Alexander Letov, in full Alexander Mikhailovich Letov, was a world-renowned scientist in control theory and applications. Who would have thought that he, a perfect aristocrat with a permanent bow tie, had begun his career as an ordinary worker? However, in 1937, Letov graduated from the Faculty of Mechanics and Mathematics (Moscow State University). From 1938 to 1941, he was a research engineer at the Research Institute of the USSR People’s Commissariat of Aviation Industry. In 1941—1943, during the Great Patriotic War, Letov worked as a shop supervisor at one of the Commissariat’s defense plants.

From 1943 to 1956, Letov headed a laboratory at one of the research institutes of the USSR Ministry of Aviation Industry. During that period, he obtained interesting theoretical and significant practical results on the dynamics of Soviet aircraft autopilots. In 1950, Letov became Dr. Sci. (Phys.—Math.). The years 1943—1956 were also remarkable for his fundamental results in the theory of nonlinear automatic control systems. They were published in Letov’s famous monograph (1956).

In 1956, Letov joined the Institute of Automation and Remote Control (IARC), the USSR Academy of Sciences (nowadays, Trapeznikov Institute of Control Sciences, the Russian Academy of Sciences). There, he was Senior Researcher and even Deputy Director but was remembered primarily as Head of the Laboratory of Mathematical Methods of Control Theory. While working at IARC, Letov proved to be a major expert in optimal control. At the beginning of the 1960s, he published a series of research works on the analytical design of controllers. This problem was further developed in the USSR and abroad. Letov was the first to point out a deep connection between the optimal control problem and the method of Lyapunov functions.

As Laboratory’s Head, Letov paid much attention to real applications of the theoretical results. Some examples of applications include the optimization of a continuous steel casting process, the selection of an optimal control law for aircraft trajectories, and the optimal distribution of water resources in the Volga River basin. The results of Letov’s research are widely known in the country and abroad. They were published in over 50 scientific papers and two books. One of them was translated in the USA and China.

Since 1956, Letov represented the USSR in the International Federation of Automatic Control (IFAC) and worked actively as Member of the Preparatory Committee (1956—1957), First Vice President (1957—1959), President (1959—1960), and Past-President and Member of the Executive Council. As IFAC President, Letov organized and held the 1st IFAC World Congress (Moscow, 1960). Since 1959, he was Deputy Chairman of the USSR National Committee on Automatic Control and organized many international symposia and scientific meetings. Letov repeatedly and honorably represented Soviet science abroad. In 1968, he was elected Corresponding Member of the USSR Academy of Sciences.

Letov spent much time on tutoring and the promotion of scientific achievements. For many years, he was Professor at the Department of Flight Dynamics (Ordzhonikidze Moscow Aviation Institute). Since 1968, he headed the Department of Mathematical Control Methods at the Lumumba Peoples’ Friendship University (nowadays, the RUDN University). Letov trained over 400 highly qualified specialists in control theory; 35 dissertations were defended under his supervision. Also, Letov was the Deputy Editor-in-Chief of Automation and Remote Control, IARC’s famous peer-reviewed journal.

Letov’s main books are as follows:

1. Matematicheskaya teoriya protsessov upravleniya (Mathematical Theory of Control Processes), Moscow: Nauka, 1981. — 256 p.;
2. Tochnye metody issledovaniya nelineinykh sistem avtomaticheskogo upravleniya (Exact Analysis Methods for Nonlinear Automatic Control Systems), Moscow: Mashinostroenie, 1971. — 322 p. (coauthors V.M. Kuntsevich, B.N. Naumov, R.A. Nelepin, B.N. Petrov, V.Ya. Platov, E.P. Popov, G.S. Pospelov, E.N. Rozenvasser, B.M. Shamrikov, V.M. Shelenkov, R.M. Yusupov, E.Ya. Kesler, and N.A. Levin);
3. Teoriya avtomaticheskogo regulirovaniya (Automatic Regulation Theory), Moscow: Mashinostroenie, 1969. — 606 p. (coauthors A.M. Batkov, Yu.I. Borodin, V.V. Petrov, and A.B. Ioannesian);
4. Dinamika poleta i upravlenie (Flight Dynamics and Control), Moscow: Nauka, 1969. — 360 p.;
5. Stability in Nonlinear Control Systems, Princeton: Princeton University Press, 1961. — 315 p.;
6. Ustoichivost’ nelineinykh reguliruemykh sistem (Stability of Linear Regulated Systems), Moscow: Gostekhizdat, 1955. — 312 p.

These books are presented in the Institute’s database:
https://www.ipu.ru/d7ipu/books_library_grid?combine=Летов

Here is the list of Letov’s papers in Avtomatika i Telemekhanika:

https://www.mathnet.ru/php/search.phtml?jrnid=at&tjrnid=at&wshow=search&option_lang=engM

For their English versions, see the microfilm collection of Automation and Remote Control (1956—1994):
https://archive.org/details/pub_automation-and-remote-control

Articles about A.M. Letov

https://www.mathnet.ru/php/search.phtml?jrnid=at&tjrnid=at&wshow=search&option_lang=eng

Also, see the Wikipedia page devoted to Letov:
https://ru.wikipedia.org/wiki/Летов,_Александр_Михайлович

Scopus Author ID: 6603176167