Home | Tutorials | Wiki | Issues
Ask Your Question

Revision history [back]

click to hide/show revision 1
initial version

Can not move model by joint tab or published command.

Gazebo model does not move....if I apply force or velocity to the joints in the joints tab. Also I tried sending commands via rqt plugin shown below. None of these methods move the model. No errors are generated. Any thoughts on why this is the case.

Using Publisher plugin from rqt_gui. 
Sending /rrbot/joint1_position_controller/command std_msgs/Float64 rate(100) date(sin(i))
Sending /rrbot/joint2_position_controller/command std_msgs/Float64 rate(100) date(sin(i))

***** From the Terninal *****

*****viki:~$ rostopic echo /rrbot/joint1_position_controller/command
data: -0.989367016834
---
data: -0.656941145733
---
data: 0.279473385116
---
data: 0.958941374547
---
data: 0.756763086604
---
data: -0.141179693171
---
data: -0.909322514128
---
data: -0.841438409151



***** ros graph shows the command topics subscribed to by gazebo
*****viki:~$ rostopic info /rrbot/joint1_position_controller/command
Type: std_msgs/Float64

Publishers: 
 * /rqt_gui (http://ubuntu:45977/)

Subscribers: 
 * /gazebo (http://ubuntu:43662/)


=====================Model Model Model urdf side =============================

<?xml version="1.0"?>
<!-- Revolute-Revolute Manipulator -->
<robot name="rrbot" xmlns:xacro="http://www.ros.org/wiki/xacro">

  <!-- Import all Gazebo-customization elements, including Gazebo colors -->
  <xacro:include filename="$(find rrbot_description)/urdf/rrbot.gazebo" />
  <!-- Import Rviz colors -->
  <xacro:include filename="$(find rrbot_description)/urdf/materials.xacro" />


   <link name='base_link'>
      <collision name='collision'>
        <origin xyz="0 0 .1 " rpy="0 0 0"/>
        <geometry>
          <box  size=".4 .2 .1">
            <size>.4 .2 .1</size>
          </box>
        </geometry>
      </collision>

      <visual name='visual'>
        <origin xyz="0 0 .1 " rpy="0 0 0"/>
        <geometry>
          <box  size=".4 .2 .1">
            <size>.4 .2 .1</size>
          </box>
        </geometry>
      </visual>

      <collision name='caster_collision'>
        <origin xyz="-0.15 0 0" rpy="0 0 0"/>
        <geometry>
          <sphere radius=".05">
            <radius>.05</radius>
          </sphere>
        </geometry>

        <surface>
         <friction>
          <ode>
            <mu>0</mu>
            <mu2>0</mu2>
            <slip1>1.0</slip1>
            <slip2>1.0</slip2>
          </ode>
         </friction>
        </surface>

      </collision>

      <visual name='caster_visual'>
        <origin xyz="-0.15 0 0" rpy="0 0 0"/>
        <geometry>
          <sphere radius=".05">
            <radius>.05</radius>
          </sphere>
        </geometry>
      </visual>

     <inertial>
        <mass value="1e-5" />
        <origin xyz="0 0 .1 " rpy="0 0 0"/>
        <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
     </inertial>
  </link> 



  <link name="left_wheel">
    <collision name="collision">
      <origin xyz="0.1 0.13 0.0" rpy="0 1.5707 1.5707"/>
      <geometry>
         <cylinder length="0.1" radius="0.05">
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </collision>
    <visual name="visual">
      <origin xyz="0.1 0.13 0.0" rpy="0 1.5707 1.5707"/>
      <geometry>
        <cylinder length="0.1" radius="0.05">
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </visual>
    <inertial>
      <mass value="1e-5" />
      <origin xyz="0.1 0.13 0.0"/>
      <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
    </inertial>
  </link>

  <link name="right_wheel">
    <collision name="collision">
      <origin xyz="0.1 -0.13 0.0" rpy="0 1.5707 1.5707"/>
      <geometry>
         <cylinder length="0.1" radius="0.05">
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </collision>
    <visual name="visual">
      <origin xyz="0.1 -0.13 0.0" rpy="0 1.5707 1.5707"/>
      <geometry>
        <cylinder length="0.1" radius="0.05">
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </visual>
    <inertial>
      <mass value="1e-5" />
      <origin xyz="0.1 -0.13 0.0"/>
      <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
    </inertial>
  </link>


  <joint type="revolute" name="joint1">
    <origin xyz="0 0 0" rpy="0 0 0"/>
    <child link="left_wheel">left_wheel</child>
    <parent link="base_link">base_link</parent>
    <axis xyz="0 4 0">
      <xyz>0 1 0</xyz>
    </axis>
    <limit effort="30" velocity="1.0"  />
  </joint>

  <joint type="revolute" name="joint2">
    <origin xyz="0 0 0." rpy="0 0 0"/>
    <child link="right_wheel">right_wheel</child>
     <parent link="base_link">base_link</parent>
     <axis xyz="0 1 0">
      <xyz>0 1 0</xyz>
    </axis>
    <limit effort="30" velocity="1.0"  />
  </joint>

  <transmission name="tran1">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="joint1"/>
    <actuator name="motor1">
      <hardwareInterface>EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>

  <transmission name="tran2">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="joint2"/>
    <actuator name="motor2">
      <hardwareInterface>EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>


</robot>

==============================Model gazebo side ================================

<?xml version='1.0'?>
<robot name="rrbot">

  <gazebo>
    <plugin name="ros_control" filename="libgazebo_ros_control.so">
      <robotNamespace>/rrbot</robotNamespace>
      <controlPeriod>0.001</controlPeriod>
      <robotSimType>gazebo_ros_control/DefaultRobotHWSim</robotSimType>
    </plugin>
  </gazebo>

  <gazebo reference="base_link">
    <mu1>0.2</mu1>
    <mu2>0.2</mu2>
    <material>Gazebo/Red</material>
  </gazebo>

  <gazebo reference="left_wheel">
    <mu1>0.2</mu1>
    <mu2>0.2</mu2>
    <material>Gazebo/Red</material>
  </gazebo>

  <gazebo reference="right_wheel">
    <mu1>0.2</mu1>
    <mu2>0.2</mu2>
    <material>Gazebo/Red</material>
  </gazebo>

</robot>

Can not move model by joint tab or published command.

