Fix Unitree Go2 calf actuator limits

[sylvesterkaczmarek]

Description

Fixes #7479.

UNITREE_GO2_CFG currently applies the same DC-motor effort and velocity limits to the hip, thigh, and calf joints. The Go2 calf sits behind an additional knee reduction, so using the hip/thigh limits underestimates calf torque and allows an unrealistically high motor-curve velocity.

This change keeps the existing hip/thigh actuator settings and gives the calf joints their own actuator group with reduction-adjusted limits:

• effort / saturation effort: 45.05 N·m
• velocity limit: 15.65 rad/s

The stiffness, damping, and friction settings are unchanged.

Tests

Adds a configuration regression test verifying the calf group and its reduced joint-side limits.

Changelog

Adds the required isaaclab_assets changelog fragment.

[isaaclab-review-bot]

Isaac Lab Review Bot

The Go2 calf joints are correctly split into a dedicated DC-motor group with reduction-adjusted effort and velocity limits, while existing gains and friction are preserved. The changelog should also document the changed actuator-group layout and migration impact for downstream overrides.

• Design and architecture: Using a separate DCMotorCfg group is appropriate because the calf joints require different effort and velocity limits from the hip and thigh joints. The group split preserves the previous stiffness, damping, and friction values.
• API: UNITREE_GO2_CFG.actuators now narrows base_legs to hip and thigh joints and introduces the calves key. Because downstream configurations overriding actuators["base_legs"] will no longer affect calves, the changelog must identify the new group and provide migration guidance for that changed behavior.
• Implementation: The calf joint expression and reduction-adjusted limits are applied consistently, and the regression test directly checks the new group boundaries and limit values. The remaining fix is limited to documenting the actuator-group restructuring in the changelog fragment.

Minor fixes needed. Posted 1 actionable finding inline.

Automated review; human maintainers own approval decisions.

[isaaclab-review-bot]

🟡 Warning · Api — Changelog omits actuator group restructure guidance

The fragment only mentions limit values, but the public config layout also changed: UNITREE_GO2_CFG.actuators["base_legs"] no longer matches .*_calf_joint, and a new "calves" group was added. Downstream configs that override actuators["base_legs"] (stiffness, damping, limits, joint expressions) now silently skip calf joints. Repository rules require migration guidance for changed behavior; state the narrowed base_legs scope and the new group name.

[greptile-apps]

Greptile Summary

The PR separates Unitree Go2 calf joints into their own DC-motor actuator group so their effort and velocity limits account for the knee reduction, and adds a configuration regression test and changelog entry.

• Preserves the existing hip and thigh motor limits.
• Assigns reduction-adjusted effort, saturation-effort, and velocity limits to calf joints.
• Adds direct assertions for the new actuator-group layout and limits.

Confidence Score: 4/5

The PR should not merge until the new calf actuator group receives the existing Go2 backend-specific armature preset.

The limit conversion is internally consistent, but splitting the actuator group causes current rough and flat Go2 environments to leave calf armature at the USD value while applying their configured preset only to hip and thigh joints.

Files Needing Attention: source/isaaclab_assets/isaaclab_assets/robots/unitree.py and source/isaaclab_tasks/isaaclab_tasks/core/velocity/config/go2/rough_env_cfg.py

Important Files Changed

Filename	Overview
source/isaaclab_assets/isaaclab_assets/robots/unitree.py	Correctly separates the calf motor limits, but the new group no longer receives the Go2 environments' existing backend-specific armature preset.
source/isaaclab_assets/test/test_unitree.py	Covers the group split and numeric limits but does not cover inherited actuator properties such as backend-specific armature overrides.
source/isaaclab_assets/changelog.d/fix-go2-calf-reduction.rst	Accurately documents the intended actuator-limit correction.

_{Reviews (1): Last reviewed commit: "docs: add Go2 actuator changelog fragmen..." | Re-trigger Greptile}

[greptile-apps]

Calves lose armature presets

When Go2 rough or flat velocity environments initialize, their backend-specific armature preset updates only base_legs; moving the calf joints into calves leaves them at the USD-authored armature instead of the configured 0.0 or 0.02 value, unintentionally changing calf dynamics.

[AntoineRichard]

Thanks for the PR @sylvesterkaczmarek I think we want to go a slightly different route by avoiding the creation of two actuator groups, it can be a bit slower. Also looks like Go1 is affected by similar issues. Some other unitree assets are also affected (like G1 or H1) but for this we likely need new assets. #7564 to replace