RACER, a RApid Collaborative ExploRation approach using a fleet of decentralized UAVs.

We develop a fully decentralized approach for exploration tasks using a fleet of quadrotors. The proposed system features robustness against unstable communication and a high degree of coordination. The quadrotor team operates with asynchronous and limited communication and does not require any central control. The coverage paths and workload allocations of the team are optimized and balanced in order to fully realize the system's potential. The associated paper has been published in IEEE Transactions on Robotics.

Try Quick Start to run a demo in a few minutes!

Complete video: video.

Authors: Boyu Zhou from SYSU STAR Group, and Hao Xu, Shaojie Shen from the HUKST Aerial Robotics Group.

Please cite our paper if you use this project in your research:

• RACER: Rapid Collaborative Exploration with a Decentralized Multi-UAV System, Boyu Zhou, Hao Xu, Shaojie Shen, IEEE Transactions on Robotics (T-RO) ,

@article{zhou2023racer,
  title={Racer: Rapid collaborative exploration with a decentralized multi-uav system},
  author={Zhou, Boyu and Xu, Hao and Shen, Shaojie},
  journal={IEEE Transactions on Robotics},
  year={2023},
  publisher={IEEE}
}

Please kindly star ⭐ this project if it helps you. We take great efforts to develope and maintain it 😁😁.

• RACER
  • Table of Contents
  • Quick Start
  • Exploring Different Environments
  • Known issues
    • Compilation issue
    • Unexpected crash
  • Acknowledgements

This project has been tested on Ubuntu 16.04(ROS Kinetic) and 18.04(ROS Melodic). Take Ubuntu 18.04 as an example, run the following commands to install required tools:

  sudo apt-get install libarmadillo-dev ros-melodic-nlopt libelf-dev libdw-dev 

After that, you need to install LKH-3(LKH-3.0.6 version is recommended) with the following commands. Please make sure the executable file LKH is correctly placed at /usr/local/bin.

wget http://akira.ruc.dk/~keld/research/LKH-3/LKH-3.0.6.tgz
tar xvfz LKH-3.0.6.tgz
cd LKH-3.0.6
make
sudo cp LKH /usr/local/bin

Then simply clone and compile our package (using ssh here):

  cd ${YOUR_WORKSPACE_PATH}/src
  git clone https://github.com/SYSU-STAR/RACER.git
  cd ../ 
  catkin_make

After compilation you can start a sample swarm exploration demo. Firstly run Rviz for visualization:

  source devel/setup.bash && roslaunch exploration_manager rviz.launch

then run the simulation (run in a new terminals):

  source devel/setup.bash && roslaunch exploration_manager swarm_exploration.launch

By default you can see a pillar-like environment. Trigger the quadrotor to start exploration by the 2D Nav Goal tool in Rviz. A sample is shown below, where unexplored structures are shown in grey and explored ones are shown in colorful voxels. The FoV and trajectories of the quadrotor are also displayed.

The exploration environments in our simulator are represented by .pcd files. We provide several sample environments, which can be selected in swarm_exploration.launch:

  <!-- Change office.pcd to specify the exploration environment -->
  <!-- We provide office.pcd, office2.pcd, office3.pcd and pillar.pcd in this repo -->
  <node pkg ="map_generator" name ="map_pub" type ="map_pub" output = "screen" args="$(find map_generator)/resource/pillar.pcd"/>    

Other examples can be found in map_generator/resource. If you want to use your own environments, simply place the .pcd files in map_generator/resource, and follow the comments above to specify it. You may also need to change the bounding box of explored space in exploration.launch:

    <arg name="box_min_x" value="-10.0"/>
    <arg name="box_min_y" value="-15.0"/>
    <arg name="box_min_z" value=" 0.0"/>
    <arg name="box_max_x" value="10.0"/>
    <arg name="box_max_y" value="15.0"/>
    <arg name="box_max_z" value=" 2.0"/>

To create your own .pcd environments, you can use this tool.

When running this project on Ubuntu 20.04, C++14 is required. Please add the following line in all CMakelists.txt files:

set(CMAKE_CXX_STANDARD 14)

If you get the following error message, please try to recompile this project with catkin_make .

fatal error: plan_env/ChunkStamps.h: No such file or directory

If the exploration_node dies after triggering a 2D Nav Goal, it is possibly caused by the ros-nlopt library. In this case, we recommend to uninstall it and install nlopt following the official document. Then in the CMakeLists.txt of bspline_opt package, change the associated lines to link the nlopt library:

find_package(NLopt REQUIRED)
set(NLopt_INCLUDE_DIRS ${NLOPT_INCLUDE_DIR})

...

include_directories( 
    SYSTEM 
    include 
    ${catkin_INCLUDE_DIRS}
    ${Eigen3_INCLUDE_DIRS} 
    ${PCL_INCLUDE_DIRS}
    ${NLOPT_INCLUDE_DIR}
)

...

add_library( bspline_opt 
    src/bspline_optimizer.cpp 
    )
target_link_libraries( bspline_opt
    ${catkin_LIBRARIES} 
    ${NLOPT_LIBRARIES}
    # /usr/local/lib/libnlopt.so
    )  

We use NLopt for non-linear optimization and use LKH for travelling salesman problem.