Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[Tom]

Kirk Wallace  writes:

... I learned this from
> trial and error rather than informed design, which is not the best way
> to do things connected with high voltages, currents, mass, dollars, etc.
> 

Chuckle. OK Kirk. I will exercise due caution. Yes, the vfd is switching up to
350Vdc/25 amps in the 8kHz region, very serious stuff...
btw I keep several fire extinguishers in prominent view near the exits. 

regards,
Tom




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Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[Kirk Wallace]

On Thu, 2008-12-18 at 06:26 +, Tom wrote:
> Kirk Wallace  writes:
> 
> > 
> > If you are using a VFD on your spindle (or coolant pump), having one a
> > filter on the power input solved my noise problems.
> > 
> > http://www.eastek-intl.com/images/PreoSeriesEB.pdf
> > http://www.wallacecompany.com/cnc_lathe/HNC/00024-1a.jpg
> > 
> > If not, using a filter or ferite beads for other power lines might help.
>  
>  --
> 
> I checked your photo link. That was helpful. I think I will get a few EMI
> filters for the Opto boards and signal power supplies. 
> 
> Thanks Kirk!
> Tom

Please don't spend your money just because of my comment, just keep it
in mind if problems come about. Because VFD's use higher frequency
switching, at decent currents, they can create noise on the mains input
or other places, but before you spend money, get a second opinion from
others on this list, who may have better advise.

Another experience I learned from was, with the original motor lead
filters on my Hardinge lathe, when I added the VFD, the filters
overheated, melted and smoked. Apparently, they tried to do their job of
filtering out high frequencies, which VFD's normally put out allot of.
The ferrite beads didn't seem have that problem. But I learned this from
trial and error rather than informed design, which is not the best way
to do things connected with high voltages, currents, mass, dollars, etc.

-
Kirk
http://www.wallacecompany.com/machine_shop/


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Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[Tom]

Kirk Wallace  writes:

> 
> If you are using a VFD on your spindle (or coolant pump), having one a
> filter on the power input solved my noise problems.
> 
> http://www.eastek-intl.com/images/PreoSeriesEB.pdf
> http://www.wallacecompany.com/cnc_lathe/HNC/00024-1a.jpg
> 
> If not, using a filter or ferite beads for other power lines might help.
 
 --

I checked your photo link. That was helpful. I think I will get a few EMI
filters for the Opto boards and signal power supplies. 

Thanks Kirk!
Tom




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Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[Kirk Wallace]

On Wed, 2008-12-17 at 19:06 +, Tom wrote:
... snip
>  What you are pointing out seems to imply that
> you are concerned about noise in the lines. It looks like I am going to
> physically connect some test pigtails to the 5i20 in the controller so I can
> scope what is happening in the signal lines there. I have had glitches on the
> limit switch inputs that stop the machine in the middle of a cut. Putting a
> debounce filter on the limit inputs has helped here... but it does suggest 
> that
> there is a larger noise issue underlying some, if not all, of my problems. 

If you are using a VFD on your spindle (or coolant pump), having one a
filter on the power input solved my noise problems.

http://www.eastek-intl.com/images/PreoSeriesEB.pdf
http://www.wallacecompany.com/cnc_lathe/HNC/00024-1a.jpg

If not, using a filter or ferite beads for other power lines might help.

--
Kirk
http://www.wallacecompany.com/machine_shop/



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Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[Jeff Epler]

On Wed, Dec 17, 2008 at 12:14:13PM -0700, Sebastian Kuzminsky wrote:
> I'm not sure how the m5i20/hostmot driver handles this...

the old driver simply has this setting hardcoded, and can't chage it
without a recompile.  I forget what value is hardcoded, though.

Jeff

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Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[Sebastian Kuzminsky]

Tom wrote:
> How do I check to make sure that quadrature filtering is turned on? Is this a
> "config modparam" statement that goes in the ini file? 
> Can you give an example?

Are you using m5i20 (hostmot) or hm2_pci/hm2_5i20 (hostmot2)?  If you're 
using hostmot2, you enable encoder filtering in HAL by setting 
hm2_5i20.0.encoder.XX.filter to 1, as described here:




I'm not sure how the m5i20/hostmot driver handles this...


