CrazySim: A Software-in-the-Loop Simulator for the Crazyflie

2024-04-15 | Christian Llanes | Leave a comment

This week we have a guest blogpost by Christian Llanes, a Robotics PhD of from Formal Methods & Autonomous Control of Transportation Systems Lab of the Georgia Institute of Technology. Enjoy!

Why do we need simulators?

Simulators are one of the most important tools used in robotics research. They usually are designed for different purposes with different levels of complexity. For example, simulators with low computational overhead that are parallelizable are mainly used for either training reinforcement learning algorithms or Monte Carlo sampling for verification of task completion in a nondeterministic environment. Some simulators also use rendering engines for the graphical display of models and the environment or when cameras are intended to be used in the robotics platform. Simulation is also useful for the development and deployment of new robotics firmware features where the firmware is compiled on a test machine and run in the loop with a simulated sensor suite. This simulator configuration is known as software-in-the-loop (SITL) because the vehicle firmware is intended to be run in the loop with the simulated vehicle physics and/or rendering engine. This feature is supported by autopilot suites such as PX4, ArduPilot, CogniPilot, and BetaFlight. This feature is not officially supported yet for Crazyflies because it requires a large overhaul of the firmware to be able to compile on a desktop machine and interact with different simulators such as Gazebo, Webots, PyBullet, CoppeliaSim, Isaac Sim, or Unreal Engine.

CrazySim

Last summer I began working with Crazyflies and noticed this Crazyflie simulator gap. I stumbled on a community-developed project for Crazyflie SITL called sim_cf. This project is exactly what I was looking for. However, the firmware used by the project is from July 2019 and the official firmware has had over 2000 commits made since then. The project also uses ROS 1, Gazebo Classic, and doesn’t support the Crazyflie Python library (CFLib). Using this project as a starting point I set out to develop CrazySim–a Crazyflie SITL project that doesn’t require ROS, uses Gazebo Sim, and supports connectivity through CFLib. Using CFLib we can connect the simulator to external software such as Crazyswarm2 or the Crazyflie ground station client. Users test their control algorithms in the external software using the simulator interface before deploying to real flight hardware.

Using the Crazyflie Client for PID Tuning

We have also provided a modified Crazyflie client for CrazySim support. The Crazyflie client is a cool tool for testing a single drone in hardware. We can perform command based flight control, look at real time plots, save log data, and tune PID values in real time. The PID values are typically tuned for an out of the box Crazyflie. However, when we modify the Crazyflie and add extra weight through batteries, decks, and upgraded thrust motors then the behavior of the Crazyflie will change. If a user wants to tune a custom Crazyflie setup, then they can add additional models in this folder with their own motor and mass properties. Then they just need to add it to the list of supported models in either of the launch scripts. There is already an example model for the thrust upgrade bundle. Documentation for installing the custom client can be found here.

PID tuning a simulated Crazyflie using CrazySim on the Crazyflie PC client.

Crazyswarm2

We can now connect to the simulated Crazyflie firmware using CFLib. Therefore, we can set up a ROS 2 interface through Crazyswarm2 for swarm command and control through ROS 2 topics and services. To do this we first startup the drones using any of the launch scripts.

bash tools/crazyflie-simulation/simulator_files/gazebo/launch/sitl_multiagent_square.sh -n 16 -m crazyflie

Then, we bring up Crazyswarm2 after setting up the configuration file for the number of drones chosen.

ros2 launch crazyflie launch.py backend:=cflib

We demonstrate an example of how we can control a swarm of drones using Crazyswarm2 GoTo service commands.

Crazyswarm2 GoTo service commands using CrazySim.

ICRA 2024

CrazySim is also being presented as a paper at the 2024 IEEE International Conference on Robotics and Automation in Yokohama, Japan. If you are attending this conference and are interested in this work, then I invite you to my presentation and let me know that you are coming from this blog post after. For the paper, I created a multi agent decentralized model predictive controller (MPC) case study on ROS 2 to demonstrate the CrazySim simulation to hardware deployment workflow. Simulating larger swarms with MPC may require a high performance computer. The simulations in this work were performed on an AMD Ryzen 9 5950X desktop processor.

