Abstract
This paper presents a new optimization method to design a rotor structure for a permanent magnet motor that can reduce vibration. The optimization problem is formulated with a multi-objective function to minimize the fluctuation of the radial magnetic force and the torque ripple. To obtain the optimal rotor shape consisting of a permanent magnet and ferromagnetic material, a multiple level set model is employed to express the structural boundaries and magnetic properties of each material. The updating process of the level set function based on the adjoint sensitivity and the time evolutional equation makes it possible to obtain a novel rotor configuration of the motor. To verify the usefulness of the proposed method, a rotor design example of the surface-mounted permanent magnet motor for electric power steering system is performed.
Highlights
Since mechanical vibration is harmful to the robustness of an integration system and generates audible noise, which is a critical factor in human sensitivity, vibration reduction has become an important issue in motor design [1]-[3]
The optimizations are performed with different volume fractions of permanent magnet (PM) ( VFPM ) and the volume constraint of ferromagnetic material (FM) ( VFPM ) and FM ( (VFFM) ) is set to the same value (0.45) as the initial design
It is noted that the outer surface of the PM becomes an uneven shape for adjusting the path of the magnetic flux and the airgap is increased for minimizing the magnetic force on the stator
Summary
Since mechanical vibration is harmful to the robustness of an integration system and generates audible noise, which is a critical factor in human sensitivity, vibration reduction has become an important issue in motor design [1]-[3]. In the surface-mounted permanent magnet (SPM) motor where the permanent magnet (PM) dominates the magnetic flux path, the shape change of the rotor is the key to vibration reduction [9]. An optimization method that incorporates localized geometrical change [10] is introduced to get an innovative rotor design that guarantees a decrease in the motor vibration. The optimization problem is formulated to minimize the fluctuation of the magnetic forces, such as the local force on the stator and the driving torque, which can cause mechanical deformation of the stator. Of the proposed method and achieve an optimum rotor design that promises reduction of the vibration without deterioration of the output torque
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