Adaptive Control for Spacecraft Rendezvous Subject to Time-Varying Inertial Parameters and Actuator Faults

A novel adaptive fault-tolerant control strategy is proposed for a spacecraft rendezvous maneuver. The six-degree-of-freedom (6-DOF) nonlinear model is expressed in the pursuer's body frame, which consists of relative attitude and orbit dynamics in the presence of unknown time-varying inertia parameters, bounded disturbances, and actuator faults. A continuous adaptive control strategy is developed for the pursuer where a modification term and projection algorithm are employed in the adaptation laws to ensure the estimates of the unknown parameters remain positive and bounded. It is proven that the proposed strategy ensures the ultimate boundedness of all the signals in the closed-loop system and the asymptotic stability of the relative dynamics. Numerical simulations verify the effectiveness of the proposed control strategy.