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Heterogeneous Trajectory Planning with Crazyflie and BigQuad Deck

  2018-04-02  |     |    Leave a comment

Here at the USC ACT Lab we conduct research on coordinated multi-robot systems. One topic we are particularly interested in is coordinating teams consisting of multiple types of robots with different physical capabilities.

A team of three quadrotors all controlled with Crazyflie 2.0 and a Clearpath Turtlebot

Applications such as search and rescue or mapping could benefit from such heterogeneous teams because they allow for more flexibility in the choice of sensors and locomotive capability. A core challenge for any multi-robot application is motion planning – all of the robots in the team need to make it to their target locations efficiently while avoiding collisions with each other and the environment. We have recently demonstrated a scalable method for trajectory planning for heterogeneous robot teams utilizing the Crazyflie 2.0 as the flight controller for our aerial robots.

A Crazier Swarm

To test our trajectory planning research we wanted to assemble a team with both ground robots and multiple sizes of aerial robots. We additionally wanted to leverage our existing Crazyswarm software and experience with Crazyflie firmware to avoid some of the challenges of working with new hardware. Luckily for us the BigQuad deck offered a straightforward way to super-size the Crazyflie 2.0 and gave us the utility we needed.

With the BigQuad deck and off-the-shelf components from the hobbyist drone community we built three super-sized Crazyflie 2.0s. Two of them weigh 120g (incl. battery) with a motor-to-motor size of 130mm, and the other is 490g (incl. battery and camera) with a size of 210mm.

120g, 130mm

490g, 210mm

We wanted to pick components that would be resistant to crashing while still offering high performance. To meet these requirements we ended up picking components inspired by the FPV drone racing community where both reliable performance and high-impact crashes are expected. Full parts lists for both platforms are available here

Integrating the new platforms into the Crazyswarm was fairly easy. We first had to re-tune the PID controller gains to account for the different dynamics of the larger platforms. This didn’t take too long, but we did crash a few times — luckily the components we chose were able to handle the crashes without any breakages. After tuning the platforms behave very well and are just as easy to work with as the original Crazyflie 2.0. We additionally updated the Crazyswarm package to be able to differentiate between BigQuad and regular Crazyflie types and those updates are now available for use by anyone!

In future work, we are excited to do hands-on experiments with a prototype of the CF-RZR. This new board seems like a promising upgrade to the CF 2.0 + BQD combination as it has upgraded components, an external antenna, and a standardized form factor. Hopefully we will see the CF-RZR as part of the Crazyswarm in the near future!

Mark Debord
Master’s Student
Automatic Coordination of Teams Laboratory
University of Southern California		 Wolfgang Hönig
PhD Student
Automatic Coordination of Teams Laboratory
University of Southern California

 

Playing with a swarm show

  2018-03-26  |     |    7 Comments

We have been flying swarms in our office plenty of times. There is kind of a limitation to this though, our flying space is only around 4 x 4 meters. Flying 8 – 10 Crazyflies in this space is challenging and it is hard do make it look good. Slight position inaccuracy makes it look a bit sloppy. To mitigate this we decided to have a small swarm show using a a bigger flying space and to invite families and friends, just to raise the stake a bit.

As usual we had limited time to accomplish this, and this time the result should be worth looking at. Well, we have managed to pull off hard things in one day before so why not this time… The setup is basically a swarm bundle with added LED-rings. Kristoffer took care of the choreography, Tobias setting up the drones and Arnaud configuring the Loco positioning system.

Choreography

Kristoffers pre-Bitcraze history involves some dancing and he has been playing a bit earlier with the idea of creating choreographies with Crazyflies. One part of this was a weekend-hack a few months back when he tried to write a swarm sequencer that is a bit more dance oriented. The goal was to be able to run a sequence synchronized to music and define the movements in terms of bars and beats rather than seconds. He also wanted to be able to define a motion to end at a specific position at a beat as opposed to start on the beat. As Kristoffer did not have access to a swarm when he wrote the code he also added a simple simulator to visualize the swarm. The hack was not a complete success at that time but turned out to be useful in this case.

The sequences are defined in a YML file as a list of time stamps, positions and, if needed the color of the LED-ring. After a few hours of work he had at least some sort of choreography with 9 Crazyflies moving around, maybe not a master piece from a dance point of view but time was running out.

The simulator is super basic but turned out to be very useful anyway (the color of the crosses indicates the color of the LED ring). We actually never flew the full sequence with all drones before the performance, but trusted the simulation to be accurate enough! We did fly most of the sequence with one Crazyflie, to at least make it plausible that we got it all right.

