On Thu, Jun 27, 2013 at 09:42:37AM -0500, Charles Steinkuehler wrote:

> I was trying some small I gains, mostly between .001 and .024.  I
> _think_ the PID thread rate is being accounted for, but if not that
> could easily explain things (I'll have to dig through the code).

The pid manpage tells you how the scaling works, and even gives an
example for Igain.

> I suspect, however, that given the slow rates my temperature moves
> around, I may have been dealing more with integrator wind-up than with
> bad gains.  

Yes I assume you have a step command in temperature, say from 0 to
180 degrees.  You'll immediately get huge error and the output will
saturate.  This saturated output is actually what you want.  But
this causes I to start accumulating and it'll wind up quite a bit
before your feedback catches up.

I doubt you want I gain at all in this situation where you expect to
have big errors.  You'll probably want P and D only; D will be the
one that you tune to prevent overshoot and oscillation.  


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