ROS 2 with SITL

After the ROS2 environment, Micro-XRCE-DDS-Gen and the ROS2 package micro-ROS-Agent are correctly installed following Install ROS2, you still need to build the simulator of Ardupilot to launch SITL in ROS2.

The simulator will be built from the source code in the ardu_ws/src/ardupilot that is cloned in Installation (Ubuntu).

You need to install the ArduPilot dependencies first.

cd ardu_ws/src/ardupilot
./Tools/environment_install/install-prereqs-ubuntu.sh -y

Then, build Ardupilot for SITL with DDS enabled. The example below shows how to build the copter firmware, but you can replace copter with plane, rover, etc.

You can build the ROS2 packages ardupilot_msgs, micro_ros_agent, ardupilot_sitl and ardupilot_dds_tests as

cd ardu_ws/
colcon build --packages-up-to ardupilot_sitl

Then, source your workspace

cd ~/ardu_ws
source ./install/setup.bash

and you are able to launch the SITL in ROS2 with the following command

source /opt/ros/humble/setup.bash
cd ~/ardu_ws/
colcon build --packages-up-to ardupilot_sitl
source install/setup.bash
ros2 launch ardupilot_sitl sitl_dds_udp.launch.py \
transport:=udp4 \
refs:=$(ros2 pkg prefix ardupilot_sitl)/share/ardupilot_sitl/config/dds_xrce_profile.xml \
synthetic_clock:=True \
wipe:=False \
model:=quad \
speedup:=1 \
slave:=0 \
instance:=0 \
defaults:=$(ros2 pkg prefix ardupilot_sitl)/share/ardupilot_sitl/config/default_params/copter.parm,$(ros2 pkg prefix ardupilot_sitl)/share/ardupilot_sitl/config/default_params/dds_udp.parm \
sim_address:=127.0.0.1 \
master:=tcp:127.0.0.1:5760 \
sitl:=127.0.0.1:5501

More modules of mavproxy such as map and console can be added in the above command. For example, map:=True console:=True.

It launches three three processes:

  • micro-ROS-Agent is a wrapper around Micro-XRCE-DDS-Agent and provides connection to ROS2

  • ardupilot_sitl is a ROS2 package that start the SITL binary connected to ROS2 through micro-ROS-Agent

  • mavproxy is a GCS that connects to SITL through the MAVLink protocol

For more information refer to ardupilot/Tools/ros2/README.md. There you can find examples of launches using serial connection instead of udp, as well as a step-by-step breakdown of what the launch files are doing.

ROS 2 CLI

Once everything is running, you can now interact with ArduPilot through the ROS 2 CLI.

source ~/ardu_ws/install/setup.bash
# See the node appear in the ROS graph
ros2 node list
# See which topics are exposed by the node
ros2 node info /ap
# Echo a topic published from ArduPilot
ros2 topic echo /ap/geopose/filtered

DDS is responsible for ROS2 communication. If the ROS2 topics are not published, first check if DDS_ENABLE is set to 1 or not. If not, set as 1. It can be done through Mission Planner, QGroundControl, or the commands in mavproxy as below, then reboot the launch.

export PATH=$PATH:~/ardu_ws/src/ardupilot/Tools/autotest
# a Copter is simulated in this example, but you can replace it with Plane, Rover, etc.
sim_vehicle.py -w -v ArduCopter --console -DG --enable-DDS

param set DDS_ENABLE 1

The second aspect to check, ensure the ArduPilot parameter DDS_DOMAIN_ID matches your environment variable ROS_DOMAIN_ID.The default is 0 for ArduPilot, which corresponds to the environment variable being unset. You may need to relaunch the SITL after changing the parameters.

MAVProxy

To test and fly around, you can launch a mavproxy instance in yet another terminal:

mavproxy.py --console --map --aircraft test --master=:14550

Next up

Add Gazebo in ROS 2 with Gazebo