CAN bus based multi-purpose vehicle traveling data recorder design
This paper describes the CAN bus-based multi-purpose vehicle traveling data recorder design
1. Overview
Vehicle traveling data recorder, also known as "car black box", is the vehicle speed, time, mileage and the vehicles of other state information recorded, stored data can be output through the interface of digital electronic recording devices [1]. Multi-vehicle traveling data recorder can record in detail the starting time for each vehicle, mileage, driving time, maximum speed and maximum speed for each duration of speeding drivers in the car alarm sound when the issue of speeding, store 20 seconds before stopping vehicle information, and can collect data using USB mobile disk with a GSM / GPRS remote data transmission, GPS positioning and other functions. Zhongxin the same time can create a monitor to manage multiple terminals to facilitate the administrative departments of Suo Ji Lu Jiao Tong of the data right Cheliangjinhang 有效 of management and thus greatly De Tigao the Jiashi Yuan of security responsibility, Conger can significantly reduce the accident to the Fa Sheng.
For vehicle emissions, comfort, stability, power and braking and so on technical indicators have reached certain requirements, CAN bus has developed into the mainstream of automotive electronic systems bus. At present, China's car already has electronic control and networking capabilities. 2006 buses in Beijing have to meet Euro Ⅲ emission standard, and has developed a communication protocol based on CAN bus as trucks and SAE J1939 bus communications standards [2]. CAN bus based multi-purpose vehicle traveling data recorder, in accordance with this trend, as a CAN bus, car and developed the interface reserved for the CAN node, so that it can collect data through the CAN bus, enhanced multi-car scalability drive recorder. The event of a failure, you can detect problems as soon as possible, easy for maintenance.
2. CAN bus technology
CAN-bus (Controller Area Network) or Controller Area Network, BOSCH, Germany in the early 80s to address the many modern vehicle control and test equipment for data exchange between the developed a serial data communication bus, is an international most widely used fieldbus one. Its high reliability, high cost performance, adaptability. Many foreign cars such as Mercedes Benz, BMW, Volkswagen, Volvo, Renault and Pariaud cars using CAN bus technology [3]. CAN communication protocol mainly describes the way transmission of information between devices. CAN protocol communication interface integrated physical layer and data link layer features to handle the communication of data frames. To the special environment in the automotive application, provided a guarantee [3,4]:
(1) the reliability of CAN bus data communication information for each frame has a CRC checksum error detection and other measures, has excellent error detection results, and the CAN node in the case of a serious error has automatically shut down output in order to make the bus operation of other nodes are not affected.
(2) real-time data communication CAN bus communication speed up to 1Mbps, the message identifier on, CAN nodes into different priority, high priority data have occupied bus priority, high priority maximum data transfer within the 134ms.
(3) the flexibility of CAN bus data communication is a multi-master bus architecture, each node independent of each other, the bus can be any node on the network its own initiative at any time other nodes send messages. Means of communication for the data block, each frame is 8 bytes of data, communication medium is twisted pair, coaxial cable or optical fiber. As the CAN communication protocol includes only the physical layer and data link layer Yue Ming, did not 应用 layer functions and achieve Jinhangdingyi, therefore, users can either use the international CAN Zongxian 用户 and create commerce and associations and other organizations have developed a 开放 High-rise agreement can be flexible in the types of projects to realize their application layer.
Trucks and buses will be SAE J1939 communication standard for automotive application layer specific implementation of a set of common definitions of address coding system, so different manufacturers of controllers (ECU) can access the same network system, data sharing, thus reducing Harness the electronic system, to reduce redundant sensors, and reduce the cost and improve the system's versatility and reliability, while improving the flexibility of the system [5].
3. System Architecture Design
Multi-vehicle traveling data recorder mainly by the CPU, data memory, CAN controller / transceiver, power conversion modules, GPS modules, GSM / GPRS module, IC card interface, digital input, USB interface, and optical isolation circuit and other components. Overall system structure shown in Figure 1: Each part of the collected data, through the CAN bus communication with the recorder, and ultimately by the recorder for data storage. As a result of field bus mode, the actual wiring is very simple and requires only one dual-core cable can be extended easily. Multi-vehicle traveling data recorder data can be done through the USB interface to export, by the management and analysis software to complete the data analysis.
3.1 CAN Interface
CAN interface module, the bus used between the recorder and data acquisition. Node module on the CAN bus various data collection and transmission to the bus, the recorder, through its internal CAN interface module, access to a variety of analog signals and pulse frequency signal. CAN bus transmit data structure shown in Figure 2. This collection of data, has good scalability and portability. For some relatively fixed and common parameters, such as: speed, engine rotational speed, the sensor analog input, etc., can be directly designed as a CAN node module, hanging on the bus for various vehicles; for less frequently used parameters can be expand as needed, made the activities of CAN nodes, such as: temperature sensor, can be added to the CAN node module, measured the temperature inside the seat distribution. CAN node for the activities at the same time can also be designed as a common module, depending on the model and the need to change the CPU in the software section, you can get all the data you want.
CAN bus based multi-purpose vehicle traveling data recorder design
Figure 1 System Architecture diagram
CAN bus based multi-purpose vehicle traveling data recorder design
Figure 2 CAN-bus to transfer data structure diagram
Recorder's internal CAN interface module by the watchdog, CAN controller, CAN transceiver, RS232, switch input components. CAN interface module shown in Figure 3.
(1) CAN controller, Philips selected the SJA1000, it is a separate controller, for moving targets and general industrial environment control area network CAN. The PeliCAN SJA1000 which support this mode has many new features of CAN2.0B agreement.
