Abstract: A method for determining the NH3 loading of an SCR catalytic converter in the exhaust-gas section of an internal combustion engine, in which the NH3 concentration in the exhaust gas is determined by way of at least one sensor, preferably an NOx sensor, downstream of the SCR catalytic converter.

Abstract: A method for a model-based feedback control of an SCR system having at least one SCR catalytic converter. An SCR catalytic converter model of the SCR catalytic converter is used to control an injection of a reductant upstream of the SCR catalytic converter. In the SCR catalytic converter model, at least one reduction rate based on an Arrhenius approach and/or an SCR efficiency of at least one relevant reaction in the SCR catalytic converter is calculated. Deviations between a real system behavior and a simulated system behavior are adjusted using adaptation logic. In order to minimize the deviations between the model and the real system behavior and to achieve enhanced control accuracy, at least one adjustment parameter is used in the calculation of at least one reaction rate and/or the SCR efficiency, the adjustment parameter taking into consideration deviations between the real system behavior and the simulated system behavior.

Abstract: A method for determining the NH3 loading of an SCR catalytic converter in the exhaust-gas section of an internal combustion engine, in which the NH3 concentration in the exhaust gas is determined by way of at least one sensor, preferably an NOx sensor, downstream of the SCR catalytic converter.