Study On Load Mechanism And Load Extraction Method Of Electric Vehicle Transmission System

In the course of running,the electric vehicle transmission system transmits the complex dynamic load of the interaction between the driving motor and the road surface.The output speed of the driving motor is high,the peak torque is large,and it is accompanied by shock and high-frequency fluctuation.The electric vehicle transmission system is characterized by simple overall structure and complex local structure.The change of the excitation source and its own structure makes the operating environment worse and the driving load more complex than that of the traditional automobile driveline.In order to ensure the design and verification of electric vehicle transmission system close to its real load,avoid the conservative or dangerous design of important parts,and improve the accuracy and efficiency of design and development,it is very important to study the load mechanism of electric vehicle transmission system and master the load extraction method.Based on the electromagnetic theory and automobile test technology,the two-stage reducer driven by permanent magnet synchronous motor,which is widely used in electric vehicles,is selected as research objects in this paper.From the experimental simulation of permanent magnet synchronous motor electromagnetic torque and half shaft load test,combined with the coupled multi-body dynamics theory,the electric vehicle drive train multibody dynamics model is set up,the electric vehicle drive train input-output load characteristics and load transfer characteristics were analyzed,on this basis,a load extraction method close to the actual load of electric vehicle transmission system is established,the main research contents include:(1)The analytical expression of permanent magnet synchronous motor electromagnetic torque and the sources and characteristics of torque fluctuation are systematically analyzed.The transient and steady-state electromagnetic torques under the influence of the motor structure,switching power supply and control mode are obtained by establishing the fieldcircuit coupling simulation model of permanent magnet synchronous motor and analyzing the simulation.Through the time-frequency analysis of the electromagnetic torque obtained by simulation,the load characteristics of the input end of the electric vehicle transmission system are extracted.(2)In order to analyze the load characteristics of the output end of electric vehicle transmission system,a load spectrum acquisition system of electric vehicle transmission system was established.The road load spectrum of an electric vehicle and a gasoline vehicle of the same grade under PASCAL condition is collected.Based on the collected half-shaft torque and speed,the amplitude and frequency characteristics of the torque are analyzed,and the differential analysis of the torque speed with the input end is carried out.(3)Based on the dynamic load excitation in the meshing process of the transmission gear,the rigid-flexible coupling multi-body dynamics model of the electric vehicle transmission system is established by using the multi-body dynamics software Recurdyn to comprehensively consider the meshing action of each pair of gear pairs,and the joint simulation model of the electromagnetic torque model and the multi-body dynamics model of the reducer is further established.Through joint simulation analysis,the paper analyzes the electric vehicle drive train frequency filtering characteristics of input signal and the amplitude attenuation characteristics,so as to obtain the characteristics of load transfer of the electric vehicle drive train.(4)Based on electric vehicle drive train load characteristics,combining the electromagnetic torque and speed reducer joint simulation model of multibody dynamics,respectively,puts forward the half shaft of motor speed and torque as the input and the electric vehicle drive train model calculation load for the input torque of drive train load extraction method,and the gear meshing force and load was extracted,so as to set up the two kinds of suitable for electric vehicle drive train load in different development phase extraction method.