),

(8)

where TS is the type of swarm (permanent, variable). If new individuals appear during swarm merging, the swarm is considered variable, if previous individuals remain, the swarm is static. R– swarm size, SA – metric (distance, weight, speed, cognitive behavior, social behavior, etc.) of population association, can be variable or constant. It should be noted that the rules for organizing a swarm are determined by a specific type of algorithm and are set in the following form of a set of actions: A = (set of actions, CA),

(9)

where CA - is the complexity of the algorithm. Algorithms are simple (an iteration contains one process) and complex (contains several processes) in terms of complexity. Based on the proposed indicators of quality and effectiveness of swarm algorithms, a method of selecting a swarm algorithm and free parameters for clustering was developed. The scheme of the method of choosing a swarm algorithm and free parameters for basic IT clustering is shown in Fig. 1. The scheme of the clustering method as a basic IT is shown in Fig. 2. During the development of these methods, in accordance with the main GIS models, it was proposed to use swarm algorithms – for clustering, which differ in numerical characteristics of variation, and a hybrid approach – for dividing a complex problem into separate problems, which differ in their composition and requirements for restrictions. The application of the hybrid approach as part of the clustering method assumes that the values obtained at the output of the implementation of swarm algorithms will give optimal results for the decision-maker, and the expert who is the decision-maker determines the clustering assessment.

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Determination of quality and efficiency indicators of the clustering method

It is carried out taking into account apriori uncertainty and the possibility of having a multimodal character

Determination of system quality criteria

It is carried out taking into account the impact on it of the selected indicators of quality and efficiency of clustering

Data entry

The required value of the system quality criterion is entered

Determining the values of the quality and efficiency indicators of the clustering method taking into account the system quality criterion

It is performed to ensure the required value of the system quality criterion

Definition of researched clustering methods

The choice is made from the clustering method used in the IT clustering method

Building a cluster

For example, containing all the necessary restrictions

Construction of dependencies of the swarm algorithm on the values of indicators of quality and efficiency of clustering

It is carried out for methods of swarm intelligence selected from the literature

Determining the values of the parameters of the swarm algorithm for a given value of the quality of the system

Making a decision on the feasibility of the application of the researched swarm algorithm

Definition of a swarm algorithm that has clustering optimality for selected parameter values

This swarm algorithm is characterized by the maximum indicator of clustering quality Output of information about the selected swarm algorithm

Fig. 1. Scheme of the method of choosing the type and parameters of the swarm algorithm for basic IT clustering.

The Method of Clustering Geoinformation Data

Forming the training sample and determining the number of clusters

It is performed to ensure the required value of the system quality criterion

Finding the initial coordinate vector of the cluster centers

The coordinates of the cluster center are determined according to an iterative scheme determined by the requirements of the chosen swarm optimization method using a conceptual model

Evaluation of the objective function at the first iteration

The clustering method works

Setting the clustering parameters, which are selected by conceptual modeling of the swarm method

Clustering iterations are performed using the selected optimization method

Evaluation of the objective function on the nth interaction

The direction of movement to the extremum is estimated by the chosen swarm method. The coordinates of the cluster centers are determined

Clustering completion condition

Quantitative assessment of clustering quality

It is carried out by calculating the matrix of clustering inaccuracies using a comparison with the known method of kmeans using the known test data set "Fisher's iris"

Analysis of the obtained results Fig. 2. Scheme of the method of clustering as a basic IT.

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4 Study of the Developed Clustering Method According to the accepted approach to clustering, the optimal coordinate vector of the cluster centers c = copt is determined, which, satisfying the constraints, would give an extreme value F(x, c) – the functional of the vector c = (c1 , . . . , cN ), which depends on x = (x1 , . . . , xM ). The centers of plural x ∈ X and their limits are determined by the indications of images Xk [5, 8, 11]. The coordinates of the center of the cluster are determined by an iterative scheme determined by the requirements of the swarm optimization method chosen using the conceptual model. The objective function for clustering has the form F(x, c) =

P0 → max, Pi

(10)

where P0 and Pi are the average intercluster and average intracluster distance, respectively (calculated on the basis of the Euclidean metric). The clustering method (for two clusters (r = 1, 2)) can be represented as follows. Phase 1. Formation of the training sample. Phase 2. Setting the number of clusters. Phase 3. Evaluation of the objective function F(x, c) on the first iteration. Phase 4. Setting the parameters of the swarm method selected through conceptual modeling, δ1 is an error that meets the requirements of the applied problem; c1 [0] and c2 [0] are the initial values of the coordinates of the cluster centers; iteration number n = 1. Phase 5. Evaluation of the objective function F(x, c) at iteration n. The direction of movement to the extremum is estimated by the chosen swarm method. The coordinates of the cluster centers are determined. Phase 6. If cr [n] − cr [n − 1] ≤ δ1 , then the search ends at the current start, otherwise n = n + 1 and the transition to phase 5. Quantitative assessment of the quality of clustering is carried out when calculating the matrix of inaccuracies by comparing it with the well-known method of k - averages using the well-known test data set "Fisher’s irises" (Table 1). The element at the intersection of the i-th row and the j-th column of the inaccuracy matrix shows the percentage of members of the i-th cluster that belong to the j-th cluster. At the next stage, clustering methods based on combined swarm methods were investigated for practical applications in IGIS industries, where practice requirements for quality may be increased (Table 2).

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Table 1. Quantitative assessment of clustering quality. Method name

The name of the data set

k-means method

Method under investigation

Bee colonies

Fisher’s irises

8,2

7,9

Fisher irises replicated 20 times

4,6

3,2

Fisher’s irises

7,2

6,3

Fisher irises replicated 20 times

4,1

3,0

Colonies of wolves

Table 2. Quality of the studied clustering methods based on combined swarm methods. Method name

The name of the data set

Gray wolves + vampires Fisher’s irises

Ant colony + nest of birds

k-means method

Method under investigation

5,1

4,5

Fisher irises replicated 20 3,7 times

2,1

Fisher’s irises

4,3

3,7

Fisher irises replicated 20 3,2 times

2,8

As an example of the developed method of clustering, consider the process of formation of territorial communities. The clustering process consists of the following steps: 1. Initiating the creation of working groups. At this stage, the chairman of the council the initiator prepares the order “On initiating the voluntary association of territorial communities”; 2. The regional state administration creates a working group that develops a perspective plan. The working group includes: representatives of the Regional State Administration, local self-government bodies, self-organization bodies of the population and the public; 3. Determining the boundaries of the district where modeling will be carried out, settlements, or the list of territorial communities (TC) that can be part of a capable territorial community; 4. Determination of potential centers of united communities; 5. Determination of the main powers of local self-government bodies of territorial communities to ensure its development (criteria of capacity); 6. Determination of accessibility zones of a potential administrative center of a capable territorial community, which is suboptimal for providing administrative and other services to the residents of the community;

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7. Formation of a set of TCs, by determining which populated areas will be part of the united community and whether a potential identified center can remain a center; 8. Determination of the infrastructural capacity of the potential united community. The presence of a secondary school and a hospital is mandatory; 9. Determination of centers and boundaries of TC Determination of the list of territorial communities whose territories are not covered by the accessibility zones of potential administrative centers; 10. In order to take into account, the interests of the communities themselves, consultations with self-government bodies and public hearings are held during the development of the plan; 11. Creation of perspective plans, which consist of: a graphic part that reflects the boundaries of capable TCs, potential administrative centers of such communities and all settlements; passport of a competent territorial community with a description of each such community; consultation protocol with community representatives. According to the developed basic IT, the clustering method consists of the following steps: 1. The map on which the administrative-territorial division will be modeled is selected. 2. When choosing the allocation range, the settlements that expressed a desire to form territorial communities will be chosen. 3. Determination of signs of the presence of infrastructure (schools, preschools, hospitals, ambulance stations, law enforcement agencies, fire safety agencies). 4. Determination of the feature of contiguity. 5. Determination of the feature of compactness (area of accessibility of settlements to the administrative center within 25 km.) 6. Selection of the swarm algorithm for clustering. 7. Selection of free parameters of the swarm algorithm for clustering. 8. Division between settlements – the stage at which it will be determined which communities a settlement can belong to. 9. The formation of communities includes a stage in which it is determined how many communities are planned to be created. 10. Dual connection involves the case when a settlement can enter more than one community at the same time. 11. Entry into one of the communities is a stage that indicates which community a specific settlement belongs to. 12. Determining the administrative centers of the formed communities makes it possible to choose the best candidate for the administrative center among the settlements. 13. The stage where the formed clustering forms formed communities with proposed administrative centers. The IT formation of the TC was developed for such an information system. This IT consists of two stages – the first stage uses IT clustering (dividing the territory into communities) and the second stage – IT determination of administrative centers (Fig. 3). The result of the information system (IS) implementation of the developed IT formation of the TC is shown in Fig. 4.

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Fig. 3. Fragment of the structural scheme of the formation of territorial communities.

Fig. 4. Map of potential territorial communities.

5 Conclusions A method and a fundamental information technology for geoinformation data clustering have been developed. This approach utilizes swarm methods to combine data into clusters based on the compactness criterion, taking into account both quantitative and logical features. Consequently, the quality of geoinformation data clustering has been significantly improved. A novel clustering method has been developed, resulting in improved clustering quality. The selection of the swarm optimization method is based on a developed methodology, leading to clustering quality enhancements of 1.08 to 1.2 times compared to existing methods. An efficiency study was conducted to assess clustering using swarm intelligence methods. The results of the research indicate a 12% increase in clustering efficiency, satisfying the practical requirements for stationary IGIS.

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References 1. Kozhemyako, V., Timchenko, Yu., Yarovoy, A.: Parallel-hierarchical transformation as a system model of optoelectrical means of artificial intelligence. Monograph. Universal, Vinnytsia (2003) 2. Hu, Z., Tereikovskyi, I., Chernyshev, D., Tereikovska, L., Tereikovskyi, O., Wang, D.: Procedure for processing biometric parameters based on wavelet transformations. Int. J. Mod. Educ. Comput. Sci. (IJMECS) 13(2), 11–22 (2021). https://doi.org/10.5815/ijmecs.2021.02.02 3. Pratt, W.: Digital Image Processing. John Wiley & Sons, Hoboken (2001) 4. Krylov, V., Antoshchuk, S.G.: Methods of noise-immune segmentation of binarized images. In: Proceedings of Odessa Polytechnic University, Odessa, vol. 1, no. 21, pp. 164–167 (2004) 5. Shcherbakova, G.: Subgradient method of classification in the space of wavelet transform for technical diagnostics. Electrotech. Comput. Syst. 1, 136–142 (2010) 6. Antoshchuk, S., Nikolenko, A., Bilonenko P.: Methods of transformation of a graphically specified function into a discrete signal. In: Proceedings of the Luhansk Branch of the International Academy of Informatization, Luhansk, vol. 2, no. 7, pp. 57–60 (2003) 7. Uhryn, D.: Information technologies of decision support for geographic information systems. In: Bulletin of modern information technologies: Information Technologies in SocioEconomic and Organizational-Technical Systems, Odesa, vol. 02, no. 03, pp. 47–58 (2019) 8. Geographic information systems. http://um.co.ua/12/12-1/12-103779.html. Accessed 06 Apr 2023 9. Tereikovskyi, I., Hu, Z., Chernyshev, D., Tereikovska, L., Korystin, O., Tereikovskyi, O.: The method of semantic image segmentation using neural networks. Int. J. Image Graph. Signal Process. (IJIGSP) 14(6), 1–14 (2022). https://doi.org/10.5815/ijigsp.2022.06.01 10. Sun, F., Ngo, H.C., Sek, Y.W.: Combining multi-feature regions for fine-grained image recognition. Int. J. Image Graph. Signal Process. (IJIGSP) 14(1), 15–25 (2022). https://doi.org/10. 5815/ijigsp.2022.01.02 11. Antoshchuk, S., Krylov, V., Davydov, V.: Preliminary processing of signals and images. In: Proceedings of the Fifth All-Ukrainian International Conference “Signal Processing and Pattern Recognition”, pp. 261–265. UkrOBRAZ-2000, Kyiv (2000) 12. Boyun, V., Dovgan, V.: Intellectualization of circular inspection systems. In: Proceedings of the Fifth All-Ukrainian International Conference “Signal and Image Processing and Pattern Recognition” (UkrOBRAZ 2000), pp. 283–286. Ukrainian Association for Information Processing and Pattern Recognition, Kyiv (2000) 13. Kozhem’yako, V., Kutayev, Yu., Svechnikov S., Timchenko, L. Yarovoy, A.: Parallelhierarchical transformation as a system model of optoelectrical means of artificial intelligence. Monograph. Universal, Vinnytsia (2003) 14. Hu, Z., Tereykovskiy, I., Zorin, Y., Tereykovska, L., Zhibek, A.: Optimization of convolutional neural network structure for biometric authentication by face geometry. In: Hu, Z., Petoukhov, S., Dychka, I., He, M. (eds.) ICCSEEA 2018. AISC, vol. 754, pp. 567–577. Springer, Cham (2019). https://doi.org/10.1007/978-3-319-91008-6_57 15. Chen, J., Dosyn, D., Lytvyn, V., Sachenko, A.: Smart data integration by goal driven ontology learning. In: Angelov, P., Manolopoulos, Y., Iliadis, L., Roy, A., Vellasco, M. (eds.) INNS 2016. AISC, vol. 529, pp. 283–292. Springer, Cham (2017). https://doi.org/10.1007/978-3319-47898-2_29 16. Hu, Z., Ivashchenko, M., Lyushenko, L., Klyushnyk, D.: Artificial neural network training criterion formulation using error continuous domain. Int. J. Mod. Educ. Comput. Sci. (IJMECS) 13(3), 13–22 (2021). https://doi.org/10.5815/ijmecs.2021.03.02

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The Influence of Structure on Mechanical Properties of Multilayered Cu – Ta Composites at Room Temperature Eugene Yascheritsin(B)

and Oleksandr Terletskyi

National Technical University “Kharkiv Polytechnic Institute”, Kharkiv 61000, Ukraine {yevhen.yashcheritsyn,Oleksandr.Terletskyi}@khpi.edu.ua

Abstract. One of problematic issues in present-day material science is production of new electrical materials combining excellent mechanical properties at high homological operation temperatures with specific electrical resistance close to resistance of pure cuprum. Copper-based composites with layers of such insoluble refractory metals as tungsten, rhenium and tantalum meet these seemingly opposite requirements to the fullest extent. This study is devoted to the technology of manufacturing of Cu–Ta layered composite materials (LCM) by means of diffusive welding through a layer of nickel with the Ta volume fractions of 1; 2.8; 7; 11.1; 15.8 and 25%, as well as to analyzing the relation between their structure and physical- and mechanical properties at room temperature. Experimental concentration dependences of the copper-tantalum LCM are considered, assessment of contribution of both the Ta layers and the thickness of the copper matrix to the strength characteristics has been carried out. An interpretation of the positive deviation of mechanical characteristics of the studied multilayered composites from theoretically calculated ones on the basis of the additivity relation is proposed. This interpretation is relying on accounting the inhibition of dislocation slip transfer in the copper matrix layers by the interphase boundaries at increased volume fractions of Ta. Keywords: Multilayer Cu-Ta Composites · Diffusive Welding · Mechanical Properties · Concentration Dependence · Copper Matrix · Ni-Foil Layer

1 Introduction Development of modern equipment requires designing of new materials based on copper with excellent mechanical properties at both the ambient and raised temperatures with retaining high heat- and electricity conductivity characteristic of copper along with preferably low cost of production. Such combination of properties is needed for small-sized structural and conductive elements of electronic devices, conductive bus-bars in electrical devices. One of ways to solve this scientific problem is to design layered composite materials (LCM) on the copper base. Usually, such refractory metals as W and Mo are used as strengthening layers. Nevertheless, in designing of layered composites, preference should be given to © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 554–565, 2023. https://doi.org/10.1007/978-3-031-40628-7_45

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metals which are not only refractory and practically insoluble in copper but also possess ductility at ambient temperature and are non-toxic for humans. Tantalum meets these requirements despite its being inferior in terms of melting temperature to wolfram, osmium, rhenium, nevertheless it is most ductile of all refractory metals, with its alloys being non-toxic as the metal itself. The previously known fiber composite Cu–Ta used to be manufactured through the melt infiltration method [1] which is energy consuming (melting of copper is required) and therefore uneconomical as well as having limitations related to copper structure control. That is why to improve the technology of the Cu–Ta composites production, a less complicated method – diffusion welding of the Cu and Ta foils – has been offered. Therefore, it is necessary to establish the optimal modes for this technological process, for it is known that when changing the reinforcement material or the technology of a composite manufacturing, not only prognosticated quantitative changes in its characteristics are possible, but also new qualitative effects of structure-property relationship may arise.

2 Literature Review Analysis of earlier researches demonstrates that among layered composites based on copper, the most common are the systems of Cu–W, Cu–C, Cu–Fe, Cu–Mo, Cu–Nb, with such LCMs as Cu–Ta, Cu–Cr, Cu–B and others having been studied to a lesser extent [1, 2]. Of the mentioned composites, the systems of Cu–W, Cu–C and Cu–Ta are of greatest interest due to the absence of mutual solubility of their components. Note that for Cu–Ta solubility is not observed even at 1300 °C, and in the ternary system Cu–Ni–Ta at this temperature liquid copper atoms dissolve, in addition to Ni, only in a number of intermetallic compounds Nix Tay partially [3]. These composites are produced through methods of reinforcing fibers infiltration with molten copper, diffusion welding, dynamic hot pressing, explosive welding, baking of copper powder with reinforcing fibers, joint drawing, and others. Of them, only the Cu–W composites obtained by hot pressing [4], sintering and infiltration [5] and Cu–Ta obtained by extrusion [6] are ductile at ambient temperature due to carbon fibers being brittle owing to the covalent type of interatomic bond. However, wolfram fibers following high-temperature treatment acquire brittleness due to high sensitivity to interstitial impurities (O, N, and others). Contrary to that, tantalum fibers retain a greater ductility owing to a greater impurities solubility than that of wolfram at the identical heat treatment conditions. Therefore, for obtaining Cu–W plastical composites, special and more expensive technological methods are required – using an oxygen-free copper block, for instance [5]. At the same time, such composites as Cu–Ta do not require them. We also note that during infiltration and some other methods, poor adhesion between the matrix and the reinforcement is often observed. This slows down the fabrication process, leading to unwanted reaction products at the interface [1]. With regard to the Cu–Ta system without intermediate phases, this is an important line of research [7–10]. To some extent, this problem is solved by the explosion technology itself, since the interfacial surface acquires a wavy relief [11, 12]. However, the noted problems are significantly overlapped by the structural stability of the Cu–Ta system, inhibition of matrix recrystallization, and increased resistance to high-temperature deformation [13].

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When analyzing the mechanical properties of unidirectional composites, both the structural strengthening mechanisms [1, 2] and the effect of reinforcement from the standpoint of mechanics are analyzed. The last aspect has been worked out quite well by various scientific schools, e.g. [14]. For the case of a plastic matrix-brittle fiber (layer), the qualitative form of the concentration dependence should be similar, as shown in Fig. 1.

Fig. 1. Schematic illustration of the variation of the strength of a unidirectional (brittle fibre– ductile matrix) composite with fibre content.

There are two key parameters, V min and V crit , which are usually evaluated and analyzed [15, 16], since V max is a case of discontinuous reinforcement.

3 Research Methodology As raw materials for manufacturing of Cu–Ta LCM, copper foils 45 µm thick with purity of 99.96%, tantalum foils 15 µm thick with purity of 99.99%, and nickel foils 10 µm thick with purity of 99.98% were used. Technological methods and operation modes of production of Cu–Ta LCM by the diffusion welding method were varied to clarify the role of a number of factors that impact adhesion of the combined layers and the composites’ mechanical properties. Thus, relying on research data [17], it should be noted that diffusion welding of tantalum with copper is usually made through a layer of beryllium bronze at 1000 °C in vacuum, which means in fact, according to the copper-beryllium state diagram, soldering, which is undesirable in this case. Diffusion welding of copper with wolfram, molybdenum, niobium is also carried out through a layer of nickel which forms hard solutions with these metals [18], while being infinitely dissolvable with copper. Therefore, this metal was naturally suitable as an intermediate layer between copper and tantalum. Technologically, a layer of nickel can be used in the form of foil 10–15 µm thick or applied through electron-beam or galvanic method. However, our research has demonstrated that galvanic deposition of nickel onto tantalum foil, their welding (800 °C during

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1 h) with consequent mechanical testing of the Ni + Ta bimetal lead to considerable deterioration of the tantalum foil’s strength characteristics with ductility of these sample falling practically to zero (due to Ta interaction with the working solution in the bath and formation of tensile stresses in Ni layers). Therefore, it was decided to use the aforementioned 10 µm thick nickel foils as the material for the intermediate diffusion layer. Resulting from these preliminary researches, diffusion welding of copper layers through the nickel foil layer in a vacuum furnace at 1000 °C and the vacuum of 0.027 Pa for 1 h was chosen as the finalized technology for producing copper-tantalum LCM. Structurally, all composites consisted of three layers of copper, four layers of nickel (pair per layer of Ta), and two layers of tantalum. By varying the number of copper foils and, consequently, the thickness of identical three matrix copper layers, we obtained LCMs with different volume fractions of Ni and Ta with practically unchanged thicknesses of tantalum and nickel. Mechanical tests of tantalum, copper, nickel and copper-tantalum LCMs at ambient temperature were carried out in the active distension mode on the TIRATEST-2200 appliance. The rate of clasps movement was 0.27 mm/min, the relative deformation rate of the samples was 3.0·10–4 s–1 . The rigidity of the force sensor was 8·109 N/m. The length and width of the working part of samples were 15 × 3 mm with their thickness varying from 0.09 mm to 2.2 mm depending on the tested material. The thickness of the layered composite materials was: 1) 1% Ta, 1.8% Ni, 97.2% Cu – 2.2 mm; 2) 2.8% Ta, 4.0% Ni, 93.2% Cu – 1 mm; 3) 7% Ta, 10% Ni, 83% Cu – 0.4 mm; 3) 11.1% Ta, 22.2% Ni, 66.7% Cu – 0.215 mm; 4) 12.4% Ta, 20.8% Ni, 66.8% Cu – 0.19 mm; 5) 15.8% Ta, 24.4% Ni, 59.8% Cu – 0.165 mm; 6) 25% Ta, 22.7% Ni, 52.3% Cu – 0.09 mm. Out of every batch of samples for tests at ambient temperature, ten (or more) samples were taken, and the obtained outcomes were averaged. Following testing of foils and the composites in the distension mode by primary diagrams, some characteristics according to ISO 6892-1:2019 were determined. These include: proof strength Rp0.05 – as elasticity limit; proof strength Rp0.2 – as conditional yield strength in the absence of a yield plateau; Rm – tensile strength; A – percentage elongation after fracture; Z – percentage reduction of area after fracture. For studying the microstructure of the foils of tantalum and copper-tantalum composite materials, the diffusion welding quality, and microstructure photography, the MIM-7 microscope was applied. For each of the studied materials, such magnification was selected that would enable confident identification and comparison of the main structural elements at different extents of their dispersion depending on their structural state. Their values were × 120 and × 450. After scaling the images, the corresponding scale bar was applied. Foils and composites intended for the manufacture of thin sections were poured into copper mandrels with the AST-T composition (dental plastic). Then they were first ground on abrasive sandpapers, then polished on felt wheels using Cr2 O3 abrasive, and following that finished on polishing wheels without abrasive. To reveal the composites’ microstructure, the etchant of the following composition was used: FeCl3 – 10 g, HCl – 20 ml, H2 O – 100 ml. It was applied on a sample, kept for several seconds, then washed away with running water and dried with filtering paper and hot air. For etching Ta foils, the etchant containing 10 ml of concentrated HF and 10 ml of concentrated HNO3 was applied. The etchant was applied to a sample and kept for 2–3 min,

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then washed away under running water and dried as described above. The etching of nickel foils was made with concentrated nitric acid with applying the etchant for 1–2 s, then washing and drying.