Links

Other Crazyflie SITL projects:

Diversity Scholarship ROSCon 2024

2024-03-11 | Kimberly McGuire | 2 Comments

This week it will be a bit of a different blogpost than you are used to read from us. Usually we talk about cool prototypes, explain bits and pieces from the Bitcraze ecosystem or let external parties/researchers show case their awesome work that they’ve done on the Crazyflie. Today’s blogpost will be more about a societal topic that plays a big part within the robotics world: diversity! Bitcraze is helping out with the Diversity Scholarship of this year’s ROSCon, which we’d like to advertise about, but is also complimented by some words about diversity in robotics and how this topic is reflected upon within Bitcraze itself.

Diversity & Robotics

It’s widely acknowledged that the field of robotics lacks diversity. While there have been improvements, significant underrepresented groups remain, including women, individuals in LGBTQIA+ communities, people with disabilities, and those from racial and/or ethnic minorities. There are some interesting communities to look into if you are part of these groups yourself. However, if you know of any other ones that are interesting, of course, let us know.

Women in Robotics: https://www.womeninrobotics.org/
Women in AI and Robotics https://www.womeninairobotics.de/
Women of Open Source: https://womenofopensource.org/
Women and Drones: https://womenanddrones.com/
IEEE Women in Engineering: https://wie.ieee.org/
Black in robotics: https://blackinrobotics.org/

Other than these earlier mentioned groups, we do not regard ourselves as the absolute expert on diversity in robotics, but we have perhaps a simple but interesting statistic to share from our experience. We usually receive requests for guest blog posts on our website from external researchers and engineers looking to showcase their work with the Crazyflie. We thought it would be interesting to graph the gender distribution of these guest bloggers:

*Gender of our guest blogposters on bitcraze.io*

As you may have noticed, before 2020, all of our guest bloggers were male, and only in recent years has that changed. It’s also worth mentioning that to our knowledge, none of the bloggers has openly identified as anything other than cis-gender male or female. While this shift represents progress, it’s important to acknowledge that there is still room for improvement. Additionally, it is essential to recognize that this tiny statistic does not fully reflect the diversity of the robotics community but rather (perhaps) pertains to a specific subset, such as aerial robotics.

Diversity & Bitcraze

So let me just cut to the chase, Bitcraze is a very small company with currently only 6 full-time employees. Currently, we don’t have any formal policies on hiring and promoting diversity. However, we do have a very open culture within the company where we can discuss these topics at our coffee breaks without restrictions or judgment. There is a genuine interest in sharing and discussing negative experiences related to the lack of diversity at previous workplaces, so we do talk about it a lot.

In terms of our impact internally and externally, for now, we don’t come across enough hiring opportunities to implement diversity policies. We can perhaps also invite more diverse guest bloggers to contribute to our website, or make our developer meetings more welcoming. However, there is only a limited influence that we can exert here with our small company. Therefore, the choice to support other communities we love to improve diversity is perhaps the most we can do to contribute to this cause.

We are already involved in the ROS community by helping out with the ROS aerial community working group (blogpost1, blogpost2) and we loved the atmosphere during ROSCon when we were in Kyoto. When the opportunity arrived to be a co-chair of the diversity committee of ROSCon 2024, together with Belén Torres from Wymaq, we gladly took it and are hoping that is were we can make more of a difference.

Diversity Scholarship at ROSCon 2024

This year’s ROSCon will be held in Odense, Denmark, between October 21st and 23rd. Since 2016, the ROSCon organization has launched a diversity scholarship opportunity, and this year’s event is expected to be the biggest one yet. Individuals belonging to the underrepresented groups in robotics, as mentioned earlier, are invited to apply for the scholarship. The deadline is April 5th, so please don’t wait too long to apply. Check here for the ROS discourse post and here for the diversity scholarship application on the ROSCon website.

