Strain energy shuttle apparatus and method for vibration energy harvesting

• US 20060175937A1
• Filed: 02/01/2006
• Published: 08/10/2006
• Est. Priority Date: 07/30/2003
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Clingman, Dan J., Ruggeri, Robert T.
• Granted Patent: US 7,521,841 B2
• Time in Patent Office: Days
• US Class Current: 310/339
• CPC Class Codes: H02N 2/186 Vibration harvesters
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

An apparatus for use in low frequency vibration energy harvesting (VEH) and with actuators requiring a low deflection force. The apparatus includes a piezo flexure that is loaded with a compressive pre-load force to place the piezo flexure under compression. The piezo flexure may be supported at an intermediate point or at one end thereof. The compressive pre-load force produces flexes the piezo flexure into one or the other of two stable positions, these positions being offset on opposite sides of a longitudinal centerline representing the position of the piezo flexure that would be produced without the compressive pre-load force applied thereto. The compressive pre-load effectively provides a negative spring constant which “softens” the piezo flexure and enhances a responsiveness of the piezo flexure to low frequency vibration energy. The piezo flexure also operates over a much wider frequency bandwidth than conventional systems incorporating a tip mass.

Claims

17. An energy harvesting apparatus comprising:

a support substrate;

a piezoelectric wafer secured to a surface of said support substrate;

a base for supporting said support substrate in a manner to enable oscillating motion of said support substrate and said piezoelectric wafer; and

a biasing element operatively associated with opposite longitudinal ends of said support substrate for supplying a mechanical compressive pre-load force to said piezoelectric wafer, sufficient to deflect said wafer into one of two flexed orientations in the absence of vibration energy, to thus soften said piezoelectric wafer to facilitate oscillating motion of said wafer in response to vibration experienced by said base.

1. A vibration energy harvesting apparatus, comprising:

a piezoelectric wafer;

a support for supporting said piezoelectric wafer and allowing oscillating motion of said piezoelectric wafer; and

a biasing element operatively associated with said support and said piezoelectric wafer for applying a compressive pre-load force to said piezoelectric wafer sufficient to deflect said wafer from a linear orientation into one of two stable non-linear orientations, to assist in initiating oscillating movement of said piezoelectric wafer in response to vibration energy experienced by said support, between said two stable positions.

2. The apparatus of claim 1, wherein said support comprises:

a flexible substrate on which said piezoelectric wafer is secured; and

a base secured to said flexible substrate.

3. The apparatus of claim 1, wherein said support comprises:

a flexible substrate on which said piezoelectric wafer is secured;

a base for supporting said substrate;

a pair of link arms secured to opposite ends of said flexible substrate; and

wherein the biasing element is coupled at opposite ends thereof to the link arms to place the piezoelectric wafer under compression such that the flexible substrate has two stable flexed conditions.

4. The apparatus of claim 3, wherein:

at least one of said link arms includes a first pair of spaced apart retaining pins; and

a first coupling flexure having a first end and a second end, said first end being retained by said first pair of retaining pins and said second end being coupled to one end of said biasing member.

5. The apparatus of claim 4, wherein a second one of said pair of link arms includes a second pair of spaced apart retaining pins;

and

wherein said apparatus further includes a second coupling flexure having a first end and a second end, said first end of said second coupling flexure being coupled to said second link arm and said second end of said second coupling flexure being coupled to an end of said biasing element opposite said one end.

6. The apparatus of claim 1, wherein said support supports said piezoelectric wafer from an intermediate point along a length thereof.

7. The apparatus of claim 1, wherein said support supports said piezoelectric wafer at an approximate midpoint thereof.

8. The apparatus of claim 1, wherein a pair of said biasing elements are operatively associated with said support and said piezoelectric wafer and extend parallel to said piezoelectric wafer and within a common longitudinal plane within which said piezoelectric wafer resides.

9. The apparatus of claim 1, further including:

a cantilever beam supported for pivoting motion at one end thereof from said support; and

wherein said cantilever beam has a free end coupled to one end of said biasing element.