-- 
Sebastian Kuzminsky
"Okay, people. Now is the time to start discussing the rules of war for
autonomous robots. Now, when it's still theoretical." --  Bruce Schneier

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Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[Gene Heskett]

On Tuesday 16 December 2008, John Kasunich wrote:
>Tom wrote:
>> But... the dependencies make a non-networked install/upgrade very
>> difficult.
>>
>> It might be easier to run a network cable 100ft out to the barn.
>
>OK, my tact filter is on overload, but so be it.
>
>(begin-rant)
>
>Free Software comes from the internet.
>
>The operating system that Free software runs on comes from the internet.
>
>The tools to build Free software come from the internet.
>
>If you want to use Free software, either connect your computer to the
>internet, or deal with the extra steps needed to get Free software from
>the internet to your disconnected computer.
>
>(end-rant)
>
>Regards,
>
>John Kasunich
>

I think that is what I was trying to say also, John.  With everything else 
essentially free, surely a nic ($20) for the machine box, some cable and a 
cheap switch ($40-50 maybe) downstream of the firewall can be bought. Cable 
connectors are peanuts and often the crimper to install them right can be 
borrowed.  Info on how to install the connectors is just a google search 
away.

Here I have the verizon supplied dsl modem, which is handled by an old x86 
box, anything p2/k6 based with 64 Megs of ram is more than good enough, its 
running dd-wrt (also free) between 3 nics, one facing the internet, the next 
hard wired to an 8 port netgear switch (it isn't a real switch though, its 
actually a hub) and the third nic is an atheros card so I don't have to 
hardwire the lappy when its in use.  This machine is plugged into that 8 port 
switch, as is the cable to the shop, and several other cables here in the 
house so I can hook up a box I'm working on in case I am.

With dd-wrt in the path to the internet, I don't run a firewall on any of the 
local boxes, dd-wrt stops all that crap.  That old x86 box has been stripped, 
no drives at all, but has a compact flash adapter ($4) on the end of the 
primary IDE cable, and it boots dd-wrt from the cf card.  dd-wrt is the best 
kept secret in the firewall business.  Anything I want to do, works.  If 
someone wants into it from the internet to play their games, they'll have to 
know a 20 some character password.  Not worth their effort.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Kime's Law for the Reward of Meekness:
Turning the other cheek merely ensures two bruised cheeks.

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Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[Chris Radek]

On Tue, Dec 16, 2008 at 07:02:38PM +, Tom wrote:
> 
> I stand corrected, Chris. 
> 
> But... the dependencies make a non-networked install/upgrade very difficult. 

Only if upgrading between major versions.  I didn't see whether that's
the case for you or not.

> It might be easier to run a network cable 100ft out to the barn.

Yep, that's sure what I'd do, either way.


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Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[John Kasunich]

Tom wrote:

> 
> But... the dependencies make a non-networked install/upgrade very difficult. 
> 
> It might be easier to run a network cable 100ft out to the barn.
> 

OK, my tact filter is on overload, but so be it.

(begin-rant)

Free Software comes from the internet.

The operating system that Free software runs on comes from the internet.

The tools to build Free software come from the internet.

If you want to use Free software, either connect your computer to the
internet, or deal with the extra steps needed to get Free software from
the internet to your disconnected computer.

(end-rant)

Regards,

John Kasunich


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Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[Chris Radek]

On Tue, Dec 16, 2008 at 05:57:06AM +, Tom wrote:
> 
> Sebastian,
> 
> My machine control computer is not networked and I only have a USB thumbdrive 
> to
> transfer files. I am going to have to either rip it out of the machine to
> upgrade it, or jump through hoops to install the build essentials, then
> recompile ver. 2.2.8 from the source package. Grr 


Not true.

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


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Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[Sebastian Kuzminsky]

Tom wrote:
> Sebastian Kuzminsky  writes:
> 
>> Stephen Wille Padnos wrote:
>>
>> The hostmot2 driver in 2.2.8 has the new velocity estimation code.
>>
> 
> 
> Is there a new signal name for this?

The new pin is called "encoder.XX.velocity".

It's documented in the hostmot2 manpage, which gets installed when you 
install emc2.deb, and also available here:




-- 
Sebastian Kuzminsky
"Okay, people. Now is the time to start discussing the rules of war for
autonomous robots. Now, when it's still theoretical." --  Bruce Schneier

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Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[Sebastian Kuzminsky]

Stephen Wille Padnos wrote:
> The newer Mesa drivers have an estimated velocity output, which should 
> be pretty accurate.  The scaling (*60) should be able to run in the 
> servo thread just fine.  I'm not sure when the velocity output was 
> added, but I'm pretty sure it's in the hostmot2 drivers in EMC2 2.2.8.

