Fusing absolute position information and IMU-data using the ekf_localization_node

edit

Hello,

I have a robot car with a laser-scanner and an imu and would like to fuse the position information of the two sensors.

For laser based localization I am using the hector_mapping node which produces a /poseupdate topic. Additionally I am using an imu producing the /imu/data topic.

Those two shall be fused to provide a more accurate position estimate at a higher rate.

After incorporating the suggestions from Tom Moore my launch files look like this:

Edit 1

I am getting better behaviour now. What I did is based on the following thoughts: The odom->baselink transformation according to Rep105 should only be computed by odometry sources (by def. relativ/differential information). However before I was using differential set to false in the /imu0 data of the odom->baselink ekf, so the odometry got the absolute heading information from the imu. Could this have caused the orientation errors?

As I understood Rep105 the map->odom transform is computed indirectly by using absolute sensory information. So I thought it needs the absolute information from all source. That is why I set, differential to false for the imu topic of the map->odom ekf.

Here are my updated launchfiles (the mess with hector frames reverted):

The odom-baselink ekf-instance:

    <launch>
  <!-- Start Navigation Stack -->

  <node pkg="hector_mapping" type="hector_mapping" name="hector_mapping" output="screen">
    <param name="map_frame" value="map"/>   
    <param name="odom_frame" value="odom"/>  

    <param name="map_size" value="2048"/>
    <param name="pub_map_odom_transform" value="false"/>
    <param name="pub_map_scanmatch_transform" value="false"/>
  </node>


  <node pkg="robot_localization" type="ekf_localization_node" name="ekf_localization_node" output="screen">
  <param name="print_diagnostics" value="true"/>
  <param name="frequency" value="100"/>
  <param name="two_d_mode" value="true"/>

  <param name="map_frame" value="map"/>  
  <param name="odom_frame" value="odom"/>
  <param name="world_frame" value="odom"/>   
  <param name="base_link_frame" value="base_link"/>

  <param name="pose0" value="/poseupdate"/>
  <rosparam param="pose0_config">  
    [true, true,  false,    <!-- You have two_d_mode on, so making Z true does nothing -->
    false, false, true,  
    false, false, false,
    false, false, false,
    false, false, false]
  </rosparam>
  <param name="pose0_differential" value="true"/>

  <param name="imu0" value="/imu"/>
  <param name="imu0_remove_gravitational_acceleration" value="true"/>    

  <rosparam param="imu0_config">  
    [false, false, false,
     false,  false,  true,     <!-- 2D mode, so roll and pitch do nothing -->
     false, false, false,
     false,  false,  true,     <!-- As above -->
     true,  true,  false]    <!-- Start with these turned off, verify that everything works, then turn X and Y back on (Z does nothing in 2D mode) -->
  </rosparam>
  <param name="imu0_relative" value="true"/>
  <param name="imu0_differential" value="true"/> 

  </node>

The map-odom ekf:

<launch>

  <node pkg="robot_localization" type="ekf_localization_node" name="aux_ekf_localization_node" output="screen">
   <param name="print_diagnostics" value="true"/>
  <param name="frequency" value="100"/>
  <param name="two_d_mode" value="true"/>

  <param name="map_frame" value="map"/>  
  <param name="odom_frame" value="odom"/>
  <param name="world_frame" value="map"/>   
  <param name="base_link_frame" value="base_link"/>

  <param name="pose0" value="/poseupdate"/>
  <rosparam param="pose0_config">  
    [true, true,  false,
    false, false, true,  
    false, false, false,
    false, false, false,
    false, false, false]
  </rosparam>
  <param name="pose0_differential" value="false"/>

  <param name="imu0" value="/imu"/>
  <param name="imu0_remove_gravitational_acceleration" value="true"/>    

  <rosparam param="imu0_config">  
    [false, false, false,
     false,  false,  true,    
     false ...