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/map not connecting to tf links for loading multiple robots in rviz

I am trying to load two robots in Gazebo and visualize them in Rviz to eventually do a leader-follower application. I believe I have the robots initialized in Gazebo correctly and mostly in Rviz, but am having trouble getting the /map topic to link up to either of the robots. I can teleop with the robots separately in Gazebo using their respective namespaces. I am simulating using a turtlebot3 waffle_pi. I'm thinking the problem has something to do with remapping from "map" to "/map" or in how my amcl node is called under the tf_prefixes for my two robots.

From running rosrun rqt_graph rqt_graph I can see that both of my two robots are initialized with their respective connections to /tf and /gazebo. (would upload output image but not enough user points).

From running rosrun tf view_frames I can see that both robots have root parents of "bot1_tf/odom" and "bot2_tf/odom" where "botX_tf" is the tf_prefix. The children connections seem to match output from running a single robot in Gazebo/Rviz. The only thing different seems to be that "/map" is the parent for "/odom" for the single robot, while there is no "/map" parent for the two robots.

Upon loading Rviz I see a green check next to URDF making me thing Rviz is reading in the model correctly, though all other tf topics have errors. When I manually enter either tf_prefix in the "TF Prefix" field in Rviz under "RobotModel" I see errors saying "No transform from [tf_prefix/base_footprint] to [map]" and so on for the other tf topics (base_footprint, base_link, base_scan, camera_link, camera_rgb_frame, camera_rgb_optical_frame, caster_back_left_link, caster_back_right_link, imu_link, wheel_left_link, wheel_right_link).

Running rosnode list results in the following:

/bot1/amcl
/bot1/move_base
/bot1/robot_state_publisher
/bot2/amcl
/bot2/move_base
/bot2/robot_state_publisher
/gazebo
/gazebo_gui
/map_server
/rosout
/rviz

Running rostopic list results in the following:

/bot1/amcl_pose
/bot1/camera/parameter_descriptions
/bot1/camera/parameter_updates
/bot1/camera/rgb/camera_info
/bot1/camera/rgb/image_raw
/bot1/camera/rgb/image_raw/compressed
/bot1/camera/rgb/image_raw/compressed/parameter_descriptions
/bot1/camera/rgb/image_raw/compressed/parameter_updates
/bot1/camera/rgb/image_raw/compressedDepth
/bot1/camera/rgb/image_raw/compressedDepth/parameter_descriptions
/bot1/camera/rgb/image_raw/compressedDepth/parameter_updates
/bot1/camera/rgb/image_raw/theora
/bot1/camera/rgb/image_raw/theora/parameter_descriptions
/bot1/camera/rgb/image_raw/theora/parameter_updates
/bot1/cmd_vel
/bot1/imu
/bot1/initialpose
/bot1/joint_states
/bot1/move_base/current_goal
/bot1/move_base/goal
/bot1/move_base_simple/goal
/bot1/odom
/bot1/particlecloud
/bot1/scan
/bot2/amcl_pose
/bot2/camera/parameter_descriptions
/bot2/camera/parameter_updates
/bot2/camera/rgb/camera_info
/bot2/camera/rgb/image_raw
/bot2/camera/rgb/image_raw/compressed
/bot2/camera/rgb/image_raw/compressed/parameter_descriptions
/bot2/camera/rgb/image_raw/compressed/parameter_updates
/bot2/camera/rgb/image_raw/compressedDepth
/bot2/camera/rgb/image_raw/compressedDepth/parameter_descriptions /bot2/camera/rgb/image_raw/compressedDepth/parameter_updates
/bot2/camera/rgb/image_raw/theora
/bot2/camera/rgb/image_raw/theora/parameter_descriptions
/bot2/camera/rgb/image_raw/theora/parameter_updates
/bot2/cmd_vel
/bot2/imu
/bot2/initialpose
/bot2/joint_states
/bot2/move_base/current_goal
/bot2/move_base/goal
/bot2/move_base_simple/goal
/bot2/odom
/bot2/particlecloud
/bot2/scan
/clock
/gazebo/link_states
/gazebo/model_states
/gazebo/parameter_descriptions
/gazebo/parameter_updates
/gazebo/set_link_state
/gazebo/set_model_state
/initialpose
/map
/map_metadata
/map_updates
/move_base/DWAPlannerROS/global_plan
/move_base/DWAPlannerROS/local_plan
/move_base/NavfnROS/plan
/move_base/global_costmap/costmap
/move_base/global_costmap/costmap_updates
/move_base/local_costmap/costmap
/move_base/local_costmap/costmap_updates
/move_base/local_costmap/footprint
/move_base_simple/goal
/particlecloud
/rosout
/rosout_agg
/scan
/tf
/tf_static

