On-Orbit Experiments of Frequency-Shaped H.INF. Control for Flexible Space Structure.

Flexible control experiments have been performed as one type of on-orbit experiment for the Engineering Test Satellite VI (ETS-VI) which was launched in August, 1994. The aim of the flexible control experiments is the feasibility study of new attitude control schemes for future flexible space structures. We have designed two types of controllers. One is a controller designed according to the Low Authority Control (LAC)/High Authority Control (HAC) scheme. The purpose of LAC is damping augmentation of structural vibration modes, while that of HAC is achievement of high control performance. The other controller is a HAC-only controller: this HAC controller is designed for high-performance attitude control of a rigid body, as well as for damping augmentation of the vibration modes. The HAC controllers in both cases are designed using H∞ control theory with the frequency-shaping technique. These control schemes have been tested on orbit by ETS-VI. The experimental results have been analyzed in both time and frequency domains. It is shown from the analysis that both control schemes can be accurately realized on orbit and perform well with respect to damping augmentation and attitude control.