Time-varying sliding mode control for spacecraft attitude maneuver with angular velocity constraint

In this paper, the attitude control problem for uncertain spacecraft under angular velocity constraint is addressed. Both parametric uncertainty and external disturbance are considered in the spacecraft´s dynamics. The spacecraft´s attitude is represented by modified Rodrigues parameter (MRP) for its non-redundancy. A time-varying sliding mode control (TVSMC) algorithm is derived for attitude control system. The proposed control algorithm eliminates the reaching phase of the conventional time-invariant sliding mode control (SMC) and guarantees the sliding mode occurrence all the time. Moreover, the control parameter is adjusted to avoid the angular velocity constraint during the maneuver. Finally, a numerical simulation is employed to verify the proposed control algorithm.