[Emc-users] syncing two motors to one axis

[Len Shelton]

So let's say you have two drives, two motors, and two home switches on the
same axis (gantry type machine). The problem with this arrangement is
synchronization. The control needs to be aware of the two motors and needs
to home both at the same time. While homing, we need to bring both motors
towards the home switches together then independently home each motor when
it reaches the home switch. 

How can this be done in EMC2?

Thanks,
>Len







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Re: [Emc-users] Need Help With Classicladder

[Jeff Epler]

On Wed, Apr 01, 2009 at 02:11:34AM +, Chris Morley wrote:
> the pin motion.motion-inpos doen't seem to exist anymore
> try changing it to motion.in-position.

I made a note about this incompatible change on the wiki:
http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?UPDATING

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Re: [Emc-users] MESA 7I43 and 7I33 OR 5I20 and 7I33 OR MOTENC-LITE(7544)

[Sebastian Kuzminsky]

Shabbir Hussain wrote:
> Is there any significant difference (in rapid moves) by running the machine 
> with 7i43-P or 5i20?

The 7i43 and the 5i20 can both command movements of much higher speed 
than any reasonable machine can move.

Really the only practical differences between them is how they connect 
to the computer (EPP for the 7i43, PCI for the 5i20) and how many I/O 
pins they have (48 for the 7i43, 72 for the 5i20).


-- 
Sebastian Kuzminsky
All my desires and ruminations are no more and no less than eddy
currents generated by the gradual exhalation of our universe.
And until this great exhalation is finished, my thoughts live on.


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Re: [Emc-users] Need Help With Classicladder

[Kirk Wallace]

On Tue, 2009-03-31 at 22:04 -0400, Dean wrote:
> Kirk:
> That statement was already in my .hal file.  But, I did comment out the
> 'motion.motion-inpos' line in the postgui.hal file and that did allow EMC to
> run.  Thanks for the suggestion and I'll keep plugging away.
> 
> Dean

>From Jeff's message:
"
I made a note about this incompatible change on the wiki:
http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?UPDATING
"
It looks like all you need to do is change:

"net in_pos motion.motion-inpos => classicladder.o.in-02"

to

"net in_pos motion.motion-inposition => classicladder.o.in-02"

When I looked at the Motion page I didn't bother to read that
motion.in-position has the same function as motion.in-pos, which has
apparently been deleted. 
---
Kirk
http://www.wallacecompany.com/machine_shop/



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Re: [Emc-users] syncing two motors to one axis

[Jon Elson]

Len Shelton wrote:
> So let's say you have two drives, two motors, and two home switches on the
> same axis (gantry type machine). The problem with this arrangement is
> synchronization. The control needs to be aware of the two motors and needs
> to home both at the same time. While homing, we need to bring both motors
> towards the home switches together then independently home each motor when
> it reaches the home switch. 
>
> How can this be done in EMC2?
>   
We've gone over this a dozen times, at least.  It would take about 10-15 
lines of HAL and several HAL components to perform the logic.
Basically, you make the two motors run at the same rate.  As each motor 
hits the home switch, it stops.  When both have touched home, they move 
together again to complete the precision home sequence to the encoder 
index pulse.  EMC2 already has features in HAL to handle tandem axes 
like this, once homing is done.  You feed the lettered axis (as in "X") 
position to two numbered "joints" as in zero and one.  So, the only 
detail up in the air is how to do the homing.

Jon

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Re: [Emc-users] syncing two motors to one axis

[Len Shelton]

So, are you saying that it can't presently be done because no one has
written the hal components to do it?

I have searched the archives and found very little.

FWIW - this machine uses steppers and no encoders.

