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I am using Ros Kinetic on Ubuntu 16.04. I am trying to simulate a quadrotor with lidar attached to it.

I have found the Rotors_Simulator repository and manually added a Hokuyo lidar for simulation in Gazebo using the following code:

 <!-- Hokuyo Lidar Range Sensor -->
    <xacro:macro name="hokuyo_utm30lx" params="robot_namespace *origin update_rate ray_count min_angle max_angle">
      <link name="${robot_namespace}/laser_lidar_link12">
  <inertial>
    <mass value="0.001" />
    <origin xyz="0 0 0" rpy="0 0 0" />
    <inertia ixx="0.0001" ixy="0" ixz="0" iyy="0.0001" iyz="0" izz="0.0001" />
  </inertial>
  <visual>
          <geometry>
            <!--<mesh filename="package://turtlebot_description/meshes/sensors/hokuyo_utm30lx/hokuyo_utm_30lx.dae"/> -->
            <box size="0.05 0.05 0.02"/>
          </geometry>
  </visual>
  <collision>
    <origin xyz="0 0 -0.0115" rpy="0 0 0" />
          <geometry>
            <box size="0.058 0.058 0.087" />
            <!--<mesh filename="package://hector_sensors_description/meshes/hokuyo_utm30lx/hokuyo_utm_30lx.stl"/>-->
          </geometry>
  </collision>
      </link>
      <joint name="laser_lidar_joint" type="fixed">
        <xacro:insert_block name="origin"/>
  <parent link="${robot_namespace}/base_link"/>
  <child link="${robot_namespace}/laser_lidar_link12"/>
      </joint>
      <gazebo reference="${robot_namespace}/laser_lidar_link12">
        <sensor type="ray" name="iris_laser_lidar">
            <pose>0 0 0 0 0 0</pose>
            <visualize>false</visualize>
            <update_rate>${update_rate}</update_rate>
      <ray>
      <scan>
        <horizontal>
          <samples>$(ray_count)</samples>
          <resolution>1</resolution>
          <min_angle>${min_angle}</min_angle>
          <max_angle>${max_angle}</max_angle>
        </horizontal>
      </scan>
      <range>
        <min>0.10</min>
        <max>20.0</max>
        <resolution>0.01</resolution>
      </range>
      <noise>
        <type>Gaussian</type>
        <mean>0.0</mean>
        <stddev>0.01</stddev>
      </noise>
      </ray>
      <plugin name="ray" filename="libgazebo_ros_laser.so">
      <topicName>/scan</topicName>
      <frameName>iris/laser_lidar_link12</frameName>
      <!-- <interface:laser name="gazebo_ros_${laser_suffix}_iface" /> -->
            </plugin>
        </sensor>
      </gazebo>
    </xacro:macro>
 <xacro:hokuyo_utm30lx robot_namespace="${namespace}" min_angle="-1.047" max_angle="1.047"
    update_rate="40" ray_count="120">
    <origin xyz="0 0 0.5" rpy="0 0 0"/>
  </xacro:hokuyo_utm30lx>

I could see the lidar in the simulation, and I did "rostopic echo /scan" to view the messages from the lidar. This happens only when I am using an empty world for simulation. When I am adding an obstacle in the world in lidar's range, the simulation stops with the following message:

Segmentation fault (core dumped) [gazebo-2] process has died [pid 2836, exit code 139, cmd /opt/ros/kinetic/lib/gazebo_ros/gzserver -u -e ode /home/viswa/rotors_pravin/src/rotors_gazebo/worlds/basic.world __name:=gazebo __log:=/home/viswa/.ros/log/d05c3eec-3cf8-11e9-b7d9-bc855666be67/gazebo-2.log]. log file: /home/viswa/.ros/log/d05c3eec-3cf8-11e9-b7d9-bc855666be67/gazebo-2*.log

Further I added a callback with a subscriber:

void callback(const sensor_msgs::LaserScan::ConstPtr& input)
{
  ROS_INFO("Laser Scan Message recieved");
}

The subscriber keeps displaying the following message:

[ INFO] [1551537504.870564767, 5.000000000]: Laser Scan Message recieved

The simulation stops when it detects an obstacle with the same Segmentation Fault.

What needs to be added to make this work?

Originally posted by viswa_1211 on ROS Answers with karma: 1 on 2019-03-02

Post score: 0

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There is something wrong with your macro which prevent you from setting the parameters as desired. At the beginning you define parameters (*origin -> is that a typo ?) and then you don't actually use them.

For example this : <update_rate>1</update_rate>, should be <update_rate>${update_rate}</update_rate>.

So when you call your xacro here :

  <xacro:hokuyo_utm30lx robot_namespace="${namespace}" min_angle="-1.047" max_angle="1.047"
    update_rate="40" ray_count="10">
None of your parameters are actually set to those values (and why is it `${namespace}` here ? It should be an actual value).

So you end up with a really odd configuration, I would suggest few things :

  • You tried to set the update rate to 40 which is better than 1 because this is an extremely low value for the update rate so just make sure you actually change the parmeter (as the example above).
  • You have samples set to 3 with a resolution of 10. The resolution is multiplied by the number of samples to define the number of range data points returned. Moreover, if the resolution is greater than 1 the range data is average so I would suggest to set the resolution to 1 and directly define the samples as the number of data you want. For example if you have a 360° lidar and you want a data every 1° I would just set the samples to 360 and resolution to 1.

