A precise and robust control strategy for rigid spacecraft eigenaxis rotation

Eigenaxis rotation is generally regarded as a near-minimum time strategy for rapid attitude maneuver due to its constitution of the shortest angular path between two orientations. In this paper, the robust control problem of rigid spacecraft eigenaxis rotation is investigated via time-varying sliding mode control (TVSMC) technique. Both external disturbance and parameter variation are taken into account. Major features of this robust eigenaxis rotation strategy are first demonstrated by a TVSMC algorithm. Global sliding phase is proved as well as the closed-loop system stability. Additionally, the necessary condition for eigenaxis rotation is provided. Subsequently, to suppress the global chattering and improve the control accuracy, a disturbance observer-based time-varying sliding mode control (DOTVSMC) algorithm is presented, where the boundary layer approach is used to soften the chattering and a disturbance observer is designed to attenuate undesired effect. The spacecraft attitude is represented by modified Rodrigues parameter (MRP) for the non-redundancy. Finally, a numerical simulation is employed to illustrate the effectiveness of the proposed strategy, where the pulse-width pulse-frequency (PWPF) technique is utilized to modulate the on-off thrusters.