Hendrik Wade Bode

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Dr. Hendrik Wade Bode

Hendrik Wade Bode (pronounced Boh-dee in English, Boh-dah in Dutch),^[1] (24 December 1905 Madison, Wisconsin – 21 June 1982 Cambridge, Massachusetts) was a gifted researcher, prolific inventor and eloquent and nuanced engineer, author and scientist, an American 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.

In addition, his research impacted many other engineering disciplines and laid the foundation for a diverse array of modern innovations such as computers, robots and mobile phones among others.

Long admired in academic circles worldwide,^[2][3] he is also widely known to modern engineering students mainly for developing the asymptotic magnitude and phase plot that bears his name: Bode plot. His famous asymptotic plot technique, however, was just a small part of his great contribution to science as well as his country.

His research contributions in particular were not only multidimensional but far reaching as well, extending as far as the U.S. space program.^[4][5][6]

[edit] Education: To Graduate School and M.A.

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,^[7] and being a gifted student he rapidly advanced through the Urbana school system to graduate from High School at the age of 14.^[1]

Barely a teenager at 14 and already a high school graduate, he applied for admission to the University of Illinois but was denied because of his age. Decades later, in 1977, the same University, as if to compensate, would grant him an Honorary Sc.D. Degree.^[1]

He eventually applied and was accepted at Ohio State University, where his father also taught, and he received his B.A. degree in 1924, at the young age of 19, and his M.A. Degree in 1926, both in Mathematics.^[8] After receiving his M.A. he remained at his Alma Mater, working as a Teaching Assistant, for an additional year.^[1]

[edit] Early contributions at Bell Labs and Ph.D.

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.^[9] Subsequently, in 1929, he was assigned to the Mathematical Research Group,^[10] 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 Ph.D. in Physics in 1935.^[11]

In 1938 he developed his asymptotic phase and magnitude plots. 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.^[12] 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 is as popular today as it was groundbreaking then.

[edit] World War II and new inventions

[edit] Change of direction

With the inexorable onset of World War II,^[13] Bode turned his sights on the military applications of his Control Systems research, a change of direction that would last in various degrees to the end of his career. He came to the service of his country by working at the National Defense Research Committee (NDRC) Section D-2 funded Director Project at Bell Labs,^[14] developing automatic anti-aircraft control systems, whereby radar information was used to provide data about the location of the enemy aircraft, that was then fed back to the anti-aircraft artillery servomechanisms enabling automatic radar augmented enemy aircraft ballistic tracking,^[15] 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 antiaircraft guns.

[edit] First wireless feedback loop and robot weapons

[edit] Closing the loop

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 optimum amount of time, long enough to fire at the calculated (predicted) coordinates of the target and thus successfully track, i.e. blow up, the target.

[edit] A computer by any other name

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.^[16] 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.^[14][17]

[edit] Shotgun marriage

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,^[4][18] referring to the antiaircraft artillery origins of his historic invention.

[edit] A robot is born

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.

[edit] Working on Fundamental Director Studies: Enter the Future

[edit] Director T-15

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.^[14]

NDRC, the funding agency of this project, was operating under the aegis of the Office of Scientific Research and Development (OSRD).^[19]

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.

[edit] Director T-10 difficulties

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.^[14]

[edit] Director T-15: Tracking the target with new math methods

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.^[14] 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 it is known as the backward difference algorithm.^[20] In addition the Director T-15 operated only in polar 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 it converged on a target twice as fast.^[14]

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,^[21] the operational amplifier based forefather of today's digital computers.

Inventions such as these, ironically, given their military research origins, have had a profound and lasting impact in the civilian domain and have forever altered its landscape.

[edit] Success in the Battlefield

[edit] Anzio and Normandy

The automated anti-aircraft guns that Bode helped develop were successfully used in numerous instances during the war. In February 1944 the 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 thirty nine units were deployed in Normandy to protect the allied invading force against Hitler's Luftwaffe.^[14]

