Hybrid modeling of paper machine grade changes

Abstract

A grade change is a product quality change on a paper machine. A grade change is typically a basis weight change but on some machines the production concept is changed from the raw materials to the finishing of the product. Only small grade changes are executed with automatic grade change applications or the change is started with automatics and then continued with manual actions.

A new hybrid model is proposed as a basis for the development of a grade change automation on a paper machine. The hybrid modeling method combines simple physical models with empirical models. In practice the goal was to develop models that could predict the outcome of a grade change accurately enough by comparing the modeling results to the actual measurements collected from a paper machine. The standard deviation of the prediction error of the proposed hybrid model was found to be about 40 % better than the performance PLS model.

The thesis contains for the first time an overall approach to the paper machine grade change covering the process from raw materials to the on-machine coaters. Also a presentation of coat weight and coat moisture grade change is given that has not been reported earlier.