Niederdimensionales three-way catalytic model for control and diagnostics

The present invention relates to the control of the air-fuel ratio in an internal combustion engine. The method comprising: setting a fuel injection quantity on the basis of a partial oxidation state of a catalyst, wherein the partial oxidation state to the reaction rates of several gas species over a catalyst longitudinal axis and a set of axially averaged Massengleichgewichts- and energy balance equations for a fluid phase and a washcoat of the catalyst is based. In this way, a simplified catalyst model can be used for controlling the air-fuel ratio.