I am wondering how the Denavit-Hartenberg representation is able to describe rototranslations with 6 DOF with only 4 parameters?
Some context: Denavit-Hartenberg representations can be used to describe the rototranslation from frame 1 to frame 2. Frame 2 can be rotated as well as translated. Usually this involves 6 degrees of freedom (DOF).
I am pretty sure that's impossible and that I am missing something else.
EDIT (my current solution): Systems that can be described using DHs only use joints with one joint variable. For example, a prismatic joint which can only move along one axis or a rotational joint which can only rotation around one axis. Then you lose 2 degrees of freedom => 6-2 = 4, thus 4 free variables are sufficient to describe the system.