# Category: Lighthouse

As many European countries, Sweden is now suffering the effects of the second COVID-19 wave. In line with current local restrictions we’re limiting the number of people at our office, which for us means no external guests and only a few people at a time. Although for customers there won’t be any difference since we’re still keeping our regular shipping (1-2 days after placing the order).

## Stock levels

During the next couple of weeks we’re going to be short on some of our products, specifically the Swarm bundle, Loco Positioning deck and AI deck. We’re working hard to get them back into stock, and they are scheduled to arrive first weeks of December.

## Lighthouse progress

Lately we have been working on finalizing the support for two lighthouse base stations (V1 as well as V2) in the firmware and python lib, which means that we are messing around with large portions of the lighthouse code. As some of you may have noticed it also means that the code base is unstable from time to time. It is likely that it will take a couple of more weeks before it settles down and it might be a good idea to avoid the latest commit if you are looking for a fully working and documented system. Hopefully we will have a good base for future releases and functionality when we are done.

The latest official stable release is 2020.09 and this is also what we recommend for now.

Last Wednesday we had our first live tutorial event, explaining our Spiral Swarm Demo that we usually show at conferences. About 60 people signed up and it seems that we have about 40-50 people that were able to join from all parts of the world. There were even several Crazyflie users from Asia that stayed up late especially for this, so we definitely appreciated the dedication!

For those who missed it, you can find the recordings and slides on this event page.

## The Tutorial

The first hour we were mostly talking about the Lighthouse positioning system and in particular focusing on the base station V2. In real time, we had hands-on sessions where we actually showed how we setup the system, how to retrieve the calibration data and how to achieve geometry. The hour ended with showing a Crazyflie flying in the lighthouse system itself.

After the break , we focused on how to achieve more autonomy in the swarm, where we talked about the limitation of communication, the high level commander and the app layer. This was also shown with hands-on with multiple flying Crazyflies and the full automatic demo at the end. We were able to keep showing the demo in the end for a 30 minutes more while we were resting up with a drink :)

We were using Discord and Mozilla Hubs simultaneously to stream the tutorial. Discord worked out nicely since we could have one channel for the stream and one channel for the chat, which one of us was able to look at continuously. Mozilla hubs was a nice add-on however it definitely had some hiccups and streaming quality issues, which is not ideal for following a tutorial. Also being in Virtual Reality for 2 hours is very exhausting we heard from headset-using participants.

## What next?

We really liked doing the tutorial and speaking one-on-one with our users very much so we are likely to organize one again. Not sure at what frequency though but of course we will announce it first. We have already some requests for topics so we will look into those first. Next time it probably will be a shorter tutorial on Discord only. Mozilla Hubs might still be used but as a virtual gallery where we put 3D visualizations of what we are working on (like how the base station sweeps work for instance), so that people can get a better understanding. If you have any request for topics please leave a comment below.

We will also try out to use our new Discord Server as a digital ‘watering hole’ for our users. Here everybody will have the opportunity to chat with each-other, to share awesome projects and to maybe help each-other out with certain questions. However, we will not be on Discord ourselves all the time and still advise to use forum.bitcraze.io as the main place to ask questions and to seek for support.

As mentioned in this blog post, we added the possibility to write apps for the Crazyflie firmware a while ago. Now we have added more functions in the Firmware to make it possible to use apps for an even wider range of tasks.

The overall idea of the app API is to mirror the functionality of the python lib. This will enable a user to prototype an application in python with quick iterations, when everything is working the app can easily be ported to C to run in the Crazyflie instead. The functions in the firmware are not identical to the python flavour but we have tried to keep them as close as possible to make the translation simple.

An app is also a much better way to contain custom functionality as the underlying firmware can be updated without merging any code. The intention is that the api API will be stable over time and apps that work one version of the firmware also should work with the next version.

### Improvements

We used our demo from IROS and ICRA (among others) with a fairly autonomous swarm as a driver for the development. The demo used to be implemented in a branch of the firmware with various modifications of the code base to make it possible to do what we wanted. The goal of the exercise was to convert the demo into an app and add the required API to the firmware to enable the app to do its thing. The new app is available here.

The main areas where we have extended the API are:

#### Log and parameters framework

The log framework is the preferred way for an app to read data from the firmware and this has been working from the start. Similarly the parameter framework is the way to set parameters. Even though this has worked, it broke a basic assumption in the setup with the client, that only the client can change a parameter. Changing a parameter from an app could lead to that the client and Crazyflie had different views of the state in the Crazyflie, but this has now been fixed and the client is updated when needed.

