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Hello,

I am using ROS indigo in combination with the included Gazebo version. I am trying to control a robot arm in combination with ROS control in Gazebo. The robot arm I am controlling is the Kinova Mico arm. I am using the URDF model from the WPI Jaco package, however I needed to modify it slightly to be able to have the robot use the correct inertias for each link.

When I spawn the arm in a paused physics simulation, the arm spawns with all the joints in the correct position. However, when the simulation is unpaused, the arm collapses and all links jump to the origin of the world. I have a figure of this, however cannot upload it due to the lack of points. For the same reason, I cannot upload the URDF model.

I found a possible solution that said that the inertias are too low. The inertias for the different links are however in the order of 10e-4 so should be fine. At least, I believe the URDF model asks for inertia in kg*m2.

If any of you have experience with this or know a possible solution, that would help be out greatly. Thanks.


Originally posted by Laurens Verhulst on ROS Answers with karma: 167 on 2016-05-19

Post score: 0

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I think my answer here covers the most common knobs you can try tweaking. If you're spawning the robot without controllers, the combination of inertial parameters of the robot and physics engine parameters appear to be to blame.


Originally posted by Stefan Kohlbrecher with karma: 24361 on 2016-05-20

This answer was ACCEPTED on the original site

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Original comments

Comment by Laurens Verhulst on 2016-05-20:
Thanks for your reply! I will try this out and post the results here.

Comment by Laurens Verhulst on 2016-05-23:
I have located the issue, it is because 2 of the 6 links are weirdly shaped. This causes the simulation to be instable. I am still trying to fix this issue.

Comment by Laurens Verhulst on 2016-05-23:
Ok, I fixed the issue, it was indeed a combination of inertia and mass of two specific links.

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