Rename IMU sensor to PVA and add real IMU sensor (#5247)

## Summary

- Renamed the existing IMU sensor (pose + velocity + acceleration) to
**PVA** (`Pva`, `PvaCfg`, `PvaData`, `BasePva`, `BasePvaData`) across
both `isaaclab` and `isaaclab_physx` packages.
- Created a new lightweight **IMU** sensor (`Imu`, `ImuCfg`, `ImuData`,
`BaseImu`, `BaseImuData`) that only provides the two physical quantities
a real inertial measurement unit measures: **angular velocity**
(gyroscope) and **linear acceleration** (accelerometer).
- Updated all consumers: observation functions (`pva_orientation`,
`pva_projected_gravity`, `imu_ang_vel`, `imu_lin_acc`), mock interfaces,
tests, demo scripts, and changelogs.

### Why

The old "IMU" sensor was a misnomer — it provided full pose, velocity,
and acceleration data, far more than a real IMU measures. The rename
clarifies the API:
- **PVA** = full state sensor (pose, velocity, acceleration) for
simulation use
- **IMU** = realistic sensor model (angular velocity + linear
acceleration only)

### What changed

| Area | Change |
|------|--------|
| `isaaclab/sensors/imu/` → `isaaclab/sensors/pva/` | Renamed all
classes, factory, config |
| `isaaclab_physx/sensors/imu/` → `isaaclab_physx/sensors/pva/` |
Renamed PhysX impl, kernels |
| New `isaaclab/sensors/imu/` | Lightweight IMU base classes |
| New `isaaclab_physx/sensors/imu/` | PhysX IMU impl with simplified
Warp kernels |
| `observations.py` | `imu_orientation`→`pva_orientation`,
`imu_projected_gravity`→`pva_projected_gravity` |
| Mock interfaces | Split `MockImu` (2 fields) / `MockPva` (8 fields) |
| Tests | `test_pva.py` (8 tests), `test_imu.py` (8 tests), mock tests
updated |
| Demos | `pva_sensor.py` + `imu_sensor.py` |

## Test plan

- [x] `test_pva.py` — 8 tests pass (constant velocity, constant
acceleration, pendulum, indirect attachment, offset, validity, env_ids,
print)
- [x] `test_imu.py` — 8 tests pass (same test suite adapted for IMU-only
fields)
- [x] `test_mock_sensors.py` — 29 tests pass (IMU + PVA + contact +
frame transformer mocks)
- [x] `test_mock_data_properties.py` — 254 tests pass
- [x] Pre-commit hooks all pass

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: AntoineRichard

docs/source/migration/migrating_to_isaaclab_3-0.rst

@@ -113,11 +113,19 @@ The following sensor classes also remain in the ``isaaclab`` package with unchan
 
 - :class:`~isaaclab.sensors.ContactSensor`, :class:`~isaaclab.sensors.ContactSensorCfg`, :class:`~isaaclab.sensors.ContactSensorData`
 - :class:`~isaaclab.sensors.Imu`, :class:`~isaaclab.sensors.ImuCfg`, :class:`~isaaclab.sensors.ImuData`
+- :class:`~isaaclab.sensors.Pva`, :class:`~isaaclab.sensors.PvaCfg`, :class:`~isaaclab.sensors.PvaData`
 - :class:`~isaaclab.sensors.FrameTransformer`, :class:`~isaaclab.sensors.FrameTransformerCfg`, :class:`~isaaclab.sensors.FrameTransformerData`
 
 These sensor classes now use factory patterns that automatically instantiate the appropriate backend
 implementation (PhysX by default), maintaining full backward compatibility.
 
+.. note::
+
+   The ``Imu`` sensor in Isaac Lab 3.0 is **not** the same as the ``Imu`` sensor in 2.x.
+   The old ``Imu`` (full state sensor) has been renamed to :class:`~isaaclab.sensors.Pva`.
+   The new :class:`~isaaclab.sensors.Imu` is a lightweight sensor that only provides angular velocity
+   and linear acceleration. See :ref:`imu-to-pva-migration` below for details.
+
 If you need to import the PhysX sensor implementations directly (e.g., for type hints or subclassing),
 you can import from ``isaaclab_physx.sensors``:
 
