Adaptive Tracking Control for a Class of Exoskeletons with Saturation Inputs and External Disturbances

This paper presents an adaptive tracking control method for a class of lower limb hip rehabilitation exoskeletons. With this scheme, saturation input and external disturbance are considered. Firstly, the exoskeleton can be modeled as a second-order nonlinear system according to the Newton-Euler equation, and it is transformed into a nonlinear system with an unknown control coefficient by using saturation approximation. Then, an adaptive tracking controller is proposed, which ensures uniformly ultimately bounded performance of the closed-loop system, and at the same time, it realizes that the tracking error has a preset convergence accuracy by introducing a prescribed performance function (PPF). Finally, Simulation results show the effectiveness of the proposed approach.