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Summary With the depletion of fossil fuels and the aggravation of environmental pollution, the research and development speed of electric vehicles has been accelerating, and the thermal management of battery pack has become increasingly important. This paper selects the electric vehicle battery pack with natural air cooling as the study subject, conducts simulation analysis of the heat dissipation performance of battery packs with and without vents. Then this paper researches on the influence of internal flow field and external flow field. Field synergy principle is used to analyze the effect of velocity field and temperature field amplitude. The results show the following: it is found that the maximum temperature rise and the internal maximum temperature difference of the battery pack with vents are reduced by about 23.1% and 19.9%, raising speed value can improve the heat dissipation performance, and raising temperature value can decrease the heat dissipation performance. Reasonable design of the vents can make the inner and outer flow field work synergistically to achieve the best cooling effect. Then the reference basis for the air cooling heat dissipation performance analysis of electric vehicle, battery pack structure arrangement, and air‐inlet and air‐outlet pattern choosing are offered.

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The integrated system of electromagnetic brake and frictional brake of car can improve braking performance effectively. Reasonable control strategy is the key of the integrated brake system. In this paper, it is analyzed and compared to the fuzzy control, PID control and fuzzy PID control. Based on that, fuzzy PID control is used to control the amount of current flowing in the electromagnetic brake coil by considering the nonlinear and time-varying of the integrated system of electromagnetic brake and frictional brake of car. The vehicle slip ratio deviation and rate of the slip rate deviation are used as the input. The electromagnetic brake coil current is used as the output. Thus, the fuzzy PID controller of the system is designed. A car equipped with the integrated system of electromagnetic and frictional brake is taken as an example. Matlab/Simulink software is utilized to carry out simulation analysis of the system. It is analyzed and compared the simulation output current curves of three control methods, braking time and braking distance. The simulation result shows that the integrated brake system using fuzzy PID strategy can effectively reduce braking time and shorten braking distance.