Issues of Correlation of Starting Points Between Robot and GH Simulation.

[tenn6064]

Hello all,

I am newish to using KukaPRC, and I am trying to run my first program on the robot using the code generated from my grasshopper script. However, I am having a very difficult time getting the robot in the simulation to match what the robot in the real world is reporting as its starting values.

I'll try to be as descriptive as I can to clear up any confusion:


https://imgur.com/a/Bv8ha1L
Here is the robot with its orientation in GH. The base is the same as the real world example, with the base being the global origin. The tool coordinate frame is also accurate, being measured from the real world example as well as models of the tool, etc. However, the tool's starting position is directly inside of the workpiece (also accurately modeled), having an inaccurate/invalid starting location.

https://imgur.com/a/U4xSR9Z
These are the start position values from the robot. I have them as the start and end position in the KukaPRC core settings.

Why could this be happening? Is there a calibration issue or something else?

any help would be greatly appreciated.

[Johannes @ Robots in Architecture]

Hello,

In your screenshot it shows that you are using base number 6 with XYZABC all set to 0. Can you double-check that base 6 is also set to zero on the robot? KUKA|prc by default only references the base number but does not overwrite the current base numbers. That can be useful if you e.g. mount a new piece that is only off by a few millimetres.

Best,
Johannes

[tenn6064]

I was using base number 6, but the base on the robot was base 0, or the null. To my understanding that is the base with the origin of the global coordinate frame set to the base of the robot, but I could be wrong. In any case, I tried a different base calibrated with the table but yielded similar if not worse results.

https://imgur.com/a/T2fqPLH

Am I doing something incorrect? I'm a little confused. I looked through the calibration post pinned to this page but these calibrations I am using were already provided by another group, and I would like not to overwrite them if possible. I could try to create my own though, if necessary.

[Johannes @ Robots in Architecture]

Hello,

From the screenshots it looks like you are doing everything right. The tool and base values look plausible and in the visualization you see that the XYZABC of the tooltip also matches with the mesh of the endeffector.

Do you maybe just need to place the toolpaths somewhere else? In KUKA|prc the base origin is always the Rhino origin. So if you calibrate for the corner of the table, place the table at the intersection of the coordinate axes.

Best,
Johannes

[tenn6064]

Well the problem is the simulation has the tool inside of the table on its startup and ending position, crashing the robot when it tries to go to those positions. So running it as is isn't an option unfortunately and I am struggling to figure out why they aren't correlating. For example, the robot with me has its tool directly vertical to the workpiece while the simulation has it off to the side: https://imgur.com/a/nHy7RvI

[Johannes @ Robots in Architecture]

Sorry, that is very hard to troubleshoot remotely. Are you sure that it would crash and that you haven't just moved the table geometry in Rhino to the wrong location in relation to the robot?

Looking at the screenshot of the tool I would assume the the tool is not mounted the same way as you placed the mesh.
I would recommend moving the robot to it's standard position (0, -90, 90, 0, 0, 0) by hand and then looking at the tool. If it's not looking downwards, rotate A6 until it is and then rotate the mesh geometry with the same value so that they match.

Similarly to, activate the same tool and base as you are using in KUKA|prc and manually move the tooltip e.g. to the calibrated origin. Then look at the axis values. Enter the axis values e.g. as start values in KUKA|prc, move the simulation slider to 0 and then see if the tool is pointing to the Rhino origin as well.

Best,
Johannes

[alicebell]

I am also new to this. I use this: https://discourse.mcneel.com/t/kuka-prc-grasshopper-robot-arm-with-rotary-table/60149 for resolving these types of problem which I have to face during my work.