Adding a camera to my urdf

edit

Hello,

I am trying to add a camera to the end of an arm using xacros. The camera link URDF is:

<robot xmlns:xacro="http://www.ros.org/wiki/xacro">
  <xacro:macro name="camera" params="parent">
    <link name="camera">
      <collision>
        <origin xyz="0 0 0" rpy="0 0 0"/>
        <geometry>
            <mesh filename="package://sensors_and_actuators/meshes/camara.stl" scale="0.1 0.1 0.1"/>
        </geometry>
      </collision>

      <visual>
        <origin xyz="0 0 0" rpy="0 0 0"/>
        <geometry>
            <mesh filename="package://sensors_and_actuators/meshes/camara.stl" scale="0.1 0.1 0.1"/>
        </geometry>
      </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>

    <joint name="sensor_joint" type="fixed">
        <parent link="${parent}"/>
        <child link="camera"/>
        <origin rpy="0 1.5620 0" xyz="0.0475 0.0 0.0"/>
        <axis xyz="1 0 0" />
    </joint>

    <gazebo reference="camera">
      <sensor type="camera" name="camera_sensor">
        <parent link="camera"/>
        <update_rate>30.0</update_rate>
        <camera>
          <horizontal_fov>1.3962634</horizontal_fov>
          <image>
            <format>R8G8B8</format>
            <width>800</width>
            <height>800</height>
          </image>
          <clip>
            <near>0.01</near>
            <far>100</far>
          </clip>
        </camera>

        <plugin name="${name}_camera_controller" filename="libgazebo_ros_camera.so">
          <cameraName>arm_sensors/camera</cameraName>
          <alwaysOn>true</alwaysOn>
          <updateRate>0.0</updateRate>
          <imageTopicName>image_raw</imageTopicName>
          <cameraInfoTopicName>camera_info</cameraInfoTopicName>
          <frameName>camera</frameName>
        </plugin>
      </sensor>
    </gazebo>

  </xacro:macro>
</robot>

When I run the launch file it reports an error saying that the parent param is missing:

samper@samper:~$ roslaunch cern_tim_arm_simulator arm_tim_simulator.launch spawn_arm:=true robotic_arm:=schunk_lwa4p world:=tunnel spawn_collimator:=true camera_on_arm:=true
... logging to /home/samper/.ros/log/2c17a290-4b39-11e5-b79f-605718079cbb/roslaunch-samper-16690.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

Traceback (most recent call last):
  File "/opt/ros/indigo/share/xacro/xacro.py", line 60, in <module>
    xacro.main()
  File "/opt/ros/indigo/lib/python2.7/dist-packages/xacro/__init__.py", line 696, in main
    eval_self_contained(doc)
  File "/opt/ros/indigo/lib/python2.7/dist-packages/xacro/__init__.py", line 626, in eval_self_contained
    eval_all(doc.documentElement, macros, symbols)
  File "/opt/ros/indigo/lib/python2.7/dist-packages/xacro/__init__.py", line 552, in eval_all
    (",".join(params), str(node.tagName)))
xacro.XacroException: Parameters [parent] were not set for macro camera
while processing /home/samper/ROS_Workspaces/ROS_Cern/src/ros_cern/tim_gazebo/load_world.launch:
while processing /home/samper/ROS_Workspaces/ROS_Cern/src/ros_cern/robotic_arm/launch/schunk_lwa4p_and_tim.launch:
Invalid <param> tag: Cannot load command parameter [robot_description]: command [/opt/ros/indigo/share/xacro/xacro.py '/home/samper/ROS_Workspaces/ROS_Cern/src/ros_cern/robotic_arm/arm_description/robots/schunk_lwa4p/schunk_lwa4p_arm_and_tim_camera.urdf.xacro'] returned with code [1]. 

Param xml is <param command="$(find xacro)/xacro.py '$(find robotic_arm)/arm_description/robots/schunk_lwa4p/schunk_lwa4p_arm_and_tim_camera.urdf.xacro'" if="$(arg camera_on_arm)" name="robot_description"/>
The traceback for the exception was written to the log file

I would really appreciate if someone could give me any clue. Thank you in advance.

JLuis Samper

PS: it only works if i delete the <camera> tag and its content