Adaptive control of time-varying systems: an application to the attitude-momentum control of the space station

The authors consider an application of adaptive techniques to control the space station in orbit with a moving payload. The nonadaptive counterpart of this problem has been considered by B. Wie et al. (1984). Such a controller, designed to tolerate constant parametric uncertainty, may exhibit unsatisfactory behavior when the variation of the system parameters is not sufficiently slow. Motivated by this practical problem, the theory and application of adaptive techniques in up-dating the parameters of the controller designed by Wie et al. is discussed. The main theoretical problem arising in this application is associated with the adaptive identification and control of multivariable linear time-varying systems. Other theoretical problems arise from the decentralized nature of the controller of Wie et al., and a hybrid implementation of the adaptive control scheme to reduce the required computational effort. Such problems have been studied individually in the literature, and are integrated in the present study to provide a complete theoretical justification of the adaptive approach to the application at hand