JaredMoore's profile - activity

ROS Kinetic
Gazebo 7.0
RedHat Linux

I'm running into an issue with a roslaunch file that attempts to start a Gazebo node within a group tag that has the namespace parameter set. The Gazebo node appears to start, but other nodes that wait on gazebo services hang. Specifically, when using rospy, the following calls do not complete.

rospy.wait_for_service('/gazebo/get_world_properties')
rospy.wait_for_service('/gazebo/reset_world')
rospy.wait_for_service('/gazebo/reset_simulation')
rospy.wait_for_service('/gazebo/pause_physics')
rospy.wait_for_service('/gazebo/unpause_physics')

The launch file is as follows:

<launch>

<!-- ********************* Begin Gazebo Defaults ******************************** -->

<!-- these are the arguments you can pass this launch file, for example paused:=true -->
  <arg name="paused" default="true"/>
  <arg name="use_sim_time" default="true"/>
  <arg name="gui" default="false"/>
  <arg name="headless" default="true"/>
  <arg name="debug" default="false"/>

  <!-- these are the arguments you can pass this launch file, for example paused:=true -->
  <arg name="extra_gazebo_args" default=""/>
  <arg name="physics" default="ode"/>
  <arg name="verbose" default="true"/>
  <arg name="world_name" value="$(find basicbot_gazebo)/worlds/basicbot.world"/>
  <arg name="respawn_gazebo" default="false"/>
  <arg name="use_clock_frequency" default="false"/>
  <arg name="pub_clock_frequency" default="100"/>

  <!-- set use_sim_time flag -->
  <group if="$(arg use_sim_time)">
    <param name="/use_sim_time" value="true" />
  </group>

  <!-- set command arguments -->
  <arg unless="$(arg paused)" name="command_arg1" value=""/>
  <arg     if="$(arg paused)" name="command_arg1" value="-u"/>
  <arg unless="$(arg headless)" name="command_arg2" value=""/>
  <arg     if="$(arg headless)" name="command_arg2" value="-r"/>
  <arg unless="$(arg verbose)" name="command_arg3" value=""/>
  <arg     if="$(arg verbose)" name="command_arg3" value="--verbose"/>
  <arg unless="$(arg debug)" name="script_type" value="gzserver"/>
  <arg     if="$(arg debug)" name="script_type" value="debug"/>

  <group if="$(arg use_clock_frequency)">
    <param name="gazebo/pub_clock_frequency" value="$(arg pub_clock_frequency)" />
  </group>

<!-- ********************* End Gazebo Defaults ******************************** -->    

<!-- <group ns="basicbot_ga_1"> -->
<group ns="ga1">
  <!-- start gazebo server-->
  <env name="GAZEBO_MASTER_URI" value="http://localhost:11345"/>
  <node name="gazebo" pkg="gazebo_ros" type="$(arg script_type)" respawn="$(arg respawn_gazebo)" 
    output="screen" args="$(arg command_arg1) $(arg command_arg2) $(arg command_arg3) -e $(arg physics) 
    $(arg extra_gazebo_args) $(arg world_name)">
  </node>

  <!-- Load the transporter node -->
  <node name="basicbot_transporter" pkg="basicbot_ga" type="basicbot_transporter.py" output="screen"></node>

    <!-- Load the turn_drive_scan node -->
    <node name="turn_drive_scan" pkg="basicbot_ga" type="turn_drive_scan_node.py" output="screen"></node>

    <!-- Load the step world node -->
  <node name="step_world" pkg="world_step" type="step_world_server"/>

  <!-- Load the URDF into the ROS Parameter Server -->
  <param name="robot_description"
    command="$(find xacro)/xacro '$(find basicbot_description)/urdf/basicbot.xacro'" />

  <!-- Run a python script to the send a service call to gazebo_ros to spawn a URDF robot -->
  <node name="urdf_spawner" pkg="gazebo_ros" type="spawn_model" respawn="false" output="screen"
    args="-urdf -model basicbot -param robot_description"/>
</group>

</launch>

I've tried the following while troubleshooting the problem.

