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Hi Guys,
It's been a long time since the last update. At least 5 versions of linuxcnc
I have done some interesting modifications to the machine.
I have attached the valve shaft to a lead screw with backlash compensated nut. 
Later, I am going to replace that with the Ball Screw.
Then, the valve is moved via a timing belt connected to the stepper motor.
With a 2mm screw pitch It is possible to locate valve shaft with decent acuracy.
Please see the attached picture.
For the past couple of weeks, I've been trying to tune the PID for that setup. But it is hard.
It oscillates a lot, or it is not compensating the steady state error.
I would love to hear your advice on a couple of points:

1) What is the typical following error for an axis with a linear scale of 0.001mm resolution(1 micron)? In steady state it is able to position the axis within +-0.005 accuracy. Do you think it is possible to get more from that scale resolution?
During acceleration and deceleration, an error jumps up to 0.1mm at 1500mm/min speed. What is a typical result for well well-tuned PID loop?
2) Do you think I should set up a two-stage PID control loop? One stage is to control the position of the valve shaft based on the velocity feedback from the scale. And that another loop to control the position and give a commanded velocity as an output?

Thank you!

PS. I do have some videos that I can share in case you are interested.


 

These issues have been around for a long time. It is just that we never released a version of Linuxcnc on Debian 11 so we did not know about it. Plus at that time, there was no path to install Ethercat on Debian 11 except for a Deb that Grotius made for me. The PC was running a Realtek R8125 NIC and de driver was first released with Debian 11 as it was a rock and a hard place situation, Eventually I migrated my other PC's to Debian 12 before it was released because of this problem.

At one stage while trying to solve this issue on Debian 12, one of the RT devs indicated it was probably introduced in about kernel version 5.9 and Bullseye was released with kernel 5.10, The other issue is it is mostly to do with the Realtek R8111/R8168 NIC and it is not part of the kernel so nobody cares and if they do, there is a non-free driver (that is not in the non-free-firmware included with Debian 12)

This issue has mainly resulted in Error finishing read on Mesa HM2 connected (Ethernet) cards. I never experienced problems with Ethercat on PC's that had issues with Mesa cards.

Some of the issues are due to us never needing to do cpu affinity settings that were routinely used in the RT world. Then the implementation of new  features like energy efficient ethernet also impacted.

Personally, I think the problem is under control if you follow my guidelines. I will say, I think the days of using 2 core PC's are over, although some have got them going with my kernel.I will say my old J1900 has never displayed better performance than it gets on Dsbian 12

However what concerns me is this a new issue you guys have uncovered. I think the correct course is to raise an issue with iGH etherlabmaster on their gitlab repo.

Hi Grotius,

Thank you very much for your help !!
Now my problem is solved

The new line in the hal file :
net signal-name motion.digital-in-01 <= parport.0.pin-11-in

And the lines of my program :
M66 P1 L0
o100 if [#5399 EQ 1]

Here I attach the var file.

Hi, Thanks for that.
It appears that just manually turning the spindle on isn't what you're supposed to do. When i give an M03 S2000 command in the MDI, it does turn on, and show 2000 on screen.
Actual speed seems to vary quite a bit.
Getting the 0-10 output from the VFD into the 7i67 and LinuxCNC for the feedback would be a win. But would that go to one of the ports labeled as mpg1a/b 2a/b? (that's where i currently have my homing switches)

For the prefs saving problem, try to replace the existing file, with the attached file.
Maybe the repository is not updated.

Thanks for the suggestions about the guide. They seem more professional than mine.
I'll update the doc.

Regards
Giovanni 

besriworld wrote:

Well, the reason is very simple Each additional Beckhoff module is a bag of money for the small user.

You need to consider this before selecting a control method.
I've been scouring eBay for various beckhoff modules and the price is not too bad but they are never in Australia so the wait time sucks!
But AUD $132 for above module landed was not bad v's a THCAD given our appalling exchange rate.

It can be the 4.19 kernel in debian 10 that perform must better than kernel 6.1 in debian 12.
When I was working on my own EtherCAT board a year ago I had some timing issues
and compared the network adapters and linux kernel version in the computers I had around.

 
linux 4.19 performed better especially with Intel adapters.
Often I had to go up to 2 millisecond servo loop to get acceptable performance.

This is just  to show that there are several factors that influence the timing performance
and when you compare with debian 12 and 10, the kernel version is definitely a factor.
The network adapter is another. If you have a Realtek network adapter and have tried
all settings that rodw lay out in his document and you have a free PCI-e slot in the computer
you can try with a cheap Intel network adapter. I210, I225, I226 for example. I have had good luck with them.
Not sure how that comes in here, but you should nevertheless bring down the normal real-time jitter
to single digits, less than +- 10 microseconds, the one you check with latency-histogram.

The WARNING you get, and the delay, is a nuisance more than a real problem. The Ethercat master
will synchronize the time of clients, it just takes longer than 5 seconds. Googling around for this issue
one can see that this issue has been there for more than 10 years and one way to get rid of the warning
is to just increase the 5000 ms level when compiling the ethercat master yourself. You will get the delay though

Here is a short article on DC clock synchronization www.acontis.com/en/dcm.html

I absolutely agree, he is/has the best hardware support on planet earth!

Well, the reason is very simple Each additional Beckhoff module is a bag of money for the small user.

Hallo Robert,

werden die Vorträge oder die Folien im Anschluss veröffentlicht? Ich hätte Interesse kann jedoch aus zeitlichen Gründen leider nicht teilnehmen.

Verkauft ihr auch PCs mit Linux CNC? Ich habe mittlerweile den zweiten PC der bezüglich realtime Probleme hat. Bevor ich jetzt auf Verdacht noch einen dritten PC kaufe und mein Glück versuche ...
Falls ihr keine PCs verkauft hast du eine Empfehlung welche PCs problemlos funktionieren?

Grüße Erwin

Hakan wrote:

Is it the same if you just install the ready apt package with ethercat instead of building ethercat master yourself?

I think it would be but the released version might be locked to a tag branch like we do with 2.9.4 vs 2.10

JT wrote:

I even added LED's to the reload and save button if you want them you just have to add a Dynamic Property. Big thanks to Chris for helping me understand the LED's

Now thats cool, I wanna try that.

JT wrote:

blazini36 wrote:

Any chance of adding a "save" button for the code viewer? I see the "save_as_pb", I'd rather just overwrite the existing file without a prompt if it's possible.
 
I never thought about that but it makes sense because you can edit the nc file in Flex you should be able to save your edits then reload.

Save menu item and button added.

JT
 

Exactly, didn't realize it's one of those things you only wish you had when you realize you don't have it.

The option to open an editor or save as a new file is great if that's convenient for the arrangement you have. My particular setup on this machine it's super convenient just to edit in the code viewer, and just save it in case I wanna run it again. I don't really have any desire to open a text editor or save it as a new file since I'd rather just walk over to the desktop that has a good keyboard and edit it there. I don't necessarily wanna do that just to change a spindle speed line or something

andypugh wrote:

Apparently it was this: forum.linuxcnc.org/10-advanced-configura...ives-ethercat#315703

The PID has changed.

I'm excited to see Andy wading in where angels fear to tread! Welcome to the dark side!
ethercat slaves -v 
or
ethercat slaves --verbose

Will list the VID (Vendor ID) and PID (Product ID)  and these must be used in the Ethercat xml config file