LASER Fast-LIO Core

This package serves as the core integration point for the Fast-LIO (Fast LiDAR-Inertial Odometry) algorithm within the Laser UAV System (LUS). It acts as a configuration manager and launch wrapper, ensuring that the standard fast_lio node runs correctly with the specific parameters, topic remappings, and namespace configurations required by the drone architecture.

Overview

The laser_fast_lio_core package is responsible for:

1. Orchestration: Launching the Fast-LIO mapping node with dynamic ROS 2 namespaces.
2. Configuration Management: storing specific parameter files for different LiDAR/IMU setups (e.g., Livox Mid360 with internal or external IMU).
3. Topic Abstraction: Handling the remapping of input PointCloud and IMU topics to match the LUS standard.

How It Works

This package creates an abstraction layer over the standard FAST_LIO launch process. Instead of hardcoding paths or editing core configuration files for different setups, the launch files here accept arguments to select the hardware profile and topics dynamically.

1. Dynamic Parameter Loading

The system uses the fast_lio_config_file_path argument to locate the specific configuration file for the algorithm.

• Inside the params/ directory, you can define different YAML files for various sensor setups (e.g., mid360_internal.yaml for internal IMU usage or mid360_external.yaml for external IMU integration).
• When the launch file runs, it passes this specific path to the underlying FAST_LIO mapping node.
• This allows you to switch between different LiDAR models or mounting configurations (extrinsics) without modifying the source code.

2. Topic and Namespace Abstraction

The launch file accepts generic arguments for sensor topics (topic_imu, topic_pcl) and handles the remapping to the estimator's expected inputs.

• It relies on the namespace argument (defaulting to the UAV_NAME environment variable) to ensure multi-robot compatibility.
• This ensures that the FAST_LIO node publishes odometry and map data under the correct robot namespace (e.g., /uav1/fast_lio/...).

3. Visualization Helpers

To make debugging easier in multi-agent simulations, this package includes scripts (specifically scripts/refactor_rviz_config.sh) that automatically update RViz configuration files.

• Before launching RViz, the script creates a temporary copy of the default config and replaces generic placeholders (like uav1) with the current UAV_NAME.
• This prevents the common issue of RViz listening to /uav1/fast_lio/cloud_registered when you are actually flying uav2.

Launch Files

1. fast_lio.launch.py

This is the main launch file to start the LiDAR-Inertial Odometry estimator. It wraps the standard mapping.launch.py from the fast_lio package but exposes arguments for easy integration.

• Usage:

  ros2 launch laser_fast_lio_core fast_lio.launch.py \
      topic_imu:=/uav1/livox/imu \
      topic_pcl:=/uav1/livox/lidar \
      fast_lio_config_file_path:=$(ros2 pkg prefix --share laser_fast_lio_core)/params/mid360_external.yaml

• Arguments:

  • namespace (default: uav1): Top-level namespace for the drone.
  • use_sim_time (default: false): Set to true if running in simulation.
  • topic_pcl (default: empty): The input PointCloud2 topic name.
  • topic_imu (default: empty): The input IMU topic name.
  • fast_lio_config_file_path: Full path to the YAML configuration file. Defaults to params/mid360_internal.yaml.

Configuration

The params/ directory contains configuration files for specific sensor settings. These files control the behavior of the Fast-LIO filter, including extrinsic parameters, covariance adjustment, and point cloud preprocessing.

• mid360_external.yaml: Configuration for performing external flights. Defines the extrinsic parameters between the LiDAR and the internal inertial unit.

• mid360_internal.yaml: Configuration for performing internal flights. Defines the extrinsic parameters between the LiDAR and the internal inertial unit.

Helper Scripts

The package includes scripts in the scripts/ directory to facilitate visualization:

• refactor_rviz_config.sh: Automatically updates RViz configuration files with the correct UAV namespace.
• refactor_plotjuggler_config.sh: Automatically updates PlotJuggler layouts.

Packages Included

Package	Description	Repository
fast_lio	Contains the node that implements the FAST-LIO algorithm.	Link to repo