Sonar on Pioneer 3-AT

edit

I have to simulate the Pioneer3-AT. Therefor I got a model in gazebo. It lookes very fine. But in the model there ist only the visual of the front and back sonar. I need them to publish the messages. So I tried to use a gazebo plugin:

<gazebo reference="front_sonar_box2">
<sensor type="ray" name="front_sonar_box2">
<pose>0 0 0 0 0 0</pose>
<visualize>false</visualize>
<update_rate>40</update_rate>     <!--update rate-->                  
<ray>
    <scan>
    <horizontal>
        <samples>30</samples>               <!--ray -->
        <resolution>1</resolution>
        <min_angle>-0.131</min_angle>       <!-- -${field_of_view/2} -->
        <max_angle>0.131</max_angle>        <!-- -${field_of_view/2} -->        
    </horizontal>
  </scan>
  <range>
    <min>0.08</min>
    <max>10</max>
    <resolution>0.01</resolution>
  </range>
  <noise>
    <type>gaussian</type> 
    <mean>0.0</mean>
    <stddev>0.01</stddev>
  </noise>
</ray>

<plugin name="gazebo_ros_front_sonar_controller" filename="libgazebo_ros_laser.so">
    <topicName>/pioneer/sonar/scan2</topicName>
    <frameName>front_sonar_box2</frameName>
</plugin>
</sensor>
</gazebo>

But in use there is no topic named /pioneer/sonar/scan2 and I can't see it in Rviz. Have anybody an idea why this doesn't work? Thanks in advance!