With the continuous development of modern automotive technology, CAN bus has gradually become an indispensable technology for modern automobiles, and it has greatly promoted the rapid development of automotive technology. This article will briefly introduce the working principle, characteristics and advantages of the automotive CAN bus technology, the application and development trend of the CAN bus in automobile manufacturing, and specifically follow the Xiaobian together to find out.
The origin of CAN busAs the technological level of Hyundai Motors has increased substantially and it is required to be able to control more vehicle operating parameters, the number of automotive controllers is constantly on the rise, starting from several to tens to hundreds of control units. The increase in the number of control units makes the exchange of information between them more and more intensive. For this purpose, Germany's BOSCH company (along with the inter company) has developed an advanced design solution, the CAN data bus, which provides a special local area network for data exchange between controllers of cars.
CAN is the abbreviation of Controller Area Network, which is called Local Area Network of the control unit. It is a transmission form of information transmitted by the vehicle control unit.
CAN bus technology introductionThe CAN bus, also called the car bus, is called "Controller Area Network," which means a regional network controller. It connects all the individual control units in some form (mostly stars) to form a single one. Complete system. In this system, each control unit exchanges and shares data with the same rules, which is called a data transmission protocol. The CAN bus was originally a serial communication protocol developed by Germany's Bosch company to solve the data exchange between numerous electronic control modules (ECUs) in modern automobiles.
In engineering practice, the CAN bus is the customary name for the standard serial data transmission system in automobiles. With more and more automotive electrical equipment, from the engine control to the drive system control, from the driving, braking, steering system control to the security assurance system and instrument alarm system, so that the automotive electronic systems form a complex large system, and all Focus on cab control. In addition, with the development of the Intelligent Transport System (ITS) in recent years and the emergence of new electronic communication products represented by 3G (GPS, GIS, and GSM), it raises a higher level for the integrated wiring and information sharing and interaction of automobiles. Claim. The CAN bus is designed to meet these requirements.
The CAN bus is mainly composed of four parts: wires, controllers, transceivers, and termination resistors. The wire is a twisted pair twisted together by two ordinary copper wires. The role of the controller is to translate received and transmitted signals. The transceiver is responsible for receiving and sending the information shared on the network. The resistance is a reflection that prevents the CAN bus signal from producing a changing voltage. When the resistor fails, the signal from the control unit becomes invalid.
How CAN Bus Technology Works
The CAN bus uses serial data transmission. It can operate on a 40m twisted pair at a rate of 1Mb/s, or it can be connected using an optical cable. The bus protocol supports multiple master controllers on this bus. CAN is very similar to the I2C bus in many details, but there are some obvious differences.
When a node (station) on the CAN bus transmits data, it broadcasts it to all nodes in the network in the form of a message. For each node, it receives data regardless of whether it is sent to itself. The 11-characters at the beginning of each message are identifiers that define the priority of the message. This message format is called a content-oriented addressing scheme. In the same system, the identifier is unique and it is not possible for two stations to send a message with the same identifier. This configuration is important when several stations simultaneously compete for bus reads.
When a station wants to send data to other stations, the CPU of the station transmits the data to be sent and its own identifier to the CAN chip of the station, and is in the ready state; when it receives the bus allocation, it transfers to send the message. status. The CAN chip sends the data according to the protocol and forms a certain message format. At this time, other stations on the network are in receiving state. Each station in the receiving state detects the received message and judges whether these messages are sent to itself to determine whether to receive it.
Since the CAN bus is a content-oriented addressing scheme, it is easy to establish a high-level control system and configure it flexibly. We can easily add new stations to the CAN bus without making changes in hardware or software. When the new station provided is a pure data receiving device, the data transmission protocol does not require that the independent portion have a physical destination address. It allows the distribution process to be synchronized, that is, when the controller on the bus needs to measure data, it can be obtained on the Internet without having each controller have its own independent sensor.
CAN Bus Technology Features and Benefits1, the characteristics of CAN bus technology
As a multi-master bus, CAN supports distributed real-time control communication networks. It adopts many new technologies and unique designs with reliability, real-time and flexibility. Its characteristics are as follows:
CAN works in multi-master mode. Any point on the network can actively send information to other nodes on the network at any time, regardless of master-slave, and the communication mode is flexible.
