sensor_fusion

sensor_fusion.py

Overview

sensor_fusion.py is a fusion node that synthesizes data from a planar LiDAR scanner and a single-beam sonar into a unified sensor_msgs/LaserScan. This lightweight placeholder lets sensor-fusion and obstacle-avoidance pipelines be exercised without complex probabilistic filters or real hardware.

Interfaces (strongly-typed, stateless)

Direction	Topic	Message type / Notes
Required (sub)	/{robot}/lidar	sensor_msgs/LaserScan – 180° planar scan
Required (sub)	/{robot}/sonar	sensor_msgs/Range – single-beam ultrasound
Provided (pub)	/{robot}/fused_scan	sensor_msgs/LaserScan – LiDAR + centred sonar reading fused

Contract

Pre-conditions

• LiDAR and sonar topics publish at compatible rates (~10 Hz).

• LiDAR ranges length matches the pseudo-scan length generated from sonar.

Post-conditions

• Each call to publish_fused() emits exactly one fused LaserScan.

• Fused ranges = element-wise sum of LiDAR ranges and the adapted sonar array.

Invariants

• Sonar reading is placed at the centre index; all other beam values are unchanged.

Implementation notes

• Fusion is attempted on every sonar callback and in a fixed-rate loop.

• Adapter expands a scalar sonar reading into a zero-filled list with the value at the centre.

• Holds no extra state beyond the last messages, ideal for hot-reload and tests.

Classes

Adapter()	Expand a scalar sonar range into a list matching the LiDAR beam count.
SensorFusionNode()	Merge LiDAR and sonar information into a single LaserScan.