Active Vibration Isolation Demonstration System Using the Piezoelectric Unimorph with Mechanically Pre-stressed Substrate

Abstract

In this article, a pre-stressed piezoelectric actuator made at room temperature using a mechanically pre-stressed substrate is applied as an actuator for an active vibration isolation system. The fabricated piezoelectric actuator, called PUMPS (piezoelectric unimorph with mechanically pre-stressed substrate), is a kind of unimorph actuators in which actuation stroke level is enhanced by displacement amplification mechanism that converts longitudinal piezoelectric in-plane deformation to large bending/pumping motion. Despite its much simpler fabrication process, PUMPS actuation performance is comparable to that of conventional pre-stressed piezoelectric unimorphs due to its special pre-stress level inside piezoelectric layer. In applying PUMPS as an actuator for active vibration control, multilayer stack configuration using three PUMPS actuators was adapted in order to obtain higher actuation force because unimorph actuators are displacement amplified actuators in which displacement amplification is attained with a sacrifice of the actuation force. Preliminary vibration tests were performed to check the performance of PUMPS as actuators for active vibration control in a lab environment. Two feedback control schemes, the positive position feedback and negative velocity feedback, were applied for active vibration control and about 10 dB vibration reduction was achieved near the resonant frequency region. With the promising results obtained in the preliminary vibration test, PUMPS actuators in multilayer stack configuration were used to develop an integrated active vibration isolation demonstration system. The purpose of the developed system is to demonstrate the need for vibration isolation system to remove degrading effects of jitter and improve the performance of optical payloads in satellites such as its observation and image acquisition abilities. The test results with the demonstration system show that severe blur observed in the image taken without the vibration control is reduced visibly in the image taken during the operation of the active vibration isolation system.