#### High level commander

The high level commander was not accessible from an app earlier and the functions in the python lib have been added to make it easy to handle autonomous flight.

#### Custom LED sequences

It is now possible to register custom LED sequences to control the four LEDs on the Crazyflie to signal events or state.

#### Lighthouse functionality

Functions for setting base station geometry data as well as calibration data have been added. These functions are also very useful for those who are using the lighthouse system as it now can be done from an app instead of modifying lighthouse_position_est.c.

### Remaining work

We have taken a step forward with these changes but there is more to be done! The two main areas are support for custom CRTP packets and memory mapping through the memory sub system. There might be more, let us know if there is something you are missing. The work will continue and there might even be some documentation at some point :-)

## Tutorial

One reason for doing this API work now was to prepare for the tutorial about the lighthouse 2 positioning system, swarm autonomy and the demo app that we will run this Wednesday on-line, don’t miss out! You can read more about the event here.

Li-Ion batteries have packed more energy per gram for a long time compared to Li-Po batteries. The problem for UAV applications has been that Li-Ion can’t deliver enough current, something that is starting to change. Now there are cells that are supposed to be able to deliver 30-35A continuously in the 18650 series, at least according to the specs. Therefor we thought it was time to do some testing and decided to build a 1 cell Li-Ion drone using the Crazyflie Bolt as base.

Since a 18650 battery is 18mm in diameter and 65mm long, the size would affect the design but we still wanted to keep the drone small and lightweight. The battery is below 20mm wide which means we can run the deck connectors around it, that is nice. We chose to use our 3D printer to build the frame and use off the shelf ESCs, motors and props. After a couple of hours of research we selected 3″ propellers, 1202.5 11500kv motors and tiny 1-2s single ESCs for our first prototype.

Parts list:

• 1 x Custom designed 130mm 3D printed frame
• 1 x Crazyflie Bolt flight controller
• 4 x Eachine 3020 propeller (2xCW + 2xCCW)
• 4 x Flywoo ROBO RB 1202.5 11500 Kv motors
• 4 x Flash hobby 7A 1-2S ESC
• 1 x Li-Ion Sony 18650 VTC6 3000mAh 30A
• Screws, anti vib. spacers, zipties, etc.

The custom designed frame was developed in iterations, and can still be much improved, but at this stage it is small, lightweight and rigid enough. We wanted the battery to be as central as possible while keeping it all compact.

## Assembly and tuning

The 3D printed frame came out quite well and weighed in at 13g. After soldering the bolt connectors to the ESCs, attaching motors and props, adjusting battery cable and soldering a XT30 to the Li-Ion battery it all weighed ~103g and then the battery is 45g of these. It feels quite heavy compared to the Crazyflie 2.1 and we had a lot of respect when we test flew it the first time. Before we took off we reduced the pitch and roll PID gains to roughly half and luckily it flew without problems and quite nicely. Well it sounds a lot but that is kind of expected. After increasing the gains a bit we felt quite pleased with:

#define PID_ROLL_RATE_KP  70.0
#define PID_ROLL_RATE_KI  200.0
#define PID_ROLL_RATE_KD  2
#define PID_ROLL_RATE_INTEGRATION_LIMIT    33.3

#define PID_PITCH_RATE_KP  70.0
#define PID_PITCH_RATE_KI  200.0
#define PID_PITCH_RATE_KD  2
#define PID_PITCH_RATE_INTEGRATION_LIMIT   33.3

#define PID_ROLL_KP  7.0
#define PID_ROLL_KI  3.0
#define PID_ROLL_KD  0.0
#define PID_ROLL_INTEGRATION_LIMIT    20.0

#define PID_PITCH_KP  7.0
#define PID_PITCH_KI  3.0
#define PID_PITCH_KD  0.0
#define PID_PITCH_INTEGRATION_LIMIT   20.0

This would be good enough for what we really wanted to try, the endurance with a Li-Ion battery. A quick measurement of the current consumption at hover, 5.8A, we estimated up to ~30 min flight time on a 3000mAh Li-Ion battery, wow, but first a real test…

## Hover test

For the hover test we used lighthouse 2 which is starting to work quite well. We had to change the weight and thrust constants in estimator_kalman.c for the autonomous flight to work:

#define CRAZYFLIE_WEIGHT_grams (100.0f)

//thrust is thrust mapped for 65536 &amp;lt;==> 250 GRAMS!
#define CONTROL_TO_ACC (GRAVITY_MAGNITUDE*250.0f/CRAZYFLIE_WEIGHT_grams/65536.0f)

After doing that and creating a hover script that hovers at 0.5m height and was set to land when the voltage reached 3.0V. We leaned back with excitement, behind a safety net, and started the script… after 19 min it landed… good but not what we hoped for and quite far from the calculated 30 min. Maybe Li-Ion isn’t that good when it needs to provide more current…? A quick internet search and we could find that Li-Ion can run all the way down to 2.5V, but we have to stop at 3.0V because of electronics and loosing thrust, so we are missing quite a bit of energy… Further investigations are needed.

