Stiffness Optimization and Comparison of Tensile Trusses With Constant Envelope and Cable Material

We evaluate and compare the stiffness properties of 6 different configurations of tensile trusses. More specifically, given a constant structural envelope and amount of homogeneous isotropic linear elastic cable material, the stiffness properties of the configurations are analyzed with constant cross-sectional area cables. The configurations include: (1) a Stewart platform, (2) Stewart platform with full spine, 3 cable tie-offs, and slip joint, (3) 6-loop dual-reeved system with partial spine, (4) 4-node/4-loop dual-reeved system, (5) double Stewart platform, and (6) 3D extension of a 2D 2 cable system. In each case, we use analytical results for the evaluation of the stiffness matrix, with some new stiffness matrix results being presented. Of the 6 competing configurations considered, no one configuration was uniformly better than all others, but both the double Stewart platform and the Stewart platform with full spine, 3 cable tie-offs, and slip joint performed quite well, of course given free, massless, rigid body material.