Spacecraft attitude fault tolerant control with terminal sliding-mode observer

A velocity-free attitude fault tolerant control scheme is presented to stabilize spacecraft attitude. A terminal sliding-mode observer is developed to reconstruct system states. With the reconstructed attitude and angular velocity, a control law is synthesized without any knowledge on actuator faults. The controller guarantees all the signals of the closed-loop attitude system to be uniformly ultimately bounded even in the presence of actuator fault and external disturbance. The control power is rigorously ensured to be within the maximum magnitude of output torque. An illustrative example is presented to evaluate the control performance.