nav2d can't find path [closed]

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Hello, I am currently tring to use the nav2d package to make my turtlebot robot do an autonomous exploration of a unknown room. I am using ROS Indigo with Ubuntu 14.04. I am using the tutorial3.launch file with some modificaitons to adapt the topics to the turtlebot, and both the costmap and the global map ( on /map topic ) are created. But when i try to use the rosservice call /StartMapping 3, i obtain

response: 0

and it goes back to command line Here are my files : tutorial3.launch

<launch>

    <!-- Some general parameters -->
    <param name="use_sim_time" value="false" />
    <rosparam file="$(find nav2d_tutorials)/param/ros.yaml"/>

    <!-- Start Stage simulator with a given environment 
    <node name="Stage" pkg="stage_ros" type="stageros" args="$(find nav2d_tutorials)/world/tutorial.world">
        <param name="base_watchdog_timeout" value="0" />
    </node>-->

    <!-- Start the Operator to control the simulated robot -->
    <node name="Operator" pkg="nav2d_operator" type="operator" >

        <rosparam file="$(find nav2d_tutorials)/param/operator.yaml"/>
        <rosparam file="$(find nav2d_tutorials)/param/costmap.yaml" ns="local_map" />
    </node>

    <!-- Start Mapper to genreate map from laser scans -->
    <node name="Mapper" pkg="nav2d_karto" type="mapper">        
        <rosparam file="$(find nav2d_tutorials)/param/mapper.yaml"/>
    </node>

    <!-- Start the Navigator to move the robot autonomously -->
    <node name="Navigator" pkg="nav2d_navigator" type="navigator">

        <rosparam file="$(find nav2d_tutorials)/param/navigator.yaml"/>
    </node>

    <node name="GetMap" pkg="nav2d_navigator" type="get_map_client" />
    <node name="Explore" pkg="nav2d_navigator" type="explore_client" />
    <node name="SetGoal" pkg="nav2d_navigator" type="set_goal_client">
        <remap from="goal" to="move_base_simple/goal"/>
    </node>

    <!-- Start the joystick-driver and remote-controller for operation
    <node name="Joystick" pkg="joy" type="joy_node" />
    <node name="Remote" pkg="nav2d_remote" type="remote_joy" />-->

    <!-- Pioneer model for fancy visualization -->
    <!-- Comment this out if you do not have the package 'p2os' available! 
    <include file="$(find p2os_urdf)/launch/pioneer3at_urdf.launch" />
    <node name="front_left_wheel" pkg="tf" type="static_transform_publisher" args="0 0 0 0 0 0 p3at_front_left_hub p3at_front_left_wheel 100" />
    <node name="front_right_wheel" pkg="tf" type="static_transform_publisher" args="0 0 0 0 0 0 p3at_front_right_hub p3at_front_right_wheel 100" />
    <node name="back_left_wheel" pkg="tf" type="static_transform_publisher" args="0 0 0 0 0 0 p3at_back_left_hub p3at_back_left_wheel 100" />
    <node name="back_right_wheel" pkg="tf" type="static_transform_publisher" args="0 0 0 0 0 0 p3at_back_right_hub p3at_back_right_wheel 100" />
-->
    <!-- RVIZ to view the visualization 
    <node name="RVIZ" pkg="rviz" type="rviz" args=" -d $(find nav2d_tutorials)/param/tutorial3.rviz" />-->

</launch>

rqt-graph http://hpics.li/b05718e

EDIT : I tried running the rqt_console while calling the services : When i run rosservice call /StartMapping 3 , i have an Info message saying Navigator is now initialised. But when i run rosservice call /StartExploration 2, i obtain a Warning message saying

Navigator is busy!
Location:
/tmp/binarydeb/ros-indigo-nav2d-navigator-0.1.4/src/RobotNavigator.cpp:receiveExploreGoal:798

then 5 min after , every second :

Robot cannot move further in this direction!
Location:
/tmp/binarydeb/ros-indigo-nav2d-operator-0.1.4/src/RobotOperator.cpp:executeCommand:268

So i tried to move the robot with Rviz, and it show an error message saying

no way between robot and goal
no way between robot and goal