Learning LEGO MINDSTORMS EV3

Table of Contents

Learning LEGO MINDSTORMS EV3

Credits

About the Author

About the Reviewers

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Free access for Packt account holders

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Downloading the color images of this book

Errata

Piracy

Questions

1. Engineering Notebook

The engineering design process

Content Editor features

New pages and page actions

Computer-aided Design and building instructions

LEGO Digital Designer

LDraw

Commenting on your code

Summary

2. Mechanical Design

Mechanical advantage

Motors

Large motors and gears

Writing a program

Bevel gears at right angles

Worm gear

Using wires and parallel threads

Summary

3. Drive Train and Chassis

Chassis

Skid-bot with the Retail kit

Caster-bot with the Educational kit

Tread-bot with the Retail kit

Tread-bot with the Educational kit

Programming the robot to move forward

Summary

4. Sensors and Control

Using sensors

Programming blocks

LEGO EV3 sensors

Touch Sensors

Color Sensors

Motor Rotation sensors

Gyro Sensors

Ultrasonic motion sensors

Infrared Sensors

Third-party sensors

Dexter Industries

Mindsensors

HiTechnic sensors

MATRIX motor controllers and metal parts

Vernier sensors

Summary

5. Interacting with EV3

Push buttons

IR remote buttons

Bluetooth control

Smart device control

Wi-Fi control

Summary

6. Output from EV3

Display

Image Editor

Display data

Brick lights

Legacy NXT/RCX lights

Sound

Music

Summary

7. Advanced Programming

Loop and the Motor Rotation sensors

Loop and the Gyro Sensor

Troubleshooting with the Gyro Sensor

Switch or two-level controller

Three-level controller

Subroutines or My Blocks

Arrays

Summary

8. Advanced Programming and Control

Distance controller

Infrared versus Ultrasonic

Proportional algorithm

Line following using the Color Sensor

Setpoint for line tracking

Two-level or bang-bang controller

Proportional line follower

Entering gain and speed

PID controller

Gyro Sensor

IR sensor navigation and beacon tracking

Tracking a circle

Triangulation

Summary

9. Experiment Software and Data Logging

Data logging software

Improving dead reckoning

Analyzing gain constants

Graphical programming

Other bang-bang controllers

Summary

10. Other Programming Languages

LabVIEW

Front Panel and Block Diagram

Programming blocks

Loops

Line following VI

Robot tools

Data

Front Panel and clean Block Diagrams

SubVIs

RobotC

Simple code

Commands

Variables

Remote control

Graphical programming

Summary

11. Communication between Robots

Enabling communication

Messaging

Follow the leader

Maintain a distance

Search and rescue

Completing the search

Summary

12. Advanced Robot – Gyro Boy

Concept of a balancing robot

The Gyro Boy model

Sensor feedback

Programming bugbears

The main program

The control program

The RST My Block

The gOS My Block

The GT My Block

The GG My Block

The GM My Block

The EQ My Block

The cntrl My Block

The CHK My Block

Summary

Index

Learning LEGO MINDSTORMS EV3

Learning LEGO MINDSTORMS EV3

Copyright © 2015 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: January 2015

Production reference: 1200115

Published by Packt Publishing Ltd.

Livery Place

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Birmingham B3 2PB, UK.

ISBN 978-1-78398-502-9

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Cover image by Gary Garber

Credits

Author

Gary Garber

Reviewers

Barbara Bratzel

Michael duPont

Jeroen Hartsuiker

David Lechner

Diego Kartones Muñoz

Geoff Shannon

Commissioning Editor

Akram Hussain

Acquisition Editor

Neha Nagwekar

Content Development Editor

Susmita Sabat

Technical Editor

Vivek Arora

Copy Editor

Laxmi Subramanian

Project Coordinator

Neha Thakur

Proofreaders

Simran Bhogal

Stephen Copestake

Maria Gould

Ameesha Green

Paul Hindle

Indexers

Hemangini Bari

Mariammal Chettiyar

Monica Ajmera Mehta

Graphics

Valentina D'silva

Production Coordinator

Shantanu N. Zagade

Cover Work

Shantanu N. Zagade

About the Author

Gary Garber teaches physics, math, and engineering at Boston University Academy. Gary is the president of the New England Section of the American Association of Physics Teachers and has led dozens of professional development workshops in education at both the local and national levels.

Gary runs the Boston University FIRST Robotics program. He has run and hosted numerous robotics workshops in VEX, Tetrix, and LEGO platforms. He has run dozens of LEGO robotics tournaments and spoken on robotics education at both local and national conferences. His robotics team has worked with Engineers Without Borders, NASA, and the National Science Teachers Association on a variety of engineering and education projects.

