Correct tf-order for odom frame in cartographer

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Hi,

I am currently trying to improve the accuracy of the cartographer_ros by adding an odometry. However, the first result was not very satisfying as the cartographer automatically places the origin of the odom frame directly into the origin of the base_link frame. My first attempt was to create the odom-frame in the robot model and link it to the base_link with the correct frame offset:

<robot name="broetje_Prototype_AGV">

  <material name="gray">
    <color rgba="0.7 0.7 0.7 0.5" />
  </material>
  <material name="red">
    <color rgba="1.0 0.0 0.0 1.0" />
  </material>
  <material name="yellow">
    <color rgba="1.0 0.73 0.0 0.5" />
  </material>

  <!--LINK: Map-->
  <!--link name="map">
    <visual>
      <origin rpy="0 0 0" xyz="0 0 0"/>
    </visual>
  </link-->
  <!--JOINT: Odometry-->
  <!--joint name="map_to_odom" type="fixed">
    <parent link="map" />
    <child link="odom" />
    <origin rpy="0 0 0" xyz="0.5 -0.3 0"/>
  </joint-->

  <!--LINK: Odometry-->
  <!--link name="odom">
    <visual>
      <origin rpy="0 0 0" xyz="0 0 0"/>
    </visual>
  </link-->
  <!--JOINT: Base-->
  <!--joint name="odom_to_base" type="fixed">
    <parent link="odom" />
    <child link="base_link" />
    <origin rpy="0 0 0" xyz="-0.5 0.3 0"/>
  </joint-->

  <!--LINK: Base-->
  <link name="base_link">
    <visual>
      <geometry>
        <mesh filename="package://cartographer_ros/meshes/Cobot2019_origin.dae"/>
        <!--box size="1 0.6 0.45"/-->
      </geometry>
      <origin rpy="0 0 0" xyz="0.5 -0.3 0"/>
      <material name="red"/>
    </visual>
  </link>
  <!--JOINT: Safety Scanner 1-->
  <joint name="base_to_scan_1" type="fixed">
    <parent link="base_link" />
    <child link="scan_1" />
    <origin rpy="3.1416 0 2.3561925" xyz="0.055 -0.055 0.18"/>
  </joint>
  <!--JOINT: Safety Scanner 2-->
  <joint name="base_to_scan_2" type="fixed">
    <parent link="base_link" />
    <child link="scan_2" />
    <origin rpy="3.1416 0 -0.7853975" xyz="0.956 -0.556 0.18"/>
  </joint>
  <!--JOINT: Odometry-->
  <joint name="base_to_odom" type="fixed">
    <parent link="base_link" />
    <child link="odom" />
    <origin rpy="0 0 0" xyz="0.5 -0.3 0"/>
  </joint>

  <!--LINK: Safety Scanner 1-->
  <link name="scan_1">
    <visual>
      <geometry>
        <mesh filename="package://cartographer_ros/meshes/sick_scanner_origin.dae"/>
      </geometry>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <material name="yellow"/>
    </visual>
  </link>

  <!--LINK: Safety Scanner 2-->
  <link name="scan_2">
    <visual>
      <geometry>  
        <mesh filename="package://cartographer_ros/meshes/sick_scanner_origin.dae"/>
      </geometry>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <material name="yellow"/>
    </visual>
  </link>

    <!--LINK: Odometry-->
  <link name="odom">
    <visual>
      <origin rpy="0 0 0" xyz="0.5 -0.3 0"/>
    </visual>
  </link>

</robot>

If I proceed as displayed above, base_link or odom starts jumping around while rotating ... (more)