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I'm trying to simulate a custom gripper in Webots. For this purpose, I use an active-passive connector to simulate the custom gripping mechanism. So far, so good. The gripping works fine.

However, then I move the object together with the gripper. The fingers of the gripper seem to fall of the gripper. I've used SliderJoints similar to the Kuka Youbot example (in general, I tried to replicate the Youbot gripper), but the fingers still seem to be movable in other directions than the joint axis.

Here is a short video demonstrating the problem: https://youtu.be/VNdWUMkHEcM

Any ideas what could be the reason and how to debug this? I'm happy to share parts of the simulation code if required.

UPDATE 1: After a little of research if found this FAQ article: https://cyberbotics.com/doc/guide/modeling#my-robotsimulation-explodes-what-should-i-do

This helped me to reduce the problem by changing the size of my bounding boxes.

Thanks to this I now found the source of the error: When moving the object around, the object "lags" behind the gripper. When decelerating, the gripper then collides with the object.

A simple solution would be to further reduce the size of grippers bounding box. However, I think it would be better to disable collisions between my passive connector objects and the active connector gripper. However, I'm not sure how to do that.

machinekoder
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  • Have you tried removing some bounding objects/Phyics? For example for the Connector itself? – David Mansolino Oct 07 '19 at 06:40
  • If I remove Physics from the Finger/Object, moving the object with the Connector doesn't work anymore.Reducing the bounding objects does indeed reduce the problem. Just wondering whats the best practice. Especially when I want to use the gripper using the Connector and without (friction gripping). – machinekoder Oct 07 '19 at 07:54
  • Ok I understand, to be honest, it is indeed sometimes tricky to find a good setup and it may require some experience to find the perfect setup. If you need help it might help to share your simulation, you can do this on the Webots discord channel: https://discordapp.com/invite/nTWbN9m – David Mansolino Oct 07 '19 at 08:44

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