Identification and control of web processes: Polymer film extrusion

The paper describes an approach to the identification and control of the cross-directional (CD) properties of web-forming processes, and its application to polymer film extrusion. Discrete orthonormal Chebyshev polynomials are used to model the CD behaviour. This allows a Chebyshev domain estimator for CD profile response to be formulated, and constrained Chebyshev domain optimisation of the CD profile to be used. The result is an identification and control procedure for the CD profile problem which is consistent in its use of the Chebyshev framework, and which is also applicable to other web-forming processes.