Force controller design based on PQ method for dual-stage actuators in polishing machines

This paper presents a controller design approach to realize a precise force control of load devices in polishing machines. In the load device, a pneumatic actuator and a voice coil motor are combined as dual-stage actuators to expand the servo bandwidth. However, the interference between the dual actuators may deteriorate the servo performance, especially at around the cross-over frequency. In this paper, therefore, PQ method is adopted to achieve the high precision force control by the expansion of servo bandwidth, where the compensators are especially designed to suppress the interference. The proposed approach has been verified by experiments using an actual load device of the polishing machine.