Development of a film profile control system in a film plant

An automatic profile digital control system is presented which is based on a fundamental control system. The fundamental control system measures the film thickness at five points corresponding to five actuators, and controls the thickness at the location corresponding to the position of the central actuator at the specified value by using the five actuators. The basic idea is that in order to effect thickness control along the total width of the film, the fundamental control system will be applied to every thickness control point. It was designed by the state-prediction servo control theory, which solves such difficulties as a large amount of dead time and interaction between film thickness and actuators. Its practicality has been verified through testing. Tests were conducted for biaxially oriented polyester film by using a lip heater type die and for nonoriented polypropylene film by using a heat bolts type die. It was found that in this control system, the time to reach steady state was reduced and an accurate profile was obtained.<>