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It looks like there may be as many as 10 teams using PicoPilots in the Outback Challenge this year. Plus many using other commercial and DIY autopilots, no doubt. This year, the contest's second, promises to be far more competitive than last year. Anybody going who wants to file a report for DIYDrones?

Here's what it is:

A custom PCB with an embedded processor (ATMega168) combined with circuitry to switch between RC control and autopilot control (that's the multiplexer/failsafe, otherwise known as a "MUX"). This controls navigation (following GPS waypoints) and altitude by controlling the rudder and throttle. These components are all open source. This autopilot is fully programmable and can have any number of GPS waypoints (including altitude) and trigger camera or other sensors

As with the Basic Stamp autopilot, to make a fully autonomous aircraft you need to combine this navigation autopillot with a stabilization system, for which we turn to our old friend, the FMA Co-Pilot (off-the-shelf infrared sensors and control board to keep the plane flying level), which controls the ailerons and elevator.

By using Jordi's MUX, which allows us to switch from autopilot to manual RC control in hardware, we gain several advantages over the Basic Stamp:

1) Because the switching isn't handled by the processors, we don’t need to drive servos in real time, which means we don't need stand-alone servo driver chips (thus a simpler board)

2) We also don't need “mirroring” subroutines to pass through servo commands in RC mode (simpler code)

3) Don’t need power regulator, since we’re using regulated output from the RC receiver (simpler board)

4) The built-in MUX failsafe is cheaper and simpler than using a stand-alone one.

I've taken a quick pass at the schematic and PCB (Eagle 5.0 format) for ArduPilot, although this will evolve as we go through the hardware testing cycle: Schematic, PCB board. You can buy the board here. Arduino code coming soon in alpha now.

All together, this can be the basis of a sub-$500 UAV:

Autopilot:

--ArduPilot PCB: $10

--Boarduino kit + FTDI cable: $35 (subtract $17.50 if you already have a FTDI cable)

--PicoSwitch: $20 (we'll probably build this in the board in the next rev)[UPDATE: Jordi's now incorporated that into the board above. It's a TinyAVR chip ("IC3", $2.75) and its associated programming interface jumpers ("ISP")]

--EM-406 GPS module: $60

--Multiplexer chip : $1

--8 Samtec TSW-108-25-G-T-RA right angle servo connectors (available as a free sample): $0

(That's a $110 autopilot, thanks to the open source hardware. By comparison, the Basic Stamp version of this, with processor, development board and failsafe board, would run you $300, and it's not as powerful)

Stabilization:

--FMA Co-Pilot: $70

Plane and RC equipment:

--Hobbico SuperStar (includes motor, battery and ESC): $109

--6-Channel radio system (with proportional control for channel 6, to calibrate FMA system): $109

--Three servos: $45

For very small UAVs, especially those used indoors, an interesting way to navigate is using a technique called "optical flow". Basically, it's the way flies see: they detect motion rather than resolve images. As you move, the objects closest to you appear to move the fastest, which for a camera chip means pixels shifting position faster.

The video above is from a Swiss team that have used optical flow to steer indoor blimps and microlight aircraft (video here). They've got pretty fancy equipment and lots of money--but is there a way to do the same on the cheap? Yes. It turns out that the sensor on an optical mouse (you probably have a few laying around) can do the job. Here are instructions on how to take the chip from an old mouse and connect it to a Basic Stamp (an Arduino would work even better) and create a low-budget optical flow sensor. Taking the dx, dy information from that and using it to drive the airplane's servos or actuators to move in the opposite direction from the highest optical flow should be a pretty easy matter. The only tricky thing is integrating the mouse chip and processor into a package no larger and heavier than the RC receiver that this optical autopilot replaces. The schematic on the mouse chip to Basic Stamp circuit is below:

Along with sharing some imaging technology with our UAVs, FPVs often use autopilots because they can fly further away than you can see from the ground. When pilots get lost or lose the wireless connection (and thus their view), the autopilots can bring the planes back into range.

The initial kit, which costs $549, has the basics and looks like quite a good deal (Hobby Lobby has a great reputation, and the company that makes the equipment, Intelligent Flight, is one of the best in the business). But if you happen to be independently wealthy, you might want to wait for some forthcoming accessories that will complete the full FPV experience: a pan-tilt camera mount, which can be connected to a gyro in your video goggles so the camera will turn where you're looking; an On Screen Display that integrates telemetry data into the video stream (and has a basic "return home" GPS-only autopilot for very stable aircraft), and a directional antenna that can greatly increase the range.

I wouldn't be surprised if all that together runs over $1,000, so it's a bit out of our range. But if you can afford it, this is the ultimate RC experience.

From the description: "The PICO-GS program performs four basic functions: 1. Provides a graphical view of your waypoints on the map image. 2. Permits "point-n'click" waypoint programming on the map image. 3. Provides realtime GPS tracking and flight data on the map image ( requires a radio modem ) 4. Includes the standard PICOPILOT line item editor." It costs $100 for a CD and a license key for a single installation. They're sending me a review copy, so I'll give you a hands-on report as soon as I get it.