[homepage.git] / blog / tags / linuxcnc / linuxcnc.rss

<?xml version="1.0" encoding="utf-8"?>
<rss version='2.0' xmlns:lj='http://www.livejournal.org/rss/lj/1.0/'>
        <channel>
                <title>Petter Reinholdtsen - Entries tagged linuxcnc</title>
                <description>Entries tagged linuxcnc</description>
                <link>https://people.skolelinux.org/pere/blog/</link>

        
        <item>
                <title>The 2024 LinuxCNC Norwegian developer gathering</title>
                <link>https://people.skolelinux.org/pere/blog/The_2024_LinuxCNC_Norwegian_developer_gathering.html</link>
                <guid isPermaLink="true">https://people.skolelinux.org/pere/blog/The_2024_LinuxCNC_Norwegian_developer_gathering.html</guid>
                <pubDate>Fri, 31 May 2024 07:45:00 +0200</pubDate>
                <description>&lt;p&gt;&lt;a href=&quot;https://linuxcnc.org/&quot;&gt;The LinuxCNC project&lt;/a&gt; is still
going strong.  And I believe this great software system for numerical control of
machines such as milling machines, lathes, plasma cutters, routers,
cutting machines, robots and hexapods, would do even better with more
in-person developer gatherings, so we plan to organise such gathering
this summer too.&lt;/p&gt;

&lt;p&gt;The Norwegian LinuxCNC developer gathering take place the weekend
Friday July 5th to 7th this year, and is open for everyone interested
in contributing to LinuxCNC and free software manufacturing.  Up to
date information about the gathering can be found in
&lt;a href=&quot;https://sourceforge.net/p/emc/mailman/emc-developers/thread/123eaae0-f3b9-4170-a251-b7d608f1e974%40bofh.no/&quot;&gt;the
developer mailing list thread&lt;/a&gt; where the gathering was announced.
Thanks to the good people at

&lt;a href=&quot;https://www.debian.org/&quot;&gt;Debian&lt;/a&gt; as well as leftover money
from last years gathering from
&lt;a href=&quot;https://www.redpill-linpro.com/&quot;&gt;Redpill-Linpro&lt;/a&gt; and
&lt;a href=&quot;https://www.nuugfoundation.no/no/&quot;&gt;NUUG Foundation&lt;/a&gt;, we
have enough sponsor funds to pay for food, and probably also shelter
for the people traveling from afar to join us.  If you would like to
join the gathering, get in touch and add your details on
&lt;a href=&quot;https://pad.efn.no/p/linuxcnc-2024-norway&quot;&gt;the pad&lt;/a&gt;.&lt;/p&gt;
 
&lt;p&gt;As usual, if you use Bitcoin and want to show your support of my
activities, please send Bitcoin donations to my address
&lt;b&gt;&lt;a href=&quot;bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&quot;&gt;15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&lt;/a&gt;&lt;/b&gt;.&lt;/p&gt;
</description>
        </item>
        
        <item>
                <title>The 2023 LinuxCNC Norwegian developer gathering</title>
                <link>https://people.skolelinux.org/pere/blog/The_2023_LinuxCNC_Norwegian_developer_gathering.html</link>
                <guid isPermaLink="true">https://people.skolelinux.org/pere/blog/The_2023_LinuxCNC_Norwegian_developer_gathering.html</guid>
                <pubDate>Sun, 14 May 2023 20:30:00 +0200</pubDate>
                <description>&lt;p&gt;The LinuxCNC project is making headway these days.  A lot of
patches and issues have seen activity on
&lt;a href=&quot;https://github.com/LinuxCNC/linuxcnc/&quot;&gt;the project github
pages&lt;/a&gt; recently.  A few weeks ago there was a developer gathering
over at the &lt;a href=&quot;https://tormach.com/&quot;&gt;Tormach&lt;/a&gt; headquarter in
Wisconsin, and now we are planning a new gathering in Norway.  If you
wonder what LinuxCNC is, lets quote Wikipedia:&lt;/p&gt;

