Shape-morphing space frame apparatus using unit cell bistable elements

Patent metadata

Field	Value
Publication number	US-9783977-B2
Application number	US-201615197203-A
Country	US
Kind code	B2
Filing date	Jun 29, 2016
Priority date	Nov 20, 2015
Publication date	Oct 10, 2017
Grant date	Oct 10, 2017

Abstract

Unit cell bistable elements, and particular arrangements thereof, that can transform or morph a structure from one shape to another. In certain embodiments, the current invention includes unit cell bistable elements, and particular arrangements and uses thereof, that can transform or morph a structure from one shape to another. In an embodiment, the current invention provides a method/ability to transform any four-bar compliant mechanism into a bistable compliant mechanism. It is an object of the current invention to facilitate structures morphing from one specific shape to another specific shape using unit cell bistable elements.

First claim

What is claimed is:

1. A shape-morphing space frame apparatus using unit cell bistable elements, comprising:
a first structural framework formed of a plurality of nodes and a plurality of links, including at least one bistable link,
said first structural framework having a first stable position and a second stable position, said first structural framework further having a first quadrilateral-shaped constraint in said first stable position and a second quadrilateral constraint in said second stable position, said first quadrilateral-shaped constraint being different from said second quadrilateral-shaped constraint for said first structural framework,
said first structural framework having a first end and a second end;
a first plurality of second structural frameworks each formed of a plurality of nodes and a plurality of links, including at least one bistable link,
said each second structural framework of said first plurality of second structural frameworks having a first stable position and a second stable position, said each second structural framework further having a first quadrilateral-shaped constraint in said first stable position and a second quadrilateral constraint in said second stable position, said first quadrilateral-shaped constraint being different from said second quadrilateral-shaped constraint for said each second structural framework of said first plurality of second structural frameworks,
wherein said first plurality of second structural frameworks are adjacent to each other, are straight in said first stable position, and are curved in said second stable position,
said first plurality of second structural frameworks collectively having a first end and a second end;
a second plurality of second structural frameworks each formed of a plurality of nodes and a plurality of links, including at least one bistable link,
said each second structural framework of said second plurality of second structural frameworks having a first stable position and a second stable position, said each second structural framework further having a first quadrilateral-shaped constraint in said first stable position and a second quadrilateral constraint in said second stable position, said first quadrilateral-shaped constraint being different from said second quadrilateral-shaped constraint for said each second structural framework of said second plurality of second structural frameworks,
wherein said second plurality of second structural frameworks are adjacent to each other, are straight in said first stable position, and are curved in said second stable position,
said second plurality of second structural frameworks collectively having a first end and a second end,
said first end of said first plurality of second structural frameworks coupled to said first end of said first structural framework, said first end of said second plurality of second structural frameworks coupled to said second end of said first structural framework, and said second end of said first plurality of second structural frameworks coupled to said second end of said second plurality of second structural frameworks,
such that said apparatus is a straight triangular prism in a first stable position and is a curved triangular prism in a second stable position, wherein a bistability of said apparatus is achieved by said at least one bistable link in each framework of said first structural framework, said each second structural framework of said first plurality of structural frameworks, and said each second structural framework of said second plurality of structural frameworks.

2. A shape-morphing space frame as in claim 1 , wherein said first quadrilateral-shaped constraint of said each second structural framework of said first and second pluralities of second structural frameworks is a square-shaped constraint, and wherein said first quadrilateral-shaped constraint of said first structural framework is a rectangular constraint.

3. A shape-morphing space frame apparatus as in claim 2 , wherein said second quadrilateral-shaped constraint of said each framework is a trapezoidal constraint.

4. A shape-morphing space frame apparatus as in claim 1 , further comprising:
a single rigid link positioned between two nodes if a relative displacement between said two nodes is zero, and
two or more rigid links positioned between said two nodes if said relative displacement between said two nodes is collinear, wherein a node disposed between said two or more rigid links is a revolute joint.

5. A shape-morphing space frame apparatus as in claim 1 , wherein said plurality of links in said each framework remain in a single plane, such that none of said plurality of links interfere with each other within said each framework.

6. A shape-morphing space frame apparatus as in claim 1 , wherein a first stable position of said apparatus is a disk and a second stable position of said apparatus is a hemisphere.

7. A shape-morphing space frame apparatus as in claim 6 , wherein:
radial lines on a surface of said disk bend but do not stretch, said radial lines becoming longitude lines on said hemisphere, and
circumferential lines on said surface of said disk compress, said circumferential lines becoming latitude lines on said hemisphere.

8. A shape-morphing space frame apparatus as in claim 7 , wherein transition between said first stable position and said second stable position is accomplished by applying an inward radial force on said first and second pluralities of second structural frameworks.

9. A shape-morphing space frame apparatus as in claim 6 , wherein:
said disk is formed of at least three (3) sectors, such that said at least three (3) sectors are connected together in a circular pattern as one layer to form said disk that can morph into said hemisphere, and
said plurality of links does not include any curved links.

10. A shape-morphing space frame apparatus as in claim 1 , wherein a first stable position of said apparatus is a two-layered disk and a second stable position of said apparatus is a sphere, wherein said two-layered disk is formed of an upper layer that forms an upper hemisphere and a lower layer that forms a lower hemisphere.

11. A shape-morphing space frame apparatus as in claim 10 , wherein said upper layer is formed of an odd number of evenly-spaced sectors with a gap formed between each sector, said lower layer is formed of an equal number of evenly-spaced sectors with a gap formed between each sector, and said sectors of upper and lower layers are configured to window each other's gaps in said two-layered disk.

12. A shape-morphing space frame apparatus as in claim 11 , wherein said upper layer and lower layer are connected using the sectors' vertices located mid-plane, the apparatus further comprising a flange disposed at each vertex with an aperture disposed therein to function as a hinge between said upper layer and said lower layer.

13. A shape-morphing space frame apparatus as in claim 12 , wherein no curved links are used in said apparatus.

14. A shape-morphing space frame apparatus as in claim 13 , wherein said sphere is approximated as a polyhedron.

15. A shape-morphing space frame apparatus as in claim 1 , wherein bistability of said apparatus is achieved without use of a hard stop.

16. A method of fabricating predictable and controllable length or shape changes in a bistable, shape-morphing mechanism, allowing the morphing from an initial specific shape into a resulting specific shape that is different from said initial specific shape, without use of a hard stop, said method comprising:
identifying said initial sp

Assignees

• Alqasimi Ahmad
• Lusk Craig
• Univ South Florida

Inventors

• Alqasimi Ahmad
• Lusk Craig

Classifications

• E04B1/3441 Primary

  with articulated bar-shaped elements · CPC title

• E04B2001/1957

  Details of connections between nodes and struts · CPC title

• E04B1/1903

  Connecting nodes specially adapted therefor · CPC title

• E04B1/34384

  Assembling details for foldable, separable, collapsible or retractable structures · CPC title

• F16S3/08 Primary

  forming frameworks, e.g. gratings · CPC title