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Full Autopilot

The full autopilot can fly outside, in high wind. It's the same basic VTOL autopilot you would find in any commercial copter. It uses the following sensors:

Gyros: ADXRS613 * 3
Accelerometers: ADXL330 * 1
Magnetometers: Micromag 3 * 1
Barometer: SCP1000
GPS: uBlox 5

It uses 3 gyros for short term rotation sensing, 2 accelerometers for long term tilt sensing, 3 magnetometers for long term heading sensing, a high quality GPS module for horizontal position, a barometer for altitude sensing. A 3rd accelerometer was too sensitive to vibration & altitude changes to be any good. Because of the long term sensors & the very stable gyros, the orientation is always pretty accurate & doesn't drift.

Although GPS can provide altitude data, it depends on the satellite positions & the GPS constellation is deteriorating, so we went to a barometer for altitude. The barometer didn't work on the single rotor vehicles because of the rotor wash, but works well on the tri rotor because of the large space between propellers.

Position sensing uses no ordinary GPS module but a uBlox5. This was the cheapest module which sensed sub meter/sec velocity & output ECEF coordinates at 4Hz. High precision at 4Hz was necessary to get autonomous hovering to work. There are probably cheaper alternatives now.