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I tried to draw a picture to ilustrate the issue with the 2D clothoids stacked on each other to approximate a 3D clothoid.We want to connect a straight line in y with another line in x. The second one isI tried to draw a picture to ilustrate the issue with the 2D clothoids stacked on each other to approximate a 3D clothoid.We want to connect a straight line in y with another line in x. The second one is also shifted up in z. The 1) picture shows a 3D drawing of the situation. Pictures 2) and 3) show the xy and xz planes respectively with how the 2D clothoids would look like respectively.

 

The 2 clothoids look fine by themself, the one in xy is also close to the correct one I guess. The issue is with the second one in xz. The clothoid optimizes curvature in this xz projection so you get linear increasing and decreasing curvature relative to arc length in this projection but not linear in total 3D  arc length. In this example the difference is quite extreme because the curve is initially moving mainly in y and not in x. So the resulting curve does not behave as expected. Picture 4) shows the resulting curve in the yz plane, the tool is barely moving in z for quite some time (because the machine is mostly using in y and this direction got ignored for the clothoid calculation. Then it suddenly needs to move quite a lot in z and jerk is much higher than expected from the xz clothoid.
I hope I managed to explain this, it’s kind of hard to visualize 3D clothoids.

So in summary this approach leads to a smooth curve with fitting curvatures at the ends but in between the change in curvature and torsion is not linear and jerk might be higher than expected. The resulting connection curve also dependens on the orientation in the coordinate system. If the example was rotated for example by 45° the resulting clothoids would look differntly. This is of course kind of unintuitive.
So it does work to some extend but is not the best solution and there might be more extreme edge cases where this might  go wrong.

tommylight wrote:

Anyone against deleting this topic?

 

Delete away

not Hererunterfahren , sondern Herunterfahren. "drive down"?

AI tells me on a short "Ethernet controller setup LinuxCNC" search, what the "hottest 10 Windows11 Laptops of 2025 are".
Maybe how to fix the Wifi on my phone?

Just for fun translate: "vibration tumbler" to Chinese with an AI translator. Then feed the result back into picture search. (just for safety do not do it when someone is watching)

German for bicycle = "Biobike" (what???) it was Fahrrad, when i left.
Dictionaries made from dead trees were still a thing. it is a mess!

The closed form solution from the Frego paper only works if the clothoid starts with curavture and torsion = 0 aka from a straight line. So for our usecase this can not be used in all situation, only if we we want to connect to a straight line and not to arcs or splines etc.

Thanks for the new paper, I will read it later.

Hobby 3-axis mill, Raspberry Pi 4B, official download - reports as Gmoccapy 3.4.6.
Done several jobs since swapping from AXIS.

Running code - then stop.
No pop-up messages.
Found the Gmoccapy Log - nothing.

Cancelled job, but machine would not jog.
De-activate controls (Green/Red PB), then activate - machine jogs.

Need some hints on where to look, or a list of typical problems.
Thanks,
John.

 

Aciera wrote:

Oh, I just realized, 'pyvcp' panels are for the AXIS GUI.
Gmoccapy uses 'GladeVCP'
linuxcnc.org/docs/html/gui/gmoccapy.html#cha:gmoccapy
 

Ok, not sure how I do that as I used the stepconf wizard to create the config files and it created the pyvcp files.
Do I need to install a different version of linuxcnc if so which one as I just selected the latest 2.9.4 version?

Thanks again for taking the time to help, I really do appreciate it. 

You are of course free to try, all you need is on github. And I am happy to answer questions if there are any.
I just have no working experience with this card.
I did run the previous version in my lathe, so it is does work. I just want to see it work for hours before I put my stamp of approval on it, and it hasn't run for hours.
I do have working experience with other cards, I run the latest EaserCAT-6000 in my plasma cutter and it works just fine for hours, so the concept is validated.
 

Oh, I just realized, 'pyvcp' panels are for the AXIS GUI.
Gmoccapy uses 'GladeVCP'
linuxcnc.org/docs/html/gui/gmoccapy.html#cha:gmoccapy

If you are not loosing steps, like the spindle end up in a different position after you are done, I would guess something mechanical.
45 degree rotated ellipses reminds me of backlash.

I obviously forgot to rename the signals.
motion-type isn't used anymore, so naming should be:
tool-number-s32 and tool-number-float.

Thanks JT, this might be exactly what I am looking for. And is very well documented with many youtube tutorials.

I did manage to get the demo up and running. Will keep you posted about the progress in the next few days.

Thanks all for the help!

Lcvette spent a few hours helping me last night and I learned a ton and made notes and screenshots so that I can do it again later, if needed. The linux kernel was not a realtime version, after following the install directions, so he guided me through fixing that and manually setting the network card and doing auto login for debian. I had done last two items before but did not remember how, and I had no idea how to fix the kernel, but did realize it wasn't listed as rt when seeing it while working through different screens. It was great to have someone walk me through doing it in a way that I knew would be correct. I mention all this so that if someone else finds this thread and has the same problems, they can learn a little more about their situation.

Now, my system is up to date and I was able to get a working Axis installation going. It all seems to run properly, but my ping to the mesa card is high so I will make a new post to ask for help with that (it isn't stopping me from continuing work on the machine setup).

The next steps are to copy the sim.var file and then to copy other files and folders from the machine setup directory.

My "machine setup directory" is missing “user_buttons” folder and the pbsplash.png file.

The left is my folder and the right is from the instructions page for installing Probe Basic.

 

Could I please get firmware for the 7i92 + 7i85 with the index-enable signals and a PWMgen? I've got the control box lying out on the floor until I can get the new firmware going. Thanks!

unknown wrote:

No always 4 cores.

For some reason the RPi docs say to use -j6.
 

Thank you Rob.

No always 4 cores.

For some reason the RPi docs say to use -j6.