Gazebo model does not move....if I apply force or velocity to the joints in the joints tab. Also I tried sending commands via rqt plugin shown below. None of these methods move the model. No errors are generated. Any thoughts on why this is the case.

 Using Publisher plugin from rqt_gui. 
 Sending /rrbot/joint1_position_controller/command std_msgs/Float64 rate(100) date(sin(i))
 Sending /rrbot/joint2_position_controller/command std_msgs/Float64 rate(100) date(sin(i))

 ***** From the Terninal *****

 *****viki:~$ rostopic echo /rrbot/joint1_position_controller/command
 data: -0.989367016834
 ---
 data: -0.656941145733
 ---
 data: 0.279473385116
 ---
 data: 0.958941374547
 ---
 data: 0.756763086604
 ---
 data: -0.141179693171
 ---
 data: -0.909322514128
 ---
 data: -0.841438409151



 ***** ros graph shows the command topics subscribed to by gazebo
 *****viki:~$ rostopic info /rrbot/joint1_position_controller/command
 Type: std_msgs/Float64

 Publishers: 
  * /rqt_gui (http://ubuntu:45977/)

 Subscribers: 
  * /gazebo (http://ubuntu:43662/)


 =====================Model Model Model urdf side =============================

 <?xml version="1.0"?>
 <!-- Revolute-Revolute Manipulator -->
 <robot name="rrbot" xmlns:xacro="http://www.ros.org/wiki/xacro">

   <!-- Import all Gazebo-customization elements, including Gazebo colors -->
   <xacro:include filename="$(find rrbot_description)/urdf/rrbot.gazebo" />
   <!-- Import Rviz colors -->
   <xacro:include filename="$(find rrbot_description)/urdf/materials.xacro" />


    <link name='base_link'>
       <collision name='collision'>
         <origin xyz="0 0 .1 " rpy="0 0 0"/>
         <geometry>
           <box  size=".4 .2 .1">
             <size>.4 .2 .1</size>
           </box>
         </geometry>
       </collision>

       <visual name='visual'>
         <origin xyz="0 0 .1 " rpy="0 0 0"/>
         <geometry>
           <box  size=".4 .2 .1">
             <size>.4 .2 .1</size>
           </box>
         </geometry>
       </visual>

       <collision name='caster_collision'>
         <origin xyz="-0.15 0 0" rpy="0 0 0"/>
         <geometry>
           <sphere radius=".05">
             <radius>.05</radius>
           </sphere>
         </geometry>

         <surface>
          <friction>
           <ode>
             <mu>0</mu>
             <mu2>0</mu2>
             <slip1>1.0</slip1>
             <slip2>1.0</slip2>
           </ode>
          </friction>
         </surface>

       </collision>

       <visual name='caster_visual'>
         <origin xyz="-0.15 0 0" rpy="0 0 0"/>
         <geometry>
           <sphere radius=".05">
             <radius>.05</radius>
           </sphere>
         </geometry>
       </visual>

      <inertial>
         <mass value="1e-5" />
         <origin xyz="0 0 .1 " rpy="0 0 0"/>
         <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
      </inertial>
   </link> 



   <link name="left_wheel">
     <collision name="collision">
       <origin xyz="0.1 0.13 0.0" rpy="0 1.5707 1.5707"/>
       <geometry>
          <cylinder length="0.1" radius="0.05">
           <radius>.1</radius>
           <length>.05</length>
         </cylinder>
       </geometry>
     </collision>
     <visual name="visual">
       <origin xyz="0.1 0.13 0.0" rpy="0 1.5707 1.5707"/>
       <geometry>
         <cylinder length="0.1" radius="0.05">
           <radius>.1</radius>
           <length>.05</length>
         </cylinder>
       </geometry>
     </visual>
     <inertial>
       <mass value="1e-5" />
       <origin xyz="0.1 0.13 0.0"/>
       <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
     </inertial>
   </link>

   <link name="right_wheel">
     <collision name="collision">
       <origin xyz="0.1 -0.13 0.0" rpy="0 1.5707 1.5707"/>
       <geometry>
          <cylinder length="0.1" radius="0.05">
           <radius>.1</radius>
           <length>.05</length>
         </cylinder>
       </geometry>
     </collision>
     <visual name="visual">
       <origin xyz="0.1 -0.13 0.0" rpy="0 1.5707 1.5707"/>
       <geometry>
         <cylinder length="0.1" radius="0.05">
           <radius>.1</radius>
           <length>.05</length>
         </cylinder>
       </geometry>
     </visual>
     <inertial>
       <mass value="1e-5" />
       <origin xyz="0.1 -0.13 0.0"/>
       <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
     </inertial>
   </link>


   <joint type="revolute" name="joint1">
    <origin xyz="0 0 -.03 0" rpy="0 0 0"/>
    <child link="left_wheel">left_wheel</child>
    <parent link="base_link">base_link</parent>
    <axis xyz="0 4 1 0">
      <xyz>0 1 0</xyz>
    </axis>
    <limit effort="30" velocity="1.0"  />
  </joint>

  <joint type="revolute" name="joint2">
    <origin xyz="0 0 0." .03 0" rpy="0 0 0"/>
    <child link="right_wheel">right_wheel</child>
     <parent link="base_link">base_link</parent>
     <axis xyz="0 1 0">
      <xyz>0 1 0</xyz>
    </axis>
    <limit effort="30" velocity="1.0"  />
  </joint>

