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Abstract Ring origami has emerged as a robust strategy for designing foldable and deployable structures due to its impressive packing abilities achieved from the snap-folding mechanism. In general, polygonal rings with rationally designed geometric parameters can fold into compacted three-loop configurations with curved segments, which result from the internal bending moment in the folded state. Inspired by the internal bending moment-induced curvature in the folded state, we explore how this curvature can be tuned by introducing initial natural curvature to the segments of the polygonal rings in their deployed stress-free state, and study how this initial curvature affects their folded configurations. Taking a clue from straight-segmented polygonal rings that fold into overlapping curved loops, we find it is possible to reverse the process by introducing curvature into the ring segments in the stress-free initial state such that the rings fold into a straight-line looped pattern with “zero” area. This realizes extreme packing. In this work, by a combination of experimental observation, finite element analysis, and theoretical modeling, we systematically study the effect of segment curvature on folding behavior, folded configurations, and packing of curved ring origami with different geometries. It is anticipated that curved ring origami can open a new avenue for the design of foldable and deployable structures with simple folded configurations and high packing efficiency.
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Electronically Reconfigurable Virtual Joints by Shape Memory Alloy-Induced Buckling of Curved Sheets
This paper presents the concept of creating virtual joints in soft robotic structures by modifying the local curvature of non-stretchable thin-walled structures through shape memory alloy (SMA)-based surface actuation. A thin planar flexible material can be stiffened by curving it along one axis, which increases stiffness by increasing the effective thickness. Locally deforming the curved sheet by making a flat region reduces this thickness, creating a defect. The material buckles and bends in a controlled manner at that location under an external force, producing a virtual compliant joint. We use tailored wire placement techniques to embed a continuous SMA wire in a serpentine pattern into denim cloth stiffened by a thin plastic film. When curved, joints can be created in this structure by activating small segments of the SMA wire using Joule heating which induces local curvature, with each of these segments able to exert up to 1.6 N of force. Finally, we present a circuit and algorithm for routing current through any desired SMA wire segment(s). Experimental results show that compliant joints can be created anywhere along the structure, resulting in a reconfigurable system.
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- Award ID(s):
- 1935324
- PAR ID:
- 10356460
- Date Published:
- Journal Name:
- Proceedings of IEEE SoutheastCon 2022
- Page Range / eLocation ID:
- 598 to 604
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/SoutheastCon48659.2022.9763962
