On Thursday 06 August 2015 13:00:23 Peter C. Wallace wrote: > On Thu, 6 Aug 2015, Gene Heskett wrote: > > Date: Thu, 6 Aug 2015 11:22:54 -0400 > > From: Gene Heskett <[email protected]> > > Reply-To: "Enhanced Machine Controller (EMC)" > > <[email protected]> > > To: [email protected] > > Subject: Re: [Emc-users] Encoder filtering > > > > On Thursday 06 August 2015 10:23:30 andy pugh wrote: > >> On 6 August 2015 at 15:12, Gene Heskett <[email protected]> wrote: > >>> Control is very stiff, but still not rpm > >>> accurate, asking for 2100 revs gets about 2650. > >> > >> There is a closed-loop spindle speed + orientation sample HAL file > >> here: > >> http://git.linuxcnc.org/gitweb?p=linuxcnc.git;a=blob;f=configs/sim/ > >>axi > >> s/vismach/VMC_toolchange/spindle.hal;h=867a593045fc6a20a227b08173f6 > >>32ec 583db328;hb=3a6ab378e8c5d6759914e08f61cd28e6bd526e3d > > > > To Peter C. Wallace: All this brings up a need for an edge detected > > output pin from the encoders, one that is read by the read, and > > cleared by that same read after being recorded into a .hal variable. > > > > Could that be added to a future version of the firmware? That would > > simplify the hal code needed to do this job. > > > > Cheers, Gene Heskett > > No firmware changes are needed to detect edges as a timestamp change > is sufficient to determine whether 1 (or many) edges have occured > And this timestamp pin is available by what name? I don't recall seeing it in the docs I have. 2.6.3 is my last downloaded copy of the hal manual. And I just looked at the halconfig screen of a running instance of 2.8.0-pre#####, updated yesterday and cannot find anything that looks like a timestamp, so I guess you'll have to teach me how to obtain it.
> Honestly though, I dont think its worth the effort, if you want good > spindle velocity feedback at low speeds, the best way by far is a > higher resolution encoder. Patching around velocity estimation noise > and bandwidth issues with a low resolution encoder with large > quadrature error by making changes in the driver does not seem to me > to have general benefit. This encoder is actually pretty good in that regard. Its the similar one of the lathe that is an excedrin headache. Its thin enough to drop into the relatively coarse thread on the back of the spindle, and that results in an eccentricy problem it is quite difficult to tap around and make work well. I would make it with a thicker hub to help center it, but that would use up a thread, which is in short supply already. 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
