Geometric design and kinematics of spatial deployable structures using tripod-scissor units

Abstract

Scissor structures made of either straight or angulated members have been successfully used in retractable roofs and other deployable applications. A deployable unit made of three members, namely the tripod-scissor unit (TSU), is assembled for large-scale deployable grid structures. In this paper, deployable structures made of TSUs are developed using a novel assembly method and modified members leading to new forms with better deployability. Parametric design of a four-TSU assembly was done to examine the relationship between its member geometry and the overall form. The resulting structures have counterintuitive motion paths when compared to those using conventional scissor units. Subsequently, the motion characteristics and the torque required for deployment of the structure were calculated using kinematics and inverse dynamics. The results revealed a generation of structures with a high deployment-to-stowage ratio, curling motion trajectory, self-supporting in the deployed state, and stress-free in all intermediate stages. These merits lend themselves well for some useful architecture and aerospace engineering applications discussed herein.