Robust Motion Control System Design With Scheduled Disturbance Observer

Abstract

A novel disturbance observer (DOB)-based switching control strategy is proposed to achieve fast, smooth, and accurate control performance in the presence of both external disturbances and internal uncertainties. This methodology consists of two DOBs designed with different frequency responses, and the switching mechanism is designed meticulously to schedule different DOBs. To further study the DOB-based control, a novel model transformation is introduced to alleviate the conservatism of robust stability of the closed-loop system. Thus, $H_{\infty }$ theory is adopted to establish the cost function for performance evaluation and $Q$ filter optimization. Different weighting functions can be selected for specific requirements of smooth dynamic responses or high disturbance rejection performance. A critical switching mechanism is proposed to schedule the different parameters according to the variation of output error and settling time. Experiments on dc servo system show that both smooth dynamic responses at transient state and high-accuracy performance at steady state can be achieved, and the effectiveness of the proposed control scheme is verified.