Map is rotating with the robot

asked 2022-10-09 08:48:40 -0500

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updated 2022-10-09 08:49:30 -0500

My fixed frame is Map . While the robot is moving linear the map is staying still but when the robot starts rotating the map is rotating too .

My odom data are very accurate and i've checked them with tf in rviz .

My transforms are :

map -> odom from gmapping package
odom -> base_link , from odom package i've created to process odom data
base_link -> laser , from urdf file

Any thoughts why is this happening ?

answered 2022-10-09 16:22:16 -0500

ct2034
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updated 2022-10-11 15:41:47 -0500

Hi. I think what's happening is that gmapping gives the transformation from map -> odom, as it should. But if you then give odom -> base_link, this will rotate the map, when the odometry rotates.

You will have to change your package to publish base_link -> odom and also the urdf must give laser -> base link. I think both of those transformations are published the wrong way round. It should also be mentioned here http://wiki.ros.org/amcl?distro=noeti... and here https://wiki.ros.org/gmapping?distro=...

EDIT: I think the way you write the transformations is correct, I just think that maybe the implementation does not match that which would give the indicated behaviour.

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I don't think that's right because now my tree frame is broken into map->odom and laser->base_link . Are you sure this is the right way ?

Kostas Tzias ( 2022-10-11 08:28:07 -0500 )edit

just to be clear, the arrow x->y indicates a transformation of frame y in terms of x. Saying where y is within x. Note that this is the way, the tf documentation uses the arrow directions and also the link i posted from gmapping uses this orientation of arrows. The amcl documentation has the arrows the other way around but means the same thing. And just to make things even more complicated, rviz uses the wrong orientation, i.e. the one that also the amcl documentation uses.