A Study on High Accuracy Discrete-Time Sliding Mode Control

In this paper a discrete-time sliding-mode based controller design for high accuracy motion control systems is presented. The controller is designed for a general SISO system with nonlinearity and external disturbance. Closed-loop behavior of the general system with the proposed control and Lyapunov stability is shown and the error of the closed loop system is proven to be within an o(T²). The proposed controller is applied to a stage driven by a piezo drive that is known to suffer from hysteresis nonlinearity in the control gain. Proposed SMC controller is proven to offer chattering-free motion and rejection of the disturbances represented by hysteresis and the time variation of the piezo drive parameters. As a separate idea to enhance the accuracy of the closed loop system a combination of disturbance rejection method and the SMC controller is explored and its effectiveness is experimentally demonstrated. Closed-loop experiments are presented using PID controller with and without disturbance compensation and sliding-mode controller with and without disturbance compensation for the purpose of comparison