Abstract:
The present invention is an energy harvester having a mechanical natural frequency that can be mechanically tuned to the natural frequency of the vibrating environment without having to add or subtract mass to seismic/proof mass, change the mass of the mechanical spring or change the physical dimensions of the mechanical spring of the energy harvester. In another embodiment, the electromagnetic natural frequency of the energy harvester is electronically tuned by adding a tuning circuit comprising a variable dissipative element without changing the mechanical natural resonant frequencies of the energy harvester.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. patent application Ser. No. 14/199,916 filed on Mar. 6, 2014, now pending, which claims priority to U.S. Provisional Application Ser. No. 61/937,330 filed on Feb. 7, 2014, now pending, both of which applications are hereby incorporated into this specification by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Most vibration energy harvesters are resonant type and suffer from narrow frequency response, which limits them to operate at a specific frequency that may not match an ambient energy source. The natural frequency of an energy harvester is an intrinsic property of the harvester where absorbed energy is amplified in the form of resonance A composition of at least a moving mass (also called a proof or a seismic mass), m, and a spring, K, together create resonance either as the harvester&#39;s own natural frequency or as coupled natural frequency of the vibration source. Natural frequency changes when either mass or stiffness of the device is changed. For energy harvesters to have their absorbed energy amplified at other frequencies, tuning of their natural frequencies has been widely proposed. To the proof mass, an extra mass can be added to change the natural resonant frequency at which energy is harvested. The extra mass added must correspond to the needed mass for attaining the desired new natural resonant frequency. For most devices, addition or subtraction of mass is inconvenient for users as it cannot be done when a conventional energy harvester is factory packaged. However, tuning by mass is the industrial state-of-the-art, as used by Midé Technology Corporation for its piezoelectric cantilever beam based harvesters. Tuning by stiffness at commercial level is uncommon but there were laboratory investigations based on cantilever beams, which are objects of entwined stiffness and mass, such that a physical change in mass of the beam, e.g. coating with thin film, is a change in stiffness due to a change in one or more of the beam&#39;s physical dimensions, and vice-versa. Pre-loading, pre-deflection, centrifugal force, magnetic force, gravity center of the tip mass, and actuating piezoelectric transducer are methods that were explored to adjust stiffness of the non-commercial laboratory cantilever beam based harvesters (L. Tang, Y. Yang, C. K. Soh, in Advances in Energy Harvesting Methods, eds. N. Elvin and A. Erturk, Springer Science and Business Media New York 2013). Stiffness change in these methods is predominantly due to a change in Young&#39;s modulus as applied stress and beam strain vary. The demonstrated tunability, or, for all the methods is less than 100%, with only ca. 24% of the methods achieving tunability above 50%. An alternative to cantilever beam is mechanical spring that is not entwined with mass, such as helical or plate spring, to which a proof mass is then suspended. In this case, change of stiffness is achieved by changing original physical dimensions (length, width or thickness) of the spring, which could directly mean mechanical extension, contraction, changing of its mass, or use of another mechanical spring that matches the required new resonant frequency. Magnetic and gravitational springs are other kinds of springs that are not naturally entwined with mass, as with the case cantilever beams, and can be used directly for resonant frequency tuning where their stiffness is varied by their variable forces due to varying separations between their sources. 
         [0003]    Harvesting electromagnetic energy (electromagnetic radiations at least within radio frequency spectrum (RF) range of &lt;3 Hz (tremendously low frequency, TLF) to 300 GHz (tremendously high frequency, THF)) simultaneously with mechanical or kinetic energy is uncommon. Consequently, the ways to couple and tune resulting resonant frequency due to the synchronized electromagnetic energy harvesting are not known. RF electromagnetic radiations have both an electric and a magnetic component, and electromagnetic field is always produced by conductors when they transport electric current and. An energy harvester with its own magnetic field, as the device in the present invention, can couple by mutual attractive/repulsive interaction, or. mutual inductance, to any electromagnetic field in its environment, such as magnetic field of an AC power cord, power transmission lines, unshielded electronic instruments, broadcasting towers, radars, operating machineries, auroras, etc. This coupling between the harvester and electromagnetic source takes place when their magnetic field lines cross into each other, and occurrence of any resonance is a function of the harvester structural arrangements, electromagnetic radiation source, transducer of the harvester, and electrical power delivering circuitry associated with the harvester. As with mechanical tuning of natural resonant frequency by stiffness, tuning of the electromagnetic resonant frequency brings along the benefit of augmenting harvested vibration energy. 