## Lighthouse 2 flight test

As a final test we launched some flight scripts to fly in a square and in a spiral so we would get a feel for Lighthouse 2 + Bolt with PID controller combination. We think it turned out quite nicely, and this with almost no optimization effort:

## Summary

Li-Ion felt like it could be a game changer when it comes to flight time but was not as promising as we hoped for. It doesn’t mean we can’t get there though. More research and development is required.

We’re happy to announce that we have taken an important step forward in the development of the lighthouse positioning system, we have improved the calibration compensation. The changes improves the correctness of the coordinate system, especially for lighthouse V2 base stations.

As mentioned in this blog post one of the remaining areas to solve was handling of calibration data and this is what we have addressed lately. In the manufacturing process mechanical elements are mounted within some tolerances but since the precision of the system is so good, also a very fine tolerances makes a big difference in the end result. Each base station is measured in the factory and the calibration data describing these imperfections are stored in the base station. The calibration data is transmitted in the light sweeps to enable a receiver to use it to correct for the errors in the measured angles.

As with everything else related to lighthouse, there is no official information of how to interpret the calibration data so we (and the community) had to make educated guesses.

### Lighthouse 1

The compensation model for lighthouse 1 has been known for quite long, see the Astrobee project by Nasa and Libsurvive. The most important parameter is the phase and until now this is the only part of the calib data that we have used in the firmware. In the new implementation we use all parameters.

The parameters of the lighthouse 1 calibration model are phase, tilt, gib mag, gib phase and curve.

### Lighthouse 2

The compensation data for lighthouse 2 is similar to lighthouse 1 but there are two new parameters, ogee mag and ogee phase. It also seems as some parameters that are sharing names between lighthouse 1 and 2 have different meanings, for instance curve.

Libsurvive has implemented compensation for lighthouse 2 but we have unfortunately not managed to use their work with good results, instead we have tried to figure out what the model might look like and match it to measurements. We have managed to get good results for the phase, tilt, gib mag and gib phase, while we don’t know how to use curve and ogee mag and ogee phase. The solution seems to be pretty good with a subset of the parameters and we have decided to leave it at that for now.

### Use of calibration data

The way we have used the calibration data so far has been to apply it to the measured angles to get (more) correct sweep angles that have been fed into the position estimation algorithms. The problem is that the compensation model is designed the other way around, i.e. it goes from correct angles to measured angles, and an iterative approach is required to apply it to the measured angles. A better way (most likely by design) is to apply it in the kalman estimator instead where it simply becomes part of the measurement model.

Currently we do calculate the corrected angles as well and expose them as log data, but it is not required for the standard functionality of the lighthouse system. We may make it possible to turn it on/off via a parameter in the future to save some CPU power.

### Functional improvements

So what kind of improvements will the calibration add?

The first improvement is the base station geometry estimation. With more correct angles the estimated base station position and orientation will be better. This is important to be able to get a good estimation of the Crazyflie position since poor geometry data will give the position estimator conflicting data.

Secondly more correct angles will straighten the coordinate system. With angular distortion the position estimator will not be able to estimate the correct position and the coordinate system will be warped, bent or stretched. The improvement can be seen when flying parallel to the floor at constant height for instance.

Thirdly the stability will hopefully be improved. When the angles from two base stations match better, the estimated position will change less when one base station is occluded and generally make life easier for the position estimator. We will take a look at the outlier filter to see if it can be improved as well.

### Remaining problems

The calibration data is transmitted as a part of the sweeping light planes with a low bitrate. For lighthouse 1 the decoding process works well and all calibration data is usually received within 20-30 seconds. For lighthouse 2 it does not work as well in our current implementation it takes (much) longer before all data has been received correctly from both base stations.

