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Dragoslav D. Šiljak

For fundamental contributions to the theory of large-scale systems, decentralized control, and parametric approach to robust stability

Dragoslav D. Šiljak received his doctorate degree (D.Sc.) in Electrical Engineering from the University of Belgrade, Serbia, in 1963. He joined the Department of Electrical Engineering at the Santa Clara University in 1964, where he is presently the Benjamin and Mae Swig University Professor. 

Upon the arrival to Santa Clara, Dr. Šiljak continued his research on parameter space methods for robust control design, which he presented in a monograph Nonlinear Systems: The Parameter Analysis and Design (Wiley, 1969). He established collaboration with control groups at NASA Ames Research Center and Marshal Space Flight Center, which focused on parameter methods for control design of space vehicles.   

In the early 1970s, Dr. Šiljak introduced the concept of connective stability of large-scale dynamic systems within the framework of comparison principle and vector Lyapunov functions. He applied the concept to a wide variety of models, in areas as diverse as population biology, arms race, large space structures, competitive equilibrium in mathematical economics, and electric power systems. Within the same framework, he introduced robust decentralized feedback and developed graph-theoretic methods for decentralization and stabilization of uncertain large-scale systems. These concepts and results appeared in a monograph entitled Large-scale Dynamic Systems: Stability and Structure (North Holland, 1978) which, after almost thirty years, was reprinted as a paperback by Dover Publications (2007). 

In the 1980s, Dr. Šiljak and his collaborators developed a large number of new and highly original concepts and methods for the decentralized control of uncertain large-scale interconnected systems. Structurally fixed modes, multiple controllers for reliable stabilization, decentralized optimization, and hierarchical, epsilon, and overlapping decompositions laid the foundation for a powerful and efficient approach to a broad set of problems in control design of large complex systems. This development was reported in a comprehensive monograph Decentralized Control of Complex Systems (Academic Press, 1991). 

Over the past two decades, Dr. Šiljak and his collaborators have raised the research on complex systems to a higher level. Decomposition schemes involving inputs and outputs have been developed for and applied to complex systems of unprecedented dimensions. Dynamic graphs have been defined in a linear space as one parameter groups of transformations of the graph space into itself. This new mathematical entity opened the possibility to include continuous Boolean networks in a theoretical study of gene regulation and modeling of large-scale organic structures. These new and exciting developments have been published in a recent monograph Control of Complex Systems: Structural Constraints and Uncertainty (Springer, 2010, coauthor A. I. Zečević).

Dr. Šiljak’s research on large complex systems has involved a large number of collaborators, including researchers and students who came from all over the world to Santa Clara to study complex dynamic systems. Over the years, this research has been generously supported by NASA, NSF, DOE, and DARPA. 

In 1981, Šiljak served as a Distinguished Scholar of the Japan Society for Promotion of Science, lecturing on large-scale systems at major universities and companies in Japan. He was selected as a Distinguished Professor of the Fulbright Foundation in 1984, and in 1985 became an Honorary Member of the Serbian Academy of Arts and Sciences. In 1986, he served as a Director of the NSF Workshop “Challenges to Control: A Collective View,” organizing a forum of top control scientists at Santa Clara University for the purpose of assessing the state of the art of the field and outline directions of research. In 1991, he gave a week-long seminar on decentralized control at the Seoul National University as a Hoam Distinguished Foreign Scholar. In 2001, he became a Life Fellow of the IEEE. He has presented many plenary talks at conferences and served on editorial boards of a variety of journals in the fields of applied mathematics and engineering. 

Text of Acceptance Speech: 

July 1, 2010. Baltimore, MD

I am exceedingly happy to receive the Richard Bellman Control Heritage Award. I am thankful to the American Automatic Control Council for recognizing my work as worthy of this award, and I am deeply humbled when I consider the previous recipients of the award.

My first thanks go to my dear wife Dragana who put up for a long time with a workaholic husband with an oversized ambition. I am grateful to Santa Clara University and, in particular, to the School of Engineering for providing institutional support to our research. I am exceedingly thankful to many people from all around the world who came to Santa Clara to work on our projects as fellow researchers on an exploratory journey; and what a journey it has been!

At this occasion, it gives me a great pleasure to recall my visit to University of Southern California and my brief encounter with Professor Bellman. After my talk, he invited me to his office, and among myriad of his interests, he chose to talk with me about his recent work in Pharmacokinetics. At that time, I was deeply into the competitive equilibrium in economics, and we had a very stimulating discussion on the connection of the two fields via the Metzler matrix which I have been using since then in a wide variety of models to this very day.

Looking at this award in a prudential light, my obtaining this award is as much a compliment to the Control Council as it is to me. My winning of this award at Santa Clara University, which is not a research 1 university but prides itself as an excellent teaching institution, proves that the system is open, and that any of you wherever you are can win this award solely by the merit of your research.

I recall when at eighteen I made the Yugoslav Olympic Water Polo Team for the 1952 Helsinki Olympic Games. We won all our games except the final one, which ended in a draw. At that time, there were no overtimes and penalty kicks; the winner was determined by the cumulative goal ratio. I continued playing water polo, but did not make the team for the 1956 Melbourne games; I broke my right hand and stayed home. I kept playing on and in 1960 made the team for the Rome Olympics. We did not win a medal in Rome, let alone the gold. At that point I was already a committed researcher in control systems. I continued the research for many years and to borrow from a song by Neil Young:

"I kept searching for a heart of gold, and I was getting old ... "

Today I found a heart of gold. Thank you all very much for your attention, and God bless!