Iterative learning observer-based fault-tolerant control for on-orbit serving spacecraft with coupled orbit and attitude dynamics

This article investigates the problems of coupled orbit and attitude dynamics modeling and control for an on-orbit serving spacecraft that is going to dock with a target spacecraft. First, a coupled relative orbit and attitude dynamics model of the servicing spacecraft with respect to the target spacecraft is constructed, considering external disturbances and actuators faults. To deal with such effects, two iterative learning observers are then designed respectively for orbit dynamics and attitude dynamics, which are capable of estimating interferences and faults. Combining the estimation information, the final control law is proposed based on the back stepping method. Through the Lyapunov approach, the stability of the closed-loop control system is analyzed. Finally, a numerical simulation is carried out to bear out the effectiveness of the proposed control scheme.