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How does turtlebot broadcast its transform?

asked 2012-01-03 16:50:40 -0500

weiin gravatar image

I'm learning how to use the navigation stack from the navigation tutorials

It is stated that "The navigation stack requires that the robot be publishing information about the relationships between coordinate frames using tf." However, looking at the turtlebot_node.py code I do not see any "odom_broadcaster.sendTransform" sort of command anywhere.

Can anyone tell me why this is so? Does this have anything to do with the "JointState" variable? I'm not quite sure what this variable is for.

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answered 2012-01-04 04:45:33 -0500

fergs gravatar image

The transform is actually published by the robot_pose_ekf filter, which fuses the wheel odometry and IMU data to get a better result.

The joint states are used to tell where the robot's parts are. A separate node (robot_state_publisher) turns joint_states + the URDF specification into a series of transforms. On the stock turtlebot, this isn't very interesting, but if you have a turtlebot arm attached, the joint states output allows you to see the arm moving in RVIZ.

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So there is actually no need to do a tf broadcast when publishing the odom (http://www.ros.org/wiki/navigation/Tutorials/RobotSetup/Odom), as long as I launch the robot_pose_ekf node?
weiin gravatar image weiin  ( 2012-01-04 11:16:20 -0500 )edit
That is correct.
tfoote gravatar image tfoote  ( 2012-01-24 03:57:28 -0500 )edit

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Asked: 2012-01-03 16:50:40 -0500

Seen: 1,798 times

Last updated: Jan 04 '12