Talk:Feedback

Older comments

is external linking allowed?, in any case much good info in http://prof.usb.ve/williamc/Mejoramiento/historia.html should be made available here

in electronics the para are disordered, positive feedback (suject of great Armstrong deForset patent dispute)predates Black's negative feedback amplifier and should be refered to first, PID is a subset of negative feedback control techniques :jcox

--- I don't believe that the explanation of audio feedback is correct. It identifies the frequency of feedback noise as related to the transit time through the system (Implying it's a matter of repeating the waveform, the effect you might get with digital echo or flange). But I'm 95% sure that's completely irrelevant in a system like this, the waveform is completely obliterated by all the transitions made, all you're left with is frequencies that approximate those you started with.

OK, a quick test: I was able to get audible feedback with a 1/2 second delay in the loop, which should give a frequency of 2 hz, 5 octaves below audible.

So I'm rather sure the frequency of feedback is not determined by transit time, but by the frequency response of the whole system. All real world systems contain some capacitance and inductance, meaning they all act as very wide, low, bandpass filters. But when you amplify and feedback the filtered sound into the filtered sound, you've naturally created an oscillator (the simplest forms of analog oscillators work on exactly this principle).

So unless anyone objects I'm going to change the explanation to reflect this. User:Wji

---

Although feedback was perhaps discovered during the course of the development of electronics, it exists in many natural processes and the word (although not present in earlier dictionaries, for example the original OED) represents a concept in general use outside engineering. Therefore the article should begin with the general concept but include a substantial section on control theory. I was first introduced to feedback during training on servo mechanisms many years ago and am a bit rusty, but I clearly remember it took both positive and negative feedback to make them work. What we call feedback like with a microphone is perhaps not feedback in the sense we are using it here. User:Fredbauder

I agree that there is more than one sense of the word feedback. The Penguin Dictionary of Electronics, for example, has separate entries for feedback in the general sense and feedback control loop in the specific context of control systems. The Chambers Science and Technology Dictionary has headings for feedback (acoustic), feedback (telecommunications) and feedback control loop, so perhaps there are really three different concepts. If we wish to separate the general from the particular, I would suggest the following structure for the Wikipedia (with separate articles for hunting and feedback):

• Hunting (known to mechanical engineers as early as 1880, according to OED2)
• Feedback
  • as originally defined, i.e. in electronic amplifiers (see OED2 citation from 1920)
    • acoustic feedback in public address amplifiers (OED2 has a 1921 citation of howl) - perhaps this could be a separate article
  • feedback theory applied to control loops (probably first applied in World War II)
    • control loops in nature, i.e. natural systems that can be analysed with control loop theory (existing since prehistory but only understood by humans in the light of control theory)

Do you think this is reasonable? Unfortunately it contradicts your idea of putting the natural phenomena first. My scheme lists things in the order of discovery by man, whereas yours is nature-based. I cannot say which is better.

As for the microphone example, this is an illustration of feedback in the electronic (or electroacoustic) sense, not in the control loop sense. The feedback is always positive, because sound from the loudspeakers is always added to, never subtracted from, the sound entering the microphone. What changes is the loop gain, which varies as the user moves the microphone relative to the speakers. As soon as the loop gain exceeds unity, the system howls. This effect is independent of frequency. I believe that a system with negative feedback can only become unstable if the signal frequency exceeds the bandwidth of the feedback loop.

In control theory you can have multiple feedback paths (often three: proportional, integral and derivative) and it is meaningless to talk about overall positive or negative feedback, because the three paths may have different characteristics. --Heron

What I suggest is a simple introduction which includes the general case, followed by as much specialized technical information as you feel appropriate. I agree the notion of postive and negative is applicable only to 2 dimensional systems, but I think it should remain in the introduction. I don't think organization around order of discovery is good; I prefer organization to start with a brief general introduction using simple language and concepts followed by (in this case) an engineering section, followed by the ways the concept has been adapted to natural systems. I guess runaway positive feedback is what we are talking about with apmplifiers. Fred Bauder

I divided the article into sections, without changing the words much. I may go further and remove the acoustic example to a separate article, but I'll leave 'hunting' where it is. --Heron

---

I have been bold and removed the acoustic feedback section totally. I have linked the existing article at Audio feedback to the disambiguation page. The main differences in the removed section (reproduced below) lacking in the original page are the points about the band-pass filter and the electronic oscillator.