Developer and Aerial ROS meetings so far

2023-08-07 | Kimberly McGuire | Leave a comment

As of this year around March/April we started with both Bitcraze developer meetings and Aerial-ROS meetings (the latter in collaboration with Dronecode Foundation). Now that summer is around and our office is a bit empty, we had a bit of a summer break, however we will start the meetings back up again soon! The next ROS-aerial meeting will be on the 16th of August and we will also have a Bitcraze developer meeting planned on the Wednesday the 6th of September (keep an eye on our announcements in discussions). In this blogpost we like to take the opportunity to show an overview of the meetings we had so far.

Aerial ROS meetings

In March we started a [ROS community working group] for aerial Vehicles together with our friends at Dronecode foundation, aka Aerial-ROS! We have biweekly meetings with some standard discussion meetings (with a topic) and with an invited guest presentation.

Here are the discussion topic meetings we had:

Tue March 21: First explorative meeting
Wed April 26: Startup meeting – Autonomy
May 24 : Discussion: Tutorials and Education
Wed June 21 : Swarming

And we had several guest speakers as well! Like Miguel Fernandez-Cortizas from CAR-UPM talking about Aerostack2:

ROS-aerial Meeting guest presentation about Aerostack2

Then we had a guest presentation from Gerald Peklar from NXP talking about the Drones4Bats project:

ROS-aerial Meeting guest presentation about Drones4Bats

And the last before the summer was from Alejandro Hernández Cordero (Open Robotics Consultant) about the ROS2 Project Vehicle Gateway.

ROS-aerial Meeting guest presentation about Vehicle Gateway

The next meeting for ROS-aerial is planned on the 16th of August. Keep an eye on the ROS discourse forum.

Bitcraze Developer Meetings

We already had a couple of developer meetings before but we started recording them since April. The first recorded one was about the loco positioning system. Here first we gave a presentation about the system itself, with the latest developments cooking in our pot and time for questions afterwards.

Dev meeting about Loco positioning.

Then we had a meeting about the development of safety features in the Crazyflie in light of the Bolt developments:

Bitcraze Dev meeting about Safety features.

Then we had a meeting where Kristoffer highlighted the autonomous swarm demo we showed at ICRA 2023.

Bitcraze dev meeting about the autonomous swarm demo

And the last before the summer holiday, we had a meeting where Kimberly explained about the Crazyflie simulationmodel intergrated into Webots

Bitcraze Dev meeting about Simulation

We are still planning to have developer meeting every first wednesday of the month starting with September 6th (keep an eye on our announcements in discussions).

EPFL 101 Crazyflie presentation

Oh yeah, by the way, we also were invited by the EPFL-lis lab to give another Crazyflie 101 presentation in Lausanne last April! We made a prerecording of it so you can check it out right here:

EPFL LIS crazyflie 101 presentation.

See you all after summer!

Online courses in Aerial Robotics

2023-07-03 | Kimberly McGuire | Leave a comment

In our ROS-aerial community working group, we had a meeting a few weeks ago to discuss education and tutorials within Aerial Robotics (see the ROS discourse thread here). The general conclusion was that there should be more courses and tutorials since the learning curve is too steep. But… is that actually the case? According to a LinkedIn post by Kimberly, asking for suggestions, we found out that might not be true! There are loads of tutorials out there! So in this blog post, we will provide an overview of the suggested tutorials and the ones that have materials available online.

Stable diffusion with prompt ‘A drone flying in front of a school blackboard’

Online books

One of the first suggestions was to explore the online free book titled ‘Small Unmanned Aircraft: Theory and Practice.’ This book has been written by Randy Beard and Tim McLain of Brigham Young University, and it covers everything from the absolute basics of coordinate frames and quadrotor dynamics to path planning and cameras. It is a must-read for anybody starting in UAVs and Aerial robotics.

The physical book can be found here: http://press.princeton.edu/titles/9632.html

The available PDFs can be accessed on GitHub: https://github.com/randybeard/uavbook“

Courses specified on Aerial Robotics

Here are some suggestions for courses specifically focused on Aerial Robotics. These received the most recommendations! Many universities have made their courses available online, accessible to anyone interested.

