We have recently moved to a new bigger office. With the summer arriving in Sweden, it was time to organize a small move-in after-work party with friends and family. For the occasion we wanted to play around with a small swarm of Crazyflies and the new Lighthouse positioning. Time being a sparse resource, we setup the ICRA2019 demo in the flight lab so that we would be able to fly during the party. We also started looking at our old swarm show that we ran with the LPS a year ago to see if we could run it with Lighthouse:
The show was a essentially a sequence of setpoints sent from a python script and controlling 9 Crazyflies 2.1 equipped with Lighthouse deck on the top and led-ring deck on the bottom synchronized on music. We setup the Crazyflie in the Lighthouse positioning system and converted the script to use the high-level-commander GOTO setpoints. We look forward at trying more advance control problems like trajectories to make more impressive synchronized flight choreography in the future but for now it already look quite good even with only GOTOs:
While running our ICRA demo, we came across a bug in the Crazyflie python-lib radio handling, limiting the number of Crazyflie that could be controlled using one Crazyradio PA. Communication with many Crazyflies is crucial as flying swarms is becoming more of an interesting topic for research and education. So we decided to take the problem at hand and create a radio test-bench:
To make the test-bench we have attached 10 roadrunner boards to a plank of wood together with USB switches that can provide enough power to the roadrunners. We used the roadrunner because it is mechanically easier to use in this context and it has an identical architecture to the Crazyflie 2.1 when it comes to the radio implementation.
Initially we will use the test-bench to run test scripts that pushes the communication to its limits and that consistently test the communication stack functionalities. This should allow us to find bug and verify that we solve them as well as discovering and documenting limitations.
Eventually we want to connect a raspberry-pi to the test-bench and run tests for each commit and pull-request to the crazyflie-firmware, crazyflie2-nrf-firmware and crazyflie-lib-python projects. This will guarantee that we do not introduce new limitations in the communication stack. The test-bench will also be very useful in implementing new functionalities like direct crazyflie-to-crazyflie P2P communication.
As a final note, the Crazyswarm project is not affected by the Crazyflie-lib bug since it is using the C++ implemented crazyflie-ros driver. Hence Crazyswarm can control more Crazyflies per Crazyradio PA, so it is still the preferred way to fly a swarm mostly when using a motion capture system. Though, with the progress made on LPS and Lighthouse positioning, running swarms, using the python API directly is a probably a more lightweight alternative.
3 of us where at ICRA 2019 in Montreal last week, where we met a lot of interesting people and a lot of Crazyflie users. Thanks a lot to everyone that drop by our booth, and for the ones that missed it we are planning on being at iROS2019 later this year so we might see you there :-).
We have already described our demo in a previous post, now that we run it we can update on how it went. We are also updating the ICRA2019 page with the latest source code and information so that anyone interested can reproduce the demo.
In its final state at the conference, the demo contained 8 Crazyflies 2.1 equiped with Lighthouse deck and Qi charger deck. There were 8 3D-printed charging pads on the floor with Ikea Qi wireless chargers and two HTC Vive base stations (V1) on tripods. The full system was contained in a cage, built from 50 cm-long tubes or aluminium and nets.
The full setup of the booth took us about 4 hours, this included about 3 hours for the cage, 15 min for the demo including calibration of the lighthouse base-station geometry and the rest to fine-tune things. This is by far our best setup time, we still need to prettify the cage a bit and to make is easier to install, but we will most likely re-use this system for upcoming conferences.
In this demo we aimed at keeping a Crazyflie in the air at every moment, to do so we had a computer connected to all 8 Crazyflies sending to one of them the signal to start flying if no other where actually in the air flying a trajectory. The flight was completly autonomous as we explained in our previous blog post. We setup the Crazyflie to fly 2 cycles and then land, which increase the rate of swap and so increased the ‘action’, though it also meant that during the swap two Crazyflies where flying. This drained the batteries a bit more than expected and meant that after about an hour all the Crazyflies where bellow the take-off threshold and we had to wait ~30 seconds between flights. Here is a video of it in action:
The demo was very care-free, we had very few Crashes and we mostly restarted the Crazyflies to swap batteries manually to add a bit of power in the swarm. The last day we decided to spice it up a little bit by adding a chair in the cage and by calibrating the chair position and flight trajectory, we managed to have the Crazyflie partly fly under it. This worked quite well most of the time and showed that the lighthouse positioning is repeatable and works fairly well with short occlusion in the path. Though we also found out that even though a single Crazyflie would always fly the same trajectory, two different Crazyflies will not. We think differences in propeller stiffness and the fact that the our Mellinger position controller has not been calibrated for changing YAW are the main reasons.
