Design and Control of Lower Limb Assistive Exoskeleton for Hemiplegia Mobility by Abdullah Khaled Alshatti A thesis submitted to the University of Sheffield for the degree of Doctor of Philosophy Department of Automatic Control and Systems Engineering The University of Sheffield Mappin Street, Sheffield, S1 3JD United Kingdom August 2019 Abstract Mobility is one of the most vital abilities for human being that enables her/him to preserve independence while performing physical daily life activities. Currently, exoskeletons are considered as significant addition to the assistive technology, in which interest has been intensified in the last decade. There are many challenges related to assistive robotics developments such as safety, efficient power source, lightweight design and affordability. This research aims to develop assistive exoskeleton system to support hemiplegic patient mobility. The developments involve designing humanoid and exoskeleton models in MSC. VisualNastran and implementing a control strategy in MATLAB Simulink to control the active joint trajectories of the humanoid lower limbs and exoskeleton models according to predefined joint angle position for walking, standing up and sitting down motions. Two types of control methods are considered in this research to control the humanoid and exoskeleton models while simulating the assistance mechanism for the designated mobility task. The control methods are Proportional Integral Derivative (PID) and fuzzy- based Proportional Derivative (PD) controllers. Moreover, Spiral Dynamic Algorithm (SDA) optimisation approach is used to tune the controller’s parameters. Evaluation of the developed controllers is based on a comparative assessment of the obtained simulation results and examining the dynamics of the models. The controller with optimum performance is verified by subjecting the humanoid and exoskeleton models to disturbance forces, constant loads and different speeds of motion cycles. It is demonstrated that the objectives of this research are fulfilled, and the exoskeleton is capable to provide the humanoid with the necessary assistance under different conditions. i Acknowledgments All thanks and praises be for Allah s.w.t, for allowing me to achieve this goal, and awarded me health and strength during the course of this research. My appreciation to my supervisor Professor M. O. Tokhi for his priceless support. It would have been difficult for me to complete this work without his motivation, time, efforts and helpful guidance throughout this research. A special thanks to my research colleagues for their continuous help and support especially those in room 307. Thanks to my employee ministry of defence, the government of Kuwait for sponsoring my PhD study and gave me the opportunity to be here. My outmost appreciation to my parents, wife, sons and family for their sacrifices and moral encouragement. ii Table of Contents Abstract ................................................................................................................................. i Acknowledgments ............................................................................................................... ii Table of Contents .............................................................................................................. iii List of figures ...................................................................................................................... vi List of tables ........................................................................................................................ ix Abbreviations ....................................................................................................................... x Chapter 1: Introduction ...................................................................................................... 1 1.1 Background and motivation ........................................................................................ 1 1.2 Hemiplegia .................................................................................................................. 2 1.3 Lower limb joints ........................................................................................................ 5 1.3.1 Hip ........................................................................................................................ 5 1.3.2 Knee ..................................................................................................................... 6 1.3.3 Ankle .................................................................................................................... 7 1.4 Aim and Objectives of the research ............................................................................ 7 1.5 Contributions ............................................................................................................... 9 1.6 Thesis outline ............................................................................................................ 10 Chapter 2: Exoskeleton systems ....................................................................................... 12 2.1 Exoskeletons and wearable robots ............................................................................ 12 2.1.1 Lower extremity exoskeleton and human biomechanics ................................... 14 2.2 Exoskeleton design considerations ............................................................................ 17 2.2.1 Exoskeleton frame and material ......................................................................... 17 2.2.2 Actuators ............................................................................................................ 18 2.2.3 Sensors ............................................................................................................... 19 2.2.4 Power supply ...................................................................................................... 21 2.2.5 Control strategy .................................................................................................. 22 2.3 Lower limb exoskeleton ............................................................................................ 26 iii 2.4 Summary ................................................................................................................... 31 Chapter 3: Modelling of humanoid and single leg exoskeleton .................................... 32 3.1 Introduction ............................................................................................................... 32 3.2 SOLIDWORKS ......................................................................................................... 33 3.3 MSC. visualNastran 4D (MSC.vN4D) ...................................................................... 33 3.4 Model Design ............................................................................................................ 36 3.4.1 Humanoid ........................................................................................................... 36 3.4.2 Exoskeleton ........................................................................................................ 39 3.4.3 Models integration in MSC.vN4D and MATLAB Simulink ............................. 43 3.4.4 Humanoid and exoskeleton models validation ................................................... 45 3.5 Summary ................................................................................................................... 47 Chapter 4: Control strartegy of the humanoid and single leg exoskeleton .................. 48 4.1 Introduction ............................................................................................................... 48 4.2 Control strategy ......................................................................................................... 48 4.2.1 PID controller ..................................................................................................... 50 4.2.2 Fuzzy logic control ............................................................................................. 53 4.2.3 Proportional-Derivative based Fuzzy control .................................................... 60 4.2.4 Spiral dynamic optimisation algorithm .............................................................. 61 4.3 Summary ................................................................................................................... 66 Chapter 5: Control of assistive single leg exoskeleton and humanoid for walking mobility ............................................................................................................................... 67 5.1 Introduction ............................................................................................................... 67 5.2 Cycle of human gait .................................................................................................. 67 5.3 Implementation of closed-loop PID control .............................................................. 71 5.3.1 Humanoid model control .................................................................................... 72 5.3.2 Control of humanoid and exoskeleton with SDA tuned PID parameters .......... 78 5.4 Implementation of fuzzy-based PD controller .......................................................... 85 5.4.1 SDA optimisation of PD-fuzzy scaling parameters ........................................... 88 5.4.2 Simulation with different gait speeds ................................................................