Book Image

ROS Robotics By Example

Book Image

ROS Robotics By Example

Overview of this book

The visionaries who created ROS developed a framework for robotics centered on the commonality of robotic systems and exploited this commonality in ROS to expedite the development of future robotic systems. From the fundamental concepts to advanced practical experience, this book will provide you with an incremental knowledge of the ROS framework, the backbone of the robotics evolution. ROS standardizes many layers of robotics functionality from low-level device drivers to process control to message passing to software package management. This book provides step-by-step examples of mobile, armed, and flying robots, describing the ROS implementation as the basic model for other robots of these types. By controlling these robots, whether in simulation or in reality, you will use ROS to drive, move, and fly robots using ROS control.
Table of Contents (17 chapters)
ROS Robotics By Example
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

Baxter's arms and forward kinematics


Considering Baxter's arms up to the wrist cuff, each arm has seven values that define the rotation angle of each joint. Since the link lengths and joint angles are known, it is possible to calculate the position and orientation of the gripper attached to the wrist. This approach to calculating the pose of the gripper given the configuration of the arm is called forward kinematic analysis.

Fortunately, ROS has programs that allow calculation and publishing of the joint angles given a particular position and orientation of the gripper. The particular topic for Baxter is /robot/joint_states.

Joints and joint state publisher

Baxter has seven joints in each of its two arms and two more joints in its head. The topic /robot/joint_states publishes the current joint states of the head pan (side-to-side) joint and the 14 arm joints. These joint states show position, velocity, and effort values for each of these joints. Joint position values are in radians, velocity...