Research Focus and Key Technology of Automobile Bus

The research and development of automobile bus system can be divided into three stages: the first stage is to study the basic control system of automobile (also known as comfort bus system), such as lighting, power windows, centralized control lock, etc. The second stage is to study the main control system of the car (also known as the power bus system), such as the 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 car. According to the development plan of China's automotive electronic technology, after entering the 21st century, automotive electronic technology can reach the level of foreign cars in the 1990 s. In order to shorten the gap with foreign automobile technology and improve their competitiveness, relying solely on the introduction of technology is not conducive to development. Own car bus and network application system research and development is emerging. At present, the research and application of automobile and bus in China is still in its infancy, and the application trend of automobile and bus is obvious. Now is a good time to get involved in this research. The research focus of automobile passenger car. Since my country's models are mainly European and American models, and European and American models are mainly based on CAN bus, almost all domestic models that use bus technology use CAN bus. Therefore, the research and development of automobile bus should be selected according to the actual situation at home and abroad. CAN bus. CAN conforms to the ISO/OSI reference model, but only specifies the protocols of the physical layer and the data link layer, and the protocols of the application layer need to be defined by the user. There are many chips that support the underlying CAN protocol, including on-chip MCUs and off-chip CAN controllers. In addition, there are 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. Honeywell's SDS bus also defines its own application layer on the basis of CAN. It can be seen that the research focus of automotive CAN bus is to develop ECU hardware and application layer software for specific models, and form a vehicle network. The key technology uses CAN bus to build a vehicle network. The key technical problems to be solved are 1) the rate, capacity, priority, node capacity and other technical problems of bus transmission information; 2) reliable data transmission in high electromagnetic interference environment; 3) determining the maximum transmission delay time; 4) network fault tolerance technology; 5) network monitoring and fault diagnosis function; overview of bus network system With the improvement of the performance of automobile electronic control system, in particular, with the improvement of controller chip and software performance, the automobile bus network system can not only share information and save wiring harness, but also provide richer software functions, enhance the value and competitiveness of products, and meet the needs of automobile reliability and comfort. The bus technology corresponding to these functions includes network management: the controller monitors the running state of the network through network management, and immediately performs fault handling once a communication fault is found. Network-managed sleep and wake-up functions coordinate power management across controllers to reduce battery drain when the vehicle is parked. Diagnosis: The diagnosis can not only read the fault code, but also realize the two important functions of offline configuration, detection and program download. The automatic offline configuration and detection function can quickly and comprehensively configure and test the various functions of the controller (such as window zero configuration and anti-pinch detection) to ensure vehicle quality and speed up the production line. Through the program download function, automakers can refresh the controller software at the 4S shop, thereby reducing the cost of recalls due to software defects. Measurement and calibration: During the development of new models, the rapid control prototype controller using measurement and calibration technology can adjust control parameters and algorithms in real time and conveniently through computer and network systems, greatly shortening the development cycle and reducing development costs. This technology has been 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 automakers such as FAW, Dongfeng, SAIC, Changan, GAC, Chery, etc., have integrated bus technology into the general network platform of high, medium and low models. In this way, the change of the network system is reduced, the software reuse rate is improved, and the development cost is reduced. The network platform of automobile manufacturers consists of network standards, test specifications and protocol stacks (embedded software related to the network). The network platform of commercial vehicles meets SAEJ1939 standards; the network platform of passenger vehicles has its own characteristics for vehicle manufacturers, but more and more vehicle manufacturers 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 network platform construction and network system development adopt V mode development process, as shown in the following figure. V mode defines a clear and effective development process: the vehicle factory completes the formulation of system requirements and component requirements from system requirements to component requirements, and sends the component requirements to the supplier; After the supplier completes the component development, from component testing to system testing, the vehicle factory completes the integration and verification on multi-wheel prototype vehicles and sample vehicles.