If you know a little about Sweden, you know about Midsommar. Nothing like the 2019 horror film (thankfully), though we do wear flower crowns and dance around the pole. It’s usually an occasion to celebrate with family (and alcohol) those long days and short nights. We actually celebrated a little bit early today with a nice team barbecue.
Midsommar is next Friday, and it marks the official kickoff to summer here in Sweden. That also means that for the coming 2 months, Bitcraze will be operating with a slightly smaller team. So, what does that mean for you? This should not impact you too much, of course, but here are the most important things to note:
Developer Meetings: First up, our regular developer meetings will be on hiatus during July and August. It’s a great time for everyone, including you, our regular attendees, to take a breather. We’ll be back in action come September, resuming our usual schedule of one meeting per month.
GitHub: With fewer team members around, our response time on GitHub discussions might be a bit slower. We strive to answer every question, but with less manpower, some issues might only get resolved when the person with the right expertise returns from their vacation. We appreciate your patience and understanding during this time.
Orders: Shipping and deliveries should have the same pace, so don’t worry about your order coming on time, we’ve got that covered!
Ongoing projects and maintenance
Our focus during the summer will shift primarily to maintenance and continuing work on ongoing projects. We’re putting the final touches on the Brushless project of course, and will keep working on its charger solution too.
We’re excited to announce our participation in Robotics Developers Day on July 5th. We’re not only sponsors of this event, we’re also thrilled that Kimberly will be hosting a live learning session about ROS 2 on the Crazyflie.
For us at Bitcraze, summer is a wonderful opportunity to slow down a bit and focus on projects we don’t usually have time for. This could mean diving deeper into learning RUST, reorganizing the office, or trying some prototypes out. It’s a chance to reset and prepare for the busy months ahead.
We hope you have a fantastic summer filled with sunshine, relaxation, and lots of new adventures. Glad Midsommar, as we say here!
As we mentioned earlier, ICRA Yokohama was full of exciting encounters – we really enjoyed meeting researchers, tech companies, and enthusiastic roboticists during those 4 days.
One challenge was to bring back as many research posters featuring the Crazyflies as possible. The goal was to decorate the walls of the office with them, as a “hall of fame”. And I’m really, really proud to show you how it turned up!
This was beforeAnd this is now!
In total, we received 6 new posters. Here they are:
This paper presents a strategy for optimizing the collaborative transportation of payloads in an under-capacitated vehicle routing scenario. The Crazyflies work together to dynamically adjust routes based on real-time data and transport capacities, and collaborate to lift and transport heavier payloads.
The paper describes a method for enabling a swarm of Crazyflies to dynamically seek and locate a moving target or source in constrained, GNSS-denied environments. Using a simple rule-based approach, the drones track dynamic source gradients and navigate obstacles autonomously with fully onboard systems.
The paper presents TinyMPC, a high-speed model-predictive control (MPC) solver designed for resource-constrained microcontrollers on small robots like the Crazyflie. TinyMPC efficiently handles real-time trajectory tracking and dynamic obstacle avoidance, outperforming traditional solvers.
The paper introduces a lightweight obstacle avoidance system for nano quadcopters, leveraging a novel 64-pixel multizone time-of-flight (ToF) sensor to safely and effectively navigate complex indoor environments. Tested on the Crazyflie 2.1, the system achieves 100% reliability at a speed of 0.5 m/s, all while using only 0.3% of the onboard processing power, demonstrating its suitability for autonomous operations in unexplored settings.
This paper introduces a method for autonomous localization in nano-sized UAVs like the Crazyflie by fusing geometric data from time-of-flight sensors with semantic information extracted from images. The approach leverages annotated floor plans to improve navigation accuracy without adding extra deployment costs. The system operates efficiently with limited onboard computational resources, achieving a 90% success rate in real-world office environments.
A big thanks, once again, to all of those who gave us their posters!
Two weeks ago, Arnaud, Barbara and Rik were at ICRA 2024 in Yokohama. At our booth we showed our current products as well as the upcoming brushless Crazyflie and the camera deck prototype.