10. The apparatus of claim 9, further comprising a flexure element disposed between said free end of said cantilever beam and said piezoelectric wafer.

11. The apparatus of claim 1, wherein:

said support comprises a flexible substrate on which said piezoelectric wafer is secured;

a base for supporting said flexible substrate at one end thereof to enable oscillating pivotal motion of said piezoelectric wafer relative to said base.

12. The apparatus of claim 1, further comprising a pair of said piezoelectric wafers mounted on opposing surfaces of said support.

13. The apparatus of claim 1, wherein:

said support comprises a flexible substrate on which said piezoelectric wafer is secured, and a base for supporting a first end of said flexible substrate to enable oscillating pivotal movement of said piezoelectric wafer about said first end; and

wherein said biasing element is operatively coupled between a second end of said flexible substrate and said base.

14. The apparatus of claim 13, further comprising a cantilever beam disposed in between said base and biasing member, said cantilever beam being pivotally coupled at a first end to said base.

15. The apparatus of claim 14, further comprising a flexure member disposed in between a second end of said cantilever beam and said biasing element.

16. The apparatus of claim 14, wherein said biasing element comprises a coil spring.

18. The apparatus of claim 17, wherein said base comprises a frame having a boss portion for supporting said support substrate from an approximate midpoint thereof.

19. The apparatus of claim 17, further comprising a pair of link arms coupled to opposite longitudinal ends of said support substrate;

and

wherein said biasing element is coupled between said link arms.

20. The apparatus of claim 17, further comprising a pair of said piezoelectric wafers secured to opposing surfaces of said support substrate.

21. The apparatus of claim 19, wherein a pair of said biasing elements are disposed parallel to said support substrate and each coupled at opposite ends thereof to portions of said link arms.

22. The apparatus of claim 17, wherein said biasing element comprises a coil spring.

23. The apparatus of claim 17, further comprising a cantilever beam disposed in between a first end of said support substrate and said base.

24. The apparatus of claim 17, wherein said support substrate is supported at a first longitudinal end by said base for oscillating motion relative to said base.

25. The apparatus of claim 24, wherein said biasing element is operatively coupled to said base and to a second longitudinal end of said support substrate to thus place said biasing element generally longitudinally in line with said support substrate when said piezoelectric wafer is at rest.

26. The apparatus of claim 17, further comprising a flexure element disposed in between said biasing element and said support substrate.

22-1. The apparatus of claim 17, wherein said piezoelectric wafer comprises a piezoelectric ceramic wafer.

27. A method for vibration energy harvesting, comprising:

disposing a piezoelectric wafer on a support substrate;

supporting said support substrate to enable oscillating motion of said support substrate;

applying a compressive stress to said support substrate that is sufficient to deflect said piezoelectric wafer from a central, non-flexed position, into one of two flexed positions, said compressive stress operating to soften said piezoelectric wafer to enhance a response of said wafer to vibration energy.

28. The method of claim 27, further comprising securing said support surface in a manner to enable oscillating motion of opposite longitudinal ends of said piezoelectric wafer.

29. The method of claim 27, further comprising supporting said support surface in a manner to enable oscillating motion of one longitudinal end of said piezoelectric wafer.

30. The method of claim 27, wherein applying a compressive stress comprises using a biasing element operatively coupled to said piezoelectric wafer to apply said compressive stress.

31. A method for forming an actuator using a piezoelectric wafer, comprising:

supporting the piezoelectric wafer on a support substrate to enable motion of said piezoelectric wafer; and

placing said support substrate and said piezoelectric wafer under a compressive pre-load stress sufficient to hold said piezoelectric wafer in a flexed, non-linear configuration, said compressive pre-load operating to soften said wafer and enhance a sensitivity of wafer.

32. The method of claim 31, wherein placing said piezoelectric wafer under a compressive pre-load stress comprises using a biasing element to generate said compressive pre-load stress.

33. The method of claim 31, further comprising supporting said support substrate to enable motion of opposite longitudinal ends of said piezoelectric wafer.

34. The method of claim 31, further comprising supporting said support substrate to enable motion of one longitudinal end of said piezoelectric wafer(s).