Piezoelectric Stack Actuators and Control System Design: Strategies and Pitfalls

An evaluation is presented of two control strategies for piezoelectric stack actuators: voltage feedback control and charge feedback control. The study consists of two principal parts: an experimental determination of the nonlinearities inherent in piezoelectric actuators using different control strategies and an analysis of how those nonlinearities would affect the stability and performance of feedback control systems that utilize piezoelectric actuators. The voltage control responseof thepiezoelectricactuator tested wasdemonstrably more nonlinear than thesameactuatorwithchargefeedback circuitry. Nyquistdesign analysisrevealsthatthesenonlinearitiestranslate into lower stability margins and potential system performance for voltage control of piezoelectric actuators as compared to charge control. The improved system stability that can be achieved with charge control as compared to voltage control is demonstrated to be signie cant in multi-degree-of-freedom systems but almost negligible when the system dynamics are essentially single degree of freedom.