Author Topic: Undetected Unreachable Position and Unnecessary Axis Rotation  (Read 324 times)

pawelsapiecha

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Undetected Unreachable Position and Unnecessary Axis Rotation
« on: February 18, 2021, 03:15:59 AM »
Hi All!
My name is Pawel. I'm a student at the University of Arizona. I'm trying to do a simple task with Kuka, but the PRC doesn't detect the faulty path (tool and one of the axis sometimes blinks red during the simulation). On the other hand the robot won't start the program because of the "KSS01444 Array index inadmissible" error. At one point of the operation axis 4 has to make 180 deg turn but instead of stopping at 180 it rotates couple negative and positive degrees more exceeding the axis limit. I've tried multiple settings with different movement radius, direction, planes orientation, tool orientation. No success so far. I'd be grateful for any advice how to solve that problem as I'd like to execute much more complicated command based on this circular movement.
Best,
Pawel

pawelsapiecha

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Re: Undetected Unreachable Position and Unnecessary Axis Rotation
« Reply #1 on: February 18, 2021, 03:16:43 AM »
RH + GH FILES

Johannes @ Robots in Architecture

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Re: Undetected Unreachable Position and Unnecessary Axis Rotation
« Reply #2 on: February 18, 2021, 06:06:31 PM »
Hello Pawel,

I just looked at your files, some remarks:
Only use one mesh for the robot cell (or use Mesh Join to combine them!), at the moment you generated two robots which really slowed down KUKA|prc.
The problem with A4 is because you are moving through a singularity where A4 and A6 basically share a rotational axis. It's best to solve that by tweaking the position of your object in relation to the robot. In your case, setting the base to 100 in X and 140 in Z (40 was set by you) solves the problem. I've then also set the Initial Posture (next to the start/end position) to "010" and it now looks fine.
Alternatively you could also experiment with the angle of your tool to solve singularities.

Ultimately, I usually recommend against using SPLine movements, as they are splines that are not defined geometrically (e.g. Bezier curves, Akima spline etc.) but calculated by the machine in realtime to achieve a smooth motion through a set of points. A spline may look different depending on which robot you are using. Consider using simple LIN movements instead, they are the most simple and robust movements. Otherwise just be prepared for possible differences between the simulation and actual robot movement.

Hope that helps!
Best,
Johannes

Johannes @ Robots in Architecture

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Re: Undetected Unreachable Position and Unnecessary Axis Rotation
« Reply #3 on: February 18, 2021, 06:36:32 PM »
...and regarding the "KSS01444 Array index inadmissible", it should provide you with a line number so that it's possible to locate the problematic section.

Thanks!
Johannes

pawelsapiecha

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Re: Undetected Unreachable Position and Unnecessary Axis Rotation
« Reply #4 on: February 19, 2021, 07:14:39 AM »
Thank you very much for the response! I'm very glad that it was fairly easy to solve!