Tf tree for multiple turtlebots

edit

Hello, I am trying to run two turtlebots in a gazebo simulation. I'm wondering about the tf tree for the robots. This is what I get:

Sometimes if I refresh this I get:

so the wheel_right_link and wheel_left_link switch between tb3_0/robot_state_publisher and tb3_1/robot_state_publisher.

The launch file I am using is an edited version of the gazebo_simulations file found here: https://github.com/ROBOTIS-GIT/turtle....

When running the unedited version you get the same tf tree, just that it the wheel links switch between tb3_0/robot_state_publisher, tb3_1/robot_state_publisher and tb3_2/robot_state_publisher. Here is the tf tree for the unedited launch file:

This is the launch file I'm using:

<launch>
  <arg name="model" default="$(env TURTLEBOT3_MODEL)" doc="model type [burger, waffle, waffle_pi]"/>
  <arg name="first_tb3"  default="tb3_0"/>
  <arg name="second_tb3" default="tb3_1"/>

  <arg name="first_tb3_x_pos" default="0.0"/>
  <arg name="first_tb3_y_pos" default="1.0"/>
  <arg name="first_tb3_z_pos" default=" 0.0"/>
  <arg name="first_tb3_yaw"   default=" 1.57"/>

  <arg name="second_tb3_x_pos" default=" 0.0"/>
  <arg name="second_tb3_y_pos" default="0.0"/>
  <arg name="second_tb3_z_pos" default=" 0.0"/>
  <arg name="second_tb3_yaw"   default=" 1.57"/>



  <include file="$(find gazebo_ros)/launch/empty_world.launch">
    <arg name="world_name" value="$(find turtlebot3_gazebo)/worlds/custom_world2.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>  


    <!-- Start marker detector--> 
  <node name="aruco_detect" pkg="aruco_detect" type="aruco_detect">
    <param name="image_transport" value="compressed" />
    <param name="publish_images" value="true" />
    <param name="fiducial_len" value="0.15" />
    <param name="dictionary" value="0" />
    <param name="do_pose_estimation" value="true" />
    <param name="ignore_fiducials" value="" />
    <param name="fiducial_len_override" value="" />
    <remap from="/camera/compressed" to="/tb3_1/camera/rgb/image_raw/compressed"/>
    <remap from="/camera_info" to="/tb3_1/camera/rgb/camera_info"/>
  </node> 


  <group ns = "$(arg first_tb3)">
    <param name="robot_description" command="$(find xacro)/xacro --inorder $(find turtlebot3_description)/urdf/turtlebot3_$(arg model).urdf.xacro" />

    <node pkg="robot_state_publisher" type="robot_state_publisher" name="robot_state_publisher" output="screen">
      <param name="publish_frequency" type="double" value="50.0" />
      <param name="tf_prefix" value="$(arg first_tb3)" />
    </node>

    <node name="spawn_urdf" pkg="gazebo_ros" type="spawn_model" args="-urdf -model $(arg first_tb3) -x $(arg first_tb3_x_pos) -y $(arg first_tb3_y_pos) -z $(arg first_tb3_z_pos) -Y $(arg first_tb3_yaw) -param robot_description" />
  </group>

  <group ns = "$(arg second_tb3)">
    <param name="robot_description" command="$(find xacro)/xacro --inorder $(find turtlebot3_description)/urdf/turtlebot3_$(arg model).urdf.xacro" />

    <node pkg="robot_state_publisher" type="robot_state_publisher" name="robot_state_publisher" output="screen">
      <param name="publish_frequency" type="double" value="50.0" />
      <param name="tf_prefix" value="$(arg second_tb3)" />
    </node>

    <node name="spawn_urdf" pkg="gazebo_ros" type="spawn_model" args="-urdf -model $(arg second_tb3) -x $(arg second_tb3_x_pos) -y $(arg second_tb3_y_pos) -z $(arg second_tb3_z_pos) -Y $(arg second_tb3_yaw) -param robot_description" />
  </group>

</launch>

and this is my world file:

<sdf version='1.6'>
  <world name='default'>
    <!-- A global light source -->
    <include> ...