Sliding mode observer based composite controller for spacecraft attitude control system with reaction wheel friction

An anti-disturbance controller which considers the reaction wheel friction dynamic is proposed for spacecraft attitude control system to overcome the deterioration of performance under reaction wheel friction. The dynamic model of the system, including the reaction wheel dynamic and the spacecraft dynamic, is given beforehand. Then in order to counteract the effect of the reaction wheel friction, a sliding mode observer is designed to obtain the friction estimation. Finally a H∞ controller is adopted to attenuate the estimate error and other bounded disturbances, such as the environment disturbance. The simulation on the microsatellite attitude control system demonstrates the correctness and effectiveness of the proposed method.