@@ -126,6 +134,7 @@ you can import from ``isaaclab_physx.sensors``:
    # Direct PhysX implementation imports
    from isaaclab_physx.sensors import ContactSensor, ContactSensorData
    from isaaclab_physx.sensors import Imu, ImuData
+   from isaaclab_physx.sensors import Pva, PvaData
    from isaaclab_physx.sensors import FrameTransformer, FrameTransformerData
 
 
@@ -156,11 +165,81 @@ If you need to import Newton implementations directly (e.g., for type hints or s
    from isaaclab_newton.assets import RigidObject as NewtonRigidObject
 
 
+.. _imu-to-pva-migration:
+
+IMU Sensor Renamed to PVA; New Lightweight IMU Sensor
+-----------------------------------------------------
+
+The old ``Imu`` sensor has been renamed to **PVA** (Pose Velocity Acceleration) because it provided
+full pose, velocity, and acceleration data — far more than a real inertial measurement unit measures.
+A new lightweight **IMU** sensor has been introduced that only provides the two physical quantities
+a real IMU measures: angular velocity (gyroscope) and linear acceleration (accelerometer).
+
+If you were using the old ``Imu`` sensor, you need to decide which new sensor to use:
+
+- Use :class:`~isaaclab.sensors.Pva` / :class:`~isaaclab.sensors.PvaCfg` if you need full state
+  data (pose, linear velocity, angular velocity, linear and angular acceleration, projected gravity).
+- Use :class:`~isaaclab.sensors.Imu` / :class:`~isaaclab.sensors.ImuCfg` if you only need angular
+  velocity and linear acceleration (as a real IMU provides).
+
+**Import changes:**
+
+.. code-block:: python
+
+   # Before (Isaac Lab 2.x) — the old IMU provided full state
+   from isaaclab.sensors import Imu, ImuCfg, ImuData
+
+   # After (Isaac Lab 3.x) — use PVA for the same full-state sensor
+   from isaaclab.sensors import Pva, PvaCfg, PvaData
+
+   # Or use the new lightweight IMU for angular velocity + linear acceleration only
+   from isaaclab.sensors import Imu, ImuCfg, ImuData
+
+**Configuration changes:**
+
+The ``gravity_bias`` configuration parameter has been removed from both sensors:
+
+- **PVA** reports raw kinematic acceleration (no gravity contribution), as the acceleration
+  is derived from finite differencing of velocities which do not include gravity.
+- **IMU** unconditionally includes gravity in its accelerometer readings, matching the behavior
+  of a real accelerometer. The gravity vector is automatically queried from the simulation.
+
+.. code-block:: python
+
+   # Before (Isaac Lab 2.x)
+   imu_cfg = ImuCfg(
+       prim_path="{ENV_REGEX_NS}/Robot/base",
+       gravity_bias=(0.0, 0.0, 9.81),  # had to be configured manually
+   )
+
+   # After (Isaac Lab 3.x) — PVA (no gravity in acceleration)
+   pva_cfg = PvaCfg(prim_path="{ENV_REGEX_NS}/Robot/base")
+
+   # After (Isaac Lab 3.x) — IMU (gravity always included automatically)
+   imu_cfg = ImuCfg(prim_path="{ENV_REGEX_NS}/Robot/base")
+
+**Observation function changes:**
+
+.. code-block:: python
+
+   # Before (Isaac Lab 2.x)
+   from isaaclab.envs.mdp import imu_orientation, imu_projected_gravity
+
+   # After (Isaac Lab 3.x)
+   from isaaclab.envs.mdp import pva_orientation, pva_projected_gravity
+
+**Data property changes:**
+
+The new ``ImuData`` only provides ``ang_vel_b`` and ``lin_acc_b``. If you were accessing other
+properties (``pos_w``, ``quat_w``, ``lin_vel_b``, ``ang_acc_b``, ``projected_gravity_b``), switch
+to :class:`~isaaclab.sensors.PvaData` which provides all of them.
+
+
 Sensor Pose Properties Deprecation
 ----------------------------------
 
 The ``pose_w``, ``pos_w``, and ``quat_w`` properties on :class:`~isaaclab.sensors.ContactSensorData`
-and :class:`~isaaclab.sensors.ImuData` are deprecated and will be removed in a future release.
+are deprecated and will be removed in a future release.
 
