Peozoelectric Polymer Actuators for Active Vibration Isolation in Space Applications

摘要

A lightweitht actuator for active vibration isolationin space applications is being developed to replace the heavyelectromagnetic systems now in use. The actuator has a loweffective spring constant that provides for passive vibrationdamping down to sub-Hertz frequencies while allowing theisolated experiment to follow the near-dc bias motion of thespacecraft. The actuator is currently optimized for te vibrationlevel of the Space Shuttle and assembled from a pair of dimorphsin a leaf-spring configuration. Changing the size and number ofsheets used in construction can vary electromechanical properties.Passive damping has been demonstrated in one and two-dimensional tests. For large (greater than a few kilograms)suspended masses, the system is underdamped and relative velocityfeedback must be used to remove the resonance. Real-time controlof the resonance frequency is achieved by controlling the voltageapplied to the actuator with feedback from a displacement sensor.A folded pendulum seismic monitoring device was adapted for useas a one-dimensional low frequency test platform and has obtainedaccurate measurements of the effective spring constant anddamping coefficient. Single-degree-of-freedom active feedbacktesting is also being conducted using this device. Two-dimensional(three-degree-of-freedom) passive damping tests were conductedon NASA's KC-135 Reduced Gravity Platform in March 1998.