The Research Of Anti-Demagnetization Technology Of Permanent Magnet In High Density Permanent Magnet Motor

With advantages of high efficiency, high density, wide speed range, permanentmagnet motors have widely used in electric automobile, aerospace, robotics andother fields. But because of small volume, strong armature reaction, high heatdensity and large change of environmental temperature, high density permanentmagnet motors have the risk of performance decline, even complete loss of drivingability result from irreversible demagnetization. Anti-demagnetization technology ofhigh density permanent magnet motor has become the key technology in highdensity permanent magnet motor system. On this background, combined with thenational project of "Research of industrialization technology of permanent drivemotor and its control system with high cost-effective"(No.2011AA11A236),"Research of motor system key technology and evaluation system"(No.2011AA11A238), and project of "Research of industrial robot servo drive motorand Engineering"(No.2011AA04A105), based on the need of anti-demagnetizationin design and control of high density permanent magnet motor, this thesis carry onthe research of demagnetization model, multi-objective optimization design ofpermanent magnet motor and the state observation and control online and so on.The main contents and contributions are as follows:1. Research of demagnetization mechanism and model of high densitypermanent magnet motor.Demagnetization of permanent magnet motors usually are due to multiplefactors that affect each other. At the same time, different analytic results ofpermanent magnet demagnetization effect using existing model cause confusion ineffect analysis and state estimation of permanent magnet demagnetization.Based on permanent magnet magnetic theory, combined with the applicationfeatures of the vehicle motor; on the basis of magnetic domain wall pinning theory of permanent magnet, this thesis analyze remarkable demagnetization effect oftemperature, armature reaction, chemical, vibration and aging, obtain the conclusionthat the temperature and armature reaction is main factor of demagnetization in highdensity permanent magnet motor, and induces application and limitation of variousof demagnetization model.2. Research of bidirectional magnetic network model of demagnetization withtemperature parameterUsing traditional magnetic circuit, the design of permanent magnet motor is fastand simple, but has not ability of analysis and evaluation of demagnetization. Finiteelement method has high accuracy, but the demagnetization analysis using couplingsimulation of temperature field and the magnetic field is time consuming, alsocannot reflect relation between the design parameters and capability ofanti-demagnetization to effectively guide design of anti-demagnetization.Based on the conclusion that temperature and magnetic field are the main andsignificant factor in magnet demagnetization, this thesis establish bidirectionalmagnetic network model and temperature parameters database of permanent magnetin Matlab/Simulink simulation platform to rapidly assess the basic design parametersand ability of anti-demagnetization of motor. The bidirectional magnetic networkmodel can simultaneous calculate radial and circumferential magnetic fielddistribution of permanent magnet motor, in order to improve the calculationprecision of the magnetic network model.3Research of multi-objective optimum design with anti-demagnetization ofpermanent magnet motorBased on research of anti-demagnetization design, this thesis carry onmulti-objective optimum design of permanent magnet motor. Multiple objectivesinclude: anti-demagnetization ability, quantity of permanent magnet and costanalysis, torque ripple, iron core loss. These objectives and design parameters aremutual restriction and difficult to express using explicit function that give difficulty to the multi objective optimal design.This thesis carry on finite element simulation test with multi-parameters, and dorefined simulation test in the key parts of motor. Based on the simulation data tobuild multi-objective regression model that and its definitely coefficient exceeds0.96, with high fitting degree. It solves the model of multi-objective optimizationproblem. On this basis, this thesis search multi-objective optimization result usinggenetic algorithm that can achieve fast and efficiently global optimal solution.4. Research of state observer of permanent magnet in running stateA permanent magnet armature reaction temperature, intensity and distribution isthe operation process of the motor permanent magnet demagnetization of the twomain factors, based on permanent magnet motor thermal network model and lossmodel solving rotor permanent magnet temperature observation problem, on thebasis of the permanent magnet temperature, shaft and Zhou Dingzi current, establishthe permanent magnet motor running state observer, implementation when the motoris running with the temperature parameters of the permanent magnet stateobservation.5. Research of vector control system and its experimental verification with stateobserver of permanent magnetBased on the research of state observer of permanent magnet and current vectorcontrol strategy, this thesis design motor control system and and experimentalplatform with state observer of permanent magnet. As the carrier of national projectelectric vehicle special issue we construct the permanent magnet motor, its drivingdevice and control system, and carry out a series of experiments that containelectromagnetic properties of prototype experiment, temperature observationexperiment and anti-demagnetization control strategy to verify the feasibility of themethod of design and anti-demagnetization control system.