Science & Engineering Fair: Designing a small UAV (need pointers!)

[skatj]

Me and two of my friends are entering our state's Science and Engineering Fair and we decided to build a small UAV, we have a budget of about 400$.

We're using this as the brain of the UAV.

http://www.parallax.com/detail.asp?product_id=27807

From there on, we're pretty much flying blind, none of us have any experience in electronics or aviation, just two years in working with Lego Mindstorms robotics.

We want to build either a fixed-wing airplane or a quadrocopter. So far we are leaning towards the quadrocopter because of its unique design (it'll impress the judges!). However we are a little confused as to the logistics.

1. Assuming we use a NiMh 9V square battery to power the microcontroller, would we need to use separate batteries for each of the four motors?

2. What motor controllers can we use that are compatible with a brushless motor? http://www.parallax.com/html_pages/products/motorcontrol/motor_control.asp

3. Do we need a certain type of brushless motor for a quadrocopter? A certain type of propeller?

4. What sort of sensors should we buy? We aren't looking for truly autonomous flight, our main priority is just to get it off the ground and be able to stabilize itself.

5. Do you think a regular brushed DC motor could be able to power it (Again, it doesn't have to be really powerful, just enough to get off the ground, speed doesn't matter that much).

6. Any suggestions for motors/motor controllers/batteries?

[hg1]

You will find a lot of discussion about quads here -
http://www.rcgroups.com/multi-rotor-helis-200/

For example -
http://www.rcgroups.com/forums/showthread.php?t=706305
http://www.rcgroups.com/forums/showthread.php?t=720446

Also, see
http://en.wikipedia.org/wiki/Quadrotor
http://www.uavp.de/index.php?lang=en

You have chosen a difficult project, and powering the microcontroller is the least of your challenges. You can run everything (motors, processor, sensors) off the same battery with addition of a voltage regulator, and your microcontroller can generate the servo control signals that are required by the brushless motor controllers. If you are using 3-phase brushless motors, you need to specifically look for brushless controllers - the controllers shown on the parallax website are for brushed DC motors. You can power a quad from brushed DC motors (e.g. do a search on Draganflyer), and it will be cheaper, but efficiency is lower.

To simplify the task, you might want to look at adding your microcontroller to an existing low-cost quad such as X-UFO. An alternative might be to add a microcontroller to a coaxial rotor heli such as a Blade CX2. This type of approach is probably the only way you will be able to keep things within your $400 budget. Anyhow, that's my $0.02 ...

[zlite]

We built one fixed-wing UAV with the Basic Stamp controller. The components and code are here (http://diydrones.com/profiles/blog/show?id=705844%3ABlogPost%3A731). You could switch to a cheaper airframe, but you'll still struggle to hit your $400 target.

The Basic Stamp chip is only appropriate for navigation (and it can only just barely handle that), since it doesn't have floating point operations or enough power to handle an IMU. We used a FMA Co-Pilot to handle stabalization and just had the Stamp processor handle steereing to GPS waypoints.

If you wanted to do it all one one chip, you'd have to upgrade to the Parallax Propeller chip, but the IMU programming challenge is no easy thing. Give yourself a year at least--this is grad school stuff.

[macboffin]

Regardless of the technical issues involved, presumably the evaluators will be reasonably "Aware of the art" and thus aware that this is not a "Unique" design approach.There are a bunch of quadcopters out there already, well publicised in the media.

[dmgoedde]

Give yourself a year at least--this is grad school stuff.

Amen! But - if you catch the bug.... and get addicted then watch out. No barrier will get in your way permanently (but it may take years to get a working systems though).

