June 26, 2019, 06:25:04 PM
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 Stops due to singularity

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January 07, 2013, 02:23:46 PM
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RoboticsMan


Hi

I am working on a project that involves bin-picking with an ABB robot. Once in a while, the robot moves too close to a singularity, and stops with an error message. It is not easy to avoid this, as the movements of the robot are controlled by a vision system that does not have a full model of the robot. Does anyone know whether it is possible to handle this type of error (stops near singularities), and let the robot program continue without input from the operator? And if so, how to do it?

Thanks in advance!

Today at 06:25:04 PM
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January 07, 2013, 03:47:02 PM
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TygerDawg


I wouldn't know if this would be useful to you or not since your positions are vision-system driven, but...

Many of us gray-haired grumpy old robot guys learned to add some slight angles to the tooling to reduce the probability of encountering a singularity.  Pallets, trays, robot mounting bases, EOATs, everything is usually designed by machine designers, not robotics guys.  So they build it in nice, square, orthogonal arrangements because it's easy to do so in the CAD systems.  I've found that's one of the worst things one can do in robot systems.  If you add some tilts, twists, and angles to the tooling elements, you are less likely to create the situation that develops into a singularity.  Still could happen, though.

Other than that, I could imagine you set up a separate task (if possible in your operating system) to monitor rates of change of joint links.  Then react accordingly if the joints start to spin too fast (indicating an imminent singularity).
TygerDawg
Blue Technik
Virtuoso Robotics Engineering
www.bluetechnik.com

January 07, 2013, 04:58:08 PM
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RoboticsMan


Hi

Thanks for you answer!
You are right, putting an angle on the tool helps in some situations, but not all. Thats why I hope that it is possible to make a solution where the singularity error is handled, and the robot is sent back where it came from. Then it can try to grip the part from another direction afterwards. Do you think that it is possible to handle the singularity-error in this way?


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