The research and development of the automobile bus system can be divided into three stages: the first stage is to study the basic control system of the automobile (also known as the comfort bus system), such as lighting, power windows, and centralized control locks. The second stage is to study the main control system of the automobile (also called the power bus system), such as electronic injection ECU control system, ABS system, automatic transmission, etc. The third stage is to study the integration, real-time control and information feedback between the various electronic control systems of the automobile. According to my country's automotive electronic technology development plan, after entering the 21st century, car electronic technology can reach the level of foreign cars in the 1990s. In order to shorten the gap with foreign car technology and improve its own competitiveness, simply relying on technology introduction is not conducive to development. Research and development of one's own car bus and network application system are on the rise. At present, the research and application of automobile bus in my country is still in its infancy, and the application trend of automobile bus is obvious. Now it is a good time to intervene in this research. The focus of research on automobile bus. As my country’s models are mainly European and American models, and European and American models are mainly CAN bus, the current domestic models using bus technology almost all use CAN bus. Therefore, the research and development of automobile bus should be selected based on the actual situation at home and abroad. CAN bus. CAN conforms to the ISO/OSI reference model, but only specifies the protocol of the physical layer and the data link layer, and the protocol of the application layer needs to be defined by the user. There are many chips that support CAN low-level protocols, including on-chip MCUs and off-chip CAN controllers. There are also many application layer protocols developed by users. For example, the DEVICENET protocol defined by AB is an application layer protocol based on the CAN protocol. The SDS bus launched by Honeywell also defines its own application layer on the basis of CAN. It can be seen that the focus of the research on the automotive CAN bus is to develop ECU hardware and application layer software for specific models, and form an in-vehicle network. Key technology Use CAN bus to build an in-vehicle network. The key technical issues that need to be resolved are: 1) Technical issues such as the rate, capacity, priority, and node capacity of information transmitted by the bus; 2) Reliable data transmission in a high electromagnetic interference environment; 3) Determine the maximum transmission delay time; 4) Network fault-tolerant technology; 5) Network monitoring and fault diagnosis functions; Overview of the bus network system As the performance of the automotive electronic control system improves, especially the controller chip and software performance With the improvement of the automobile bus network system, not only can share information and save wiring harnesses, but also provide richer software functions to enhance the value and competitiveness of products and meet the needs of automobile reliability and comfort. The bus technologies corresponding to these functions include: Network management: The controller monitors the network operation status through the network management, and once a communication failure is found, it immediately takes failure processing. The sleep and wake-up functions of network management can coordinate the power management of each controller, thereby reducing the battery power consumption when the vehicle is parked. Diagnosis: Diagnosis can not only read the fault code, but also realize the two important functions of offline configuration and detection, and program download. Automated offline configuration and detection functions can quickly and comprehensively configure and detect the functions of the controller (such as window zero configuration and anti-pinch detection), so as to ensure the quality of the car and speed up the production line. Through the program download function, the automaker can refresh the controller's software in the 4S shop, thereby reducing the cost of recalls caused by software defects. Measurement and calibration: In the development process of new models, the rapid control prototype controller using measurement and calibration technology can adjust the control parameters and algorithms in real time and conveniently through the computer and network system, which greatly reduces the development cycle and cost. This technology is widely used in the development of new energy vehicles in Europe, the United States and Japan. Foreign GM, Ford, Volkswagen, etc., as well as domestic FAW, Dongfeng, SAIC, Changan, GAC, Chery and other automakers have integrated bus technology into a generalized network platform for high, medium and low models. In this way, changes in the network system are reduced, software reuse is increased, and development costs are reduced. The network platform of the vehicle manufacturer is composed of network standards, test specifications and protocol stacks (network-related embedded software). The network platform of commercial vehicles complies with SAEJ1939; the network platform of passenger vehicles has its own characteristics for OEMs, but more and more OEMs adopt international standards to share supplier resources. At the same time, more and more suppliers choose to develop protocol stacks by professional companies, thereby reducing development manpower and cycles. Bus network system development process The network platform construction and network system development adopt the V mode development process, as shown in the figure below. The V model defines a clear and effective development process: the OEM completes the formulation of system requirements and component requirements from system requirements to component requirements, and issues the component requirements to suppliers; after the supplier completes the component development, From component testing to system testing, OEMs complete integration and verification on multi-round prototypes and prototype vehicles.
Talking about the research focus and key technology of automobile bus