ROS2 Gazebo Simulation for the Crazyflie

This project is based on the Gazebo Simulation for Crazyflie CRTP sim_cf from https://github.com/wuwushrek/sim_cf

It features

• Full software-in-the-loop (SITL) Crazyflie firmware implementation utilizing the FreeRTOS Linux Port https://www.freertos.org/FreeRTOS-simulator-for-Linux.html#SimulatorApp
• Compatibility with the Crazyflie python library (cflib)
• Integration of the Crazyflie firmware for SITL build process into KBuild
• Build for ROS2 and Gazebo 11

In contrast to the original sim_cf, hardware-in-the-loop (HITL) is not supported.

Beside this ROS2 package you will need

• Crazyflie firmware with modifications for SITL https://github.com/CrazyflieTHI/crazyflie-firmware
• Crazyflie python library with additional simlink driver https://github.com/CrazyflieTHI/crazyflie-lib-python

Installation - Ubuntu 22.04 with ROS2 Humble and Gazebo 11

Tested on an Ubuntu 22.04 LTS machine

Dependencies

Basic dependencies

sudo apt-get install cmake build-essential genromfs ninja-build

Protobuf, eigen3 and google-glog dependencies

sudo apt-get install protobuf-compiler libgoogle-glog-dev libeigen3-dev libxml2-utils

Cyclone DDS

sudo apt install ros-humble-rmw-cyclonedds-cpp

Xacro library

sudo apt install ros-humble-xacro

Additional ROS2 Packages

Clone ROS2 version of mav_comm into your colcon overlay (assuming ~/dev_ws)

cd ~/dev_ws/src

git clone https://github.com/CrazyflieTHI/mav_comm.git

Build the Packages

Move into your colcon overlay (assuming ~/dev_ws) and use colcon build

cd ~/dev_ws

colcon build

Setting Up the Simulation

Running the simulation requires

• sim_cf2 package built
• Crazyflie firmware compiled for SITL
• Crazyflie python library installed containing the simlink driver

Adjust the Launch Script

The number of simulated Crazyflies is determined by the main launch file main.launch.xml in the sim_cf2/launch folder. By default, two Crazyflies are simulated and code for the instantiation of four further Crazyflies is present but commented out. Adjust the launch file to your needs by adding or removing Crazyflies. Initial pose and rotor color is set in the main.launch.xml file.

Run the Simulation

1. Start Gazebo

Open a terminal and source the ROS2 workspace if not done already (assuming the overlay or workspace in ~/dev_ws)

source ~/dev_ws/install/local_setup.bash

Use the ROS2 launch command to start the sim_cf2 simulation

ros2 launch sim_cf2 main.launch.xml

Gazebo will start in paused mode and will try to establish a connection to the software-in-the-loop Crazyflie firmware instances.

2. Run Crazyflie Firmware SITL Instances

Open a new terminal and move to the scripts/sim_cf2 folder in the Crazyflie firmware repository (assuming ~/repos/crazyflie-firmware)

cd ~/repos/crazyflie-firmware/scripts/sim_cf2

Run the run_cfs.sh script with as many instances of simulated Crazyflies as needed by providing the amount of Crazyflies as argument (e.g. two)

./run_cfs.sh 2

The SITL instances will establish a connection to Gazebo

Press PLAY in Gazebo

3. Run a Python Script

Start your cflib-based python script with activated simlink driver. Example scripts can be found in the Crazyflie python library https://github.com/CrazyflieTHI/crazyflie-lib-python/tree/master/examples/sim_cf2

Run for example the autonomousSequence.py script

python autonomousSequence.py

4. Exit Gazebo and SITL

Press Ctrl+C in the terminals running Gazebo and the SITL instances

Processes should get killed and POSIX message queues should get deleted. If POSIX message queues are not deleted due to errors, they eventually may cause issues when starting the simulation again. The queues are located in /dev/mqueue

If problems occur, delete the queues manually

Show queues

ls /dev/mqueue

Delete the queues

sudo rm /dev/mqueue/<sim_cf2_queues>

Experimental Multi-Ranger Deck

An experimental Multi-ranger deck can be used in the simulation. It consists of four Hokuyo range sensors mounted on a rigid platform attached on top of the Crazyflie.

Enable the Multi-ranger Deck

To use the Multi-ranger deck, enable it in the main.launch.xml file for every Crazyflie individually.

<arg name="enable_mr_deck_1" default="true" />
<arg name="mr_deck_visualize_1" default="true" />

By setting mr_deck_visualize_ to true the laser ray will be visualized.

Run Wall Following Example

With the simulated Multi-ranger deck, Bitcraze's wall following example can be run. Load a world that contains walls, such as lab_aux.world, by specifying the world name in start_gazebo_world.launch.py

def generate_launch_description():
    world_file_name = 'lab_aux.world' # Select world from worlds folder
    package_name = "sim_cf2"
    ...

A slightly modified version of the wall following example script is located in https://github.com/CrazyflieTHI/crazyflie-lib-python/tree/master/examples/sim_cf2

Start the Gazebo Simulation, an instance of the firmware SITL and run the example.