Stewart Platform: how can i connect multiple joints to the same child link but different parent links ?!

I want to simulate and control the famous stewart platform in ROS and gazebo. I started with modeling the system in Solidworks and when i wanted to export the assembly to a URDF description i ran into a problem that the URDF description doesn't allow multiple joints to have the same child with different parents. Thus when i try to connect the different arms to the platform i end up with an error stating that there are multiple links with the same name. My question is: Is there any work around for this? I have searched for the problem and i found that SDF description supports closed loop joints, is this a solution to my problem ?! Here's link to a picture of my model in Solidworks to help you visualize the system:

Stewart Platform

Thanks in Advance

Asked by Mahmoud Abdul Galil on 2015-08-19 02:49:02 UTC

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Answers

You currently can NOT create links with multiple parents in URDF.

Asked by David Lu on 2015-08-19 16:39:30 UTC

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What about SDF ?

Asked by Mahmoud Abdul Galil on 2015-08-20 03:21:56 UTC

I was able to get this working using SDF and a simple plugin to make the Gazebo joints visible to ROS. It's still a work in progress, but here's the repository!

https://github.com/daniel-s-ingram/stewart_ros

Asked by daniel-s-ingram on 2017-12-20 16:50:46 UTC

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I think that my problem is similar to this one. I want to simulate a robot in Gazebo. This robot contains a kind of delta machine. It consists in : • three cylinders, • three conrods, linked with the pistons rods (tige_verin) on one side and with one plate (plate_camera_support) on the other side, • a plate (plate_camera_support). My objective is to control the altitude and the orientation of the plate (plate_camera_support) around the X axis and Y axis.

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Here is the tf_tree of my URDF model. But unfortunately, I’m not able to introduce the last 2 joints of the model (in red on the picture below). Is the last answer still relevant? Is there a trick to face this « problem » ?

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PS: I’m working on Ubuntu 16.04 LTS and ROS Kinetic. Thanks in Advance

Asked by Abdel on 2019-01-19 19:49:32 UTC