Research On Coupling Dynamics Of Integrated Electric Drive System Of Pure Electric Vehicle

The electric drive system is one of the key components of pure electric vehicles.With the development of the electric drive system toward high-speed,integration,and light weight,the vibration and noise problems caused by it become more and more obvious.The electric drive system interacts with multiple physical fields during the operation process,and its internal and external excitation and nonlinear factors are abundant,which leads to the complex and diverse dynamic characteristics of the system.The dynamic performance directly affects the comfort,safety and reliability of the vehicle.Therefore,the study of the influence of the internal and external excitations of the integrated electric drive system on the electric drive system and the study of the dynamic characteristics of the integrated drive system under different operating conditions are the keys to achieving the safe operation of pure electric vehicles and ensuring the stable and reliable operation of the system.This thesis is based on the National Key Research and Development Program(Development of High-performance Pure Electric Sport Utility Vehicle(SUV),Grant No.2018YFB0106100)and National Natural Science Foundation(The Investigation on Coupling Dynamic Mechanism and Design Method of High-speed Flexible Planetary Gear Transmission System,Grant No.51705042).Taking a certain type of pure electric vehicle integrated electric drive system as the object,an electromechanical coupling dynamics model of the integrated drive system suitable for variable speed conditions is proposed.The electromagnetic excitation characteristics of the permanent magnet synchronous motor and the time-varying gear system are taken into account.Non-linear excitation of meshing stiffness,gear meshing error,and structural flexibility of the box and rotating components.This paper focuses on the dynamic behavior of the electric drive system under the combined action of steady-state/acceleration and other operating conditions,motor fluctuating torque,time-varying meshing stiffness,gear meshing error,box flexibility and other internal and external excitations,and has mastered the system’s internal and external excitations.The influence of external incentives and typical operating conditions on the dynamic characteristics of the system can provide theoretical support for the design and dynamic performance improvement of the integrated electric drive system of pure electric vehicles.The main contents of this thesis are as follows:1.The finite element method is used to establish a permanent magnet synchronous motor model considering the radial and tangential electromagnetic force distribution in time and space.Based on the modal polycondensation method,a finite element polycondensation model of fixed components such as boxes is established.For rotating components,calculation methods of centrifugal force,inertial force and Coriolis force are proposed,and gears,shafts,differential housings,etc.are established.The finite element polycondensation model of rotating components.Angular displacement and translational displacement are used as generalized coordinates to establish a six-degree-of-freedom intensive parameter dynamic model of parallel-axis helical gears.The time-varying meshing stiffness and error excitation of the gear are expressed as a function of gear angular displacement,making it suitable for variable speed conditions.kinetics analysis.Based on the Newton’s law of non-inertial system,a dynamic model of the differential is established.Finally,the electromechanical coupling dynamics model of the integrated electric drive system is established by coupling the motor model and the gear dynamics model.2.By means of inherent characteristic analysis and dynamic simulation,the correctness of the deduction of the condensation model and the centrifugal force of the rotating component was verified.The dynamic characteristics of the integrated electric drive system under steady-state conditions are studied,combined with time domain and frequency domain analysis,the influence of dynamic parameter excitation such as motor ripple torque,rotating component centrifugal force,gear meshing error on the system dynamics characteristics is studied Laws: The difference in the dynamic characteristics of the system before and after the coupled box is studied,and the influence of the box flexibility on the dynamic meshing torque of the gear,the dynamic displacement of the gear center,the bearing reaction force and the vibration response of the box are analyzed,and the system parameter selection and dynamic design are analyzed.Provide guidance.3.The complex eigenvalues of the integrated electric drive system before and after the coupled box body are calculated under consideration of damping,and the influence of the box body flexibility on the natural frequency of the system is analyzed.Under acceleration conditions,the dynamic simulation of the integrated electric drive system before and after the coupling box was carried out,and the influence of gear meshing error on system resonance was studied.The resonance speed and resonant frequency of the system before and after the coupled box are analyzed,the influence of box flexibility on the low-order resonance of the system is studied,and the box vibration response during acceleration is analyzed.