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strange pitch direction

asked 2017-05-04 01:57:37 -0500

eugene.katsevman gravatar image

updated 2017-05-04 01:58:17 -0500

Hello! I have some troubles understanding rpy. Here is my simple URDF file:

<robot name="test">
<link name="Body">
  <inertial>
    <mass value="4.0" />
    <origin xyz="1 0 0"/>
    <inertia ixx="1" ixy="1" ixz="1" iyy="1" iyz="1" izz="1" />
  </inertial>
  <visual>
    <geometry>
      <box size="0.1 0.02 0.02"/>
    </geometry>

  </visual>
</link>


<link name="link1">
  <inertial>
    <mass value="4.0" />
    <origin xyz="1 0 0"/>
    <inertia ixx="1" ixy="1" ixz="1" iyy="1" iyz="1" izz="1" />
  </inertial>
  <visual>
    <geometry>
      <box size="0.1 0.02 0.02"/>
    </geometry>

  </visual>

</link>


<joint name="j1" type="revolute" >
  <parent link="Body"/>
  <child link="link1"/>
  <origin xyz="0.1 0 0" rpy="0 -0.5 0" />
  <axis xyz="1 0 0"/>
  <limit lower="-1.57" upper="1.57" effort="10" velocity="10"/>
</joint>


</robot>

As you see, there are two links with a revolute joint between them. There is a pitch of -0.5 radians in the joint. And here is the rviz image :

image description

The question is why link1 is rotated upwards instead of downwards?

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answered 2017-05-04 02:07:07 -0500

rbbg gravatar image

You specify a pitch of -0.5 rads, this is a rotation around the y axis. The y axis is denoted in green. As (by convention) a right handed frame is used, you can use the right-hand rule to determine the direction or rotation. From what I can tell, the rotation on the picture is correct.

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thank you!

eugene.katsevman gravatar image eugene.katsevman  ( 2017-05-06 09:24:20 -0500 )edit

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Asked: 2017-05-04 01:57:37 -0500

Seen: 14 times

Last updated: May 04 '17