As usual, the conference has been very busy with a lot of visitors and a lot of very interesting discussion. Thanks to everyone that passed by the booth, we have come back to Sweden with a lot of energy and new ideas!
The autonomous lighthouse swarm demo demo has worked pretty well. If you are interested to know more about it you can visit our event page. It is an autonomous demo with 3 brushless Crazyflies and 6 Crazyflie 2.1s flying autonomously. With the extended battery life of the brushless, we could operate the demo pretty much continuously.
If you’ve been at the conference, you may have spotted someone proudly sporting our exclusive ‘Bitcraze took my poster’ button. We’re excited to have received posters covering a wide range of topics, the walls of our office are eagerly awaiting these visual representations of your hard work and dedication. Thank you to everyone who has contributed.
One of the great features of the stock Crazyflie 2.1 is that it is more or less harmless. The Crazyflie 2.1 brushless weighs roughly the same but has almost twice the amount of thrust force, so a little bit of more care is needed. We therefore decided to provide optional propeller guards. While propeller guards adds safety they also add weight and disrupt the air flow from the propellers. Adding to that, the weight is located far from the center which increases the inertia even further, resulting in a less agile drone. For some applications this is not a problem but for others it is, this is why we are making them optional, meaning they are easy to replace with simple landing legs by utilizing a snap-on fitting.
The design is not fully finalized yet but we are getting close, voilá!
If the design goes according to plan they will also withstand some bumping against walls which will be a very nice feature for many applications.
Further the landing legs and propeller guards are designed in a way so they will detach during high force impacts to prevent the PCB arms from breaking.
“What? You are in Japan? Again!?”. Yup that is right! We loved IROS Kyoto 2022 so much that we just couldn’t wait to come back again. Barbara, Arnaud and Rik are setting up the booth as we speak to show some Bitcraze awesomeness to you! Come and say hi at booth IC085.
The gang before the rush starts!
Crazyflie Brushless and Camera expansion
Of all the prototypes we are the most excited of showing you the Crazyflie Brushless and the ‘forward facing expansion connector prototype’ aka the Camera deck. Here you can see them both in action at a tryout of our demo. We have also written blogposts about both so make sure to read them as well (Brushless blogpost, Camera expansion blogpost)
The Crazyflie Brushless flying with a Camera deck.
Also we will explain about the contact charging prototype (see the blogpost here) and will be showing all of our decks at the booth as well. And of course our fully autonomous, onboard, decentralized peer-to-peer and avoiding swarm demo will be displayed as always. Make sure to read this blogpost of when we showed this demo at IROS 2022 to understand what is fully going on!
We will be providing a ‘special disposal service’ for your conference poster! We would love to see what you are working on and get your poster, because we have a lot of space in our updated office/flight space but a lot of empty walls.
If you hand in your poster at the booth, you’ll get a special, one-of-a-kind, button badge that you can wear proudly during the conference! So we will see you at booth IC085!
My name is Joseph La Delfa, I started in December last year as an industrial postdoc at Bitcraze. This means I work across Bitcraze HQ in Malmö and the division of Robotics Perception and Learning at KTH in Stockholm. I have been designing and researching interactions that involve bodily control of drones for a few years now.
In order of appearance: Demonstrating at a conference, mucking around with the Qualisys tab, coaching at Drone Arena I, playing judge at Drone Arena II, and finally Drone Chi.
Here at Bitcraze I will be using lighthouse decks on the body to control Crazyflie/s, with the aim to produce a wearable sensor that integrates into the Bitcraze ecosystem. The lighthouse positioning system is showing great potential for this application as it gives relatively clean and high-fidelity positional data. Plus now that more than two base stations can be used, we can potentially track the deck from top down and bottom up.
Three motor-less crazyflies are strapped to my arms and tracked using two lighthouse basestations.
This research is a continuation of my PhD thesis, where I designed drone interactions that respond differently to different people, and advocated for a human-drone relationship that evolves over time. Ultimately I hope to demonstrate new use cases for the Crazyflie and expand the already impressive community of researchers who use Bitcraze products!
