robot_localization: how to deal with imu data
Recently, i am reading robot_localization and want to understand how it works. Previously, i have read and understood code and logics in robot_pose_ekf package.
I am confused about how imu data is processed in robot_localization. It seems to me that if config of differential was set to false, then imu can't work in robot_localization. The orientation of imu in 'world' fixed frame is transformed to orientation of base_link in 'world' fixed frame and set as measurement and send to ekf or ukf. But how can this data in world frame be fused with other data in other frame(such as 'odom' frame) ?
Hope i was wrong in understanding robot_localization and someone can fix me.