Analysis And Optimization Of Vibration And Noise Characteristics Of PMSM On Vehicles

In recent decades,with the continuous increase of automobile production and sales in China,the problem of exhaust emission problem is becoming more serious.Therefore,for the purpose of environmental protection and energy saving,the development of new energy automobile industry begin to receive support from the state.Although the new energy vehicle motor is simpler in structure and has lower overall sound pressure level than the traditional fuel car engines.Because the frequency domain masking effect of motors is weaker than the traditional fuel car engines,which make single frequency noise is more outstanding in the middle and high frequency band.Therefore,how to improve the new energy automobile motor NVH(Noise Vibration Harshness)performance at current is one of the most active subject in the new energy automotive industry.In order to deeply study the noise mechanism of the new energy automobile motor and improve the motor NVH performance,this paper takes an interior permanent magnet synchronous motor as example for analysis and discussion.Firstly,on the basis of the electromagnetic equivalence principle and the subdomain model,this paper presents a theoretical solution of no-load air gap magnetic field distribution of the motor,and considers the influence of the slotted air gap through conformal mapping.In view of the difficulty in solving the air gap magnetic field of the motor under load condition,this paper improves the equivalent circuit model to make it consider the superposition relation between the winding magnetic field and the permanent magnet magnetic field,and verifies its rationality through finite element simulation.On this basis,this paper uses Maxwell stress tensor method to theoretically solve the electromagnetic excitation generated by the air gap magnetic field,compares and verifies the results with the finite element simulation results,and analyzes its spatial fluctuation characteristics.Secondly,through theoretical solution,simulation calculation and modal testing,this paper analyzes the dynamical characteristics of the motor stator assembly,the rotor assembly and the shell.Thirdly by combining the electromagnetic excitation at different speeds with the dynamic characteristics of the motor parts,this paper simulates and predicts the noise emission of the motor at different speeds,and verifies it through experiments.Finally,aiming at the different NVH-related problems in the noise testing,based on the previous theoretical and simulation analysis results,this paper first adopts the topology optimization to improve the structural response,and then optimizes the electromagnetic excitation through the BP neural network prediction model.The theoretical analysis and experimental results show that,compared with the traditional fuel vehicle engine,the electromagnetic excitation generated by the new energy vehicle motor contains a large number of harmonics,and its noise radiation presents an obvious order characteristic,resulting in the structure resonance becomes difficult to avoid.The theoretical method and optimization method described in this paper can be used to analyze the excitation characteristics from the root,and study the dynamic characteristics of each part of the motor,so as to effectively improve the NVH performance of the motor.