This project was started in November , electronics and control loops. Because I always need a cool project to learn new things, it was clear that something that can fly had to be built.
The project started as a "tricopter-only" project, but as I wanted to build smaller vehicles with more payload capacity, I decided to make some quadrotor, hexacopter and Y6 hexacopter firmwares too. My main interest is to build very small MAVs that fly as good as larger ones (or even better) and that can be controlled by wireless video link. I also experimented with autonomous flight in GPS-denied areas (video), and with GPS assisted autonomous hover (video). It would be cool to add more features to this project but I am pretty busy with my PhD research. But maybe one day I could combine my scientific interests with my hobby projects...
-- William

Contact: Shrediquette @ g m x . d e --- All content published under CC Attribution-Noncommercial-Share Alike 3.0 Germany

12" multirotor propeller tests

Recently, I tested some 12" propellers as I want to make a 12" hexrotor (nothing special, existing 3rd party frame). There are some different opinions about these propellers, but I was missing a direct comparison. I tested 3S (12 Volts) and 4S (16 Volts) and measured the thrust and the current on a test stand, simulating hovering flight. I used a RCtimer HP2814(3536)-710KV motor and an AfroESC 20A slim speed controller.

Here are the props I tested:
The propellers under test: APC Multi Rotor 12x4.4" ; Xoar Electric precision 12x4" ; Maxxprod EPP 12x4.5" ; Aeronaut CAM Carbon light 12x5" ; Graupner E PROP 12x6"
The results clearly show that the popular Graupner E PROP isn't really the first choice for hovering. It requires about 13% more power than the Aeronaut prop for the same amount of thrust during hovering flight. I think the chord length is too small close to the tip (I know that high aspect ratio wings have less induced drag, but here, other effects seem to dominate). The Graupner propeller also makes much more noise than the Aeronaut prop - which is the most quiet prop and also my favourite propeller. Interestingly, it has the largest (mean) chord length and the largest blade area of all props I tested. The APC multirotor is very similar, but has a higher weight. The Maxxprod is not stiff enough for these motor speeds and really shouldn't be used for heavier multirotors. I included it just because I had one lying around. The Xoar wood propellers are really beautiful, very well manufactured and light, but they have a pretty thick airfoil.
Here are the measurements:
Thrust and power at 3S (12 Volts)

Thrust and power at 4S (16 Volts)
The weight of propellers is also pretty crucial, as lighter propellers enable faster prop accelerations and decelerations which is advantageous for the flight stability. Here are the weights:

Graupner E PROP 12x6"21 g
APC Multi Rotor 12x4.4"22 g
Aeronaut CAM Carbon light 12x5"17 g
Maxxprod EPP 12x4.5"9 g
Xoar Electric precision 12x4"16 g

So, my choice is the Aeronaut CAM carbon light propeller (they exist in quite a number of diameters).

"Die Große Show der Naturwunder" - some images...

I found some images of my TV show appearance (to be broadcasted on 31.07.14) in the web:
Images taken from (note to the copyright owners: if you don't want to see your images here, drop me an email!)
Hosts and celebreties
Yogeshwar and me
GEMiNi flight in the studio
Quiz show elements

Die große Show der Naturwunderam 31.07.2014 um 20:15 Uhr auf ARD Heiß her geht es diesmal in "Die große Show der Naturwunder". Frank Elstner und Ranga Yogeshwar präsentieren ein geniales Löschmittel und einen neuartigen Flugroboter, der die Natur zum Vorbild hat.Zu Gast sind Comedian Guido Cantz, die Schauspielerinnen Stefanie Stappenbeck und Marie Bäumer sowie Fernsehkoch Horst Lichter. Sie stellen sich den Quizfragen, müssen aber auch außerhalb des Studios ran.Bildvia TVinfo

IMAV 2014 !

The 2014 International Micro Air Vehicle Conference and Competition (IMAV 2014) will take place on August 12-15 in Delft, The Netherlands. I am very happy that I can join this event again this year (after my longer 'baby-break' last year). Just as in the previous IMAV competitions, I'll team up with Tumba. He will use several autonomous and FPV-controlled "Alpha" quadrotors and I will take some FPV BOLTs and GEMiNis with me. This year, the competition is especially fun, because the organization committee from TU Delft decided to combine the indoor and outdoor competitions in a single event. Tasks include to create a photomap of a village, detect obstacles, street numbers and open windows, and to finally enter some houses and explore the rooms. This might be pretty challenging, depending on the wind conditions and the video link quality. You can have a look at the competition rules here.
I am very much looking forward to the event, and I expect to see a lot of very interesting and great autonomous systems from different teams all over the world!

