A relationship between unbalance vibration compensators for five-axes active magnetic bearing systems and vibration suppression utilized its relation

Abstract

An active magnetic bearing (AMB) is utilized widely in vacuum apparatuses such as a turbo molecular pump (TMP). The rotor supported by the AMB in the TMP is vibrated by the unbalance of the mass of the rotor, the electromagnetic force of the AMB and the location of the AMB. As the methods to suppress this vibration, phase-variable type Peak-of-Gain Control (JIS B 0913-1, Unbalance Force Counteracting Control: UFCC), phase-variable type Automatic Balancing System (JIS B 0913-1, Unbalance Force Rejection Control: UFRC) and Phase-Variable Control (PVC) have been reported. The UFCC (UFRC) suppresses the vibration by increasing (decreasing) the bearing stiffness and giving the damping effects at the rotational frequency. However, the relationship between the UFCC and the UFRC is not expressed. Accordingly, we investigate the UFCC (UFRC) is corresponded to the UFRC (UFCC) by using the phase changes. On the other hand, the repetitive control which is one of the periodic disturbance suppression methods also has been proposed. The control suppresses the unbalance vibration based on the internal model principle. For the unbalance vibration compensation, we clarify the UFCC is considered as repetitive control by using the pole assignment. Moreover, we show the unbalance vibration is further suppressed by using the UFCC which is corresponded to the rotational frequency and the second harmonic.

Keywords

• turbo molecular pump
• magnetic bearing
• unbalance vibration
• peak-of-gain control
• automatic balancing system
• repetitive control
• internal model principle