Model-based Grade Change Support

Abstract: Abstract Customer demands for board adapted for their specific needs make a flexible production with many different qualities advantageous. The board quality changes can include a change in the composition or only a change in grammage. A grade change is a product quality change in a paper or board machine. Grade changes may however cause problems in the production. When changing the production from one kind of cartonboard to another, losses of time and raw material are sometimes inevitable. Sometimes the losses may be reduced by optimizing the grade change control. The losses due to control that is not optimized can be separated into two different groups. The first group contains losses due to a non-optimal grade change strategy, where the grade change control is badly planned. The other kind of losses is result of a poor control scheme execution such as important steps being forgotten or not successfully performed. In this report a Sequential Function Charts (SFC) model developed in JGrafchart is suggested to address both of these problems. The result is a computerized tool meant to help operators by suggesting control strategies and remind them if important steps are not carried out. Control laws and strategies are derived from physical models of the cartonboard making process together with information collected from experienced operators and engineers at AssiDomän Frövi. Timing issues and other optimization is handled with the Matlab, Simulink and GESOP tools. The goal of the thesis was to present an example which shows how a semi-automatic grade change control with JGrafchart could contribute to the grade change control at AssiDomän Frövi.