4 Results Mechanical tests of Cu-Ta LCMs obtained with diffusion welding through the nickel foil layer (Fig. 2) have revealed a number of significant peculiarities on concentration dependency. They did not quite fit into the classical form of the concentration dependence for a composite material with a ductile matrix and brittle reinforcement (Fig. 1) to which the studied material pertains.

Fig. 2. Dependence of strength characteristics of Cu-Ta layered composites with nickel layers on the volume fraction of Ta: Rm – tensile strength; Rp0.2 – yield strength in the absence of a yield plateau; Rp0.05 – elasticity limit; Z – percentage reduction of area after fracture of copper layers; A – percentage elongation after fracture; ↓ and ↑ – calculated values V min and V crit resp.

According to the theory [14], the concentration dependences of the strength characteristics should have a V-shaped form. Initially, with an increase in the volume fraction V of the hardener, the strength decreases, reaching a minimum value at V min . Then, with increasing V, the strength increases, reaching at V crit the strength of the matrix, continuing to increase further. Analyzing the curves in Fig. 2, certain similarity in curves Rp0.05 , Rp0.2 and Rm can be seen. Thus, starting with the volume fraction of 2.8% Ta, abrupt growth of these characteristics is observed, but after 7% Ta – another slow rate of

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their growth. As to the section between 0 and 2.8% Ta, either a small decrease and slow growth (Rp0.05 curve), slow increase (Rp0.2 curve), or abrupt growth (between 0 and 1% Ta) and abrupt fall (Rm curve) are observed. In order to explain non-monotonicity of the strength characteristics graphs, the minimal and the critical volumes of reinforcement layers of tantalum were determined. When calculating V min and V crit it was needed to account for the third component (nickel) present in the composite, its volume fraction ranging between 1.8 and 23% with increase of tantalum content. However, with tantalum content lower than 3%, the nickel content does not exceed 4%. In this case, in the Cu + Ni bimetal which served as matrix for the LCM with the volume fraction 2.8% of Ta, the content of nickel was 4%. Considering the strength of the copper and nickel annealed foils being 117 and 133 MPa respectively, the strength of the bimetal with 95.9% Cu + 4.1% Ni differs from that of copper by only 0.76% according to the additivity relation for plastic layers or fibers. Accordingly, at 25% Ta, the calculation by the same method gives an increase in the strength of the matrix due to the Ni interlayer by only 6%. Therefore, it was assumed that the value of the matrix strength (Rm )matrix includes 95.9% Rm of copper and 4.1% Rm of nickel, which is preferable for key calculations. The calculations V min and V crit also require the strength of the layers (Rm )layer and the flow stress of the matrix R matrix at the moment of destruction of the layers. The latter characteristic was evaluated according to the tensile diagram of the LCM with the volume fraction 2.8% of Ta for the first stress release in the elastic-plastic region. It was assumed that, since tantalum is brittle, the plastic deformation of the composite is due only to the matrix layers. Accordingly, from the tensile diagrams of copper foils, from the value of the plastic deformation of the composite at the moment of release, one can also estimate the magnitude of the stress R matrix . Further calculations were carried out according to the equations [14] and the above notation. Vmin = [(Rm )matrix − Rmatrix ] / [(Rm )layer + (Rm )matrix − Rmatrix ]

(1)

Vcrit = [(Rm )matrix −Rmatrix ] /[(Rm )layer −Rmatrix ]

(2)

The calculations showed that V min = 2.9% Ta, and V crit = 4.2% Ta. Therefore, strength characteristics of the composites with 1% and 2.8% Ta respectively are to be less than the matrix strength characteristics, but this is not observed in Fig. 2. To explain this effect, calculation of the theoretical elasticity limit was made with presumption that due to the low level of Rp0.05 in copper foils compared with tantalum, plasticity deformation of LCM up to 0.05% was also determined by copper only. Then elastic deformation of the other components (εelast ) of composite in relative units at the elasticity limit Rp0.05 of copper with plastic deformation 5·10–4 can be estimated as: εelast = (εelast )Cu + 5 · 10−4 = (Rp0.05 )Cu /ECu + 5 · 10−4 , where (εelast )Cu – elastic deformation of copper at the elasticity limit; (Rp0.05 )Cu – elasticity limit of copper after annealing (1000 °C) in the free state; E Cu – modulus of normal elasticity of copper in the free state.

(3)

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Thus, the formula for the theoretical elastic limit of composites (Rp0.05 )LCM has the following form: (Rp0.05 )LCM = (Rp0.05 )Cu · VCu + εelast · ENi · VNi + εelast · ETa · VTa ,

(4)

where E Ni , E Ta – moduli of normal elasticity for Ni and Ta respectively; V Cu , V Ni , V Ta – volume fractions of Cu, Ni and Ta respectively. Determining of the theoretical elasticity limit (Fig. 2) has demonstrated that a good coincidence with the experimental values is observed only for the composites containing 1% and 2.8% of tantalum. For other composites 1.5–2-fold exceeding of the experimental values of Rp0.05 over the calculated ones is observed, as well as considerable difference in the rate of growth of these curves. This is especially noticeable in the section between 2.8% and 7% of tantalum, while further on the rates of growth become close. A similar quality is observed for other strength properties and, it seems, only the nickel interlayer, the contribution of which is estimated above, is difficult to explain. The undertaken analysis attests to the fact that exceeding of the experimental value of Rp0.05 of the calculated one, the absence of distinct points of V min and V crit is explained by the peculiarity of the copper matrix’ structure. Thus, in the composite with 1% of tantalum it houses ~16 grains per copper layer thickness; for 2.8% Ta – 7 grains; for 7% Ta – 3 grains, and in the composites with 11.1%, 15.8% and 25% Ta – one grain per layer thickness. Hence, this difference in the number of grains (layers) in the copper matrix is what leads to nontrivial outcomes in concentration dependence for mechanical properties. Therefore, the difference between the experimental and the calculated elasticity limit is explained by the fact that at distension of a layered composite, a slide in its copper layers is initiated whose development depends on the number of grains in its layers [19]. Due to a high level of tensions, it rapidly spreads from grain to grain of the matrix material, however it is effectively blocked at the inter-phase boundary because development of slide in the reinforcement layer requires tensions of a higher order [19]. As stated before, the difference between the experimental and the theoretical elasticity limits in the section between 0% and 2.8% Ta is not large. It means that in the matrix structure close to polycrystalline and at small volume fractions of tantalum, the slide occurs by the usual for polycrystals pattern and reinforcement by A.A. Yavor model [19] does not take place. As for the “bamboo” matrix structure (composites with 7% to 25% Ta), the slide following blockage by commonly oriented planes occurs on unfavorably oriented slip planes. It is this phenomenon that stipulates additional strengthening and it is observed during the transition from the volume fraction 2.8% to 7% Ta, and then becomes a permanent additive component. It should be noted as well that certain contribution to strengthening the whole of the composite is also made by solid-solution hardening of boundary copper layers, as well as change in the structure caused by diffusion of nickel into it during the manufacturing [20]. According to calculations, the nickel atoms manage “to travel” ~15 µm in the copper layer at 1000 °C. Notably, in composites with 1% and 2.8% Ta, this diffusion zone can be neglected, although some change in microstructure and mechanical properties respectively certainly occurs within (Fig. 3). As for other composites, the width of the diffusion zone, where grain change occurs, becomes commensurable with the copper matrix layer thickness (Fig. 4).

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Fig. 3. Microstructure of the Cu–Ta LCM (1% Ta; 1.8% Ni; 97.2% Cu) after tensile test: 1 – tantalum layer; 2 – nickel layers; 3 – boundary layers (nickel + copper); 4 – copper layers; 5 – cracks in tantalum and nickel layers.

Fig. 4. The microstructure of the Cu–Ta LCM (15.8% Ta; 24.4% Ni; 59.8% Cu) after tensile test: 1 – tantalum layer; 2 – nickel layers; 3 – copper layers.

It should be noted that the structural state of tantalum, its purity, conditions of heat treatment make a significant impact on its mechanical properties in the initial and, particularly, in the annealed state. A significant factor considerably influencing the mechanical properties of a layered composite is gas saturation of Ta layers with residual gases in the working zone of the vacuum furnace. Thus, being a getter-metal, tantalum absorbs from the working zone of furnace (at the lower-order vacuum less than 10–2 Pa) residual gases: oxygen, nitrogen and others. Therefore, to understand the impact of this phenomenon on strength characteristics of the studied composites, an examination of the structure and mechanical properties of Ta foils to be used further for manufacturing the Cu–Ta LCM was carried out for different annealing temperatures of vacuum furnace (Fig. 5). That is why at annealing in the studied interval of temperatures (400–1300 °C) and vacuum ≈10–2 Pa, in outline the strength characteristics in tantalum samples increase while its ductility decreases. However, in tantalum foils with 99.99% purity, strength

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Fig. 5. Dependence of mechanical properties of tantalum foils with 99.99% purity on annealing temperature: Rm – tensile strength; Rp0.2 – yield strength in the absence of a yield plateau; Rp0.05 – elasticity limit; A – percentage elongation after fracture.

characteristics improve only up to the annealing temperature of 800 °C (Fig. 5). Following this, a drop in ductility virtually to zero occurs and, probably due to this factor, an abrupt decrease in strength characteristics. In explaining this character in changes of the tantalum foils’ strength characteristics, it should be noted that the decisive impact on them was determined by its structure in the state as delivered (Fig. 6).

Fig. 6. Microstructure of Ta foils in the initial state.

The study of the microstructure of the 99.99% tantalum foil demonstrated (Fig. 6) that as delivered state it is completely recrystallized with grains of quite large size. That is why in the course of gas saturation, the impurities surface concentration on the grains’ boundaries turned out to be rather high, which led to brittle failure at the tensile test, particularly after annealing above 800 °C. An additional factor in this process were the thermal etching groves located alongside the grains’ boundaries. For check these

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considerations, data on the strength properties Rp0.05 , Rm of composites containing 7– 25% Ta were approximated by four experimental points per axis corresponding to 100% Ta. At these Ta contents, as discussed, additional strengthening of copper due to sliding along unfavorably oriented planes is effective. Dispersion for this approximation was calculated as well (Fig. 7).

Fig. 7. Concentration dependences of elasticity limit Rp0.05 and tensile strength Rm for Cu–Ta LCM and their approximation to 100% Ta together with its dispersion

It follows from Fig. 7 that the properties of tantalum within an LCM and in its free state are similar. Really, as can be seen from the Fig. 5, the strength of free Ta foils after annealing at 1000 °C is within the dispersion interval for approximated values of this parameter on Fig. 7. So why have such unexpected results been obtained? It is probably related with the tantalum’s microstructure. It is known that fine-grained material is much more superior in mechanical properties to a large-grained material. The studies of microstructure of Ta foils that were used for the researched composites have demonstrated that tantalum possesses a large-grain structure (Fig. 6). With the increase in annealing temperature, adsorption of residual gases in vacuum by tantalum intensifies. As it is known, the impurities concentration on grains boundaries exceeds the intra-grain one and therefore its mean value per sample. A significant unevenness of impurities distribution in large-grained tantalum transforms the grains boundaries into low adhesion surfaces, which consequently leads to its brittleness.

5 Conclusion The possibilities of the previously known method for obtaining copper-based composites reinforced with tantalum by the melt infiltration, which is rather complicated and does not allow controlling the mechanical properties of copper as a component, are evaluated. Instead, production of multilayered copper-tantalum composites has been offered by

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means of diffusion welding through a layer of nickel foil. Technological modes of a simpler and less expensive method of diffusion welding (welding time, pressure on the layers during welding, vacuum degree) are proposed. A comprehensive research of the structure and mechanical properties at ambient temperature of these composites with volume fractions of tantalum ranging between 1% and 25% has been carried out. It has been demonstrated that concentration changes in mechanical properties do not correspond to the known pattern characteristic of a unidirectional composite with a ductile matrix and brittle reinforcement. This is determined by the copper matrix structure transition from polycrystalline (7–8 grains per thickness of each copper layer) to the honeycomb structure (2 – 3 grains and less). In the latter case, additional strengthening occurs due to the blocking of slip through the interphase boundary and its initiation within copper on unfavorable planes. It has been demonstrated that at 20 °C the relative reduction of area of copper matrix in an LCM for all the studied fractions of Ta is about 40%, which is twice less of the same characteristic for Cu in its free state. This is determined by the fact that copper layers in LCMs at distension tests are not in the unilateral, but in a more rigid tensioned state of a biaxial tension state. In view of the foregoing, it has been established that the optimal mechanical properties (Rp0.05 ; Rp0.2 ; Rm and A) at ambient temperature are inherent in composites with tantalum content between 3% and 7%.

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13. Darling, R., et al.: Mechanical properties of a high strength Cu–Ta composite at elevated temperature. Mater. Sci. Eng., A 638, 322–328 (2015) 14. Harris, B.: Engineering Composite Materials, 2nd edn. IOM, London (2010) 15. Shah, D., et al.: Determining the minimum, critical and maximum fibre content for twisted yarn reinforced plant fibre composites. Compos. Sci. Tech. 72(15), 1909–1917 (2012) 16. Bowen, C., et al.: Failure and volume fraction dependent mechanical properties of composite sensors and actuators. Proc. IMechE Part C J. Mech. Eng. Sci. 220(11), 1655–1663 (2006) 17. Bagin, V.: Tyeoriya, tyehnologiya i oborudovaniye diffuzionnoy svarki. Mashinostroyeniye, Moskva (1991). (In Russian) 18. Massalski, T.: Binary Alloy Phase Diagrams, vol. 2. ASM Int., Metals Park, Ohio, (1986) 19. Yavor, A.: Strain hardening of the matrix in laminated composites. Fiz. Khim. Obrab. Mater. 2, 112–117 (1977) 20. Terleckij, A.: Prochnost i plastichnost mnogoslojnyh kompozitov Cu-Ta. Deformaciya i razrushenie materialov 8, 45–47 (2005). (In Russian)

Monitoring the Operation of the Internal Combustion Engine Based on the Processing of Indirect Measurement Data Oleksandr Yenikieiev1 , Dmytro Zakharenkov2 , Magomediemin Gasanov2 Fatima Yevsyukova2(B) , Olena Naboka2 , Anatolii Borysenko2 , and Nikolay Sergienko2

,

1 Donbas State Engineering Academy, 72, Akademicheskaia str., Kramatorsk 84313, Ukraine 2 National Technical University “Kharkiv Polytechnic Institute”, 2, Kyrpychova str.,

Kharkiv 61002, Ukraine [email protected]

Abstract. The cylinder torques are approximated using the Fourier transform, and the concept of adjusting the processes of supplying the fuel-air mixture to the cylinders of the power unit in the form of weighting coefficients is introduced. A mechanical system with ten degrees of freedom under the conditions of taking into account friction is proposed as a deterministic mathematical model of the rotation of the masses of the crankshaft of the power unit. Based on the methods of similarity theory, the parameters of the system of linear differential equations of mass movements of the mathematical model of the torque circuit of the 10D100 diesel generator were normalized, and the Laplace transformation was used under zero initial conditions for its solution. With the help of the method of determinants and the Mathcad software environment, the information links between the cylinder torques and the fluctuation signals of the rotation speed of the first and tenth masses of the crankshaft were established. Using the Matlab software environment, the frequency characteristics of mechanical torque transmission channels were investigated. Special points were established and as a result of their analysis, a simplified representation of the transmission functions of mechanical channels was obtained. In the Mathcad software environment, a circuit for computer modeling of signals of fluctuations in the speed of rotation of the first and tenth masses of the crankshaft was built, which can be used to study the effectiveness of the application software for processing the data of indirect measurements. Algorithmic support for assessing the identity of power unit operating cycles is based on the solution of a redefined system of algebraic equations with the procedure of minimizing the obtained results, which implements the method of least squares. As a result of computer modeling and statistical processing of experimental data, the influence of additive and multiplicative components of random disturbance on the uncertainty of calculating the weighting coefficients of cylinders was investigated. Uncertainty graphs for the calculation of weight coefficients of cylinders were constructed, which made it possible to formulate requirements for the metrological characteristics of measuring transducers of frequency-modulated fluctuation signals.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 566–585, 2023. https://doi.org/10.1007/978-3-031-40628-7_46

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Keywords: Hardware · Mathematical Model · Transfer Function · Information Technology · Fluctuation Signal · Uncertainty

1 Introduction The distribution of phases of the processes of supplying the fuel-air mixture to the cylinders of internal combustion engines (ICE) determines their technical and economic indicators [1–3]. Well-known mechanical systems for setting the indicated phases use for this purpose crankshafts and camshafts, which are connected to each other with the help of gear wheels. The manufacturing tolerances of the shafts and several gears of the connection, the kinematic uncertainty of which is normalized by the value in the reference literature, form the interval of uncertainty around the optimal angles of fuel and air supply to the cylinders. The quality of setting the working cycles of ICE determines the width of this interval. To reduce it, hardware means of setting individual angles of fuel and air supply to the cylinders of ICE are used. A well-known direct method of establishing the identity of the working cycles of the power unit involves measuring the pressure in the cylinders and constructing a certain number of indicator diagrams [4, 5]. Further comparison of these diagrams allows establishing the identity of the power unit duty cycles and taking action, if necessary, to make the appropriate adjustments [6]. The use of manual labor, a sufficiently large number of cylinders, and the absence of output electrical signals from the primary pressure transducers significantly limit the performance of the direct evaluation method. The authors propose an information technology for establishing the identity of the working cycles of ICE based on the processing of the frequency-modulated signal of the speed of rotation of the crankshaft with the subsequent formation of software changes to the settings of the phases of the fuel-air mixture supply processes. This will make it possible to save fuel at the level of 5% [7], increase the life of the power unit and reduce the costs of prevention, maintenance and repair. Therefore, the development of information technology for establishing the identity of the working cycles of ICE, which provides less uncertainty and increased productivity of processing the frequency-modulated signal of the speed of rotation of the crankshaft determines the relevance of this scientific and applied problem.

2 Literature Review Sufficient attention is given in the technical literature to the issue of ensuring the identity of the working cycles of ICE based on the processing of indirect measurement data in the form of a signal of crankshaft rotation speed fluctuations. In works [8–11], a linear periodically correlated random process is proposed for modeling the fluctuation signal, which satisfactorily describes the dynamics of the cylinder power of the 10D100 diesel generator. Methods of constructing estimates of some parameters of the specified processes are proposed and the effectiveness of their use as diagnostic signs of the technical condition of the cylinder-piston group is proven. In [12], a technique for adjusting the amount of cyclic supply of the fuel-air mixture to the cylinders of the power unit is proposed, the identity of which is established on the basis of the processing of the crankshaft

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rotation unevenness signal. In [13], the results of studies of the unevenness of rotation signal of the crankshaft of the 6NVD48UA diesel engine are given. A measuring transducer and information technology for processing the input signal have been developed in order to establish the average effective pressure, engine power, excess air coefficient and exhaust gas temperature. In [14] proposed a method of controlling the fuel supply processes of ICE based on measurements of the amplitude of oscillations of the angular speed of rotation of the crankshaft and the phase shifts of their extremes relative to the top dead center of an individual cylinder. The work [15] proposed a method of diagnosing multi-cylinder ICE using a signal of unevenness of the crankshaft rotation frequency, which was obtained as a result of computer simulation. Identification of model parameters was carried out on the basis of experimental data processing. The method takes into account the peculiarities of the operation of engines in the case of superposition of neighboring torques. In [16], the impact of torque unevenness on the dynamic characteristics and power indicators of engines was investigated. The relationship between indicators of unevenness of the indicator torque and unevenness of the crankshaft rotation was established, and their influence on the change in the indicator power of four-stroke auto tractor ICE was established. In [17], an expert system for identifying the condition of tractor ICE based on the use of a learning computer model is proposed. The expressions of the amplitude-frequency and energy spectra and the autocorrelation function for the angular acceleration in the free acceleration mode, which are averaged over all cylinders, were obtained. The criteria for evaluating the unevenness of cylinder operation and tightness, as well as the possible values of fuel supply advance angles, have been established. In [5], it is proposed to use a high-frequency filter with a finite impulse response to reduce the influence of random disturbances on the information signal of fluctuations. A technique for processing the signal of uneven rotation of the crankshaft of ICE using the capabilities of the Matlab software environment has been developed. The work [18] proposed a method for assessing the identity of the working cycles of internal combustion engines using the signal of fluctuations in the speed of rotation of the crankshaft of ICE, which was obtained as a result of computer simulation in the Matlab software environment. Identification of the model parameters was carried out on the basis of processing experimental data on the speed of rotation of the crankshaft. The methodology also takes into account the peculiarities of the operation of multi-cylinder ICE in the case of superposition of neighboring torques. The lack of uncertainty analysis of the computational procedure for assessing the identity of the working cycles of ICE based on the processing of a frequency-modulated crankshaft rotation speed signal is a drawback of known hardware and software tools.

