NationMaster - Encyclopedia: Feedback mechanism

In cybernetics and control theory, feedback is a process whereby some proportion or in general, function, of the output signal of a system is passed (fed back) to the input. Often this is done intentionally, in order to control the dynamic behaviour of the system. Feedback is observed or used in various areas dealing with complex systems, such as engineering, architecture, economics, and biology. This article is in need of attention from an expert on the subject. ... In engineering and mathematics, control theory deals with the behavior of dynamical systems over time. ... Engineering applies scientific and technical knowledge to solve human problems. ... Depending on the nature of the structure, the skills of the architect ranges from the complex, such as a hospital or a stadium, to something more simple, such as planning buildings in a residential area. ... U.S. Economic Calendar Economics at the Open Directory Project Economics textbooks on Wikibooks The Economists Economics A-Z Daily analysis of economics in the news (UK focus) Institutions and organizations Bureau of Labor Statistics - from the American Labor Department Center for Economic and Policy Research (USA) National Bureau... Main articles: Life The most salient example of biological universality is that all living things share a common carbon-based biochemistry and in particular pass on their characteristics via genetic material, which is based on nucleic acids such as DNA and which uses a common genetic code with only minor...

Feedback loop

In diagrams that depict information flow in a system, arrowed lines are usually drawn, directed from input through the system and to output. The feedback is shown by another arrowed line, directed from output outside the system to an input, resulting in a loop on the diagram, called feedback loop. This notion is important; for example, the feedback loop is a convenient place for a control device.

The following is an example of a feedback loop used in web-based workflows. Feedback Loops are established by ISPs for permission e-mail marketers to manage subscribers who click the "This is Spam" button in their web mail clients. The Feedback Loop sends a message back to the marketer letting them know to unsubscribe the subscriber.

Types of feedback

Main articles: Negative feedback, Positive feedback This article needs to be cleaned up to conform to a higher standard of quality. ... Positive feedback is a type of feedback. ...

Feedback may be negative, which tends to reduce output, (but in amplifiers, stabilises and linearises operation), or positive, which tends to increase output. Systems which include feedback are prone to hunting, which is oscillation of output resulting from improperly tuned inputs of first positive then negative feedback. Audio feedback typifies this form of oscillation. This article needs to be cleaned up to conform to a higher standard of quality. ... Positive feedback is a type of feedback. ... OSCILLATION IS THROUGH AND FRO MOTION OF ELECTRONS IN DEVICE Oscillation is the periodic variation, typically in time, of some measure as seen, for example, in a swinging pendulum. ...

Feedback in electronic engineering

The processing and control of feedback is engineered into many electronic devices and may also be embedded in other technologies. Two digital voltmeters The field of electronics is the study and use of systems that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. ... See also: Innovation By the mid 20th century humans had achieved a level of technological mastery sufficient to leave the surface of the planet for the first time and explore space. ...

The most common general-purpose controller is a proportional-integral-derivative (PID) controller. Each term of the PID controller copes with time. The proportional term handles the present state of the system, the integral term handles its past, and the derivative or slope term tries to predict and handle the future. A Proportional-Integral-Derivative controller or PID controller is a common feedback loop component in industrial control applications (see also control theory). ...

If the signal is inverted on its way round the control loop, the system is said to have negative feedback; otherwise, the feedback is said to be positive. Negative feedback is often deliberately introduced to increase the stability and accuracy of a system, as in the feedback amplifier invented by Harold Stephen Black. This scheme can fail if the input changes faster than the system can respond to it. When this happens, the negative feedback signal begins to act as positive feedback, causing the output to oscillate or hunt. Positive feedback is usually an unwanted consequence of system behaviour. The word stability has a number of technical meanings, all related to the common meaning of the word. ... A feedback amplifier, also known as negative feedback amplifier is an amplifier which uses a feedback network, generally for improving performance (gain stability, linearity, frequency response etc. ... Harold Stephen Black (1898-1983) is an electrical engineer who revolutionized the field of applied electronics by inventing the negative feedback amplifier in 1927. ... OSCILLATION IS THROUGH AND FRO MOTION OF ELECTRONS IN DEVICE Oscillation is the periodic variation, typically in time, of some measure as seen, for example, in a swinging pendulum. ...

Harry Nyquist was an electrical engineer who contributed the Nyquist plot for determining the stability of feedback systems. Harry Nyquist (February 7, 1889 - April 4, 1976) was an important contributor to information theory. ... A Nyquist plot is a graph used in signal processing in which the magnitude and phase of a frequency response are plotted on orthogonal axes. ...

