When feedback acts in response to an event/phenomenon, it can influence the input signal in one of two ways:
Negative feedback, which tends to reduce the input signal that caused it, is also known as a self-correcting or balancing loop.[2] Such loops tend to be goal-seeking, as in a thermostat, which compares actual temperature with desired temperature and seeks to reduce the difference. Balancing loops are sometimes prone to hunting: an oscillation caused by an excessive or delayed negative feedback signal, resulting in over-correction, wherein the signal becomes a positive feedback.
The terms negative and positive feedback can be used loosely or colloquially to describe or imply criticism and praise, respectively. This may lead to confusion with the more technically accurate terms positive and negative reinforcement, which refer to something that changes the likelihood of a future behaviour. Moreover, when used technically, negative feedback leads to stability that is, in general, considered good, whereas positive feedback can lead to unstable and explosive situations that are considered bad. Thus, when used colloquially, these terms imply the opposite desirability to that when used technically.
Negative feedback was applied by Harold Stephen Black to electrical amplifiers in 1927, but he could not get his idea patented until 1937.[3] Arturo Rosenblueth, a Mexican researcher and physician, co-authored a seminal 1943 paper Behavior, Purpose and Teleology[4] that, according to Norbert Wiener (another co-author of the paper), set the basis for the new science cybernetics. Rosenblueth proposed that behaviour controlled by negative feedback, whether in animal, human or machine, was a determinative, directive principle in nature and human creations.[citation needed] This kind of feedback is studied in cybernetics and control theory.
- An in-phase feedback signal, where a positive-going wave on the input leads to a positive-going change on the output, will amplify the input signal, leading to more modification. This is known as positive feedback.
- A feedback signal which is inverted, where a positive-going change on the input leads to a negative-going change on the output, will dampen the effect of the input signal, leading to less modification. This is known as negative feedback.
- Note that an increase or decrease of the feedback signal here refers to the magnitude relative to the input signal's absolute value, without regard to the polarity or sign of the feedback signal. For example if the input signal changes by 100 then a change in feedback signal value from +5 to +10 is a positive feedback. If the input signal changes by -100 then a change in the feedback signal from -5 to -10 is also a positive feedback.
Negative feedback, which tends to reduce the input signal that caused it, is also known as a self-correcting or balancing loop.[2] Such loops tend to be goal-seeking, as in a thermostat, which compares actual temperature with desired temperature and seeks to reduce the difference. Balancing loops are sometimes prone to hunting: an oscillation caused by an excessive or delayed negative feedback signal, resulting in over-correction, wherein the signal becomes a positive feedback.
The terms negative and positive feedback can be used loosely or colloquially to describe or imply criticism and praise, respectively. This may lead to confusion with the more technically accurate terms positive and negative reinforcement, which refer to something that changes the likelihood of a future behaviour. Moreover, when used technically, negative feedback leads to stability that is, in general, considered good, whereas positive feedback can lead to unstable and explosive situations that are considered bad. Thus, when used colloquially, these terms imply the opposite desirability to that when used technically.
Negative feedback was applied by Harold Stephen Black to electrical amplifiers in 1927, but he could not get his idea patented until 1937.[3] Arturo Rosenblueth, a Mexican researcher and physician, co-authored a seminal 1943 paper Behavior, Purpose and Teleology[4] that, according to Norbert Wiener (another co-author of the paper), set the basis for the new science cybernetics. Rosenblueth proposed that behaviour controlled by negative feedback, whether in animal, human or machine, was a determinative, directive principle in nature and human creations.[citation needed] This kind of feedback is studied in cybernetics and control theory.
No comments:
Post a Comment