Noncontact Rotor Vibration Velocity Sensor and Its Application to Vibration Control of a Flexible Rotor on Active Magnetic Bearings

Existing vibration displacement control strategies in active magnetic bearing (AMB) flexible rotor systems suffer from a trade-off between damping and noise, which makes it difficult for the system to pass the critical speeds of bending modes. To solve this problem, a rotor vibration velocity and acceleration feedback control strategy based on a noncontact velocity sensor technique is proposed in this article. The noncontact rotor vibration velocity sensor (NRVVS) uses the induced electromotive force (EMF) caused by changes in the air gap reluctance to measure the rotor vibration velocity. First, an analytical model of the sensor was developed and validated by the finite element method (FEM). Then, the structure of the vibration velocity and acceleration feedback control was proposed. Analytical and numerical calculations demonstrated that the rotor vibration velocity feedback is more effective for low-frequency vibrations, whereas the acceleration feedback is utilized to deal with resonances of higher-order bending modes and the weak controllability of the rotor system. To avoid excessive control gains at high frequencies, the least mean square (LMS) algorithm was adopted to extract the synchronous components of the acceleration. Finally, the experiments were carried out in the AMB flexible rotor test setup. The results showed that the vibration velocity sensor can be used to assist the proportional-integral–derivative (PID) controller to obtain extra damping without significantly increasing the current noise. Low-frequency vibrations were significantly reduced by damping from the rotor vibration velocity feedback. The vibrations at the critical speed of the second bending mode were substantially suppressed by the rotor vibration acceleration feedback.