Design of a Feedback Control System for Real-time Control of Flow in a Single-screw Extruder

A closed loop controller is designed for regulation of the volumetric output flow in a polymer extruder. To this aim, temperature and pressure at the machine output must be controlled on the basis of real time measurements. It has been verified that temperature and pressure regulations can be achieved by solving two disjoint control problems. The temperature controller acts on the heat delivered to the plastic material by the heater electric resistance bands on the barrel; the pressure controller uses as a control action the voltage applied to the screw electrical engine in order to obtain real time modulation of the screw revolution speed. The designed control system shows very good performances in regulation of the flow output and good robustness properties to variations in the operating conditions and the material properties.