Nonlinearity analysis, modeling and compensation in PZT micro actuator of dual-stage actuator system

A dual-stage actuator system consists of a coarse actuator for large motion and a micro-actuator facilitating small but precise motion to improve tracking performance. Piezoelectric micro-actuator made from PZT (Lead-Zirconium-Titanium) has been a popular choice as the secondary stage. However, the advantage gained by the precision of secondary actuator is somewhat lost by the inherent hysteresis nonlinearity of PZT actuator, if not compensated. This paper presents a rigorous analysis and modeling of the hysteresis of PZT actuator and its compensation in a dual-stage servo system. For the controller of dual-stage, a simple design approach is followed. The coarse actuator loop is first designed for basic performance and stability, using composite nonlinear feedback control. The compensator for the micro-actuator is then designed to achieve better performance of the overall system and it also includes the hysteresis compensator. Simulation results underscore the effectiveness of the design.