angular momentum is not defined

Discussion in 'Modeling' started by Parijat Dewangan, Oct 12, 2017 at 5:36 AM.

  1. Hey,
    We generated the xml using a urdf file. When we are trying to see the angular momentum being calculated, its coming out as 'nan' for all the bodies. I have attached the xml file with this post. I guess the problem is with the xml design of bodies. Could you please check why is this happening?

    Another unusual thing is, even though we defined 29 bodies, mjmodel->nbody is 30.
     
    Last edited: Oct 12, 2017 at 5:56 AM
  2. Problem resolved. The mistake was that there was a massless frame attached to the end effectors.
     
  3. Emo Todorov

    Emo Todorov Administrator Staff Member

    Indeed, many existing URDF models have dummy bodies with zero mass that make no physical sense. A few years ago the MuJoCo compiler generated errors when it encountered such bodies, but that made it difficult to import URDF models, so this is now allowed (even though it is a bad idea).