I built my first autopilot using two basic stamps: BS2pe to handle the navigation and hold waypoints in the EEPROM. It also read 1 Hz GPS data from an EM-406 module I bought at sparkfun for perhaps $70. The other STAMP was the BS2Px because it runs fast for a STAMP (about 19,000 lines of code/second). That stamp did a 50 Hz loop of measuring and integrating readings from two single axis gyros for a very crude IMU, and also did the PI calculations and fed pulses to the servos. The two stamps are connected by two lines for full duplex serial. Navigation stamp sends steering updates to the PI loop STAMP. Both stamps are connected to the R/C receiver and can sense when manual control is desired.

In all, it was difficult and BARELY doable with the 16 bit integer math. In particular, making provisions for divide or multiply of negative numbers was a pain. I relied on a very stable airframe, so that a "real" or robust IMU was not required.

The electronics alone cost about $350 or $400 once I had a workable design. Airplane with all the trimmings is another $200-400.

Might I suggest a semi-autonomous design? Perhaps a 2m glider with polyhedral wings... the autopilot could probably be composed of JUST a BS2px and a GPS unit... about $150 in parts, and would merely do rudder steering while you handle the throttle and elevator by R/C. It would be a great accomplishment to see it steer through waypoints in the sky. You would probably catch the bug, and attention of the judges.

Dean

[mlbco]

Skatj,

If you really want to stick to your budget the best approach is to build a minimal system. A friend of mine built a GPS-only UAV based on an inherently stable platform. The aircraft could fly waypoints, but not much more than that. Here is a link to his project:

http://online.sfsu.edu/~meholden/Publications/min_sense_airplane.pdf




Steve

[skatj]

Alright I think a quadrocopter is out of the question.

So a fixed-wing aircraft, we don't really need truly autonomous flight. We just want to a build a flight capable aircraft that's powered by the Basic Stamp and can fly in a preprogrammed, predetermined flight path in controlled conditions (such as a high ceiling gym with no wind). Afterall, we're only high school students. :)

Anyway, I picked out a list of products and hopefully you guys will let me know if it'll be enough for the job.

http://www.parallax.com/detail.asp?product_id=29144 HB-25 Motor Controller

http://www.parallax.com/detail.asp?product_id=910-27207 Basic Stamp Discovery Kit (Basic Stamp 2 Module + Board of Education Development Board)

http://www.parallax.com/detail.asp?product_id=28823 Parallax Servo Controller

http://www.parallax.com/detail.asp?product_id=28017 Memsic 2125 Dual-axis Accelerometer (Err, can anyone tell me exactly what kind of info does sensor will give me?)

- 9V NiMh square battery

Any suggestions for motors, propellers, and servos? Preferably the ones that are the easiest to set up. Plane will probably be made out of balsa wood or maybe foam, so hopefully a brushed motor can get it off the ground!

[dmgoedde]

...can fly in a preprogrammed, predetermined flight path in controlled conditions (such as a high ceiling gym with no wind). You won't be flying a GPS guided plane in a high-school gym, unless the gym is huge and your plane flies at only 5 mph. The waypoints will probably be way too close together.


http://www.parallax.com/detail.asp?product_id=29144 HB-25 Motor ControllerI would scrap the motor controller - what do you need it for? Use a brushed motor controller (to stay in budget) that is standard for R/C planes, as a bonus it provides around 5 volts froom BEC to power servos and your STAMP and GPS.


http://www.parallax.com/detail.asp?product_id=910-27207 Basic Stamp Discovery Kit (Basic Stamp 2 Module + Board of Education Development Board)Sure, a BS2 will be enough if all you are doing is reading a couple GPS nmea strings and simple navigation calcs, and calculating position required for 1 servo. I drove a small R/C truck around my neighborhood with nothing more than a simple BS2 on the simplest training board Parallax offers (Stamps in class education series)


http://www.parallax.com/detail.asp?product_id=28823 Parallax Servo ControllerTo keep under budget, I think you can scrap this. If your ystem is feedng pulses to just 1 servo, you can make a software scheme for the BS2 that sends pulses to servo near 50Hz, then periodically checks for new GPS data and updates the navigation calculations. It works, I have done it.