Coursera offers the ‘Robotics: Aerial Robotics’ course as part of the Robotics specialization. Taught by Prof. Vijay Kumar from Penn University, this 4-week course covers the mechanics and control of aerial vehicles using Matlab. It starts from 1 dimension and gradually progresses to the 3rd dimension in simulation. The course is part of a paid educational program, but you can audit the lessons for free.

Link: https://www.coursera.org/learn/robotics-flight

Udacity has been offering a course on Aerial Vehicles for quite some time. The lessons are taught by top names in the industry and cover key aspects of Aerial Robotics, such as motion planning, controls, and estimation, with lab assignments involving a real drone. The course duration is 4 months, and access is available for a fee.

Link: https://www.udacity.com/course/flying-car-nanodegree–nd787

The University of Maryland offers a course on Autonomous Aerial Robotics, making all videos, slides, and assignments available. Taught by Nitin J. Sanket and Chahat Deep Singh, the course covers everything from basic control and dynamics to full autonomy. It’s a comprehensive resource for aerial robotics. The course utilizes the Parrot Bebop 2.0, and while a Mocap system is required, you may explore the possibility of adapting the course to a different platform.

Link: http://prg.cs.umd.edu/enae788m

Additionally, there’s the course ‘Applied Control System 3: UAV Drone (3D Dynamics & Control)’ which is part of a series by Mark Misin. This course delves deep into the dynamics, control, and modeling of quadrotors.

Link: https://www.udemy.com/course/applied-control-systems-for-engineers-2-uav-drone-control/

Courses specified on Robotics applied to UAVs

Here are some suggestions for courses that focus on robotics but utilize UAVs/drones to demonstrate the implementation of the studied materials.

‘Visual Navigation For Autonomous Vehicles’ is a course available on MIT Open Courseware, taught by Prof. Luca Carlone. As the name implies, the course primarily focuses on autonomous navigation for any autonomous vehicle. It includes exercises where students implement vision algorithms on both ground robots and drones. Additionally, the course covers working with ROS and applying the knowledge to a simulated drone in Unity.

Link: https://ocw.mit.edu/courses/16-485-visual-navigation-for-autonomous-vehicles-vnav-fall-2020/

The ‘Bio-inspired Robotics’ course at the University of Washington, led by Prof. Sawyer Fuller, explores the realm of drawing inspiration from nature rather than reinventing the wheel. It covers various robots inspired by creatures capable of swimming, walking, hopping, and of course, flying. Lab assignments in this course involve working with a Crazyflie drone.

Link: https://faculty.washington.edu/minster/bio_inspired_robotics/

Brown University offers a course called ‘Introduction to Robotics,’ taught by Prof. Stefanie Tellix. While the introduction covers generic robotics, the focus of the full course is on building and programming the Duckiedrone. The course dives straight into autonomy and also teaches students how to work with ROS.

Link: https://cs.brown.edu/courses/cs1951r/

Update (4th of July)

Princeton University (see this blogpost) have also decided to release their ‘Intro to Robotics’ lectures and materials for the public. Can’t believe I forgot this one!

Link: https://irom-lab.princeton.edu/intro-to-robotics/

Youtube tutorials

If you’d like to start hands-on right away, here are a couple of suggestions for YouTube tutorials or series about aerial robotics.

Drone Programming with Python: This popular tutorial/course teaches viewers how to program a real drone using Python with the DJI Tello. It offers a great opportunity for anyone looking for a short and enjoyable project to undertake, especially on a rainy day, while still working with a real platform.

Link: https://youtu.be/LmEcyQnfpDA

Intelligent Quads YouTube Channel: This channel is entirely dedicated to creating autonomous UAVs, covering topics from Ardupilot to MAVlink to ROS and Gazebo. It appears to be a valuable resource for beginners in the field of autonomous UAVs.

Link: https://www.youtube.com/@IntelligentQuads

But wait, there is more!

There are some extra recourses for you to also take a look at.

