Mecanum proto rewrite in b3cf990 made the wheels truly omnidirectional
in Webots, but with asymmetric slip: forward command produces ~89% of
textbook speed while strafe produces only ~38% plus a consistent
~28% backward bleed-through. v1 BC/RL trained on perfect mecanum
gym kinematics could not herd the new dynamics. To unblock that:
* `mecanum_kinematics_step` gains two parameters that scale the
realised motion to match a deployed-platform calibration:
- strafe_efficiency ∈ (0, 1] default 1.0
- strafe_to_forward_bleed default 0.0
Forward motion is untouched (textbook X-pattern continues to apply
to vx_body); only the lateral channel is scaled and bleed is added.
* `RobotConfig` exposes both as drive-config fields with the same
pass-through defaults so existing diff-drive code and existing
mecanum training pipelines see no behaviour change.
* `HERDING_MEC_WEBOTS` preset bakes in the values measured against the
current Webots mecanum proto (strafe_efficiency=0.4,
strafe_to_forward_bleed=-0.28). Training mecanum BC/RL with this
preset produces policies that compensate for the imperfect
physical mecanum at deploy.
* `HerdingEnv` plumbs `RobotConfig.strafe_*` through to
`mecanum_kinematics_step` so the preset takes effect.
* tools/gen_mecanum_wheels.py is added so the proto's 32 roller
hinges can be regenerated by editing a single set of constants
rather than hand-editing 1500+ lines of VRML.
Tests:
* 4 new mecanum_kinematics_step tests (default pass-through, strafe
scaling, backward bleed, forward unaffected by strafe params).
* 3 new RobotConfig tests (defaults, validation, preset shape).
* Sanity check: gym strafe with HERDING_MEC_WEBOTS over 100 steps
reproduces the Webots calibration to 2 decimal places.
126 unit tests pass (was 120).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Adds RecurrentPPO-based training as an alternative to MLP+frame-stack.
The LSTM gives the policy unbounded temporal memory, addressing the
partial-obs failure mode of the 140° Webots LiDAR (tracker briefly
empties when the dog turns; sporadic phantom tracks confuse decisions).
* training/rl/train_lstm.py: from-scratch RecurrentPPO trainer (no BC
init, no KL term since there's no reference). Uses HERDING_WEBOTS
preset so the obs distribution matches deployment.
* training/eval.py: auto-detects RecurrentPPO zips, maintains LSTM
hidden state across steps, resets between episodes.
* controllers/shepherd_dog/policy_loader.py: PolicyHandle supports
recurrent policies — state managed inside, reset_recurrent() exposed.
Result on diff/field after 3M steps:
- Gym (default 360°): 69% avg success across n=1..10
- Gym (HERDING_WEBOTS preset, training env): 2% — penning 3-4/5 but
rarely all 5
- Webots LiDAR 140°: 0/5 (same wall as DAgger and v1 policies)
Conclusion: architectural changes (LSTM vs MLP) don't close the
perception sim-to-real gap. The gym LiDAR sim doesn't faithfully
reproduce Webots phantom-track distribution; any policy trained on the
gym proxy fails to handle real Webots phantoms regardless of
architecture. Closing this gap requires either modeling Webots phantom
patterns in the gym sim (multi-day work) or Webots-in-the-loop
training (very slow). See memory/lstm_results.md for details.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Today's session worked across the full Webots delivery stack — found and
fixed a cluster of bugs blocking the BC/RL transfer, then explored
training-side mitigations for the residual perception gap.
Bug fixes:
- Makefile FP_RATE default 2.0 → 0.0: BC demos used fp_rate=0 but RL
fine-tune defaulted to fp_rate=2, poisoning the BC obs distribution
and stalling PPO at 0% success across 1.46M+ steps.
- controllers/{shepherd_dog,sheep}/runtime.ini: Webots was launching
controllers under system python3 (no numpy) and they were crashing
silently. Pinned to the conda tir env.
- herding/config.py HERDING_WEBOTS preset: pen_latch_depth 0.5 → 2.0,
max_new_tracks_per_step 3 → 1, static_reject 0.8 → 1.2. Stops phantom
FPs near the gate from latching as permanently-penned tracks.
- herding/perception/sheep_tracker.py: penned tracks now decay at
forget_steps × 8 instead of living forever. Adds get_positions
min_freshness filter for deploy-time use.
Training/eval matches deployment:
- training/bc/collect.py: --dagger-policy flag for DAgger rollouts
(policy drives, teacher labels) + --use-webots-preset for matched
140° tracker + DR config.
- controllers/shepherd_dog/shepherd_dog.py: scan-fallback (0, 0.6) when
BC/RL sees empty sheep_positions — recovers from FOV gaps.
Tooling:
- tools/dagger_round.sh: one-shot DAgger round (collect + concat + bc).
- tools/webots_sweep_gt.sh: full sweep with HERDING_USE_GT=1 for the
perception-gap diagnosis matrix.
- protos/ShepherdDog360.proto: 360° FOV variant for the FOV-ablation
comparison. Canonical proto stays at 140° per project spec.
Artifacts: v1 BC/RL policies for all 4 (drive × world) combos trained
in clean gym (success: diff/field 90-100%, diff/round 58%, mec/field
60-100%, mec/round 50-100%). DAgger r1/r2 BCs for diff/field show
12%→38% progression on gym HERDING_WEBOTS proxy but did not close
to actual Webots LiDAR (0/5 throughout). Next: LSTM policy or
learned tracker per the project-state memory.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Johnny Fernandes