Control method of engine system, and engine system

Abstract

A control method of an engine system is a method of controlling the engine system including an engine with a combustion chamber; a fuel injection valve configured to supply fuel to the engine; and an air-fuel ratio sensor provided in a flow path of exhaust gas from the engine. In the control method, feedback control is performed so that an air-fuel ratio in the combustion chamber becomes a target value by controlling the fuel injection valve, using an air-fuel ratio measured value obtained by the air-fuel ratio sensor. In the feedback control, a transfer function is used, the transfer function being obtained by system identification of a plant having the air-fuel ratio in the combustion chamber serve as an input and the air-fuel ratio measured value obtained by the air-fuel ratio sensor serve as an output. In the control method, a filtering process is performed to an air-fuel ratio measured value used in the feedback control, the filtering process cutting a component having a response speed faster than a delay indicated by the transfer function.