Nonlinear robust adaptive trajectory tracking control for spacecraft proximity operations

Six degrees of freedom (6DOF) relative motion trajectory tracking control is studied for a chaser spacecraft with parametric uncertainties and external disturbances to approach a tumbling target in deep space. After modeling the nonlinear and coupled relative motion dynamics in the chaser body-fixed frame, reference trajectories of the relative attitude and relative position are designed, then a 6DOF integrated trajectory tracking controller is developed based on a robust adaptive method. Asymptotic stability of the 6DOF closed-loop system is derived within the Lyapunov framework. The performance of proposed controller is demonstrated through a numerical simulation example.