On Wed, 4 Mar 2020, Gene Heskett wrote:
Date: Wed, 4 Mar 2020 22:12:47 -0500
From: Gene Heskett <[email protected]>
Reply-To: EMC developers <[email protected]>
To: [email protected]
Subject: Re: [Emc-developers] 2.7.15 PID Fix
On Wednesday 04 March 2020 12:52:09 andy pugh wrote:
On Wed, 4 Mar 2020 at 17:26, Peter C. Wallace <[email protected]> wrote:
It was first added to 2.8 and them merged into 2.7 before the
2.7.15 release AFAIK
I think that they were added in 2010:
https://github.com/LinuxCNC/linuxcnc/commit/44586b831e1ef5e826003190ab
317cda76b6e8e3#diff-912d11dfa52738be509f63e4ff1922a4 (And that commit
also includes documentation of the pins)
Sort of. But it does provide some hints as to how to utilize it to
improve control, If you have encoder feedback on axis axis then you
could feed the feedback.deriv pin with the velocity of that axis's
encoder. But from reading that, I fail to deduct a source for cmd.deriv.
I am envisioning a differential, for instance between current command
and previous command or maybe a sum2 with one input set for a gain of -1
and an rc lag from the command input to the other input giving a
differential output according to the charge across the cap. Since we
don't have a cap in hal components, we'ed have to use a low pass. But I
quickly run out of imagination as to the rc time constant to synthesize.
just discussing the howto's would I think be educational for those of us
who never got the transcendental stuff in school 70+ years ago.
Help?
Thanks
Normally you would just connect the joint velocity pin to the PID command
derivative
Cheers, Gene Heskett
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