Research On Dynamic Characteristics Of Electric Vehicle Powertrain Mounting System Under Transient Impact Conditions

The global warming trend is becoming more and more severe.Vehicle exhaust emission standards have been repeatedly raised.Zero-emission pure electric vehicles have become the key development goals of major car companies.The powertrain of a pure electric vehicle consists of a drive motor,a fixed gear ratio reducer and a differential.As a bridge between the powertrain and the frame,the mounting system not only supports the powertrain and restricts the displacement of the powertrain,but also isolates vibration.Therefore,a reasonable design of the powertrain mounting system can improve the NVH of the vehicle.And it plays a vital role in improving ride comfort.This paper takes the powertrain mounting system of a pure electric vehicle as the research object,establishes a dynamic model of the powertrain mounting system of an electric vehicle,and obtains the inertial parameters and static stiffness of the powertrain of a certain pure electric vehicle through experiments.The excitation force of the electric vehicle powertrain is analyzed.The vehicle was tested under transient impact conditions on the rotating hub test bench.Obtained the vibration acceleration of the mount active and passive sides and the driver’s cab seat rail under WOT,Tip in/out and sudden deceleration conditions.By analyzing the test results,it is found that the Y-direction vibration isolation rate of each mount of the test vehicle is poor under WOT conditions;the vibration acceleration of the driver’s seat rail under Tip in/out conditions and rapid deceleration conditions is relatively large.The mounting system of the test car needs to be optimized.At the same time,the dynamic model of the electric vehicle powertrain mounting system is solved,and the simulation value of the vibration acceleration of the assembly is obtained.Compared with the actual measured value,the peak error of the two is 6.94%.The accuracy of the kinetic model of the electric vehicle powertrain mounting system is verified.Using this kinetic model,the impact degree,pitch angle and longitudinal acceleration of the center of mass of the powertrain are used as evaluation indicators to simulate and analyze the influence factors of the transient impact dynamic characteristics of the powertrain mounting system.The influence of the four factors of excitation torque loading rate,torque amplitude,feedback torque during energy recovery and mounting layout on the transient response of the mounting system is discussed.Using the theory of energy decoupling and taking the stiffness of the rubber mounts as the design variables,the mounting system of the test vehicle was optimized.The robustness analysis of the optimized mounting system was carried out based on the Monte Carlo method.The change amplitude of the energy decoupling rate is 4.98%,which meets the robustness requirement.Finally,using the measured motor output torque as excitation,the transient response of the mounting system before and after optimization under WOT,Tip in/out and sudden deceleration conditions are calculated.After optimization,the impact amplitude of the system is reduced by 59.25%,and the acceleration amplitude is reduced by 62.30%.