University of Twente UAV Centre: The University of Twente has created a portal with a variety of UAV-related courses. You can find a wealth of information and educational materials on their website. Link: https://www.itc.nl/facilities/centres-of-expertise/uav-centre/

Self-Driving Car Specialization: If you are interested in learning more about SLAM (Simultaneous Localization and Mapping) and sensors, this specialization is tailored for self-driving cars but the theory can be useful for drones as well. Link: https://www.coursera.org/specializations/self-driving-cars

Autonomous Navigation for Flying Robots: This older course is still highly relevant for anyone interested in autonomous navigation for flying robots. It offers valuable insights and knowledge. Link: https://www.edx.org/course/autonomous-navigation-for-flying-robots

Drone Dojo: For those looking to build their own drones, Drone Dojo provides useful instructions and courses to get started on DIY drone projects. Link: https://dojofordrones.com/

Bachelor Majors in UAV Engineering: If you are fully committed to pursuing a career in aerial robotics, both Embry-Riddle Aeronautical University and the University of North Dakota offer full bachelor’s majors in becoming a UAV engineer. Embry-Riddle Aeronautical University: https://erau.edu/degrees/bachelor/unmanned-aircraft-systems University of North Dakota: https://und.edu/programs/unmanned-aircraft-system-operations-bs-aero/

To conclude

Indeed, it appears that there are plenty of courses and tutorials available for people interested in getting started with aerial robotics. The range of resources is vast, and it’s possible that we might still be missing some, which could lead to a part 2 of this blog post in the future! And perhaps also we would need to delve into these to see why the learning curve is considered steep. However, aerial robotics is not an easy subject anyway so perhaps it is good to start from the basics. Nevertheless, this compilation should provide a solid starting point for anyone eager to delve into the world of aerial robotics. A major thank you to everyone who has contributed so far (linked to in the original LinkedIn post); your valuable input has made this possible!

ICRA 2023

2023-05-29 | Kristoffer Richardsson | Leave a comment

As mentioned in a previous blog post, we have a both at ICRA in London this week. If you are there too, come and visit us in booth H10 and tell us what you are working on!

Barbara and Arnaud is getting the booth ready

We are showing our live autonomous demo and our products in the booth, including the flapping drone Flapper Nimble, don’t miss it!

The autonomous demo

The decentralized autonomous demo that we are showing is based on technologies in the Crazyflie ecosystem. The general outline is that Crazyflies are autonomously flying in randomized patterns without colliding. The main features are:

Positioning using the Lighthouse positioning system, all positioning estimation is done in the drone. The Lighthouse positioning system provides high accuracy and ease of use.

Communication is all peer-to-peer, no centralized functionality. Each Crazyflie is transmitting information about its state and position to the other peers, to enable them to act properly.

Collision avoidance using the on-board system without central planing. Based on the position of the other peers, each Crazyflie avoids collisions by modifying its current trajectory.

Wireless charging using the Qi-deck. When running out of battery, the Crazyflies go back to their charging pads for an automatic re-fill.

The App framework is used to implement the demo. The app framework provides an easy way of writing and maintaining user code that runs in the Crazyflie.

We are happy to answer any questions on how the technology works and implementation details. You can also read more about the demo in the original blog post by Marios.

Developer meeting

The next developer meeting is next week, Wed June 7 15:00 CEST and the topic will be the demo and how it is implemented. If you want to know about any specific technologies we used, how it is implemented or if you are just curious about the demo in general, please join the developer meeting. We will start with a presentation of the different parts of the demo, and after that a Q&A. As always we will end up with a section where you can ask any question you like related to our ecosystem. Checkout this announcement on our discussion platform for information on how to join.

Adding Wings to ROS: Forming an Aerial Robotics Community Working Group

2023-05-22 | Kimberly McGuire | Leave a comment

If you have been following the ROS Discourse on a regular basis, you might have seen a bit more activity on the Aerial Vehicles category than usual. We very recently started an Aerial Robotics Working Group in collaboration with Dronecode Foundation! It will be a community-driven working group initially, but we will hold biweekly meetings on Wednesday at 2:00 PM UTC, and build up a community members and gather information on the ROS Aerial community’s Github organization. This blogpost aims to explain how this working group came to light, what our current plans are and how you can participate.

