Disturbance observer based control for spacecraft proximity operations with path constraint

This paper investigates the application of a nonlinear feedback control strategy for driving a chaser spacecraft to rendezvous and dock with a target spacecraft in space. The nonlinear coupled models are established to describe the relative position and relative attitude dynamics, while a nonlinear disturbance observer is employed to estimate and compensate the external disturbances. Furthermore, a specific potential function is designed to prevent the chaser from entering into the forbidden zone or colliding with the target during the final phase of rendezvous and docking. Within the Lyapunov framework, the ultimate boundedness of the closed-loop system is guaranteed in the existence of external disturbances. Numerical simulations are performed to illustrate the feasibility and effectiveness of the proposed control strategy for motion synchronization as well as collision avoidance.