Lateral response and control of a multi-span web system to dynamic changes to the web and conveyance hardware

Abstract

A multi-span model that predicts the lateral response of webs to changes in the upstream position of the web and any type of motion of the included rolls is presented. The model uses a beam approximation for the deflection in the web spans. The actual, rather than idealized, web spans, roll diameters, wrap angles and sensor locations are used. Equations are derived including web span interactions, roll motion such as occur in steering devices and feedback control systems. Example cases are included showing the value of this type of analysis and accuracy through comparisons with experimental results. Web steering devices of different types are used widely both to control the web in less than ideal circumstances and to accurately position the web for key operations in processes. The design of these devices is often based on idealized configurations that don't fully match the geometry of the equipment in question. As a result problems arise such as non-stable operation, web oscillation downstream of the guide system and the formation of shear wrinkles. The work presented here describes a method of analyzing an entire web path including steering devices and evaluating the response of the system to all sorts of dynamic inputs. A computer program is described that can handle up to a 10 span system.