When you think of a robot, you would probably think of a human-sized one with arms, a lot of sensors, and a wide field of locomotion systems.

Now that we know how to write programs in ROS and that we know how to create robot models and simulate their behavior, we are going to work with real sensors and actuators-things that can interact with the real world. In the first section, we are going to learn how to control a DIY robot platform using ROS. Then, we are going to see how to interface different sensors and actuators that you can typically find in robotics laboratories.

Sensors and actuators can be organized into different categories: rangefinders, cameras, pose estimation devices, and so on. They will help you find what you are looking for more quickly.

In this chapter, we will deal with the following topics:

• Cheap and common actuators and sensors for your projects
• Using Arduino to connect them
• 2D laser rangefinders, Kinect 3D sensors, GPS, or servomotors

We know that it is impossible to explain all the types of sensors in this chapter. For this reason, we have selected some of the most commonly used sensors that are affordable to most users-regular, sporadic, or amateur. With them, we are going to connect all the elements needed to have a small robot platform working.