Displacement Varieties for Some PUP Linkages

In this work sub-varieties of the Study quadric of rigid-body displacements are investigated. The particular sub-varieties considered are the possible displacements which can be performed by the end-effector of certain PUP linkages. In general these varieties are linear projections of a 4-dimensional Segre variety in 15-dimensional projective space. The different linkages correspond to projections with different centres. For one particular linkage the intersection of three such sub-varieties is studied, this intersection corresponds to the assembly configurations of a parallel robot with 3 such PUP legs.