Nonlinear feed forward control on attitude and orbital coupling model for spacecraft

Precise relative orbit and attitude model play a significant role in the spacecrafts formation flying, rendezvous and docking. Nevertheless, the independent relative orbital model can't meet the high-precision requirements. Based on the nonlinear relative motion dynamics equations and attitude kinematics equations described by modified Redrigues parameters (MRPs), a relative dynamic model of 6-DOF was developed. The accuracy of the model is guaranteed with couplings and nonlinear terms' supporting. Nonlinear feed forward control law was designed for the coupled nonlinear dynamic model, whose close-loop system was proved to be global asymptotic stable by Lyapunov direct method. The numerical simulations results verify the effectiveness of the model and control law.