On Wednesday 11 January 2017 22:37:46 Peter C. Wallace wrote:
> On Wed, 11 Jan 2017, Gene Heskett wrote:
> > Date: Wed, 11 Jan 2017 21:50:19 -0500
> > From: Gene Heskett <ghesk...@shentel.net>
> > Reply-To: "Enhanced Machine Controller (EMC)"
> > <emc-users@lists.sourceforge.net>
> > To: emc-users@lists.sourceforge.net
> > Subject: Re: [Emc-users] Two questions.
> >
> > On Wednesday 11 January 2017 13:34:50 Peter C. Wallace wrote:
> >> On Wed, 11 Jan 2017, Jon Elson wrote:
> >>> Date: Wed, 11 Jan 2017 10:36:18 -0600
> >>> From: Jon Elson <el...@pico-systems.com>
> >>> Reply-To: "Enhanced Machine Controller (EMC)"
> >>> <emc-users@lists.sourceforge.net>
> >>> To: "Enhanced Machine Controller (EMC)"
> >>> <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] Two
> >>> questions.
> >>>
> >>> On 01/10/2017 10:45 PM, Gene Heskett wrote:
> >>>> On Tuesday 10 January 2017 23:02:28 Jon Elson wrote:
> >>>>> On 01/10/2017 08:39 PM, Gene Heskett wrote:
> >>>>>> But if I hook up the halscope, the apparent quadrature error is
> >>>>>> worthless due to the 1KHz servo-loop timing limiting the
> >>>>>> bandwidth.
> >>>>>
> >>>>> Well, that's why we use hardware encoder counters, as
> >>>>> sampling the quadrature at 1 KHz just isn't fast enough.
> >>>>>
> >>>>> Jon
> >>>>
> >>>> Plz elucidate Jon. Something has got to be better than this. See
> >>>> the pix I posted with the last reply to Peter & the list. The
> >>>> top, white trace in the halscope screen is the quadrature noise,
> >>>> easily 10x the timing wibbles I see on the hitachi's screen.
> >>>
> >>> If you are looking at the quadrature signals at a 1 KHz
> >>> sampling rate, then unless the encoder is moving quite
> >>> slowly, the sampling will be too coarse. That screen shot
> >>> is kind of small (you can take just a single window as the
> >>> screenshot, by the way) but it looks like the duty cycle of
> >>> the encoders is not 50%. That may well be aliasing, as the
> >>> quadrature signals seem to be moving much too close to 1000
> >>> Hz. You'd get much better results below 100 Hz. Or, with
> >>> Mesa hardware, you can sample these with the base thread.
> >>>
> >>> I can't comment on the velocity output from the Mesa, as I
> >>> don't know their gear (or driver). But, the scale is 2/div,
> >>> meaning the scaled velocity output is jumping around 2 user
> >>> units up and down at a KHz rate. Clearly, not good.
> >>>
> >>> Jon
> >>
> >> The velocity output is calculated by using the number of counts
> >> divided by the time between the counts (time measured via a 1 MHz
> >> timestamp). If you have less than 2 counts per servo period the
> >> velocity estimation accuracy depends heavily the quadrature
> >> phase/symmetry since the edge spacing entirely determines the
> >> estimated velocity at this speed range.
> >>
> >> I suspect what Genes plot shows is that he has significant
> >> quadrature phase/symmetry errors at the FPGA inputs.
> >>
> >>
> >> Again here is a velocity plot of a accurate 100 Hz quadrature
> >> signal:
> >>
> >> http://freeby.mesanet.com/100_Hz_quadrature_velocity.png
> >
> > I've not played with the stepgen type 2 yet, but I have adjusted the
> > quadrature a few thousandths and reduced it by about 1/3rd. Thats
> > helpfull as I can filter to smooth a tach dial once I have defeated
> > the noise.
> >
> > But I have another concern. I have had to do a full powerdown reset
> > to clear a watchdog bite. The original config was I think intended
> > to clear it by re-enabling the machine, but I could nolinuxcnct, so
> > I disconnected
>
> that
>
> > reset in the hal file I started with as the logic was self feeding,
> > locking out the ability to reset the disabled machine. And I
> > couldn't even do it from the halconfig as it claimed another signal
> > was driving it when I tried to setp that pin.
> >
> > Do you, Peter, have a logic diagram I can re-construct for that,
> > that actually works?
>
> You need to restart linuxcnc to clear a watchdog bite
>
> >> Peter Wallace
> >> Mesa Electronics
> >>
That didn't work, I have since had to do full power downs with at least
15 seconds off time. 5 or 6 times now.
> >> (\__/)
> >> (='.'=) This is Bunny. Copy and paste bunny into your
> >> (")_(") signature to help him gain world domination.
> >>
> >>
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> >
> > 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>
> >
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> > Access to Intel Xeon Phi processor-based developer platforms.
> > With one year of Intel Parallel Studio XE.
> > Training and support from Colfax.
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>
> Peter Wallace
> Mesa Electronics
>
> (\__/)
> (='.'=) This is Bunny. Copy and paste bunny into your
> (")_(") signature to help him gain world domination.
>
>
> ----------------------------------------------------------------------
>-------- Developer Access Program for Intel Xeon Phi Processors
> Access to Intel Xeon Phi processor-based developer platforms.
> With one year of Intel Parallel Studio XE.
> Training and support from Colfax.
> Order your platform today. http://sdm.link/xeonphi
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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>
------------------------------------------------------------------------------
Developer Access Program for Intel Xeon Phi Processors
Access to Intel Xeon Phi processor-based developer platforms.
With one year of Intel Parallel Studio XE.
Training and support from Colfax.
Order your platform today. http://sdm.link/xeonphi
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