I believe the band-pass filter point is incorrect anyway. True, all systems have some kind low and high pass filter in them, but this is generally well outside the human range of hearing, and in any case, makes no difference to the presence of feedback. The deleted section was also vague as to whether this was affecting the presence or nature of the feedback, but if it were just the latter, there are plenty of other factors involved (at the very least, the inherant EQ of the system would be much more important).

Also, the electronic oscillator point seems slightly amibiguous too, although I could understand if people wanted this link in the main article. It might be worth pointing out that the simplicity is certainly not in the waveform, but in the construction. --postglock 07:49, 6 Jun 2005 (UTC)

Feedback in audio systems

Main article: Audio feedback.

A well-known example of runaway positive feedback in electronic systems is called "howl" or "howl-round". This occurs in public address systems when sound from the loudspeakers reaches the microphone, is amplified by the system, and is then fed back into the system at even higher volume. All electrical systems contain capacitance and inductance and so act as band-pass filters responding better to certain frequencies. In a single loop through the system, this effect is negligible, but it becomes severe when the signal passes through the system repeatedly. This effect is the basis of the simplest kinds of analogue electronic oscillator.

on mention of "audio feedback"at top

postglock- lemme know if my last version works for you. thankz, Ished-out amounts of Vonn-ness 14:19, 10 September 2005 (UTC)

Problems with the current definition of "Feedback"

> Feedback is the signal that is looped back to control a system within itself.

The mention of "signal" and "control" seem overly teleological. Here are some definitions of feedback loop from around the net; a definition of feedback ought to work well with these sorts of definitions:

• "A feedback loop is a system where outputs are fed back into the system as inputs, increasing or decreasing effects." (from this wikipedia's "feedback loop" article)
• "a linkage of two or more system components that forms a round-trip flow of information."
• "the output of some process or system is fed back into the system as a partial input, modifying the process."
• "a self-perpetuating mechanism of change and response to that change."
• "A series of actions which affect one another in a way that circles back to the original action."
• "In the climate system a “feedback loop” refers to a pattern of interacting processes where a change in one variable, through interaction with other variables in the system, either reinforces the original process (positive feedback) or suppresses the process (negative feedback)."
• "In a system where a transformation occurs, there are inputs and outputs. ... In every feedback loop, as the name suggests, information about the result of a transformation or an action is sent back to the input of the system in the form of input data."

What is your favorite, least constraining definition of feedback?

love, raiph 05:11, 10 October 2006 (UTC)

Proposal to refactor content

There's a long laundry list of important theories, phenomena and more built directly on top of feedback loops that aren't mentioned on this page but should, imo, be considered. (I think I could easily list a dozen, and maybe a hundred, but the specifics aren't my point and I really don't want to get into that game yet if we can avoid it.)

Conversely, much of what's on the page right now seems too detailed, even for me, someone who's been intellectually focused on feedback loops for over a decade.

I propose I/we refactor the page. The introduction should be as general as possible. A History section seems a natural. Maybe an Examples section. I see most of the details of particular feedback phenomena going on their own pages.

