On-line system identification and control design of an extrusion cooking process: Part II. Model predictive and inferential control design

Abstract

A non-linear model-based predictive control law to regulate specific mechanical energy (SME) using screw speed is developed. Operating variable setpoints are determined using an inferential model that correlates SME with product density and melt moisture content. Additionally, a ratio control strategy is used to regulate melt moisture content and an output noise filter is added to attenuate sensor noise. When combined with an on-line system identification procedure, the resulting system provides good servo and regulatory control response that is robust to modeling errors and disturbances. This paper represents the second of two papers that describe our investigation into the use of on-line system identification for automatic tuning and adaptive control of high-shear twin-screw extrusion processes. The resulting control design addresses the need for a comprehensive system that can be used to regulate extrudate density in extrusion cooking and puffing processes.