He is currently an educational consultant, working to develop new software tools for the classroom, at the Tufts Center for Engineering Education and Outreach, which is a pioneer in LEGO Robotics Education. He is the author of Instant LEGO MINDSTORMS EV3, Packt Publishing. He currently resides in Massachusetts, US. When he is not playing with LEGO, robots, or toy trains, he enjoys spending time with his wife, Catalina, and their two children, Alejandro and Leonardo.

I would like to thank the people of the Tufts Center for Engineering Education and Outreach for teaching me about LEGO robotics and helping make this book possible, including Chris Rogers, Ethan Danahy, Barbara Bratzel, and Bill Church. I would like to thank the students of Boston University Academy, in particular, the class of 2016, who remind me of how much fun students of all ages can have with LEGO. I would also like to thank Alejandro and Leonardo for reteaching me how to play with LEGO and making me watch the LEGO movie over and over again.

About the Reviewers

Barbara Bratzel is a science teacher at the Shady Hill School, a PreK-8 independent school in Cambridge, Massachusetts. In addition, she is a consulting teacher at the Center for Engineering Education and Outreach at Tufts University. Her most recent book, STEM by Design, a collection of classroom activities using the LEGO EV3, was published in February 2014.

Michael duPont is a maker, pilot, and theatre technician based in Central Florida. He recently graduated from Centre College in Danville, Kentucky. His specialties include microcontrollers such as the Raspberry Pi and Arduino, robotics, wearables, and other small electronics. You can find many of his open source projects on GitHub and on his website (http://mdupont.com/).

Jeroen Hartsuiker (born in 1971) played with LEGO Technic until his early teens. His dark ages (time when a person stops collecting and using the Danish bricks) ended while visiting LEGOLAND Billund in 1998, when he attended a workshop exploring the first generation of the MINDSTORMS Robotics Invention System. Since then, he has owned and used every generation of the LEGO robot, and he wrote courseware and delivered a presentation on how to control the MINDSTORMS NXT robot using Microsoft® Robotics Developer Studio. He occasionally contributes a module to the Great Ball Contraption (GBC) at LEGO WORLD in the Netherlands. Furthermore, a MINDSTORMS robot is sometimes used to make the software-development classes he teaches even more interesting. You can visit his blog at www.dotnetjes.nl.

David Lechner works mostly as a freelance computer programmer and occasionally as a Mad Scientist teaching robotics as an after-school program in elementary schools. He also just completed his rookie year, coaching a FIRST LEGO League team, and has devoted much of his time to reverse engineering the EV3 as a core contributor to the ev3dev project. Prior to being self-employed, he spent 8 years doing industrial automation in the water and wastewater industry. He has a bachelor's degree in electrical and computer engineering from Oklahoma State University.

Diego Kartones Muñoz, more commonly known by his nickname, Kartones, is a multidisciplinary developer who lives in Madrid, Spain. Having worked for more than 12 years with all kinds of desktop, mobile, and web applications, he has used quite a few languages such as C++, C#, PHP, and more recently, Ruby and JavaScript.

Regarding LEGO MINDSTORMS, he fell in love with RCX and then the NXT, both of which he liked to code in C instead of the default firmware and brick system. Now, with MINDSTORMS EV3, he seeks to code robot logic in Node.js. He's also been a technical reviewer for LEGO Mindstorms EV3 Essentials, Packt Publishing.

He loves learning about anything he comes across and keeps a few blogs. He sometimes speaks at events or user groups, and he would love to do more open source work. He can be reached at http://portfolio.kartones.net.

I'd like to acknowledge my girlfriend and my cats, for without their patience with my endless hours around computers and technology, 
I wouldn't be so happy.

Geoff Shannon has been an enthusiastic hardware hacker from a young age; his first job was building automated production equipment with Provel Inc. He has a bachelor's degree in computer science and recently attended a batch at Hacker School in New York City. In late 2013, he started working with LEGO robots by exploring the leJOS project and using it to run a Clojure REPL on his EV3. He currently lives in Seattle, WA, working as a software engineer.

To see what Geoff is currently working on and thinking about, check out his blog at www.zephyrizing.net. You can also follow him on Twitter at @RadicalZephyr.

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Preface

Welcome to Learning LEGO MINDSTORMS EV3.

