Disturbance estimation and compensation for drag-free satellite based on frequency domain disturbance observer

Gravity gradient measurement satellite is a kind of drag-free satellite and suffers from multiple disturbances in the low earth orbit. So the disturbances estimation and compensation for the drag-free satellite is very important to improve measurement precision. In this paper, the characteristics of multiple disturbances are analyzed. Then, the frequency domain disturbance observer is designed for disturbance estimation and compensation. Next, a composite controller combining the frequency domain disturbance observer with PID controller is presented to reject and attenuate the multiple disturbances. At last, the simulation verification is carried out to verify the effectiveness of the proposed method.