Differential analyser
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The differential analyser is a mechanical analogue computer designed to solve differential equations by integration, using wheel-and-disc mechanisms to perform the integration.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }} Archived</ref> It was one of the first advanced computing devices to be used operationally.<ref>Template:Cite encyclopedia</ref> In addition to the integrator devices, the machine used an epicyclic differential mechanism to perform addition or subtraction - similar to that used on a front-wheel drive car, where the speed of the two output shafts (driving the wheels) may differ but the speeds add up to the speed of the input shaft. Multiplication/division by integer values was achieved by simple gear ratios; multiplication by fractional values was achieved by means of a multiplier table, where a human operator would have to keep a stylus tracking the slope of a bar. A variant of this human-operated table was used to implement other functions such as polynomials.
HistoryEdit
Research on solutions for differential equations using mechanical devices, discounting planimeters, started at least as early as 1836, when the French physicist Gaspard-Gustave Coriolis designed a mechanical device to integrate differential equations of the first order.<ref>Template:Cite journal</ref>
The first description of a device which could integrate differential equations of any order was published in 1876 by James Thomson, who was born in Belfast in 1822, but lived in Scotland from the age of 10.<ref>Template:Cite journal Reprinted in Template:Cite book</ref> Though Thomson called his device an "integrating machine", it is his description of the device, together with the additional publication in 1876 of two further descriptions by his younger brother, Lord Kelvin, which represents the invention of the differential analyser.<ref>Template:Cite journal. Lord Kelvin's descriptions: Template:Cite journal Template:Cite journal</ref>
One of the earliest practical uses of Thomson's concepts was a tide-predicting machine built by Kelvin starting in 1872–3. On Lord Kelvin's advice, Thomson's integrating machine was later incorporated into a fire-control system for naval gunnery being developed by Arthur Pollen, resulting in an electrically driven, mechanical analogue computer, which was completed by about 1912.<ref>Template:Cite book</ref> Italian mathematician Ernesto Pascal also developed integraphs for the mechanical integration of differential equations and published details in 1914.<ref>Template:Cite book See also Integraph.</ref>
However, the first widely practical general-purpose differential analyser was constructed by Harold Locke Hazen and Vannevar Bush at MIT, 1928–1931, comprising six mechanical integrators.<ref>Karl L. Wildes and Nilo A. Lindgren, A Century of Electrical Engineering and Computer Science at MIT, 1882-1982 (Cambridge, Massachusetts: MIT Press, 1985), pages 90-92.</ref><ref>Template:Cite journal. Hartree, D.R. (September 1940), op. cit.</ref><ref>Bush's differential analyser used mechanical integrators. The output of each integrator was intended to drive other parts of the machine; however, the output was too feeble to do so. Hazen recognized that a "torque amplifier", which had been invented in 1925 by Henry W. Nieman and which was intended to allow workers to control heavy machinery, could be used to provide the necessary power. See: Stuart Bennett, A History of Control Engineering 1930-1955 (London, England: Peter Peregrinus Ltd., 1993), page 103. See also Nieman's U.S. patents: (1) "Servo mechanism", U.S. patent no. 1,751,645 (filed: 28 January 1925; issued: 25 March 1930); (2) "Servo mechanism", U.S. patent no. 1,751,647 Template:Webarchive (filed: 8 January 1926; issued: 25 March 1930); (3) "Synchronous amplifying control mechanism", U.S. patent no. 1,751,652 Template:Webarchive (filed: 8 January 1926; issued: 25 March 1930).</ref> In the same year, Bush described this machine in a journal article as a "continuous integraph".<ref>Template:Cite journal.</ref> When he published a further article on the device in 1931, he called it a "differential analyzer".<ref>Template:Cite journal.</ref> In this article, Bush stated that "[the] present device incorporates the same basic idea of interconnection of integrating units as did [Lord Kelvin's]. In detail, however, there is little resemblance to the earlier model." According to his 1970 autobiography, Bush was "unaware of Kelvin’s work until after the first differential analyzer was operational."<ref>Robinson, Tim (June 2005), op. cit., citing Template:Cite journal.</ref> Claude Shannon was hired as a research assistant in 1936 to run the differential analyzer in Bush's lab.<ref>Template:Cite book</ref>
Douglas Hartree of Manchester University brought Bush's design to England, where he constructed his first "proof of concept" model with his student, Arthur Porter, during 1934. As a result of this, the university acquired a full-scale machine incorporating four mechanical integrators in March 1935, which was built by Metropolitan-Vickers, and was, according to Hartree, "[the] first machine of its kind in operation outside the United States".<ref>Robinson, Tim (June 2005), op. cit., Hartree, D.R. (September 1940), op. cit. Hartree and Porter wrote about the model in their paper Template:Cite journal.</ref> During the next five years three more were added, at Cambridge University, Queen's University Belfast, and the Royal Aircraft Establishment in Farnborough.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }} Includes summaries of "Meccano Differential Analyzers" and "Full Scale Differential Analyzers".</ref> One of the integrators from this proof of concept is on display in the History of Computing section of the Science Museum in London, alongside a complete Manchester machine.
