Analysis and compensation of hysteresis of PZT micro-actuator used in high precision dual-stage servo system

Abstract

Piezoelectric micro–actuator made from (PZT) has been a suitable choice as the secondary actuator of a dual–stage actuator system. However, like any other piezoelectric actuator, this secondary PZT micro–actuator also exhibits hysteresis which is the inherent nonlinearity characteristic of piezoelectric material. Therefore, the advantage gained by the precision of secondary actuator is somewhat lost by this hysteresis, if not compensated. This paper proposes a rigorous technique for analysing, identifying and compensating the hysteresis of PZT actuator used in dual–stage actuator system. Identification and compensation are the two parts of the paper. In the first part of the paper, the parameters of generalised Prandtl–Ishlinskii (GPI) model are identified offline by particle swarm optimisation (PSO) technique. In compensation part, inverse GPI as the hysteresis compensator is obtained from the identified hysteresis model. Then in case of parameter uncertainty, PSO–based online tuning method is employed to adaptively adjust the parameters of inverse GPI model. For the linear controller of dual–stage, a simple design approach is followed. Simulation results show that the proposed technique can be efficiently used for the identification and compensation of hysteresis of PZT micro–actuator.