contact sensor no data output
Hello! I am using ros hydro and gazebo-1.9.5 (my os is Ubuntu precise 32bit). I encounter a problem when testing the contact sensor. Part of my urdf file regarding the contact sensor is listed below:
<joint name="base_link_simple_collision_joint" type="fixed">
<origin xyz="0 0 0.1"/>
<parent link="base_link"/>
<child link="simple_collision_link" />
</joint>
<link name="simple_collision_link">
<inertial>
<mass value="0.1" />
<origin xyz="0 0 0" />
<inertia ixx="0.1" ixy="0.0" ixz="0.0"
iyy="0.1" iyz="0.0"
izz="0.1" />
</inertial>
<visual>
<origin xyz="0 0 0"/>
<geometry>
<box size="0.001 0.001 0.001" />
</geometry>
</visual>
<collision name="segbot_simple_collision">
<origin xyz="0 0 0.1"/>
<geometry>
<cylinder length="0.2" radius="0.8" />
</geometry>
</collision>
</link>
<gazebo reference="simple_collision_link">
<selfCollide>false</selfCollide>
<sensor type="contact" name="simple_collision_sensor">
<always_on>true</always_on>
<update_rate>100.0</update_rate>
<contact>
<collision>segbot_simple_collision</collision>
<topic>simple_contact</topic>
</contact>
<plugin name="simple_collision_gazebo_ros_bumper_controller" filename="libgazebo_ros_bumper.so">
<alwaysOn>true</alwaysOn>
<updateRate>100</updateRate>
<frameName>base_link</frameName>
<bumperTopicName>simple_collision_bumper</bumperTopicName>
</plugin>
</sensor>
</gazebo>
The problem is that neither the gazebo topic nor ros topic outputs any collision information, when I control the robot to "crash" into a wall in the environment, even though the robot can stop against the obstacle within the distance which I set in the collision tag ("radius"). Thanks for any suggestions and helps in advance!