This is a ROS package for use in developing multi-quadcopter applications. It is capable of generating multiple flight controller instances, which can be simulated using SITL in Gazebo (master or michael-vel branches) or run on hardware (hardware branch). Below are instructions for setting this up as well as running the modules.
- Run ubuntu_sim_ros_gazebo.sh from https://dev.px4.io/en/setup/dev_env_linux_ubuntu.html
- This installs ROS along with the tools (gazebo, mavros, px4 sitl) necessary for running/visualizing drones.
wget https://raw.githubusercontent.com/PX4/Devguide/master/build_scripts/ubuntu_sim_ros_gazebo.sh chmod +x ubuntu_sim_ros_gazebo.sh ./ubuntu_sim_ros_gazebo.sh - Install PX4 firmware
- Check that under ~/src/Firmware, the PX4 firmware repository exists, which can be found here: https://github.com/PX4/Firmware
- This is referenced in gen_models.py (can change location here if PX4 is installed somewhere else) which is used later to generate launch file with n number of drones.
git clone https://github.com/PX4/Firmware.git cd Firmware git checkout stable make posix_sitl_default make posix_sitl_default sitl_gazebo - Clone this repo to your machine
git clone https://github.com/UCSD-SEELab/ROS_Multidrone.git
- Ensure paths in launch_sim.sh and gen_models.py are set up properly.
- ROS_SIM_DIR should point to where ROS_Multidrone was cloned: ie. ~/ROS_Multidrone
- FIRMWARE_DIR should point to where PX4's firmware was cloned: ie. ~/Firmware
- Run launch_sim to build project, generate models, and start ROS/Gazebo/PX4.
cd ROS_Multidrone/scripts
chmod +x launch_sim.sh
./launch_sim.sh <num_drones>
- When exiting, ctrl+c the gazebo terminal on top right and wait for it to clean up before closing terminal
- The Python and C++ controllers can be closed at any time without leaving artifacts behind.
On NAVIO2 + Raspberry Pi hardware, the connections would be set up according to the following:
In software, connections are as follows:
can be found under scripts/README.md
- Port number indicates starting port in the range [starting_port, starting_port + 4 * number_of_drones] which must be a free block of ports that can be allocated to mavros->ROS/Gazebo interactions. Something like 9000 or 10000 usually works well here.
- Note for future: After investigating more recent changes to PX4 Firmware, it looks like it is buggy on the port assignments. They are moving towards a single, unified vehicle startup model, which would require modifications to Firmware/ROMFS/px4fmu_common/init.d-posix/rcS to properly assign ports.
When running simulation, it is possible to tap into ROS topics to see what is happening in the system:
rostopic list
rostopic echo <topic_name>
(ctrl+c to exit)
ROS Topics
- mavros/state - tells current flight mode of the drone [https://dev.px4.io/en/concept/flight_modes.html]
- droneObj - custom topic that tells drone the next objective in LLA format
- mavros/global_position/global - GPS information
- mavros/setpoint_position/global - tells drone where to go in LLA
- PX4 does not have LLA setpoint function. this topic will take in LLA format and translate it into x,y,z format and send to FCU. However I encountered a problem with the time stamp safty feature, I managed to get it working after removing such safty feature in the source code then rebuild mavros.
- In "~/catkin_ws/src/mavros/mavros/src/plugins/setpoint_position.cpp" at line 225 remove the if-else statement and just let it call "send_position_target(req->header.stamp, sp);" rebuild mavros by running "catkin build" in "~/catkin_ws"
Services
- mavros/cmd/arming - arm the drone
- mavros/set_mode - set the current flight mode