Getting contact sensor/bumper Gazebo plugin to work

edit

it can be more complicated that a simple _collision add but this is indeed the general idee ;) More details in the link in my answer ;)

This trick is very important. I spend a week on this. Really don't know why gazebo not give a demo directly.

I can not solve the problem, I also added the _collision, but it did not work, here is my xml in turtlebot3_burger.urdf.xacro

<gazebo reference="bump_sensor">
    <sensor name="main_bumper" type="contact">
        <selfCollide>true</selfCollide>
        <alwaysOn>true</alwaysOn>
        <updateRate>15.0</updateRate>
        <material>Gazebo/Red</material>
        <contact>
            <collision>bump_sensor_collision_collision</collision>
        </contact>
        <plugin name="gazebo_ros_bumper_controller" filename="libgazebo_ros_bumper.so">
            <bumperTopicName>bumper_vals</bumperTopicName>
            <frameName>world</frameName>
        </plugin>
    </sensor>
</gazebo>

here is my full bumper xml: https://ideone.com/Exwz1Z

This is why I didn't only say to add collision but to check the full explanation on my answer .... It has been later clarified for the simple case and this has become the accepted answer but the full explanation lie in my post in answer.gazebosim linked in my answer below.

@TTDM, thank you a lot, that is my mistake because of not checking your specific and wondrous answer. By checking the sdf with (gz sdf -p turtlebot3_burger.urdf.xacro), I found that your supplementary note is likely my problem. After seeing the collision name in the sdf file, I modified the turtlebot3_burger.urdf.xacro But the state output is still empty, I have checked by parse to sdf again and in the sdf file:

<collision name='base_footprint_fixed_joint_lump__bump_sensor_collision_collision_1'>
    <pose frame=''>0.05 0 0.03 0 -0 0</pose>
    ...
  </collision>

and the sensor tag,

<sensor name='main_bumper' type='contact'>
        <contact>
          <collision>base_footprint_fixed_joint_lump__bump_sensor_collision_collision_1</collision>
          <topic>__default_topic__</topic>
        </contact>
        ...

Did I miss or do anything wrong? here is my turtlebot3_burger.urdf.xacro: https://ideone.com/XGmhIQ Again, thank you a lot!

Hi, you forgot to declare "update rate" and "always on" on this last file. Also, in my code, i have them twice, once in the <gazebo> tag and once inside the <plugin> tag; even if i'm not sure its useful (but since i didn't tested it i still gives you the differences i see). Here is my code :

 <gazebo reference="${namespace}/base_link">
        <sensor name="collision_sensor" type="contact">
       <plugin name="gazebo_ros_bumper_controller" filename="libgazebo_ros_bumper.so"> 

            <bumpertopicname>bumper_vals</bumpertopicname>
            <framename>world</framename>
            <alwayson>true</alwayson>
            <updaterate>1000.0</updaterate>
        </plugin>
          <always_on>true</always_on>
          <update_rate>1000.</update_rate>
          <contact>
            <collision>hummingbird/base_link_fixed_joint_lump__mav_collision_box_collision</collision>
          </contact>
        </sensor>
      </gazebo>