The Research Of Data Fusion And Network Bridge Based On CAN Bus

Automotive Electronics is a field with complex high technologies, numerous classes and intensive knowledges, which are related to many subjects such as electronics, mechanism, computer and so on. The new generation automobiles, which is named the electronic-automobile, are the products of the auto industry and electronic technologies. Nowadays, it can be saied that there would be no automobiles without electronics. The technology and products of the automotive electronics have been developing very fast because of the progresses of the skills in electronic-control, computer and communication. Auto-electronic is an important standard of the auto industry development level of one country. The development of automobile industry has reached an immense level in the world, including the technology, the management, and the scale. In recent years, with the development of the IT technique, there are higher demands for the car integrated wiring and information sharing, due to the appearance of the new electronic communication productions standard by 3G (GIS, GPS and GSM).From the status and developing trend of the auto electronic, we can see the following three features. Firstly, automotive has becoming a major intelligent control system instead of the minor self-help system, involving various kinds of MCU, sensors, controllers, buses, net-nods. So how to choose an apt and worth hardware is a key problem. Secondly, because of the differences of the kinds, forms and complex rates of the control signals, how to classify the network and choose the proper MCU for the nod is also one important issue. Thirdly, how to choose a reasonable algorithm and make a reliable data-transmission protocol for the efficient transmission of the data is one of the significant problems as well.In view of the above problems, the main works of this paper are as follow.(1) Hardware. The hardware can be divided to three functional modules as the core module, the net-host module and the network bridge module. The core module includes the main MCU LPC2292, SDRAM, FLASH, crystal and the reset circuit. The net-host module consists of the power supply module for the core and the entire board, a UART for the ISP downloads and normal communication, another UART for the MODEM communication, the interface for the JTAG, and two CAN bus convertible modules. The net-work bridge module comprises all of the net-host function, and additionally, it possesses the LCD240128 module for displaying the massages and the keyboard for the users, the network chip, the interface for transmitting the data or files in the OS, and a clock chip with the battery to provide the accurate time and date. The advantages of this design are being able to update the main board without changing the core board and changing the different core MCU in the same main board. Furthermore, this design is of the low cost, high flexibility.(2) Software. Based on the hardware, the software is also divided into two parts net-host and net-bridge. The main works of the net-host are operating and managing all the net-guest, dealing the data request from the net-guest, receiving and responsing the net-bridge's orders and transmitting the massages across the nets. The key jobs of the net-bridge are reading the users'massages and doing the corresponding treatment, managing all the net-host, responsing and dealing the data request between nets, sending data in terms of the protocols, and displaying the data and massages.(3) Data Fusion. This paper designs a three-level hybrid data fusion structure. For the first level, each net-guest MCU possesses many sensors. It starts the data fusion when receiving the sensors'data and sends the first data file to the net-host. For the second level, the net-host deals this file, and then transmits the second data file to the net-bridge. For the last level, the net-bridge makes the final arbitrate. The advantages of this dealing way are filtering all the data, deleting the redundant, invalid and unlikehood data, combining and disposing all the data from different nods thus reducing the transport layer, and improving the data gathering efficiency from all the nods.(4) System debugging. Because of the numerous functions, we debug the module one by one after the welding of the hardware to ensure all the system functions. The first is the power module, and then the LED, keyboard and LCD modules, at last the CAN bus module. After the tests of all the modules, we take the monolithic feature debugging, achieve the basic action and reach the expected targets.The main novelties of this thesis are as follows.(1) In view of the advantages and disadvantages of the star, ring and bus network, we employ an mixed topology structure with the high channel utilizing rate and the good function extending.(2) According to the complexity of the signal in the monitor, we propose the principle of network function classification, and present a gradation module of the network.(3) Considering the multi-signals and complex types in the system, we describe a three-level data fusion technique. It can improve the real-time, reliability and stability tremendously when disposing the data.(4) We divide the hardware into core board and main board, and this can update the main board without changing the core board, and can choose the different MCUs in the same main board. This structure has good flexibility, extensibility and compatibility for the upgrading and updating of the system.Now the basic functions have been realized, but still there are some problems to be solved during the design. The issues which should be improved are as follows.(1) Considering the processing ability of the different MCU, we just give the method of the data classification and fusion , but don't propose a preferable algorithm. (2) In view of the time-arrangement and cost, we don't use the EOS(Embedded Operating System), and this would affect the uses of the PS2 mouse, CF card, SD card, USB flash disk and so on.(3) Due to the progress restriction of the program, the data fusion and net classification described in this paper are just implemented in the laboratory and not in the practice yet.(4) In this design, we don't consider the system power consumption, and this may result in impacts to the practical use of the system. So we should give the low-consumption measure and the new hardware and software implementation design.(5) Because of the limit of conditions, the EMC and the stability in different environment of the system are not tested, and this should be considered and improved in the following work.(6) We don't take the security into account and also don't test the limitation performance such as excess data flow, multi-connect and so on. So a series of capability parameters such as the stability of temperature and moisture should be determined to realize the quality of the system.