Vibration Suppression: Reduced-order Model/residual Mode Filter Control Using Smart Structures - Aerospace Conference, 1998 IEEE

For spacecraft with large flexible antennas, andor flexible support structures, suppressing vibrations caused by on-orbit operational disturbances (e.g., antenna slew maneuvers and thruster firings) is a challenging problem. In the past several years, advances in smart structure technologies have made their use in real-time dynamic control cif a structure possible. This paper discusses analytical investigations that are focused on the development of improved vibration suppression techniques for flexible spacecraft structures using smart structure actuators and sensors. In general, active control of large flexible structures can be used to improve performance, e.g., shape fidelity, line-ofsight pointing accuracy, and vibration and disturbance suppression. Large-scale models of such structures (e.g., finite element models) are appropriate for dynamic simulation but cannot be used as a basis for control algorithms, whch must be implemented via computer in real-time. Therefore, control algorithms are often based on Reduced-Order Models (ROM) of the structure dynamics. Whenever such a controller operates in closed-loop with the actual structure, unwanted Controller-Structure Interaction (CSI) occurs due tci un-modeled dynamics. CSI can cause performance degradation and even instability. These instabilities can easily be relieved by the use of low-order Residual Mode Fih’ers (RMF). These filters can be added on after the original ROM controller has been designed, and they produce very little degradation of designed performance while yielding an acceptable stability margin for closed-loop operation. The research presented in this paper integrates smart structure control technologies with the ROM-RMF control technique for aciive vibration control of a flexible spacecraft structure. This smart structure control technique is applied to a model of the U.S. Naval Postgraduate School’s Flexible Spacecraft Simulator (FSS). The FSS simulates motion about the pitch axis of a spacecraft, and is comprised of a rigid central body and a reflector supported by a two-link flexible antenna support structure. The flexible arm representing the antenna support structure has two sets of piezoclxamic sensors and actuators, which are used for active vibration control. The ROM-RMF control technique, used in conjunction with optimal control laws, is amawal@,aa.ntx.navv.mil 408-656-3338 developed for use with these smart sensors and actuators. The performance of this controller is then compared with the performance of other smart structure controllers previously developed for FSS control. TABLE OF CONTENTS