The Effect of Tension on the Lateral Dynamics and Control of a Moving Web

Experimental studies of lateral motion of a moving web were carried out. For some typical operating conditions, it was found that the existing model does not properly describe the lateral behavior of the moving web with this simulator in the laboratory. It was found out that there is a critically correlated zone of operating conditions which exerts influence on the lateral behavior of the web, and that it is also associated with slippage phenomena between the moving web and a roller surface. If the web tension is not sufficiently high, the lateral dynamic motion is seriously related with web tension and increases lateral position error in a lateral position control system. A factor to describe the influence of the slippage on the lateral dynamic response of the web was derived based on a widely known traction-coefficient estimation model. The traction coefficient can be estimated from an air-gap thickness model with which slip condition can be determined. The slip condition is a function of web tension and speed and velocity of a roller. The ratio of the axial displacement of a guider roller and the lateral position of the web was measured in an open-loop condition for many different operating tension and speed, and the factor was fitted and verified from the experimental data which represents the effect of web tension on a lateral behavior of the web. Finally, the new factor was used in designing a cross-couple controller which includes the effect of operating tension or the variation of it on the lateral motion to properly regulate disturbances generated by web tension. The proposed factor is updated at each sampling period from measured signals such as web tension and velocity of web and roller, and used to calculate variable control gain