Analysis And Decoupling Control For Magnetic Bearing High-speed Motors Rotor System

At present,high-speed motors are playing an important role of rotating equipments.Compared with traditional rolling element bearings and fluid journal bearings,active magnetic bearings(AMBs)with some specific properties,such as free of contact,absence of lubrication,controlled dynamic behavior,are particularly useful for high-speed motors.This paper aimed at the analysis and control method for an AMB-rigid rotor of magnetically suspended high-speed motors.Based on the introduction of the main components of the AMB-rigid rotor system,the model of ABM-rigid rotor radial four degree-of-freedoms system considering the rotor imbalance is built.Due to the instability behavior of the open-loop system,the closed-loop control is of necessity.For the AMB-rigid symmetric rotor,the natural vibrations of the system under PD control are analyzed,and the modal eigenvalues are solved.Then the influences of the proportional feedback gain P and the velocity feedback coefficient D acted on the natural behavior of the system are studied.The forced vibration due to the rotor imbalance is also analyzed in order to demonstrate the resonance characteristics.The method to adjust to parameters P and D,and the frequency characteristics of the system are given.Besides,the disadvantages of PD control for coupled AMB-rigid rotor system are analyzed.For the AMB-general rigid rotor system,the coupling characteristics under two coordinate systems are analyzed.A feedforward decoupling control for magnetically suspended rigid rotor system is proposed,and two kinds of the rotor imbalance compensation methods are used when the rotor system has been decoupled.In order to improve the performances of feedforward decoupling control and imbalance compensation,a time-optimal tracking-differentiator is used to get the differential signals.At last,the hardware and software of the magnetically suspended high-speed motor experiment platform are introduced,and the effectiveness of the designed coupling and imbalance compensation methods are confirmed by several experiments.