How to Train Your Drone was a one-month field study in a shared home, where three housemates taught their drones how to fly.
This industrial postdoc is funded by the Wallenberg AI, Autonomous Systems and Software Program (WASP), and you can find out more about my work at www.cafeciaojoe.com :D
Dumping and loading persistent parameters to and from a file
We have a small quality-of-life update that will allow users to dump and load persistent parameters to and from a file that has recently been merged #PR443 and #PR706. A new persistent parameter management area is introduced to the parameters tab of the client, with buttons for dumping and loading persistent parameters, as well as clearing all stored persistent parameters from the Crazyflie. The persistent parameters are stored in .yml format, allowing for manual editing if desired. If you have any improvement suggestions please drop us a comment!
A new persistent parameter management area is introduced to the parameters tab of the client, with buttons for dumping, loading and clearing stored persistent parameters.An information dialog notifies users of the dumped persistent parameters and their values. Loading parameters will result in a similar pop-up.A confirmation dialog prevents accidental clearing of persistent parameters.
System-id code merged to master
Back in 2021, we created the system-id deck which we talked about in this blog post. It has not been officially released but a few users have gotten some PCBs and built it themselves. The functionality for the system-id deck has previously been in a branch, but as code in branches tends to become outdated, we have now moved this into the master branch utilizing the kbuild system instead. Building for the system-id deck is now as easy as doing “make sysid_defconfig” and then compiling. While talking about the system-id deck, let’s check the interest of releasing it as a product. It can help with system identification, tuning of controllers, improving efficiency etc. With enough interest there might be an economy in manufacturing it.
Out of stock
Unfortunately, we’re out of stock of Crazyflies at the moment. We expect some at the end of next week, so hopefully, you should be able to find them back in the store quickly.
Developer meeting
The next developer meeting will be on the 6th of March 2024, Arnaud will talk about the Crazyflie Client past, present and future, based on its last blog post. The client is still very useful but starts to show its age so we are looking at what should be kept, what should be improved and what should be removed. We will present what we have in mind, please come and discuss with us so we can shape the next 10 years of Crazyflie client!
The Crazyflie client has a quite long history, like a lot of things in the Crazyflie ecosystem it has been started when the Crazyflie was used alone using mainly manual control. It has evolved to follow new use-cases of the Crazyflie but it still has traces of its origins and some limitation are still there with us. Moreover, the Crazyflie client and lib are written in python, one the main goal was to make it easily cross-platform. Unfortunately making a cross platform graphical program that accesses hardware in Python has proven to be quite challenging and we feel Python is not the way to go anymore. In this blog post we would like to discuss a bit the current state of the Client and what we are looking at for the future.
A Crazyflie connected to the CFclient
The Crazyflie client was originally design to be able to fly, inspect and work with one Crazyflie. It still serves this purpose quite well: with the client you can connect your Crazyflie, observe graphs of internal log values in real time, setup different decks and sets and store parameters. It is a very good tool to explore and work with the Crazyflie.
However, it is only working with one Crazyflie at a time will take over the radio, so another script cannot talk to the Crazyflie at the same time using the radio. Unless the script uses the ZMQ API that allows an external program to control client and so to control the Crazyflie while the client is connected and active. This functionality can be very useful but, since it is disabled by default, has not seen a lot of use.
The worst, for us, in the current client state is Python and PyQT distribution situation: we used to have an easy-to-use installer on windows, a Linux Snap package and plan for a Mac App. All these have been pretty much abandoned because they kept breaking down over time and the support weight for us was too big. So the only way to install the client is via Pip, the python package manager. This means that you already need a well setup Python environment to run the client. That is nice unless you have a Mac or a Raspberry pi: the latest MacOS broke part of the client that prevents it to run and there is no PyQT build for raspberry-pi available on PyPi. This is the kind of paper-cut that keeps happening at regular interval with distributing a Python application and that we keep having to look at.
