The 48 V hybrid power system and Battery Management System (BMS) control principle were analyzed, the influence of 12 V power supply voltage variation on 48 V power batteries was tested and studied, it is found that, when the 12 V power supply voltage is low, the BMS Microcontroller Unit (MCU) chip has a cyclic reset phenomenon and BMS no respond issue. For this problem, this paper proposed a BMS control logic optimization. The BMS detects that the battery state data will not be saved in MCU chip when the 12 V power supply voltage is lower than 6 V. This control logic can solve the BMS no respond issue by preventing the MCU writing the fault value. It is verified by real vehicles that the control logic can effectively improve the anti-low voltage ability of BMS.

In order to satisfy the requirements of rapid iteration of software covering the whole scene and life cycle of intelligent vehicles, this paper proposed a near-field software upgrade technology suitable for the pre-sales stage of automobiles. The near-field software upgrade equipment master completed the upgrading of all Electronic Control Unit (ECU) software on the vehicle in turn. Based on the existing Over-The-Air (OTA) car cloud system, this method used portable computer, cell phone or USB equipment to rapidly upgrade software of each vehicle real time, upgraded vehicle software baseline version of batch vehicle by factory server via LAN. Bench test results indicate that the method upgrades software faster and more flexible.

In order to solve the issue of fatigue failure caused by repeated bending of high-voltage harness, the flexible pipeline wiring model was established, and the stress change and fatigue life distribution cloud map of each part in the process of wire bending were calculated based on IPS flexible wiring simulation software, ABAQUS finite element calculation software and Fe-Safe fatigue life calculation software. The simulation results show that, in the process of repeated bending, the stress of the wire at the fixed points is high and the fatigue life is low. The stress level at the outer layer of the wire core is higher than that of the inner layer, and the fatigue life is lower. The bending fatigue life test of wire was carried out by using vibration table. Both the test results and the simulation results show that the bending fatigue life of the wires can be prolonged by appropriately increasing the length between the fixed points within an appropriate range.

To investigate the influence of transmission system speed ratio of vehicle equipped with 2-speed AMT on vehicle’s performance, this paper, taking a pure electric logistics vehicle as an research object, matched and designed the vehicle’s driving motor, battery pack and transmission system speed ratio according to the vehicle’s basic parameters. The vehicle model was established based on the AVL_CRUISE simulation platform, the rationality of matching parameters was verified by simulation, and Particle Swarm Optimization (PSO) algorithm was selected to improve the vehicle’s power and economy, and the speed ratio of transmission system matching two-gear AMT was optimized. The simulation results show that the 0-100 acceleration time of the pure electric logistics vehicle is shortened by 2.31 s after optimization, the energy consumption of the vehicle is reduced by 3.14% under single NEDC cycle condition, and the power performance and economy of the vehicle are obviously improved.

A method of real time warning for slow tires leakage based on machine learning was proposed to detect slow tire leakage in time. Firstly, data preprocessing such as abnormal data cleaning, sliding window mean filtering, isochromatic data interpolation and temperature compensation were carried out based on the original tire pressure data acquired real time. Secondly, the data segment of slow tires leakage was labeled by using the starting time when the absolute value of the tires pressure comparison difference of the self-owned tire for a vehicle was greater than a certain threshold value, and using the ending time at the moment before the first low pressure alarm, and select slow gas leakage data set and construct eigenvalue engineering. Then, data set division, model training, model evaluation and model parameter optimization were made. Finally, the slow leakage for tires predicted by the online model was selected for expert argumentation and user verification. The results show that the model accuracy rate is close to 98%, the average time of model warning is 106.3 h earlier than the low tire pressure alarm at vehicles, which verifies feasibility and reliability of the model algorithm.

In order to accurately express the damping characteristics of the built-in switch valve hydraulic shock absorber when the coil is energized, the built-in switch valve hydraulic shock absorber damping force model is constructed under conditions such as the recovery stroke and compression stroke, using the theory including annular gap flow, nozzle flow, thin-walled small hole flow, slender hole flow, series fluid and parallel fluid. ADAMS/Hydraulics simulation and experiments show that the damping characteristic of the hydraulic shock absorber coil obtained with this damping force model is in good consistency with experiment results, proving accuracy of this model.

In order to solve the problem of excessive road noise transmitted to the interior of battery electric vehicles in driving, this article investigated the tire, rear torsion beam and body panel by using the method of “source-path-response”, to identify the coupling between the mode of rear torsion beam and road excitation, which amplified road noise. By dynamical property analysis of body panel through virtual verification, it was identified that the coupling between the mode of rear side wall area and the mode of acoustic cavity was the main cause for excessive road noise in the vehicle. By adding a support structure between the side wall outer plate and C-pillar and D-pillar, the local stiffness of the side wall outer plate was improved, so as to optimize the modal frequency and vibration amplitude in the rear side wall area. The vehicle interior road noise test was carried out. The results show that vehicle interior noise is reduced obviously in the frequency ranges of 78~90 Hz, 120 Hz and 200 ~220 Hz, and its subjective evaluation of interior road noise meets the requirements.

Firstly, the typical environment of power battery affecting the balance of air pressure inside and outside the pack were analyzed in the paper. Secondly, the operational principle of waterproof breather valve was explained, the waterproof breather valve was selected and calculated according to the requirement of amount of breather air and explosion-proof pressure under typical condition. Finally the “condensation” phenomenon caused by the application of breather valve was discussed and tested in typical environment. The results show that the application of breather valve on the power battery pack will not cause water accumulation in the pack due to “condensation”, which will affect the high-voltage insulation in the battery pack, proving the feasibility of application of waterproof breather valve in the power battery design.