Effect of backlash on web tension in roll-to-roll manufacturing systems: Mathematical model, mitigation method and experimental evaluation

Abstract

This paper describes the effect of transmission backlash on web tension in roll-to-roll manufacturing systems and provides a method to mitigate this effect. The term web is used to refer to flexible materials which are manufactured and processed in a continuous form by transporting the material on rollers through processing machinery; this type of manufacturing is referred to as Roll-to-Roll (R2R) manufacturing. Control of web tension and web transport velocity is essential for successful operation of roll-to-roll machines. The web is unwound from a material roll, transported on rollers via frictional contact between the surfaces of the rollers and the web through processing machinery and the processed web is rewound onto rollers. Web transport is facilitated by some rollers whose shafts are driven using electromechanical actuators. Typically a mechanical transmission containing gears is used to transfer power from the motor shaft to the roller shaft. In this paper we present a mathematical model for the dynamics of the R2R process line considering backlash in the mechanical transmission. Effect of backlash on the controlled tension is analyzed using the mathematical model and experimentally. A method for mitigating the effect of backlash that consists of loading the roller shaft with an external brake is given. This method is evaluated on a large R2R experimental platform by conducting a series of experiments. A representative sample of the experimental results are presented and discussed.