The full open-source codebase to fly a multi-UAV slung load system using PX4 and pixhawk-controlled drones. The system is built using C++ and python ROS2 modules primarily to run research experiments. It can be used in simulation, in a motion capture room, or outdoors with GNSS.
If you use this code in a research setting, please cite:
@inproceedings{merton2026dynamics,
title={Dynamics Modeling of a Multi-UAV Slung Load System Using a Discrete-Link Cable Approach},
author={Merton, Harvey and Hunter, Ian W},
booktitle={2026 IEEE International Conference on Robotics and Automation (ICRA)},
pages={15757--15764},
year={2026},
organization={IEEE}
}
The repository that contains the data and processing scripts for this paper can be found here. For a more complete discussion of the design of the drone-load system, and some other ideas tested with the system, see:
@thesis{merton_2024,
title={State and Dynamics Estimation in an Outdoor Multi-Drone Slung Load System},
url={https://hdl.handle.net/1721.1/157197},
school={Massachusetts Institute of Technology},
author={Merton, Harvey},
year={2024},
month=Sep}
- ICRA 2026 accompanying overview video: https://www.youtube.com/watch?v=VATTPYYDwYY
- Gazebo simulation: https://youtu.be/L-jx-SenBfA
- Real world flight: https://youtu.be/4FRBUPgz-X4
- Flight in testing apparatus: https://bit.ly/3Xrp9rz
- Docker apt install (preferred if Linux) or Docker Desktop
Allow X11 connections to Docker by running this in a host Linux terminal:
xhost +local:root - VS code + containers extension (sign in to sync extensions)
- Git with appropriate authentication such as
gh auth login
Authenticate GitHub and Balena at runtime when needed. Docker image builds do not require authentication tokens or SSH keys. Keep credentials outside image layers and never publish images built with the former embedded credentials.
- Clone
git clone -b feature/mocap https://github.com/hmer101/multi_drone_slung_load_master.git --recurse-submodules
- Setup submodules
cd multi_drone_slung_load_master
git submodule update --init --recursive
-
Open devcontainer in VSCode
- Open VSCode
- Open the multi_drone_slung_load_master folder
- Open VSCode's command pallet (Cntrl + shift + p) and type: 'rebuild and reopen in container'. Run this command
-
Run setup inside the container (may be done automatically by devcontainer)
-
In VSCode terminal inside the container, run:
cd /multi_drone_slung_load_master source ./setup.sh source ./activate_simulation.sh #OR: source ./activate_physical.sh depending on if you want to run the simulation or physical world version
-
The deveopment environment is now set up and built so code can be run in the environment as normal.
- (In real world) Set the required variables on each PX4 drone (through QGC):
- UXRCE_DDS_DOM_ID=10
- UXRCE_DDS_PTCFG=1
(In simulation) To remove noise from simulated GPS (line 117-119): /multi_drone_slung_load_master/repos/PX4-Autopilot/src/modules/simulation/sensor_gps_sim/SensorGpsSim.cpp
- Gazebo GUI not appearing. Must run 'xhost +local:root' on host machine on every restart.
When using CycloneDDS:
- "failed to run multicast on lo" or similar -> Look in setup.sh and run the commands around line 79 to address this.
- Drones getting stuck waiting for flags to be set before takeoff -> This is due to weird node and topic discovery problems in Cyclone. (Fastrtps is better for simulation). Restart VSCode (shouldn't have to rebuild container) and this might be better
- With ROS_LOCALHOST_ONLY=1, cannot echo PX4 topics. Need to set up PX4 variables using QGC. Set: UXRCE_DDS_DOM_ID=10, UXRCE_DDS_PTCFG=1 (so can use ROS_LOCALHOST_ONLY=1)
On physical drone:
- Can ping PX4 from container (ping 192.168.4.11), but cannot echo ros2 topics.
- Need to set up PX4 variables using QGC. Set: UXRCE_DDS_DOM_ID=10, UXRCE_DDS_PTCFG=1 (so can use ROS_LOCALHOST_ONLY=1)
Not required/Old:
- (UXRCE_DDS_CFG = 1000, UXRCE_DDS_PRT - only if not starting in the 'extras' file on the SD card)
- (Perhaps set: UXRCE_DDS_SYNCC to stop 'timesync' issue esp. in simulation)
- (CycloneDDS) Topics aren't coming through a particular interface robustly -> Change the NetworkInterface in the cyclonedds.xml file to the interface that you would like to use (e.g. the ethernet interface)
- Ubuntu 22.04
- ROS2 Humble
- Install all prerequisites
- Clone the repository and all submodules to your home directory (~/) with:
git clone https://github.com/hmer101/multi_drone_slung_load_master.git --recurse-submodules
- Build the PX4-Autopilot included as a submodule in this repository. For help with this, follow the instructions here: https://docs.px4.io/main/en/ros2/user_guide.html.
- If you properly cloned this repo using '--recurse-submodules', you will not need to clone the PX4-Autopilot repository again; simply use the one provided in this repo.
- You will have to run the ubuntu.sh setup script, install the MicroXRCEAgent, and make the px4 firmware with 'make px4_sitl gz_x500' (for simulation) and 'make px4_fmu-v6x_default' for hardware (all documented above).