>Len



-Original Message-
From: Jon Elson [mailto:el...@pico-systems.com] 
Sent: Wednesday, April 01, 2009 11:28 AM
To: Enhanced Machine Controller (EMC)
Subject: Re: [Emc-users] syncing two motors to one axis

Len Shelton wrote:
> So let's say you have two drives, two motors, and two home switches on the
> same axis (gantry type machine). The problem with this arrangement is
> synchronization. The control needs to be aware of the two motors and needs
> to home both at the same time. While homing, we need to bring both motors
> towards the home switches together then independently home each motor when
> it reaches the home switch. 
>
> How can this be done in EMC2?
>   
We've gone over this a dozen times, at least.  It would take about 10-15 
lines of HAL and several HAL components to perform the logic.
Basically, you make the two motors run at the same rate.  As each motor 
hits the home switch, it stops.  When both have touched home, they move 
together again to complete the precision home sequence to the encoder 
index pulse.  EMC2 already has features in HAL to handle tandem axes 
like this, once homing is done.  You feed the lettered axis (as in "X") 
position to two numbered "joints" as in zero and one.  So, the only 
detail up in the air is how to do the homing.

Jon


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Re: [Emc-users] Need Help With Classicladder

[Dean]

Thanks Chris and Kirk.  EMC will load on my desktop with the change.  Now
I'm headed out to the shop to see if I can make this work in the real world.

Thanks again.
Dean

-Original Message-
From: Kirk Wallace [mailto:kwall...@wallacecompany.com] 
Sent: Wednesday, April 01, 2009 11:43 AM
To: Enhanced Machine Controller (EMC)
Subject: Re: [Emc-users] Need Help With Classicladder

On Tue, 2009-03-31 at 22:04 -0400, Dean wrote:
> Kirk:
> That statement was already in my .hal file.  But, I did comment out the
> 'motion.motion-inpos' line in the postgui.hal file and that did allow EMC
to
> run.  Thanks for the suggestion and I'll keep plugging away.
> 
> Dean

>From Jeff's message:
"
I made a note about this incompatible change on the wiki:
http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?UPDATING
"
It looks like all you need to do is change:

"net in_pos motion.motion-inpos => classicladder.o.in-02"

to

"net in_pos motion.motion-inposition => classicladder.o.in-02"

When I looked at the Motion page I didn't bother to read that
motion.in-position has the same function as motion.in-pos, which has
apparently been deleted. 
---
Kirk
http://www.wallacecompany.com/machine_shop/




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Re: [Emc-users] syncing two motors to one axis

[Rob Jansen]

Len,

steppers makes this problem very easy and it has indeed been discussed 
before.
Searching on the term "two motors" I was able to retrieve a number of my 
own posts about this.

http://article.gmane.org/gmane.linux.distributions.emc.user/8147/match=two+motors
 
is an older post describing a possible solution in words.
http://article.gmane.org/gmane.linux.distributions.emc.user/10276/match=two+motors
 
is a later posting with some boolean algebra (not HAL though - I decided 
to use standard 74LSxx gate logic).

There are more mail about this. Use 
http://news.gmane.org/gmane.linux.distributions.emc.user to search the 
archives - it's nicer than the sourceforge archives ...

Regards,

Rob

Len Shelton wrote:
> So, are you saying that it can't presently be done because no one has
> written the hal components to do it?
>
> I have searched the archives and found very little.
>
> FWIW - this machine uses steppers and no encoders.
>   

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Re: [Emc-users] m5i20_pidtest.hal

[Dave Engvall]

Am back from the beach and have tried things again.

Finally found a fundamental mistake. 1525BR amps expect a  
differential input; so battery boxes give the expected result.
However, the dacs are ground referenced. After I finally caught on I  
wired the 1525 inputs with gnd to gnd and + dac to -amp input.
Now things move.

The only problem is that both axes move in the wrong direction. So:  
how do I cleanly reverse the movement without having to
fool with the encoders?

BTW-the X axis that has absolutely awful response like 200 ms to  max  
velocity tuned to about 0.001 at 60 ips and 0.4" at 10 ipm.
We'll see what we can get out of the Y axis. ;-)

So the m5i20 does  really run right out of the box. The same cannot  
be said of my aging brain.

