Adaptive Control of Melt Pressure in Polymer Extrusion Processes Using Extremum-Seeking Control

In polymer extrusion processes, melt pressure is used as a key indicator of melt stability. Fluctuations in melt pressure can lead to variations in the dimensions of the extruded product in continuous extrusion processes, adversely affecting the product quality. Hence, it is important to maintain the melt pressure at a desired level while minimizing pressure fluctuations, to ensure melt stability and quality. This study proposes an adaptive controller based on the extremum-seeking control technique to regulate the melt pressure by adjusting the screw rotational speed. The controller was implemented and tested through simulation. To evaluate the adaptation capabilities of the controller, its performance was assessed across two polymeric materials (i.e., LDPE and LLDPE) and two screw designs (i.e., barrier-flighted and rapid compression), which were processed under three temperature conditions and five screw speed settings. Simulation results confirmed that the controller could regulate the melt pressure at the desired level regardless of the processing conditions. The findings of this study will aid control engineers in designing adaptive melt pressure controllers for industrial polymer extrusion processes.