Modeling and frequency response of web tension with a pendulum dancer, and comparison of load-cell and dancer based tension control systems

Abstract

In web processing lines, web tension is typically regulated using an outer loop that provides a trim to the velocity reference of the inner velocity loop. The feedback signal for the outer tension loop is either a position signal from a dancer or tension signal from load cells mounted on a roller. Both these strategies are used extensively in the web processing industry, but a systematic analysis, based on mathematical models and experimental observations, on the benefits and limitations of the strategies is lacking. The paper will report two investigations. First, a model that describes the action of a pendulum dancer on web tension will be developed, and frequency response of web tension in the presence of the pendulum dancer will be discussed. Second, a comparison of tension control strategies based on force feedback from load cells and position feedback from dancer motion will be given.