It is possible to get the calibration data via the USB port on lighthouse 2 and we are considering storing the calibration data in the Crazyflie somehow instead. This will be even more important when we support larger systems (2+ base stations) and all base stations are not within range at startup.

During the summer we were discusses at the office of what would be a good substitute of us not being able to go to conferences or fairs anymore (see this blogpost). We sparred with a few ideas, ranging from organizing an online competition to an seminar. Although we initially were quite enthusiastic about organizing the competition, the user questionnaire from the previous blog-post showed us that many of you are rather interested in online tutorials. Based on that we actually started to make some more step-by-step guides, however we definitely would agree that is not the same as meeting each-other face-to-face!

So now we are planning to organize one for real this time! So our first online live tutorial will be on:

#### Wednesday 4th of November, 18:00 (CET, Malmö Sweden)

Register for the first session here to indicate your interest and to receive up-to-date information. There are of course no cost involved!

## First topic: Spiraling Swarm Demo (Live!)

The last couple of years we have been showing our demo at many robotics conferences and fairs, such as ICRA, IMAV and IROS. Since we do not have a opportunity to do that anymore (at least for the foreseeable future), we thought that a suitable first topic of the online tutorial to be about the Spiraling Swarm demo! We will go through the different elements of the demo, which includes the implementation details on the Crazyflie and the Lighthouse Positioning system. We hope to explain all of in about 20-30 minutes and that this would enable you to set the demo up yourself if you want.

We have been thinking about just doing a prerecorded tutorial, however we also really like to talk with our users about their needs and research topics. That is why we think it is important to do it live where we can answer your questions on the go or after the tutorial. This also means that we will be demonstrating the demo live as well! Afterwards we will have a social interaction where we have a friendly chat :)

## Mozilla Hubs and Discord

There are so many options on how to exactly host this event, as there are a gazillion alternatives for video conferencing. Currently we have are looking at Mozilla hubs. which fits nicely with our interests in the lighthouse positioning system with the HTC Vive basestations. The nice thing aspect of Hubs is that you don’t need a fancy headset to join, since it is possible to join via your browser or your phone. Me (Kimberly) has joined a Virtual Reality seminar at the beginning of the pandemic, organized by Roland Meertens of pinchofintelligence.com, and it was definitely a very interesting and fun experience. When giving a presentation, it really felt like people were paying attention and were engaged. So, we recently recreated our own flight-lab in VR (using Hub’s environment creator Spoke) and tested it out ourselves. This way you will be able to see our workplace as well!

Of course, we can imagine not everybody is waiting to go full VR. That is why we will combine the online tutorial with Discord, where we will make a video channel where we will stream the live demo and tutorial. It will also be possible to send messages that are visible in both the VR space and the Discord chat channel with Hub’s discord bot. You can choose where to follow the tutorial — fully in VR, or first discord and afterwards socialize in VR — that is totally up to you.

We still need to figure out the specifics, but if you register with your email we will send all the necessary information for the first session to you directly.

## IOT conference Malmö

Now something else: tomorrow, namely Tuesday the 5th of October, we will also present at the IOT conference 2020 in Malmö. It is free for participants and it is still possible to register! Come and join if you can not wait to see us until the 4th of November.

For the users that have subscribed to our github repository this does not come as an surprise, but for the rest, we have released a new version of our Crazyflie firmware (both STM and NRF) last week!

We know that it is quite close to our last release in February, but we had so many changes and contribution that we deemed it necessary to add a stamp to this current version. In this blog-post, we will give an overview on which features to expect in this update.

## UART communication

With courtesy of Saarland University, it is now possible to connect the Crazyflie through its UART to a port on your raspberry pi or through an FTDI cable directly to your computer. This is an extra port for communicating with CRTP will open up new possibilities to interact with your crazyflie.

This is compatible with CFlib version 0.1.10, however there was a fix implemented in the current master (see the ticket here). Please see the ticket for the UART communication here if you are interested in the implementation details.

## Lighthouse

It is now possible to get the lighthouse geometry (the position and orientation of the base stations) without SteamVR. We made a script based on the latest stable release of openCV, to calculate the base station geometry based on the received sweep angles on the lighthouse deck. Check these full instructions on how to use this new script. It is a very new and fresh implementation, so if you are experiencing any trouble, please leave an issue on this page or leave a comment on the forum.

Also, FPGA v4 is now integrated in 2020.04, which support Basestation v2. This is still in a very early phase and not yet fully integrated in the firmware, so please keep an eye on this ticket for the implementation process in the latest master of the crazyflie-firmware. There was also a blogpost a few weeks ago about the current state of the lighthouse v2 development.

