| --- |
| license: mit |
| tags: [robotics, reinforcement-learning, quadruped, mjx, brax] |
| --- |
| |
| # wojtek-stiff-height-locomotion |
|
|
| Height-commandable joystick locomotion policy for the Wojtek quadruped |
| (kp=40 / kd=1.6 / ±9 Nm stiff line). Schema-2 deployment contract: |
| `policy.npz` + `policy_meta.json`; the ROS stack loads it by reference |
| (`policy:=hvsr-robotics/wojtek-stiff-height-locomotion`). |
|
|
| ## Capabilities (courses battery, 8 seeds/scenario, evidence in courses.json) |
|
|
| - **Live height command**: 4th command dim, trained box [0.11, 0.18] m, |
| tracked to ≤5 mm over the mechanically reachable range (saturates |
| gracefully at the ~0.154 m knee-guard ceiling). The runtime re-anchors |
| per command using the `height_table` field (calibrated kinematic |
| mapping — REQUIRES the 2026-07-27 `wojtek_policy` with height_table |
| support; older runtimes would anchor ~0.38 rad off). |
| - Pivots in place BOTH directions at 0.8 and 1.2 rad/s (spin scores |
| 2.07–2.15; the previous keeper could not complete any spin). |
| - Slalom, slow (0.2 m/s) and fast (1.0 m/s) walking, push recovery; |
| every catalogue scenario completes 8/8, zero falls in the battery. |
| |
| ## Lineage |
| |
| From-scratch 1.57B steps (early-stopped, zero-fall training run), MJX/ |
| Brax PPO, `+experiment=stiff_h7_height` at the repo state of 2026-07-27 |
| (uncommitted-era presets archived here: run_h7.resolved.yaml). Stack: |
| mirror-symmetry augmentation, product-gated + relative velocity |
| tracking, per-swing apex shaping, pre-contact landing softness, |
| real-pose (kinematic) references. Sibling `wojtek-stiff-h6-apex` line |
| scores higher on flat-height polish without the height command. |
|
|
| ## Deployment |
|
|
| kp=40 / kd=1.6 / ±9 Nm (must match `wojtek_real.urdf.xacro` + launch |
| max_torque). Send height as the 4th command dim; omit it and the runtime |
| pins 0.145 m (`command_fill`). |
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|
