Lidar

lidar.py

Overview

lidar.py is a synthetic 2-D LiDAR publisher that emits planar laser scan messages at 10 Hz. It lets navigation, SLAM, and obstacle-avoidance stacks run without real hardware or recorded bags.

Interfaces (strongly-typed, stateless)

Direction	Topic	Message type / Notes
Provided	/{robot}/lidar	sensor_msgs/LaserScan – 10 Hz, 180 beams spanning –90° to +90°.

Contract

Pre-conditions

• Node launched with positional robot_id argument.

• Downstream subscribers expect LaserScan at ~10 Hz.

Post-conditions

• Publishes exactly one LaserScan per loop iteration.

• ranges list length = 181, each entry fixed at _FIXED_RANGE (5.0 m).

• Header frame_id = “laser”, stamp = rospy.Time.now().

Invariants

• angle_max – angle_min = π radians, angle_increment = π/180.

• range_min = 0.1 m, range_max = 10.0 m.

Quality-of-Service KPIs

Metric	Target	Rationale
Message rate	10 Hz ± 0.5 Hz	Keeps real-time filters stable.
Latency	< 50 ms	Avoids stale obstacle data.
CPU load	< 1 %	Safe on embedded CPUs.

Implementation notes

• Uses rospy.Rate(_RATE) for loop timing.

• All scan parameters defined as module-level constants for easy tweaking.

• No state beyond the loop – perfect for hot-reload or unit tests.

lidar.publish()

Advertise /lidar and stream constant LaserScan messages until shutdown.