Robust fault-tolerant control for satellite attitude control system based on iterative learning observer

Based on Iterative learning-unknown input observer (IL-UIO), a robust fault-tolerant control scheme is putford to deal with actuator failures and external disturbances of on-orbit satellite. It decouples disturbances with UIO, meanwhile the IL technique are used to update current fault signal by means of immediate past system output errors and the last step IL-UIO information, thus reconstructing actuator fault on-line. Furthermore, the robust stability of the full-order IL-UIO and uniformly boundness of angular velocity errors are proved by using the Lyapunov stability theory. Simulation results of the closed-loop satellite attitude control system used in a satellite attitude control system validate the effectiveness of the proposed method.