On Thursday 12 January 2017 00:27:15 Peter C. Wallace wrote:
> On Wed, 11 Jan 2017, Gene Heskett wrote:
> > Date: Wed, 11 Jan 2017 23:11:51 -0500
> > From: Gene Heskett
> > Reply-To: "Enhanced Machine Controller (EMC)"
> >
> > To: emc-users@lists.sourceforge.net
> > Subject: Re: [Emc-users] Two questions.
> >
> > 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
> >>> Reply-To: "Enhanced Machine Controller (EMC)"
> >>>
> >>> 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
> > Reply-To: "Enhanced Machine Controller (EMC)"
> >
> > To: "Enhanced Machine Controller (EMC)"
> > 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.
>
> That probably means the watchdog bite is not the issue but a symptom
> of some kind of system crash.
Which is a puzzle. Despite standing there looking at the "watchdog has
bit" message, only the power led is lit.
I have it running fairly noise free today, and had no such problems.
However it appears that I may have blown the #0 stepgen, as data is
going in, its enabled, but nothing is coming out of other either pin 1-1
(step) or p