Study On Vibration Characteristics Of Pure Electric Vehicle Dynamic System Based On Mechanical-Electrical Magnetic Coupling

The vibration and noise of the variable-frequency driving pure electric vehicles is much smaller than the traditional internal combustion engine vehicle's,but there is still much middle and high frequency noise from the power system in pure electric vehicles.For the variablefrequency diving pure electric vehicle power system which integrates the motor and gearbox,using frequency converter and gear motor integrating motor and gearbox to do the simulation,establishing the corresponding vibration characteristic analysis model.From the source of vibration excitation,the vibration characteristics of the geared motor under the condition of electromechanical coupling are analyzed,and this will not only help us grasp the electric vehicle integrating power system the vibration and noise's generating mechanism,but also provide a reasonable vibration and noise reduction measures for the power system design,which is important for pure electric vehicle power systems aiming for low vibration and low noise in the development stage.The main research work and conclusions are as follows:(1)The vibration response model of the variable-frequency geared motor under electromechanical coupling condition is established.Based on the existing frequency converter and the geared motor,a 1D-3D joint simulation model of the variable-frequency geared motor is established,and the excitation force applied to the bearing housing when the gear motor is in operation is calculated.The finite element model of the two-dimensional electromagnetic field of the motor body is established by JMAG,and the radial electromagnetic force applied to the stator core under the joint simulation is calculated.Finally,based on the three-dimensional model of the flexible shell,a model is built for the analysis of the geared motor's vibration response under the condition of electromechanical coupling.(2)The vibration characteristics of the variable-frequency geared motor are systematically studied.The characteristics of the motor line current,the excitation force applied to bearing housing and the electromagnetic excitation force are analyzed.Under the condition of frequency converter-driven,the line current,excitation force applied to bearing housing and electromagnetic force all produce some additional harmonic components next to the carrier frequency of frequency converter,but the frequency distribution of harmonics produced by them in this frequency band is different.Compared with the traditional gear system simulation method,the joint simulation method of electromechanical coupling can simulate the influence of the change of the load and the change of the voltage and current on the vibration characteristics of the motor.The analysis results show that the high frequency part of the response is contributed by the excitation force applied to bearing housing and the electromagnetic excitation force,the intermediate frequency part is mainly contributed by the electromagnetic excitation force,and the low frequency part of the response is mainly contributed by the bearing force.Finally,the line current and vibration response are analyzed through experiments,and the results show that the main frequency components in the experiment and simulation are consistent,therefore the correctness of the simulation analysis is verified.(3)For some frequency components of the current frequency and some other frequency components with smaller amplitude in the low frequency band of the line current spectrum when the load driven by frequency converter,based on the theoretical analysis,the harmonic expression of the line current in the load is deduced under the condition that the dead time and the conduction voltage drop are taken into account and the voltage-source inverter uses asymmetric rule sampling.The results show that the 5,7,11,13 times the current fundamental frequency in the low frequency band of the current spectrum when the inverter drives the RL load,is caused by the dead time effects of the inverter bridge and the conduction voltage drop of the IGBT and diode,and the other frequency components with smaller amplitude are caused by the dead zone effect of the inverter bridge.Finally,the correctness of the theoretical analysis is verified by simulation and experiment.