Hi, i was trying to use the compile.cpp to get a coverted file (urdf-mjb or txt) but it gives me this error URDF body has multiple parents. how could i solve this issue the best? im not that into urdf and roboter modeling., so i would appreciate your hints! thnx
The error message suggests that the same body/link in the URDF is defined as having two parents. This is not allowed, since the model has to be a tree. URDFs are not easy to read and edit by hand, but in this case the only solution is to read the file carefully and find out where that body is. There is additional documentation re URDF here: http://www.mujoco.org/book/modeling.html#CURDF Of course you can also read the documentation of URDF itself.
Hi @Emo Todorov , i guess it is the part of the leg CD part to the main body AND leg BC part (as you can see on the canvas.png). This is tricky given the fact the robot uses this motion model (see canvas2.png) where the CD part is linked to both main and BC to convert the rotation into a translation. is there any way around?
The joints in MuJoCo define a kinematic tree. If you want to have loop joints, you should add them as equality constraints. So in order to import such a URDF, you have to make it a tree, import, and then add constraints manually to the MJCF.