| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 91 === Axial-flux permanent magnet (AFPM) motors can be designed to achieve a higher torque-to-weight ratio and motor efficiency, and are suitable for wheel motor applications. This thesis discusses the reduction of torque ripples for a brushless DC motor, and its optimal design by minimizing the torque ripple and maximizing the output torque. First, the equivalent magnet circuit model governing the relationship between alignment torque, phase current, and back EMF of the DC brushless motor are established depending on the real wheel motor geometry. The reduction of torque ripple is then discussed by the design of current waveform through harmonics analysis, as well as by the shape design of the motor to achieve a sinusoidal backemf. Second, the new procedure of an optimal design of brushless DC motor is developed by integrating the 3-D finite element analysis software and a multi-objectives optimization system tool. The optimal shape of the wheel motor is determined by main objectives under various constraints of space and materials. Finally, a novel design of the wheel motor with a new magnet, which has high magnetic energy, is proposed. To meet rigorous specifications on torque and speed, the pole ratio of stator and rotor is designed at 16:12, and the driving voltage 60 Volt is suggested.
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