On Wed, 21 Feb 2001, Mike Mansheim wrote:

>
> I think it is more typical to have a PI only system - and only use the
> derivative term when absolutely necessary.  It is simply a means to let

  I'm not a software specialist, but I've done many analogical regulators
P, PI but never PID. Real application demonstrate ( for me ) that PID is
almost pure theoretical. So could you point just one *real* example in
which derivative term must be implemented ?


> the control system react to the rate of change of the error, and often
> isn't needed.
> Finally, going way back to the original post on this, they said that it
> can take a while to get a speed reading.  I just wanted to mention that you
> must pay attention to how often the pid calculation is done.

Usual when the electronic system ( including hardware and firmware
) is  interacting with a mechanical one, PI theoretical calculation
could not match with reality. The crude result is the whole electronic
system "must be learned" and some adjusting point must be added.
A good and painfull example for this is the response reaction time...
Vasile

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