On Thursday 05 March 2020 10:54:49 Peter C. Wallace wrote: > On Thu, 5 Mar 2020, Gene Heskett wrote: > > Date: Thu, 5 Mar 2020 10:42:19 -0500 > > From: Gene Heskett <ghesk...@shentel.net> > > Reply-To: EMC developers <emc-developers@lists.sourceforge.net> > > To: emc-developers@lists.sourceforge.net > > Subject: Re: [Emc-developers] 2.7.15 PID Fix > > > > On Thursday 05 March 2020 09:25:01 Peter C. Wallace wrote: > >> On Wed, 4 Mar 2020, Gene Heskett wrote: > >>> Date: Wed, 4 Mar 2020 22:12:47 -0500 > >>> From: Gene Heskett <ghesk...@shentel.net> > >>> Reply-To: EMC developers <emc-developers@lists.sourceforge.net> > >>> To: emc-developers@lists.sourceforge.net > >>> 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 <p...@mesanet.com> > > > > 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/44586b831e1ef5e826003 > >>>>19 0ab 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 > > > > Ok, but thats the signal I disconnected around 2 years back to get > > rid of an instant following error for a movement of 1/10 the > > MIN_ERROR. So hooking it back back up now does what to my FF# > > settings? > > It requres somewhat different tuning because of differening delays > in the TPs idea of velocity and velocity calculated in PID via DP/DT > Changing anything now is likely a waste of time
I get that impression from some too slow to see it moves. The pid vels look sane, but the pid_n.error gradually builds up to slightly over .0001002xxxmm and stays there bouncing around like its moving from stiction, with an error polarity opposite to the velocity. Backlash comp too high by .0001 maybe. In any event I suspect thats very close to the theoretical resolution given its steppers at either 8 or 16 microsteps. If it won't move with similar errors at G0 speeds when I get to where I can see it move, I'll check the docs for enlightenment. Thanks Peter. > >>> Cheers, Gene Heskett > >>> -- > >>> "There are four boxes to be used in defense of liberty: > >>> soap, ballot, jury, and ammo. Please use in that order." > >>> -Ed Howdershelt (Author) > >>> If we desire respect for the law, we must first make the law > >>> respectable. - Louis D. Brandeis > >>> Genes Web page <http://geneslinuxbox.net:6309/gene> > >>> > >>> > >>> _______________________________________________ > >>> 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 > > > > Cheers, Gene Heskett > > -- > > "There are four boxes to be used in defense of liberty: > > soap, ballot, jury, and ammo. Please use in that order." > > -Ed Howdershelt (Author) > > If we desire respect for the law, we must first make the law > > respectable. - Louis D. Brandeis > > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > > > > _______________________________________________ > > 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 Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
