Persistent Screw Systems of Dimension Four

The subalgebras of the Lie algebra se(3) of the Euclidean group are at the basis of most families of mechanisms with special motion capabilities. Recently, it was shown that, by conveniently composing subalgebra generators, persistent screw systems (PSSs) may be obtained. PSSs are not subalgebras of se(3), but they still exhibit remarkable invariant properties. For this reason, they may play an important role in both mobility analysis and mechanism design. This paper presents all generators of PSSs of dimension 4