To improve the thermal management performance and solve the refrigerant carbon emissions issue of electric vehicle, this article proposed a transcritical CO₂ heat pump air conditioning system suitable for electric vehicle with natural CO₂ as refrigerant, and performance analysis was conducted. The results show that: this system can still ensure a heating capacity of 5 kW and 36 ℃ at the outlet in an environment of -20 ℃. As the compressor speed increases, the heating capacity increases, but Coefficient Of Performance (COP) decreases. The appropriate increment in the air volume of the internal gas cooler can effectively increase the heating capacity and COP, but excessive air volume will lead to low outlet air temperature, which is not conducive to heating. At ambient temperature of 40 ℃ and compressor speed of 7 000 r/min, the cooling capacity is 4.2 kW and the COP is 1.1. As the air volume of the internal evaporator increases, the cooling capacity and COP increase, indicating that the appropriate increment in air volume can effectively improve cooling performance.

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.

In order to obtain a suitable shape curve of the CO₂ adjustable ejector regulating probe for automobile air conditioning, this paper proposed three kinds of probe schemes including linear, concave and convex probe based on the Homogeneous Equilibrium Model (HEM), and the analyzed changes of the ejector flow rate and elicitation ratio in the process of probe movement with the aid of the Computational Fluid Dynamics (CFD) tool, and compared the differences in the performance of the adjustable ejector with the three kinds of probe schemes. The results show that: When the probe radius at the throat is small, with the increase of the probe radius at the throat, the entrainment ratios of the ejector of each scheme increase slowly due to the decrease of the primary flow rate, and when the probe radius at the throat exceeds the high efficiency adjustment radius, the entrainment ratios of the ejector of each scheme decrease dramatically until they can’t be induced; compared to the other 2 probe schemes, the concave probe scheme has a larger entrainment ratio within the high efficiency working area, and it has a stronger overall performance.

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.

In order to efficiently realize the measurement of vehicle wheel brows, a non-contact vehicle wheel fender clearance measurement system is designed based on image processing technology, and corresponding measurement software is created with the Graphical User Interface (GUI) of MATLAB. The verification results show that for actual clearance of at least 15 mm, the error of the wheel fender clearance calculated by the system under different shooting distance conditions is controlled within 2%, which exhibiting a high degree of measurement accuracy.

In order to replace Positive Temperature Coefficient (PTC) electric heater in vehicle thermal management, this paper studied the heating characteristics of the triangular cycle through experimental and theoretical methods and proposed corresponding control strategy. First of all, in terms of component selection, the paper proposed that the triangular cycle had higher performance requirements for the condenser and electric expansion valve. Secondly, the bench test obtained a heating capacity of approximately 6 kW. Thirdly, the impact of different electronic expansion valve openings, air conditioner unit inlet air temperature and inlet air volume on performance was studied through the checked model, and it was found that the larger opening help the compressor to exert greater capacity and obtain greater heating capacity. Under high inlet air temperature and high outlet pressure condition, the triangular cycle has greater heating capacity. Finally, the paper proposed a triangular cycle control map covering 2 000 ~ 6 500 r/min compressor speed and -20~-10 ℃ inlet air temperature.

In order to improve the accuracy, stability and flexibility of the vehicle chassis geometric parameter detection system, a vehicle chassis geometric parameter measurement system consisting of LED type 3D surface measurement sensors is designed based on stereo photogrammetry, using a structured LED light source to form a “spatial measurement area” based on the entire wheel side surface and wheel cover edge. By using 3D photography technology to obtain point cloud data under dynamic measurement, and combining with x-line software, a 3D wheel hub model is established to analyze and calculate the front toe camber angle of the chassis, the linearity and repeatability of the measurement system. The results show that linearity error of this measurement system is 1.528', repeatability error of front toe angle and camber angle are ±0.03' and ±0.05' respectively, verifying stability and reliability of the measurement system.

In order to realize active equalization of 48 V mild hybrid battery pack, and improve energy utilization rate, firstly the group design and consistency check of 48 V mild hybrid system battery of a vehicle were conducted, then the topological structure of the active equalization circuit was determined, and then the equalization opening threshold and equalization control strategy of active equalization circuit were designed based on the information of the battery terminal voltage collected by the BMS. The results of simulation analysis indicate that the State Of Charge (SOC) bias errors of the battery module after active equalization does not exceed 0.005.

