Nonlinear robust controller design for an upper limb rehabilitation robot via variable gain super twisting sliding mode

Mirrashid, Naghmeh; Alibeiki, Esmail; Rakhtala, Seyed Mehdi

Abstract

Rehabilitation robots have an effective role in helping patients with physical disabilities. Therefore, improving their performance is very important. In this paper, a robust nonlinear controller is proposed for the upper limb rehabilitation robot. The proposed controller has time-varying gains, which this property allows the gains to be adjusted online to external disturbances. The variable gain super twisting algorithm (VGSTA) controller is designed based on Lyapunov stability analysis, and the variable gains of the controller are determined by examining the bounds of the perturbation. Also, the convergence time is calculated. To demonstrate the desired performance of the VGSTA controller, it is compared with the fixed gain super-twisting controller and PID controller. The results show that the proposed controller ensures accurate tracking, finite-time convergence, robustness against uncertainty, internal (external) perturbations with an unknown bound, reduced chattering, and stability. The simulation results show that minimum values of RMS, Mean, and Sd of tracking error in different conditions correspond to the VGSTA controller.

• Journal Article Type: Article
• Acceptance Date: Nov 28, 2021
• Online Publication Date: Mar 18, 2022
• Publication Date: Dec 31, 2022
• Deposit Date: Aug 15, 2023
• Journal: International Journal of Dynamics and Control
• Print ISSN: 2195-268X
• Electronic ISSN: 2195-2698
• Publisher: Springer Verlag
• Peer Reviewed: Peer Reviewed
• Volume: 10
• Issue: 6
• Pages: 1996-2010
• DOI: https://doi.org/10.1007/s40435-021-00902-4
• Public URL: https://uwe-repository.worktribe.com/output/11001564