| (Jonny the author here) I plan to write this up more completely, but here are some more technical details: Most of the bits (the foam plane, servos, speed controller, radio modules, IMU, barometer and GPS) came from eBay or HobbyKing. I started off with a little USB development board with an Atmel SAM7 on it, and then moved to the PCB and a newer Atmel SAM3 (partly after discovering how cheap prototype PCBs are from ITEAD). I initially wrote the algorithms in python, using pyserial to talk to the built-in bootloader the chips come with, through which you can manipulate registers and control the peripherals. This made writing and debugging the C much easier. The chip runs TNKernel, a little RTOS, which handles the radio and IMU processes (and soon GPS and barometer). Control is currently simple proportional control based on the IMU output, but I may add integral and differential terms once I'm more comfortable flying it, to see if can improve stability. It is remarkable how happy it is flying with the relatively crude algorithm it currently uses. Launching it is still slightly nerve-wracking - you have to throw it quite hard and hope that it is going to go up rather than down. There's also the risk that it'll fly out of radio range and keep on going, but if this happens it automatically cuts the throttle, in theory at least! |