       SUMMARY OF THE INVENTION 
       [0004]    One object of the present invention is to provide a method for mechanically tuning the natural frequency response of an energy harvesting device to match the frequency of an energy source, for example ambient vibration without addition or subtraction of mass, replacement of mechanical spring or change in physical dimensions of mechanical spring by stretching (e.g. length), contraction (e.g. length) and coating (e.g. thickness). 
         [0005]    Another object of the present invention was to develop a method for electronically tuning coupled electromagnetic natural resonant frequency of an energy harvester without changing the mechanical resonant frequency of the energy harvester. 
         [0006]    The present invention is a device and method for harvesting energy from a vibrating environment having a natural frequency. In one embodiment, the device comprises a first housing, left and right sidewalls engaged with the first housing by first and second fasteners, a mechanical spring engaged with the left and right sidewalls; a first magnet engaged with the mechanical spring; and a composite structure comprising a fixed magnet and a piezoelectric material. The first magnet and the fixed magnet apply a force upon the piezoelectric material when the mechanical spring is in a static state to produce a base voltage. Adjustment of the first fastener to a first position and excitation of the mechanical spring by the vibrating environment causes the piezoelectric material to generate a first alternating voltage output comprising a first peak voltage at a first frequency greater than the base voltage. The first frequency is different from the natural frequency of the vibrating environment. Adjustment of the first fastener to a second position and excitation of the mechanical spring by the vibrating environment causes the piezoelectric material to generate a second alternating voltage output comprising a second peak voltage at a second frequency greater than the base voltage. The second frequency being closer to the natural frequency of the vibrational environment than the first frequency. The energy harvester allows a person to tune the mechanical natural frequency by tightening or loosening of the first fastener without any need for adding/subtraction of mass or changing the physical dimensions of the mechanical spring. The energy harvester may further comprise an electromagnetic resonant frequency tuning circuit connected with the piezoelectric material. The electromagnetic resonant frequency tuning circuit comprises a variable dissipative element, which can be in the form of a variable electronic resistor. The electromagnetic resonant frequency tuning circuit allows electronic tuning of the electromagnetic resonant frequency of the energy harvester without changing the mechanical resonant natural frequencies of the energy harvester. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The following description of the invention will be further understood with reference to the accompanying drawings, in which: 
           [0008]      FIG. 1  is a perspective view of an energy harvesting device according to the present invention; 
           [0009]      FIG. 2  is an exploded view of the device; 
           [0010]      FIG. 3  is a cross section view of the device taken along line  3 - 3  of  FIG. 2 ; 
           [0011]      FIG. 4  is a top view of a first housing according to the present invention; 
           [0012]      FIG. 5  is a left side view of the first housing; 
           [0013]      FIG. 6  is a right side view of the first housing; 
           [0014]      FIG. 7  is a top view of a second housing according to the present invention; 
           [0015]      FIG. 8  is a left side view of the second housing; 
           [0016]      FIG. 9  is a right side view of the second housing; 
           [0017]      FIG. 10  is a top view of a left sidewall according to the present invention; 
           [0018]      FIG. 11  is a side view of the left sidewall housing; 
           [0019]      FIG. 12  is a top view of a right sidewall according to the present invention; 
           [0020]      FIG. 13  is a side view of the right sidewall housing; 
           [0021]      FIG. 14  is a perspective view of a grid according to the present invention; 
           [0022]      FIG. 15  is a top view of the grid; 
           [0023]      FIG. 16  is a cross-section view of the grid taken along line  16 - 16  of  FIG. 15 ; 
           [0024]      FIG. 17  is a top view of a composite structure according to the present invention having a magnet attached to a piezoelectric material; 
           [0025]      FIG. 18  is a front view of the composite structure; 
           [0026]      FIG. 19  is a top view of a grid according to the present invention having nine (9) cavities and a composite structure disposed in each cavity of the grid; 
           [0027]      FIG. 20  is a cross section view taken along line  19 - 19  of  FIG. 19 ; 
           [0028]      FIG. 21  is a perspective view of a first mechanical spring according to the present invention; 
