PITA Fiscal Year 2009 Projects - Product and Process Design and Optimization

Modern Control Technology for the Threading of the Tandem Hot Metal Rolling Process

Principal Investigators: Dr. Marwan A. Simaan, Dr. John Pittner

A great many companies which process metals such as steel and aluminum are located in the Commonwealth of Pennsylvania and especially in the Pittsburgh area. An important part of the overall process of the manufacturing and processing of metal is the rolling of hot metal strip. In the case of steel, for example, almost one-half of the finished product made in the world is in the form of steel strips originally produced in a tandem hot strip rolling process. The investigation proposed herein will focus on the application of modern control technology for improving the performance during threading, which is a significant phase of tandem hot metal rolling, in order to obtain a better quality metal. This will be an important expansion of our initial work funded by PITA in 2008 on control of the hot rolling process to provide a comprehensive control strategy that covers all phases of the entire process.

Tandem rolling of hot metal strip is a complex multistage highly nonlinear dynamic process that is performed at temperatures in excess of 850 degrees C. These temperatures, plus other environmental considerations, preclude the availability of reliable measurements of significant process variables. Further, the metal properties are heavily dependent on temperature and the process includes a large number of interacting components and variables, all of which contribute to making the modeling and control of the hot process a very difficult and challenging task. This is exacerbated in the threading mode where additional complexities are introduced as the head of the hot metal strip is sequentially introduced into the individual mill stands at the start of the strip processing.

Work done recently at the University of Pittsburgh has shown that the application of a State-Dependent Riccati Equation (SDRE) technique was quite successful in control of the tandem cold rolling process. This proposal considers expansion of similar work in progress under the PITA 2008 project which applies SDRE-based methods to hot metal rolling, to include the threading mode of the process. The application of this technology is completely new and is expected to considerably improve the hot rolling process in all regimes of operation, especially in improving quality by reducing dimensional variations in the final product.