3 Research Methodology Unsatisfactory metrological characteristics of known hardware for establishing the identity of working cycles of ICE, as well as the lack of algorithmic and application software for monitoring the reliable operation of the power unit, which improve the performance of indirect measurement data processing, determine the relevance of this study. The purpose of the work is to reduce the uncertainty and increase the productivity of the

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computational process of establishing the identity of the working cycles of ICE based on the processing of the frequency-modulated crankshaft speed signal. To achieve the set goal, the following tasks were solved in the work: • computer simulation of torques was carried out based on the processing of experimental data of the pressure of the first cylinder of the power unit; • mathematical modeling of the torque circuit of the 10D100 diesel generator was performed and described by the system of linear differential equations of the dynamics of rotation of cylinder masses; • with the help of modern integrated software environments, the frequency characteristics of the mechanical channels for the transmission of cylinder torques were investigated; • schemes of computer simulation of signal fluctuations of the rotation speed of the first and tenth masses of the crankshaft of the power unit have been compiled; • algorithmic support for establishing the identity of the working cycles of ICE based on the processing of the frequency-modulated rotation speed signal has been developed; • uncertainties of the application software for establishing the identity of the working cycles of ICE were studied and, on their basis, the requirements for the uncertainty of the measuring converter of the fluctuation signal were formulated. 3.1 Representation of Cylinder Torques As a mathematical apparatus for research, the authors used the continuous Laplace transform under zero initial conditions and the frequency representation of the measurement information signal [19, 20]. The verification of the results of theoretical research was carried out using the capabilities of integrated software environments that implement the methods of modern computer mathematics [21–25]. When evaluating the uncertainty of applied software, the methods of measurement theory, in particular, the informational approach and mathematical statistics, were used. Let’s proceed to the development of a mathematical model of torque cylinders of a 10D100 diesel generator. The torque created by a separate cylinder on the crankshaft is the input signal of the mathematical model of the torque circuit of the 10D100 diesel generator. It was obtained as a result of processing experimental data of the pressure of the first cylinder. When setting the graph of the torque of the first cylinder due to the action of gas forces, the indicator diagram was used as the initial information. The discrete frequency spectrum of the torque is presented in Table 1. Table 1. Amplitudes of sine and cosine harmonic components. An , Nm

8772

7076

4108

2506

1453

871

Bn , Nm

−2389

−4590

−3422

−2518

−2074

−1433

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Based on the data of this table, the torque of the first cylinder due to the action of gas forces is mathematically represented by the following expression M1 (t) =

6 

(An sin nt + Bn cos nt).

(1)

n=1

The useful work performed by the torque of an individual cylinder in the absence of fuel supply to it is zero within one revolution of the crankshaft. The authors propose to introduce the concept of differential torque, which ensures the rotation of the crankshaft of the 10D100 diesel generator with a given angular velocity, and is defined using the following expression [25] Mp (t) = M1 (t) − M2 (t),

(2)

where M1 (t) – torque from gas forces; M2 (t) – torque, which is obtained as a result of processing the compression diagram. Let’s introduce the concept of weighting coefficients for adjusting the processes of supplying the fuel-air mixture to the cylinders of the power unit Di = 0 . . . 1. Software control of the identity of fuel supply processes to individual cylinders of ICE is organized as follows Di − 1 → 0. Therefore, it is proposed to present the differential torque of an individual cylinder in the form of expression (2), the amplitude of which is determined by the weight coefficients of the cylinders Di = 0 . . . 1. Accordingly, establishing the values of these weighting factors is the main task of assessing the identity of the working cycles of the 10D100 diesel generator. Based on this, expression (2) takes the following form M1 (t) = Di Mp (t) + M2 (t).

(3)

The phase delay of the torques of the 10D100 diesel generator cylinders relative to the first is a multiple of 36° and is calculated taking into account the following sequence of their operation: 1–6–10–2–4–9–5–3–7–8. Accordingly, the presentation of the torque of an arbitrary cylinder takes the following form Mi (t) = M1 (t)e−jτi ,

(4)

where τi – phase delay of the cylinder relative to the first. The rotation of the crankshaft of the power unit at a given speed provides the average final torque. Accordingly, the signal of fluctuations in the rotational speed of the crankshaft of the internal combustion engine is presented in the form of a sum of convolution integrals ϕ1 (t) =

10  

t

Wi (t − τ )Mi (τ )d τ,

(5)

i=1 0

where Wi (t) – the weighting function of the contribution of an individual cylinder, which will be established in further studies on the basis of the transmission. Let’s proceed to the development of a deterministic mathematical model of the torque circuit of the 10D100 diesel generator.

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3.2 Mathematical Modeling of the Kinematic Scheme of the Power Unit The complete torque diagram of the 10D100 diesel generator shaft line is a 28-mass mechanical system with two nonlinear elements. The lower crankshaft is connected to the generator, the moment of inertia of which is equal to 7732.28 Nm2 . A pendulum antivibrator with a moment of inertia of 286.15 Nm2 is connected to its other end. These two masses significantly smooth the torsional oscillations of the lower shaft, so it is advisable to use the upper crankshaft to receive the input signal. We present the torque diagram of the shaft line of the 10D100 diesel generator with a deterministic mechanical system that has ten degrees of freedom (according to the number of cylinders). Nonlinear elements were not included in the model, so it is linear. Taking into account the study of the work [26] and the design features of the construction of the 10D100 diesel generator, the authors suggest installing the primary converters near the first and tenth cylinders, as well as taking into account the effect of friction. The dynamics of rotation of cylindrical masses of a mechanical system with ten degrees of freedom is described by the following system of linear differential equations:     Ji ϕi (t) + βϕi (t) − e−1 ϕi+1 (t) − ϕi (t) + e−1 ϕi (t) − ϕi−1 (t) = Mi (t), (6) where i = 1, 2, . . . 10; ϕi (t) – angle of rotation of the mass; Mi (t) – torque; e = 5.102 · 10−8 (Nm)−1 – flexibility of connections; β = 6.54 Nms – friction; J = 2.254 Nm2 – mass moments of inertia. The speed of rotation of the crankshaft of the 10D100 diesel generator is 6.667 ÷ 14.167 s−1 . Provided that 20 harmonic components are taken into account in the measurement information signal, the frequency range of the torque presentation is 133.33 – 283.33 s−1 . The direct solution of the system of differential Eqs. (6) using the Runge-Kutta numerical integration method provides a relatively low performance of calculations, since the integration procedure involves significant expenditure of machine time. The application of the Laplace transform under zero initial conditions allows obtaining a system of algebraic equations, the solution of which significantly simplifies the calculation procedure [27]. The use of frequency representation of information signals when solving a system of algebraic equations involves the use of a certain number of simple computational procedures, but compared to the Runge-Kutta method, it has significantly better performance. To generalize the research results, let us reduce the system of differential Eqs. (6) to a dimensionless form using the theorems of the similarity theory [18]. Let’s choose the and introduce the following notation following basic values for this

At the same time, all values with a superscript will be dimensionless. Let’s multiply each parameter of the system of differential Eqs. (6) by the ratio of basic values. This procedure does not change the system itself. After multiplication and taking into account the notation, we have (7)

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Simplification of the system of dimensionless equations is ensured by the fulfillment of the following conditions (8) on the basis of Having chosen . Thus, by choosing the conditions (8) we determine basic values accordingly, we achieve a complete match between the dimensional and dimensionless forms of recording the system of differential equations. The Laplace transformation under zero initial conditions gives the system of differential Eqs. (7) the following form   Ji p2 + p + 2 ϕi (p) − ϕi+1 (p) − ϕi−1 (p) = Mi (p). (9) To simplify further transformations, we introduce the following notations  −1  −1  −1  −1 a = p2 + p + 1 , b = p2 + p + 1 , c = p2 + p + 2 , d = p2 + p + 2 . (10) Taking into account these notations, the system of Eqs. (9) takes the following form ⎧ ϕ1 − aϕ2 = bM1 ⎪ ⎪ ⎪ ⎨ ϕ2 − d ϕ3 − d ϕ1 = cM2 . (11) .. ⎪ ⎪ . ⎪ ⎩ ϕ10 − aϕ9 = bM10 Design features of the 10D100 diesel generator make it possible to install sensors of the instantaneous speed of rotation near the first and tenth cylinders of the upper crankshaft. Accordingly, as input information, we will use the signals of fluctuations in the speed of rotation of the first and tenth masses. Under this condition, the system of algebraic Eqs. (11) takes the form     ϕ1 (p) = 5j=1 j Mj (p) = 5j=1 Wj Mj (p) , (12)  10 j ϕ10 (p) = 10 j=6  Mj (p) = j=6 Wj Mj (p) where ϕ1 (p), ϕ10 (p) – Laplace transformation of the signal of fluctuations in the speed of rotation of the first and tenth masses; Wj (p) – transfer functions that establish information links between the torques of individual cylinders and the fluctuation signal; , j – the main and all determinants of the system of equations, which are set using the Mathcad software environment in the following form where ϕ1 (p), ϕ10 (p) – Laplace transformation of the signal of fluctuations in the speed of rotation of the first and tenth masses; Wj (p) – transfer functions that establish information links between the torques of individual cylinders and the fluctuation signal; , j – the main and all determinants of the system of equations, which are set using the Mathcad software environment in the following form  = 6c2 d 6 − c2 d 8 − 5c2 d 4 + c2 d 2 + 8cd 7 − 20cd 5 +12cd 3 − 2cd + d 8 − 10d 6 + 15d 4 − 7d 2 + 1;

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1 = a − 7ad 2 + 15ad 4 − 10bd 6 + ad 8 + bc − bc2 d 2 +4bc2 d 3 + 3bc2 d 4 − 4bc2 d 5 − 2bc2 d 6 − acd +bcd + 6acd 3 − 10acd 5 + 4acd 7 + acd 8 −5bcd 2 − bc2 d − 4bcd 3 + 7bcd 4 + 4bcd 5 − 5bcd 6 ; 2 = b − 6ad 3 + 10ad 5 − 4ad 7 + ad 8 − 5bd 2 − 4bd 3 + 7bd 4 +4bd 5 − 2bd 6 + ad + bd − bcd − acd 2 + 5acd 4 − 6acd 6 +acd 8 − bcd 2 + 4bcd 3 + 3bcd 4 − 4bcd 5 − 2bcd 6 ; 3 = b + ad 2 − 5ad 4 + 6ad 6 + ad 7 − ad 8 − 4bd 2 − 8bd 3 +4bd 4 + 8bd 5 − bd 7 + 2bd + bc2 d 2 + bc2 d 3 −3bc2 d 4 − 2bc2 d 5 + 2bc2 d 6 + bc2 d 7 − 2bcd −acd 3 + 4acd 5 − 3acd 7 − acd 8 − 3bcd 2 + 7bcd 3 +9bcd 4 − 6bcd 5 − 6bcd 6 ; 4 = b + ad 3 − 4ad 5 + ad 6 + 3ad 7 − ad 8 − 3bd 2 −7bd 3 + bd 4 + 6bd 5 + bd 6 − bd 7 + 2bd + bc2 d 2 −2bc2 d 3 − 2bc2 d 4 − 4bc2 d 5 + bc2 d 6 + bc2 d 7 −2bcd − acd 4 + 3acd 6 − acd 7 − acd 8 − 4bcd 2 +5bcd 3 + 11bcd 4 − 2bcd 5 − 6bcd 6 ; 5 = b + ad 4 + ad 5 − 3ad 6 − 2ad 7 + ad 8 − 3bd 2 −6bd 3 + 2bd 4 + 3bd 5 − bd 6 + 2bd + bc2 d 2 + 2bc2 d 3 −bc2 d 4 − 3bc2 d 5 − bc2 d 6 − 2bcd − acd 5 − acd 6 +2acd 7 + acd 8 − 4bcd 2 + 4bcd 3 + 9bcd 4 − 2bcd 6 . The script for setting the main determinant is presented in Fig. 1. When analyzing the obtained expressions for the determinants, it was established that 1 = 10 , 2 = 9 , 3 = 8 , . . .. This also confirms the correctness of using two-channel measurements of signals of fluctuations in the speed of rotation of the crankshaft of the 10D100 diesel generator.

Fig. 1. Script to set the master determiner.

Let’s move on to analyzing the frequency characteristics of the mechanical torque transmission channels of individual cylinders of the 10D100 diesel generator.

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3.3 Study of Frequency Characteristics of Mechanical Torque Transmission Channels The calculation of logarithmic amplitude-frequency characteristics (LAFC) of mechanical torque transmission channels was performed using the Matlab software environment [23]. Information technology consists of the following computing actions: • the command line of the Matlab software environment for specifying expressions (10) has, for example, the following form a = tf([1], [1 1 1]); • transmission functions of mechanical torque transmission channels are established using expression (12); • their LAFC is constructed using the bode (W1, W2, W3, W4, W5) command. The calculation results are presented in Fig. 2; • the Nyquist hodograph is constructed using the Nyquist (W1, W2, W3, W4, W5) command.

Fig. 2. LAFC of mechanical torque transmission channels.

As a result of the analysis of the LAFC of the mechanical torque transmission channels, the following conclusions were made. Taking friction into account in the system of differential Eqs. (4) some what smoothes out the oscillations on the LACH graphs. In the frequency band 0.2–10, significant oscillations are observed, which causes unstable behavior of mechanical torque transmission channels. Accordingly, the LAFC need to be adjusted to reduce oscillations. The methods of correction of LAFC were developed in works [28, 29] using the methods of neural network technologies and focused on the computing capabilities of modern software environments. Presentation of transfer

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functions of mechanical torque transmission channels in the form of a serial connection of elementary chains is possible when setting the values of special points. For these calculations, it is convenient to use the capabilities of the Matlab software environment. Analyzing the values of the roots of the numerator and denominator allows to simplify the expressions for the transfer functions of the mechanical torque transmission channels. The technique of simplifying transfer functions involves the following actions [28, 29]: • rejection of unstable roots; • repayment of the roots, the values of which are sufficiently close in magnitude; • discarding the roots of the second order of smallness, as they affect the beginning of the transition process. Table 2 shows the values of the zeros and poles of the transfer functions that meet the specified conditions. Table 2. Roots of transfer functions

zero

pole

W1

W2

W3

W4

W5

−14.5881

−13.8344

−23.4088

−21.8183

−18.5710

−4.0462

−1.9385

−4.0039

−6.9354

−7.1547

−2.8644

−1.1093

−1.1148

−3.6318

−5.9453

−1.5254

−0.9923

−0.9938

−1.9542

−4.6993

−2.5152

−9.4111

−7.2650

−11.2300

−5.6124

−1.8722

−6.9045

−2.2117

−5.0232

−5.2884

−1.6126

−3.1931

−0.7308

−2.6960

−4.3940

−0.6514

−2.2051

−0.5692

−2.1437

−1.8613

−0.5024

−1.6531

−0.4357

−1.1354

−1.1502

Analysis in the Matlab software environment of the mathematical model of mechanical torque transmission channels is also convenient to perform using the root hodograph technique. The construction of root hodographs based on the transfer function was performed under the following conditions: • a system with one input and one output is considered; • the degree of the polynomial of the numerator of the transmission function of the mechanical torque transmission channel must be less than the degree of the denominator. The formation of transfer functions is performed in the Matlab software environment by factoring the numerator and denominator with given transfer coefficients zpk (zeropole-gain), where the symbol k represents the gain command. The roots of the numerator and denominator are denoted []. Command lines, which are compiled on the basis of the data in the Table 2, have the following form

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W1 = zpk([−14.59 − 4.05 − 2.86 − 1.53], [ −2.52 − 1.87 − 1.61 − 0.65 − 0.50].

(13)

The mathematical model of the mechanical torque transmission channel of the first cylinder was investigated using the root hodograph method. We create a ZPK object based on the given expression of the transfer function s = zpk(‘s’); W = 103.74 * (0.07 * s + 1) * (0.25 * s + 1) * (0.35 * s + 1) * (0.66 * s + 1)/(0.4 * s + 1) * (0.54 * s + 1) * (0.62 * s + 1) * (1.54 * s + 1) * (1.99 * s + 1). Let’s launch the sisotool program. After importing the input information, we will get graphs of the transient characteristic, the impulse transient characteristic and the Nyquist hodograph, choosing the appropriate program settings for this (Fig. 3).

Fig. 3. Results of the sisotool program.

On the basis of the obtained roots and simple mathematical transformations, the transfer functions of the mechanical torque transmission channels take the following form 4 

W1 (p) =

(p − pi )

i=1 5  

p − pj



=

p4 + 20.024p3 + 88.262p2 + 135.309p + 66.856 . p5 + 7.154p4 + 19.034p3 + 17.651p2 + 11.291p + 2.485

j=1

(14)

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After carrying out simple simplifications, we will obtain expressions for the transfer functions of mechanical torque transmission channels in a form that is convenient to enter into the Matlab software environment  26.9 0.015p4 + 2.3p3 + 1.32p2 + 2.024p + 1 . (15) W1 (p) = 0.402p5 + 2.88p4 + 7.66p3 + 7.1p2 + 4.54p + 1 The command lines, which are compiled on the basis of expressions (14), have the following form. W1 = tf([0.015 2.3 1.32 2.024 1], [0.402 2.88 7.66 7.1 4.54 1]); W2 = tf([0.0013 0.605 2.07 2.5 1], [0.0013 0.03 0.26 0.77 1.48 1]); W3 = tf([0.01 0.28 1.47 2.19 1], [0.34 3.85 5.56 10.4 11.5 1]); W4 = tf([0.0009 0.032 0.29 0.98 1], [0.0027 0.06 0.44 1.08 1.81 1]); W5 = tf([0.00027 0.0098 0.12 0.57 1], [0.0036 0.066 0.45 1.11 1.81 1]). The LAFC of mechanical torque transmission channels and the Nyquist hodograph were obtained similarly. The calculation results are shown in Fig. 4 and Fig. 5.

Fig. 4. LAFC of torque transmission paths, which are given by expression (14).

A comparison of the graphs of the LAFC (Figs. 2 and 4) shows that the curves W2, W4 and W5 do not have oscillations. Curves W1 and W3 have oscillations, respectively, at a frequency of 0.9 and 1.7. Thus, the performed mathematical transformations significantly improved the LAFC of the mechanical torque transmission channels of individual cylinders. The appearance of the Nyquist loops indicates that the contributions of the

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cylinders to the signal of fluctuations in the speed of rotation of the first mass differ significantly in magnitude. Further studies of the expressions for the transfer functions are connected with the transition to the frequency domain, which is performed as follows p = in. If this condition is fulfilled, the expression for the transfer function of the mechanical channel “first cylinder-first mass” takes the following form    k1 1 − 88.262n2 2 + i 135.309n − 20.024n3 3  , W1 (in) = 2.485 + 7.154n4 4 − 17.651n2 2 + i 1 + 11.291n − 19.034n3 3 (16) where k1 = 26.9 – amplification factor, set on the basis of expressions (13).

Fig. 5. Nyquist hodograph of torque transmission paths given by expressions (14)

The contribution of the first cylinder of the power unit to the signal of fluctuations in the speed of rotation of the first mass is determined as follows ϕ11 (in) = W1 (in)M1 (in).

(17)

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As a result of summing up the contributions of all cylinders, we will get a signal of fluctuations in the speed of rotation of the first mass of the crankshaft of the power unit   5  6  An1 sin(nt + arg W1i − τi ) |W1i | . (18) ϕ1 (t) = +Bn1 cos(nt + arg W1i − τi ) i=1 n=1 Based on the obtained expression in the Mathcad software environment, we will build a scheme for computer modeling of measurement information signals. 3.4 Construction of a Circuit for Computer Modeling of a Fluctuation Signal To specify the torque of the first cylinder in the Mathcad software environment, we will use representation (1) provided that it is brought to a normalized form (19) The torques of cylinders 2…5 can be obtained using expression (4) and the known order of their operation in this form M2 (t) = M1 (t)e−j0.6π , M3 (t) = M1 (t)e−j1.4π , . M4 (t) = M1 (t)e−j0.8π , M5 (t) = M1 (t)e−j1.2π

(20)

The procedure for identifying the parameters of the computer simulation scheme (Fig. 6) involves the use of the learning model method [30, 31]. The authors chose the weight coefficients of the cylinders μi , which change when setting the parameters of the computer model.

Fig. 6. Scheme of computer simulation

The function of setting model parameters is performed by component B1 . When summing the torques by reducing their number to five, a phase mismatch occurs. To

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compensate for it, component B2 is used in the computer simulation scheme of the signal of fluctuations in the speed of rotation of the first mass of the crankshaft. The architecture of its construction is similar to the B1 component, however, its difference lies in the use of such values of cylinder weight coefficients μi = 1. The scheme of computer modeling of the signal of fluctuations in the rotational speed of the tenth mass of the crankshaft has a similar construction structure. The setting of component B2 corresponds to the weighting factors μi , and the setting of component B1 corresponds to the weighting factors μi = 1. The results of computer modeling are shown in Fig. 7.

Fig. 7. Results of computer simulation of signals of fluctuations of the first and tenth masses.