           [0029]      FIG. 22  is a top view of the first mechanical spring; 
           [0030]      FIG. 23  is a side view of the first mechanical spring; 
           [0031]      FIG. 24  is a perspective view of an assembly of the first mechanical spring and a first magnet according to the present invention; 
           [0032]      FIG. 25  is a perspective view of an assembly of the first mechanical spring and first and second magnets according to the present invention; 
           [0033]      FIG. 26  is a cross section view of the device showing static magnetic energy available for electromagnetic transduction; 
           [0034]      FIG. 27  is an example of real-time data from a data logger demonstrating the harvesting of energy by the device within bandwidth of 50 Hz across a frequency range up to 50 Hz from a random noise base input from a vibration shaker and the linear behavior of the device at such frequencies; 
           [0035]      FIG. 28  is an enlarged view of the wave form of  FIG. 27  demonstrating harvesting of energy by the device within wider bandwidths at frequencies above 50 Hz and the non-linear behavior of the device at such frequencies; 
           [0036]      FIG. 29  is a perspective view of the device having a one-piece housing; 
           [0037]      FIG. 30  is a perspective view of the device having a two-piece housing; 
           [0038]      FIG. 31  is an exploded view of the device having a two-piece housing; 
           [0039]      FIG. 32  is a perspective exploded view of a conductor panel assembly according to the present invention removably mounted to an open side of the device for harvesting energy from electromagnetic transduction to provide a second and independent source of harnessed energy; 
           [0040]      FIG. 33  is a front view of the conductor panel assembly; 
           [0041]      FIG. 34  is a rear view of the conductor panel assembly, 
           [0042]      FIG. 35  is a front view of a frame of the conductor panel assembly, 
           [0043]      FIG. 36  is a side view of the frame; 
           [0044]      FIG. 37  is a rear view of the frame; 
           [0045]      FIG. 38  is a cross section view of the frame taken along line  38 - 38  of  FIG. 35 ; 
           [0046]      FIG. 39  is a cross-section view of the frame taken along line  39 - 39  of  FIG. 35 ; 
           [0047]      FIG. 40  is a perspective view of the energy harvester device as shown in  FIG. 1  with one or more screws that allow tuning of the mechanical resonant frequency of the energy harvester device by tightening or loosening of the screw(s); 
           [0048]      FIG. 41  is a frequency response data plot showing adjustment or tuning of the mechanical resonant frequency of the energy harvester device after tightening or loosening of one screw; 
           [0049]      FIG. 42  is a block diagram showing an energy harvester device connected to a charge to voltage converter by an electromagnetic resonant frequency tuning circuit; 
           [0050]      FIG. 43  is a block diagram showing the electromagnetic resonant frequency tuning circuit comprising a variable dissipative resistor; 
           [0051]      FIG. 44  is a frequency response data plot showing adjustment or tuning of the electromagnetic (EM) resonant frequency of the energy harvester device using the electromagnetic resonant frequency tuning circuit in the form of a variable resistor; and 
           [0052]      FIG. 45  is a frequency response data plot showing adjustment or tuning of the electromagnetic (EM) resonant frequency of the energy harvester device using the electromagnetic resonant frequency tuning circuit in the form of a variable resistor. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0053]    Referring to  FIG. 1 , where an energy harvesting device  10  according to the present invention is shown. Device  10  collects energy from movements, noise, sound, and stray electromagnetic signals and generates electricity. Movements can be generated from many sources such as transportation systems (for example, cars, trains, bicycles, and airplanes); infrastructures (for example, buildings, bridges, tunnels, and airports); anatomical (for example, human, animals, and plants); and machinery (for example, industrial plants, vacuum pumps, milling machines, and heavy duty vehicles). Noises can be of thermal, electromagnetic perturbations, colored noise, and white noise. Device  10  captures energy sources in the form of sinusoid, random noise, impulse and their different combinations. In the embodiment shown, device  10  has an overall length of 31 mm, a width of 24 mm, and a height of 24 mm. Unlike conventional energy harvesting devices, device  10  captures energy from movements, noise, sound, and stray electromagnetic signals and generates an alternating voltage output having wide bandwidths across an extended range of frequencies allowing more usable and flexible energy extraction in many different types of environments and/or applications. 
