CHATTERING ANALYSIS of the SYSTEM with HIGHER ORDER SLIDING MODE CONTROL THESIS Presented in Partial Fulfillment of the Requirem
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CHATTERING ANALYSIS OF THE SYSTEM WITH HIGHER ORDER SLIDING MODE CONTROL THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Abdalla Swikir Graduate Program in Electrical and Computer Engineering The Ohio State University 2015 Master's Examination Committee: Prof. Vadim I. Utkin, Advisor Prof. Lisa Fiorentini Copyright by Abdalla Swikir 2015 Abstract Sliding mode control methodology (SMC) is considered as an efficient technique in several aspects for control systems. Nevertheless, applying first-order sliding mode control method in real-life has what so-called chattering phenomenon. Chattering is a high frequency movement that makes the state trajectories quickly oscillating around the sliding surface. This phenomenon may lead to degrade the system effectiveness, or even worst it may lead to fast damage of mechanical parts of the system. Presently, the major solutions to this drawback are asymptotic observers and high-order sliding mode control. The higher order sliding mode control is an expansion of the conventional sliding mode, and it can cancel the imperfection of the conventional sliding mode methodology and sustain its advantages. Since the second-order sliding mode controller, for example, super twisting algorithm, has unsophisticated construction and requires a lesser amount of acquaintance, it is the most extensively technique that used in the higher order sliding mode methodology. However, in several cases, the chattering amplitude result from conventional method is less than the one result from super twisting algorithm. In this thesis, the describing function method, most suitable technique to analyze nonlinear systems, is used to make comparison between the two methods, the conventional and the super twisting sliding mode control. A simulation is performed to confirm the results that describing function method shows. Several situations illustrate the efficiency of first order sliding mode control over the higher order sliding mode control are represented. ii Dedication I wish to dedicate this thesis to my family: My wife Fatma My son Mohammed My son Mahmud My mother, my father, my brothers, my sisters, and my friends. iii Acknowledgments First and Foremost, I would like to thank Allah, the Almighty, for having given me courage, power, and the strength to pursue this degree. I would like to offer my deepest gratitude to my family for their unending love and support; this thesis could not have been done without them. Special thanks go to my loving and supportive wife, Fatma Algowify. I am also grateful to my wife’s family for their support. A special thanks to my older brother, Aiman Swikir, for his continuous support. I would like to express my thanks to my friends in USA and my friends in Libya. I wish to thank all those who helped me complete my M.S. I want to extend my deepest thanks to my teacher and friend Abd Almula Gebreel and his family, thank you for your endless love, support, and for being my inspiration. Finally, my sincere gratitude goes to my advisor Prof. Vadim I. Utkin for his unlimited support, motivation, enthusiasm, patience, and immense knowledge. His instruction helped me in all the time of my master study. I cannot imagine having a better advisor than Prof. Utkin. Besides my advisor, I would like to thank Prof. Lisa Fiorentini to her guidance and helpful notes. iv Vita January 22, 1986 ...........................................………………Born – EL-BIEDA – LIBYA August 2008 ………………………………………………..B.S. Electrical Engineering, Omar Al-Mukhtar University EL-BIEDA - LIBYA October 20010 – December 2012 ………………………….. Teaching Assistance Omar Al-Mukhtar University EL-BIEDA – LIBYA May 2014-Present …………………………………………. M.S student Dept. Electrical & Computer Eng. The Ohio State University Columbus, OH, USA Fields of Study Major Field: Electrical and Computer Engineering v Table of Contents Abstract ............................................................................................................................... ii Dedication ......................................................................................................................... iiii Acknowledgments............................................................................................................. iiv Vita ...................................................................................................................................... v List of Figures .................................................................................................................... ix List of Tables .................................................................................................................... xii Chapter 1: Introduction ...................................................................................................... 1 1.1 Sliding Mode Control (overview) ................................................................................. 1 1.2 The Chattering Problem ................................................................................................ 7 1.2.1 Causes of Chattering .............................................................................................. 7 1.2.2 Solutions for Chattering Problem ........................................................................... 8 1.2.2.1 Boundary Layer Solution................................................................................. 9 1.2.2.2 Observer-Based Solution................................................................................ 10 1.2.2.3 State-Dependent Gain Solution ..................................................................... 10 1.2.2.4 Equivalent Control-Dependent Gain Solution ............................................... 11 Chapter 2: Higher Order Sliding Mode ............................................................................ 13 vi 2.1 Introduction ................................................................................................................. 13 2.2 Second Order Sliding Mode Algorithms .................................................................... 14 2.2.1 Twisting Algorithm .............................................................................................. 14 2.2.2 Sub-Optimal Algorithm........................................................................................ 16 2.2.3 Super Twisting Algorithm .................................................................................... 17 Chapter 3: Describing Function Method (overview) ........................................................ 20 3.1Introduction .................................................................................................................. 20 3.2 Types ........................................................................................................................... 20 3.2.1 Single-sinusoid Input Describing Function (SIDF) ............................................. 22 3.2.2 Two-sinusoid Input Describing Function (TSIDF) .............................................. 27 3.2.3 Random Input Describing Function (RIDF) ........................................................ 28 Chapter 4: analysis of conventional and super twisting sliding mode control ................. 31 4.1Introduction .................................................................................................................. 31 4.2 Part one: The disturbance .............................................................................. 31 4.2.1 Analysis of conventional sliding mode control .................................................... 31 4.2.2 Analysis of super twisting sliding mode control .................................................. 34 4.3 Part two: The disturbance .............................................................................. 44 4.3.1 Analysis of conventional sliding mode control .................................................... 44 4.3.2 Simulation for conventional and super twisting methods .................................... 50 vii Conclusion ........................................................................................................................ 58 Bibliography ..................................................................................................................... 60 viii List of Figures Figure 1.1: sliding mode along the intersection of multiple discontinuity surfaces ........... 4 Figure 2.1. Phase trajectory of Twisting algorithm .......................................................... 15 Figure 2.2. Phase trajectories of Sub-optimal algorithm .................................................. 16 Figure 2.3. Phase trajectory of Super-twisting algorithm ................................................. 17 Figure 3.1 General nonlinear control system .................................................................... 25 Figure 4.1 Simplified representation of CSMC scheme ................................................... 32 Figure 4.2 Chattering amplitude (A) and frequency (w) VS the unmodeled dynamic μ for CSMC ............................................................................................................................... 34 Figure 4.3 Simplified representation of STSMC scheme ................................................. 35 Figure 4.4 Simplified representation of STSMC scheme after applying the describing function. ...........................................................................................................................