Indirect tension control method for an intermittent web transport system

Tension and conveyance in web-handling machines should be controlled accurately to ensure high product quality. Unlike typical web handling applications, the motions in discontinuous web transport process are typically fast, and thus, dynamically more demanding. Conveying the web in a discontinuous way brings new performance requirements for position and tension control. In this paper, a simple control method is proposed for dynamic tension regulation in a discontinuous web transport system. The web tension is controlled indirectly based on feedback information about position difference between two rollers. The tension controller is implemented in parallel with the speed controller. The parallel control structure improves dynamic reaction to changes in the web tension. The performances of the mathematical model and the controller designed are tested with experimental tests. The tension controller is implemented as part of the frequency converter control structure. The effectiveness of the tension control in dynamical web handling is studied with simulations and by experimental tests.