&lt;blockquote&gt;
&quot;LinuxCNC is a software system for numerical control of
machines such as milling machines, lathes, plasma cutters, routers,
cutting machines, robots and hexapods. It can control up to 9 axes or
joints of a CNC machine using G-code (RS-274NGC) as input. It has
several GUIs suited to specific kinds of usage (touch screen,
interactive development).&quot;
&lt;/blockquote&gt;

&lt;p&gt;The Norwegian developer gathering take place the weekend June 16th
to 18th this year, and is open for everyone interested in contributing
to LinuxCNC.  Up to date information about the gathering can be found
in
&lt;a href=&quot;https://sourceforge.net/p/emc/mailman/emc-developers/thread/sa64jp06nob.fsf%40hjemme.reinholdtsen.name/#msg37837251&quot;&gt;the
developer mailing list thread&lt;/a&gt; where the gathering was announced.
Thanks to the good people at
&lt;a href=&quot;https://www.debian.org/&quot;&gt;Debian&lt;/a&gt;,
&lt;a href=&quot;https://www.redpill-linpro.com/&quot;&gt;Redpill-Linpro&lt;/a&gt; and
&lt;a href=&quot;https://www.nuugfoundation.no/no/&quot;&gt;NUUG Foundation&lt;/a&gt;, we
have enough sponsor funds to pay for food, and shelter for the people
traveling from afar to join us.  If you would like to join the
gathering, get in touch.&lt;/p&gt;
 
&lt;p&gt;As usual, if you use Bitcoin and want to show your support of my
activities, please send Bitcoin donations to my address
&lt;b&gt;&lt;a href=&quot;bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&quot;&gt;15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&lt;/a&gt;&lt;/b&gt;.&lt;/p&gt;
</description>
        </item>
        
        <item>
                <title>LinuxCNC MQTT publisher component</title>
                <link>https://people.skolelinux.org/pere/blog/LinuxCNC_MQTT_publisher_component.html</link>
                <guid isPermaLink="true">https://people.skolelinux.org/pere/blog/LinuxCNC_MQTT_publisher_component.html</guid>
                <pubDate>Sun, 8 Jan 2023 19:30:00 +0100</pubDate>
                <description>&lt;p&gt;I watched &lt;a href=&quot;https://yewtu.be/watch?v=jmKUV3aNLjk&quot;&gt;a 2015
video from Andreas Schiffler&lt;/a&gt; the other day, where he set up
&lt;a href=&quot;https://linuxcnc.org/&quot;&gt;LinuxCNC&lt;/a&gt; to send status
information to the MQTT broker IBM Bluemix.  As I also use MQTT for
graphing, it occured to me that a generic MQTT LinuxCNC component
would be useful and I set out to implement it.  Today I got the first
draft limping along and submitted as
&lt;a href=&quot;https://github.com/LinuxCNC/linuxcnc/pull/2253&quot;&gt;a patch to the
LinuxCNC project&lt;/a&gt;.&lt;/p&gt;

&lt;p&gt;The simple part was setting up the MQTT publishing code in Python.
I already have set up other parts submitting data to my Mosquito MQTT
broker, so I could reuse that code.  Writing a LinuxCNC component in
Python as new to me, but using existing examples in the code
repository and the extensive documentation, this was fairly straight
forward.  The hardest part was creating a automated test for the
component to ensure it was working.  Testing it in a simulated
LinuxCNC machine proved very useful, as I discovered features I needed
that I had not thought of yet, and adjusted the code quite a bit to
make it easier to test without a operational MQTT broker
available.&lt;/p&gt;

&lt;p&gt;The draft is ready and working, but I am unsure which LinuxCNC HAL
pins I should collect and publish by default (in other words, the
default set of information pieces published), and how to get the
machine name from the LinuxCNC INI file.  The latter is a minor
detail, but I expect it would be useful in a setup with several
machines available.  I am hoping for feedback from the experienced
LinuxCNC developers and users, to make the component even better
before it can go into the mainland LinuxCNC code base.&lt;/p&gt;

