Multiple Robot Exploration

Hello Everyone,
I hope you will be in good health. Currently I am working on multiple robot exploration on KUKA youBot mobile manipulator, when i launch multiple youBots i cant see laser scan data in rviz for any of the robots, it give me error that Frame [base_laser_front_link] does not exist while it does exist screen shot attached. On the other hand when i launch single robot it works fine i can see laser scan data. The only thing i have change in multibot exploration live class tutorial is kubokis.launch file in which i have replaced kubokis description and meshes with youBot description and meshes. pictures are attached below, kindly help me out please.

kobukis.launch file

<!-- Launch file for running the multirobot simulation on gazebo -->

<!-- Launches Kobuki Gazebo simulation in an empty world -->
   <env name="GAZEBO_RESOURCE_PATH" value="$(find youbot_description)/includes/meshes"/>

<!-- start Gazebo with an empty world -->
<include file="$(find gazebo_ros)/launch/empty_world.launch">
<arg name="paused" value="false"/>
<arg name="use_sim_time" value="true"/>
<arg name="gui" value="false"/>
<arg name="headless" value="false"/>
<arg name="debug" value="false"/>
<arg name="world_name" value="$(find rrt_exploration_tutorials)/launch/includes/worlds/"/>

<!-- spawn robot 1-->
<group ns="/robot_1">
<include file="$(find multiple_youbot_sim)/launch/robot.launch.xml">
	<arg name="robot_name" value="robot_1"/>
	<arg name="init_pose" value="-x 0.0 -y 0.0 -z 0.0"/>


<!-- spawn robot 2-->
<group ns="/robot_2">
<include file="$(find multiple_youbot_sim)/launch/robot.launch.xml">
	<arg name="robot_name" value="robot_2"/>
	<arg name="init_pose" value="-x 0.0 -y -0.8 -z 0.0"/>


<!-- spawn robot 3-->
<group ns="/robot_3">
<include file="$(find multiple_youbot_sim)/launch/robot.launch.xml">
	<arg name="robot_name" value="robot_3"/>
	<arg name="init_pose" value="-x 0.0 -y 0.8 -z 0.0"/>


<!-- transformation between robots -->
<node pkg="tf" type="static_transform_publisher" name="robot2_to_robot1" args="0 -0.8 0 0 0 0 /robot_1/map /robot_2/map 20" />
<node pkg="tf" type="static_transform_publisher" name="robot3_to_robot1" args="0 0.8 0 0 0 0 /robot_1/map /robot_3/map 20" />

<!-- Map megring (know inital position case)-->

<!-- run RViz node (visualization) 
<node pkg="rviz" type="rviz" name="rviz" args="-d $(find multiple_turtlebots_sim)/rviz_config/three.rviz">
<remap from="move_base_simple/goal" to="robot_1/move_base_simple/goal"/>


robot.launch.xml file

<!-- Spawns Kobuki inside a Gazebo simulation -->
      <arg name="robot_name"/>
      <arg name="init_pose"/>

     <param name="robot_description"
    command="$(find xacro)/ '$(find youbot_description)/robots/youbot_base_only.urdf.xacro'"/>
     <node pkg="gazebo_ros" type="spawn_model" name="spawn_$(arg robot_name)"
    args="$(arg init_pose) -unpause -urdf -param robot_description -model $(arg robot_name)" respawn="false">

    <node pkg="robot_state_publisher" type="robot_state_publisher" name="robot_state_publisher">
    <param name="publish_frequency" type="double" value="30.0" />
    <param name="use_tf_static" type="bool" value="true" />
    <param name="tf_prefix" type="string" value="$(arg robot_name)"/>


Problem is Solved, after very hard work and trouble shooting i finally figured it out. the problem was in laser urdf file some changes has to be made for multiple robots exploration.