Robust Lyapunov-based motion control of a redundant upper limb cable-driven rehabilitation robot

Abstract

This research presents an upper limb cable-driven rehabilitating robot with one degree of redundancy to improve the movements of the injured. A spatial trajectory is planned through the joint limit avoidance approach to apply the limits of the joint angles, which is a new method for trajectory planning of joints with an allowed definite interval. Firstly, a Lyapunov-based control is applied to the robot with taking uncertainty and disturbances into consideration. To derive the best responses of the system with considering uncertainty and disturbances, a novel robust tracking controller, namely a computed-torque-like with independent-joint compensation, is introduced. The mentioned new robust controller has not been applied to any cable robot which is the novelty of this paper to derive a superior output and the robustness of the given approach. Stability analysis of both controllers is demonstrated and the outputs of the controllers are compared for an exact three-dimensional motion planning and desirable cable forces. Eventually, the proposed novel controller revealed a better function in the presence of uncertainties and disturbances with about 28.21% improvement in tracking errors and 69.22% improvement in the required cable forces as control inputs, which is a considerable figure.