Translated Abstract
Permanent magnet AC servo motors have a lot of advantages such as small size, high efficiency, light weight and reliable operation. However, their use in precision control application are limited，because the inherent cogging torque in the motor will result torque pulsation and increase motor vibration and noise. Therefore, it is of significant to study the cogging torque reduction methods.
Firstly, the surface mounted permanent magnet AC servo motors were concerned in this thesis. Based on the analysis of cogging torque production mechanism and its analytical expression, the effects of stator and rotor structure to cogging torque were discussed, such as pole-arc optimization, the number of slots per pole, the emphases were put on the selection methds of auxiliary slot parameters at stator tooth-top including slot number and width as well as depth, and the stator slot width for reducing cogging torque. Processing method of unequal thickness magnent was introduced as well. These methods were verified with Ansoft simulation.
Secondly, the asymmetrical stator tooth-top configuration for cogging torque reduction was analyzed in detail. The cogging torque of the motor with asymmetrical stator tooth-top configuration were computed using 3D and 2D Finite Element Method(FEM). The general expression was given, which can be used to determine the structure dimensions for asymmetrical tooth-top to reduce the cogging torque. Simulation results show that, comparad with the symmetrical tooth-top structure, the configuration studed could not only reduce the cogging torque and torque pulsation, but improve the waveform of induced EMF and ensure the operation performances of the motor also.
Finally, the experiments on the cogging torque, induced EMF, temperature rise and load performances of a 750W motor with 4 poles 6 slots have been done. The results show that the cogging torque can be decreased significantly and the motor’s performance can be optimized by the combined use of different methods. The simulation results are consistent with that of the experiments, which further validates the correctness of the proposed method.
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