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Hello everyone,

I am working on a robot (turtlebot) to make autonomous navigation in an unknown environment with some extra skills (objet recognition, object localization, ...).

The robot is equipped with a Hokuyo UTM-30LX and a Asus XtionPRO. On the Turtlebot there is a small laptop (Ubuntu 12.04, ROS Hydro) to get the data from the sensors (scan from the lidar and images from the camera) and to receive the cmd_velocity to move the robot. Another computer (Ubuntu 12.04, Ros Groovy) is used to process all this data and for example to calculate the path of the robot. For the map&localization I'm using Hector SLAM. For the navigation, I'm using Hector Navigation Stack (hector_costmap, hector_exploration_node, hector_ecploration_controller). Here is my launchfile for the navigation part:

<launch>
<node pkg="hector_costmap" type="hector_costmap" name="hector_costmap" output="screen" respawn="false">
    <!-- Frame names -->
    <param name="cost_map_topic" value="cost_map" />
    <param name="map_frame_id" value="map" />
    <param name="local_transform_frame_id" value="base_footprint" />
    <param name="elevation_map_topic" value="elevation_map_local" />
    <param name="grid_map_topic" value="scanmatcher_map" />
    <param name="sys_msg_topic" value="syscommand" />
    <param name="cloud_topic" value="openni/depth/points" />

    <!-- Costmap parameters -->
    <param name="use_elevation_map" value="false" />
    <param name="use_grid_map" value="true" />
    <param name="use_cloud_map" value="false" />

    <param name="initial_free_cells_radius" value="0.3" />
    <param name="update_radius" value="1.0"/>
    <param name="costmap_pub_freq" value="1.0" />
</node>

<node pkg="hector_exploration_node" type="exploration_planner_node" name="hector_exploration_node" output="screen">
    <rosparam file="$(find hector_exploration_node)/config/costmap.yaml" command="load" />
</node>

<node pkg="hector_exploration_controller" type="simple_exploration_controller" name="hector_exploration_controller" output="screen" respawn="true">
    <remap from="/cmd_vel" to="/mobile_base/commands/velocity"/>
</node>
</launch>

And here is the costmap config file:

global_costmap:
    map_type: costmap
    track_unknown_space: true
    unknown_cost_value: 255
    obstacle_range: 2.5
    raytrace_range: 3.0
    footprint: [[0.15, 0.0],
              [0.15, 0.15],
              [0.0, 0.17],
              [-0.15, 0.15],
              [-0.15,0.0],
              [-0.15,-0.15],
              [0.0, -0.17],
              [0.15, -0.15]
              ]
    inflation_radius: 0.50

    #transform_tolerance: 0.5
    inscribed_radius: 0.3
    circumscribed_radius: 0.32
    global_frame: /map
    robot_base_frame: /base_link
    update_frequency: 0.5
    publish_frequency: 0.1
    static_map: true
    rolling_window: false
    cost_scaling_factor: 10.0

It seems to work well, Hector packages find frontiers, can calculate the path. The velocity command is well sent to the robot, but this latter is like a drunk robot ! It is making circles and don't follow the path.... (see Figure: https://www.dropbox.com/s/w4tuocrf1py... )

I'm sure it's because I miss something or put bad parameters. Do you have any idea ?

Thank you for your help ! :)

Edit : I make new tests and the robot still have the same behaviour: turning on itself. I noticed that the robot stops for a short moment when a new path was calculated and it still turn on itself. It's like if the robot can't be on the exact location of the path and turns to try being on the path... Is there any parameters to give it more tolerance ? Moreover I just use the cmd_velocity generated by the hector_exploration_controller, is it enough ? I saw that there is also the hector_path_follower but ... (more)