Fault Tolerant Attitude Control for spacecraft with SGCMGs under actuator partial failure and actuator saturation

A Fault Tolerant Attitude Control algorithm for the spacecraft using Single Gimbal Control Moment Gyros (SGCMGs) as actuator is proposed. The controller is designed using the sliding mode control theory to control the gimbal rate directly and there is no singular point in the control algorithm, which means that we don't need to design the steering laws again and the singularity problems can be avoided. Also the gimbal rate saturation is considered when designing the control method. The adaptive control algorithm is used to estimate the disturbance and the boundary of the fault and saturation, which means that no prior information of the fault is needed. Although the controller is designed based on the SGCMGs, it can also be employed when reaction wheels work as the actuator of the spacecraft. Also the complete failure of several SGCMGs is allowed. It is proved based on the Lyapunov stability theorem that the designed control algorithm can achieve the attitude asymptotic stability both on the fault or fault-free condition. The simulation results show that the proposed method has a strong robustness.