sh4d0w0lf
Posts: 20
Joined: Thu Jul 28, 2011 9:40 am

Re: UAV

Sun Aug 21, 2011 4:54 pm

That certainly helps, I didn't think of radio communications.. that would however present some problems that would need looking into. WiFi would be pointless on a long range UAV (it would never be in range for long enough).

Might have to revive my idea that I mentioned above :P

AmyS3
Posts: 173
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Re: UAV

Sun Aug 21, 2011 5:58 pm

wifi will only be used if the uav is at the homebase so i can up/download data at a higher bandwidth.. like downloading pictures/videos or upload programm updates.

the radio link is just some kind of emergency medium since it will use quite some power to establish a realy long range connection (>3000miles). and since i can only use low frequencys and bandwidth to get that range it is realy just emergency.. like moving the homebase to a different location or "help im going down at location xy please rescue me"
the radio link will be triggered only at fixed time periods and dependig on the location of the uav to save energy.
if for example the uav can connect to a mobile phone network it will not trigger the radio at all, and will send a text message to the homebase that it uses this type of communication.

AmyS3
Posts: 173
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Re: UAV

Sun Aug 21, 2011 5:59 pm

damn double posts..

btw. satelite communication would be great, but is way to expensive.
depending on the carrier it costs ~5 pound just to send a text message...
not to mention ~10 pound per minute for a voice connection.

cadack
Posts: 5
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Re: UAV

Sun Aug 21, 2011 7:14 pm

For a budget UAV, is there any point in communication over such long ranges? Leave it to the r-pi to navigate itself into a mobile reception / wifi area making it's own decisions across the oceans. it will have gps/maps. For the price of adding long range coms, you could build another UAV that tries a slightly different flight plan. No point rescuing a £1000 UAV

AmyS3
Posts: 173
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Re: UAV

Sun Aug 21, 2011 9:29 pm

well i get what you mean, but it is quite important to have those kind of long range communication.
for example: you gave the uav the order to fly from paris to new york. while it is on its way over the big sea, you reconsider and want the uav to fly to japan instead...
it takes quite some time for the uav to reach the us and try to get a wifi or cellular network link.
so if you cannot reach the uav on its way you are doomed to wait until you can make contact with it..

the raspi will make its own decisions based on the gps/maps but you still need to give it a target or at least a order what it should do.. imagine the raspi gets bored while the uav is half way over the ocean and thinks "fu** it im staying here.." ;-)

for the budged i´m targeting... so far the cost are ~150 pound which includes the mayority of the electric parts and the raspi. i think i can even stay below 500 pound.
but its better to target a higher cost and do it with less, than target lower costs and end up paying more..

AmyS3
Posts: 173
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Re: UAV

Sun Aug 21, 2011 9:29 pm

double post...

Cool.Majkl
Posts: 15
Joined: Thu Aug 18, 2011 9:10 am

Re: UAV

Mon Aug 22, 2011 8:45 am

That is just superb. AmyS3 you are from germany right ? Till what distance can communicate the AM RF Transreciever ? Maybe there should be two RasPi on board in case, that the first one would stop working. What about safety features ? For example, what if there was a low flying aircraft ? And don't you think that we could get in trouble with air trafic control ?

AmyS3
Posts: 173
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Re: UAV

Mon Aug 22, 2011 6:17 pm

yes im german :-)
the radio transreciever can theoretically send/recieve around the whole world.. it mainly depends on the frequency which is used and the antenna design of course.
there will be only one raspi inside but it will be secured with other microcontrollers to ensure a minimal functionality if the raspi goes bad. same with the mcu´s which are backed by the raspi.
any system can reboot the other one and can sense if it is not working.

the question about other aircrafts is quite important. but i can tell you that i try to get all major commercial flight routes into my gps map so i can avoid those. but it is a different topic when it comes to private flights. but they can only fly in specific heights due restrictions they have to obey.
i think the most work i have to do in this project will be the gps map, to get all the airports(commercial/private) and flight routes into it. well there will be more data in it than that, but hey its necessary for a save trip.
i will also try to get my hands on a honeywell anti aircraft colission beacon but it bet its out of my budget..

