Posted by Josh Hathaway on October 14, 2009 at 7:17am
I just wanted to say hello to everyone on this great website and I can't wait to get started on my project!I'm out in Orlando, FL and me and a few guys are looking at pricing components for our system. I want to work with the UAVDevBoard b/c I'm familiar w/ programming PICs. Any suggestions for data recorder boards that work well with it?Is it really possible to control an aircraft just from a single microcontroller? Don't autopilots need inertial navigation, guidance, and control algorithms? That seems like a lot of number crunching for these little guys...
High kv motors should be geared down for best performance, but at the weight & friction cost of the gear box, it is usually worth the effort. 6:1 is a common reduction, for small 4300kv motor at 11.2v & 1300 mah it will turn a 11x4p propeller with 8+ minute run. But low kv motor with direct drive are getting more efficient. I use an Exceed 25 size direct drive in the nose of my new Ventus 2cx with 2.6m wingspan from NitroPlanes. Powered with a 5 cell 3700 mha, driven thru a Castle Creations 80. I modified wings with flaps, and extended the cord also, this should improve lift and slow this ship down a bit, I hope !
Mike, Have you tried a lower KV motor for more torque? For my MiniMag and I bought a 1300KV motor because everyone said get a bigger prop 9x6 and slower motor and you'll get more low end torque. The high speed motors are like high gear and the small 6x4 props they have don't have a lot of guts. Also, high speed motors don't run efficiently if you don't run them at a high throttle.
Let me know how your's works out.
Josh, power affects top speed some, but mostly climb performance. Once you get past the initial checkout and tuning, the riskiest parts of UAV flights are takeoff and landing, when you're low and slow. (IMHO, YMMV) Once I get the basic setup trimmed out, I'm going to try a technique that the free-flight modelers use. They launch their planes at a very steep angle, and "bunt" (pitch down to cruise) at their desired altitude. This requires a burst of high power for launch, as well as particular trim settings to get a good climb. That's why I chose the Series-6. (How this will work on the software side, I'm not sure yet -- I need to dig into the Ardupilot code to see what my options are.) In any case, everyone here seems to agree that the stock motor at 80 watts is underpowered.
For mine, I'm using a Castle Creations Thunderbird-54 ESC. I probably could have gotten away with the -36, but having headroom on the controller will improve lifetime & reliability. It's too big to fit in with the motor (1.1 x 2 inches), so I'm going to mount it flush on the side of the fuselage. (Better to not stick a 54 amp controller in a foam box anyway.)
Jason, right now I only have the standard ESC that came with the Apprentice trainer. I believe its rated to 30A. What is the driving force on the power? The increase in payload weight due to the autopilot?
I'm in the build process right now -- I have the autopilot together, and just got the power hardware for my Easystar yesterday. I decided to upgrade the motor to an E-flite EFLM2005. (It's oversized, but I want a steep climbout.) Given my school schedule, I'm still 2 or 3 weeks away from a first flight.
I'm in the Orlando area as well! (Up north, in DeLand.) I'm currently building up a EasyStar/Ardupilot -- we should set up a time/place for a UAV meetup.
Comments
Let me know how your's works out.
Mike, that would be awesome. How far along on your project are you?
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