&lt;p&gt;Since I started on the MQTT component, I came across
&lt;a href=&quot;https://yewtu.be/watch?v=Bqa2grG0XtA&quot;&gt;another video from Kent
VanderVelden&lt;/a&gt; where he combine LinuxCNC with a set of screen glasses
controlled by a Raspberry Pi, and it occured to me that it would
be useful for such use cases if LinuxCNC also provided a REST API for
querying its status.  I hope to start on such component once the MQTT
component is working well.&lt;/p&gt;
 
&lt;p&gt;As usual, if you use Bitcoin and want to show your support of my
activities, please send Bitcoin donations to my address
&lt;b&gt;&lt;a href=&quot;bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&quot;&gt;15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&lt;/a&gt;&lt;/b&gt;.&lt;/p&gt;
</description>
        </item>
        
        <item>
                <title>Automatic LinuxCNC servo PID tuning?</title>
                <link>https://people.skolelinux.org/pere/blog/Automatic_LinuxCNC_servo_PID_tuning_.html</link>
                <guid isPermaLink="true">https://people.skolelinux.org/pere/blog/Automatic_LinuxCNC_servo_PID_tuning_.html</guid>
                <pubDate>Sat, 16 Jul 2022 22:30:00 +0200</pubDate>
                <description>&lt;p&gt;While working on a CNC with servo motors controlled by the
&lt;a href=&quot;https://en.wikipedia.org/wiki/LinuxCNC&quot;&gt;LinuxCNC&lt;/a&gt;
&lt;a href=&quot;https://en.wikipedia.org/wiki/PID_controller&quot;&gt;PID
controller&lt;/a&gt;, I recently had to learn how to tune the collection of values
that control such mathematical machinery that a PID controller is.  It
proved to be a lot harder than I hoped, and I still have not succeeded
in getting the Z PID controller to successfully defy gravity, nor X
and Y to move accurately and reliably.  But while climbing up this
rather steep learning curve, I discovered that some motor control
systems are able to tune their PID controllers.  I got the impression
from the documentation that LinuxCNC were not.  This proved to be not
true.&lt;/p&gt;

&lt;p&gt;The LinuxCNC
&lt;a href=&quot;http://linuxcnc.org/docs/html/man/man9/pid.9.html&quot;&gt;pid
component&lt;/a&gt; is the recommended PID controller to use.  It uses eight
constants &lt;tt&gt;Pgain&lt;/tt&gt;, &lt;tt&gt;Igain&lt;/tt&gt;, &lt;tt&gt;Dgain&lt;/tt&gt;,
&lt;tt&gt;bias&lt;/tt&gt;, &lt;tt&gt;FF0&lt;/tt&gt;, &lt;tt&gt;FF1&lt;/tt&gt;, &lt;tt&gt;FF2&lt;/tt&gt; and
&lt;tt&gt;FF3&lt;/tt&gt; to calculate the output value based on current and wanted
state, and all of these need to have a sensible value for the
controller to behave properly.  Note, there are even more values
involved, theser are just the most important ones.  In my case I need
the X, Y and Z axes to follow the requested path with little error.
This has proved quite a challenge for someone who have never tuned a
PID controller before, but there is at least some help to be found.

&lt;p&gt;I discovered that included in LinuxCNC was this old PID component
at_pid claiming to have auto tuning capabilities.  Sadly it had been
neglected since 2011, and could not be used as a plug in replacement
for the default pid component.  One would have to rewriting the
LinuxCNC HAL setup to test at_pid.  This was rather sad, when I wanted
to quickly test auto tuning to see if it did a better job than me at
figuring out good P, I and D values to use.&lt;/p&gt;

