Model-based evaluation of the effect of horizontal roll offset on cross-directional control performance in cold-strip rolling

Some modern rolling mills allow for the work and intermediate rolls to be offset in the plane of the strip, allowing three-dimensional roll deformation. A generalised extension to existing roll-stack models is proposed in order to characterise this effect. The model is used to explore the influence of three-dimensional roll deformation on the prediction of actuator sensitivities used in cross-directional control systems in cold rolling. It is shown that horizontal work-roll offset alters the magnitude and form of all existing actuator responses. The effect is dependent on the degree of offset and on the work-roll diameter and is most pronounced in the parabolic component of bulk actuators. Further, the horizontal roll offset can itself be used as an actuator, although the magnitude of its sensitivity varies significantly with the degree of offset.