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Minimal Autopilot

The minimal autopilot can fly inside or outside in calm air. It uses 3 gyros for all rotation sensing & 1 sonar transducer to emit pings. The tilt reading constantly drifts. Only changes in tilt are used for flight. Heading is adjusted by sensing horizontal movement.

The IMU uses an IDG300 for the XY gyros & a LISY300AL for the heading gyro. Best results require the IMU to reach a stable temperature before flight.

The sonar system consists of an array of 3 receivers on the ground & 1 transmitter on the airframe. The time of ping reception at each array sensor is converted into distance for triangulating the position of the transmitter.

Sonar uses 4 Matsushita 0D24K2's from allelectronics.com. The lower the frequency the better, to get more omnidirectional range. The minimal autopilot can fly in a 2x2x12 meter box directly over the array.