Short snippet from the simulation

Setting up drones

Handling swarms can be tedious and time consuming. Just making sure all drones are assembled, fully operational and charged is a challenge when the number increases. Tobias decided to do manual flight test of every drone. If it flies well manually it will most likely fly well autonomously.  The testing resulted in switching out some motors and props as vibrations is a crippling factor, especially for Z accuracy. Takeaway from this exercise is to implement better self testing so this can be detected automatically and fixed much quicker.

Loco Positioning System

We ran the positioning system with standard firmware in TDoA mode to support multiple Crazyflies simultaneously. The mapped space was around 7 x 5 x 2.5 meters and the anchors were placed more or less in the corners of the flying space box.

The result

The audience (families and friends) was enthusiastic and expectations high! Even though not all drones made it all the way through the show, the spectators seemed to be duly impressed and requested a re-run.
 

Android Crazyflie Client status and release

  2018-03-19  |     |    Leave a comment

This is a guest blog post written by Fred, the maintainer of the Android Crazyflie client and Java Crazyflie lib.

As a follow-up to last week’s blog post about the different Crazyflie clients, I would like to describe the current status of the Android client in a bit more detail.

After more than a year, Version 0.7.0 of the Android client has been released last Friday (March 16). Most importantly this release fixes a very annoying UI bug that appeared on newer Android versions, where the on-screen joystick did not show up when the app was started for the first time. It also adds support for height hold mode when using the zRanger or Flow deck, it adds a console view (can be enabled in Settings -> App settings -> Show console) and also shows the link quality for BLE connections now. You can read the full changelog on Github. You can find the release in the Google Play Store and as an APK on GitHub.

Connection quality and console messages now work on a BLE connection

Apart from the obvious/visible new features and bug fixes, quite a lot has happened “under the hood”. Some parts of the code were cleaned up, refactored, decoupled, etc. This is still a work in progress though.

There is still plenty of stuff to do for future releases, especially in the realm of Bluetooth support. On the short list are:

  • Param/Log support for BLE connections
  • bootloading over BLE
  • support for Flow deck sequences

Admittedly there was almost no documentation for the Android client and some features are hidden (too well). In an effort to change that, I’ve started to document some features on the project’s Github wiki.

If you find bugs in the app, want to request a feature or see errors in the documentation, please open a GitHub issue.

If you are interested in the development of the Crazyflie Android client and want to get involved, let me know. The fastest way to get new features added or bugs fixed is to contribute a pull request.

Last but not least, I’d like to thank the Bitcraze team for creating and developing the Crazyflie and amazing new decks. Maintaining the Crazyflie Android client is still one of my favorite past times. :)

Crazyflie clients

  2018-03-12  |     |    3 Comments

We though we could use this Monday blog post to do a small state of the Crazyflie clients. What we call a Crazyflie client is a piece of software that connects a Crazyflie and allows to control it and get telemetry back from it. In this post we will concentrate on single-crazyflie client we have on our GitHub page, there exists a lot of libraries and software to control one or many Crazyflies, we will write another blog post about them.

Crazyflie PC client

The Crazyflie PC client, is what we consider the reference client. It supports connecting one Crazyflie using the Crazyradio (PA) dongle or direct USB connection to Crazyflie 2.0. It supports the full Crazyflie telemetry (ie. log), parameters (ie. params) and firmware update. It has support for all the Crazyflie 2.0 deck that can use client support. It is updated each time it is needed when new functionalities are added in the Crazyflie which makes it actively developed and maintained by the community and Bitcraze. A bluetooth link has not been prioritize so far since its multi-platform implementation is non-obvious and bluetooth will introduce some latency and lower the radio bandwidth compared to Crazyradio. However, if anyone would want bluetooth support for the Crazyflie PC client, we welcome contributions :-). The Crazyflie PC client is using the crazyflie-lib-python to communicate with the Crazyflie.

We have three mobile clients on our Github. They have various level of functionality depending on community involvement. Our philosophy is to have the mobile clients at least able to control a Crazyflie, this allows to use them to test Crazyflies without requiring to setup a computer. We will help and support anyone that is interested in adding functionalities to the mobile clients but we generally do not have time to add much functionalities by ourselves.

The Andoid crazyflie client is currently maintained by Fred from the community. It is mobile Crazyflie client with the most feature. It supports both Crazyradio and Bluetooth link. Using Crazyradio it currently supports the part of telemetry and parameter required to support a couple of deck like the led-ring and buzzer deck and supports updating the firmware. Using bluetooth there is currently no telemetry, parameter or firmware update functionality so no deck support. Development is in progress to support more decks and to bring the bluetooth link to the same functionality as the Crazyradio link. The Android client is written in Java and Fred has developed a Crazyflie Java library that is used in the Android client but that can also be used in any other Java program.

