Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Feed-Forward vs Feed-Back

  1. Jan 30, 2012 #1
    I'm reading about feedback and I came across the following paragraph from http://en.wikipedia.org/wiki/Feedback: [Broken]
    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?
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Jan 30, 2012 #2

    jim hardy

    User Avatar
    Science Advisor
    Gold Member
    2018 Award

    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.
  4. Jan 30, 2012 #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.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook