Re: [Emc-users] spindle index, again - now actually got it to work with spindle-synced motion

[Gene Heskett]

On Saturday 25 July 2009, Haberler Michael wrote:
>a while ago I described how I added a simple optical encoder wheel to
>my lathe. Meanwhile, I eventually got it to work with G33 threading,
>but it wasnt as straightforward as I would have believed, so I thought
>I'd describe my experience.
>
>My first attempt was to use the encoder component as described in the
>Spindle Feedback example (User Manual chapter 34). Trying that with
>the threading.ngc example failed miserably - the synced-motion
>threading part was everything but synchronized - heavy speed
>variations in the Z axis (see http://www.youtube.com/watch?
>v=efiNyzhGFbQ , starting around second 27).
>
>I traced the problem to serious noise on the encoder.0.velocity signal
>(red signal in http://mah.priv.at/gallery2/main.php?g2_itemId=69102).
>I first tried to feed it through a lowpass (white signal) but that a)
>didnt work either and b) massaging a feedback signal would be
>counterproductive to start with.
>
>I admit that the codewheel finish left to be desired - I managed to
>glue it onto the pulley with maybe 0.5mm runout (the outer diameter is
>18cm). And the disk isnt perfectly flat on the pulley - too much glue
>here and there, so the disk-sensor distance varies as well. These
>inaccuracies cause periodic fluctuations in the index signals, the
>relation to the spindle revolution can clearly be seen (note blue
>index pulse). So that introduced some phase noise on the signal, and
>that in turn causes the position estimate to fluctuate wildly, hence
>causing the strange Z move pattern.
>
>Adjusting the sensors and pulley brought some improvement but not
>sufficient. So I played around with encoder options.
>
>The fix was finally to turn off x4-mode and use encoder.0.position-
>interpolated instead of encoder.0.position to feed into motion.spindle-
>revs.
>
>The noise is pretty much gone
> (http://mah.priv.at/gallery2/main.php?g2_itemId=69105 ) - except for the
> wobble introduced by the runout of the codewheel (which btw can be clearly
> heard from the Z stepper during the
>threading run :-).
>
>The setup works fine for threading now, but I'll eventually change
>this to a more precise encoder wheel.
>
There is a bit of python code on the wiki that when fed to a 3 axis mill, will 
carve a quite good encoder wheel from a sheet of alu, say about 16 to 18 
gauge.  I took that and modified it to fit the much smaller spindle, trapped 
between the bearing adjuster nuts at the left end of the spindle of my 7x12.  
I also reduced the number of holes so the hole to space was about 50%, I think 
in half from that code.  And used a 1/16" diameter end mill and several passes 
so as not to push the light alu out of shape or out of flat.  It is on the 
lathe now, and I might have it working but when I built the interrupter opto 
assembly, I thought I would hook it up and test it while laying on the table, 
and due to a lack of docs on the opto unit, apparently hooked it up in reverse 
polarity & blew all 3 of them.  So now I need to get some fresh ones, with a 
smaller air gap, and make it again.  Bummer.  So many projects, so little time 
left.

>hal of test setup is at:
> http://mah.priv.at/cgi-bin/viewvc.cgi/emc-drehbank-test/drehbank-k12a.hal?r
>evision=1.6&root=CVS&view=markup
>
>
>out of curiosity - anybody got spindle-synced motion with *just* an
>index puls (1ppr) to work?

Work, maybe.  Reliably? Very doubtful.

>-Michael
>
>
>btw - I'm stunned by EMC2's capabilities - great piece of work, folks!

So am I, amazed at what it can do if I can just write the code, but I'm 
usually yelling for help on IRC.  Dunno what I'd do without these guys.

>
>
>
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[Emc-users] spindle index, again - now actually got it to work with spindle-synced motion

[Haberler Michael]

a while ago I described how I added a simple optical encoder wheel to  
my lathe. Meanwhile, I eventually got it to work with G33 threading,  
but it wasnt as straightforward as I would have believed, so I thought  
I'd describe my experience.

My first attempt was to use the encoder component as described in the  
Spindle Feedback example (User Manual chapter 34). Trying that with  
the threading.ngc example failed miserably - the synced-motion  
threading part was everything but synchronized - heavy speed  
variations in the Z axis (see http://www.youtube.com/watch? 
v=efiNyzhGFbQ , starting around second 27).

