| 摘要 |
<P>PROBLEM TO BE SOLVED: To accurately diagnose the abnormality of an air fuel ratio control device using "an air fuel ratio behavior model estimating the behavior of air fuel ratio from fuel injection quantity" indicated by using ARX model. Ž<P>SOLUTION: An A/F behavior model with respect to fuel injection quantity is constructed individually for each of a supercharged state and a non-supercharged state based on the past time series data of fuel injection quantity and actual A/F. Prediction decision on whether it is the supercharged state or the non-supercharged state, and the estimation of predicted A/F are done using the model. Actual decision on whether it is the supercharged state or the non-supercharged state is done based on the actual operation state of an engine, and actual A/F is acquired from the A/F sensor. It is decided that "the air fuel ratio control device is normal", when a result of prediction decision and a result of actual determination agree and difference between predicted A/F and actual A/F is not greater than threshold. It is decided that "the air fuel ratio control device is abnormal", when the result of prediction decision and the result of actual determination do not agree and difference between predicted A/F and actual A/F exceeds the threshold. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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