Explaining the URDF file

When we check the code, we can add a <robot> tag at the top of the description:

<?xml version="1.0"?>
<robot name="pan_tilt">

The <robot> tag defines the name of the robot that we are going to create. Here, we named the robot pan_tilt.

If we check the sections after the <robot> tag definition, we can see link and joint definitions of the pan and tilt mechanism:

  <link name="base_link">
    <visual>
      <geometry>
      <cylinder length="0.01" radius="0.2"/>
      </geometry>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <material name="yellow">
        <color rgba="1 1 0 1"/>
      </material>
    </visual>
  </link>

The preceding code snippet is the base_link definition of the pan and tilt mechanism. The <visual> tag can describe the visual appearance of the link, which is shown on the robot simulation. We can define the link geometry (cylinder, box, sphere, or mesh...