Isaac version
6.0.0
5.1.0
5.0.0
4.5.0
4.2.0
4.1.0
4.0.0
4.5.0
2023.1.1
2023.1.0-hotfix.1
Other (please specify):
Operating System
Ubuntu 24.04
Ubuntu 22.04
Ubuntu 20.04
Windows 11
Windows 10
Other (please specify):
GPU Information
- Model: RTX 4090
- Driver Version: 580.126.09
- CUDA Version: 13.0
Topic Description
Differential controller omnigraph with WASD keyboard input stop working after entering Play for a second time.
Detailed Description
When loading a .usd scene with a robot containing an Omnigraph with differential controller configured to read keyboard WASD keys as input, the robot will move around only the first time we press play after loading the scene on isaacsim, subsequent attempts after pausing and playing again will do nothing.
As a reference, I have added a simple robot created by following the instructions on the tutorial: Getting Started: Simulating Your First Robot in Isaac Sim . So I have uploaded the .usda containing the reproducible scene as a GitHub Gist.
While the GitHub gist shared is based on this tutorial, I have also confirmed that the same error happens on a different robot containing a similar omnigraph that I am not able to share at the moment.
Steps to Reproduce
- Execute ./isaac-sim.sh to open isaac sim 5.1.0
- From isaac sim editor, Open FirstTest.usda
- Press play button
- Use the WASD keys to move robot around, robot moves around.
- Press stop button
- Press play button again
- Use WASD to try to move robot around, robot does not move around.
- Open FirstTest.usda again.
- Press play button again.
- Use WASD to move robot around, robot moves around.
- Press stop button again
- Press play button again.
- Use WASD to try to move robot around, robot does not move around.
Error Messages
The following warning log shows up the second time we press play, but not during the first. Believe it may be related to the cause of the issue.
2026-03-06 04:32:32 [Warning] [omni.graph.core.plugin] /Graphs/differential_controller/ArticulationController: [/Graphs/differential_controller] OmniGraph Warning: ‘NoneType’ object has no attribute ‘apply_action’.
The following error messages show up when pausing the simulation:
2026-03-06 05:03:15 [Error] [omni.kit.app._impl] [py stderr]: Traceback (most recent call last):
2026-03-06 05:03:15 [Error] [omni.kit.app._impl] [py stderr]: File “/home/username/isaacsim/exts/isaacsim.core.nodes/isaacsim/core/nodes/impl/base_reset_node.py”, line 35, in on_stop_play
2026-03-06 05:03:15 [Error] [omni.kit.app._impl] [py stderr]: self.custom_reset()
2026-03-06 05:03:15 [Error] [omni.kit.app._impl] [py stderr]: File “/home/username/isaacsim/exts/isaacsim.core.nodes/isaacsim/core/nodes/ogn/python/nodes/OgnIsaacArticulationController.py”, line 71, in custom_reset
2026-03-06 05:03:15 [Error] [omni.kit.app._impl] [py stderr]: self.node.get_attribute(“inputs:positionCommand”).set(np.empty(shape=(0, 0), dtype=np.double))
2026-03-06 05:03:15 [Error] [omni.kit.app._impl] [py stderr]: TypeError: Unable to write from unknown dtype, kind=f, size=0
2026-03-06 05:03:15 [Error] [omni.kit.app._impl] [py stderr]: Traceback (most recent call last):
2026-03-06 05:03:15 [Error] [omni.kit.app._impl] [py stderr]: File “/home/username/isaacsim/exts/isaacsim.core.nodes/isaacsim/core/nodes/impl/base_reset_node.py”, line 35, in on_stop_play
2026-03-06 05:03:15 [Error] [omni.kit.app._impl] [py stderr]: self.custom_reset()
2026-03-06 05:03:15 [Error] [omni.kit.app._impl] [py stderr]: File “/home/username/isaacsim/exts/isaacsim.core.nodes/isaacsim/core/nodes/ogn/python/nodes/OgnIsaacArticulationController.py”, line 71, in custom_reset
2026-03-06 05:03:15 [Error] [omni.kit.app._impl] [py stderr]: self.node.get_attribute(“inputs:positionCommand”).set(np.empty(shape=(0, 0), dtype=np.double))
2026-03-06 05:03:15 [Error] [omni.kit.app._impl] [py stderr]: TypeError: Unable to write from unknown dtype, kind=f, size=0
What I’ve Tried
- Tried adding some Draw Screen Space Text nodes to debug the values of data on the graph. I have found that the Keyboard input is correctly setting the Desired Angular Velocity and Desired Linear Velocity of the Differential Controller. So I am guessing the error happens downstream from it, maybe at the Articulation Controller
Additional Context
I know the recommendation was to create a GitHub issue for these sort of isaac sim topics, and I did but it didn’t get any engagement for a few days, so I thought I could try posting here as well.