Patent ID: 6619277
Filing Date: 2003-09-16
Classification: F02D,G05B

Abstract:
An air-fuel ratio control device for an engine with a combustion chamber for burning a mixture of air and fuel, comprising:means for regulating an air-fuel ratio of the mixture; means for detecting the air-fuel ratio of the mixture from a composition of an exhaust gas of the engine; means for calculating a state quantity (&sgr;(n)) of a switching function based on a preset target air-fuel ratio (TGABF), a detected air-fuel ratio (AFSAF) detected by the detecting means, a state equation derived from a transfer function (Geng(q)) of a secondary discrete system representing the correlation between the air-fuel ratio of the mixture in the combustion chamber and the detected air-fuel ratio, and a predetermined switching function gain mat (S); means for calculating a non-linear input (unl(n)) for a sliding mode control process based on the state quantity (&sgr;(n)) of the switching function, the predetermined switching function gain mat (S), a predetermined non-linear gain (&eegr;) and a predetermined disturbance input (&bgr;(n)); means for calculating a linear input (ueq(n)) for the sliding mode control process based on a difference between the target air-fuel ratio (TGABF) and the detected air-fuel ratio (AFSAF), and the switching function gain mat (S); means for calculating an air-fuel ratio feedback correction value (ALPHA) from the non-linear input (unl(n)) and the linear input (ueq(n)); and means for feedback controlling the air-fuel ratio regulating means based on the air-fuel ratio feedback correction value (ALPHA).