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Feedback: LEDE edit

 
"...'feedback' exists between two parts when each affects the other."[1]: 53, §4/11 

Feedback is the return of information about a system or process that may effect a change in the process, for example, the regulation or optimization of performance.[2] "Feedback" originally referred to the action of feeding the output of a process back to the input[], and "feedback" is still used in that sense in some disciplines such as control theory.[3]

Subsequent authors defined feedback more generally in terms of circular causality[4][1]. When components of a system form part of a chain of cause-and-effect that forms a circuit or loop, the system is said to "feed back" into itself.

The term "feedback" is also used as an abbreviation for:

  • Feedback signal – the embodiment of feedback information in some form: electrical, neural, mechanical, chemical etc.
  • Feedback mechanism – the action or means used to act upon feedback information
  • Feedback loop – the closed path made up of the system itself and the path that transmits the feedback about the system from its origin (for example, a sensor) to its destination (for example, an actuator).

Negative Feedback: HISTORY edit

Self-regulating mechanisms have existed since antiquity, and were used to maintain a constant level in the reservoirs of water clocks as early as 200 BCE.[5] Cornelius Drebbel had built thermostatically-controlled incubators and ovens in the early 1600s,[6] James Watt employed centrifugal governors to regulate the speed of steam engines, and James Clerk Maxwell in 1868 described "component motions" associated with these governors that lead to a decrease in a disturbance or the amplitude of an oscillation.[7]

The general idea of feedback was well established by the 1920s, in reference to a means of boosting the gain of an electronic amplifier.[8] Friis and Jensen described this action as "positive feedback" and made passing mention of a contrasting "negative feed-back action" in 1924.[9] Harold Stephen Black detailed the use of negative feedback in electronic amplifiers in 1934, where he defined negative feedback as a type of coupling that reduced the gain of the amplifier, in the process greatly increasing its stability.[10] Nyquist and Bode built on Black’s work to develop a theory of amplifier stability, but chose to define "negative" as applying to the polarity of the loop (rather than the effect on the gain) which gave rise to confusion over basic definitions.[8]

Early researchers in the area of cybernetics generalised the idea of negative feedback to cover any goal-seeking or purposeful behavior.[11]

All purposeful behavior may be considered to require negative feed-back. If a goal is to be attained, some signals from the goal are necessary at some time to direct the behavior.

Cybernetics pioneer Norbert Wiener helped to formalize the concepts of feedback control, defining feedback in general as "the chain of the transmission and return of information",[4] and negative feedback as the case when:

The information fed back to the control center tends to oppose the departure of the controlled from the controlling quantity...: 97 

While the view of feedback as any "circularity of action" helped to keep the theory simple and consistent, Ashby pointed out that it can clash with definitions in other fields that require "a more tangible connexion."[12]

[The] practical experimenters and constructors ... want to use the word to refer, when some forward effect from P to R can be taken for granted, to the deliberate condition of some effect back from R to P by some connexion that is physically or materially evident.: 54 

Further confusion arose after BF Skinner introduced the terms positive and negative reinforcement,[13] both of which can be considered negative feedback mechanisms in the sense that they try to minimize deviations from the desired behavior.[14] In the context of human behaviour, Herold and Greller used the term "negative" to refer to the valence of the feedback: that is, cases where a subject receives an evaluation with an unpleasant emotional connotation.[15]

A common theme for the 10 items [in the feedback analysis] is their valence, all representing negative feedback. Examples are being removed from a job or suffering some adverse consequence due to poor performance or receiving more or less direct indications of dissatisfaction from co-workers or the supervisor.

To reduce confusion, some authors have used alternative terms such as degenerative[16], self-correcting,[17] balancing,[18] or discrepancy-reducing[19] in place of "negative".


References edit

  1. ^ a b W. Ross Ashby (1957). An introduction to cybernetics (PDF). Chapman & Hall. See also: Google books, ISBN 9781258693817
  2. ^ Christopher G. Morris, ed. (1992). Academic Press Dictionary of Science and Technology. Academic Press Inc. p. 812. ISBN 0122004000.
  3. ^ United States Naval Academy, "Elements of Feedback Control", Chapter 3, Fundamentals of Naval Weapons Systems (accessed August 29, 2014)
  4. ^ a b Norbert Wiener "Cybernetics, or control and communication in the animal and the machine". Cambridge, Massachusetts: The Technology Press; New York: John Wiley & Sons, Inc., 1948.
  5. ^ Breedveld, Peter C. "Port-based modeling of mechatronic systems." Mathematics and Computers in Simulation 66.2 (2004): 99-128.
  6. ^ "Tierie, Gerrit. Cornelis Drebbel. Amsterdam: HJ Paris, 1932" (PDF). Retrieved 2013-05-03.
  7. ^ Maxwell, James Clerk (1868). "On Governors" (PDF). 16. Proceedings of the Royal Society of London: 270–283. {{cite journal}}: Cite journal requires |journal= (help)
  8. ^ a b David A. Mindell (2002). Between Human and Machine : Feedback, Control, and Computing before Cybernetics. Baltimore, MD, USA: Johns Hopkins University Press.
  9. ^ Friis,H.T., and A.G.Jensen. "High Frequency Amplifiers" Bell System Technical Journal 3 (April 1924):181-205.
  10. ^ Black, H.S. (January 1934). "Stabilized Feedback Amplifiers". Bell System Tech. J. 13 (1). American Telephone & Telegraph: 1–18.
  11. ^ Rosenblueth, Arturo, Norbert Wiener, and Julian Bigelow. "Behavior, purpose and teleology." Philosophy of science 10.1 (1943): 18-24.
  12. ^ W. Ross Ashby, "An introduction to cybernetics", Chapman & Hall, London, 1956. - books.google.com Internet (1999)
  13. ^ BF Skinner, The Experimental Analysis of Behavior, American Scientist, Vol. 45, No. 4 (SEPTEMBER 1957), pp. 343-371
  14. ^ Arkalgud Ramaprasad, On The Definition of Feedback, Behavioral Science, Volume 28, Issue 1. 1983. Accessed on 16-03-2012.
  15. ^ Herold, David M., and Martin M. Greller. "Research Notes. Feedback: The definition of a construct." Academy of management Journal 20.1 (1977): 142-147.
  16. ^ Hermann A Haus and Richard B. Adler, Circuit Theory of Linear Noisy Networks, MIT Press, 1959
  17. ^ Peter M. Senge (1990). The Fifth Discipline: The Art and Practice of the Learning Organization. New York: Doubleday. p. 424. ISBN 0-385-26094-6.
  18. ^ John D.Sterman, Business Dynamics: Systems Thinking and Modeling for a Complex World McGraw Hill/Irwin, 2000. ISBN 978-0-07-238915-9
  19. ^ Charles S. Carver, Michael F. Scheier: On the Self-Regulation of Behavior Cambridge University Press, 2001
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