If necessary, it is possible to build a two-stage structure of the circuit for computer modeling of the signal of fluctuations in the speed of rotation of the first and tenth masses of the crankshaft of ICE. To do this, it is necessary to decompose the expressions of the transfer functions of mechanical torque transmission channels into simple factors. The first stage of the computer simulation scheme performs the summation of elementary chains with weighting coefficients νi with the aim of obtaining transmission functions of mechanical torque transmission channels, and the second - summing up the contributions of cylinders with weighting coefficients μi in the signal of fluctuations in the speed of rotation of the first and tenth masses of the crankshaft. 3.5 Algorithmization of the Work Cycle Assessment Procedure Algorithmic support for the assessment of the identity of the 10D100 operating cycles is focused on establishing the values of the weight coefficients Di of the cylinders. For this, a system of algebraic equations of the following form is solved [26] BD = ϕ1 − ϕ1,0 ,

(21)

where B – is the matrix, the coefficients of which are determined on the basis of the LFC transfer functions W1 . . . W5 and the corresponding torques of the cylinders, depending

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on the selected calculation method; D – column vector of weighting coefficients; ϕ1 – column vector of the frequency representation of the measuring signal; ϕ1,0 – is a column vector of the signal of fluctuations of the first mass, in the absence of fuel supply to the cylinders. In case of frequency representation of the information signal, the coefficients of the matrix are determined as follows Bn,m =

5 6  

W1m (in)Mm,p (in).

(22)

n=1 m=1

In the case when the frequency spectrum of signals of fluctuations in the speed of rotation of the first and tenth masses exceeds 5 harmonic components, then the system of algebraic Eqs. (12) is overdetermined. To calculate the optimal values of cylinder coefficients Di you can, for example, use the routine “LLSQ” of the library of standard mathematical support. Its algorithmic support is built using the procedure of minimizing the involvedness of the system of Eqs. (12) based on the method of least squares. According to the results of the calculation, the appropriate hardware forms software changes to the settings of the fuel and air supply processes in the cylinders of the 10D100 diesel generator.

4 Results The requirements for the metrological characteristics of the measuring transducer of the crankshaft rotation speed signal are formulated on the basis of processing the data of computer modeling of the computational procedure for solving the system of algebraic Eqs. (12). When calculating the weighting factors, the following are taken into account: additive random influence on measurement information signals, random change of phase delays of individual cylinders relative to the first; the width of the spectrum of the frequency representation of the rotation speed signals of the first and tenth masses. Information technology for processing the results of calculations consists of the following actions: • we determine the average value of the real and imaginary parts of the complexes of weight coefficients of cylinders Di ; • we calculate the absolute and relative value of the uncertainty of the calculation results; • with the help of the Mathcad software environment, we build graphs of the uncertainties of the weighting coefficients. The sources of random disturbances that affect the uncertainty of monitoring the cylinder capacity of the 3TD-1 DH are: • technological uncertainty of manufacturing crankshafts, which manifests itself in the change of phase lags between the torques of individual cylinders and the first; • temporary instability of fuel combustion processes in cylinders; • accidental hardware failures. We will assume that these components are additive in nature. The difference between them is that the first and second uncertainties act at the input of the system, and friction

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at the output. For the computer simulation of random disturbances, the authors used the Monte Carlo method as a mathematical tool. All known primary converters of the speed of rotation of crankshafts when forming signals of measurement information implement individual cases of the Lamer circuit xn+1 = (axn + c) mod m, n ≥ 0,

(23)

where a ≥ 0 - is the multiplier, m > x0 , m > a, m > c - is the module, x0 ≥ 0 - is the initial value, c ≥ 0 - is the increment. The graphs (Fig. 8a) are constructed using the Mathcad software environment when the system of algebraic Eqs. (20) is presented in this form BD = ϕ1 + δ4 (t),

(24)

where δ4 (t) - random disturbance that acts on the measurement information signal. δ, %

δ, % D5

D5

D4 D4

D3 D3 D2

D2 D1

D1

δ5, deg

δ4, % b)

a) δ, %

δ, % D5 D5

D4 D4 D3 D3 D2 D1

D2 D1

δ5, deg c)

n d)

Fig. 8. Uncertainty graphs of the calculation of coefficients.

Uncertainty graphs for the calculation of weighting coefficients Di (Fig. 8b) obtained at different levels of interference (δ5 ), which changes the phase delay of individual cylinders relative to the first. It modifies the left-hand side of the system of Eqs. (20) by introducing a random lag or lead. A standard algorithm was used for the computer simulation of a random disturbance. The following system of algebraic equations is solved BDejδ5 (t) = ϕ1 .

(25)

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In Fig. 8c shows the graphs of the uncertainty of the weighting coefficients of cylinders Di , in the calculation of which the following is applied: additive random disturbance (δ4 = 1.0%), which is generated according to the Lamer scheme and affects the measurement signal of fluctuations in the speed of rotation of the first mass; accidental disturbance (δ5 ), which changes the phase delays of the cylinders, and a standard algorithm was used for its computer simulation. In this case, the following system of equations is solved BDejδ5 (t) = ϕ1 + δ4 (t).

(26)

It was established that a random disturbance, which changes the phase delay of an individual cylinder relative to the first one, significantly affects the uncertainty of the calculation. Therefore, when developing a computer system for software control of fuel and air supply processes to the cylinders of internal combustion engines, it is advisable to use hardware for measuring and adjusting gas distribution phases. Uncertainty graphs for the calculation of weighting coefficients Di with additive random interference (δ4 = 0.4%), which is formed according to the Lamer scheme for the case of a change in the width of the spectrum of the frequency representation of the measurement signal of fluctuations is presented in Fig. 8d. When choosing the number of harmonic components for the presentation of the signal of fluctuations in the speed of rotation of the crankshaft, we limit ourselves to ten, and their possible increase is not appropriate.

5 Conclusions The torque of the first cylinder from the action of gas forces was obtained by processing experimental pressure data. An indicator diagram was used as the source information. The torques of individual cylinders were approximated using the Fourier transform and taking into account the phase delays relative to the first one. To develop an algorithmic support for the task of monitoring the identity of the working cycles of the 10D100 diesel generator, the concept of differential torque was introduced. The measurement information signal of the power unit is presented in the form of a summary of the integrals of the convolution of the weighting functions of the contributions of individual cylinders and the corresponding torques. A mechanical system with ten degrees of freedom under the conditions of taking into account friction was used as a deterministic mathematical model of the power unit. The oscillatory movements of the masses of the mathematical model are described by a linear system of differential equations, the parameters of which are normalized based on the methods of similarity theory. The Laplace transform under zero initial conditions was used to solve the system of differential equations. As a result of mathematical transformations, a system of algebraic equations was obtained, the solution of which significantly simplifies the procedure for monitoring the identity of the working cycles of the 10D100 diesel generator. The information links between the torques of the cylinders and the signal of fluctuations of the rotation speed of the first and tenth masses establish the transfer functions, which are obtained as the ratio of the determinants of the system of algebraic equations.

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Logarithmic amplitude-frequency characteristics of “cylinder-crankshaft” signal transmission paths were constructed in the Matlab software environment. It was established that the contributions of the cylinders to the fluctuation signal differ in magnitude. In the Mathcad software environment, a two-stage structure of the circuit for computer modeling of signals of fluctuations in the speed of rotation of the first and tenth masses of the crankshaft was built. The procedure for identifying circuit parameters implements the method of adjusting the length of connections in the form of a change in gain coefficients. The information technology for assessing the identity of the working cycles of the 10D100 diesel generator was developed based on the frequency representation of the signal of fluctuations in the speed of rotation of the first and tenth masses of the crankshaft. By solving a redefined system of algebraic equations using the algorithm of minimization of the unsolved, we establish the weighting coefficients of the cylinders. According to the value of these coefficients, the computer system makes software changes to the settings of the processes of supplying fuel and air to the cylinders of the power unit. In the Mathcad software environment, by computer simulation of the procedure for solving the system of equations, graphs of the uncertainty of the calculation of the weighting coefficients under the conditions of the action of additive random disturbances on the signal of measurement information and gas distribution phases were obtained. It has been established that when developing a computer system for controlling the processes of fuel and air supply to the cylinders, hardware means should be used for measuring and adjusting gas distribution phases. Analyzing graphs also provides an opportunity to form requirements for the metrological characteristics of the measuring transducer of the information signal.

References 1. Challen, B., Baranescu, R.: Diesel Engine Reference Book. 2 edn. Butterworth-Heinemann (1999) 2. Gawande, S., Navale, L., Nandgaonkar, M., Butala, D., Kunamalla, S.: Cylinder imbalance detection of six cylinder di diesel engine using pressure variation. Int. J. Eng. Sci. Technol. 2(3), 433–441 (2010) 3. Gawande, S., Navale, L., Nandgaonkar, M., Butala, D.: Harmonic frequency analysis of multi-cylinder inline diesel engine genset for detecting imbalance. Int. Rev. Mech. Eng. 3(6), 782–787 (2009) 4. Bilyk, S., Bozhko, E.: Analysis of methods and methods of diagnosing internal combustion engines by non-assembly control methods. Bull. Nat. Tech. Univ. “KhPI” Ser. New Solutions Modern Technol. Kharkiv NTU “KhPI” 4(10), 3–8 (2021). https://doi.org/10.20998/24134295.2021.04.01. (UKR) 5. Bodnar, B., Ochkasov, O., Chernyayev, D.: Determination of the method of filtering the signal of non-uniformity of the crankshaft speed of the diesel engine. Bull. DNURT 1(43), 113–118 (2013). (UKR) 6. Sergienko, N., Kalinin, P., Pavlenko, I., et al.: Synthesis of the energy-saving dry dual clutch control mechanism. Appl. Sci. 13, 829 (2023). https://doi.org/10.3390/app13020829 7. Grachev, V.: Experimental estimation of diagnostic method of diesel engines due to uneven rotation of the crankshaft. In: Progressive Processes of Technological Operation of Automobiles Conference, pp. 46–50 (1982). (RUS)

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8. Marchenko, B., Myslovich, M.: The theory of diagnostics of energy aggregates by deviation of rotating units and its practical application for diesel-electric generators: Part 1. Tekhnichna Elektrodynamika 5, 36–40 (1998). (RUS) 9. Part 2: Tekhnichna Elektrodynamika 6, 39–42 (1998). (RUS) 10. Part 3: Tekhnichna Elektrodynamika 1, 59–63 (1999). (RUS) 11. Part 4: Tekhnichna Elektrodynamika 4, 40–45 (1999). (RUS) 12. Bashirov, R., Insafuddinov, S., Safin, F.: Uneven fuel supply in diesels: problems and methods of their solution. Izvestiya OGAU 1(75), 78–82 (2019). (RUS) 13. Pokusayev, M., Sibiryakov, K., Shevchenko, A.: Experimental determination of the degree of irregularity of the collapse of the shaft of the machine-propulsion complex of the ship 1557. Vestnik AGTU 2(43), 140–144 (2008). (RUS) 14. Grebennikov, S., Grebennikov, A., Nikitin, A.: Adaptive control of fuel supply by ICE according to indices of uneven rotation of the crankshaft. Vestnik SGTU 2(71), 80–83 (2013). (RUS) 15. Polyakova, T.: Solution of differential equations of free and forced torsion co-oscillations of a single-mass shaft. Vestnik SibADI 4(26), 90–94 (2012). (RUS) 16. Podrygailo, N.: The effect of torque unevenness on dynamic and power indicators of internal combustion engines of wheeled vehicles. Uchenyie Zapiski KIPU 38, 18–24 (2013). (RUS) 17. Savchenko, O., Dobrolyubov, I.: Modeling of the process of identifying the state of tractor engines. Prob. Comput. Appl. Math. 4(6), 4–12 (2016). (RUS) 18. Sivyakov, B., Truber, S.: Diagnostics of multi-cylinder engines by speed unevenness. Vestnik of SGTU 1(44), 76–82 (2010). (RUS) 19. Enikeev, A., Borisenko, A., Samsonov, V., Kiseleva, G.: Diagnosis of a diesel generator by the deviation in shaft speed. Meas. Tech. USSR 31(9), 868–871 (1988). https://doi.org/10. 1007/BF00863884 20. Dorf, R., Bishop, R.: Modern Control Systems. Pearson Education, Limited (2010) 21. Chaparro, L.: Signals and Systems Using MATLAB. Academic Press, Burlington (2011) 22. Lazarev, Yu.: Modeling Processes and Systems in Matlab: Tutorial (2005) 23. D’yakonov, V.: Matlab and Simulink for Radio Engineers (2011) 24. Domnisoru, C.: Using mathcad in teaching power engineering. IEEE Trans. Educ. 48(1), 157–216 (2005). https://doi.org/10.1109/TE.2004.837043 25. Ayasun, S., Nwankpa, C.: Transformer tests using MATLAB/Simulink and their integration into undergraduate electric machinery courses. Comput. Appl. Eng. Educ. 14(2), 142–150 (2006). https://doi.org/10.1002/cae.20077 26. Yenikieiev, O., et al.: A computer system for reliable operation of a diesel generator on the basis of indirect measurement data processing. In: Cioboat˘a, D.D. (ed.) Conference 2022, LNCS, pp. 30–44. Springer, Heidelberg (2022). https://doi.org/10.1007/978-3-031-15944-2_4 27. Yenikieiev, O., Scherbak, L.: Information technology for protecting diesel-electric station reliable operation. Tekhnichna Elektrodynamika 4, 85–91 (2019). https://doi.org/10.15407/ techned2019.04.085 28. Yenikieiev, O., Zakharenkov, D., Gasanov, M., Yevsyukova, F., Naboka, O., Ruzmetov, A.: Improving the productivity of information technology for processing indirect measurement data. In: Cioboat˘a, D.D. (ed.) Conference 2022. LNCS, pp. 80–94. Springer, Heidelberg (2022). https://doi.org/10.1007/978-3-031-15944-2_8 29. Yenikieiev, O., Yevsiukova, F., Prihodko, O., Ivanova, M., Basova, Ye., Gasanov, M.: Analysis of the frequensy characteristics of the automatic control system of manufacturing prosess parameters. Acta Technica Naposensis 62(111), 473–482 (2019). WOS: 000489767000015 30. Wassermen, F.: Neurocomputer technology: theory and practice (1992) 31. Yenikieiev, O., Isikova, N., Korotenko, Ye., Reshetnyak, T.: Analysis of characteristics of hardware means for software control of the longitudinal feed of the grinding wheel. Acta Technica Naposensis 63(11), 149–158 (2020). WOS: 000550992100006

Comparison of Metrological Characteristics of Measuring Transducer of Parameters Frequency-Modulated Signals Oleksandr Yenikieiev1 , Dmytro Zakharenkov2 , Magomediemin Gasanov2 Fatima Yevsyukova2(B) , Olena Naboka2 , Anatolii Borysenko2 , and Natalia Pavlova2

,

1 Donbas State Engineering Academy, 72, Akademicheskaia Str., Kramatorsk 84313, Ukraine 2 National Technical University “Kharkiv Polytechnic Institute”, 2, Kyrpychova Str.,

Kharkiv 61002, Ukraine [email protected]

Abstract. To build the architecture of measuring converters of the parameters of frequency-modulated signals, the method of discretization by time of the intervals between consecutive rectangular pulses produced by the primary converter of the rotation speed was chosen, and several devices were developed based on it. Using the methods of probability theory, mathematical statistics and measurement theory, a methodology for processing experimental data of a number of measurements with multiple observations was created. The Monte Carlo method was used to construct a scatter histogram and the distribution laws of the random functions of the experimental data were established. The information technology for processing a number of measurements with multiple observations based on the information approach of measurement theory was developed in order to establish the metrological characteristics of measuring transducers. Uncertainty of measuring transducers for processing the frequency-modulated signals of the speed of rotation of the crankshaft of power units belongs to category A. A method of organizing multi-channel measurements of time intervals, which are formed by a certain stroke of the primary converter and correspond to one complete rotation of the shaft, is proposed. The practical implementation of this method made it possible to significantly reduce the uncertainty of the primary converters of frequency-modulated signals and to build measuring converters with satisfactory metrological characteristics. A methodology for testing measuring transducers has been developed and hardware for its implementation has been selected. Uncertainties of the proposed frequency-modulated signals converters were established by statistical processing of experimental data in the form of series of measurements with multiple observations. The choice of a specific type of device depends on the optimal strategy for measuring the parameters of frequency-modulated signals. Keywords: Hardware · Frequency-Modulated Signals · Measuring Transducers · Metrological Characteristics · Uncertainty · Information Technology · Fluctuation Signal

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 586–603, 2023. https://doi.org/10.1007/978-3-031-40628-7_47

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1 Introduction The technical performance of the powertrains depends on the set phases of the fuel-air mixture processes in the cylinders and their identity [1–3], and the transmissions used [4]. The most widespread direct method of monitoring the distribution of cylinder power of the power unit is the measurement of cylinder pressure using the L-Card E14-140 analogto-digital converter (L-783 system board), the AVL primary converter (PC) 8QP505CS and the “Power Graph” application software. As a result of the measurements, we will get indicator diagrams of individual cylinders, the further comparison of which allows us to establish the identity. If there is a need, at the stage of engine tuning, the service personnel changes the settings of the phases of the processes of supplying the fuel-air mixture to the cylinders of the power unit. The need to modify the internal combustion engine in order to install a pressure sensor, the use of manual labor, the presence of a certain number of cylinders and, accordingly, excessive hardware costs significantly limit the use of the direct method of monitoring cylinder capacities. A well-known indirect method of estimating the identity of the cylinder capacities of the power unit [5–9] uses the frequency-modulated signals (FM-signals) of the crankshaft rotation speed [10] as a source of input information. Algorithmic support of the indirect method is focused on obtaining a signal of fluctuations followed by an assessment of the identity of the cylinder capacities. The method of processing the data of indirect measurements involves the following actions: approximation of the torques of individual cylinders based on the Fourier series; introduction of the concept of weight coefficients of cylinders; construction of a deterministic mathematical model of the torque circuit of the power unit in the form of a system of linear differential equations of mass movements, the further solution of which is performed by one of the numerical methods in order to establish the values of the weight coefficients of the cylinders. Comparison of the obtained values of the coefficients will allow establishing the deviation of the identity of the working cycles. Further setting of individual fuel-air mixture supply angles to power unit cylinders will ensure fuel economy at the level of 5% [5, 7], increase the life of the power unit and reduce costs for prevention, maintenance and repair. The modern state of the machine-building industry has made it possible to introduce injectors with electro-hydraulic or piezoelectric control as mechanisms that perform the processes of supplying the fuel-air mixture to the cylinders of power units. This circumstance, in turn, created the conditions for the rapid development of hardware and software tools for individually specifying the phases of fuel supply processes to cylinders with feedback based on the state of the crankshaft speed fluctuation signal. When solving this applied problem, the main component of the computer system, which significantly affects the metrological and dynamic characteristics of the control of the processes of supplying the fuel-air mixture to the cylinders, is the measuring converter (MC) of the parameters of the FM-signals of the speed of rotation of the crankshaft. Thus, the development of new methods of measuring the parameters of FM-signals and, on their basis, the construction of hardware and software tools with improved metrological characteristics and increased processing speed of indirect measurement data determines the relevance of this scientific and applied task.

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2 Literature Review Sufficient attention is given in the technical literature to the issue of building a MC for the parameters of FM-signals of the speed of rotation of the crankshaft. The uncertainty of the transformation of the input signal by the device is established using the combinational distortion coefficient [11]  0.5  −1 2 δKOM = U Uω−n , (1) n

where U - the amplitude of the spectrum component of the fluctuation signal with frequency modulation; Uω−n - the amplitude of the combinational component of the spectrum; ω – angular carrier of the transducer output signal. Pulse detectors of the integrating type [12, 13] use low-pass filters (LPF) to obtain a fluctuation signal. The metrological characteristics of the MC of the parameters of the FM-signals are ensured by the fact that each pulse of the PC has a calibrated amplitude and duration. However, at the same time, the LPF provides a relatively large uncertainty of the conversion, which makes it impractical to use pulse detectors of the integrating type in hardware with increased requirements for metrological characteristics. Detectors that monitor the signal [12–14] are made based on the application of the phase autofrequency adjustment scheme. Their construction is based on the principle of phase comparison of the output signal of the PC and the constant frequency reference signal. The reference signal is obtained thanks to the transformation of the signal of the PC with the help of a LPF and a voltage-frequency converter. Comparison of these two output signals is performed by a phase detector. Signal-following detectors provide satisfactory metrological performance, but have relatively narrow conversion ranges and poor stability when changing the frequency of the input signal. This is due to the limitation of the limit value of the shift, which is uniquely transformed by the phase detector, and the stability conditions of the phase auto-frequency adjustment scheme. Phase-frequency detectors use the phase-frequency characteristic of a frequencydependent passive quadrupole to isolate the fluctuation signal [2]. These devices provide satisfactory uncertainty, but have a narrow conversion range. Phase generator converters [15] use an autogenerator that is synchronized with the output signal of the sensor to extract the fluctuation signal. The phase difference between the control signal and the voltage on the autogenerator circuit is a measurement information signal. Phase generator converters of the parameters of FM-signals have a small uncertainty in a narrow conversion range due to the fact that the capture takes place within certain limits of the change in the frequency of the input signal. Digital crankshaft speed fluctuation signal meters have become widely used due to their relatively small conversion uncertainty. Fluctuation signal measurements are based on the time discretization procedure of intervals between consecutive rectangular pulses produced by the primary rotation speed converter. The fluctuation signal is the difference between the duration of the current time interval and the average value over the entire sample. Calculation of the signal of fluctuations in the speed of rotation of the crankshaft can be performed using the means of microprocessor technology. For example, in work [16] it is proposed to use a calculator to implement a MC of the specific fuel consumption

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of a direct current diesel generator. The disadvantages of digital meters are the relative complexity of their hardware construction and the limited speed of the element base. In works [17–20], a model of the dynamics of the cylinder power of the 10D100 diesel generator was proposed in the form of a linear random process. Methods of constructing estimates of some parameters of the specified processes have been developed and the effectiveness of their use as diagnostic signs of the technical condition of the cylinderpiston group has been proven. The results of studies of the uneven rotation signal of the 6NVD48UA diesel engine are given in [21]. A measuring transducer (MT) and information technology for processing the input signal have been developed in order to establish the average effective pressure, engine power, excess air coefficient and exhaust gas temperature. The work [22] proposed a method of controlling fuel supply processes based on measurements of the amplitude of oscillations of the angular speed of rotation of the crankshaft and the phase shifts of their extrema relative to the top dead center of an individual cylinder. The work [23] proposed a method for diagnosing the cylinder capacities of multicylinder engines using the crankshaft rotation unevenness signal, which was obtained as a result of computer simulation. In [6], it is proposed to use a high-frequency filter with a finite impulse response to reduce the influence of random disturbances on the information signal of fluctuations. A technique for processing the unevenness of the crankshaft rotation signal using the capabilities of the Matlab software environment has been developed. In [24], a technique for monitoring the cylinder capacities of engines using the signal of crankshaft rotation speed fluctuations, obtained as a result of computer simulation, is proposed. Identification of model parameters was carried out on the basis of experimental data processing. The method takes into account the peculiarities of the operation of engines in the case of superposition of neighboring torques. The disadvantage of known MC of the parameters of FM-signals is the unsatisfactory metrological characteristics of the processing of measurement information.

