| Because of the advantages of the high performance, flexible control method, high starting torque and overload ability, small volume, light weight and the long life, Permanent Magnet Brushless DC Motor is applied in the various fields. However, the most prominent problem of PM-brushless DC motor is the torque ripple. The main content of this thesis is the optimize design by Genetic Algorithm and the finite element analysis of electromagnetic field, and the necessary theoretical basis to weaken the torque ripple of PM-brushless dc motor is provided by the conclusion.The main content of this dissertation is as follows,1.The composition of PM-brushless DC motor, the principle and the research status are introduced, the contributing factor and inhibitory method of the torque ripple are summarized.2.Genetic Algorithm mathematics model, design goal, optimization variables and constraints, crossover operator, mutation operator, electromagnetic torque formula and the convergence problem of GA are introduced. 3.The mathematical model of optimum design based on the improved adaptive Genetic Algorithm in the Visual Basic language environment is established, the optimization of motor structure parameter and detailed performance parameters are calculated.4.Through the finite element analysis software Maxwell, two-dimensional steady electromagnetic field model of PM-brushless DC motor is established, and the field air-gap flux density distribution is analyzed. Then the dynamic characteristics including voltage, current, back-EMF, torque and speed waveform are analyzed.5.According to the specific structural characteristics of the motor, the three-dimensional finite element simulation steady-state model is established, and the field air-gap flux density distribution is analyzed. Then the dynamic characteristics including voltage, current, back-EMF, torque and speed waveform are analyzed. The analysis results are the complement and checking of 2d finite element analysis results.
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