Difference between <dynamics damping="0.7" friction="100.0" /> and <mu1>1</mu1>

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Hi,

Could anyone give me some explanation the difference between dynamics damping, and mu1, mu2 in the urdf ?

As I understand it, mu1 and mu2 are tangential friction forces applied between body and surface, so that the tangential friction force applied to the body as the body weight when mu=1.

<dynamics damping="0.7" friction="100.0"/> is the damping force which is proportional to the velocity of the moving body.

What should I do in the urdf to applying the damping force which is proportional to the velocity in the simple sliding box? Below is the sliding box urdf code:

<robot name="sliding_box"
       xmlns:body="http://playerstage.sourceforge.net/gazebo/xmlschema/#body"
       xmlns:controller="http://playerstage.sourceforge.net/gazebo/xmlschema/#controller"
       xmlns:interface="http://playerstage.sourceforge.net/gazebo/xmlschema/#interface" >

  <link name="base_link">
    <inertial>
      <mass value="1"/>
      <origin xyz="0 0 0"/>
      <inertia ixx="0.05" ixy="0" ixz="0" iyy="0.05" iyz="0" izz="0.05"/>
    </inertial>
    <visual>
      <origin rpy="0 0 0" xyz="0 0 0.0"/>
      <geometry>
        <box size="1.0 1.0 1.0"/>
      </geometry>
    </visual>
    <collision>
      <origin rpy="0 0 0" xyz="0 0 0.0"/>
      <geometry>
        <box size="1.0 1.0 1.0"/>
      </geometry>
    </collision>
  </link>

  <gazebo reference="base_link">
    <mu1>0</mu1>
    <mu2>0</mu2>
    <fdir1 value = "1 0 0"/>
 <dynamics damping="0.7" friction="100.0" />
    <material>Gazebo/Black</material>
    <turnGravityOff>false</turnGravityOff>
  </gazebo>

  <gazebo>
        <controller:gazebo_ros_force name="box_force_controller" plugin="libgazebo_ros_force.so">
         <alwaysOn>true</alwaysOn>
         <updateRate>15.0</updateRate>
         <topicName>box_force</topicName>
         <bodyName>base_link</bodyName>
        </controller:gazebo_ros_force>
  <controller:gazebo_ros_p3d name="p3d_base_controller" plugin="libgazebo_ros_p3d.so">
    <alwaysOn>true</alwaysOn>
    <updateRate>15.0</updateRate>
    <bodyName>base_link</bodyName>
    <topicName>base_pose_ground_truth</topicName>
    <gaussianNoise>0</gaussianNoise>
    <frameName>map</frameName>
    <xyzOffsets>0 0 0</xyzOffsets> 
    <rpyOffsets>0 0 0</rpyOffsets>
    <interface:position name="p3d_base_position"/>
  </controller:gazebo_ros_p3d>
  </gazebo>

</robot>