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Objects pushed away without collision when approached by robot

Posted: Wed Jan 27, 2021 2:46 pm
by sejnogab
Hello, we have observed a strange bug - in many cases, when a robotic arm approaches an object on the table, the object seems to be pushed away by the robot even when they are not in contact at all. This seems to be robot and object independent, we have tested the scenario with Panda Franka Emika robot and several versions of KUKA iiwa (the urdfs are from official online sources). We have also tested with different object urdfs. It is even stranger that it does not happen every time the robot gets close to the object, sometimes the object reacts just after collision, as expected.
Here is a video where the problem is recorded, below is an example urdf of the cube that is being pushed away.

Would anyone please have any idea what might be causing this or how to even debug such thing? I wonder if it could be a bad combination of restitution and friction values of the cube urdf, but the object starts moving before it is in any collision with the robot.

Thank you.

Cube urdf:

Code: Select all

<?xml version="1.0" ?>
<robot name="cube_holes">
  <link name="baseLink">
            <restitution value="0.5" />
            <rolling_friction value="0.03"/>
            <spinning_friction value="0.03"/>
      <origin rpy="0 0 0" xyz="0.0001 0.0 0.0"/>
       <mass value="10.084"/>
       <inertia ixx="0.0053" ixy="9e-05" ixz="0.00014" iyy="0.00534" iyz="0.0003" izz="0.00155"/>
      <origin rpy="0 0 0" xyz="0.0001 0.0 0.0"/>
        <box size="0.06 0.06 0.06" />
       <material name="black">
        <color rgba="0 0 0 1"/>
    <collision concave="yes">
      <origin rpy="0 0 0" xyz="0.0001 0.0 0.0"/>
	 	<box size="0.06 0.06 0.06" />