Sliding-Mode Control for High-Precision Motion of a Piezostage
In this paper, control of piezostage using sliding-mode control (SMC) method is presented. Due to the fast dynamics of the piezostage and since high accuracy is required the special attention is paid to avoid chattering. The presence of hysteresis characteristics represents main nonlinearity in the system. Structure of proposed SMC controller is proven to offer chattering-free motion and rejection of the disturbances represented by hysteresis and the time variation of the piezostack parameters. In order 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. The disturbance observer is constructed using a second-order lumped parameter model of the piezostage and is based on SMC framework. Closed-loop experiments are presented using a proportional-integral-derivative controller and sliding-mode controller with disturbance compensation for the purpose of comparison