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In one of the problems of the rotary machine, unbalance vibration synchronized with rotational frequency is well known. This vibration is caused by the unbalance of the mass of the rotor, the electromagnetic force of the active magnetic bearing (AMB), and the location of the AMB. As the methods to suppress this vibration, Peak-of-Gain Control (PGC) and Automatic Balancing System (ABS) using the tracking filter synchronized with the rotational frequency have been reported. By using the PGC (ABS), the bearing stiffness at the rotational frequency is increased (decreased). In addition, the phase is advanced by applying the compensation with the phase-variable type tracking filter, the N-cross control, and the compensation with the differentiator. The damping effects are increased in these compensation methods, however a change of the bearing stiffness is caused. Moreover, the compensation methods advanced phase cannot adjust the bearing stiffness and damping effects independently and cannot confirm only the damping effects. Accordingly, we investigate the mutual relationship between the compensation methods increased damping effects and indicate that the compensation method to minimize a change of the bearing stiffness with increasing the damping effects is the method with the phase-variable type tracking filter. These methods advanced phase can be considered as gain stabilization methods, and we propose Phase-Variable Control (PVC) classified as a phase stabilization method. The characteristics of the proposed PVC are adjusting the bearing stiffness and damping effects independently, having both characteristics of the conventional PGC and ABS, and changing the bearing stiffness and damping effects seamlessly. Furthermore, the proposed PVC can adjust the bearing stiffness and damping effects appropriately as the rotational speed increases, and we show that the whirling of the rotor is suppressed from the experimental results concerning rotational tests.

A design method for an unbalance vibration compensator of five-axes active magnetic bearing systems