Decouple implicit-actuator effort limit from solver clamp

[ooctipus]

Description

This is the effort-limit mirror of #6481 and extracts the actuator dependency from #6891.

Actuator configs expose two effort-limit fields with different responsibilities, but implicit actuators currently require them to be equal and raise ValueError when both carry different values.

This PR gives each field one clear job and lets them coexist:

• effort_limit — the actuator-facing rated force or torque. Explicit actuator models use it for output clipping; implicit actuators retain it as their model-facing limit.
• effort_limit_sim — the solver-level clamp. Physics backends write this value to the simulated joint drive.

Keeping them independent lets a configuration retain a rated limit while deliberately selecting a different solver clamp. This is needed by the Factory Franka configuration, which carries datasheet limits separately from its contact-stability solver guards.

Backwards compatibility: configurations that set only one field, set equal values, or set neither behave as before. The narrow behavior change is that setting both to different values is now valid instead of raising, and an effort_limit-only implicit actuator no longer emits a deprecation warning.

Type of change

• Breaking change (narrow: differing implicit-actuator limits are accepted instead of raising)

Validation

• Existing implicit-actuator effort-limit matrix: 72 passed
• PhysX articulation effort-limit matrix: 24 passed
• Newton articulation effort-limit matrix: 24 passed
• Regression check fails on unmodified develop at the differing-limit case
• uv run isaaclab -f
• Changelog fragment validation

[greptile-apps]

Greptile Summary

The PR separates an implicit actuator's model-facing rated effort limit from its solver-level clamp while preserving existing fallback behavior for single-field configurations.

• Removes rejection of differing effort_limit and effort_limit_sim values.
• Updates actuator API documentation and changelog entries to describe the independent responsibilities.
• Expands core, PhysX, Omniverse, and Newton tests to verify both actuator-facing and solver-facing values.

Confidence Score: 5/5

The PR appears safe to merge, with the intended independent effort-limit semantics consistently documented and covered across the affected simulation backends.

The constructor preserves prior behavior for zero-, one-, and equal-field configurations, while differing values are resolved separately and backend tests verify that only the solver-facing value is written to physics.

Important Files Changed

Filename	Overview
source/isaaclab/isaaclab/actuators/actuator_pd.py	Removes the differing-limit validation while retaining bidirectional fallback when only one effort field is configured.
source/isaaclab/isaaclab/actuators/actuator_base_cfg.py	Documents the distinct model-facing and solver-facing effort-limit contracts and their compatibility fallbacks.
source/isaaclab/test/actuators/test_implicit_actuator.py	Covers scalar combinations of absent, equal, and differing effort limits and verifies both resolved tensors.
source/isaaclab_newton/test/assets/test_articulation.py	Verifies that Newton receives the solver clamp while the actuator retains its independently configured rated limit.
source/isaaclab_ov/test/assets/test_articulation.py	Verifies independent actuator and solver effort limits through the Omniverse articulation path.
source/isaaclab_physx/test/assets/test_articulation.py	Verifies independent actuator and solver effort limits through the PhysX articulation path.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  Config["ImplicitActuatorCfg"]
  Rated["effort_limit<br/>rated/model-facing limit"]
  Solver["effort_limit_sim<br/>solver clamp"]
  Model["Implicit actuator<br/>effort estimate"]
  Physics["Physics backend<br/>joint drive"]

  Config --> Rated
  Config --> Solver
  Rated --> Model
  Solver --> Physics

Loading

_{Reviews (1): Last reviewed commit: "Decouple implicit-actuator effort limit ..." | Re-trigger Greptile}

[isaaclab-review-bot]

Isaac Lab Review Bot

The implicit-actuator effort-limit split is consistently implemented and tested, but the updated public configuration docstrings need the required SI unit notation before merge.

• Design and architecture: The separation of model-facing effort_limit from solver-facing effort_limit_sim is coherent with the fallback behavior and backend write paths covered by the updated tests.
• API: The rewritten public docstrings for ActuatorBaseCfg.effort_limit and effort_limit_sim omit inline [N or N·m] units, contrary to the repository documentation requirements and the corresponding runtime attribute documentation. Add the unit notation to both fields.
• Implementation: The fallback branches preserve single-field behavior, while differing configured values remain independent and only effort_limit_sim reaches the solver. No implementation issue is evidenced beyond the public documentation omission.

Minor fixes needed. Posted 1 actionable finding inline.

Automated review; human maintainers own approval decisions.

[isaaclab-review-bot]

🔵 Suggestion · Api — Config effort-limit docstrings omit SI units

The rewritten docstrings for effort_limit and effort_limit_sim describe force/torque quantities without the required inline unit notation, while the matching ActuatorBase attributes were updated in this diff to [N or N·m]. Add the same [N or N·m] annotation to both config fields so the public configuration surface states units consistently with the runtime attributes.