Randomizes viscous and dynamic joint friction based on IsaacSim 5.0 (#3318)

# Description

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This PR fixes https://github.com/isaac-sim/IsaacLab/issues/3266, adding
the possibility to randomize the friction coefficient when isaacsim is
higher than 5.0.0

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## Type of change

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- New feature (non-breaking change which adds functionality)

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## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] I have updated the changelog and the corresponding version in the
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---------
Signed-off-by: Giulio Romualdi <giulio.romualdi@gmail.com>
Signed-off-by: Mayank Mittal <12863862+Mayankm96@users.noreply.github.com>
Co-authored-by: James Tigue <166445701+jtigue-bdai@users.noreply.github.com>
Co-authored-by: Mayank Mittal <12863862+Mayankm96@users.noreply.github.com>

source/isaaclab/config/extension.toml

 [package]
 
 # Note: Semantic Versioning is used: https://semver.org/
-version = "0.46.2"
+version = "0.46.3"
 
 # Description
 title = "Isaac Lab framework for Robot Learning"

source/isaaclab/docs/CHANGELOG.rst

 Changelog
 ---------
 
+0.46.3 (2025-09-17)
+~~~~~~~~~~~~~~~~~~~
+
+Added
+^^^^^
+
+* Modified setter to support for viscous and dynamic joint friction coefficients in articulation based on IsaacSim 5.0.
+* Added randomization of viscous and dynamic joint friction coefficients in event term.
 