The LEGO MINDSTORMS EV3 is a programmable LEGO brick that can control motors and receive feedback from a wide range of sensors. In this book, you will learn how to write programs in the LEGO MINDSTORMS EV3 software. This book is a practical guide that will show you how to advance beyond the basic lessons included in your EV3 kit, combine core programming commands, and implement tested design principles when building your own robot using the LEGO MINDSTORMS EV3 kit. You will become familiar with resources beyond your EV3 kit and enhance your robot designs.

The MINDSTORMS EV3 kit contains over 500 plastic interlocking parts. These parts are made with high-precision moulds. The LEGO Technic bricks in your kit include beams, axles, pines, gears, shafts, and bushings that will allow you to design a wide variety of robots. The LEGO bricks in your LEGO MINDSTORMS kit are compatible with all LEGO bricks made over the past 50 years.

The LEGO MINDSTORMS EV3 Intelligent Brick contains an ARM9 processor running Linux. This allows you to program the brick with a wide variety of languages, such as C, C++, Java, Python, and LabVIEW, but we will focus on the official LEGO MINDSTORMS EV3 software. This software is a visual programming language. Programming in the LEGO MINDSTORMS EV3 software consists of dragging-and-dropping blocks onto a programming canvas. You draw wires to connect the command blocks, such as command flow wires and data wires. There are blocks that store data, control motors, acquire sensor data, and initiate flow structures such as loops and switches. The beauty of a visual programming language is that with a programming hierarchy, you can create easy-to-follow programs where you can visually see the entire program at once.

The EV3 Intelligent Brick connects to motors and a wide variety of sensors, which LEGO builds via electrical wires, including Touch Sensors, Ultrasonic Sensors, Light Sensors, Infrared Sensors, and Gyro Sensors. The motors have built-in shaft encoders, which allow you to control exactly how far they turn. There is an even larger array of sensors produced by third-party vendors that you can use with your EV3. You can download and run your computer programs on the EV3 via a USB cable, Bluetooth, or Wi-Fi. All these features will take your LEGO MINDSTORMS EV3 beyond the category of a simple toy into an impressive robotics kit, which can be used to explore your environment and navigate a complex set of obstacles.

What this book covers

Chapter 1, Engineering Notebook, covers how to use the Content Editor to keep a multimedia record of your work building robots.

Chapter 2, Mechanical Design, covers how to use gears to increase either speed or torque in your robots.

Chapter 3, Drive Train and Chassis, explains how to build a chassis and attach either wheels or treads to create a moving robot.

Chapter 4, Sensors and Control, covers how to use sensors to receive feedback from your environment.

Chapter 5, Interacting with EV3, explains how to control your EV3 via the brick buttons, the infrared beacon, Bluetooth, and Wi-Fi.

Chapter 6, Output from EV3, covers how to send output from the EV3 brick using the display screen, lights, and the speaker.

Chapter 7, Advanced Programming, covers topics such as loops, switches, arrays, My Blocks, and navigation using sensor feedback.

Chapter 8, Advanced Programming and Control, covers advanced navigation techniques, including proportional controllers, PID controllers, course correction, and triangulation.

Chapter 9, Experiment Software and Data Logging, explains how to use the data logging features of the Educational Edition of the LEGO MINDSTORMS software.

Chapter 10, Other Programming Languages, provides a brief overview of RobotC and LabVIEW, which are the next steps up from using the LEGO MINDSTORMS software.

Chapter 11, Communication between Robots, explains how to send messages via Bluetooth to allow two EV3 robots to communicate, send commands, and collaborate.

Chapter 12, Advanced Robot – Gyro Boy, reviews and explains in depth the Gyro Boy program written by LEGO.

What you need for this book

You will need a LEGO MINDSTORMS EV3 kit to build the robots in this book. There are two versions of the kit: the LEGO MINDSTORMS EV3 Home Edition (Lego Set # 31313) and the LEGO MINDSTORMS EV3 Education Core Set (Lego Set # 45544). Both of these kits can be purchased for about $350. I have provided build instructions in this book, so you can build your robots no matter which set you have. The hardware differences include the type of wheels, treads, and casters. Between the kits, most of the pieces are the same but of different colors. The Home Edition has a Touch Sensor, Color Sensor, Infrared Sensor, and Infrared beacon. The Education Edition has a Touch Sensor, Color Sensor, Gyro Sensor, Ultrasonic Sensor, and a rechargeable battery. You can buy all of these parts at http://shop.lego.com/en-US/ or any general toy supplier.

If they did not come with your kit, you may want to buy the following:

EV3 rechargeable battery (Part # 45501), which is $60

EV3 Ultrasonic