Hi, I’m trying to change ‘turtlebot3_burger.urdf.xacro’ =>‘turtlebot3_burger.gazebo.xacro’ in launch file
``` <arg name="first_tb3_x_pos" default="-3.0"/>
<arg name="first_tb3_y_pos" default=" 0.0"/>
<arg name="first_tb3_z_pos" default=" 0.0"/>
<arg name="first_tb3_yaw" default=" 0.0"/>
<arg name="second_tb3_x_pos" default=" 0.0"/>
<arg name="second_tb3_y_pos" default="-3.0"/>
<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/empty.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>
<group ns = "$(arg first_tb3)">
<param name="robot_description" command="$(find xacro)/xacro $(find turtlebot3_description)/urdf/turtlebot3_$(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 $(find turtlebot3_description)/urdf/turtlebot3_$(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>
But error was occurred,
[ERROR] [1663053304.204205318]: No link elements found in urdf file
[ERROR] [1663053304.253578520]: No link elements found in urdf file
[tb3_0/robot_state_publisher-4] process has died [pid 8066, exit code 1, cmd /opt/ros/melodic/lib/robot_state_publisher/robot_state_publisher __name:=robot_state_publisher __log:=/home/kim/.ros/log/c9313124-3333-11ed-8795-000c29792c73/tb3_0-robot_state_publisher-4.log].
log file: /home/kim/.ros/log/c9313124-3333-11ed-8795-000c29792c73/tb3_0-robot_state_publisher-4*.log
[tb3_1/robot_state_publisher-6] process has died [pid 8068, exit code 1, cmd /opt/ros/melodic/lib/robot_state_publisher/robot_state_publisher __name:=robot_state_publisher __log:=/home/kim/.ros/log/c9313124-3333-11ed-8795-000c29792c73/tb3_1-robot_state_publisher-6.log].
log file: /home/kim/.ros/log/c9313124-3333-11ed-8795-000c29792c73/tb3_1-robot_state_publisher-6*.log
what's wrong?