TMS320TCI6612/14 helps small cell base stations achieve high performance

1 Introduction

There are many electronic control units in electric vehicles, small internal space, and large environmental interference, which puts higher requirements on the control system and communication system. CAN is particularly suitable for communication between various electronic control units in electric vehicles with its good operating characteristics, extremely high reliability and unique design. In order to better conduct research in the laboratory, a relatively complete experimental test platform was established to study the CAN bus system and its network protocol. First, the communication program of the motor controller node was designed based on DSP development. Secondly, the application requirements of the CAN bus in electric vehicles were deeply understood, and the application layer protocol of the CAN bus was designed. Finally, in order to verify the feasibility of the designed protocol, the monitoring system of the electric vehicle was developed using VB6.0, and a database was established for the monitoring data to facilitate data management.

2 Design of Motor Controller Node

According to the characteristics of the electric vehicle motor controller, TI's TMS320LF2407 chip is selected as the processor of the motor controller. The communication program of the motor controller node is written with a modular design concept, which can be easily transplanted to the DSP-based motor controller or other control units. In the CAN bus system of electric vehicles, the motor controller has high real-time requirements and belongs to a high-speed node with a baud rate of 1 megabit. The motor controller node mainly receives control information such as the motor working mode, SOC, vehicle speed, accelerator pedal position and brake pedal position transmitted on the bus, and sends real-time information such as the motor's working temperature, motor fault, and working status. In this paper, mailbox 2 of DSP2407 is used as the receiving mailbox, and mailbox 5 is used as the sending mailbox, which is sent once every 20 milliseconds.

3 Design of Electric Vehicle Monitoring System

The electric vehicle CAN bus system is simulated in the laboratory, and a PC (with USB-CAN module) is used as the general controller of the electric vehicle. Using the operating mechanism and working principle of the CAN-bus general test software, a PC-based electric vehicle CAN bus technology monitoring system is designed.

3.1 Monitoring System Overview

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. It can send and receive parameters in the CAN bus as needed to monitor and control each node of the bus. For example, motor parameters include 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 in the Microsoft Access database, which can be displayed in real time in a table form and can be opened by the software Excel through the output button.

3.2 Monitoring system communication protocol

Only two protocols, data link layer and physical layer, are defined in the CAN protocol, lacking the specification of information processing. A complete network system cannot do without the application process of human-computer interaction, so the application layer protocol must be defined by the user. According to the characteristics of electric vehicle operation, the communication protocol of the monitoring system is designed. Generally speaking, the electronic control units ( ECUs ) on electric vehicles are divided into two categories: high-speed and low-speed nodes. Among them, high-speed nodes include motor controllers, engine controllers, battery controllers, ABS/ASR control units and energy management units, etc., and their ID codes are set with higher priorities. Low-speed nodes include air conditioning systems, instrument display systems, and headlight systems. Table 1 shows the types of signals received and sent between nodes in electric vehicles. According to the data received and sent between nodes in electric vehicles, the types of information that need to be exchanged between nodes, the parameters contained, and the representation methods are specifically described. 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), and one byte as spare. Table 1 Data received and sent between nodes in electric vehicles. For example, the 8 bytes sent by 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), operating mode (single byte) and one byte as spare.

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 windows, including the main window, motor controller monitoring window, battery controller monitoring window, clutch controller monitoring window and node creation window, and modular design is carried out. The node creation window can conveniently create a monitoring window, set the node ID number and monitoring variables as needed. The flow chart of the monitoring system program design is shown in Figure 2.

4 Testing of monitoring system

After completing the design of the PC monitoring system program, in order to verify whether the program works normally, and to verify the correctness of the designed lower computer DSP data acquisition and communication program. Here, the DSP data acquisition and communication program and the PC program are combined for debugging. The baud rate of both parties is set to 1M baud. The test program of the DSP node includes A/D sampling (simulating the accelerator pedal position) and communication program. After the DSP runs, the timer interrupt (20ms) performs data acquisition and processing, and uploads the signal to the upper computer (PC) through the CAN bus. On the other hand, the DSP automatically determines whether there are instructions sent by the PC, such as battery voltage, battery current, accelerator pedal position and working mode. After receiving the data, the upper computer processes it and sends it to the monitoring system for display. The test interface of the motor controller node is shown in Figure 3.

5 Conclusion

In order to meet the needs of electric vehicle monitoring, an electric vehicle simulation test platform based on CAN bus is established. After being equipped with professional test instruments, a CAN-BUS laboratory can be established. The system has good scalability and can easily add automotive electronic control units (ECUs) that need to be monitored. In addition, through the good connection between VB and ACCESS technology, data can be saved in real time, providing conditions for later data processing. In order to ensure that each message can be collected and processed by the relevant nodes in a timely manner, it is necessary to conduct in-depth research on the message scheduling strategy and further optimize network management, especially network fault diagnosis and processing mechanism.