A Mirrored Approach to Generate Spatial Deployable Assemblies Using Tripod-Scissor Units

Abstract

A tripod-scissor unit, unlike planar scissor pairs, consists of three rods connected at an intermediate joint thus forming a spatially transformable unit. Geometrically, a tripod-scissor unit is axisymmetric but does not possess reflectional symmetry. This paper proposes a mirrored assembly approach wherein two units are connected symmetrically about the mirroring plane. The assembly approach results in different geometric conditions and motion characteristics. Two types of four-unit deployable blocks were made – one out of straight and the other of angulated members. Design equations were developed to study the influence of member geometry and assembly method on the structure's form and transformation. Digital models helped to validate the analytical results and to simulate the motion of the structures. More sample structures are presented to demonstrate the assembly of multiple units using the mirrored approach. The analysis shows that the mirrored assembly tripod-scissors result in a new generation of mechanisms with different transformation characteristics. Closed polyhedral forms with a high expansion ratio are possible.