Comments?

love, raiph 03:44, 3 October 2006 (UTC)

Merge Feedback loop into Feedback

• Support: It's the same content. Certainly feedback loops are everywhere, so this is in a way a disambiguation page.+mwtoews 21:40, 22 December 2006 (UTC)
• Support: The concepts are directly related. Zarggg 19:22, 1 January 2007 (UTC)
• Support: Same stuff --Pgreenfinch 19:44, 1 January 2007 (UTC)
• Lets do it: see above Sancho McCann 18:20, 3 January 2007 (UTC)
• Support; the other article has a pretty little picture, and links bordering upon the metaphorical, but it all belongs here. Jim.henderson 21:06, 24 January 2007 (UTC)
• Support: Presumably it's standard practice when making major changes like this to ensure the new page reads smoothly as a link from other Wikipedia pages. I'm thinking in particular of Cybernetics, which is basically the study of (higher order effects of) feedback loops. love, raiph 18:14, 7 February 2007 (UTC)
• Comment: It appears that the redirection has been put in place, so I removed the Merge discussion header. Nitsky416 05:47, 5 March 2007 (UTC)

Content for first paragraph

I am used to finding concise explanations in the first paragraphs of a Wikipedia article, and would propose the following thumbnail sketch of "feedback" for the first para. I haven't edited an article so won't presume, but this example is technically accurate and memorable:

Feedback: an action changes a system and then the system changes the action.
Positive feedback increases the action: you step on the brake pedal in a moving car, and the car slows, pushing your foot down harder on the brake.
Negative feedback decreases the action: you step on the gas pedal and the car accelerates, pulling your foot off the gas pedal.

If this is appropriate perhaps someone will include it. 68.98.117.241 23:25, 27 January 2007 (UTC)

---

I agree with the above change, and suggest that the current definitions in Types of Feedback are in fact incorrect and misleading. An example of negative feedback is a thermostat heating a room that is too cold. This is not reducing output, but increasing output (from the heater) or increasing input (into the room).
I also feel that the "bipolar feedback" definition is confusing - both positive and negative feedback mechanisms can cause output to change in either direction, so both are bipolar. But feedback can't be positive and negative at the same time.
Finally, hunting is more correctly a case of over-control, where a negative feedback signal overshoots the mark. This is a type of oscillation, but doesn't strictly involve positive feedback at all.
I suggest that this article could benefit from better clarity of the terms positive and negative earlier on. I had started to edit, but realized that my background (electronics) is probably too narrow for a general article.
Trevithj (talk) 20:56, 18 August 2008 (UTC)

Other Uses of the Word "Feedback"

There is a Rush album called Feedback that should be included in the disambiguation page. --The Fwanksta

The winning contestant from Who Wants to be a Superhero was called Feedback (Matthew Atherton). This should be included on the disambiguation page.

Feedback is also widely used to refer to suggestions given to people or companies in order to help improve behaviour, services, results or products. Feedback to students about homework results, to workers about team performance, to companies about product quality and so on. There is literature and research about effective feedback, impact of feedback and so on. It appears that Wikipedia does not have articles about this kind of feedback, other than 360-degree feedback - josei 19:06, 21 August 2007 (UTC)

A possible article splitt should be cancelled

A splitting of the article has been proposed on 15 March 2007. Nobody made any suggestions about this untill I yesterday removed the splitting tag. Now today User:Intgr reversed this with the argument:

• I don't think it's outdated: the article still documents different loosely related meanings for "feedback" -- different concepts should have different articles

Now I think there are at least four good reasons not to split:

• A splitting proposal should be cancelled if nobody reacts. You can keep those ideas for ever.
• A splitt is not a good idea because:
  • there are no real different meanings of feedback in cybernetics, mechanical engineering and in economics.
  • They are all kind of control theory related.
  • Maybe only the super expert see all different things.
  • The article is about strong related meanings
• The fact that a band exist called Feedback (Matthew Atherton) shouldn't be a reason to make a disambiguation page
• I agree with josei. There is yet only a 360-degree feedback article, which can exist beside this article.

I think this article is only in need of an expert, who creates a more general introduction, which shows how all these aspects are related to one central concept. For example this article is comparable with the complexity article. This is also one paradigm, with different applications in the disciplines. - Mdd 18:53, 28 August 2007 (UTC)

The fact that nobody has done the split yet doesn't mean that it shouldn't be split at all. If the tag hasn't been discussed or contested since March then I'd think that most passers-by have been agreeing with the split, but haven't really bothered to do it themself.