I traced the problem to serious noise on the encoder.0.velocity signal  
(red signal in http://mah.priv.at/gallery2/main.php?g2_itemId=69102).  
I first tried to feed it through a lowpass (white signal) but that a)  
didnt work either and b) massaging a feedback signal would be  
counterproductive to start with.

I admit that the codewheel finish left to be desired - I managed to  
glue it onto the pulley with maybe 0.5mm runout (the outer diameter is  
18cm). And the disk isnt perfectly flat on the pulley - too much glue  
here and there, so the disk-sensor distance varies as well. These  
inaccuracies cause periodic fluctuations in the index signals, the  
relation to the spindle revolution can clearly be seen (note blue  
index pulse). So that introduced some phase noise on the signal, and  
that in turn causes the position estimate to fluctuate wildly, hence  
causing the strange Z move pattern.

Adjusting the sensors and pulley brought some improvement but not  
sufficient. So I played around with encoder options.

The fix was finally to turn off x4-mode and use encoder.0.position- 
interpolated instead of encoder.0.position to feed into motion.spindle- 
revs.

The noise is pretty much gone 
(http://mah.priv.at/gallery2/main.php?g2_itemId=69105 
) - except for the wobble introduced by the runout of the codewheel  
(which btw can be clearly heard from the Z stepper during the  
threading run :-).

The setup works fine for threading now, but I'll eventually change  
this to a more precise encoder wheel.

hal of test setup is at: 
http://mah.priv.at/cgi-bin/viewvc.cgi/emc-drehbank-test/drehbank-k12a.hal?revision=1.6&root=CVS&view=markup


out of curiosity - anybody got spindle-synced motion with *just* an  
index puls (1ppr) to work?

-Michael


btw - I'm stunned by EMC2's capabilities - great piece of work, folks!


  

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Re: [Emc-users] about latency test

[Alex Joni]

Look at:
http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?TroubleShooting#On_board_video

Regards,
Alex

- Original Message - 
From: "pola ali" 
To: 
Sent: Saturday, July 25, 2009 2:21 PM
Subject: [Emc-users] about latency test


> hi everyone
> i run latency test  . i found this result MAX jitter for servo thread
> nearly 400,000 NS and MAX jitter for Base thread nearly 160,000 NS.
> which is not good rate , i would be grateful if anyone tell me how reduce
> this rate .
> the PC i run ubuntu  8.04 on it is Pentium  3 , ram 512 MB .
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05:58:00


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Re: [Emc-users] about latency test

[Andy Pugh]

2009/7/25 pola ali :
>
> hi everyone
>  i run latency test  . i found this result MAX jitter for servo thread
> nearly 400,000 NS and MAX jitter for Base thread nearly 160,000 NS.
> which is not good rate

Is it an Intel motherboard?
It might be due to SMI.

http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?FixingSMIIssues

-- 
atp

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Re: [Emc-users] about latency test

[Sven Wesley]

Is this a laptop?

2009/7/25 pola ali 

> hi everyone
>  i run latency test  . i found this result MAX jitter for servo thread
> nearly 400,000 NS and MAX jitter for Base thread nearly 160,000 NS.
> which is not good rate , i would be grateful if anyone tell me how reduce
> this rate .
> the PC i run ubuntu  8.04 on it is Pentium  3 , ram 512 MB .
>
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[Emc-users] about latency test

[pola ali]

hi everyone
 i run latency test  . i found this result MAX jitter for servo thread
nearly 400,000 NS and MAX jitter for Base thread nearly 160,000 NS.
which is not good rate , i would be grateful if anyone tell me how reduce
this rate .
the PC i run ubuntu  8.04 on it is Pentium  3 , ram 512 MB .
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[Emc-users] compile emc2_2.3.2 error

[sedonc]

hi.
i builded linux2.6.28+rtai3.7.1 environment on my embedded PC(advantech 
pcm9388) and digit I/O card(pcm3730)
there are some error massage displayed when i make emc2 .
WARNING: "fabs" [/home/xoj/emc2-2.3.2/src/steptest.ko] undefined!
WARNING: "ceil" [/home/xoj/emc2-2.3.2/src/motmod.ko] undefined! 
then make process stoped. who can tell me what wrong with it
thanks

xujun
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