Advanced control methods in rolling applications

Continuously increasing quality demands in recent years have led to a considerable reduction of the permissible thickness tolerances for hot as well as cold rolled steel. However, conventional control concepts cannot completely compensate for the effects of various disturbances resulting from the rolling process. The utilization of high performance computer systems for the automation allows the application of advanced control techniques to overcome existing dynamic limitations. Particularly if older mechanical equipment is utilized, which is typical for revamping projects, these new concepts allow a significant improvement of the quality. In this paper, different examples of such technologies are presented: a new concept for advanced thickness control in hot strip mills based on a feedforward strategy combined with a Kalman filter, a statistical online identification tool; to enhance existing tension control systems via looper arms in finishing mills; a massflow control concept; and a predictive control concept to compensate reel tension variations. The development of these methods was based on extensive simulations as a development and testing tool. In the meantime, the simulation results have been verified by practical application of the methods. Some results of these practical implementations are added to demonstrate the potential improvements possible with these concepts.