Research On Electromechanical Magnetism And Solid Coupling Vibration Of Electric Vehicle With Four In-wheel Motors

The in-wheel motor drive will become an important driving way for electric vehicles in the future due to its compact structure,short transmission chain,high efficiency and high utilization of vehicle interior space.However,under the coupling excitation of road and electromagnetic force,the electric vehicle with four in-wheel motors may encounter complex electro-mechanical-magnetic-solid coupling vibration,which affects the ride comfort of the electric vehicle.Therefore,it is necessary to study the vibration characteristics of the electric vehicle with four in-wheel motors under multi-mode and multi-vibration source coupling excitation.Vector control modeling and current harmonics analysis of external rotor permanent magnet synchronous motor(PMSM).Based on the mathematical model of the external rotor PMSM,the vector control simulation model of the external rotor PMSM was established,and the amplitude-frequency characteristics of the current harmonics was revealed.The experiment on unsteady current harmonics of external rotor PMSM was carried out,the time-frequency characteristics of unsteady current harmonics was verified.The results show that the current harmonics is mainly composed of low-order current harmonic(6h±1)fc and side-band current harmonic of switching frequency of inverter k1fs+k2fc,the current harmonics frequency and motor speed show obvious order characteristics under non-stationary conditions(6h±1)pn/60 and k1fs±k2pn/60,where fc is the fundamental current frequency,fs is switching frequency of inverter,k1 and k2 are positive integer,h=0,1,2,3…,p is the pole number of the motor and n is the rotational speed of the motor.Analytical modeling and analysis of magnetic field and electromagnetic force of the external rotor PMSM with circumferential eccentricity.An analytical calculation model of air gap magnetic field and electromagnetic force of external rotor PMSM with circumferential eccentricity was established,when the magnetic field is not saturated,the permanent magnet magnetic field and the armature reaction magnetic field are superimposed to obtain the air gap magnetic field of external rotor PMSM without considering slotting effect.The air gap magnetic field of the slotted external rotor PMSM was obtained by the complex relative magnetic permeability method,the electromagnetic force of the external rotor PMSM was obtained by Maxwell stress tensor,the air gap magnetic field and electromagnetic force of the external rotor PMSM with static eccentricity or dynamic eccentricity were obtained by the permeability correction coefficient.The results show that static eccentricity and dynamic eccentricity result in±1 space order to the air gap magnetic field and ±1,±2 space order to the electromagnetic force of the external rotor PMSM in the stator coordinate.Static eccentricity does not affect the frequency characteristics of the air gap magnetic field and electromagnetic force of the external rotor PMSM while dynamic eccentricity causes the frequency component of the air gap magnetic field to appear ±fr and the frequency component of the electromagnetic force to appear ±fr and ±2fr component in the stator coordinate,fr is mechanical frequency.The effects of static eccentricity and dynamic eccentricity on the air gap magnetic field and electromagnetic force space order of the external rotor PMSM in rotor coordinate are consistent with those in stator coordinate.The dynamic eccentricity does not affect the air gap and electromagnetic force frequency characteristics of the external rotor PMSM in rotor coordinate,static eccentricity causes the frequency component of the air gap magnetic field to appear ±fr and the frequency component of the electromagnetic force to appear ±fr and ±2fr component in the rotor coordinate.Analytical modeling and analysis of magnetic field and electromagnetic force of external rotor PMSM with tilting eccentricity.The air gap magnetic field and electromagnetic force of the external rotor PMSM with tilting eccentricity were established in stator and rotor coordinates,based on the permeability correction coefficients of static eccentricity and dynamic eccentricity,the permeability correction coefficients of the tilt static eccentricity and tilt dynamic eccentricity were established,the air gap magnetic field and electromagnetic force of external rotor PMSM with tilt static eccentricity or tilt dynamic eccentricity were obtained by the permeability correction coefficient.The results show that the effects of tilt static eccentricity and tilt dynamic eccentricity on the air gap magnetic field and electromagnetic force space order and frequency characteristics of external rotor PMSM in stator and rotor coordinates are the same with those of static and dynamic eccentricity in stator and rotor coordinates respectively,the influence of the tilt eccentricity on the air gap magnetic field and electromagnetic force amplitudes are different from the circumferential eccentricity.Study on longitudinal-vertical coupled vibration characteristics of the electric vehicle with four in-wheel motors.The mathematical model and simulation model of longitudinal-vertical coupled vibration of the electric vehicle were established based on the longitudinal-vertical coupled vibration mechanics model,the longitudinal-vertical coupled vibration characteristics of electric vehicle under road excitation,road excitation and electromagnetic force coupling excitation were studied.Research shows that with the increase of road surface roughness,the body pitch angle,body vertical vibration acceleration and motor eccentricity increase significantly.Under non-stationary conditions,the electromagnetic force excitation of the in-wheel motor will cause the order vibration of the electric vehicle with four in-wheel motors,the vibration frequency and the motor speed show obvious low harmonic order hpn/60 and the inverter switching frequency sideband harmonic order k1fs±k2 pn/60,specifically,the 2th,6th,18th order vibrations of the vehicle body,the 2th,6th,18th,frequency of fs±3fc,2fs+2fc and 2fs±6fc order vibrations of the wheel stator.Experimental study on vertical vibration of electric vehicle with four in-wheel motors.Taking an electric vehicle with four in-wheel motors as the test object,the vertical vibration of the electric vehicle under different speeds,different road surfaces and accelerations were tested,the accuracy of the longitudinal-vertical vibration model of the electric vehicle with four in-wheel motors was verified.The results show that when the road surface roughness and vehicle speed increase,the vertical vibration acceleration of the electric vehicle with four in-wheel motors increases,the electromagnetic force excitation will cause order vibration to electric vehicle with four in-wheel motors.