Body Electronicl Control System With CAN/LIN Buses

IntroductionVehicles are required increasingly to have sophisticated and inventive featuressuch as safety, stability, control, comfort, convenience. So a lot of electronic controlunits are introduced to a vehicle for satisfying these requirements. It is necessary forthese electronic control units to share large quantity of data and exchangeinformation in time, which is difficult for traditional wiring system to perform. Theincorporation of these applications requires a range of advanced and reliablenetwork technologies and protocols that enable the efficient and effectivenetworking of distributed electronic systems in a vehicle. This is aiding thedevelopment, introduction of several application-specific network protocols. Thevehicles from the U.S and Europe which equip in-vehicle network are very common.However, the networks still are seldom found in Chinese cars.CAN-bus is a in-vehicle network protocol, which is adopted widely by theautomakers from the U.S and Europe. ISO standards have been set up for the bus.Country standards (GBxxxx) which are relative to the bus application are building inChina. It has excellent error detection and confinement capabilities and is ahigh-integrity serial data communications bus for real-time control applications.LIN-bus has been developed for slow rate network with low price at end oftwentieth century.Main ContentsThis paper is about a body electronic control system with CAN/LIN buses. Toachieve body electronic control function requirements, the system uses controllersand buses. The main matters are showed as follows:Analysis for body electronic control system, which describes requirementsfor the system in detail.System ProposalBased on function requirements and characteristics of CAN and LIN, a systemproject is made. The system includes a body module, a door & window main module,four door area modules, a column switch module and a drive module. The LIN andCAN buses are used to connect modules.System Hardware DesignModules are shown in function, construction and principle as follows:Body ModuleBody module is the main module of the system. It has a LIN port, a CAN port,RKE and drivers. The main controller is dsPIC30F6011 with two CAN ports andtwo UART ports. Battery system is made of LM2937, which is specific IC forvehicle. CAN transceiver is MCP2551, which incorporates to CAN2.0B. LINtransceiver is MCP201. RKE system applies KEELOG code hopping technology,and the encoder is HCS300, which is designed for secure Remote Keyless Entry(RKE) systems. The receiver is special module with frequency of 443.93Hz. Thedrivers include a flasher, which is constructed by special IC-MC33288 and a motordriver which is constructed by MC3387 and relays for lamps and rear wiper motor.Door & Window Sub-System Main ModuleThe module is applied for CAN port, LIN port, input circuit of switch signalsand P/W motor driver. The main controller is PIC18F248, with a CAN port and aUART port. The transceivers of CAN and LIN are same as that of body module. Theinput of switches is main switches of P/W and door switch. P/W motor is drivenby relays.Door Area ModuleThe module is applied for LIN port, switch input circuit and motor driver. Italso has a system to protect driver circuit by the means of inspecting temperatureand current of motor. The transceiver of LIN, switch input circuit and motor driverare same as that of main module.Column switch module is applied for input of switch signals which is fromswitches in the column switch, and transmits them to BCM with the LIN bus. Drivemodule is used to drive lamps and front wiper motor by relays, which are controlledby BCM with LIN bus. What construct these modules are same as those of door areamodule.System Protocol DesignCAN protocol is CAN2.0B, the application layer is J1939. The LIN protocol isLIN 1.3. The door & window sub-system is used to show the definition of IDs anddata field.Software designThe chapter shows the main flow of modules.The main program flow of the body module includes initialization, decodingof RKE, CAN communication processing, LIN communication processing, andswitches inspection. Decoding of RKE with software applies special library function.ISR is applied for switches inspection etc.The main program flow of the door & window module includes initialization,CAN communication processing, command frame transmitting, slave node conditioninspection, assembly inspection. ISR is applied for CAN bus interrupt, system basicclock, LIN bus timing and LIN port interrupt. A program also is designed to preventswitch signal from shiver.The main program flow of door area module includes initialization, receivedmessage frame processing, transmitting message frame processing, LINcommunication faulty processing, processing for no bus signal active, Inputprocessing for motor current, over-time and knob. The LIN communication of slavenodes is achieved by means of ISR.The main program and LIN communication processing of column switchmodule and drive module are same as that of door area module.PostscriptThe purpose of the design is to achieve control of multiplex signals by applyingin-vehicle network, which can improve performance of body electronic system. Thepaper includes software and hardware of the system, which is based on in-vehiclenetwork. In the paper, there are function requirement, system structure, hardwarestructure, ID definition, data definition, software design etc.In the paper, we analyse CAN and LIN protocols in detail, and compare them.The distributed system and application range of the buses are also discussed.The paper introduces some function achievement in detail, such as RKE withKEELOG code hopping, lamp control, lock control, P/W control, measure methodof motor current, etc.