So, we have been looking at ways to improve the situation. The Crazyflie client is more than 10 years old now, so a rewrite would not be such a crazy thing to consider. There are at least 2 angle of attack to make a new client better suited for the next 10 years of Crazyflie development:
Multi-platform and distribution
Making a multi-platform program is and will always be challenging. However, we have discovered that doing it in a dynamic interpreted language like python is even more so. The main challenge come from the fact that things tend to break on the user side depending of the user configuration: we all run a slightly different version of python, python evolve and package management evolves as well, so when things break it breaks at random depending of how up-to-date a particular system.
One solution would then be to switch to a compiled programming language. This increases the probability of finding problem at compile time and not at runtime, which means that we will hopefully be the first to know then Apple decided to change the location of one fundamental piece of library and so allow us to hopefully fix the problem before any user is impacted (assuming we can run CI on the latest version of MacOS early enough…).
So, as you might have guessed, our current idea is to write the client in Rust. We are currently looking at Tauri for the UI which is Web based. We still have ideas of also making a web-client so having a web-based IU on PC would simplify development of that.
We are not letting Python go away though, the idea is still to support Python, but to use it for what it is good at: a great language for developer and experimentation. Rust has great bindings to python so in this plan, the python lib is backed by the Rust lib.
Modularity
The other side of the current client limitation is the fact that it connects one Crazyflie taking over the radio. We actually love using the client to observe and poke the state of a Crazyflie so it would be really great to use it when writing a script or controlling a swarm with Crazyswarm. The current ZMQ implementation was designed to solve this issue, but it goes at it the wrong way around: the client becomes the gateway to the Crazyflie and must always be ON. It would be much nicer to be able to launch the client to connect and inspect a Crazyflie currently control by a script.
One design we are currently looking at would be to use use a protocol like Zenoh between the client and the lib. Basically, when connecting a Crazyflie, be it from a script or from the client, a server would be launched in the background that would handle the connection. All communication would pass through this server and so multiple programs would be able to communicate simultaneously with the Crazyflie.
This would allow us to build easily bridges to ROS to get the client to communicate with a Crazyflie currently connected in ROS. And since ROS2 is working on supporting Zenoh officially a bridge might not even be required.
As an added bonus, the Crazyflie server idea would greatly improve the situation when it comes to supporting Virtual Machines and WSL on Windows: it would move the USB connection handling to a Windows program and only require fast network connections which is something that works really well on WSL or VMs.
Conclusion
In this blog post I have tried to describe our current challenges and some way forward we see. The main message though is that we want to change things when it comes to the client, if you have wishes or ideas now is a good time to get in touch. Let’s make the next 10 years of Crazyflie client problem-free.
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.
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.
Today we have a guest blogpost by Simon D. Levy (Washington and Lee University) about using Haskell to warp parts of the Crazylife-firmware. We also have some announcements from Bitcraze itself at the bottom. Enjoy!
As Richard Feynman famously said, What I cannot create, I do not understand. My less ambitious version of this motto is What I can translate into another language, I might better understand.
In order to better understand the Crazyflie firmware, I first undertook to translate the C-based firmware into C++. By separating out the general-purpose algorithmic code (state estimator, closed-loop control) from the Crazyflie-specific / Hardware Abstraction Layer (HAL) component of the firmware, I ended up with a nice, header-only C++ library of algorithms that can work with both a simulator like Webots and on a Crazyflie 2.1 or Crazyflie Bolt flight controller (with the remaining Crazyflie firmware translated into the standard C++ .h/cpp format).
As a fan of functional languages like OCAML and Haskell (and Rust, which was strongly influenced by their approach), I wondered whether I couldn’t push this idea further, to get an even higher-level implementation of the algorithms. Having played a bit with Rust and encountered issues getting it to work efficiently with C++ (something that is thankfully now being addressed), I thought it might be work trying NASA Copilot, a Haskell extension that compiles Haskell into C with a fixed memory footprint (i.e., no malloc() or garbage-collection).
