How to retrieve actual actuator torque (ImplicitDrive output), not joint reaction forces?

[SHO252]

I am trying to retrieve the actual actuator torques produced by the ImplicitDrive (PD drives) in IsaacSim / IsaacLab (Humanoid environment).

Currently, I can retrieve:

joint command torque (PD target torque)
→ via my own logging (joint_torque from IsaacLab robot.data.joint_effort)

joint reaction forces / torques
→ via

articulation.root_physx_view.get_link_incoming_joint_force()

and logged as body_joint_wrench
(Fx, Fy, Fz, Tx, Ty, Tz)

However, I cannot retrieve the actual actuator torque produced by the drive.
The API get_dof_actuation_forces() always returns 0.0, regardless of stiffness/damping/target.

📌 What I have tested

1. get_dof_actuation_forces()

Always returns zeros:

forces = articulation.get_dof_actuation_forces()
print(forces) # → all zeros

Even when:

ImplicitDrive (PD) is enabled

non-zero stiffness / damping

position or velocity targets are set

queried after the physics step

2. Forum discussion suggests it should work

PeterL (NVIDIA) mentions that get_dof_actuation_forces() “should reflect actuation forces”, and that 0.0 may come from a timing or configuration issue.

But IsaacSim Python docs say:

set_dof_actuation_forces() applies external force override,
not internal PD drive forces.

So behavior seems different between documentation, forums, and actual IsaacLab behavior.

3. Reaction force is retrievable

get_link_incoming_joint_force() works correctly, but this is the joint reaction force/torque (environment + contacts + inertia), not the muscle-like drive torque.

❓ My actual question
How can I retrieve the actual actuator torque generated by ImplicitDrive (the PD controller)?

I want the net torque the drive generates each step, before the physics solver combines it with reaction forces.

Is there an API such as:

get_measured_joint_effort()

get_dof_drive_forces()

get_dof_internal_forces()

or any PhysX API that exposes joint drive output?

Or is this currently not exposed in IsaacSim/IsaacLab?

If it's not exposed yet, could you clarify:

whether it is possible at the PhysX level

if there are plans to expose actuator output torque in future releases

or recommended workarounds to estimate the actual actuator torque

🙏 Request

Could you clarify:

How to retrieve the actual actuator torque?

Whether this is supported in PhysX / OmniDynamics?

If not available, is it planned to be exposed?

Any recommended workaround in IsaacLab?

Thank you very much!