TITLE: Modelling and Grey-Box Identification of Curl and Twist in Paperboard Manufacturing


The talk can be divided into two parts. The first one is about the development of an identification methodology for the modelling of complex industrial processes. The second one is about the application of this methodology to the curl and twist problem.

The main purpose behind the proposed methodology is to provide a schematic planning, together with some suggested tools, when confronted with the challenge of building a model of a complex industrial process. Particularly, the problems of outlier detection and variable selection will be discussed in more detail.

The second part of the talk is about the development of a curl predictor. Curl is the tendency of paper of assuming a curved shape and is a long-standing problem in paperboard manufacturing because it may seriously affect the processing of the paper. Unfortunately, curl cannot be measured online, but only in the laboratory after that an entire roll has been produced. Hence, the main aim of my thesis was to develop a model for curl and twist, and eventually to implement it as an on-line predictor to be used by the operators and process engineers as a tool for decision/control.

Our approach for this problem is based on grey-box modelling since the physical process is very complex and nonlinear, the influence of some inputs is not entirely understood, and it depends on a number of unknown parameters and unmodelled/unmesurable disturbances.

Simulations on real data show a good agreement with the measurement, particularly for MD and CD curl, and hence we believe that the model has an usable accuracy for being implemented as an on-line predictor.