Feedback in mechanical engineering

In ancient times, the float valve was used to regulate the speed of Greek and Roman water clocks; similar float valves are used to regulate fuel in a carburettor and also used to regulate tank water level in the flush toilet. A float valve is a mechanical feedback mechanism that regulates fluid level by using a float to drive an inlet valve such that a higher fluid level will force the valve closed whilst a lower fluid level will force the valve open. ... A water clock or clepsydra is a device for measuring time by letting water regularly flow out of a container usually by a tiny aperture. ... The carburetor (or carburettor, carb for short) is a device which mixes air and fuel for an internal_combustion engine. ... Flush toilet A flush toilet or water closet (WC) is a toilet that disposes of the waste products by using water to sweep them away down a drainpipe. ...

The windmill was enhanced in 1745 by blacksmith Edmund Lee who added a fantail to keep the face of the windmill pointing into the wind. In 1787 Thomas Mead regulated the speed of rotation of a windmill by using a centrifugal pendulum to adjust the distance between the bedstone and the runner stone (i.e. to adjust the load). Pitstone Windmill, believed to be the oldest windmill in the British Isles A windmill is an engine powered by the energy of wind to mill grain, often contained in a large building as in traditional post mills, smock mills and tower mills. ... // Events May 11 - War of Austrian Succession: Battle of Fontenoy - At Fontenoy, French forces defeat an Anglo-Dutch-Hanoverian army including the Black Watch June 4 â€“ Frederick the Great destroys Austrian army at Hohenfriedberg August 19 - Beginning of the 45 Jacobite Rising at Glenfinnan September 12 - Francis I is elected... 1787 was a common year starting on Monday (see link for calendar). ...

The use of the centrifugal governor by James Watt in 1788 to regulate the speed of his steam engine was one factor leading to the Industrial Revolution. Steam engines also use float valves and pressure release valves as mechanical regulation devices. A mathematical analysis of Watt's governor was done by James Clerk Maxwell in 1868. A centrifugal governor controls the speed of an engine by regulating the amount of fuel admitted, so as to maintain a near constant speed whatever the load or fuel supply conditions. ... This article is about the Scottish engineer and inventor. ... 1788 was a leap year starting on Tuesday (see link for calendar). ... A steam engine is a heat engine that makes use of the thermal energy that exists in steam, converting it to mechanical work. ... The Industrial Revolution was the major technological, socioeconomic and cultural change in the late 18th and early 19th century resulting from the replacement of an economy based on manual labour to one dominated by industry and machine manufacture. ... Analysis is the generic name given to any branch of mathematics which depends upon the concepts of limits and convergence, and studies closely related topics such as continuity, integration, differentiability and transcendental functions. ... James Clerk Maxwell (June 13, 1831â€“November 5, 1879) was a Scottish mathematical physicist, born in Edinburgh. ... 1868 was a leap year starting on Wednesday (see link for calendar). ...

The Great Eastern was one of the largest steamships of its time and employed a steam powered rudder with feedback mechanism designed in 1866 by J.McFarlane Gray. Joseph Farcot coined the word servo in 1873 to describe steam powered steering systems. Hydraulic servos were later used to position guns. Elmer Ambrose Sperry of the Sperry Corporation designed the first autopilot in 1912. Nicolas Minorsky published a theoretical analysis of automatic ship steering in 1922 and described the PID controller. SS Great Eastern shortly before her launching, 1858 This article describes the ship the Great Eastern. ... 1866 is a common year starting on Monday. ... The term servo can refer to: Servomechanism - usually just shortened to servo, is a device used to effect mechanical motion for a specified distance. ... 1873 was a common year starting on Wednesday (see link for calaber). ... Elmer Ambrose Sperry (October 12, 1860 - June 16, 1930) was an inventor and entrepreneur. ... Sperry Corporation was a major American equipment and electronics company whose existence spanned more than seven decades of the twentieth century. ... Autopilots mechanically guide a vehicle without assistance from a human being. ... 1912 (MCMXII) was a leap year starting on Monday. ... 1922 (MCMXXII) was a common year starting on Sunday (see link for calendar). ... A Proportional-Integral-Derivative controller or PID controller is a common feedback loop component in industrial control applications (see also control theory). ...

