ABB IRB 2400 Joint 2 and Joint 3 coupline

[jodle001]

This isn't so much an issue as a question I suppose. But currently I am customizing the ABB Hardware Interface to handle coupled joints like for the ABB IRB2400. So inside the read and write methods I'm applying a coupling factor to those joint positions .

SO my question is: Is joint coupling something that should be handled by defining something in the URDF? Is this already handled somewhere automatically using the configuration of the robot?

Any help is appreciated. Thank you.