Henry J. Kelley (1926-1988) was

Christopher C. Kraft Christopher Columbus Kraft Jr. (February 28, 1924 – July 22, 2019) was an American aerospace and NASA engineer who was instrumental in establishing the agency's Mission Control Center and shaping its organization and culture. His protégé ...

Professor of

Aerospace Aerospace is a term used to collectively refer to the atmosphere and outer space. Aerospace activity is very diverse, with a multitude of commercial, industrial and military applications. Aerospace engineering consists of aeronautics and astrona ...

and

Ocean Engineering Marine engineering is the engineering of boats, ships, submarines, and any other marine vessel. Here it is also taken to include the engineering of other ocean systems and structures – referred to in certain academic and professional circl ...

at the

Virginia Polytechnic Institute Virginia Tech (formally the Virginia Polytechnic Institute and State University and informally VT, or VPI) is a Public university, public Land-grant college, land-grant research university with its main campus in Blacksburg, Virginia. It also ...

. He produced major contributions to

control theory Control theory is a field of mathematics that deals with the control of dynamical systems in engineered processes and machines. The objective is to develop a model or algorithm governing the application of system inputs to drive the system to a ...

, especially in

aeronautical engineering Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecraft. It has two major and overlapping branches: Aeronautics, aeronautical engineering and Astronautics, astronautical engineering. A ...

and flight

optimization Mathematical optimization (alternatively spelled ''optimisation'') or mathematical programming is the selection of a best element, with regard to some criterion, from some set of available alternatives. It is generally divided into two subfi ...

.E. M. Cliff (1989)
"Editorial: In Memory of Henry J. Kelley"
''Journal Of Optimization Theory And Applications'': Vol. 60, No. 1, January 1989 In 1948, he received a Bachelor of Science from

NYU New York University (NYU) is a private university, private research university in New York City. Chartered in 1831 by the New York State Legislature, NYU was founded by a group of New Yorkers led by then-United States Secretary of the Treasu ...

in aeronautical engineering, and began to work for

Grumman Aircraft The Grumman Aircraft Engineering Corporation, later Grumman Aerospace Corporation, was a 20th century American producer of military and civilian aircraft. Founded on December 6, 1929, by Leroy Grumman and his business partners, it merged in 1994 ...

in the same year. His studies continued as a part-time student leading to a Master of Science in mathematics (1951) and to the Sc.D. in aeronautical engineering (1958). In 1963, he left Grumman (as Assistant Chief of the Research Department) and founded Analytical Mechanics Associates with two partners. In 1978, he became a professor in the Aerospace and Ocean Engineering Department at the

. His paper o
"Gradient Theory of Optimal Flight Paths"
(1960)Henry J. Kelley (1960)
"Gradient theory of optimal flight paths"
''Ars Journal'', 30(10), 947-954
Online
/ref> is considered a major contribution to the field. In the context of control theory, Kelley derived basics of

backpropagation In machine learning, backpropagation (backprop, BP) is a widely used algorithm for training feedforward neural network, feedforward artificial neural networks. Generalizations of backpropagation exist for other artificial neural networks (ANN ...

Stuart Dreyfus A native of Terre Haute, Indiana, Stuart E. Dreyfus is professor emeritus at University of California, Berkeley in the Industrial Engineering and Operations Research Department. While at the Rand Corporation he was a programmer of the JOHNNIAC com ...

(1990)
"Artificial Neural Networks, Back Propagation and the Kelley-Bryson Gradient Procedure"
''J. Guidance, Control and Dynamics'', 1990.

Jürgen Schmidhuber Jürgen Schmidhuber (born 17 January 1963) is a German computer scientist most noted for his work in the field of artificial intelligence, deep learning and artificial neural networks. He is a co-director of the Dalle Molle Institute for Artif ...

(2015)
"Deep Learning"
''Scholarpedia'', 10(11):32832
Section on Backpropagation
/ref> now widely used for

machine learning Machine learning (ML) is a field of inquiry devoted to understanding and building methods that 'learn', that is, methods that leverage data to improve performance on some set of tasks. It is seen as a part of artificial intelligence. Machine ...

and

artificial neural networks Artificial neural networks (ANNs), usually simply called neural networks (NNs) or neural nets, are computing systems inspired by the biological neural networks that constitute animal brains. An ANN is based on a collection of connected unit ...

. Kelley received NYU's Founder's Day Award in 1959, the IAS New York Section Award in 1961, the AIAA Guidance and Control of Flight Award in 1973, and the AIAA Pendray Award in 1979. He was a Fellow of the AIAA, and member of the AAS, the IEEE and SIAM, and founder and first chairman of IFAC's Mathematics of Control Committee.

Notes

1926 births 1988 deaths 20th-century American mathematicians Fellows of the Society for Industrial and Applied Mathematics Fellows of the American Institute of Aeronautics and Astronautics New York University alumni Control theorists Virginia Tech faculty {{US-mathematician-stub