Internal combustion engines of the late 20th century employed mechanical feedback mechanisms such as vacuum advance but mechanical feedback was replaced by electronic engine management systems once small, robust and powerful single-chip microcontrollers became affordable. (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the...

Feedback in economics and finance

A system prone to hunting (oscillating) is the stock market, which has both positive and negative feedback mechanisms. This is due to cognitive and emotional factors belonging to the field of behavioral finance. For example, The stock market is the market for the trading of company stock, both those securities listed on a stock exchange as well as those only traded privately. ... Bank of Sweden Prize in Economic Sciences winner Daniel Kahneman, was an important figure in the development of behavioral finance and economics and continues to write extensively in the field. ...

George Soros used the word reflexism to describe feedback in the financial markets and developed an investment theory based on this principle. A bull market is a financial market where prices of instruments (e. ... See stock (disambiguation) for other meanings of the term stock In financial terminology, stock is the capital raised by a corporation, through the issuance and sale of shares. ... The Gettier problem: Justified true belief? Theory of Knowledge: The Gettier problem The Duality of Knowledge Philosophy of Knowledge Glossary Categories: ‪Knowledge‬ | ‪Epistemology‬ | ‪Philosophical terminology‬ ... A bear market is a phase in the life of a financial market, such as a stock market, in which the prices of most securities fall consistently, as reflected by a downward movement of one or more key stock market or other financial market indices. ... George Soros George Soros (born August 12, 1930 in Budapest, Hungary as Schwartz GyÃ¶rgy) is a financial speculator, stock investor, philanthropist, and political activist. ...

The conventional economic equilibrium model of supply and demand supports only ideal linear negative feedback and was heavily criticized by Paul Ormerod in his book "The Death of Economics" which in turn was criticized by traditional economists. This book was part of a change of perspective as economists started to recognise that Chaos Theory applied to nonlinear feedback systems including financial markets. In economics, economic equilibrium often refers to an equilibrium in a market that clears: this is the case where a market for a product has attained the price where the amount supplied of a certain product equals the quantity demanded. ... Theoretical Economist researching complexity, complex systems, nonlinear feedback, the boom and bust cycle of business and economic competition. ... In mathematics and physics, chaos theory deals with the behavior of certain nonlinear dynamical systems that (under certain conditions) exhibit the phenomenon known as chaos, most famously characterised by sensitivity to initial conditions (see butterfly effect). ...

Feedback in nature

In biological systems such as organisms, ecosystems, or the biosphere, most parameters must stay under control within a narrow range around a certain optimal level under certain environmental conditions. The deviation of the optimal value of the controlled parameter can result from the changes in internal and external environments. A change of some of the environmental conditions may also require change of that range to change for the system to function. The value of the parameter to maintain is recorded by a reception system and conveyed to a regulation module via an information channel. Main articles: Life The most salient example of biological universality is that all living things share a common carbon-based biochemistry and in particular pass on their characteristics via genetic material, which is based on nucleic acids such as DNA and which uses a common genetic code with only minor... In biology and ecology, an organism (in Greek organon = instrument) is a complex adaptive system of organs that influence each other in such a way that they function as a more or less stable whole and have properties of life. ... In ecology, an ecosystem is a naturally occurring assemblage of organisms (plant, animal and other living organismsâ€”also referred to as a biotic community or biocoenosis) living together with their environment (or biotope), functioning as a loose unit. ... The biosphere is that part of a planets outer shellâ€”including air, land, surface rocks and waterâ€”within which life occurs, and which biotic processes in turn alter or transform. ...

Biological systems contain many types of regulatory circuits, among which positive and negative feedbacks. Positive and negative don't imply consequences of the feedback have positive or negative final effect. The negative feedback loop tends to slow down a process, while the positive feedback loop tends to accelerate it.

Feedback and regulation are self related. The negative feedback helps to maintain stability in a system in spite of external changes. It is related to homeostasis. Positive feedback amplifies possibilities of divergences (evolution, change of goals); it is the condition to change, evolution, growth; it gives the system the ability to access new points of equilibrium. Homeostasis is the property of an open system, especially living organisms, to regulate its internal environment to maintain a stable, constant condition, by means of multiple dynamic equilibrium adjustments, controlled by interrelated regulation mechanisms. ... Equilibrium or balance is any of a number of related phenomena in the natural and social sciences. ...

For example, in an organism, most positive feedbacks provide for fast autoexcitation of elements of endocrine and nervous systems (in particular, in stress responses conditions) and play a key role in regulation of morphogenesis, growth, and development of organs, all processes which are in essence a rapid escape from the initial state. Homeostasis is especially visible in the nervous and endocrine systems when considered at organism level. The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and processes input from the senses, and initiates actions. ... Major endocrine glands. ...

Feedback is also central to the operations of genes and gene regulatory networks. repressor (see Lac repressor) and activator proteins are used to create genetic operons, which were identified by Francois Jacob and Jacques Monod in 1961 as feedback loops. This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... A gene regulatory network (also called a GRN or genetic regulatory network) is a collection of DNA segments in a cell which interact with each other and with other substances in the cell, thereby governing the rates at which genes in the network are transcribed into mRNA. // Overview Genes can... The lac repressor is a DNA-binding protein which inhibits the expression of genes coding for proteins involved in the metabolism of lactose in bacteria. ... An activator is a DNA-binding protein that regulates one or more genes by increasing the rate of transcription. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... An operon is a group of key nucleotide sequences including an operator, a common promoter, and one or more structural genes that are controlled as a unit to produce messenger RNA (mRNA). ... François Jacob (born June 17, 1920) is a French biologist, who together with Jacques Monod, originated the idea that control of enzyme levels in all cells happens through feedback on transcription. ... Jacques Lucien Monod (February 9, 1910 â€“ May 31, 1976) was a French biologist and a Nobel Prize Winner in Physiology or Medicine in 1965. ... 1961 (MCMLXI) was a common year starting on Sunday (link will take you to calendar). ...

Any self-regulating natural process involves feedback and is prone to hunting. A well known example in ecology, is the oscillation of the population of snowshoe hares due to predation from lynxes. (Ecology is sometimes used incorrectly as a synonym for the natural environment. ... Snowshoe hare Conservation status: Secure Categories: Stub | Leporids ... Species Lynx lynx Lynx canadensis Lynx pardinus Lynx rufus A Lynx is any of several medium-sized wild cats. ...

In zymology, feedback serves as regulation of activity of an enzyme by its direct product(s) or downstream metabolite(s) in the metabolic pathway. Zymology is the science of fermentation. ...

There is an ice-albedo positive feedback loop whereby melting snow exposes more dark ground (of lower albedo), which in turn absorbs heat and causes more snow to melt. This is part of the evidence of the danger of global warming. The albedo is a measure of reflectivity of a surface or body. ... Global mean surface temperatures 1856 to 2004 Mean temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980 Global warming is an increase in the average temperature of the Earths atmosphere and oceans. ...

Compare with: feed-forward Feed-forward is a term describing a kind of system which reacts to changes in its environment, usually to maintain some desired state of the system. ...

Feedback in organizations

As an organization seeks to improve its performance, feedback helps it to make required adjustments. An organization (U.S. spelling) or organisation (U.K. spelling) is a formal group of people with one or more shared goals. ...

This article needs to be cleaned up to conform to a higher standard of quality. ... One phase of the annual performance management cycle is performance appraisal, the process of reviewing employee performance, setting new performance objectives, documenting the review, and delivering the review verbally in a face-to-face meeting. ... A shareholder or stockholder is an individual or company (including a corporation) that legally owns one or more shares of stock in a joint stock company. ... In human resources, 360-degree feedback is employee development feedback that comes from all around the employee. ...

Feedback in gaming

In computer games, feedback is an important and heavily exploited mechanism for controlling resources. Both positive and negative feedback loops can be used to alter the pacing, challenge, and sense of accomplishment in a game. For example, Unreal Tournament's practice mode offers an auto-adjust setting that causes the bots to attempt to match the player's skill level, keeping a more consistent level of challenge for different players; this is negative feedback. On the other hand, in Starcraft, a player who has a small advantage in resources will be able to build more units, enabling them to seize more resource-rich territory and so gain a much larger advantage in resources; this is positive feedback. A computer game is a game composed of a computer-controlled virtual universe that players interact with in order to achieve a defined goal or set of goals. ... Unreal Tournament or UT is a popular first-person shooter computer game. ... This article needs to be cleaned up to conform to a higher standard of quality. ... StarCraft (SC) is a real-time strategy computer game by Blizzard Entertainment. ... Positive feedback is a type of feedback. ...

Sources

MIT Press Books The MIT Press is a university publisher affiliated with the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts. ...

Contents

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