Notch Filter Design Based on Two-Frequency Bode Diagram for Elastic Vibration Depression of Magnetically Suspended High-Speed Rotor

In control moment gyroscope (CMG) based on magnetically suspended rotor (MSCMG), owing to wide controller bandwidth required by nutation stability at high rotational speed, bending mode between disk and axis of rotor with I-shaped configuration becomes unstable and tends to self-exciting vibration within the range of rotor speed. This elastic vibration can be depressed through adopting notch filter (NF) in original controller of active magnetic bearing (AMB), but NF design is still an issue since high-speed flat rotor features strong gyroscopic effect and coupling radial motions. By introducing complex representation, four DOFs (degrees of freedom) of dynamic model of magnetically suspend rotor considering unstable first-order bending mode is converted into single variable form without changing poles and stability. An illustrative and robust method of two-frequency Bode diagram is proposed to analyze elastic mode stability. Correction angle requirements of bending mode at various rotor speeds are summarized and parameters including NF grade, center frequency and pole damp are designed optimally. Employing the optimized notch filter, elastic vibration amplitude of statically suspended rotor of MSCMG was attenuated by -50.0dB comparing to original and the rotor is robustly stable within the entire speed range up to 20000r/min.