The key point and key technology of automobile bus
The research and development of vehicle bus system can be divided into three stages: the first stage is to study vehicle's basic control system (also called comfort bus system), such as lighting, power windows, central centralized control lock, etc. The second stage is the main control system of the automobile (also called the power bus system), such as the ECU control system, the ABS system and the automatic transmission. The third stage is to study the comprehensive, real-time control and information feedback between the electronic control systems of the automobile. According to the development plan of China's automotive electronic technology, after entering in twenty-first Century up to 90s foreign car electronic technology level, in order to shorten the gap with foreign car technology level, improve their own competitiveness, simply by the introduction of technology is not conducive to digestion, absorption, development, research and develop their own car and bus network application system in the potential for. At present, the research and application of automobile bus in our country is still in the beginning stage, and the application trend of the bus bus is obvious. Now it is a good time to intervene in this research. The research focus on the vehicle bus because of our cars to Europe and the United States models, and models in Europe and America with the CAN bus as the mainstream, domestic use of bus technology models almost all use CAN bus, so the research and development of automotive bus should be combined with the actual situation at home and abroad with CAN bus. CAN conforms to the reference model of the ISO/OSI, but only specifies the protocol of the physical layer and the data link layer, and the protocol of its application layer needs the user's own definition. There are many chips that support the CAN low layer protocol, both in the MCU of the chip and the CAN controller outside the chip. There are many application layer protocols developed by users. For example, the DEVICENET protocol defined by AB is the application layer protocol based on CAN protocol. The SDS bus introduced by Honeywell also defines its application layer on the basis of CAN. It can be seen that the focus of research on automobile CAN bus is to develop the hardware and application layer software of ECU for the specific vehicle, and make up the internal network of the car. The key technology to build a vehicle network using the CAN bus, the key technical problems to be solved are: 1) rate, capacity, priority, node capacity, technical problems such as bus transmission information; 2) reliable data transmission with high electromagnetic interference environment; 3) to determine the maximum transmission delay fault size; 4) the technology of the network; 5) the function of monitoring and fault diagnosis network; bus network system with the performance of automotive electronic control system, especially the controller chip and software to enhance the performance of the car, bus network system not only can share information, save the wiring harness, but also can provide a rich software function, to enhance product value and competitiveness the car, meet the reliability, comfort and other aspects of the demand. The bus technologies corresponding to these functions include: Network Management: the controller monitors the running state of the network through network management, and once failure is found, the failure is dealt with immediately. The sleep and wake-up functions of network management can coordinate the power management of various controllers, thereby reducing the consumption of battery power during vehicle parking. Diagnosis: the diagnosis can not only read the fault code, but also can realize two important functions of downline configuration and detection and program downloading. The automatic offline configuration and detection function can quickly and comprehensively configure and detect the functions of the controller, such as window zero location 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 vehicle can refresh the software of the controller at the 4S store, thereby reducing the recall cost caused by the software defects. Measurement and calibration: in the development process of new car, the fast control prototype controller using measurement and calibration technology can adjust parameters and algorithm conveniently and conveniently through computer and network system, which makes the development cycle and cost greatly reduced. This technology is widely used in the development of new energy vehicles in Europe, the United States and Japan. Foreign GM, Ford, Volkswagen, and China FAW, Dongfeng, SAIC, Changan, Guangzhou, Chery and other OEMs will integrate bus technology as a common network platform, used in high, medium and low all kinds of models, thereby reducing the network system changes, increase software reusability, reduce development cost. The network platform of the vehicle factory is composed of network standard, test specification and protocol stack (network related embedded software). Commercial vehicle network platform follows SAEJ1939; passenger vehicle network platform and vehicle plant have their own characteristics, but more and more vehicle manufacturers adopt international standards, so as to share supplier resources. At the same time, more and more suppliers choose to develop protocol stacks from professional companies, thus reducing development manpower and cycle. The development process of the bus network system development process network platform and the development of network system use the V mode development process, as shown in the following chart. V defines a set of clear and effective development process: from system requirements to OEM parts demand, complete the system requirement specification and component requirements specification, and will be issued to the supplier parts requirement specification; supplier development components, OEMs from the component test and system test, complete the integration and validation of the wheel parts and vehicle.