当一个系统的输出作为输入被送回,并作为形成回路或循环的因果链的一部分时,就会产生'''反馈 feedback'''。<ref name=Ford>{{cite book |title=Modeling the Environment |author=Andrew Ford |chapter=Chapter 9: Information feedback and causal loop diagrams |pages=99 ''ff'' |publisher=Island Press |year=2010 |isbn=9781610914253 |chapter-url=https://books.google.com/books?id=38PJahZTzC0C&pg=PA99lpg |quote=This chapter describes [[causal loop diagram]]s to portray the information feedback at work in a system. The word ''causal'' refers to cause-and-effect relationships. The word''loop'' refers to a closed chain of cause and effect that creates the feedback.}}</ref>这个系统可以说是反馈到了自身。在因果关系应用于反馈系统时,必须谨慎处理其概念。
当一个系统的输出作为输入被送回,并作为形成回路或循环的因果链的一部分时,就会产生'''反馈 feedback'''。<ref name=Ford>{{cite book |title=Modeling the Environment |author=Andrew Ford |chapter=Chapter 9: Information feedback and causal loop diagrams |pages=99 ''ff'' |publisher=Island Press |year=2010 |isbn=9781610914253 |chapter-url=https://books.google.com/books?id=38PJahZTzC0C&pg=PA99lpg |quote=This chapter describes [[causal loop diagram]]s to portray the information feedback at work in a system. The word ''causal'' refers to cause-and-effect relationships. The word''loop'' refers to a closed chain of cause and effect that creates the feedback.}}</ref>这个系统可以说是反馈到了自身。在因果关系应用于反馈系统时,必须谨慎处理其概念。
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对于一个反馈系统,很难进行简单的因果推理,因为第一个系统影响第二个系统,第二个系统影响第一个系统,产生了一个循环论证。这就使得基于因果关系的推理变得很困难,因此有必要将系统作为一个整体进行分析。——卡尔·约翰·阿斯特洛姆·马丁 Karl Johan Åström和查德·M·默里 Richard M.Murray
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::对于一个反馈系统,很难进行简单的因果推理,因为第一个系统影响第二个系统,第二个系统影响第一个系统,产生了一个循环论证。这就使得基于因果关系的推理变得很困难,因此有必要将系统作为一个整体进行分析。——卡尔·约翰·阿斯特洛姆·马丁 Karl Johan Åström和查德·M·默里 Richard M.Murray
“正面”和“负面”这两个词在第二次世界大战之前首次用于反馈。20世纪20年代,随着再生电路的引入,正反馈的概念已经流行起来。<ref name=mindell>{{Cite book|author=David A. Mindell|title=Between Human and Machine : Feedback, Control, and Computing before Cybernetics.|year= 2002|publisher=Johns Hopkins University Press|location=Baltimore, MD, US|url=https://books.google.com/books?id=sExvSbe9MSsC|isbn=9780801868955}}</ref> 弗里斯 Friis和延森 Jensen(1924)将一套电子放大器中的再生回路描述为"反馈"作用是正的例子,以此和他们顺便提及的负反馈作用相区别。<ref name=friis>Friis, H.T., and A.G.Jensen. "High Frequency Amplifiers" Bell System Technical Journal 3 (April 1924):181–205.</ref>哈罗德·史蒂芬·布莱克 Harold Stephen Black1934年的经典论文首次详细阐述了负反馈在电子放大器中的应用。布莱克认为:
The terms "positive" and "negative" were first applied to feedback prior to WWII. The idea of positive feedback was already current in the 1920s with the introduction of the [[regenerative circuit]].<ref name=mindell>{{Cite book|author=David A. Mindell|title=Between Human and Machine : Feedback, Control, and Computing before Cybernetics.|year= 2002|publisher=Johns Hopkins University Press|location=Baltimore, MD, US|url=https://books.google.com/books?id=sExvSbe9MSsC|isbn=9780801868955}}</ref>Friis and Jensen (1924) described regeneration in a set of electronic amplifiers as a case where ''the "feed-back" action is positive'' in contrast to negative feed-back action, which they mention only in passing.<ref name=friis>Friis, H.T., and A.G.Jensen. "High Frequency Amplifiers" Bell System Technical Journal 3 (April 1924):181–205.</ref> [[Harold Stephen Black]]'s classic 1934 paper first details the use of negative feedback in electronic amplifiers. According to Black:
The terms "positive" and "negative" were first applied to feedback prior to WWII. The idea of positive feedback was already current in the 1920s with the introduction of the regenerative circuit. Friis and Jensen (1924) described regeneration in a set of electronic amplifiers as a case where the "feed-back" action is positive in contrast to negative feed-back action, which they mention only in passing. Harold Stephen Black's classic 1934 paper first details the use of negative feedback in electronic amplifiers. According to Black:
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“正面”和“负面”这两个词在第二次世界大战之前首次用于反馈。20世纪20年代,随着再生电路的引入,正反馈的概念已经流行起来。<ref name=mindell>{{Cite book|author=David A. Mindell|title=Between Human and Machine : Feedback, Control, and Computing before Cybernetics.|year= 2002|publisher=Johns Hopkins University Press|location=Baltimore, MD, US|url=https://books.google.com/books?id=sExvSbe9MSsC|isbn=9780801868955}}</ref> 弗里斯 Friis和延森 Jensen(1924)将一套电子放大器中的再生回路描述为"反馈"作用是正的例子,以此和他们顺便提及的负反馈作用相区别。<ref name=friis>Friis, H.T., and A.G.Jensen. "High Frequency Amplifiers" Bell System Technical Journal 3 (April 1924):181–205.</ref>哈罗德·史蒂芬·布莱克 Harold Stephen Black1934年的经典论文首次详细阐述了负反馈在电子放大器中的应用。布莱克认为:
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{{Quote|Positive feed-back increases the gain of the amplifier, negative feed-back reduces it.<ref name=black>H.S. Black, "Stabilized feed-back amplifiers", ''Electrical Engineering'', vol. 53, pp. 114–120, January 1934.</ref>}}
According to Mindell (2002) confusion in the terms arose shortly after this:
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据Mindell(2002年)说,在这之后不久就出现了术语上的混乱。
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{{Quote|...Friis and Jensen had made the same distinction Black used between "positive feed-back" and "negative feed-back", based not on the sign of the feedback itself but rather on its effect on the amplifier's gain. In contrast, Nyquist and Bode, when they built on Black's work, referred to negative feedback as that with the sign reversed. Black had trouble convincing others of the utility of his invention in part because confusion existed over basic matters of definition.<ref name=mindell/>{{rp|page=121}}}}
Even prior to the terms being applied, [[James Clerk Maxwell]] had described several kinds of "component motions" associated with the [[centrifugal governor]]s used in steam engines, distinguishing between those that lead to a continual ''increase'' in a disturbance or the amplitude of an oscillation, and those that lead to a ''decrease'' of the same.<ref name=maxwell>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|url=http://en.wikipedia.org/wiki/File:On_Governors.pdf|journal=Proceedings of the Royal Society of London|volume= 16|year= 1868 |pages= 270–283|doi=10.1098/rspl.1867.0055|s2cid=51751195}}</ref>
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Even prior to the terms being applied, James Clerk Maxwell had described several kinds of "component motions" associated with the centrifugal governors used in steam engines, distinguishing between those that lead to a continual ''increase'' in a disturbance or the amplitude of an oscillation, and those that lead to a ''decrease'' of the same.
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甚至在这些术语被应用之前,詹姆斯·克莱克·麦克斯韦 James Clerk Maxwell就已经描述了几种与蒸汽机中使用的离心式调速器相关的 "运动分量",并区分了那些导致扰动或振荡幅度持续''增加''的运动和那些导致其减少的运动。 <ref name=maxwell>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|url=http://en.wikipedia.org/wiki/File:On_Governors.pdf|journal=Proceedings of the Royal Society of London|volume=16|year=1868|pages=270-283|doi=10.1098/rspl.1867}。 .0055|s2cid=51751195}}</ref>
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====Terminology====
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术语
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The terms positive and negative feedback are defined in different ways within different disciplines.
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甚至在这些术语被应用之前,詹姆斯·克莱克·麦克斯韦 James Clerk Maxwell就已经描述了几种与蒸汽机中使用的离心式调速器相关的“运动分量”,并区分了那些导致扰动或振荡幅度持续增加的运动和那些导致其减少的运动。<ref name=maxwell>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|url=http://en.wikipedia.org/wiki/File:On_Governors.pdf|journal=Proceedings of the Royal Society of London|volume=16|year=1868|pages=270-283|doi=10.1098/rspl.1867}。 .0055|s2cid=51751195}}</ref>
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====术语====
正反馈和负反馈在不同的学科中有不同的定义。
正反馈和负反馈在不同的学科中有不同的定义。
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# the altering of the ''gap'' between reference and actual values of a parameter, based on whether the gap is ''widening'' (positive) or ''narrowing'' (negative).<ref name="Ramaprasad" />
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#the altering of the gap between reference and actual values of a parameter, based on whether the gap is widening (positive) or narrowing (negative).
