URDF/MoveIt parental relationship reverse

edit

Hi, This questions is 'how to best approach this problem in ROS' type of question.

I have a robot crawler arm where the start or end may become fixed or the end effector at any point. Something like this: http://news.mit.edu/2019/robots-large...

I am thinking on what is the best approach to model this in URDF so that I can use MoveIt etc. My major concerns are:

say This is the robot: World--virtual_fixed_joint--L0--J0--L1--J1--L2

• Code reuse when flipping parent -child relationship. You cant simply reverse parent-child relationship. One issue arises from L_i+1 visuals/collisions being defined with respect to J_i. And if That same links parent is flipped to J_i+1, this could be wrong. I solved this by using dummy links/joints, but this causes non-chain topology and kinematics plugins dont support that.
• Ability to use meveit groups to flip which part of the robot is fixed. For this I tried to essentially describe the robot twice, using dummy joints again, but then I'd need to remap joint names because for every real hardware joint, 2 joints would appear in urdf.

Any thoughts appreciated! Thanks

So far I have considered creating duplicate links/joints or using dummy joints/links