## Bluetooth management

We also provided an update of the bluetooth management of the Crazyflie communication by the NRF chip. Before, it was (unintentionally) possible to connect to the Crazyflie over Bluetooth while it also connected to the CFclient through the crazyradio PA. This caused a lot of unwanted elements such as package loss and unresponsiveness. Now, whenever a Crazyradio packet has been received, Bluetooth will automatically be disabled. The same goes for the peer-2-peer packet, so the NRF firmware no longer needs to be flashed without Bluetooth support. The Crazyflie needs to be restarted after connecting through the CF dongle or P2P in order to connect to it again with the Crazyflie mobile app.

## General fixes and improvements

Here are the general fixes and improvements listed that has been fixed in release v2020.04:

• BMI088 (IMU of the CF2.1) has an self-test now.
• Fixed memory issue with the Micro SD card deck.
• High-level commander improvements.
• Documentation improvements.
• LPS TDoA (2 and 3) improvements.

See the release notes of the crazyflie-firmware and crazyflie-nrf-firmware to see the full list of improvements and issues that were fixed in 2020.04. The zip files for the firmware for both the roadrunner (tag) and crazyflie (cf2) can be found here.

The Lighthouse V2 implementation has been simmering away for a long time in the Bitcraze kitchen and in this blog post we will give you an update on the current status and what is remaining for a full release of this tasty dish.

We believe we have solved most of the major technical hurdles (last famous words) on the way to a working implementation that uses Lighthouse V2 base stations for positioning, now it is mostly work to implement the functionality that is remaining. As described in this post we now have a new FPGA binary that has the ability to decode both V1 and V2 base stations, and this was a major step forward. This new binary is used in the Crazyflie firmware master branch, and if the Lighthouse deck is used with the latest Crazyflie firmware, the new FPGA binary will automatically be flashed to the deck.

## What has changed?

The new FPGA binary uses a different UART protocol to communicate with the Crazyflie. This protocol has been implemented in the firmware and hopefully there is no functional difference compared to the previous FPGA binary when using Lighthouse V1 base stations.

We have added a first version of Lighthouse V2 base station decoding, but it is still a bit limited. As a start we decided to “emulate” V1 base stations to be able to reuse as much of the existing code as possible. For now we support only 2 base stations and they must use channel 1 and 2 (used to be called modes). The V2 angles are transformed into V1 angles and fed into the old positioning logic and are handled exactly the same way as before. Even though this works, it is not the optimal solution and we hope to be able to refine it later on.

We have also written a python script to estimate base station geometry (positions and orientation) using the Lighthouse deck. This removed the requirement to use software from Steam which should simplify the set up process. Please see the (still limited) documentation. Note that this calibration method only supports the basestation V1… for now!

There is a lot of code that has been modified and the FPGA implementation is completely new, it is not unlikely that there is functionality that is unstable or broken, or configurations that are not supported. If you happen to notice any bugs, please let us know!

## What is remaining?

The functional areas that needs to be implemented or cleaned up before we leave the Early Access stage is the following:

### Calibration data

The calibration data is embedded in the modulated light from the base stations and describes imperfections from the manufacturing process for each individual. This data is not read yet for V2 and will increase the precision when available.

### Support for more than 2 base stations

Lighthouse V2 base stations are designed for systems with more than 2 base stations. The Crazyflie firmware needs to be extended for this functionality to work, including handling of geometry data, logging, memory management and some other bits and pieces.

### Native V2 positioning

The angles from the V2 base station should be fed directly into the kalman filter for positioning, instead of first being transformed into V1 angles. This will increase robustness and reduce data loss.

### Client support

We want to add a tab in the python client where a Lighthouse system can be monitored, configured and managed. It should, for instance enable the user to configure and visualize base station geometry.

### FPGA binaray management

Currently the FPGA binary is included in the Crazyflie firmware and it is automatically uploaded to the deck when booted. This is not a viable long term solution and we hope to be able to find a more generic way of handling deck binaries.

## Conclusions

As can be seen, there is still quite some work to be done before the Lighthouse V2 stew is ready to be served, but we are definitely starting to smell some nice flavours from the kitchen!

