Multivariable controller design for a hot rolling mill

This paper describes a controller design for a hot rolling mill. The main purpose of the algorithm is to improve the control of the cross-width thickness profile of the plates. This is obtained by designing a controller which makes independent thickness control possible at the two sides of the rolling mill. This is achieved by first linearizing the positioning systems using feedback linearization and then using linear quadratic eigenspace design on the linearized multivariable system. Integral control is included to ensure zero stationary thickness error. The design is done using derived dynamical multivariable models. To ensure that the design is stable, the stability of the system is investigated using the small gain theorem. The performance of the controller is evaluated using models estimated from data obtained from the hot plate mill at The Danish Steel Works Ltd.