If you want to know more about the demo or if you want to reproduce it do not hesitate to visit the ICRA 2019 page that explains it in more details and links to the source code of everything including 3D printed parts for the cage and the landing pads.
Last week we posted about painting with the Lighthouse deck. This week we continue on the same track but add a new dimension, all in our “let’s try this crazy idea” spirit. So last Friday, after having a lot of fun painting with the Crazyflie led-ring using long exposure photo and the Lightouse deck for positioning, we had one extra crazy idea. Can we use the Crazyflie to show a raster image, very much like the way a CRT monitor works by sweeping line by line and displaying the pixel color one by one, using the led-ring? Unfortunate we did not have enough time that day…
However the idea was so intriguing that Kristoffer couldn’t stop himself from writing a prototype script during the week-end. So last Monday, just after publishing the blog post, we went to the flight arena and tried it. After a couple of trial and error we found a display algorithm that showed a pretty good result:
Crazy-Lisa
The source for this image is this very low resolution Mona Lisa:
It was a very fun experiment, it is magic to see the Crazyflie going back and forth blinking for ~3 minutes, click on the camera and see the resulting picture. It is also a really nice way to observe the current state of the lighthouse positioning. The lines are spaced by about 3 cm and the Crazyflie is controlled using the PID controller. The controller do a decent job of keeping the Crazyflie in lines and the space seems a little bit ’tilted’.
As a side note, we will be exhibiting at the ICRA 2019 conference May 20-24, 2019 in Montreal, Canada. We will running demo of the LPS and Lighthouse (though I am not sure we can print long exposure picture, this is not so exciting to look in real-time :). We hope you would like to come and meet us there!
The lighthouse deck allows the Crazyflie to estimate its position using the HTC Vive tracking base-station normally used for Virtual Reality. The positioning is done by tracking the timing of rotating infra-red laser beams emitted from the base-stations. This system has the advantages of having a very good precision and of allowing the Crazyflie to acquire its position autonomously: once the Crazyflie knows the position and orientation of the base-station, it can calculate its own position without the help of any external systems.
The release as Early Access means that we have finished the hardware and we are confident that the hardware is working properly. Though we have not yet finished all the software and firmware, by releasing the hardware early we can get the hardware into the hands of users quickly to try it out. In return we hope we can get some help making the software better.
Current state
The Crazyflie can calculate its position from the received Vive Base-Station V1 signals.
Direct line of sight should be kept to both base-stations. The Lighthouse deck has 4 receivers so in the future it will be possible to get a position from seeing only one base station.
Base-Station V2 support is still being worked-on, it will only require a software update.
The Base-station position is hard-coded in the Crazyflie and found using SteamVR. Ideally this should be sent from the ground and the Crazyflie should calculate the positions of the Base-Stations automatically.
The previous point means that a full VR system or at least two base stations and a controller or tracker is required to setup the system. In the future we hope to setup the system with only a Crazyflie and two base stations.
Since this version of the deck only has horizontal sensors, it is important that the base-stations are placed above the flight space and the Crazyflies should fly ~40cm bellow the base-stations
As long as the deck is in early access, the main documentation will be the lighthouse positioning page in the wiki. This page is going to be updated a lot in the near future and will track the progress in development.
Demo
We have written a small demo script that allows to set the position of the Crazyflie using a Vive controller. It is a good demo to experiment with the precision of the system and the ability to mix VR and Crazyflie since they are in the same tracking space:
In this demo, a python script connects to two Crazyflies and acquire the controller position using OpenVR and makes the Crazyflies take-off above the controller. Then, when the controller trigger is pushed, the setpoint to the closest Crazyflie is changed to follow the controller movement, the Crazyflies are flying autonomously only getting position setpoints from the python script. The position estimation and control is handled onboard.
We are pretty excited by this release since we think this positioning technology will be very useful for a lot of use-case. Let us know what you think and do not hesitate to contribute if you want to improve the system :).
