The effect of tension on the lateral dynamics and control of a moving web

An experimental study was carried out to find the correlation between web tension variation and the lateral motion of a moving web. The experimental results said that if the web tension is not sufficiently high, the lateral dynamic motion is closely related with the web tension variation. A new ´factor´ to describe the influence of the web tension on the lateral dynamic response was defined based on a well known traction coefficient estimation model. A factor to describe the influence of the slippage on the lateral dynamic response of the web was derived based on a well 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 a web tension, a web speed and a velocity of a roller. The ratio of the axial displacement of a guider roller and the lateral position of the web was measured with an open loop condition in a wide range of operating tension and speed, and the factor which represented the effect of web tension on a lateral behavior of the web was fitted and verified from the experimental data. Finally the new factor was used in designing of a cross-couple controller which included the effect of operating tension or the variation of it on the lateral motion to regulate properly disturbances generated by a web tension. The proposed factor was updated at each sampling period from measured signals such as the web tension and the velocity of both web and roller, and used to calculate variable control gain.