A NONLINEAR TENSION CONTROL SCHEME FOR WEB TRANSPORT THROUGH HEATING PROCESSES

In this paper we develop a model-based nonlinear tension control scheme for transport of flexible materials (webs) through heating processes. Heat transfer processes are widely employed in Roll-to-Roll (R2R) process machines that are used to perform processing operations on a moving web on rollers. Heat transfer processes induce thermal expansion/contraction of the flexible material during transport. Because web strain and elastic modulus are functions of temperature distribution in the web, web tension resulting from elastic strain is affected by heating/cooling of the web. Based on a web tension governing equation that includes both elastic and thermal effects, a nonlinear tension control scheme is developed for control of tension in each tension zone of an R2R system. The control scheme is implemented on an R2R experimental platform containing two heat transfer rollers, one for heating the web and one for subsequently cooling the web prior to winding of the web. Experimental results are presented and discussed.