Headbox modelling for cross-direction basis weight control

Abstract

This paper considers the representation of cross-directional (CD) basis weight on paper machines where the two-dimensional (2D) coupling between CD and machine direction (MD) is important and must be controlled. Indeed, because the flow pattern from the headbox exhibits 2D interactive behaviour, any simple non-interacting CD control model must be inadequate, hence the need for appropriate models. One solution, short of a complex hydrodynamic model, is to provide the necessary control structure with a function representing the interaction determined by considering the behaviour of the flow field. From a 2D control point of view, the mean of the control signal would relate strongly to the MD controller, with the rest being the CD controller. It thus should be possible to contrive a 2D control strategy for the headbox system based essential upon the modelling work shown here.