Finally a view from Kristoffer’s home lab, currently in the summer house. Three base stations are set up as a Fun Friday hack to see what it would take to use more than 2. Luckily it did not take too much time to get this to work :-)

In this blog-post we wanted to give you guys an overview of our running projects and a general update of the status of things! We got settled in our home-labs and are working on many projects in parallel. There are a lot of development happening at the moment, but the general feeling is that we do miss working with each other at our office! With our daily slack Bitcraze sync meetings and virtual fikapause (Swedish for coffee breaks), we try to substitute what we can. In the mean time, we are going on a roll with finishing all our goals we have set at our latest quarterly meeting, so here you can read about those developments.

## AI-deck

The last time we gave an update about the AI-deck was in this blog post and in the final post of our intern Zhouxin. Building on his work, we are now refocusing on getting the AI-deck ready for early release. The last hurdle is mostly software wise on which we are considering several approaches together with the manufacturer of the Gap8 chip Greenwaves technologies. Currently we are preparing small testing functions as examples of the different elements of the AI-deck in our repo, which are all still in a very primarily phase.

Even though we still need some time to finalize the AI-deck’s early release, we will consider sending an early version of the AI-deck if you are willing to provide feedback while working with it. Please fill in the form and we will get back to you.

## Lighthouse

We have made quite some progress on the development for the lighthouse V2. Kristoffer has been working hard from his homelab to get a seamless integration of both V1 and V2 in our firmware (check out this github issue for updates). Currently it is still very untested and very much in progress, however we do have a little preview for you to enjoy.

## Documentation

Right now, we are also doing a lot of revamping of the large web of documentation. Unfortunately this is a lot of work! As you noticed by now, we have added overview pages to guide the reader to the right information. We also have moved the tutorials to another part of the menu to avoid clutter on our website. In general we try to go through the repository docs to see if there is any information missing or outdated, however please let us know if you have encountered an error in any description or are missing crucial elements.

Our latest task is revamping the product pages as well, by putting all the necessary information about the hardware in just one place. Also, we are planning to make (video) tutorials soon about many elements of the Crazyflie and how to work with it. More about that later!

## Production and Shipment

Production at our manufacturers in China are slowly starting up again. Although it is not yet back at full force, it does enable us to already start ordering to replenish our stock and to get started with finishing our test rigs. Moreover, we are also negotiating to resolve the propeller issue we mentioned earlier, but there is no update on that so far.

As mentioned in this blogpost, we are still shipping orders about twice a week. Both DHL and Fedex are functioning as normal, but we do notice that there is a delay of a few extra days on some deliveries. Please keep that in mind when ordering at our webshop.

Many people in the world have now settled in the reality of working from home. We have also taken precautions ourselves by not go to our office as normal and only ship out packages a few times per week instead of every day (see this blogpost). This also means that we do not have full access to our lab with all our equipment and positioning systems in our big 10 x 10 meter flight lab at the office. In this blogpost we will show how we manage to keep on developing and flying, even in the current situation.

### In(light)house positioning

Currently we started to use the Lighthouse positioning system to setup up the remote home lab at our houses. As of recent additions to the Crazyflie firmware, it has been made easy to get the geometry data from the base station. Now the only items we need for indoor flight are just two (or only one) lighthouse basestations V1’s and a Crazyflie, and that is it! There is no need for an HTC Vive headset or hub, or third-party software like SteamVR and the setup is finished in 2 minutes! Check out the new documentation here if you want to know more about the new setup of the lighthouse positioning system.

Also, we recently got a very primarily version of the lighthouse V2 working (see here) and we of course want to keep the momentum going! We will be working on full compatibility from our homes so stay tuned. For now, see this video of the Crazyflie flying with just a single base-station, taken from one of our team-member’s home lab.

### Remote Lecture Hall and Practicals

We were invited by Dario Floreano and Fabrizio Schiano from the EPFL-LIS laboratory to do a lecture for the ‘Aerial Robotics’ Course as part of EPFL’s Master’s program in Robotics. Due to the virus, we had to cancel our trip to go there physically… but luckily we were able to do the lecture remotely anyway!

The lecture consists of two parts. In the first hour we mostly explained about the Crazyflie ecosystem, hardware and sensors. In the second hour we focused on how the stabilization module worked, including the controllers and the state estimation. During both sessions, we alternated between the theory slides with actual hands-on demos. The lighthouse positioning system was setup in a kitchens, so that we were able to show full flights and practicals with the Crazyflie. At the end there was also the push-demo with just the flowdeck and multiranger, which didn’t use any external positioning at all.

The lectures can be found below and the documentation has been updated as well with the covered material (see here). Be sure to check out the controller tuning presented in part 2 of the lecture (25:00 – Cascaded PID controller).