Book Image

Effective Robotics Programming with ROS - Third Edition

By : Anil Mahtani, Luis Sánchez, Aaron Martinez, Enrique Fernandez Perdomo
Book Image

Effective Robotics Programming with ROS - Third Edition

By: Anil Mahtani, Luis Sánchez, Aaron Martinez, Enrique Fernandez Perdomo

Overview of this book

Building and programming a robot can be cumbersome and time-consuming, but not when you have the right collection of tools, libraries, and more importantly expert collaboration. ROS enables collaborative software development and offers an unmatched simulated environment that simplifies the entire robot building process. This book is packed with hands-on examples that will help you program your robot and give you complete solutions using open source ROS libraries and tools. It also shows you how to use virtual machines and Docker containers to simplify the installation of Ubuntu and the ROS framework, so you can start working in an isolated and control environment without changing your regular computer setup. It starts with the installation and basic concepts, then continues with more complex modules available in ROS such as sensors and actuators integration (drivers), navigation and mapping (so you can create an autonomous mobile robot), manipulation, Computer Vision, perception in 3D with PCL, and more. By the end of the book, you’ll be able to leverage all the ROS Kinetic features to build a fully fledged robot for all your needs.
Table of Contents (18 chapters)
Effective Robotics Programming with ROS Third Edition
About the Authors
About the Reviewer
Customer Feedback

Creating a base controller

A base controller is an important element in the navigation stack because it is the only way to effectively control your robot. It communicates directly with the electronics of your robot.

ROS does not provide a standard base controller, so you must write a base controller for your mobile platform.

Your robot has to be controlled with the message type geometry_msgs/Twist. This message was used on the Odometry message that we saw before.

So, your base controller must subscribe to a topic with the name cmd_vel, and must generate the correct commands to move the platform with the correct linear and angular velocities.

We are now going to recall the structure of this message. Type the following command in a shell to see the structure:

$ rosmsg show geometry_msgs/Twist

The output of this command is as follows:

The vector with the name linear indicates the linear velocity for the axes x, y, and z. The vector with the name angular is for the angular velocity on the axes.