The difference between our autopilots and those of the pros

What do you get for the hundreds of thousands or millions of dollars cost difference between our UAVs and those of the pros? Well, a lot (even after you take out defense contractor markups). Ours are one-offs that need a lot of hand tweaking, care and knowledge to use. They have limited range and altitude, and as we know all too well, sometimes they don't work at all. (But hey, losing a $1,000 UAV doesn't hurt as much as losing a $10 million one!)

In addition, they have only a small fraction of a pro UAV's feature set. I was reminded of this as I was looking at the source code for the Micronav software for the Crossbow hardware (shown), which one of the more sophisticated open source autopilot programs (but is still at the bottom end of the pro autopilot range).

Here are some of the things the Micronav software code has that we don't:

--Full avionics and telemetry data downlinked to the ground.
--A proper custom inertial measurement unit (IMU), using gyros and accelerometers and Kalman filters in software
--Data logging
--Smart ("look ahead") waypoint finding algorithms, that don't just get to a point but get to it efficiently and along a predictable line.
--Corrections for what part of the Earth you're flying over (northern or southern hemisphere).
--Use standard UAV commands for dynamic mission/waypoint changes, such as "loitering" over a target.
--Ground station software

Other autopilots have such features as:

--Automatic adaptation to different airframe platforms after inputting a pre-recorded flight from that aircraft.
--Auto-land and take-off
--Communications between camera and autopilot so you can steer the camera and let the plane steer itself

We'll get some of those feautures someday in our own UAVs, but for now we take all sorts of shortcuts to stay within the reach of amateurs. For instance, we usually don't build our own IMUs. The DIY Drones approach is to let some off-the-shelf hardware handle the tricky job of stabilization and our custom hardware and software just handles the easier 2D job of GPS navigation. We don't have any ground station software for real-time control and communications (just software for post-processing of imagery). You've got to hand-tweak the autopilots for each new airframe. And we let commercial GPS receivers handle the job of data logging.

Anyway, if you want to be reminded of how much math you've forgotten since college, check out the source code. And then be thankful for all we've spared you!

Views: 254

Comment by Paul Gregory on December 22, 2007 at 11:41am
Any idea of the prices on the Crossbow unit? I have tried looking at the web site, but it only seems to have access for distributors.

3D Robotics
Comment by Chris Anderson on December 22, 2007 at 11:49am
I've seen them on eBay on the order of $2,500 for the hardware. I think they're usually sold new as part of a system (much more expensive)
Comment by Jack Crossfire on December 24, 2007 at 5:04am
Don't forget about DGPS. Amazing what before-tax business expenses can buy.

3D Robotics
Comment by Chris Anderson on December 24, 2007 at 11:40am
It stands for differential GPS, and it's a technique, not a product. See more here:
Comment by Ritchie on December 12, 2010 at 11:55am

Just found this thread while searching for dGPS information and my hasn't technology moved.


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