Note: The method is under paper submission, please be cautious to use or write the paper based on this repo to follow research ethics

FAST-LIO-MULTI

• This repository is a FAST-LIO2's extended version of multi-LiDAR
• Optionally, user can choose one of bundle update method vs asynchronous update vs adaptive update method

Related video: https://youtu.be/YQmjKMoBPNU

Dependencies

• ROS, Ubuntu, PCL >= 1.8, Eigen >= 3.3.4
• livox_ros_driver

cd ~/your_workspace/src
git clone https://github.com/Livox-SDK/livox_ros_driver
cd ..
catkin build -DCMAKE_BUILD_TYPE=Release

How to build and run

• Get the code, and then build

cd ~/your_workspace/src
git clone https://github.com/engcang/FAST_LIO_MULTI

cd ..
catkin build -DCMAKE_BUILD_TYPE=Release
. devel/setup.bash

• Then run

roslaunch fast_lio_multi run.launch update_method:=bundle
roslaunch fast_lio_multi run.launch update_method:=async
roslaunch fast_lio_multi run.launch update_method:=adaptive

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