Discrete sliding mode control for a VCM positioning system

In this paper, a discrete control system is implemented for a positioning device using a voice-coil motor (VCM). The VCM positioning system is configured with a proportional-Integrator observer (PIO) and discrete sliding mode controller (DSMC). Since the PIO could estimate system unmeasurable parameters for compensation, the implemented control system subject to uncertainty might feature high robustness. Through experimental examinations of step response for a sliding stage under dry friction and with a mass of 728 g, the position error of 7.3 µm was obtained for a step command of 3 mm. The percentage of position error is 0.25%. Compared with that obtained by using the PID controller is 0.57%, the superiority of the implemented control system is demonstrated.