&lt;p&gt;I decided to have a look if the situation could be improved.  This
involved trying to understand the code and history of the pid and
at_pid components.  Apparently they had a common ancestor, as code
structure, comments and variable names were quite close to each other.
Sadly this was not reflected in the git history, making it hard to
figure out what really happened.  My guess is that the author of
&lt;a href=&quot;https://github.com/LinuxCNC/linuxcnc/blob/master/src/hal/components/at_pid.c&quot;&gt;at_pid.c&lt;/a&gt;
took a version of
&lt;a href=&quot;https://github.com/LinuxCNC/linuxcnc/blob/master/src/hal/components/pid.c&quot;&gt;pid.c&lt;/a&gt;,
rewrote it to follow the structure he wished pid.c to have, then added
support for auto tuning and finally got it included into the LinuxCNC
repository.  The restructuring and lack of early history made it
harder to figure out which part of the code were relevant to the auto
tuning, and which part of the code needed to be updated to work the
same way as the current pid.c implementation.  I started by trying to
isolate relevant changes in pid.c, and applying them to at_pid.c.  My
aim was to make sure the at_pid component could replace the pid
component with a simple change in the HAL setup loadrt line, without
having to &quot;rewire&quot; the rest of the HAL configuration.  After a few
hours following this approach, I had learned quite a lot about the
code structure of both components, while concluding I was heading down
the wrong rabbit hole, and should get back to the surface and find a
different path.&lt;/p&gt;

&lt;p&gt;For the second attempt, I decided to throw away all the PID control
related part of the original at_pid.c, and instead isolate and lift
the auto tuning part of the code and inject it into a copy of pid.c.
This ensured compatibility with the current pid component, while
adding auto tuning as a run time option.  To make it easier to identify
the relevant parts in the future, I wrapped all the auto tuning code
with &#39;#ifdef AUTO_TUNER&#39;.  The end result behave just like the current
pid component by default, as that part of the code is identical.  The
&lt;a href=&quot;https://github.com/LinuxCNC/linuxcnc/pull/1820&quot;&gt;end result
entered the LinuxCNC master branch&lt;/a&gt; a few days ago.&lt;/p&gt;

&lt;p&gt;To enable auto tuning, one need to set a few HAL pins in the PID
component.  The most important ones are &lt;tt&gt;tune-effort&lt;/tt&gt;,
&lt;tt&gt;tune-mode&lt;/tt&gt; and &lt;tt&gt;tune-start&lt;/tt&gt;.  But lets take a step
back, and see what the auto tuning code will do.  I do not know the
mathematical foundation of the at_pid algorithm, but from observation
I can tell that the algorithm will, when enabled, produce a square
wave pattern centered around the &lt;tt&gt;bias&lt;/tt&gt; value on the output pin
of the PID controller.  This can be seen using the HAL Scope provided
by LinuxCNC.  In my case, this is translated into voltage (+-10V) sent
to the motor controller, which in turn is translated into motor speed.
So at_pid will ask the motor to move the axis back and forth.  The
number of cycles in the pattern is controlled by the
&lt;tt&gt;tune-cycles&lt;/tt&gt; pin, and the extremes of the wave pattern is
controlled by the &lt;tt&gt;tune-effort&lt;/tt&gt; pin.  Of course, trying to
change the direction of a physical object instantly (as in going
directly from a positive voltage to the equivalent negative voltage)
do not change velocity instantly, and it take some time for the object
to slow down and move in the opposite direction.  This result in a
more smooth movement wave form, as the axis in question were vibrating
back and forth.  When the axis reached the target speed in the
opposing direction, the auto tuner change direction again.  After
several of these changes, the average time delay between the &#39;peaks&#39;
and &#39;valleys&#39; of this movement graph is then used to calculate
proposed values for Pgain, Igain and Dgain, and insert them into the
HAL model to use by the pid controller.  The auto tuned settings are
not great, but htye work a lot better than the values I had been able
to cook up on my own, at least for the horizontal X and Y axis.  But I
had to use very small &lt;tt&gt;tune-effort&lt;tt&gt; values, as my motor
controllers error out if the voltage change too quickly.  I&#39;ve been
less lucky with the Z axis, which is moving a heavy object up and
down, and seem to confuse the algorithm.  The Z axis movement became a
lot better when I introduced a &lt;tt&gt;bias&lt;/tt&gt; value to counter the
gravitational drag, but I will have to work a lot more on the Z axis
PID values.&lt;/p&gt;

&lt;p&gt;Armed with this knowledge, it is time to look at how to do the
tuning.  Lets say the HAL configuration in question load the PID
component for X, Y and Z like this:&lt;/p&gt;
 
&lt;blockquote&gt;&lt;pre&gt;
loadrt pid names=pid.x,pid.y,pid.z
&lt;/pre&gt;&lt;/blockquote&gt;

