Attitude Tracking Control of Uncertain Flexible Spacecraft Systems Subject to External Disturbances*

In this paper, we consider the attitude tracking and disturbance rejection problem of uncertain flexible spacecrafts. Compared with existing works, we consider two types of uncertainties of flexible spacecrafts, that is, the uncertain parameters of the inertial matrix, and the unknown external disturbance with unbounded energy. Inspired by the internal model principle, we design a class of dynamic compensators and some auxiliary dynamic systems to compensate the external disturbance. Then, by introducing a series of coordinate transformations, we convert the attitude tracking and disturbance rejection problem into an adaptive regulation problem of an augmented system. Finally, we design the adaptive control law and show that attitude tracking of uncertain flexible spacecrafts can be achieved in the presence of unknown disturbances. The effectiveness and robustness of the controller are illustrated by some numerical simulations.