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When working with two robots (UR5) is it advisable to keep the base_link frame of each robot at the origin?

asked 2019-10-07 17:35:59 -0600

mkb_10062949 gravatar image

updated 2019-10-08 02:49:33 -0600

Hello, I am working with two robots (UR5)...using arg init_pose I have set the robot 1 at x1, y1 and z1 position and robot 2 at x2y2 and z2 position. Since the base_link to world joint in the urdf ur5_robot.urdf.xacro is 0.0 0.0 0.0 therefore, when I run rosrun rviz rviz I see that both the base_link of the two robots are at the same origin (0,0,0) even though in gazebo they are at different positions because of the arg init_pose. My question is whether it is advisable to have multiple robots with a base link set at the origin so that it can increase the scalability to real-world applications? Or should I set the robots base_links at different positions in the urdf itself (i.e. hard-code the exact position of the base_link joint of each robot in the urdf itself) which option is better? Or is there any other better solution?

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answered 2019-10-08 03:53:03 -0600

gvdhoorn gravatar image

When working with two robots (UR5) is it advisable to keep the base_link frame of each robot at the origin?

No. There is no need for this, in general or with the UR5 models (from ros-industrial/universal_robot that is).

There is a world frame in the ur5_robot.urdf.xacro file, which should actually not be there. See here.

This is also a known issue with these .xacros: ros-industrial/universal_robot#284.

I'd recommend to read the comments on that PR and use a custom top-level .xacro which does not include that world frame for composite scenes (ie: scenes consisting of multiple robots, spawned individually).

See also #q334644.

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Okay I followed that page and incorporated the changes in the urdf and also in the virtual joint but now the base of the robots are not fixed to the ground it just keeps moving

mkb_10062949 gravatar image mkb_10062949  ( 2019-10-08 04:15:20 -0600 )edit

For Gazebo, you'll still have to attach the robots to its world link. What the linked PR is meant to fix is that not every robot should include a world link in its base .xacro macro.

gvdhoorn gravatar image gvdhoorn  ( 2019-10-08 04:50:26 -0600 )edit

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Asked: 2019-10-07 17:35:59 -0600

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Last updated: Oct 08 '19