Adaptive backstepping fault-tolerant control for flexible spacecraft with bounded unknown disturbances

A robust adaptive fault-tolerant control approach to attitude tracking of flexible spacecraft is proposed for use in situations when there are actuator (reaction wheels) failures, external disturbances and unknown inertia-parameter uncertainties. The controller is designed based on a backstepping sliding mode control scheme. It ensures that the equilibrium points in the closed-loop system exhibits uniform ultimate bounded stability in the presence of unknown uncertainties and bounded disturbances, incorporating constraints on actuator failures, whose failure time instants, patterns and values are unknown, as motivated from a practical spacecraft control application. It is proved to be effective also in the presence of disturbance due to the flexibility, provided that appropriate robustness conditions on the controller gains are satisfied. Complete stability and performance analysis are presented and illustrative simulation results of an application to flexible spacecraft show that the high precise attitudes control and vibration suppression are successfully achieved when considering various scenarios of control effect failures.