Kinematics for XYZAB mill

Thanks for the feedback Aciera! First things first, you certainly win on the style points with the embedded pdf and actually using superscripts, numbering your equations etc

Secondly, I'm glad that we are largely in agreement with the structure of the solutions, just disagreeing on signs. It means that the old eng maths hasn't let me down too much.

Onto the disagreements in our solutions: 
1) I 100% forgot to multiply my Rtq by (-1) during the inverse transformation. so that is missing from my solution.
2) We have the same solution until eqn(25) in your solution. Slightly different structure: you use Ca(Py-Dy) and I use -Ca(Dy-Py) but they are equivalent. From there we diverge onto the transformation to eqn(26). The only difference seems to be at row 2 col 3.

I'm trying to work through that at the moment, but I have to head out and be and adult for a while. I'll get back into it tonight. 

Thanks for the flowers on the style. I try to think like a designer: The solution might be wrong but at least it looks right.

Anyway I took a stab at reconciling our solutions and I may have found a little contradiction in your write up. Would be great if you could look that over and see what you think:

 


Rod, once we're sure that the math is correct and the kinematic works I can go over the document again. No problem. 

Aciera wrote:

Thanks for the flowers on the style. I try to think like a designer: The solution might be wrong but at least it looks right.

I must say I was impressed too! In fact, I watched a relevant video today

Aciera wrote:

Rod, once we're sure that the math is correct and the kinematic works I can go over the document again. No problem. 

Yeh, that will be great. Its awesome to have some cross checks! It confirms the power of open source!
Also great to see you guys are both on the same track.
I should have some STL's of a real machine in a few days. So I will turn my attention to the C code. There is existing switchable kinematics for XYZBC and XYZAC so I'd like to extend that for our XYZAB model in the core code.

I might ask questions on the other thread about 5 axis I linked to earler. I know the right people are watching there. I might link them to this thread.

> There is existing switchable kinematics for XYZBC and XYZAC

For custom kinematics, using a .comp file is a much simpler method:

1) no makefile updates needed
2) build with halcompile
3) user-installable

For simple cases see src/hal/components/userkins.comp

For cases requiring switchable kinematics, see
src/hal/components/millturn.comp

Refs:
github.com/LinuxCNC/linuxcnc/blob/master...onents/userkins.comp
github.com/LinuxCNC/linuxcnc/blob/master...onents/millturn.comp

Man pages:
linuxcnc.org/docs/devel/html/man/man9/userkins.9.html
linuxcnc.org/docs/devel/html/man/man9/millturn.9.html

Example usage (switchable kinematics):
github.com/LinuxCNC/linuxcnc/tree/master...xis/vismach/millturn

Thanks Dewey, I just cobbled a comp together.

I got all enthusiastic and made a sim-config too (requires 2.9 as it uses switchable kinematics): 

[Superceded by forum.linuxcnc.org/10-advanced-configura...mill?start=60#258432 ]

To install the kinematic comp:
$ halcompile --install halcompile --install <yourpathhere>/xyzab_trt.comp

I also whipped up a vismach model called 'xyzab-trt-gui.py' which you might need to set as executable.

All very good, only that the kinematics don't seem to be right or the vismach model isn't or both.
Anyway I'm out of time again...



[edit]Thanks for the video Rod, right to the point.

I think that I would have fiddled about with maxkins swapping axes around until it worked.

github.com/LinuxCNC/linuxcnc/blob/master...kinematics/maxkins.c

I would previously have started with xyzac-trtkins but since switchkins was introduced I can't figure out how those kins modules work any more.