Piezoelectric polymer actuators in a vibration isolation application

Abstract

We present results from development and testing of lightweight actuators made of the piezoelectric polymer PVDF. The prototype being developed is intended for microgravity applications in space and has been tested aboard NASA's Reduced Gravity Platform. The design has been driven by the requirements for a full 3D environment. Incorporation of additional electrical leads into the actuators themselves may remove the need for a separate umbilical to the suspended experiment. Linear equations describing the displacement of piezoelectric bimorphs were developed and applied to the bellows actuator including the epoxy layer. Properties for the piezoelectric layers were obtained from the literature; properties for the epoxy layer were obtained through ultrasonic testing. To assess the validity of the assumed linearity of the actuator, we conducted nonlinear finite element analysis, which indicated a high degree of linearity on contraction and up to a maximum of 5% deviation on expansion to full deflection (about 6 mm). We have developed and tested a proportional-plus-derivative (PD) control system for use with the actuator in 1D using a novel folded pendulum to simulate a zero-g environment. Passive and active characteristics are both in agreement with theoretical predictions.