   <transmission name="tran1">
     <type>transmission_interface/SimpleTransmission</type>
     <joint name="joint1"/>
     <actuator name="motor1">
       <hardwareInterface>EffortJointInterface</hardwareInterface>
       <mechanicalReduction>1</mechanicalReduction>
     </actuator>
   </transmission>

   <transmission name="tran2">
     <type>transmission_interface/SimpleTransmission</type>
     <joint name="joint2"/>
     <actuator name="motor2">
       <hardwareInterface>EffortJointInterface</hardwareInterface>
       <mechanicalReduction>1</mechanicalReduction>
     </actuator>
   </transmission>


 </robot>

 ==============================Model gazebo side ================================

 <?xml version='1.0'?>
 <robot name="rrbot">

   <gazebo>
     <plugin name="ros_control" filename="libgazebo_ros_control.so">
       <robotNamespace>/rrbot</robotNamespace>
       <controlPeriod>0.001</controlPeriod>
       <robotSimType>gazebo_ros_control/DefaultRobotHWSim</robotSimType>
     </plugin>
   </gazebo>

   <gazebo reference="base_link">
     <mu1>0.2</mu1>
     <mu2>0.2</mu2>
     <material>Gazebo/Red</material>
   </gazebo>

   <gazebo reference="left_wheel">
     <mu1>0.2</mu1>
     <mu2>0.2</mu2>
     <material>Gazebo/Red</material>
   </gazebo>

   <gazebo reference="right_wheel">
     <mu1>0.2</mu1>
     <mu2>0.2</mu2>
     <material>Gazebo/Red</material>
   </gazebo>

 </robot>

Can not move model by joint tab or published command.

Gazebo model does not move....if I apply force or velocity to the joints in the joints tab. Also I tried sending commands via rqt plugin shown below. None of these methods move the model. No errors are generated. Any thoughts on why this is the case.

I also added a gazebo plugin following :http://www.gazebosim.org/wiki/Tutorials/1.3/control_robot/mobile_base making changes to my joint defs. The OnUpdate method is called but the model still does not move. How can I debug this? I can move it manually with the move tool only.

    Using Publisher plugin from rqt_gui. 
    Sending /rrbot/joint1_position_controller/command std_msgs/Float64 rate(100) date(sin(i))
    Sending /rrbot/joint2_position_controller/command std_msgs/Float64 rate(100) date(sin(i))

    ***** From the Terninal *****

    *****viki:~$ rostopic echo /rrbot/joint1_position_controller/command
    data: -0.989367016834
    ---
    data: -0.656941145733
    ---
    data: 0.279473385116
    ---
    data: 0.958941374547
    ---
    data: 0.756763086604
    ---
    data: -0.141179693171
    ---
    data: -0.909322514128
    ---
    data: -0.841438409151



    ***** ros graph shows the command topics subscribed to by gazebo
    *****viki:~$ rostopic info /rrbot/joint1_position_controller/command
    Type: std_msgs/Float64

    Publishers: 
     * /rqt_gui (http://ubuntu:45977/)

    Subscribers: 
     * /gazebo (http://ubuntu:43662/)


    =====================Model Model Model urdf side =============================

    <?xml version="1.0"?>
    <!-- Revolute-Revolute Manipulator -->
    <robot name="rrbot" xmlns:xacro="http://www.ros.org/wiki/xacro">

      <!-- Import all Gazebo-customization elements, including Gazebo colors -->
      <xacro:include filename="$(find rrbot_description)/urdf/rrbot.gazebo" />
      <!-- Import Rviz colors -->
      <xacro:include filename="$(find rrbot_description)/urdf/materials.xacro" />


       <link name='base_link'>
          <collision name='collision'>
            <origin xyz="0 0 .1 " rpy="0 0 0"/>
            <geometry>
              <box  size=".4 .2 .1">
                <size>.4 .2 .1</size>
              </box>
            </geometry>
          </collision>

          <visual name='visual'>
            <origin xyz="0 0 .1 " rpy="0 0 0"/>
            <geometry>
              <box  size=".4 .2 .1">
                <size>.4 .2 .1</size>
              </box>
            </geometry>
          </visual>

          <collision name='caster_collision'>
            <origin xyz="-0.15 0 0" rpy="0 0 0"/>
            <geometry>
              <sphere radius=".05">
                <radius>.05</radius>
              </sphere>
            </geometry>

            <surface>
             <friction>
              <ode>
                <mu>0</mu>
                <mu2>0</mu2>
                <slip1>1.0</slip1>
                <slip2>1.0</slip2>
              </ode>
             </friction>
            </surface>

          </collision>

          <visual name='caster_visual'>
            <origin xyz="-0.15 0 0" rpy="0 0 0"/>
            <geometry>
              <sphere radius=".05">
                <radius>.05</radius>
              </sphere>
            </geometry>
          </visual>

         <inertial>
            <mass value="1e-5" />
            <origin xyz="0 0 .1 " rpy="0 0 0"/>
            <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
         </inertial>
      </link> 



      <link name="left_wheel">
        <collision name="collision">
          <origin xyz="0.1 0.13 0.0" rpy="0 1.5707 1.5707"/>
          <geometry>
             <cylinder length="0.1" radius="0.05">
              <radius>.1</radius>
              <length>.05</length>
            </cylinder>
          </geometry>
        </collision>
        <visual name="visual">
          <origin xyz="0.1 0.13 0.0" rpy="0 1.5707 1.5707"/>
          <geometry>
            <cylinder length="0.1" radius="0.05">
              <radius>.1</radius>
              <length>.05</length>
            </cylinder>
          </geometry>
        </visual>
        <inertial>
          <mass value="1e-5" />
          <origin xyz="0.1 0.13 0.0"/>
          <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
        </inertial>
      </link>

