On-orbit modal identification for vibration suppression of flexible aerospace structure using reaction wheel actuator

Abstract

Flexible aerospace structure presents dynamic characteristics of low natural frequency and slow amplitude attenuation. Attitude adjustment or orbital maneuver for the spacecraft can excite the vibration of its flexible appendages/structures, which is prone to affect the normal operation of spacecraft. To address such problems, this paper introduces a feasible methodology by using reaction wheel (RA). The active feedback control strategy is established based on the relation of the measured bending moment and the wheel's rotating speed. The control law with a PD controller is adopted. The torque induced by the speed change of RA can be considered as an artificial damping to accelerate structural vibration attenuation. To guarantee the vibration suppression effectiveness and efficiency for engineering application, a modal identification approach using RA is proposed. The identification algorithm is designed by a vector fitting algorithm of rational polynomial combined with Fast Fourier Transform algorithm. The identified modal parameters are also utilized to design input shaper for the RA braking speed function, which is well verified to avoid undesired excitation. Both the numerical simulation and experimental research demonstrated the success of adopting reaction wheel as an actuator. For a full-scale solar array, the time required for vibration attenuation to the same amplitude is reduced from 602.8 sec to 162.4 sec.