Cannot generate robot description: Cannot select robot's links


I am trying to generate a yaml file for using motion generator tool. And I am using Lula Robot Descriptor Editor for that purpose. The manipulator I am using is Panda from the Isaac Examples. And I am using Ubuntu 22.

As shown in the picture, At Select Panel > Select Articulation, the selection is /panda/panda_link0. The option is different from the tutorials.

In the tutorials you can select the links in Select Link and only robot name can be selected in Select Articulation, (e.g: Select Articulation: /panda; Select Link: (panda_link0)).

But for my case, Select Articulation: /panda/panda_link0; Select Link: {nothing shown}.

Thank you for any support.

@hslktestmail i am just a passerby, see if the clip below help walk you through the process:


@Simplychenable Thank you for your help. I am able to select the Panda’s links as shown in your videos.

But come to think of it, I cannot generate a yaml file using Lula Robot Descriptor Editor after following the 5.1 tutorials. And I also copied and pasted the Python script to HelloWorld example as well.

Link: 5.1. Import URDF — Omniverse IsaacSim latest documentation

As for the NVIDIA assets, the stage panel is different form the stage panel that I will have if I follow tutorial 5.1
[NVIDIA assets]

[Result from tutorial 5.1]

Thank you again.

that seems to be correct, the snippet you copy/pasted from 5.1.4 to does affect the asset hiearchy a bit, so it won’t be a 1:1 match to the source asset (franka.usd).

regarding generating a yaml file, i would probably recommend checking out section 6.1 of the doc and see if you have everything in order prior to exporting the robot description file (section :

i think the tutorial from 5.1.4 was only to show how you can import URDF via python and not sure if the edited file is meant to be used to generate the yaml, but that’s just my interpretation.

OK, I partially solve it.

The reason why Select Articulation shows /panda/panda_link0 is that panda_link0 is the Articulation Root. Now we need to fix that. Read the instruction in Tut # 2.4: 2.4. Assemble a Simple Robot — Omniverse IsaacSim latest documentation

So we need to go to Property > Physics delete the wrong Articulation Root by clicking the X mark at the right side and the add the Articulation Root in /panda not /panda/panda_link0.

Maybe they can consider put this into the tutorial for person who never read the tuts from a to z like me.

the tutorial being chopped up perhaps have made things less contiguous to follow along, as well. would be wonderful if there’s video per section from start to finish with voiceover to keep the continuity (in addition to the subsection as how they have it now for detailed description).

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@hslktestmail It looks like you have noticed a bug arising from changes in the URDF importer where the base path of the Articulation is no longer considered to be the Articulation root, violating some assumptions made in the robot description editor. We are aware of this problem, and it will be fixed in the next release. The best fix for now is indeed to change the Articulation root of the asset back to the base path (this can be done with a copy of your USD file so that its not a permanent change and it will not affect the resulting robot description file)

OK, That is a good news

What I am doing are:

  1. Obtain a urdf file from a ROS robot; so I have the meshes in stl format and a urdf file
  2. Import the robot to Isaac sim
  3. Change the Articulation root
  4. Follow Avi’s tutorial about extension and reproduce the result

So in my case, the usd file is not that important.

Anyway, I will leave this topic here. I hope you guy can come up with a solution.

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