1. Remove group tag completely. Behavior: Simulation runs fine, nodes initialize and execute after the initial spool up.
2. Add group tag without ns attribute. Behavior: Simulation again runs fine.
3. Add ns attribute. Behavior: Gazebo node appears to launch, but the previously mentioned services do not appear to be available to other nodes inside the group tag. rostopic list and gz topic -l do not show the topics being published either.

As far as I can tell, adding the ... (more)

ROS Kinetic
Gazebo 7.0
RedHat Linux

I'm running into an issue with a roslaunch file that attempts to start a Gazebo node within a group tag that has the namespace parameter set. The Gazebo node appears to start, but other nodes that wait on gazebo services hang. Specifically, when using rospy, the following calls do not complete.

rospy.wait_for_service('/gazebo/get_world_properties')
rospy.wait_for_service('/gazebo/reset_world')
rospy.wait_for_service('/gazebo/reset_simulation')
rospy.wait_for_service('/gazebo/pause_physics')
rospy.wait_for_service('/gazebo/unpause_physics')

The launch file is as follows:

<launch>

<!-- ********************* Begin Gazebo Defaults ******************************** -->

<!-- these are the arguments you can pass this launch file, for example paused:=true -->
  <arg name="paused" default="true"/>
  <arg name="use_sim_time" default="true"/>
  <arg name="gui" default="false"/>
  <arg name="headless" default="true"/>
  <arg name="debug" default="false"/>

  <!-- these are the arguments you can pass this launch file, for example paused:=true -->
  <arg name="extra_gazebo_args" default=""/>
  <arg name="physics" default="ode"/>
  <arg name="verbose" default="true"/>
  <arg name="world_name" value="$(find basicbot_gazebo)/worlds/basicbot.world"/>
  <arg name="respawn_gazebo" default="false"/>
  <arg name="use_clock_frequency" default="false"/>
  <arg name="pub_clock_frequency" default="100"/>

  <!-- set use_sim_time flag -->
  <group if="$(arg use_sim_time)">
    <param name="/use_sim_time" value="true" />
  </group>

  <!-- set command arguments -->
  <arg unless="$(arg paused)" name="command_arg1" value=""/>
  <arg     if="$(arg paused)" name="command_arg1" value="-u"/>
  <arg unless="$(arg headless)" name="command_arg2" value=""/>
  <arg     if="$(arg headless)" name="command_arg2" value="-r"/>
  <arg unless="$(arg verbose)" name="command_arg3" value=""/>
  <arg     if="$(arg verbose)" name="command_arg3" value="--verbose"/>
  <arg unless="$(arg debug)" name="script_type" value="gzserver"/>
  <arg     if="$(arg debug)" name="script_type" value="debug"/>

  <group if="$(arg use_clock_frequency)">
    <param name="gazebo/pub_clock_frequency" value="$(arg pub_clock_frequency)" />
  </group>

<!-- ********************* End Gazebo Defaults ******************************** -->    

<!-- <group ns="basicbot_ga_1"> -->
<group ns="ga1">
  <!-- start gazebo server-->
  <env name="GAZEBO_MASTER_URI" value="http://localhost:11345"/>
  <node name="gazebo" pkg="gazebo_ros" type="$(arg script_type)" respawn="$(arg respawn_gazebo)" 
    output="screen" args="$(arg command_arg1) $(arg command_arg2) $(arg command_arg3) -e $(arg physics) 
    $(arg extra_gazebo_args) $(arg world_name)">
  </node>

  <!-- Load the transporter node -->
  <node name="basicbot_transporter" pkg="basicbot_ga" type="basicbot_transporter.py" output="screen"></node>

    <!-- Load the turn_drive_scan node -->
    <node name="turn_drive_scan" pkg="basicbot_ga" type="turn_drive_scan_node.py" output="screen"></node>

    <!-- Load the step world node -->
  <node name="step_world" pkg="world_step" type="step_world_server"/>

  <!-- Load the URDF into the ROS Parameter Server -->
  <param name="robot_description"
    command="$(find xacro)/xacro '$(find basicbot_description)/urdf/basicbot.xacro'" />

  <!-- Run a python script to the send a service call to gazebo_ros to spawn a URDF robot -->
  <node name="urdf_spawner" pkg="gazebo_ros" type="spawn_model" respawn="false" output="screen"
    args="-urdf -model basicbot -param robot_description"/>
</group>

</launch>

I've tried the following while troubleshooting the problem.