# 改变差距的行动或效果的'''效价 valence''',基于它对接受者或观察者是否具有快乐(积极)或不快乐(消极)的情感内涵。<ref name=herold1977>Herold, David M., and Martin M. Greller. "Research Notes. FEEDBACK THE DEFINITION OF A CONSTRUCT." Academy of management Journal 20.1 (1977): 142-147.</ref>
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# the [[Valence (psychology)|valence]] of the ''action'' or ''effect'' that alters the gap, based on whether it has a ''happy'' (positive) or ''unhappy'' (negative) emotional connotation to the recipient or observer.<ref name=herold1977>Herold, David M., and Martin M. Greller. "Research Notes. FEEDBACK THE DEFINITION OF A CONSTRUCT." Academy of management Journal 20.1 (1977): 142-147.</ref>
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这两种定义可能会引起混淆,比如当激励(奖励)被用来提高糟糕的表现(缩小差距)。针对定义1,一些作者使用了替代术语,分别用自强化/自纠正<ref name="senge">{{Cite book|author=Peter M. Senge|title=The Fifth Discipline: The Art and Practice of the Learning Organization|year=1990|publisher=Doubleday|location=New York |isbn=978-0-385-26094-7|page=424|url=https://archive.org/details/fifthdisciplineasen00seng}}
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# the valence of the ''action'' or ''effect'' that alters the gap, based on whether it has a ''happy'' (positive) or ''unhappy'' (negative) emotional connotation to the recipient or observer.
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#改变差距的行动或效果的<font color="#ff8000"> 效价 valence</font>,基于它对接受者或观察者是否具有''快乐''(积极)或''不快乐''(消极)的情感内涵。<ref name=herold1977>Herold, David M., and Martin M. Greller. "Research Notes. FEEDBACK THE DEFINITION OF A CONSTRUCT." Academy of management Journal 20.1 (1977): 142-147.</ref>
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The two definitions may cause confusion, such as when an incentive (reward) is used to boost poor performance (narrow a gap). Referring to definition 1, some authors use alternative terms, replacing ''positive/negative'' with ''self-reinforcing/self-correcting'',<ref name="senge">{{Cite book|author=Peter M. Senge|title=The Fifth Discipline: The Art and Practice of the Learning Organization|year=1990|publisher=Doubleday|location=New York |isbn=978-0-385-26094-7|page=424|url=https://archive.org/details/fifthdisciplineasen00seng}}
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</ref> ''reinforcing/balancing'',<ref name="sterman">John D. Sterman, ''Business Dynamics: Systems Thinking and Modeling for a Complex World'', McGraw Hill/Irwin, 2000. {{ISBN|978-0-07-238915-9}}</ref> ''discrepancy-enhancing/discrepancy-reducing''<ref name="carver">Charles S. Carver, Michael F. Scheier: ''On the Self-Regulation of Behavior'' Cambridge University Press, 2001 </ref> or ''regenerative/degenerative''<ref>Hermann A Haus and Richard B. Adler, ''Circuit Theory of Linear Noisy Networks'', MIT Press, 1959</ref>respectively. And for definition 2, some authors advocate describing the action or effect as positive/negative ''[[Reinforcement#Reinforcement|reinforcement]]'' or ''[[Reinforcement#Punishment|punishment]]'' rather than feedback.<ref name="Ramaprasad" /><ref name="skinner">BF Skinner, ''The Experimental Analysis of Behavior'', American Scientist, Vol. 45, No. 4 (SEPTEMBER 1957), pp. 343-371</ref>Yet even within a single discipline an example of feedback can be called either positive or negative, depending on how values are measured or referenced.<ref>"However, after scrutinizing the statistical properties of the structural equations, the members of the committee assured themselves that it is possible to have a significant positive feedback loop when using standardized scores, and a negative loop when using real scores."
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For feedback in the educational context, see corrective feedback.
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Ralph L. Levine, Hiram E. Fitzgerald. ''Analysis of the dynamic psychological systems: methods and applications'', {{ISBN|978-0306437465}} (1992) page 123</ref>
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The two definitions may cause confusion, such as when an incentive (reward) is used to boost poor performance (narrow a gap). Referring to definition 1, some authors use alternative terms, replacing positive/negative with self-reinforcing/self-correcting, reinforcing/balancing, discrepancy-enhancing/discrepancy-reducing or regenerative/degenerative respectively. And for definition 2, some authors advocate describing the action or effect as positive/negative reinforcement or punishment rather than feedback. Yet even within a single discipline an example of feedback can be called either positive or negative, depending on how values are measured or referenced.
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这两种定义可能会引起混淆,比如当激励(奖励)被用来提高糟糕的表现(缩小差距)。针对定义1,一些作者使用了替代术语,分别用自强化/自纠正<ref name="senge">{{Cite book|author=Peter M. Senge|title=The Fifth Discipline: The Art and Practice of the Learning Organization|year=1990|publisher=Doubleday|location=New York |isbn=978-0-385-26094-7|page=424|url=https://archive.org/details/fifthdisciplineasen00seng}}
</ref>、强化/平衡<ref name="sterman">John D. Sterman, ''Business Dynamics: Systems Thinking and Modeling for a Complex World'', McGraw Hill/Irwin, 2000. {{ISBN|978-0-07-238915-9}}</ref>、离散增强/离散减少<ref name="carver">Charles S. Carver, Michael F. Scheier: ''On the Self-Regulation of Behavior'' Cambridge University Press, 2001 </ref>或再生/退化<ref>Hermann A Haus and Richard B. Adler, ''Circuit Theory of Linear Noisy Networks'', MIT Press, 1959</ref>来替代正/负。对于定义2,一些作者主张将行为或效果描述为积极/消极的强化或惩罚,而不是反馈。<ref name="Ramaprasad" /><ref name="skinner">BF Skinner, ''The Experimental Analysis of Behavior'', American Scientist, Vol. 45, No. 4 (SEPTEMBER 1957), pp. 343-371</ref>然而,即使是在一个单一的学科中,反馈的例子也可以被称为正的或负的,这取决于如何衡量或引用其含义。<ref>"However, after scrutinizing the statistical properties of the structural equations, the members of the committee assured themselves that it is possible to have a significant positive feedback loop when using standardized scores, and a negative loop when using real scores."
</ref>、强化/平衡<ref name="sterman">John D. Sterman, ''Business Dynamics: Systems Thinking and Modeling for a Complex World'', McGraw Hill/Irwin, 2000. {{ISBN|978-0-07-238915-9}}</ref>、离散增强/离散减少<ref name="carver">Charles S. Carver, Michael F. Scheier: ''On the Self-Regulation of Behavior'' Cambridge University Press, 2001 </ref>或再生/退化<ref>Hermann A Haus and Richard B. Adler, ''Circuit Theory of Linear Noisy Networks'', MIT Press, 1959</ref>来替代正/负。对于定义2,一些作者主张将行为或效果描述为积极/消极的强化或惩罚,而不是反馈。<ref name="Ramaprasad" /><ref name="skinner">BF Skinner, ''The Experimental Analysis of Behavior'', American Scientist, Vol. 45, No. 4 (SEPTEMBER 1957), pp. 343-371</ref>然而,即使是在一个单一的学科中,反馈的例子也可以被称为正的或负的,这取决于如何衡量或引用其含义。<ref>"However, after scrutinizing the statistical properties of the structural equations, the members of the committee assured themselves that it is possible to have a significant positive feedback loop when using standardized scores, and a negative loop when using real scores."
For feedback in the educational context, see corrective feedback.
For feedback in the educational context, see corrective feedback.
Ralph L. Levine, Hiram E. Fitzgerald. ''Analysis of the dynamic psychological systems: methods and applications'', {{ISBN|978-0306437465}} (1992) page 123</ref>
Ralph L. Levine, Hiram E. Fitzgerald. ''Analysis of the dynamic psychological systems: methods and applications'', {{ISBN|978-0306437465}} (1992) page 123</ref>
::定量反馈告诉我们多少。定性反馈告诉我们多好、多坏或二者之间。<ref name=Connellan>Thomas K. Connellan and Ron Zemke, "Sustaining Knock Your Socks Off Service" AMACOM, 1 July 1993. {{ISBN|0-8144-7824-7}}</ref>
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This confusion may arise because feedback can be used for either ''informational'' or ''motivational'' purposes, and often has both a ''[[Qualitative property|qualitative]]'' and a ''[[Quantitative property|quantitative]]'' component. As Connellan and Zemke (1993) put it:
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====正反馈和负反馈的限制====
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This confusion may arise because feedback can be used for either informational or motivational purposes, and often has both a qualitative and a quantitative component. As Connellan and Zemke (1993) put it:
{{Quote|''Quantitative'' feedback tells us how much and how many. ''Qualitative'' feedback tells us how good, bad or indifferent.<ref name=Connellan>Thomas K. Connellan and Ron Zemke, "Sustaining Knock Your Socks Off Service" AMACOM, 1 July 1993. {{ISBN|0-8144-7824-7}}</ref>{{rp|page=102}}}}
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{{Quote|''定量''反馈告诉我们多少。''定性''反馈告诉我们多好、多坏或二者之间。<ref name=Connellan>Thomas K. Connellan and Ron Zemke, "Sustaining Knock Your Socks Off Service" AMACOM, 1 July 1993. {{ISBN|0-8144-7824-7}}</ref>{{rp|page=102}}}}
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====Limitations of negative and positive feedback====
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正反馈和负反馈的限制
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While simple systems can sometimes be described as one or the other type, many systems with feedback loops cannot be so easily designated as simply positive or negative, and this is especially true when multiple loops are present.
