Servo - November 2012

Introduction

Thanks in part to affordable frames and components, and also in part to enthusiastic support from selfless open source developers, building a DIY quadcopter is no longer an arduous, expensive proposition. Quadcopter frames, motors, and electronic speed controllers (ESCs) are commodity items that can be cherry-picked to your speed and payload constraints, and of course, your budget. For robotics enthusiasts, the only remaining challenge in the world of quadcopters is developing the perfect microcontroller-based autopilot.

As with microcontroller platforms in general, there's a world of possible autopilot options available — from the $15 AVR-based minimalist controllers offered by HobbyKing and the $120 Parallax Propeller-based HoverFly Open Board (which I discussed in the September 2012 issue), to the $200 ArduPilot 2. 5, featured here. These three autopilots target very different audiences. And, of course, everyone has their favorite microcontroller platform.

A major distinction of the ArduPilot

2. 5 (referred to hereafter as simply

'ArduPilot') and the accompanying freely available Mission Planner software is that it supports true hands-off, autonomous flying. The system allows you to control a quadcopter, airplane, rover, or other vehicle without ever using a traditional R/C transmitter-receiver system.

As long as you can use a mouse and keyboard, you can direct the autopilot and it will take care of the details. The platform also leverages the largest, most active user and developer base for civilian, non-commercial quadcopter research and development.

The Hardware

pads clearly identified, with enough space around the corner holes to actually mount the board. The board is packed with sensors and LED status lights. The 41 mm x 66 mm ArduPilot is packed with the latest generation three-axis gyro, accelerometer, magnetometer, and barometer. The barometer isn't for forecasting the weather, but for measuring altitude.

There's 4 MB of Flash memory on board, and Atmel's ATMEGA2560 for the heavy lifting. There's also AMEGA32U- 2 chips for USB functions. What's more, the board is designed to handle a variety of extra sensors and peripherals, such as GPS receivers and ultrasonic range finders. An ultrasonic range finder is best for low level, relatively high accuracy altitude measurements. The barometer is best for estimating elevation above about 10 meters. Adding standard sensors is as easy as attaching the leads to the ArduPilot and then clicking a few buttons within the Mission Planner software.