Adaptive fixed-time fault-tolerant control for noncooperative spacecraft proximity using relative motion information

This paper studies the control issue of noncooperative spacecraft proximity. In particular, a pursuer spacecraft approaches a noncooperative target while synchronizing its attitude with the target. The pursuer spacecraft is subject to actuator faults and parametric uncertainties. Due to the existence of spatial disturbances on both the target and pursuer, the six-dof (degree-of-freedom) relative motion dynamics are first established in the pursuer's body frame. Then, by merely using the relative information, a novel adaptive fixed-time fault-tolerant control strategy is proposed under a backstepping framework. Specifically, the relative attitude and position controllers are designed by using an adaptive robust control scheme against parametric uncertainties and spatial disturbances, where a virtual control coefficient-based adaptive algorithm is also introduced to offset the actuator fault effects. It is shown that the relative states driven by the proposed controllers are bounded and converge to a small neighborhood of origin in a fixed time. Simulation comparisons further highlight the proposed control strategy.