Different output with two different computers

Started by Henri_A, January 11, 2024, 09:16:01 PM

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I have use basically one computer to produce robot programs to our Kuka for some years now. Today I wanted to edit one of those programs with another computer. I opened exactly same rhino file and exactly same grasshopper file with another computer and I noticed that the output .srv file was different. Rhino version is also the same.

There is some simple linear movements only. All XYZ coordinates was same, but the wrist angles A,B and C where slightly different (few degrees).

Of course slight difference with wrist angles doesn't usually cause any problems, but accidentally this time that caused an alert of possible singularity.

Generally it would be nice to have same output with different computers as we could make some small adjustments for old programs without any doubt of the functions of rest of the program.

Any ideas what causes the difference or is there a way to prevent it?

Thanks a lot!

Johannes @ Robots in Architecture

Hello Henri,

That's a very interesting observation, are you sure that the KUKA|prc versions were the same? Because I occasionally finetune some the algorithms a bit for edge-cases. As any PC calculates with limited accuracy, 90 degree can sometimes become 90.0000001 degrees, you have probably observed that in Grasshopper somewhere.

For the ABC calculation those values are sometimes rounded, to get more consistent ABC values - that should be more aesthetic than functional, though it also helps when the toolpath is not wobbling around (i.e. 90.00001, 89.99999, 90.000001, so going back and forth). There are multiple ways to express the same orientation in ABC, so these small changes can also create quite drastically different numbers, though the frame will be more or less the same.

But a difference by a few degrees is very unexpected, we're usually talking about 1/100-1/1000 degrees here.
Do you have an example of the ABC values before and after? That would help a lot!



Hi Johannes,

You were right, the Kuka PRC version at the two computers was not the same. Now we updated both computers with the latest version and the output files are identical.

Thanks a lot!
Br, Henri

Johannes @ Robots in Architecture