Sliding-mode control for staring-mode spacecraft using a disturbance observer

This article studies the attitude control problem for spacecraft staring-mode observation. The staring mode of spacecraft is initially presented, and its advantages for observation are analysed. Then, based on the dynamic equation and kinematic equation using error quaternion and angular velocity error, a sliding-mode controller is designed to improve control effect, which prolongs observation time and enhances observation precision. Afterwards, a disturbance observer is devised and included in this proposed controller to reduce inherent chattering of sliding-mode control and to improve the stability of the spacecraft platform. Besides, the convergence of the proposed disturbance observer is proved theoretically. Finally, simulations are performed, and the results demonstrate that the proposed controller has quicker response, better robustness to uncertainty of spacecraft inertia parameters and external disturbance, and effectively weakens the chattering.