         [0054]    Referring to  FIGS. 2 and 3 , device  10  generally comprises a first housing  12 , a second housing  32 , and a left side wall  52  engaged with first and second housings  12  and  32  by fasteners such as bolts  190 ,  192 ,  194 , and  196 , and a right side wall  66  engaged with first and second housings  12  and  32  by fasteners such as bolts  198 ,  200 ,  202 , and  204 . Device  10  further comprises a first mechanical spring  80  engaged with left and right sidewalls  52  and  66 . Device  10  further comprises a second mechanical spring  82  engaged with left and right sidewalls  52  and  66 . Device  10  further comprises a first magnet  108  engaged with first mechanical spring  80  and a second magnet  110  engaged with second mechanical spring  82 . Device  10  further comprises first and second grids  112  and  114  freely engaged with first and second housings  12  and  32 , respectively. Device  10  further comprises composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  securely disposed within cavities (to be described) of first and/or second grids  112  and  114 . Device  10  further comprises one or more pieces of a non-conductive tape  188  applied to and substantially covering the entire inner face of first housing  12  so that first grid  112  may freely move within a cavity  16  (to be described) of first housing  12 . Similarly, device  10  further comprises a second piece of non-conductive tape  189  applied to and substantially covering the inner face of second housing  32  so that second grid  114  may freely move within a cavity  36  (to be described) of second housing  32 . Wires  182  and  184  of composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  pass thru openings  30  and  50 , of first and second housings  12 , and  32 , respectively. 
         [0055]    In the static state, first magnet  108  and fixed magnets  186  (to be described) of composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  embedded within first housing  12  repel each other applying a force upon piezoelectric blocks  180  (to be described) of composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178 , producing an alternating base voltage across wires  182  and  184  of piezoelectric blocks  180 . Similarly, second magnet  110  and fixed magnets  186  (to be described) of composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176  embedded with second housing  32  repel each other applying a force upon piezoelectric blocks  180  (to be described) of composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178 , producing an alternating base voltage across wires  182  and  184  of piezoelectric blocks  180 . Excitation of first spring  80  causes oscillation of first magnet  108  to and from the fixed magnets of composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  embedded within first housing  12  creating an alternating high voltage across wires  182  and  184  of piezoelectric blocks  180  of composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  within wide bandwidths. Similarly, excitation of second spring  82  causes oscillation of second magnet  110  to and from the fixed magnets  186  of composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  embedded within second housing  32  creating an alternating high voltage across wires  182  and  184  of a piezoelectric blocks  180  of composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  within wide bandwidths. Unlike conventional energy harvesting devices, device  10  produces a high output voltage over wide bandwidths thereby making its dramatically easier to extract energy from device  10  using presently and/or future developed conventional circuit designs. Further, unlike conventional energy harvesting devices, within frequencies greater than 50 Hz, device  10  has unexpected results, namely, non-linear characteristics between different configurations of device  10  thereby allowing each configuration to provide a different voltage level and energy to be exacted from device  10 . 