http://www.parallax.com/detail.asp?product_id=28017 Memsic 2125 Dual-axis Accelerometer (Err, can anyone tell me exactly what kind of info does sensor will give me?)For a simple system to stay under budget scrap this. This sensor tells you information you won't need if an inherently stable plane is used with a minimal working design to stay in your budget. The info would be state of pitch and roll under certain ideal conditions such as the only acceleration force felt by plane is gravity (i.e. no hard banking or accel/deccel of forward motion)


9V NiMh square battery
Scrap this - use BEC power from the throttle speed controller.

If I were mentoring you directly I would suggest this to get your feet wet with minimal working system and stay in budget, and best chance of success:
1) BOE with BS2
2) EM-406 GPS module from sparkfun.com
3) a $12 GWS 5 amp speed control with BEC for brushed motors
4) 2 Hitec HS-55 servos (about $15 each, high quality, and only about 7 or 8 grams)
5) GWS pico receiver - again maybe just $25, 4 channel output... channel 2 goes straight to elevator and channel 3 to the speed control that you fly by R/C. Channel 1 or 4 goes through BS2 BOE and then on to the servo. If channel 1 is the steering, then use channel 4 from transmitter to control wether plane is in auto/manual mode. IF channel 4 is the steering, use channel 1 to control auto/manual. In manual mode the BS2 reads pulse width from receiver then reproduces it and sends it on to the servo, in automode it ignores your steering command and generates steering commands to hit the waypoints.
6) batteries - for safety and economoy perhaps a 7-cell NiMh that comes with a beginner plane (see #7)
7) plane: something pre-built. Hobby-lobby.com carries several planes like this. many include charger and NiMH battery, fly nice and stable with upswept wings. Checkout the Wing Dragon http://www.hobby-lobby.com/wingdragon.htm It has radio system, batteries, charger, transmitter all for only about $110. If you already have radio/battery/charger then the Wingo USA would be ideal http://www.hobby-lobby.com/hlwingo.htm

Dean

[skatj]

You won't be flying a GPS guided plane in a high-school gym, unless the gym is huge and your plane flies at only 5 mph. The waypoints will probably be way too close together.

No need for waypoints, we just want to get it to fly and do a few turns or whatever and land using only the computer (no human involvement). Nothing too fancy. We also won't be using GPS (at least for now, if we manage to get it flying and stable we'll look into expanding our possibilities).




I would scrap the motor controller - what do you need it for? Use a brushed motor controller (to stay in budget) that is standard for R/C planes, as a bonus it provides around 5 volts froom BEC to power servos and your STAMP and GPS.

I'm using it simply for safety's sake, this is all uncharted territory for me so using a Parallax product with another Parallax product seems safer to me. Although if I did just use an R/C brushed motor controller, would I be able to program/control it with the Basic Stamp?



To keep under budget, I think you can scrap this. If your ystem is feedng pulses to just 1 servo, you can make a software scheme for the BS2 that sends pulses to servo near 50Hz, then periodically checks for new GPS data and updates the navigation calculations. It works, I have done it.

I think I read somewhere that the Stamp can only power two servos, so a servo controller would be needed to move the control surfaces.


For a simple system to stay under budget scrap this. This sensor tells you information you won't need if an inherently stable plane is used with a minimal working design to stay in your budget. The info would be state of pitch and roll under certain ideal conditions such as the only acceleration force felt by plane is gravity (i.e. no hard banking or accel/deccel of forward motion)

Alright, I'll scrap it.



Scrap this - use BEC power from the throttle speed controller.

Sorry, could you clarify what "BEC power" is? :(


4) 2 Hitec HS-55 servos (about $15 each, high quality, and only about 7 or 8 grams)

Why only two? I was under the impression that 4 would be needed, 2 for ailerons, 1 for rudder, and 1 for the elevator. (I've never flown R/C planes before, so forgive me if this is wrong).