- Note that the PX4-Autopilot repo in this repository is a fork of the original with some minor tweaks. As such, using the original PX4-Autopilot repo in place of this fork will not work.
- Install all python requirements with:
pip install -r requirements.txt
Note that colcon does not work with virtual environments so don't use one!
- Make frame transforms .so. In the folder:
cd multi_drone_slung_load_master/ws_ros2/src/multi_drone_slung_load/multi_drone_slung_load/frame_transforms
make the frame_transforms object file:
mkdir -p build && \
cd build && \
cmake .. && \
make && \
cp frame_transforms.cpython-310-x86_64-linux-gnu.so ../../frame_transforms.so
- Build the ros2 workspace by changing into the 'ws_ros2' directory and running:
colcon build
- Source the ros workspace (can add this to the .bashrc file) with:
source /opt/ros/humble/setup.bash
source ~/multi_drone_slung_load_master/ws_ros2/install/local_setup.bash
A Docker container is coming soon.
- Change configuration files in /ws_ros2/src/multi_drone_slung_load/config. Always rebuild and source before running.
The system can either be run in simulation, in a motion capture room, or outdoors. The aliases found at the end of the Dockerfile provide all of the commands required to run the simulation and the real-world system.
The following section describes how to build the real-world system capable of outdoor flight.
Running aerial drone experiments outdoors is dangerous; there are many variables that could make previously functioning code malfunction. Always simulate and test on the testing rig described below before attempting unconstrained flight. Ensure you comply with local drone flying regulations. The authors make no guarantees that the provided code will function as expected, and are not liable for any accidents that occur as a result of running this code.
Multi-drone slung load system BOM
| Item | Cost ($) | Quantity | Total cost ($) |
|---|---|---|---|
| Drones | |||
| Holybro X500 v2 ARF kit | 260.99 | 3 | 782.97 |
| Holybro Pixhawk 6x v3 set | 317.99 | 4 | 1271.96 |
| Holybro H-RTK F9P GNSS - rover | 296.99 | 4 | 1187.96 |
| Holybro power distribution board | 8.59 | 4 | 34.36 |
|
|
57.49 | 4 | 229.96 |
| Radiomaster R81 RC receiver | 17.99 | 3 | 53.97 |
| SiK telemetry radio v3 - |
58.99 | 4 | 235.96 |
| RJ45 Ethernet splitter 1 to 2 |
9.99 | 4 | 39.96 |
| Intel RealSense D435 | 297.13 | 3 | 891.39 |
| Realsense camera mounts - 3D printed | 1.20 | 3 | 3.60 |
| Drones + load | |||
| Raspberry Pi (RPi) 5 | 80.00 | 4 | 320.00 |
| RPi 5 fans | 5.00 | 4 | 20.00 |
| MicroSD card |
18.45 | 4 | 73.80 |
| UBEC SMPS |
7.99 | 4 | 31.96 |
| 4-outlet, USB-powered Ethernet hub | 31.99 | 1 | 31.99 |
| Ethernet cables - cat 6 |
9.99 | 1 | 9.99 |
| Ethernet cables - cat 6 |
9.49 | 3 | 28.47 |
| Load | |||
| Kevlar rope with nylon sheathe - |
39.99 | 1 | 39.99 |
|
|
31.99 | 1 | 31.99 |
| 6-pack tri-glide plastic buckles (3/4" combo set) | 9.59 | 1 | 9.59 |
|
|
125.39 | 1 | 125.39 |
| Auxiliary | |||
| Holybro H-RTK F9P RTK GNSS - base | 325.99 | 1 | 325.99 |
| Radiomaster TX16S II RC | 209.99 | 3 | 629.97 |
| TX16S battery |
24.99 | 3 | 74.97 |
| Total | $ 6486.19 | ||
| Bill of materials with approximate costs for the full multi-drone slung load system as at August 2024. All $ are in USD. |
Testing apparatus BOM
| Item | Cost ($) | Quantity | Total cost ($) |
|---|---|---|---|
| 8020 aluminium t-slot profile extrusion: 30-3030 | 400.82 | 1 | 400.82 |
| Frame connecting plates | 1.69 | 48 | 81.28 |
| 8020 frame angle pieces: 30-4332 | 4.23 | 24 | 101.44 |
| 8020 t-nuts: 13024 | 2.30 | 180 | 414.00 |
| Cap screw, M6 × 1.00 mm, 15 mm long, 10pk | 7.30 | 13 | 94.90 |
| 8020 40 to 40 series roller wheel: 40-2290 | 23.59 | 8 | 188.72 |
| Al rolling wheel holder - custom 3D print | 0.82 | 2 | 1.64 |
| 4" caster wheels - 4pk | 25.99 | 1 | 25.99 |
| Dial a-distance retractable dog leash, 0--15 ft | 34.99 | 2 | 69.98 |
| Rabbitgoo dog harness small | 19.98 | 1 | 19.98 |
| Leash holder - custom 3D print | 2.09 | 2 | 4.18 |
| Total | $ 1402.93 | ||
| Bill of materials with approximate costs for the drone testing apparatus as at August 2024. All $ are in USD. |
- Slung load: https://bit.ly/471B8il
- Testing apparatus frame: https://bit.ly/3z2u6gN
- On-drone camera mount: https://bit.ly/3T1c4SU