Dave

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Re: [Emc-users] syncing two motors to one axis

[Jon Elson]

Len Shelton wrote:
> So, are you saying that it can't presently be done because no one has
> written the hal components to do it?
>
>   
No, actually I do not believe any new HAL components are needed.  You 
need an and gate to detect when both home switches have been tripped.  
This AND output sets a flip-flop.  The flip-flop is cleared when you 
start the home sequence.  When the FF is clear, an and gate stops each 
side of the gantry from moving when that home switch trips.  When the FF 
is set, all move commands pass through.
> I have searched the archives and found very little.
>
> FWIW - this machine uses steppers and no encoders.
>   
OK, your homing is not going to be as precise with this, but it can 
still be plenty good enough for a hobby level machine.  it is also 
simpler, as there is no complex homing sequence to use encoder index 
pulses.  I'm less familiar with the internal hook-up of step generators 
to the parallel port, but what you want to do is stop the first side 
that hits home, and not terminate the homing sequence until BOTH sides 
have hit their home switches.  Sounds quite simple.

Jon

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Re: [Emc-users] m5i20_pidtest.hal

[Kirk Wallace]

On Wed, 2009-04-01 at 18:43 -0700, Dave Engvall wrote:
> 
> 
> Am back from the beach and have tried things again.
> 
> Finally found a fundamental mistake. 1525BR amps expect a  
> differential input; so battery boxes give the expected result.
> However, the dacs are ground referenced. After I finally caught on I  
> wired the 1525 inputs with gnd to gnd and + dac to -amp input.
> Now things move.
> 
> The only problem is that both axes move in the wrong direction. So:  
> how do I cleanly reverse the movement without having to
> fool with the encoders?
> 
> BTW-the X axis that has absolutely awful response like 200 ms to  max  
> velocity tuned to about 0.001 at 60 ips and 0.4" at 10 ipm.
> We'll see what we can get out of the Y axis. ;-)
> 
> So the m5i20 does  really run right out of the box. The same cannot  
> be said of my aging brain.
> 
> Dave

I'm glad your making progress. It has been a while since I have had to
think about this, but I believe you can change the direction of an axis
by changing the .ini file OUTPUT_SCALE = 1 for the axis, to OUTPUT_SCALE
= -1. If you have encoders, the .hal encoder settings may need to be
adjusted too. Also I would have connected your amp inputs DAC signal
ground to - input and DAC signal to + input, but I haven't studied your
particular setup.
---
Kirk
http://www.wallacecompany.com/machine_shop/



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Re: [Emc-users] m5i20_pidtest.hal

[Dave Engvall]

On Apr 1, 2009, at 7:34 PM, Kirk Wallace wrote:

> On Wed, 2009-04-01 at 18:43 -0700, Dave Engvall wrote:
>> 
>>
>> Am back from the beach and have tried things again.
>>
>> Finally found a fundamental mistake. 1525BR amps expect a
>> differential input; so battery boxes give the expected result.
>> However, the dacs are ground referenced. After I finally caught on I
>> wired the 1525 inputs with gnd to gnd and + dac to -amp input.
>> Now things move.
>>
>> The only problem is that both axes move in the wrong direction. So:
>> how do I cleanly reverse the movement without having to
>> fool with the encoders?
>>
>> BTW-the X axis that has absolutely awful response like 200 ms to  max
>> velocity tuned to about 0.001 at 60 ips and 0.4" at 10 ipm.
>> We'll see what we can get out of the Y axis. ;-)
>>
>> So the m5i20 does  really run right out of the box. The same cannot
>> be said of my aging brain.
>>
>> Dave
>
> I'm glad your making progress. It has been a while since I have had to
> think about this, but I believe you can change the direction of an  
> axis
> by changing the .ini file OUTPUT_SCALE = 1 for the axis, to  
> OUTPUT_SCALE
> = -1. If you have encoders, the .hal encoder settings may need to be
> adjusted too.


> Also I would have connected your amp inputs DAC signal
> ground to - input and DAC signal to + input, but I haven't studied  
> your
> particular setup.

Indeed that ( + and - ) would be the intuitive way to do it but it  
doesn't work.

I tried changing the sign on INPUT SCALE  and the sign on OUTPUT_SCALE
independently but that doesn't work either. Axis moves on command and  
then
faults on following error.
So I have more work to do.

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