6) batteries - for safety and economoy perhaps a 7-cell NiMh that comes with a beginner plane (see #7)

So far I've read about volts, amps, and watts so I know what they are, but what are cells and what difference is it if you get batteries with different amounts of cells?


7) plane: something pre-built. Hobby-lobby.com carries several planes like this. many include charger and NiMH battery, fly nice and stable with upswept wings. Checkout the Wing Dragon http://www.hobby-lobby.com/wingdragon.htm It has radio system, batteries, charger, transmitter all for only about $110. If you already have radio/battery/charger then the Wingo USA would be ideal http://www.hobby-lobby.com/hlwingo.htm


Unfortunately the science fair rules strictly forbid against kit building/premade stuff, and I would also get more satisfaction if we made it ourselves. Although I was considering buying a cheap R/C plane just to fly around and then eventually dissect to found out how everything works (admittedly I have only a very rough idea as to how servos actually control the control surfaces).


Thanks for all your help :)

If this is a success I hope to continue this project, robotics has always interested me since middle school and this is a whole new frontier. :D

[hg1]

Unfortunately the science fair rules strictly forbid against kit building/premade stuff, and I would also get more satisfaction if we made it ourselves. Although I was considering buying a cheap R/C plane just to fly around and then eventually dissect to found out how everything works (admittedly I have only a very rough idea as to how servos actually control the control surfaces).That's the best suggestion you've made so far. Once you learn to fly, you can start to replace the radio controls with the microcontroller, and perhaps eventually strip your R/C plane for parts to use in the science fair build.

[dmgoedde]

That's the best suggestion you've made so far. Once you learn to fly, you can start to replace the radio controls with the microcontroller, and perhaps eventually strip your R/C plane for parts to use in the science fair build.

Definately agree. I flew planes starting as a kid, did R/C the last 25+ years, so I can attest that having some experience with the planes will translate to greater chance of success as you gradually replace R/C with a microcontroller.

BEC = Battery Eliminator Circuitry built into the speed control. You end up using one main battery to power the entire airplane. This single pack powers the flight motor (propeller for thrust) and some power is diverted, at the proper voltage, to R/C radio and servos. You can also use this BEC output to power your autopilot or microcontroller.

For starting with minimal system, no need for ailerons. The plane types I suggested are automatically stable in roll axis. You'll have your hands and head full enough of work to go from start to successfull system you want to build, even if it were "just" a simple automatic steering controlled by GPS or whatever you want to do.

Not sure what you want to do to have the plane land itself if no GPS is used. You need some sensors to the outside world. GPS is a lot of data for just $60 or $75, and can fit the bill. You could build a semi-large very low wing load plane that flies slowly in your gym... GPS would work perhaps. You mention not wanting to use GPS, so not sure how you want to have the craft fly itself.


So far I've read about volts, amps, and watts so I know what they are, but what are cells and what difference is it if you get batteries with different amounts of cells?Cell is the basic physical/chemical unit and a bunch of them make a battery (battery is plural - like a battery of cannons for example). A NiMH cell produces about 1.2 Volts of electrical pressure, and multiple cells in a battery wired in series has more electrical pressure... 1.2 per cell in the battery. A 7 cell NiMH is common for small R/C planes, or a 2 or 3 cell Lithium battery (lithium polymer cells makes about 4.3 Volts when fully charged).

[kd7ost]

I don't see how a GPS would help in landing. It might be pretty iffy to even get a decent GPS lock, (If any at all) inside the gymnasium. Especially depending on the building and roof material. Also the altitude doesn't reconcile that well with a 2D lock or even with a 3D. Even if they use WAAS. I think a plane set up to flair properly, (fixed elevator position) with the proper balance and throttle off, it will desend and set down in a suitable fasion. Maybe leave off the LG and just belly land once the programmed flight is complete. That makes programming easier to since you won't have to parse the GPS strings.

