Experimental investigation of a SMC high precision control

In this paper a discrete-time sliding-mode (SM) based controller for high accuracy position control is investigated. The controller is designed for a general SISO system with nonlinearity and external disturbance. It would be shown that application of the proposed controller forces the state trajectory to be within an O(T_s ²). The proposed controller is applied to a stage driven by a piezo drive that is known to suffer from nonlinearity. 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