Dynamic Modeling And Response Research On Electromechanical Coupling Of Electric Bus Drive System

With the progress of technology and the improvement of people’s living standards,cars have appeared in every corner of society.Although the development of the automotive industry has become mature,the new energy vehicle industry has also emerged and developed rapidly in response to the current energy background and environmental factors.Electric vehicles are the main body of the current new energy vehicle group.In addition to household cars,electric buses are also widely used in various cities.However,during the operation of electric buses,there are always some unusual torsional vibrations in their drive systems,which may lead to the failure of components such as gears in the transmission system.This will bring hidden dangers to the safe operation of vehicles,thereby threatening the safety of people’s lives and property.Therefore,it is necessary to investigate the causes in order to solve this problem.For the torsional vibration problem of electric vehicle drive systems,scholars in related fields have mostly studied the causes from the motor control parameters and the characteristics of mechanical transmission systems themselves.However,this paper studies it from a new perspective.Firstly,the capacitance and inductance between the windings in the motor are equivalently separated from the motor entity into independent parts,and the electric and magnetic field energies are obtained by combining the current and voltage parameters of the battery.Then,the kinetic energy and potential energy during the torsional deformation of the motor shaft are calculated and substituted into the Maxwell Lagrange equation to obtain the dynamic model of the battery motor subsystem.After that,the long shaft and gear in the transmission,reducer/differential,half shaft,and wheel are separated,and the elastic deformation of the long shaft is described using the finite element method and an elastic model is established.The corresponding rigid model is established without considering the deformation of the gear.Finally,all models were renumbered as a whole,and integrated into a electromechanical coupled nonlinear dynamic model of the electric bus drive system that comprehensively considered the unstable discharge characteristics of the on-board battery,the electromagnetic field factors in the motor,and the elastic deformation of the long shaft in the entire transmission system.Based on the established model,programming simulation analysis is conducted using matlab software.After inputting the driving system parameters of a certain type of electric bus,the newmark method is used for numerical iterative calculation.The time and frequency domain responses of the first 10 natural frequencies and the angular displacement,angular velocity,and angular acceleration of nodes 4,14,and 22 during the first and second gear operation of the system are obtained,and the time domain response of the angular displacement is converted into a dynamic stress response signal.After that,conduct a real vehicle torsional vibration test,measure the actual torsional vibration at the corresponding nodes,and compare the simulation results.The results show that the angular displacement response of each node conforms to the torsional vibration characteristics and is basically consistent with the experimental data.The angular velocity and angular acceleration responses also exhibit unusual fluctuations.Comparing the natural frequencies of the system,the frequency domain results show that the system resonates at frequencies of 22 Hz,31Hz,51 Hz,65Hz,and 142 Hz in the first gear,and resonates at frequencies of 20 Hz,28Hz,48 Hz,59Hz,and 137 Hz in the second gear,which is approximately the same as the distribution of resonance frequencies in the test.Subsequently,road excitation is added to the original electromagnetic interference,and the results show that road excitation affects the response characteristics of the system.The torsional elastic deformation at nodes 4 and 14 slightly decreases,while at node 22 it becomes larger,and the fluctuations in angular velocity and acceleration become more complex and intense.Moreover,road excitation also provides a new resonance frequency for the system.In the first gear,the system resonates at frequencies of 1.5 Hz and 103 Hz,and in the second gear,resonates at 96 Hz.