In Norway, the locally built Oslo Analyser was finished during 1938, based on the same principles as the MIT machine. This machine had 12 integrators, and was the largest analyser built for a period of four years.<ref>Template:Cite journal</ref>
In the United States, further differential analysers were built at the Ballistic Research Laboratory in Maryland and in the basement of the Moore School of Electrical Engineering at the University of Pennsylvania during the early 1940s.<ref>Randell, Brian (ed.), The Origins of Digital Computers Selected Papers (3rd edition, 1982), Berlin, Heidelberg, New York: Springer-Verlag. p. 297. Google Books. Retrieved 25 July 2010.</ref> The latter was used extensively in the computation of artillery firing tables prior to the invention of the ENIAC, which, in many ways, was modelled on the differential analyser.<ref>Bunch, B. & Hellemans, A., The History of Science and Technology: A Browser's Guide to the Great Discoveries, Inventions, and the People who Made Them, from the Dawn of Time to Today (2004), New York: Houghton Mifflin, p. 535. Google Books. Retrieved 25 July 2010.</ref> Also in the early 1940s, with Samuel H. Caldwell, one of the initial contributors during the early 1930s, Bush attempted an electrical, rather than mechanical, variation, but the digital computer built elsewhere had much greater promise and the project ceased.<ref>Template:Cite journal</ref> In 1947, UCLA installed a differential analyser built for them by General Electric at a cost of $125,000.<ref name=UCLADA>Template:Cite magazine</ref> By 1950, this machine had been joined by three more.<ref name=UCLA4DA>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The UCLA differential analyzer appeared in 1950's Destination Moon, and the same footage in 1951's When Worlds Collide, where it was called "DA". A different shot appears in 1956's Earth vs. the Flying Saucers.
At Osaka Imperial University (present-day Osaka University) around 1944, a complete differential analyser machine was developed (illustrated) to calculate the movement of an object and other problems with mechanical components, and then draws graphs on paper with a pen. It was later transferred to the Tokyo University of Science and has been displayed at the school's Museum of Science in Shinjuku Ward. Restored in 2014, it is one of only two still operational differential analyzers produced before the end of World War II.<ref name="KABATA">Template:Citation</ref>
In Canada, a differential analyser was constructed at the University of Toronto in 1948 by Beatrice Helen Worsley, but it appears to have had little or no use.<ref>Template:Cite journal For more on Beatrice Worsley, see UTEC.</ref>
A differential analyser may have been used in the development of the bouncing bomb, used to attack German hydroelectric dams during World War II.<ref>Irwin, William (2009-07). Op. cit. "It is rumoured that a differential analyser was used in the development of the "bouncing bomb" by Barnes Wallis for the "Dam Busters" attack on the Ruhr valley hydroelectric dams in WW2. This was first mentioned in MOTAT [New Zealand] literature in 1973. However after extensive enquiries and literature searches over the last few years, no evidence can be found that the [differential analyser held by MOTAT Template:Webarchive, nor any other differential analyser, was used for this purpose. Considering the secrecy surrounding war time activities at the time it could still be possible, but most people from that era are now deceased. Two remaining personalities still alive from that era were consulted, namely Arthur Porter and Maurice Wilkes, but neither could substantiate the rumour."</ref> Differential analysers have also been used in the calculation of soil erosion by river control authorities.<ref>Template:Citation.</ref>
The differential analyser was eventually rendered obsolete by electronic analogue computers and, later, digital computers.
Use of MeccanoEdit
The model differential analyser built at Manchester University in 1934 by Douglas Hartree and Arthur Porter made extensive use of Meccano parts: this meant that the machine was less costly to build, and it proved "accurate enough for the solution of many scientific problems".<ref name=CamDA>Template:Harv,{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> A similar machine built by J.B. Bratt at Cambridge University in 1935 is now in the Museum of Transport and Technology (MOTAT) collection in Auckland, New Zealand.<ref name=CamDA/> A memorandum written for the British military's Armament Research Department in 1944 describes how this machine had been modified during World War II for improved reliability and enhanced capability, and identifies its wartime applications as including research on the flow of heat, explosive detonations, and simulations of transmission lines.<ref>Cairns, W. J., Crank, J., & Lloyd, E. C. Some Improvements in the Construction of a Small Scale Differential Analyser and a Review of Recent Applications, Armament Research Department Theoretical Research Memo. No. 27/44, 1944 (see {{#invoke:citation/CS1|citation |CitationClass=web }}). The memorandum is now in The National Archives, UK:
{{#invoke:citation/CS1|citation |CitationClass=web }} For the "Armament Research Department", see Fort Halstead, and cf. the entry for 1944 in {{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
It has been estimated, by Garry Tee that "about 15 Meccano model Differential Analysers were built for serious work by scientists and researchers around the world".<ref>Irwin, William (2009-07). Op. cit. "It is estimated by Garry Tee of Auckland University that about 15 Meccano model Differential Analysers were built for serious work by scientists and researchers around the world." For Garry Tee, see {{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
See alsoEdit
NotesEdit
BibliographyEdit
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- Worsley, Beatrice Helen (1947). A mathematical survey of computing devices with an appendix on an error analysis of differential analyzers (Master's Thesis, MIT).
- Crank, J. (1947). The Differential Analyser, London: Longmans, Green (this is the only book that describes how to set up and operate a mechanical differential analyser).
- MacNee, A.B. (1948). An electronic differential analyzer (RLE, Technical Report 90, MIT. Note that this paper describes a very early electronic analogue computer, not a mechanical differential analyser: it is included because the author clearly felt that the only way to introduce such an innovation was to describe it as an "electronic differential analyser").