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>
Johnny Fernandes