Cartographer SLAM - TF Tree Errors

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Hi everyone,

I am completely stuck on a tf problem. What I try to do is slam with a laser sensor and an imu with cartographer_ros. According to the related tutorial, I define my physical layout of the robot in a urdf file:

<robot name="robot_3d">
<material name="orange"> <color rgba="1.0 0.5 0.2 1"/> </material>
<material name="gray"> <color rgba="0.2 0.2 0.2 1"/> </material>

<link name="imu_link"> <visual> <origin xyz="0.0 0.0 0.13"/> <geometry> <box size="0.06 0.04 0.02"/> </geometry> <material name="orange"/> </visual> </link>

<link name="base_laser_link"> <visual> <origin xyz="0.0 0.0 0.035"/> <geometry> <cylinder length="0.15" radius="0.08"/> </geometry> <material name="gray"/> </visual> </link>

<link name="base_link"/>

<joint name="imu_link_joint" type="fixed"> <parent link="base_link"/> <child link="imu_link"/> <origin xyz="0 0 0" rpy="0 0 0"/> </joint>

<joint name="base_laser_link_joint" type="fixed"> <parent link="base_link"/> <child link="base_laser_link"/> <origin xyz="0.0 0. 0.0" rpy="0 0 0"/> </joint>

</robot>

This file clearly defines the transformation between base_link and imu_link as well as base_link with base_laser_link. Than I call cartographer to do slam which is calling state_publisher. However, cartographer shows an error that it cannot relate the imu_link to the base_link. Also in tf viewer in rqt it is visible, that imu_link and base_link are not connected via a transformation, while base_link and base_laser_link are connected without problems. Did anyone of you have a similar issue? Why doe the state_publisher not relate the imu_link with the base_link?

* Update *

The TF tree appears to be constructed correctly just using the robot state publisher. This means the base_link is parent to imu_link and base_laser_link. However, as soon as I start cartographer_ros node the tf tree is ripped apart. Then it shows the new topic odom (which shall be generated by the slam) which is parent to imu_link. Separatly (unconnected) to this also we still have the base_link topic which is parent to "base_laser_link". The error the cartographer is throwing is:

"Could not find a connection between 'imu_link' and 'base_laser_link' because they are not part of the same tree.Tf has two or more unconnected trees.

Before starting cartographer After starting cartographer:

* Update * I could further break down the error, that the imu manager is causing this tf fault. The imu is based one the phidget imu package:

sudo apt install ros-melodic-phidgets-imu

Which is called with the following launch file:

<launch>
  <node pkg="nodelet" type="nodelet" name="imu_manager" 
    args="manager" output="screen" />

  <node pkg="nodelet" type="nodelet" name="PhidgetsImuNodelet" 
    args="load phidgets_imu/PhidgetsImuNodelet imu_manager" 
    output="screen">
    <param name="period" value="4"/>
    <param name="frame_id" value="imu_link"/> 
  </node>

  <node pkg="nodelet" type="nodelet" name="ImuFilterNodelet" 
    args="load imu_filter_madgwick/ImuFilterNodelet imu_manager" 
    output="screen">

    <param name="use_mag" value="true"/>
    <param name="use_magnetic_field_msg" value="true"/>
  </node>

</launch>

However, I cannot find out why this imu manager is creating a tf connection between frame /odom and /imu_link and at the same time breaking /imu_link and ... (more)