 

Crazyflie Android client

The iOS Crazyflie client, works on iPhone and iPad. It supports bluetooth link. It does not have any telemetry or parameter support, so no deck control support. It has firmware update support over bluetooth. It has mainly been developed by me with great contributions from the community for, among others, the port to swift.  The iOS client is written in swift. The Crazyflie and Bluetooth part of the code could be a good starting point if anyone wanted to make a native mac Crazyflie client.

Crazyflie iOS client

Finally we have a prototype of a Windows UWP client developed by theseankelly. It supports Bluetooth low energy. It currently does not supports any telemetry or parameters. It is working both on Windows phone and on Windows 10 on computer, it is currently the only way to connect a Crazyflie using Bluetooth from a laptop. The windows client supports manual control of the Crazyflie using a gamepad or with gesture using HoloLens. This original set of functionality makes it both the most simple and the most advanced Crazyflie client :-).

If you are interested in developing for any of these client, of by making your own, feel free to make a ticket on the relevant github repo or open a thread in the forum. We migh not have much time to develop for the mobile clients, but we will always be glad to help and guide anyone that wants to implement software in relation with the Crazyflie. The Crazyflie clients (running in a computer or phone) and the Crazyflie firmwares (running in the Crazyflie itself) are open source and in active development, it means that is possible to modify both side, this makes it a great target to experiments and to play around with new ideas :-).

 

Collaboration with Udacity

  2018-03-05  |     |    2 Comments

We are excited to announce that the Crazyflie 2.0 and the STEM bundle has been chosen by Udacity for their Flying Car Nanodegree Program. For the students that want to try out their skills on a real world flying drone, the core curriculum has been augmented with supplemental lessons and Udacity announce that they will provide thorough instructions for the Crazyflie.

 

Udacity is providing on-line learning and their mission is 

“to democratize education through the offering of world-class higher education opportunities that are accessible, flexible, and economical”

We are super happy that Udacity likes the Crazyflie and that more people will have the opportunity to explore the world of robotics!

Collaboration with Qualisys

  2018-02-26  |     |    Leave a comment

Qualisys is a Motion Capture (Mocap) system manufacturer based in Gothenburg in Sweden. Since we are also based in Sweden, Qualisys have been able to visit us a couple of times and we now have one of their Motion capture system installed at the office. This collaboration allows us to have access to a Mocap system, something we did not have previously. It means that we can better support people using motion capture systems with Crazyflie.

We are currently implementing support for Qualisys in the Crazyswarm project. Crazyswarm currently supports a couple of motion capture system including Vicon and Optitrack, with the addition of Qualisys we and everyone with a Qualisys system will be able to fly swarms of Crazyflie in their mocap.

We are also planning on having a combined booth, Bitcraze and Qualisys, at IROS 2018. We are planning to demo flying both with the Mocap and with the Loco Positioning System. We will keep updating on this when we have more details.

We look forward to this collaboration since it will allow us to use and better support motion capture positioning for the Crazyflie.

Merging Crazyswarm functionality into the official Crazyflie firmware

  2018-02-19  |     |    Leave a comment

We have seen a big interest in flying swarms of Crazyflies and there are many challenges in doing so. The USC ACT Lab has developed Crazyswarm, a collection of software and firmware that allows to fly big swarms of Crazyflie using a motion capture system. This project has been used by USC and other universities to fly the most impressive swarms of Crazyflie 2.0 to date. 

Picture from “Downwash-Aware Trajectory Planning for Large Quadrotor Teams” publication using Crazyswarm

We are very happy that we together with Wolfgang and James, the main developer of Crazyswarm, have started to merge the firmware part into the official Crazyflie firmware. Merging the code will have two great consequences: people will be able to use Crazyswarm with a Crazyflie 2.0 running the stock firmware and everybody else will be able to use functionalities that has been developed for Crazyswarm.

There is currently a couple of parts that are in the works. The state controller has been merged already. There is currently some discussion on Github on how to merge the high-level commander, a commander that would allow the Crazyflie to autonomously follow trajectories as well as other high level commands. Finally there will be some work required to adapt the Kalman filter to make it more suited to accepts measurements from a motion capture system. The Crazyflie was not developed as an autonomous platform from the beginning but it is becoming one in big part thanks to the great contributions from the community.

