Wideband vibration energy harvester

• US 7,839,058 B1
• Filed: 01/29/2008
• Issued: 11/23/2010
• Est. Priority Date: 01/29/2007
• Status: Expired due to Fees

• Current Assignee: Hottinger Bruel & Kjaer Incorporated
• Original Assignee: MicroStrain, Inc. (Spectris PLC)
• Inventors: Hamel, Michael J., Arms, Steven W., Churchill, David L., Leas, James Marc
• Primary Examiner(s): Benson; Walter
• Assistant Examiner(s): ROSENAU, DEREK JOHN
• Application Number:
  US12/011,702
• Time in Patent Office: 1,029 Days
• Field of Search: 310/311, 310329-332, 310/338, 310/339
• US Class Current: 310/339
• CPC Class Codes: H02N 2/181 Circuits; Control arrangements or methods
• CPC Class Codes: H02N 2/186 Vibration harvesters
• CPC Class Codes: H10N 30/304 Beam type
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

In one embodiment a device comprises a composite structure that includes a piezoelectric flexure and a length-constraining element. The length-constraining element provides the piezoelectric flexure with a bowed shape. The piezoelectric flexure has a first stable bowed position and a second stable bowed position. The length-constraining element is one from the group consisting of a planar sheet and a columnar rod. In another embodiment a device comprises a piezoelectric flexure having a bowl shape. The piezoelectric flexure has a first stable bowl-shaped position and a second stable bowl-shaped position.

Claims

1. A device for harvesting energy from a support structure, comprising a composite structure, wherein said composite structure has a first end region and a second end region, wherein said first end region includes a member for attaching to the support structure and for receiving energy from the support structure while said second end region is unconstrained, wherein said composite structure includes a piezoelectric flexure and a length-constraining element, wherein said piezoelectric flexure has a first piezoelectric flexure end and wherein said length-constraining element has a first length-constraining element end, wherein said first piezoelectric flexure end is located in said first end region and wherein said first length-constraining element end is located in said first end region, wherein said length-constraining element provides said piezoelectric flexure with a bowed shape, wherein said piezoelectric flexure has a first stable bowed position and a second stable bowed position.

2. A device as recited in claim 1, wherein said length-constraining element length is adjustable.

3. A device as recited in claim 1, wherein said composite structure further comprises a plurality of said length-constraining elements.

4. A device as recited in claim 1, wherein said composite structure further comprises a plurality of said piezoelectric flexures.

5. A device as recited in claim 1, wherein said length-constraining elements are positioned to protect said piezoelectric flexure from an overload.

6. A device as recited in claim 1, wherein said piezoelectric flexure includes a piezoelectric patch and a substrate, wherein said piezoelectric patch is mounted on said substrate.

7. A device as recited in claim 6, wherein said substrate includes a first side and a second side, wherein said piezoelectric flexure includes a first piezoelectric patch mounted on said first side and a second piezoelectric patch mounted on said second side.

8. A device as recited in claim 6, wherein said substrate includes at least one from the group consisting of steel, titanium, and a nickel-titanium alloy.

9. A device as recited in claim 6, wherein said composite structure includes a mass.

10. A device as recited in claim 9, wherein said mass is located in said second end region.

11. A device as recited in claim 1, further comprising at least one from the group consisting of a storage device and an energy using element, wherein said storage device is for storing electricity generated by said piezoelectric flexure and wherein said energy using element is for using electricity generated by said piezoelectric flexure.

12. A device as recited in claim 11, wherein said energy using element includes at least one from the group consisting of a light, a sensing node, a wireless communications device and a processor.

13. A device as recited in claim 1, wherein said piezoelectric flexure provides a voltage, further comprising a circuit for reducing voltage provided by said piezoelectric flexure.

