Modelling and control of co-rotating twin-screw extrusion process Modelación y control de procesos de extrusión bi-tornillo

Abstract

In this work a distributed parameter bi-zone dynamic model with moving interface of an extrusion process is presented. The interconnection of the moving interface is performed under the assumption of variable viscosity along the extruder. A nite volume method is proposed for discretizing the dynamic model. The steady state values of the variables were calculated by using an e cient optimization algorithm without the need of performing back calculations. Experimental tests performed with an industrial type twin screw extruder are compared against simulations for the case of variable screw speed and constant feed rate. The comparison shows good qualitative agreement between experimental and simulation results. An energy based controller for the validated extrusion process model is derived using internal energy as a storage function and controlled variable with the screw speed as control input. The stability of the controller is proved through the use of a Lyapunov-like candidate function. Finally, the practical usefulness of the method is illustrated by closed-loop simulations of the experimentally veri ed model of the extrusion process. This model can be used to design observers for estimating non-measurable variables as well as advanced control strategies.