My DIY RC autopilot

First try on aerial photography

Conclusion: it’s difficult without an Autopilot to hold it steady to aim the camera

Conclusion:

it’s difficult

without an

Autopilot

to hold it steady

to aim the camera

Autopilot design goals User selects object on Google Maps Plane flies to location and starts circling Camera takes pictures always pointed to target Pictures can be “glued together” in viewer (Not: ortho pictures to add on google maps) Goal: easy photography of buildings / landscapes

User selects object on Google Maps

Plane flies to location and starts circling

Camera takes pictures always pointed to target

Pictures can be “glued together” in viewer

(Not: ortho pictures to add on google maps)

Goal: easy photography of buildings / landscapes

PRINCIPLES

Forces on an airplane Thrust: Controls heigth Elevator: Controls speed Rudder: Controls direction Ailerons: Control roll

What is a servo, how does it work ?

Pitch / roll sensing IR sensors (thermophiles)

GPS navigation Yaw/height: calculated Waypoints: straight circular Failsafe $gprmc,114019.489,A,5048.9524,N,00511.8268,E,0.00,130.10,190907,,,A*60 $gpgga,114019.489,5048.9524,N,00511.8268,E,1,08,01.4,57.9,M,45.6,M,,*52 gga = time,latitude,ns,longitude,ew,posfix,sats,precision,altitude latitude=xxx.zzzz to xxxxx.zzzz (degrees*100+minutes=deel voor komma) longitude=xxx.zzzz to xxxxx.zzzz (degrees*100+minutes=deel voor komma)

GPS navigation

Yaw/height:

calculated

Waypoints:

straight

circular

Failsafe

Microcontroller: a computer on a chip (but no OS) RAM + FLASH EPROM Timers Interrupts I/O ports (digital) Analog ports Serial interface (usb, bluetooth) Bus (I2C, SPI, CAN)

HARDWARE COMPONENTS

KISS : just plug board between servo’s and receiver (dsPIC30F4012 from Microchip)

Paper adhesive tape provides intended point of failure upon impact (crash tested)

Only 3 things to connect and install IR sensor Autopilot CPU GPS module

CODE SAMPLES

Input pulse collection: Interrupt on change

Output pulse generation: Interrupt on timer

Flight logic: Continious loop

Calculation of stabilisation: Use of floating point Watch out for the math Error TRAP (code stops)

TOOLS

PIC Programmer: Velleman K8048 (15€)

Programmer software: Freeware WIN PIC

IDE: free MPLAB available from Microchip

Alternative microcontrollers Good: AVR: very powerfull, more expensive/compex Arduino: pre-integrated, less effort Ti Bad: BASIC stamp: ripoff with lousy programming LEGO Mindstorms: expensive plastic PIC16, PIC18: voorbijgestreefd I stick with dsPIC since the learning curve was not too steep

Good:

AVR: very powerfull, more expensive/compex

Arduino: pre-integrated, less effort

Ti

Bad:

BASIC stamp: ripoff with lousy programming

LEGO Mindstorms: expensive plastic

PIC16, PIC18: voorbijgestreefd

I stick with dsPIC since the learning curve was not too steep

OTHER AUTOPILOTS

Tompycke.be : a Belgian, 10x better then I am at this stuff

Paparazzi: Very comprehensive, open source, starts to get a bit long in the tooth

Attopilot: The best, very recent effort by a dedicated ex-intel engineer

ArduPilot: Arduino based and open source, recent but very basic SW, From Chris “The Long Tail” Anderson (& others)

Let’s go fly!