Let's Make Robots!

ATROPOS: Fonera Quadrocopter. An insanely home-made UAV

Flies scaring everybody that is too near...

Aimed by fritsl last post :)   ...

Atropos is a wifi operated quadrocopter system. It uses a Fonera 2201 with a custom compiled version of GNU/Linux OpenWRT.

A set of wii sensors gives the information to the router throughout custom CPU GPIO pins. To achieve I2C communication a especial linux kernel module is used to make an emulated i2c port with every 2 GPIO pins available.


[UPDATE 2/10/2014]

There is a talk at congress "NavajaNegra" in Spain that I show the Atropos with it's last flight control. Much more stable, but I still need a pilot class :P. The small flight is without any correction from my part but the gas.


[UPDATE 07/01/2013]


Here it comes a major upgrade of Atropos, as you can see in the front image. I have redesigned all mass distribution, putting all ESC together, and making a case for the whole system. To the cosmetic changes comes software changes, like scaled realtime graphs, and the most important thing, Pitch and Roll PID controller values has much more fine tunning.

Now I have to tune YAW PID and then Atropos will be on 1.0 version!.


New tests and flights in the new videos.

Atropos is remotely operated by a wifi link, powered by a Fonera router. The user can pilot the aircraft with a HTML5 and canvas web interface, making AJAX request on every key stroke or mouse movement. Telemetry is received with COMET (SERVER Push) HTTP information and Javascript is used to manage the entire page.

Fonera sends rotor commands to a 16F876 PIC, which generates PPM signals to manage ESC ( Electronic Speed Controllers). Those ESC are the power stage to trifasic motors.

To achieve very fast and less time consuming requests, http router web server has been modified on it's source code, to process all the AJAX requests in a RAM shared memory portion on the router.

Software control is completely home-made, and suited to be run into Fonera. It reads nunchuck and motion+ wii sensors, applies a low-pass filter, and a 2ndcomplementary filter on every loop which has been previously readed. Finally three PID controls manage rotor speed to guarantee stability.

Managing the aircraft with keyboard control is almost impossible. Due to this I developed a C program to translate USB Gamepads events into fixed-timed HTTP requests. This can be ported to any other control, making very easy to adapt to mobile devices, like phones, tablets, etc.

Will post more pics, videos & data ASAP!

[UPDATE 6/9/12]

I have posted a new video showing a test flight to observe compensated yaw lock implementation with HMC5883. There is a lot of pid tuning work left...

I recoded a huge part of HTML5 telemetry interface as you can see in the video, also software control has been updated with DCM  algorithm.

IP camera is kinda messed up with colors since a early crash during another test flight. :(

[UPDATE 19/10/12]

This is the whole architecture of Atropos system. I hope it will help to make you a better idea of how this mess of wires works :)

Also I have attached a new video, (see at the top of the page) showing the last version of HTML5 interface, with attitude real time graphics   (Where I live, windy season is starting and a new test flight is kind of uncomfortable, so this is a PID tuning session, by the see-saw method).

Video has several parts:

-First, I show how I will control the quad moving the mouse along a squared shape. The web part is functional but since it has to be completed with GPS+IMU filters in the flight control, that part is for the moment under construction. Also on the center of that shape, there are two arrows, green tell you real yaw degrees, and orange target yaw degrees. That works entirely

-Then, I enable three on-fly attitude graphics, on the right. That graphics are also canvas objects. Red line is target position on each plane, pitch, roll and yaw, and there is also a blue line. Thats the current position. The closer they are both lines, the better PID is tuned.

-Last, I disable graph attitude, to enable a HUD version of attitude indicator. That was the first component I made for this copter, but
for my first tests 1 year ago, that was not much helpfull in the debugging process, so I decided to make it optional, and enable it when fligths become more stable.

-Extra: you can see a terminal window running at bottom. That is the USB R/C trainer to UDP packet translator, to achieve faster and more efficient control of the copter, that HTTP requests. My intention is to make it unnecessary almost all the time, when I implement entire GPS Hold. It will make keytrokes+mouse a more user friendly control.