3 Research Methodology The purpose of the work is to study the metrological characteristics of the hardware for measuring the parameters of the FM-signals based on the statistical processing of experimental data and to develop new methods for their construction that reduce the uncertainty of the fluctuation signal. To achieve the set goal, the following tasks were solved in the work: • on the basis of the methods of measurement theory and mathematical statistics, develop a methodology for researching the metrological characteristics of the MC of the parameters of FM-signals; • build a test signal generator; • on the basis of the possibilities of modern means of digital circuitry, develop new methods of measuring the parameters of FM-signals; • to build the architecture of the MC of the parameters of FM-signals and to establish their metrological characteristics based on the processing of experimental data; • to perform a comparison of the developed MC of the parameters of FM-signals.

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3.1 Research Data Processing Methodology Among the above-considered methods of building a MC of the parameters of FMsignals, the most promising is the time discretization of the periods of passage of pulse sequences, which are formed by the PC. The authors used the methods of probability theory, mathematical statistics, and measurement theory, in particular, the information approach [25–27], when studying the metrological characteristics of the MC of the parameters of FM-signals. Let’s move on to the development of methodological principles for processing the measurement information signal. In the conditions of the rapid development of industrial production, the problem of correctly choosing the optimal strategy for performing measurements becomes especially important. The following criteria are used for its development: reduction of costs for solving the task as a whole, reduction of measurement time and results processing, achievement of minimum uncertainty and reliability of final results. Algorithmic support for processing the output information of the MC of the parameters of FM-signals involves the following computational actions [28–30]: • measurement of instantaneous periods of a FM-signals Ti ; • setting the average value of the FM-signals period Tav ; • calculation of the array of discrete values of the fluctuation signal using the expression xi = Tav − Ti . The G 5-54 laboratory pulse signal generator was used to test the proposed MC of the parameters of FM-signals in order to establish their metrological characteristics. The generator generates a sequence of pulse signals with the following parameters: a repetition period of 10–3 C and a duration of 3 * 10–4 C. The MC of the parameters of FM-signals records the measurement information in the form of a repetition period for the duration of the next pulse to the memory of the computer system. The information of the database of the computer system is a series of periodic measurements with repeated observations of the periods of passage of the generator signal. Accordingly, the uncertainty of the MC of the parameters of FM-signals belongs to category A and finds its quantitative manifestation in the scattering of measurements. Information technology for processing experimental data for the purpose of establishing statistical characteristics of the distribution of a random series of measurements with multiple observations of the periods of passage of the generator signal consists of the following computational actions: • measurement information is such a series x1 , x2 , x3 , . . . , xn ; • we set the mathematical expectation of a series of measurement X = • we calculate the variance of a series of measurements D = √ • we calculate the mean square deviation σ = D;

1 n

n   X

1 n

n 

i=1

n  3  • we determine the third moment of the distribution M3 = 1n X − xi ;  i=1 • we calculate the asymmetry of the distribution A = M3 σ 3 ; n  4  • we calculate the fourth moment of the distribution M4 = 1n X − xi ; i=1

xi ;

i=1 2 − xi ;

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• under the condition of normalization relative to the normal distribution of experimental data, we establish the excess of a number of measurements with multiple 4 − 3. observations of the periods of the generator signal as follows ε = M σ4 Mathematical expectation, mean square deviation, asymmetry and kurtosis form the statistical characteristics of the distribution of the random value of the periods of passage of the signal of the generator G 5-54. The Monte Carlo method was used to construct a histogram of the dispersion of the periods of passage of the generator signal, which were obtained at the output of the MC of the parameters of FM-signals: • we find the maximum and minimum value of a series of measurements xmin , xmax ; • we set the interval of change of random variables  = xmax − xmin ; • segment [xmin , xmax ] covers all sample values of the random function. We divide it into several equal intervals r = 6, 8, 10, . . . and when choosing a value 1 rounding to the nearest higher level; • we set the number of sample values of measurements of periods of passage of the generator signal that fell into each interval ±1 , ±2 , . . . , ±0.5r ; • we build a histogram of the dispersion of experimental data. The histogram of the dispersion of experimental data of the periods of passage of the signal of the generator G 5-54 is a stepped line. Based on the histogram, we select the distribution law of the random function F(x) experimental data under the following condition xmax N 1  F(x)dx − p(xi )i → min . N xmin

(2)

i=1

To establish the uncertainty of the MC of the parameters of FM-signals, the authors used the informational approach of measurement theory. The main advantage of its use for the mathematical description of the random components of the uncertainties of the periods of signal passage of the G 5–54 generator is that the size of the entropy interval can be calculated quite accurately with any distribution law. Information technology for processing a number of measurements with repeated observations consists of the following actions: • the equation of the smoothed dispersion curve of the source code of the MC of the parameters of FM-signals has the form f (x) =

1 − |x| e σ with x ∈ (xmin , xmax ). 2σ

(3)

• for the obtained law of distribution of the uncertainty of measurements with multiple observations of the periods of passage of the signal of the generator G 5-54 we have ln f (x) = − ln 2σ −

|x| . σ

(4)

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• hence the entropy of the uncertainty of the proposed MC of the parameters of FMsignals takes the following form 

   −1 . H x xn = ln 2σ eμ1 σ

(5)

• the entropy interval of uncertainty of the source code of the MC of the parameters of FM-signals has the form −1

 = σ eμ1 σ .

(6)

When applying the informational approach to working out the uncertainty of measurement results with multiple observations of the periods of passage of the signal of the G 5-54 generator, according to the work [26], operate with half the entropy interval. When developing the architecture of the MC of the parameters of FM-signals, we will apply the method of time discretization of the intervals between successive pulses of the PC. The lack of recorders of the source code of the MC of the parameters of FMsignals with the appropriate speed results in significant difficulties in their development [30]. We will solve the problem of recording the measurement information signal by using a microcomputer or a non-volatile memory device with an individual power source that works in direct memory access mode. Algorithmic and application software of the microcomputer also allows to use the central processor for direct measurements of time intervals in the start-stop mode. However, the rate of change of the output code of the MC of the parameters of FM-signals imposes significant limitations on the use of this measurement method. Therefore, it is advisable to organize the measurement of time intervals by hardware with further input of information in the mode of direct access to memory. Let’s move on to the analysis of the developed MC parameters of the FM-signals of the speed of rotation of the crankshaft of the power unit. 3.2 MC Parameters of the FM-Signals Based on a Microcomputer The bit rate of the microcomputer database for storing the output information of the measuring transducer is chosen taking into account the following requirements: • ensuring the specified metrological characteristics of the MC parameters of the FMsignals; • limited speed of entering measurement information into the microcomputer memory; • limitation of the modern elementary base on the frequency of the discretization signal of time intervals. The range of changes in the average speed of rotation of the crankshaft of the diesel generator 3TD-1 is 600–1400 s−1 . Given the uncertainty of the measurement of the period of the rotation speed signal, the minimum sampling frequency is 7 MHz. In this case, about 1100 pulses fall into the time interval between successive pulses of the output signal of the PC. Eleven bits of a binary counter are required to sum this number of pulses. Since microcomputer data buses usually have eight bits, it is advisable to choose a pulse counter volume of sixteen bits. For better use of the bit grid of the counter, the frequency

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of the pulses that perform the discretization procedure is chosen equal to 14 MHz. This choice also reduces the uncertainty of the MC parameters of the FM-signals based on a microcomputer, the architecture of which is shown in Fig. 1.

Fig. 1. Architecture of a MC parameters of the FM-signals based on a microcomputer.

The measuring transducer of the instantaneous speed signal has the following components: two generators of short rectangular pulses (F1, F2); generator (G), the oscillation frequency of the output signal is stabilized by a quartz resonator; two RS triggers (T1, T2); three schemes of coincidence (AND1-AND3); two counters of impulses (C1, C2); single vibrator (SV); code switcher (CS); agreement block (AB) with a microcomputer. Signals PR, CD, MAN and DS organize data exchange between the C2 unit and the microcomputer. The technical implementation of the MC parameters of the FM-signals based on the microcomputer was carried out on the basis of microcircuits of the K155 series. The MC parameters of the FM-signals based on the microcomputer was used for measurements in the frequency range from 300 Hz to 3 kHz [8]. The determination of the uncertainty of the MC parameters of the FM-signals based on the microcomputer was carried out on the basis of statistical processing of experimental data. The sample size was 132 measurements. In Fig. 2 shows the histogram of the dispersion of the output code of the MC based on a microcomputer. The main statistical parameters of this distribution are as follows X = 0,

σ = 0.031,

A = 0,

E = 3.19.

(7)

The histogram after performing the smoothing procedure is described by an exponential law of distribution, which is quite close to the triangular one. The probability of manifestation of the proposed hypothesis according to the Kolmogorov agreement criterion was 0.879 when λ = 0.612. The equation of the smoothed curve, after applying the Stat graft program, has the form f2 (x) =

1 −|x|σ −1 e with x ∈ (−0.03, 0.03). 2σ

(8)

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Fig. 2. Scattering histogram of the source code of the MC parameters of the FM-signals.

Hence the entropy of the measurement uncertainty of the period of the MC parameters of the FM-signals based on the microcomputer    H x xn = ln 0.032 . (9) Therefore, the entropy interval of uncertainty of the MC parameters of the FM-signals based on a microcomputer was 2 = 0.016. Such measurement uncertainty indicates the expediency of using the device. The architecture of the MC parameters of the FM-signals allows using a sufficiently large RAM instead of a microcomputer [30, 31]. 3.3 MC Parameters of the FM-Signals Parameters with Discrete Registration of Measurement Information The disadvantage of the previous MC parameters of the FM-signals is that its construction requires the use of sufficiently powerful hardware with a high speed of registration of the measurement information signal. It is possible to eliminate this shortcoming due to the use of the method of random samples in the construction of the structural diagram of the measuring transducer with a significant increase in the time of the experiment for recording the measurement results [8]. The architecture of the MC parameters of the FM-signals with discrete registration is presented in Fig. 3. The MC has the following components: three generators of short rectangular pulses (F1-F3); frequency multiplier (FM); three counters (C1-C3), moreover, C1 is reversible; comparison device (CD); three schemes of coincidence (AND1-AND3); two triggers (T1, T2), encoder of the average value of the rotation frequency of the shaft (Z), auxiliary register (R), decoder (D), two indication blocks (IB1, IB2). The fixation time of the next measurement is determined by the average frequency of rotation of the crankshaft, the number of lines PC and the volume of L3. The ratio of the volume to the number of strokes is chosen as follows N = E + 1. z where E - whole number, N – volume L3, z – the number of strokes PC.

(10)

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595

Fig. 3. Architecture of the MC parameters of the FM-signals with discrete registration.

Fulfillment of this condition ensures consistent measurement of all time intervals during a complete rotation of the crankshaft of the power unit. The speed of fixation of the measuring parameter by the device is given by the average speed of rotation of the crankshaft and the value E. The uncertainty of the MC parameters of the FMsignals with discrete registration will be established on the basis of statistical processing of experimental data. The sample size was 128 measurements. The main statistical parameters of the uncertainty distribution of the output code of the FM-signals parameters MC are as follows X = 0,

σ = 0.028,

A = 0,

E = 5.02.

(11)

The scatter histogram of the source code after performing the smoothing procedure is described by an exponential distribution law, which is quite close to the triangular one. The equation of the smoothed curve, after applying the Stat graft program, has the form f3 (x) =

1 −|x|σ −1 e with x ∈ (−0.09, 0.09). 2σ

(12)

For the obtained distribution law of dispersion of the source code of the MC parameters of the FM-signals with discrete registration, the uncertainty interval is equal to 3 = σ e

μ1 σ −1

= 0.029.

(13)

The value of the entropy interval of uncertainty of the MC parameters of the FMsignals with discrete registration is 0.0145, which proves the feasibility of using the device. 3.4 MC Parameters of the FM-Signals with a Device for Compensating the Kinematic Uncertainty of the PC The main element of the MC parameters of the FM-signals is the PC in the form of a disk with slots cut into it. The accuracy class of the PC is determined by the technology for its manufacture and the equipment used at the same time. The tolerance for manufacturing the PC in the form of kinematic uncertainty is indicated in the reference literature [32]. The authors analyzed the kinematic uncertainty of gears, which are widely used as the

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PC of the rotational speed of the crankshaft of power units. The following ratio was used to estimate its value δ4 =

m 100%, m

(14)

where m - gear manufacturing permit; m - gear module [32]. Numerical values of kinematic uncertainty of gear wheels according to different classes of accuracy are given in the Table 1. The uncertainty of the conversion of a FM-signals at a modulation depth of 0.05 is also given there. As a result of analyzing the data in the Table 1 it is established that the kinematic uncertainty of the gears makes a significant contribution to the final uncertainty of the FM-signals conversion. Such uncertainty values of the FM-signals conversion are inappropriate when implementing hardware for processing the FM-crankshaft speed signal. It is advisable to search for new methods of measuring the parameters of the FM-signals, which will reduce the influence of the kinematic uncertainty of the PC. Table 1. Value of kinematic uncertainty of gears Gear accuracy class

4

5

6

7

8

δ4 ,%

0.80

1.25

2.00

2.75

4.00

Uncertainty of FM-signals measurements,%

16.0

25.0

40.0

55.0

80.0

The influence of kinematic uncertainty can be reduced by the following methods: • carry out certification of the PC; • to develop a method in which the kinematic uncertainty of the PC does not affect the result of the conversion of the FM-signals. You can measure the distance between two adjacent marks of the PC using a micrometer. In this way, we form an array of distances that form a complete rotation of the shaft of the PC. The technology for processing input information is as follows: • we calculate the average value of the passage period T av ; • we calculate the array of corrections i = T av −T i . It is also possible to measure the fluctuations of the FM-signals of the PC, which rotates at a constant angular velocity. This condition is ensured by the use of a powerful DC motor. As a result of certification, we will receive an array of corrections, the consideration of which will compensate for the kinematic uncertainty of the PC. In this case, the method of measuring the period of the FM-signals consists in discretization by time of the intervals between the moments of passage near the sensitive element of the transducer of the neighboring labels of the PC. The measurement procedure itself also involves the use of a signal that synchronizes the operation of the PC with the phase of rotation of the crankshaft of the power unit. The information technology for extracting the fluctuation signal takes into account the corrections, which are also synchronized with the shaft rotation phase. Accordingly, the procedure of certification of

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the PC involves the use of manual labor and is individual in nature. This circumstance significantly limits the field of application of this method. To build the architecture of the MC parameters of the FM-signals in [9], a method of organizing multi-channel measurements of time intervals, which are formed by a certain line of the PC and correspond to one complete rotation of the shaft, is proposed. With this method of measuring the periods of the FM-signals of the speed of rotation of the crankshaft, the kinematic uncertainty of the PC leads to a displacement in time of the sampling points. The time shift of the sampling points of the analog signal of fluctuations determines the dynamic uncertainty of the PC, the absolute value of which is described by the following equation [12] 1 [ω(it + σdev ) − ω(it)], z z−1

dyn =

(15)

i=0

where t - the average timeof two adjacent marks of the PC passing near the sensitive sensor element, σdev = m tS - root mean square deviation of the kinematic uncertainty of the PC, tS - Student’s coefficient for the chosen value of the confidence probability. With accuracy up to the value of the second order of smallness with respect to the dynamic uncertainty of the PC, the sum can be replaced by an integral dyn

1 = T

T [ω(t + σdev ) − ω(t)] dt.

(16)

0

For a harmonic signal, expression (16) takes the form after transformations dyn,i =

2Ai sin(ϕi − 0.5iσdev ) sin(iσdev ). π

(17)

Hence, the relative value of the dynamic uncertainty of the harmonic signal has the form δi =

2 sin(φi − 0.5iσdev ) sin(iσdev ). π

(18)

We determine the dynamic uncertainty of the PC taking into account the contributions of harmonic components  10

10

  δdyn =  A2i . (19) (Ai δi )2 i=1

i=1

The results of the calculation of the dynamic uncertainty, which is characteristic of the PC of the parameters of the FM-signals, are presented in the Table 2. As a result of comparing the data in the Table 1 and 2, we conclude about the correctness of the proposed method of measuring the periods of a FM-signals. The number of channels for measuring the periods of the FM-signals is equal to the number of slots of the PC disk. The measuring transducer block measures time

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Gear accuracy class

4

5

6

7

8

Uncertainty of FM-signals measurements,%

3.1

4.8

7.4

9.9

14.1

intervals, the duration of which is equal to the time of passage near the sensitive element of the frequency sensor of the selected slot. In this case, the kinematic uncertainty of the disc does not affect the duration of the time intervals formed by the PC. The resulting time intervals are input to the multi-channel duration measurement device, which implements the time sampling method. The frequency of the output signal of the generator is stabilized by a quartz resonator. The output signals of individual channels of the device for duration measurements are superimposed on each other. In order to eliminate possible overlaps during the formation of the measurement information signal, a large part of the measured time interval is cut out using pulse counters. Rational selection of counter volumes and generator signal frequency completely eliminate mutual overlapping of output signals of duration measurement devices. Since the conversion factor of the counter is constant, the duration of the time interval that is cut out is determined by the stability of the generator signal. Therefore, the end of the time interval that is cut is rigidly tied to its beginning. The rest of the time interval are information signals and are summed into a measurement information signal using an OR circuit. Thus, at the output of the OR logical element, a measurement information signal is obtained, in which the kinematic uncertainty of the PC is compensated. Accordingly, the main uncertainty component of the FM-signal with the kinematic uncertainty compensation device of the PC is the dynamic component. The structural diagram of the MC of the parameters of a FM-signals with a device for compensating the kinematic uncertainty of the PC is presented in the Fig. 4. The structural diagram of the device consists of the following components: the start button; matching schemes (AND1-AND4); generators of pulses of a given duration (F1F3); triggers (T1-T5); frequency multiplier (FM); pulse counters (C1-C3), moreover, C1 is made reversible; decoders (D1-D4); switch; sensor of the average value of the crankshaft rotation frequency (Z); indication blocks (IB1-IB3); registers for temporary data storage (R1-R2); shaft rotation speed sensor (FT); sensor of the top dead center of the first cylinder (TDCS) provides synchronization of the MC with the phase of the working process of the DG 3TD-1; OR scheme; Nx - a measurement information signal that can be used to build a computer system [28]; logical blocks, which are outlined by a dashed line in the diagram. Their number is equal to the number of lines of the PC. The structure of the logical block is formed by: counters C(2i + 1) and C(2i + 2); schemes AND(4i + 1), AND(4i + 2), AND(4i + 3) and AND(4i + 2); triggers T(3i + 1), T(3i + 2) and T(3i + 3). The number of logical blocks is equal to the number of lines of the PC of the FM-signal (FT). The circuit combines the output signals of the logic blocks into a measurement information signal OR. A feature of the device is the presence in its structure of hardware means for fixing the cylinder number (IB3) and measuring the value (IB2) and fixing the sign (IB1) of the acceleration of the crankshaft rotation, which have exceeded the set limits.

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Fig. 4. The architecture of the MC parameters of the FM-signals from the compensation of the kinematic uncertainty of the PC.

To establish the uncertainty of the MC parameters of the FM-signals, statistical processing of the experimental data was performed. The sample size was 151 measurements. The main statistical parameters of the distribution of the uncertainty of the output code of the MC parameters of the FM-signals with a device for compensating the kinematic uncertainty of the PC are as follows X = 2.0 · 10−4 ,

σ = 0.014248,

A = 0.0536,

E = −0.449.

(20)

Accordingly, the entropy interval of uncertainty of the MC parameters of the FMsignals with the device for compensating the kinematic uncertainty of the PC is obtained in the following form f5 (x) =

1 −|x|σ −1 e with x ∈ (−0.04, 0.04). 2σ

(21)

Hence, the relative value of the dynamic uncertainty of the harmonic signal has the form 5 = σ e

μ1 σ −1

= 0.015.

(22)

The value of the entropy interval of uncertainty of the MC parameters of the FMsignals with the device for compensating the kinematic uncertainty of the PC is 5 = 0.0075, which proves the expediency of using the device.

