Title: Self-Motion of the 3-PPPS Parallel Robot with Delta-Shaped Base,
Abstract: This paper presents the kinematic analysis of the 3-PPPS parallel robot with
an equi-lateral mobile platform and an equilateral-shaped base. Like the other
3-PPPS robots studied in the literature, it is proved that the parallel
singularities depend only on the orientation of the end-effector. The
quaternion parameters are used to represent the singularity surfaces. The study
of the direct kinematic model shows that this robot admits a self-motion of the
Cardanic type. This explains why the direct kinematic model admits an infinite
number of solutions in the center of the workspace at the "home" position but
has never been studied until now.