Custom robotic stage (inverse kinematics setup)

bobteal wrote:

By the way I have already used EMC2 and have one setup running a mill. Is there a way I can play around with the new setup without messing up the current setup

Yes, just make a duplicate of the config directory. Optionally change the names of the INI and HAL files in the new directory to match.

As for compiling the new kinematics file, you can probably compile and install it with "comp" so there is no need to download all the LinuxCNC source.
It's probably easiest to start with trivkins and modify it, it's here:
git.linuxcnc.org/gitweb?p=linuxcnc.git;a...082c4cafa137f7c7a16d

Most of it you can leave untouched. But you need to change the KINEMATICS TYPE to "BOTH"
Then just change the equations that define the positions in terms of joints, and vice-versa.

Alternatively, you might be able to use Genserkins if your robot can be described by Denavit-Hartenberg parameters.

bobteal wrote:

I installed emc2 from a livecd. Does this version have all that is required to compile it? Or do I need to get it to a network to download source files?

You need to get to the internet.
I do most of my compilation with SSH from the comfort of the living room, while the CNC machine and its computer stay in the garage.

Also I just dont know what the procedure is to doing this. What files do I need in total? Do I need to place them all in a folder?

What version of EMC2/Linuxcnc are you using?
The first step is to network the PC and in a terminal
sudo apt-get install build-essential
That makes sure you have all the compilers and suchlike.
The, if you are running EMC2
sudo apt-get install emc2-dev
Or if you are running a LinuxCNC version (2.5 upwards)
sudo apt-get install linuxcnc-dev

You should then be able to put a kinematics file in any folder and compile/install it with
sudo comp --install mykinematicsfile.c

Start with trivkins (change the file name so you don't break linuxCNC, and change the author info so it's still true.)
It is also imperative that you change line 83 where the module declares it's HAL name, or it will all go wrong.
Note that once it has gone wrong, RTAI often stays wrong, and you will find that you still can't reload it after fixing the problem in your kins file. You will have to restart the PC.
(I am currently restarting a VM after crashing RTAI due to not changing line 83 of the new "andykins" )
of the file, then right-click the trivkins.c link near the top, and save-as that file.

bobteal wrote:

I'm wondering, if I dont have the 'lengths' correct for a kinematic robot, and I wish to 'fine tune' these settings to make things more precise, do I need to recompile since the kinematic lengths are in the inverse kinematics file?

Which kinematics file are you using? Most of them take the lengths as parameters which can be easily changed in the HAL file (or the INI file if the HAL file has been set up with INI file links).
If the lengths are hard-coded into the kinematics file then you do need to recompile that file, but that can often be done using "comp" rather that compiling the whole application from source.

I'm wondering if as you say it may mess up my current setting, should I then do this on a spare HDD instead so I dont screw up my current setup?

There is no need to go that far, just make a copy of the configuration folder for the machine and change the name of the INI file. I have two different configs for my machine and that co-exist without any problems.

Also unrelated I suppose, but can you run EMC2 under emulation in linux or windows (say virtualbox)?

Yes. I run it on my Mac under VMWare.
I am not sure why you would bother with emulation under Linux, though. You can simply use the "pure simulator" version if the issue is one of kernel compatibility.