Frequency response of web systems containing load cells and dancers, dimensional analysis, and model reference adaptive schemes for tension control

Scope and method of study. The focus of this study is on understanding the behavior of web tension using frequency response analysis and design of tension control systems for improved tension regulation. Two key tension sensing elements, load cells and dancers, are studied. Development of a model for the pendulum dancer is considered. Dimensional analysis is used as a tool to obtain reference values for parameters and process variables for a candidate web line by using dimensional equivalence of the candidate web line with a well developed web line with a well tuned controller. Model reference adaptive control techniques are investigated for web tension control. Experiments on a large web platform and computer simulations of models are used throughout to reinforce discussions.;Findings and conclusions. Comparisons of results from experiments and model simulations shows that the developed model is able to predict the frequency content found in the experimental results. Experimental results also show that the tension control system with dancer feedback attenuates low frequency tension variations better than that with load cell feedback. The minimum resonant frequency with the dancer system is lower than that of the load cell system, which may mean the dancer system may be more susceptible to resonances. Dimensional analysis of various scenarios of web transport system indicates that it can be effectively used to scale process parameters and variables. Results from implementation of various model reference adaptive schemes indicate that adaptive schemes provide better tension regulation than fixed gain PI controllers under changing process parameters.