Long time readers here will know of my love for LEGO Mindstorms NXT, and my first NXT autopilot many years ago. So I was delighted to see this project, which uses an Arduino IMU plus NXT and the official First Robotics League TETRIX parts to create a LEGO quadcopter!
The NXT reads orientation information from the Arduino, calculates the motor speeds required to maintain stable flight, and sends these motor commands back to the Arduino, which spins the motors via the speed controllers.
So does it fly? Yep. Is it graceful? Nope. Check out the video of its first (and only) flight.