Design And Implementation Of Body Control System Based On J1939

With the development of electronic and automobile technology, more and more electrical equipments have been widely used in the automobile. They become the effective necessities to assist the automobile drive and improve the safety. Automotive electronic has already worked as an economic growth point of the world automotive industry. Take our country as an example, the need of onboard equipment has been increasing. The electrical equipments make the automobile more intelligent and bring people more comfort and convenience. People can feel a taste of high technology and fashion while driving. However, some problems also appear. The wires in automobile increase. so it is more complex to arrange them and the weight of the automobile also increases. In order to solve these problems, the network and the fieldbus technology has been introduced into automobiles. Among all the fieldbus technologies, the CAN bus technology becomes the first choice of many automobile body networks because of their high speed, low cost, anti-interference, light weight, flexibility and other advantages.According to data types and transmission rates, the automobile networks can be divided into three subnets---power transmission electronic control system, safe and chassis electronic control system, automobile body control system. The automobile body network is an important branch of the automobile network. Automobile Body Control System (also called Body Controller or BCM, short for Body Control Module) is an electronic and electrical control system, which operates the electrical equipments in vehicle, according to the operations of the drivers and motorists. Its control objects mainly include the dashboard, the lights, the electric windows, the electric locks, the wipers and the wash pumps. It effects on the visibility, convenience, comfort and entertainment in vehicle. At the same time, the network can reduce the connection of the wires, the weight and cost of manufacture. the network structure and communication protocol in the distrbuted automobile body control system. There are three main parts.Part I: In the paper,the automobile body control system is made up of a central control node and some child nodes.And the central control node communications with child nodes through three CAN buses to control and communication with the body electrical equipment.The three CAN buses are automobile body CAN bus, comfortable CAN bus and chassis CAN bus. By body CAN bus, the central node controls and accepts the feedback messages from the child nodes: the lights, the electric windows, the electric locks, the wipers and the wash pumps air-condition. The central node achieves temperature of the automobile through comfortable CAN bus. The central node achieves the information of the ABS, ECM, TCM, though chassis CAN bus. The central node not only is a control center but also is a gateway. The central node can communication data base on the transport protocols accurately, crediblely, immediately.Part II: The hardware design of the distributed automobile body control system. The hardware circuit of the automobile body control system includes a central control node and some CAN child nodes. The central control node is the core of the distributed body network.And its MCU is LPC2294,which has an ARM7 core.The hardware includes the following modules:the microcontroller minnmum system module,JTAG debug module,power module,reset module,switch signal input module,analog input module,switch signal module,PWM output module,three CAN buses interfaces and LIN bus interface.The CAN bus interface is composed of CAN controller in LPC2294 and CAN transceiver TJA1050.To enchance the expansibility of the hardware, the LIN interface has been reserved.The hardware circuit of the child nodes is composed of communication circuits and drive circuits. Every child node has the same communication circuit,which mainly includes microcontrollers AT89S52, CAN controller SJA1000 and CAN transceiver PCA82C250. SJA1000 is the core of CAN communication model,which executes the communication task of the CAN bus. PCA82C250 is the interface of CAN controller and physical bus,which provides the differential transmitting ability for the CAN bus and the differential receiving ability for the CAN controller.The drive circuits of the child nodes are different according to different drive devices.The child nodes in the system mainly drive various kinds of lights and motors. Different kinds of driving modes are used for the power of different lights. The low power lights can be driven by triodes. The high power lights can be driven by triodes and relays.The coils of the relays connect or not can be used to control the headlights on or off. According to this, triode 74LS06 is used to drive low power lights and relay JQC-3F is used to drive high power lights.There are many dofferent kinds of motors in the system.And the motors are deiven by different chips.For example, MC33887 drives low power motors such as fastener motor,MC33291 drives wiper motor,MC33486 drives window motor and L298 drives rearview mirror motor.Part III: The software design of the distributed automobile budy control systerm. Corresponding to the hardware of the system,the software system includes central control node software and child nodes softwares.The software design uses the modular design method.The software in central control node includes the following parts: the system target board configuration and startup module,the initial module,the CAN bus drive module,the LED display module,the dynamic database module and the main control logic module.The central control node in the foreground and background system architecture,and the program modules which relate with data table,combine the software system to implement the function of the automobile body control system.Although the program in the CAN child nodes of the automobile body control system are different,but the overall design of the program is the same.According to the modular design method, the program of the child nodes include the following parts:monitoring the switch state module, sending data module,receiving data module and execeting the command module.When the switch or other states changes,the child nodes will send the message to the central node.When the child nodes receive the command messages,they will analyse the messages and execute them.So the central control node can realize its control ability.By putting up the experiment platform according to the hardware design in the paper, we build the automobile control network, test the hardware and software with Zhou Ligong's USB-to-CAN combining with the program in central control node and child nodes and implement the function of the automobile body control system. All the experiments prove that we have achieved the expect goal and the harware design,software deesign and the protocol design is proper and feasible.