Foldable/Deployable Spherical Mechanisms Based on Regular Polygons

The possibility of satisfying special geometric conditions, either through their architecture or through their configuration, makes a mechanism acquire changeable motion characteristics (kinematotropic or metamorphic behavior, multi-mode operation capability, etc.) that are of interest. Aligning revolute (R)-pair axes is one of such special conditions. In spherical linkages, only R-pairs, whose axes share a common intersection (spherical motion center (SMC)), are present. Investigating how R-pair axes can become collinear in a spherical mechanism leads to the identification of those that exhibit changeable motion features. This approach is adopted here to select non-redundant spherical mechanisms coming from regular polygons that are foldable/deployable and have a wide enough workspace for performing motion tasks. This analysis shows that the ones with hexagonal architecture prevail over the others. These results are exploitable in many contexts related to field robotics (aerospace, machines for construction sites, deployable antennas, etc.)