 If you need to track sensor poses in world frame, please use a dedicated sensor such as
 :class:`~isaaclab.sensors.FrameTransformer` instead.
@@ -787,7 +866,7 @@ All ``.data.*`` properties on asset and sensor classes now return ``wp.array`` i
 :class:`~isaaclab.assets.RigidObject`, :class:`~isaaclab.assets.RigidObjectCollection`,
 :class:`~isaaclab_physx.assets.DeformableObject`) and all sensor classes
 (:class:`~isaaclab_physx.sensors.ContactSensor`, :class:`~isaaclab_physx.sensors.Imu`,
-:class:`~isaaclab_physx.sensors.FrameTransformer`).
+:class:`~isaaclab_physx.sensors.Pva`, :class:`~isaaclab_physx.sensors.FrameTransformer`).
 
 To convert back to ``torch.Tensor`` for use with PyTorch operations, wrap the property
 access with ``wp.to_torch()``:
@@ -851,6 +930,8 @@ Common patterns that need updating:
      - ``isaaclab_physx``
    * - :class:`~isaaclab_physx.sensors.Imu`
      - ``isaaclab_physx``
+   * - :class:`~isaaclab_physx.sensors.Pva`
+     - ``isaaclab_physx``
    * - :class:`~isaaclab_physx.sensors.FrameTransformer`
      - ``isaaclab_physx``
 

scripts/demos/sensors/imu_sensor.py

@@ -42,7 +42,7 @@
 
 @configclass
 class ImuSensorSceneCfg(InteractiveSceneCfg):
-    """Design the scene with sensors on the robot."""
+    """Design the scene with IMU sensors on the robot."""
 
     # ground plane
     ground = AssetBaseCfg(prim_path="/World/defaultGroundPlane", spawn=sim_utils.GroundPlaneCfg())
@@ -55,9 +55,9 @@ class ImuSensorSceneCfg(InteractiveSceneCfg):
     # robot
     robot = ANYMAL_C_CFG.replace(prim_path="{ENV_REGEX_NS}/Robot")
 
-    imu_RF = ImuCfg(prim_path="{ENV_REGEX_NS}/Robot/LF_FOOT", debug_vis=True)
+    imu_RF = ImuCfg(prim_path="{ENV_REGEX_NS}/Robot/LF_FOOT")
 
-    imu_LF = ImuCfg(prim_path="{ENV_REGEX_NS}/Robot/RF_FOOT", gravity_bias=(0, 0, 0), debug_vis=True)
+    imu_LF = ImuCfg(prim_path="{ENV_REGEX_NS}/Robot/RF_FOOT")
 
 
 def run_simulator(sim: sim_utils.SimulationContext, scene: InteractiveScene):
@@ -73,9 +73,6 @@ def run_simulator(sim: sim_utils.SimulationContext, scene: InteractiveScene):
             # reset counter
             count = 0
             # reset the scene entities
-            # root state
-            # we offset the root state by the origin since the states are written in simulation world frame
-            # if this is not done, then the robots will be spawned at the (0, 0, 0) of the simulation world
             root_pose = wp.to_torch(scene["robot"].data.default_root_pose).clone()
             root_pose[:, :3] += scene.env_origins
             scene["robot"].write_root_link_pose_to_sim_index(root_pose=root_pose)
@@ -93,11 +90,8 @@ def run_simulator(sim: sim_utils.SimulationContext, scene: InteractiveScene):
             scene.reset()
             print("[INFO]: Resetting robot state...")
         # Apply default actions to the robot
-        # -- generate actions/commands
         targets = wp.to_torch(scene["robot"].data.default_joint_pos)
-        # -- apply action to the robot
         scene["robot"].set_joint_position_target_index(target=targets)
-        # -- write data to sim
         scene.write_data_to_sim()
         # perform step
         sim.step()
@@ -110,16 +104,12 @@ def run_simulator(sim: sim_utils.SimulationContext, scene: InteractiveScene):
         # print information from the sensors
         print("-------------------------------")
         print(scene["imu_LF"])
-        print("Received linear velocity: ", scene["imu_LF"].data.lin_vel_b)
         print("Received angular velocity: ", scene["imu_LF"].data.ang_vel_b)
         print("Received linear acceleration: ", scene["imu_LF"].data.lin_acc_b)
-        print("Received angular acceleration: ", scene["imu_LF"].data.ang_acc_b)
         print("-------------------------------")
         print(scene["imu_RF"])
-        print("Received linear velocity: ", scene["imu_RF"].data.lin_vel_b)
         print("Received angular velocity: ", scene["imu_RF"].data.ang_vel_b)
         print("Received linear acceleration: ", scene["imu_RF"].data.lin_acc_b)
-        print("Received angular acceleration: ", scene["imu_RF"].data.ang_acc_b)
 
