Vibration suppression of flexible spacecraft during attitude maneuver using CMGs

In this paper, control moment gyroscope (CMG) system is employed to suppress vibration of flexible spacecraft during attitude maneuver. Direct modal force generated by CMGs is exerted to elastic dynamics due to interaction between CMGs and flexibilities of structure. A novel control strategy based on a modal force compensator is proposed, which is simple and efficient to reduce vibration during attitude maneuver. The proposed modal force compensator avoids exciting vibration by the means of canceling out disturbance input to elastic dynamics using modal force generated by CMGs. No modal information is required in the modal force compensator. A concept named as modal force singularity is introduced and analyzed in depth. A restriction on gimbal angles is developed to avoid modal force singularity. Subsequently, a steering logic based on pseudo-inverse is proposed to allocate modal force commands without introducing force errors. Numerical simulations are presented to show the effectiveness of the proposed approaches.