The BOLT Y6 hexrotor
The GEMiNi FPV racing hexrotor

This is the training village where the competition will take place
Größere Kartenansicht

HEXO+ autonomous aerial cam, kickstarter campaign

Maybe you've already heard of the HEXO+ follow-me copter. The kickstarter campaign recently ended and it was really successful. Check it out here:

HEXO+ on Kickstarter

As you might already guess from the look of this hexrotor, I was involved in designing the airframe and selecting the electrical components for this project. Here are some pictures of early prototypes:

The idea was to make something pretty aerodynamic. The booms are flat plates (each is a very stiff and light sandwich of glas fibre / balsa end-grain / glas fibre) that are arranged parallel to the airflow of the propellers (8"). They hence have very low aerodynamic drag, similar to the body of the copter which is tilted 30° with respect to the propeller plane. Unfortunately, my time for supporting the development of the HEXO+ project will be very limited in the future. But as I really like these kind of projects, I'll try to stay involved somehow.

HEXO+: Your Autonomous Aerial Camera -- Kicktraq Mini

William Thielicke in the TV-Show "Die Große Show der Naturwunder"

A few weeks ago, I was invited as a guest to the "Große Show der Naturwunder" with Frank Elstner and Ranga Yogeshwar (guests in the show are Guido Cantz, Stefanie Stappenbeck, Marie Bäumer and Horst Lichter. Produced by FirstEntertainment GmbH).

I am giving a short demo flight with the GEMiNi and video goggles. Ranga Yogeshwar also does a short interview with me. The show will be broadcasted on the 31. Juli 2014 at 20.15h in the ARD.
It took around 4 days to produce this show, so my partner, my twin (gemini) girls an me spent a very nice week in a lovely hotel in south Germany. I really enjoyed the time over there, it is so interesting to get insights in such kind of TV productions!

Here's a description of the "multirotor part" in the show. 

I can not show pictures of the show itself or give further details, but here's an image with the host Ranga Yogeshwar (as I expected, I was impressed that he is such a clever and friendly person)  at the after-show party, and  another one of my "personal wardrobe" (this is the proof that I was there ;-D).
Ranga Yogeshwar and William Thielicke

My wardrobe ;-)

Lange Nacht der Wissenschaften 2013 in Nordhausen

On the 30th of october 2013, Prof. Klaus-Peter Neitzke and me gave a talk and flight demo during the "Lange Nacht der Wissenschaften Nordhausen" (Long Night of the Sciences). The talk was titled "Fliegen am Limit und dahinter. Die Indoor-Flug-Show mit Flugrobotern", and we really had great fun during the presentations and the flight demo. I presented some of my PhD work on the aerodynamics of the flapping flight in birds, and Klaus-Peter talked about multirotors and control loops, actually the things he does with his students at the university. In the end, we had a pylon-race-deathmatch, which was pretty tough as the space was very limited. We crashed often during this race, and I was surprised how robust the GEMiNi actually is...Thanks to the Fachhochschule Nordhausen for giving us this opportunity!

Here are photographs and some more information (in german however...):

Photo: Karin Lehmann, Peter Blei
Photo: Neitzke

Photo: Neitzke
Photo: Karin Lehmann, Peter Blei

Photo: Neitzke

Photo: Neitzke

Photo: Karin Lehmann, Peter Blei

Some more photographs by Fotoservice Kötz
NNZ article
Thüringer Allgemeine article

GEMiNi - first competition :)

We had a small multirotor-meeting here in Bremen last weekend, and there were also some people that were up for a FPV-competition. So the GEMiNi had its first opportunity to do what is was built for: Race!
A track was quickly built from chairs, tape and some other stuff we found. It was a lot of fun (well I could do FPV-competitions every day because I like it very much to fly "for a reason"), and the GEMiNi finished first.

See the video here:

GEMiNi FPV in the park...

Photo by Kai

The GEMiNi is extremely fun to fly, it seems to be very fast and agile - better than any copter I built before. The "real" GEMiNi video is still in progress (but almost done), so here is a quick video that shows one FPV flight in a nearby park:

Director's Cut: A nice place to fly - Hexacopter in Cameroon / Africa

One of my videos - the MM6 cameroon video - received more than 1000 likes on Vimeo, and about one million views in total (until march 2013). Thank you all very much!! Here I present the Director's cut, showing some additional scenes and longer sequences.

 Watch the video here.