In order to analyze the influence of random and impulse road surface on the smoothness of commercial vehicles, a commercial vehicle is taken as the research object to construct the vehicle dynamics model containing front and rear suspension, tire, body, steering system and human body-seat system by using the ADAMS/Car software. The smoothness analysis of impulse and random input is carried out for the vehicle, and simulation results show that the smoothness of the vehicle increases after increasing the vehicle speed under the excitation of pulse road surface; the effect of smoothness is more significant on Class C road compared with Class B road under the random road surface input condition, which is more effective in the evaluation and improvement of driving comfort of commercial vehicles.

To address the issue of the unsuitability of the original suspension parameters after upgrading a central motor electric vehicle to a In Wheel motor car, A half-car passive suspension model is established in MATLAB/Simulink to analyze the problem. The spring stiffness and damping coefficients of the front and rear suspensions are taken as independent variables, while the root mean square values of the vehicle’s center of gravity acceleration, pitch angle acceleration, suspension deflection, and tire load are considered as optimization objectives. The grey wolf optimization algorithm is employed to search for the optimal stiffness and damping parameters. The simulation results show that after optimization, the handling stability of the suspension remains within a reasonable range, while the comfort level is improved by 12.73%.

In order to improve the vehicle driving range of a pure electric light commercial vehicle, this paper proposes to reduce the electric power consumption per 100 kilometers by reducing power consumption and increasing coasting energy recovery power. Firstly, for ECO energy-saving mode, the paper proposes the energy-saving control technology based on different vehicle usage scenarios and working conditions, which significantly reduces the energy consumption of the vehicle in the whole scenario. Secondly, in the view of the coasting energy recovery deceleration of commercial vehicles with empty and full load varies greatly, the paper proposes the energy recovery control based on the vehicle mass to achieve the same coasting deceleration under different loads to recover more energy. Then, for the problem that coasting energy recovery is usually designed with low adhesion coefficient road surface, the paper proposes adaptive adjustment of coasting energy recovery based on road adhesion coefficient. Finally, the pure electric light truck is tested on real road. The results show that the ECO mode reduces the electricity consumption per 100 kilometers by 2.9%, and by 2.1% for scenarios of turning on the air conditioning and opening the car door. The energy recovery strategy based on the vehicle’s mass shows a 2.7% reduction in electricity consumption per 100 kilometers.

To improve the low efficiency of the current diagnosis method using subjective evaluation method, this paper proposed a method for identifying vehicle abnormal noise based on Convolutional Neural Network (CNN). A four post vibration test stand was used to collect raw abnormal noise signals with high signal-to-noise ratio in a semi anechoic chamber environment as the research object to extract the Mel-spectrogram of the signal as input to the neural network, then, a convolutional neural network was constructed to perform deep level feature extraction, compression, and classification recognition on the data. It was found that the average recognition rate can reach 90.5%. Finally, the transfer learning method was used to optimize the model. The test results indicate that VGG and ResNet models can improve recognition accuracy, and the ResNet network has better recognition performance in the test set.

In order to realize automatic test and effectiveness verification of Automatic Mechanical Transmission (AMT), an automatic testing sequence is constructed based on the Hardware-in-the-Loop (HiL) testing system and automated testing software for the low gear shifting stuck fault of AMT front auxiliary gearbox. The fault diagnosis response is tested, and the test results show that the fault diagnosis response meets expectations, verifying the accuracy of the test sequence and fault diagnosis. Based on the test sequence, the normal gear shifting at high speed, gear shifting without fault and the low gear shifting of the front auxiliary gearbox under fault response are established. Test results show that the Transmission Control Unit (TCU) recognizes and responds in time when the front auxiliary gearbox low gear shift stuck fault occurs. The response is in line with expectations, and it also can keep the vehicle running normally under the fault diagnosis response, which verifies the effectiveness of the fault diagnosis response.

A testing device for air pressure resistance of door seal has been designed to simulate the changes of air pressure in door cavity of a car under side crash condition and test the ultimate air pressure resistance of door seal. Based on this, this article studied the influence of different temperatures, material hardness, and part structure on air pressure resistance of the door seal in combination with a high and low temperature environment box. Through multiple experimental comparisons, it has been proven that the ultimate air pressure resistance of door seal is negatively correlated with temperature. Increasing the back plate ribs and appropriately increasing the material hardness can significantly improve air pressure resistance.