world link defined in URDF/Xacro and SRDF

[christian-rauch]

The URDF/Xacro files define the world link as the root of the kinematic chain, which is connected via connect_root_and_world to the actual root of the robot kinematic chain (frame root).
The SRDF defines a virtual joint world_joint with the same connection.

Taking both joints into account, this is not a kinematic tree anymore since there are two paths from world to root. Consequently it can cause issues when determining the root for planning. See also: ros-industrial/universal_robot#347 and ros-industrial/universal_robot#284.

[sbrisebois]

Hi Christian,

Thank you for you work.
I will have a look to your PR very soon. I have to investigate if this does not broke demos and other development with the package.

Sincerely,
Sylvain Brisebois