Design of a fuzzy logic control system for biaxial extrusion thickness gauging

Three typical approaches for controlling the flatness of polystyrene or polypropylene on a biaxially oriented line by a beta gauge are examined based upon control of product flatness, simplicity, and cost. A new approach is developed using the best features of each while improving other features.; The new approach uses a downstream Krypton beta gauge, a downstream data to die bolt alignment algorithm, and a fuzzy logic controller to control the flatness of the product. The downstream data to die bolt alignment algorithm assigns downstream measured product to a particular die bolt on the die. The alignment uses nylon line placed inside the product in 5 zones. The beta gauge detects the nylon line and determines the stretching in each zone. Accurate alignment of downstream product to die bolt is achieved. The fuzzy logic controller adjusts PID loop control gains and outputs a product flatness control correction signal to the die bolts.