The hostmot2 driver in 2.2.8 has the new velocity estimation code.


-- 
Sebastian Kuzminsky
"Okay, people. Now is the time to start discussing the rules of war for
autonomous robots. Now, when it's still theoretical." --  Bruce Schneier

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Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[Stephen Wille Padnos]

Tom wrote:

>Tom  writes:
>  
>
>>I will look at
>>the outputs on the scope tomorrow. Also, I connected my cable shield to power
>>ground in the computer ribbon cable, so that may be causing excessive noise
>>feedback. 
>>You have to jumper the Mesa 7i33 for differential inputs, and I think it  has
>>noise filtering. 
>>
>>Thanks,
>>Tom
>>
>>
>Well, I checked the differential encoder outputs on a scope on the machine 
>while
>running, and they are clean as a whistle all the way up to max motor rpm. I
>re-routed the cable shield to chassis Gnd instead of power Gnd, and that helped
>a little.  
>  
>
OK, noise reduction is a good thing :)  (Incidentally, I was asking 
about additional external filtering that might have reduced the 
bandwidth of the signal, not the filtering mode of the 7i33)

>My pyVCP spindle speed bar display (the one that jumps around above 3000rpm) is
>linked to "rev-scaled" which runs in a slow thread. I may need to adjust the
>thread timing, and route the raw encoder counts through a lowpass filter. 
>  
>
The newer Mesa drivers have an estimated velocity output, which should 
be pretty accurate.  The scaling (*60) should be able to run in the 
servo thread just fine.  I'm not sure when the velocity output was 
added, but I'm pretty sure it's in the hostmot2 drivers in EMC2 2.2.8.

- Steve


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Re: [Emc-users] Am I overloading the servo loop with my spindle encoder?

[Stephen Wille Padnos]

Tom wrote:

>I am using the Mesa 5i20/7i33 system to retrofit my knee mill. I just finished
>installing a 500 line (2000 ppr) encoder on the spindle, it is connected to the
>Enc03 quadrature inputs on P2. 
>My timing settings in my ini file are:
>BASE_PERIOD =35000
>  
>
Unless you're using "fast" I/O on the parallel port or similar, you 
probably don't need the BASE thread at all.

>SERVO_PERIOD =   100
>TRAJ_PERIOD =1000
>  
>
These are fine, though these days the TRAJ thread often gets run at the 
same rate as the servo thread (1ms).

>My spindle is capable of turning at a max of about 6000 rpm. But above 3000 
>rpm,
>my floating point value on the hal pin: "rev-scaled" starts to bounce all over
>the place. At full spindle speed my encoder is turning at the rate of 120,000Hz
>(pulses per second).
>  
>
I think there's something off in your calculations :)

2000 counts/rev * 3000 revs/min = 6,000,000 counts/minute
Dividing by 60 gives 100,000 counts/second at 3000 RPM, at 6000 RPM it 
would be 200 kHz.

Are you sure the encoders are up to it?  Do you have differential or 
single ended encoders?  Is there noise filtering on the encoder lines?

>My question is:  Is this too fast for my servo thread? If so, is it possible to
>read every other pulse? 
>  
>
No, this isn't too fast.  The Mesa board can count at 1 MHz (x4 = 4 
million counts/sec) in single ended mode, or ~10 MHz (40 M counts/sec) 
in differential mode.  The manual does have a note: "The maximum input 
frequency may be lower with encoders that have high value (>1K Ohm) 
pullup resistors on open collector outputs."  The counter in the Mesa 
card shouldn't overflow between reads (at a 1ms servo rate) until you 
get to 32 million counts/sec (or 8 billion if it's 24 bits, I don't 
remember which it is :) )

- Steve


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[Emc-users] Am I overloading the servo loop with my spindle encoder?

[Tom]

I am using the Mesa 5i20/7i33 system to retrofit my knee mill. I just finished
installing a 500 line (2000 ppr) encoder on the spindle, it is connected to the
Enc03 quadrature inputs on P2. 
My timing settings in my ini file are:
BASE_PERIOD =35000
SERVO_PERIOD =   100
TRAJ_PERIOD =1000
My spindle is capable of turning at a max of about 6000 rpm. But above 3000 rpm,
my floating point value on the hal pin: "rev-scaled" starts to bounce all over
the place. At full spindle speed my encoder is turning at the rate of 120,000Hz
(pulses per second).

My question is:  Is this too fast for my servo thread? If so, is it possible to
read every other pulse? 

Thanks,
Tom


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