Robust adaptive backstepping control for autonomous spacecraft proximity maneuvers

The control problem of autonomous proximity phase during rendezvous and docking is studied for a chaser spacecraft subject to parametric uncertainty and unknown external disturbance approaching to a tumbling non-cooperative space target. A coupled relative motion model is established for the autonomous spacecraft proximity missions based on the relative motion information and chaser’s motion information. Based on the cascaded structure of the six degrees-of-freedom coupled model, the backstepping technology combined with element-wise and norm-wise adaptive control methods is used to design a relative position controller firstly, then the same method is also applied to the design of the relative attitude controller. Asymptotic stability is proven uniformly for the six degrees-of-freedom closed-loop system, and the performance of the controlled overall system is demonstrated via a representative numerical example.