VIBRATION ELEMENT COUPLED WITH NON-LINEAR FORCE TO IMPROVE NON-RESONANT FREQUENCY RESPONSE

• US 20110048133A1
• Filed: 08/30/2010
• Published: 03/03/2011
• Est. Priority Date: 08/31/2009
• Status: Abandoned Application

• Current Assignee: University of Louisville
• Original Assignee: University of Louisville
• Inventors: Alphenaar, Bruce, Lin, Ji-Tzuoh
• Application Number:
  US12/871,524
• Publication Number:
  US 20110048133A1
• Time in Patent Office: Days
• US Class Current: 73/514.34
• CPC Class Codes: G01P 15/09 by piezoelectric pick-up
• CPC Class Codes: H02K 33/00 Motors with reciprocating, oscillating or vibrating magnet, armature or coil system arrangements for handling mechanical energy structurally associated with motors H02K7/00, e.g. H02K7/06
• CPC Class Codes: H02K 35/00 Generators with reciprocating, oscillating or vibrating coil system, magnet, armature or other part of the magnetic circuit arrangements for handling mechanical energy structurally associated with generators H02K7/00, e.g. H02K7/06
• CPC Class Codes: H02N 2/188 adapted for resonant operation
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

Embodiments of the invention couple a non-linear force to a vibration element such as a piezoelectric cantilever to introduce chaotic, i.e., non-resonant vibration in the vibration element and thereby improve the non-resonant response of the vibration element. By doing so, the vibration element is responsive to a wider frequency range of vibrations and thus may be more efficient in scavenging energy in environments where the vibration frequency is not constant, e.g., in environment subject to multi-mode or random vibration sources.

Claims

1. An apparatus, comprising:

a vibration element having a resonant frequency, wherein the vibration element is coupled to a non-linear force that improves a response of the vibration element to non-resonant vibrations; and

a circuit coupled to the vibration element and configured to output an electrical signal in response to vibration of the vibration element.

2. The apparatus of claim 1, wherein the non-linear force is applied symmetrically and bi-directionally to the vibration element.

3. The apparatus of claim 1, wherein the vibration element is a linear vibration element.

4. The apparatus of claim 1, wherein the vibration element comprises a cantilever.

5. The apparatus of claim 4, wherein the cantilever comprises a piezoelectric cantilever.

6. The apparatus of claim 4, further comprising first and second permanent magnets configured to subject the cantilever to the non-linear force, wherein the first permanent magnet is disposed proximate a free end of the cantilever, and wherein the second permanent magnet is disposed opposite the first permanent magnet generally along an axis of the cantilever and in a repelling orientation relative to the first permanent magnet.

7. The apparatus of claim 6, wherein the first and second permanent magnets have a coupling threshold that is below an acceleration to which the vibration element is subjected by a source of vibration.

8. The apparatus of claim 6, wherein the second permanent magnet is fixed relative to the cantilever.

9. The apparatus of claim 6, wherein the second permanent magnet is disposed proximate a free end of a second cantilever oriented generally along the axis of the first cantilever.

10. The apparatus of claim 1, wherein the circuit includes an energy scavenging circuit.

11. The apparatus of claim 1, wherein the circuit includes a sensing circuit.

12. The apparatus of claim 1, wherein the coupling of the non-linear force to the vibration element does not substantially alter the resonant frequency of the vibration element.

13. The apparatus of claim 1, wherein the coupling of the non-linear force to the vibration element does not substantially increase damping of the vibration element at the resonant frequency.

14. The apparatus of claim 1, wherein the coupling of the non-linear force to the vibration element does not substantially decrease an amplitude of the vibration element at the resonant frequency.

15. The apparatus of claim 1, wherein the non-linear force introduces at least one sub-harmonic component of the resonant frequency.

16. A method of scavenging energy responsive to a source of vibration, the method comprising:

subjecting a vibration element to the source of vibration, wherein the vibration element has a resonant frequency;

exposing the vibration element to a non-linear force while the vibration element is subjected to the source of vibration to improve a response of the vibration element to non-resonant vibrations generated by the source of vibration; and

generating an electrical signal responsive to vibration of the vibration element.

17. The method of claim 16, wherein the non-linear force is applied symmetrically and bi-directionally to the vibration element.

18. The method of claim 16, wherein the vibration element is a linear vibration element.

19. The method of claim 16, wherein the vibration element comprises a cantilever.

20. The method of claim 19, wherein the cantilever comprises a piezoelectric cantilever.

21. The method of claim 19, wherein exposing the vibration element to the non-linear force is performed by first and second permanent magnets, wherein the first permanent magnet is disposed proximate a free end of the cantilever, and wherein the second permanent magnet is disposed opposite the first permanent magnet generally along an axis of the cantilever and in a repelling orientation relative to the first permanent magnet.

22. The method of claim 21, wherein subjecting the vibration element to the source of vibration includes subjecting the vibration element to an acceleration that is greater than a coupling threshold between the first and second permanent magnets.

23. The method of claim 21, wherein the second permanent magnet is fixed relative to the cantilever.

24. The method of claim 21, wherein the second permanent magnet is disposed proximate a free end of a second cantilever oriented generally along the axis of the first cantilever.

25. The method of claim 16, wherein the coupling of the non-linear force to the vibration element does not substantially alter the resonant frequency of the vibration element.

26. The method of claim 16, wherein the coupling of the non-linear force to the vibration element does not substantially increase damping of the vibration element at the resonant frequency.

27. The method of claim 16, wherein the coupling of the non-linear force to the vibration element does not substantially decrease an amplitude of the vibration element at the resonant frequency.

28. The method of claim 16, wherein the non-linear force introduces at least one sub-harmonic component of the resonant frequency.