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Linked joints?

Hi,
I’m reading a lot of docs on URDF but a little lost on how to describe a robot with linked joints. It seems there is no support for parallel links, which maintain that the roll/pitch/yaw of the child joint is exactly the same as the parent, but only moving its xyz position of the joint but maintaining its euclidian distance to the parent?

Here’s an example of such a robot which I built, and I think a lot of palletizing arms do the same as well.

Unfortunately, “parallel robots” are not really supported - see the third paragraph of http://wiki.ros.org/urdf/XML/model - all robots must be a “tree structure”. Now, you can certainly still model your parallel robot, but you’ll have to model multiple joints and do the math in your drivers to keep the parallel constraints correct.

I believe the SRDF (the format used for Gazebo) actually does support parallel structures - which means if you’re trying to simulate such a robot, that is still possible.