Edit :

I found from here that we could insert a block by * prefix

You're right it's possible to do that but when you choose to do this you need to insert the block like this :

<xacro:insert_block name="origin" />

Also there might be another thing wrong here when you call the xacro :

<xacro:hokuyo_utm30lx robot_namespace="${namespace}" min_angle="-1.047" max_angle="1.047"
    update_rate="40" ray_count="10">
    <origin xyz="0 0 0.5" rpy="0 0 0"/>
  </xacro:hokuyo_utm30lx>

I'm not sure what will happen and where the origin tag will end up but following the wiki I would call the xacro like this and define the origin inside the macro :

<xacro:hokuyo_utm30lx robot_namespace="${namespace}" min_angle="-1.047" max_angle="1.047"
update_rate="40" ray_count="10" />

Originally posted by Delb with karma: 3907 on 2019-03-05

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Comment by viswa_1211 on 2019-03-05:
Thanks Delb for the reply. About the *origin, I found from here http://wiki.ros.org/xacro that we could insert a block by * prefix. About $namespace, I had created a property, but I hadn't mentioned it here. Also, I chose small values for resolution just for debug purpose. It still doesn't work.

Comment by Delb on 2019-03-05:\

It still doesn't work

Do you still have the segfault or another error ? Also can you edit your question to show the modifications you've made ?

Comment by viswa_1211 on 2019-03-05:
I finally found out what was wrong with the code. It was the block. It looks like I had given wrong values. Without noise block, it works fine.

Comment by Delb on 2019-03-05:
Glad it works. But have you checked if the data is correct ? By setting <visualize>true</visualize> you can easliy see that in Gazebo. (I ask you that because with your parameters I have incorrect laser data)

Comment by Delb on 2019-03-05:
Thanks for the update but I see you've just changed the update_rate meaning your min and max angles won't have the value +/- 1.047 (but 1 instead). Same for your ray_count param.

Comment by viswa_1211 on 2019-03-05:
I have updated that, please check. As mentioned earlier, the model is working fine, if I add the block. Can you help me with that?

Comment by Delb on 2019-03-05:
I don't understand your question, is there still an issue ? For me the noise block isn't problematic I have the same one in an URDF and it doesn't create issues.

Comment by viswa_1211 on 2019-03-05:
Ya. I still have that issue. If I remove the block, it works fine.

Comment by Delb on 2019-03-05:
If you keep the noise block but set resolution to 1 and samples to 120 do you still have the issue ? (120 because you have min and max angle to +/-1.047 rad (+/-60° so 120 samples if you want a data for each degree)

Comment by viswa_1211 on 2019-03-06:
Ya Delb. I still have the problem with noise block.

Comment by Delb on 2019-03-06:
I can't think of something to change for this noise block. You have almost the same description as in other tutorials so that's odd. Can you try to put the same parameters (only for all the params in the ray block) as in this example ?

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Same issue here. In my case, gzserver crashes with the following stack trace:

> #0  gazebo::sensors::Noise::Apply (this=0x0,
> _in=_in@entry=1.527150313825224) at /build/gazebo-nhSAPd/gazebo-7.0.0+dfsg/gazebo/sensors/Noise.cc:108                                                                                                                            
> #1  0x00007f1376924cf7 in gazebo::sensors::RaySensor::UpdateImpl
> (this=0x7f12e20f3e70) at
> /build/gazebo-nhSAPd/gazebo-7.0.0+dfsg/gazebo/sensors/RaySensor.cc:574
> 
> #2  0x00007f137692c984 in gazebo::sensors::Sensor::Update
> (this=0x7f12e20f3e70,
> _force=_force@entry=false) at /build/gazebo-nhSAPd/gazebo-7.0.0+dfsg/gazebo/sensors/Sensor.cc:250
> 
> #3  0x00007f1376933195 in gazebo::sensors::SensorManager::SensorContainer::Update
> (this=0x2e3d240, _force=<optimized
> out>) at
> /build/gazebo-nhSAPd/gazebo-7.0.0+dfsg/gazebo/sensors/SensorManager.cc:579
> 
> #4  0x00007f1376936d4b in gazebo::sensors::SensorManager::SensorContainer::RunLoop
> (this=0x2e3d240) at
> /build/gazebo-nhSAPd/gazebo-7.0.0+dfsg/gazebo/sensors/SensorManager.cc:534
> 
> #5  0x00007f13741805d5 in ?? () from /usr/lib/x86_64-linux-gnu/libboost_thread.so.1.58.0
> 
> #6  0x00007f13766956ba in start_thread (arg=0x7f12fe8ba700) at
> pthread_create.c:333                  
> 
> #7  0x00007f1376c9741d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

After some digging into various sources, it turns out the type specification of <noise> block was causing the problem: in Gazebo's official documentation, its type property is spelled gaussian, not capitalized Gaussian as found in some tutorials. After making this change, I was able to run the simulated 2d sensor without a problem. Hope this will help you out.

Originally posted by dingningyang with karma: 11 on 2019-06-11

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Post score: 1

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Comment by dingningyang on 2019-06-11:
By the way, my setup is Gazebo 7.0.0 with ROS Kinetic running on Ubuntu 16.04.

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