{{Quote|When there are only two parts joined so that each affects the other, the properties of the feedback give important and useful information about the properties of the whole. But when the parts rise to even as few as four, if every one affects the other three, then twenty circuits can be traced through them; and knowing the properties of all the twenty circuits does not give complete information about the system.<ref name=Ashby/>{{rp|page=54}}}}
In general, feedback systems can have many signals fed back and the feedback loop frequently contain mixtures of positive and negative feedback where positive and negative feedback can dominate at different frequencies or different points in the state space of a system.
术语'''双极反馈 bipolar feedback'''是指生物系统中正反馈系统和负反馈系统可以相互作用,一个系统的输出会影响另一个系统的输入,反之亦然。<ref name = Smit>{{cite book |title=Introduction to Bioregulatory Medicine |author1=Alta Smit |author2=Arturo O'Byrne |chapter-url=https://books.google.com/books?id=RzXAOUnCM3oC&pg=PA6 |page=6 |chapter=Bipolar feedback |isbn=9783131469717 |year=2011 |publisher=Thieme}}</ref>
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The term bipolar feedback has been coined to refer to biological systems where positive and negative feedback systems can interact, the output of one affecting the input of another, and vice versa.<ref name = Smit>{{cite book |title=Introduction to Bioregulatory Medicine |author1=Alta Smit |author2=Arturo O'Byrne |chapter-url=https://books.google.com/books?id=RzXAOUnCM3oC&pg=PA6 |page=6 |chapter=Bipolar feedback |isbn=9783131469717 |year=2011 |publisher=Thieme}}</ref>
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术语<font color="#ff8000"> 双极反馈 bipolar feedback</font> 是指生物系统中正反馈系统和负反馈系统可以相互作用,一个系统的输出会影响另一个系统的输入,反之亦然。<ref name = Smit>{{cite book |title=Introduction to Bioregulatory Medicine |author1=Alta Smit |author2=Arturo O'Byrne |chapter-url=https://books.google.com/books?id=RzXAOUnCM3oC&pg=PA6 |page=6 |chapter=Bipolar feedback |isbn=9783131469717 |year=2011 |publisher=Thieme}}</ref>
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Some systems with feedback can have very complex behaviors such as [[Chaos theory|chaotic behaviors]] in non-linear systems, while others have much more predictable behaviors, such as those that are used to make and design digital systems.
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Some systems with feedback can have very complex behaviors such as chaotic behaviors in non-linear systems, while others have much more predictable behaviors, such as those that are used to make and design digital systems.
Feedback is used extensively in digital systems. For example, binary counters and similar devices employ feedback where the current state and inputs are used to calculate a new state which is then fed back and clocked back into the device to update it.
[[File:Mandel zoom 00 mandelbrot set.jpg|322px|thumb|Feedback can give rise to incredibly complex behaviors. The [[Mandelbrot set]] (black) within a continuously colored environment is plotted by repeatedly feeding back values through a simple equation and recording the points on the imaginary plane that fail to diverge|alt=]]
{{Main|Dynamical system|Chaos theory|Edge of chaos|Control theory}}
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{{主要|动力系统|混沌理论|混沌边缘|控制理论}}
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By using feedback properties, the behavior of a system can be altered to meet the needs of an application; systems can be made stable, responsive or held constant. It is shown that dynamical systems with a feedback experience an adaptation to the [[edge of chaos]].<ref>{{cite journal|last1=Wotherspoon|first1=T.|last2=Hubler|first2=A.|title=Adaptation to the edge of chaos with random-wavelet feedback|journal=J. Phys. Chem. A|date=2009|doi=10.1021/jp804420g|pmid=19072712|volume=113|issue=1|pages=19–22|bibcode=2009JPCA..113...19W}}</ref>
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By using feedback properties, the behavior of a system can be altered to meet the needs of an application; systems can be made stable, responsive or held constant. It is shown that dynamical systems with a feedback experience an adaptation to the edge of chaos.
通过使用反馈属性,可以更改系统的行为以满足应用程序的需求;可以使系统稳定、响应迅速或保持恒定。结果表明,具有反馈的动力系统会适应混沌边缘现象。<ref>{{cite journal|last1=Wotherspoon|first1=T.|last2=Hubler|first2=A.|title=Adaptation to the edge of chaos with random-wavelet feedback|journal=J. Phys. Chem. A|date=2009|doi=10.1021/jp804420g|pmid=19072712|volume=113|issue=1|pages=19–22|bibcode=2009JPCA..113...19W}}</ref>
通过使用反馈属性,可以更改系统的行为以满足应用程序的需求;可以使系统稳定、响应迅速或保持恒定。结果表明,具有反馈的动力系统会适应混沌边缘现象。<ref>{{cite journal|last1=Wotherspoon|first1=T.|last2=Hubler|first2=A.|title=Adaptation to the edge of chaos with random-wavelet feedback|journal=J. Phys. Chem. A|date=2009|doi=10.1021/jp804420g|pmid=19072712|volume=113|issue=1|pages=19–22|bibcode=2009JPCA..113...19W}}</ref>
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===生物===
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===Biology===
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生物
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{{See also|Homeostasis|Allostasis}}
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{{另请参见|内环境稳态|稳态}}
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In [[biology|biological]] systems such as [[organism]]s, [[ecosystem]]s, 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. An example of this is [[insulin oscillation]]s.
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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. An example of this is insulin oscillations.
Biological systems contain many types of regulatory circuits, both positive and negative. As in other contexts, positive and negative do not imply that the feedback causes good or bad effects. A negative feedback loop is one that tends to slow down a process, whereas the positive feedback loop tends to accelerate it. The mirror neurons are part of a social feedback system, when an observed action is "mirrored" by the brain—like a self-performed action.
正常组织的完整性是通过粘附分子和作为介质的分泌分子介导的不同细胞类型之间的反馈相互作用来保持的;癌症中关键反馈机制的失效会破坏组织功能。<ref>{{cite journal|last1=Vlahopoulos|first1=SA|last2=Cen|first2=O|last3=Hengen|first3=N|last4=Agan|first4=J|last5=Moschovi|first5=M|last6=Critselis|first6=E|last7=Adamaki|first7=M|last8=Bacopoulou|first8=F|last9=Copland|first9=JA|last10=Boldogh|first10=I|last11=Karin|first11=M|last12=Chrousos|first12=GP|title=Dynamic aberrant NF-κB spurs tumorigenesis: A new model encompassing the microenvironment.|journal=Cytokine & Growth Factor Reviews|date=20 June 2015|pmid=26119834|doi=10.1016/j.cytogfr.2015.06.001|volume=26|issue=4|pages=389–403|pmc=4526340}}</ref>在受伤或感染的组织中,炎症介质会引起细胞的反馈反应,改变基因表达,改变细胞表达和分泌的分子群,包括诱导不同细胞合作的分子和恢复组织结构和功能的分子。这种类型的反馈很重要,因为它能够协调免疫反应、使机体从感染和损伤中恢复。在癌症过程中,这种反馈的关键要素会失效,进而破坏组织功能和免疫力。<ref>{{cite journal | last1 = Vlahopoulos | first1 = SA | title = Aberrant control of NF-κB in cancer permits transcriptional and phenotypic plasticity, to curtail dependence on host tissue: molecular mode. | journal = Cancer Biology & Medicine | date = August 2017 | pmid = 28884042 | doi = 10.20892/j.issn.2095-3941.2017.0029 | volume = 14 | issue = 3 | pages = 254–270 | pmc = 5570602}}</ref><ref>{{cite journal|last1=Korneev|first1=KV|last2=Atretkhany|first2=KN|last3=Drutskaya|first3=MS|last4=Grivennikov|first4=SI|last5=Kuprash|first5=DV|last6=Nedospasov|first6=SA|title=TLR-signaling and proinflammatory cytokines as drivers of tumorigenesis.|journal=Cytokine|date=January 2017|volume=89|pages=127–135|doi=10.1016/j.cyto.2016.01.021|pmid=26854213}}</ref>
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Normal tissue integrity is preserved by feedback interactions between diverse cell types mediated by adhesion molecules and secreted molecules that act as mediators; failure of key feedback mechanisms in cancer disrupts tissue function.<ref>{{cite journal|last1=Vlahopoulos|first1=SA|last2=Cen|first2=O|last3=Hengen|first3=N|last4=Agan|first4=J|last5=Moschovi|first5=M|last6=Critselis|first6=E|last7=Adamaki|first7=M|last8=Bacopoulou|first8=F|last9=Copland|first9=JA|last10=Boldogh|first10=I|last11=Karin|first11=M|last12=Chrousos|first12=GP|title=Dynamic aberrant NF-κB spurs tumorigenesis: A new model encompassing the microenvironment.|journal=Cytokine & Growth Factor Reviews|date=20 June 2015|pmid=26119834|doi=10.1016/j.cytogfr.2015.06.001|volume=26|issue=4|pages=389–403|pmc=4526340}}</ref> In an injured or infected tissue, inflammatory mediators elicit feedback responses in cells, which alter gene expression, and change the groups of molecules expressed and secreted, including molecules that induce diverse cells to cooperate and restore tissue structure and function. This type of feedback is important because it enables coordination of immune responses and recovery from infections and injuries. During cancer, key elements of this feedback fail. This disrupts tissue function and immunity.<ref>{{cite journal | last1 = Vlahopoulos | first1 = SA | title = Aberrant control of NF-κB in cancer permits transcriptional and phenotypic plasticity, to curtail dependence on host tissue: molecular mode. | journal = Cancer Biology & Medicine | date = August 2017 | pmid = 28884042 | doi = 10.20892/j.issn.2095-3941.2017.0029 | volume = 14 | issue = 3 | pages = 254–270 | pmc = 5570602}}</ref><ref>{{cite journal|last1=Korneev|first1=KV|last2=Atretkhany|first2=KN|last3=Drutskaya|first3=MS|last4=Grivennikov|first4=SI|last5=Kuprash|first5=DV|last6=Nedospasov|first6=SA|title=TLR-signaling and proinflammatory cytokines as drivers of tumorigenesis.|journal=Cytokine|date=January 2017|volume=89|pages=127–135|doi=10.1016/j.cyto.2016.01.021|pmid=26854213}}</ref>
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反馈机制首次在细菌中得到阐明,是一种营养物质会引起其部分代谢功能的变化的机制。<ref>{{cite journal|last1= Sanwal|first1=BD| title= Allosteric controls of amphilbolic pathways in bacteria.|journal= Bacteriol. Rev.|date=March 1970|volume=34|issue=1|pages=20–39 |pmid=4315011 |pmc=378347|doi=10.1128/MMBR.34.1.20-39.1970}}</ref>反馈也是基因和基因调控网络运作的中心。用'''阻遏蛋白 Repressor'''(参见Lac阻遏蛋白)和'''激活蛋白 activator protein'''来创造'''基因操纵子 genetic operons protein''',这被弗朗索瓦·雅各布 Francois Jacob和雅克·莫诺德 Jacques Monod在1961年确定为反馈回路。<ref>{{cite journal|last1= Jacob|first1=F|last2=Monod|first2=J|title= Genetic regulatory mechanisms in the synthesis of proteins.|journal= J Mol Biol|date=June 1961|volume=3|issue=3|pages=318–356 |pmid=13718526|doi=10.1016/S0022-2836(61)80072-7}}</ref>这些反馈回路可能是正的(例如糖分子和将糖输入细菌细胞的蛋白质之间的结合),也可能是负的(例如代谢消耗中经常出现的情况)。
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Normal tissue integrity is preserved by feedback interactions between diverse cell types mediated by adhesion molecules and secreted molecules that act as mediators; failure of key feedback mechanisms in cancer disrupts tissue function.In an injured or infected tissue, inflammatory mediators elicit feedback responses in cells, which alter gene expression, and change the groups of molecules expressed and secreted, including molecules that induce diverse cells to cooperate and restore tissue structure and function. This type of feedback is important because it enables coordination of immune responses and recovery from infections and injuries. During cancer, key elements of this feedback fail. This disrupts tissue function and immunity.
