Coupled Pose Tracking Control For On-orbit Tumbling Target Spacecraft

There exists a coupling phenomenon of relative orbital motion and attitude motion between one service spacecraft and a tumbling target spacecraft in proximity operations.Account for that, the traditional control model would be no longer suitable for much more complicated space missions nowadays.It’s assumed in this thesis that the service spacecraft perform autonomous rendzvous and proximity operations to a tumbling target in space.With this background,a coupled pose dynamic model of relative motion based on dual quaternion is established, a coupling tracking control law is designed,and realize a high fidelity performance.First of all, screw theory,quaternion and dual quaternion are introduced as basic mathematical tools,which provide a way for establishing dynamic model and designing a coupling control law. Then Lyapunov stability theory and model reference adaptive control(MRAC) is introduced, which provide theoretical foundation for coupling control stability provement.Coordinate system is established according to the mission,including inertial coordinate system, service spacecraft body coordinate system and target spacecraft body coordinate system. Based on the dual quaternion,pose coupling dynamic model of relative motion of rigid body is established, and a coupled PD control law is designed, then whose stability is proved. Through mathmatical simulation, the accuracy of the dynamic model and the high fidelity of the control law is validated. Compared with the pose coupling dynamic model established here and the traditional attitude/translation divided model, pose coupling model shows much better performance, and consume much less fuel.In real mission, it’s common to find that the mass property of service spacecraft is unknown or uncertain. To solve this problem, a model reference adaptive control law is designed,which is capable of estimating the mass propert of service spacecraft. Through mathmatical simulation and compared with the non-adaptive controller, the MRAC system shows higher level adaptation of the parameter uncertainty and better accuracy. Since the estimated parameters could not fit the true value well, then a recursive least square algorithm is designed to identify the mass property on orbit during the maneuvering of the service spacecraft. At last, the identification accuracy stays about 95%.