Method of controlling an internal combustion engine

In order to improve performance and more precise emission controls of an internal combustion engine, there is provided a method of controlling an internal combustion engine, the engine including a variable flow exhaust gas recirculation (EGR) system driven in response to an EGR command signal to recirculate exhaust to an engine intake mixture, wherein the method comprises determining a desired engine intake mixture composition composed of a plurality of different components; estimating an actual engine intake mixture composition; comparing the desired engine intake mixture composition to the estimated actual engine intake mixture composition; and controlling the engine based on the comparison such that the actual engine intake mixture composition tracks the desired engine intake mixture composition.