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正常组织的完整性是通过粘附分子和作为介质的分泌分子介导的不同细胞类型之间的反馈相互作用来保持的;癌症中关键反馈机制的失效会破坏组织功能。.<ref>{{cite journal|last1=Vlahopoulos|first1=SA|last2=Cen|first2=O|last3=Hengen|first3=N|last4=Agan|first4=J|last5=Moschovi|first5=M|last6=Critselis|first6=E|last7=Adamaki|first7=M|last8=Bacopoulou|first8=F|last9=Copland|first9=JA|last10=Boldogh|first10=I|last11=Karin|first11=M|last12=Chrousos|first12=GP|title=Dynamic aberrant NF-κB spurs tumorigenesis: A new model encompassing the microenvironment.|journal=Cytokine & Growth Factor Reviews|date=20 June 2015|pmid=26119834|doi=10.1016/j.cytogfr.2015.06.001|volume=26|issue=4|pages=389–403|pmc=4526340}}</ref>在受伤或感染的组织中,炎症介质会引起细胞的反馈反应,改变基因表达,改变细胞表达和分泌的分子群,包括诱导不同细胞合作的分子和恢复组织结构和功能的分子。这种类型的反馈很重要,因为它能够协调免疫反应、使机体从感染和损伤中恢复。在癌症过程中,这种反馈的关键要素会失效,进而破坏组织功能和免疫力。<ref>{{cite journal | last1 = Vlahopoulos | first1 = SA | title = Aberrant control of NF-κB in cancer permits transcriptional and phenotypic plasticity, to curtail dependence on host tissue: molecular mode. | journal = Cancer Biology & Medicine | date = August 2017 | pmid = 28884042 | doi = 10.20892/j.issn.2095-3941.2017.0029 | volume = 14 | issue = 3 | pages = 254–270 | pmc = 5570602}}</ref><ref>{{cite journal|last1=Korneev|first1=KV|last2=Atretkhany|first2=KN|last3=Drutskaya|first3=MS|last4=Grivennikov|first4=SI|last5=Kuprash|first5=DV|last6=Nedospasov|first6=SA|title=TLR-signaling and proinflammatory cytokines as drivers of tumorigenesis.|journal=Cytokine|date=January 2017|volume=89|pages=127–135|doi=10.1016/j.cyto.2016.01.021|pmid=26854213}}</ref>
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Mechanisms of feedback were first elucidated in bacteria, where a nutrient elicits changes in some of their metabolic functions.<ref>{{cite journal|last1= Sanwal|first1=BD| title= Allosteric controls of amphilbolic pathways in bacteria.|journal= Bacteriol. Rev.|date=March 1970|volume=34|issue=1|pages=20–39 |pmid=4315011 |pmc=378347|doi=10.1128/MMBR.34.1.20-39.1970}}</ref>Feedback is also central to the operations of [[gene]]s and [[gene regulatory network]]s. [[Repressor protein|Repressor]] (see [[Lac repressor]]) and [[activator protein|activator]] [[protein]]s are used to create genetic [[operon]]s, which were identified by [[Francois Jacob]] and [[Jacques Monod]] in 1961 as ''feedback loops''.<ref>{{cite journal|last1= Jacob|first1=F|last2=Monod|first2=J|title= Genetic regulatory mechanisms in the synthesis of proteins.|journal= J Mol Biol|date=June 1961|volume=3|issue=3|pages=318–356 |pmid=13718526|doi=10.1016/S0022-2836(61)80072-7}}</ref> These feedback loops may be positive (as in the case of the coupling between a sugar molecule and the proteins that import sugar into a bacterial cell), or negative (as is often the case in [[metabolic]] consumption).
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Mechanisms of feedback were first elucidated in bacteria, where a nutrient elicits changes in some of their metabolic functions.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. These feedback loops may be positive (as in the case of the coupling between a sugar molecule and the proteins that import sugar into a bacterial cell), or negative (as is often the case in metabolic consumption).
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反馈机制首次在细菌中得到阐明,是一种营养物质会引起其部分代谢功能的变化的机制。<ref>{{cite journal|last1= Sanwal|first1=BD| title= Allosteric controls of amphilbolic pathways in bacteria.|journal= Bacteriol. Rev.|date=March 1970|volume=34|issue=1|pages=20–39 |pmid=4315011 |pmc=378347|doi=10.1128/MMBR.34.1.20-39.1970}}</ref>反馈也是基因和基因调控网络运作的中心。用<font color="#ff8000"> 阻遏蛋白 Repressor</font>(参见 Lac 阻遏蛋白)和<font color="#ff8000"> 激活蛋白 activator protein</font>来创造<font color="#ff8000"> 基因操纵子 genetic operons protein</font>,这被弗朗索瓦·雅各布 Francois Jacob 和雅克·莫诺德 Jacques Monod 在1961年确定为反馈回路。<ref>{{cite journal|last1= Jacob|first1=F|last2=Monod|first2=J|title= Genetic regulatory mechanisms in the synthesis of proteins.|journal= J Mol Biol|date=June 1961|volume=3|issue=3|pages=318–356 |pmid=13718526|doi=10.1016/S0022-2836(61)80072-7}}</ref>这些反馈回路可能是正的(例如糖分子和将糖输入细菌细胞的蛋白质之间的结合) ,也可能是负的(例如代谢消耗中经常出现的情况)。
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On a larger scale, feedback can have a stabilizing effect on animal populations even when profoundly affected by external changes, although time lags in feedback response can give rise to [[Lotka–Volterra equation|predator-prey cycles]].<ref>CS Holling. "Resilience and stability of ecological systems". Annual Review of Ecology and Systematics 4:1-23. 1973</ref>
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On a larger scale, feedback can have a stabilizing effect on animal populations even when profoundly affected by external changes, although time lags in feedback response can give rise to predator-prey cycles.
尽管反馈反应的时间滞后可能引起捕食者-猎物循环,在受到外部变化的深刻影响的情况下,反馈也能对动物种群产生稳定作用。<ref>CS Holling. "Resilience and stability of ecological systems". Annual Review of Ecology and Systematics 4:1-23. 1973</ref>
尽管反馈反应的时间滞后可能引起捕食者-猎物循环,在受到外部变化的深刻影响的情况下,反馈也能对动物种群产生稳定作用。<ref>CS Holling. "Resilience and stability of ecological systems". Annual Review of Ecology and Systematics 4:1-23. 1973</ref>
In [[fermentation (biochemistry)|zymology]], feedback serves as regulation of activity of an enzyme by its direct {{Not a typo|product(s)}} or downstream {{Not a typo|metabolite(s)}} in the metabolic pathway (see [[Allosteric regulation]]).
