Air/fuel ratio estimation system for internal combustion engine

• Main Authors: HASEGAWA; YUSUKE, KOMORIYA; ISAO, KIMURA; EISUKE, AKAZAKI; SHUSUKE, NISHIMURA; YOICHI
• Format: Patent
• Language: English
• Published: 20.08.1996
• Edition: 6
• Subjects: BLASTING; CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TOTRANSPORTATION; COMBUSTION ENGINES; CONTROLLING COMBUSTION ENGINES; CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES; ENGINE PLANTS IN GENERAL; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; HEATING; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS; LIGHTING; MACHINES OR ENGINES IN GENERAL; MECHANICAL ENGINEERING; STEAM ENGINES; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS; TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINSTCLIMATE CHANGE; WEAPONS

A system for estimating air/fuel ratios in the individual cylinders of a multicylinder internal combustion engine from an output of an air/fuel ratio sensor installed at an exhaust system of the engine. In the system, the exhaust system behavior is derived by a model in which X(k) is observed from a state equation and an output equation in which an input U(k) indicates air/fuel ratios in the individual cylinder and an output Y(k) indicates of the estimated air/fuel ratio asX(k+1)=AX(k)+BU(k)Y(k)=CX(k)+DU(k)where A, B, C and D are coefficients. And an observer is expressed by an equation using the output Y(k) as an input and the air/fuel ratios in the individual cylinders is estimated from the state variable +E,cir X+EE . In the system, the coefficient C is set to zero for a cylinder other than most recent m (2</=m<n) cylinders. Alternatively, a plurality of the observer matrices are prepared in advance and calculated at the same time. Depending on the engine operating condition or a valve timing switched between a plurality of characteristics one among the calculation results is selected.