Dan

[hg1]

I don't see how a GPS would help in landing. It might be pretty iffy to even get a decent GPS lock, (If any at all) inside the gymnasium. Especially depending on the building and roof material. Also the altitude doesn't reconcile that well with a 2D lock or even with a 3D. Even if they use WAAS. I think a plane set up to flair properly, (fixed elevator position) with the proper balance and throttle off, it will desend and set down in a suitable fasion. Maybe leave off the LG and just belly land once the programmed flight is complete. That makes programming easier to since you won't have to parse the GPS strings.
DanOff topic, but is there a standard technique for ground sensing using onboard sensors for autonomous landings ?

==========
edit: found some answers here -
http://www.ee.byu.edu/faculty/beard/papers/preprints/BarberGriffithsMcLainBeard05.pdf
http://prism2.mem.drexel.edu/~billgreen/Bibliography/griffithsRAM2006.pdf

[kd7ost]

Something else to keep in mind.

The Parallax BS2 can only command 1 I/O at a time. You need to give the servo's pulses at ~50hz rate. If the stamp is tasked to parse a GPS string, it can't keep commanding the servos. Even if you aren't parsing strings from a GPS unit, the fact that the BS2 processor is multi-tasking you need to have something that keeps the servo's happy when the processor is off doing other tasks. Like talking to a different servo. Something the the Scott Edwards servo controller, (I'm sure there are others but I haven't looked into it in quite a while) would need to come into play.

What this device does is simple. Your Stamp tells a servo what position to go to. The Servo controller is wired between the Stamp and the servo. The servo controller interprets the pulse then continues to replicate it at the correct rate and at the pulse width it was told. It will do this while the Stamp moves on to other functions to keep the servo happy. Not until the Stamp talks to it again and changes the servo pulse width will it command the servo to the new position.

You can't pull off servo control in a small UAV like this with a Parallax BS2 alone.

Dan

Edited, I just did a search on the Scott Edwards site and don't see that product available any more. I'm sure someone out there makes a similar unit.

[_helitron_]

This here for example

http://www.acroname.com/robotics/parts/R193-SD20.html

Cheers,

//Erwin

[dmgoedde]

Dan - you are SO right, I just recalled that in my first design (one single stamp to drive a truck and parse GPS strings) the BS2 actually did NOT drive the servo directly... it sent updates to a digital potentiometer that was in the timing loop of a 555 timer that fed pulses to the servo. Essentially I made a servo control module to relieve burden of the Stamp to not need feeding 50Hz pulses.

I agree to scrap the GPS for a landing controller... you could use a senstitive digital barometer like the SCP1000... at take off the base pressure is noted... and upon landing you flare just below that pressure. It is sensitive enough, and sparkfun.com sells a breakout board that has all required passives already. Just need to handle the 3V logic safely with a 5V stamp.

Dean

Something else to keep in mind.

The Parallax BS2 can only command 1 I/O at a time. You need to give the servo's pulses at ~50hz rate. If the stamp is tasked to parse a GPS string, it can't keep commanding the servos. Even if you aren't parsing strings from a GPS unit, the fact that the BS2 processor is multi-tasking you need to have something that keeps the servo's happy when the processor is off doing other tasks. Like talking to a different servo. Something the the Scott Edwards servo controller, (I'm sure there are others but I haven't looked into it in quite a while) would need to come into play.

What this device does is simple. Your Stamp tells a servo what position to go to. The Servo controller is wired between the Stamp and the servo. The servo controller interprets the pulse then continues to replicate it at the correct rate and at the pulse width it was told. It will do this while the Stamp moves on to other functions to keep the servo happy. Not until the Stamp talks to it again and changes the servo pulse width will it command the servo to the new position.

You can't pull off servo control in a small UAV like this with a Parallax BS2 alone.

