Events Calendar

CONTROL OF NONLINEAR DISTRIBUTED PROCESS SYSTEMS

Speaker: Panagiotis D. ChristofidesDepartment of Chemical Engineering
University of California, Los AngelesABSTRACT:While most undergraduate control courses still deal with dynamics and control of lumped parameter systems using linear transfer function models, key technological needs in growth areas such as semiconductor manufacturing, nanotechnology and biotechnology have motivated extensive research on analysis and control of complex nonlinear distributed processes. Examples include the chemical vapor deposition of thin films for semiconductor manufacturing, as well as the crystallization of proteins and the aerosol-based production of nanoparticles. From a control point of view, the distinguishing feature of complex distributed processes is that they give rise to nonlinear control problems that involve the regulation of highly distributed control variables by using spatially-distributed control actuators and measurement sensors. Thus, complex distributed processes cannot be effectively controlled with control methods which assume that the state, manipulated and to-be-controlled variables exhibit lumped behavior or with linear control algorithms derived on the basis of linear/linearized distributed models.We have pioneered the development of a general and practical framework for the synthesis of practically implementable nonlinear feedback controllers for complex distributed processes based on fundamental models that accurately predict their behavior. The key difficulty in developing model-based control methods for distributed processes lies in the ``infinite-dimensional'' nature of the process models, which prohibits their direct use for control system synthesis. We have developed nonlinear order reduction techniques for deriving low-dimensional approximations that accurately reproduce the dynamics and solutions of distributed process models. We have used these approximate models for the synthesis of nonlinear feedback controllers via geometric methods and Lyapunov techniques. The controllers can be readily implemented in practice and enforce the desired control objectives in the infinite-dimensional closed-loop system. In addition to our order reduction and control work, we will present recent results on state estimation and control using multiscale (deterministic/stochastic) distributed models. We will present applications of the theoretical results to: a) temperature profile control in rapid thermal chemical vapor deposition and crystal growth, b) control of microstructure and composition in thin film growth including an experimental implementation, and c) control of size distribution in pharmaceutical crystallization. BIOGRAPHICAL SKETCH:Panagiotis D. Christofides was born in Athens, Greece, in 1970. He received the Diploma in Chemical Engineering degree in 1992, from the University of Patras, Greece, the M.S. degrees in Electrical Engineering and Mathematics in 1995 and 1996, respectively, and the Ph.D. degree in Chemical Engineering in 1996, all from the University of Minnesota.Since July 1996 he has been with the Department of Chemical Engineering at the University of California, Los Angeles, where he is currently Associate Professor. His theoretical research interests include nonlinear control, singular perturbations, and analysis and control of distributed parameter systems, multiscale systems and hybrid systems, with applications to advanced materials processing, particulate processes, biological systems and fluid flows. His research work has resulted in a large number of articles in leading scientific journals and conferences and two books entitled "Nonlinear and Robust Control of Partial Differential Equation Systems: Methods and Applications to Transport-Reaction Processes," Birkhäuser, Boston, 2001 and "Model-Based Control of Particulate Processes,'' Kluwer Academic Publishers, 2002. He has also co-authored the forthcoming book "Control of Nonlinear and Hybrid Process Systems: Designs for Uncertainty, Constraints and Time-Delays", Springer, 2005. A description of his research interests and a list of his publications can be found at http://www.chemeng.ucla.edu/pchristo/index.html.Professor Christofides has been a member of the Control Systems Society Conference Editorial Board and is an Associate Editor of "IEEE Transactions on Automatic Control", the 2004 Program Coordinator of the Applied Mathematics and Numerical Analysis Area of AIChE and the Program Vice-Chair for Invited Sessions for the 2004 American Control Conference.Professor Christofides has received the Teaching Award from the AIChE Student Chapter of UCLA in 1997, a Research Initiation Award from the ACS-Petroleum Research Fund in 1998, a CAREER award from the National Science Foundation in 1998, the Ted Peterson Student Paper Award from the Computing and Systems Technology Division of AIChE in 1999 and a Young Investigator Award from the Office of Naval Research in 2001. He has also received twice the O. Hugo Schuck Best Paper Award in 2000 (with Antonios Armaou) and 2004 (with D. Ni, Y. Lou, L. Sha, S. Lao and J. P. Chang), and the Donald P. Eckman Award in 2004, all from the American Automatic Control Council.Host: Petros Ioannou; ioannou@usc.edu

Location: Hughes Aircraft Electrical Engineering Center (EEB) - 248

Audiences: Everyone Is Invited

Contact: Irina Strelnik