Research On The Universal Magnetic-Suspension Models Of Bearingless Motor And Decoupling Control System

The bearingless motor has breached the theory category on running of conventional motor with mechanical bearing, and is a newly type of motor which integrates the function of revolving drive and that of rotor's self-levitation. All kinds of bearingless motor have the same or similar magnetic rules and characteristics, and the control-model is the foundation of reliable self-levitation control for bearingless rotor. Surrounding the principle how the magnetic suspension force be produced, and aiming at 4-pole bearingless motor with 2-pole magnetic suspension windings and cylindrical stator, a series of universal models have been analyzed and derived in detail, including the universal analytical models on inductance coefficients and inductance matrixes, the universal model on controllable magnetic suspension force. The decoupling control system of magnetic suspension system has been constructed, and relevant experiments have been made.Taking the 4-pole induction type bearingless motor with 2-pole magnetic suspension windings as example, and taking the influence of rotor eccentricity on airgap magnetic field into account, the Maxwell magnetic suspension principle of bearingless motor are analyzed. The radial electromagnetic force derived from Lorenz force which drives the rotor is analyzed in detail also, and the fundamental conditions are derived. When the fundamental conditions are satisfied, the radial electromagnetic force would be derived from tangent Lorenz force.The paper has made 4-pole beaingless salient-pole motor with 2-pole magnetic suspension windings as the generalized bearingless model-motor, whose salient-pole arc-width equals to"2ρ"radians. Based on the generalized model-motor, the influence of rotor eccentricity on the distributing principle of airgap magnetic field has been analyzed firstly. After then, based the distributing principle of airgap magnetic field, the universal models on inductance coefficients and inductance matrixes of bearingless motor are analyzed and derived in detail. The universal models on inductance not only be applicable to those bearingless motors with salient-pole rotor, but also be applicable to bearingless motors with cylindrical rotor. The validity of universal inductance models are validated by parameter experiment of induction type bearingless motor.According to the universal inductance models, and based on the virtual displacement principle of electromagnetic field, the universal model on controllable magnetic suspension force of bearingless motor are analyzed and derived in detail. The set of universal models on magnetic suspension force include universal model on revolving magnetic suspension force and universal model on magnetic suspension force in stationary directions. In the paper, the stationary magnetic suspension force experiment has been made, and the validity of universal model on controllable magnetic suspension force has been validated. The frequency characteristic of control current which controls the revolving magnetic suspension force is analyzed also. To producing revolving controllable magnetic suspension force with synchronous speed, half-frequency control current should be injected into the 2-pole suspension windings. And to produce revolving controllable magnetic suspension force with asynchronous speed, the angle frequency of control current should be"0.5(1+s)". Here,"s"is the difference ratio of the revolving speed of controllable magnetic suspension force relative to the synchronous speed of motor.The magnetic suspensions decoupling control system of three-phase bearingless induction motor has been designed based on the controllable magnetic suspension force model. After simulink simulation of decoupling control system, the experimental device on control system of bearingless induction motor are devised based on TMS320LF2407A CMOS chip, and the decoupling control experiment has been made. The simulation and experiment of decoupling control system have validated the decoupling characteristic of controllable magnetic suspension force model of bearingless induction motor, and the validity of the universal magnetic suspension force are validated in an applied example.At last, the periodic revolving inertia vibration and its control technology of bearingless motor are studied based on the controllable revolving magnetic suspension force model. The validity of revolving magnetic suspension force in controlling the periodic revolve-inertia vibration has been validated by the Simulation results and the half-frequency characteristics of control current has been validated also.