A device for rolling a metal strip, in particular a steel strip, comprising a roll stand formed by a pair of stands,
- a pair of work rolls and an upper and lower backup roll, wherein the work rolls and the backup rolls are supported by respective associated chocks on the roll stand, wherein a roll gap is able to be formed between the work rolls and the work rolls are able to be supported by at least one respectively assigned backup roll, and a measuring device by which the value of the roll gap between the work rolls can be determined,
- wherein
- the chocks are movably guided by at least one backup roll in the roll stand and can be adjusted vertically by a hydraulic cylinder,
- the measuring device comprises at least one upper sensor with which a distance from at least one point on the upper backup roll to a predetermined upper reference point can be measured, and at least one lower sensor with which a distance can be measured from at least one point on the lower backup roll to a predetermined lower reference point,
- the measuring device comprises a force measuring device, which is positioned between a chock of a backup roll, preferably the lower backup roll, and the roll stand, wherein a rolling force generated with the roll stand can be measured by the force measuring device,
- a control device is provided, which is connected to the measuring device in terms of signals, wherein the control device is equipped with at least one mathematical model with which a strain of the roll stand can be calculated, taking into account the rolling force generated, and
- the control device is set up programmatically in such a way that an absolute value of the roll gap and thus the resulting thickness of the rolling stock can be determined on the basis of the measured values of the upper/lower sensor with regard to the measured position of the upper/lower backup roll and a strain of the roll stand calculated by the mathematical model wherein this absolute value for the roll gap can be compared with a target value for the roll gap by the control device and on the basis of which the hydraulic cylinder can then be controlled for the vertical displacement of the associated backup roll, in order to thereby set the roll gap or the resulting thickness of the rolling stock in the form of the metal strip to the desired target value in a controlled manner.