Fuzzy Sliding Mode Control of An Upper-Limb Exoskeleton Robot

In this paper, the position tracking control problem of a wheelchair upper-limb exoskeleton robot is investigated. The dynamic model of an upper-limb exoskeleton is a multi input multi-output nonlinear system that usually suffers complex couplings among joints, modeling errors and uncertainties, and variance in payload that caused by the human upper limb. Instead of traditional proportional-derivative control method, a combination of sliding mode control and fuzzy logic, i.e., the fuzzy sliding mode control, is developed in this work. The fuzzy sliding mode control is free of modeling of system dynamics, thus it is robust to couplings and uncertainties within the exoskeleton dynamical model. Moreover, due to its simplicity in control algorithm design, it can be implemented for real-time and embedded control. Experiment results on the wheelchair exoskeleton are provided to show the effectiveness of the fuzzy sliding mode control approach.