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Modelling and Control of HIV/AIDS

In this talk, we will look at the model from a control system's point of view. First of all, the principles and immunological background of HIV models are reviewed. Secondly, process variables are identified as the control system input, measured system output and controlled system output. The identification of output is related to the practical clinical tests and measurement, and the identification of input is related to the prevailing HIV/AIDS drugs. After setting up the control system framework, basic issues such as controllability, observability, identifiability and transmission zeros/zero dynamics, can be then studied in connection with the relevant medical discoveries. As an application, we discuss the problem of estimating HIV/AIDS parameters. We make the same basic assumptions that the viral titer and CD4+ T cell count are measured in plasma blood. Our objective is to estimate all parameters in the basic three dimensional model. For this purpose, through an observability analysis, we first obtain the minimal number of measurement samples for the CD4+ T cell and viral load, for a complete model parameter estimation. We then determine the HIV progression stages when an estimation of all parameters is impossible. Outside these stages, we propose the static least-square estimation and on-line estimations of all parameters through two well-known techniques in control theory: adaptive identifiers and adaptive observers. Conditions for parameter convergence will be discussed. Finally, the controllability of the HIV/AIDS chemotherapy is studied.

Type of Seminar:
Public Seminar
Prof. Xiaohua XIA
Dept of Electrical, Electronic & Computer Engineering, University of Pretoria, South Africa
Oct 29, 2001   17:15

ETH Zentrum Building ETZ Room E6 Gloriastrasse 35 8006 Zurich
Contact Person:

Prof. M. Morari
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Biographical Sketch:
Mr. Xia got his D.Eng at Beijing University of Aeronautics and Astronautics, Beijing, China in 1989. After working for 5 years in the same university after PhD, he went to University of Stuttgart as an Alexander von Humboldt fellow for about two years. He made two short stays in Ecole Centrale de Nantes/France and National University of Singapore during the period of two years from 1996 to 1997, both as a post-doctoral fellow. He joined the University of Pretoria since 1998 first as an associate professor then a full professor. Dr. Xia is a Senior IEEE member, is currently the South African IEEE Section/Control Chapter Chair. He also serves for IFAC as an associate editor of Automatica. His research interests include: Non-linear feedback control, observer design, time-delay systems, hybrid systems, very recently control applications to HIV/AIDS. He is supported as scientist (B classification) by the National Research Foundation of South Africa.