Transformations

Frame hopping.

Use minkindr to represent transformations.

GitHub - ethz-asl/minkindr: A minimal library for transformations, following the kindr interface. Uses active quaternions of rotation in Hamilton notation.GitHub

Further details on the transformation notation, frame names and conventions can be found on the wiki page.

GitHub - ethz-asl/mav_tools_public: General launch files, parameters and wiki entries on our systems and related issuesGitHub

TF2

tf-remapping

Here,

• old: contains the name of tf that needs to be remapped

• new: new name of tf

<launch>
 
 <!--tf remmapper node-->
  <node pkg="tf" type="tf_remap" name="tf_remapper" output="screen">
    <rosparam param="mappings">
      [{old: /imu, new: /base_link}]
    </rosparam>
  </node>

 <!--node whose tf needs to be remapped-->
  <node pkg="rosbag" type="play" name="player" args="/home/drive/test.bag">
    <remap from="tf" to="tf_old" />
  </node>

</launch>

The topic subscribed to is:

/tf_old (tf/tfMessage) -- Old transform tree. This is usually published by remapping playback of a bag file. You may need to set use_sim_time as true for the bag file transforms to be accepted.

The topic published is:

/tf (tf/tfMessage) -- Current transform tree. This is the normal /tf topic.

publish-static-transforms

static_transform_publisher x y z yaw pitch roll frame_id child_frame_id period_in_ms

Publish a static coordinate transform to tf using an x/y/z offset in meters and yaw/pitch/roll in radians. (yaw is rotation about Z, pitch is rotation about Y, and roll is rotation about X). The period, in milliseconds, specifies how often to send a transform. 100ms (10hz) is a good value.

static_transform_publisher x y z qx qy qz qw frame_id child_frame_id period_in_ms

Publish a static coordinate transform to tf using an x/y/z offset in meters and quaternion. The period, in milliseconds, specifies how often to send a transform. 100ms (10hz) is a good value.

static_transform_publisher is designed both as a command-line tool for manual use, as well as for use within roslaunch files for setting static transforms. For example:

<launch>
<node pkg="tf" type="static_transform_publisher" name="link1_broadcaster" args="1 0 0 0 0 0 1 link1_parent link1 100" />
</launch>