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In zymology, feedback serves as regulation of activity of an enzyme by its direct product(s) or downstream metabolite(s) in the metabolic pathway (see Allosteric regulation).
In [[psychology]], the body receives a stimulus from the environment or internally that causes the release of [[hormone]]s. Release of hormones then may cause more of those hormones to be released, causing a positive feedback loop. This cycle is also found in certain behaviour. For example, "shame loops" occur in people who blush easily. When they realize that they are blushing, they become even more embarrassed, which leads to further blushing, and so on.<ref>{{cite magazine|last=Scheff |first=Thomas |url=http://www.psychologytoday.com/blog/lets-connect/200909/the-emotionalrelational-world |title=The Emotional/Relational World |magazine=Psychology Today |date=2009-09-02 |accessdate=2013-07-10}}</ref>
In psychology, the body receives a stimulus from the environment or internally that causes the release of hormones. Release of hormones then may cause more of those hormones to be released, causing a positive feedback loop. This cycle is also found in certain behaviour. For example, "shame loops" occur in people who blush easily. When they realize that they are blushing, they become even more embarrassed, which leads to further blushing, and so on.
The climate system is characterized by strong positive and negative feedback loops between processes that affect the state of the atmosphere, ocean, and land. A simple example is the [[Ice-albedo feedback|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.
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The climate system is characterized by strong positive and negative feedback loops between processes that affect the state of the atmosphere, ocean, and land. A simple example is the 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.
Feedback is extensively used in control theory, using a variety of methods including [[state space (controls)]], [[full state feedback]], and so forth. Note that in the context of control theory, "feedback" is traditionally assumed to specify "negative feedback".<ref name=mees>''"There is a tradition in control theory that one deals with a ''negative feedback loop'' in which a negative sign is included in the feedback loop..."'' A.I.Mees, "Dynamics of Feedback Systems", New York: J. Wiley, c1981. {{ISBN|0-471-27822-X}}. p69</ref>
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Feedback is extensively used in control theory, using a variety of methods including state space (controls), full state feedback, and so forth. Note that in the context of control theory, "feedback" is traditionally assumed to specify "negative feedback".
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===控制理论===
反馈广泛应用于控制理论中,使用的方法很多,包括状态矢量空间(控制)、全状态反馈等。需要注意的是,在控制理论的背景下,“反馈”通常特指“负反馈”。<ref name=mees>''"There is a tradition in control theory that one deals with a ''negative feedback loop'' in which a negative sign is included in the feedback loop..."'' A.I.Mees, "Dynamics of Feedback Systems", New York: J. Wiley, c1981. {{ISBN|0-471-27822-X}}. p69</ref>
反馈广泛应用于控制理论中,使用的方法很多,包括状态矢量空间(控制)、全状态反馈等。需要注意的是,在控制理论的背景下,“反馈”通常特指“负反馈”。<ref name=mees>''"There is a tradition in control theory that one deals with a ''negative feedback loop'' in which a negative sign is included in the feedback loop..."'' A.I.Mees, "Dynamics of Feedback Systems", New York: J. Wiley, c1981. {{ISBN|0-471-27822-X}}. p69</ref>
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{{Further|PID controller}}
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{{进一步|PID控制器}}。、
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The most common general-purpose [[controller (control theory)|controller]] using a control-loop feedback mechanism is a [[PID controller|proportional-integral-derivative]] (PID) controller. Heuristically, the terms of a PID controller can be interpreted as corresponding to time: the proportional term depends on the ''present'' error, the integral term on the accumulation of ''past'' errors, and the derivative term is a prediction of ''future'' error, based on current rate of change.<ref>{{Citation | url = http://www.eolss.net/ebooks/Sample%20Chapters/C18/E6-43-03-03.pdf | title = PID Control | last = Araki | first = M. }}</ref>
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The most common general-purpose controller using a control-loop feedback mechanism is a proportional-integral-derivative (PID) controller. Heuristically, the terms of a PID controller can be interpreted as corresponding to time: the proportional term depends on the present error, the integral term on the accumulation of past errors, and the derivative term is a prediction of future error, based on current rate of change.
最常见的采用控制回路反馈机制的通用控制器是比例-积分-导数(PID)控制器。从启发式的角度看,PID控制器的项可以解释为与时间相对应:比例项取决于现在的误差,积分项取决于过去误差的积累,而导数项则是根据当前的变化率,对未来误差进行预测。<ref>{{Citation | url = http://www.eolss.net/ebooks/Sample%20Chapters/C18/E6-43-03-03.pdf | title = PID Control | last = Araki | first = M. }}</ref>
最常见的采用控制回路反馈机制的通用控制器是比例-积分-导数(PID)控制器。从启发式的角度看,PID控制器的项可以解释为与时间相对应:比例项取决于现在的误差,积分项取决于过去误差的积累,而导数项则是根据当前的变化率,对未来误差进行预测。<ref>{{Citation | url = http://www.eolss.net/ebooks/Sample%20Chapters/C18/E6-43-03-03.pdf | title = PID Control | last = Araki | first = M. }}</ref>
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===教育===
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关于教育方面的反馈,见'''纠正性反馈 corrective feedback'''。
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===Education===
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===机械工程===
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教育
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For feedback in the educational context, see [[corrective feedback]].
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For feedback in the educational context, see corrective feedback.
In ancient times, the [[float valve]] was used to regulate the flow of water in Greek and Roman [[water clock]]s; similar float valves are used to regulate fuel in a [[carburettor]] and also used to regulate tank water level in the [[flush toilet]].
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In ancient times, the float valve was used to regulate the flow of water in 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.
荷兰发明家克尼利厄斯·雅布斯纵·戴博尔 Cornelius Drebbel(1572-1633)制造了恒温器(c1620)用于控制鸡的孵化器和化学炉的温度。1745年,铁匠埃德蒙·李 Edmund Lee对风车进行了改进,他增加了一个扇形尾翼,使风车的正面始终面向风。1787年,汤姆·米德 Tom Mead通过使用离心摆调节基石和动石之间的距离(即调节负荷)来调节风车的转速。
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The Dutch inventor [[Cornelius Drebbel]] (1572-1633) built thermostats (c1620) to control the temperature of chicken incubators and chemical furnaces. In 1745, the windmill was improved by blacksmith Edmund Lee, who added a [[windmill fantail|fantail]] to keep the face of the windmill pointing into the wind. In 1787, [[Tom Mead]] regulated the rotation speed of a windmill by using a [[conical pendulum|centrifugal pendulum]] to adjust the distance between the bedstone and the runner stone (i.e., to adjust the load).
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1788年,詹姆斯·瓦特 James Watt使用离心调速器来调节他的蒸汽机的速度是导致工业革命的一个因素。蒸汽发动机也使用浮阀和泄压阀作为机械调节装置。詹姆斯·克拉克·麦克斯韦 James Clerk Maxwell在1868年对Watt的调节器进行了数学分析。<ref name=maxwell/>
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The Dutch inventor Cornelius Drebbel (1572-1633) built thermostats (c1620) to control the temperature of chicken incubators and chemical furnaces. In 1745, the windmill was improved by blacksmith Edmund Lee, who added a fantail to keep the face of the windmill pointing into the wind. In 1787, Tom Mead regulated the rotation speed 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).
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“Great Eastern”是当时最大的汽轮之一,采用了由约翰·麦克法兰·格雷 John McFarlane Gray在1866年设计的带有反馈机制的蒸汽舵。约瑟夫·法尔科 Joseph Farcot在1873年创造了“'''伺服系统 servo'''”一词来描述蒸汽动力转向系统,后来伺服系统被用来定位喷枪。斯佩里公司 Sperry Corporatio的埃尔默·安布罗斯·斯佩里 Elmer Ambrose Sperry在1912年设计了的第一台自动驾驶仪 autopilot。尼古拉斯·米诺尔斯基 Nicolas Minorsky在1922年发表了关于自动船舶操纵的理论分析,并描述了PID控制器。<ref name="Minorsky">{{cite journal |author=Minorsky, Nicolas |year=1922 |title=Directional stability of automatically steered bodies |journal=J. Amer. Soc of Naval Engineers |volume=34 |issue= 2|pages=280–309 |doi= 10.1111/j.1559-3584.1922.tb04958.x}}</ref>
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荷兰发明家克尼利厄斯·雅布斯纵·戴博尔 Cornelius Drebbel (1572-1633)制造了恒温器(c1620)用于控制鸡的孵化器和化学炉的温度。1745年,铁匠埃德蒙·李 Edmund Lee对风车进行了改进,他增加了一个扇形尾翼,使风车的正面始终面向风。1787年,汤姆·米德Tom Mead通过使用离心摆调节基石和动石之间的距离(即调节负荷)来调节风车的转速。
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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 [[relief valve|pressure release valves]] as mechanical regulation devices. A [[mathematical analysis]] of Watt's governor was done by [[James Clerk Maxwell]] in 1868.<ref name=maxwell/>
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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.
