Hendrik Wade Bode

Hendrik Wade Bode (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, 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.

He 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.

Bode was one of the great engineering philosophers of his era.

Long respected in academic circles worldwide, he is also widely known to modern engineering students mainly for developing the asymptotic magnitude and phase plot that bears his name, the Bode plot.

His research contributions in particular were not only multidimensional but also far reaching, extending as far as the U.S. space program.

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 by the time young Hendrik was ready for elementary school.

He entered Leal Elementary School and rapidly advanced through the Urbana school system to graduate from high school at the age of 14.

Immediately after graduation from high school he applied for admission to the University of Illinois but was denied because of his age.

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.

After receiving his M.A. he remained at his alma mater, working as a teaching assistant, for an additional year.

Fresh from graduate school he was promptly hired by Bell Labs in New York City, where he began his career as designer of electronic filters and equalizers.

Subsequently, in 1929, he was assigned to the Mathematical Research Group, where he excelled 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.

With the inexorable onset of World War II, Bode turned his sights on the military applications of his control systems research, a change of direction that would last in varying degree to the end of his career.

He came to the service of his country by working on the Director Project at Bell Labs (funded by National Defense Research Committee (NDRC) Section D-2), developing automatic anti-aircraft control systems, whereby radar information was used to provide data about the location of the enemy aircraft, which was then fed back to the anti-aircraft artillery servomechanisms, enabling automatic, radar-augmented enemy aircraft ballistic tracking, in other words, automatic shooting down of enemy aircraft with the help of radar.

The servomotors used were both electrically and hydraulically powered, the latter being used mainly for positioning the heavy anti-aircraft guns.

The radar signal was locked on target, and its data was wirelessly transmitted to a ground receiver that was connected to the artillery servomechanism feedback control system, causing the servo to accurately modify its angular position and maintain it for an optimal amount of time, long enough to fire at the calculated (predicted) coordinates of the target and thus successfully track the target.

The prediction of the coordinates was the function of director T-10, a form of electrical computer so named because it was used to direct the positioning of the gun with respect to the airborne target.

It also calculated the target average velocity based on the location information provided by the radar and predicted the future target location based on its assumed flightpath equation, usually a linear function of time.

This system functioned as an early version of the modern anti-ballistic missile defence model.

Statistical analysis was also employed to aid in the computation of the exact position of the enemy aircraft and to smooth the data acquired from the target due to signal fluctuations and noise effects.

Bode therefore realized the first wireless data feedback loop in the history of automatic control systems by combining wireless data communications, electrical computers, statistics principles and feedback control systems theory.

He showed his dry sense of humour by calling this multidisciplinary linkage a shotgun marriage, referring to the antiaircraft artillery origins of his historic invention, saying: "This, I said, was a sort of shotgun marriage forced upon us by the pressures of military problems in World War II."

He also described it further as "a sort of 'shotgun marriage' between two incompatible personalities" and characterised the product of that linkage as a "son of shotgun marriage".

The product of this "marriage", i.e. the automated artillery gun, can also be considered as a robot weapon.

Its function required to process data that was wirelessly transmitted to its sensors and make a decision based on the data received using its onboard computer about its output defined as its angular position and the timing of its firing mechanism.

In this model we can see all the elements of later concepts such as data processing, automation, artificial intelligence, cybernetics, robotics etc.

Decades later, in 1977, the same university would grant him an honorary Sc.D. degree.