Classification and development trend of the hottes

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Classification and development trend of Automobile Network Abstract: This paper introduces the classification of automobile network, analyzes the development trend of various networks from the characteristics and use of each network, and finally analyzes the overall development trend of automobile network

keyword: Automobile network, bus standard, bus protocol

1 Overview

since 1980, many international well-known automobile companies have been actively committed to the research and application of automobile network technology. The use of automobile network solves the problems caused by point-to-point body wiring, makes the body wiring (tend to) be standardized, reduces the cost and enhances the stability. So far, there are many network standards, such as can of Bosch, J1850 of SAE, van of ISO, D2B of Philips, Lin of Lin Association, etc. For the convenience of research, design and use, the society of Automotive Engineers (SAE) divides the automobile network into three categories A, B and C according to the speed, as shown in Table 1. Table 1 Division of automobile network

considering the function, bit transmission rate and other factors, the existing automobile bus also includes multimedia information system bus, safety bus and diagnosis system bus

2. Specific classification of automobile network

2.1 class a network standard

from the current development and use (as shown in Table 2), the main buses of class A are ttp/a (time triggered protocol/a) and Li n (local interconnect net work). Table 2 usage of class a network

⑴ ttp/a protocol was originally developed by Vienna Institute of technology. It is a time triggered network protocol, which is mainly applied to the real-time fieldbus integrated with intelligent converter. It has a standard UART, which can automatically identify the master node and the slave node joining the bus. The node triggers the communication within a known period of time, but does not have the internal fault-tolerant function

⑵ Lin is an open low-cost serial communication standard for automotive distributed electronic control system, which was launched in 1999 with the joint efforts of Lin association composed of European automobile manufacturers Audi, BMW, DaimlerChrysler, Volvo, Volkswagen, VCT and Motorola. It has been used since 2003

lin is a single line 12V bus communication system based on UART data format and master-slave structure, which is mainly used for serial communication of intelligent sensors and actuators. In terms of hardware, software and electromagnetic compatibility, Lin ensures the interchangeability of network nodes. This greatly improves the development speed and ensures the reliability of the network

lin protocol application development focuses on the United States, Europe and Japan. It is estimated that in the next 10 years, each vehicle will have about 20 Lin nodes on average. In this way, the world will produce 1.2 billion Li n nodes every year. It can be seen that there is a huge potential market for the application of Li n, and the protocol itself will be improved in the continuous application

to sum up, Lin network has been widely accepted by most automobile companies and parts manufacturers in the world, and is expected to become a de facto class a network standard

2.2 class B network standard

the use of class B network is shown in Table 3. At present, there are three types of class B bus standards mainly applied: low speed can, J1850 and van. Table 3 use of class B network

⑴ SAE officially took J1850 as the standard protocol of class B network in 1994. SAE J1850 was first used in the automobiles of Ford, GM and Chrysler in the United States. Now, J1850 protocol is widely used in automotive products as diagnosis and data sharing. However, J1850 is not a single standard. The physical layer of J1850 standard adopted by Ford is different from that used by GM and Chrysler. GM and Chrysler use different data frame formats on the same physical layer, and the three companies use their own message protocols. It is expected that it will be out of use in 2006 or 2007, and then all will be transferred to can bus

⑵ van standard was introduced by ISO in June, 1994. It is based on is011519 -3 and is mainly used by French automobile companies. However, as far as the power and transmission system is concerned, it is concentrated on the CAN bus even in France

⑶ can is a serial data communication protocol developed by Bosch Company in Germany in the early 1980s to solve the data exchange between many control and test instruments in modern vehicles. It is a multi master bus. The communication medium can be twisted pair, coaxial cable or optical fiber. The communication rate can reach 1Mbps. It was first realized in Mercedes Benz S Series cars in 1991. In the same year, Bosch officially issued the can technical specification (version 2.0), which includes two parts A and B. In november1993, ISO officially issued the international standard is011898, paving the way for the standardization and standardization of can. Since then, more and more North American and Japanese automobile companies have also begun to adopt can network. In 1994, the SAE truck and bus control and communication sub Association selected can as the basis of SAEJ1939 standard. Low speed can has many fault-tolerant functions, which are generally used in the electronic control of vehicle body, while high-speed can is mostly used in the electronic control of vehicle chassis and engine

to sum up, can bus has become the mainstream protocol of class B bus accepted by the world by virtue of its outstanding reliability, real-time and flexibility

2.3 class C network standard

class C standard is mainly used in places related to automobile safety and with high real-time requirements, such as power systems, so its transmission rate is relatively high, usually between 125kb/s and 1mb/s, and must support real-time periodic parameter transmission. Table 4 use of class C network

at present, the main protocols in class C network include high-speed can (iso11898 -2), ttp/c, FlexRay and other protocols under development

