ACTIVE SHARE AND VIBRATION CONTROL OF FLEXIBLE SPACE STRUCTURES

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1. Fundamental studies have been done for developing methods of shape measurement, estimation and control for active shape control of flexible structure. The major subjects of the active shape control consists of estimating the deformed shape of a flexible structure from multi-point spatially distributed measurement of the structural deflections and determining the optimal static control force that yields the minimum integrated restoration errors. The estimation and control designs are based on an infinite-dimensional approach that introduces the necessary finite element truncation and approximation after solving the estimation problem. The proposed estimation and control design methods have been applied to a tendon shape control system for a cantilevered beam. The results of numerical simulation show that the magnitude of the restoration errors largely depends on the number of available actuators and their locations.2. A prototype remote optical sensing device has been developed for the static shape measurement. The main component of the optical sensing system consists of a laser scanner and retro-reflectors (corner cubes) mounted to the experiment structure. The measurement system determines the line of sight vector pointing the target corner cube. Since the laser beams scan all the corner cubes sequentially in each rotation cycle, the proposed method is fitted to the multi-point measurement in short time. The prototype laser scanner has been built in the laboratory and tested for measuring the position translation of the target corner cubes that simulates the structural deflections.3. A method of robust eigenstructure assignment has been developed for the vibration control of flexible space structures. The proposed method generates attractive gain matrices which reduce the H^* norm to achieve the robust stability for plant perturbations and residual modes. The usefulness of the proposed design approach was validated through numerical simulations.