      <link name="right_wheel">
        <collision name="collision">
          <origin xyz="0.1 -0.13 0.0" rpy="0 1.5707 1.5707"/>
          <geometry>
             <cylinder length="0.1" radius="0.05">
              <radius>.1</radius>
              <length>.05</length>
            </cylinder>
          </geometry>
        </collision>
        <visual name="visual">
          <origin xyz="0.1 -0.13 0.0" rpy="0 1.5707 1.5707"/>
          <geometry>
            <cylinder length="0.1" radius="0.05">
              <radius>.1</radius>
              <length>.05</length>
            </cylinder>
          </geometry>
        </visual>
        <inertial>
          <mass value="1e-5" />
          <origin xyz="0.1 -0.13 0.0"/>
          <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
        </inertial>
      </link>


      <joint type="revolute" name="joint1">
    <origin xyz="0 -.03 0" rpy="0 0 0"/>
    <child link="left_wheel">left_wheel</child>
    <parent link="base_link">base_link</parent>
    <axis xyz="0 1 0">
      <xyz>0 1 0</xyz>
    </axis>
    <limit effort="30" velocity="1.0"  />
  </joint>

  <joint type="revolute" name="joint2">
    <origin xyz="0 .03 0" rpy="0 0 0"/>
    <child link="right_wheel">right_wheel</child>
     <parent link="base_link">base_link</parent>
     <axis xyz="0 1 0">
      <xyz>0 1 0</xyz>
    </axis>
    <limit effort="30" velocity="1.0"  />
  </joint>

      <transmission name="tran1">
        <type>transmission_interface/SimpleTransmission</type>
        <joint name="joint1"/>
        <actuator name="motor1">
          <hardwareInterface>EffortJointInterface</hardwareInterface>
          <mechanicalReduction>1</mechanicalReduction>
        </actuator>
      </transmission>

      <transmission name="tran2">
        <type>transmission_interface/SimpleTransmission</type>
        <joint name="joint2"/>
        <actuator name="motor2">
          <hardwareInterface>EffortJointInterface</hardwareInterface>
          <mechanicalReduction>1</mechanicalReduction>
        </actuator>
      </transmission>


    </robot>

    ==============================Model gazebo side ================================

    <?xml version='1.0'?>
    <robot name="rrbot">

      <gazebo>
        <plugin name="ros_control" filename="libgazebo_ros_control.so">
          <robotNamespace>/rrbot</robotNamespace>
          <controlPeriod>0.001</controlPeriod>
          <robotSimType>gazebo_ros_control/DefaultRobotHWSim</robotSimType>
        </plugin>
      </gazebo>

      <gazebo reference="base_link">
        <mu1>0.2</mu1>
        <mu2>0.2</mu2>
        <material>Gazebo/Red</material>
      </gazebo>

      <gazebo reference="left_wheel">
        <mu1>0.2</mu1>
        <mu2>0.2</mu2>
        <material>Gazebo/Red</material>
      </gazebo>

      <gazebo reference="right_wheel">
        <mu1>0.2</mu1>
        <mu2>0.2</mu2>
        <material>Gazebo/Red</material>
      </gazebo>

    </robot>

Can not move model by joint tab or published command.

Gazebo Yet another restatement of problem.

I ran this file as its original model.sdf and it works fine!!! Force tab works fine , the model does not move....if I apply force or velocity moves. When modifed to run as a urdf file it stops working. Can any one see what the joints error if any in the joints tab. Also I tried sending commands via rqt plugin shown below. None of these methods move the model. No errors are generated. Any thoughts on why this conversion is? Here is the case.sdf file and the two xarco files that generate the urdf.

I also added a gazebo plugin following :http://www.gazebosim.org/wiki/Tutorials/1.3/control_robot/mobile_base making changes to my joint defs. The OnUpdate method is called but the model still does not move. How can I debug this? I can move it manually with the move tool only.============================sdf model============================

    Using Publisher plugin from rqt_gui. 
    Sending /rrbot/joint1_position_controller/command std_msgs/Float64 rate(100) date(sin(i))
    Sending /rrbot/joint2_position_controller/command std_msgs/Float64 rate(100) date(sin(i))

    ***** From the Terninal *****

    *****viki:~$ rostopic echo /rrbot/joint1_position_controller/command
    data: -0.989367016834
    ---
    data: -0.656941145733
    ---
    data: 0.279473385116
    ---
    data: 0.958941374547
    ---
    data: 0.756763086604
    ---
    data: -0.141179693171
    ---
    data: -0.909322514128
    ---
    data: -0.841438409151



    ***** ros graph shows the command topics subscribed to by gazebo
    *****viki:~$ rostopic info /rrbot/joint1_position_controller/command
    Type: std_msgs/Float64

    Publishers: 
     * /rqt_gui (http://ubuntu:45977/)

    Subscribers: 
     * /gazebo (http://ubuntu:43662/)


<?xml version='1.0'?>
<sdf version='1.3'>
  <model name="my_robot">
    <link name='base_link'>
      <pose>0 0 .1 0 0 0</pose>
      <collision name='collision'>
        <geometry>
          <box>
            <size>.4 .2 .1</size>
          </box>
        </geometry>
      </collision>

      <visual name='visual'>
        <geometry>
          <box>
            <size>.4 .2 .1</size>
          </box>
        </geometry>
      </visual>

      <collision name='caster_collision'>
        <pose>-0.15 0 -0.05 0 0 0</pose>
        <geometry>
          <sphere>
          <radius>.05</radius>
        </sphere>
      </geometry>

      <surface>
        <friction>
          <ode>
            <mu>0</mu>
            <mu2>0</mu2>
            <slip1>1.0</slip1>
            <slip2>1.0</slip2>
          </ode>
        </friction>
      </surface>
    </collision>

    <visual name='caster_visual'>
      <pose>-0.15 0 -0.05 0 0 0</pose>
      <geometry>
        <sphere>
          <radius>.05</radius>
        </sphere>
      </geometry>
    </visual>
  </link>     
  <link name="left_wheel">
    <pose>0.1 0.13 0.1 0 1.5707 1.5707</pose>
    <collision name="collision">
      <geometry>
        <cylinder>
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </collision>
    <visual name="visual">
      <geometry>
        <cylinder>
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </visual>
  </link>

