Category: Loco Positioning

Quite a lot has happened in the community in the latest month so we though we would dedicate this Monday post to you :-).

On the firmware side, the loco positioning system has sparked a lot of contribution. Most prominently is the Extended Kalman Filter by Mike Hammer and later improvement by multiple contributors. The Crazyflie is getting more stable and capable week after week which is awesome. Wolfgang from USC has also pushed enhancement coming from its CrazySwarm which will one day gives to everyone the capability to fly big Crazyflie swarm more easily.

On the clients side, we just pushed a new version of the iOS app to the app-store. The main improvement is the new tilt control mode implemented by EMart002 and beta-tested by a community member.

There has also been a new release of the Android client by Fred. This new version adds support for log and param using the Crazyradio. This way it is possible to get telemetry from the Crazyflie like the battery voltage and there is an experimental implementation of altitude-hold when using gamepad.

Running a beta (test-flight) version for the iOS client has been a good experience as it allowed to get direct feedback on functionalities. If there is interest we could release and announce beta versions for both Android and iOS in the future.

Finally last but not the least, there will be a new Crazyflie client in town: The Crazyserver created by Mike Hamer and written in go. It is a cross-platform, install-less, dependency-less server for a fleet of Crazyflies. It exposes a language-independent API, an HTTP rest API, to be able to connect and control any number of Crazyflie from any programming language. It will also include sockets (UDP, TCP and Websockets) to carry real-time data like setpoint and telemetry. It is still very much work in progress and not ready for real-world usage but if you are curious and/or would like to help check the code is on github.

 

For the third year we will be at FOSDEM on Saturday 4 and Sunday 5 February 2017 in Brussels. The last two years we have been present and Fred, the Android client maintainer, has had a lightning talk about the Crazyflie.

This year Fred will present a lightning talk about “News from the Crazyflie universe” and Arnaud will have a talk about the Loco Positioning System in the embedded dev-room. The LPS talk will contain a demo of one or more autonomous Crazyflies.

If you are planing at being at FOSDEM and want to meet with us just tell us in the comment, we would be really happy to meet Crazyflie users. There will be almost all of the Bitcraze team and we will have Crazyflie and a Loco Positioning System so it might even be possible to do some flight or demo on the side.

This year we decided to do a short Merry Christmas video. The video was done during one chaotic evening last week were both time and technology seemed to be against us. We are anyway happy with the result which we hope will spread some Christmas joy!
 

 
PS. All flights, except the first take-off, where autonomous using the loco positioning system. Code and documentation to come later ;-). DS

Merry Christmas from all of Bitcraze!

Last week we reached a milestone for our Loco Positioning System: we got 5 Crazyflie 2.0 to fly in a swarm with Time Difference of Arrival measurements. This is a great step closer to making the LPS leave the early-access state.

Until now, positioning has been done using a method called Two Way Ranging (TWR). The advantage of TWR ranging is that it allows us to easily get ranges to the anchors by actively pinging them in sequence. Based on these ranges we can then calculate the current Crazyflie position and control the Crazyflie to move to a wanted position. The big drawback though is that since each Crazyflie has to actively transmit packets to ping anchors, flying many Crazyflie means sharing the air and so the more we want to fly the less ranging each Crazyflie can do. In other words: it does not scale.

TDoA measurement consist of measuring the difference of flight time between packets coming from different anchors and this is harder to achieve since the anchor clocks must be synchronized to each other. The killer feature of TDoA is that it can be implemented using unidirectional packet sent from the anchor system and received by the tag/Crazyflie. It means that as soon as you get one Crazyflie flying with TDoA, you can get as many as you want since the Crazyflies do not have to transmit anything.

This is what happened last week: on Thursday evening we got 1 Crazyflie to fly with TDoA measurements. On Friday we tried 3 and then 5 without much effort. It was just matter of modifying the ROS launchfile to connect more crazyflies, a copy-paste operation.

Then

There still seems to be a margin for progression to get even more stable flight with TDoA and we are also working on making the LPS and Swarm work with our Python client which will make it easier to use outside a robotic lab.

If you want to try the (very experimental!) TDoA mode with your loco positioning system we have documented how to get it to work on the wiki.

Thanks a lot to the growing community that is supporting us and allow us to move faster towards a Crazyflie swarm.

