David L. Elliott: An Appreciation

ISR’s dear colleague Dr. David L. Elliott died suddenly on July 2, 2020, not long after being discharged from Johns Hopkins after a short stay for an infection. David is survived by his wife Pauline Tang.

Elliott was a Professor Emeritus of Mathematical Systems at Washington University in St. Louis. He learned automatic control theory as a working applied mathematician at the Naval Ordnance Test Station's Underwater Ordnance Department from 1955-69, and obtained his Ph.D. at UCLA with Navy support. His work on the geometric approach to nonlinear control systems has been foundational, including work on bilinear systems, controllability, and observability.

He joined Washington University in St. Louis in 1971 as faculty in its (then) Department of Systems Science and Mathematics, and became a full professor there in 1980. He advised the late University of Maryland ECE Professor W. P. Dayawansa, as well as other future academics such as Nick Kalouptsidis (University of Athens), Dirk Aeyels (University of Gent), RenJeng Su (Portland State), and Riccardo Marino (University of Rome II).

Professor Prakash Narayan (ECE/ISR) remembers being taught by Elliott as a Washington University student:

“Before doing my Ph.D. in Electrical Engineering, I did my Master's degree in Systems Science and Mathematics—both at Washington University in St. Louis. During my M.S. studies, David Elliott was my teacher in his graduate course on Nonlinear Systems. We students would never know what exciting and extemporaneous (and pleasantly disorganized) idea he would pull out of thin air in any given lecture!”

“The textbook (J. L. Willems’ “Stability Theory of Dynamical Systems”) was but a prop. He was a maverick who was always interesting! And I still recall with warmth his having scolded me—in front of the entire class and deservedly so—when he caught me playing “hangman” with a classmate during one of his lectures. I shall miss the colorful David Elliott.”

Starting in 1992 and up until his death, Elliott held a senior visiting faculty appointment with ISR, where he continued to conduct research on bilinear systems and interacted with ISR faculty and students.

Former ISR Director and Professor Eyad Abed (ECE) shares that Elliott worked with several graduate students as an informal research mentor along with their advisors and thesis committee members. For example, Priya Ranjan (EE Ph.D. 2003), currently a professor at SRM University, Andhra Pradesh, Amaravati, India, was greatly helped by his association with Elliott.

Priya writes:

“He was instrumental in developing my thought process on my PhD problem. In my mind he will always be alive as a great inspiring scientist and applied mathematician. For me the loss is very personal.”

During his affiliation with ISR, Elliott wrote the book Bilinear Control Systems—Matrices in Action, published by Springer in 2009. Previously, he had written Neural Systems for Control with Omid Omidvar in 1997. Elliott has an author biography on Amazon.

He also has five papers in ISR’s Technical Reports archive on DRUM. David was very proud to include his work in our archive, delivering each hard-copy paper in person for uploading. He was especially insistent on adding his 1969 UCLA Ph.D. thesis, Controllable Nonlinear Systems Driven by White Noise, which he wrote under the supervision of A.V. Balakrishnan. This work was the first to apply a Lie algebra approach to stochastic dynamical systems.

For his dedication and service to ISR, he was awarded a commemorative crystal clock at our 20th anniversary celebration.

ISR-affiliated Professor Ben Kedem (Math), fondly remembers conversations with Elliott over the years, and writes that “David Elliot was a remarkable person who was interested in ‘everything.’”

Distinguished University Professor Tony Ephremides (ECE/ISR) writes:

“David Elliott belonged to a class of scientists that are nowadays sorely missed. He was truly devoted to his Science and to his Profession as a researcher and Teacher (with a capital T). He was gentle, interesting, pleasant, reliable, humorous, inspiring. In short, he was a true Gentleman. Some of us old-timers had the pleasure of knowing him in his prime. We were so lucky that he gravitated towards us at the ISR for several years after he retired. His intellect was always alive and charming. I cannot say how much he meant to many of us whose careers intertwined with his. Let his memory be blessed.”

Elliott continued to live near campus until his passing. Until recently, David and Pauline made regular trips to the university to attend ISR seminars and visit with faculty and students.

David Elliott was a true friend of ISR and he will be greatly missed. May he rest in peace.

Published July 7, 2020