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3.5 MC Parameters of the FM-Signals with a Device for Compensating the Kinematic Uncertainty of the PC and with Discrete Registration of Measurement Information The large number of traces of the PC, which is used to obtain a FM-signals, significantly complicates the schematic diagram of the MC and requires the use of a sufficiently large number of integrated circuits for its construction. At the same time, the reliability of the FM-signals parameter MC significantly decreases and its cost increases. To eliminate the specified shortcoming, the use of the method of random sampling of the measurement information signal with a significant increase in the time of the experiment allows the construction of the MC of the parameters of the FM-signals. In Fig. 5 presents the architecture of the MC of the parameters of a FM-signals with a device for compensating the kinematic uncertainty of the PC and with discrete registration of measurement information. The structure of the MC parameters of the FM-signals is formed by the following components: pulse shapers (F1-F3); matching scheme (AND1-AND3); triggers (T1-T3); system generator (G); pulse counters (C1C3); decoder (D); shaft rotation speed sensor (FT); sensor of the top dead center of the first cylinder (TDCS); RC-circuit for initial setup of counters and triggers. Block K has the following inputs: informational (D0…DN), to which outputs are connected D; control (I0…IN). The volume of the counter C2 is always equal to the number of lines of the PC. The measuring information signal is generated at the output of the AND3 block in the form of a sequence of pulse signals of limited duration. This is ensured by the appropriate selection of the AND3 counter volume. After applying the supply voltage, the start of the measuring transducer with the device for compensating the kinematic uncertainty of the PC and with the discrete registration of the measurement information provides the first pulse of the TDCS sensor. The device measures time intervals, which are determined by the moments of passage near the FT sensor of a certain line and correspond to a complete revolution of the crankshaft. This ensures the exclusion of the kinematic uncertainty of the PC from the measurement information signal.

FT

F1

C1

D

I0 I1

Us R

C2

...

Т2

...

F2

AND2

C3

Т3

AND3

Nx

...

DN

TDCS

G

D0 D1 ...

AND1

K

Т1

F3

«lateness»

IN

C

Fig. 5. Architecture of the MC parameters of the FM-signals with compensation of the kinematic uncertainty of the PC and with discrete registration of measurement information.

When establishing the uncertainty of the measuring transducer, statistical processing of the experimental data was performed. The sample size was 154 measurements. The main statistical parameters of the uncertainty distribution of the output code of the FM-signals parameters MC are as follows

Comparison of Metrological Characteristics of Measuring Transducer

X = 2.3 · 10−4 ,

σ = 0.0142,

A = 0.054,

E = −0.45.

601

(23)

The histogram of the dispersion of the source code of the FM-signals parameters MC with a device for compensating the kinematic uncertainty of the PC and with discrete registration of measurement information after performing the smoothing procedure is described by an exponential distribution law, which is quite close to the triangular one. The equation of the smoothed curve, after applying the Stat graft program, has the form 1 −|x|σ −1 e with x ∈ (−0.041, 0.041). (24) 2σ Accordingly, the entropy interval of uncertainty of the MC parameters of the FMsignals with the device for compensating the kinematic uncertainty of the PC and with the discrete registration of the measurement information is obtained in the following form f6 (x) =

6 = σ e

μ1 σ −1

= 0.014.

(25)

The value of the entropy interval of uncertainty was 6 = 0.007, which proves the feasibility of using a FM-signals parameters MC with a device for compensating the kinematic uncertainty of the PC and with discrete registration of measurement information.

4 Results Several methods of measuring the parameters of FM-signals are proposed and a measuring transducer is developed on their basis. A laboratory pulse signal generator G 5-54 was used to test the developed MC parameters of the FM-signals. The information technology for processing a number of measurements with multiple observations of experimental data of testing the measuring transducer was developed on the basis of the methods of measurement theory and mathematical statistics. The kinematic uncertainty of gear wheels, which are widely used as the PC of the rotational speed of the crankshaft of power units, was studied, and a method of organizing multi-channel measurements of time intervals was proposed. A significant improvement of the metrological characteristics of the MC parameters of the FM-signals has been established. The use of the method of discrete registration of the signal of measurement information simplifies the construction of the MC parameters of the FM-signals, however, it significantly increases the time of the experiment. When choosing a method for building a measuring transducer, it is advisable to correctly choose the optimal strategy for performing measurements.

5 Conclusions It has been established that the time discretization of the pulse sequences of the PC is the most promising method of building a MC of the parameters of FM-signals. Methods of measurement theory, probability theory, and mathematical statistics were used to develop the methodological foundations of research into the metrological characteristics of hardware.

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The information technology for processing a number of measurements with multiple observations of the source code of the MC parameters of the FM-signals is built on the basis of the information approach of the theory of measurements. At the same time, the size of the entropy interval of uncertainty of the dispersion of the source code of the periods of passage of the generator signal is calculated accurately enough for any distribution law. Several methods of measuring the periods of generator signal passage are proposed, and on their basis, the architecture of the MC parameters of the FM-signals is built. As a result of processing experimental data in the form of a series of measurements with repeated observations, the metrological characteristics of the measuring transducer were established. The expediency of using this MC parameters of the FM-signals has been established. The choice of a specific MC parameters of the FM-signals depends on the optimal strategy for performing measurements.

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Using an Object-Oriented Approach in Foundry Production Olga Ponomarenko1 , Nataliia Yevtushenko1(B) , Oleg Khoroshylov2 , Stepan Yevtushenko1 , Tatyana Berlizeva1 , Mikhailo Vorobyov1 , and Ihor Lukianov1 1 National Technical University “Kharkiv Polytechnic Institute”, 2 Kirpicheva St.,

Kharkiv 61002, Ukraine [email protected] 2 Ukrainian Engineering and Pedagogical Academy, 16 Universitetskaya St., Kharkiv 61003, Ukraine

Abstract. In the current conditions, the use of modern technologies and equipment is an important factor in the survival and further development of the foundry. And this, in turn, requires a partial or complete reconstruction of the foundry. Therefore, improving the quality of designed objects based on the use of computer technology, a systematic approach to the design and reconstruction of modern industries, increasing their efficiency is an urgent problem of foundry production. The purpose of the work is to develop a methodology for designing and reconstructing foundries and sites using an object-oriented approach. The article proposes a new method in the design and reconstruction of foundries and their subsystems, based on the use of system analysis, reliability theory, hierarchical structures of graph theory, probabilistic automata, mathematical and simulation modeling. In the practice of foundry production, a mathematical model was proposed that made it possible to link the reliability parameters of equipment operation with the technology used and made it possible to create optimal structures for foundry subsystems. The use of the methodology allows, on the one hand, to reduce project costs, and on the other hand, to improve the quality of designed facilities by viewing a large number of options, reduce the degree of risk in the implementation of design solutions and the development of new production orders. An object-oriented approach in design and reconstruction can be used to evaluate the performance of existing foundries and their subdivisions; to select the optimal conditions for the production of castings obtained according to various technological schemes; during the development of new technologies; during the reconstruction of workshops with different nomenclature and serial production; in databases of expert systems; in the system of automated design and management of technological processes, structural divisions and the workshop as a whole; in the system of education of students of foundry specialties. Keywords: Design · Reconstruction · Modeling · Automated Production · Quality

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 604–615, 2023. https://doi.org/10.1007/978-3-031-40628-7_48

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1 Introduction In the current conditions, the use of modern technologies and equipment is an important factor in the survival and further development of foundry production. And this, in turn, requires a partial or complete reconstruction of the foundry [1, 2]. The need for design in the foundry arises when creating new, previously non-existing facilities, as well as during the reconstruction of existing ones, adaptation and repair. In connection with the computerization of design, design methodology issues are of particular importance, since they allow, on the one hand, to reduce project costs, and on the other hand, to improve the quality of designed objects by viewing a large number of options, to reduce the degree of risk in the implementation of design decisions, development of new production orders [3]. The problem of reconstruction of old foundries is already relevant and will become especially acute in the coming years, since the technical level of fixed assets of foundry production in Ukraine does not meet modern requirements. The formation of the structure and the main parameters of the production process of the foundry shop takes place at the stage of its design, while a fundamental restructuring can be carried out only during the reconstruction of the working shop. Therefore, the efficiency of the foundry shop is largely determined by the quality and validity of design solutions [4, 5].

2 Literature Review Unfortunately, in the practice of designing and reconstructing foundries and workshops, an empirical approach is widespread, in which the adoption of technical and organizational decisions is based on regulatory data and the professional experience of designers and production workers. When designing and reconstructing, the production capacities of the foundry are calculated, which ensures the production of high-quality products, the necessary productivity of equipment, and the optimal cost of castings. The calculation of the production capacity of workshops for mass and large-scale production is carried out for the leading groups of equipment, as a rule, for molding or for molding and mixing equipment. First, the productivity of the molding department is determined, and then, similarly, the capacity of other departments with the introduction of a certain margin that ensures the smooth operation of the molding department [6]. At the same time, the experience of their operation shows that the assessment of the options for the structure and parameters of the production complex based on the knowledge of the characteristics of individual units, without a sufficient quantitative analysis of their interactions and taking into account individual factors in the dynamics of equipment operation, can lead to gross miscalculations. So, due to the presence of downtime, the potential of automatic molding lines is realized on average by 40…60% [7, 8]. One of the main reasons for this is the imperfection of the methods used in the design [9]. So they do not take into account the fact that a modern foundry is a complex dynamic system, the functioning of which is determined by the stochastic nature of the interaction of various equipment and its structure. Therefore, when calculating the

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production capacity of the foundry, it is necessary to take into account such factors as the reliability of the work of the foundry departments. At the design stage, it is necessary to solve the issues of synchronizing the work of its departments and providing automatic casting lines with liquid metal, molding sand, cores, etc. [10, 11]. To solve practical problems related to increasing the efficiency of foundry technological systems at the stages of design and reconstruction, the most promising direction is an object-oriented approach [12, 13]. The use of computer technologies, the methodology of system analysis and applied mathematical methods make it possible to carry it out at a qualitatively new level [14]. The aim of the work is to develop a methodology for the design and reconstruction of foundries and sites using an object-oriented approach. To achieve this goal, it is necessary, based on the use of graph theory, to analyze the structures of workshops and their divisions; justify and choose a mathematical apparatus to describe their work; develop general mathematical models; computer programs for their implementation, describing the dynamics of their functioning; based on the cost characteristics and the main performance indicators of the units, determine the best option for the project of a foundry shop or section [15].

3 Research Methodology To simulate the work of production units and the workshop as a whole, it is advisable to use simulation-probabilistic models that allow, with the minimum necessary mathematical description, to fully reflect the whole variety of processes occurring in foundry technological systems [16, 17]. The probabilistic-automaton approach to modeling a complex system involves dividing it into a finite number of subsystems with the preservation of connections that ensure their interaction. The dismemberment process continues until elements are obtained that, under the conditions of the problem under consideration, are considered simple and convenient for mathematical description. As a result of such a structuring process, the foundry working shop is presented as a multi-level structure of interconnected elements, combined into subsystems of various levels [18]. When modeling complex systems using probabilistic automata, the output signal of one automaton serves as the input for another. The functioning of the automaton is reduced to the fact that at its input at discrete moments of time signals are received that make up the input alphabet, while the automaton, depending on the input signal and its internal state, produces an alphabet according to the rules determined by the output function. The exit function reflects the transformations carried out on the object under study, and the transition function describes the dynamics of its internal state [19]. For technical devices integrated into a system of foundry technological equipment, it is advisable to take the probability of failure-free operation of the unit at a given time as a function of the internal state [20]. The dynamics of changes in the main characteristics of technological processes and equipment can be reproduced using computer technology and the use of a combination of analytical and simulation models. This creates the basis for the transition from empirical methods for solving the problem of choosing the structure of foundry subsystems to a machine search for optimal solutions using modern mathematical methods [21].

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To study the work of foundries workshop, a special modeling algorithm was created. Depending on the method of advancing the model time, two approaches were used to construct a modeling algorithm - according to special states and using a fixed step. If the moments of occurrence of events are not known in advance, are evenly distributed over the entire simulation interval, or there are many events and they appear in groups, the second approach was used. In other cases, the first approach was used as more economical [22, 23].

4 Results The structural-software complex for describing the functioning of the foundry is a program in the Delphi language, which describes the structures of states of probabilistic automata, the structures of emitted and received signals, their response to a special state, and adjusts the initial states of probabilistic automata to the characteristics of a particular simulated system. In addition to modules of probabilistic automata that simulate the functioning of the elements of the simulated system, the structural and software complex uses modules that implement algorithms for solving research problems [24]. Data for creating a model and conducting experiments on it are presented in the form of an order. The advantage of the structural software complex shown in Fig. 1 is that the description of the system being modeled is separated from the description of the experiment with the model. This makes it easy to vary both experiments with models and change the models themselves. Such a structural-functional approach to the formalization of the object under study reduces the restrictions on complexity that inevitably arise when trying to represent the process of functioning of the system as a whole, as a sequence of interrelated system events for writing it in the modeling language. The main part of the software package is the simulation support program, designed to reproduce the trajectory of the state change of the simulated system in model time and is a mandatory part of all software models [25]. The imitator performs the following functions: organizes and issues a calendar of events, transmits signals from one probabilistic automaton to another, provides quasi-parallel execution of planned events, and formalizes simulation results [26, 27]. Structural and software complex for modeling the work of the foundry also includes databases on alloys and charge materials, compositions and properties of molding sands, castings, sand preparation, melting, molding, transport equipment and equipment for finishing operations. There is a library of models, which is made up of mathematical models for calculating the properties of molding sands, the dependence of the parameters of sands on the time of their mixing, mathematical models of failures of the main equipment, functions of changing metal parameters over time. It also stores software packages for calculating the amount of equipment based on economic criteria for the minimum of reduced costs, which is then refined during modeling, calculation of the foundry charge and operational planning of the production of castings [28, 29]. The structural-software complex has an extensive reference subsystem. By changing the intensity of the input flow, the cycle of the line, the metal capacity and the need for the mixture, the composition of the equipment (introducing additional

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Fig. 1. Structural-software complex for modeling the work of a foundry

elements) and its performance, and, tracing the corresponding changes in the production process during the simulation, we obtain data on the functional the capabilities of the entire system and its individual elements [30]. Both the technological process itself and the internal state of the simulation object are modeled.

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The program works as follows. The appearance of the software package for modeling the melting system is shown in Fig. 2.

Fig. 2. External view of the software package for modeling the melting subsystem of the foundry

First of all, the structure of the simulated production is created on the monitor screen in the visual design mode. To do this, the database provides several groups and types of equipment or processes. The equipment (process) is built on the monitor screen according to the existing technology according to its intended purpose. Equipment connections between each other are established in a dialog mode. Each equipment (process) is given the necessary characteristics or parameters: operating time; technical characteristics of the equipment of the melting system, molding, mixture preparation, transport equipment and equipment for finishing operations; its original state; scheme of equipment operation; the laws of its failure; mathematical models of processes occurring in the system; critical moments; the metal consumption of molds, the need for a mixture, etc.

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After the structure is created, the program is launched on the account. In the process of modeling, the necessary indicators are fixed: the total operating time of the system as a whole and its subsystems, as well as each piece of equipment (process) separately; the amount of the prepared alloy, mixture, forms; the amount of alloy poured into molds; the amount of alloy drained into the molds or returned to the system for various reasons; the amount of the mixture sent to the dump; downtime for each piece of equipment, indicating the reason. The list of indicators can be changed depending on the purpose of the problem being solved. At the initial moment of time (τ0 = 0), each of the N-aggregates of the system is characterized by one of its states ZI (τ), where i is the number of the system element. In each next sufficiently small specified period of time, the internal state of the element is generated. The goal is to determine its healthy state, downtime or other critical states. The state is determined using a random number generator by the method of hitting a random variable X in the interval of failure or operation. Simulation can be performed both in real time and with any time scale. This makes it possible to analyze the technological process that occurs for a long time in a few seconds. It is advisable to use a program with a fixed time step. It is set quite small compared to the duration of the operation and the time of equipment failure. During the program operation, at any time, you can interrogate the state of the equipment or process. This is done by moving the cursor to the specified equipment and pressing the left mouse button. At the same time, a window is displayed with the current parameters, a report on the operating time, downtime and their reasons. For clarity, all data are presented in the form of graphs, diagrams, histograms. The technological process can be stopped or continued at any point in time. The structures of foundry subsystems and equipment, the technological process used and the results of the calculation can be saved in databases, edited or deleted. Each interface element of the system has a context hint. As a base class, the TOper class was created, which includes methods for creating and deleting an operation object from memory, methods for drawing input and output connections of virtual abstract models, controlling metal and mixture consumption, controlling metal temperature, and also implementation of the transfer of metal, mixture, cores, forms through bonds. The base class contains the internal identification code of the operations. Logical properties of operation states: state of waiting for inputs, state of operation or idle state, state of transmission over communications, emergency states (during operation - equipment failure due to technical reasons, during transmission - the metal or mixture has run out, the temperature of the metal has decreased to a critical state, etc.). In addition, it contains logical properties that show the “success”, “completion” of the process or its stage. The base class contains variables for the current time of the operation, passport data (technical characteristics) of equipment or processes, as well as methods for manipulating databases. In addition, a special connection class TConnection has been created. It includes methods for creating and deleting connections from memory, drawing them, and moving them. The properties of the TConnection class are the coordinates of the beginning and end of the connection, as well as pointers to the connected operations or equipment

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(Oper - from, Oper - to). The described objects (classes) are manipulated by the global object (class) – TProcess. This class contains procedures for moving, deleting, combining operations and their links. This class allows the system to respond to user requests. The key procedure is the “Timer” procedure, in which the cycle of generating states, polling equipment and their connections is implemented. At each point in time given by the available machine interface. The process is formally stopped so that the parameters of each of the simulated processes do not change, and in the cycle each piece of equipment is polled, and the technological process, while in each of the operations (subprocesses) generates its own new state corresponding to the current value of time and performs reactions to the state of the operations associated with it. The process continues until the specified time point. The software package for modeling the work of a foundry shop is designed to perform calculations of time diagrams of the work of designed foundry shops and simulate their work from molding to the output of castings. The main data are: weight of the casting; Its cooling time; time of production of one form; safety factor of flasks; working hours of the shop per day; estimated number of days of workshop simulation; furnace capacity; duration of melting; specific electricity consumption kW*h/t. The complex allows you to get: optimal number of ovens; Schedules for loading furnaces; graphs of finished metal spill; the number of received castings for the billing period; amount of waste; required number of flasks; Total oven operating time. The complex allows optimizing the work of the workshop according to the criteria of energy consumption and the yield of suitable castings. The system contains reference databases on furnaces and equipment of foundry shops. The system is installed in a directory named MODEL. This directory contains executable and auxiliary files. In addition, it contains a data directory - DATA. With the help of the structural software complex, it is possible to simulate the work of both the foundry subsystem and the workshop as a whole and make a rational choice of the workshop structure, the type and quantity of the main and auxiliary equipment, the main parameters of technological and transport flows, and also organize the interaction of the functional divisions of the foundry. At the operation stage, it becomes possible not only to identify “bottlenecks” in the technological chain of equipment and evaluate the influence of various factors on the operation process, but also to increase its reliability due to structural and parametric optimization. It was found that the quality of design solutions in the design and reconstruction of foundries is determined, in addition to the main factors, by the dynamics of changes in equipment reliability over time, the technology used and its mathematical model, and the availability of software. This allows us to reduce the problem of the optimal solution to finding the best value of the objective function under the constraints imposed on individual variables. An object-oriented approach in design and reconstruction can be used to evaluate the performance of existing foundries and their subdivisions. Also, to select the optimal conditions for the production of castings obtained according to various technological schemes; when developing new technologies; during the reconstruction of workshops with different nomenclature and serial production; in databases of expert systems; in

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the system of automated design and management of technological processes, structural divisions and the workshop as a whole; in the system of teaching students of foundry specialties. The practical application of this approach at a number of workshops of agricultural engineering plants made it possible to draw reasonable conclusions about ways to improve the efficiency of these industries. The proposed technique allows for newly designed shops by improving its layout solution, eliminating “bottlenecks”, installing new equipment to increase productivity by 20… 25%, and for reconstructed shops by 13… 20%.

5 Conclusions The formation of the structure and the main parameters of the production process of the foundry shop takes place at the stage of its design, while a fundamental restructuring can be carried out only during the reconstruction of the shop. Therefore, the efficiency of the foundry shop is largely determined by the quality and validity of design solutions. In connection with the computerization of design, design methodology issues are of particular importance, since they allow, on the one hand, to reduce project costs, and on the other hand, to improve the quality of designed objects by viewing a large number of options, to reduce the degree of risk in the implementation of design solutions, development of new production orders. To solve practical problems related to improving the efficiency of foundry technological systems at the stages of design and reconstruction, the most promising direction is an object-oriented approach. The use of the system analysis methodology and applied mathematical methods make it possible to carry it out at a qualitatively new level. To achieve this goal, an analysis of the structures of workshops and their subdivisions was carried out based on the use of graph theory; selected mathematical apparatus to describe their work; developed general mathematical models; computer programs for their implementation, describing the dynamics of their functioning; based on the cost characteristics and the main performance indicators of the units, create the best version of the project of the foundry shop. To imitator the work of production units and the workshop as a whole, imitationprobabilistic models were used, which allow, with the minimum necessary mathematical description, to fully reflect the whole variety of processes occurring in foundry technological systems. By changing the intensity of the input flow, the cycle of the line, the metal consumption and the volume of the mixture in the mold, the composition of the equipment (introducing additional elements) and its performance, and by tracing the corresponding changes in the production process during the simulation, we obtain data on the functionality of the entire system and its individual elements. Both the technological process itself and the internal state of the simulation object are modeled. With the help of the structural software complex, it is possible to simulate the work of both the foundry subsystem and the shop as a whole and make a rational choice of the shop structure, the type and quantity of the main and auxiliary equipment, the main parameters of technological and transport flows, as well as organize the interaction of the functional divisions of the foundry workshops. At the operation stage, it becomes

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possible not only to identify “bottlenecks” in the technological chain of equipment and evaluate the influence of various factors on the operation process, but also to increase its reliability due to structural and parametric optimization. An object-oriented approach in design and reconstruction can be used to evaluate the performance of existing foundries and their subdivisions; to select the optimal conditions for the production of castings obtained according to various technological schemes; when developing new technologies; during the reconstruction of workshops with different nomenclature and serial production; in databases of expert systems; in the system of computer-aided design and management of technological processes, structural divisions and the workshop as a whole; in the system of teaching students of foundry specialties. The proposed technique allows for newly designed shops by improving its layout solution, eliminating "bottlenecks", installing new equipment to increase productivity by 20… 25%, and for reconstructed shops by 13… 20%. The practical application of this approach at a number of workshops of agricultural engineering plants made it possible to draw reasonable conclusions about ways to improve the efficiency of these industries.