Dan

Edited, I just did a search on the Scott Edwards site and don't see that product available any more. I'm sure someone out there makes a similar unit.

[skatj]

Hey guys, I need some tips about designing the actual plane.

We want to make it as stable as possible, and slow too.

Would a flat bottomed fuselage (say, a balsa wood board with electronics strapped on to it plus a clear plastic dome covering) be very aerodynamic? How would this affect stabillity/speed/lift?

If the wings are positioned on the bottom, middle, or top, how does that affect the plane's flight capabilities?

Does it matter if the wings are rounded, rectangular, sharpened at the ends?

Does wing length matter?

Does rudder and elevator size matter?

Keep in mind we only will have a low-power brushed motor.

edit: Also what's the difference between a biplane and a regular plane?

[arshomette]

Oh man... Blind leading blind here...

However, what I can say is this:

Unfortunately, everything matters!!!

If the wings are positioned on the top, then the plane will be the most stable. The middle and bottem are less stable but more manuverable (iirc)

Rectagular wings are the best for stability, the others are getter for speed or control.

A biplane has two wings. A regular plane has one (although to be fair biplanes were around a lot longer than a "regular" plane... a monoplane is more appropriate terminology)

Hoped this helps!

Edit~You could make a project out of these variables

[Arthur P.]

You might also want to have a look at http://www.mikrokopter.de/, in particular some of the videos demonstrating GPS controled flight. Quadrotor is a bit more expensive as you need four motors and four speed controlers, but these machines are quite stable and the software is open source and available. And cost can be kept down with some careful choices.

More and more info on the site is now available in English. Also have a look at the build thread under aerial photography: http://www.rcgroups.com/forums/showthread.php?t=716870.

[skatj]

Thanks for the replies everyone =) I've done some research over the past 2 weeks or so and learned alot, unfortunately I do have some more questions =[

To Dean: I read your post on the other beginning UAV thread, and I think its a really good idea to test my electronics on a hacked r/c car before I crash everything, so im gonna do that too.

I've ordered my BASIC stamp discovery kit and i'll be tinkering with it over the weekend

After doing a bit of reading on aerodynamics i've decided on a few design goals to make the plane as stable and as easy to fly as possible.

- Wing mounted high on the fuselage
- Light wing loading
- Moderate dihedral
- Moderate swept-back wing
- Rectangular wing
- Modified flat bottom airfoil

However I was wondering about the differences between a pusher prop and a regular prop, I looked on Wikipedia and it said that a pusher prop is generally more stable, but I was wondering what did you guys think?

I want to set up a dual r/c system and autopilot but it seems complicated, if I can I will add on some r/c capability so I can manual pilot if theres an emergency

Some other ideas are a parachute landing system (it seems to be much easier and safer than trying to do an autonomous landing, any suggestions to implement this?) and possibly adding in some solar power once we become more familiar with our plane's design.

tentative list of electronics parts:

- BASIC Stamp 2 Module
- Board of Education Development Board
- Some kind of GPS sensor (maybe just scrap this)
- Altitude sensor? (I don't know where to get one, any suggestions? keep in mind the plane won't be flying much higher than 20-30 feet probably)
- x5 servos for control surfaces and digital camera
- 20$ digital camera (will this work with my BASIC stamp?)
http://www.sparkfun.com/commerce/product_info.php?products_id=637
this seems really cheap, am I missing something here?
- Motor controller
- Parallax Servo Controller

My team and I are going to start drawing up some plans, hopefully we can get some funding from our school if we be really thorough and give them a good presentation of our project!




edit: also we were considering maybe adding on a copilot (second BASIC stamp) in the far far future, how would we go about establishing some sort of communication between the two computers?

edit2: so just a quick double check to be careful =] one 9V battery will power the whole system right? I don't really have any experience in electronics so I dont know if one battery has any limitation on how much it can power

and sorry for all these questions, I hope to one day be a robotics or aerospace engineer so I'm very curious and eager to learn :D

[hg1]

Your airframe might be okay, but you have a long way to go in figuring out the electronics ...