My rationale: As you stated, the common meaning of "feedback" is its meaning in control theory — this which also embraces the positive/negative/bipolar feedback types. The overlap of how feedback applies to other fields (acoustics, optics, electronics, economics, nature or organizations) is strictly limited to the control theoretical meaning, so there is little reason to keep some of them together. In fact, almost universally, when you want to link to an article on "feedback" from another, you want to link to the term as it applies to a particular field.

The current sections on the fields in this article could surely be expanded, but right now they're stuck in a no-man's land: they do not form a part of a larger article, but they're not first-class articles either. You're saying that you are looking for an expert on this topic, but you will indeed need a "super expert" — rarely does a specialist grasp more than one of these fields.

So, as far as I can tell, this fits the pattern for disambiguation pages, and there are heaps of precedents like this.

Your mentioning of 360-degree feedback is inexhaustive: There also exist articles on audio feedback, optical feedback and low-key feedback. And the electronics meaning (which is currently a section in this article) even has its own category: Category:Electronic feedback.

My proposal: Either keep the control theory stuff here, or move to feedback (control theory) or some such. The rest should be split into feedback (electornics), feedback (biology) and feedback (economics) respectively; not quite sure what to do with the "organizations" section. -- intgr ^#%@! 22:12, 28 August 2007 (UTC)

Their is no need to spread so related knowledge over a number of small articles - Mdd 05:49, 29 August 2007 (UTC)

As I stated above, the only thing related between them is the control theory aspect. This concept will remain as a separate article, and will not be "spread" over the splitted articles. The fact that they currently exist as sections here actually limits their growth, since more specific content is irrelevant to feedback in control theory, even if it would be relevant in the particular field; just see the nature section: it briefly lists several phenomena without much further explanation, but is quite long already.

If there is no need to "spread knowledge", would you for instance consider merging audio feedback, optical feedback, and articles in Category:Electronic feedback here? Obviously not. -- intgr ^#%@! 08:26, 29 August 2007 (UTC)

Their are more arguments agains spliting the article:

1. The current article offers far to little information to justify the creation of separate articles
2. International there is also one article; See for example in the French, German and Dutch articles
3. An alternative can be an Feed back (disambiguation) page.

I also think that:

1. This article should first be expended and improved
2. Links should be made here to audio feedback, optical feedback and Electronic feedback

Now I think I look at the concept of feed back from a kind of fundamental "systems science point of view". In this perspective the control theory aspect is not whole separate aspects beside e.g. biological, economical, electronical, ergonomic and mechanical forms of feed back. The control theory aspects with their mathematical forms of representation are the fundamentals for all kind of specialized applications.

I do agree something has to be done with this article. In it's current form it's just a collection of seemingly unrelated facts. I'll see if I can improve this a little. - Mdd 20:14, 7 September 2007 (UTC)

Tag to split this article removed

I removed the tag to split the article because there was no response the last four weeks. - Mdd 19:59, 12 November 2007 (UTC)

Sorry, I just ran across this article now. This definitely needs to be split. As somebody mentioned above, the only thing linking these things together is a really broad concept of the term "Feedback". The methods by which feedback occurs within each of these fields - electronics, biology, communication - are really distinct, and feel haphazardly jammed together in one article like this. Put it this way: nobody is going to be looking for information about "feedback" at such a macroscopic level as to benefit from a one-size-fits-all article like this; they're probably going to be looking for it as it relates to a specific field. I can take this on as a personal project to split these off and build a worthwhile disambiguation page. Torc2 (talk) 21:57, 28 November 2007 (UTC)

Not haphazard, the article header explains it. Feedback is when the output of come process loops around back to become an input to the process. It simply is a broadly applied principle. —Preceding unsigned comment added by 203.206.220.108 (talk) 10:14, 5 October 2008 (UTC)

