Nutation Mode Suppression of Magnetically Levitated Turbo-Rotor via Damping Optimization

The significant nutation will degrade the stability of high-speed magnetically levitated turbo-rotor system. This article presents a damping optimization method to suppress the nutation mode. The proposed method consists of two parts: nutation compensation and damping optimization. The nutation compensation with the cross-channel displacement signal is designed in detail to increase the damping force of nutation mode in the first part. The root locus of the closed-loop rotor system is used to analyze the effect of damping compensation. The control parameters are iterated to configure the pole of the nutation mode with the goal of making the rotor system have the optimal damping ratio at the nutation mode. Finally, simulation results show that the nutation damping ratio of the rotor system with the proposed method is greater than 0.658, and the experiment results on a magnetically levitated turbomolecular pump prototype validate that the proposed damping optimization method can effectively suppress the nutation mode and its power spectrum level is below $-$60 dB over the entire speed range.