Last week was interrupted, disrupted and generally chopped up as a few of us had to stay home fighting germs and viruses. Today all of us were present again and hopefully we will all be well this week to participate in the fun. Even though last week will not make it to the hall of fame when it comes to productivity we still made some progress.

TDoA mode of the Loco Positioning system

We are happy to announce that we have calculated the first TDoA (Time Difference of Arrival) based position in the Crazyflie. This might not sound very spectacular but it is one step closer to being able to position an infinite (in theory) number of Crazyflies simultaneously. We used test driven development (TDD) to implement the functionality and we think it helped us to manage the complexity and write better code. We have written a few unit tests earlier, but this is our first serious attempt at test driven pair programming. We have based the unit tests on Unity and mocking on CMock from Throw The Switch.  The result of our efforts can be seen in lpsTdoaTag.c and TestLpsTdoaTag.c.

New Logo

We have used a few different variations of logos up to now, the historical logo was good for electronic boards (PCBs) but hard to make look good in other contexts like the webpage and so we ended up in a situation where we do not have a consistent logo for everything. We have decided that we probably should try to find one that we all like and want to use everywhere. Björn has made a bunch of different designs that we all have discussed together and after a few iterations we are converging towards something really good. We will not show any previews, just stay tuned to see the final result.

bitcraze_logo_white_back_sq_spaced_1400x1400

The logo currently used on Bitcraze PCBs

Marcus Greiff

We want to welcome Marcus to the team, he will work with algorithms one day a week. Marcus is currently studying at LTH where he has been using the Crazyflie 2.0 platform in his studies.

SD-card expansion deck in production

Production materials for the SD-card expansion deck has been sent to the factory. Hopefully it will be available in the shop in a few weeks time.

We attended Øredev last week and showed off our demo with an autonomous Crazyflie with a light and sound show. It was the same demo as we had in Maker Faire Berlin earlier this autumn that we wrote about last week. It is noticeable how much better the system has become since Maker Faire Berlin when it comes to performance, the Crazyflie is almost completely static when hovering in one spot now and the motions are much more snappy and exact. Hats off to the community that contributed the improvements!

 

At Øredev we met Ray Arkaei, the DJ that played at the party in the evening. When he realized that we used MIDI to control the position of the Crazyflie and the color of the LED-ring, he immediately offered to create his own sequence to a bit more contemporary music. This is what we love with events like Øredev, we meet people and exciting (and unexpected) events take place! He plugged in his machines and we set the goal of making a short sequence, film it and upload it to facebook. After just 10-20 minutes of experimenting (and recap from our side of how we had implemented the demo) Ray got going and soon he had had a pretty cool sequence going!

 

We shot this video with a phone

 

Ray Arkaei
Arkaei shot the sequence with his 4K camera (yes, we would love to have one too!) but unfortunately did not have time finish the editing. We are eagerly awaiting the final results and will publish a link here on the blog when it is live!

Thanks to Ray and Øredev for a memorable day!

Bitcraze forum

We have been discussing the information architecture on the Bitcraze forum after getting some really good feedback from Fred (derf) one of our forum members. Before starting to make changes to the forum we thought it would be a good idea to take the opportunity and ask all of our forum members for feedback about how the forum is structured. The forum should be easy to navigate and comprehensible for both new and old members so feedback from people actually using our forum is very valuable. So if you have any suggestions post a comment to this post or send us an email.

Öredev

Also this week on Thursday 10/11-16 we are going to the developer conference Öredev that is taking place here in Malmö. We are exhibiting the same demo as we did at Maker Faire Berlin so if you are going to the conference expect to see an autonomously flying Crazyflie 2.0 enabled by our Loco positioning system (code and doc for demo published here). We are there the whole day so come by and have a chat :-).

infographics-oredev

New Crazyflie 2.0 firmware release

We released a maintenance release of the Crazyflie 2.0 firmware last week. The new release improves the stand-by time for the Crazyflie 2.0 and doesn’t effect the Crazyflie 1.0. The release can be found here.

Progress on TDoA for Loco positioning

We’ve started working towards positioning using TDoA and last week we pushed updates to both the Loco positioning node and to the Crazyflie 2.0 firmware. The changes are still largely untested but we’ll be continuing the work during this week. We’re really excited about the possibilities this brings, virtually unlimited number of Crazyflie 2.0s being positioned at the same time!

