Space Frames with Multiple Stable Configurations

Abstract

This paper is concerned with beamlike space frames that include a large number of bistable elements, and exploit the bistability of the elements to obtain structures with multiple stable configurations. By increasing the number of bistable elements, structures with a large number of different configurations can be designed. A particular attraction of this approach is that it produces structures able to maintain their shape without any power being supplied. The first part of this paper focuses on the design and realization of a low-cost snap-through strut, whose two different lengths provide the required bistable feature. A parametric study of the length-change of the strut in relation to the peak force that needs to be applied by the driving actuators is carried out. Bistable struts based on this concept have been made by injection molding nylon. Next, beamlike structures based on different architectures are considered. It is shown that different structural architectures produce structures with workspaces of different size and resolution, when made from an identical number of bistable struts. One particular architecture, with 30 bistable struts and hence over 1 billion different configurations, has been demonstrated.

Bistable Mechanisms for Space Applications

“…They have also been proposed for use in architectural structures [26] as well as in origami-inspired structures and mechanisms [27, 28]. Tape springs have often been used in cube-sats and proposed for other space applications to enable bistability of space structures [29–31]. Bistable composites and laminates have also been developed for active shape control [32–35].…”

Concept and Design of a Multistable Plate Structure

“…This inherent multistability is one of the primary advantages of the proposed structure over alternative concepts for morphing surfaces. Multistability may be achieved by material selection, for example, by exploiting anisotropy [3,4] or by snapthrough behavior [5][6][7]. It is this approach that is adopted here; the proposed solution provides a wider range of alternative configurations than previously proposed surfacelike multistable structures.…”

“…A practical realization of this concept requires a specific bistable element that could actually be incorporated in a multistable plate. The starting point for our search for such an element was a recent study of multiconfiguration space frames [7] in which bistable struts based on the concept of the von Mises snap-through truss were used to form a space frame. The concept that was adopted in this study is shown in Fig.…”

“…This structure consists of three adjacent units forming equilateral triangles with a side length of $100 mm. Each bistable element consists of a pair of cardboard plates forming a snapthrough truss, based on the concept adopted by Schiøler and Pellegrino [7]. All connections between the plates are made with thin sheets of paper.…”

“…[7] in which the members forming the three main longerons are replaced with linear bistable elements. This results in a reconfigurable multistable structure with 2 n discrete stable states, where n is the number of bistable actuators.…”