Re: [Emc-users] Tormach writing open sorce ROS2/Machiekit/LCNC bridge.

[Ralph Stirling]

That AR3 robot is indeed interesting.  In the event
that anyone else wants to know the specs on the
robot, here is what I found on page 298 of the manual:

Reach – 24.75 inches (62.9cm)
Payload – 4.15 lbs (1.9kg)
Repeatability - .2mm
Robot weight (aluminum) – 27lbs (12.25kg)
Enclosure weight – 12.5lbs (5.6kg)
Max Power Consumption – 8.25amp (198 watts)

Reach and payload are decent, but repeatability is 10x
worse than typical industrial arms.  Still a very intriguing
system.  Not sure I envy the designer trying to support
buyers of his kits though.  There are an awful lot of bits
and pieces and assembly steps.

-- Ralph

From: Rob C [rclandro...@gmail.com]
Sent: Tuesday, January 4, 2022 10:25 AM
To: Enhanced Machine Controller (EMC)
Subject: Re: [Emc-users] Tormach writing open sorce ROS2/Machiekit/LCNC bridge.

CAUTION: This email originated from outside the Walla Walla University email 
system.


Interesting looking at the AR2/AR3
https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.anninrobotics.com%2Fdata=04%7C01%7Cralph.stirling%40wallawalla.edu%7Cc2fc608fe31b49905c3e08d9cfaf96e2%7Cd958f048e43142779c8debfb75e7aa64%7C0%7C1%7C637769175325588286%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=1OEAmYT8Al3yGr6i5FuTXiRgXEF2oNOsibOvSqLdrTg%3Dreserved=0

On Tue, 4 Jan 2022 at 18:14, andy pugh  wrote:

> On Tue, 4 Jan 2022 at 17:41, Robin Szemeti via Emc-users
>  wrote:
> >
> > Out of interest, how is PathPilot related to LinuxCNC?
>
> It's LinuxCNC with their own GUI on top. But maybe v2.7 as I don't
> _think_ that they have the joints-axes changes in.
>
> --
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics."
> — George Fitch, Atlanta Constitution Newspaper, 1912
>
>
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Re: [Emc-users] Very good software backlash control demo.

[dave engvall]

Hi,
I ran across an article by one of the servo drive firms that said the 
using two sensors/axis improved motion. I think they used a resolver on 
the drive and an encoder on the ball screw. While this improves motion 
that assumes you have very good ball screws. I think that a better 
approach would be to use glass scales and  then another sensor on the 
ball screw or drive. Right now I have a mill with glass scales on X and 
Y with Z being considered. Planned is implementation of stepper-servos 
like Gene's setup. First iteration will be stepper-servos plus a DRO 
simply to tell me how bad things are.
BTW -- on X using the hand wheel vis a vis an accu-rite 5 um glass scale 
was dead on moving X  in the positive direction  I won't admit how bad 
it is on reversal. ;-) Y is damaged but still pretty good going positive 
but really bad in Y neg. No scale on Z so no estimate but not perfect. 
The X  does have a 40 K count/inch in quadrature encoder on it.
Note: Chinese glass scales are now mounted on X and Y since the 
Accu-rite scales do not play well with the Chinese DRO.


Cheers,
Dave



On 1/3/22 6:58 PM, Sam Sokolik wrote:

This has been done at a bigger scale...  (2 feedback loops)

https://web.archive.org/web/20160222165548/http://jmkasunich.com/cgi-bin/blosxom/shoptask/wichita-trip-02-20-08.html

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

On Mon, Jan 3, 2022, 8:42 PM Chris Albertson 
wrote:


CNC is about precision motion control.   Here is a new idea where this
builder gets 0.05mm accuracy but uses hobby level R/C servo  Not only that,
but he connects three of these in series, one to the next to the next so
all the backlashes and poor tolerances add together.  Then he uses this to
do precise motion.  He loads a mechanical pencil with this chain of cheap
parts.

What does this means for LCNC?  It means that someone has found a software
solution to backlash.   What he does is place a quadrature encoder on both
the motor and the output shaft.The difference in encoder reading is an
exact measure of mechanical backlash and effective gear ratio.He can
measure the backlash under different conditions and store the
measurements.  Then he places a cascaded PID controller and Kalman filter
over this hardware.

Technically the problem with backlash control via software is the delay
from input to output pays poorly with the PID algorithm.  He applies a
predictive model.

