Method, processing unit, and computer program for ascertaining fill levels of a first exhaust gas catalytic converter and of a second exhaust gas catalytic converter

A processing unit configured to ascertain a fill level of a first exhaust gas catalytic converter, and a fill level of a second exhaust gas catalytic converter which is situated downstream from the first exhaust gas catalytic converter, in an exhaust gas system downstream from an internal combustion engine with respect to at least one exhaust gas component, the processing unit configured to:

• detect, using a sensor upstream from the first exhaust gas catalytic converter, at least one operating parameter of the exhaust gas system;
• ascertain the fill level of the first exhaust gas catalytic converter based on the detected at least one operating parameter using a first calculation rule;
• ascertain a total fill level of the first exhaust gas catalytic converter and second exhaust gas catalytic converter based on the ascertained at least one operating parameter using a second calculation rule, wherein the fill level of the first exhaust gas catalytic converter and the total fill level are both ascertained based on the at least one operating parameter detected by the sensor upstream from the first exhaust gas catalytic converter and to the exclusion of any operating parameter obtained from a sensor downstream of the first exhaust gas catalytic converter;
• ascertain the fill level of the second exhaust gas catalytic converter as a difference between the total fill level and the fill level of the first exhaust gas catalytic converter, wherein each of the first calculation rule and the second calculation rule includes an integrator model, which integrates the at least one detected operating parameter over the time;
• and
• control a physical operation of the exhaust gas system based on at least one of the fill level of the first exhaust gas catalytic converter and the fill level of the second exhaust gas catalytic converter.

A non-transitory machine-readable memory medium on which is stored a computer program for ascertaining a fill level of a first exhaust gas catalytic converter, and a fill level of a second exhaust gas catalytic converter which is situated downstream from the first exhaust gas catalytic converter, in an exhaust gas system downstream from an internal combustion engine with respect to at least one exhaust gas component, the computer program, when executed by a processing unit, causing the processing unit to perform the following steps:

• detecting, using a sensor upstream from the first exhaust gas catalytic converter, at least one operating parameter of the exhaust gas system;
• ascertaining the fill level of the first exhaust gas catalytic converter based on the detected at least one operating parameter using a first calculation rule;
• ascertaining a total fill level of the first exhaust gas catalytic converter and second exhaust gas catalytic converter based on the ascertained at least one operating parameter using a second calculation rule, wherein ascertaining the fill level of the first exhaust gas catalytic converter and ascertaining the total fill level are both based on the at least one operating parameter detected by the sensor upstream from the first exhaust gas catalytic converter and to the exclusion of any operating parameter obtained from a sensor downstream of the first exhaust gas catalytic converter;
• ascertaining the fill level of the second exhaust gas catalytic converter as a difference between the total fill level and the fill level of the first exhaust gas catalytic converter, wherein each of the first calculation rule and the second calculation rule includes an integrator model, which integrates the at least one detected operating parameter over the time;
• and
• controlling a physical operation of the exhaust gas system based on at least one of the fill level of the first exhaust gas catalytic converter and the fill level of the second exhaust gas catalytic converter.