Fails to initialize contact reporters for Franka Panda

[HarrisonDeurwaarder]

Isaac fails to initialize contact reporters for panda hand prim. Contact sensor has been placed in the same prim as the issue is occurring. Any help would be appreciated!
scene_cfg.py

[RandomOakForest]

It seems the main missing piece is that activate_contact_sensors=True must be set on the spawn cfg itself (not only on the replaced ArticulationCfg attribute), and you should double‑check that panda_hand is actually the rigid body link name in your FRANKA_PANDA_HIGH_PD_CFG USD.¹²³⁴

1. Fix how activate_contact_sensors is applied

Right now you have:

robot: ArticulationCfg = FRANKA_PANDA_HIGH_PD_CFG.replace(
    prim_path='{ENV_REGEX_NS}/Robot',
    init_state=FRANKA_PANDA_HIGH_PD_CFG.init_state.replace(
        pos=(0.0, 0.0, thickness),
    ),
)
robot.spawn.activate_contact_sensors = True

In Isaac Lab, the recommended way is to set activate_contact_sensors as part of the spawn replacement, so that it is baked into the cfg that is passed to the spawner. For example:⁴¹

robot: ArticulationCfg = FRANKA_PANDA_HIGH_PD_CFG.replace(
    prim_path="{ENV_REGEX_NS}/Robot",
    spawn=FRANKA_PANDA_HIGH_PD_CFG.spawn.replace(
        activate_contact_sensors=True,
    ),
    init_state=FRANKA_PANDA_HIGH_PD_CFG.init_state.replace(
        pos=(0.0, 0.0, thickness),
    ),
)

Then remove the separate line robot.spawn.activate_contact_sensors = True. This pattern is exactly how the docs and GitHub issues show enabling contact reporters on all rigid bodies of an asset.²³¹⁴

If the flag is not set in spawn at construction time, the internal schemas.activate_contact_sensors call may never run for the Panda, and the contact reporter API will not be applied to panda_hand, causing the “could not find any bodies with contact reporter API” error.⁵⁶¹

2. Confirm the hand link name and prim path

Your sensor cfg:

contact_forces: ContactSensorCfg = ContactSensorCfg(
    prim_path='{ENV_REGEX_NS}/Robot/panda_hand',
    update_period=0.0,
    history_length=...,
    debug_vis=True,
)

Two things to verify in USD / Stage tree for FRANKA_PANDA_HIGH_PD_CFG:⁷³⁸⁴

• The actual hand link prim is really called panda_hand and sits under …/Robot/panda_hand.
  • In many Franka assets, the hand link is indeed panda_hand, but if your high‑PD cfg uses a slightly different USD (e.g., different namespace or instanceable variant), the link name could differ or be nested (.../Robot/panda/panda_hand, etc.).⁹¹⁰
• That prim is a rigid body with contact reporter API. After fixing activate_contact_sensors, check in Isaac Sim that /World/envs/env_0/Robot/panda_hand has PhysxRigidBodyAPI, collision APIs, and PhysxContactReportAPI.¹¹⁴

If the link name is different, update the cfg accordingly, e.g.:

contact_forces = ContactSensorCfg(
    prim_path="{ENV_REGEX_NS}/Robot/<actual_hand_link_name>",
    update_period=0.0,
    history_length=...,
    debug_vis=True,
)

The prim_path in ContactSensorCfg is a regex‑style expression; {ENV_REGEX_NS}/Robot/panda_hand expands to /World/envs/env_.*/Robot/panda_hand. If that pattern matches zero rigid bodies with contact reporter API, initialization fails.⁶³²

3. Optional: restrict contacts via filter

You do not need a filter for initialization, but if you only care about contacts with specific objects, you can also set filter_prim_paths_expr, as the docs show:³⁶

contact_forces = ContactSensorCfg(
    prim_path="{ENV_REGEX_NS}/Robot/panda_hand",
    update_period=0.0,
    history_length=...,
    debug_vis=True,
    # e.g., only contacts with the walls
    # filter_prim_paths_expr=["{ENV_REGEX_NS}/wall.*"],
)

This does not affect whether the reporter initializes, just which bodies the net force is summed over.³

If you make the spawn=...replace(activate_contact_sensors=True) change and confirm the exact prim path for the hand, the contact reporter should initialize cleanly for panda_hand.⁸¹³⁴

Footnotes

1. https://github.com/isaac-sim/IsaacLab/issues/2985 ↩ ↩² ↩³ ↩⁴ ↩⁵

2. https://isaac-sim.github.io/IsaacLab/main/source/api/lab/isaaclab.sensors.html ↩ ↩² ↩³

3. https://isaac-sim.github.io/IsaacLab/main/source/overview/core-concepts/sensors/contact_sensor.html ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

4. https://isaac-sim.github.io/IsaacLab/main/source/tutorials/04_sensors/add_sensors_on_robot.html ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

5. https://github.com/isaac-sim/IsaacLab/issues/2643 ↩

6. https://github.com/isaac-sim/IsaacLab/discussions/2026 ↩ ↩² ↩³

7. https://github.com/isaac-sim/IsaacLab/issues/1945 ↩

8. https://github.com/isaac-sim/IsaacLab/issues/4332 ↩ ↩²

9. https://github.com/isaac-sim/IsaacLab/issues/1052 ↩

10. https://isaac-sim.github.io/IsaacLab/main/source/tutorials/05_controllers/run_osc.html ↩

11. https://docs.isaacsim.omniverse.nvidia.com/5.0.0/sensors/isaacsim_sensors_physics_contact.html ↩