Hi all,

I'm using gazebo 7 to simulate a differential drive robot. Following the ROS tutorials online, I created an urdf file to describe my robot:

• https://github.com/schizzz8/lucrezio_description/blob/master/urdf/lucrezio.urdf.xacro

If I launch an empty world:

roslaunch gazebo_ros empty_world.launch

and then I spawn the robot with this launch file:

• https://github.com/schizzz8/lucrezio_description/blob/master/launch/robot.launch

everything goes fine.

Now, I wrote a simple plugin for the logical_camera sensor:

• https://github.com/schizzz8/lucrezio_logical_camera

and I try to mount it on the robot by adding these lines to the urdf:

  <!-- LOGICAL CAMERA -->
  <link name="logical_camera_link">
    <collision>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
    <box size="${camera_size} ${camera_size} ${camera_size}"/>
      </geometry>
    </collision>    
    <visual>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
    <box size="${camera_size} ${camera_size} ${camera_size}"/>
      </geometry>
      <material name="red"/>
    </visual>

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


  <!-- LOGICAL CAMERA JOINT -->
  <joint name="logical_camera_joint" type="fixed">
    <axis xyz="0 1 0" />
    <origin xyz="0 0 1.0" rpy="0 0 0"/>
    <parent link="base_link"/>
    <child link="logical_camera_link"/>
  </joint>


  <!-- LOGICAL CAMERA SENSOR -->
  <gazebo reference="logical_camera_link">
      <sensor name="logical_camera" type="logical_camera">
        <plugin name="logical_camera_plugin" filename="liblogical_camera_plugin.so"/>

          <logical_camera>
            <near>0.02</near>
            <far>5.0</far>
            <horizontal_fov>${60.0*M_PI/180.0}</horizontal_fov>
            <aspect_ratio>1.778</aspect_ratio>
          </logical_camera>

          <visualize>true</visualize>
          <always_on>true</always_on>
          <update_rate>10</update_rate>
      </sensor>
  </gazebo>

If I now spawn the robot, this is what happens:

• https://youtu.be/9duCT1FotSI

Basically, it seems that the ground plane gets shifted up of one meter.

Can please someone explain me what is happening?

Thanks.