We are glad to announce that we have manufactured the fist batch of Lightouse positioning decks and hopefully it will be ready to ship by the end of the month!
The Lighthouse positioning deck is a Crazyflie 2 deck capable of receiving IR signals from HTC Vive tracking base station (ie. Lighthouses). The basestations works by spinning IR laser beams that are received by the deck to measure the angle at which the base station sees the receiver. This allows the Crazyflie to estimate its position with great accuracy and so to fly autonomously.
The board we produced is very similar architecture-wise to the prototype we showed in previous blog posts. The main physical difference is that we now only have horizontal receivers. This change was made because we do not yet have a satisfactory mechanical solution to mount vertical IR receivers and we arbitrated that horizontal-only sensor already provides great performance for autonomous flight. Functionally it means that the Crazyflie should fly bellow the base stations to be able to position itself, we found that flying ~40cm bellow the base station gave good flying performance. We will continue looking at solution to make a deck with more receiver to increase the flight space in the future.
The lighthouse deck acquires the IR pulses transmitted by the lighthouses, the Crazyflie can then interpret these pulses to estimate its position. We also added soldering pads for a 2.54mm pin header which would allow to interface other microcontroller boards to the deck:
Lighthouse deck architecture
HTC has released 2 versions of the base stations that are incompatible with each other. Version 1 supports 2 base stations per system, and version 2 can support more than 2. We have good initial support for version 1 both in the deck and in the Crazyflie. Version 2 is currently being worked-on but early work shows that the deck should be compatible with version 2 with only a firmware update.
This leads to the current state of the product. The boards have been manufactured and we have received them but they are currently programmed with a test firmware. As previously stated the basic functionality is there but we still don’t have any finished bootloader. As soon as this is finished and tested we will start flashing all the boards. After that is is just a matter of adding them to the web-store stock and they will be ready to ship!
For now we consider this deck as early access, which means that we will document it in the wiki and that the software will still be heavily developed. For example an early limitation that will be worked-on is that it is currently required to run SteamVR on a computer to setup the system, this means that you need to have a full Vive VR setup or at least a vive gamepad or tracker to setup your flight space. Eventually we want to make it possible to setup the system with only base stations and a Crazyflie, without using steamVR.
We have added the deck to our web store so that you can subscribe to get notified as soon as it is in stock, we will of course post on the blog with more informations when this happens. In the mean time we can share again the video we did for the holidays that was made with 3 Crazyflie 2.1 equipped with the lighthouse deck using 2 V1 base stations:
While Crazyflie is nowaday mostly used connected to a computer, we have mobile clients that can be used to fly a Crazyflie using either Bluetooth Low Energy or a Crazyradio with an Android device or an iphone.
The Android client is currently the most advanced one with support for some decks. The goal of these mobile clients is to at least allow to fly a Crazyflie manually, though a lot more could be done by supporting the various decks of the Crazyflie (for example using the flow deck, one might imagine drawing a trajectory on the phone and having the Crazyflie following it :-).
As for development, we have not been very active in the development of the mobile clients and are relying mostly on contributions. So if you are interested into adding functionalities do not hesitate to drop by the Github page of the Android or iOS clients and to propose functionalities and pull requests.
Android client
In 2018, Fred the maintainer of the Android client, has worked hard to stabilize the current app and solve the last few bugs and problem in the current app. A new version was released last week that incorporate all the fixes.
Last years the Android client has seen big internal changes including separating all Crazyflie protocol handling in a separate java library. All these changes will make it easier to implement new functionality in the future and to make the functionality available to android as well as, to any Java program using the Crazyflie java lib.
Iphone client
The iPhone client has seen much less activity in 2018. It has been kept updated with the new versionsd of the Swift language and have seen some bugfixes, all thanks to Github contributors.
There have been reports of a couple of pretty bad bugs that have appeared in the latest release, as soon as these bugs are fixed we plan to release a new version of the iPhone client. The new version will also include the possibility to control the Crazyflie by tilting the phone, and with the bug fixes in place we should be off for a good start of 2019.
Windows client
The Windows UAP Crazyflie client is the least advance of all the mobile Clients. It has the particularity to work on Windows 10 for computers as well as for Phones. This makes it the only implementation of a Bluetooth low energy Crazyflie client for computers. However, Windows 10 for phones being pretty much dead now, the future of this client might be more on the Computer side if any.