If you don't know the original video, I recommend to watch it first, and then decide if you would like to see the extended Director's cut:


GEMiNi in the TV

A pretty spontaneous interview for a report on the new i-phone app of the European Space Agency (ESA).
Radio Bremen TV asked me to do a quick FPV flight in their foyer:

Video: ARD Nachtmagazin

Flower power!!

Wind tunnel test data

This morning, I did some wind tunnel tests with the GEMiNi chassis. The GEMiNi was designed for FPV air races at high flight velocities, therefore the aerodynamic properties are important (well, it was also designed to look good of course...). I measured the aerodynamic forces generated by the frame (excluding the influence of the propeller's downwash) at a flight velocity of 12 m/s (= 43 km/h, maybe half the top speed) in a wind tunnel using a 2-axes force balance.

Angles of attack between 0 (hovering flight) and 90 degrees (vertical climb) were tested. The angle of attack is defined as the angle between the oncoming flow and the propeller disk. Both the lift coefficient (perpendicular to the oncoming flow) and the drag coefficient (parallel to the oncoming flow) were determined for each angle of attack (n = 3). The coefficients are based on the planform area of the copter.

Four different setups were tested:
  • "canopy-tilt-" refers to the hexrotor without canopy and without the inclination of the rotors. This setup is very much comparable to a conventional, standard hexrotor like e.g. the MM6.
  • "canopy+tilt-" includes the canopy, but no rotor inclination.
  • "canopy-tilt+" is without canopy, but with rotor inclination.
  • "canopy+tilt+" is finally the GEMiNi as I am currently flying it.
The results reveal that the inclination of the rotors has a large positive effect on the overall performance. In combination with the effect of the canopy, the rotor inclination reduces the negative lift by 17 % to 70 % at angles of attack relevant to fast forward flight (10° to 45°). Negative lift pushes the copter down in forward flight and must be compensated by additional thrust. This would reduce the maximum flight velocity and requires additional energy.

Lift coefficient vs. angle of attack. Large lift coefficients at angles of attack between 10 and 45° result in lower thrust requirements to keep the copter in the air. The application of a canopy and rotor inclination enhances the performance.

Additionally (and more importantly), the drag of the copter is reduced by 14 % to 40 %. Aerodynamic drag slows the copter down, so any reduction is clearly beneficial.

Drag coefficient vs. angle of attack. The drag of the copter is reduced quite dramatically by using the canopy and rotor inclination. Top-speeds will be much higher compared to the conventional setup.

To conclude: The analyses have shown, that the canopy and the rotor inclination both improve the aerodynamic properties of a hexrotor substantially. Higher top speeds, respectively a larger endurance during cruising flight will be possible. The additional weight of the canopy is negligible and will hardly influence these conclusions.

P.s.: It is constantly raining here in Bremen, and I am going snowboarding tomorrow, so the outdoor flights are a bit delayed...

Done. Looking forward to first outdoor flights...

What I really dislike in small copters is that they have the same amount of cables as larger ones, but almost no space...
The very first flights were done yesterday night. I used the default parameters from the BOLT S|2, and it seems to fly very nicely. There is a bit too much power, I prefer when my copters hover at about 50% throttle (like the BOLTs). This one hovers at 33% throttle. However, the GEMïNï is built for speed, and too much power will certainly not harm. It will also be possible to carry the GoPro HD Hero I think. The GEMïNï looks amazing in hovering flight...: Due to the tilted rotors, the tail hangs a bit lower than the rest (see my 3D animation), which gives it a crazy look :-D .  

Here are some images I shot this morning:

More propeller tests

Recently, I discovered some small counter-rotating propellers that I didn't know before. I ordered some and did some tests. The red 4x4.5" props look really good, nice thin airfoils and a good precision. During the tests, they made the least amount of noise, and are currently my preferred ones. The performance of the 4x2.5" props is even better, but they have a pretty terrible sound and seem to be less balanced. Both propellers outperform the AirAce propellers, but this is not really a surprise because the AirAce have a smaller diameter and more blades. What is also interesting is the weight of the propellers. A propeller with a lower weight potentially has a lower moment of inertia which is beneficial for the control loops:
  • AirAce: 2.1 g
  • 4x2.5": 1.5 g
  • 4x4.5": 1.3 g
So this is an advantage for the 4x4.5" propellers, especially because the weight of this propeller is more concentrated to the center, which should further lower the momentof inertia.

The difference in endurance is quite dramatic, up to additional 2.5 minutes (+20 %) are possible when using the 4x2.5" instead of the AirAce.

Test setup

Left to right: 'AirAce', '4x4.5', '4x2.5'

Static thrust vs power input (@ 12 V)
Endurance vs take-off weight