ADVANCED GAUGE CONTROL TECHNOLOGY FOR HOT STRIP MILL

An advanced gauge control technology has been developed for a hot strip finishing mill. A linear numerical model which is able to discribe the rolling phenomena, the gauge control system and the looper control system was derived for integrating the following control system. First, a looper angular velocity feedback control for the unstationary parts of the strip was developed in order to compensate for the strip tension fluctuation and the material mass flow fluctuation caused by the quick adjustments of screw down positions. The looper angular velocity is estimated by a minimal order state observer and the feedback gain is determined according to the pole assignment method. Second, a new gauge and strip tension control which is a multivariable control based on the optimal regulator theory was developed for the stationary parts of the strip. The purpose of the control is to minimize the finishing mill exit thickness deviation by means of improving the response of the automatic gauge control without unstabilizing the strip rolling. The superiority of these new controls to the conventional controls was proved by the simulation and experimental results.