Shape Change Analysis and Design of Cylindrical Tensegrity Booms

Abstract

In space applications, the pursuit of deployable structures with high packaging efficiency and low mass is essential. Tensegrity structures, prestressed networks of struts and cables, offer a promising approach. In this work, a Class-2 cylindrical triplex tensegrity bay is explored for use in booms, where select cables are allowed to change length in order to modify the overall shape of the structure. A novel approach to characterize the range of equilibrated shapes a triplex can achieve is first presented. The results are then used in combination with consideration of bending stiffness, packaging efficiency, and mass to explore the effects of different configuration parameters, namely the ratio of bay height to circumscribing radius (h/r), the member cross-sectional radii, and the number of bays. This design analysis offers new insight into how triplex tensegrity structures can be modified to achieve specific design objectives. Increasing h/r for a single bay increases the range of achievable active tip motion as well as packaging efficiency. Increasing member radii decreases the range of achievable shapes and packaging efficiency while increasing stiffness and mass. When increasing the number of bays for a fixed overall height, a larger number of bays generally increases the range of achievable shapes and mass while reducing stiffness. Packaging efficiency was found to be discontinuous dependent upon the exact number of bays, but generally decreases with increasing number of bays. An example design study is conducted using the Canadarm2 for comparison and illustrates the potential utility of tensegrities for boom structures.