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With SW controls, the first rule is never to command a control to move in a way .... — Parallax Forums

With SW controls, the first rule is never to command a control to move in a way ....

ErNaErNa Posts: 1,753
edited 2010-08-19 00:01 in Propeller 1
I found this in my mailbox and find it adequate to forward the link: http://www.eetimes.com/design/embedded/4206216/The-basics-of-doing-PID-design-Part-1-Classical-control-theory?pageNumber=0.

I liked this : With software controls, the first rule is never to command a control to move in a way it clearly cannot track., because that is exactly, what we often don't care about. We overstress a system and then we try to find a way around, creating additional load.

The propeller allows to do experiments easily, others can't do. Start the P, I and D part in different cogs, have them running in parallel, and than watch, what happens.

And remember: "This subject is deep and broad, and engineers spend their entire careers mastering it. "

Comments

  • Heater.Heater. Posts: 21,230
    edited 2010-08-18 23:35
    Erna, great article, I look forward to the next parts.
    The desired position of the robot or one of its servos is often referred
    to as the rabbit and the position of the actual robot or servo is referred to as
    the hound.

    In all the years of reading about control systems, PIDs and all, since the 1980s and having had
    a very good friend who was a graduate of control systems engineering I have never heard the
    "rabbit" and "hound" thing before. I like it.
    If you studied calculus, you know that position is the integral of velocity, velocity is the
    integral of acceleration, and acceleration is the integral of jerk.

    Brilliant, never heard it put like that before either.
  • Heater.Heater. Posts: 21,230
    edited 2010-08-19 00:01
    Well I never. It seems "jerk" is a common term for the derivative of acceleration with respect to time.http://en.wikipedia.org/wiki/Jerk_%28physics%29

    How on earth did I get a degree in Physics (1979) and be knee deep in calculus for some years before starting that without ever coming across that use of the word?
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