Adaptive Quaternion Feedback Control and Oscillation Suppression for Liquid-Filled Flexible Spacecraft

Purpose To ensure the stability of the system and suppress the liquid sloshing and vibration of flexible attachments during the attitude maneuvering for a liquid-filled flexible spacecraft with external disturbances and unknown state variable, the attitude maneuver dynamics and adaptive hybrid control strategies are investigated in this paper. Methods The coupling dynamic equation of the spacecraft is derived by the conservation theorem of moment of momentum, where the liquid sloshing is equivalent as a spring-mass model and the flexible panel is modeled as an Euler-Bernoulli beam. As the angular velocity measurement is unavailable, the quaternions are used in place of the angular velocity, and an adaptive output feedback control scheme is proposed based on the backstepping technique. To suppress the liquid sloshing and vibrations of flexible attachments caused by the attitude maneuver, the command smoothing technique is implemented to the control system as a feedforward controller. Results and Conclusion The numerical simulation results demonstrate the effectiveness of the hybrid controller for ensuring the stability of the system attitude maneuvering and suppressing the system vibrations. The presented approach can guarantee the attitude control performance to be robust to the unknown state variables and external disturbances during the attitude maneuver.