A Multi-roll Eccentricity Controller for Strip Rolling Mills

This paper describes an improved strip thickness controller design for a metal strip rolling mill with two work-rolls supported by larger diameter backup-rolls. The strategy is based on a model that represents the effects of multiple roll eccentricities, the plastic deformation process and elastic strains in the mill stand components. The strategy overcomes many of the fundamental difficulties inherent in earlier approaches. An important feature of the design is its ability to track multiple roll induced eccentricity disturbances whose waveforms change with time. The feedback controller design compensates for force, mill dependent parameters and for the inherently non-linear response of the force adjusting mechanism. Simulation studies are presented showing the advantages of the new design and its insensitivity to plant parameter variations. The system has modest computation requirements and has been implemented on a modern, computer-controlled, five stand tandem cold mill.