Previous discussions stated that the ros_control project made the explicit decision to not impose URDF in its core. However, specific controllers and interfaces are free to use URDF when needed.

I mentioned at some point in the past that loading a URDF could be very slow for complex models. I just revisited my previous statement to make it more exact: Loading a complex URDF to the ROS parameter server can indeed be expensive (seconds), but parsing it from the parameter server to a `urdf::Model` data structure is rather fast (tens of milliseconds).

If there are still good arguments for depending on URDF at the core of ros_control, we can discuss it in a separate issue, and evaluate all pros and cons.