On Sunday 02 May 2021 16:34:43 Jon Elson wrote:

> On 05/02/2021 01:00 PM, Chris Albertson wrote:
> > The below is exactly true.  The problem is that PID is widely used
> > and PID is only "reactive" it can only deal with what has already
> > happened and the time lag is the source of oscillations.    In the
> > past, PID was the only control option because we had limited
> > computing power.
>
> True for classic PID.  The PID calculation in LinuxCNC also
> has feedforwards (FF0 - FF2) which
> are quite useful, as they give an approximation of the
> required drive to the motor without the output, move, sample
> delay.
>
Yes, and that I have found usefull.  But using them intelligently isn't 
at all well explained by the docs we have. Time constants and their 
effects are are not at all well explained. The bottom line is that if 
and when you hit the magic settings, you still have no idea why this 
works and that doesn't.
> Jon
>
>
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Cheers, Gene Heskett
-- 
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 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
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 - Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>


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