(2) CAN driver selection PCA82C250, namely CAN protocol controller and the physical bus interface. This device provides differential transmit capability to the bus, the CAN controller provides differential receive capability, it is primarily for the car high-speed communication (up to 1Mbps) applications designed to meet "ISO11898" standard, limiting circuit and thermal protection function. CANH, CANL two lines in the automotive environment to prevent possible electrical transients.
3.2 CPU and Memory
Recorder receives data on the bus, after the summary data storage, and according to predetermined warning value for voice alarm. Core is accurate and reliable data storage.
CPU selection here, produced by Taiwan's Winbond 8-bit microcontroller W77E58, and MCS51 MCU has the same kernel, more powerful, multiple programming, in the same frequency, the speed is 3-4 times higher than 89S52. It has 32KB of internal integration of reprogrammable Flash ROM, 256 bytes of on-chip memory, 1KB MOVX instruction is used to access the SRAM, a programmable watchdog timer, three 16-bit timers, two enhanced full-duplex serial port, on-chip RC oscillator, dual 16-bit data pointer, and many other features.
Multifunction Vehicle Traveling Data Recorder high requirements on memory, to a large number of data storage, the needs of expanding data storage. It records the data consists of two parts: one is parking in front of doubtful data kept stopping the first 20 seconds of data for the analysis of accident causes and accident liability; two for the historical record and store vehicle data in the process of moving for the assessment driver and vehicle operating conditions.
In the storage module, using ferroelectric memory (FRAM) and DATA FLASH and use way. Ramtron's FRAM is the core technology the United States, with random access memory (RAM) and non-volatile storage characteristics, data transfer can be kept for 10 years. It can erase more times, 5V FRAM supply of 100 billion write endurance, low voltage FRAM of rewritable times for the 100 million billion times. Speed, low power consumption, can be used to stop the first 20 seconds of data storage. DATA FLASH selected Atmel Corporation production AT45DB041, it has a 4Mbit of Flash memory cell, can store 26,000 records, thanks to SPI serial mode operation, can easily communicate with the CPU. In the storage module, which uses
To store historical data. Different chips, increasing the capacity of different main memory, such as AT45D081, AT45D161, AT45D321 capacity respectively, 8M, 16M, 32Mbits.
3.4 Communication Interface
According to GB / T 19056-2003 of the national standard, standard configuration recorder should be at least two standard interfaces: (1) USB (Universal Serial Bus) standard interface; (2) Standard RS232D type 9-pin interfaces.
Directly through RS232 serial port for transferring data easier to achieve, widely popular, high reliability. Chip select MAX232, which is a Dual Driver / receiver chip includes a capacitive voltage generator, a single 5V power supply can provide EIA/TIA-232-E level.
Standard interface to transfer data using USB, U disk small size, large capacity, easy to carry, easy to read data. Produced by CYPRESS USB-HOST interface chip SL811 as a USB interface chip. The chip supports USB1.1 protocol, low price and outstanding performance, high reliability, can be ideal for a variety of peripherals. It has 256 bytes of internal RAM data buffers can be used to control registers and data buffers. High-speed mode supports 12Mbps, low-speed mode supports 1.5Mbps. For most manufacturers of USB removable disks (such as USB Netac, Aigo USB, etc.) can successfully access.
4. Software design
Multi-vehicle traveling data recorder software design system software and management software into two parts.
The main function of the system software is the recorder, and special registers of each module is initialized, each switch state detection circuit and analog [6]. If the recorder module initialization settings, including the record interval, the speed threshold alarms, car license etc., memory initialization, GPS / GSM module initialization and so on. It is mainly through the Keil C programming of the microcontroller, to achieve the above functions.
Management software is multi-functional vehicle traveling data recorder package management software, through the Global Positioning System (GPS) and geographic information systems (GIS) to realize the tracking of vehicles, various vehicle violation incidents reflected an intuitive, easy to treatment. It is built on Microsoft Windows, based on the second map to Mapinfo's development control MAPX for the GIS software development platform, you can use VB, VC and other languages, to develop [7].
Intelligent management software with data analysis. On the recorder noted the large amount of data screening, preliminary evaluation, is given intelligence reports. The data analysis functions can be analyzed the following data: 1, questionable data; 2, vehicle speed and mileage data (date, time, speed, distance); 3, continuous driving time data (start date, start time, end date, the end of time, driver's license number); 4, vehicle identification number, vehicle characteristics factor, plate number, license plate Category; 5, driver code, driver's license 证号. In order to improve the efficiency of data analysis, can be divided into three types of analysis: 1, speed (start date, start time, end date, end time); 2 miles (start date, start time, end date, end time, mileage); 3, fatigue driving (start date, start time, end date, end time). Speed is based on the database record corresponding to the corresponding section to check the memory speed value within 1 h in speeding data; miles within 30 d to provide any-time mileage; fatigue driving is that the fatigue of two calendar days driving data.
5. Conclusion
This paper describes a multi-purpose vehicle based on CAN bus driving recorder, on the CPU of choice, CAN interface module, memory, communication module, the internal software, and manage the building made a thorough analysis and explanation. In the standard vehicle traveling data recorder based on the increased data acquisition USB mobile disk, GSM / GPRS remote data transmission and other functions, and combined with the CAN bus, enhanced scalability. The multi-vehicle traveling data recorder has been developed, and made the corresponding experimental, work stability, anti-jamming performance, with favorable results.