Performance analysis of cross-direction process control usingmultivariable and spectral models

摘要

The paper addresses two interrelated problems in cross-directional(CD) control of papermaking processes. The first problem is that ofpaper property streaks observed in many CD control installations. Thestreaks usually correspond to the high-resolution error profileharmonics with wavelength dose to twice the actuator spacing. Typically,the streaks of paper weight or moisture are very stable. A question,which often arises, is if the streaks can be compensated by bettertuning of the CD controller. The second, related, problem addressed inthis paper is how the achievable high-resolution error profile and itsspectrum depend on the CD controller tuning. The paper compares theperformances of a mapped controller and an optimal multivariablecontroller. It also describes spectral characteristics of CD errorprofile around the Nyquist frequency. Applications of the developedanalysis methodology to a paper mill data where weight streaks are aproblem are demonstrated