Application classification of vehicle network Chengdu Panfeng Technology

Application classification of in-vehicle networks
In-vehicle networks can be roughly divided into systems according to applications: body system, power transmission system, safety system, and information system.
． Power transmission system
In the power transmission system, the locations of the power transmission system modules are relatively concentrated, and very short communication cables are used to connect the modules in the engine compartment into a network. Since the main factors of these systems in the car are running, stopping and turning, which require strong real-time information sharing, higher network communication speeds can be achieved with shorter communication cable lengths.
The power data bus generally connects block computers, which are engine, D and automatic transmission computers (the power data bus can actually connect computers such as airbags, four-wheel drive and combination instruments, depending on the design requirements of the vehicle manufacturer and the actual network real-time requirements, information capacity and many other factors). The bus can simultaneously transmit group data to the engine computer group, D computer group and automatic transmission computer group. The data bus transfers data at a rate of approximately 1. Each data group transfer requires each electronic control unit to send data once. The order of priority is D electronic control unit r engine electronic control unit r automatic transmission electronic control unit.
In the power transmission system, data transmission should be as fast as possible so that others who need the data can use the data in time, so a high-performance transmitter is needed. A high-speed transmitter will speed up the data transmission between systems so that the received data can be received immediately. Apply to the next one. The data bus connection point is usually located in the wiring harness outside the control unit. In special cases the connection point may also be located inside the engine electronic control unit.
． Body system
Compared with the power transmission system, body system components are installed everywhere on the car. As a result, the wire harness becomes longer and is susceptible to interference. In order to prevent interference, the communication speed should be reduced as much as possible. In the body system, as the number of human-machine interface modules and nodes increases, the application of bus networks will greatly reduce the use of direct lines and make it easier to add or remove functions. Newly added functional modules often only need to be added to the network. Obtaining corresponding network information in the system can increase functionality. In addition, lower-priced transceiver modules and processor units can be used for low-speed communications to reduce hardware costs.
The comfort data bus connection generally connects seven control units, including a central control unit, one controlled unit at the front and rear of the vehicle, and four door control units. Comfort data transmission has seven major functions: central door locks, electric windows, lighting switches, air conditioning, instrument cluster, rear view heating and self-diagnosis function. The individual transmission lines of the control unit converge at one point in the form of a star. The advantage of this is that if one control unit fails, the other control units can still send their own data. This system makes it simple to reduce the number of wires running through the door. If there is a short circuit to ground, short circuit to positive pole or short circuit between lines somewhere in the line, the system will immediately switch to emergency mode to operate independently or switch to single line mode.
The data bus transfers data at a rate. Each set of data transfer requires approximately one data transmission from each electronic control unit. The order of priority is: central control unit r driver's door control unit r front passenger's door control unit r left rear door control unit r right rear door control unit. The transmitter performance is lower than that of the powertrain transmitter since data in the comfort system can be transferred at a lower rate.
There are three main circuits in the entire automobile body system: main control unit circuit, controlled unit circuit, and gate control unit circuit.
After the main control unit presses and receives the switch signal, it first analyzes and processes it, and then sends the control instructions to each controlled terminal through the bus. Each controlled terminal responds and takes corresponding actions. The front and rear control terminals of the vehicle only receive instructions from the main control terminal and execute them according to the requirements of the main control terminal and feed back the execution results to the main control terminal. The door control unit not only receives the instructions from the main control terminal but also receives the switch signal input on the door. According to the instructions and switch signals, the gate control unit will take corresponding actions and then send the execution results to the main control unit.
Safety system
This refers to a system that activates airbags based on information from multiple sensors. Because the safety system involves human life safety, and there are many airbags in the car and many collision sensors, the safety system must be It has the characteristics of fast communication speed and high communication reliability.
Information system
Information systems are widely used in cars, such as car phones, audio and other systems. The requirements for the information system communication bus are: large capacity and very high communication speed. Communication media generally uses optical fiber or copper wire because the transmission speed of these two media is very fast and can meet the high-speed needs of information systems.
Key technologies for the application of bus technology in automobiles
The key technical issues that need to be solved when using the bus to build an in-vehicle network are:
The rate, capacity, priority, node capacity, etc. of bus transmission information Technical issues
Reliable data transmission in high electromagnetic interference environments
Determining the maximum transmission delay
Network fault-tolerance technology
Network monitoring and fault diagnosis functions
Real-time control of the time characteristics of the network
Cabling during installation and maintenance
Addition of network nodes and software and hardware updates (scalability)
Bus as a reliable automotive computer network bus has now begun It is applied in advanced automobiles so that each automobile computer control unit can share all information and resources through the bus to simplify wiring, reduce the number of sensors, avoid duplication of control functions, improve system reliability and maintainability, reduce costs, and more The purpose of well matching and coordinating the various control systems and leaving more space for the later upgrade and application of the vehicle electronic control system will make it easier to upgrade and increase the functions of the electronic control system. With the development of automotive electronics technology, bus communication protocols with high flexibility, simple scalability, excellent anti-interference and error correction capabilities will be more widely used in automotive electronic control systems.