A Web Tension Control Strategy for Multi-span Web Transport Systems in Annealing Furnace

Abstract

This paper presents a web tension control strategy for multi-span web transport in a continuous annealing process (CAP) used in steel manufacture. In the CAP, the temperature of the steel web is varied over a wide range, and this generates a thermal strain in the web. In addition, in order to save workspace, vertical type web transport systems are usually used, and the weight of the web causes a gravity strain in the web. These strains in the web induce the variation of the web tension. To control the web tension in the CAP, a feed-forward tension control scheme is suggested, which is based on a mathematical model considering the additional strains due to thermal and gravity effects. The performance of the proposed feed-forward tension control scheme is experimentally evaluated in an actual CAP. In addition, to respond to the variations of many system parameters, a feedback tension control scheme based on the tension observer is proposed. The performance of the feedback tension control system is evaluated by computer simulation.