&lt;p&gt;Armed with the new and improved at_pid component, the new line will
look like this:&lt;/p&gt;

&lt;blockquote&gt;&lt;pre&gt;
loadrt at_pid names=pid.x,pid.y,pid.z
&lt;/pre&gt;&lt;/blockquote&gt;

&lt;p&gt;The rest of the HAL setup can stay the same.  This work because the
components are referenced by name.  If the component had used count=3
instead, all use of pid.# had to be changed to at_pid.#.&lt;/p&gt;

&lt;p&gt;To start tuning the X axis, move the axis to the middle of its
range, to make sure it do not hit anything when it start moving back
and forth.  Next, set the &lt;tt&gt;tune-effort&lt;/tt&gt; to a low number in the
output range.  I used 0.1 as my initial value.  Next, assign 1 to the
&lt;tt&gt;tune-mode&lt;/tt&gt; value. Note, this will disable the pid controlling
part and feed 0 to the output pin, which in my case initially caused a
lot of drift.  In my case it proved to be a good idea with X and Y to
tune the motor driver to make sure 0 voltage stopped the motor
rotation.  On the other hand, for the Z axis this proved to be a bad
idea, so it will depend on your setup.  It might help to set the
&lt;tt&gt;bias&lt;/tt&gt; value to a output value that reduce or eliminate the
axis drift.  Finally, after setting &lt;tt&gt;tune-mode&lt;/tt&gt;, set
&lt;tt&gt;tune-start&lt;/tt&gt; to 1 to activate the auto tuning.  If all go well,
your axis will vibrate for a few seconds and when it is done, new
values for Pgain, Igain and Dgain will be active.  To test them,
change &lt;tt&gt;tune-mode&lt;/tt&gt; back to 0.  Note that this might cause the
machine to suddenly jerk as it bring the axis back to its commanded
position, which it might have drifted away from during tuning.  To
summarize with some halcmd lines:&lt;/p&gt;

&lt;blockquote&gt;&lt;pre&gt;
setp pid.x.tune-effort 0.1
setp pid.x.tune-mode 1
setp pid.x.tune-start 1
# wait for the tuning to complete
setp pid.x.tune-mode 0
&lt;/pre&gt;&lt;/blockquote&gt;

&lt;p&gt;After doing this task quite a few times while trying to figure out
how to properly tune the PID controllers on the machine in, I decided
to figure out if this process could be automated, and wrote a script
to do the entire tuning process from power on.  The end result will
ensure the machine is powered on and ready to run, home all axis if it
is not already done, check that the extra tuning pins are available,
move the axis to its mid point, run the auto tuning and re-enable the
pid controller when it is done.  It can be run several times.  Check
out the
&lt;a href=&quot;https://github.com/SebKuzminsky/MazakVQC1540/blob/bon-dev/scripts/run-auto-pid-tuner&quot;&gt;run-auto-pid-tuner&lt;/a&gt;
script on github if you want to learn how it is done.&lt;/p&gt;

&lt;p&gt;My hope is that this little adventure can inspire someone who know
more about motor PID controller tuning can implement even better
algorithms for automatic PID tuning in LinuxCNC, making life easier
for both me and all the others that want to use LinuxCNC but lack the
in depth knowledge needed to tune PID controllers well.&lt;/p&gt;

&lt;p&gt;As usual, if you use Bitcoin and want to show your support of my
activities, please send Bitcoin donations to my address
&lt;b&gt;&lt;a href=&quot;bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&quot;&gt;15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&lt;/a&gt;&lt;/b&gt;.&lt;/p&gt;
</description>
        </item>
        