14. A device as recited in claim 12, wherein said circuit for reducing voltage includes a voltage dependent switch and an inductor, wherein said voltage dependent switch is connected between said piezoelectric flexure and said inductor, wherein said voltage dependent switch has a first threshold and a second threshold, wherein said second threshold is below said first threshold, wherein said voltage dependent switch remains open until voltage applied across said voltage dependent switch from said energy harvesting device to said inductor reaches said first threshold, wherein when said voltage applied across said voltage dependent switch reaches said first threshold said voltage dependent switch closes so charge from said piezoelectric flexure flows through said voltage dependent switch and through said inductor, wherein when said voltage applied across said voltage dependent switch then falls below said second threshold said voltage dependent switch reopens.

15. A device as recited in claim 14, wherein said voltage dependent switch is a solid state voltage dependent switch.

16. A device as recited in claim 1, wherein said length-constraining element includes a columnar rod wherein said columnar bar has an effective length, wherein said columnar bar includes a threaded end, wherein said threaded end provides for adjusting said effective length.

17. A device as recited in claim 1, wherein said length constraining element has an effective length, wherein said length constraining element further comprises a spring, wherein said spring is positioned to provide for an increase in said effective length when sufficient force is applied to allow movement between said first stable bowed position and said second stable bowed position.

18. A device as recited in claim 17, wherein said composite structure further comprises a mass, wherein said piezoelectric flexure has a central region, wherein said mass is mounted to said central region.

19. A device as recited in claim 1, wherein said piezoelectric flexure includes a substrate, wherein said length constraining element is included in said substrate.

20. A device as recited in claim 19, wherein said substrate has a bowl shape.

21. A device as recited in claim 1, wherein said length constraining element is shorter than said piezoelectric flexure.

22. A device as recited in claim 1, wherein said piezoelectric flexure is under compressive loading.

23. A device as recited in claim 22, further comprising a mechanism for adjusting said compressive loading.

24. A device as recited in claim 1, wherein said length constraining element includes one from the group consisting of a planar sheet and a columnar rod.

25. A device as recited in claim 9, wherein said mass is positioned in a single location along said piezoelectric flexure.

26. A device as recited in claim 9, wherein if sufficient force is provided to said mass said piezoelectric flexure snaps from said first stable bowed position to said second stable bowed position.

27. A device as recited in claim 17, wherein said spring is flat.

28. A device as recited in claim 17, further comprising said support structure, wherein said support structure provides an expected loading, wherein said composite structure has a stiffness to match said expected loading to allow said piezoelectric flexure to move from said first stable bowed position to said second stable bowed position.

29. A device as recited in claim 27, wherein said piezoelectric flexure extends as a single piece from said first end region to said second end region.

30. A device as recited in claim 1, wherein said piezoelectric flexure moves from said first stable bowed position to said second stable bowed position when energy received by said piezoelectric flexure exceeds a threshold.

31. A device as recited in claim 30, wherein said composite structure is adjustable to vary said threshold.

32. A device as recited in claim 1, wherein said piezoelectric flexure includes a vibrating member and wherein said length constraining element is a stop against which said vibrating member strikes when sufficient energy is available.

33. A device as recited in claim 32, further comprising a plurality of said stops.

34. A device as recited in claim 26, further comprising a restoring spring, wherein said restoring spring is positioned so when said piezoelectric flexure snaps toward said second stable bowed position, said restoring spring acts to restore said piezoelectric flexure to said first stable bowed position.

35. A device as recited in claim 34, wherein said restoring spring is positioned so said restoring spring does not apply a force on said piezoelectric flexure until said piezoelectric flexure snaps toward said second stable bowed position.

36. A device as recited in claim 26, wherein said force includes an inertial load.

37. A device as recited in claim 9, wherein said mass is affixed to said piezoelectric flexure.

38. A device as recited in claim 1, wherein if sufficient force is provided to said piezoelectric flexure said piezoelectric flexure snaps from said first stable bowed position to said second stable bowed position.

39. A device as recited in claim 1, further comprising a restoring spring, wherein said restoring spring is positioned so when said piezoelectric flexure snaps toward said second stable bowed position said restoring spring acts to restore said piezoelectric flexure to said first stable bowed position.

40. A device as recited in claim 39, wherein said restoring spring is positioned so said restoring spring does not apply a restoring force on said piezoelectric flexure until said piezoelectric flexure snaps toward said second stable bowed position.