Fault-tolerant attitude control for spacecraft under loss of actuator effectiveness

The attitude stabilization of rigid spacecraft in the presence of partial loss of actuator effectiveness was investigated. Based on adaptive backstepping technique, a nominal attitude controller was derived first for the normal spacecraft system in the face of external disturbances. Then the case of the partial loss of reaction wheel-effectiveness fault is considered, and the faulty attitude system with time-varying gain was ultimately decoupled into three auxiliary systems by appropriate transformation. An implicit estimation filter is proposed to estimate the actuator fault correspondingly, and in the meantime, a new adaptive fault-tolerant controller is synthesized according to the estimated fault to guarantee that outputs of the auxiliary system can follow the normal attitude control command signals. It is noted that the proposed controllers design method can significantly decrease the attitude stabilization maneuver time and improve the attitude control accuracy over the PD method in both theory and simulations.