  <link name="right_wheel">
    <pose>0.1 -0.13 0.1 0 1.5707 1.5707</pose>
    <collision name="collision">
      <geometry>
        <cylinder>
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </collision>
    <visual name="visual">
      <geometry>
        <cylinder>
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </visual>
  </link>
  <joint type="revolute" name="joint1">
    <pose>0 0 -0.03 0 0 0</pose>
    <child>left_wheel</child>
    <parent>base_link</parent>
    <axis>
      <xyz>0 1 0</xyz>
    </axis>
  </joint>

  <joint type="revolute" name="joint2">
    <pose>0 0 0.03 0 0 0</pose>
    <child>right_wheel</child>
    <parent>base_link</parent>
    <axis>
      <xyz>0 1 0</xyz>
    </axis>
  </joint>
   </model>
</sdf>





      =====================Model Model Model urdf side =============================

     <?xml version="1.0"?>
     <!-- Revolute-Revolute Manipulator -->
     <robot name="rrbot" xmlns:xacro="http://www.ros.org/wiki/xacro">

       <!-- Import all Gazebo-customization elements, including Gazebo colors -->
       <xacro:include filename="$(find rrbot_description)/urdf/rrbot.gazebo" />
       <!-- Import Rviz colors -->
       <xacro:include filename="$(find rrbot_description)/urdf/materials.xacro" />


        <link name='base_link'>
           <collision name='collision'>
             <origin xyz="0 0 .1 " rpy="0 0 0"/>
             <geometry>
               <box  size=".4 .2 .1">
                 <size>.4 .2 .1</size>
               </box>
             </geometry>
           </collision>

           <visual name='visual'>
             <origin xyz="0 0 .1 " rpy="0 0 0"/>
             <geometry>
               <box  size=".4 .2 .1">
                 <size>.4 .2 .1</size>
               </box>
             </geometry>
           </visual>

           <collision name='caster_collision'>
             <origin xyz="-0.15 0 0" rpy="0 0 0"/>
             <geometry>
               <sphere radius=".05">
                 <radius>.05</radius>
               </sphere>
             </geometry>

             <surface>
              <friction>
               <ode>
                 <mu>0</mu>
                 <mu2>0</mu2>
                 <slip1>1.0</slip1>
                 <slip2>1.0</slip2>
               </ode>
              </friction>
             </surface>

           </collision>

           <visual name='caster_visual'>
             <origin xyz="-0.15 0 0" rpy="0 0 0"/>
             <geometry>
               <sphere radius=".05">
                 <radius>.05</radius>
               </sphere>
             </geometry>
           </visual>

          <inertial>
             <mass value="1e-5" />
             <origin xyz="0 0 .1 " rpy="0 0 0"/>
             <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
          </inertial>
       </link> 



       <link name="left_wheel">
         <collision name="collision">
           <origin xyz="0.1 0.13 0.0" rpy="0 1.5707 1.5707"/>
           <geometry>
              <cylinder length="0.1" radius="0.05">
               <radius>.1</radius>
               <length>.05</length>
             </cylinder>
           </geometry>
         </collision>
         <visual name="visual">
           <origin xyz="0.1 0.13 0.0" rpy="0 1.5707 1.5707"/>
           <geometry>
             <cylinder length="0.1" radius="0.05">
               <radius>.1</radius>
               <length>.05</length>
             </cylinder>
           </geometry>
         </visual>
         <inertial>
           <mass value="1e-5" />
           <origin xyz="0.1 0.13 0.0"/>
           <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
         </inertial>
       </link>

       <link name="right_wheel">
         <collision name="collision">
           <origin xyz="0.1 -0.13 0.0" rpy="0 1.5707 1.5707"/>
           <geometry>
              <cylinder length="0.1" radius="0.05">
               <radius>.1</radius>
               <length>.05</length>
             </cylinder>
           </geometry>
         </collision>
         <visual name="visual">
           <origin xyz="0.1 -0.13 0.0" rpy="0 1.5707 1.5707"/>
           <geometry>
             <cylinder length="0.1" radius="0.05">
               <radius>.1</radius>
               <length>.05</length>
             </cylinder>
           </geometry>
         </visual>
         <inertial>
           <mass value="1e-5" />
           <origin xyz="0.1 -0.13 0.0"/>
           <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
         </inertial>
       </link>


   <joint type="revolute" name="joint1">
    <origin xyz="0 -.03 0" xyz="0.0 0.0 -0.03" rpy="0 0 0"/>
    <child link="left_wheel">left_wheel</child>
    <parent link="base_link">base_link</parent>
    <axis xyz="0 1 0">
      <xyz>0 1 0</xyz>
    </axis>
    <limit effort="30" velocity="1.0"  />
  </joint>

  <joint type="revolute" name="joint2">
    <origin xyz="0 .03 0" xyz="0.0 0.0 0.03" rpy="0 0 0"/>
    <child link="right_wheel">right_wheel</child>
     <parent link="base_link">base_link</parent>
     <axis xyz="0 1 0">
      <xyz>0 1 0</xyz>
    </axis>
    <limit effort="30" velocity="1.0"  />
  </joint>

       <transmission name="tran1">
         <type>transmission_interface/SimpleTransmission</type>
         <joint name="joint1"/>
         <actuator name="motor1">
           <hardwareInterface>EffortJointInterface</hardwareInterface>
           <mechanicalReduction>1</mechanicalReduction>
         </actuator>
       </transmission>

       <transmission name="tran2">
         <type>transmission_interface/SimpleTransmission</type>
         <joint name="joint2"/>
         <actuator name="motor2">
           <hardwareInterface>EffortJointInterface</hardwareInterface>
           <mechanicalReduction>1</mechanicalReduction>
         </actuator>
       </transmission>


