Development of 18650 battery 2500mahmanagement system monitoring platform based on LabVIEW

　　As one of the core technologies of electric vehicles, power 18650 battery 2500mahintegration plays a decisive role in the performance of electric vehicles. In order to ensure the safe and efficient application of power batteries, it is necessary to monitor their operating status online in real time and control them at the same time. 18650 battery 2500mahmanagement The system plays a key bridge role between the power 18650 battery 2500mahand vehicle control. In order to ensure that the 18650 battery 2500mahmanagement system provides accurate and reliable power 18650 battery 2500mahinformation for electric vehicles and reliably manages the battery, it is necessary to monitor the various functions of the 18650 battery 2500mahmanagement system itself in real time, collect and analyze 18650 battery 2500mahoperation data, and at the same time, When the power 18650 battery 2500mahsystem fails, it needs to be diagnosed. The 18650 battery 2500mahmanagement system monitoring platform based on LabVIEW is developed and designed to meet the above needs.

　　LabVIEW (LaboratoryVirtualINStrumentatiONEEngineeringWorkbench, laboratory virtual instrument engineering platform) is a graphical software development environment developed by NationalInStruments (referred to as NI) in the United States. This development environment perfectly combines industrial measurement and control with computers. Its graphical interface makes programming as simple, intuitive and easy to understand as operating an instrument panel or drawing a circuit board. However, in order to develop a reliable, efficient, and flexible 18650 battery 2500mahmanagement system monitoring platform, in-depth principle analysis, detailed structural design, and flexible interface implementation are required for its program design. The monitoring platform utilizes LabVIEW's DLL (dynamic link library), multi-threading, data recording, operation control and other technologies.

　　2 platform structure

　　The monitoring platform is designed based on the 18650 battery 2500mahmanagement system, which is mainly composed of hardware part and software part. The hardware mainly implements communication between the PC and the 18650 battery 2500mahmanagement system, because the 18650 battery 2500mahmanagement system mainly uses CAN (Controller Area Network) for external communication, and the PC interface is mostly USB (Universal Serial Bus). The CAN bus was first proposed by the German Bosch company and is one of the most widely used field buses in the world. It has high bit rate, high resistance to electromagnetic interference, and can detect any errors on the bus; USB is a plug-and-play The new serial interface used has been widely used in the external interface of PC. Solving the conversion between CAN and USB solves the communication between the 18650 battery 2500mahmanagement system and PC. Using Zhou Ligong USBCAN-II's smart CAN interface card, this function can be easily realized. The monitoring platform hardware is based on PC as the main body. It is connected to the CAN interface card and connected to the 18650 battery 2500mahmanagement system through the CAN bus. The Zhouligong smart CAN card is equipped with a PC-side driver, and also provides interface functions for PC-side applications. The dynamic link library technology in the LabVIEW development environment can be used to operate the Zhouligong smart CAN interface card well, and implement integration with the 18650 battery 2500mahmanagement system. Communication.

　　As can be seen from Figure 1, the system hardware realizes transparent transmission of data between the monitoring platform and the 18650 battery 2500mahmanagement system. The Zhou Ligong intelligent CAN interface card plays a very good bridge role. The built-in photoelectric isolation module enables the USB CANII interface card to avoid Damage caused by ground circulation improves system reliability in harsh environments. Therefore, the monitoring platform has good hardware support, and the main design task is the LabVIEW implementation of the monitoring platform.

　　In view of the requirements for 18650 battery 2500mahmanagement system data collection, parameter calibration, fault diagnosis and 18650 battery 2500mahdata analysis, the structure of the monitoring platform software should include modules such as information display, system calibration, fault diagnosis, data storage and platform configuration (see Figure 2). The information display function provides intuitive power 18650 battery 2500mahinformation, including cell voltage, total voltage, current, temperature, SOC and fault status, etc.; the system calibration function provides convenient operations for parameter setting and status revision of the 18650 battery 2500mahmanagement system; The fault diagnosis function is mainly aimed at the maintenance of the power 18650 battery 2500mahsystem; the data storage function provides good data support for further analysis of 18650 battery 2500mahperformance and functional verification of the 18650 battery 2500mahmanagement system; the platform configuration function is to realize a flexible, friendly interface of the monitoring platform. Ease of operation is key. Software design based on LabVIEW mainly focuses on these aspects.