Checkup this video.  It is unimpressive if you have a  $100,000 CNC milling
machine, but he is using a linked chain of hobby servos.  The novel idea is
his software.   It is on github, you can read it.
https://youtu.be/gq-P39rfRqU

He explains it  here.   Notice in the video he shows the backlash.  The
gear-slop is at the 1/4 inch level but using his software backlash
correction you can see the results in the dial indicator is about 0.05mm
(or about 0.002 in American units)  Not bad given the truly horrible
mechanics.
https://youtu.be/SioCwvR_PYY

Why do I care?   I have a robot-dog leg here on my workbench using hobby
servos, let's say performance could be improved.   But the anti-lash
technique might be used on a real milling machine. Maybe one of the
experts here could look and see if it could be applied?I will use parts
of his idea on my dog-bot.

--

Chris Albertson
Redondo Beach, California

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Re: [Emc-users] Tormach writing open sorce ROS2/Machiekit/LCNC bridge.

[Rob C]

Interesting looking at the AR2/AR3
https://www.anninrobotics.com/

On Tue, 4 Jan 2022 at 18:14, andy pugh  wrote:

> On Tue, 4 Jan 2022 at 17:41, Robin Szemeti via Emc-users
>  wrote:
> >
> > Out of interest, how is PathPilot related to LinuxCNC?
>
> It's LinuxCNC with their own GUI on top. But maybe v2.7 as I don't
> _think_ that they have the joints-axes changes in.
>
> --
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics."
> — George Fitch, Atlanta Constitution Newspaper, 1912
>
>
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
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Re: [Emc-users] Tormach writing open sorce ROS2/Machiekit/LCNC bridge.

[andy pugh]

On Tue, 4 Jan 2022 at 17:41, Robin Szemeti via Emc-users
 wrote:
>
> Out of interest, how is PathPilot related to LinuxCNC?

It's LinuxCNC with their own GUI on top. But maybe v2.7 as I don't
_think_ that they have the joints-axes changes in.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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Re: [Emc-users] Tormach writing open sorce ROS2/Machiekit/LCNC bridge.

[Robin Szemeti via Emc-users]

Out of interest, how is PathPilot related to LinuxCNC?

On Tue, 4 Jan 2022 at 17:03, Rick Moscoloni  wrote:

> Nice Work Done by Them!
> https://www.youtube.com/watch?v=xFjR_Kr6JOE
>
> El lun, 3 ene 2022 a las 1:21, Ralph Stirling (<
> ralph.stirl...@wallawalla.edu>) escribió:
>
> > Tormach has an interesting 6-axis robot fully controlled by ROS,
> > and multiple CNC machines running Linuxcnc/Machinekit, so it
> > makes perfect sense for them to integrate the two worlds better.
> >
> > I also find this to be an excellent development.  Frankly, I'd enjoy
> > trading our two Yaskawa Motoman robots for a couple of these
> > new Tormach arms to get that ROS integration.  Yaskawa has a
> > very tortuous and limited solution for ROS that we never got to
> > work.
> >
> > -- Ralph
> > 
> > From: Chris Albertson [albertson.ch...@gmail.com]
> > Sent: Sunday, January 2, 2022 7:26 PM
> > To: Enhanced Machine Controller (EMC)
> > Subject: [Emc-users] Tormach writing open sorce ROS2/Machiekit/LCNC
> bridge.
> >
> > CAUTION: This email originated from outside the Walla Walla University
> > email system.
> >
> >
> > Has anyone else noticed the activity on Tormach's Git Hub repository.
> >  There seem to be multiple commits each day to
> >
> >
> https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Ftormach%2Fhal_ros_control%2Ftree%2Ffoxy-develdata=04%7C01%7Cralph.stirling%40wallawalla.edu%7C2cb70e771b614bbd867d08d9ce68e5aa%7Cd958f048e43142779c8debfb75e7aa64%7C0%7C0%7C637767772215404228%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=sP5t%2FV3obq1Z6YWdI3gnSuhW6xiUeg35znj%2BUCSoei4%3Dreserved=0
> >
> > In a nutshell, they are making HAL a ROS2 node.From a LNCN user's
> view
> > point this means machine tool can become part of a larger automated
> robotic
> > system and from the robotic engineer's view this means he can use the HAL
> > infrastructure to control robot parts.
> >
> > Interesting because it is Tormach not some hobby user working part-time.
> > It is in Tormach's github.
> >
> > I can imagine a work cell where robots load and unload milling machines
> or
> > move parts between machines and then pack the finished parts in boxes.
> > Then palletize the boxes and load them onto self-driving trucks that
> carry
> > them to a "lights out" factory where they make robots.   We all become
> > redundant.
> >
> > More seriously,  this about doubles what each group can do.  And Tormach
> > seems to be investing real money in this.
> >
> >
> >
> >
> >
> >
> >
> > --
> >
> > Chris Albertson
> > Redondo Beach, California
> >
> > ___
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> >
> >
> https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.sourceforge.net%2Flists%2Flistinfo%2Femc-usersdata=04%7C01%7Cralph.stirling%40wallawalla.edu%7C2cb70e771b614bbd867d08d9ce68e5aa%7Cd958f048e43142779c8debfb75e7aa64%7C0%7C0%7C637767772215404228%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=PkIj53YMqmBQk%2B%2BF8tw02hkzOzuAT3m4hgZ%2FH5rDt3s%3Dreserved=0
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Re: [Emc-users] Tormach writing open sorce ROS2/Machiekit/LCNC bridge.

