Hi, I'm trying to build a modular robot in MuJoCo 150. I want to attach a module to another module, and each module has a hinge joint. I would like to simply connect two bodies that are regarded as a single rigid body, shown in the attachment. When I tried to use equality constraints(weld and connect) to connect them, the whole robot seemed to become a rigid body and joint of the module are disabled. Is there a good way to do it? Thanks, Jerry