CAN/LIN Bus And Application On Automobile

At present, the development of electric vehicle has been paid high attention, and the electric vehicle has become the main direction of the future car. The CAN/LIN bus technique applied on the economic electric vehicle exists a big blank, it is still at the starting stage. To decrease the cost of the electric vehicle system, the CAN network is used as the main component and the LIN as the complementary part in the control of electric vehicle. The CAN/LIN bus technique application on car can decrease the body wiring and increase the system reliability and market competitiveness.The standard of automotive network consist the CAN of Bosch, the J1850 of SAE, the VAN of ISO, the D2B of Philips, the LIN, and so on. According to its transmission speed and the function, the automotive network divided into three types: A, B and C in SAE J2057 by the SAE. The principle, the topology and the protocol of CAN and LIN are introduced respectively based on the summary and analysis of the automobile bus technique. The protocol of CAN/LIN transmission network is designed. The MC68HC908 chips are utilized as the MCU. Considering the processing speed and requirement of CAN/LIN network, the MC68HC908AZ60 is used at the CAN node and theMC908QB8CDWE at the LIN node. And The MC33388 and the MC33399 chip is selected as the CAN interface device and the LIN interface device respectively.When the bus scheduling is not considered in the design of the automobile, the refresh rate of the high-priority message will be too high. This causes a difficulty in the transmission of the low-priority message and finally leads to a scheduling failure of the whole system. To predict the scheduling performance and optimize the system, the RM (rate monotonous) algorithm is used to optimize the CAN application layer in the automobile network control system. The Rate monotonous analysis has been used to analyze the CAN bus scheduling of the CAN/LIN network. The message format of the electrical machine ECU and the battery management ECU is designed. A big spare capacity and good performance is achieved by this optimization method. Then the bus occupation time and the message occupation time of network scheduling are analyzed. The bus monitor program is devised. And the parameters of network-control automobile are optimized. And the transmission statuses are researched with the bus transmission rate, the priority class and the delay time between the messages increased respectively.LIN bus is a low-cost network. LIN standard has defined the transmission protocol, the transmission medium specification, the interface standard of the development tools and the software program interface. It can ensure interoperability of the network nodes and decrease the development cycle and the workload of developer. LIN bus is applied to the software and hardware design of the automobile electric-window. The system consists of four nodes. The left front door is the master node and controlled by single relay mode. The other three doors are slave nodes. The lift motor and door-lock motor of each door are controlled by its own node. The over-head lamp of cockpit and other signals are controlled by the master node. Dual power supply is adopted to enable the lift motor supplied separately. The 12V voltage form the battery is mainly applied for the motor drive, over-head lamp and the MC33399 chip. Other chips are supplied by the 5V voltage which is obtained from the LM7805. The 5V voltage is grounded with a capacitance to increase the anti-disturbance ability. The 16-pin and 8-bit CPU of Freescale Inc, namely the MC908QB8CDWE, is selected as the CPU of the master controller. The MC33399 chip is chosen for design the LIN interface. The LIN bus based automobile electric-window has follow functions: manual or auto lift and auto lift out the car, auto anti-pinch, enable/disable the lift motor, Central Controlled Door Lock, door-controlled over-head lamp of cockpit, auto unlocking and locking, and so on. The over-head lamp of cockpit is lighten when any door is open. And when all doors are closed, the over-head lamp of cockpit is switched off with 5 seconds delay. Electric-window is used to enhance the comfort of automobile. It can lighten the labor intensity of the driver and passengers and make the operation easily. But the high rising velocity of the electric-window may cause the driver and passengers injured. Thus the anti-pinch ability becomes one of the essential functions of the automobile electric-window. To improve the anti-pinch ability and realize the sensorless control approach, the multiplexing current sampling technique is used to solve the disadvantages of the traditional grouping current sampling. The multiplexing current sampling and the distance estimation combined method is proposed and the distance estimation algorithm is given. This control approach can better the reliability of the sensorless anti-pinch electric-window. Finally, the electromagnetic compatibility and the reliability of the system are summarized and some important anti-disturbance methods are presented.To summarize, this paper offers a powerful assist and establishes the foundation for the CAN/LIN bus application on the automobile in future. Proper selecting the bus and its topology can decrease the wiring complexity and provide a more opening extensibility and extra freedom degree for the automobile.