How do I fix it?

[1878720579]

from omni.isaac.kit import SimulationApp

simulation_app = SimulationApp({“headless”: False})
import omni.isaac.core.utils.stage as stage_utils
from omni.isaac.core.utils.nucleus import get_assets_root_path
from omni.isaac.core import World
from omni.isaac.core.utils.types import ArticulationAction
from omni.isaac.core.articulations.articulation import Articulation

my_world = World(stage_units_in_meters=1.0)
my_world.scene.add_default_ground_plane()
usd_path = “/home/user/Downloads/assets/robot/shadow_hand_description/xarm_shadow/xarm_shadow.usd”
prim_path=“/xarm_shadow”
stage_utils.add_reference_to_stage(usd_path=usd_path, prim_path=prim_path)
xarm_shadow = Articulation(prim_path=prim_path,name = “xarm_shadow”)
xarm_shadow = my_world.scene.add(xarm_shadow)
my_world.reset()

i = 0
while simulation_app.is_running():
my_world.step(render=True)
if my_world.is_playing():
i += 1
simulation_app.close()

Traceback (most recent call last):
File “/home/user/.local/share/ov/pkg/isaac_sim-2023.1.0-hotfix.1/xarm_shadow/xarm_shadow.py”, line 19, in
my_world.reset()
File “/home/user/.local/share/ov/pkg/isaac_sim-2023.1.0-hotfix.1/exts/omni.isaac.core/omni/isaac/core/world/world.py”, line 283, in reset
self._scene._finalize(self.physics_sim_view)
File “/home/user/.local/share/ov/pkg/isaac_sim-2023.1.0-hotfix.1/exts/omni.isaac.core/omni/isaac/core/scenes/scene.py”, line 318, in _finalize
articulated_system.initialize(physics_sim_view)
File “/home/user/.local/share/ov/pkg/isaac_sim-2023.1.0-hotfix.1/exts/omni.isaac.core/omni/isaac/core/articulations/articulation.py”, line 164, in initialize
self._articulation_view.initialize(physics_sim_view=physics_sim_view)
File “/home/user/.local/share/ov/pkg/isaac_sim-2023.1.0-hotfix.1/exts/omni.isaac.core/omni/isaac/core/articulations/articulation_view.py”, line 204, in initialize
assert self._physics_view.is_homogeneous
File “/home/user/.local/share/ov/pkg/isaac_sim-2023.1.0-hotfix.1/extsPhysics/omni.physics.tensors-105.1.10-5.1/omni/physics/tensors/impl/api.py”, line 167, in is_homogeneous
return self._backend.is_homogeneous
AttributeError: ‘NoneType’ object has no attribute ‘is_homogeneous’

How do I fix it? And I follow the tutorial"import URDF" and encounter the issue.

[1878720579]

How do I make the “xarm7” as a “articulation”?

[1878720579]

Can you help me solve this problem?

[rthaker]

Hi @1878720579 - Here’s the snippet of how to add articulation

Here’s the doc link: 5.5. Rigging Robots — Omniverse IsaacSim latest documentation

[1878720579]

I don’t think that can solve my problem. The importer carry over joint information.

I use the "xarm_shadow.urdf"URDF files as follows:
shadow_hand_description.zip (7.0 MB)
I follow the turtorial “import urdf” and transform it to the USD.

from omni.isaac.kit import SimulationApp
simulation_app = SimulationApp({“headless”: False})
import omni.isaac.core.utils.stage as stage_utils
from omni.isaac.core.utils.nucleus import get_assets_root_path
from omni.isaac.core import World
from omni.isaac.core.utils.types import ArticulationAction
from omni.isaac.core.articulations.articulation import Articulation

my_world = World(stage_units_in_meters=1.0)
usd_path = “/home/user/Downloads/assets/robot/shadow_hand_description/xarm_shadow/xarm_shadow.usd”
prim_path = “/xarm_shadow”
stage_utils.add_reference_to_stage(usd_path=usd_path,prim_path=prim_path)
xarm_shadow = Articulation(prim_path=“/xarm_shadow/link_base”,name = “xarm_shadow”)
xarm_shadow = my_world.scene.add(xarm_shadow)
my_world.reset()
print(xarm_shadow.num_dof)

i = 0
while simulation_app.is_running():
my_world.step(render=True)
if my_world.is_playing():
i += 1

simulation_app.close()

I found when the prim path is “/xarm_shadow/link_base”, the “Articulation” is work. I don’t understamd. Why?

[rgasoto]

@1878720579

prim_path=“/xarm_shadow”

your prim path here needs to point to the articulation root - When you change it to the path as listed below you selected the prim that contains the ARticulation Root API, and that’s why making that change makes it work

@1878720579

xarm_shadow = Articulation(prim_path=“/xarm_shadow/link_base”,name = “xarm_shadow”)

[rodineye]

if you use 2022.2.1 urdf importer, the articulation root path will be “/xarm_shadow”, if you use 2023.1.1 urdf importer, the articulation root path will be “/xarm_shadow/link_base”