 0.46.2 (2025-09-13)
 ~~~~~~~~~~~~~~~~~~~
@@ -31,7 +39,6 @@ Added
   during the traversal. Earlier, instanced prims were skipped since :meth:`Usd.Prim.GetChildren` did not return
   instanced prims, which is now fixed.
 
-
 Changed
 ^^^^^^^
 

source/isaaclab/isaaclab/assets/articulation/articulation.py

@@ -827,24 +827,33 @@ class Articulation(AssetBase):
     def write_joint_friction_coefficient_to_sim(
         self,
         joint_friction_coeff: torch.Tensor | float,
+        joint_dynamic_friction_coeff: torch.Tensor | float | None = None,
+        joint_viscous_friction_coeff: torch.Tensor | float | None = None,
         joint_ids: Sequence[int] | slice | None = None,
         env_ids: Sequence[int] | None = None,
     ):
-        r"""Write joint static friction coefficients into the simulation.
+        r"""Write joint friction coefficients into the simulation.
 
-        The joint static friction is a unitless quantity. It relates the magnitude of the spatial force transmitted
-        from the parent body to the child body to the maximal static friction force that may be applied by the solver
-        to resist the joint motion.
+        For Isaac Sim versions below 5.0, only the static friction coefficient is set.
+        This limits the resisting force or torque up to a maximum proportional to the transmitted
+        spatial force: :math:`\|F_{resist}\| \leq \mu_s \, \|F_{spatial}\|`.
 
-        Mathematically, this means that: :math:`F_{resist} \leq \mu F_{spatial}`, where :math:`F_{resist}`
-        is the resisting force applied by the solver and :math:`F_{spatial}` is the spatial force
-        transmitted from the parent body to the child body. The simulated static friction effect is therefore
-        similar to static and Coulomb static friction.
+        For Isaac Sim versions 5.0 and above, the static, dynamic, and viscous friction coefficients
+        are set. The model combines Coulomb (static & dynamic) friction with a viscous term:
+
+        - Static friction :math:`\mu_s` defines the maximum effort that prevents motion at rest.
+        - Dynamic friction :math:`\mu_d` applies once motion begins and remains constant during motion.
+        - Viscous friction :math:`c_v` is a velocity-proportional resistive term.
 
         Args:
-            joint_friction_coeff: Joint static friction coefficient. Shape is (len(env_ids), len(joint_ids)).
-            joint_ids: The joint indices to set the joint torque limits for. Defaults to None (all joints).
-            env_ids: The environment indices to set the joint torque limits for. Defaults to None (all environments).
+            joint_friction_coeff: Static friction coefficient :math:`\mu_s`.
+                Shape is (len(env_ids), len(joint_ids)). Scalars are broadcast to all selections.
+            joint_dynamic_friction_coeff: Dynamic (Coulomb) friction coefficient :math:`\mu_d`.
+                Same shape as above. If None, the dynamic coefficient is not updated.
+            joint_viscous_friction_coeff: Viscous friction coefficient :math:`c_v`.
+                Same shape as above. If None, the viscous coefficient is not updated.
+            joint_ids: The joint indices to set the friction coefficients for. Defaults to None (all joints).
+            env_ids: The environment indices to set the friction coefficients for. Defaults to None (all environments).
         """
         # resolve indices
         physx_env_ids = env_ids
@@ -858,15 +867,38 @@ class Articulation(AssetBase):
             env_ids = env_ids[:, None]
         # set into internal buffers
         self._data.joint_friction_coeff[env_ids, joint_ids] = joint_friction_coeff
+
+        # if dynamic or viscous friction coeffs are provided, set them too
+        if joint_dynamic_friction_coeff is not None:
+            self._data.joint_dynamic_friction_coeff[env_ids, joint_ids] = joint_dynamic_friction_coeff
+        if joint_viscous_friction_coeff is not None:
+            self._data.joint_viscous_friction_coeff[env_ids, joint_ids] = joint_viscous_friction_coeff
+
+        # move the indices to cpu
+        physx_envs_ids_cpu = physx_env_ids.cpu()
+
         # set into simulation
         if int(get_version()[2]) < 5:
             self.root_physx_view.set_dof_friction_coefficients(
-                self._data.joint_friction_coeff.cpu(), indices=physx_env_ids.cpu()
+                self._data.joint_friction_coeff.cpu(), indices=physx_envs_ids_cpu
             )
         else:
             friction_props = self.root_physx_view.get_dof_friction_properties()
-            friction_props[physx_env_ids.cpu(), :, 0] = self._data.joint_friction_coeff[physx_env_ids, :].cpu()
-            self.root_physx_view.set_dof_friction_properties(friction_props, indices=physx_env_ids.cpu())
+            friction_props[physx_envs_ids_cpu, :, 0] = self._data.joint_friction_coeff[physx_envs_ids_cpu, :].cpu()
+
+            # only set dynamic and viscous friction if provided
+            if joint_dynamic_friction_coeff is not None:
+                friction_props[physx_envs_ids_cpu, :, 1] = self._data.joint_dynamic_friction_coeff[
+                    physx_envs_ids_cpu, :
+                ].cpu()
+
+            # only set viscous friction if provided
+            if joint_viscous_friction_coeff is not None:
+                friction_props[physx_envs_ids_cpu, :, 2] = self._data.joint_viscous_friction_coeff[
+                    physx_envs_ids_cpu, :
+                ].cpu()
+
+            self.root_physx_view.set_dof_friction_properties(friction_props, indices=physx_envs_ids_cpu)
 
     def write_joint_dynamic_friction_coefficient_to_sim(
         self,

source/isaaclab/isaaclab/envs/mdp/events.py

@@ -714,8 +714,56 @@ class randomize_joint_parameters(ManagerTermBase):
                 operation=operation,
                 distribution=distribution,
             )
+
+            # ensure the friction coefficient is non-negative
+            friction_coeff = torch.clamp(friction_coeff, min=0.0)
+
+            # Always set static friction (indexed once)
+            static_friction_coeff = friction_coeff[env_ids[:, None], joint_ids]
+
+            # if isaacsim version is lower than 5.0.0 we can set only the static friction coefficient
+            major_version = int(env.sim.get_version()[0])
+            if major_version >= 5:
+                # Randomize raw tensors
