docs/POSE_TRANSFER.md

Pose-transfer adapter

The repository includes two complementary mechanisms for teaching semantic motion while respecting the Dropbear articulation.

Playback constraint projection

dropbear_walk/pose_guidance.py defines named stand and crouch poses and a test sequence:

stand -> walk with arm swing -> crouch -> stand up -> walk

ConstrainedPoseGuide maps named semantic targets into the 14-dimensional policy action order, clamps targets to softened mechanical joint limits, and rate-limits guided joints below their configured actuator velocity limits. During walking, the policy retains leg ownership and the adapter guides only reciprocal shoulder swing.

This is useful for visualization, mechanical-range discovery, and generating curriculum references. It is not a substitute for a learned balance policy.

Learned residual pose control

The environment also supports pose-reference observations and reward terms for joint pose, COM height, and height-trajectory velocity. The training wrapper can:

• append pose/COM feedback channels to older checkpoints;
• zero-initialize added network columns to preserve inherited behavior;
• train a policy residual around a semantic pose;
• bias pelvis pitch, knees, and ankle joints by name;
• stagger pose phases across vectorized environments;
• evaluate stand/crouch phases and report joint/height errors.

Relevant flags begin with --pose-*, --com-*, --adapt-pose-checkpoint, and --calibrate-*-normalizer.

What v0.1.0 does and does not claim

The included model_8745.pt is the validated upright planar locomotion checkpoint. The pose-transfer stack is included and has been exercised in simulation, but crouched locomotion and floor-to-stand recovery are not release-qualified policies in v0.1.0.

Recommended progression:

1. hold zero velocity while lowering COM height smoothly;
2. recover to standing at zero velocity;
3. add low-speed forward/back/left/right commands at fixed crouch height;
4. randomize target height within mechanically reachable bounds;
5. train ground recovery separately with staged initial poses, contact-aware rewards, and strict actuator/impact limits;
6. combine skills only after each policy passes deterministic transition gates.