     </robot>

     ==============================Model urdf files gazebo side ================================

part ==========================

        <?xml version='1.0'?>
     <robot name="rrbot">

       <gazebo>
         <plugin name="ros_control" filename="libgazebo_ros_control.so">
           <robotNamespace>/rrbot</robotNamespace>
           <controlPeriod>0.001</controlPeriod>
           <robotSimType>gazebo_ros_control/DefaultRobotHWSim</robotSimType>
         </plugin>
       </gazebo>

       <gazebo reference="base_link">
         <mu1>0.2</mu1>
         <mu2>0.2</mu2>
         <material>Gazebo/Red</material>
       </gazebo>

       <gazebo reference="left_wheel">
         <mu1>0.2</mu1>
         <mu2>0.2</mu2>
         <material>Gazebo/Red</material>
       </gazebo>

       <gazebo reference="right_wheel">
         <mu1>0.2</mu1>
         <mu2>0.2</mu2>
         <material>Gazebo/Red</material>
       </gazebo>

     </robot>

Can not move model by joint tab or published command.

Yet another restatement of problem.

I ran this file as its original model.sdf and it works fine!!! Force tab works fine , the model moves. When modifed to run as a urdf file it stops working. Can any one see what the error if any in the conversion is? Here is the sdf file and the two xarco files that generate the urdf.

============================sdf model============================

<?xml version='1.0'?>
<sdf version='1.3'>
  <model name="my_robot">
    <link name='base_link'>
      <pose>0 0 .1 0 0 0</pose>
      <collision name='collision'>
        <geometry>
          <box>
            <size>.4 .2 .1</size>
          </box>
        </geometry>
      </collision>

      <visual name='visual'>
        <geometry>
          <box>
            <size>.4 .2 .1</size>
          </box>
        </geometry>
      </visual>

      <collision name='caster_collision'>
        <pose>-0.15 0 -0.05 0 0 0</pose>
        <geometry>
          <sphere>
          <radius>.05</radius>
        </sphere>
      </geometry>

      <surface>
        <friction>
          <ode>
            <mu>0</mu>
            <mu2>0</mu2>
            <slip1>1.0</slip1>
            <slip2>1.0</slip2>
          </ode>
        </friction>
      </surface>
    </collision>

    <visual name='caster_visual'>
      <pose>-0.15 0 -0.05 0 0 0</pose>
      <geometry>
        <sphere>
          <radius>.05</radius>
        </sphere>
      </geometry>
    </visual>
  </link>     
  <link name="left_wheel">
    <pose>0.1 0.13 0.1 0 1.5707 1.5707</pose>
    <collision name="collision">
      <geometry>
        <cylinder>
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </collision>
    <visual name="visual">
      <geometry>
        <cylinder>
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </visual>
  </link>

  <link name="right_wheel">
    <pose>0.1 -0.13 0.1 0 1.5707 1.5707</pose>
    <collision name="collision">
      <geometry>
        <cylinder>
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </collision>
    <visual name="visual">
      <geometry>
        <cylinder>
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </visual>
  </link>
  <joint type="revolute" name="joint1">
    <pose>0 0 -0.03 0 0 0</pose>
    <child>left_wheel</child>
    <parent>base_link</parent>
    <axis>
      <xyz>0 1 0</xyz>
    </axis>
  </joint>

  <joint type="revolute" name="joint2">
    <pose>0 0 0.03 0 0 0</pose>
    <child>right_wheel</child>
    <parent>base_link</parent>
    <axis>
      <xyz>0 1 0</xyz>
    </axis>
  </joint>
   </model>
</sdf>





      =====================Model urdf side =============================
 <?xml version="1.0"?>
 <!-- Revolute-Revolute Manipulator -->
 <robot name="rrbot" xmlns:xacro="http://www.ros.org/wiki/xacro">

   <!-- Import all Gazebo-customization elements, including Gazebo colors -->
   <xacro:include filename="$(find rrbot_description)/urdf/rrbot.gazebo" />
   <!-- Import Rviz colors -->
   <xacro:include filename="$(find rrbot_description)/urdf/materials.xacro" />

    <link name='base_link'>
       <collision name='collision'>
         <origin xyz="0 0 .1 " rpy="0 0 0"/>
         <geometry>
           <box  size=".4 .2 .1">
                    <size>.4 .2 .1</size>
                  </box>
        .1"/>
        </geometry>
       </collision>

       <visual name='visual'>
         <origin xyz="0 0 .1 " rpy="0 0 0"/>
         <geometry>
           <box  size=".4 .2 .1">
                    <size>.4 .2 .1</size>
                  </box>
        .1"/>
        </geometry>
       </visual>

       <collision name='caster_collision'>
         <origin xyz="-0.15 0 0" rpy="0 0 0"/>
         <geometry>
           <sphere radius=".05">
                    <radius>.05</radius>
                  </sphere>
        radius=".05"/>
        </geometry>

         <surface>
          <friction>
           <ode>
             <mu>0</mu>
             <mu2>0</mu2>
             <slip1>1.0</slip1>
             <slip2>1.0</slip2>
           </ode>
          </friction>
         </surface>

       </collision>

       <visual name='caster_visual'>
         <origin xyz="-0.15 0 0" rpy="0 0 0"/>
         <geometry>
           <sphere radius=".05">
                    <radius>.05</radius>
                  </sphere>
        radius=".05"/>
        </geometry>
       </visual>

      <inertial>
         <mass value="1e-5" />
         <origin xyz="0 0 .1 " rpy="0 0 0"/>
         <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
      </inertial>
   </link> 



