Control customized robot via Articulation Inspector after URDF importing

Hi, guys.
I imported 2 robots via URDF importer successfully.
However, one of them can be inspected by the Articulation Inspector but cannot be driven while the other cannot be inspected Even.

Is there any way to solve the issue or documents I can follow?

thk u.

Here is the msgs showed in the terminal.

2023-09-07 11:37:13 [1,252,267ms] [Error] [omni.ui.python] TypeError: ‘NoneType’ object is not subscriptable

/home/walker2/.local/share/ov/pkg/isaac_sim-2022.2.1/exts/omni.isaac.articulation_inspector/omni/isaac/articulation_inspector/ get_articulation_values
/home/walker2/.local/share/ov/pkg/isaac_sim-2022.2.1/exts/omni.isaac.articulation_inspector/omni/isaac/articulation_inspector/ _refresh_ui
/home/walker2/.local/share/ov/pkg/isaac_sim-2022.2.1/exts/omni.isaac.articulation_inspector/omni/isaac/articulation_inspector/ _on_selection
/home/walker2/.local/share/ov/pkg/isaac_sim-2022.2.1/exts/omni.isaac.articulation_inspector/omni/isaac/articulation_inspector/ _on_combobox_selection
/home/walker2/.local/share/ov/pkg/isaac_sim-2022.2.1/exts/omni.isaac.articulation_inspector/omni/isaac/articulation_inspector/ set_item_value_model
/home/walker2/.local/share/ov/pkg/isaac_sim-2022.2.1/exts/omni.isaac.articulation_inspector/omni/isaac/articulation_inspector/ _refresh_selection_combobox
/home/walker2/.local/share/ov/pkg/isaac_sim-2022.2.1/exts/omni.isaac.articulation_inspector/omni/isaac/articulation_inspector/ _on_stage_event

I found its the problem of joint type floating in my URDF file.
But whats the corresponding one in Isaac Sim ?

Hi @ShawnZhou997 - In Isaac Sim, the corresponding joint type to the “floating” joint type in URDF is the “Free” joint type. A “Free” joint in Isaac Sim allows for 6 degrees of freedom, similar to a “floating” joint in URDF. This means the joint can move in any direction and rotate about any axis.

Thank you, @rthaker.
There is no joint type named free in URDF files though.
I solved it by add the D6 joint manually, but it could be a catastrophe in a huge URDF with lots of floating ones.
If possible, hope it can be fixed soon.