Adaptive attitude control and active vibration control of the flexible spacecraft

In the attitude and vibration control of three-axis-stabilized flexible spacecraft, the problems of attitude kinematics coupling and torque coupling, dynamic coupling of flexible modes with rigid body, and parameter uncertainty caused by large flexible appendages should be dealt with. Based on 'bandwidth insulation method', attitude controller and vibration controller were designed independently. The influence of vibration on attitude was considered as a time-variant disturbance. The attitude controller consists of the fast angular velocity loop and the slow attitude angular loop in terms of singular perturbation theory. Further an integral state-dependent Riccati equation (SDRE) controller to resist strong disturbance was designed for the two loops. To control the flexible vibration, a positive position feedback (PPF) controller related to the independent modes was constructed, which ensures the robustness of the system for the uncertainties of the structure or the parameters. The simulation results show the good performance of the attitude stabilization in spite of the disturbance torque, and the fast decay of vibration.