| Today, under the background of energy shortage and environmental pollution that caused by the development of traditional automobile industry, pure electric vehicles have received serious attention from lots of governments and automobile companies, for their unique advantages such as zero emissions, no pollution, high efficiency, etc. In different kinds of pure electric vehicles, the high-speed in-wheel motor driving electric vehicle is gradually becoming a research hotspot because its four wheels are driven by independent hub motors and use drive-by-wire technology. As a high-speed in-wheel motor driving electric vehicle’s working must rely on the power batteries to provide energy, so taking timely and effective online monitoring and management on the power batteries is also becoming a key technology of electric vehicles. With the usage requirements of high-speed in-wheel motor driving electric vehicle for power batteries, this paper develops a Li-ion Battery Management System(BMS) based on the centrally-distributed structure type. This BMS is mainly composed of a MCU module and six battery parameter acquisition modules.In the study of battery pack’s State Of Charge(SOC) estimation method, this paper analyzes related factors which influence the SOC estimation and several common SOC estimation methods, then uses an estimation method which combines the Open Circuit Voltage method and Ah Counting method. A time variable in the battery pack’s standing mode is introduced to make a weighted calculation in the Open Circuit Voltage method. The power battery pack’s SOC value is respectively worked out under the standing mode or working mode.In the hardware and software design process, this paper divides the whole system’s hardware circuit into four parts, namely the hardware circuits of MCU module, battery parameters acquisition boards, master-slave communication circuit for SPI communications and the vehicle’s power conversion circuit, based on the general structure of the car’s BMS and the modular and hierarchical design principles. All of the circuits’ schematics and PCB boards are finished in the Altium Designer. A variety of anti-jamming measures are used to improve the reliability and stability of the BMS. Software design is divided into two parts, namely the software design of MCU and the battery parameter acquisition control unit. Software flow chart is given for each program and the realization process is introduced or analyzed in detail. All of the BMS’s programs and subroutines are completed in the Keil uVision5.Finally, this thesis completes the BMS’s experimental prototype and the system’s hardware and software debugging. By carrying out two functional verification experiments, the vehicle’s power conversion circuit and the LCD module are validated. The final field testing is conducted to estimate the BMS’s acquisition error and the SOC feasibility. The results show that the BMS can work normally, and the measuring error for the temperature is less than 1℃, for the battery pack’s total voltage is less than 1 V, for the total current is less than 0.3 A. The SOC estimation result is feasible and effective. This paper not only gives a valid solution for power battery’s energy management of the high-speed in-wheel motor driving electric vehicle, but also provided a technical reference for the research of other BMS. |
