| Distributed drive electric vehicles have become an important direction for the development of electric vehicles in the future with their distinctive structural features and performance advantages.Permanent magnet synchronous motor becomes the mainstream driving motor of distributed drive electric vehicle with high efficiency,high power density and excellent control performance,while the permanent magnet synchronous motor system for vehicle has structural design and process deviation,cogging torque and air gap magnetic field harmonic wave,magnetic circuit saturation,inverter nonlinearity,sensor error and other factors can cause motor torque fluctuations.Since the motor is directly connected to the wheel,the high frequency excitation caused by the torque ripple directly affects the vibration characteristics and grounding characteristics of the tire.This paper aims to investigate coupling characteristics between torque ripple and tire in distributed drive electric vehicle.To this end,the traditional dq model of permanent magnet synchronous motor which turn towards control is established.The model ignores the factors affecting the motor torque ripple as the ideal motor model,and then analyzes from the three aspects of motor body,inverter nonlinearity and sensor error.The mechanism of torque ripple generation of permanent magnet synchronous motor and the corresponding extended dq mathematical model are derived,revealing the magnitude and frequency characteristics of torque ripple.Secondly,based on JMAG-designer,the finite element model of hub motor in the distributed drive electric vehicle is established.The rotor flux harmonic is extracted according to the finite element model,and the extended dq model considering the rotor flux harmonic is constructed.In order to more accurately consider the torque ripple factor of the motor body,the motor finite element model is used to generate the JMAG-RT real-time model of the motor,and the nonlinear model of the inverter considering the dead time built in Matlab/Simulink and the feedforward compensation.The motor torque ripple model is obtained by joint simulation of id=0 control algorithm,and the simulation results are consistent with the analysis results.Then,in order to study the dynamic characteristics of the tire under high frequency excitation caused by torque fluctuation,a dynamic model of the tire that is efficient and can accurately express the high frequency mechanical properties of the tire is established.The TMPT(Tire Model Procedure Test)test data is established.The tire model was subjected to parameter identification and model verification.Finally,the influence of motor torque ripple on tire vibration characteristics and grounding characteristics is discussed.The effects of motor torque ripple on tire longitudinal force,vertical force and slip rate under four typical conditions are studied.The results show that the motor the torque fluctuation causes the longitudinal force of the tire to fluctuate to a certain extent,and the main frequency component of the torque fluctuation does not disappear by the moment of inertia and damping of the tire,but also appears in the response of the longitudinal force and the slip rate.At the same time,the torque fluctuation excitation generates resonance near the natural frequency of the tire’s own mode,causing large fluctuations.Torque fluctuation is caused by electromagnetic tangential force fluctuation.It causes vertical grounding force fluctuation to induce longitudinal vibration of electric wheel through the adhesion of tire and road surface.Longitudinal vibration is the main form of torque fluctuation excitation.Torque fluctuation is vertical to tire.The impact of force is small. |