   <link name="left_wheel">
     <collision name="collision">
       <origin xyz="0.1 0.13 0.0" rpy="0 1.5707 1.5707"/>
       <geometry>
          <cylinder length="0.1" radius="0.05">
                  <radius>.1</radius>
                  <length>.05</length>
                </cylinder>
        radius="0.05"/>
      </geometry>
     </collision>
     <visual name="visual">
       <origin xyz="0.1 0.13 0.0" rpy="0 1.5707 1.5707"/>
       <geometry>
         <cylinder length="0.1" radius="0.05">
                  <radius>.1</radius>
                  <length>.05</length>
                </cylinder>
        radius="0.05"/>
      </geometry>
     </visual>
     <inertial>
       <mass value="1e-5" />
       <origin xyz="0.1 0.13 0.0"/>
       <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
     </inertial>
   </link>

   <link name="right_wheel">
     <collision name="collision">
       <origin xyz="0.1 -0.13 0.0" rpy="0 1.5707 1.5707"/>
       <geometry>
          <cylinder length="0.1" radius="0.05">
                  <radius>.1</radius>
                  <length>.05</length>
                </cylinder>
        radius="0.05"/>
      </geometry>
     </collision>
     <visual name="visual">
       <origin xyz="0.1 -0.13 0.0" rpy="0 1.5707 1.5707"/>
       <geometry>
         <cylinder length="0.1" radius="0.05">
                  <radius>.1</radius>
                  <length>.05</length>
                </cylinder>
        radius="0.05"/>
      </geometry>
     </visual>
     <inertial>
       <mass value="1e-5" />
       <origin xyz="0.1 -0.13 0.0"/>
       <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
     </inertial>
   </link>


  <joint type="revolute" name="joint1">
    <origin xyz="0.0 0.0 -0.03" rpy="0 0 0"/>
    <child link="left_wheel">left_wheel</child>
    <parent link="base_link">base_link</parent>
    <axis xyz="0 1 0">
      <xyz>0 1 0</xyz>
    </axis>
    <limit effort="30" velocity="1.0"  />
  </joint>

  <joint type="revolute" name="joint2">
    <origin xyz="0.0 0.0 0.03" rpy="0 0 0"/>
    <child link="right_wheel">right_wheel</child>
 link="left_wheel">left_wheel</child>
    <parent link="base_link">base_link</parent>
     <axis xyz="0 1 0">
      <xyz>0 1 0</xyz>
    </axis>
0"/>
    <limit effort="30" velocity="1.0"  />
  </joint>

   <joint type="revolute" name="joint2">
    <origin xyz="0.0 0.0 0.03" rpy="0 0 0"/>
    <child link="right_wheel">right_wheel</child>
     <parent link="base_link">base_link</parent>
     <axis xyz="0 1 0"/>>
    <limit effort="30" velocity="1.0"  />
  </joint>

  <transmission name="tran1">
     <type>transmission_interface/SimpleTransmission</type>
     <joint name="joint1"/>
     <actuator name="motor1">
       <hardwareInterface>EffortJointInterface</hardwareInterface>
       <mechanicalReduction>1</mechanicalReduction>
     </actuator>
   </transmission>

   <transmission name="tran2">
     <type>transmission_interface/SimpleTransmission</type>
     <joint name="joint2"/>
     <actuator name="motor2">
       <hardwareInterface>EffortJointInterface</hardwareInterface>
       <mechanicalReduction>1</mechanicalReduction>
     </actuator>
   </transmission>


 </robot>
 
        ==============================Model urdf files gazebo part ==========================

        <?xml version='1.0'?>
        <robot name="rrbot">

          <gazebo>
            <plugin name="ros_control" filename="libgazebo_ros_control.so">
              <robotNamespace>/rrbot</robotNamespace>
              <controlPeriod>0.001</controlPeriod>
              <robotSimType>gazebo_ros_control/DefaultRobotHWSim</robotSimType>
            </plugin>
          </gazebo>

          <gazebo reference="base_link">
            <mu1>0.2</mu1>
            <mu2>0.2</mu2>
            <material>Gazebo/Red</material>
          </gazebo>

          <gazebo reference="left_wheel">
            <mu1>0.2</mu1>
            <mu2>0.2</mu2>
            <material>Gazebo/Red</material>
          </gazebo>

          <gazebo reference="right_wheel">
            <mu1>0.2</mu1>
            <mu2>0.2</mu2>
            <material>Gazebo/Red</material>
          </gazebo>

        </robot>

Can not move model by joint tab or published command.

Yet another restatement of problem.

HINT: if I change the joint type to "continuous" the applying force via the force tab works. Why is this???

I ran this file as its original model.sdf and it works fine!!! Force tab works fine , the model moves. When modifed to run as a urdf file it stops working. Can any one see what the error if any in the conversion is? Here is the sdf file and the two xarco files that generate the urdf.

============================sdf model============================

<?xml version='1.0'?>
<sdf version='1.3'>
  <model name="my_robot">
    <link name='base_link'>
      <pose>0 0 .1 0 0 0</pose>
      <collision name='collision'>
        <geometry>
          <box>
            <size>.4 .2 .1</size>
          </box>
        </geometry>
      </collision>

      <visual name='visual'>
        <geometry>
          <box>
            <size>.4 .2 .1</size>
          </box>
        </geometry>
      </visual>

      <collision name='caster_collision'>
        <pose>-0.15 0 -0.05 0 0 0</pose>
        <geometry>
          <sphere>
          <radius>.05</radius>
        </sphere>
      </geometry>

      <surface>
        <friction>
          <ode>
            <mu>0</mu>
            <mu2>0</mu2>
            <slip1>1.0</slip1>
            <slip2>1.0</slip2>
          </ode>
        </friction>
      </surface>
    </collision>

    <visual name='caster_visual'>
      <pose>-0.15 0 -0.05 0 0 0</pose>
      <geometry>
        <sphere>
          <radius>.05</radius>
        </sphere>
      </geometry>
    </visual>
  </link>     
  <link name="left_wheel">
    <pose>0.1 0.13 0.1 0 1.5707 1.5707</pose>
    <collision name="collision">
      <geometry>
        <cylinder>
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </collision>
    <visual name="visual">
      <geometry>
        <cylinder>
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </visual>
  </link>