Anyway, if anyone is interested in improving the Windows client, we will gladly test and merge pull requests when they come.
The post this week is going to be a bit more about ‘how we work’. In our daily work we often have to solve problems that are not directly technical, though we tend to solve them in a technical way. Our new automated printing system is an example of that.
Last year we have started our own e-shop to be able to sell our products by ourselves. At first we used an external warehouse which ended up causing a lot of problem so we decided to have all stock for our e-shop in our office and started shipping from Sweden. Part of the plan was to make the shipping process as efficient as possible to understand what it takes to handle stock and shipping worldwide. The latest addition is an automated printing system.
When you order in the Bitcraze store, the order is sent to a system we made to handle stock and production. In the morning, one of us will log-in in this system and start handling the orders of the night. The system is generating all documents and ordering shipping for the order, this means that all we have to do is to print the picking list and all required documentation, put the products in a box and stick all the document on the box. This level of automation was already saving us a lot of time but we still had to print manually the right amount of every required document.
We now have a Raspberry-pi connected to all the printers. A program (written in Rust, because I want to experiment with the language :) connects the management system using WebSocket and waits for a print order. When we connect to the management system we just have to click ‘print’ on the next order to get all the required instructions and documents printed, ready to use.
We are still not sure we will keep shipping from the office in the long run, but making it as efficient as possible allows us to ensure good quality and high flexibility. This kind of project is also a good excuse to play with various technologies.
2018 has ended, we at Bitcraze are now back from a short holiday break and we are looking forward to 2019. There is already a lot of things rolling that will give results in 2019 and we wanted to do a short post about what we are currently planning.
Product wise, we still have a couple of product in final state of production that we will be releasing during Q1 or early Q2 2019, Crazyflie 2.1 production is on-going and we have started a first batch of the Lighthouse deck.
We have talked about both projects in previous post but if you want to see what the lighthouse positioning is capable of you can look at the Holiday video we pushed two weeks ago:
This video was made using two HTC Vive base station V1 and prototypes of the lighthouse deck we are currently producing. We intend this deck to be the first version of a series of Lighthouse receiver deck: we had to simplify the design by using only horizontal IR receivers in order to be able to produce a first batch now, this meant making some compromises on the usable flight space. We will talk more on that in a future block post but as you can see in the video the system is promising.
We will also try to travel a bit more this year to meet you. IROS 2018 was an awesome experience and allowed us to meet a lot of our users and to get a better understanding on how Crazyflie is and can be used. This year we are aiming at visiting Fosdem 2019 in Brussels as well as exhibiting at ICRA 2019 in Montreal and IROS 2019 in Macau. None of them are completely finalized yet so stay tuned on the blog for future announcement. If you have other suggestion of conferences or event you would like to see us attending, please tell us in the comments or drop us an mail.
Finally on a company side, we are looking at growing the team and changing office. We are currently 5 at Bitcraze which means that we have a lot to do and growing would allow us to expand the Crazyflie ecosystem with more functionality and cool stuff. We are also going to move to a new office where we will have a dedicated flight lab. Until now we have had our office in a co-working space and we used about 4x4m of our office space as a flight lab. In the new office we will have a dedicated 100m² flight space which will allow us to work more on swarm support and to improve the LPS system in a bigger space.
The Crazyflie Z-ranger and Flow decks share one sensor: the VL53 ranging sensor that provides mm-precision by measuring the time of flight of laser pulses. The manufacturer of this sensor has released an improved version, the VL53L1x that works for longer distances compare to the old one. The old sensor worked for distances up to 1 meter while the new one works up to 2 meters.
The Z-ranger deck interfaces a VL53 sensor facing downwards underneath the Crazyflie, it allows to implement very precise altitude-hold by using the ranging to the floor as absolute height.
The Flow deck has both a down-facing VL53 for height measurements as well as an optical flow sensor for position measurements that allows the Crazyflie to hold its height and fly at constant velocity.
We have released both the Z-ranger V2 and Flow V2 which allows to achieve accurate altitude hold and position hold at much higher heights. With the Flow V2 and Z-ranger V2 it is possible to fly almost all the way up to the ceiling in an ordinary room!
