Adaptive complete suppression of imbalance vibration in AMB systems using gain phase modifier

Synchronous vibration can be caused by rotor imbalance in high-speed rotors of momentum exchange devices, and the imbalance vibration is the main disturbance for attitude control of spacecrafts. Active magnetic bearing (AMB) is widely used in momentum exchange devices due to its active vibration control ability. To suppress the imbalance vibration completely, an adaptive control approach based on the AMB is proposed. First, dynamics of the AMB rotor with both static imbalance and dynamic imbalance are introduced, and the model of power amplifier is particularly analyzed. Large temperature change range and overpowering cosmic ray will induce considerable errors and variations in parameters of the power amplifier, which has to work in space for about ten years. Therefore, adaptive compensation should be made for these errors and variations. Conditions, on which the imbalance vibration can be completely suppressed, are analyzed, and the results show that these conditions can be satisfied with notch filters and feedforward compensations (FFCs). However, the FFC contains an inverse function of the power amplifier, whose errors and variations can result in gain and phase differences and changes between the output voltage of the controller and the actual output current of the power amplifier. Consequently, the FFC becomes inaccurate, and residual vibration occurs. Finally, a gain phase modifier (GPM) is proposed to form two closed loops to tune the gain and phase of the FFC adaptively and precisely. The effectiveness of the proposed approach has been demonstrated by simulations and experiments. Compared with the existing methods, this method can achieve adaptive complete suppression of the imbalance vibration unaffected by the errors and variations of the power amplifier.