  <link name="right_wheel">
    <pose>0.1 -0.13 0.1 0 1.5707 1.5707</pose>
    <collision name="collision">
      <geometry>
        <cylinder>
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </collision>
    <visual name="visual">
      <geometry>
        <cylinder>
          <radius>.1</radius>
          <length>.05</length>
        </cylinder>
      </geometry>
    </visual>
  </link>
  <joint type="revolute" name="joint1">
    <pose>0 0 -0.03 0 0 0</pose>
    <child>left_wheel</child>
    <parent>base_link</parent>
    <axis>
      <xyz>0 1 0</xyz>
    </axis>
  </joint>

  <joint type="revolute" name="joint2">
    <pose>0 0 0.03 0 0 0</pose>
    <child>right_wheel</child>
    <parent>base_link</parent>
    <axis>
      <xyz>0 1 0</xyz>
    </axis>
  </joint>
   </model>
</sdf>





      =====================Model urdf side =============================
<?xml version="1.0"?>
<!-- Revolute-Revolute Manipulator -->
<robot name="rrbot" xmlns:xacro="http://www.ros.org/wiki/xacro">

  <!-- Import all Gazebo-customization elements, including Gazebo colors -->
  <xacro:include filename="$(find rrbot_description)/urdf/rrbot.gazebo" />
  <!-- Import Rviz colors -->
  <xacro:include filename="$(find rrbot_description)/urdf/materials.xacro" />

   <link name='base_link'>
      <collision name='collision'>
        <origin xyz="0 0 .1 " rpy="0 0 0"/>
        <geometry>
          <box  size=".4 .2 .1"/>
        </geometry>
      </collision>

      <visual name='visual'>
        <origin xyz="0 0 .1 " rpy="0 0 0"/>
        <geometry>
          <box  size=".4 .2 .1"/>
        </geometry>
      </visual>

      <collision name='caster_collision'>
        <origin xyz="-0.15 0 0" rpy="0 0 0"/>
        <geometry>
          <sphere radius=".05"/>
        </geometry>

        <surface>
         <friction>
          <ode>
            <mu>0</mu>
            <mu2>0</mu2>
            <slip1>1.0</slip1>
            <slip2>1.0</slip2>
          </ode>
         </friction>
        </surface>

      </collision>

      <visual name='caster_visual'>
        <origin xyz="-0.15 0 0" rpy="0 0 0"/>
        <geometry>
          <sphere radius=".05"/>
        </geometry>
      </visual>

     <inertial>
        <mass value="1e-5" />
        <origin xyz="0 0 .1 " rpy="0 0 0"/>
        <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
     </inertial>
  </link> 



  <link name="left_wheel">
    <collision name="collision">
      <origin xyz="0.1 0.13 0.0" rpy="0 1.5707 1.5707"/>
      <geometry>
         <cylinder length="0.1" radius="0.05"/>
      </geometry>
    </collision>
    <visual name="visual">
      <origin xyz="0.1 0.13 0.0" rpy="0 1.5707 1.5707"/>
      <geometry>
        <cylinder length="0.1" radius="0.05"/>
      </geometry>
    </visual>
    <inertial>
      <mass value="1e-5" />
      <origin xyz="0.1 0.13 0.0"/>
      <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
    </inertial>
  </link>

  <link name="right_wheel">
    <collision name="collision">
      <origin xyz="0.1 -0.13 0.0" rpy="0 1.5707 1.5707"/>
      <geometry>
         <cylinder length="0.1" radius="0.05"/>
      </geometry>
    </collision>
    <visual name="visual">
      <origin xyz="0.1 -0.13 0.0" rpy="0 1.5707 1.5707"/>
      <geometry>
        <cylinder length="0.1" radius="0.05"/>
      </geometry>
    </visual>
    <inertial>
      <mass value="1e-5" />
      <origin xyz="0.1 -0.13 0.0"/>
      <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
    </inertial>
  </link>


  <joint type="revolute" name="joint1">
    <origin xyz="0.0 0.0 0.03" rpy="0 0 0"/>
    <child link="left_wheel">left_wheel</child>
    <parent link="base_link">base_link</parent>
    <axis xyz="0 1 0"/>
    <limit effort="30" velocity="1.0"  />
  </joint>

  <joint type="revolute" name="joint2">
    <origin xyz="0.0 0.0 0.03" rpy="0 0 0"/>
    <child link="right_wheel">right_wheel</child>
     <parent link="base_link">base_link</parent>
     <axis xyz="0 1 0"/>>
    <limit effort="30" velocity="1.0"  />
  </joint>

  <transmission name="tran1">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="joint1"/>
    <actuator name="motor1">
      <hardwareInterface>EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>

  <transmission name="tran2">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="joint2"/>
    <actuator name="motor2">
      <hardwareInterface>EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>


</robot>




        ==============================Model urdf files gazebo part ==========================

        <?xml version='1.0'?>
        <robot name="rrbot">

          <gazebo>
            <plugin name="ros_control" filename="libgazebo_ros_control.so">
              <robotNamespace>/rrbot</robotNamespace>
              <controlPeriod>0.001</controlPeriod>
              <robotSimType>gazebo_ros_control/DefaultRobotHWSim</robotSimType>
            </plugin>
          </gazebo>

          <gazebo reference="base_link">
            <mu1>0.2</mu1>
            <mu2>0.2</mu2>
            <material>Gazebo/Red</material>
          </gazebo>

          <gazebo reference="left_wheel">
            <mu1>0.2</mu1>
            <mu2>0.2</mu2>
            <material>Gazebo/Red</material>
          </gazebo>

          <gazebo reference="right_wheel">
            <mu1>0.2</mu1>
            <mu2>0.2</mu2>
            <material>Gazebo/Red</material>
          </gazebo>

        </robot>