Stability Analysis Method of Magnetically Suspended High-Speed Rotor Based on Two-Frequency Bode Diagram

In magnetically suspended high-speed rotor, the strong gyroscopic effect causes radial rotations of the rotor coupled and leads to precession and nutation, which exhibits different stabilities at different rotor speeds and influences rotor system stability primarily. For direct-viewing and robust stability design, a new stability analysis method based on two-frequency Bode diagram is proposed to discriminate precession and nutation stability of magnetically suspended symmetric high-speed rotor. Complex transformation is introduced and two-variable rotor dynamics model with real-coefficient is converted to equivalent single variable form with complex-coefficient, thus the Bode diagrams of equivalent open-loop transfer function are plotted within both negative and positive frequency fields. Subsequently, classic frequency field stability criterion is generalized to two-frequency Bode diagram, and precession and nutation stability and its margins are analyzed, which provides important foundation for stability design. Relevant experiments verified the benefits of the above-mentioned method.