Hendrik Wade Bode ( , ;Van Valkenburg, M. E. University of Illinois at Urbana-Champaign, "In memoriam: Hendrik W. Bode (1905-1982)", IEEE Transactions on Automatic Control, Vol. AC-29, No 3., March 1984, pp. 193–194. Quote: "Something should be said about his name. To his colleagues at Bell Laboratories and the generations of engineers that have followed, the pronunciation is boh-dee. The Bode family preferred that the original Dutch be used as boh-dah." December 24, 1905 – June 21, 1982) was an American engineer, researcher, inventor, author and scientist, of Dutch ancestry. As a pioneer of modern control theory and electronic telecommunications, he revolutionized both the content and methodology of his chosen fields of research. His synergy with Claude Shannon, the father of information theory, laid the foundations for the technological convergence of the Information Age.
He made important contributions to the design, guidance and control of anti-aircraft systems during World War II. He helped develop the automatic artillery weapons that defended London from the V-1 flying bombs during WWII. After the war, Bode, along with his wartime rival Wernher von Braun—who was the developer of the V-2 rocket, and, later, the father of the US space program—served as members of the National Advisory Committee for Aeronautics (NACA), the predecessor of NASA. During the Cold War, he contributed to the design and control of missiles and anti-ballistic missiles.
Bode also made important contributions to control systems theory and mathematical tools for the analysis of stability of linear systems, inventing Bode plots, gain margin and phase margin. His contributions to the field led to him being described as one of the great engineering philosophers of his era by the National Academy of Engineering.Memorial tributes By National Academy of Engineering p. 54
Education Bode was born in Madison, Wisconsin. His father was a professor of education, and a faculty member at the University of Illinois at Urbana-Champaign. He entered Leal Elementary School and rapidly advanced through the school system to graduate from high school at the age of 14.Leal Elementary School
Immediately after graduation from high school he applied for admission to the University of Illinois but was denied because of his age. Decades later, in 1977, the same university would grant him an honorary Sc.D. degree.
He eventually applied and was accepted at Ohio State University, where his father also taught, and he received his BA degree in 1924, at age 19, and his M.A. degree in 1926, both in Mathematics.National Academies Press Tribute by Harvey Brooks. After receiving his M.A. he remained at his alma mater, working as a teaching assistant, for an additional year.
Early contributions at Bell Labs and Ph.D. Bode was hired directly from graduate school by Bell Labs in New York City, where he began his career as designer of electronic filters and equalizers.Filter Design Subsequently, in 1929, he was assigned to the Mathematical Research Group,Mathematical Research Group at Bell Laboratories via Internet Archive where he was recognized for his aptitude in research related to electronic networks theory and its application to telecommunications. Sponsored by Bell Laboratories he reentered graduate school, this time at Columbia University, and he successfully completed his PhD in physics in 1935.
In 1938, he developed asymptotic phase and magnitude plots, now known as Bode plots, which displayed the frequency response of systems clearly. His work on automatic (feedback) control systems introduced innovative methods to the study of system stability that enabled engineers to investigate time-domain stability using the frequency-domain concepts of gain and phase margin, the study of which was aided by his now famous plots. In essence, his method made stability transparent to both the time and frequency domains and, furthermore, his frequency-domain-based analysis was much faster and simpler than the traditional time-domain-based method. This provided engineers with a fast and intuitive stability analysis and system design tool that remains widely used today. He, along with Harry Nyquist, also developed the theoretical conditions applicable to the stability of amplifier circuits.
