Are Feed-Forward Processes Reversible?

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In summary, feedback is when you examine the output of a system and compare it to a desired output. You then use that information to alter the input to the system to bring the output to the state you want. When you do this a new dynamic system is created that is different in behavior from the original system.
  • #1
mXSCNT
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I'm reading about feedback and I came across the following paragraph from http://en.wikipedia.org/wiki/Feedback:
The natural sense of feedforward is defined chemically by some irreversible reaction, or electronically by an active circuit element that has access to an auxiliary power supply, so as to be able to provide power gain to amplify the signal as it propagates from input to output. For example, an amplifier can use power from its controlled power reservoir, such as its battery, to provide power gain to amplify the signal; but the reverse is not possible: the signal cannot provide power to re-charge the battery of the amplifier.

This seems to imply that a feed-forward process is irreversible. The reason the signal can't provide power to recharge the battery is the 2nd law of thermodynamics.

Is the converse true - are feed-back processes reversible in some sense?
 
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  • #2
to my simple way of thinking,,

It sounds to me like a chemist has drawn a poor analogy.

Power conversion equipment can be bi-directional but not 100% efficient,
but your average analog amplifier indeed puts out mostly heat and that is irreversible.

I personally have never seen a computer make anything besides heat and frustration.
 
  • #3
Yes, bad analogy.

Feedback is when you examine the output of a system and compare it to a desired output. You then use that information to alter the input to the system to bring the output to the state you want. When you do this a new dynamic system is created that is different in behavior from the original system.

Feed forward control is when you make a "look-up table" of expected outputs for given inputs. To control the system, you simply command it to the desired output. The original system dynamics are retained but there can be error in the output which goes uncorrectd.
 

What is the difference between feed-forward and feed-back?

Feed-forward and feed-back are two types of control systems used in engineering and science. The main difference between them is the direction of the information flow. In feed-forward systems, the input signal is used to predict and correct for disturbances, while in feed-back systems, the output signal is used to adjust the input signal and achieve the desired output.

Which type of control system is more commonly used?

Both feed-forward and feed-back systems have their advantages and disadvantages, and their usage depends on the specific application. However, feed-back control is generally more commonly used as it allows for more precise and accurate control of the output.

What are the advantages of using feed-forward control?

Feed-forward control has several advantages, including the ability to anticipate and compensate for disturbances, faster response time, and the ability to handle nonlinear systems. It can also reduce the need for feedback control, which can be beneficial in systems with limited resources or where feedback control is not possible.

What are the disadvantages of using feed-back control?

Feed-back control has some limitations, such as the potential for instability if the feedback loop is not properly designed, and the fact that it can only correct for disturbances that have already occurred. It also requires a sensor to measure the output, which can add complexity and cost to the system.

Can feed-forward and feed-back control be used together?

Yes, it is possible to use both feed-forward and feed-back control in a system. This is known as a hybrid control system and combines the advantages of both types of control. Feed-forward control can be used to anticipate and compensate for disturbances, while feed-back control can be used to fine-tune the output and ensure accuracy. This approach is often used in complex and critical systems, such as aircraft control systems.

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