In time, each of the following components should have its own dedicated page for further details and images or videos.
Until then, here is an image of the complete prototype (wiring mayhem :) )
An inertial measurement system
A set of tension referenced and temperatured calibrated multi-axis accelerometers and gyroscopes for the purpose of determining attitude of the UAV. This unit is a Sparkfun 6DOF IMU v1 with custom firmware for higher output frequency.
A dual pressure sensor system (ADC x 2)
A set of two Freescale pressure sensors, one static and one dynamic to determine airspeed and altitude from a mix of both readings. These interface with the Sensor MUX.
An ultrasonic ranger (ADC)
Used for automated landings. The sensor has a range of 6 cm to 6 meters which is perfect for precise ground altitude determination during final landing procedure.
A digital magnetic compass (I2C)
This unit is the heading equivalent of the accelerometer. It is used to feed long-term heading estimation (balanced with gps bearing) into the heading estimate of the kalman filter.
A GPS receiver (UART)
A multichannel micro GPS receiver to determine position and groundspeed as well as heading (redundant).
A sensor multiplexer board (Sensor MUX)
An Atmega128 based board to multiplex sensor data and send it to the flight director computer and to receive actuator instructions from the flight director to the servos controlling ailerons, elevators, throttle and rudder. The Atmega is a wonderful machine with loads of timers, UARTs and SPI. This processor runs my sensor acquisition and multiplexing code written in C and compiled with avr-gcc.
The board is an off-the-shelf Robostix.
A flight director computer
A PXA based computer that receives sensor streams from the systems interface computer and actuates servos (through the same computer) based on error estimation (heading versus desired heading, altitude versus desired altitude, etc). Actuator software runs on PID feedback loops and applies simple Kalman filtering to accelerometer and gyro readings to smooth drift and bias. This computer is responsible for interfacing with the platform's radio modem and downstream telemetry data to the groundstation. It can receive data, such as emergency landings overriding and directly inject PPM from the modem control packets to the RC receiver PPM tap.
This computer's PID loop code and flight directing algorythms were tested with X-Plane. The code successfuly and consistently flew flight plans using RC models and UDP control/acquisition from/to X-Plane.