Abstract: A method of eliminating thickness changes in material exiting a stand or stands of a rolling mill, the changes being caused by the eccentricity of one or more rolls of the mill. The method includes the steps of engaging the material with a device that measures the tension of the material entering or leaving the mill and using said device to measure directly a change in the tension of the material due to roll eccentricity. Samples of the change in tension are provided during the time required for a roll of the mill to make one revolution. The samples are then processed by characterizing them as frequency, magnitude and phase angle components of the change in tension. The components are then used in an update algorithm to provide a current estimate of a cyclically occurring change in tension.

Abstract: A method of controlling a rolling mill in which eccentricity of one or more of the rolls of the mill ordinarily cause cyclic change in the thickness of the material exiting the mill. The method includes the steps of locating a device for measuring thickness downstream from the mill, and using the device to measure directly cyclic change in the thickness of the mill due to roll eccentricity. Samples of the cyclic change in thickness are provided during a time period defined by a revolution of at least one of the rolls. The samples are processed by characterizing them as frequency, magnitude and phase angle components of the change in thickness. These components are then directed to an update algorithm to provide a current estimate of the change in thickness. The delay between the occurrence of the change in thickness in the mill and the occurrence of the measurement of the change by the thickness measuring device is calculated and translated into a phase angle component.