LinuxCNC S-Curve Accelerations

Hi,

Grotius wrote: There is no real scurve math inside. It looks like they hide it somewhere else.

Ok, what about this one, from line #670?

rmu wrote: you can look at this github.com/rmu75/linuxcnc/tree/rs_6otp for an implementation of the 6th order bezier curve. the discrete diff math is not needed in linuxcnc, cpus powerful enough to run linuxcnc are powerful enough to use floating point and "direct evaluation".

I've sucessfully resolve all building/compiling dependencies and will try your approach in a couple of days.

If I build by "dpkg -i ..." - get pic.2
If I build by "make ..." - my ethercat configuration not start. lcec is broken pic1 (
In "hello world" configuration - everything start, but I can't check the robot physically

TheRoslyak: we might be getting close! Those errors look to be unrelated to my changes.

Looking at Nico2017's EtherCAT build instructions perhaps the only thing needed is to copy (or link) your system lcec.so into the folder indicated in pic 1?

My system lcec.so is in /usr/lib/linuxcnc/modules/lcec.so.

about lcec.so - Yes agree. On linuxcnc-master same if build by "make".
This means ethercat will only work by "dpkg".
If you have problems with git commits, you can subscribe *.tar.
I'd better build by "dpkg"(without errors) - so I can check on ethercat robot

So doesn't make it work? Do you still get the same error message?

Edit: Sorry, I can't help you with the dpkg build, I've never used that myself.

In general, I started testing on a real robot and get problem:
I can't home with your configuration. and get error (pic).
First. I tested on PICO316HGA-N4200 computer and received the same error + latency error.
Then. I test on i9900k and get same error.
I homed robot by linuxcnc-master and start your configuration without homing parameter. I can play my test program but I didn't see the difference in physical.
What parameters I scope to see the difference. (Motion.-vel-cur , "x-pos=>ddt=>ddt=>x-axis-acc" and etc . is not change)

The "Cannot reset free planner position while in motion" error means that LinuxCNC does things to the planner while homing that I did not anticipate. This is one of the things I wanted to have tested and is very valuable information - thanks! It means I have to look more closely at that part of the code. There is no quick fix unfortunately; it will take some time: I have to set up some kind of testing rig and figure out how to handle these cases.

---

A good parameter to look at would be joint.N.acc-cmd. Without a jerk-limited planner you will see step changes (or just a flat line - so trigging best done on joint.N.vel-cmd) while jogging a joint. With smooth1d you should see a gradual, linear change in acc-cmd.

But again, at the moment I've only replaced the joint jogging planner, so you will not see any difference on axis jogs nor on coordinated motion, i.e. while running a G-code program. Only on un-homed joint jogs.

hI arvidb
Wanted to know if progress in work?
What equipment do you have to check it? Mesa, ethercat driver or any else?

Hi!

I have EtherCAT servos running with LinuxCNC and also a Mesa 6i25+7i77 combo and analog servos that I can hook up. But I don't have a machine to hook them to. For testing the current issue I need an actual axis including limit switches, which I'm putting together - I have linear rails, ball screws, switches etcetera. But I don't have access to a workshop (I live in an apartment) so it's a bit slow going. Can't make too much noise, weld or do heavy metal working etc.

Hi,
I just ran across some new research for Jerk limited trajectory generation.
arxiv.org/abs/2105.04830
The code is MIT licensed and available at:
github.com/pantor/ruckig
Looks like they are solving cubics and quartics in realtime ( and by the looks of it without iterative methods).
-automata