Citations

Hello. This article has two references, which is good. I added a "citations missing" tag because most sections have no inline citations and thus there is no way for the reader to know to which of the two refs any particular piece of information is sourced. OK in advance from my point of view to remove or move or change this tag. Best wishes. -Susanlesch 18:43, 12 November 2007 (UTC)

Tahnks, I think there are no references at all in this article. So I replaced this tag. - Mdd 20:00, 12 November 2007 (UTC)

The concept of "feedback" is such a broad and high level concept that the primary purpose of this article is to provide an overview and to lead the reader to links that get deeper into more specific topics. Since wikipedia provides extensive in-depth details elsewhere, it would be a complete waste of time to replicate a huge list of references here. Please don't be simple minded trying to apply rules about citations, it is of benefit to no one. If there are examples where the information on this page disagrees with other more in-depth articles in Wikipedia then that should be fixed. 10:11, 5 October 2008 (UTC) —Preceding unsigned comment added by 203.206.220.108 (talk)

Bogus examples

The example of vacuum advance control in older automotive ignition systems is bogus. Such systems did not employ any kind of feedback mechanism; i.e., they did not sense or react to any change they produced. —Preceding unsigned comment added by 24.22.7.221 (talk) 21:31, 17 January 2008 (UTC)

Incorrect sentence

The overview starts with the following sentence:

• Feedback is both a mechanism, process and signal that is looped back to control a system within itself

both is followed by three items instead of two. Hence, both should be removed. [Georg] —Preceding unsigned comment added by 206.113.192.12 (talk) 17:04, 25 January 2008 (UTC)

Ok, go ahead. -- Mdd (talk) 21:56, 25 January 2008 (UTC)

Bipolar feedback

This seems confusing. How can feedback be both positive and negative at the same time? These are exclusive, surely. If this means a switching function, where the feedback changes between positive and negative, then the definition should clarify this. If it means a balancing, then two feedback loops must be involved (one positive, one negative.)
I have searched several online sources, and they all seem to cite each other (including this one) but I can't find an original definition. I have noted several references to "bipolar feedback transistors", but suspect that means a feedback loop involving a bipolar transistor, rather than "bipolar feedback" involving a transistor.
If bipolar feedback is present in many systems, can someone provide an example?
Trevithj (talk) 02:43, 10 September 2008 (UTC)

Types of feedback

I suggest that the primary purpose of the "Types of feedback" section is to distinguish negative feedback from positive feedback and outline other commonly used terms for types of feedback. This section should not get bogged down into fine details. The material that discusses the history of negative feedback should be moved into the Negative Feedback article. 203.206.220.108 (talk) 00:44, 8 November 2008 (UTC)

However, the origin of the term "feedback" may be relevant, if that is what the Black and Rosenblueth citations are trying to do. Maybe some clarity is needed here, since the original use of "feedback" seems to have described what we now call "audio feedback", which is a more specific term.

See for example http://www.manager-tools.com/2008/03/the-etymology-of-feedback/

--Trevithj (talk) 02:21, 25 November 2008 (UTC)

In electronic engineering

The subsection "In electronic engineering" re-explains the concepts of negative feedback and positive feedback, which are not particularly specific to electronic engineering. Anyway, the section that contains this subsection is "Applications" so this is not the right place for explaining a general principle. 203.206.220.108 (talk) 01:28, 8 November 2008 (UTC)

Feedback equals No Feedback

• 3 - the feedback signal does not change when the input signal changes, in which case there is no feedback. This is known as a Linear system.

If no feedback is an example of feedback then sitting on your bum is an example of flying. In addition linear systems can have feedback, and non-linear systems do not require feedback. Thus the above should be deleted. 203.206.220.108 (talk) 12:31, 28 December 2009 (UTC)

Bad example, When everytime I've been on an airplane, I was sitting on my bum. —Preceding unsigned comment added by RaptorHunter (talk • contribs) 02:37, 21 November 2010 (UTC)