Robust sliding mode control design for a dual-stage actuator system

To improve the positioning accuracy of servomechanisms with one single actuator only, the dual-stage actuator (DSA) systems have been proposed and widely used for industrial applications for the benefits of both large working range, high positioning accuracy and fast response. However, it is common that servomechanisms suffer from plant uncertainties and external disturbances which will affect the positioning accuracy. As such, this paper studies a robust control method called fast non-singular terminal sliding mode (FNTSM) control for a class of DSA systems. Compared with conventional sliding mode control, the FNTSM control can guarantee a faster convergence rate of the tracking error in the presence of system uncertainties including payload variations and external disturbances. Furthermore, it has the inherent feature of chattering-free in the control input. We also discuss the selection criteria of the controller parameters and then the FNTSM control method is applied to design the two control inputs of the DSA system. Simulations are studied to verify that the FNTSM controller can offer robust performance with respect to the mass variations and disturbance. Tracking performance achieved by conventional linear controllers is also presented for comparison.