　　3Software design

　　Using NI's LabVIEW8.2 as the development platform for the monitoring platform software, it can not only easily realize the functions required by the monitoring platform, but also make the software design intuitive and fast. At the same time, the software has flexibility, scalability, Maintainability, code reusability, and readability.

　　In order to realize the various functions of the above monitoring platform and ensure the efficient performance of the platform, the software design uses LabVIEW's multi-threading technology. The so-called thread refers to the running process of a set of codes (instruction groups) further derived from the process. Multi-threading technology allows the same program to have several parallel running paths, thereby improving the running speed of the program. The system resources occupied by threads are smaller than those of processes. In a program, the more threads the better, nor the more threads the program will execute faster. For the situation where the computer has only one CPU, when one thread is executing, other threads are suspended or blocked, and the memory usage efficiency of the program will be very low. In view of the functions of the monitoring platform, it is required to consider the efficient operation of the platform at the same time. The software is designed with four threads, namely data collection and display through the CAN bus; platform parameter configuration; data storage; system calibration and fault diagnosis.

　　3.1 Data collection and display

　　The platform uses a USBCAN-II smart CAN interface card to connect the PC and the 18650 battery 2500mahmanagement system to receive and display data from the 18650 battery 2500mahmanagement system CAN bus in real time. The USBCAN-II smart CAN interface card provides a callable dynamic link library for applications. The call library function node (CallLibraryFunction, referred to as CLF) in LabVIEW can be used to achieve flexible operations on the USBCAN-II smart CAN interface card. Applying CLF requires Configure it. The configuration mainly sets the calling specification to stdcall (WINApI) according to the interface function, and sets the parameters of CLF according to the function parameters. The finally set CLF provides a convenient interface for programming and also provides convenience for the platform parameter configuration function. Through the device type number and device index number, you can flexibly choose between COM1 and COM2 of the USBCAN-II smart CAN card. Configuring the calls of other interface functions of USBCAN-II according to similar setting rules allows flexible operation of USBCAN-II smart CAN.

　　According to the USBCAN-II operating requirements, the data collection process is shown in Figure 3. For ease of operation, the received data is encapsulated into subVIs.

　　SubVIs in LabVIEW are similar to subfunctions in C language and can be called by other VIs. The data receiving subVI also provides a configuration interface for platform parameter configuration. The received data is packaged into cluster variables in LabVIEW. Cluster is a data type in LabVIEW. It can contain multiple elements of different data types, similar to C Structures in language. Packaging of data facilitates the display and storage of received data. Data reception adopts the loop reception mode until the stop reception command is received.

　　Figure 3 Data collection process.

　　The data sent by the existing 18650 battery 2500mahmanagement system to the CAN bus includes cell voltage, total voltage, current, SOC, SOH, temperature, maximum and minimum cell voltage, maximum and minimum temperature, etc. Each slave board is responsible for cell voltage and temperature. For measurement, each slave board has 60 voltages, 16 temperatures, and fault information, etc., a total of 4 slave boards. These data need to be displayed and stored to facilitate real-time monitoring of 18650 battery 2500mahstatus, in-depth analysis of 18650 battery 2500mahdata, and 18650 battery 2500mahmaintenance based on fault information. Use LabVIEW to design a friendly display interface, and display the above information according to different tabs from the board number setting, as shown in Figure 4.

　　Figure 4 shows the interface.

　　3.2 Platform parameter configuration

　　Use LabVIEW multi-threading technology to allocate a thread specifically for platform parameter configuration and set the monitoring platform parameters. Monitoring platform parameters can be divided into the following categories: USBCAN-II smart CAN card configuration, including CAN channel selection, CAN communication baud rate, etc.; display configuration, including the number of slave boards, the number of slave board voltage sections, the number of slave board temperatures, etc. ;Data storage configuration, including storage period, location, format, etc.; System calibration and fault diagnosis configuration, including calibration parameter type, location, and fault type for fault diagnosis, etc.

