Design and development of electric vehicle monitoring platform
Abstract: Based on the DSP development platform, this paper designs the communication program of the electric vehicle motor controller node. In order to effectively monitor the electric vehicle and various subsystems, the application layer protocol and monitoring system of the electric vehicle CAN bus are designed. Experiments show that the monitoring system can communicate with other nodes via CAN bus, and then realize real-time online data monitoring and fault diagnosis.
Keywords: CAN bus; electric vehicle; TMS320LF2407
Design and Development of a Test Platform for the Electric Vehicle
Yao Zhen Xie Guo-lin Li You-xin Liu Fang-ming
Luo Zhu-wen Deng Xian-quan
(1. Guangdong University of Technology, Guangzhou, Guangdong, china,
510006; 2. Shenzhen Wuzhoulong Automobile Co., Ltd. Shenzhen,
Guangdong, china, 518116)
Abstract: Based on the DSP platform, the author designs a communicaTIon
program for motor controller. In order to control and monitor the dynamic
system and other subsystems of an electric vehicle (EV) effecTIvely, the monitor
system and EV CAN bus applicaTIon layer protocol are developed. It is proved in
the condiTIon of lab that the monitor system can be used to communicate with
other nodes of the car through the CAN bus so as to realize the on-line data
monitoring and fault diagnosis.
Key Words: Controller Area Network, Electric Vehicle, TMS320LF2407
1 Introduction There are many electric control units in electric vehicles, small internal space, and large environmental interference, which put forward higher requirements for control systems and communication systems. With its good operating characteristics, high reliability and unique design, CAN is especially suitable for communication between electronic control units of electric vehicles. In order to better conduct research in the laboratory, a test platform with relatively complete functions has been established, which can study the CAN bus system and its network protocol. First, the communication program of the motor controller node is designed based on the development of DSP. Secondly, in-depth understanding of the application requirements of CAN bus in electric vehicles, designed CAN
The application layer protocol of the bus. Finally, in order to check the feasibility of the design agreement, a monitoring system for electric vehicles was developed using VB6.0, and a database was established for the monitoring data to facilitate data management.
2 The design of the motor controller node According to the characteristics of the motor controller of the electric vehicle, the TMS320LF2407 chip of TI company is used as the processor of the motor controller. Using the modular design idea, the communication program of the motor controller node is written, which can be easily transplanted to the DSP-based motor controller or other control units. In the CAN bus system of electric vehicles, the real-time requirement of the motor controller is high, which belongs to the high-speed node, and the baud rate is set to 1 megabaud. The motor controller node mainly receives control information such as motor working mode, SOC, vehicle speed, accelerator pedal position, and brake pedal position uploaded from the bus, and also sends real-time information such as motor working temperature, motor failure, and working status. In this paper, the mailbox 2 of DSP2407 is used as the receiving mailbox, and the mailbox 5 is used as the sending mailbox, which is sent once every 20 milliseconds.
3 Design of electric vehicle monitoring system Simulate electric vehicle CAN bus system in the laboratory, with PC (with USB-CAN module) as the general controller of electric vehicle. Using the operating mechanism and working principle of the CAN-bus universal test software, a monitoring system based on the CAN bus technology of electric vehicles based on PC was designed.
3.1 Overview of the monitoring system The monitoring system monitors the motor controller, battery controller and clutch controller through the console (PC with USB-CAN module). The main operation interface is shown in Figure 1. According to need
Send and receive parameters in the CAN bus to realize monitoring and control of each node of the bus. For example, motor parameters,
Including SOC, vehicle speed, fault level, working mode, fault code, working temperature, etc. The monitoring system can also provide the function of creating nodes according to the needs of system expansion. In addition, it also provides data management functions.
During the execution of the monitoring system, the collected data will be recorded to the Microsoft Access database, which can be displayed in real time in the form of a table, and can also be opened by the software Excel through the output button.
Figure 1 Operation interface of electric vehicle monitoring system
3.2 The communication protocol of the monitoring system only defines the two-layer protocol of the data link layer and the physical layer in the CAN protocol, which lacks the specification of information processing, and the application process of human-computer interaction is inseparable in a complete network system, so it must be User-defined application layer protocol. According to the characteristics of electric vehicle operation, the communication protocol of the monitoring system is designed. Generally speaking, the electronic control units (ECU) on electric vehicles are divided into two categories: high-speed and low-speed nodes. High-speed nodes include motor controller, engine controller, battery controller, ABS / ASR
The control unit, energy management unit, etc., set a higher priority in their ID codes. Low-speed nodes include air-conditioning systems, instrument display systems, and car lighting systems. Table 1 shows the types of signals received and sent between nodes of electric vehicles. According to the data received and sent between the nodes of the electric vehicle, there is a specific description of the type of information that needs to be exchanged between the nodes, the included parameters and the representation method. For example, the 8 bytes sent at the motor controller node are defined as: motor speed (double byte), motor torque (double byte), operating temperature (single byte), error level and code (single byte) , Working mode (single byte) There is one byte as a spare. Table 1 The data received and sent between each node of the electric vehicle is clear. For example, the 8 bytes sent at the motor controller node are defined as: motor speed (double byte), motor torque (double byte), operating temperature (single byte), error level and code (single byte) , Working mode (single byte) There is one byte as a spare.
Table 1 Data received and sent between nodes of electric vehicles
3.3 Monitoring system program design The monitoring system is to complete the monitoring of each node. According to the design requirements, the entire design can be divided into five design forms, including the main form, the motor controller monitoring form, and the battery controller monitoring form , Clutch controller monitoring form and creating node form, and modular design. Among them, creating a node form can easily create a monitoring window and set the node ID number and monitoring variables as needed. The flow chart of program design of the monitoring system is shown in Figure 2.
Figure 2 Flow chart of the monitoring system program
4 Test of the monitoring system After the PC's monitoring system program design is completed, in order to verify whether the program works normally, and at the same time, to verify the correctness of the designed lower computer DSP data acquisition and communication program. Here, the DSP data acquisition, communication program and PC program are combined for debugging. Set the baud rate of both sides to 1M baud. The test program of the DSP node includes A / D sampling (simulating the position of the accelerator pedal) and a communication program. After the DSP runs, the data is collected and processed by a regular interrupt (20ms), and the signal is uploaded to the host computer (PC) through the CAN bus. On the other hand, the DSP automatically determines whether there are commands sent from the PC, such as battery voltage, battery current, accelerator pedal position, and operating mode. After the host computer receives the data, it processes it and gives it to the monitoring system for display. The test interface of the motor controller node is shown in Figure 3.
Figure 3 Test interface of electric controller
5 Conclusion In order to meet the needs of electric vehicle monitoring, an electric vehicle simulation test platform based on CAN bus has been established. After being equipped with professional test instruments, a CAN-BUS laboratory can be established. The system has good scalability, which can easily increase the need to monitor the automotive electronic control unit (ECU). In addition, through the good connection between VB and ACCESS technology, it has real-time data storage, which provides conditions for later data processing. In order to ensure that each message can be collected and processed in time by related nodes, it is necessary to conduct in-depth research on the scheduling strategy of the message and further optimize network management, especially network fault diagnosis and processing mechanism.
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