Gazebo launch file: A UR3 robot arm on a tabletop.

tabletop_robot.launch

<?xml version="1.0"?>
<launch>
  <arg name="limited" default="false"
       doc="If true, limits joint range [-PI, PI] on all joints." />
  <arg name="paused" default="true"
       doc="Starts gazebo in paused mode" />
  <arg name="gui" default="true"
       doc="Starts gazebo gui" />
  <!-- Robot pose -->
  <arg name="x" default="0"/>
  <arg name="y" default="0"/>
  <arg name="z" default="1"/>
  <arg name="roll" default="0"/>
  <arg name="pitch" default="0"/>
  <arg name="yaw" default="0"/>

  
  <!-- startup simulated world -->
  <include file="$(find gazebo_ros)/launch/empty_world.launch">
    <arg name="world_name" default="$(find simulation_tabletop)/world/Gazebo/tabletop.world"/>
    <arg name="paused" value="$(arg paused)"/>
    <arg name="gui" value="$(arg gui)"/>
  </include>

  <!-- send robot urdf to param server -->
  <param unless="$(arg limited)" name="robot_description"
         value="$(find simulation_tabletop)/urdf/ur3_robot.urdf"/>
  <param if="$(arg limited)" name="robot_description"
         value="$(find simulation_tabletop)/urdf/ur3_joint_limited_robot.urdf"/>
  
  <include file="$(find ur_description)/launch/ur3_upload.launch">
    <arg name="limited" value="$(arg limited)"/>
  </include>

  <!-- push robot_description to factory and spawn robot in gazebo -->
  <node name="spawn_gazebo_model" pkg="gazebo_ros" type="spawn_model"
        args="-urdf -param robot_description -model robot
              -x $(arg x) -y $(arg y) -z $(arg z)
              -R $(arg roll) -P $(arg pitch) -Y $(arg yaw)"
        respawn="false" output="screen" />

  <include file="$(find ur_gazebo)/launch/controller_utils.launch"/>

  <!-- start this controller -->
  <rosparam file="$(find ur_gazebo)/controller/arm_controller_ur3.yaml"
            command="load"/>
  <node name="arm_controller_spawner" pkg="controller_manager"
        type="controller_manager" args="spawn arm_controller"
        respawn="false" output="screen"/>

  <!-- load other controllers -->
  <node name="ros_control_controller_manager" pkg="controller_manager"
        type="controller_manager" respawn="false" output="screen"
        args="load joint_group_position_controller" />

</launch>