         [0056]    Referring to  FIGS. 4-6 , first housing  12  comprises a base  13  having inside and outside surfaces  14  and  15 , an end portion  18 , and an end portion  20 . First housing  12  further comprises threaded holes  22  and  24  formed at end portion  18 . First housing  12  further comprises threaded holes  26  and  28  formed at end portion  20 . First housing  12  further comprises a cavity  16  disposed within base  14  having a floor  17 . In the embodiment shown, cavity  16  has a width of 20 mm, a length of 20 mm, and a depth of 5 mm. As will be described more fully herein, first grid  112  can freely move within cavity  16  in all directions to add vibrational energy to device  10  for harvesting. First housing  12  further comprises an opening  30  disposed in floor  17  of cavity  16 . As will be described more fully herein, opening  30  is provided so that wires  182  and  184  (to be described) from composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  of first grid  112  can pass outside of device  10  for connection to external circuitry to extract the energy from device  10 . In the embodiment shown, first housing  12  is made from a highly conductive material such as copper, stainless steel, or graphene. First housing  12  may be fabricated by conventional machining processes. 
         [0057]    Referring to  FIGS. 7-9 , second housing  32  is identical to first housing  12 . Second housing  32  comprises a base  33  having inside and outside surfaces  34  and  35 , an end portion  38 , and an end portion  40 . Second housing  32  further comprises threaded holes  42  and  44  formed at end portion  38 . Second housing  32  further comprises threaded holes  46  and  48  formed at end portion  40 . Second housing  32  further comprises a cavity  36  disposed within base  34  having a floor  37 . In the embodiment shown, cavity  36  has a width of 20 mm, a length of 20 mm, and a depth of 5 mm. As will be described more fully herein, second grid  114  can freely move within cavity  36  in all directions to add vibrational energy to device  10  for harvesting. Second housing  32  further comprises a central opening  50  disposed in floor  37  of cavity  36 . As will be described more fully herein, opening  50  is provided so that wires  182  and  184  from composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  of second grid  114  can pass outside of device  10  for connection with external circuitry to extract the energy from device  10 . In the embodiment shown, second housing  32  is made from a highly conductive material such as copper, stainless steel, or graphene. Second housing  32  may be fabricated by conventional machining processes. 
         [0058]    Referring to  FIGS. 10-11 , left side wall  52  comprises an end portion  54  and an end portion  56 . Left side wall  52  further comprises a lower boss  58  extending from end portion  54  to end portion  56 . Left side wall  52  further comprises an upper boss  60  extending from end portion  54  to end portion  56 . Left side wall  52  further comprises a lower channel or slot  62  formed in lower boss  58  extending from end portion  54  to end portion  56 . Left side wall  52  further comprises an upper channel or slot  64  formed in upper boss  60  extending from end portion  54  to end portion  56 . As will be described more fully herein, lower slot  62  is adapted to removably engage and receive first mechanical spring  80 . Similarly, upper slot  64  is adapted to removably engage and receive second mechanical spring  82 . Left side wall  52  further comprises threaded holes  53  and  55  disposed at end portion  54  to receive bolts  190  and  192 . Left side wall  52  further threaded holes  57  and  59  disposed at end portion  56  to receive bolts  194  and  196 . In the embodiment shown, left side wall  52  has a thickness of 1 mm, lower and upper bosses  58  and  60  have a depth of 1 mm, and lower and upper slots  62  and  64  have a depth of 1 mm. In the embodiment shown, left sidewall  52  is made from a highly conductive material such as copper, stainless steel, or graphene. Left side wall  52  may be fabricated by conventional machining processes. 