World War II and new inventions
Defense research With the outbreak of World War II, Bode began researching military applications for his control systems research in order to support the U.S. war effort. Much of his work during this period was conducted as part of the National Defense Research Committee (NDRC) funded Director Project at Bell Labs.Mindell, David A., "Automation's Finest Hour: Bell Labs and Automatic Control in World War II", IEEE Control Systems, December 1995, pp. 72–80. This project developed automatic anti-aircraft control systems which used radar information to provide targetting information to anti-aircraft artillery systems which could automatically track the ballistic trajectory of airborne targets. Crucially, this first-of-its-kind target tracking system was able to wirelessly transmit target data and make use of director T-10 military computers to make predictive calculations about where a target would be by the time anti-aircraft artillery reached it in flight. The artillery guns would automatically adjust based on this statistical analysis and would be in position to fire when triggered by a human operator.From Communications Engineering to Communications Science: Cybernetics and Information Theory in the United States, France, and the Soviet Union by David Mindell, Jérôme Segal, Slava Gerovitch pp. 1–19. (From the book: Science and Ideology: A Comparative History, sous la direction de Mark Walker, Routledge, London, 2003, pp. 66–95.)
Bode would go on to describe the creation of this integrated wireless signals and artillery servomechanism system as "a sort of shotgun marriage forced upon us by the pressures of military problems in World War II."U.K. Gonville & Caius College Engineering student tribute. .
Working on director studies Bode, in addition, applied his extensive skills with feedback amplifiers to design the target data smoothing and position predictor networks of an improved model of director T-10, called the director T-15. The work on director T-15 was undertaken under a new project at Bell Labs called Fundamental Director Studies in cooperation with the NDRC under the directorship of Walter McNair.
NDRC, the funding agency of this project, was operating under the aegis of the Office of Scientific Research and Development (OSRD).
His NDRC-funded research at Bell Labs under the section D-2 (Control Systems section) contract eventually led to other important developments in related fields and laid the cornerstone for many present-day inventions. In the field of control theory, for example, it aided in the further development of servomechanism design and control, a crucial component of modern robotics. The development of wireless data communications theory by Bode led to later inventions such as mobile phones and wireless networking.
The reason for the new project was that director T-10 encountered difficulties in calculating the target velocity by differentiating the target position. Due to discontinuities, variations and noise in the radar signal, the position derivatives sometimes fluctuated wildly, and this caused erratic motion in the servomechanisms of the gun because their control signal was based on the value of the derivatives. This could be mitigated by smoothing or averaging out the data, but this caused delays in the feedback loop that enabled the target to escape. As well, the algorithms of director T-10 required a number of transformations from Cartesian (rectangular) to polar coordinates and back to Cartesian, a process that introduced additional tracking errors.
Bode designed the velocity computing networks of director T-15 by applying a finite difference method instead of differentiation. Under this scheme the target positional coordinates were stored in a mechanical memory, usually a potentiometer or a cam. The velocity was then calculated by taking the difference between the coordinates of the current position and the coordinates of the previous reading that were stored in memory and dividing by the difference of their respective times. This method was more robust than the differentiation method, and it also smoothed out signal disturbances, since the finite time-step size was less sensitive to random signal impulses (spikes). It also introduced for the first time an algorithm better suited to modern digital signal processing theory rather than to the classical calculus-based analog signal processing approach that was followed then. Not coincidentally it is an integral part of modern digital control theory and digital signal processing and is known as the backward difference algorithm.Eric W. Weisstein. "Backward Difference". From MathWorld—A Wolfram Web Resource. In addition, the director T-15 operated only in rectangular coordinates, thus eliminating coordinate-transformation-based errors. These design innovations paid performance dividends, and the director T-15 was twice as accurate as its predecessor and converged on a target twice as fast.
The fire control algorithm implementation of his artillery design research and his extensive work with feedback amplifiers advanced the state of the art in computational methods and led to the eventual development of the electronic analog computer,Analog Computer. . the operational amplifier based alternative of today's digital computers.
Inventions such as these, despite their military research origins, have had a profound and lasting impact in the civilian domain.
Military uses
Anzio and Normandy The automated anti-aircraft guns that Bode helped develop were successfully used in numerous instances during the war. In February 1944, an automated fire control system based on the earlier version of the director T-15, called the director T-10 by Bell Labs or director M-9 by the military, saw action for the first time in Anzio, Italy, where it helped down over one hundred enemy aircraft. On D-day 39 units were deployed in Normandy to protect the allied invading force against Hitler's Luftwaffe.
Use against the V-1 flying bomb