Question -- CoM Displacement

[itaouil]

Hi :),

I remember that the robot in RVIZ used to also move around, instead of being fixed on the place. Is there a parameter I can change to undock it again?

The reason for it is that I want to extract the absolute CoM displacement every footstep, but for that I need to have the CoM position w.r.t the world frame so that I can compute the actual displacement, or maybe the wbc is already publishing somewhere the CoM displacement?

[graiola]

Hi @itaouil , you can change in the params the type of estimation for the position, in your case you want to use the ground_truth from gazebo:

estimation_position_type: ground_truth

this will give you the position of the robot wrt the world in gazebo. Let me know if it works :)

[itaouil]

Hi,

Yes, by changing the estimation_position_type the /aliengo/wb_controller/CoM topics publishes CoM pose with respect to world.

But I also noticed that even if the estimation_position_type is set to estimated_z a topic called /aliengo/ground_truth is published that additionally also has a non-zero orientation :).

I guess I will use /aliengo/ground_truth instead as it has the additional orientation of the body and just keep the estimation_position_type set to estimated_z for ease of visualization.

[graiola]

Be aware that the ground_truth represents the position of the robot's base and not its com. It would be cool to have a proper state estimation one day ;)

[itaouil]

Ah ok. Did not even realise that :).

The difference in the pose between CoM and base is "minimal" for my purpose so that won't be an issue I think :).