Getting Started w/ UAVs

[mystrdylan]

Hi everyone,

I'm new to UAVs, but I'm really interested in building one. I've built a couple of RC flying wings before and I've got some unused sensors (yaw gyros and accelerometers) from my high school FIRST robotics team www.usfirst.org (http://www.usfirst.org/). I put two and two together and started looking for info on hobby scale UAVs.

This forum has a wealth of information, but are there any other websites you know of that have great UAV info or discussion?

As a newcomer I've got a few questions:

-What sort of programming skills are necessary to build a simple UAV? Is there a microcontroller used to process the data from the sensors? What sort of sensors do I need to use? Where can you get this equipment?

-I'm used to building flying wings, and I like many of their design attributes (especially their foam durability). Would you reccomend I stay away from the wing design for my first UAV? How much more difficult is the autopilot for the flying wings?

-Is there any particular kit or design that you would reccomend instead?

-What other advice could you share before I start off on good old-fashioned trial and error?

Thanks,

Dylan, CA
mystrdylan@earthlink.net
FIRST Team 1722

[copperclad]

hi Dylan
i'm just trying to get started too , but i thought you might find this link interesting , it's a UAV truck , and i'm sure it's only a half step to whats involved with a plane , but i thought it made good reading as far as the basics go , dana :)
http://www.stoneflyers.com/gps_guided_truck.htm

this link is to a site that has a lot more info
http://www.elkhart.net/~miked/Ulinks.htm

[lvspark]

If you like wings, you will love these guys...
http://www.et.byu.edu/groups/magicc/movies.html

[Vindication]

I wouldn't recommend a wing for hobby scale UAV's (aka less than 3-5 thousand dollars). I say this because wings require a more advanced type of autopilot.

If you want cheap - go with a stable(but still durable) airframe and then use a PDC-10 (look in the forums.. it's not for sale) or check out http://u-nav.com/.

Vind

[Tuner]

Nice link to the BYU.
Very interesting I love their videos.

Thanks

[mystrdylan]

The BYU site is great! Thanks!

[radiohound]

Here's some more:

Opensource autopilot:
http://www.scalerobotics.com/store/catalog

Other links:
http://www.uavs.net

[AntonK]

let me also throw this out

http://www.recherche.enac.fr/paparazzi/doc2/

:)

Anton

[MattChave]

-What sort of programming skills are necessary to build a simple UAV?

Not a lot, it depends though really how experimental/technical you want to get, you could easily get by with learning as you go. That's the point of the exercise i guess.


Is there a microcontroller used to process the data from the sensors?


Using the latest arm7 chip from Phillips meant that we had to first make a power supply for our microprocessor which was dual rail 1.8 and 3.3V.
Then since we wanted our design to be freely open source and available we didn’t want to use the Phillips c port to the processor which was proprietary so we had to make our own....(this will be available given some time). we had a play with fourth for a while but decided c was the way to go in the end.
The processor is a RISC processor so doesn’t support the divide operation... so after a look around for some open source maths libraries we settled on making our own. (this will also be available given time), this is probably where you might come into problems as far as programming knowledge. I'd suggest using what is available and working i.e. ported. As far as a processor goes, if your short for time.


What sort of sensors do I need to use? Where can you get this equipment?

We'll if you listen to everybody you'll cram 3xgyros, 3xaccelerometers, 3xmagnetometers, gps, pressure sensors, 4 or 6xhorizon sensors into your control system.
We made a flight control system using only a 3-axis magnetometer over 7 months last year for my Honours year at the University of Otago, to complete a physics degree. I didn’t believe Honeywell who use a 2-axis accelerometer to tilt compensate their magnetometers see:
http://www.honeywell.com/sites/portal?smap=aerospace&page=Magnetic-Sensors-FAQ&theme=T17#faq6

or the autopilot project at rotomotion when they said it cant be done, see:
http://autopilot.sourceforge.net/faq.html#magnetometer_attitude

Using only three magnetometers you can only deduce 2 rotations(attitudes), choose what you wand to be done this way, i used pitch and yaw, and used a roll stabilised airframe, but you can detect the actual roll and use it as an input into the equations. using one of the other sensors.

see my project here:
http://uav.bravehost.com

It will all be open source soon but I have to go through and add the gpl licence headers to everything of course and tidy it up a bit.
If you go to the documents section you can read my thesis, soz for the spelling and grammatical errors it was written in a hurry.

You can get magnetometers from www.farnell.com or www.digi-key.com or from Honeywell or Phillips or from many consumer items if they won’t sell them in your country. Or make your own flux gate one, I haven’t tried but it might be possible.


I'm used to building flying wings, and I like many of their design attributes (especially their foam durability). Would you recommend I stay away from the wing design for my first UAV? How much more difficult is the autopilot for the flying wings?

Cool, I’d like to move onto a flying wing soon too. I started with the cheapest plane we could find, a GWS e-starter. Whatever you use make sure you can afford to smash them to pieces and glue it together or have a spare to slap the system in and keep testing, but don’t choose one you'll spend weeks repairing
luckily we never had a crash while the plane was in autopilot, ha-ha of course it was the humans in the loop taking it off and landing which caused the problems, ha-ha, I guess that’s why were doing this. we're still using our first crash test dummy as we continue into the waypoint navigation. We have so far only had to glue the landing gear back on prom a pilots hard landing.


-What other advice could you share before I start off on good old-fashioned trial and error?

Define your goals, set low ones, to succeed you need to be able to see a clear path to what you want to achieve and how you want to achieve it. They’ll inevitably change but you will move along much faster. it's easy to get stuck in the clouds making gadgets and endless airframes, but if your into control theory and want to make a hax control system, don’t get too tied down with the marketing crud of flashy things proprietary uav's use as selling points.

hope this is useful....gidday everyone in this UAV community :)

[MattChave]

Has anyone here experimented or used pitot tubes? just in the middle of adding one to the Apeliotes project (http://uav.bravehost.com) mentioned above. Will order the differential pressure sensor soon,

What i'm wondering is what velocity pressures you get in real life?

from the equations it looks as though i'll go with a 0-1PSI sensitivity range which will give it a range up to 385kph.

p = (d.v.v)/2
pressure, density , and velocity.

i currently have a 1"H2O sensor that should be able to go up to 73kph
does anyone know any different?

[LukeZ]

Matt,

For more than you ever wanted to read about airspeed calculations, you can check out the airspeed section on my website, http://www.kansasflyer.org/index.asp?nav=Avi&sec=Asi&tab=Intro.

However, your math seems to be pretty much spot on. A 1 psi sensor should give you all the speed you need unless you're flying some kind of super jet or something.


Luke

[MattChave]

great looking site luke, very consise too, thanks.
I've ordered the parts so will let ya know the results early next week.