A study of actuator reconfiguration and related implementation issues in active vibration damping

Abstract

This thesis reports a study in the area of active vibration damping focused primarily on reconfiguration of control actuators following failure of one or more components. Several related issues concerning practical implementation were considered, and these also were discussed. These subjects were studied with reference to a particular laboratory structure, a hanging plane grid in the Spacecraft Controls Branch at NASA Langley Research Center. The structure had dynamics representative in many respects of a large, highly flexible space structure (LSS), and this study was intended to contribute toward the development of vibration control for LSS. A numerical analysis of the reconfiguration by computer simulation is presented. The possible future experimental validation of this numerical analysis motivated examination of some auxiliary problems related to implementation of vibration control with real, nonideal hardware. One of these problems is the effect of the dynamics of real sensors, actuators, and filters on a vibration control system. An experimental analysis of this problem was conducted, and the results presented here include hardware induced performance degradation and system instability. Another problem considered is prediction of response for use in feedback control by a digital controller that introduces a significant computational delay. A prediction technique is described, and some results of open-loop experimental evaluation of this technique are presented. Also, a computer simulation of closed-loop application of this technique was conducted, and the results, which include system instabilities, are presented.