         [0059]    Referring to  FIGS. 12-13 , right side wall  66  is identical to left side wall  52 . Right side wall  66  comprises an end portion  68  and an end portion  70 . Right side wall  66  further comprises a lower boss  72  extending from end portion  68  to end portion  70 . Right side wall  66  further comprises an upper boss  74  extending from end portion  68  to end portion  70 . Right side wall  66  further comprises a lower channel or slot  76  formed in lower boss  72  extending from end portion  68  to end portion  70 . Right side wall  66  further comprises an upper channel or slot  78  formed in upper boss  74  extending from end portion  68  to end portion  70 . As will be described more fully herein, lower slot  76  is adapted to removably engage and receive first mechanical spring  80 . Similarly, upper slot  78  is adapted to removably engage and receive second mechanical spring  82 . Right side wall  66  further comprises threaded holes  67  and  69  disposed at end portion  68  to receive bolts  198  and  200 . Right side wall  66  further comprises threaded holes  71  and  73  disposed at end portion  70  to receive bolts  202  and  204 . In the embodiment shown, right side wall  66  has a thickness of 1 mm, lower and upper bosses  72  and  74  have a depth of 1 mm, and lower and upper slots  76  and  78  have a depth of 1 mm. In the embodiment shown, right side wall  56  is made from a highly conductive material such as copper, stainless steel, or graphene. Right side wall  66  may be fabricated by conventional machining processes. 
         [0060]    Referring to  FIGS. 14-16 , first grid  112  is identical to second grid  114 . Each of grids  112  and  114  comprise a front wall  116 , a rear wall  118 , a left sidewall  120 , and a right sidewall  122 . Each of grids  112  and  114  further comprise an internal wall  124 , an internal wall  126 , and internal walls  128  and  130  that form nine (9) hollow cavities, namely, a cavity  132 , cavity  134 , cavity  136 , cavity  138 , cavity  140 , cavity  142 , cavity  144 , cavity  146 , and a cavity  148 . Each of grids  112  and  114  further comprise a channel  150  formed in each of internal walls  128  and  130  forming cavity  132 ,  134 ,  136 ,  140 ,  142 ,  144 ,  146 , and  148 . Channels  150  of grid  112  are provided so that wires  182  and  184  (to be described) from piezoelectric block  180  (to be described) of composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  may pass thru channels  150  of first grid  112  and out of first housing  12  for connection with external circuitry. Similarly, channels  150  of grid  114  are provided so that wires  182  and  184  (to be described) from composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  may pass thru channel  150  of grid  114  and out of second housing  32  for connection with external circuitry. Each of grids  112  and  114  have a length of 19 mm, a width of 19 mm, and a height of 5 mm. As such, grids  112  and  114  may freely move within cavity  16  and cavity  36 , respectively, by an amount equal to 1 mm. Free movement of grids  112  and  114  within cavity  16  and  36 , respectively, provides an additional degrees of freedom and thus an additional mechanism to capture vibrational energy. Front wall  116 , rear wall  118 , left sidewall  120 , and right sidewall  122  each have a thickness of 1 mm and a length of 19 mm. Internal wall  124  and internal wall  126  each have a thickness of 1 mm and extend from front wall  116  to rear wall  118 . Internal wall  128  and internal wall  130  each have a thickness of 1 mm and extend from left sidewall  120  to right sidewall  122 . Cavity  132 , cavity  134 , cavity  136 , cavity  138 , cavity  140 , cavity  142 , cavity  144 , cavity  146 , and cavity  148  each have a width of 5 mm, a length of 5 mm, and a height of 5 mm. In the embodiment shown, each of grids  112  and  114  is made from a highly conductive material such as copper, stainless steel, or graphene. Each of first and second grids  112  and  114  may be fabricated by conventional machining processes. 