 
 def main():

scripts/demos/sensors/pva_sensor.py

@@ -0,0 +1,148 @@
+# Copyright (c) 2022-2026, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
+# All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+"""Launch Isaac Sim Simulator first."""
+
+import argparse
+
+from isaaclab.app import AppLauncher
+
+# add argparse arguments
+parser = argparse.ArgumentParser(description="Example on using the PVA sensor.")
+parser.add_argument("--num_envs", type=int, default=1, help="Number of environments to spawn.")
+# append AppLauncher cli args
+AppLauncher.add_app_launcher_args(parser)
+# demos should open Kit visualizer by default
+parser.set_defaults(visualizer=["kit"])
+# parse the arguments
+args_cli = parser.parse_args()
+
+# launch omniverse app
+app_launcher = AppLauncher(args_cli)
+simulation_app = app_launcher.app
+
+"""Rest everything follows."""
+
+import torch
+import warp as wp
+
+import isaaclab.sim as sim_utils
+from isaaclab.assets import AssetBaseCfg
+from isaaclab.scene import InteractiveScene, InteractiveSceneCfg
+from isaaclab.sensors import PvaCfg
+from isaaclab.utils import configclass
+
+##
+# Pre-defined configs
+##
+from isaaclab_assets.robots.anymal import ANYMAL_C_CFG  # isort: skip
+
+
+@configclass
+class PvaSensorSceneCfg(InteractiveSceneCfg):
+    """Design the scene with sensors on the robot."""
+
+    # ground plane
+    ground = AssetBaseCfg(prim_path="/World/defaultGroundPlane", spawn=sim_utils.GroundPlaneCfg())
+
+    # lights
+    dome_light = AssetBaseCfg(
+        prim_path="/World/Light", spawn=sim_utils.DomeLightCfg(intensity=3000.0, color=(0.75, 0.75, 0.75))
+    )
+
+    # robot
+    robot = ANYMAL_C_CFG.replace(prim_path="{ENV_REGEX_NS}/Robot")
+
+    pva_RF = PvaCfg(prim_path="{ENV_REGEX_NS}/Robot/LF_FOOT", debug_vis=True)
+
+    pva_LF = PvaCfg(prim_path="{ENV_REGEX_NS}/Robot/RF_FOOT", debug_vis=True)
+
+
+def run_simulator(sim: sim_utils.SimulationContext, scene: InteractiveScene):
+    """Run the simulator."""
+    # Define simulation stepping
+    sim_dt = sim.get_physics_dt()
+    sim_time = 0.0
+    count = 0
+
+    # Simulate physics
+    while simulation_app.is_running():
+        if count % 500 == 0:
+            # reset counter
+            count = 0
+            # reset the scene entities
+            # root state
+            # we offset the root state by the origin since the states are written in simulation world frame
+            # if this is not done, then the robots will be spawned at the (0, 0, 0) of the simulation world
+            root_pose = wp.to_torch(scene["robot"].data.default_root_pose).clone()
+            root_pose[:, :3] += scene.env_origins
+            scene["robot"].write_root_link_pose_to_sim_index(root_pose=root_pose)
+            root_vel = wp.to_torch(scene["robot"].data.default_root_vel).clone()
+            scene["robot"].write_root_com_velocity_to_sim_index(root_velocity=root_vel)
+            # set joint positions with some noise
+            joint_pos, joint_vel = (
+                wp.to_torch(scene["robot"].data.default_joint_pos).clone(),
+                wp.to_torch(scene["robot"].data.default_joint_vel).clone(),
+            )
+            joint_pos += torch.rand_like(joint_pos) * 0.1
+            scene["robot"].write_joint_position_to_sim_index(position=joint_pos)
+            scene["robot"].write_joint_velocity_to_sim_index(velocity=joint_vel)
+            # clear internal buffers
+            scene.reset()
+            print("[INFO]: Resetting robot state...")
+        # Apply default actions to the robot
+        # -- generate actions/commands
+        targets = wp.to_torch(scene["robot"].data.default_joint_pos)
+        # -- apply action to the robot
+        scene["robot"].set_joint_position_target_index(target=targets)
+        # -- write data to sim
+        scene.write_data_to_sim()
+        # perform step
+        sim.step()
+        # update sim-time
+        sim_time += sim_dt
+        count += 1
+        # update buffers
+        scene.update(sim_dt)
+
+        # print information from the sensors
+        print("-------------------------------")
+        print(scene["pva_LF"])
+        print("Received linear velocity: ", scene["pva_LF"].data.lin_vel_b)
+        print("Received angular velocity: ", scene["pva_LF"].data.ang_vel_b)
+        print("Received linear acceleration: ", scene["pva_LF"].data.lin_acc_b)
+        print("Received angular acceleration: ", scene["pva_LF"].data.ang_acc_b)
+        print("-------------------------------")
+        print(scene["pva_RF"])
+        print("Received linear velocity: ", scene["pva_RF"].data.lin_vel_b)
+        print("Received angular velocity: ", scene["pva_RF"].data.ang_vel_b)
+        print("Received linear acceleration: ", scene["pva_RF"].data.lin_acc_b)
+        print("Received angular acceleration: ", scene["pva_RF"].data.ang_acc_b)
+
+
+def main():
+    """Main function."""
+
+    # Initialize the simulation context
+    sim_cfg = sim_utils.SimulationCfg(dt=0.005, device=args_cli.device)
+    sim = sim_utils.SimulationContext(sim_cfg)
+    # Set main camera
+    sim.set_camera_view(eye=[3.5, 3.5, 3.5], target=[0.0, 0.0, 0.0])
+    # design scene
+    scene_cfg = PvaSensorSceneCfg(num_envs=args_cli.num_envs, env_spacing=2.0)
+    scene = InteractiveScene(scene_cfg)
+    # Play the simulator
+    sim.reset()
+    # Now we are ready!
+    print("[INFO]: Setup complete...")
+    # Run the simulator
+    run_simulator(sim, scene)
+
+
+if __name__ == "__main__":
+    # run the main function
+    main()
+    # close sim app
+    simulation_app.close()

