We can extend the capabilities of the robot xacro by including the xacro definition of sensors using the xacro:include tag. The following code snippet shows how
to include a sensor definition in the robot xacro:

  <xacro:include filename="$(find mastering_ros_robot_description_pkg)/urdf/sensors/xtion_pro_live.urdf.xacro"/> 

Here, we include a xacro definition of sensor called Asus Xtion pro, and this will be expanded when the xacro file is parsed.

Using "$(find mastering_ros_robot_description_pkg)/urdf/sensors/xtion_pro_live.urdf.xacro", we can access the xacro definition of the sensor, where find is to locate the current package mastering_ros_robot_description_pkg.

We will discuss more on vision processing in Chapter 16, Building and Interfacing Differential Drive Mobile Robot Hardware in ROS.