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BMS mass data storage system design history

In Electronic Infomation Category: B | on April 19,2011

Battery hybrid electric vehicles as a key part of one of the reasons because of its consistency easily lead to poor performance of the entire group of cells decreased, which directly affect the vehicles reliability and TD62501P datasheet and security. In order to meet the needs of the actual vehicle control and TD62501P price and optimize the controller to adjust the control parameters, needed a lot of work to collect data for offline analysis for system performance and TD62501P suppliers and calibration of the battery. The traditional method is usually used for data collection serial or CAN-bus real-time data will be read into the computer, but the method is also limited to the experimental stage, it normally takes PC, participation in the practical work of data difficult to obtain. Produced abroad based on CAN bus traffic recorder, larger and expensive, only for the use of OEM vehicle research and development. Using SD card (Se-cure DIGItal Memory Card) light, transmission speed, high-capacity, low cost, easy to read and write the advantages and battery management system in the original configuration and convenient features, the paper design used a small battery management system mass of historical data storage system, using the standard Windows system FAT32 file format, you can easily import the data into the computer. 1 year changing the card can record a data management system for the battery and battery characteristics of the data for a large number of first-hand.

1 SD card hardware circuit design

SD card is a new generation of semiconductor memory devices, the shape and pin definitions shown in Figure 1, Table 1 below. SD card working voltage is 2.0 ~ 3.6 V, the maximum read speed of 10MB / s (4 bit data lines and use), and provides both SD and SPI communication mode. In use, the host can only be one way to communicate with the SD card, the pattern detected by Reset command after power to decide. SPI mode operation of the system uses SD cards, because the method has a simple interface circuit (DSP chips provide TMS320LF2407A SPI interface), and the communication protocol is very simple and advantages. Because the SPI module DSP chip high TMS320LF2407A exactly 3.3 V, so the SD card connector can be directly connected with the TMS320LF2407A the SPI pins, the connection method shown in Figure 2.


Figure 1 SD card form factor

Table 1 SD card pin definitions



Figure 2 SD card connector circuit

2 software program

Software design is the main difficulty with the SD card FAT32 file system drives a combination of formats. FAT32 file system to achieve a certain degree of complexity, if designed to not only will waste a lot of CPU resources, and may cause loss of data, coverage and other serious consequences. With traditional data-flow program design is more difficult to implement, Debug is also very convenient. Reference to the design of modern Windows operating system by the usual method of hierarchical models developed based on the SD card FAT32 file system protocol suite, with a structured, compact portability and features a clear logic.

2.1 FAT32 file system

FAT32 designed by Microsoft and used very successfully in the file system. So far Microsoft Windows FAT32 still occupy an important position in the file system. FAT32 FAT16 and FAT12 are not improved support for large partitions, the capacity of the cluster unit that excessive waste of space and other shortcomings sharply. By the boot sector, FAT table, root directory and data area 4 major components. Figure 3 marked a FAT32 partition of the basic structure, FAT2 is FAT1 backup, used to repair damaged FAT1.



Figure 3 FAT32 file storage system configuration

FAT table (File AllocatiON Table File Allocation Table) file records the placement on the media, that cluster number sequence. Records of each table are 32-bit cluster numbers, so this method is called FAT32. Table 2 shows a simplified FAT table, root directory 2 records storage location clusters, 3 clusters of records stored in a file under the cluster number (the file from the cluster that the cluster began to store 3) is 6, the first 6, also recorded the next cluster number ... ... to the end of file marker FF said. Similarly starting from the 12th storage cluster to another file, the file stored at the end of 93 clusters. As can be seen from the table file is stored in non-continuous, so you can take full advantage of SD storage media space, and can be collected to ensure that data is not stored BMS overlap, washed away before the data. Table 3 lists the FAT table entry records the value of all meaning.

Table 2 FAT table and the corresponding relationship between the location of the file storage


Table 3 FAT32 meaning of the values ??of log entries


Store a file system in the first cluster to calculate the space needed to store a few, and then from the FAT table to find the corresponding number of free clusters, and the change log entries to the sum of the values ??in series . Then in the directory table to create a new file entry and record its first store in the media cluster number. In reading this document, as long as the table directly from the directory to find the files log entries, the first cluster number to get it can read out the document. FAT32 file system directory entry structure definition of records as shown in Table 4.

Table 4 FAT32 directory record entry structure definition


2.2 SD card SPI communication protocol

Commands sent to the SD card is a 6-byte format shown in Table 5. The first one byte of the command by the 6-bit command code with hex code 0x40 16 operations are carried out or. If the command requires, in the next 4 bytes in a 32-bit parameters and the last 1 byte contains from 1 byte to 5 bytes of CRC-7 checksum. Table 6 lists some of the SD Memory Card SPI command interpretation.

Table 5 SD card SPI Mode 6-byte command format


Table 6 SD Memory Card SPI mode, the command


2.3 lower computer software design

Lower machine SD memory card driver design using hierarchical methods, the relationship from bottom to top as shown in Figure 4. Provide for a layer under the layer of the interface support. SPI hardware layer which is used in the BMS-related chip TMS320LF2407A, SD Card command set is achieved with the SD memory card DSP communication needs of a subset of SPI command set, SD card, SD card packed layer API command set, so that easy to use the FAT32 file system layer. FAT32 file system layer that implements the FAT32 file system in accordance with the requirements of document storage solutions. BMS application layer The top layer is responsible for the BMS system state information collected by the battery pack packaged and stored in FAT32 to SD card. Because the system only need to save the file function, it FAT32 file system layer and SD cards have done the hard layer to streamline processing, significantly reducing the drive so that the complexity of the design.


Figure 4 Hierarchical SD card driver

3 data processing

Electric vehicles in operation, BMS continuously produce large amounts of monitoring data, these data points can be diagnostic for monitoring the amount and the amount. Monitoring the amount of power bus for real-time measurement of the voltage, current, battery voltage and temperature inside the module, etc.; diagnostic capacity of BMS amount of processing results in real time, including the SOC, SOH and fault codes. Table 7 shows the record installed in a motor vehicle hybrid car on the 144 V Ni-MH RMS data.

Table 7 data recording format


Record of historical data for the optimization of battery technology, the vehicle controller (VMS), and BMS R & D R & D has important significance. If the recorded total voltage, total current, and SOC single drawing in Figure 5. The size of the total current distribution analysis can be positive and negative working conditions of ISG motor; analysis of SOC can be the vehicle controller (VMS) control strategy efficiency; of the total voltage of the battery performance information can be obtained.


Figure 5, details of cases of data analysis

4 Conclusion

PSD cards designed in this technology based on the electric vehicle battery management system mass of historical data storage system, to solve the battery management system, online data work hard to get the problem. Parameter optimization for the battery management system provides a lot of work to the state historical data, help to improve the accuracy of the system parameter optimization, and characteristics of electric vehicle battery pack provides the basis for data modeling. Experiments show a streamlined SD memory card drive model has the following features: storage of data speed, does not affect normal cell management; fault tolerance is good, may appear

More small size file, but no data loss. Experimental results show that the data recorded in the case of a period of 10 ms, using 2 G-capacity SD card, you can continuously record xx years of historical data.

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