Fuzzy decoupling to reduce propagation of tension disturbances in roll-to-roll system

Control of web tension is crucial for maintaining quality of products processed on roll-to-roll (R2R) system. An R2R system can be divided into different tension spans which interact with each other. But converting industries tend to neglect these interactions and use decentralized single-input–single-output (SISO) control approaches to deal with tension control. Multi-input–multi-output approaches have been reported in literatures but are practically not in use. Interaction between the various tension spans is unavoidable as they are all connected by a single web. Disturbances produced in a span tend to travel further downstream along the direction of web travel. When the number of spans is less or the disturbance amplitudes are small, this does not present a big challenge and simple SISO control is sufficient. But when the amplitudes of disturbances produced in processing is large—as is the case with printed electronics—or the number of spans is large or both, then the interactions cannot be neglected. R2R-based offset printers have the potential for mass production of precision-printed electronics. In this paper, a fuzzy logic-based hybrid approach has been followed that specifically targets the printed electronics industry and this method considerably reduces the interactions. The algorithm has been designed such that it takes information from previous span to reduce the propagation of tension disturbances to the given span. This has been achieved through online computation of correlation coefficient and reducing the interaction through fuzzy feedback control.