Sliding mode friction observer based control for flexible spacecraft with reaction wheel

A novel composite anti-disturbance control scheme is proposed for attitude control system (ACS) of flexible spacecraft with the reaction wheel friction. The proposed control scheme can overcome the performance degradation of controller under the condition of reaction wheel friction and flexible appendage vibration. First, the dynamic model of the flexible spacecraft is modelled, including disturbance torque of the reaction wheel. A sliding mode friction observer is designed to estimate the reaction wheel friction torque for feed-forward compensation. Then, a flexible appendage vibration observer is constructed to estimate and compensate for the flexible appendage vibration. Finally, an H_∞ controller is adopted to attenuate the estimation error and other bounded disturbances, such as the environment disturbance. Simulations on the ACS of a flexible spacecraft demonstrate the robustness and effectiveness of the proposed method.