On equiform Stewart Gough platforms with self-motions

A STEWART GOUGH (SG) manipulator, where the platform is similar to the base, is called equiform SG manipulator. It is well known that these SG manipulators with planar platform and planar base only have selfmotions, if they are architecturally singular; i.e. the anchor points are located on a conic section. Therefore this study focuses on the non-planar case. We prove that an eq uiform SG manipulator has translational self-motions, if and only if it is a so-cal led reflection-congruent one. Moreover we give a necessary geometric property of non-plan ar equiform SG platforms for possessing non-translational self-motions by me ans of bond theory. We close the paper by discussing some non-planar equiform SG platfor ms with non-translational self-motions, where also a set of new examples is presented.