1. What are you going to use for a radio link ? If you are going to transmit photos from the plane via a digital radio link, you need a data rate of at least 100kbps, and ideally more than 1Mbps, and the images need to be compressed via JPEG or MPEG.

2. The Sparkfun digital camera won't work for you - read the full blog.

3. Not sure what you mean by a 9V battery - are you thinking of the type that powers a smoke alarm ? That won't give you nearly enough capacity to drive a motor of any size.

4. The Basic Stamp is seriously underpowered (computationally) for this type of application. If you read the thread about the AttoPilot, you will see that he is using a Parallax Propellor processor that has 8 cores each running at 20MHz, and he's certainly not processing video.

Sorry for the bucket of cold water, but you want to have any hope of success, you need to go back to the drawing board and make a realistic assessment of computation and sensor requirements and figure out a power budget for all components of the system. As has been suggested before, this is not a simple project that can be hacked together from spare parts from Radio Shack.

[kd7ost]

I'll throw another bucket of cold water on. Please bear in mind I am trying to be helpful.

You are discussing an advanced project. But you're starting from extreme square one by the nature of your questions. It's hard enough to get a functional autonomous system designed, built and incorporated into your plane with it's flight characteristics. If you're wondering what kind of plane to even use, and weren't sure the difference between a bi-plane and monoplane, this tells of a pretty extreme lack of experience and knowledge across the board. I don't want to discourage you. Dreams are great and goals need to be worked towards. But you can't realistically bite this all off in one step unless you have some skilled engineers on tap. The plane is a model. The power system is a model. The computer systems are a model. The interface to the world, (computer to mechanics) is a model. All these pieces have to be integrated into each other in order to have even reasonable success.

I would highly recommend that you stick with an autonomous car or similar as the first stage of progress. You need to have someone building and flying an RC plane that you plan to use. It should be dialed in with gentle flight characteristics before even trying to incorporate electronics systems. Again, I credit your goals and wish you well, but I think you're biting a pretty big chunk with a steep learning curve in every area in front of you. There would be no shame in scaling back a bit to get a handle on the pieces and parts first. It needs to grow in steps but your journey seems to start at the very beginning. You don't want to set yourself up for failure. You need to collect a fair amount of knowledge and skill along the way. I agree that you need to make small steps along the way and not introduce each new technology until your team has a firm handle on each current phase.

Dan

[clolson]

I'll chime in to say mostly the same thing from a different perspective. I believe that to build a successful UAV, you need to have success in at least 3 major areas: airframe, hardware/electronics, software.

I don't know if I've met anyone who is really strong in all three areas, probably there are a few (maybe even a few hanging around here?)

I think for the average person to have a chance at success, they need to be pretty strong in 2 of those three areas. And then for the third area where they are weaker, you have to come up with something. Either you go really simplistic and off the shelf and live with the limitations, or you spend a lot of money, or you start cashing in favor points with your friends, or you spend a lot of time trying to at least get up to speed with some basics so you can bluff your way through your weaknesses.

But hey, we all start off knowing pretty much nothing about any of this. Often, the best way to learn is to set a goal and start battling through the road blocks. There are a lot of helpful people here, so if/when you jump in and start working on a project, this is a great place to ask specific questions.

[skatj]

About the camera, I was thinking there would be no processing needed at all, couldn't we just get a plain old digital camera, mount it on the plane, and then retrieve the photos from it after the flight?

My friend's dad is a very good model aircraft builder so I'm confident the airframe will be stable.

I will definitely stick to using R/C cars to test our electronics before putting them in the air.

I also have a Lego Mindstorms NXT computer, do you think I could implement this somehow because it's a very powerful processor.

And lastly, any suggestions for reading in order to figure out a power budget for all components of the system ?

