1. Introduction: Currently, due to increasingly serious environmental pollution and energy crises, the development of electric vehicles has begun to receive high attention from various countries and has become the mainstream direction of future automotive development. Electric vehicles mainly possess three key technologies: drive control system, battery power supply, and vehicle electronic control system. The vehicle electronic control system must meet the design concept of pure electric vehicles, making it both energy-efficient and simple and reliable. Given the current level of battery technology, solving these two key technologies will help electric vehicles achieve market penetration in China first, and its economic significance is self-evident. The power system structure of electric vehicles is complex and diverse, with numerous component types. An advanced and efficient control system architecture can ensure that data exchange between various power systems in electric vehicles meets requirements such as simplicity and speed, high reliability, strong anti-interference ability, good real-time performance, and strong system error detection and isolation capabilities. This paper designs a CAN bus-based vehicle electronic control system for electric vehicles. This system is applied to pure electric vehicles driven by switched reluctance motors, which can greatly reduce the number of in-vehicle sensors and significantly improve the overall performance of the vehicle. 2. Performance characteristics and control methods of switched reluctance motors in electric vehicles: Switched reluctance motors are a type of motor with a long history. They were invented more than 160 years ago. After more than 100 years of development, especially the research and improvement in the last 20 years, the performance of switched reluctance motors has been continuously improved. At present, they can outperform other types of motors in a wide power range. Moreover, the performance characteristics of switched reluctance motors are particularly suitable for pure electric vehicles. 2.1 Performance characteristics of switched reluctance motors: (1) Simple structure and high efficiency; The structure of switched reluctance motors is simpler and more reliable than that of induction motors. They are particularly suitable for high-speed, low-speed, high-torque, and low-current systems. They are also highly efficient. In particular, the rotor has no windings, making them suitable for frequent forward and reverse rotation and impact load conditions. (2) Simple and reliable control circuit; The drive power circuit uses fewer power switching elements, and the circuit is simpler. The power elements are connected in series with the motor windings, making it less prone to short circuits. (3) Wide speed range, good torque and braking characteristics; A wide speed range can be achieved using a relatively simple control circuit. It also has characteristics such as low-speed high torque and braking energy feedback. Therefore, the switched reluctance motor drive system is particularly suitable for electric vehicles. 2.2 Control methods of switched reluctance motors in electric vehicles: (1) Starting and stopping the vehicle; The switched reluctance motor controller can realize the control of motor starting, stopping, acceleration, deceleration, forward rotation, and reverse rotation. When applied to electric vehicles, the starting and stopping of the vehicle can be realized through the start key system. (2) Acceleration and deceleration of the vehicle; Acceleration and deceleration are controlled by adjusting the throttle output voltage by pressing the accelerator pedal to control the VI setpoint. (3) Forward and reverse movement of the vehicle; Forward and reverse movement can be controlled by the gear lever. (4) Emergency braking of the vehicle; Emergency braking can be achieved by activating the regenerative braking system through the brake pedal. Therefore, the switched reluctance motor can easily control the basic operation of electric vehicles, which can greatly simplify the extremely critical motor control unit on the control system bus. 3. Technical characteristics of CAN bus: CAN (Controller Area Network) is a serial communication network developed by Bosch in Germany to solve the data exchange between many control and testing instruments in modern automobiles. It can effectively support distributed control and real-time control and belongs to the fieldbus category. The CAN bus has the advantages of reliability, flexibility and real-time performance. (1) The CAN bus adopts a multi-master structure, and any node on the network can send information to other nodes at any time, making the communication method flexible. (2) Nodes on the network can respond within 134μs at the fastest, depending on their access priority to the bus. (3) The non-destructive bus arbitration technology can greatly save the bus conflict arbitration time, and the network will not be paralyzed in the event of congestion. (4) CAN uses NRZ encoding, and the direct communication distance can reach up to 10km (speed 5kbps), and the communication rate can reach up to 1Mbps (at which time the communication distance is up to 40m). (5) It adopts a short frame structure, which has a short transmission time and low probability of interference. (6) CAN nodes have an automatic output shutdown function in the event of a serious error, so that the operation of other nodes on the bus is not affected. (7) The communication medium can be twisted pair, coaxial cable or optical fiber, which can be selected flexibly. 