ROS LinuxCNC Link

Hi,

For info. In python you can do a system command.
For example : "halcmd setp ..." as a system command will work.

This is not very elegant, but it helps you in the process.

If you need any python examples how to set up port's and pin's. I have them somewhere on my hdd.

Thanks,

If you could post the examples in this thread when you get a spare minute I am sure it will help more that just myself.

Does LinuxCNC also support plug able trajectory planners?

ROS is not a black box, rather a framework of libraries. It has trajectory planers purpose built for robots. Could I use the LinuxCNC framework but substitute the default planner for a robot specific one?

I am not sure at this point but I will keep that in mind.

Hi,

If you could post the examples in this thread when you get a spare minute I am sure it will help more that just myself.
I accidentaly whiped one of my usb's last week when i left it in the pc, when doing writing a iso to usb.
Begin next week i can download the python examples from a production machine.

Does LinuxCNC also support plug able trajectory planners?
This is a pain in the ass.
If it was so. We could load userspace trayectory planners, wich can do amazing stuff. Then you could do motion profiles
for humanoid robot's etc, Or exotic dmg-mori profiles.

If it was waypoints on a 1mS clock (realtime) then you could connect it to output devices in LinuxCNC HAL.

Most handy is to connect to the stepgen and use the stepgen as pid. Then the waypoints may have a non realtime interval.
The stepgen kernel module does the realtime thing.

The stepgen tuning is important. For robot's there is a mathamatical thing to consider.
When motor 'a' has a acc of 10 and motor 'b' has a acc of '5' with the same reduction, the lineair path isn't correct.
A fix for this is calulate the ratio and sent the 'acc' value for each motor motion to hal.

I am curious if Ros has this important issue build in.

One thing about Ros. It uses kdl kinematics.
This library has a iteration value that can be set. For example 120.
That is performing 120 calculation's to optimize the inverse kinematics.

This will result that a cyclustime of 1ms is not possible. Therefore the stepgen as pid is
imporant to take away gap's between the iterations.

Hi,

I was thinking a little bit more about your Ros project.

Maybe i can help a little bit more.

My proposal is to set up a Ros environment and a Linuxcnc environment in a Linux distribution for Robot's.

In this distro i would like to embed the Ros environment, the Kdl (kinematic library), the Opencascade (CAD) library, wich is also used by Freecad, with a basic and simple coding example, wich i have to create.

Also i would embed a basic matix calcuation example how to multiply matrixes to do a workpiece xyz (roll,pitch,yaw) offset.
This sounds quite complex, but in fact, it's quite easy when you know what to do.

For universaties and students, this distro would be helpfull worldwide.

Do you work with Mesa or something else ?

Do you have already played around with Ros? I have no clue and never used Ros. So for me it's totally new.

The connection from Ros to Linuxcnc Hal should not be a time consuming operation to get this fixed.
I already have c++ code for this. I can not write python.

Grotius, I think you should devote 3-5 days learning Python by following the Google Python tutorials. I find I don't use it enough so its hard for me but when I do get it, I can write in 100 lines of Python what would take 1000 lines in C.

developers.google.com/edu/python

Video of lesson 1