Plenary sessions



TIME-DELAYED SYSTEMS (TDS) STABILITY: CLUSTER TREATMENT OF CHARACTERISTIC ROOTS (CTCR) AND APPLICATIONS

by Prof. Nejat Olgac, (To read the biography, please put the mouse cursor on the photo)
Mechanical Engineering Department,
University of Connecticut, Storrs.
Olgac@engr.uconn.edu
http://www.engr.uconn.edu/alarm/

TDS are infinite dimensional systems. As such, they offer mathematically very rich and challenging stability and control problems, which kept many system specialists occupied in the past 6+ decades. This talk covers an umbrella paradigm called the 'Cluster Treatment of Characteristic Roots (CTCR)'. It is, in fact, equivalent to Routh-Hurwitz criterion with a crucial exception that it is for infinite-dimensional structures. CTCR starts with some earlier-unrecognized features of the LTI-Time Delay Systems, and proposes a unique resolution to the stability assessment of TDS via a substantially different perspective than the competing methodologies. It results in a paradoxical finding that states the stability of systems may be improved by artificially increasing the existing delays. Most importantly this new paradigm declares these stability islands non-conservatively and exhaustively. This capability leads to a new stabilizing control concept which the speaker named "the Delay Scheduling". It provides some interesting robustness properties of feedback control systems against delay variations. We will also express some future research directions in this uncharted venue.
End product of this treatment has broad practical implications. Some example research findings on an interesting field, design and control of combustors without Thermo-acoustic Instability (TAI) will be discussed in the talk. We will also display some experimental observations on "Delay Scheduling".

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