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World's First Lego Autopilot
zlite writes "What's the best way to create a UAV for less than $1,000? Use the new Hitechnic gyro sensor for Mindstorms NXT to create a Lego autopilot! This one can turn a R/C plane into a drone, keeping the aircraft level and returning it to the launch area. Add a Bluetooth GPS module and a microcam and you've got a fully autonomous surveillance platform."
That's not to say that you can't tweak the firmware of the receiver or something, but it may not be _that_ easy.
Of course, 'buy a gps which lets you do altitude' is also a solution :)
GPS Altitude is a rough approximation at best. The system was optimized for lat/lon position on the globe, not up-down. I've stood on the Blue Ridge Parkway and watched the ground soar up and down in a hundred foot range as I looked at my eTrex.
For this reason, Garmin builds (built?) at least one eTrex unit with a barometer built in for accurate altitude readings.
100 feet of slop is not good if you're trying to land the plane automatically.
I'd imagine
And the error on the altitude with GPS is likely to be twice as big as the horizontal error.
He won't be able to do much with a single-axis gyro. Also I didn't see any mention of an accelerometer, or an altitude sensor. He would be much better off (and save some money) by learning how to solder and use real components instead of the overpriced lego stuff. For example, my current RC autopilot setup uses 2x IDG300 dual-axis gyro IC's and an ADXL330 3-axis accelerometer. Also a SiRF III 20-channel GPS module, a pressure sensor for altitude, and a set of Nordic 2.4 GHz wireless tranceivers. Right now I have everything tied into an ARM7 but a Nano or Pico-ITX might be in my future.
? products_id=741? products_id=698? products_id=8161? products_id=465? products_id=152
5-axis IMU ($109.95): http://www.sparkfun.com/commerce/product_info.php
2-axis gyro (use with above to make a 6-axis (double up on one axis) ($69.95): http://www.sparkfun.com/commerce/product_info.php
Altimeter: ($49.95): http://www.sparkfun.com/commerce/product_info.php
GPS receiver, SiRF-III ($55.95): http://www.sparkfun.com/commerce/product_info.php
And finally, 2.4 GHz 1Mbit transciever to control it ($24.95 each): http://www.sparkfun.com/commerce/product_info.php
Add a GWS slowstick RC airplane ($35) and miscellaneous electronic pieces for a grand total of $370 or so. Not to troll, but I really don't see why people invest so much in doing things in legos when there's so much real hardware out there to play with.
Nothing is stopping you playing with Lego now, and the AFOL community (Adult Fans Of Lego) is one of the friendliest communities to be a part of. Visit Lugnet to see what's going on, upload your models to Brickshelf to share what you do with everyone else, check if there are any Lego shows in your area, and maybe join a local user group. Have fun.
Probably, but a lot less expensive. Tho about the PDA ... for anything too far you would probably have to give it a program to follow rather than control it manually ... bluetooth, for as far as it works, only works in the general area.
GPS can be good at altitude measurements, except you need to use the P(Y) code, which is encrypted. You could get away with using carrier phase or differential or RTK but then you start getting into the realm of some quite expensive gear.
The article just talks about a bluetooth GPS module, so I'll assume something commercial that likely includes WAAS. As he says, it'll be good enough to maintain flight but if he wants to land he'll need something more.
There are only 10 kinds of people in this world... those who understand binary and those who don't
When you yaw an aircraft you change the relative speed that the left and right wings are traveling through the air. Since the amount of lift produced by an airfoil is a result of (among other things) the speed of the airflow over the airfoil you are making one wing produce more lift than the other wing. In the case where you are using left rudder for example, the right wing will travel faster and produce more lift. The difference in lift between the two wings will cause the aircraft to roll. In our example, since the right wing is producing more lift, the aircraft will roll to the left.
When the aircraft rolls, the lift vector (a mathematical construct that represents the sum of lift over the entire airfoil showing its strength and direction as an arrow sticking out of the top of the aircraft) changes from pointing straight up as it would in level flight to pointing somewhat to the side. You can view this lift vector as the force that is holding the aircraft in the air. This change in the direction of lift "pulls" the aircraft around in a turn. Since some of the lift that was previously used to support the weight of the aircraft is now being used to turn the aircraft the aircraft will descend.
To understand how altitude is controlled you need to first consider the concept of trim. The aircraft is trimmed, or aerodynamically balanced, so that it will gently climb as long as power is being applied. When the power stops the aircraft will glide down. You can control the altitude of the aircraft by either starting and stopping the engine or, with a constantly running engine, by letting the aircraft fly straight to climb and turning it when you want to descend.
The early R/C airplanes were single channel (rudder only) control. You could do some amazing aerobatics with them once you got the hang of it. On a good day you could actually intend to do the aerobatic maneuvers.
Well; you jest, but this has already been addressed by the FAA: http://cryptome.org/faa021307.htm. Under this policy, I believe that you could be arrested for flying an aircraft like this without explicit authorization from the government. I do aerial photography with rc helicopters for my wife's real-estate company and you wouldn't believe the crap I have to deal with when people see that I have a flying camera in their neighborhood.
Personally, I'd rather use purpose built avionics in my models than try to jerry-rig lego sensors. I don't want to be liable if the electronics fail in my aircraft and it damages someone's property or worse.