The uniform tension at a preferred value of polyester (PET) films in processing or rewinding is important to product quality, which can be achieved by tension control. Furthermore, the uniform transport speed is helpful in creating uniform film tension. In this article, a simplified version of PET film processing systems, consisting of an unwinding roll, a sensor roller, and a rewinding roll, is considered. The unwinding roll and rewinding roll are driven by a torque-controlled motor and speed-controlled motor, respectively. A control signal to the torque-controlled motor, generated by a conventional sliding-mode controller or a fuzzy sliding-mode controller, regulates the film tension. Moreover, the speed-controlled motor adjusts the transport speed at the winding section. To improve the speed fluctuation, an external proportional-plus-integral-plus-derivative (PID) controller for the speed-controlled motor was implemented. The experimental results demonstrate that fuzzy sliding-mode control gives the tension response with smaller variation than the conventional sliding-mode control does, and the external PID control for speed diminishes fluctuations in speed, thus leading to more uniform tension, while maintaining it at the preferred value.
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