[UPDATE 07/01/2013]-> See top of the page









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I loved it :D

This is like my dream project: some sort of flying robot. I'm workin' my way there by backtracking and re-learning the fundemental electronics stuff. I'm a web developer by trade, so I fully understand your HTML5/jQuery stuff (I would think you'd use jQuery for your AJAX requests, right?). The mechanics and the electronics....that's why I'm glad this site exists, so I can watch what bright guys like you do to wire it all up and make it all work :) Awesome, awesome job, and way to realize a dream I'm sure many of us who frequent this site have. Now, how about building enough to form a swarm and to do some cross-communication between them? :)

Glad to see how own projects can inspire others to make their own. I'm a web developer by day too, and I miss that nowadays companies don't  take too much into account transversal knowledge and want only "experts", at least on my country. For me this is a escape valve, and guess it is too for may LMR members.

Ajax stuff is made using Prototype because that was the library I used on my work, but nowadays I would use jQuery, no doubt ;)

Next steps are, fine pid tuning, gps hold, some kind of fireworks "weapon" maybe kinect implementation, object avoidance and so on...

Very nice flying machine, I'm interested in your html / ajax script used to control the machine and send back live video to the control page. I also use a basic html / ajax script for my bot, but I am kinda new to html and if you could share your sript, or at least how you embeded the live video that would be great.


Nice Work !!

The html video is very camera-dependent. You have to see how your camera is showing the video on it's interface. Some cameras work with an ActiveX component, it is not good, cause you have to see that on IE ... Some others, you simply call a web page like


if the camera asks you for the login, you can launch as:


Or, like my case ( with this camera) you have  static jpgs. Every call to the target page, returns to you a frame. On the camera web interface, there is a javascript function that retrieves seamlessly every frame.

Once you have this functionality (whatever your case is) on a fresh page, you put all together, calling this page from your control page with an iframe.

for direct retrieving example

<iframe style="blahblah" src="http://login:pass@ipcamera/video.cgi"></iframe>

or if you need a fresh page to retrieve in background every frame

<iframe style="blahblah" src="http://ipcamera/page_that_I_made_to_retrieve_frames.html"></iframe>

On the other side, my intention is to put the code and html5 interface on GPL license, but I know that it is a little mess of spaggheti for the moment ;).

If you had some trouble with this, tell me you ip camera model, and I will see what we can do :)

Wow, this is getting really, really nice! I'm close to saying that it's one of the coolest Quads I have "seen" - if it was more stable in air, it would be!

"The user can pilot the aircraft with a HTML5 and canvas web interface, making AJAX request on every key stroke or mouse movement." - Let me know when you want that interface up on front page of LMR, just let me know :)

Really nice setup - and so unfair you have mountains to fly in ;/ Next tep must be something like an Easy Star II with FPV and head tracking, 2 DOF - fly on air preassure from mountains for hours :)

fritsl, since this new post, take whatever you want to put it on front page. Ask me if you need more pics etc... :)

Glad to see you like it  fritsl! Wow, putting my interface on front page, would be great for me!. Let me take another video, with the HUD enabled (yes, it has an Actitude Indicator stacked on the ip camera image, but, it is hidden in the test). If the flight is good enough, I will post it and will tell you.

Now, I'm testing other PID values, that are the lacking part of the robot. It is being very hard to me finding better values...

Other stuff that I haven't wrote on this update, but it is very important, is that I took costyn advice, and I coded an UDP implementation of my USB trainer. Quad is accepting UDP requests making it much faster tan accepting AJAX requests (Thanks costyn ).  Yes, you could control the quad by web, but it will be more affordable when I implement GPS Hold ^^

Nice project. What ESC are you using, and what frequency are you updating them at?  I'm working on one using wii motion plus gyro and ADXL335 accelerometer, but I can't get the damned thing to stop oscillating wildly, not matter how much I tweak the PID values.

Short answer: 125Hz.

Long answer: 50Hz is the "standard" freq for hobby servos but it is too slow response for quadrocopters. Some projects claim to be 50hz refreshed, but I believe that it is too slow. Other projects make oversampling on the sensors (about 1kHz) and then averaged to 200 or 100 Hz.

However, I have been for 2 months tuning the PID control. It is a very frustrating stage. If you have a decent loop speed (+100Hz), the problem should still be the PID.

You can tune PID by see-saw method: let the quad to balance in one of it's axis, and test PID:

Simply put 0 values to I and D, start with P:0,5 and continue increasing until violent oscillation starts. Then increase D in very little steps (0.01), until the response start to improve.