[Rick Moscoloni]

Nice Work Done by Them!
https://www.youtube.com/watch?v=xFjR_Kr6JOE

El lun, 3 ene 2022 a las 1:21, Ralph Stirling (<
ralph.stirl...@wallawalla.edu>) escribió:

> Tormach has an interesting 6-axis robot fully controlled by ROS,
> and multiple CNC machines running Linuxcnc/Machinekit, so it
> makes perfect sense for them to integrate the two worlds better.
>
> I also find this to be an excellent development.  Frankly, I'd enjoy
> trading our two Yaskawa Motoman robots for a couple of these
> new Tormach arms to get that ROS integration.  Yaskawa has a
> very tortuous and limited solution for ROS that we never got to
> work.
>
> -- Ralph
> 
> From: Chris Albertson [albertson.ch...@gmail.com]
> Sent: Sunday, January 2, 2022 7:26 PM
> To: Enhanced Machine Controller (EMC)
> Subject: [Emc-users] Tormach writing open sorce ROS2/Machiekit/LCNC bridge.
>
> CAUTION: This email originated from outside the Walla Walla University
> email system.
>
>
> Has anyone else noticed the activity on Tormach's Git Hub repository.
>  There seem to be multiple commits each day to
>
> https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Ftormach%2Fhal_ros_control%2Ftree%2Ffoxy-develdata=04%7C01%7Cralph.stirling%40wallawalla.edu%7C2cb70e771b614bbd867d08d9ce68e5aa%7Cd958f048e43142779c8debfb75e7aa64%7C0%7C0%7C637767772215404228%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=sP5t%2FV3obq1Z6YWdI3gnSuhW6xiUeg35znj%2BUCSoei4%3Dreserved=0
>
> In a nutshell, they are making HAL a ROS2 node.From a LNCN user's view
> point this means machine tool can become part of a larger automated robotic
> system and from the robotic engineer's view this means he can use the HAL
> infrastructure to control robot parts.
>
> Interesting because it is Tormach not some hobby user working part-time.
> It is in Tormach's github.
>
> I can imagine a work cell where robots load and unload milling machines or
> move parts between machines and then pack the finished parts in boxes.
> Then palletize the boxes and load them onto self-driving trucks that carry
> them to a "lights out" factory where they make robots.   We all become
> redundant.
>
> More seriously,  this about doubles what each group can do.  And Tormach
> seems to be investing real money in this.
>
>
>
>
>
>
>
> --
>
> Chris Albertson
> Redondo Beach, California
>
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Re: [Emc-users] Very good software backlash control demo.

[gene heskett]

On Monday, January 3, 2022 11:45:13 PM EST Sam Sokolik wrote:
> I think it is just easy to have 2 pid's and sum them..  (one on the motor
> encoder with P,D and feed forward - the other with scales and the I term)
> Then you are not re-writing the pid component for some odd corner case.
> 
> sam

Corner case?

Assuming addf's are in order, a block diagram plz.

...

One of the targets in my case would be the pi that's running my Sheldon. It 
has the 3 phase stepper servos, but their are no PID's, whatever comes out 
of motion goes direct to the stepgen, and the stepgen is its own feedback 
source. The encoder in these motors is not fed back to LCNC, only to the 
drive, which does its own thing, among others using only enough motor 
current to get to where it is told to go. Quite a large improvement in 
energy used right there. 

If its loaded too hard, or has run into the immovable object and can't get 
there, it kills the motor driver and reports the error to LCNC. In my case 
it toggles F2 off, which in turn kills the AC power to the machine, which is 
the reset/re-enable for these drivers. I pull the tool from the tool post, 
hit F2 to power up the machine again, rehome the machine, figure out what I 
did wrong, fix it, put the tool back on the toolpost and touch r.

I do not know how the additional loop time of adding 2 PID's to its control 
would be handled by a pi4. This started out as a pi3, and the 3 was pushed 
quite a bit to keep up with a 1 kilohertz servo loop, so much so I moved the 
hand dial controls to a separate, only 200hz thread, the pi4 has lots more 
reserve. If your don't mind an occasional stutter the pi4 can cruise the web 
while making burn holes your shirt swarf. FF is not kind to irq latency, but 
we all knew that.

I'm also not sure how scales could be mounted on the Sheldon and be 
protected against hot swarf.  Might need some pix from others that have done 
it before me.

Just thinking out loud. And as near as I can tell its working fine as as is.

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, 1940)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 





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