⑴ ttp/C protocol is developed by Vienna Institute of technology and is based on TDMA access mode. Ttp/c is a complete communication protocol applied to distributed real-time control system. It can support a variety of fault-tolerant strategies, provide fault-tolerant time synchronization and a wide range of error detection mechanisms, and also provide node recovery and re integration functions. The speed of the engineering sample transmitted by optical fiber is responsible for the society and its contribution will reach 25mb/s. Ttp/C supports data transmission triggered by time and event. Members of TTP management organization ttagroup include Audi, SA, Renault, NEC, ttchip, Delphi, etc

⑵ FlexRay is a powerful communication network protocol developed by BWM, Daimler Chrysler, Motorola, Philips and other companies. Based on the deterministic access mode of ftdma, it has fault-tolerant function and determined communication message transmission time. At the same time, it supports event triggered and time triggered communication, and has the ability of high-speed communication. FlexRay adopts redundant backup method, and high-speed equipment can be connected with FlexRay bus controller in a point-to-point manner to form a star structure, and low-speed networks can be connected in a manner similar to can bus

⑶ European automobile manufacturers basically adopt the high-speed can bus standard is011898. The bus transmission rate is usually between 125kb/s and 1mb/s. According to the statistics of strategy analytics, the number of CAN nodes used in automobiles exceeded 100million in 2001 However, as an event driven bus, can cannot provide the required fault-tolerant function or bandwidth for the next generation control by wire system, because the X-by-wire system has high requirements for real-time and reliability, and time triggered communication protocols, such as ttp/C or FlexRay, must be used

at present, can protocol is still the mainstream of class C network protocol, but with the introduction of X-by-wire system in the next generation of vehicles, ttp/C and FlexRay will show advantages. The competition between them will continue for some time. It is still difficult to decide which standard has more vitality in the future wire control system

2.4 diagnostic system bus standard

fault diagnosis is an essential function of modern vehicles. The purpose of using emission diagnosis is mainly to meet the OBD-II (on board diagnosis), obd-iii or E-OBD (European on board diagnosis) standards

obd- Ⅱ (on board diagnosis) second generation on-board computer diagnostic system was proposed by the American Society of automotive engineering in 1994. Since 1994, some major automobile manufacturers in the United States, Japan and Europe have gradually used obd- Ⅱ on-board diagnostic system for maintenance convenience. This system integrates the software and hardware structure of the fault self diagnosis system, fault code, communication mode system and self inspection test mode, and has the ability to monitor the engine microcomputer and emission system components

in 2004, GM, Ford and DC adopted j2480 diagnostic system communication standard based on can for passenger cars. In Europe, ISO9141, a communication standard based on UART, was used in the previous diagnostic system. Since 2000, European automobile manufacturers have begun to use a diagnostic system communication standard iso15765 based on CAN bus. Iso15765 is formulated in accordance with ISO and ISO related diagnostic services. Therefore, ISO 15765 is fully compatible with ISO 14230 application layer services and parameters, but not limited to the occasions specified in these international standards. Table 5 usage of diagnostic system protocol standard

at present, in addition to can network, Lin protocol has also become the bus standard for automotive diagnosis

2.5 multimedia information system bus standard

automobile information entertainment and remote information equipment, especially automobile navigation system, need powerful operating system and connection ability. The main bus protocols currently used are shown in Table 6. Table 6 multimedia information system bus usage

⑴ the most network is developed by oasis silicon system of Germany. Most technology is optimized for plastic optical fiber media and adopts a ring topology to provide high reliability and scalability at the device layer. It can transmit synchronous data (mobile data such as audio signals and video signals), asynchronous data (data packets accessing networks and databases) and control data (control messages and data controlling the whole network). Most is supported by BMW, Daimler Chrysler, Harman/Becker and oasis, and has been applied to many models, such as BMW7 series, Audi A-8, Mercedes e series, etc

⑵ idb-c and idb-1394 buses and standard interfaces are managed by the IDB forum. Idb-c is based on CAN bus and has become SAE standard, namely sae2366. Idb-1394 is designed for high-speed multimedia applications. The idb-1394 network adopts optical fiber technology, allowing 1394 compatible portable consumer electronic devices to connect to the automotive internal network and realize interoperability. For example, Za yante provides 1394 physical layer devices for the consumer market. A recent demonstration with Ford included a digital video camera and Sony play station TM2 game console, as well as plug and play of two video monitors and a DVD player. Compared with most, idb-1394 makes full use of the civil equipment market and solves the cost problem by applying existing components to on-board equipment

⑶ D2B is a network protocol for multimedia data communication, which can integrate digital audio, video and other high data rate synchronous or asynchronous signals. It mainly uses smart wiretm unshielded twisted pair or single fiber. This communication network is driven by c&ceelectronics in the UK and supported by Jaguar and Mercedes Benz. D2B aims to evolve with new technologies while maintaining backward compatibility. D2B is based on an open architecture. Only one polymer optical fiber is used to process the multimedia data and control information in the vehicle, simplifying the expansion. When a new device or function is added to the optical fiber ring, the connecting cable does not need to be changed

⑷ Bluetooth wireless technology is used for mobile devices and WAN/LAN access points

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