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Examination of the Effect of Hyperparameters on Object Detection in the Orchard Using Deep Learning Sahin ¸ Yıldırım1(B) and Burak Ulu2 1 Engineering Faculty, Mechatronic Engineering Department, Erciyes University,

Kayseri, Turkey [email protected] 2 Erciyes University, 38039 Kayseri, Turkey

Abstract. Automated systems are needed to count the yield in industrial orchards. Computer vision and artificial intelligence techniques offer very promising results for such counting problems. In particular, the use of deep learning methods in outdoor experimental studies, where errors due to the reflection of light are experienced, makes computer vision applications more reliable. In this study, the hyperparameters of the deep learning model applied to autonomously determine the yield in the orchard were optimized and the effect on the result was examined. Apples are determined and counted using the deep learning method on the images obtained from the Multirotor Micro Aircraft (MAVs) developed for this study. To increase the performance of this process, some improvements can be made during the deep learning training phase. Optimizing the hyperparameters is one of these improvements, and it has been observed that it can increase the success performance by up to 30% with the random search method. Keywords: Deep Learning · Autonomous Systems · Smart Agriculture

1 Introduction Spraying, examining, and harvesting fruits is an extremely labor-intensive and costly process. The problem of finding workers for this process, which is mostly labor-based, and the productivity of the work has become an increasing problem. Especially the examinations conducted during the growth period of the fruits are very important in predicting the yield and in the early intervention of diseases. Efficiency and time losses can be enormous in the traditional method based on labor. For this reason, it would be highly advantageous to benefit from autonomous robotic systems for the examination of orchards. Drone-type aerial vehicles can be presented as a solution to the problems related to the process both in terms of speed and the benefits they can provide. There are studies in which computer vision method is used to perform inspections in orchards autonomously. Sample references can be consulted to review the problems and methods in this field [1–4]. Object detection is an important sub-branch of computer © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 616–621, 2023. https://doi.org/10.1007/978-3-031-40628-7_49

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vision and is used in various applications. It can be used for object detection, tracking plant species [4], animals [5] and even humans [6] in open areas such as garden. In this study, a deep learning model has been developed for object detection. Some hyperparameters are determined for the training of the model. The values of these hyperparameters can affect the performance of the object detection algorithm. Therefore, the effect of optimization of hyperparameters on the performance of object detection algorithms is investigated. In this study, the effect of hyperparameters of an algorithm used to perform object detection in the garden was investigated. A series of experiments were carried out to understand the effect of the algorithm’s hyperparameters on object detection accuracy. In these experiments, object detection performances of the algorithm were compared using different learning rate parameter values. In addition, the best hyperparameter values were tried to be determined to increase the accuracy of object detection by performing hyperparameter optimization with the random search method. This study is performed to understand the effect of hyperparameters of algorithms used for object detection in the garden and to explore the use of hyperparameter optimization to improve object detection accuracy. Our results may highlight the importance of hyperparameter optimization to improve the performance of algorithms in object detection applications in the garden.

2 Methodology The hyperparameter optimization study for the artificial intelligence-assisted detection used in the corridors in the orchards, is carried out in the following steps: Step 1: Training the deep learning model, Step 2: Object detection with deep learning, Step 3: Hyperparameter optimization. 2.1 Training the Deep Learning Model In the first step of the study, approximately 1000 images of apples ripening between August and November were acquired manually in-flight trajectory with the camera on the flying system. Then, after labeling these images, the dataset was created. This dataset has been converted to record format to work properly with the Python codes developed for the application. Then, the deep learning network model is trained with this custom dataset with the Faster R-CNN architectural approach, Fig. 1. 2.2 Object Detection with Deep Learning In this paper, a deep learning model has been developed with the custom-created data set. For this model to perform object detection, a script in Python language has been developed for this modeling to perform object detection. While developing this software, the TensorFlow library and object recognition programming interface were used. According to the parameters determined, new neural network models were trained with the custom data set, using the Faster R-CNN architectures. As a result, the successful performances of the developed neural network models under different conditions were examined comparatively.

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Fig. 1. The Convolutional Neural Network Model Structure.

2.3 Hyperparameter Optimization Hyperparameters are parameters that affect performance in machine learning models. Therefore, determining the correct hyperparameters is extremely important for better performance of the model. Traditionally, hyperparameters are determined by trial-and-error method. However, this method can take a lot of time. For this reason, more systematic hyperparameter optimization methods such as random search and grid search methods may be preferred. In this study, the effect of optimum hyperparameters on the performance of the deep learning model was investigated by using random search algorithm. Specifically, the effect of the learning rate hyperparameter is studied. The following Eqs. (1) and (2) show the effect of learning rate on the loss function. The update calculation of the weight variable is given in Eq. (1), and the calculation of the loss function in Eq. (2). δ J(θ) δθ    2 hθ x(i) − y(i)

θ =: θ− ∝ J(θ) =

1 m i=1 2m

(1) (2)

  where J(θ) is loss function, θ is weight variable, ∝ is learning rate, hθ x(i) is the predicted value and y(i) is the real value.

3 Experimental System The apple orchard, where real-time experiments were implemented, is located in the Ye¸silhisar district of Kayseri. In this garden, production is carried out on an area of 350 decares covered with awnings. Experimental studies were performed in a corridor determined by the quadrotor robotic system, Fig. 1, developed for this study. Odroid XU-4 [8] with ARM architecture is used to provide offboard control in the MAV system. Pixhawk Cube controller was preferred to perform the flight control of the robotic system. The Hokuyo URG04-LX lidar sensor was chosen as the required laser scanner for mapping and positioning. The neural network model is trained on the Intel i7-2600 CPU 3.40 GHz processor [9] for object detection from the obtained images. In future studies where the model will be trained with larger data, GPU processors will be used over the NVIDIA GeForce GTX 1050 Ti graphics card [10].

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Fig. 2. The developed quadrotor robotic system.

4 Results As a result, the parameters of the deep neural network models trained using different hyperparameters and the obtained loss values are given in Table 1. In addition, the learning rate (a) and loss values (b) are shown graphically in Fig. 3. Table 1. The hyperparameters of the deep neural network models Heading level

Model1

Model2

Model3

Activation Function

RELU

RELU

RELU

Learning Rate ˙ Iteration Number

0.03–.07

0.03–0.09

0.0001–0.04

3000

2000

4000

Batch Size

2

4

4

Min Loss

0.117

0.104

0.037

In this study, which was carried out with a limited number of samples, the observed changes in the learning rate are expected to be a reference in the parameter selection in the continuation of the hyperparameter optimization. As can be seen from the results in Fig. 2, while the increase in the learning rate enables rapid changes in the loss function, it also led to problems in finding the global minimum value. For this reason, the learning

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Fig. 3. (a) Learning Rate-Iteration graph. (b) Loss Function-Iteration graph.

rate should not be chosen either too large or too small. Another result obtained from these graphs is that the error value decreases further when the learning rate changes are spread over longer iterations. However, if this iteration value is chosen more than necessary, this time may instability of the loss function.

References 1. Itakura, K., Narita, Y., Noaki, S., Hosoi, F.: Automatic pear and apple detection by videos using deep learning and a Kalman filter. OSA Continuum 4, 1688–1695 (2021) 2. Chen, S.W., et al.: Counting apples and oranges with deep learning: a data-driven approach. IEEE Robot. Autom. Lett. 2, 781–788 (2017) 3. Gao, F., et al.: A novel apple fruit detection and counting methodology based on deep learning and trunk tracking in modern orchard. Comput. Electron. Agric. 197, 1–11 (2022) 4. Rivas, A., Chamoso, P., González-Briones, A., Corchado, J.M.: Detection of cattle using drones and convolutional neural networks. Sensors 18 (2018). https://doi.org/10.3390/s18 072048 5. Katherine, J., Karen, B.: Detecting plant species in the field with deep learning and drone technology. Methods Ecol. Evol. 11(11), 1509–1519 (2020)

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6. Katherine, J., Karen, B.: Detection of cattle using drones and convolutional neural networks. Sensors 18(7), 1–15 (2018) 7. Sasa, S., Marina, I.: Automatic person detection in search and rescue operations using deep CNN detectors. IEEE Access 9, 37905–37922 (2021) 8. Odroid XU4, 12 May 2023. https://wiki.odroid.com/odroid-xu4/odroid-xu4 9. Intel Core I7-2600, 12 May 2023. https://www.intel.com.tr/content/www/tr/tr/products/sku/ 52213/intel-core-i72600-processor-8m-cache-up-to-3-80-ghz/specifications.html 10. Geforce GTX 1050 Ti, 12 May 2023. https://www.nvidia.com/tr-tr/geforce/10-series/#1050ti-spec

Structural and Kinematic Synthesis Algorithms of Adaptive Position-Trajectory Control Systems (In the Case of Assembly Industrial Robots) Oripjon Zaripov(B)

and Dildora Sevinova

Tashkent State Technical University, Tashkent, Uzbekistan [email protected]

Abstract. Intelligent robots and robotic technologies are widely used in the management of object processes in automated technological complexes. Their performance is directly related to the assembly-module components and kinematic pairs of the robot manipulator and the flexible industrial robot. In most studies, the kinematic issues of flexible industrial robots, dynamics and structural synthesis methods have been considered in the example of moving objects, but not enough attention has been paid to the service and control process of structural and kinematic synthesis of flexible industrial robots for adaptive position control systems. In the article, the structural and kinematic synthesis of adaptive position-trajectory control systems of moving objects is mathematically developed for the construction of a composition based on the principle of aggregate-module construction of flexible industrial robots. A structural kinematic synthesis algorithm for the composition of a flexible industrial robot manipulator as a moving object in adaptive position-trajectory control systems of moving objects has been developed, which allows structural synthesis of various industrial robots. Based on the high accuracy and speed of service of the industrial robot, the selection of the composition of the industrial robot and the kinematic synthesis scheme have been developed. Kinematic schemes based on mathematical models were developed to calculate the positional accuracy of the service time of the industrial robot. Keywords: Kinematic structure · Adaptive control · Structural synthesis · Module construction · High precision

1 Introduction Intelligent robots and robotic technologies are widely used in the management of object processes in automated technological complexes. Their performance is directly related to the assembly-module components and kinematic pairs of the robot manipulator and the flexible industrial robot. In recent years, not enough attention has been paid to the process of service and control of multiple machine tools of structural and kinematic synthesis of flexible industrial robots for adaptive position control systems [1, 2]. As an object in adaptive position-trajectory control systems of moving objects, the kinematic scheme of a flexible industrial robot manipulator can be represented by kinematic pairs © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 622–637, 2023. https://doi.org/10.1007/978-3-031-40628-7_50

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connected by rotary or prismatic links [3, 4]. The structural and kinematic synthesis of industrial robots is based on the principles of aggregate-module construction. In the adaptive position-trajectory control systems of moving objects, one of the important tasks is to choose the kinematic scheme and structure of the modular composition of the flexible industrial robot and to design the robots in mutual adjustment with the object [4, 5]. The modular construction of such a flexible industrial robot is one of the urgent tasks of solving the problem of certain lifting mechanisms, servicing of machine tools, and the structural and kinematic synthesis of several components of robots.

2 Research Methodology In order to synthesize the modular components of the industrial robot in the adaptive position-trajectory control systems of the objects, it is necessary to determine the criteria characterizing the qualitative operation of the robot with the selected structures of this object [5, 6]. In the article, we consider the structural and kinematic synthesis of adaptive positiontrajectory control systems as an iterative process that includes various stages of the construction of a flexible industrial robot. For this purpose, we need to choose the composition of intelligent industrial robots based on the principle of aggregate-module construction, structural and kinematic analysis, synthesis of the position of aggregatemodules, dynamic synthesis of kinematic schemes, and economic efficiency indicators [6, 7]. This process is called kinematic selection of the modular structure of the industrial robot assembly with adaptive position-trajectory control, kinematic calculations and structural kinematic synthesis [7, 8] and includes several stages based on the condition of maximum use of the modules of the modular industrial robot (Fig. 1). The algorithm of structural and kinematic synthesis of adaptive position-trajectory control systems of moving objects consists of the following steps: In Step 1, the number of adaptive robots used in adaptive position-trajectory control systems and the number of modules in robotic systems is selected taking into account their interconnection links and possibility [8, 9]. In Step 2, inverse problems of kinematics for modular schemes of assembly industrial robots are solved [8, 9]. In the adaptive position-trajectory control systems of moving objects, inverse problems of kinematics are solved for states and schemes: – inverse problem for the position of the manipulator with rotation of kinematic pairs; – the inverse problem for the movement speed of the manipulator with rotation of kinematic pairs; – the inverse problem of the compatibility of modules and the rotation and return movements of the manipulator [10, 11]. In Step 3, the assembly and structures of the modular parts are checked to move to the specified position of the object of manipulation in the adaptive position-trajectory control systems. In Step 4, the modular composition of the adaptive assembly industrial robot according to its trajectory movement is checked. In Step 5, in the process of determining the position of the assembly industrial robot and the stationary elements of the machine tools in the adaptive position-trajectory

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control systems, the absolute positions of the links are checked for the accuracy of the executive elements of the robot. In this case, it is based on the values of the generalized coordinates in the solution of the inverse problems seen in the second stage of the algorithm.

Fig. 1. Algorithm of structural and kinematic synthesis of the modules of the harvesting robot in terms of high accuracy and speed.

In Step 6, the generalized coordinate system of the robot with the object is checked based on the principle of building an aggregate module of the robot while moving along the trajectory and on the basis of the issues considered in the 2nd stage [12, 13]. In Step 7, the positional accuracy and kinematic structure and composition of the flexible robot are checked. The linear and angular errors detected in the working areas of the robot are compared with the permissible values determined based on the determination of the desired position. In Step 8, in the kinematic synthesis of the machine and robot components, the speed of the robot according to the generalized coordinate system is constant and is set as a technical characteristic of the robot module. Based on the established technical

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specifications, the accuracy of positional control and execution of actions is checked according to the coordinate system. In step 9, the motion trajectory calculation and high-accuracy motion speed are checked for the assembled kinematic pairs and generalized coordinates of the flexible industrial robot. Therefore, the transit time between each start and end point is calculated and the time values found are summed. However, it should be noted that the problem of transition between the initial and final coordinate system is more complicated, because it is necessary to consider inverse problems for each link and kinematic pairs seen in step 2 when moving to different trajectories [14–16]. In steps 10–11, structural and kinematic synthesis of the assembled robot assembly is carried out, and checks are completed for all stages of the algorithm and directed to the next stage of the assigned task. In steps 12–13, the configuration of the adaptive industrial robot for Fig. 2 is selected according to the most important criteria of adaptive position-trajectory control systems or several criteria, taking into account additional control parts of the object. In this case, flexible industrial robots are required to operate with high precision and speed in terms of generalized coordinates and position.

3 Analysis and Results According to the conditions of high accuracy and speed in adaptive position-trajectory control systems, it can be seen in the example of calculations on the technical characteristics of the ECR 5 assembly industrial robot (Fig. 2). Here, it is required to choose mod components based on their high accuracy and speed when servicing one-third of the machine tools [12, 16, 17]. The service time for the modular assembly №1 of the adaptive assembly industrial robot can be calculated according to the positional accuracy (Fig. 3). To do this, we write the coordinates of the handle of the robot manipulator in the following form:  xcx = R cos ϕ1 = h2 + s32 cos ϕ1 ; ycx = R sin ϕ1 =

 h2 + s32 sin ϕ1 ;

(1)

zcx = s2 . In order to determine the positional errors in the assemblies of the assembly industrial robot, we write the following expressions for the generalized coordinate system according to the law of motion of kinematics:  s3 x = h2 + s32 sin ϕ1 ϕ1 + cos ϕ1  s3 ; h2 + s32  s3 y = h2 + s32 cos ϕ1 ϕ1 + sin ϕ1  s3 ; (2) h2 + s32

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Fig. 2. a) A view of the adaptive ECR5 assembly industrial robot in a service facility; b) Schematic of selection of adaptive ECR5 assembly industrial robot configuration according to service accuracy and speed condition.

Fig. 3. Kinematic schemes for calculating service time and position-trajectory accuracy of an assembly industrial robot.

z = s2 . According to the law of motion of assembly industrial robot kinematics in composition №1, the coordinate system of the loading point on the machine tool can be considered as having the following values: xct = 0; yct = 1,8 m; zct = 1, 7 m, and from the matching condition of the field, comparing the position of this point of the robot handle and the machine, we create the following system of equations. ⎧  2 2 ⎪ ⎪ ⎨  h + s3 cos ϕ1 = 0; h = 0,5 m ; (3) h2 + s32 sin ϕ1 = 1,8; ⎪ ⎪ ⎩ s2 = 1,7 m;

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When solving this system of equations, we find the errors of the generalized coordinates based on the law of motion of kinematics for the following values: ϕ1 = 90◦ ; s3 = 1,8 m. By converting the values determined from the generalized coordinate system into pre-obtained expressions for the position verification errors and determining the translation and rotation errors from the module specifications, we find the grip errors at each link and position of the robot:   s3 s = − 0,52 + 1,82 · x = − h2 + s32 sin ϕ1 · ϕ1 + cos ϕ1  h2 + s32 1,8 · 103 0,8 = −1,35 mm. ·10 sin 90◦ + 7,2 · 10−4 + cos 90◦  0,52 + 1,82 · 103   s3 y = h2 + s32 cos ϕ1 + sin ϕ1  s3 = 0,52 + 1,82 · h2 + s32 ·103 cos 90◦ · 7,2 · 10−4 + sin 90◦ 

1,8 · 103 0,52 + 1,82 · 103

0,8 = 0,77 mm;

z = s2 = 0,4 mm. In adaptive position-trajectory control systems, the maximum positional error of the assembly industrial robot module in generalized coordinates is equal to:   ρ1 = x2 + y2 + z 2 = (−1,35)2 + 0,772 + 0,42 = 1,66 mm. In composition №2, we also accept the value of the coordinates given according to the law of motion of the loading point of the assembly industrial robot and the lathe as follows: xct = 1,8 cos 30◦ = 1,56 m; yct = 1,8 cos 120◦ = −0,9 m; zct = 1,95 m. From the condition xcx = xct , ycx = yct , zcx = zct − we write the following system of equations: ⎧ 2 2 ⎪ ⎪ ⎨  h + s3 cos ϕ1 = 1,56 m; h2 + s32 sin ϕ1 = −0,9 m; ⎪ ⎪ ⎩ z = s2 = 1,95 m.

Using this given system of equations, we find the time of movement of the generalized coordinates from the following given values based on the law of motion of kinematics: ϕ1 = −30◦ ; s3 = 1,8 m; ϕ1 = 60◦ ; s3 = 0; s2 = 0,25; t1 = 3,2 sek; t2 = 2 sek; t3 = 0 sek.

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We replace the found values of generalized coordinates with expressions for errors [12, 18]. Taking into account the extension and rotation errors, we determine the errors in the movement time according to the coordinates for each of the links:  x = − 0,52 + 1,82 · 103 sin(−30◦ ) · 7,2 · 10−4 + cos(−30◦ )  y =



1,8 · 103 0,52 + 1,82 · 103

0,8 = 1,31 mm.

0,52 + 1,82 · 103 cos(−30◦ ) · 7,2 · 10−4

1,8 · 103 + sin(−30◦ )  0,8 = 1, 5 mm. 0,52 + 1,82 · 103 z = s2 = 0,4 mm. The positional error of the module in terms of coordinates for each of the links, taking into account the translation and rotation errors in the composition №2, is equal to the following:   ρ2 = x2 + y2 + z 2 = 1,312 + 1,52 + 0,42 = 2,03 mm. According to the law of motion of kinematics in composition №3, the given coordinates of the work point of the assembly industrial robot and the table are as follows: xct = 1,3 cos 45◦ = −0,92 m; yct = −1,3 sin 45◦ = −0,92 m; zct = s2 = 1,5 m. Provided that the position of the robot handle and the position of this working point of the machine correspond to the position, we get the following system of equations: ⎧ ⎪ ⎪ h2 + s32 cos ϕ1 = −0,92 m; ⎨  h2 + s32 sin ϕ1 = −0,92 m; ⎪ ⎪ ⎩ s2 = 1,5 m. By solving this system of equations, we find the values of generalized coordinates and the time of movement by links: ϕ = 225◦ ; s2 = 1,2 m; s3 = 1,3 m; ϕ1 = 255◦ ; s2 0,75 m; s3 = 0,5 m; t1 = 4,6 sek; t2 = 3 sek; t3 = 3,5 sek. We replace the determined values of generalized coordinates with expressions for determining the error of the robot module. Taking into account the extension and rotation errors, we can determine the modulus errors for each of the links:  x = − 0,52 + 1,32 · 103 sin 225◦ · 7,2 · 10−4 + cos 225◦ 

1,3 · 103 0,52 + 1,32 · 103

0,8 = 0,15 mm;

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 y = − 0,52 + 1,32 · 103 cos 225◦ · 7,2 · 10−4 1,3 · 103 + sin 225◦  0,8 = −1,19 mm; 0,52 + 1,32 · 103 z = s2 = 0,4 mm. The error of the robot module, taking into account the transmission and module rotations, in the table assembly №3 is as follows:   ρ3 = x2 + y2 + z 2 = 0,152 + (−1,19)2 + 0,42 = 1,38 mm. Also, in this composition, the error of the average position determined by the robot in serving the object is equal to the following: ρaverage =

3 

ρi /3 = (1,6 + 2,03 + 1,38)/3 = 1,67 mm.