A great thanks to James and Wolfgang for their effort in merging CrazySwarm in the Crazyflie code-base!

Out of stock
Unfortunately we miscalculated how much China slows down during Chinese new year which has caused some products to become out of stock. One of them is the Crazyradio PA which is also causing some bundles to become out of stock as well. The good news is that the products are in transit to the warehouse and will hopefully be back in stock any day now. Until then you can use the “Item out of stock – notify me!” functionality to get notified as soon as the product is back in stock.

 

Multi-ranger deck update

  2018-02-12  |     |    9 Comments

During the fall we did two blog-posts (1, 2) about a new prototype named Obstacle Avoidance/SLAM deck, but since then it’s been a bit quiet about it. So we thought it was due for an update! First of all, after a lot of discussions, we decided to rename the deck to Multi-ranger. It better describes what the board does and matches the naming of the Z-ranger. We’ve sent out some samples to customers and so far the response has been great. So we’re pushing forward and preparing for production that’s estimated to begin in March. Below is a picture of the latest prototype.

The biggest change for the final prototype is adding a LDO regulator to power the sensors. We’ve seen that depending on the settings for the sensors they might consume a lot more than when we initially tested. Using the same settings as for the Z-ranger brings the consumption to 90 mA, which together with the Crazyflie 2.0 electronics, comes close to filling the power budget for the Crazyflie 2.0 VCC LDO regulator. Aside from that we’re making some minor changes to simplify production and testing.

We’ll keep you updated on the progress!

Bitcraze VM and Crazyflie development environment

  2018-02-05  |     |    1 Comment

We just released a new version of the Bitcraze VM, version 2018.01. Nothing very new in this version, the VM has been rebuilt so that all the projects included in it are now up-to-date. This solves an issue where the Crazyflie client was blocked in the previous revision.

The current VM is running a quite old version of Ubuntu, the 14.04 LTS version. We are planning at refreshing the VM by making a new one when Ubuntu 18.04 LTS is released.

Since the Crazyflie 1 time we have been documenting the VM as a standard development environment. This has a couple of advantages:

  • We can distribute a fully setup development environment that has minimal dependencies with the host system
  • If someone has a problem with the VM, there is a bit chance we can reproduce and fix it, everyone is running the same system
  • Everything is pre-setup so it should be fairly quick to get started with the actual firmware or software development

However the VM solution also has drawbacks:

  • It requires to install and somewhat configure VirtualBox or other virtual machine software
  • It has some cost in performance, mostly for USB as it slows down the communication with the Crazyflie
  • The USB implementation seems to have bugs on Windows, which makes the communication with the Crazyflie buggy. This is currently the biggest problem!

So, the situation is not ideal, and we would love to get some feedback from the community.

There are two very different parts in the system: the lib and client in Python, and the firmwares in C.

  • Starting development of the python parts, on Windows/Mac/Linux, is fairly straightforward. Basically one has to install python and git, clone the projects, install dependencies and it runs. Different python IDEs can be used and work pretty much out of the box.
  • Starting development for the embedded C part can be a bit more challenging. On Linux and Mac it is pretty easy since it only requires to download the arm-embedded-gcc compiler and adding it to the path. On windows things are a bit more complex because you also need Make and I haven’t yet figured-out the best way to install that. Having an IDE requires to configure Eclipse CDT.

What do you think about the VM as a development environment and would you prefer other solutions like documentation for each operating system on how to install a development environment?

Release of the Loco Positioning System TDoA mode, a.k.a. Swarm mode

  2018-01-29  |     |    Leave a comment

 

We have been writing a couple of times already about the new TDoA2 algorithm for the Loco Positioning System. A TDoA mode has been experimental from the day we released the LPS but we are now proud to announce that TDoA is an official positioning mode for the Loco Positioning System and the Crazyflie.

Practically it means that the Loco Positioning System now has an officially supported mode to locate and fly a swarm of Crazyflie 2.0.

We have worked these last weeks at updating documentation, the “Getting started” tutorial and releasing all the affected firmware and software. One of our goals was to make the new TDoA mode as seamless and as easy as possible to work with, this meant having everything working without having to recompile the Crazyflie or any other part of the system. The Crazyflie is now detecting the LPS mode automatically and it is possible to configure the anchors position and ranging mode remotely from the within Crazyflie client LPS tab.

What we have just released is:

If you have 8 anchors and want to convert your local positioning system to TDoA, this can be done very easily by following the new version of the getting started with loco positioning system guide.

If you want more information about the different positioning modes, we have also updated the system description.