Explaining the xacro model of the seven-DOF arm

After defining the elements that we must insert in the robot model file, we are now ready to include 10 links and 9 joints (7 for the arm and 2 for the gripper) on this robot, and 2 links and 2 joints on the robot gripper.

Let's start by looking at the xacro definition:

<?xml version="1.0"?> 
<robot name="seven_dof_arm" xmlns:xacro="http://ros.org/wiki/xacro"> 

Because we are writing a xacro file, we should mention the xacro namespace to parse the file; then, we can start to define the geometric properties of the arm.

Using constants

We use constants inside this xacro to make the robot descriptions shorter and more readable. Here, we define the degree-to-radian conversion factor, the PI value, the length, the height, and the width of each of the links:

  <property name="deg_to_rad" value="0.01745329251994329577"/> 
  <property...