Trajectory tracking control of lower limb exoskeleton rehabilitation robot based on extended state observer

Abstract

This paper presents a linear active disturbance rejection control (LADRC) method for lower limb exoskeleton rehabilitation robot. Because the lower limb exoskeleton control system has variability, nonlinearity and model parameter uncertainty, it is difficult to achieve accurate control of gait trajectory tracking. In this paper, a linear extended state observer (LESO) is designed to estimate the total disturbance inside and outside the system, and linear active disturbance rejection control (LADRC) is used to suppress the total disturbance, in order to transform a nonlinear, time-varying and uncertain system into a linear, time invariant and known system. A linear state error feedback control law (LSEF) is designed to realize the tracking control of gait trajectory. We have simulated and verified the controller in MATLAB. Compared with ordinary PD controller, it is proved that the controller not only has good tracking effect, but also can effectively suppress interference.