Einladung zum Vortrag im Kolloquium Technische Kybernetik

Control-Oriented Modeling for Vapor Compression Cycles

Prof. Andrew Alleyne, Ph.D.

    Zeit: Dienstag · 13. 5. 2003 · 16:00 Uhr
    Ort: Hörsaal V 9. 31 · Pfaffenwaldring 9 · Campus Stuttgart-Vaihingen

Abstract

In this talk we will discuss a modeling approach that we have taken for understanding and predicting transient dynamic phenomena in Vapor Compression Cycle systems: i.e. air conditioning & refrigeration. The overall goal of the modeling process is to develop control-oriented models that can be used for designing multivariable controllers. However, this talk will focus primarily on the model development and modeling environment. The component models are developed via a combination of first principles and justifiable assumptions. These components are then connected using typical thermodynamic relationships. The system components can be separated along fast and slow time scales with the fast time scale components being reduced to static functions. The slow dynamic components are the heat exchangers. A procedure is given for converting a heat exchanger from a spatio-temporal system, represented by PDE’s, into one that it a collection of temporal elements, ODE’s. This allows for a very compact system representation amenable to system level understanding and controller design.
The modeling approach has been undertaken in a framework that is suitable for both subcritical and transcritical Vapor Compression Systems. Results from both types of systems will be presented. A model reduction approach, based partially on further time-scale separation of the heat exchanger dynamics, indicates that a relatively low order system model can be used to capture the essential dynamics of a simple Vapor Compression Cycle system; albeit with a reduction in accuracy. The conscious tradeoffs between modeling accuracy and simplicity are also illustrated and the ramifications for closed loop control are discussed.
In addition to the modeling developments, a modular simulation environment using a MATLAB/Simulink platform will be presented. The modular environment, which has been termed the “Thermosys Toolbox for Simulink,” allows for a rapid model development, modification, and verification. Several representative examples of the modeling approach, as well as the model validation, will be presented. These examples include experimental data taken from test rigs within the Air Conditioning and Refrigeration Center (ACRC) at UIUC.
Time permitting, the talk will conclude with interesting recent findings on closed loop control for subcritical (R134a) systems typical of automotive applications as well as future directions in multiple component system networks.

Biographical Information

Professor Alleyne received his B.S. in Engineering Degree from Princeton University in 1989 in Mechanical and Aerospace Engineering. He received his M.S. and Ph.D. degrees in 1992 and 1994, respectively, from The University of California at Berkeley. He joined the Department of Mechanical and Industrial Engineering at the University of Illinois, Urbana-Champaign in 1994 and is also appointed in the Coordinated Science Laboratory of UIUC. He currently holds the Ralph M. and Catherine V. Fisher Professorship in the College of Engineering and is a 2002-2003 Fulbright Fellow. His research interests are a mix of theory and implementation with an application focus that covers Automotive, Manufacturing, and Aerospace fields. He has been active in the ASME, the IEEE, and several other societies where he has contributed extensively as an author, reviewer, and organizer. He is currently an Associate Editor of the ASME Journal of Dynamic Systems, Measurement and Control as well as a co-editor for Vehicle System Dynamics and has contributed to his community in several other editorial aspects. Further information about the toys he and his students play with can be found at the following website: http://mr-roboto.me.uiuc.edu.