Investigating the /map topic by running rostopic info /map shows:

Type: nav_msgs/OccupancyGrid

Publishers: 
 * /map_server (http://alex-UbuntuROS:40709/)

Subscribers: 
 * /rviz (http://alex-UbuntuROS:35671/)

When I loaded a single robot for navigation into Rviz I saw that /move_base was also subscribed to /map, which is why I think there is an issue with /map and/or node connections to it.

The error output I get from ROS is: (repeatedly printed in yellow)

[ WARN] [1561024615.579003098, 3390.937000000]: Timed out waiting for transform from base_footprint to map to become available before running costmap, tf error: canTransform: target_frame map does not exist. canTransform: source_frame base_footprint does not exist.. canTransform returned after 0.1 timeout was 0.1.

The files I'm using are as follows:


tutorial_custom_world_2bots.launch (load world and two robots into Gazebo)

<launch>

  <!-- make world -->
  <arg name="custom_world" default="plaza" />
  <include file="$(find gazebo_ros)/launch/empty_world.launch" >
    <arg name="world_name" value="$(find nus_bot)/worlds/$(arg custom_world).world"/>
    <arg name="paused" value="false"/>
    <arg name="use_sim_time" value="true"/>
    <arg name="gui" value="true"/>
    <arg name="headless" value="false"/>
    <arg name="debug" value="false"/>
  </include>

  <!-- make robots -->
  <include file="$(find nus_bot)/launch/tutorial_robots.launch" />

</launch>

tutorial_robots.launch (call launch file to initialize two robots)

    <launch>

    <arg name="model" default="$(env TURTLEBOT3_MODEL)" doc="model type [burger, waffle, waffle_pi]"/>
    <param name="robot_description" command="$(find xacro)/xacro --inorder $(find turtlebot3_description)/urdf/turtlebot3_$(arg model).urdf.xacro" />

  <!-- bot1 -->
  <group ns="bot1">
    <param name="tf_prefix" value="bot1_tf" />
    <include file="$(find nus_bot)/launch/tutorial_one_robot.launch" >
      <arg name="init_pose" value="-x 0.0 -y 0.0 -z 0.0" />
      <arg name="robot_name" value="Bot1" /> 
    </include>
  </group>

  <!-- bot2 -->
  <group ns="bot2">
    <param name="tf_prefix" value="bot2_tf" />
    <include file="$(find nus_bot)/launch/tutorial_one_robot.launch" >
      <arg name="init_pose" value="-x 0.5 -y 0.5 -z 0.0" />
      <arg name="robot_name" value="Bot2" />
    </include>
  </group>

</launch>

tutorial_one_robot.launch (create a single robot, supposed to be called twice under different namespaces)

<launch>

    <arg name="robot_name"/>
    <arg name="init_pose"/>

    <node name="spawn_urdf" pkg="gazebo_ros" type="spawn_model" args="-urdf $(arg init_pose) -param /robot_description -model $(arg robot_name)" />

    <node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher" output="screen" />

</launch>

tutorial_navigation_2bots.launch (launch robots from Gazebo simulation to Rviz)

<launch>
  <!-- Arguments -->
  <arg name="map_file" default="plaza_map"/>
  <arg name="open_rviz" default="true"/>

  <!-- Map server -->
  <node name="map_server" pkg="map_server" type="map_server" args="$(find nus_bot)/maps/$(arg map_file).yaml" >
    <param name="frame_id" value="/map" />
  </node>

  <!-- bot1 -->
  <group ns="bot1">
    <param name="tf_prefix" value="bot1_tf" />

    <!-- AMCL node -->
    <include file="$(find nus_bot)/launch/amcl.launch" />

    <!-- move_base -->
    <include file="$(find nus_bot)/launch/tutorial_move_base.launch" />

  </group>

  <!-- bot2 -->
  <group ns="bot2">
    <param name="tf_prefix" value="bot2_tf" />

    <!-- AMCL node -->
    <include file="$(find nus_bot)/launch/amcl.launch" />

    <!-- move_base -->
    <include file="$(find nus_bot)/launch/tutorial_move_base.launch" />

