Vibration isolation for spacecraft using the piezoelectric polymer PVF2

Abstract

Throughout the remainder of the current decade and through the 1990s, the pointing requirements of spaceborne scientific payloads will grow increasingly more stringent, yet, for reasons of cost effectiveness, the trend will be away from single-payload-dedicated free-flying spacecraft and toward large, multipayload space vehicles. The basebody structural frequencies of space station/space platforms will be significantly lower than those for previous missions, making the traditional separation between pointing controller bandwidth and structural modes impossible to maintain. Man motion and machine vibration disturbances will likely limit the space station attitude control to relatively coarse levels. In the face of such a demanding dynamic environment, future space stations will host attached payloads, some of whose pointing requirements approach those of the free-flying space telescope. These issues drive the need for the development of advanced pointing mount technology that can provide a high degree of precision while simultaneously isolating a payload from a disturbance rich host vehicle. A finite element model of an active softmount based on the piezoelectric polymer poly (vinylidene fluoride) has been developed. The model includes the geometric nonlinearities that are associated with the large deflection capability of the softmount. This model is put together with a simple space station model and then both linear frequency domain and time domain simulations are carried out. The wideband disturbance rejection capabilities of the design are demonstrated, both in the frequency domain and in nominal operations.