Started eighth chapter of ROS Robot Modeling

Unified robot description format --URDF

 1. Create a robot description Feature Pack

catkin_create_pkg mrobot_description urdf xacro

 mrobot_description features included in the package urdf, meshes, launch, config four folders.

• urdf: robot model URDF used to store files or xacro
• meshes: model rendering file URDF cited for placing
• luanch: Related boot file for saving
• config: configuration file used to save rviz

2. Create a model URDF 

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

    <link name="base_link">
        <visual>
            <origin xyz=" 0 0 0" rpy="0 0 0" />
            <geometry>
                <cylinder length="0.005" radius="0.13"/>
            </geometry>
            <material name="yellow">
                <color rgba="1 0.4 0 1"/>
            </material>
        </visual>
    </link>

    <joint name="base_left_motor_joint" type="fixed">
        <origin xyz="-0.055 0.075 0" rpy="0 0 0" />        
        <parent link