Study On Vertical Coupled Vibration Of Electric Vehicle Driven By Four In-wheel Motors

The electric vehicle driven by in-wheel motors has the advantages of high energy utilization,environmental protection,high transmission efficiency and high space utilization.It has become one of the main directions of the development of new energy vehicles in the future.However,under the excitation of road roughness,the vertical electromagnetic force induced by the eccentric in the in-wheel motor will cause a new vertical coupled vibration problem.Therefore,it is of great significance to study the vertical coupling vibration characteristics of electric vehicle driven by four in-wheel motors.Firstly,the modeling of air gap magnetic field and electromagnetic force of external rotor permanent magnet synchronous motor are carried out and the characteristic is analyzed.The analytical calculation model of air gap magnetic field and electromagnetic force under the non eccentricity,static eccentricity and dynamic eccentricity of the outer rotor in-wheel permanent magnet synchronous motor is established by using the magnetic field superposition method,the complex relative ratio magnetic conductivity method,the eccentricity correction coefficient method and the Maxwell tensor method etc.The correctness of the analytical calculation is verified by the finite element simulation of the air gap magnetic field of a 24-pole-27-slot external rotor permanent magnet synchronous motor.The magnetic field characteristics of the air gap magnetic field of the external rotor in-wheel permanent magnet synchronous motor with no eccentricity,static eccentricity and dynamic eccentricity,the force wave characteristics of the electromagnetic force wave and the frequency characteristics of the eccentricity produced by the eccentricity,the influence of the different eccentricity on the electromagnetic force are studied..Then,the vertical vibration characteristics of electric vehicle coupled by four in-wheel motors are studied.The vertical vibration model of electric vehicle driven by four in-wheel motors is established,and the inherent characteristics of vertical vibration of electric vehicle driven by four in-wheel motors are analyzed.The vertical vibration simulation model is set up,and the influence of vehicle speed and road roughness on vertical vibration acceleration of the body,the dynamic deflection of the suspension and the dynamic load of the tire are discussed.The influence of the static eccentricity or dynamic eccentricity of the in-wheel motor on the vertical acceleration of the body,the dynamic deflection of the suspension,the dynamic load of the tire and the vertical vibration acceleration of the stator are analyzed.The results show that the vertical vibration acceleration of the body,the dynamic deflection of the suspension and the dynamic load of the tire will increase,and the stability and handling stability of the vehicle will be reduced.The introduction of electromagnetic force produces a new frequency characteristic of the vertical vibration acceleration of the stator part of the wheel,which is an integral multiple of the fundamental frequency of the current.Finally,the vertical coupling vibration test of electric vehicle driven by four in-wheel motors is carried out.Vertical vibration acceleration signals of four in-wheel motors' stator parts and car body are collected during vehicle driving.The experimental results are compared with the simulation results to verify the influence of the introduction of the electromagnetic force of the wheel motor on the vertical vibration characteristics,and to explore the effect of the speed and the pavement on the vertical vibration of each part.