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PID contollers

Discussion in 'Electronic Basics' started by karthik, Dec 22, 2005.

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  1. karthik

    karthik Guest

    What r PID controllers.pls brief me
  2. A PID controller is a device that compares a measurement to a setpoint
    and produces a control output signal that drives something that alters
    the condition being measured, such that the measurement is forced
    toward the setpoint.

    I have written a non mathematical tutorial that explains the function
    of the P (proportional), I (integral) and D (derivative) terms
    generated in the controller, and how to tune them. It will give you a
    feel for what a PID controller does.
  3. Dan Hollands

    Dan Hollands Guest

    A controller that controls an output based on a feedback input using
    Proportion, Integral or Derivative (PID)control response

    Dan Hollands
    1120 S Creek Dr
    Webster NY 14580
  4. Rich Grise

    Rich Grise Guest

    Good on you! :)

    We need more webpages like this, that we can refer people to.

  5. Genome

    Genome Guest

    I'm an opinionated drunkard but.....

    When you see the term PID controller you would do well to steer clear of the
    general area where it was mentioned.

    PID is an excuse for people to wibble about with things until something

    As you can see from Mr Popelish's explanation.... the recommendation is that
    you wibble about until it works.

    Having wibbled about with it you explain to others about your wibbles in
    terms of P, I and D.

    Since they don't know what you are talking about and you don't either then
    you become an expert.

    Obviously, since it is working, you must have been right.

    Next Tuesday it blows up.... so, since you are the expert, they ask you back
    to wibble about some more.

    If you are an experienced wibbler then your initial wibbles might be close
    and you might make a sensible wibble but you are still a wibbler.

    Ask Tim Wescott, he knows all about it.

  6. You caught me. I am an expert wibbler. They call me in after the
    analytical types have tried and failed. The real world is very messy
    and nonlinear, and wibbling is sometimes the only way to arrive at a
    reasonable solution in a finite amount of time. The method I describe
    is orderly and goal oriented wibbling based on years of practical
    experience with enough real world systems to fill a large industrial
    museum. I do not claim it is the last word on the subject, but an
    intuitive place to start in the process of understanding loop tuning.

    The tutorial is a summary of my experience refined through several
    courses for operators and chemists I taught at a DuPont plant on the
    basics of PID control, which was used in conjunction with an elaborate
    process simulator I wrote for the Honeywell 3000 DCS system for them
    to play with.
  7. Genome

    Genome Guest

    One day I'd like to put my bum where my gob is. Next time your analyticals
    fail give me a shout and we'll see just how shit I really am.

  8. I am sure you would enjoy the educational experience.

    I have been called in to "fix" the tuning on a process that would cost
    a million dollars a day if I shut it down. It is operating
    chaotically (not cycling sinusoidally, but as if it were a strange
    attractor), interacting with a half dozen or so other control loops in
    various ways, and giving everyone heartburn. They tell me that I can
    alter the output value, manually only plus or minus 2% (less than it
    is swinging in automatic or cascade mode), but they really don't trust
    me to put the loop in manual mode, at all. Essentially all I can do
    is watch it (and the other loops) work. And I can change the P, I and
    D constants, as long as I am willing to take the blame for any
    worsening performance, and especially any out of limits operation or
    shut downs.

    Plug that into your analysis. ;-)

    The thing that is neat about the graphical method I describe in my
    tutorial, is that it gives you some simple rules to determine (in a
    "you're getting warmer" or "you're getting colder" fashion) which term
    is most likely to be causing the trouble and which way it needs to
    change to back away, gracefully from that trouble, without having to
    pass through any mine fields. And it even works, most of the time,
    too. :)
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