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1788年,詹姆斯·瓦特 James Watt 使用离心调速器来调节他的蒸汽机的速度是导致工业革命的一个因素。蒸汽发动机也使用浮阀和泄压阀作为机械调节装置。詹姆斯·克拉克·麦克斯韦 James Clerk Maxwell在1868年对Watt的调节器进行了数学分析。<ref name=maxwell/>
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The ''[[SS Great Eastern|Great Eastern]]'' was one of the largest steamships of its time and employed a steam powered rudder with feedback mechanism designed in 1866 by [[John McFarlane Gray]]. [[Joseph Farcot]] coined the word ''[[Servomechanism|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]].<ref name="Minorsky">{{cite journal |author=Minorsky, Nicolas |year=1922 |title=Directional stability of automatically steered bodies |journal=J. Amer. Soc of Naval Engineers |volume=34 |issue= 2|pages=280–309 |doi= 10.1111/j.1559-3584.1922.tb04958.x}}</ref>
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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 John 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.
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“Great Eastern”是当时最大的汽轮之一,采用了由[[约翰·麦克法兰·格雷 John McFarlane Gray]]在1866年设计的带有反馈机制的蒸汽舵。约瑟夫·法尔科 [Joseph Farcot在1873年创造了“<font color="#ff8000"> 伺服系统 servo</font>”一词来描述蒸汽动力转向系统,后来伺服系统被用来定位喷枪。 斯佩里公司 Sperry Corporatio的[埃尔默·安布罗斯·斯佩里Elmer Ambrose Sperry在1912年设计了的第一台自动驾驶仪 autopilot。尼古拉斯·米诺尔斯基 Nicolas Minorsky在1922年发表了关于自动船舶操纵的理论分析,并描述了PID控制器。<ref name="Minorsky">{{cite journal |author=Minorsky, Nicolas |year=1922 |title=Directional stability of automatically steered bodies |journal=J. Amer. Soc of Naval Engineers |volume=34 |issue= 2|pages=280–309 |doi= 10.1111/j.1559-3584.1922.tb04958.x}}</ref>
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Internal combustion engines of the late 20th century employed mechanical feedback mechanisms such as the [[Ignition timing#Vacuum timing advance|vacuum timing advance]] but mechanical feedback was replaced by electronic [[engine control unit|engine management systems]] once small, robust and powerful single-chip [[microcontroller]]s became affordable.
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Internal combustion engines of the late 20th century employed mechanical feedback mechanisms such as the vacuum timing advance but mechanical feedback was replaced by electronic engine management systems once small, robust and powerful single-chip microcontrollers became affordable.
[[File:Ideal feedback model.svg|thumb|The simplest form of a feedback amplifier can be represented by the ''ideal block diagram'' made up of [https://www.google.com/search?tbo=p&tbm=bks&q=%22A+unilateral+block+or+network+is+one+in+which+power+may+be+transmitted+in+one+direction+only.%22&num=10&gws_rd=ssl unilateral elements].<ref name="Chen">{{cite book|title=Circuit Analysis and Feedback Amplifier Theory|author=Wai-Kai Chen|publisher=CRC Press|year=2005|isbn=9781420037272|location=423825181|pages=13–1|chapter=Chapter 13: General feedback theory|quote=[In a practical amplifier] the forward path may not be strictly unilateral, the feedback path is usually bilateral, and the input and output coupling networks are often complicated.|chapter-url=https://books.google.com/books?id=ZlJM1OLDQx0C&pg=SA13-PA1}}
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[[File:Ideal feedback model.svg|thumb|反馈放大器的最简单形式可以用由单向元件组成的“理想框图”来表示。<ref name="Chen">{{cite book|title=Circuit Analysis and Feedback Amplifier Theory|author=Wai-Kai Chen|publisher=CRC Press|year=2005|isbn=9781420037272|location=423825181|pages=13–1|chapter=Chapter 13: General feedback theory|quote=[In a practical amplifier] the forward path may not be strictly unilateral, the feedback path is usually bilateral, and the input and output coupling networks are often complicated.|chapter-url=https://books.google.com/books?id=ZlJM1OLDQx0C&pg=SA13-PA1}}
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The use of feedback is widespread in the design of [[electronics|electronic]] components such as [[amplifier]]s, [[oscillator]]s, and stateful [[logic circuit]] elements such as [[flip-flop (electronics)|flip-flop]]s and [[counter (digital)|counter]]s. Electronic feedback systems are also very commonly used to control mechanical, thermal and other physical processes.
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The use of feedback is widespread in the design of electronic components such as amplifiers, oscillators, and stateful logic circuit elements such as flip-flops and counters. Electronic feedback systems are also very commonly used to control mechanical, thermal and other physical processes.
If the signal is inverted on its way round the control loop, the system is said to have ''[[negative feedback amplifier|negative feedback]]'';<ref name=KalS>{{cite book |title=Basic Electronics: Devices, Circuits and IT Fundamentals |author=Santiram Kal |url=https://books.google.com/books?id=_Bw_-ZyGL6YC&q=%22it+is+called+negative+feedback%22+%22if+the+feedback+signal+reduces+the+input+signal%22&pg=PA191 |quote=If the feedback signal reduces the input signal, ''i.e.'' it is out of phase with the input [signal], it is called negative feedback. |isbn=9788120319523 |year=2009 |publisher=PHI Learning Pvt. Ltd |page=191}}</ref> otherwise, the feedback is said to be ''positive''. Negative feedback is often deliberately introduced to increase the [[BIBO stability|stability]] and accuracy of a system by correcting or reducing the influence of unwanted changes. This scheme can fail if the input changes faster than the system can respond to it. When this happens, the lag in arrival of the correcting signal can result in over-correction, causing the output to [[oscillation|oscillate]] or "hunt".<ref>With mechanical devices, hunting can be severe enough to destroy the device.</ref> While often an unwanted consequence of system behaviour, this effect is used deliberately in electronic oscillators.
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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 by correcting or reducing the influence of unwanted changes. This scheme can fail if the input changes faster than the system can respond to it. When this happens, the lag in arrival of the correcting signal can result in over-correction, causing the output to oscillate or "hunt". While often an unwanted consequence of system behaviour, this effect is used deliberately in electronic oscillators.
如果信号在绕过控制环路的过程中发生了反转,则称系统有负反馈;<ref name=KalS>{{cite book |title=Basic Electronics: Devices, Circuits and IT Fundamentals |author=Santiram Kal |url=https://books.google.com/books?id=_Bw_-ZyGL6YC&q=%22it+is+called+negative+feedback%22+%22if+the+feedback+signal+reduces+the+input+signal%22&pg=PA191 |quote=If the feedback signal reduces the input signal, ''i.e.'' it is out of phase with the input [signal], it is called negative feedback. |isbn=9788120319523 |year=2009 |publisher=PHI Learning Pvt. Ltd |page=191}}</ref>否则,称反馈为正反馈。负反馈常常被刻意引入,通过纠正或减少不需要的变化的影响来提高系统的稳定性和准确性 如果输入的变化速度快于系统对它的响应速度,这种方案就会失效。当这种情况发生时,校正信号到达的滞后可能导致过度校正,导致输出振荡或“捕获”。<ref>With mechanical devices, hunting can be severe enough to destroy the device.</ref>虽然这种效应通常是系统行为不希望出现的结果,但它却被有意地用于电子振荡器中。
如果信号在绕过控制环路的过程中发生了反转,则称系统有负反馈;<ref name=KalS>{{cite book |title=Basic Electronics: Devices, Circuits and IT Fundamentals |author=Santiram Kal |url=https://books.google.com/books?id=_Bw_-ZyGL6YC&q=%22it+is+called+negative+feedback%22+%22if+the+feedback+signal+reduces+the+input+signal%22&pg=PA191 |quote=If the feedback signal reduces the input signal, ''i.e.'' it is out of phase with the input [signal], it is called negative feedback. |isbn=9788120319523 |year=2009 |publisher=PHI Learning Pvt. Ltd |page=191}}</ref>否则,称反馈为正反馈。负反馈常常被刻意引入,通过纠正或减少不需要的变化的影响来提高系统的稳定性和准确性 如果输入的变化速度快于系统对它的响应速度,这种方案就会失效。当这种情况发生时,校正信号到达的滞后可能导致过度校正,导致输出振荡或“捕获”。<ref>With mechanical devices, hunting can be severe enough to destroy the device.</ref>虽然这种效应通常是系统行为不希望出现的结果,但它却被有意地用于电子振荡器中。
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贝尔实验室的哈里·奈奎斯特 Harry Nyquist推导出了判定反馈系统稳定性的'''奈奎斯特稳定判据 Nyquist stability criterion Chaos theory'''。一个比较简单但不太常用的方法是使用亨德里克博德 Hendrikbode开发的Bode图来确定增益裕度和相位裕度。保证稳定性的设计往往使用频率补偿来控制放大器的极点位置。
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[[Harry Nyquist]] at [[Bell Labs]] derived the [[Nyquist stability criterion]] for determining the stability of feedback systems. An easier method, but less general, is to use [[Bode plot]]s developed by [[Hendrik Wade Bode|Hendrik Bode]] to determine the [[Gain margin|gain margin and phase margin]]. Design to ensure stability often involves [[frequency compensation]] to control the location of the [[pole (complex analysis)|pole]]s of the amplifier.
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Harry Nyquist at Bell Labs derived the Nyquist stability criterion for determining the stability of feedback systems. An easier method, but less general, is to use Bode plots developed by Hendrik Bode to determine the gain margin and phase margin. Design to ensure stability often involves frequency compensation to control the location of the poles of the amplifier.
