IDENTIFICATION AND VALIDATION OF A PRESS NIP MODEL USING THE GREY BOX IDENTIFICATION TECHNIQUE

摘要

Identification and validation of a dewatering model of a shoe press nip in a press section is considered. The approach for the modelling is the grey-box technique, i.e. a physically based model is combined with stochastic disturbances in order to get a model with good predictive capabilities for a wide range of operating points. The model considered assumes a fully saturated fibre web with transversal flow of water. Data for the identification is obtained from experiments on the research paper machine (EuroFEX) at STFI in Sweden. These experiments include changes in the grammage, the machine speed, the applied nip pressure and the dryness of the fibre web into the press nip. The parameters are estimated with one set of data and validated on another set. The identification shows that one-dimensional flow models are capable of predicting the dewatering behaviour of a press nip, during process variations like the ingoing moisture and press nip load accurately. However, improved felt models are needed, to predict the effect of variations in the ingoing felt moisture on the dewatering of the fibre web.