Harold Locke Hazen (August 1, 1901 – February 21, 1980) was an American electrical engineer. He contributed to the theory of servomechanisms and

feedback Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause and effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handle ...

control system A control system manages, commands, directs, or regulates the behavior of other devices or systems using control loops. It can range from a single home heating controller using a thermostat controlling a domestic boiler to large industrial ...

s. In 1924 under the lead of

Vannevar Bush Vannevar Bush ( ; March 11, 1890 – June 28, 1974) was an American engineer, inventor and science administrator, who during World War II, World War II headed the U.S. Office of Scientific Research and Development (OSRD), through which almo ...

, Hazen and his fellow undergraduate Hugh H. Spencer built a prototype AC network analyzer, a special-purpose analog computer for solving problems in interconnected AC power systems. Hazen also worked with Bush over twenty years on such projects as the mechanical

differential analyzer The differential analyser is a mechanical analogue computer designed to solve differential equations by integration, using wheel-and-disc mechanisms to perform the integration. It was one of the first advanced computing devices to be used ope ...

. This early work, and the binary algebra used, would be foundational to the emergence of electromechanical and digital computers in later decades.

Education and career

Hazen was born at

Philo, Illinois Philo is a village about nine miles south of Urbana in Champaign County, Illinois, United States. The population was 1,392 at the 2020 census. Geography Philo is located three miles south of Urbana township and six miles south of the city of U ...

in 1901. Several years later, his parents moved to

Three Rivers, Michigan Three Rivers is a city in St. Joseph County, Michigan. The population was 7,973 at the time of the 2020 census. Three Rivers derives its name from its location at the confluence of the St. Joseph River and two tributaries, the Rocky and Porta ...

, where he graduated from high school. He went to

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of moder ...

(MIT) as an undergraduate student in 1920. When he graduated from MIT in 1924, he briefly worked for

General Electric General Electric Company (GE) was an American Multinational corporation, multinational Conglomerate (company), conglomerate founded in 1892, incorporated in the New York (state), state of New York and headquartered in Boston. Over the year ...

. In 1925 he returned to MIT as research assistant and instructor in 1926. he obtained his master's degree in 1929 and his Doctor of Science degree in 1931. In 1934 Hazen published two papers on the theory and design of

servomechanism In mechanical and control engineering, a servomechanism (also called servo system, or simply servo) is a control system for the position and its time derivatives, such as velocity, of a mechanical system. It often includes a servomotor, and ...

s which provided clear descriptions of the operation of servos and a design methodology. After 1937 Hazen became increasingly involved in teaching and administrative work, becoming Head of department in 1938 and serving for fourteen years. From December 1942 until 1946 he was head of Division 7, "Fire Control", of the NDRC ( National Defence Research Committee). In 1952 he became Dean of the MIT Graduate School until his retirement in 1967. In 1928 he was married to Katherine Pharis Salisbury (1905-2003), eldest child of

Bert E. Salisbury Bert Eugene Salisbury (May 28, 1870 – October 20, 1946), was appointed president of Onondaga Pottery Company (O.P.Co.), later renamed to Syracuse China in 1913, and president and general manager of Pass & Seymour, Inc. in Solvay, New York, Sol ...

and Mary Patterson Pharis. They had two sons and two daughters. In his later life Dr. Hazen promoted engineering education programs both in the United States and internationally. Harold Hazen died in

Belmont, Massachusetts Belmont is a town in Middlesex County, Massachusetts, United States. It is a western suburb of Boston and is part of the Greater Boston metropolitan area. As of the 2020 U.S. census, its population was 27,295, an increase of 10.4% from 2010. H ...

, in February 1980.

Gordon S. Brown Gordon Stanley Brown (August 30, 1907 in Australia – August 23, 1996 in Tucson, Arizona) was a professor of electrical engineering at MIT. He originated many of the concepts behind automatic-feedback control systems and the numerical control of ...

, ''Harold Locke Hazen, 1901-1980 '', ''Annals of the History of Computing'', 1981 Vol. 3, Issue: 1 Pp. 4-12 Dr. Hazen and his wife resided in Belmont, Massachusetts, except for living in Columbus, Ohio during the 1934–1935 academic year when he was named the first exchange professor between MIT and Ohio State University.

References

1901 births 1980 deaths 20th-century American engineers Massachusetts Institute of Technology faculty {{US-engineer-stub