source/isaaclab/config/extension.toml

@@ -1,7 +1,7 @@
 [package]
 
 # Note: Semantic Versioning is used: https://semver.org/
-version = "4.5.32"
+version = "4.5.33"
 
 # Description
 title = "Isaac Lab framework for Robot Learning"

source/isaaclab/docs/CHANGELOG.rst

@@ -1,6 +1,46 @@
 Changelog
 ---------
 
+4.5.33 (2026-04-13)
+~~~~~~~~~~~~~~~~~~~
+
+Added
+^^^^^
+
+* Added :class:`~isaaclab.sensors.Pva` (Pose Velocity Acceleration) sensor,
+  renamed from the former ``Imu`` to better reflect its full output: pose,
+  velocity, and acceleration.
+* Added :class:`~isaaclab.sensors.Imu` sensor that models a real inertial
+  measurement unit, providing only angular velocity (gyroscope) and linear
+  acceleration (accelerometer) in the sensor's body frame.
+* Added :func:`~isaaclab.envs.mdp.observations.pva_orientation` and
+  :func:`~isaaclab.envs.mdp.observations.pva_projected_gravity` observation
+  functions for the PVA sensor.
+
+Changed
+^^^^^^^
+
+* Changed ``isaaclab.sensors.Imu`` to refer to a new lightweight IMU sensor
+  that only provides angular velocity and linear acceleration. The old
+  ``Imu``, ``ImuCfg``, ``ImuData``, ``BaseImu``, and ``BaseImuData`` names
+  now refer to this new sensor. For the original full-featured sensor, use
+  :class:`~isaaclab.sensors.Pva`, :class:`~isaaclab.sensors.PvaCfg`, etc.
+
+Removed
+^^^^^^^
+
+* Removed ``gravity_bias`` configuration parameter from
+  :class:`~isaaclab.sensors.PvaCfg`. The PVA sensor now always reports raw
+  kinematic acceleration without gravity contribution.
+* Removed ``gravity_bias`` and ``visualizer_cfg`` configuration parameters from
+  :class:`~isaaclab.sensors.ImuCfg`. The IMU sensor now unconditionally includes
+  gravity in its accelerometer readings, matching real hardware behavior. The
+  gravity vector is queried from the simulation automatically.
+* Removed ``imu_orientation`` and ``imu_projected_gravity`` observation
+  functions. Use :func:`~isaaclab.envs.mdp.observations.pva_orientation` and
+  :func:`~isaaclab.envs.mdp.observations.pva_projected_gravity` instead.
+
+
 4.5.32 (2026-04-13)
 ~~~~~~~~~~~~~~~~~~~