Design Of Body Electrical Control System Based On In-Vehicle Network

Intelligence, integration and connectivity have become trend in automotive electronics. In traditional vehicles, pear-to-pear connection is widely used in connecting various electrical equipments. Thus the harness is extremely complex and hard to fix once it goes wrong. In-vehicle network meets the challenge since it simplifies the overall harness.In this paper, a body electrical control system based on CAN bus is presented and the network architecture, hardware design, software design and diagnostic design are the focus of this paper. The paper first introduces the main trend of in-vehicle network. To meet customer's need, the whole network system is divided into distributed door system and lamp system. The Body Control Module(BCM) is designed as the gateway of Control Area Network(CAN) Communication so that the above system may communicate with each other. BCM also is the gateway between high speed CAN network and low speed CAN network. The application layer protocol is based on SAE J1939. The hardware and software design of distributed door system is stated. The whole system consists of four different nodes, these are left-front door module, right-front door module, left-rear door module and right-rear door module. The function of these modules includes the control and diagnostics of anti-pinch window lift, electrical exterior mirrors with heating, door latches and interior lamps. The signal conditioning and validating of corresponding inputs are implemented. The software design of door system includes anti-pinch window lift algorithm, network communication algorithm and system diagnostic process. Hall sensor is used in developing the anti-pinch window lift algorithm. The output of Hall sensor is PWM type which implies the rotating speed when the window lift motor is operating, thus we can induce the window postion, which is essential in deciding whether the anti-pinch function will apply or not. The design of anti-pinch meets our need.The hareware and software design of lamp system is stated in this paper. The system includes three nodes, they are front lamp module, rear lamp module, column switch module and can totally replace the traditional lamp system. The controlling function includes the drive of various lamps, diagnostic process etc. Network communication and system diagnostic algorithm are developed to safer the driving of vehicles compared with traditional lamp system. There are indications to inform drivers once an error has occurred as well.Body control module is developed. BCM is the gateway of door system and lamp system. And it can communicate with high speed CAN network in the future in the purpose of vehicle information sharing. Also BCM is the plateform of function expansion in the future, for example we may migrate the Romote Keyless Entry system into the BCM module without changing the hardware and software of other two systems.CAN bus monitoring device is developed to detect the real time data exchange in the CAN network. Both PC-end software and controller-end software enable the detecting and displaying of CAN frames on PC via RS232. The monitoring device improves the efficiency of system developing and lays solid foundation for further developing. Now the prototype has passed system test and operates normally.