　　LabVIEW is a data flow program development platform. The data flow determines the execution order of nodes in the program. Event-driven extends or communicates between different parts of the program to affect the execution of the program. The platform parameter configuration adopts an event structure, which can effectively modify and set parameters between different threads in asynchronous situations. When no events are generated, the program returns to the waiting event state, reducing the impact on the execution of other threads.

　　3.3 Storage of data

　　Commonly used methods of recording data in LabVIEW include using database technology to store data and using file systems to store data. Using the file system to manage data files has fast reading and writing speed, takes up less disk space, and is convenient and quick to retrieve. This monitoring platform sets the stored file format to csv format by default, which takes up little disk space. At the same time, this format can be viewed in Excel or imported into Matlab for analysis, which is especially helpful for research on 18650 battery 2500mahperformance.

　　Establishing an independent thread for data storage facilitates programming, but it needs to solve the problem of data synchronization, that is, the process control between the two threads of data collection and data storage. Local variables can be used to transfer data between different loops in LabVIEW, but if data is transferred between the data acquisition loop and the data storage loop, local variables are not enough. Because saving data to the hard disk is a relatively time-consuming task, and data collection requires higher cycle time. The cycle speeds of the two are different. At this time, data cannot be simply transferred through local variables. Between the data collection cycle and the data storage cycle, the message notifier in LabVIEW is used for data synchronous transmission. This monitoring platform packages the data into cluster types during data collection, transmits the data through the message notifier and stores it.

　　3.4 System calibration and fault diagnosis

　　In order to ensure the safe operation of the power 18650 battery 2500mahsystem, each parameter of the 18650 battery 2500mahmanagement system needs to be calibrated to ensure the reliability of the information detected by the 18650 battery 2500mahmanagement system and ensure the correct management of the 18650 battery 2500mahby the 18650 battery 2500mahmanagement system. When a power 18650 battery 2500mahsystem fails, it is not enough to simply rely on monitoring 18650 battery 2500mahparameters to diagnose the fault. It is also necessary to diagnose the operating parameters of the 18650 battery 2500mahmanagement system itself. These parameters include 18650 battery 2500mahmanagement system configuration parameters, software and hardware information, and software and hardware working status. etc.; the 18650 battery 2500mahmanagement system has a self-test function, which can be triggered through the reliable CAN bus, and finally returns information through the CAN bus to locate the fault point as much as possible. Another function of the monitoring platform is to realize the calibration of the 18650 battery 2500mahmanagement system and perform fault diagnosis when the 18650 battery 2500mahsystem fails. In order to realize this function, it needs to interact with the 18650 battery 2500mahmanagement system through the CAN bus, USB??

　　CAN-II provides an interface function for sending information to the CAN bus, which is similar to the receiving function. LabVIEW is used to design the sending sub-VI. At the same time, a system calibration and fault diagnosis thread is established to call the sending and receiving sub-VIs to realize interaction with the 18650 battery 2500mahmanagement system.

　　4 Conclusion

　　This monitoring platform makes full use of LabVIEW's multi-threading and flexible interface technology to achieve high-speed data collection on the CAN bus and real-time data recording of multiple format files. The monitoring platform is flexible in design and can adapt to various combination solutions of the 18650 battery 2500mahmanagement system. At the same time, the system calibration and fault diagnosis of the monitoring platform lay a good technical foundation for the mass production of the 18650 battery 2500mahmanagement system. This monitoring platform has been used in iron lithium 18650 battery 2500mahmanagement systems for various electric vehicles such as Putian, Hengtong, Geely, etc. For more than a year, the operation has been reliable and stable. It not only provides users with real-time collection data in a timely manner, but also provides developers with a convenient diagnostic interface, which provides a powerful basis for further research on 18650 battery 2500mahmanagement and analysis of the performance of lithium iron batteries. guarantee.

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