Electronic feedback loops are used to control the output of [[electronics|electronic]] devices, such as [[amplifiers]]. A feedback loop is created when all or some portion of the output is fed back to the input. A device is said to be operating ''open loop'' if no output feedback is being employed and ''closed loop'' if feedback is being used.<ref>P. Horowitz & W. Hill, ''The Art of Electronics'', Cambridge University Press (1980), Chapter 3, relating to operational amplifiers.</ref>
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Electronic feedback loops are used to control the output of electronic devices, such as amplifiers. A feedback loop is created when all or some portion of the output is fed back to the input. A device is said to be operating open loop if no output feedback is being employed and closed loop if feedback is being used.
电子反馈回路用于控制电子设备的输出,如放大器。当所有或部分输出反馈到输入时,就形成了一个反馈回路。如果没有采用输出反馈,则称为开环运行,如果采用反馈,则称为闭环运行。<ref>P. Horowitz & W. Hill, ''The Art of Electronics'', Cambridge University Press (1980), Chapter 3, relating to operational amplifiers.</ref>
电子反馈回路用于控制电子设备的输出,如放大器。当所有或部分输出反馈到输入时,就形成了一个反馈回路。如果没有采用输出反馈,则称为开环运行,如果采用反馈,则称为闭环运行。<ref>P. Horowitz & W. Hill, ''The Art of Electronics'', Cambridge University Press (1980), Chapter 3, relating to operational amplifiers.</ref>
When two or more amplifiers are cross-coupled using positive feedback, complex behaviors can be created. These ''[[multivibrator]]s'' are widely used and include:
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When two or more amplifiers are cross-coupled using positive feedback, complex behaviors can be created. These multivibrators are widely used and include:
* monostable circuits, which can be pushed into a state, and will return to the stable state after some time
* 单稳态电路,可以将其推入一个状态,并在一段时间后恢复到稳定状态。
* 单稳态电路,可以将其推入一个状态,并在一段时间后恢复到稳定状态。
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* bistable circuits, which have two stable states that the circuit can be switched between
* 双稳态电路,它有两个稳定的状态,电路可以在这两个状态之间切换。
* 双稳态电路,它有两个稳定的状态,电路可以在这两个状态之间切换。
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====负反馈====
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当反馈的输出信号相对于输入信号有180°的相对相位(上下颠倒)时,就会出现负反馈。这种情况有时被称为失相,但该术语也用于表示其他相位分离,如“90°失相”。负反馈可用于纠正输出误差或使系统对不需要的波动脱敏。<ref name=Bhattacharya>For an analysis of desensitization in the system pictured, see {{cite book |author=S.K Bhattacharya |title=Linear Control Systems |pages=134–135 |quote=The parameters of a system ... may vary... The primary advantage of using feedback in control systems is to reduce the system's sensitivity to parameter variations. |chapter=§5.3.1 Effect of feedback on parameter variations |isbn=9788131759523 |publisher=Pearson Education India |year=2011 |chapter-url=https://books.google.com/books?id=e5Z1A_6jxAUC&q=%22primary+advantage+of+using+feedback+in+control+system+is+to+reduce+the+system%27s+sensitivity+to+parameter+variations%22&pg=PA135}}</ref>在反馈放大器中,这种校正一般是为了减少波形失真或建立一个指定的增益水平。负反馈放大器的增益的一般表达式是渐进增益模型。
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====正反馈====
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====Negative feedback====
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负反馈
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A Negative feedback occurs when the fed-back output signal has a relative phase of 180° with respect to the input signal (upside down). This situation is sometimes referred to as being ''out of phase'', but that term also is used to indicate other phase separations, as in "90° out of phase". Negative feedback can be used to correct output errors or to desensitize a system to unwanted fluctuations.<ref name=Bhattacharya>For an analysis of desensitization in the system pictured, see {{cite book |author=S.K Bhattacharya |title=Linear Control Systems |pages=134–135 |quote=The parameters of a system ... may vary... The primary advantage of using feedback in control systems is to reduce the system's sensitivity to parameter variations. |chapter=§5.3.1 Effect of feedback on parameter variations |isbn=9788131759523 |publisher=Pearson Education India |year=2011 |chapter-url=https://books.google.com/books?id=e5Z1A_6jxAUC&q=%22primary+advantage+of+using+feedback+in+control+system+is+to+reduce+the+system%27s+sensitivity+to+parameter+variations%22&pg=PA135}}</ref> In feedback amplifiers, this correction is generally for waveform [[distortion]] reduction{{citation needed|date=October 2014}} or to establish a specified [[Gain (electronics)|gain]] level. A general expression for the gain of a negative feedback amplifier is the [[asymptotic gain model]].
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A Negative feedback occurs when the fed-back output signal has a relative phase of 180° with respect to the input signal (upside down). This situation is sometimes referred to as being out of phase, but that term also is used to indicate other phase separations, as in "90° out of phase". Negative feedback can be used to correct output errors or to desensitize a system to unwanted fluctuations. In feedback amplifiers, this correction is generally for waveform distortion reduction or to establish a specified gain level. A general expression for the gain of a negative feedback amplifier is the asymptotic gain model.
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当反馈的输出信号相对于输入信号有180°的相对相位(上下颠倒)时,就会出现负反馈。这种情况有时被称为失相,但该术语也用于表示其他相位分离,如 "90°失相"。负反馈可用于纠正输出误差或使系统对不需要的波动脱敏。<ref name=Bhattacharya>For an analysis of desensitization in the system pictured, see {{cite book |author=S.K Bhattacharya |title=Linear Control Systems |pages=134–135 |quote=The parameters of a system ... may vary... The primary advantage of using feedback in control systems is to reduce the system's sensitivity to parameter variations. |chapter=§5.3.1 Effect of feedback on parameter variations |isbn=9788131759523 |publisher=Pearson Education India |year=2011 |chapter-url=https://books.google.com/books?id=e5Z1A_6jxAUC&q=%22primary+advantage+of+using+feedback+in+control+system+is+to+reduce+the+system%27s+sensitivity+to+parameter+variations%22&pg=PA135}}</ref>在反馈放大器中,这种校正一般是为了减少波形失真或建立一个指定的增益水平。负反馈放大器的增益的一般表达式是渐进增益模型。
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====Positive feedback====
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正反馈
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Positive feedback occurs when the fed-back signal is in phase with the input signal. Under certain gain conditions, positive feedback reinforces the input signal to the point where the output of the device [[oscillates]] between its maximum and minimum possible states. Positive feedback may also introduce [[hysteresis]] into a circuit. This can cause the circuit to ignore small signals and respond only to large ones. It is sometimes used to eliminate noise from a digital signal. Under some circumstances, positive feedback may cause a device to latch, i.e., to reach a condition in which the output is locked to its maximum or minimum state. This fact is very widely used in digital electronics to make [[Flip-flop (electronics)|bistable]] circuits for volatile storage of information.
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Positive feedback occurs when the fed-back signal is in phase with the input signal. Under certain gain conditions, positive feedback reinforces the input signal to the point where the output of the device oscillates between its maximum and minimum possible states. Positive feedback may also introduce hysteresis into a circuit. This can cause the circuit to ignore small signals and respond only to large ones. It is sometimes used to eliminate noise from a digital signal. Under some circumstances, positive feedback may cause a device to latch, i.e., to reach a condition in which the output is locked to its maximum or minimum state. This fact is very widely used in digital electronics to make bistable circuits for volatile storage of information.
The loud squeals that sometimes occurs in [[audio system]]s, [[public address system|PA systems]], and [[rock music]] are known as [[audio feedback]]. If a microphone is in front of a loudspeaker that it is connected to, sound that the microphone picks up comes out of the speaker, and is picked up by the microphone and re-amplified. If the [[loop gain]] is sufficient, howling or squealing at the maximum power of the amplifier is possible.
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The loud squeals that sometimes occurs in audio systems, PA systems, and rock music are known as audio feedback. If a microphone is in front of a loudspeaker that it is connected to, sound that the microphone picks up comes out of the speaker, and is picked up by the microphone and re-amplified. If the loop gain is sufficient, howling or squealing at the maximum power of the amplifier is possible.
An electronic oscillator is an electronic circuit that produces a periodic, oscillating electronic signal, often a sine wave or a square wave. Oscillators convert direct current (DC) from a power supply to an alternating current signal. They are widely used in many electronic devices. Common examples of signals generated by oscillators include signals broadcast by radio and television transmitters, clock signals that regulate computers and quartz clocks, and the sounds produced by electronic beepers and video games.
A latch or a flip-flop is a circuit that has two stable states and can be used to store state information. They typically constructed using feedback that crosses over between two arms of the circuit, to provide the circuit with a state. The circuit can be made to change state by signals applied to one or more control inputs and will have one or two outputs. It is the basic storage element in sequential logic. Latches and flip-flops are fundamental building blocks of digital electronics systems used in computers, communications, and many other types of systems.
Latches and flip-flops are used as data storage elements. Such data storage can be used for storage of state, and such a circuit is described as sequential logic. When used in a finite-state machine, the output and next state depend not only on its current input, but also on its current state (and hence, previous inputs). It can also be used for counting of pulses, and for synchronizing variably-timed input signals to some reference timing signal.
Flip-flops can be either simple (transparent or opaque) or clocked (synchronous or edge-triggered). Although the term flip-flop has historically referred generically to both simple and clocked circuits, in modern usage it is common to reserve the term flip-flop exclusively for discussing clocked circuits; the simple ones are commonly called latches.
