Process interactions in a hot strip mill; possibilities for multivariable control?

In this initial research study into the possibilities of multivariable control design techniques in steel industry related control problems, a linearized part of HOOGOVENS dynamic hot strip finishing mill model was used. The rolling process in a finishing mill inherently has interactions between, for example, thickness control loops and mass flow control loops. The characteristic loci method was used to minimize looper angle and strip tension variations whilst leaving the thickness control performance unchanged. Implementing the designed multivariable controller in the finishing mill model showed reduction in looper angle variations of 25% and strip tension variations of 50%. Also the mass flow control loop has become 4 times faster despite low pneumatic looper dynamics