[edit] Clash of the Robots

Perhaps the menace best suited for the design specifications of such an automated artillery system appeared in June 1944. Not surprisingly it was another robot. The German Aeronautical Engineers under the capable stewardship of Wernher von Braun produced a robot of their own; the V-1 flying bomb, an automatically guided bomb and widely considered a precursor of the Cruise missile.^[22][23] Its flight specifications almost perfectly suited the target design criteria of Director T-10, that of an aircraft flying straight and level at constant velocity,^[14] in other words a target nicely fitting the computing capabilities of a linear predictor model such as the Director T-10. Although the Germans did have a trick up their engineering sleeve by making the bomb fly fast and low to evade radar, a technique widely adopted even today. During the London Blitz one hundred Director T-10 assisted 90 mm automated gun units were set up in a perimeter south of London, at the special request of Winston Churchill. The AA units included the SCR-584 radar unit produced by the Radiation Lab at MIT and the proximity fuse mechanism, developed by Merle Tuve and his special Division T at NDRC,^[14] that detonated near the target using a microwave controlled fuse called the VT or variable time fuse, enabling a larger detonation reach envelope and increasing the chances of a successful outcome. Between 18 June and 17 July 1944, 343 V-1 bombs were shot down or 10% of the total V-1 number sent by the Germans and about 20% of the total V-1 bombs shot down. From 17 July to 31 August the automated gun kills rose to 1286 V-1 rockets or 34% of the total V-1 number dispatched from Germany and 50% of the V-1 actually shot down over London.^[14] From these statistics it can be seen that the automated systems that Bode helped design had a considerable impact in crucial battles of World War II. It can also be seen that London at the time of the Blitz became, among other things, the original robot battlefield.

[edit] Synergy with Shannon

In 1945, as the war was winding down, the NDRC was issuing a summary of technical reports as the prelude to its eventual closing down. Inside the volume on Fire Control a special essay titled Data Smoothing and Prediction in Fire-Control Systems, coauthored by Richard B. Blackman, Hendrik Bode, and Claude Shannon, formally introduced the problem of Fire Control as a special case of transmission, manipulation and utilization of intelligence,^[14][17] in other words it modeled the problem in terms of Data and Signal Processing and thus heralded the coming of the information age. Shannon, considered to be the father of information theory, was greatly influenced by this work.^[14] It is clear that the technological convergence of the information age was preceded by the synergy between these scientific minds and their collaborators.

[edit] Further wartime achievements

In 1944 he was placed in charge of the Mathematical Research Group at Bell Laboratories.^[24]

Bode's work on Electronic Communications, especially on filter and equalizer design,^[25] continued during this time and in 1945 it culminated in the publication of his book under the title of Network Analysis and Feedback Amplifier Design,^[26] that is considered a classic in the field of Electronic Telecommunications and was extensively used as a textbook for many graduate programs at various universities as well as for internal training courses at Bell Labs.^[27] He was also the prolific author of many research papers that were published in prestigious scientific and technical journals.

[edit] Presidential Medal for Merit

In 1948 President Harry S. Truman awarded him the Presidential Medal for Merit,^[28] in recognition of his remarkable scientific contributions to the war effort and to the United States of America.^[29]

[edit] Peacetime contributions

[edit] Change of focus

As the war came to an end, his research focus shifted to include not only military but civilian research projects as well. On the military side he continued pursuing ballistic missile research, including research on antiballistic missile defence and associated computing algorithms, and in the civilian domain he concentrated on modern communication theory.

[edit] Progress and eventual twilight in a long career at Bell Labs

In 1952 he was promoted to the level of Director of Mathematical Research at Bell Labs. In 1955 he became Director of Research in the Physical Sciences, and remained there until 1958 when he was promoted again to become one of the two Vice Presidents in charge of Military Development and Systems Engineering, a position he held up to his retirement.^[8]

Pursuing applied research was rewarding in itself, but it also bore fruit in the form of numerous inventions in his name. He held a total of 25 patents in various areas of electrical and communications engineering, including signal amplifiers and artillery control systems.^[1]

He retired from Bell Labs in October 1967, at the age of 61, ending an association that spanned more than four decades and changed the face of many of the core elements of Modern Engineering.

[edit] Harvard

[edit] Gordon McKay

Retirement, however, seemed just like another career move because soon after he was elected to the academically prestigious Gordon McKay Professor of Systems Engineering position at Harvard University, an Ivy League University.^[30][31]

During his tenure there, he pursued research on military decision making algorithms and optimization techniques based on stochastic processes that are considered a precursor of modern fuzzy logic.^[32] He also studied the effects of technology on modern society and taught courses on the same subject, while supervising graduate students at the same time.

[edit] Research Legacy

Although very busy carrying out his professorial duties, he kept a keen eye on leaving his research legacy. He was simultaneously working on a new book that expounded on his extensive experience as a researcher at Bell Labs, which he published in 1971 under the title Synergy: Technical Integration and Technological Innovation in the Bell System.^[33] Using terms easily accessible even to laymen, he analyzed and expanded on technical and philosophical aspects of Systems Engineering as practised at Bell Labs. He explained how seemingly different fields of Engineering were merging into a single unified model, guided by the necessity of the flow of information between system components that transcended previously well defined boundaries and thus he introduced us to a technological paradigm shift. As it is clear from the title of the book as well as its contents, he became one of the early exponents of technological convergence, infometrics and information processing before the terms even existed.