+                dynamic_friction_coeff = _randomize_prop_by_op(
+                    self.asset.data.default_joint_dynamic_friction_coeff.clone(),
+                    friction_distribution_params,
+                    env_ids,
+                    joint_ids,
+                    operation=operation,
+                    distribution=distribution,
+                )
+                viscous_friction_coeff = _randomize_prop_by_op(
+                    self.asset.data.default_joint_viscous_friction_coeff.clone(),
+                    friction_distribution_params,
+                    env_ids,
+                    joint_ids,
+                    operation=operation,
+                    distribution=distribution,
+                )
+
+                # Clamp to non-negative
+                dynamic_friction_coeff = torch.clamp(dynamic_friction_coeff, min=0.0)
+                viscous_friction_coeff = torch.clamp(viscous_friction_coeff, min=0.0)
+
+                # Ensure dynamic ≤ static (same shape before indexing)
+                dynamic_friction_coeff = torch.minimum(dynamic_friction_coeff, friction_coeff)
+
+                # Index once at the end
+                dynamic_friction_coeff = dynamic_friction_coeff[env_ids[:, None], joint_ids]
+                viscous_friction_coeff = viscous_friction_coeff[env_ids[:, None], joint_ids]
+            else:
+                # For versions < 5.0.0, we do not set these values
+                dynamic_friction_coeff = None
+                viscous_friction_coeff = None
+
+            # Single write call for all versions
             self.asset.write_joint_friction_coefficient_to_sim(
-                friction_coeff[env_ids[:, None], joint_ids], joint_ids=joint_ids, env_ids=env_ids
+                joint_friction_coeff=static_friction_coeff,
+                joint_dynamic_friction_coeff=dynamic_friction_coeff,
+                joint_viscous_friction_coeff=viscous_friction_coeff,
+                joint_ids=joint_ids,
+                env_ids=env_ids,
             )
 
         # joint armature

source/isaaclab/test/assets/test_articulation.py

@@ -1997,10 +1997,16 @@ def test_write_joint_frictions_to_sim(sim, num_articulations, device, add_ground
     dynamic_friction = torch.rand(num_articulations, articulation.num_joints, device=device)
     viscous_friction = torch.rand(num_articulations, articulation.num_joints, device=device)
     friction = torch.rand(num_articulations, articulation.num_joints, device=device)
+
+    # Guarantee that the dynamic friction is not greater than the static friction
+    dynamic_friction = torch.min(dynamic_friction, friction)
+
+    # The static friction must be set first to be sure the dynamic friction is not greater than static
+    # when both are set.
+    articulation.write_joint_friction_coefficient_to_sim(friction)
     if int(get_version()[2]) >= 5:
         articulation.write_joint_dynamic_friction_coefficient_to_sim(dynamic_friction)
         articulation.write_joint_viscous_friction_coefficient_to_sim(viscous_friction)
-    articulation.write_joint_friction_coefficient_to_sim(friction)
     articulation.write_data_to_sim()
 
     for _ in range(100):
@@ -2010,9 +2016,58 @@ def test_write_joint_frictions_to_sim(sim, num_articulations, device, add_ground
         articulation.update(sim.cfg.dt)
 
     if int(get_version()[2]) >= 5:
-        assert torch.allclose(articulation.data.joint_dynamic_friction_coeff, dynamic_friction)
-        assert torch.allclose(articulation.data.joint_viscous_friction_coeff, viscous_friction)
-    assert torch.allclose(articulation.data.joint_friction_coeff, friction)
+        friction_props_from_sim = articulation.root_physx_view.get_dof_friction_properties()
+        joint_friction_coeff_sim = friction_props_from_sim[:, :, 0]
+        joint_dynamic_friction_coeff_sim = friction_props_from_sim[:, :, 1]
+        joint_viscous_friction_coeff_sim = friction_props_from_sim[:, :, 2]
+        assert torch.allclose(joint_dynamic_friction_coeff_sim, dynamic_friction.cpu())
+        assert torch.allclose(joint_viscous_friction_coeff_sim, viscous_friction.cpu())
+    else:
+        joint_friction_coeff_sim = articulation.root_physx_view.get_dof_friction_properties()
+
+    assert torch.allclose(joint_friction_coeff_sim, friction.cpu())
+
+    # For Isaac Sim >= 5.0: also test the combined API that can set dynamic and viscous via
+    # write_joint_friction_coefficient_to_sim; reset the sim to isolate this path.
+    if int(get_version()[2]) >= 5:
+        # Reset simulator to ensure a clean state for the alternative API path
+        sim.reset()
+
+        # Warm up a few steps to populate buffers
+        for _ in range(100):
+            sim.step()
+            articulation.update(sim.cfg.dt)
+
+        # New random coefficients
+        dynamic_friction_2 = torch.rand(num_articulations, articulation.num_joints, device=device)
+        viscous_friction_2 = torch.rand(num_articulations, articulation.num_joints, device=device)
+        friction_2 = torch.rand(num_articulations, articulation.num_joints, device=device)
+
+        # Guarantee that the dynamic friction is not greater than the static friction
+        dynamic_friction_2 = torch.min(dynamic_friction_2, friction_2)
+
+        # Use the combined setter to write all three at once
+        articulation.write_joint_friction_coefficient_to_sim(
+            joint_friction_coeff=friction_2,
+            joint_dynamic_friction_coeff=dynamic_friction_2,
+            joint_viscous_friction_coeff=viscous_friction_2,
+        )
+        articulation.write_data_to_sim()
+
+        # Step to let sim ingest new params and refresh data buffers
+        for _ in range(100):
+            sim.step()
+            articulation.update(sim.cfg.dt)
+
+        friction_props_from_sim_2 = articulation.root_physx_view.get_dof_friction_properties()
+        joint_friction_coeff_sim_2 = friction_props_from_sim_2[:, :, 0]
+        friction_dynamic_coef_sim_2 = friction_props_from_sim_2[:, :, 1]
+        friction_viscous_coeff_sim_2 = friction_props_from_sim_2[:, :, 2]
+
+        # Validate values propagated
+        assert torch.allclose(friction_viscous_coeff_sim_2, viscous_friction_2.cpu())
+        assert torch.allclose(friction_dynamic_coef_sim_2, dynamic_friction_2.cpu())
+        assert torch.allclose(joint_friction_coeff_sim_2, friction_2.cpu())
 
 
 if __name__ == "__main__":