Abdel/frenet planner config tuning

[abdel-fahmy]

feat(planning): tune velocity smoother, path sampler, and boundary departure prevention for improved curve behavior

Summary

Config parameter tuning for the sampling-based path planner to reduce excessive deceleration before curves and improve path generation at tight turns. These changes work in coordination with the code changes in the companion PR.

Companion code PR: autowarefoundation/autoware_universe/12390

Motivation

The vehicle slowed to near-zero before curves because three independent systems each applied conservative constraints that compounded into excessive deceleration. The parameters were tuned independently and did not work well as a coordinated system.

Changes

velocity_smoother.param.yaml

Parameter	Before	After	Reason
curvature_calculation_distance	2.0 m	5.0 m	Smoother lookahead for earlier, gentler deceleration
lateral_acceleration_limits	[1.0, 1.0, 1.0, 1.0] m/s²	[2.0, 2.0, 1.5, 1.0] m/s²	Higher lateral G at low speed allows faster cornering
decel_distance_before_curve	3.5 m	5.0 m	Earlier deceleration start reduces peak braking
decel_distance_after_curve	2.0 m	3.0 m	Longer maintained speed after curves for smoother transitions

path_sampler.param.yaml

Parameter	Before	After	Reason
max_curvature	0.1 m⁻¹	1.0 m⁻¹	Allow turns with radius down to 1m (was 10m minimum)
min_curvature	-0.1 m⁻¹	-1.0 m⁻¹	Symmetric for both turn directions
target_lengths	[10.0, 20.0] m	[5.0, 10.0, 20.0, 30.0] m	Short 5m paths for tight turns, 30m for highway planning
enable_bezier	true	false	Disable unused Bezier sampler
drivable_area_footprint_margin	(new)	0.5 m	Supports shrunken footprint for drivable area check at tight turns (see companion PR)

boundary_departure_prevention.param.yaml

Parameter	Before	After	Reason
th_vel_kmph.min	5.0 km/h	10.0 km/h	Avoid false slowdown triggers at very low speed
th_dist_to_boundary_m.left.max	0.5 m	0.3 m	Tighter threshold reduces false positives on normal curved paths
th_dist_to_boundary_m.right.max	0.5 m	0.3 m	Same for right boundary

Testing

• Verified the vehicle no longer slows to near-zero before moderate curves
• Verified candidate paths are generated at tight intersections with the new curvature limits
• Built and tested in simulation with the default Autoware vehicle model

Notes

• These parameters are tuned for the default Autoware vehicle model. Vehicles with significantly different dynamics (wheelbase, max steering angle) may need re-tuning.
• The drivable_area_footprint_margin parameter is used by the shrunken footprint feature introduced in the companion code PR. Setting it to 0.0 restores the original full-footprint behavior.

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