Thanks everyone
I think I'll be able to get mentoring/funding from a local electrical company so hopefully they can help me out with the electronics.

[dmgoedde]

4. The Basic Stamp is seriously underpowered (computationally) for this type of application. If you read the thread about the AttoPilot, you will see that he is using a Parallax Propellor processor that has 8 cores each running at 20MHz, and he's certainly not processing video.

I agree. My reason for recommending the Stamp is more to get your feet wet. Parallax wrote an excellent manual aimed at the beginner that will help to get familiar with microcontrollers in general, and use of 3rd part chips (digital potentiometers for one, then later you can step up to ADCs, etc...). Depending what sort of automous actions, I argue that Stamps do work (I am proof), but it is a real pain in the rear. Many people on here can steer you towards good processors. I for one vote for the Propeller.. No matter what processor you end up with, Parallax (in my opinion) seems to be gifted at helping the beginner and they have very active forums for all their chips, and their main development employees are active on the discussion threads as well. Very positive environment.

Good luck!

[hg1]

And lastly, any suggestions for reading in order to ?

Here's an example of the design process -

1. pick an airframe design, based on whatever flight characteristics you are trying to optimize

2. take a first guess at what motor and prop combination will be required to achieve the desired flight characteristics with your chosen airframe. include allowance for payload (e.g. camera), battery pack, flight electronics in your weight estimate. you probably won't get this right the first time, though having someone around who knows r/c aircraft will be a big aid

3. based on the power requirements for the selected motor (or motors), decide on your battery strategy. for example, we try to build our systems around 2S (7.4V) 2000mAh Lithium Polymer battery packs, but our applications are for hovering or low stress cruising, and we get a good deal on that configuration. designs that require higher flight performance might use 3S (11.1V) or 4S (14.8V) battery packs.

4. the capacity of the battery pack will determine how long you can fly, but 4000mAh weighs twice as much as 2000mAh, and that influences the flight characteristics of the airframe, so a larger battry pack might require a larger motor. you need to feed back the battery parameters into the motor selection, and this might even influence the airframe decision.

5. once you've worked out your basic airframe + motor + battery strategy, then you can start to look at the flight electronics. fortunately, the electronics don't add a lot of weight, and are probably insignificant in terms of battery drain relative to the motor, but there are still a lot of choices to make in regards to communications, sensors, and on-board processing. a popular approach is to use r/c radios and an on-board autopilot - you will find a lot of discussion on this forum about different options.

6. once you get to the final step where you have built an aircraft that can fly autonomously with an autopilot, you can start to look at replacing the on-board processing with your own programmable processor, but you are a LONG WAY from that step.

Hopefully this will help to give you some perspective. From your posts so far, you have really not focused on any of the important issues except the airframe, which is definitely your starting point. If you can find an advisor to help walk you through this process, you will probably save a lot of grief.

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update ... I just ran across this tutorial which employs the NXT controller in a UAV. there is a lot of good information which should help you to get started - http://diydrones.com/profiles/blog/show?id=705844%3ABlogPost%3A728

[skatj]

I looked up the lift formula and I was thinking about doing this in order to figure out some of the specifics. I was thinking that if I could find out the estimated weight of the plane, then I can use that number and plug it in as the lift value in the lift formula, and then solve for targeted wing area.

However I was wondering,

1) I read that the lift coefficient for a model aircraft is 1, but what is the "normal" velocity for a fairly slow plane that has a cheap brushed motor with a pusher prop? Just a ballpark figure.

2) At takeoff, does lift have to be equal to weight in order to get off the ground? Or does it have to be somewhat greater?


I also am not sure what kind of factors I should consider to pick a motor. Like, when I look at the catalogs I don't know what the numbers are supposed to tell me. My main concern is having enough power to take off, flight time isn't a concern for me as long as it can fly for like 5 minutes.

I will meet with my team and try to crank out a few numbers, thanks for the help.