Research On Cogging Torque Of Permanent Magnet Synchronous In-wheel Motor Based On Finite Element Analysis

The problem of environmental pollution and resource shortage has attracted more and more attention.The electric vehicle industry has become the focus of development as a new energy industry,and the in-wheel motor is an important part of the drive of electric vehicles,and has gradually become the focus of research.Permanent magnet synchronous motors（PMSM）are widely used in in-wheel motors of electric vehicles because of their miniaturization and high power factor.The cogging torque will affect the performance of the motor,causing torque fluctuations,vibration and noise.Therefore,the study of methods to suppress cogging torque is of great significance.In this thesis,the permanent magnet synchronous hub motor is used as the research object,and the finite element analysis method is used to study the suppression effect of the pole arc coefficient method and the auxiliary slot method on the cogging torque of the motor:（1）This thesis summarizes the research status and application environment of PMSM,and summarize its performance requirements.According to the development history at home and abroad,the research results of the main structure are briefly introduced,the technical introduction of the in-wheel motor is analyzed,and the current research status of the motor cogging torque is analyzed.（2）This thesis establishes a PMSM finite element model,determine the main structural dimensions of the motor,the structure and parameters of the stator and rotor of the motor,the structure of the permanent magnet,and the parameters of the main components of the permanent magnet material.In the case of suppressing the cogging torque,establish a permanent magnet synchronous hub motor The finite element model is used as a preparatory work for studying the method of restraining the cogging torque of the motor.（3）This thesis compares the analysis methods of cogging torque,energy method,Maxwell tensor method,finite element method and magnetic flux-magnetomotive force method,analyze the generation principle of cogging torque and cogging torque expression,and analyze the ability to suppress cogging torque influencing factors of,reduce B_rnz/2pand G_nin the analytical expression of cogging torque to achieve the purpose of suppressing cogging torque.（4）This thesis established a parameterized model of the pole arc coefficient of the built-in permanent magnet synchronous motor is established.From the perspective of the motor rotor,a method is proposed to reduce the cogging torque by modifying the pole arc coefficient of the motor to reach the theoretical optimal value.When the pole arc coefficient is 0.8322,the cogging torque suppression effect is the best.（5）This thesis starts from the stator side,the auxiliary slot method is adopted to suppress the cogging torque of the motor.By changing the number of auxiliary slots,slot depth,slot width,slot area and slot shape,the influence of the auxiliary slots on the cogging torque of the permanent magnet synchronous motor is analyzed by finite element method.Analyze the changes in the performance of the motor before and after opening the auxiliary slot,mainly from the changes of the back electromotive force,the fundamental wave of the air gap magnetic density and the various harmonics.The results show that the pole arc coefficient method and the auxiliary slot method can effectively suppress the cogging torque of the motor.When the optimal pole arc coefficient is0.8333,when the number of auxiliary slots is 2 and the slot shape is rectangular,the slot depth When it is 0.7mm,the slot width is 1.2mm,and the slotting area is 0.84mm²,the cogging torque suppression effect is the best.