How did it all begin?

There are actually quite some aerial enthusiasts out there dwelling in the ROS crowd, which became evident when 20-30 people showed up at the impromptu ROScon 2022 aerial roboticists meetup. This was also our first experience with ROScon as Bitcraze, and I (Kimberly) absolutely loved it. The idea popped to be able to be more active in the amazing ROS community, which we started doing with helping out more with the Crazyswarm2 project (see this blogpost) and giving a presentation about it as well. However, we did notice that there wasn’t as much online chatter about Aerial Vehicles on the ROS communication channels. Yes, the Embedded ROS working group led by eProsima (responsible for MicroROS) has done some really cool demos with Crazyflies! And the same goes for any other aerial project, that has probably contributed to some of the other staple projects like NAV2. But there aren’t any working groups that are specific for aerial robotics.

Since PX4 led by Dronecode foundation had similar ambitions to be emerged into the ROS family, since we met in person at the very same ROScon last year, we started talking about possibly starting up a working group. This started with us reaching out to the ROS community for interest with this ROS discourse post and after 25 and more replies, the obvious thing was to set up an first explorative meeting. About 30 people showed up to this, so the message was clear: yes, there is a demand for guidance, structure, and information in the ROS community regarding aerial robotics. Thus, the aerial robotics working group was born!

Current state and plans

One of the observed issues is that we have noticed that is happening is that there there are numerous projects and information about aerial robotics, and perhaps too much. That is because aerial robotics consists of a huge variety of robotic systems in different forms like multicopters or even monocopters (like in the blogpost here) but also hybrid VTOL vehicles, mini blimps (for example this hack we done) and so many more. But as you probably know, aerial vehicles come with their own set of challenges that distinguish them from ground robots, like instability, aerodynamics, and limitations related to their lift capabilities. Therefore, it offers an interesting platform for control theory, autonomy, and swarming and as a result several ROS-related projects have emerged, such as Crazyswarm2, Aerostack2, Kumar Robotics Autonomy Stack and, Agilicious. Moreover, even though a standard ROS interface for aerial robotics has been created some years ago, it has not been enforced or updated since. And also, although courses and tutorials can be found here and there scattered around on multiple projects and autopilot websites to get started with aerial robotics in ROS, but many have found the learning curve to be quite steep and usually don’t know where to start.

Due to the vast amount of systems, software, projects and information out there, we decided to gather all this information in one centralized location as an Aerial Robotics landscape instead of scattering it across various aerial robotics resources, of which we have created a simple repository with markdown files. The idea is to fill this in little by little by info that we get from the working group discussions or other input of users, or research done by ourselves. For that, we will facilitate biweekly meetings, where users will present about their project (like our last meeting about Aerostack 2) or where we engage in discussions on various aerial robotics topics (like Aerial Autonomy stacks in the startup meeting).

Future ambitions

Currently, we don’t have a specific end goal or main project in mind, as we are right at the start of the first discussions and information gathering. That is also why it will be considered a ‘community driven’ working group after some emails back and forth with Open Robotics Foundation, until we reach a stage where the landscape is adequately developed to establish specific development goals. and set up various subprojects for communication, autonomy, platforms and/or education. Additionally, incorporating direct communication protocols within swarms could be of interest, as these are a common use case within aerial robotics. Once we have established more specific development goals, we can apply to be an official ROS working group, and collaborate with other workgroups on overlapping projects. From our perspective, it would be more beneficial for the ROS ecosystem not to create a standalone aerial stack, but enhance the integration of other stacks with aerial vehicles.

Join us!

Currently I (Kimberly) representing Bitcraze and Ramon Roche from Dronecode Foundation will be in the ‘lead’ of the Aerial working group, although we prefer to act as facilitators rather than imposing our own direction. We will try our best not to geek out too much on PX4 and/or Crazyflies alone, so therefore anybody’s input will be crucial! So if you’d like to levitate ROS to new heights, come and join our meetings! Our next meeting is scheduled for Wednesday the 24th of May (2 pm UTC), and you can find the information on this ROS Discourse thread. We hope to see you there!