Based on CAN Bus City Bus Information Integrated Control System
Abstract: This multi-master network protocol, which is based on non-destructive arbitration mechanism, makes the bus with maximum You Xianquan text access reported without any delay. can as a standard vehicle network technology, its applications in the automotive network and link the process of playing the role of a bridge, the city bus information integrated collection to a new level.
1 Introduction
As electronic technology continues to evolve, automotive electronic technology the development of up rapidly, a variety of automotive electronic control unit Shumu also increasing, connecting wires significantly increased, Yinertigao communication between control units reliability and reduce the Daoxianchengben has become an urgent problem to be solved. In the 20th century, 80s, R & D and production of automotive electronics company known for this problem in Germany bosch developed a can-bus protocol, this multi-master network protocol, which is based on non-destructive arbitration mechanism to allow the bus to the highest priority the right to access messages without any delay. can as a standard vehicle network technology, its applications in the automotive network and link the process of playing the role of a bridge, the city bus information integrated collection to a new level.
2 City Bus Information Integrated Control System Overview
City bus information integrated control system is built on the vehicle network control technology based on the object from the control points, can the city bus information integrated control system is divided into powertrain electronic systems, safety and chassis electronic systems and body electronics. Control system block diagram in Figure 1 indicates.
Based on CAN Bus City Bus Information Integrated Control System
Figure 1 Block diagram of integrated control of the city bus information
Powertrain electronic system by the eec (engine electronic control engine electronic control), ect (electronic control transmission electronic control transmission), electronic control power steering etc.; instrument displays information from electronic systems, powertrain, driver information will be displayed in the instrument focus disk, display driver and passenger traffic during the relevant amount of information, such as speed, speed, mileage, oil, water temperature, fault alarm, etc.; safety and chassis electronic system, including abs (anti-lock brake system Anti-lock brake control) , asr (anti-slide retractor drive slip control), sab (safety air bag airbag control), ccs (cruise control system cruise control), retarder, suspension system control; signal control unit and body composition of electronic systems related to control automatic doors, windows, lights, air conditioning, wipers, audio-visual equipment, electronic monitors, electric mirrors, roof windows.
3 System Design
3.1 Information Integrated Control System
Information integrated control system is the city bus information integrated control system, the core of the comprehensive application of its mandate to automotive electronic control technology, vehicle network technology and intelligent control technology, the ecu city bus associated with real-time information sharing and control in order to achieve the overall increase city bus safety, comfort the purpose of reducing dependence on driver skill.
From the perspective of information exchange, city bus information integrated control system is divided into vehicle powertrain control subsystem and control subsystem. Powertrain control subsystem including the engine control system, chassis control system. Body control subsystem including body electronics systems and instrument panel control system. Powertrain Control Subsystem frequent exchange of information, control information on the highly demanding real-time; and body control subsystem exchange of information relative to the powertrain control subsystem, real-time requirements are relatively low. Powertrain control subsystem and the body control the exchange of information between subsystems exists. If a single bus architecture, which all are connected to the same ecu can-bus, the superposition of two subsystems of information transmission, is bound to increase the network load, reducing the control information in real time. We use dual bus structure, power train control subsystem uses the high speed can, information transfer rate up to 500kb / s, low speed body control subsystem can, information transfer rate up to 100kb / s, the exchange of information between the two by a small amount of network off to achieve. Gateway is the city bus information integrated control system in the core, is the basis for integrated control of the main function is to analyze all kinds of information processing, and issued directives to coordinate the control unit and the vehicle electrical equipment work. City bus information integrated control system topology shown in Figure 2.
Based on CAN Bus City Bus Information Integrated Control System
Figure 2 city bus information integrated control system topology
3.2 Gateway and bus interface
Gateway selection philips lpc2101 microcontroller company, it is a real-time simulation based on arm7tdmi-s cpu, and 8kb and 32kb with embedded high speed flash memory. 128-bit wide memory interface and a unique accelerator architecture enable 32-bit code can run at maximum clock rate. This can make an interrupt service routine and important functions in the dsp algorithm performance than the 30% increase in thumb mode. Strictly control the scale of the code application can use 16-bit thumb mode code size reduction of more than 30%, while the performance loss is very small. It can control the internal integration of two main features are: a single bus data transfer rates of up to 1mb / s; 32 bit registers and ram access; compatible can2.0b; Global Acceptance Filter can identify all of the 11 and 9 rx identifier; acceptance criteria for the selection of filters to provide full can style identifier automatically receive.
philips transceiver can use the company's tja1050 interface chip, tja1050 can send a bus to provide differential performance, as can the controller to provide differential receiver performance.
lpc2101 microcontroller through the optical coupling circuit, respectively, and high-speed bus transceiver can tja1050 in two-way can bus. Two can link the same way, can bus drivers are used with isolated dc / dc power module alone. Not only can achieve a two-way electrical isolation between interfaces, the gateway and can also achieve bus isolation. Gateway and the bus structure shown in Figure 3.
Based on CAN Bus City Bus Information Integrated Control System
Figure 3 Structure of the gateway and can bus interface
4 Software Design
can / can gateway the main function is to achieve two-way can segment the data between the filter and forwarding, as city bus information integrated control system in real time on the communication requirements of the design during the software to do data storage and forwarding time as short as possible. To achieve this requirement, data reception method using irq, and powertrain control subsystem because the data was significantly higher than vehicle traffic control subsystem, the power control assembly will connect subsystem can1 received the highest priority setting, and Connect body control subsystem can2 second priority, and interrupt service routines as concise as possible so that the response time short as possible.
As the transmission rate, high-speed data transmission between the network can be different. When the high-speed network can transmit data to the low speed can, you need to join the soft cache temporarily stores; when the low-speed network data can transfer to the high-speed networks can be directly transferred. The overall process shown in Figure 4.
Based on CAN Bus City Bus Information Integrated Control System
Figure 4 high-speed gateway communication process can
5 Conclusion
can bus with its high performance, high reliability and unique design more and more attention has been paid, and was recognized as a vehicle control network, one of the most promising of the bus. In this paper, a high-speed network, city bus information can integrate the design of control networks, introduced the lpc2101 microcontroller can network in the gateway as a high-speed hardware and software design. Automotive computer control unit can can Zongxian shared by all of the information and 資源, to Jian Hua wiring, reduce sensor Shu Liang, to avoid control Gongnengzhongfu and improve system reliability and maintenance and reducing costs, and better match, and coordinate control system for the purpose.