laser_interface.md

Laser interface

The hardware interface publishes up to two laser scans from the Omron controller through libaria:

• /scan from the front safety laser in laser_frame
• /scan_low from the low front laser in laser_frame_low

The main laser remains the primary scan used for mapping and navigation. The low laser is downward-looking and is disabled or enabled with configuration depending on the robot and use case.

Parameter layout

Laser configuration lives under amr_core.ros__parameters.laser in the robot-specific parameter files:

laser:
	main_laser:
		topic: "scan"
		frame_id: "laser_frame"
		request: "Laser_1Current"
		request_period_ms: 200
		angle_min: -2.09439510239
		angle_max: 2.09439510239
		angle_increment: 0.00872664626
		range_min: 0.02
		range_max: 15.0
	low_laser:
		enabled: true
		topic: "scan_low"
		frame_id: "laser_frame_low"
		request: "Laser_2Current"
		request_period_ms: 200
		angle_min: -1.09955742876
		angle_max: 1.09955742876
		angle_increment: 0.00872664626
		range_min: 0.02
		range_max: 4.0

Laser_1Current and Laser_2Current are the libaria current range-device streams used for the main and low scanners.

Datasheet-derived defaults

LD90

• Main safety laser: 240 degree field of view, 15 m range
• Low front laser: 126 degree field of view, 4 m range

LD250

• Main safety laser: 240 degree field of view, 40 m general sensing range
• Low front laser: 126 degree field of view, 4 m range

Angle increment behavior

The configured angle_min and angle_max define the scan span. At runtime, the interface computes the published increment from the number of points in the packet:

$$ ext{angle_increment} = \frac{\text{angle_max} - \text{angle_min}}{N - 1} $$

where $N$ is the number of returned points in that packet. This keeps the LaserScan geometry aligned with the actual point count instead of assuming a fixed angular resolution.

Notes

• The low laser is useful for close-range floor-level sensing.
• The low laser is not automatically wired into Nav2 obstacle sources.
• If the robot returns sparse data, the scan may contain NaN bins where no point landed in that angular slot.