Ray sensor not showing on urdf robot

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Hello,

I don't know if this is the right place to post this question, but this issue is driving me crazy. I couldn't solve it myself and thought I could run it over with everyone here, see if someone had the same issue.

I have created a URDF model of my robot following gazebo tutorial. This robot has a Velodyne sensor at the front, the mesh is showing, and it is somehow rotating when I press play, the ray is not showing. I do not know if I have written something wrong because the sensor tag is showing on gazebo when I select the Velodyne link, but the ray is not showing at all. Is it normal? I have not connected to my ROS project yet, and I do not know how to check if I am getting data otherwise (first time using Gazebo).

This is the part of the URDF where the Velodyne is, it is inside <robot> tag

<link name="velodyne_base">
  <origin xyz="0 0 0.029335" rpy="0 0 0" />
  <inertial>
    <mass value="1.2" />
    <inertia ixx="0.00108747" iyy="0.00108747" izz="0.00109244" ixy="0" ixz="0" iyz="0"/>
  </inertial>
  <collision name="base_collision">
    <geometry>
      <cylinder radius="0.04267" length="0.029335" />
    </geometry>
  </collision>
  <visual name="base_visual">
    <pose frame="">0 0 -0.029335 0 -0 0</pose>
    <geometry>
      <mesh filename="model://mower_description/meshes/velodyne_base.dae" />
    </geometry>
  </visual>   
</link>   
<link name="velodyne_top">
  <origin xyz="0 0 0.095455" rpy="0 0 0" />
  <inertial>
    <mass value="0.1" />
    <inertia ixx="0.000090623" iyy="0.000090623" izz="0.000091036" ixy="0" ixz="0" iyz="0" />
  </inertial>
  <collision name="top_collision">
    <geometry>
      <cylinder radius="0.04267" length="0.07357" />
    </geometry>
  </collision>
  <visual name="top_visual">
    <geometry>
      <mesh filename="model://mower_description/meshes/velodyne_top.dae"/>
    </geometry>
  </visual>   
</link>   
<gazebo reference="velodyne_base">
  <static>true</static>   
 </gazebo>   
 <gazebo reference="velodyne_top">
  <sensor name="sensor" type="ray">
    <pose frame=''>0 0 -0.004645 0 -0 0</pose>
    <update_rate>20</update_rate>
    <ray>
      <noise>
        <type>gaussian</type>
        <mean>0</mean>
        <stddev>0.1</stddev>
      </noise>
      <scan>
        <horizontal>
          <samples>96</samples>
          <resolution>1</resolution>
          <min_angle>-1.54898</min_angle>
          <max_angle>1.54898</max_angle>
        </horizontal>
        <vertical>
          <samples>8</samples>
          <resolution>1</resolution>
          <min_angle>-0.139626</min_angle>
          <max_angle>0.139626</max_angle>
        </vertical>
      </scan>
      <range>
        <min>0.1</min>
        <max>70</max>
        <resolution>0.02</resolution>
      </range>
    </ray>
  </sensor>   
</gazebo>

And this is the joint between the velodyne links

<joint name="velodyne_joint" type="revolute">
    <parent link="velodyne_base" />
    <child link="velodyne_top" />
    <limit lower="-1e+16" upper="1e+16" effort="-1" velocity="-1" />
    <origin xyz="0 0 0.05867" rpy="0 -0 0" />
    <axis xyz="0 0 1" />
 </joint>

The sensor tag on the code, I also tried just adding it by not using <gazebo> tag, as urdf supports it, but still nothing showing the ray working area that I specified. When I open gazebo and insert the Velodyne sensor SDF model by itself, it shows the working area, but once I insert my URDF robot model, the sensor on it does not show any ... (more)