On Wed, 4 Mar 2020, Jon Elson wrote:
Date: Wed, 04 Mar 2020 10:44:26 -0600
From: Jon Elson <el...@pico-systems.com>
Reply-To: EMC developers <emc-developers@lists.sourceforge.net>
To: EMC developers <emc-developers@lists.sourceforge.net>
Subject: Re: [Emc-developers] 2.7.15 PID Fix
On 03/03/2020 09:22 PM, Peter C. Wallace wrote:
No, command-deriv is only used for the FF1 feedforward calculation
But, I DO use FF1 in practically all my configs, and it does seem to work.
It will work because if the command-deriv pin is not connected the derivative
will be calculated internally
So, the problem is linking a signal to the command-deriv pin, but then NOT
feeding it the correct derivative. I can't see any way to fix this in PID.
The new 2.7.15 PID is not wrong, it just exposes an error in other code (the
configs) that hadn't been right for
some time.
I guess without linking to command-deriv then PID calculates this internally
by difference between this command and
the most recent command. If you link a signal to command-deriv but do not
provide the correct value, PID
would misbehave for sure.
Yes, you will get a 0 FF1 PID term
Not clear what to do in this case, but fixing the broken configs and the
autoconfig program that creates these
seems important. Documenting the problem is critical, and explaining what
the user needs to do to
make his system run right.
As for the docs, the generic 2.7 docs do NOT show any reference to
pid.x.command-deriv
Am I looking in the wrong place, or has it been removed?
It was added early in 2.8 and it works the same as feedback-deriv
(value calculated internally if unconnected)
Jon
_______________________________________________
Emc-developers mailing list
Emc-developers@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-developers
Peter Wallace
Mesa Electronics
(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.
_______________________________________________
Emc-developers mailing list
Emc-developers@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-developers
