The variable structure PI speed controller for AC servo system

Abstract

The high performance AC servo system is required to achieve fast response without overshoot. The traditional proportional-integral(PI) controller which utilizes fixed parameters, however, cannot well guarantee the requirement for both response and overshoot at the same time. Thus a variable structure PI(VSPI) controller is proposed in this paper, and the stability conditions of the closed-loop system based on which is given according to Lyapunov stability criterion. When the absolute value of speed error is smaller than the threshold value, the proportional gain and integral gain are regulated adaptively by a linear function; Otherwise, the proportional gain and the integral gain remain the fixed value. Experiment results show that compared with the traditional PI controller, the VSPI controller under a speed step input can achieve fast response with effectively reduced overshoot.