Adaptive compensation control for spacecraft attitude stabilization with actuator misalignment and faults

An adaptive compensation control scheme is presented to address a rigid spacecraft attitude stabilization problem. The controller is based on a sliding mode control technique that tolerates uncertainties and external disturbances. Actuator misalignment can arise from finite manufacturing tolerance, or warping of the spacecraft structure during launch, or from thermal variations. A sufficient condition for the existence of compensation control effort to accommodate actuator misalignment is presented. Two compensation terms are synthesized and integrated into the controller to handle the actuator misalignment and faults, respectively. The key feature of the proposed control law is that is it asymptotically stabilizes the resulting closed-loop system in finite time, even in the presence of actuator fault and misalignment. The attitude stabilization performance using the proposed compensation controller structure is evaluated through a numerical example.