        <item>
                <title>LinuxCNC translators life just got a bit easier</title>
                <link>https://people.skolelinux.org/pere/blog/LinuxCNC_translators_life_just_got_a_bit_easier.html</link>
                <guid isPermaLink="true">https://people.skolelinux.org/pere/blog/LinuxCNC_translators_life_just_got_a_bit_easier.html</guid>
                <pubDate>Fri, 3 Jun 2022 21:10:00 +0200</pubDate>
                <description>&lt;p&gt;Back in oktober last year, when I started looking at the
&lt;a href=&quot;https://en.wikipedia.org/wiki/LinuxCNC&quot;&gt;LinuxCNC&lt;/a&gt; system, I
proposed to change the documentation build system make life easier for
translators.  The original system consisted of independently written
documentation files for each language, with no automated way to track
changes done in other translations and no help for the translators to
know how much was left to translated.  By using
&lt;a href=&quot;https://po4a.org/&quot;&gt;the po4a system&lt;/a&gt; to generate POT and PO
files from the English documentation, this can be improved.  A small
team of LinuxCNC contributors got together and today our labour
finally payed off.  Since a few hours ago, it is now possible to
translate &lt;a href=&quot;https://hosted.weblate.org/projects/linuxcnc/&quot;&gt;the
LinuxCNC documentation on Weblate&lt;/a&gt;, alongside the program itself.&lt;/p&gt;

&lt;p&gt;The effort to migrate the documentation to use po4a has been both
slow and frustrating.  I am very happy we finally made it.&lt;/p&gt;

&lt;p&gt;As usual, if you use Bitcoin and want to show your support of my
activities, please send Bitcoin donations to my address
&lt;b&gt;&lt;a href=&quot;bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&quot;&gt;15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&lt;/a&gt;&lt;/b&gt;.&lt;/p&gt;
</description>
        </item>
        
        <item>
                <title>Run your industrial metal working machine using Debian?</title>
                <link>https://people.skolelinux.org/pere/blog/Run_your_industrial_metal_working_machine_using_Debian_.html</link>
                <guid isPermaLink="true">https://people.skolelinux.org/pere/blog/Run_your_industrial_metal_working_machine_using_Debian_.html</guid>
                <pubDate>Wed, 2 Mar 2022 18:40:00 +0100</pubDate>
                <description>&lt;p&gt;After many months of hard work by the good people involved in
&lt;a href=&quot;https://en.wikipedia.org/wiki/LinuxCNC&quot;&gt;LinuxCNC&lt;/a&gt;, the
system was accepted Sunday
&lt;a href=&quot;https://tracker.debian.org/pkg/linuxcnc&quot;&gt;into Debian&lt;/a&gt;.
Once it was available from Debian, I was surprised to discover from
&lt;a href=&quot;https://qa.debian.org/popcon.php?package=linuxcnc&quot;&gt;its
popularity-contest numbers&lt;/a&gt; that people have been reporting its use
since 2012.  &lt;a href=&quot;http://linuxcnc.org/&quot;&gt;Its project site&lt;/a&gt; might
be a good place to check out, but sadly is not working when visiting
via Tor.&lt;/p&gt;

&lt;p&gt;But what is LinuxCNC, you are probably wondering?  Perhaps a
Wikipedia quote is in place?&lt;/p&gt;

&lt;blockquote&gt;
&quot;LinuxCNC is a software system for numerical control of
machines such as milling machines, lathes, plasma cutters, routers,
cutting machines, robots and hexapods. It can control up to 9 axes or
joints of a CNC machine using G-code (RS-274NGC) as input. It has
several GUIs suited to specific kinds of usage (touch screen,
interactive development).&quot;
&lt;/blockquote&gt;

&lt;p&gt;It can even control 3D printers.  And even though the Wikipedia
page indicate that it can only work with hard real time kernel
features, it can also work with the user space soft real time features
provided by the Debian kernel.
&lt;a href=&quot;https://github.com/linuxcnc/linuxcnc&quot;&gt;The source code&lt;/a&gt; is
available from Github.  The last few months I&#39;ve been involved in the
translation setup for the program and documentation.  Translators are
most welcome to
&lt;a href=&quot;https://hosted.weblate.org/engage/linuxcnc/&quot;&gt;join the
effort&lt;/a&gt; using Weblate.&lt;/p&gt;

&lt;p&gt;As usual, if you use Bitcoin and want to show your support of my
activities, please send Bitcoin donations to my address
&lt;b&gt;&lt;a href=&quot;bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&quot;&gt;15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b&lt;/a&gt;&lt;/b&gt;.&lt;/p&gt;
</description>
        </item>
        
        </channel>
</rss>