geometry_msgs::Twist references (navigation stack / ros_control)

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Hi all,

I am currently putting in place a mecanum_drive_controller for ros_control (it transforms a desired twist into corresponding wheels velocities and computes the odometry out of the wheels encoders). This is all fine and working as expected.

Now I have a bit of an uncertainty about what to expect as input (desired twist) and what to provide as output (actual twist computed for the odometry). This is especially important as I expect to be "ros compliant" and integrate with the navigation stack and other standard packages.

So, say I have a mobile robot which is rigidly attached a frame m, of origin Om. I also have a frame odom which is used as a reference. So what I believe is that the input twist provided on topic /base_controller/cmd_vel should the twist of desired Om, seen as belonging to m, in its movement with respect to odom and expressed in the odom basis. This is the desired twist.

The observed twist provided as output should be the same (not the values obviously ;)): twist of observed Om, seen as belonging to m, in its movement with respect to odom and expressed in the odom basis.

Can you confirm?

Thanks,

Antoine.