Research On Large Capacity Data Acquisition And Monitoring System For Vehicles With CAN Bus

With the extensive application of electronic technology in the vehicle, data acquisition and state monitoring has become an important part in the process of vehicle research, development, production and driving. Through the collection and analysis of vehicle data, it is possible to prevent and remedy faults in auto parts. It is able to understand the driver's behavior habits, and provide driving assistance and risk warning. Moreover, it is also able to monitor the position and the key information, and get the running status of the vehicle. Under the support of the national 863 project “DCT industry technology development”, this dissertation studies on the large capacity data acquisition and monitoring system for vehicle based on CAN bus, the main research contents are as follows:(1)According to the experimental requirements of the DCT, the basic requirements, the expansion of demand and the application software requirements of the system are discussed, and the design scheme of the system is proposed. The scheme includes three parts, that is, terminal, wireless network and application software. Real-time data from the vehicle are obtained and stored at the terminal, at the same time the key data after compression are transmitted to PC through wireless network. Wireless networks are divided into wireless sensor networks and carrier networks, and provides access to wireless transmission for the data. The application software can obtain and process data through the wireless interface or USB, while monitor the vehicle.(2)The hardware and software of the terminal system are designed, which includes terminal hardware selection, the design of processor software, the design of data acquisition by CAN, the design of data storage software and the design of USB data transmission software. Aiming at the problem of low reliability of data acquisition through the sensor, the CAN bus communication protocol is researched, the data receiving strategy and custom data frame organization method are designed, to ensure the real-time and reliability of the data. For the problem of memory address power down volatile, a processor mode is designed, which consists of LPC1768 and STC89C52, to ensure the correctness of the memory address by using NAND flash and RAM for backup storage.(3)Aiming at the problem which there are bad blocks in the process of large capacity NAND flash storage for vehicle data, an adaptive ECC verification strategy is proposed, and two methods of bad block management and accurate data localization are designed. In this way, the problem of data error due to write bad blocks is solved, and the large capacity storage and the correctness of the data are realized.In view of the contradiction between the large amount of vehicle data and the limited bandwidth of wireless transmission, a lossless compression scheme for the custom frame format data is proposed, to decrease the power consumption of the wireless sensor networks and the traffic charges of the carrier networks, and then the validity of the transmission is ensured.(4)The application software of the system is designed, and the functions are achieved which consists of data export, data conversion, waveform display, map positioning, and so on. It can be used for the analysis of vehicle data and monitoring of vehicle location, speed and other key information.(5)The large capacity data acquisition and monitoring system for vehicles, based on CAN bus, are applied to the DCT experiment in Chongqing Tsingshan Industrial. Experimental results show that the system can complete the real-time collection and storage of the data in vehicle, and the application software can analyze the data and monitor the vehicle effectively, which achieves the required functional requirements.