In 1974 he retired for the second time and Harvard awarded him the honorary position of Professor Emeritus. He, nevertheless, kept his office at Harvard and continued working from there, mainly as an advisor to government on policy matters.^[8]

[edit] Academic and Professional Distinctions

Bode's multifaceted contributions to science and to society drew a great number of prestigious Awards and Honours.

[edit] Academic Medals and Awards

In 1969 IEEE awarded him the renowned Edison Medal for "fundamental contributions to the arts of communication, computation and control; for leadership in bringing mathematical science to bear on engineering problems; and for guidance and creative counsel in systems engineering",^[1] a tribute that eloquently summarized the wide spectrum of his innovative contributions to engineering science and applied mathematics as a researcher, and to society as an advisor and professor.

In 1975 ASME awarded him the Rufus Oldenberger Award and in 1979 he became the first recipient of the Control Heritage Award from the American Automatic Control Council.^[1]

Posthumously, in 1989, the IEEE Control Systems Society established the Hendrik W. Bode Lecture Prize in order to: recognize distinguished contributions to control systems science or engineering.^[34]

[edit] Memberships to Academic Organizations and Government Committees

He was also a member or fellow in a number of scientific and engineering societies such as the IEEE, American Physical Society, Society of Industrial and Applied Mathematics etc.^[35] and the illustrious American Academy of Arts and Sciences, an independent American Academy, that is not part of the U.S. National Academies.

In 1957 he was elected member to the National Academy of Sciences,^[36] the oldest and most prestigious U.S. National Academy established at the height of the Civil War, in 1863, by then President Abraham Lincoln.

Hendrik Wade Bode, (see enlargement on left), at the May 26 1958 meeting of the Special Committee on Space Technology, (fourth from the left). Wernher von Braun is at the head of the table facing the camera

[edit] COSPUP

From 1967 to 1971 he served as a member of the Council of the National Academy of Sciences. At the same time he served as the representative of the Academy's Engineering section on the Committee on Science and Public Policy (COSPUP).

Being a deep thinker as well as a lucid writer he significantly contributed to three important COSPUP studies: Basic Research and National Goals (1965), Applied Science and Technological Progress (1967) and Technology: Processes of Assessment and Choice (1969). These studies had the additional distinction of being the first ever to be prepared by the Academy for the Legislative Branch, or more specifically for the Committee on Science and Astronautics of the U.S. House of Representatives,^[8] thus fulfilling the Academy's mandate, under its Charter, as an advisory body to the U.S. Government.

[edit] Special Committee on Space Technology

The predecessor of NASA was NACA. NACA's Special Committee on Space Technology also called the Stever Committee after its chairman, Guyford Stever was a special steering committee that was formed with the mandate to coordinate various branches of the Federal government, private companies as well as universities within the United States with NACA's objectives and also harness their expertise in order to develop a space program.^[5] Committee members included: Bode and Wernher von Braun the father of the US space program.^[4][5]

It is a historical irony that Hendrik Wade Bode, the man who helped develop the robot weapons that brought down the Nazi V-1 flying bombs over London during WWII, was actually serving in the same committee and sitting at the same table as the chief engineer of the V-1, the weapon that terrorised London: Wernher von Braun.^[22][23]

[edit] Engineering Legacy

Bode, despite all the high distinctions he received, both from Academia and Government, did not rest on his laurels. He believed that Engineering, as an Institution, deserved a place in the Pantheon of Academia as much as Science did. With typical Engineering resourcefulness he solved the problem by helping create another Academy.

He is among the founding members and served as a regular member of the National Academy of Engineering,^[37] that was created on December 1964, only the second U.S. National Academy in one hundred and one years since the inception of the first, and which now forms part of the United States National Academies.^[38]

He thus helped sublimate the age old debate of Engineers versus Scientists and elevated it into a debate between Academics. This subtle, yet powerfully symbolic accomplishment, constitutes a compelling part of his legacy.

Hendrik Wade Bode died at the age of 76, at his home in Cambridge, Mass.

[edit] Books published

• Network Analysis and Feedback Amplifier Design (Van Nostrand, 1945)

• Synergy: Technical Integration and Technological Innovation in the Bell System (Bell Laboratories, 1971)

[edit] References

[edit] Cited References

[edit] General References