📡 Lidar Introduction and Use

1. Course Content

• Learn about the hardware specifications of the lidar sensor equipped on the A1 Pro.

• Launch the lidar driver and view real-time lidar scan point cloud in RViz2.

• Use ROS2 command-line tools to check the radar data format of the /scan topic.

2. Lidar Parameters Overview

The A1 Pro robot supports T-mini Plus and Slam C1 lidars:

2.1 T-mini Plus Lidar Parameters

2.2 Slam C1

3. Demo Examples

3.1 Launch Lidar Driver and RViz Visualization

Run in terminal:

# Launch TminiPlus lidar and open RViz visualization
ros2 launch ydyardar_ros2_driver ydlidar_launch_view.py
# Launch C1 lidar and open RViz visualization data
ros2 launch sllidar_ros2 view_sllidar_c1_launch.py

In RViz2, the red point cloud represents the lidar's real-time scan of the surrounding environment. In the LaserScan plugin panel on the left side of RViz, you can adjust the point cloud display size (Size), color style (Color Transformer), and decay time (Decay Time).

xxxxxxxxxx
# Start Tminiplus lidar
ros2 launch ydlidar_ros2_driver ydlidar_launch.py
# Start C1 lidar
ros2 launch sllidar_ros2 sllidar_c1_launch.py

4. Viewing Lidar Data

Run ROS2 CLI command in a new terminal to view raw lidar data:

xxxxxxxxxx
ros2 topic echo /scan

4.1 Core Data Field Parsing

• header.frame_id: Lidar coordinate frame name (usually laser or laser_frame).

• angle_min / angle_max: Starting and ending radians of lidar scan (0° ~ 360° corresponds to 0 to 2π).

• angle_increment: Angular resolution increment between adjacent points (radians).

• range_min / range_max: Shortest and longest valid ranging distances of the lidar (meters).

• ranges: Array of measured distances at each angle within the current scan frame (meters).