Effective dynamical model for piezoelectric stick–slip actuators in bi-directional motion

Abstract

The dynamics of piezoelectric stick–slip actuators is important for structural optimization and positioning control, yet challenging to model because of the potentially inconsistent stepping of these actuators in the forward and backward directions. This step inconsistency is found to be strongly associated with the inconsistent dynamic response of the piezoelectric feeding element arising from the contact behavior between the piezoelectric stack and its flexure-based preload mechanism. With this understanding, an improved dynamical model for the typical stick–slip actuator is established in which a non-smooth contact model is introduced. A prototype was built and tested, and with it the contact behavior was proved to cause the inconsistent responses of the piezoelectric feeding element, which in turn was verified to cause the inconsistent stepping characteristics of the stick–slip actuator. The simulated results obtained using the proposed model were in good agreement with the stepping curves of the slider in bi-directional motion under different working conditions. The proposed model provides a new perspective to explain and model the step inconsistency for stick–slip actuators in bi-directional motion, and has great potential in aiding the design and control of stick–slip actuators for bi-directional driving.