Robust Non-Singular Terminal Sliding Mode Control for Tendon-driven Hand Exoskeleton: A Numerical Study

This study addresses the challenge of hand rehabilitation, especially for those with neuromuscular impairments, by proposing a tendon-driven soft hand exoskeleton with a robust control scheme. We introduce a novel non-singular terminal sliding mode (NSTSM) control approach tailored for tendon-driven hand exoskeletons. This control strategy enhances trajectory tracking during rehabilitation exercises by addressing uncertainties and external disturbances, ensuring robust performance while avoiding singularities. Through numerical simulations, we evaluate the efficacy of the NSTSM control in accurately following desired trajectories across multiple finger joints, emphasizing singularity-free control and stability analysis based on Lyapunov theory. Our findings reveal that the NSTSM control achieves superior trajectory adherence compared to conventional PID controls, with reduced RMS error values averaging 0.005 [rad] for MCP and PIP joints, and 0.02 [rad] for DIP joint. The sliding surface analysis confirms the NSTSM control's robustness, highlighting the NSTSM control's consistent performance, and offering a promising approach to enhance rehabilitation outcomes in stroke survivors with hand impairments.