In order to improve the efficiency and safety of thermal diffusion testing for power batteries, a three-dimensional model of the laboratory is established and gas diffusion simulation analysis is carried out based on actual data from a thermal diffusion laboratory. Regarding the issue of low diffusion efficiency of laboratory gases, the paper proposes an improved scheme to install dual suction ports directly above the cooling water tank. The simulation verification results show that the improved scheme reduces the peak CO₂ concentration by 25% and increases the CO₂ gas diffusion efficiency by 22.16% compared with the original scheme,, which effectively improves experimental efficiency and safety.

In order to realize the optimization of the intrinsic characteristics of the powertrain mounting system and its robustness evaluation, this paper proposed a sensitivity analysis method based on variance to find the key parameters that have a significant impact on the system performance. A multi-objective optimization model of the mounting system is constructed, which solves to obtain a reasonable deterministic optimization scheme. Meanwhile, in order to evaluate the robustness of the intrinsic characteristics of the mounting system under the uncertainty variation of the key parameters, the skewness and kurtosis are introduced, and the robustness evaluation is conducted by combining the mean value and standard deviation, and the Monte Carlo simulation method based on Latin Hypercube Sampling is used to analyze the influence of the uncertainty factors of the mounting stiffness on the robustness of the intrinsic characteristics of the mounting system. The results show that the variance-based sensitivity analysis method can not only effectively optimize the intrinsic characteristics of the mounting system and improve the optimization efficiency, but also more accurately evaluate and enhance the robustness of the system by comprehensively considering the sensitivity of the mounting stiffness.

Focusing on the question of which test rig should be selected in vibration durability test of power battery assembly of passenger car to accurately reproduce the mechanical vibration it borne in real environment, experimental research and systematic analysis and demonstration are carried out. It is proved that the mechanical vibration borne by power battery assembly mainly came from road excitation and the mechanical vibration transmitted to power battery assembly through suspensions mainly resulted in vertical pseudo damage, which is mainly accumulated by low-frequency signals below 5 Hz. Through the analysis of virtual coherent auto-power, it is proved that the mechanical vibration of power battery assembly came from multiple independent excitation sources, which is a typical multiaxial vibration problem. Finally, it is concluded that the 6 DOF vibration test bench should be used to carry out the vibration durability test of power battery assembly of passenger car.

In response to the problem of “roaring” abnormal noise in acceleration of a light bus from 2 000~3 000 r/min, a combination of filtering and subjective evaluation is used to confirm that the main source of the noise is the engine’s 7th to 21st order radiation noise at first. Then, based on the “source-path-response” model, the engine reverse towing method is used on the test bench to analyze that the noise is mainly generated by pressure pulsation of the engine cylinder piston in the reciprocating suction and exhaust phase, and technical means such as sound source coverage method are used to identify that the noise radiation emitting from the intercooler outlet pipe. Finally, by optimizing the intercooler outlet pipe’s structure, the pipe wall’s sound insulation is improved. The verification results show that the average articulation index in the problematic area of the vehicle is increased by 5 percentage points, and the sound quality is significantly improved.

In order to evaluate the Clunk noise level of pure electric passenger vehicle under the condition of sudden pressing/releasing of the accelerator pedal (tip in/tip out) in the early stage of vehicle product development, a multi-body dynamic model of the vehicle is established considering the clearance between the splines, shaft teeth, half shaft ball cage and bearings in the transmission system. The time-domain load of the bearings is calculated using the model, and the time-domain vibration acceleration signal of the key points on the reducer housing is obtained by combining the finite element analysis method. The accuracy of the model is verified by comparing it with the experimental results. An analysis model for Clunk noise in the transmission system and a parameter tuning method are proposed to evaluate the Clunk noise level of pure electric passenger vehicles in the early planning stage.

The noise generated during the relays pick-up and disconnection of the power battery for a new energy vehicle is significant. To address the issue, the contribution of the relay noise transfer path is tested and analyzed in a semi anechoic chamber, and the results show that the contribution of the structural transfer path is higher than 70%. The paper proposes to reduce the hardness of the rubber vibration isolation pad at the Battery Distribution Unit (BDU) mounting point and past the damping material on the cover plate of the power battery. Vehicle verification results show that the sound pressure level of the optimized relay pick-up and disconnection noise is reduced by 3.9 dB(A) and 4.1 dB(A) respectively, and the noise of relays in the vehicle is improved significantly.

To analyze the reason for the abnormal increase in wind noise of the vehicle at high speed, the paper employs a seal pressure distribution testing system from the perspective of dynamic sealing. It measures the dynamic indentation of the seals, detects dynamic sealing leaks, and analyzes their impact on wind noise at high speeds, identifying the leakage as the source of the increased noise. By studying the influencing factors of dynamic seal, the research reveals that the excessive deviation of the clearance between door and the vehicle body is a main reason for the loss of the sealing contact. The paper concludes and proposes the diagnosis method for the abnormal wind noise at high speed.

In order to improve customer’s door closing experience, top-down design and development of the sound quality of an electric vehicle’s door closing are carried out. In the product design phase, target values about subjective and objective evaluation for door closing sound quality are set according to door closing sound quality data of the existing vehicle model and test analysis of the benchmarked model, the main parameters affecting the sound quality of door closing are summarized. In the prototyping stage, NVH sound detection equipment is deployed to test sound quality parameters and simulate user experience for subjective evaluation. For the problems revealed in the sound quality evaluation results in the prototyping stage, sound quality has been improved by adopting the following measures: increasing seal reaction force in the door seal strip, controlling door seal gap, optimizing door lock and increasing door window holding force, etc. Subjective and objective evaluation results show that door closing quality of this model has achieved the product definition objective.

The steering system produces stick-slip vibration and noise due to the relative rotational friction between various components, resulting in unsmooth steering. To solve this problem, this paper studies the practical problems of stick-slip caused by worm gear deceleration mechanism of steering gear. The source of the problems are identified through tests, and the relevant influencing factors are determined by establishing a theoretical force model and CAE simulation analysis model. The torque anti-drop function MSP (Mechanical Stuck Prevention) of the steering gear is developed simultaneously. The software functional architecture and module interfaces are designed and the activation parameters are set through the debugging and optimization of the software functions. Finally, the output square wave signal of the motor torque 0.03 N·m is locked, which satisfies the software real-time control requirement, and improves the handing comfort of the vehicle.

Based on the study of the three parameter control objectives of Pedal Map, a calibration control program for Pedal Map of electric vehicle is designed, and effective control of three parameter objectives are realized through MATLAB traversal interpolation. Simulation calculations and real vehicle testing results verify that the control objective based on the three parameters can effectively achieve the calibration and control of the pedal characteristics of electric vehicle. The experimental and simulation comparison results of the longitudinal acceleration curve show that the control program can accurately achieve the calibration control objective requirements and successfully achieve automatic calibration.