Thrust noise cause analysis and suppression of a cusped field thruster

Abstract

The drag-free control technology is a critical technology to guarantee the ultra-low disturbance satellite platform. Thrust noise is the primary disturbance of the drag-free control system because the thruster acts as the actuator of this system, so it would seriously affect the performance of the control system. To study and suppress thrust noise, a cusped field thruster, which has the feasibility of being applied to the drag-free control tasks, is used in this research. According to the experimental results of thrust noise, it can be seen that the thrust noise spectrum under different working conditions is different slightly, but the trend is similar. The amplitude spectrum densities of thrust in the high-frequency region present white noise characteristics, while the amplitude spectrum densities increase with the decrease of frequency in the low-frequency region. Based on the input-output thrust model and the experimental data of the anode voltage and flow rate, the effects of the anode voltage fluctuation and flow rate fluctuation on the thrust noise are analyzed. The high-frequency part (above 0.05Hz) of thrust noise is mainly caused by the flow rate noise, while the drift of thruster operation states leads to low-frequency (10−3Hz–0.05Hz) fluctuation of thrust. Finally, based on the feedback control theory, a noise suppression method is designed by controlling the anode voltage. Closed-loop simulation results of the thruster verify that the method is effective.