IMU sensor does not show the orientation of the vessel in ignition sim

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1

Hi all,
i am working on a project which involves water and ship simulation. I have a ship model which can float on a waves using the plugins available with mbzirc(GitHub - osrf/mbzirc: Simulator for the MBZIRC Maritime Grand Challenge) repository.
i am trying to measure the ship’s movement in all direction

xyz
xyz1200×900 49.6 KB

rpy
rpy1200×900 48.2 KB

using the IMU sensor. Although the ship is moving largely in z direction, IMU sensor data shows 0 in z direction. Can anyone help me in this regard.

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This kind of questions is best asked at the Robotics Stack Exchange, as this forum is rather intended for general conceptual discussions and questions.

That being said:
I have no experience with the IMU sensor, but I notice that the legends of your graphs state ‘orientation’ and ‘roll-pitch-yaw’, i.e. rotation, whereas you mention “moving largely in z direction” which I interpret as translation.

According to this description only linear acceleration is reported.

See also this documentation.

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Thank you for your response. I would ask the question on robotics stack exchange as well.