Prof.Dr. Nejat Olgac
Mechanical Engineering Department, University of Connecticut, USA
https://alarm.engr.uconn.edu/

Title: A QUICK HISTORY OF A STABILITY PARADIGM BRIDGING VARIOUS UNRELATED DYNAMICS

Abstract: The presentation is a flight over four-decade long research, with some anchoring stops. The topic is on the stability assessment of LTI-Time-Delayed Systems with multiple rationally independent delays. This class of dynamics is instilled in much broader facets of life than appeals to the eye. The underpinning paradigm is called the Cluster Treatment of Characteristic Roots (CTCR) which declares the stability disposition of the systems in the domain of the delays, exhaustively and non-conservatively. The nucleus of this development goes back to a concept of actively tuning vibration absorbers which are named the Delayed Resonators (DR, inducted in 1994). As DR evolved over the ensuing years, the group was forced to embark on a pursuit of a lacking deterministic and practical tool (such as CTCR) for assuring the stability. Core development was first publicized in 2002 (IEEE-TAC) which amassed with increasing intensity some new practical domains not foreseen earlier. Two of these deployments, which are seemingly unrelated, will constitute the anchor points in this talk:

(1) Prediction of Thermo-acoustic instability (TAI), and
(2) Optimizing the milling operations with non-uniform pitch cutters.
We will discuss the analytical underpinnings of the CTCR paradigm first, followed by the critical features of the two dynamics. Experimental verifications will also be discussed.

Biography: Nejat Olgac, Dr. Eng. Sci. Columbia Univ. 1976, M.Sc. Technical Univ. of Istanbul, Turkey 1972 (summa-cum-laude), both in Mechanical Engineering. He was engaged in manufacturing industry entrepreneurship in Istanbul (1976-81). Since 1981 he has been a professor with the Mechanical Engineering Department of the University of Connecticut. His research interests are in robust nonlinear controls, active vibration absorption, time-delayed systems, micromanipulation in bio-engineering. Dr. Olgac holds four patents, three on the Delayed Resonator active vibration suppression technique (1995-1996-1999) and a fourth one on anti-chatter concepts in simultaneous machining (2011). He is the director of Advanced Laboratory for Robotics, Automation and Manufacturing (ALARM) at UConn. Dr. Olgac was Visiting Professor at INRIA (Sophia-Antipolis, France) 1988-89, SEW Eurodrive Fellow - Guest Professor at Technical Univ. of Munich, Germany in 1995-96 and Visiting Professor at Harvard University 2002-03).Visiting Professor at Czech Technical University in Prague (CVUT) (2017-18). He served on the editorial board of the ASME Trans. of Dynamic Systems, Measurement and Control (1996-2004), and the guest editor of the Special Issue of JDSMC on Time Delayed Systems (June, 2003), is presently on the Editorial Boards of IEEE, Tran. Control System Technology, J. Vibration and Control, Int. J. of Mechatronics and Manufacturing Systems. He also served a member and later as the Chairman of the Executive Committee of the ASME Dynamic Systems and Control Division (2001-6). He was the General Chair of IFAC Time Delay Systems Workshop (TDS) 2012, and General Chairman of ASME Dynamic Systems and Controls Conference, DSCC 2013. He is a member of the ASME Systems and Design Group Operating Board, he also sits on the A2C2 (American Automatic Control Council) Board of Directors. He is the recipient of a UCONN Research Excellence Award (2015) and ASME Distinguished Engineer of the Year, Hartford Chapter, CT (2015). Prof. Olgac is a member of the Connecticut Academy of Science and Engineering (CASE), Fellow of ASME and Senior Member of IEEE. H,e was selected as the recipient of Doctor Honoris Causa ( https://www.cvut.cz/en/doctor-honoris-causa-ctu-in-prague) from the Czech Technical University, Prague (2019).