  </group>

  <!-- rviz -->
  <group if="$(arg open_rviz)"> 
    <node pkg="rviz" type="rviz" name="rviz" required="true"
          args="-d $(find nus_bot)/rviz/turtlebot3_navigation.rviz">
      <remap from="map" to="/map" />
    </node>
  </group>

</launch>

tutorial_move_base.launch (launch move_base for a robot, same as "normal" move_base but includes remapping from "map" to "/map")

<launch>
  <!-- Arguments -->
  <arg name="model" default="$(env TURTLEBOT3_MODEL)" doc="model type [burger, waffle, waffle_pi]"/>
  <arg name="move_forward_only" default="false"/>

  <!-- move_base node -->
  <node pkg="move_base" type="move_base" respawn="false" name="move_base" output="screen">

    <param name="base_local_planner" value="dwa_local_planner/DWAPlannerROS" />
    <rosparam file="$(find turtlebot3_navigation)/param/costmap_common_params_$(arg model).yaml" command="load" ns="global_costmap" />
    <rosparam file="$(find turtlebot3_navigation)/param/costmap_common_params_$(arg model).yaml" command="load" ns="local_costmap" />
    <rosparam file="$(find turtlebot3_navigation)/param/local_costmap_params.yaml" command="load" />
    <rosparam file="$(find turtlebot3_navigation)/param/global_costmap_params.yaml" command="load" />
    <rosparam file="$(find turtlebot3_navigation)/param/move_base_params.yaml" command="load" />
    <rosparam file="$(find turtlebot3_navigation)/param/dwa_local_planner_params_$(arg model).yaml" command="load" />
    <param name="DWAPlannerROS/min_vel_x" value="0.0" if="$(arg move_forward_only)" />

    <remap from="map" to="/map" />

  </node>
</launch>

amcl.launch (launch amcl.launch for robot, same as "normal" amcl.launch but includes remapping from "map" to "/map")

<launch>
  <!-- Arguments -->
  <arg name="scan_topic"     default="scan"/>
  <arg name="initial_pose_x" default="0.0"/>
  <arg name="initial_pose_y" default="0.0"/>
  <arg name="initial_pose_a" default="0.0"/>

  <!-- AMCL -->
  <node pkg="amcl" type="amcl" name="amcl">

    <param name="min_particles"             value="500"/>
    <param name="max_particles"             value="3000"/>
    <param name="kld_err"                   value="0.02"/>
    <param name="update_min_d"              value="0.20"/>
    <param name="update_min_a"              value="0.20"/>
    <param name="resample_interval"         value="1"/>
    <param name="transform_tolerance"       value="0.5"/>
    <param name="recovery_alpha_slow"       value="0.00"/>
    <param name="recovery_alpha_fast"       value="0.00"/>
    <param name="initial_pose_x"            value="$(arg initial_pose_x)"/>
    <param name="initial_pose_y"            value="$(arg initial_pose_y)"/>
    <param name="initial_pose_a"            value="$(arg initial_pose_a)"/>
    <param name="gui_publish_rate"          value="50.0"/>

    <remap from="scan"                      to="$(arg scan_topic)"/>
    <param name="laser_max_range"           value="3.5"/>
    <param name="laser_max_beams"           value="180"/>
    <param name="laser_z_hit"               value="0.5"/>
    <param name="laser_z_short"             value="0.05"/>
    <param name="laser_z_max"               value="0.05"/>
    <param name="laser_z_rand"              value="0.5"/>
    <param name="laser_sigma_hit"           value="0.2"/>
    <param name="laser_lambda_short"        value="0.1"/>
    <param name="laser_likelihood_max_dist" value="2.0"/>
    <param name="laser_model_type"          value="likelihood_field"/>

    <param name="odom_model_type"           value="diff"/>
    <param name="odom_alpha1"               value="0.1"/>
    <param name="odom_alpha2"               value="0.1"/>
    <param name="odom_alpha3"               value="0.1"/>
    <param name="odom_alpha4"               value="0.1"/>
    <param name="odom_frame_id"             value="odom"/>
    <param name="base_frame_id"             value="base_footprint"/>

    <remap from="map" to="/map" />

  </node>
</launch>

Let me know if there is anything else I should provide - this is only my first post. Any help would be appreciated.

Thank you