Saturday, January 15, 2011

Unmanned Aerial Vehicle (UAV)

As I've written on the Project List I'm thinking about building an UAV.

Now I've been thinking about this for a while now, and the more I think about it, the more I like it. I don't have much at the moment but I'll try to give you some clues about what I'm going to try.

Some of you might now I used to fly model planes. Yes those RC ones! For people in the US and Australia that isn't really a big deal but in Belgium there aren't that many people who do this.

I started flying when I was 16. I was thinking about buying a plane for almost a whole year when I started doing a student-job at the technical department of a major supermarket here in Belgium.
I think I spended little over half of the amount that I earned there to buy myself an Easyglider Electric from Multiplex


A few years later I bought my second plane. The Multiplex Gemini.
Both planes are made from a foam. This might look cheap but it has a lot of benefits. First of it's light, which is kind off a must if you want something to fly. Second it's really strong and can take a hard landing.

I'm still studying to become an Industrial Engineer and I just can't wait to finally get trough that first year! (yes I'm doing my first year for the second time) Next year I should make a project which basically means I'd have to build something. Telling me to 'build something' isn't really a good idea. Two years ago I build a Tesla coil. It wasn't totally working but it was nice to experiment with it.

Tesla Coil

Last year while at GroupT in Leuven we had a similar project to 'build something'. After a week our teachers were backing off and we just had to describe what could be build out of it.
Together with a few other sick people of my class we took this a step or two further and we build an airhockey table. (for those who wonder, yes I am the one with the 'economy sucks' shirt) <= please note my hear is a lot shorter now!
Airhockey Table (AirT) build by the FanT project team

So you might have guessed that I'm not new to taking things over the top.

The goal
Since it will be started with a school project I'll try to do as much as possible myself. I've thought about using DIYdrones as a guide, but using an ardupilot with their code would mean it isn't totally my project. It would make it harder to convince my teachers about this project to.

So I'll be starting from scratch, either (still) using an arduino or some AVR chip. That way I'm doing 2 project of the list at the same time.

The first thing I'd need is a plane. I don't think I'll use my easyglider, I might buy an easystar to start with.


It will be either that or building a plane myself. Due to stability and stuff I'm thinking of something with a shape like this:

Belgian B-Hunter

Yes it's ugly but it does the job and has everything I need. It'll probably be between 2700m and 3700m wingspan which is a lot larger than the easystar (1370mm) or the easyglider (1800mm)

Now I'm not really considered about the flying itself. Taking of should be fairly easy to program to. But the hardest part will be the landing. I've done some calculations and this is what I get:
- Landing with GPS is a no no, it's not good for precise measurements!
- IMU's, xyz-sensors and gyro's are good but not for a landing. They can have wrong values for short amount of times. When this happens on a crucial time I''m dead (or at least the plane is).
- Using soundwaves and a transciever on the ground isn't working either. If the plane would be 200m away and sound is traveling at 300m/s that would mean that a single pulse would be traveling for about 1.2seconds. Way to much!
- Using electromagnetic waves and a transciever also isn't working. Light and other electromagnetic waves are traveling at a speed of 300 000km/s or 300 000 000m/s. So even if I'd have a unit inside the plane that can read up till 1/1000000 (1 millionth of a second) I still don't know the difference between 1 and 300m.
- using a radar is way to heavy for the planes I'm willing to use.
- Using an ILS like real planes isn't my favourite either. They use the power of the waves to calculate the position. But in windy or fogy weather this can result in problems. I can't use time to calculate the position since the plane doesn't know when the wave left the ground transciever.

So the only thing that remains is something like the B-hunter is using now: IR LASER beams.

OPATS: Object Position and Tracking System

I've emailed our army about it, I'll let you guys know when I find out more. I'm not totally sure about how this system works but as I see it the ground transciever sweeps a certain line facing lets say 30° up from the ground. The plane has a reflector on it, so every beam that hits the plane there gets redirected. The ground station then knows the distance of the plane. since (distance/height)=sin(30°) we can calculate the height of the plane. Using either the cosinus or pythagoras will give us the ground distance until the station.

The biggest benefit about this system is that the plane only needs a reflector for it. All controls would be given by the ground station so the processor in the plane doesn't need to do anything during landing (except monitoring the airspeed).

Futur Goals
In the end it will be nice to have a whole set of planes that use the same basic 'OS'. With little changes I think it must be possible to make planes for different goals. One for taking scenery movies, one for spying on people (police stuff or so, since it's all for science :D)...

Ofcourse I'll be telling you guys everything about it, giving the source code and practical tips..

Please tell me what you think about this ;-)

kind regards


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