Automatica 47 (2011) 429–430

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Automatica

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Obituary

Charles A. Desoer, 1926–2010

On November 1, 2010, the systems and control community losta towering figure, Professor Charles A. Desoer, who was emeritusfaculty of electrical engineering and computer sciences at theUniversity of California, Berkeley. Charlie Desoer, as he was knownto his colleagues, friends and students, died in Oakland, Californiaat the age of 84.

Desoer was born in Brussels, Belgium on January 11, 1926.He received a radio engineer degree from the University ofLiege, Belgium, in 1949 and a Sc.D. in electrical engineering fromthe Massachusetts Institute of Technology in 1953. Immediatelyfollowing graduation, he started a career at Bell Labs inMurrayHill,New Jersey, primarily working in the field of network theory. In1958, he joined the University of California at Berkeley (hereafterUC Berkeley) as a professor of electrical engineering and computersciences, and stayed there until his retirement in 1993.

Desoer’s work contributed to substantial progress in theanalysis, design and control of linear and nonlinear circuits andsystems. These advances led to the burgeoning growth of systems,circuits and control and benefited the aerospace, transportation,process control, as well as semiconductor and other essentialsectors of industry.

In his research and teaching covering a period of more than 30years he has contributed substantially to the understanding of thebehavior and the improved use of electrical circuits and dynamicalsystems by introducing new concepts or clarifying conceptsand methods such as modes in linear circuits, interconnections,input–output stability, inverse function theorem, jump behavior,robustness issues, control of flexible structures, factorization,multiple scales behavior, algebraic design, feedback for nonlinearsystems, parasitics in nonlinear systems, controllability andobservability, and synthesis of circuits.

On each of these topics, he combined a rigorous mathematicalapproach with insights and value for the practitioners. His impactin the field of circuits and systems engineering over a period ofmore than 30 years cannot be overestimated. One can measure itin four different and complementary ways:

First is his teaching to electrical engineering students at UCBerkeley over a period of more than 30 years, where he earned adistinguished teacher award, and where his lectures were really

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jewels. Each lecture started with a brief overview, followed by acrystal clear presentation of themain points. Hewas a good listenerto his audience and cared to answer questions carefully.

Second, for over more than 30 years he supervised 42 Ph.D.students at UC Berkeley. He coached them into sharp, clear andhigh level thinking, which often was crucial for them to build latersuccessful careers in academia and industry at various importantplaces around the world. A one in five reduction of the list ofPh.D. students (and their thesis titles) can provide a good glimpseof the breadth of the topics covered in their research under hismentorship:

Robert J. Minnichelli [1990], Least Squares Identification of Fulland Reduced Order Multivariable ARX Parameterizations.

Shahram Mojaddad-Shahruz [1988], Studies of Multiple-Time-Scale Phenomena in Control Systems.

Charles L. Gustafson [1983], Algebraic Design of Linear Multivari-able Feedback Systems.

Yung-Terng Wang [1978], Contributions to Feedback Theory forNonlinear Systems: Feedback Fundamentals and the ServomechanismProblem.

Hiromasa Haneda [1972], Analysis of Computational Techniquesfor Circuit Theory.

Mehmet K. Inan [1970], Optimization of Nonlinear Characteris-tics.

Chi-TsongChen [1966],Controllability andObservability of LinearTime-Invariant Composite Systems.

Raphael Sivan [1964], Optimal Control of Systems with StochasticDisturbances.

Robert W. Newcomb [1960], Synthesis of Non-Reciprocal andReciprocal Finite Passive 2n-Poles.

Third, themore than 100 papers that hewrote over the course ofmore than 30 years, often coauthored with his Ph.D. students andvisiting researchers from around the world, have been used exten-sively and referred to by engineers and scientists worldwide. Mostremarkable was his unending passion for an original approachto classical and novel features of circuits and control systems:e.g. feedback amplifiers, Nyquist stability criterion, Routh–Hurwitzstability criterion, Pontryagin’s Maximum Principle, Kharitonov’stheorem, Tellegen’s theorem, and so on. A few representative pa-pers here are:

J. J. Anagnost and C.A. Desoer, ‘‘An elementary proof of theRouth-Hurwitz stability criterion’’, Circuits, Systems, and SignalProcessing, 10: 101–114, 1991.

R.J. Minnichelli, J.J. Anagnost, and C.A. Desoer, ‘‘An elementaryproof of Kharitonov’s stability theorem with extensions’’, IEEETransactions on Automatic Control, AC-34: 995–998, 1989.

S. S. Sastry and C.A. Desoer, ‘‘Jump behavior of circuits andsystems’’, IEEE Transactions on Circuits and Systems, CAS-28:1109–1124, 1981.

430 Obituary / Automatica 47 (2011) 429–430

C.A. Desoer and Y.T.Wang, ‘‘On the generalizedNyquist stabilitycriterion’’, IEEE Transactions on Automatic Control, AC-25: 187–196,1980.

F.M. Callier and C.A. Desoer, ‘‘On simplifying a graphical stabilitycriterion for linear distributed feedback systems’’, IEEE Transactionson Automatic Control, AC-21: 128–129, 1976.

G. F. Oster and C.A. Desoer, ‘‘Tellegen’s theorem and thermo-dynamic inequalities’’, Journal of Theoretical Biology, 32: 219–241,1971.

C.T. Chen, C.A. Desoer, A. Niederlinski, and R.E. Kalman,‘‘Simplified conditions for controllability andobservability of lineartime-invariant systems’’, IEEE Transactions on Automatic Control,AC-11: 613–614, 1966.

