Stiffness Matrix Evaluation for a Dual-Reeved Tensile Truss

Researchers have evaluated the stiffness matrix for different robots and structures, including the Stewart platform style tensile truss. However, none of the configurations analyzed to date involve “dual-reeving,” a common industrial rigging technique whereby cables are spatial loops, vs. open-loop elements, such as those represented by simple line segments. The 4-node/4-loop kinematic configuration analyzed contains 4 symmetric nodes and loops and provides competition for a comparable-sized Stewart platform from the perspective of directional stiffness. Additionally, like the Stewart platform, only a modest amount of off-diagonal compliance matrix elements are present, which from a practical and intuitive point of view, can be advantageous. The methodology used and illustrated in detail is easily generalized to adapt to more involved configurations. Numerical results are obtained for a specific example and compared with those from a Stewart platform. Lastly, some experimental results compare favorably with those derived analytically and evaluated numerically.