Hello, I’m trying to define a reinforcement learning task with our own robot. The purpose is that I try to add my robot to the stage and wish to get observations and send action to the robot. So in the set_up_scene class, I try to load my robot and add it to the stage， the code is as follow:
```
usd_path = “D:/isaac/ku/isaac_sim-2022.2.1/new/hiro_hand_rev6.usd”
create_prim(prim_path=“/World/hirohand_”, prim_type=“Xform”)
add_reference_to_stage(usd_path, prim_path=“/World/hirohand_”)
self.hiro_hand = scene.add(Robot(“/World/hirohand_”))
then the error occurs as:
2023-05-14 07:00:54 [102,345,300ms] [Warning] [omni.isaac.dynamic_control.plugin] Failed to find articulation at ‘/World/hirohand_’
2023-05-14 07:00:54 [102,345,300ms] [Error] [omni.isaac.dynamic_control.plugin] DcGetArticulationRootBody: Invalid or expired articulation handle
2023-05-14 07:00:54 [102,345,300ms] [Warning] [omni.physx.tensors.plugin] Failed to find articulation at ‘/World/hirohand_’
2023-05-14 07:00:54 [102,345,300ms] [Error] [omni.physx.tensors.plugin] Pattern ‘/World/hirohand_’ did not match any articulations
2023-05-14 07:00:54 [102,345,300ms] [Error] [asyncio] Task exception was never retrieved
future: <Task finished coro=<BaseSampleExtension._on_load_world.._on_load_world_async() done, defined at d:\isaac\ku\isaac_sim-2022.2.1\exts\omni.isaac.examples\omni\isaac\examples\base_sample\base_sample_extension.py:150> exception=AttributeError(“‘NoneType’ object has no attribute ‘is_homogeneous’”)>
Traceback (most recent call last):
File “d:\isaac\ku\isaac_sim-2022.2.1\exts\omni.isaac.examples\omni\isaac\examples\base_sample\base_sample_extension.py”, line 151, in _on_load_world_async
await self._sample.load_world_async()
File “d:\isaac\ku\isaac_sim-2022.2.1\exts\omni.isaac.examples\omni\isaac\examples\base_sample\base_sample.py”, line 47, in load_world_async
await self._world.reset_async()
File “d:\isaac\ku\isaac_sim-2022.2.1\exts\omni.isaac.core\omni\isaac\core\world\world.py”, line 314, in reset_async
self._scene._finalize(self.physics_sim_view)
File “d:\isaac\ku\isaac_sim-2022.2.1\exts\omni.isaac.core\omni\isaac\core\scenes\scene.py”, line 292, in _finalize
robot.initialize(physics_sim_view)
File “d:\isaac\ku\isaac_sim-2022.2.1\exts\omni.isaac.core\omni\isaac\core\articulations\articulation.py”, line 163, in initialize
self._articulation_view.initialize(physics_sim_view=physics_sim_view)
File “d:\isaac\ku\isaac_sim-2022.2.1\exts\omni.isaac.core\omni\isaac\core\articulations\articulation_view.py”, line 201, in initialize
assert self._physics_view.is_homogeneous
File “d:\isaac\ku\isaac_sim-2022.2.1\kit\extsphysics\omni.physics.tensors-104.2.4-5.1\omni\physics\tensors\impl\api.py”, line 156, in is_homogeneous
return self._backend.is_homogeneous
AttributeError: ‘NoneType’ object has no attribute ‘is_homogeneous’
Thanks very much for your answer!