sim.xml

<sdf version="1.6">
  <world name="default">
    <!-- A light source -->
    <include>
      <uri>model://sun</uri>
    </include>
    
    <!-- Ground plane -->
    <include>
      <uri>model://ground_plane</uri>
    </include>
    
    <!-- Drone model -->
    <model name='quadcopter'>
      <pose>0 0 0.1 0 0 0</pose>
      <link name='base_link'>
        <!-- Drone visual representation -->
        <visual name='base_link_visual'>
          <geometry>
            <mesh>
              <uri>model://quadcopter/meshes/body.dae</uri>
            </mesh>
          </geometry>
        </visual>
        
        <!-- Inertial properties -->
        <inertial>
          <mass>1.5</mass>
          <inertia>
            <ixx>0.012</ixx>
            <iyy>0.012</iyy>
            <izz>0.024</izz>
          </inertia>
        </inertial>
        
        <!-- Collision properties -->
        <collision name='base_link_collision'>
          <geometry>
            <box>
              <size>0.3 0.3 0.1</size>
            </box>
          </geometry>
        </collision>
        
        <!-- Motors -->
        <plugin name='front_left_motor_model' filename='libgazebo_motor_model.so'>
          <jointName>front_left_motor_joint</jointName>
          <turningDirection>ccw</turningDirection>
          <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
        </plugin>
        <plugin name='front_right_motor_model' filename='libgazebo_motor_model.so'>
          <jointName>front_right_motor_joint</jointName>
          <turningDirection>cw</turningDirection>
          <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
        </plugin>
        <plugin name='rear_left_motor_model' filename='libgazebo_motor_model.so'>
          <jointName>rear_left_motor_joint</jointName>
          <turningDirection>cw</turningDirection>
          <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
        </plugin>
        <plugin name='rear_right_motor_model' filename='libgazebo_motor_model.so'>
          <jointName>rear_right_motor_joint</jointName>
          <turningDirection>ccw</turningDirection>
          <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
        </plugin>
      </link>
    </model>
  </world>
</sdf>