Looper H-inf inity control for Hot Strip Mi I Is

RecentlytheH-infinitycontrol theoryhas been applied to some engineering fields including steel making process. The H-infinity control makes it possible to apply multivariable control with frequency domain design method and to get robust stable control systems. We developed a looper H-infinity multivariable control system for hotstripfinishin gmiIIs,andhavego tbetter results than convent iona I control methods. The looper control is one of the most important control items in hot strip mills. The loopers are placed between each rol I ing stands, and control the interstand strip tension. It is very important to control stably both a looper and strip tension at their each target values. Especially, we intended to reduce strip tension fluctuation than looper angle fIuctuation,because striptensionseve relyaffects thickness and width gage. This paper presents the design method of the looper H-infinity control system. Also showing some actual control data, we compare the performance of conventional PI control, non-interactive control, and the H-infinity control.