An Experimental Investigation of Vibration Suppression in Large Space Structures Using Positive Position Feedback

Abstract

A new technique for vibration suppression in Large Space Structures is demonstrated in laboratory experiments on a thin cantilever beam, resulting in substantially reduced dynamic response. This technique, called Positive Position Feedback, makes use of generalized displacement measurements to accomplish vibration suppression. The concept of a piezoelectric active-member is developed in relation to controlling space-truss type structures. The active-member functions dually as a structural member and a control actuator. Piezoelectric ceramic material is adhered to a thin cantilever beam and simulates the use of an active-member. This space-realizable control scheme makes use of strain measurements, a preferred measurement quantity for vibration suppression, and internal control forces which completely decouple the rigid-body motion from the elastic motion. A simple necessary and sufficient condition for stability with Positive Position Feedback is presented. This condition is non-dynamic and is in general easily satisfied. As a result, Positive Position Feedback is demonstrated to have superior robust stability properties. It is also demonstrated that with Positive Position Feedback, all control and observation spillover is stabilizing. Five experiments are described in which the first six modes of vibration of the cantilever beam are controlled.