Study of Air-fuel Ratio Analyzer Based on CAN bus

Air-Fuel Radio (AFR) analyzer technology is basically mastered by monopolies of developed country nowadays. Due to the lack of development in China, it has a strong practical value to study the accurate, rapid response and portable air-fuel ratio analyzer. This article is based on the AFR calculation model microcomputer hardware and software system design, background monitoring software design and debugging and measurement system, and on the choice of universal oxygen sensor calibration laboratory, establishing a wide-range of oxygen sensor output voltage and AFR model. The main features of AFR analyzer are measurement and display of air-fuel ratio, excess air coefficient or oxygen content, via RS232 communication with host computer or via Control Area Network (CAN) bus and vehicle ECU communication function. Test results showed that the error can be controlled at +/- 0.03 lambda range when comparing the Analyzer measurement values to calculated values. Compared with American Innovate company LM-2 air-fuel ratio analyser, the maximum relative error measured is +/-0.08 when exhaust flood or too dilute, the average measurement error is +/-0.04 while lambda is between 0.8 and 1.3.