confused about robot_localization usage

edit

Dear all, I am trying to use the robot_localization package (ekf_localization) to fuse odometry and IMU data to get an initial guess for a pose estimator. I have read the robot_localization documentation, but I am still confused about: 1) the REP-105 says that we should have a tf chain /map -> /odom -> /base_projected, I have a robot node that is publishing /odom->/base_projected transformation, so I should set ekf to publish to a /odom_imu->/odom transformation and then pass /odom_imu to the pose estimator? to achieve this, I set:

      <param name="map_frame" value="odom_imu"/>
      <param name="odom_frame" value="odom"/>
      <param name="base_link_frame" value="base_projected"/>
      <param name="world_frame" value="odom_imu"/>

2) I am not sure how to setup the ekf localizer, since it is jumping and losing the right position (i.e., it is worse than the odometry alone): in the _config parameters, I use only the x, y, z velocities of the odometry and the roll pitch and yaw position and velocities; both odom and imu are set to retrieve the differential data

looking at the system with rviz, I see the odom_imu very near (and following) to the base_projected, while I expected it to be near the /odom frame, am I wrong?

EDIT: this is the entire launch file, as requested:

<launch>
    <node pkg="robot_localization" type="ekf_localization_node" name="ekf_localization" clear_params="true">
      <param name="frequency" value="30"/>  
      <param name="sensor_timeout" value="0.1"/>  
      <param name="two_d_mode" value="false"/>

      <param name="map_frame" value="odom_imu"/>
      <param name="odom_frame" value="odom"/>
      <param name="base_link_frame" value="base_projected"/>
      <param name="world_frame" value="odom_imu"/>

      <param name="odom0" value="/odom"/>
      <param name="imu0" value="/imu/data"/> 

      <rosparam param="odom0_config">[true, true, true, 
                                      false, false, true, 
                                      false,  false,  false, 
                                      false, false, false]</rosparam>

      <rosparam param="imu0_config">[false, false, false, 
                                     true,  true,  true, 
                                     false, false, false, 
                                     false, false, false]</rosparam>

      <param name="odom0_differential" value="true"/>
      <param name="imu0_differential" value="true"/>

      <param name="remove_gravitational_acceleration" value="true"/>

      <param name="debug"           value="false"/>
      <param name="debug_out_file"  value="debug_ekf_localization.txt"/>

      <rosparam param="process_noise_covariance">[0.03, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0.03, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0.0, 0.4, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0.0, 0.0, 0.03, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0.0, 0.0, 0.0, 0.03, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0.0, 0.0, 0.0, 0.00, 0.06, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0.0, 0.0, 0.0, 0.00, 0.0, 0.025, 0.0, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0 ...