feat: Add Issue #350 — smooth velocity ramp controller
Adds a rate-limiting shim between raw /cmd_vel and the drive stack to
prevent wheel slip, tipping, and jerky motion from step velocity inputs.
Core library — _velocity_ramp.py (pure Python, no ROS2 deps)
- VelocityRamp: applies independent accel/decel limits to linear-x and
angular-z with configurable max_lin_accel, max_lin_decel,
max_ang_accel, max_ang_decel
- _ramp_axis(): per-axis rate limiter with correct accel/decel selection
(decel when |target| < |current| or sign reversal; accel otherwise)
- Emergency stop: step(0.0, 0.0) bypasses ramp → immediate zero output
- Asymmetric limits supported (e.g. faster decel than accel)
ROS2 node — velocity_ramp_node.py
- Subscribes /cmd_vel, publishes /cmd_vel_smooth at configurable rate_hz
- Parameters: max_lin_accel (0.5 m/s²), max_lin_decel (0.5 m/s²),
max_ang_accel (1.0 rad/s²), max_ang_decel (1.0 rad/s²), rate_hz (50)
Tests — test/test_velocity_ramp.py: 50/50 passing
- _ramp_axis: accel/decel selection, sign reversal, overshoot prevention
- Construction: invalid params raise ValueError, defaults verified
- Linear/angular ramp-up: step size, target reached, no overshoot
- Deceleration: asymmetric limits, partial decel (non-zero target)
- Emergency stop: immediate zero, state cleared, resume from zero
- Sign reversal: passes through zero without jumping
- Reset: state cleared, next ramp starts from zero
- Monotonicity: linear and angular outputs are monotone toward target
- Rate accuracy: 50Hz/10Hz step sizes, 100-step convergence verified
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
sl-perception
6592b58f65