In-line calibration of the roll gap of a roll stand

An operating method for a roll train having a plurality of roll stands for rolling a metal strip,

• the method comprising:
• operating the plurality of roll stands in a normal operation;
• wherein during the normal operation,
• setting work rolls of a respective roll stand to define a roll gap between the work rolls such that the work rolls roll the metal strip in a downstream direction, the setting of the work rolls being performed by setting an actuator position of an actuator of the respective roll stand,
• wherein the actuator position is established by predetermining a calibration value of the respective roll stand, further state parameters of the respective roll stand and a setpoint roll gap for a model describing the respective roll stand, and the model establishing the actuator position on the basis of the calibration value, the further state parameters and the setpoint roll gap;
• after the operating in the normal operation, operating the plurality of roll stands in a calibration operation;
• wherein during the calibration operation,
• initially setting a calibrated actuator position of the actuator of the respective roll stand in such a way that the metal strip passes through the roll gap of the respective roll stand without being rolled by the work rolls;
• then varying the calibrated actuator position until the work rolls roll the metal strip;
• capturing a thickness of the metal strip by means of a thickness measuring device disposed downstream of the respective roll stand, the respective roll stand having a run out side, and the thickness of the metal strip being the thickness with which the metal strip runs out of the respective roll stand;
• supplying the thickness of the metal strip, the further state parameters of the respective roll stand and the calibrated actuator position to the model, and the model establishing a new calibration value of the respective roll stand on the basis of the thickness, the further state parameters and the calibrated actuator position;
• then transitioning from the calibration operation back to the normal operation and using the new calibration value, which was established in the calibration operation for establishing a new actuator position to be set.