Author : Kaila Roffman
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (136 download)
Book Synopsis Design of Tensegrity Structures for Shape Changing Applications by : Kaila Roffman
Download or read book Design of Tensegrity Structures for Shape Changing Applications written by Kaila Roffman and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In space applications, lightweight, deployable structures are frequently studied and developed to meet launch vehicle constraints. This is particularly true for very large-scale structures, where the dimensions and volume of launch vehicle fairings can severely limit the in-space scale of structures without deployment. Tensegrity structures are very promising for such applications, offering a high stiffness-to-mass ratio and deployability through actuation of changing member lengths. Tensegrity structures are self-equilibrated, pre-stressed structures. Comprised of struts and cables, tensegrity members are modeled as uniaxial, with struts carrying compression and cables carrying tension, meeting at nodes modeled as frictionless ball joints. A tensegrity form is characterized by sets of nodal coordinates and member force densities (or forces), while a tensegrity configuration refers to how the members are connected between the nodes. Much of the literature on tensegrity structures focuses on the form-finding problem--seeking an equilibrated combination of nodal coordinates and force densities for a particular configuration. A wide variety of approaches to solving the form-finding problem are described in the literature. In general, the form-finding problem is intrinsically formulated to seek only a single equilibrated form for a particular tensegrity configuration. This is sufficient for many static applications of tensegrity structures, where only one form would be necessary. However, tensegrity structures can take on a wide variety of forms for a particular configuration, and little research has been done to-date exploring the variety of shapes a particular configuration can achieve. In shape changing applications, such as deployable structures, understanding the wider variety of shapes a structure can achieve could provide valuable insight as to how these structures can best be used. This dissertation has two main parts. First, analytical and numerical approaches are developed which can be used to describe the range of achievable shapes (forms) a particular tensegrity configuration can achieve. In the analytical approach, a minimal set of design variables describing the shapes is first developed. This minimal set is then restricted, providing bounds on the design variables which limit the resulting shapes to only those which are also equilibrated. For configurations too complex to solve analytically, a numerical approach is developed. This numerical approach can work with any set of design variables and needs only a single known equilibrated shape to begin. This shape is used as a starting point, from which parametric lines (in terms of the design variables) are extended. These lines are used to seek new equilibrium shapes in the span of the design variables. The end result is a representative numerical dataset which approximates the range of achievable shapes a tensegrity structure can achieve. These approaches demonstrate not only that a particular tensegrity configuration can achieve a wide variety of shapes, but also that the extent of these shapes can be characterized. The second part of this dissertation focuses on additional analysis methods which can be used to design a tensegrity structure specifically for shape changing applications. Methods for incorporating member length constraints are developed, including the definition of special design variables. Additionally, a path planning approach is developed that identifies equilibrated shapes through which a tensegrity can move, starting from and ending at designated shapes. Finally, finite element models are developed and used to study the tensegrity's deflections (stiffness) under station-keeping loads, as well as its natural frequencies of vibration. These tools are used in a demonstrative case study, investigating the potential utility of a modular tensegrity structure as a structural backbone of a parabolic reflector on the same scale as the James Webb Space Telescope. The resulting tensegrity structure exhibits structural characteristics comparable to if not better than those of existing parabolic reflectors in space applications. This case study not only shows the utility of the analysis methods developed when selecting a variety of design parameters with a particular application in mind, but also demonstrates that tensegrity structures have great potential for use in deployable, shape changing applications.
