Patent ID: 7797974

Claim:
A method for measuring and adjusting the flatness of a steel strip ( 1 ), especially a steel foil ( 1 a ), for the cold rolling operation in a cluster mill ( 2 ), especially in a 20-roll Sendzimir rolling mill ( 2 a ), which comprises the following steps: determination of an actual distribution of the flatness ( 22 ) of the steel strip over its width ( 7 ) on the basis of a measured strip tension distributed over the strip width ( 7 ); determination of a flatness error ( 8 , 20 ) by comparison of a determined actual distribution of the flatness ( 22 ) with a predetermined reference curve; mathematical approximation of the received flatness error ( 8 , 20 ); decomposition of an approximated flatness error into scalar flatness error components (C 1 , C 2 , C 3 , C 4 ); and computation of a first and additional controller output signals from the flatness error components to activate a plurality of actuators ( 3 , 14 a , 17 , 18 , 19 ) of the cluster mill ( 2 ); wherein the approximated flatness errors are decomposed in such a way that the resulting flatness error components (C 1 , C 2 , C 3 , C 4 ) are orthogonal to one another; a first actuator in the form of a hydraulic adjustment mechanism ( 17 ) out of the plurality of actuators is activated in response to the first controller output signal, which is obtained from the first orthogonal component (C 1 ); each of the additional controller output signals in the form of scalar correcting variable components is computed on the basis of one of the remaining orthogonal components (C 2 , C 3 , C 4 ) of the flatness error; and the scalar correcting variable components are combined into suitable activating signals for individual excenter actuators ( 14 a ) out of the plurality of actuators, wherein a residual error vector ( 13 ) is analyzed, and the residual error vector ( 13 ) is sent to directly selected actuators ( 3 ).