Frequency Response of Web Systems Containing Load Cells and Dancers, Dimensional Analysis, and Model Reference Adaptive Schemes for Tension Control

Abstract

The focus of this study is onunderstanding the behavior of web tension using frequency responseanalysis and design of tension control systems for improvedtension regulation. Two key tension sensing elements, load cellsand dancers, are studied. Development of a model for the pendulumdancer is considered. Dimensional analysis is used as a tool toobtain reference values for parameters and process variables for acandidate web line by using dimensional equivalence of thecandidate web line with a well developed web line with a welltuned controller. Model reference adaptive control techniques areinvestigated for web tension control. Experiments on a large webplatform and computer simulations of models are used throughout toreinforce discussions. Comparisons of results fromexperiments and model simulations shows that the developed modelis able to predict the frequency content found in the experimentalresults. Experimental results also show that the tension controlsystem with dancer feedback attenuates low frequency tensionvariations better than that with load cell feedback. The minimumresonant frequency with the dancer system is lower than that ofthe load cell system, which may mean the dancer system may be moresusceptible to resonances. Dimensional analysis of variousscenarios of web transport system indicates that it can beeffectively used to scale process parameters and variables.Results from implementation of various model reference adaptiveschemes indicate that adaptive schemes provide better tensionregulation than fixed gain PI controllers under changing processparameters.