Real-Time Control of Rotor Vibrations With Active Bump-Type Foil Bearings

The rotor supported by gas foil bearings (GFBs) suffers severe vibrations at extremely high rotating speed, which weakens the stability of the rotor-GFBs system. Although current solutions including increasing structural damping and mechanical preloads of GFBs suppress the rotor vibrations, they lead into larger wear during the lift-off process and higher friction torque during operation. In this article, active bump-type foil bearings with advantages of actively controlled mechanical preloads are utilized to rotor-GFBs system aiming at suppressing the rotor vibrations in real time. Open-loop control is utilized to obtain the proper U at different rotating speeds. The bifurcation diagrams of the rotordynamic responses under different voltages and rotating speeds are predicted to explain the relationship between U and real-time control of rotor vibrations theoretically. Proportional-integral-differential control method is utilized to control the vibrations of rigid rotor within relatively tight bounds under the conditions of constant rotating speed, coast-down process, and speed up and down process.