| The ride comfort of an electric vehicle is an important index for measuring the performance of the entire vehicle,and the torsional vibration of the powertrain system is a key factor affecting the ride comfort of the entire vehicle.Therefore,it is necessary to study the torsional vibration characteristics of the powertrain of the electric vehicle.This paper takes a new type of all-electric integrated powertrain system as the research object,and uses a combination of theoretical derivation,mathematical modeling,simulation calculation and experimental research to freely torsional vibration characteristics of the integrated powertrain system and multi-excitation under different operating conditions.The intensive torsional vibration characteristics under coupling effect are studied in depth.The purpose is to comprehensively grasp the torsional vibration law of a new all-electric integrated powertrain system,improve the system structure parameters,and form a set of research system for the analysis of torsional vibration of electric drive systems with electromechanical coupling characteristics.The specific research content is as follows:(1)The inherent characteristics of the torsional vibration of the new all-electric integrated powertrain system has been analyzed,and the structural parameters have been optimized.A modeling method that comprehensively considers the coupling effects of the electromagnetic stiffness and gear meshing stiffness of the motor has been proposed,and a new 8 DOF torsional vibration branch model of the system in different gears has been established.Analyzed natural frequencies and mode shapes,and verified that the relative error was within 5.2%;the resonance speed of the system in different gears has been quantitatively analyzed;the sensitivity analysis of the natural frequency has been targeted The system characteristic parameters have been optimized,and the dynamic changes of the system before and after the parameter optimization have been co-simulation analyzed.The results have showed that:considering the electromagnetic stiffness,a“zero-order”natural frequency can be obtained,which can present a wealth of dynamic phenomena;low-order vibrations appear in the wheel and body position,and high-order vibrations have appeared in the electromagnetic direct drive transmission;When the excitation source was fixed,the maximum amplitude of the input shaft was reduced by 20.5%,and the maximum amplitude of the output shaft was reduced by 32.6%before and after optimization of structural parameters.(2)A vector control simulation model of a permanent magnet synchronous motor has been established,and the torque ripple characteristics of the motor are qualitatively and quantitatively analyzed.The results showed that after applying the vector control technology with i_d=0 to the motor,the magnitude of the torque depended on the magnitude of the i_q Controlling the magnitude of the i_q could well achieve the purpose of controlling the torque and speed,and responded quickly to changes in load.In addition,current sensors caused torque fluctuations at 1 and 2 times the current frequency;non-sinusoidal air gap magnetic fields caused torque fluctuations at 6a times the current frequency,of which the amplitude of the fluctuations caused by the 6 times current frequency was the largest;the inverter the frequency of the torque ripple was an integer multiple of its switching frequency.(3)A multi-body dynamics model of the system has been established,which comprehensively considered the inter-tooth impact,pavement load,starting of shaft deformation analysis,and dynamic response of the system in emergency braking conditions.At the beginning,the peak speed of the input shaft reached 216 r/min,and then it increased linearly.The peak acceleration of the vehicle body decreased from 3.2 m/s~2 to2 m/s~2,and the overshoot was 60%.The relative displacement of the stator of the electromagnetic linear actuator in the X direction and the Y direction quickly approached 0from 0.98 mm and 0.96mm,respectively.During emergency braking,the input shaft rapidly decreased from a peak speed of 1047 r/min to 901 r/min,and then tended to decrease linearly;the body acceleration showed significant fluctuations at the beginning of the start and at 2 s,and the vehicle speed basically became linear.decrease.The first 2s of the gap between the stator and the mover was the same as the starting conditions,but the relative displacement changed greatly when the torque changed suddenly,and the amplitude in the X and Y directions reached 1.2 mm.(4)Based on the co-simulation model of ADAMS and Simulink,the torsional response of the system at three characteristic speeds has been analyzed,and the key parameters have been analyzed.At the 1st gear of 600 r/min,the overall fluctuation of the system was relatively small,the vehicle speed was maintained at 13.86 Km/h,and the wheel angular acceleration appeared relatively large fluctuations at 39.8 HZ,240.5 HZ,and 480.1HZ respectively.At the 1st gear of 1070 r/min,the input shaft angular acceleration reached 3.4rad/s~2 at 79.6 HZ,and the maximum relative displacements of the fixed and mover in the X and Y directions reached 0.18 mm and 0.22 mm,respectively.At1700 r/min in 2nd gear,the angular acceleration of the input shaft reached 8.2 rad/s~2 at115.2 HZ,and the relative displacement between the stator and the mover reached 0.12mm in the X direction.Analyzed and compared the influence of key parameters(motor torque,backlash,inertia,stiffness)on the system.When the torque changed suddenly,the tooth backlash had a greater influence on the load,and the greater the sudden torque change,the more obvious the fluctuation;When the excitation source was fixed,the maximum amplitude of the input shaft was reduced by 20.5%,and the maximum amplitude of the output shaft was reduced by 32.6%before and after optimization of structural parameters.(5)The test has verified the torsional vibration characteristics of the system.At600r/min,the angular acceleration of the output shaft showed periodic fluctuations.The maximum angular acceleration was 26 rad/s~2 and the minimum value was-26 rad/s~2.The fluctuation of the input shaft speed was small,and the relative error was 4%compared with the simulation.within.At 1070 r/min,the input shaft and output shaft both showed large fluctuations.The relative error was within 6%compared with the simulation.At 1700r/min,it could be seen that the maximum value of the input shaft speed was 1722 r/min and the minimum value was 1680 r/min.Compared with the simulation,the maximum error was 5%,and the relative error of the output shaft angular acceleration was relatively small.The test results fully showed the validity of the simulation analysis results,and at the same time provided a reference for the vibration reduction design of the integrated powertrain system. |
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