Safety control for spacecraft autonomous rendezvous and docking under motion constraints

This paper addresses the translational control problem for the final phase of spacecraft rendezvous and docking. For safety concerns, during the approach process, the pursuer spacecraft is required to strictly comply with the approaching path constraints and should also have obstacle-avoidance ability at the same time. A novel potential function is employed to describe these safety requirements. Two distinct path constrained zones are designed and the potential applications of them are analyzed as well. Then, based on a time-varying sliding manifold, an adaptive control law is developed to enable the arrival of the pursuer spacecraft at the docking port of the target without entering into the constrained zone or colliding with obstacle, even in the existence of disturbances, uncertainties, and actuator faults simultaneously. The stability of the closed-loop system is analyzed through Lyapunov method. Specific simulations for International Space Station and Tiangong-1 target spacecraft are performed to illustrate the effectiveness and robustness of the proposed method.