HINGELESS, LARGE-THROW NEGATIVE STIFFNESS STRUCTURE

• US 20160348752A1
• Filed: 12/09/2014
• Published: 12/01/2016
• Est. Priority Date: 12/09/2014
• Status: Active Grant

• Current Assignee: HRL Laboratories LLC (The Boeing Co.)
• Original Assignee: HRL Laboratories LLC (The Boeing Co.)
• Inventors: Shahan, David W., Churchill, Christopher B., McKnight, Geoffrey P., Herrera, Guillermo A.
• Granted Patent: US 9,897,161 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F16F 15/073 using only leaf springs
• CPC Class Codes: F16F 2228/063 Negative stiffness
• CPC Class Codes: F16F 3/02 with springs made of steel or of other material having low internal friction

Abstract

A negative stiffness structure for vibration isolation, shock mitigation, and/or signal processing includes a flexible tensile member and a curved compressive member. A first end of the tensile member is attached to a first structure. A first end of the curved compressive member is coupled to a first structure and a second end of the curved compressive member is coupled to a second end of the flexible tensile member. A length of the tensile member is greater than a length of the compressive member. A tip of the negative stiffness structure is configured to exhibit a negative stiffness mechanical response to a load applied to the tip. The negative stiffness mechanical response acts in a direction orthogonal to the length of the tensile member.

Claims

1. A negative stiffness structure, comprising:

at least one flexible tensile member having a first end and a second end, the first end coupled to a first structure; and

a first curved compressive member having a first end and a second end, the first end coupled to a second structure, the second end coupled to the second end of the tensile member, wherein

a length of the tensile member is greater than a length of the first curved compressive member, and

a tip of the negative stiffness structure is configured to exhibit a negative stiffness mechanical response to a load applied to the tip, the negative stiffness mechanical response acting in a direction orthogonal to the length of the tensile member.

2. The negative stiffness structure of claim 1, further comprising a second curved compressive member having a first end coupled to the second structure and a second end coupled to the second end of the tensile member.

3. The negative stiffness structure of claim 2, wherein the first curved compressive member is buckled in a first direction, and wherein the second curved compressive member is buckled in a second direction opposite the first direction.

4. The negative stiffness structure of claim 2, wherein the first and second curved compressive members are cosine shaped.

5. The negative stiffness structure of claim 2, further comprising first and second wedge-shaped inserts between the first curved compressive member and the second curved compressive member, the first wedge-shaped insert proximate the first ends of the first and second curved compressive members, and the second wedge-shaped insert proximate the second ends of the first and second curved compressive members.

6. The negative stiffness structure of claim 1, wherein the first structure comprises a pair of curved walls defining a tapered recess, and wherein the first end of the tensile member is received in the tapered recess.

7. The negative stiffness structure of claim 1, further comprising an actuator coupled to the first end of the tensile member, the actuator configured to adjust tension applied to the tensile member or adjust an effective length of the tensile member to vary the mechanical response of the tip.

8. The negative stiffness structure of claim 1, further comprising a clamping actuator coupled to the first end of the tensile member, the clamping actuator configured to clamp the tensile member at a plurality of positions along a length of the tensile member.

9. The negative stiffness structure of claim 1, wherein the second structure comprises a clutching mechanism, the clutching mechanism comprising:

a first clutching member having a convex surface; and

a second clutching member having a concave surface mating with the convex surface of the first clutching member, wherein the second clutching member is configured to slide along the convex surface of the first clutching member between a first angular position and a second angular position.

10. The negative stiffness structure of claim 1, wherein the first curved compressive member has a substantially uniform thickness.

11. The negative stiffness structure of claim 1, wherein the first curved compressive member has a non-uniform thickness.

12. The negative stiffness structure of claim 1, wherein the first curved compressive member comprises a stack of a plurality of curved compressive members.

13. The negative stiffness structure of claim 1, wherein the at least one flexible tensile member comprises a plurality of tensile members.

14. The negative stiffness structure of claim 1, wherein the at least one compressive member is a rectangular beam.

15. The negative stiffness structure of claim 1, wherein the at least one tensile member is selected from the group consisting of a beam, a rope, a cable, a rod, a chain, or a belt.

16. A negative stiffness structure, comprising:

at least one flexible tensile member having a first end and a second end;

an actuator coupled to the first end of the at least one flexible tensile member; and

first and second curved compressive members each having a first end and a second end, the first ends coupled to a structure, the second ends coupled to the second end of the flexible tensile member, wherein

a length of the tensile member is greater than a length of each of the first and second curved compressive members,

the first curved compressive member is curved in a first direction and the second curved compressive member is curved in a second direction opposite the first direction,

a tip of the negative stiffness structure is configured to exhibit a mechanical response when a load is applied to the tip, and

the actuator is configured to vary the mechanical response of the tip.

17. The negative stiffness structure of claim 16, wherein the actuator is a toothed gear.

18. The negative stiffness structure of claim 16, wherein the actuator is a pulley.

19. The negative stiffness structure of claim 16, wherein the actuator is a clamp configured to clamp the tensile member at a plurality of positions along the length of the tensile member.

20. The negative stiffness structure of claim 16, wherein the at least one tensile member is selected from the group consisting of a beam, a rope, a cable, a rod, a chain, or a belt.

21. The negative stiffness structure of claim 16, wherein the negative stiffness structure has a throw of approximately 40% of a length between the first ends and the second ends of the compressive members.