Control of Screw Extruder Delay/Partial Differential Equation (PDE) Dynamics for 3D Printing

University Of California-San Diego, La Jolla CA

Investigators

Abstract

Motivated by both the potential for a technological, economic, and social impact of additive manufacturing, the project is dedicated to the design of controllers to remove some of the key bottlenecks to achieving high speed and product quality in 3D printing. The project will build control and modeling methodologies that are both of high research value and are suitable for industrial use, going after improvements in the build speed and part quality. Compared to the standard Fused Deposition Modeling and Syringe Based extrusion processes, the novel configuration of the Screw Extruder process that we address may allow continuous feeding, speed up production, and upgrade the mixing capabilities, while efficiently reducing the thermal degradation of the melt and the cost for such processes. The PI has supervised two dozen students from underrepresented groups on past projects, such as women, Hispanics, and African-Americans, and the present project will involve specific individuals from underserved communities as advisees and collaborators. Partial Differential Equation (PDE) models of mass and thermal flows in the Screw Extruder will be used to design accurate and robust controllers, to replace the existing control methods for 3D printing, which are typically constructed using conservative black-box or lumped models, which reduces their performance for a large range of materials. Moreover, control of the melt thermal behavior that impacts viscosity evolution and the solidification process will be addressed. The control design will be based on infinite-dimensional models of screw extruders, including a bi-zone model consisting of PDEs coupled through a moving interface described by an ordinary differential equation. Novel control design techniques from the PI's infinite-dimensional backstepping toolkit will be developed for this purpose. Implementation of the designed controller will be performed on an experimental platform developed in the PI's group. The project will provide advancements to the general area of control of PDEs that are coupled through a moving interface, which, besides extruders, arise in multi-phase flows, crystal growth, freeze-drying, and distillation processes.