Hi, I'm a grad student in computer engineering and my research involves a fair amout of mechanics (forward/inverse dynamics). I'm working with rigid multibody systems with many DOFs (40 to 50) representing human characters. I've come across this http://grail.cs.washington.edu/projects/charanim/paper0129_final.pdf" [Broken] which provides an interesting solution for the Inverse Dynamics problem (see section 4). However, in the equations, you will notice that the author uses 'mass tensors' (M) instead of inertia tensors and, consequently, transformation matrices (W, in homogenous coordinates) instead of rotation/translation vectors. My problem is that the paper is hardly a thorough reference on the ID approach (it provides an overview) and that I have not yet found any other book or paper that used this notation (based on mass tensors). Has any of you ever come across this approach elsewhere? Can anyone point me to a good reference book on the subject? Thank you all!