Tendon Control System for Active Shape Control of Flexible Space Structures

Abstract

Large space structures are very flexible and are easily deformed due to any disturbances in the space environment. This paper proposes a tendon control system for the shape control of flexible space structures and presents methods of determining the structural deflections accurately and applying control forces effectively to restore the desired shape. The problem of active shape control consists of: (1) estimating the deformed shape of a flexible structure from multi-point spatially distributed measurement of the structural deflections, and (2) restoring the desired shape by means of control actuators installed on the structure. This paper develops the estimation and control designs using an infinite-dimensional approach, where the necessary finite element truncation and approximation are introduced after solving the estimation problem. The proposed shape estimation algorithm determines the deformed shape of the structure subjected to unknown disturbance forces from multi-point spatially distributed measurement of the structural deflections. Active static control force is determined so that the integrated restoration error may be minimized. The control design is based on the least squares estimation algorithm. This paper also studies the optimal actuator location that minimizes the restoration errors. The method is applied to an experimental tendon control system for a highly flexible beam. The results of numerical simulations are given for demonstrating the feasibility of the present estimation and control method and for investigating the optimal actuator location.