'Invisible Bridge' in Pick and Place - Vortex

[jack_mcevoy]

Hi All,

I am performing a pick and place task with a two finger parallel gripper, using the Vortex physics engine.

In the simulation the distance between the gripper fingers when fully closed is 16.83mm. This was verified by inserting a dummy at the center (0, 0, 0) position of each finger and noting the dummy position of the left finger relative to the right finger, in the gripper fully closed position. To calculate the distance between the gripper fingers when fully closed, I subtracted 2*(half the width of the fingers bounding box) from the total distance between the two dummies, giving me 16.83mm.

However, with the distance between the fully closed gripper fingers at 16.83mm, the gripper successfully grasps an object measuring 16mm wide, which in real life wouldn't be the case.

I have the simulation code outputting the orientation of the finger and the orientation of the object relative to the world axes, just before the grasp, and it is telling me an error of <0.02 degrees off perfect exists. I don't think this orientation error is contributing to this invisible bridge which is enabling this grasp. But I could be wrong..

Does anyone have any light to shed on why this may be happening?

[coppelia]

Hello,

several things could be happening, two come immediately to my mind:

• your visual scene and the hidden, dynamic part of the scene could be mismatching. To verify that, click the Visualize and verify dynamic content toolbar button, during simulation.
• The Vortex engines (as others too) has a lot of settings that allow you to adjust how a simulation runs. You have global physics engine settings, and also physics engine settings related to material, e.g. Skin thickness.

Cheers

[jack_mcevoy]

Perfect I'll look into this, thank you!