The node information on the CAN network is divided into different priorities, which can meet different real-time requirements. High-priority data can be transmitted within 134μs at most.
CAN only uses frame filtering to achieve point-to-point, point-to-multipoint, and global broadcast transmission of accepted data in several ways, without special "scheduling";
CAN communication medium can be twisted pair, coaxial cable or optical fiber, choose flexible;
The CAN node has the function of automatically shutting down the output in case of serious errors so that the operation of other nodes on the bus is not affected.
2. The advantages of CAN bus technology
The software implementation of the hardware solution simplifies the design and reduces the cost, and when the data is updated and new information is added, only the software upgrade is required, and the scalability is strong;
The control unit carries out real-time detection of the transmitted information, with the ability of error diagnosis and automatic recovery, saving the cost of production and maintenance;
The CAN bus complies with international standards, so data transmission between control units of different models can be applied.
Data sharing reduces duplicate data processing and saves costs. For an EFI engine with a CAN bus interface, other electrical appliances can share the speed, water temperature, and oil pressure and temperature provided by the other appliances, eliminating the need for additional water temperature, oil pressure, and oil temperature sensors.
Application of CAN Bus in Automobile ManufacturingThe application of CAN bus can reduce the body wiring and further save the cost. Due to the bus technology, only two signal lines are required for signal transmission between modules. Wiring localization eliminates the need for all lines that cross the body except the bus, saving wiring costs. The CAN bus system data is stable and reliable. The CAN bus has the characteristics of small line interference and strong anti-interference ability. The CAN bus is tailor-made for the car, taking into full consideration the harsh working conditions in the car, such as the powerful reverse charging voltage generated when the ignition coil is ignited, the surge current generated when the eddy current buffer is cut off and the car engine compartment is about 100°C. high temperature.
As safety performance is increasingly valued, airbags will also gradually increase. Previously, the airbags were installed in front of the driver. Airbags will be installed on the side and rear seats. These airbags sense the collision signal through sensors and transmit the sensor signals to the CAN bus. Within a central processor, it controls the starting and popping motion of each airbag. At the same time, advanced anti-theft design is also based on CAN bus network technology. Firstly, the verification information confirming the legality of the key is transmitted through the CAN network, and the encryption algorithm is improved. The verification information is more abundant than the previous anti-theft system; secondly, the car key, the immobilizer controller and the engine controller mutually store the other party's information. , And in the check code mixed with random code, can not be deciphered, thus improving the security of the anti-theft system. The realization of these functions is accomplished by using the CAN bus. The CAN bus has become the “destination needle†for intelligent control of automobiles.
In the design of modern cars, CAN has become a must-have device. Mercedes-Benz, BMW, Volkswagen, Volvo, Renault and other vehicles have adopted CAN as a means of controller networking. According to reports, China's first CAN network system hybrid car has been successfully installed at the Chery company and has undergone initial trial operation. The introduction of CAN bus technology has also begun in Shanghai Volkswagen's Passat and POLO cars. But generally speaking, the application of CAN bus technology in the automotive industry in China is still in the experimental and initial stage. Most of the automobiles have not yet adopted the automotive bus design. It is imperative for China to conduct "professional" network busses in technology, design, and application.
Automotive CAN Future TrendsThe advanced nature of technology is the biggest driver of CAN bus application in automobiles, and it is also the main reason why auto manufacturers compete to use CAN bus. In the design of modern cars, CAN has become a must-have device. Mercedes-Benz, BMW, Volkswagen, Volvo, Renault and other vehicles have adopted CAN as a means of controller networking. According to relevant reports, China's first CAN network system hybrid car has been successfully assembled and operated by Chery. Shanghai Volkswagen's Passat and POLO cars have also begun to cite CAN bus technology. The CAN bus control technology is a good way to improve the car's performance. However, in general, currently the total application of CAN bus technology in the automotive industry in China is still in the experimental and initial stage. Most cars have not yet adopted the design of the automotive bus. Therefore, there are many drawbacks. Just as automotive electronics introduced integrated circuits in the 1970s and introduced microprocessors in the 1980s, the introduction of data CAN bus technology will now be a milestone in the development of automotive electronics.
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