METHOD AND CONTROL UNIT FOR REGULATING A FILL LEVEL OF A RESERVOIR OF A CATALYTIC CONVERTER FOR AN EXHAUST GAS COMPONENT IN COASTING MODE

A method for regulating a filling of an exhaust gas component reservoir of a catalytic converter in the exhaust of an internal combustion engine. An actual fill level of the exhaust gas component reservoir is ascertained using a first system model, and in which a baseline lambda setpoint for a first control loop is predefined by a second control loop in which an initial value for the baseline lambda setpoint is converted, by a second system model identical to the first system model, into a fictitious fill level; the fictitious fill level is compared with a setpoint for the fill level; and the baseline lambda setpoint is iteratively modified as a function of the comparison result. At the beginning of a coasting phase, the baseline lambda setpoint is calculated based on signals of sensors and control variables which relate to the delivery of air and/or fuel to combustion chambers.