         [0061]    Referring to  FIGS. 17-18 , each of composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  are identical to each other. For ease of description, only composite structure  162  will be described. Composite structure  162  comprises a piezoelectric block  180  having a first wire  182  extending from and electrically connected to its positive face and a second wire  184  extending from and electrically connected to its negative face. Composite structure  162  further comprises a magnet  186  securely attached to the upper surface of piezoelectric block  180  by conventional means such as adhesive. Magnet  186  is centrally disposed upon and extend the entire length of piezoelectric block  180 . In the embodiment shown, piezoelectric block  180  is made from a Navy Type I (PZT-4) piezoelectric material available from APC International, Ltd., P.O. Box 180, Makeyville, Pa. 17750 USA via its online store (www.americanpiezo.com) in any desired dimension. In the embodiment shown, piezoelectric block  180  has a length of 5 mm, a width of 5 mm, and a thickness of 2.0 mm. In the embodiment shown, magnet  186  is rectangular shaped 45H Neodymium magnet having a length of 5 mm, a width of 2.5 mm, a thickness of 1.5 mm, and a performance rating of 0.35 kg Pull Force and 2900 Gauss. Magnet  186  is available as Product No. MOD2- 20  from MAGNET Expert Ltd., Walker Industrial Estate, Ollerton Road, Tuxford, Nottinghamshire, NG22 0PQ United Kingdom via its online store (www.first4magnet.com). 
         [0062]    Referring to  FIGS. 19-20 , where composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  are shown securely disposed within cavity  132 ,  134 ,  136 ,  138 ,  140 ,  142 ,  144 ,  146 , and  148  of first grid  112 , respectively. This would be the same view as the assembly of second grid  114  with composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178 . As best shown by  FIG. 20 , wire  184  from piezoelectric block  180  of composite structure  162  passes from cavity  132  of first grid  112  thru opening  30  of first housing  12 . Wire  182  from piezoelectric block  180  of composite structure  164  passes from cavity  132  thru channel  150  and outward of opening  30  of first housing  12 . Similarly, wire  184  from piezoelectric block  180  of composite structure  164  passes from cavity  134  of first grid  12  thru opening  30  of first housing  12 . Wire  182  from piezoelectric block  180  of composite structure  164  passes from cavity  134  of first grid  112  thru channel  150  and opening  30  of first housing  12 . Similarly, wire  184  from piezoelectric block  180  of composite structure  166  passes from cavity  136  of first grid  112  thru opening  30  of first housing  12 . Wire  182  from piezoelectric block  180  of composite structure  166  passes from cavity  136  of first grid  12  thru channel  150  and opening  30  of first housing  12 . This cross-section view of the assembled first grid  12  is identical to assembled second grid  114  with composite structures  162 ,  164  and  166  securely disposed within cavity  132 , cavity  134 , cavity  136  of second grid  114 , respectively. 
         [0063]    Referring to  FIGS. 21-23 , first and second mechanical springs  80  and  82  each comprise an outer body  84  having a left side portion  86 , a right side portion  88 , a front side portion  90 , and a rear side portion  92 . Each of first and second mechanical springs  80  and  82  further comprise an inner body  94  having a top surface  96  and a bottom surface  98 . Inner body  94  is attached to outer body  84  by anchors  100 ,  102 ,  104 , and  106 . Left side portion  86  and right side portion  88  of first mechanical spring  80  removably slide within lower slot  62  of left side wall  52  and lower slot  76  of right side wall  66 , respectively. Left side portion  86  and right side portion  88  of second mechanical spring  82  removably slide within upper slot  64  of left side wall  52  and upper slot  78  of right side wall  66 . In the embodiment shown, inner and outer body  84  and  94 , and anchors  100 ,  102 ,  104 , and  106 , of first and second mechanical springs  80  and  82  are made from a single piece of widely available stainless steel shim stock having a thickness of 0.20 mm. Each of anchors  100 ,  102 ,  104  and  106  have a width of 1 mm. The thickness of inner and outer body  84  and  94  and the thickness and/or width of anchors  100 ,  102 ,  104 , and  106  may be varied to adjust the resonant frequency of first and/or second mechanical springs  80  and  82 . Each of first and second mechanical springs  80  and  82  may be fabricated by conventional machining processes. 