Loco positioning system is still in Early access which means that things are moving fast. Since the release of the loco positioning system a Kalman filter has been contributed by Mike Hammer at ETH Zurich. The Kalman filter allows to calculate the position estimate in the Crazyflie and merges the Loco positioning system information with internal sensor to generate a much better estimate. We also worked on improving the anchor firmware, it is now ranging faster and we fixed a bug that was making the anchor hang sometime. Finally stephanbro on github pushed an improved position controller that improved the stability of flight a lot.

Because of all these changes we have decided to make a new video and to rewrite the documentation on the wiki a bit. Enjoy!


On the development side, we have extended the Loco Positioning system to position 2 concurrent Tags by using TDMA (Time Division Multiple Access) where each Tag is allocated a time slot to use to range to the anchors.

2crazyflies

This works fine for a few Tags, but does not scale very well for a larger numbers of tags. If you want to experiment by yourself there is some instruction in the git commit. Be aware that this is still experimental enough for us to break it without warning so keep track of the git commits when you pull the latest version of the firmware. Currently we are working on a TDoA (Time Difference Of Arrival) mode that will scale to concurrently position virtually an infinite number of tags, hopefully you will soon be able to see commits on that on our Github projects.

One week ago we where presenting Crazyflie 2.0 and the Loco Positioning System at Maker Faire Berlin 2016. It was a lot of fun being there, we enjoyed it very much, and it also required a couple of weeks of preparation. The preparation was both mechanical and markerting: out booth was built with and outdoor tent frame and we featured the first roll-ups of Bitcraze history (almost felt a bit too ‘corporate’ for us :-).

On the technical side it was an opportunity to test Crazyflie and the Loco Positioning System in real event situation. This required stabilizing the system and testing it so that no bad surprises would happen during the faire. The result is pretty good: we flew more than 91% of the opening time, we had 2 fly-away the first day, fixed the problem and had none the second day. We were flying with 2 Crazyflie sequentially and had not broken any motor mount or other part during opening hours (some crazyness did happen after-hours though, maybe more on that on a later post ;-).

For our demo the Crazyflie was flying autonomously with the loco positioning system using the Kalman filter to fly towards a given x/y/z set-point. We made a midi-to-crazyflie bridge in ROS that allowed to give control of the Crazyflie position via a midi cable. We actually used a physical midi cable which was the safest and simplest. On the other side of the midi cable was a computer running a midi sequencer, lmms. Part of the sequence was playing actual music to make the Crazyflie dance and part was just silent movement. The setup looked like that:

Bitcraze Maker Faire Berlin 2016

Midi can encode notes pitch (ie. where in the piano you play) and velocity (ie. how hard you press the piano key). The midi track contained 4 tracks: X, Y, Z and LED-ring. In X, Y, Z tracks the note pitch converted into a position and we don’t use the velocity. The led ring track maps the note pitch to a color and the velocity to a brightness. It looks like that:

llms_mfb

This setup was a bit of a test, we found it to be very reliable. Some functionality were implemented on-site after Friday morning experience: automatic landing when the battery was low and reconnect on take-off to allow taking off without restarting anything in the PC just at a press of a button. The midi link worked well even though it feels a bit hackish to setup a choreography like that. If you have any better idea what to use to make a Crazyflie dance please tell us!

Last but not the least we have share all the codes, files and documentation for this demo on github so that you can run it yourself with an loco positioning system. We also made a short video showing the demo in action:

 

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The Maker Faire Berlin is coming up and we are starting to get ready for showtime!

The last couple of weeks has been really busy getting ready for the Maker Faire Berlin. The plan is to show multiple Crazyflies flying autonomously enabled by the Loco positioning system. To spice up the experience of autonomous flight and to inspire the visitors to imagine future applications we have made a small light and sound show where the Crazyflie is dancing to a soundtrack Kristoffer made.

Here is a teaser where we are maybe stretching the limits a bit too far ;-):

Taking the opportunity to exhibit what we do at events like the Maker Faire Berlin is really exciting and we are looking forward to hanging out with cool people and getting feedback about what we do.

So come and visit us at Maker Faire Berlin is Sept 30 to Oct 2 at Station Berlin. You will find us in hall 3, stand 149.

See you there!