MRS-Crazyflies

This ROS2 package contains adapted configuration files and launch files from CrazySim, that should be used in the 2nd part of the MRS Project for the simulation part.

Simulation part is run in physics simulator Gazebo Ignition and used ROS2 packages are based on CrazySwarm2

Installation

Again, there are two ways you can set up your computer to run the simulation:

1. Using Docker (recommended!!!)
2. If you already have ROS2 installed and having hard time using docker on your laptop.

1) Docker installation (recommended!!!)

Clone the repository:

git clone https://github.com/larics/docker_files.git

And follow the setup instructions on this link. This docker automatically clones and builds ROS2 mrs_crazyflies package.

2) Manual installation (if you already have ROS2 installed)

We are assuming that you have ROS2 Humble installed.

Please follow the instructions given on the CrazySim page to setup simulation. Additionally check for aliases script: https://github.com/larics/docker_files/tree/ros-humble-cf/ros2/ros2-humble/crazyflies/to_copy and README in this repository which might come in handy.

The folder structure of this package is:

1. maps - it contains .bmp and .yaml files that are used in map server.
2. worlds - here are located .sdf files and 3D models based on the 2D files in folder maps.
3. scripts - additional node for static transformation broadcaster from world to odom is there.
4. launch - it contains file to launch gazebo simulation with crazyflies (sitl_multiagent_text.sh) with the initial poses from file in folder drone spawn list, launch file to start map server(map_server_launch.py) and launch file which starts crazyflies server, rviz and nodes for publishing velocity to crazyflies.
5. config - here is the configuration file for rviz and the main yaml file for crazyflies server
6. startup - it contains the example of starting the simulation and ROS2 nodes.

Topics and services

Velocity commands are published on /cf_x/cmd_vel to crazyflie cf_x. Odometry can be obatined from the topic /cf_x/odom . Pose can also be obtained from the topic /cf_x/pose and velocity from /cf_x/velocity, just keep in mind that for this topic message type is not Twist. To take off/land you can call services /cf_x/takeoff, /cf_x/land. Current vel_mux.py does takeoff automatically, after the first cmd_vel command, but you can call it on your own.

Test the simulation

Note

Within MRS docker, the mrs_crazyflies package is located in /root/CrazySim/ros2_ws/src/. All folders and files mentioned later in these instructions are located inside the package In docker, there is an alias cd_mrs_crazyflies which changes the directory to this package.

This example showcases how to run the simulation using sessions, tmuxinator and environment variables. You do not need to use this format if you do not find it useful.

To run the example, navigate to startup folder and run:

./start.sh

It will open one window with several panes.

1. The first pane starts the gazebo simulation:

 bash /path-to-workspace/ros2_ws/src/mrs_crazyflies/launch/sitl_multiagent_text.sh -m crazyflie -f $SPAWN_POSE_DOC -w $ENV_NAME

Please notice that an example assumes that the installation is done in the docker. If you didn't use docker, you may have different path. Bash script that starts gazebo requires several arguments -m is for the model. Please always use crazyflie. -f stands for the .txt file with the x and y iniitial positions for each crazyflie. The example for 4 crazyflies is given in the folder launch/drone_spawn_list (feel free to add yours here) and -w requires the world name which can be found in the worlds folder.

The environment variables $SPAWN_POSE_DOC and $ENV_NAME, alongside the $NUM_ROB, which defines number of robots, are located in mrs_example_setup.sh. This file should be sourced, alongside ros2 workspaces before (alias: ros2_ws and source_ros2) - check out pre_window in session.yml. :)

2. In the second pane (up right), ROS2 crazyflies server, rviz and crazyflie nodes that publish cmd_vel, are started.

 waitForCfGazebo;sleep 5; ros2 launch mrs_crazyflies cf_velmux_launch.py

The shell function waitForCfGazebo waits until crazyflies are spwaned in gazebo plus additional 5 seconds of sleep, just in case, to have enough time to start. It can be found in to_copy aliases (in docker it is copied to /root/.bash_aliases).

Crazyflies server takes the data from crazyflies_mrs.yaml. For more info please read about: CrazySim and CrazySwarm2.

Please keep in mind that the variable $NUM_ROB should correspond to the number of enabled crazyflies in the crazyflies_mrs.yaml and the number of rows in the $SPAWN_POSE_DOC also, otherwise the server won't be able to connect with gazebo. Also initial positions in $SPAWN_POSE_DOC should correspond to the ones in crazyflies_mrs.yaml. Feel free to change them according to your task.

If you are waiting in this second pane, and it doesn't say that 'All Crazyflies loggging are initialized', please check this issue and its solution. Just keep in mind that world (.sdf) files that you need to adapt are in this package's world directory.

3. The third pane (bottom left) starts the map server

waitForCfGazebo; ros2 launch mrs_crazyflies map_server_launch.py map_yaml:=/root/CrazySim/ros2_ws/src/mrs_crazyflies/maps/$ENV_NAME/$ENV_NAME.yaml

4. The fourth pane (bottom right) is given as an example to test if crazyflie cf_1 is moving.

The command is stored in history, so you need to move in that pane, press up arrow, and press enter, when everything else is already on.

history -s "ros2 run teleop_twist_keyboard teleop_twist_keyboard --ros-args --remap cmd_vel:=/cf_1/cmd_vel"

After killing the session using ctrl+b, k, there might be some ros2 nodes running in the background, please do the command: kill_ros2, which will kill all ros2 processes running, it is defined in .bash_aliases. Keep this in mind when starting next session. :)

Working on your project

For developing your solution, you can either create a new package, or you can continue to work in this package. You can write your code in Python or C++.

Feel free to add more windows or to create your own setups and sessions. :)