What does the actuator name for URDF reference?

Question

For this question I am using the code sample provided at the documentation:

http://www.ros.org/wiki/urdf/XML/Transmission

<transmission type="SimpleTransmission" name="caster_front_left_trans">
  <actuator name="caster_front_left_motor" />
  <joint name="caster_front_left_joint" />
  <mechanicalReduction>1</mechanicalReduction>
</transmission>

I understand for the most part what most of the names refer to, but I am still puzzled as to what exactly the function of the actuator name is. I did my best to grep through the shipped packages, but with no luck. Does the name reference something external to the robot model? What does it reference?

I suppose I should note I was looking at the PR2's URDF description and grepping for its actuator name(s).

Thanks for any help!

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Originally posted by OEP on ROS Answers with karma: 33 on 2012-02-14

Post score: 3

Answer 1

Actuators are defined in config files for the ethercat_hardware package: http://ros.org/wiki/ethercat_hardware

You don't really need actuators if you only use the gazebo_ros_controller_manager for simulation. In the transmission documentation it says:

The transmission element is an extension to the URDF robot description model. This extension is only used for the PR2 robot, and is not meant to be reusable for other robots.

However I should mention that you do need the transmission and actuator tags in your model for the gazebo_ros_controller_manager plugin to work, but it doesn't matter what names you specify for the actuators.

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Originally posted by Kai Bublitz with karma: 357 on 2012-02-14

This answer was ACCEPTED on the original site

Post score: 6

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Original comments

Comment by OEP on 2012-02-15:
Thank you for your answer. I am conducting research on robot models and URDF was one of the existing models I looked at. Naturally, it was bugging me that I couldn't figure out where those actuators were defined, hence the question! :)