On Wed, 11 Jan 2017, Gene Heskett wrote:
> Date: Wed, 11 Jan 2017 23:11:51 -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 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.
That probably means the watchdog bite is not the issue but a symptom
of some kind of system crash
>
>>>> (\__/)
>>>> (='.'=) 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.
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>>> Order your platform today. http://sdm.link/xeonphi
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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
> _______________________________________________
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
>
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.
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