Understanding log messages

Errors when using package

• Timestamps of odometry and imu are x seconds apart

  • This error occurs when the timestamps of the sensor messages that are received differ more than 1 second. This is probably an indication of timing issues in your system, e.g. the clocks of two hosts connected to the same ros core are not synchronized.

• Covariance specified for measurement on topic xxx is zero

  • Each measurement that is processed by the robot pose ekf needs to have a covariance associated with it. The diagonal elements of the covariance matrix cannot be zero. This error is shown when one of the diagonal elements is zero. Messages with an invalid covariance will not be used to update the filter.

• Filter time older than xxx message buffer

  • This error occurs when two sensor inputs have timestamps that are not synchronized. All sensor inputs are stored in a message buffer; this buffer keeps data for 10 seconds. When the timestamps of two sensor inputs are more than 10 seconds apart, data will get lost from the message buffer, and you'll get this error.

Warnings when using package

• Robot pose ekf diagnostics discovered a potential problem

  • This warning occurs when the internal diagnostics find that something is wrong. At this time, the diagnostics system only checks for the consistency between the odom and imu sensors. When these two sources provide very different information about the robot pose, this is a good indication that something might be wrong with some of the sensor measurements/timestamps.

Info when using package

• xxx sensor activated

  • This message indicates that a sensor source was detected and activated. After receiving this message the filter can use measurements from this sensor.

• Waiting to activate xxx, because xxx measurements are still x sec in the future

  • When a sensor signal first arrives, its timestamp is potentially newer than the latest filter update time. This message indicates that sensor will remain inactive, until the filter catches up.

• xxx sensor not active any more

  • When a sensor source is not sending any measurement for a user-specified timeout (default 1 sec), that sensor source is deactivated.

• Fiter initialized

  • This message indicates that either the odom sensor or the vo sensor has been detected and activated, and the filter has been initialized. After this message is shown, the filter will get updated at the user-specified frequency.

The robot pose ekf does not work

The robot pose ekf provides a service call to give information on its internal state. Simply run:

•  $ rosrun robot_pose_ekf wtf.py

The output will give you good clues about possible problems.

Is the robot pose ekf still running?

To check if the robot pose ekf is running, you should find out on what the name of the node is. The node name depends on the name you specified in the launch file:

•   ...
    <node pkg="robot_pose_ekf" type="robot_pose_ekf" name="my_name">
    ...

Look for the name="..." field. In this example, the node name is 'my_name'. To verify if the node is running, type:

•  $ rosnode ping my_name

Is the robot pose ekf sending output?

First you should find out on what topic name the robot pose ekf is supposed to publish data. The topic name depends on the name you specified in the launch file:

•   ...
    <node pkg="robot_pose_ekf" type="robot_pose_ekf" name="my_name">
    ...

Look for the name="..." field. In this example, the output topic name is set to 'my_name/odom_combined'. To verify if any output is published, type:

•  $ rostopic hz my_name/odom_combined

You should see an average publish rate being displayed. If not, the output is not published.

Is the robot pose ekf receiving input?

The robot pose ekf listens on three topics: '/odom', '/imu_data' and '/vo'. To check if any input is received on these topics, type:

•  $ rostopic hz /odom
   $ rostopic hz /imu_data
   $ rostopic hz /vo

You should see an average publish rate being displayed. If not, the input is not published.