Cool.Majkl
Posts: 15
Joined: Thu Aug 18, 2011 9:10 am

Re: UAV

Mon Aug 22, 2011 6:45 pm

I am from Czech Republic :).
I really love this project and I would love to build my own UAV too, but 1000 pounds is 1000 pounds. But even I'm going to try build it. Anti aircraft beacon will be really expensive. My uncle is working at Ait trafic control in Czech, and my brother is working on airport in Holland, so maybe i can get some info from them (If you are interested ;))

Cafe
Posts: 62
Joined: Thu Jul 28, 2011 2:22 am

Re: UAV

Tue Aug 23, 2011 2:28 am

Just thinking aloud: Maybe you should get the attention of Virgin Atlantic or other similar company. They can easily fund, and more importantly provide access to the right information and people about the operational aspects. (It looks like you will manage the technology bit.)

toxibunny
Posts: 1382
Joined: Thu Aug 18, 2011 9:21 pm

Re: UAV

Tue Aug 23, 2011 2:51 am

no, don't tell anyone! they'll ban you and then arrest you for spying!
note: I may or may not know what I'm talking about...

AmyS3
Posts: 173
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Re: UAV

Tue Aug 23, 2011 9:59 pm

Quote from toxibunny on August 23, 2011, 03:51
no, don't tell anyone! they'll ban you and then arrest you for spying!


hehe thats a good one XD

thx for the offered help about the beacon. a friend of mine was working for boeing and germanwings as a technican. he still got good contacts there. maybe i will be able to get a used one which they dont use/need anymore. but i dont have too much hope on that topic. the beacon uses lots of power anyway so i might cant use it...

founding is not needed from a third party like virgin since i have the money myself to cover that project.

i found a resource for a radio transreceiver which can easily cover the whole globe.
the institute is called osir and got its mainoffice in newzealand.
the will use it for interstellar radio transmissions.. so the earth would be no problem...

jonititan
Posts: 30
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Re: UAV

Fri Aug 26, 2011 11:40 am

I think you might find that the radio won't reach.
Interstellar communications are based on using a massive receving antenna like those at jodrell bank.
They also assume line of sight between the antenna and the space probe.
Have you looked at the lifting body concepts?
Also you will need to look at balloonets within the envelope of the craft to control the pressure of the gas bag as you ascend and descend.
I can find some references if you need them.

jonititan
Posts: 30
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Re: UAV

Fri Aug 26, 2011 12:09 pm

If you can work out the weight of the electronics you believe you will need i can work out what gas volume you will need and create some worked estiamtes for what your structure might weigh.

Looking at your list you seem to have quite a few items.
You might be surprised at the amount of gas you will need to lift it and the size of the resulting envelope.

langlo94
Posts: 29
Joined: Sun Aug 28, 2011 12:51 am

Re: UAV

Sun Aug 28, 2011 1:00 pm

considering that you will be using an airtight system have you thought about the possibility of using hydrogen instead?

deggy
Posts: 9
Joined: Thu Jul 28, 2011 2:28 am

Re: UAV

Mon Aug 29, 2011 3:37 am

Looking at the navigational payload - the problem with using standalone sensors is the drift rates - especially with MEMS gyroscopes and accelerometers. You could work very hard to get the filtering correct yourself and even positioning would be difficult, let alone maintaining an accurate attitude.

You want something like this...
http://www.sbg-systems.com/doc.....eaflet.pdf

A serial-interfaced IN/GPS unit that will take care of the position and attitude itself - no idea how much it costs though.

Here's a good paper.. http://bullseye.xbow.com:81/Ge.....p_Note.pdf

That said, in most countries you'll never get the clearance to fly anything like this outside visual range because it will count as an aircraft. Any airspace save for Class G will be completely out of the quesition (in the USA you are limited to 400' and below, away from airfields - the Air Navigation Order in the UK gives similar restrictions) and I am fairly sure that there are strict limits on transmitter power, altitude, speed and range for the UAV to count as a remote controlled aircraft in ICAO signatory (i.e. all) countries.

Now, if you could build DTED into an autopilot and build a terrain-following UAV that stayed below 400' that would be impressive!!

