Of the various projects concerning flatness control in thin strip cold rolling, in which Kobe Steel has been involved, two typical cases were briefly described. In cold rolling of steel strip using the 6-high rolling mill, to eliminate localized flatness defects, the entry-side coolant temperature control and the exit-side coolant ON-OFF control were introduced in place of the conventional flow rate control of the entry-side coolant in order to improve correction of the localized flatness. For mechanical control, a system using the high-accuracy AI technologies (neuro, fuzzy) was developed to flexibly meet the operational change and the operator's experience. By combining the mechanical controls with the coolant control system, the flatness of the strip has been greatly improved. In cold rolling of the 20-high rolling mill with small-size rolls, a technique to optimize the flatness using the whole flatness output of flatness detector was developed, and in addition, an algorithm with gauge interference taken into account was constructed and applied to the online equipment, and it has been confirmed that satisfactory flatness control is possible in a short time from the start of rolling. To implement further more accurate flatness control, both a technique for intellectualizing the control utilizing AI and a technique for achieving higher accuracy using mathematical models were applied. It is difficult to compare the two techniques because of the great difference in the construction of the rolling mills used, but a new control method, established by combining the advantages of the two techniques is eagerly awaited.
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