FAST-LIO-MULTI_ROS2

This repository is a ROS2 port of FAST-LIO-MULTI,
which itself is a multi-LiDAR extension of FAST-LIO2.

• Original project: FAST-LIO-MULTI (ROS1)
• This fork: FAST-LIO-MULTI_ROS2 (ROS2)
• ROS2 integration and structure inspired by: FAST_LIO_ROS2

Optionally, the user can choose one of:

• Bundle update
• Asynchronous update
• Adaptive update

The algorithmic behavior of the three update modes is kept as close as possible to the original ROS1 implementation, with only the ROS interface and required glue adapted to ROS2.

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Related video

Original FAST-LIO-MULTI demo video (ROS1):
https://youtu.be/YQmjKMoBPNU

The update methods and performance characteristics described there also apply conceptually to this ROS2 port.

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Dependencies

Core

• ROS2 (tested with Humble)
• Ubuntu (tested with 22.04)
• PCL ≥ 1.8
• Eigen ≥ 3.3.4

Livox driver (ROS2)

For Livox sensors, use the ROS2 driver:

• livox_ros_driver2

Example installation:

# In your ROS2 workspace
cd ~/your_ros2_ws/src
git clone https://github.com/Livox-SDK/livox_ros_driver2.git

cd ..
rosdep install --from-paths src --ignore-src -r -y
colcon build --cmake-args -DCMAKE_BUILD_TYPE=Release
source install/setup.bash

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How to build and run (ROS2)

1. Get the code

cd ~/your_ros2_ws/src
git clone https://github.com/Draxran/FAST_LIO_MULTI_ROS2.git
cd FAST_LIO_MULTI_ROS2
git submodule update --init --recursive

2. Build with colcon

From the workspace root:

cd ~/your_ros2_ws
rosdep install --from-paths src --ignore-src -r -y

colcon build --cmake-args -DCMAKE_BUILD_TYPE=Release
source install/setup.bash

3. Run

A ROS2 launch file is provided:

# Bundle update
ros2 launch fast_lio_multi fast_lio_multi.launch.py update_method:=bundle

# Asynchronous update
ros2 launch fast_lio_multi fast_lio_multi.launch.py update_method:=async

# Adaptive update
ros2 launch fast_lio_multi fast_lio_multi.launch.py update_method:=adaptive

The launch file wraps the same three mapping nodes (bundle / async / adaptive) as in the original ROS1 project, but using ROS2 nodes, topics, and parameters.

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Update methods: bundle vs asynchronous vs adaptive

• Bundle update: merge multi LiDAR scans into one pointcloud, and then update
  • Prevent no scan data input in extreme situation, e.g., high altitude flight of drones
  • Longer update interval (which may cause drift during aggresive and fast movement from state propagation with only IMU)
  • NOTE: current code implementation will properly work for LiDARs with same scan rates (e.g., same 10Hz)
• Asynchronous update: update the filter whenever LiDAR scan inputs
  • Shorter update interval (which may reduce drift from state propagation with only IMU)
  • Depending on the sensor configuration, none-scanned data update may occur (which may result in divergence)
• Adaptive update method
  • Asynchronous update => bundle update (only when data in FoV is not enough) => asynchronous update
  • Shorter update interval + preventing no scan data input!

Update methods - (upper): Bundle, (middle): Asynchronous, (bottom): Adaptive

• By utilizing the forward and backward propagation structure of FAST-LIO2, each update method is implemented as follows:

Update methods - (left): Bundle (right): Asynchronous

Results of each method (for better understanding, please watch the related video)

• For two sensor configurations,
  • Config1: Livox-MID360 x 2EA (each is tilted +143, -143 degree)
  • Config2: Livox-MID360 x 1EA (0 degree tilted), Livox-AVIA x 1EA (90 degree tilted)

Sensor config - (left): config1 (right): config2

• For aggresive motion and middle-altitude flight situation with sensor config1, asynchronous update method shows better performance
  • Green: ground-truth, turquoise: FAST-LIO-MULTI

Side view - (left): Bundle (right): Async

Top view - (left): Bundle (right): Async

• For high-altitude flight situation (no many scanned data) with sensor config2, bundle update method shows better and robust performance
  • Green: ground-truth, turquoise: FAST-LIO-MULTI

Top view - (left): Bundle (right): Async

Side view - (left): Bundle (right): Async