Attitude tracking control for observation spacecraft flying around the target spacecraft

This paper addresses the attitude tracking problem of observation spacecraft, which is traveling around the target spacecraft. To observe the target spacecraft completely, view planning technology is used to select the optimal viewpoints where the observation spacecraft need to achieve and scans the target spacecraft. The desired attitude and desired angular velocity are determined by the relative location and relative velocity of the observation spacecraft with respect to the target spacecraft. The attitude tracking model are globally and uniquely described in the space of SO(3)xR3. Based on the sliding mode method, a nonlinear feedback controller is designed to track the desired attitude and desired angular velocity. The convergence and stability of the closed-loop system are assured by Morse-Lyapunov theorem and LaSalle's theorem. Moreover, it is proved that the attitude error and angular velocity error converge to a tolerable error interval regardless of actuator misalignment, uncertainties of the inertia matrix and external disturbed torque. In addition, the convergence interval is determined by the parameter setting in the controller. Finally, numerical simulations are presented to illustrate the effectiveness of the proposed controller.