In order to solve the defects of decreased vehicle comfort of pure electric passenger car when air conditioning system is turned on to cool the power battery, this paper, combining actual development projects, determined the typical travel chain of electric vehicle according to the sales target area of developed vehicle, and formulated the annual calendar driving conditions of electric vehicle according to the travel chain. The vehicle bench environment simulation test was carried out according to the annual calendar driving conditions, and the statistical analysis of the battery temperature distribution in three states of the vehicle in driving, charging and storage within one year was completed according to the test results. The battery cycle life evaluation was completed, and the influence of each operating condition of the vehicle on the battery life attenuation was decomposed, and the battery cooling system control strategy was optimized. The results indicate that, the proportion of cooling system engaged in the battery cooling process decreases greatly, air conditioning comfort improves obviously.

In order to explore an effective test method for the thermal management performance of 48 V power battery, the thermal management performance of 48 V battery was studied and tested on a vehicle equipped with P0 mild hybrid system under different test conditions, ambient temperature and air conditioning mode. The results show that the World Light Vehicle Test Cycle (WLTC) is the most suitable to verify the thermal management performance of the 48 V battery. The high temperature performance of 48 V battery can be effectively verified by continuously performing 5 WLTC test cycles at a high temperature of 30~50 ℃, the low temperature performance of 48 V battery can be effectively verified by continuously performing 8 WLTC test cycles at low temperature of -25 ℃. The internal and external circulation mode of the air conditioner impacts the thermal balance temperature of the 48 V battery remarkably.

This article studied the ultimate strength bench test method of suspension system of passenger vehicle, it firstly compared and analyzed the characteristics of strength test of vehicle, suspension system and parts, and then introduced the test method of suspension ultimate strength test from the working condition and selection of the definition, the loading form of the load, test equipment and test bench design, test data acquisition and processing, and proposed the way to the evaluate test results. Finally, the paper illustrated the application of the combination of suspension system and component strength bench test with an actual case, and explained the role of suspension strength bench test in product development.

In order to find out the cause of ablation of transfer case input rear end cover of a vehicle in the driving process, this article analyzed the failure mechanism in lubrication capacity design, oil leakage from transfer case, amount of lubricating oil filling, faulty oil absorption of emergency pump, lubricating oil passage blockage, failure of lubricating oil pump and so on, and concluded that this failure was mainly caused by insufficient amount of lubrication oil filling, resulting in insufficient amount of oil splashed from the output gear in the bottom, which caused poor lubrication of the bearing. Failure reproduction proved accuracy of the failure analysis and positioning.

A three-dimensional model of the fuel cell was established by COMSOL software, and the effects of three parameters (operating temperature, oxygen concentration and membrane thickness) on the performance of the fuel cell were studied. The results show that the fuel cell performance can be improved by increasing the operating temperature, and the suitable operating temperature range is 160~180 ℃. The output performance of the fuel cell is obviously improved by increasing the oxygen concentration, but the fuel cell performance is reduced by increasing the thickness of the film. The optimal membrane thickness is 20~ 60 µm.

In order to explore the influence of ambient temperature on the fuel consumption of Hybrid Electric Vehicle (HEV), this research team selected four HEVs with different technical routes to conduct several real driving fuel consumption tests at different temperatures. The results show that fuel consumption of Plug-in Hybrid Electric Vehicle (PHEV) and Range Extended Electric Vehicle (REEV) is apparently higher than lab fuel consumption test value, and that of None Off-Vehicle-Charging Hybrid Electric Vehicle (NOVC-HEV) and PHEV increases significantly under high and low temperature environments. Therefore, it is concluded that the WLTC test at room temperature cannot accurately reflect the real fuel consumption level of NOVC-HEV, REEV and HEV models, and the ambient temperature is an important factor affecting the fuel consumption of hybrid electric vehicles.

In order to solve the problem of State Of Charge (SOC) estimation error and ill-conditioned covariance in the iteration process caused by nonlinear transformation ignoring the high-order Taylor term in Extended Kalman Filter (EKF) algorithm, a Modified Covariance Approximate Second-Order Extended Kalman Filter (MVASOEKF) algorithm was adopted. Through the hybrid pulse power characteristic experiment, the internal parameters of the equivalent model were identified offline and the second-order RC equivalent battery model was established. The SOC was estimated on MATLAB/Simulink platform. The results show that the average absolute error value of EKF algorithm is about 2.0%, and the average absolute error value of MVASOEKF algorithm is about 0.5%. Compared with EKF algorithm, although MVASOEKF algorithm has more computation amount, but the SOC estimation accuracy has been significantly improved, and the convergence is better.

With the structural characteristics of the passenger car side wall door opening as the research object to conduct compact design research, this paper elaborated systematically the principle, method and technical solution of the compact design. The hard point and section model of the door opening structure were obtained through structural disassembly. The hard point driven section was used for design, and the compact coefficient was defined and a parametric design table was established. The feasibility of battery layout and its impact on the door opening design were considered, to maximize the man-machine space within the limited vehicle size range as far as possible, improve the convenience of getting on and off the vehicle, and comprehensively consider multi-dimensional elements such as modeling, collision safety, lightweight, etc. Finally, the validity and feasibility of the design method were verified by analysis.

For the problems of high failure rate and low intelligence of the existing hidden exterior door handle, the optimization design was carried out to realize the functions of fault self-diagnosis, intelligent anti-pinch and autonomous deicing, so as to improve the safety and intelligence of the system. Experiments show that the intelligent hidden exterior door handle works properly, and the design is feasible.

In order to explore the lightweight space of multi-purpose truck body, multidisciplinary optimization was carried out in three dimensions of performance, quality and cost. With the multi-purpose truck Body-In-White (BIW) as the research object, 46 design variables were selected, covering 1 680 sample points at 73 part thickness levels, and the optimal Latin hypercube method was used to conduct the experimental design of bending torsional stiffness, mode frequency, mass, and cost, to obtain the sensitivity of the part’s contribution to the BIW performance, and to establish a second-order polynomial response surface approximation model. Specifically, three groups of optimization solutions were formulated to maintain the basic performance level of the original body, the allowable stiffness decreased by 10%, and the modal fluctuation was 2 Hz; the allowable stiffness decreased by 20%, and the modal fluctuation was 4 Hz. The Pointer automatic optimizer was used to optimize the design with the minimum mass as the objective function. The results show that three optimization solutions can reduce the mass by 14.63 kg, 20.37 kg and 25.78 kg respectively.