Fixed-time adaptive fault-tolerant control with predefined tracking accuracy for satellite systems

The development of space technology put forward higher demands on the satellite position tracking control, i.e., the system steady states behavior and transient performance. However, due to the presence of unknown dynamics uncertainties and actuator failures, the control performance of traditional adaptive control schemes is unsatisfactory. In this work, we study the position tracking control problem of uncertain nonlinear satellite systems in the presence of unknown actuator failures, which is a challenging problem when a predefined tracking accuracy and a fixed convergence time are required simultaneously. To overcome the difficulties, a backstepping recursive design based on smooth functions is proposed, and well combined with adaptive actuator failure compensation approach, based on which a prescribed fixed-time adaptive fault-tolerant control scheme is developed. With our scheme, it can be rigorously proved that all closed-loop signals are bounded, and the position-related tracking errors converge to predefined intervals in a bounded settling time regardless of the occurrence of actuator failures. The effectiveness of the proposed scheme is verified by a simulation tests based on a practical geostationary earth orbit satellite.