1

The total service time of the object is 7,8 h [12, 19]. The calculation of the positional accuracy of the assembly robot for assembly №2 is carried out by Fig. 3b. The values of positioning errors in the generalized coordinate system are obtained from the specifications of the robot components and modules: x = s1 = 0,4 mm; y = s2 = 0,8 mm; z = s2 = 0,8 mm. The average error found in the calculation of position accuracy is ρaverage = 0,89 mm. As the robot is outside the service area of the assembly №2, it is not possible to determine the desired position, and the robot cannot perform maintenance on this section. It is carried out by calculating the positional accuracy of the robot according to the generalized coordinate system for composition №3 (Fig. 3-c). Here we write the coordinate system of the robot handle as follows: xcx = [l2 cos ϕ2 + l3 cos(ϕ2 + ϕ3 )] cos ϕ1 ; ycx = [l2 cos ϕ2 + l3 cos(ϕ2 + ϕ3 )] sin ϕ1 ;

(4)

zcx = h1 + l sin ϕ2 + l3 [sin(ϕ2 + ϕ3 )]. To determine position errors, the expression is written in the form of generalized coordinates: x = − sin ϕ1 ϕ1 [l2 cos ϕ2 + l3 cos(ϕ2 + ϕ3 )] + cos ϕ1 [−l2 cos ϕ2 ϕ2 − l3 sin(ϕ2 + ϕ3 )(ϕ2 + ϕ3 )]; y = cos ϕ1 ϕ1 [l2 cos ϕ2 + l3 cos(ϕ2 + ϕ3 )] + sin ϕ1 [−l2 sin ϕ2 ϕ2 − l3 sin(ϕ2 + ϕ3 )(ϕ2 + ϕ3 )]; z = l2 cos ϕ2 ϕ2 + l3 cos(ϕ2 + ϕ3 )((ϕ2 + ϕ3 ).

(5)

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According to the law of motion of kinematics in composition №1, the coordinates given by the law of motion of the assembly industrial robot and the working point of the machine tool are as follows: xct = 0; yct = 1,7 m; zct = 1,7 m. xct = xcx , yct = ycx , zct = zcx − we get the following system of equations from the matching condition of the coordinates: ⎧ ⎨ [l2 cos ϕ2 + l3 cos(ϕ2 + ϕ3 )] cos ϕ1 = 0; [l cos ϕ2 + l3 cos(ϕ2 + ϕ3 )] sin ϕ1 = 1,7; ⎩ 2 h1 + l2 sin ϕ2 + l3 sin(ϕ2 + ϕ3 ) = 1,7, where ϕ2 = ±45◦ ; ϕ3 = ±112◦ . Also, the found values of the generalized coordinates are changed to the following expressions for the position determination errors, and here, taking into account the errors of the modules, we determine the module errors for each link: x = − sin 90◦ · 7,2 · 10−4 [700 cos(−45◦ ) + 1300 cos(112 − 45)◦ ] = −0,72 mm; y = sin 90◦ [−700 sin(−45◦ ) · 7,2 · 10−4 −1300 sin(112 − 45)◦ (7,2 · 10−4 + 7,2 · 10−4 )] = −1,37 mm; z = 700 cos(−45◦ )7,2 · 10−4 + 1300 cos(112 − 45)◦ (7,2 · 10−4 + 7,2 · 10−4 )] = 1,09 mm. The determined error of the module in the generalized coordinate system according to the law of motion of kinematics is as follows:   ρ x2 + y2 + z 2 = (0 − 72)2 + (−137)2 + (1,09)2 = 1,9 mm. According to the law of motion of kinematics in composition №2, the given coordinates of the working point of the robot and the machine tool are equal to the following: xct = 17 cos 30◦ = 1,47 mm; yct = 1,7 cos 60◦ = −0,85 m; zct = 1,95 m. xct = xcx , yct = ycx , zct = zcx − we get the following system of equations from the matching condition of the coordinates: ⎧ ⎨ [l2 cos ϕ2 + l3 cos(ϕ2 + ϕ3 )] cos ϕ1 = 1,47; [l cos ϕ2 + l3 cos(ϕ2 + ϕ3 )] sin ϕ1 = −0,85; ⎩ 2 h1 + l2 sin ϕ2 + l3 [sin(ϕ2 + ϕ3 )] = 1,95. where ϕ1 = −30◦ , ϕ1 = 120◦ , t1 = 3,2 sek. The angles ϕ2 and ϕ3 are expressed in the following form: ϕ2 = ±45◦ ; ϕ3 = ±112◦ ; ϕ2 = ±90◦ ; ϕ3 = ±90◦ ; t2 = 6 sek; t3 = 4,5 sek.

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The error values for each link in the generalized coordinate system are determined by the following expression: x = − sin(−30◦ )7,2 · 10−4 [700 cos(−45◦ ) + 1300 cos(112 − 45)◦ ] + cos(−30◦ )[−700 sin(−45◦ )7,2 · 10−4 − 1300 sin(112 − 45)◦ (7,2 · 10−4 + 7,2 · 10−4 )] = −0,82 mm; y = cos(−30◦ )7,2 · 10−4 [700 cos(−45◦ ) + 1300 cos(112 − 45)◦ ] + sin(−45◦ )[700 sin(−45◦ )7,2 · 10−4 − 1300 sin(112 − 45)◦ (7,2 · 10−4 + 7,2 · 10−4 )] = 1,56 mm; z = 700 cos(−45◦ )7,2 · 10−4 + 1300 cos(112 − 45)◦ (7,2 · 10−4 + 7,2 · 10−4 ) = 1,09 mm. The module error in each link of the robot assembly in the generalized coordinate system is as follows:  ρ2 = (−82)2 + 1,562 + 1,092 = 2,08 mm. According to the law of motion of kinematics in composition №3, the given coordinates of the working point of the robot and the machine are as follows: xct = −0,92 m; yct = −0,92 m; zct = 1,5 m. xct = xcx , yct = ycx , zct = zcx − here we also get the following system of equations from the condition of matching coordinates: ⎧ ⎨ [l2 cos ϕ2 + l3 cos(ϕ2 + ϕ3 )] cos ϕ1 = −0,92; [l cos ϕ2 + l3 cos(ϕ2 + ϕ3 )] sin ϕ1 = −0,92; ⎩ 2 h1 + l2 sin ϕ2 + l3 [sin(ϕ2 + ϕ3 )] = 1,5. where ϕ1 = 45◦ ; ϕ1 = 75◦ , t1 = 2,8 sek. The values of the angles ϕ2 and ϕ3 in generalized coordinates are as follows: ϕ2 = 75◦ ; ϕ3 = 75◦ ; ϕ2 = 30◦ ; ϕ3 = 37◦ ; t2 = 2,8 sek; t3 = 3 sek. The value of errors in each of the links is expressed by the following relation: x = − sin 45◦ · 7,2 · 10−4 [700 cos 45◦ + 1300 cos(75◦ + 75◦ )] + cos 45◦ [−700 sin 75◦ · 7,2 · 10−4 − 1300 sin(75◦ + 75◦ )14,4 · 10−4 = −0,517 mm; y = cos 45◦ · 7,2 · 10−4 [700 cos 75◦ + 1300 cos(75◦ + 75◦ )] + sin 45◦ [ − 700 sin 75◦ · 7,2 · 10−4 − 1300 sin(75◦ + 75◦ )14,4 · 10−4 ] = −1,48 mm;

z = 700 cos 75◦ · 7,2 · 10−4 + 1300 cos 150◦ · 10−4 = −1,49 mm.

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The module error of the assembly industrial robot in the composition №3 in terms of generalized coordinates is as follows:  ρ3 = (−0517)2 + (−1,48)2 + (−1,49)2 = 2,16 mm. The average value of the module error in each link of the robot assembly in the generalized coordinate system is: ρaverage =

3 

ρ1 /3 = (1,9 + 2,08 + 2,16)/3 = 2,05 mm.

1

The total service time of the object is 9 h. Calculation of the position and high accuracy of the robot assembly №4 and service time (Fig. 3, d) is increased by [12, 20]. Let’s write the coordinates of the handle for this case: xcx = s2 cos ϕ2 cos ϕ1 ; ycx = s3 cos ϕ2 sin ϕ1 ; zcx = h1 + s3 sin ϕ2 ;

(6) h1 = 0,73 m.

Determining errors in the position and accuracy of the robot assembly in the generalized coordinate system is carried out by the following expressions: y = s3 cos ϕ2 sin ϕ1 − s3 sin ϕ2 ϕ2 sin ϕ1 − s3 cos ϕ2 cos ϕ1 ϕ1 ; x = s3 cos ϕ2 sin ϕ1 − sin ϕ2 ϕ2 s3 cos ϕ1 − sin ϕ1 ϕ2 s3 cos ϕ1 ; z = s3 sin ϕ2 + s3 cos ϕ2 ϕ2 . xct = xcx , yct = ycx , zct = zcx − here we also get the following system of equations from the condition of matching coordinates: ⎧ ⎨ s3 cos ϕ2 cos ϕ1 = 0; s cos ϕ2 sin ϕ1 = 1,8; ⎩ 3 0,73 + s3 sin ϕ2 = 1,7. By solving this system of equations, we consider the values of the generalized coordinates according to the law of motion of kinematics [21–24] to be given as follows: ϕ1 = 90◦ ; ϕ2 = 28◦ ; s3 = 2.05 m. The value of the errors in each of the links according to the generalized coordinates is as follows: x = − sin 90◦ · 7,2 · 10−4 · 2,05 · 103 cos 28◦ = 1,3 mm; y = 0,8 cos 28◦ · sin 90◦ − 2,05 · 103 sin 28◦ · 7,2 · 10−4 sin 90◦ = 0,01 mm; z = 0,8 sin 28◦ + 2,05 cos 28◦ · 7,2 · 10−4 = 1,67 mm.

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According to the law of motion of kinematics, the module error of the robot assembly in generalized coordinates is equal to:  ρ1 = 1,32 + 0,012 + 1,672 = 2,12 mm. Let’s write a system of equations for the generalized coordinate system of all the compositions seen above: ⎧ ⎨ s3 cos ϕ2 cos ϕ1 = 1,56; s cos ϕ2 sin ϕ1 = −0,9; h = 0,73 m. ⎩ 3 0,73 + s3 sin ϕ2 = 1,95; The solution to this system ϕ1 = −30◦ ; ϕ2 = 34◦ ; s3 = 2,16 m; ϕ1 = 120◦ ; ϕ1 = 6◦ ; s3 = 0,11 m; t1 = 2,8 sek; t2 = 0,1 sek; t3 = 0,15 sek. Error values for each of the links in the robot assembly: x = 0,8 sin 34◦ · cos(−30◦ ) − sin 34◦ · 7,2 · 10−4 · 2,16 · 103 cos(−30◦ ) − sin(−30◦ ) − 7,2 · 10−4 · 2,16 · 103 cos 34◦ = 0,47 mm; y = 0,8 cos 34◦ sin(−30◦ ) − 2,16 · 103 cos 34◦ · 7,2 · 10−4 sin(−30◦ ) + 2,16 · 103 cos 34◦ · cos(−30◦ ) · 7,2 · 10−4 = 1,22 mm; z = 0,8 sin 34◦ + 2,16 · 103 cos 34◦ · 7,2 · 10−4 = 1,74 mm. The module error of the assembly industrial robot assembly according to the given coordinate system is equal to the following:   ρ2 = x2 + y2 + z 2 = 0,472 + 1,222 + 1,742 = 2,18 mm. Using the following system of equations for generalized coordinates ⎧ ⎨ s3 cos ϕ2 cos ϕ1 = −0,92; s cos ϕ2 sin ϕ1 = −0,92; ⎩ 3 0,73 + s3 sin ϕ2 = 1,5. given that we find the following linear and angular values: ϕ1 = 225◦ ; ϕ2 = −30◦ ; s3 = 1,5 m; ϕ1 = 225◦ ; ϕ2 = 64◦ ; s3 = 0,66 m; t1 = 3,7 sek; t2 = 4,3 sek; t3 = 3,7 sek. The error values for each link according to the generalized coordinates are equal to the following: x = 0,8 cos(−30◦ ) cos 225◦ − sin(−30◦ ) · 7,2 · 10−4 · 1,5 · 103 cos 225◦ − sin 225◦ · 7,2 · 10−4 · 1,5 · 103 cos(−30◦ ) = −0,21 mm;

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y = 0,8 cos(−30◦ ) sin 225◦ − 1,5 · 103 sin(−30◦ ) · 7,2 · 10−4 sin 225◦ + 1,5 · 103 cos(−30◦ ) · cos 225◦ · 7,2 · 10−4 = −1,53 mm. z = 0,8 sin(−30◦ ) + 1500 cos(−30◦ ) · 7,2 · 10−4 = 0,54 mm. Modulus error for each link in generalized coordinates:  ρ3 = (−0,21)2 + (−1,53)2 + 0,542 = 1,64 mm. The average value of the module error for each link: ρaverage =

3 

ρi /3 = (2,12 + 2,18 + 1,64)/3 = 1,98 mm.

1

The total service time of the facility is T = 7,1 h. According to the service accuracy and speed condition, the selection of the industrial robot composition and the calculation results of the industrial robot service time positional accuracy can be written as follows, and the service time positional accuracy of PUMA or SCARA robots of the same appearance can be compared as shown in Table 1. Table 1. Results of positional accuracy of industrial robot in service. ECR 5 robot composition

№1

№2

№3

№4

Unit of measure

ρ (lathe №1) 1,6

0,89

1,9

2,12

mm

ρ (lathe №2) 2,03

0,89

2,16

1,64

mm

ρ (lathe №3) 1,38

0,89

2,16

1,64

mm

ρaverage

1,67

0,89

2,05

1,98

mm

PUMA robot composition

№1

№2

№3

№4

Unit of measure

ρ (lathe №1)

1,8

0,89

1,9

2,15

mm

ρ (lathe №2)

2,05

0,9

2,16

1,68

mm

ρ (lathe №3)

1,46

0,89

2,26

1,64

mm

ρaverage

1,87

0,89

2,09

2,08

mm

SCARA robot composition

№1

№2

№3

№4

Unit of measure

ρ (lathe №1)

1,8

0,89

1,9

2,15

mm

ρ (lathe №2)

2,05

0,9

2,16

1,68

mm

ρ (lathe №3)

1,46

0,89

2,26

1,64

mm

ρaverage

1,87

0,89

2,09

2,08

mm

Structural and Kinematic Synthesis Algorithms of Adaptive Position

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Analyzing the results of the obtained calculation and the comparison of industrial robots based on Table 1, we can conclude that the determination of the smallest average positional error of the ECR 5 industrial robot for robot assembly №. 2 is slightly greater than that for robot assembly №1. It can be seen that the compositions of robots №3 and №4 are the same. Based on the calculation results and the comparison results of human robots, the positional accuracy of the service time of the ECR 5 industrial robot is considered more reliable.

4 Conclusion In the article, as an example of structural and kinematic synthesis of adaptive positiontrajectory control systems of moving objects, an algorithm of structural and kinematic synthesis of intelligent flexible industrial robots based on the principle of aggregatemodule construction is developed. A method for solving the direct kinematic equation and kinematic schemes are proposed through a systematic, general approach based on the selection of an industrial robot assembly based on service accuracy and speed conditions and mathematical models. In order to calculate the positional accuracy of the service time of the industrial robot, the service time of the robot components through kinematic schemes and the speed and accuracy of the service time of the generalized object are considered. It can be seen from the calculation methods that according to the law of motion of the kinematics, the average errors of the positional accuracy of the service time of the assembly industrial robot according to the generalized coordinates differ. Structural and kinematic synthesis of industrial robots with adaptive positional control, based on the principle of aggregate-module construction, allows to perform positionaltrajectory movements with high accuracy and speed. The given calculation results serve to choose the correct robot composition in automated control objects.

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Author Index

A Aksonov, Oleksandr 514 Aleksenko, Borys A. 237 Alieksieiev, Volodymyr 1 Apostolescu, Tudor Catalin

E Edl, Milan 117 El Abdi, Rochdi 127 Ermolai, Vasile 135 78, 328

B Babenko, Volodymyr 286 Badea, Cristian-Radu 17, 42 Badea, Florentina 17, 42 Badea, Sorin-Ionut 17, 42 Bairachnyi, Volodymyr 541 Barakhov, Kostiantyn 456 Baranov, Viacheslav 117 Basova, Yevheniia 66, 237 Baydullayev, Azamat 308 Begmamat, Dushanov 104, 111 Berlizeva, Tatyana 604 Bogatu, Lucian 78, 328 Bogorin-Predescu, Adrian 490 Borysenko, Anatolii 566, 586 C Cananau, Sorin 345 Caraiman, Cosmina-Constantina 374 Cartal, Laurentiu Adrian 78 Chiriac, Oana Andreea 385 Chirit, a˘ , Ionel 173 Cris, an, Ramona-Gabriela 374 D Daniel, Lipcinski 173, 186 Davydov, Denis 318 Diana-Mura, Badea 56 Dmytriienko, Olha 66 Dobrotvorskiy, Sergey 237 Dobrovolska, Ludmila 237 Dontu, Grigore Octavian 345 Dotsenko, Vladimir 155

G Gamazeliuc, George 147 Gasanov, Magomediemin 566, 586 Gnytko, Oleksandr 155 Grabovskiy, Andriy 504 Grigorescu, Adriana 17, 42 Gusan, Vasile 469 Gut, u, Mihai 173 H Havryliuk, Yurii 201 Heiden, Bernhard 1 Hošek, Jan 164 Hrechka, Iryna 504 I Igamberdiyev, Husan 426 Ilie, Cristinel 173, 186 Ionascu, Georgeta 78, 328 Ismatov, Abdikhalil 308 K Khalilovna, Makhmudova Naima 297 Khasanov, Jamshidbek 216 Khasanov, Otabek 308 Kholmirzaev, Nozimjon 216 Khoroshylov, Oleg 224, 604 Khusanov, Suban 426 Kombarov, Volodymyr 514 Kondratiyk, Oleg 224 Korniienko, Volodymyr 201 Ko´sci´nski, Mikołaj 237 Kotliar, Alexey 117 Kovalenko, Valentyn 1 Koveza, Yurii 155

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 D. D. Cioboatˇa (Ed.): ICoRSE 2023, LNNS 762, pp. 639–641, 2023. https://doi.org/10.1007/978-3-031-40628-7

640

Kozhushko, Andrii 253 Krivileva, Svetlana 263 Krol, Oleg 272 Kurennov, Sergei 456 Kuznetsova, Anna 155 L Lavrova, Inna 286 Lincaru, Cristina 17, 42 Litovchenko, Petro 201 Lukianov, Ihor 604 Lytvyn, Vasyl 541 M Manea, Elena 328 Manoilo, Eugenia 318 Manoilo, Yurii 318 Mardonov, Umidjon 308 Mardupenko, Oleksii 532 M˘arg˘aritescu, Mihai 147 Maryna Ivanova, 201 Masikevych, Andrij 541 Moiseev, Viktor 318 Moraru, Edgar 328, 345 Moskovska, N. 363 Munteanu, Iulian Sorin 374 Myronov, Kostiantyn 66 N Naboka, Olena 566, 586 Nedelcu, Adrian 173, 186 Niculae, Elisabeta 374 Nit, u, Constantin 385 P Pavlova, Natalia 586 Pershyna, Iuliia 393 Pinto, R. Leite 127 Pîrciog, Sperant, a 17, 42 Plankovskyy, Sergiy 514 Pliuhin, Vladyslav 514 Podoljak, Oleg 224 Ponomarenko, Olga 224, 604 Ponomarova, Nataliia 263 Pop, Alina Bianca 469 Popa, Marius 173, 186 Prykhodko, Vadym 237

Author Index

R Rea, Pierluigi 405 Repko, Kalif 318 Rezvaya, Kseniya 66, 532 Rizescu, Ciprian Ion 385, 418 Rizescu, Dana 418 Rolea, Eulampia 147 Rubashka, Volodymyr 1 Rudnev, Aleksandr 117 Ruggiu, Maurizio 405 S Sadikova, Nargiza 216 Saidkhodjaeva, Shokhista 216 Saidmakhamadov, Nosir 216 Sanjarbek, Bekturdiyev 104, 111 Sergienko, Nikolay 566 Sevidova, Elena 117 Sevinov, Jasur 426 Sevinova, Dildora 622 Shohrukh, Narzullayev 104, 111 Sinkevych, Iryna 532 Skorkin, Anton 224 Skvorchevsky, Alexander 440 Slipchenko, Serhii 201 Smetankina, Natalia 456 Sokolov, Vladimir 272 Sorin, Badea 374 Sover, Alexandru 135 Stanescu, Vlad-Andrei 345 Stepanov, Mykhaylo 201 Sychov, Yuriy 224 T Tanase, Nicolae 173, 186 Terletskyi, Oleksandr 554 Titarenko, Oksana 117 T, ît, u, Aurel Mihail 469, 490 Tkachuk, Hanna 504 Tkachuk, Mykola 504 Tsegelnyk, Yevgen 514 Tudose, Gabriela 42 Tulska, Alona 532 Turakhodjaev, Nodir 216 U Udrea, Ioana 78 Uhryn, Dmytro 541

Author Index

Ulerich, Oliver 147 Ulu, Burak 616 Umidjon, Khamrokulov 104, 111 Ungureanu, Liviu Marian 374 Ushenko, Yuriy 541 Utkirjon, Ubaydullayev 104, 111

V Vakal, Viktoriia 532 Valentina-Daniela, Bajenaru 56 Vladymyrenko, Vladyslava 286 Vorobyov, Mikhailo 604 Vorontsov, Serhii 66

641

Y Yascheritsin, Eugene 554 Yenikieiev, Oleksandr 566, 586 Yepifanov, Vitalii 237 Yevsyukova, Fatima 566, 586 Yevtushenko, Nataliia 224, 604 Yevtushenko, Stepan 604 Yıldırım, Sahin ¸ 616 Yurchenko, Oleksandr 117 Z Zakharenkov, Dmytro 566, 586 Zakovorotniy, Alexander 263 Zaripov, Oripjon 622