You might have seen the terms ROS, ROS 1, ROS 2, and other kinds of variations (with or without a space), which can be confusing.

Let’s clear this up now:

• ROS 1 is (was) the first version of ROS
• ROS 2 is the second and newer version of ROS and will be the focus of this book

In this book, I will use the following convention:

• ROS: When talking about general ROS concepts, philosophy, and so on
• ROS 1: When talking specifically about the first version of ROS. However, this will be quite rare since the focus here is on ROS 2
• ROS 2: When talking about the second version of ROS

Note

I may sometimes write ROS or ROS 2 interchangeably since we won’t be focusing on ROS 1 here.

It’s not impossible that, in the future (when ROS 1 has completely disappeared), the name ROS 2 becomes ROS again. If you’ve heard about Angular, it started as AngularJS, after which they released Angular2, and then a few years later...

Before we start understanding what ROS is, let’s understand why we would need it.

Why ROS?

Let’s start with a big problem that occurs often in robotics.

Imagine that you just got a new project at your job, and you have to develop a robotics application, or you are doing a new research thesis. One very important thing to take into account is that in real life, any project or thesis will have a specific duration, from a few months to a few years.

Now, what will happen?

You start to design the robotics system you need for your project and soon realize that it will take a lot of time to develop the robot because all the existing solutions you found don’t match what you need. After a few weeks, you finalize the specifications, and you start building your robot. A few months in, you’re still developing the basic software for wheel control and navigation. You underestimated how much time it would take...

To be clear, this book is all about ROS 2, not ROS 1. You will start learning ROS 2 from zero experience. This section is probably the only time I will be talking that much about ROS 1.

A quick story of ROS, and how we got to ROS 2

ROS 1 (originally called ROS) was first developed in 2007. It quickly gained popularity and grew exponentially in the following years.

In 2014, the ROS 2 project was announced. Simply put, ROS 1 was a bit too limited for industrial applications (lack of real-time support, safety, and so on) and was only used in research/education. To solve this problem, the developers decided to make ROS more “industrial friendly,” as well as make it better, thanks to all the lessons learned from the beginning of ROS.

Now, why create ROS 2 and not just continue ROS with some new changes? Well, the changes were too big, and they would have completely broken compatibility with older versions. Thus, it was decided to create a completely...

To get started with ROS and this book, there are a few things you need to know.

Knowledge prerequisites

It is best that you have some knowledge of the following:

• Linux command line: Since we’ll be using Ubuntu, being familiar with Linux is mandatory. You don’t need to be an expert—you just need to know the basics. Many tools in ROS 2 involve the command line, so knowing how to open a Terminal and write basic commands will help you tremendously.
• Python programming: The two most common languages for ROS are Python and C++. Python is easier to get started with and allows you to prototype things faster. Hence, this is the language we will use for all detailed explanations. You need to know Python basics, and object-oriented programming (OOP) is a good plus as ROS 2 is heavily using OOP everywhere.
• Optional: C++ programming. Even if the focus of the book is on Python, I still wanted to include C++ code for...

The book is divided into three parts, including 14 chapters.

Each chapter can be followed individually, although for one chapter, you need the knowledge from all previous chapters.

If you got this book because you just want to get started from scratch, then it’s simple: follow the book in the order it’s been written. I have designed it specifically so that you learn the concepts one step at a time without having to think about what directions you should take.

Then, as you progress, feel free to come back to any chapter to clear up doubts. I encourage you to do that. The first time you learn about a concept, you don’t necessarily grasp all the subtleties. As you continue with this book and use the concept along with other new concepts, you often have ‘epiphany moments’, when everything clicks together.

If you already know some ROS 2 basics (or you’ve already read this book), then feel free to jump to any chapter...

In this introductory chapter, we cleared up some of the most common confusion points regarding ROS: its name, what it is and isn’t, when to use it, and why. You also learned more about the different ROS versions (ROS 1 and ROS 2), and you learned what kind of prerequisites you need to get started with ROS 2.

You should now have a better understanding of the big picture, and even if everything still seems a bit confusing, don’t worry too much—it will all make sense when you use the ROS 2 concepts and code with them.

Now, to be able to use ROS 2, we need to install it. This will be the focus of the next chapter and will help you get your environment 100% ready for ROS 2.