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Robot is levitating in Gazebo

asked 2018-12-26 20:46:16 -0500

lukewd gravatar image

ROS Melodic. Latest code is here

Running: roslaunch scara_52900 all.launch

results in the robot appearing in the air instead of on the ground. I'm sure this is something really simple but have not been able to figure it out yet.

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I noticed if I adjust the Z to be negative in the fixed joint, like this

  <joint name="fixed" type="fixed">
<parent link="world"/>
<child link="base_link"/>
<origin xyz="0 0 -.9"/>


the robot moves lower to the ground. But I don't understand why this is necessary.

lukewd gravatar imagelukewd ( 2018-12-26 21:25:16 -0500 )edit

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answered 2018-12-26 22:38:08 -0500

This is a fixed joint with the world (think the global coordinate frame), there for that part (your base_link) will always remain at that origin (0,0,-0.9) fixed in all situations. If its floating, that means the origin of your mesh is either incorrect, that magic number as tuned is incorrect, or it was the intention of the provider to not make contact with the ground.

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Thanks for your insight! I am actually the one who wrote that code (based on tutorials and trying to learn this system). It's working as I expected except the floating robot issue, that is why I'm lost.

If I put the negative Z down low enough to where it gets close to the ground, the robot wiggles.

lukewd gravatar imagelukewd ( 2018-12-27 09:08:48 -0500 )edit

I’ve recommend finding the correct center of your base link mesh then and making that offset appropriate for the ground

stevemacenski gravatar imagestevemacenski ( 2018-12-27 15:01:19 -0500 )edit

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Asked: 2018-12-26 20:46:16 -0500

Seen: 61 times

Last updated: Dec 26 '18