1. Remove group tag completely. Behavior: Simulation runs fine, nodes initialize and execute after the initial spool up.
2. Add group tag without ns attribute. Behavior: Simulation again runs fine.
3. Add ns attribute. Behavior: Gazebo node appears to launch, but the previously mentioned services do not appear to be available to other nodes inside the group tag. rostopic list and gz topic -l do not show the topics being published either.

As far as I can tell, adding the ... (more)

I'm currently working on setting up my ROS-Gazebo environment and have encountered a problem that I can't seem to find the answer to. When running a test of dropping a sphere onto a box, the endpoint of the sphere after 4 seconds of simulation time has an element of randomness to it. This will prevent me from being able to use the simulation for my intended purpose (evolutionary robotics).

I've previously used the Open Dynamics Engine in my past research with it running deterministically after setting the random number seed. Accordingly, I am attempting to do the same with ROS-Gazebo and have found what I think are the appropriate settings. I detail them below.

First, I use a piece of code to step the Gazebo simulation in sync with ROS so there shouldn't be a desync issue between the two components. The code is:

#include <math.h>
#include <boost/thread.hpp>
#include <boost/algorithm/string.hpp>

#include <gazebo/gazebo.hh>
#include <gazebo/common/Plugin.hh>
#include <gazebo/msgs/msgs.hh>
#include <gazebo/transport/transport.hh>
#include <gazebo_msgs/LinkStates.h>

#include <ros/ros.h>
#include <ros/subscribe_options.h>

int main(int argc, char** argv)
{
  gazebo::setupClient(argc,argv);
  ros::init(argc, argv, "get_world_time_test");

  // Gazebo WorldControl Topic
  gazebo::transport::NodePtr node(new gazebo::transport::Node());
  node->Init();

  // Gazebo ServerControl Topic
  gazebo::transport::NodePtr serverNode(new gazebo::transport::Node());
  serverNode->Init();

  // Initialize the ROSNode
  ros::NodeHandle* rosnode = new ros::NodeHandle();

  // Gazebo Publishers
  gazebo::transport::PublisherPtr pub = node->Advertise<gazebo::msgs::WorldControl>("~/world_control");

  gazebo::transport::PublisherPtr serverPub = serverNode->Advertise<gazebo::msgs::ServerControl>("/gazebo/server/control");

  // Waits for simulation time update.
  ros::Time last_ros_time_;
  bool wait = true;
  while (wait)
  {
    last_ros_time_ = ros::Time::now();

    if (last_ros_time_.toSec() > 0) {
      if (last_ros_time_.toSec() >= 2.0) {
        //Removed code to print position of ball to the screen.
      }
    }    

    // Publish the step message for the simulation.
    gazebo::msgs::WorldControl msg;
    msg.set_step(1);
    pub->Publish(msg);

    // Wait for 1 second and allow ROS to complete as well.
    gazebo::common::Time::MSleep(5);
    ros::spinOnce();
  }

  // Send a server control shutdown message.
  gazebo::msgs::ServerControl serverMsg;
  serverMsg.set_stop(1);
  serverPub->Publish(serverMsg);

  return 0;
}

Second, I set the seed of Gazebo in my launch file to 1 so each simulation should be initialized with the same random number seed. In my previous experience, this was enough to have ODE run deterministically for the same robot and controller in multiple simulations. (The robot would move along the same path and the same distance provided it ran for the same amount of simulation time.) The launch file is as follows:

<launch>
  <arg name="paused" default="true"/>
  <arg name="use_sim_time" default="true"/>
  <arg name="gui" default="true"/>
  <arg name="headless" default="false"/>
  <arg name="debug" default="false"/>
  <arg name="world_name" default="$(find firstbot_gazebo)/worlds/firstbot_world.world"/> 

  <!-- set use_sim_time flag -->
  <group if="$(arg use_sim_time)">
    <param name="/use_sim_time" value="true" />
  </group>

  <!-- set command arguments -->
  <arg unless="$(arg paused)" name="command_arg1" value=""/>
  <arg     if="$(arg paused)" name="command_arg1" value="-u"/>
  <arg unless="$(arg headless)" name="command_arg2 ...