C.A. Desoer, ‘‘General formulation of theNyquist Criterion’’, IEEETransactions on Circuit Theory, 12: 230–234, 1965.

C.A. Desoer, ‘‘Nonlinear distortion in feedback amplifiers’’, IRETransactions on Circuit Theory, 9: 2–6, 1962.

C.A. Desoer, ‘‘Pontryagin’smaximumprinciple and the principleof optimality’’, Journal of the Franklin Institute, 271: 361–367,1961.

Last, but not least, the various books that he wrote andcoauthored are considered to be authoritative references in thefield of circuits, systems and control, and find their place on thebookshelves of many researchers around the world. These booksare widely regarded as classics. They are widely consulted, andthey resolve debates whenever a concept or method is beingdiscussed in engineering practice, as well as in circuit or controlengineering research topics. The books have set a high standard ofclarity of thought and presentation, as well as a deep commitmentto intellectual elegance. The complete list of his books is:

F.M. Callier and C.A. Desoer, Linear System Theory, New York:Springer-Verlag, 1991.

A. N. Gündeş and C.A. Desoer, Algebraic Theory of Linear FeedbackSystems with Full and Decentralized Compensators, Lecture Notes inControl and Information Sciences; 142, Berlin;NewYork: Springer-Verlag, 1990.

L.O. Chua, C.A. Desoer, and E. S. Kuh, Linear and NonlinearCircuits, McGraw-Hill Series in Electrical Engineering: Circuits andSystems, New York: McGraw-Hill, 1987.

F.M. Callier and C.A. Desoer, Multivariable Feedback Systems,Springer Texts in Electrical Engineering, New York: Springer-Verlag, 1982.

C.A. Desoer and M. Vidyasagar, Feedback Systems: Input-OutputProperties, Electrical Science Series, New York: Academic Press,1975; re-edited as a SIAM Classic in Applied Mathematics, 2009.

C.A. Desoer, Notes for a Second Course on Linear Systems, VanNostrand Reinhold Notes on System Sciences, New York: VanNostrand Reinhold Company, 1970.

C.A. Desoer and E. S. Kuh, Basic Circuit Theory, New York:McGraw-Hill, 1969.

L.A. Zadeh and C.A. Desoer, Linear System Theory: The StateSpace Approach, McGraw-Hill Series in System Science, New York:McGraw-Hill, 1963; re-edited by Dover Publications, Paperback,2008.

Desoer’s major awards include a Guggenheim Fellowshipin 1970; the Medal of the University of Liege in 1970; theDistinguished Teaching Award from UC Berkeley in 1971; thePrix Montefiore in 1975 and a honorary Sc.D. in 1976 from the

University of Liege; the Institute of Electrical and ElectronicsEngineers (IEEE) James Mulligan Education Award in 1975; theAmerican Automatic Control Council Education Award in 1983; theIEEE Control Systems Society Field Award in 1986; the UC BerkeleyCitation in 1991; and the Gustav Robert Kirchoff Award of theIEEE in 2011, to be presented posthumously in recognition of hisfundamental research in circuits and systems. He was a life fellowof the IEEE, a member of the National Academy of Engineering,and a fellow of the American Association for the Advancement ofScience.

Charlie Desoer was an optimist given the realities of everydaylife, and was a firm believer of what is expressed by the dictum‘‘There is nothing to fear but fear ’’ (Franklin Delano Roosevelt). Hewas very generous to his Ph.D. students. As I have experienced firsthand as one of them. He would invite them often to a restaurantor take them out for a walk for a cup of coffee, where he wouldinquire about their family. He liked physical exercise, and wasoften spotted running in the Berkeley Hills.

Charlie Desoer was also a philosopher of science and technol-ogy, communicating to people some excerpts of articles e.g. of theScientific American. Hewas aman of fewwords, but alsowould notshy away from expressing his reaction to others, particularly onpresentations at conferences. Typical Desoer reactions at confer-enceswere: ‘‘Is there anything in this paper?’’ (the paper presentedwas substandard), ‘‘Diarrhea of the mouth’’ (the speaker uses toomanywords and is confusing), ‘‘Food for thought’’ (matter to be re-flected upon). Another typical reaction of his was: ‘‘Ne sutor supracrepidam’’ (Shoemaker, not above the sandal, do not criticize thingsyou know nothing of).

I want to conclude thismemorial on a personal note, as his Ph.D.student at UC Berkeley, later as a co-author on two of his books,and as a close friend. Over the years I have observed how humbleCharlie was in his interactions with others, and how gentlemanlyhe was in handling even undeserved criticisms, letting time provehim right. I have also become more and more cognizant of hiscare for students to climb the ladder of learning. In my numerousencounters with him at meetings I always got something back inthe form of hints and comments, which helped me significantlyin my professional career. I believe these sentiments would alsobe shared by all his former Ph.D. students, and his colleagues.For all this, we owe him gratitude. Times may have changed,but his inspiring power remains, through also his exceptionalcontribution to education and research. He will be missed dearlyby his colleagues, his friends, and the entire systems and controlcommunity.

This obituary has benefited from earlier curricular researchconducted by Professor Joos Vandewalle, Dept. ESAT, CatholicUniversity of Leuven, Belgium, and by Professor Shankar Sastry,Dean of Engineering, University of California at Berkeley, USA.

Frank M. CallierDepartment of Mathematics,

University of Namur (FUNDP),Rempart de la Vierge 8, B-5000 Namur, Belgium

E-mail address: frank.callier@fundp.ac.be.Available online 5 February 2011