Modal Frequencies Identification and Suppression for Magnetically Suspended Turbine Molecular Pumps With Flexible Foundation

The requirements for low vibration, especially for the magnetically suspended turbine molecular pump (MSTMP) systems, are ever increasing in the precision scientific instruments. The flexible foundation has become massively popular due to its ability to dampen vibration transmission. However, the unpredictable flexible foundation of MSTMP will cause resonance at different modal frequencies, which is detrimental to stable operation. This article focuses on the accurate identification of multifrequency modal frequencies and the resonance suppression of the MSTMPs. First, a dynamic model is established to analyze the impact of different foundations on the MSTMP. Second, an improved phase-locked loop (PLL) is designed with the additional offset parameter loop, on which a cascaded phase-locked loop is designed. The cascaded PLL is embedded in the control system, and the notch filter is adjusted according to the identification results to suppress resonance. Finally, the simulation and experimental results validate that the method can accurately identify the modal frequencies and ensure the stability of MSTMP.