Virtual fill level sensor for a mould of a continuous casting machine

A method for determining a fill level height h1 of a metal melt, preferably made of a steel or aluminum alloy, in a mold of a continuous casting machine by means of a virtual fill level sensor, wherein the metal melt in the mold forms a meniscus having the fill level height h1, comprising the following method steps:

• estimating a volume flow QEin of the metal melt flowing into the mold by way of a first state observer (BEO1) in consideration of
• an opening of a valve sVentil, preferably a stopper or a slide, for setting a flow rate of the metal melt from a casting vessel into a casting pipe, wherein the opening of the valve sVentil is determined in real time during the continuous casting,
• a geometry of the valve dVentil, and
• a geometry of the casting pipe ASEN,
• estimating a volume flow QAus of the metal melt flowing out of the mold by way of a second state observer (BEO2) in consideration of
• a geometry AQuer of the mold,
• multiple, preferably at least three, temperature values T1 . . . T3, wherein multiple temperature sensors determine the temperature values T1 . . . T3 in the mold in real time during the continuous casting, wherein multiple temperature values (T1 . . . T3) are assigned to different fill level heights, and
• a casting velocity vC of an at least partially solidified strand, preferably having slab or thin slab cross section, wherein the strand is at least temporarily discharged from the mold (4) during the continuous casting and the casting velocity vC is determined in real time,
• calculating the fill level height h1 as a function of the inflowing volume flow QEin and outflowing volume flow QAus, in particular by the conditions
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