In4-strokeinternalcombustionengines,air-fuelratiocontrolisachallengingtaskduetotherapidchangesofenginethrottle,especiallyduringtransientoperation.Toimprovethetransientperformance,managingthecycle-to-cycletransientbehaviorofthemassoftheair,thefuelandtheburntgasisakeyissueduetotheimbalanceofcycliccombustionprocess.Thispaperaddressthemodel-basedestimationandcontrolproblemforcyclicair-fuelratioofspark-ignitionengines.Adiscrete-timemodelofair-fuelratioisproposed,whichrepresentsthecycle-to-cycletransientbehaviorofin-cylinderstatevariablesundertheassumptionsofcyclicmeasurabilityofthetotalin-cylinderchargemass,combustionefficiencyandtheresidualgasfraction.Withthemodel,aKalmanfilter-basedair-fuelratioestimationalgorithmisproposedthatenableustoperformafeedbackcontrolofair-fuelratiowithoutusinglambdasensor.Finally,experimentalvalidationresultisdemonstratedtoshowtheeffectivenessofproposedestimationandcontrolschemethatisconductedonafull-scaledgasolineenginetestbench.
