Robust adaptive relative position and attitude integrated control for approaching uncontrolled tumbling spacecraft

The six-degree-of-freedom coupling control of the relative orbit and relative attitude of a chaser approaching an uncontrolled tumbling target is studied in this paper. The chaser must reach an aimed position in the body coordinate system of the uncontrolled tumbling target spacecraft, and at the same time the attitude of the chaser should be synchronized with the attitude of the target. First, the integrated model of relative position and attitude is established based on the T-H equations and the error quaternion. Then, considering the safety of the approaching process, the nominal trajectory of the chaser is designed. Finally, a robust adaptive relative position and relative attitude controller is designed. An adaptive tuning method is used to deal with external disturbances and system uncertainties, and the upper bounds need not be known in advance. Simulation results show that the proposed method can track the aimed position of the uncontrolled tumbling target and complete the attitude synchronization, and the controller is still effective even for the target tumbling at a high angular velocity. Compared with the existing researches, the duration to complete position tracking and attitude synchronization is greatly reduced, the required maximum force and torque are smaller, and the dynamic response performance of the system is improved.