Hiroyuki Imanari

Looper H-infinity control for hot strip mills

The H-infinity control theory has been applied to some engineering fields including the steel making process. The H-infinity control theory makes it possible to apply multivariable control with frequency domain design method and to get robust stable control systems. The author developed a looper H-infinity multivariable control system for hot strip finishing mills, and have obtained better results than conventional control methods. The looper control is one of the most important control methods in hot strip mills. The loopers are placed between each rolling stand, and control the interstand strip tension. It is very important to control stably both looper and strip tension at each of their target values. Especially, the authors intended to reduce strip tension fluctuation than looper angle fluctuation, because strip tension severely affects thickness and width gage. This paper presents the design method of the looper H-infinity control system. Also showing some actual control data, they compare the performance of conventional PI control, noninteractive control, and H-infinity control.

Tension Control of a Hot Strip Mill Finisher

Abstract This paper describes interstand tension control by looper and looper less tension control of a hot strip mill finisher. The looper tension control methods are conventional, non-interactive, LQ (Linear Quadratic), H∞, and ILQ(Inverse Linear Quadratic) control.

High Accuracy Width Control System for SSM Hot Strip Mill

Abstract In compact hot strip mills, improving the accuracy of product strip width is an important factor in reducing production costs. This paper describes a newly developed width control system for the SSM hot strip mill. The features of the system are as follows: (a)Edger roll gap setup function based on accurate width change prediction, (b)Flexible learning function with classified learning result table, and (c)Dynamic control of the interstand tension between roughing stands and dynamic control for improved width accuracy in the region of variable width change at the head and tail ends of the material. Implementation of this new system has achieved a significant improvement in width accuracy.