Study On Noise Propagation Characteristics Of Three-in-one Electric Drive System Of Pure Electric Vehicle

Due to the problems of energy shortage and serious environmental pollution,pure electric vehicle has become an important direction for the development of the automobile industry.Its drive system is a three-in-one electric drive system integrated with controller,motor and reducer.However,during the operation of the vehicle,the three-in-one electric drive system will produce mechanical noise and electromagnetic noise,which will be transmitted to the vehicle through the structure and air,thus affecting the vibration noise of the vehicle and bringing a bad experience to the driver and passengers.Therefore,it is of great significance to analyze the vibration and noise characteristics of the three-in-one electric drive system and the interior,identify the source of the noise,and effectively reduce the interior noise.This paper mainly explores the vibration and noise characteristics of the three-in-one electric drive system of pure electric vehicles,identifies the source of vibration and noise of the three-in-one electric drive system,and analyzes the transmission characteristics of the three-in-one electric drive system of pure electric vehicles in the car.The main research contents of this paper are as follows:（1）Analysis of exciter characteristics of three-in-one electric drive system.Firstly,the three-phase current of the built-in permanent magnet synchronous system was collected and the amplitude-frequency characteristics of the current were analyzed.Then established the triad electric built-in electromagnetic model of permanent magnet synchronous motor drive system,the simulation calculation of triad electric built-in permanent magnet synchronous motor drive system of air-gap magnetic field,electromagnetic force and torque pulsation,and analyzes the triad electric built-in permanent magnet synchronous motor drive system of air-gap magnetic field,electromagnetic force and the torque amplitude frequency characteristics;Finally,the dynamic analysis model of the three-in-one electric drive system reducer considering the output torque ripple was established,and the gear meshing force and bearing dynamic force of the three-in-one electric drive system reducer were simulated and calculated,and the amplitude-frequency characteristics of the gear meshing force and bearing dynamic force were analyzed.The results show that the main frequency components of the built-in PMSM three-phase current are the integer frequency multiplier of the current frequency f_c and the f_s±kf_c near the inverter switching frequency f_s.The main frequency component of the electromechanical force of the built-in permanent magnet synchronous motor is2kpf_r,and the main frequency component of the output torque ripple of the motor is（2k-1）f_c.The gear meshing force of the reducer mainly contains the frequency component of kf_m,while the dynamic force of the bearing mainly contains the frequency component of kf_n and kf_m.（2）Analysis of noise characteristics of three-in-one electric drive system.Firstly,the acoustic-vibration coupling calculation model of the built-in PMSM,reducer and three-in-one electric drive system was established.The vibration and noise responses of the built-in PMSM,reducer and three-in-one electric drive system were respectively calculated under the steady state condition.Then,the vibration and noise amplitude-frequency characteristics of the built-in permanent magnet synchronous motor,reducer and three-in-one electric drive system are analyzed.The results show that the vibration noise of the built-in permanent magnet synchronous motor is mainly generated by electromechanical magnetic force,and the main frequency component is 2kpf_r.The vibration noise of the reducer is mainly generated by the torque pulsation of the motor and the gear meshing,and the main frequency components are kf_m1,kf_m2,kf_n3 and（2k-1）f_c.The noise of the three-in-one electric drive system is mainly generated by the electromechanical magnetic force and the gear meshing force of the reducer,and the main frequency components are 2kpf_r,kf_m1,kf_m2 and（2k-1）f_c.（3）Finite element modeling and modal analysis of pure electric vehicle.Firstly,the three-dimensional structure model and finite element model of the pure electric vehicle were established,and then the modes of the body in white were calculated.The results show that the low frequency modes of the body in white are mainly bending and torsion modes.（4）Analysis of interior noise characteristics of pure electric vehicle.Firstly,the three-in-one electric drive system and interior noise under acceleration and braking conditions were collected through experiments.Then,the amplitude-frequency characteristics of the three-in-one electric drive system and the interior noise are analyzed.The results show that the main frequency components of noise in the three-in-one electric drive system under acceleration and braking conditions are 22f_r,44f_r,48f_r,66f_r,f_s-12f_r,f_s+12f_r,and the main sources are electromagnetic force and gear meshing force.Under acceleration and braking conditions,the amplitude of high-frequency noise near the switching frequency of the three-in-one electric drive system with interior noise is greatly reduced,and the main frequency components are 22f_r,48f_r and other low-frequency noise.