My efforts paid off, resulting in a Haskell library of algorithms for closed-loop (PID) control and motor mixing that works with both my modified version of the Crazyflie firmware and with a simulator like Webots. For anyone wondering “why Haskell”, I refer you to this excellent discussion on the language’s advantages (purity, elegance), as well as this classic presentation on why the functional programming offers a better solution to complex tasks than object-oriented approach. For example, the code in the LambdaFlight core module cleanly reflects the dataflow (input/output) diagram for a standard flight controller:
Here is the Haskell code corresponding the component labeled Core in the diagram:
— Clock rate is 500Hz for Crazyflie, 100Hz for sim
dt = rateToPeriod clock_rate
— Make a list of PID controllers based on application order
pids = [positionPid resetPids inHoverMode dt,
pitchRollAnglePid resetPids inHoverMode dt,
pitchRollRatePid resetPids inHoverMode dt,
altitudePid inHoverMode dt,
climbRatePid inHoverMode dt,
yawAnglePid dt,
yawRatePid dt]
— Run PID controllers on open-loop (stick) demands to get demands for motor mixer
demands’ = foldl (\demand pid -> pid vehicleState demand) openLoopDemands pids
— Adjust thrust component for hover mode
thrust” = if inHoverMode then ((thrust demands’) * tscale + tbase) else tmin
— Run motor mixer on closed-loop demands to get motor spins, scaled for CF or sim
motors = quadCFMixer $ Demands thrust”
((roll demands’) * prscale)
((pitch demands’) * prscale)
((yaw demands’) * yscale)
By adjusting the values of the clock rate and scaling coefficients (tscale, tbase, prscale, …), the same PID controllers (with same Kp, Ki, Kd constants) can be used for both the simulation and the actual Crazyflie.
Two pieces complete the picture.
First, how can a pure functional language like Haskell, lacking mutation/side-effects, support an algorithm like PID control, which requires keeping state variables (error integral, previous error) across iterations? The answer to this question comes from an ingenious part of the NASA Copilot framework, namely, streams. A stream (which is similar to a lazy list in Haskell), can come from an module of the program written in C (for example, the vehicle state obtained by state estimation) or from a previous value passed into the function. This feature allows Copilot to have functions that possess state while still being “pure” in the sense of being amenable to formal verification (mathematical proof of correctness; see this thread for a discussion). Although I don’t have the mathematical background to do formal verification proofs, the ability to prove the code correct is an extremely powerful feature of languages like Haskell and is what led NASA to develop the Copilot framework for its space missions.
Second, how can Haskell be combined with C/C++ without running into the performance issues typically encountered in calling code in one language from code in another? As I alluded to before, NASA Copilot solves this issue nicely, by compiling the Haskell code to C code with a fixed memory footprint. Declaring certain C/C++ variables to be global makes them accessible to the Haskell code as streams, and causes them to be compiled into the resulting C code, which can then be compiled and linked to the Crazyflie (or simulator) C/C++ code in the usual way (thanks to the Crazyflie Makefile’s use of the Kbuild system). Hence, to compile the whole project into a form suitable for flashing with make cload, requires just the following chain of commands (where make links creates links to some external libraries I wrote for the sensors):
make cf2_defconfig && make links && make copilot && make -j 32
My current work focuses on two directions: first, I am translating Crazyflie’s Kalman filter into Haskell — a more ambitious undertaking, but one that I feel more confident in undertaking now that the core control algorithms are completed. Second, I am looking for ways of modifying the most popular robotics simulators (Webots, Gazbeo) to work with dynamics (physics engine) code custom-written for quadcopters and other aerial vehicles (like the dynamics code I wrote for this simulator), as well as faster control loops.
Announcements
There are some announcements that are not part of this guest blogpost that we’d like to share.
The 350 mAh batteries are out of stock and unfortunately have a very long lead time at our manufacturer, so you can expect them to be back in stock early May. Please take a look this blogpost which also compares this battery to the Tattu alternative, if you can’t wait and need to have a similar battery now.
We have a Bitcraze developer meeting this Wednesday to talk about the supervisor safety functionalities in the crazyflie-firmware. Please keep an eye on the GH discussion thread for information on how to join.
