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Create a Joint between Base_Link and Table object

asked 2015-04-13 02:35:49 -0500

edo_raci gravatar image

updated 2015-04-13 11:28:51 -0500

nkoenig gravatar image

Hello to all respected Gazebo Users,

I am having trouble since last month getting everything to work. I am trying to put the base link of the UR10 robot to a table which is a Gazebo element and make it static so it doesn't move.

I have found out that i need to change the ur10.urdf.xacro and the ur10_joint_limited_robot.urdf.xacro. I added these lines to the last file:

 <link name="world" />

  <joint name="world_joint" type="fixed">
    <parent link="world" />
    <child link = "base_link" />
    <origin xyz="0.0 0.0 1.2" rpy="0.0 0.0 0.0" />
  </joint>

it works fine as you can see the height is 1.2 meters away from the floor but it doesn't matter since I just wanted to see it.

What do i have to change in order for the robot model to spawn fixed to the table, instead of the World!

Thanks in advanced,

Kind Regards

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answered 2015-12-02 08:55:52 -0500

J_Schaefer gravatar image

When you insert your table inside an own xacro-file you should create it as table.urdf.xacro. Then you need another file (e.g. table.xacro). The table.urdf.xacro is the description itself. And the table.xacro is like:

<?xml version="1.0" ?>
<robot name="table" xmlns:xacro="http://ros.org/wiki/xacro">
    <xacro:include filename="$(find myworld_description)/urdf/table.urdf.xacro" />
    <xacro:table prefix=""/>
</robot>

Inside the robot-file you have to refer to the table.xacro:

<xacro:include filename="$(find myworld_description)/urdf/table.xacro" />

<joint name="Table_joint" type="fixed">
    <parent link="world" />
    <child link = "Table_link" />
    <origin xyz="0.0 -.7 0.7085" rpy="0.0 0.0 0.0" />
</joint>

It should work like this. You now just have to mount the robot like @nkoenig said.

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answered 2015-04-13 11:39:59 -0500

nkoenig gravatar image

You have to create a joint between the table and the robot, similar to this:

<joint name="table_joint" type="fixed">
  <parent link="YOUR_TABLES_LINK" />
  <child link = "base_link" />
  <origin xyz="0.0 0.0 0.0" rpy="0.0 0.0 0.0" />
</joint>

You'll have to mess around with the <origin> value to get the robot in the desired location and orientation.

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Comments

I'm getting this error: [ERROR] [1429104093.856942772]: Failed to build tree: parent link [link] of joint [tablejoint] not found. This is not valid according to the URDF spec. Every link you refer to from a joint needs to be explicitly defined in the robot description. To fix this problem you can either remove this joint [tablejoint] from your urdf file, or add "<link name="link" />" to your urdf file.

edo_raci gravatar imageedo_raci ( 2015-04-15 07:30:39 -0500 )edit

I get a quite similar error: [ERROR] [1449062411.299238060]: Failed to build tree: child link [Table1] of joint [Table1_joint] not found I tried to include a table into my world in Gazebo. The UR5, I'm using, is mounted to a foot, which is written inside the ur5_robot.urdf.xacro and this works. When the table is written inside there, too, it works quite fine, but not in an own xacro-file.

J_Schaefer gravatar imageJ_Schaefer ( 2015-12-02 07:27:41 -0500 )edit
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Asked: 2015-04-13 02:35:49 -0500

Seen: 3,698 times

Last updated: Apr 13 '15