反馈回路为控制软件和计算系统的运行、维护和升级提供了通用机制。反馈回路是自适应软件工程中的重要模型,它定义了自适应过程中控制元件之间相互作用的行为,以保证系统在运行时的性能。反馈环路和控制理论基础已成功地应用于计算系统。特别是,它们已经应用于产品的开发,如IBM的Universal Database server和IBM Tivoli。从软件的角度来看,IBM研究人员提出的自主(MAPE,monitor analyze plan execute)回路是对反馈回路应用于动态特性控制和自主软件系统设计与演化的又一宝贵贡献。
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Using this terminology, a latch is level-sensitive, whereas a flip-flop is edge-sensitive. That is, when a latch is enabled it becomes transparent, while a flip flop's output only changes on a single type (positive going or negative going) of clock edge.
Feedback loops provide generic mechanisms for controlling the running, maintenance, and evolution of software and computing systems. Feedback-loops are important models in the engineering of adaptive software, as they define the behaviour of the interactions among the control elements over the adaptation process, to guarantee system properties at run-time. Feedback loops and foundations of control theory have been successfully applied to computing systems. In particular, they have been applied to the development of products such as IBM's Universal Database server and IBM Tivoli. From a software perspective, the autonomic (MAPE, monitor analyze plan execute) loop proposed by researchers of IBM is another valuable contribution to the application of feedback loops to the control of dynamic properties and the design and evolution of autonomic software systems.
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反馈回路为控制软件和计算系统的运行、维护和升级提供了通用机制。反馈回路是自适应软件工程中的重要模型,它定义了自适应过程中控制元件之间相互作用的行为,以保证系统在运行时的性能。反馈环路和控制理论基础已成功地应用于计算系统。特别是,它们已经应用于产品的开发,如IBM的Universal Database server和IBM Tivoli。从软件的角度来看,IBM 研究人员提出的自主(MAPE,monitor analyze plan execute)回路是对反馈回路应用于动态特性控制和自主软件系统设计与演化的又一宝贵贡献。
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Feedback is also a useful design principle for designing user interfaces.
反馈也是设计用户界面时一个有用的设计原则。
反馈也是设计用户界面时一个有用的设计原则。
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Video feedback is the video equivalent of acoustic feedback. It involves a loop between a video camera input and a video output, e.g., a television screen or monitor. Aiming the camera at the display produces a complex video image based on the feedback.
乔治•索罗斯 George Soros用“'''反身性 reflexivity servo'''”一词来描述金融市场的反馈,并根据这一原则发展了一套投资理论。
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The stock market is an example of a system prone to oscillatory "hunting", governed by positive and negative feedback resulting from cognitive and emotional factors among market participants. For example:
George Soros used the word reflexivity, to describe feedback in the financial markets and developed an investment theory based on this principle.
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乔治•索罗斯 George Soros 用“<font color="#ff8000"> 反身性 reflexivity servo</font>”一词来描述金融市场的反馈,并根据这一原则发展了一套投资理论。
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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.
传统的经济供求平衡模型只支持理想的线性负反馈,保罗·奥默罗德 Paul Ormerod在他的《经济学之死》一书中对这个模型提出了严厉的批评,而传统经济学家也对她提出了批评。随着经济学家开始认识到混沌理论适用于包括金融市场在内的非线性反馈系统,这本书成为了转变观点的一部分。
传统的经济供求平衡模型只支持理想的线性负反馈,保罗·奥默罗德 Paul Ormerod在他的《经济学之死》一书中对这个模型提出了严厉的批评,而传统经济学家也对她提出了批评。随着经济学家开始认识到混沌理论适用于包括金融市场在内的非线性反馈系统,这本书成为了转变观点的一部分。
对于一个反馈系统,很难进行简单的因果推理,因为第一个系统影响第二个系统,第二个系统影响第一个系统,产生了一个循环论证。这就使得基于因果关系的推理变得很困难,因此有必要将系统作为一个整体进行分析。——卡尔·约翰·阿斯特洛姆·马丁 Karl Johan Åström和查德·M·默里 Richard M.Murray
自17世纪以来,离心调速器被用于调节风车中磨石之间的距离和压力。1788年,詹姆斯·瓦特 James Watt根据他的商业伙伴马修·布尔顿 Matthew Boulton的建议,设计了他的第一个离心调速器,应用于他们生产的蒸汽机。早期的蒸汽机采用纯粹的往复运动,用于抽水——这种应用不受工作速度变化的影响,但蒸汽机在其他应用中的使用需要更精确的速度控制。
在1868年,詹姆斯·克莱克·麦克斯韦 James Clerk Maxwell写了一篇著名的论文《论调速器》,这个论文被广泛认为是反馈控制理论的经典之作。[4]这是一篇关于控制理论和反馈数学的里程碑式的论文。
19世纪60年代,美国开始使用关于反馈的动词短语,意思是在机械过程中回到原来的位置。[5][6] 1909年,诺贝尔奖获得者卡尔·费迪南德·布劳恩 Karl Ferdinand Braun用名词“反馈”来指电子电路元件之间的(不希望有的)耦合。[7]
“正面”和“负面”这两个词在第二次世界大战之前首次用于反馈。20世纪20年代,随着再生电路的引入,正反馈的概念已经流行起来。[11] 弗里斯 Friis和延森 Jensen(1924)将一套电子放大器中的再生回路描述为"反馈"作用是正的例子,以此和他们顺便提及的负反馈作用相区别。[12]哈罗德·史蒂芬·布莱克 Harold Stephen Black1934年的经典论文首次详细阐述了负反馈在电子放大器中的应用。布莱克认为:
荷兰发明家克尼利厄斯·雅布斯纵·戴博尔 Cornelius Drebbel(1572-1633)制造了恒温器(c1620)用于控制鸡的孵化器和化学炉的温度。1745年,铁匠埃德蒙·李 Edmund Lee对风车进行了改进,他增加了一个扇形尾翼,使风车的正面始终面向风。1787年,汤姆·米德 Tom Mead通过使用离心摆调节基石和动石之间的距离(即调节负荷)来调节风车的转速。
1788年,詹姆斯·瓦特 James Watt使用离心调速器来调节他的蒸汽机的速度是导致工业革命的一个因素。蒸汽发动机也使用浮阀和泄压阀作为机械调节装置。詹姆斯·克拉克·麦克斯韦 James Clerk Maxwell在1868年对Watt的调节器进行了数学分析。[14]
“Great Eastern”是当时最大的汽轮之一,采用了由约翰·麦克法兰·格雷 John McFarlane Gray在1866年设计的带有反馈机制的蒸汽舵。约瑟夫·法尔科 Joseph Farcot在1873年创造了“伺服系统 servo”一词来描述蒸汽动力转向系统,后来伺服系统被用来定位喷枪。斯佩里公司 Sperry Corporatio的埃尔默·安布罗斯·斯佩里 Elmer Ambrose Sperry在1912年设计了的第一台自动驾驶仪 autopilot。尼古拉斯·米诺尔斯基 Nicolas Minorsky在1922年发表了关于自动船舶操纵的理论分析,并描述了PID控制器。[34]
↑"Heretofore ... it has been necessary to reverse the motion of the rollers, thus causing the material to travel or feed back, ..." HH Cole, "Improvement in Fluting-Machines", US Patent 55,469 (1866) accessed 23 March 2012.
↑"When the journal or spindle is cut ... and the carriage is about to feed back by a change of the sectional nut or burr upon the screw-shafts, the operator seizes the handle..." JM Jay, "Improvement in Machines for Making the Spindles of Wagon-Axles", US Patent 47,769 (1865) accessed 23 March 2012. Maintaining a desired system performance despite disturbance using negative feedback to reduce system error
↑"...as far as possible the circuit has no feed-back into the system being investigated."
An example of a negative feedback loop with goals
[1]
A positive feedback loop example
Karl Ferdinand Braun, "Electrical oscillations and wireless telegraphy", Nobel Lecture, 11 December 1909. Retrieved 19 March 2012.
↑Herold, David M., and Martin M. Greller. "Research Notes. FEEDBACK THE DEFINITION OF A CONSTRUCT." Academy of management Journal 20.1 (1977): 142-147.
↑Charles S. Carver, Michael F. Scheier: On the Self-Regulation of Behavior Cambridge University Press, 2001
↑Hermann A Haus and Richard B. Adler, Circuit Theory of Linear Noisy Networks, MIT Press, 1959
↑BF Skinner, The Experimental Analysis of Behavior, American Scientist, Vol. 45, No. 4 (SEPTEMBER 1957), pp. 343-371
↑"However, after scrutinizing the statistical properties of the structural equations, the members of the committee assured themselves that it is possible to have a significant positive feedback loop when using standardized scores, and a negative loop when using real scores."
For feedback in the educational context, see corrective feedback.
Ralph L. Levine, Hiram E. Fitzgerald. Analysis of the dynamic psychological systems: methods and applications,
↑"There is a tradition in control theory that one deals with a negative feedback loop in which a negative sign is included in the feedback loop..." A.I.Mees, "Dynamics of Feedback Systems", New York: J. Wiley, c1981.
↑Minorsky, Nicolas (1922). "Directional stability of automatically steered bodies". J. Amer. Soc of Naval Engineers. 34 (2): 280–309. doi:10.1111/j.1559-3584.1922.tb04958.x.