Super-Twisting Observer Based Finite-Time Backstepping Attitude Control for a Combined Spacecraft

A novel finite-time controller integrated with a disturbance observer is proposed for a combined spacecraft, which is composed of a service spacecraft and a target spacecraft with large uncertainty of inertia momentum. Firstly, a modified super-twisting disturbance observer is designed so that the reconstruction of the generalized disturbances in terms of the inertia uncertainty and the external disturbance is accomplished in finite time. Then, with the reconstructed information, a finite-time controller is synthesized with the backstepping method. Besides, the command filter is also introduced to the finite-time controller which can improve the control performance. And the closed-loop system/state is proved to be finite-time stable. The numerical simulations validate the effectiveness and feasibility of the proposed control scheme.