Whale Optimization Algorithm Enhances the Performance of Knee-Exoskeleton System Controlled by SMC

Abstract

Physiotherapeutic exoskeleton devices have recently been developed to help people rehabilitate impaired limb mobility and replace the use of physiotherapists. Such systems are characterized by high nonlinear and time-varying coefficients. In order to cope with such difficult control challenges, a need arose for reliable nonlinear controllers. While in this study the Sliding Mode Control (SMC) was used to track the trajectory of the knee exoskeleton-system (KES) while having parameter uncertainty. In addition, the whale optimization algorithm (WOA) was introduced and developed to adjust the thickness design parameters for further optimization of its performance. The simulation was performed on a calculator using the MATLAB-Simulink program to conduct a comparative study between the optimal and Classical SMC where the results of comparison with the test parameters used by the SMC showed, the results of the proposed optimal SMC revealed that the positioning inaccuracy of the knee increased by 31.8807% and it follows from this result that the controller could successfully perform tracking the track well. Also, the control system created at the optimal thickness has a better dynamic performance than the classical thickness. Index Terms— Optimal, Knee exoskeleton system, Whale optimization approach, Sliding mode control.