Design of Technical Condition Monitoring System of Vehicle Based on CAN Bus Authors ： Ruili Zeng, Yunkui Xiao Department of Automobile Engineering Academy of Military Transportation Tianjin, China Wenjun Dai, Bin Zhou, Lingling Zhang Group of Machine Repair Unit of Beijing, China Computer Science and Information Technology (ICCSIT), rd IEEE International Conference on Speaker ：陳明睿 M98G /12/7 1

Outline Introduction Overview of CAN bus Design of electronic control unit Node scheduling optimization ◦ Scheduling parameters ◦ Node optimization Analysis of data Conclusions 2015/12/72

Introduction BOSCH had develop CAN in the early 1980's and used between measurement components and executive components. Ex: ◦ Electronic fuel injection engine, electronically controlled high pressure common rail injection system, anti-lock brake system, AT(Automatic Transmission) and electrical window regulator This paper mainly discusses the development of hardware and software for the controllers and analysis of vehicle's information. 2015/12/73

Overview of CAN bus CAN is an asynchronous communications protocol used in automobile and industrial control systems. It is a high speed (I Mbit/sec), short distance, priority based protocol that can communicate using a variety of mediums Prioritized messages of length 8 bytes Error detection mechanisms 2015/12/74

Overview of CAN bus CAN Bus provides the following features ◦ A multi-master hierarchy,  Which allows building intelligent and redundant systems. ◦ Broadcast communication.  A sender of information transmits to all devices on the bus.  All receiving devices read the message and then decide if it is relevant to them. ◦ Sophisticated error detecting mechanisms and re­transmission of faulty message. CAN2.0B protocol is applied to the control of sound device and comfort, 2015/12/75

Design of electronic control unit 2015/12/76

Design of electronic control unit 2015/12/77

Node scheduling optimization 2015/12/78 Scheduling parameters ◦ CAN bus average load rate U t It is sum of all information frame occupancy percentage of CAN bus.

Node scheduling optimization Maximum delay time limit R m ◦ It is interval of node controller from begin sending information frame to finish in worst transmission condition ◦ maximum delay time limit is 2015/12/79

Node scheduling optimization Where wm is waiting time of send information frame in the worst condition hp(m) is information frame set which priority is higher than frame m. Bm is longest time delayed by frame with lower priority than frame m 2015/12/710

Node scheduling optimization Node optimization ◦ Chose optimum communication rate. Based on reliable information transmission, increasing communication rate can decrease time occupation bus of information frame and bus average load rate, improve real-time ability of net work 2015/12/711

Node scheduling optimization Node optimization ◦ Confirm stability margin of system. ◦ The more stability margin is, the more system can avoid network communication block. ◦ Redundancy a is expressed as formula. 2015/12/712

Node scheduling optimization Distribute information frame sending period. Analyze performance of CAN network, and adjust sending period according to demands. Avoid difference between two sending period is integral multiple as possible. If it is, advance or postpone a maximum delay time △ Cm=Rm. 2015/12/713

Analysis of data When there are eight nodes, set information frame of transmission system highest priority and CAN bus communication velocity 250kbps. 2015/12/714

Analysis of data Analysis results of maximum delay time limit in theory and practice is displayed as fig 3, among them, maximum delay time of node with lowest priority is reduced by 30%. 2015/12/715 bus average load rate is 10.2%, it is 10.67% after adjustment.

Analysis of data It increases a little because sending period is shorten after adjustment and is within the acceptable range of bus. A CAN analyzer made in IXXA T Inc. 1.bus average load rate 2.baud rate 3.Queue 4.error rate 2015/12/716

Analysis of data 2015/12/717

Conclusions By hardware design and optimize nodes scheduling, technical condition monitoring ECU of vehicle based on A T90CAN 128 chip is designed. maximum CAN bus information delay time after optimizing node scheduling is shorten as 30% as before Promote real-time ability of information transmission, increase CAN bus average load rate by 0.47% 2015/12/718