AmyS3
Posts: 173
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Re: UAV

Mon Aug 29, 2011 3:52 pm

that is some good information from you deggy...!
i will take a close look at the material.
staying below 400' could be possible. it is not that close to the ground to fear collisions with random objects except tall buildings. but they are normaly found in city´s only. and we dont want to go there ;-) it is possible to let the uav follow roads just like a normal satnav but maybe with a bit distance and keep away from towns/citys... that could do the trick for continental navigation. overseas is a bit easier.

the transmit power for the radio is only restricted in specific frequencies. there are open ones which can be abused like hell.. i´ve seen also some very impressive antenna designs for omnidirectional transreceiving. but i still need to do some more resarch in this direction.

about the hydrogen topic: NO WAY! it is true that i´m using a airtight construction in the end, but hydrogen is way to unsafe for this kind of project. the amount needed for the uav is high enough to be rated as a flying bomb. i will never get any flying clearance for the uav with this material inside. therefore i will only use helium.

@jonitan: it would be nice of you if you could calculate the volume needed. i´ll come back to you when i have all materials here to weight them.

all in all, there is still quite some work to do for the project. and also still some waiting time for materials from china... why the hell do they need %$#§ over 25 days to deliver... damn.

jonititan
Posts: 30
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Re: UAV

Mon Aug 29, 2011 10:11 pm

@AmyS3

While it is true that as a licensed Ham you can build radios in certain bands with a large power output in the UK you are not allowed to use that radio in an aircraft. Unmanned operation is allowed but only under certain specific circumstances. If you are not in the UK that might not apply but it does come into effect if the UAV visits the UK.

Typical radios that are used for unmanned amateur projects are more usually classified as license exempt by Ofcom. I know of some in the 700Mhz and 434Mhz frequencies.
See http://ukhas.org.uk/communicat.....nce_exempt
However typically these are low power. High altitude balloon enthusiasts depend on line of sight and like minded Hams monitoring the bands with good antennas and sensitive receivers.
I don't think they have tried for two way communication.

FearL0rd
Posts: 2
Joined: Tue Aug 30, 2011 10:55 am

Re: UAV

Wed Aug 31, 2011 1:51 am

I have a QUAD runing arduino with wiimote+ and nunchuk... I would loke to have it with a better processor

nrdb
Posts: 13
Joined: Fri Jul 29, 2011 5:35 am

Re: UAV

Sat Sep 10, 2011 2:35 pm

I think your biggest problem will be keeping this in the air. As the air pressure and temperature changes the gas envelope will need to be inflated/deflated to maintain neutral buoyancy. This will mean if you use helium you will have to carry a tank of compressed helium to correct the buoyancy.

The only way to avoid this is if the craft has a deliberately negative buoyancy and uses its motors to keep it in the air.

BTW an envelope of hydrogen can't explode, at worst it can only burn. And in this case that would be very unlikely. You need to have a major leak plus something to ignite it.

jonititan
Posts: 30
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Re: UAV

Sat Sep 10, 2011 10:28 pm

The solution is actually to have small air bladders within the envelope. Typically used to trim the vehicle fore and aft but also to adjust the density of the vehicle.
As the vessel ascends the air is forced out by the pressure of the lifting gas pushing against it.

This is a relatively simple task.

jonititan
Posts: 30
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Contact: Website

Re: UAV

Sat Sep 10, 2011 10:31 pm

But it all depends what you want the Uav to be able to do.

jonititan
Posts: 30
Joined: Sat Aug 06, 2011 2:05 pm
Contact: Website

Re: UAV

Sat Sep 10, 2011 10:40 pm

I also intend to build a uav.
However I will be using the Raspberry Pi for image processing for obstacle avoidance.
Mine will be fixed wing.
Probably a reverse delta wing similar to some of the Lippisch WIG craft.

This will be used to study obstacle avoidance.

MDC
Posts: 167
Joined: Thu Jul 28, 2011 6:27 pm

Re: UAV

Sat Sep 10, 2011 11:35 pm

a few questions. What about power lines could this not be an issue? Also how would you stop your self blowing of course even at 400' the winds on a bad day would be awful? How fast could the UAV go at top speed and how would it handle when navigating left or right?

I think you may find the below link useful

http://en.wikipedia.org/wiki/O.....Skepticism

MDC
Posts: 167
Joined: Thu Jul 28, 2011 6:27 pm

Re: UAV

Sat Sep 10, 2011 11:41 pm

Recovery scheme. I think you would need a tracking system in the UAV for collection should it go down (would have to be water proof and whole vehicle would need to float even on rough seas). Assuming it did get washed up or ended up coming down over land you could use crowd sourcing for recovery, if you got the project off the ground you could get alot of people interested and therefore say there was a probelm and my UAV is in this country at these exact co-ordinates, then you could get one of your fans to pick it up and either get it back in the sky or post it to you.

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