Overview
The aim of this project was to create a platform capable of autonomously surveying large areas. It would be completely in control of it's orientation, speed and direction, able to function with minimal external user input. I secured local business sponsorship as well as contributing my own funds in order to get such an ambitious project off the ground (pun intended).
Circuit Design
The circuit was designed in Eagle. It combined data from many different inputs: barometer, accelerometer, gyroscope, GPS and a radio module. It also had a Micro SD card and serial to USB converter for data logging and debugging. Components were chosen largely based on their reputation of ease of use and reliability within the hobbyist electronics community. Each component required datasheet interpretation. The main processor was an AVR that was running the Arduino bootloader. This allowed for it to be programmed as if it were an Arduino Mega and therefore could utilise the pre-existing arduino libraries thereby reducing the workload.
PCB Design
For the circuit board I opted for an unconventional three tier design. This was primarily due to the space constraint within the body of the aircraft. In the likely event of any issues arising during testing this also had the added advantage of offering many locations for signal probing and rerouting without needing to remake the circuit; my budget would not extend to two boards and two sets of components. I soldered the surface mount components using a hot air soldering station.
Software and Integrated Systems
This project had many different systems that had to work together to succeed. The heart of the project was the AVR microcontroller running my own program. It had to interpret signals coming from every component and combine them to get an accurate estimate of the drone's orientation and location, from this it could decide what actions could be performed to keep it on course. Throughout the design I tried to keep every component as modular as possible and this extended into the code facilitating easy debugging and integration.
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Aerospace Design
I have always had an interest in aviation and having flown my first solo flight of a light aircraft just a few months before starting on this project I had a good knowledge of what was required to get my drone to maintain stable flight. I settled on 5 methods of control: the motor speed control, the rudder, the elevator and two hybrid ailerons/flaps. The body of the drone was adapted from a hobbyist remote control aircraft shell allowing to keep manufacturing time to a minimum. I made several changes to it to allow for improved functionaility, I also opted for a mid mounted motor to protect it from any crashes that may (and did!) occur during the testing and calibration phase. The aircraft could easily disassemble for storage and transportation.
