The singularity study of spatial hybrid mechanisms based on screw theory

In this paper, a novel methodology based on screw theory to study the singularity of spatial hybrid mechanisms is presented. According to the physical meaning of inverse screws, we introduce the equivalent kinematic screws to replace the function of those of the parallel limbs, and therefore the hybrid branch can be transformed into a pure series kinematic chain which can facilitate the whole analytical process of the singularity of complex spatial hybrid mechanisms. In fact, this methodology can be widely used to solve the singularity problems of spatial hybrid mechanisms based on the analysis of their kinematic characters.