Biaxial Stage Contouring Control with a Novel Anti-Windup PID Controller Strategy

Abstract

For stage systems performing precision contouring actions under the conventional proportional–integral–derivative (PID) control structures, the phenomenon of actuator saturation is a common problem which can easily lead to the windup effect and cause unexpected results to the overall performance. To conquer this problem, this paper presents a new strategy for suppressing the windup effect in the conventional PID contouring control structures. In the proposed approach, the windup effect is modeled as a disturbance input to the PID controller such that an observer-based auxiliary control is designed to minimize the difference between the computed control force and the actual axial input based on an H-infinite optimization criterion. From theoretical analyses, it can show that the proposed anti-windup (AW) scheme can provide a more robust performance under the effects of windup than the conventional PID AW schemes. Moreover, it can also bring about better noise rejection capability to the controlled systems. Furthermore, the design of the proposed PID AW scheme is system independent and can be formulated based on the original PID controller parameters such that it can utilize a rapid on-line tuning of the controller parameters in order to prevent the windup effect. To validate the approach, a biaxial x-y stage system performing contouring action is applied which originally has obvious windup effect in both axial inputs under the conventional PID scheme. After the implementation, the experimental results show that the proposed PID AW scheme indeed improves the windup effect and also provides a better system robustness performance compared to the original one. It can be obtained that the experimental results are in accordance with the theoretical analyses, and show the effectiveness of the proposed method.