Design of Technical Condition Monitoring Design of Technical Condition Monitoring System of Vehicle Based on CAN BusSystem of Vehicle Based on CAN Bus

Authors ：Ruili Zeng, Yunkui XiaoDepartment of Automobile EngineeringAcademy of Military Transportation Tianjin, China

Wenjun Dai, Bin Zhou, Lingling Zhang Group of Machine Repair Unit of 63996 Beijing, China

Computer Science and Information Technology (ICCSIT),

2010 3rd IEEE International Conference on 

Speaker ：陳明睿 M98G0105

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OutlineOutlineIntroductionOverview of CAN bus Design of electronic control unit Node scheduling optimization◦ Scheduling parameters ◦Node optimization

Analysis of data Conclusions

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IntroductionIntroductionBOSCH 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.

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Overview of CAN busOverview of CAN busCAN 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 bytesError detection mechanisms

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Overview of CAN busOverview of CAN busCAN 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 re transmission of faulty message.

CAN2.0B protocol is applied to the control of sound device and comfort,

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Design of electronic control unit Design of electronic control unit

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Design of electronic control unit Design of electronic control unit

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Node scheduling optimizationNode scheduling optimization

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Scheduling parameters ◦ CAN bus average load rate Ut

It is sum of all information frame occupancy percentage of CAN bus.

Node scheduling optimizationNode scheduling optimization

Maximum delay time limit Rm

◦It is interval of node controller from begin sending information frame to finish in worst transmission condition

◦maximum delay time limit is

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Node scheduling optimizationNode 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

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Node scheduling optimizationNode scheduling optimizationNode 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

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Node scheduling optimizationNode scheduling optimizationNode 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.

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Node scheduling optimizationNode 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.

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Analysis of data Analysis of data When there are eight nodes, set information frame of

transmission system highest priority and CAN bus communication velocity 250kbps.

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Analysis of data 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%.

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bus average load rate is 10.2%, it is 10.67% after adjustment.

Analysis of data 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

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Analysis of data Analysis of data

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ConclusionsConclusionsBy 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%

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