4. System Design: 4.1 Network Node Configuration and Signal Types: 4.1.1 The main CAN nodes in the electric vehicle and the main CAN bus signals transmitted and received by each node are as follows: (1) Battery Management System Node: Battery State of Charge (SOC), Battery Charging and Discharging Status, Battery Fault. (2) LCD Display Node: Battery State of Charge (SOC), Vehicle Speed, Motor Speed, Forward and Reverse Status, Door and Window Opening and Closing Status, Light Switch Status, Motor Temperature, Interior Temperature, Regenerative Braking Status, Battery Charging and Discharging Status, Battery Fault, Air Conditioning Switch Status, Key Signal. (3) Motor Control Node: Motor Speed, Forward and Reverse Status, Motor Start and Stop, Motor Temperature, Regenerative Braking Status. (4) Joint Assembly Node: Interior Temperature, Vehicle Speed, Door and Window Opening and Closing Status, Light Switch Status, Air Conditioning Switch Status. (5) Human-Machine Dialogue Node: Control Door and Window Opening and Closing, Control Light Switch, LCD Display Switch, Air Conditioning Switch. (6) Operation Control Node: Start Key Signal, Accelerator Pedal, Brake Pedal, Forward and Reverse Gear lever. 4.1.2 Data types received and transmitted by the electric vehicle electronic control unit: In this scheme, the data types received and transmitted by each electric vehicle electronic control unit are shown in Table (1), where T represents transmission and R represents reception. Table (1) Data types received and transmitted by the electric vehicle electronic control unit 4.2 Network architecture: The electric vehicle electronic control system consists of two buses, namely the high-speed CAN bus and the low-speed bus. The high-speed CAN bus and the low-speed bus are two independent bus systems. In order to facilitate the management of all functions of the vehicle, the two bus networks are connected through a gateway, and the data between different buses is shared through the gateway. In this way, the two buses operate independently, and only the data that needs to be exchanged between the two buses is transmitted through the gateway. This method can separate different types of information and reduce the burden on each network bus. The high-speed CAN bus is mainly connected to the drive system of the electric vehicle, and can realize the rapid control of key systems such as motor, battery, steering, and braking. The low-speed bus is mainly used to connect the body system and is connected to the high-speed CAN bus as a subnet through the gateway to form a unified multi-network. The network architecture of this system is shown in Figure (1). Figure (1) Network Architecture 4.3 Introduction to Battery Management Node: Battery management system has always been a key technology in the development of electric vehicles. Its most basic function is to monitor the working status of the battery. By measuring parameters such as battery voltage, current and temperature, it predicts the SOC of the battery and the corresponding remaining driving range, and manages the working status of the battery. The block diagram of the battery management system is shown in Figure (2): Figure (2) Block diagram of battery management system 4.4 Introduction to LCD Display Node: This design uses LCD display, which can display more information than analog instruments, which is more conducive to centralized information management and facilitates the driver's operation. The information it displays mainly includes: battery status information, motor status information, vehicle operating status information, in-vehicle facility status information, and start key information. Its main signals are shown in Table (2): Table (2) Main signals of LCD display node 5. Conclusion: There are more and more electronic devices on modern cars. The number of electrical nodes in a high-end car has reached thousands. If the traditional method is used for wiring, the number of connections will be very surprising and there will be great potential for failure. The CAN bus-based switched reluctance motor drive system can realize the sharing of information between various nodes in the vehicle, greatly improve the layout of the vehicle and improve the overall performance of the vehicle. At present, a whole vehicle electronic control system for hybrid electric vehicles has been developed in China, but it is based on hybrid electric vehicles and has a large difference from the pure electric vehicle developed in this paper in terms of control nodes and instrument display. The whole vehicle electronic control system designed in this paper is directly applied to pure electric vehicles and adopts digital liquid crystal display, which can achieve higher requirements of energy saving, simplicity and reliability. From the perspective of the whole vehicle electronic control system of electric vehicles in various countries around the world, the motor control nodes in Europe and America mostly use AC induction motors, while Japan mostly uses DC motors, and the instrument display nodes mostly use analog instruments. The whole vehicle electronic control system designed in this paper is applied to electric vehicles driven by switched reluctance motors and adopts digital liquid crystal display, which makes up for the research in this field. References: [1] Ran Zhenya, Design of electric vehicle control system based on CAN bus, Automotive Engineering, No. 2, 2006; [2] Zhong Yong et al., Application research of general protocol of electric vehicle CAN bus, Automotive Engineering, No. 5, 2006; [3] Wu Kuanming, CAN bus principle and application system design, Beijing University of Aeronautics and Astronautics Press;