         [0064]    Referring to  FIG. 24 , where second magnet  110  is shown removably attached to second mechanical spring  82  by conventional means such as adhesive. In the embodiment shown, first magnet  108  is identical to second magnet  110  and is secured to first mechanical spring  80  in the same manner. Each of magnets  108  and  110  are circular shaped N42 Neodymium magnet having a diameter of 25 mm, a thickness of 3 mm, and a performance rating of 5.1 kg Pull Force and 1600 Gauss. Magnets  108  and  110  are available as Product No. F253-2 from MAGNET Expert Ltd., Walker Industrial Estate, Ollerton Road, Tuxford, Nottinghamshire, NG22 0PQ United Kingdom via its online store (www.first4magnet.com.). In the embodiment shown, first magnet  108 , at a static state, is spaced a distance of 1 mm from first grid  112 . Similarly, second magnet  110 , at a static state, is spaced a distance of 1 mm from second grid  114 . 
         [0065]    Device  10  may be assembled in different configurations depending upon the desired energy output. In a maximum power configuration, composite structures  162 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  are secured in first grid  112 . Second, composite structures  162 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  are secured in second grid  114 . Third, first grid  112  is freely disposed in cavity  16  of first housing  12 . Fourth, second grid  114  is freely disposed in cavity  36  of second housing  32 . Fifth, tape  188  is placed over first grid  112  and inside surface  14  of first housing  12  thereby preventing first grid  112  from falling out of cavity  16  of first housing  12  and composite structures  162 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  from falling out of first grid  112 , thereby allowing movement of first grid  112  in all directions within cavity  16  of first housing  12 . Sixth, tape  188  is placed over second grid  114  and inside surface  34  of second housing  32  thereby preventing second grid  114  from falling out of cavity  36  of second housing  32  and composite structures  162 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176 , and  178  from falling out of second grid  114  thereby allowing movement of second grid  114  in all directions within cavity  36  of first housing  12 . Seventh, left side wall  52  is secured to end portion  18  of first housing  12  by bolts  190  and  192 . Eighth, right side wall  66  is secured to end portion  20  of first housing  12  by bolts  198  and  200 . Ninth, left side wall  52  is secured to end portion  38  of second housing  32  by bolts  194  and  196 . Tenth, right side wall  66  is secured to end portion  40  of second housing  32  by bolts  202 , and  204 . Eleventh, first magnet  108  is secured to inner body  94  of first mechanical spring  80  and left and right side portions  86  and  88  of first mechanical spring  80  are inserted into lower slots  62  and  76  of left and right side walls  52  and  66 , respectively. Thereafter, second magnet  110  is secured to inner body  94  of second mechanical spring  82  and left and right side portions  86  and  88  of second mechanical spring  82  are inserted into upper slots  64  and  78  of left and right side walls  52  and  66 , respectively. In a full configuration, device  10  is standing up such that left side wall  52  acts as a mounting surface or free standing base for deployment in various vibrational energy environments such as direct mounting to an industrial machine or a person. 
         [0066]    The structure of device  10  uses multiple mechanisms for the production of electricity as a hybrid of both linearity and nonlinearity such that harvested energy can be amplified or attenuated and the frequency at which energy is harvested can be shifted according to the desire of the user. Specifically, device  10  comprises at least three mechanisms for harvesting ambient energy: (1) confluence and synergy of forces wherein there is interplay of gravitational, mechanical, electrostatic and electromagnetic forces to maximize generated power and to widen bandwidth of operation; (2) direct communication between a suspended magnetic body and a composite structure comprising a magnet and a piezoelectric block; and (3) free or regulated motion of a conductor grid holding the composite of the magnet and piezoelectric structures. As will be described more fully herein, device  10  may employ another mechanism, namely, electromagnetic induction associated with a suspended helical wire (to be described). 
         [0067]    Referring to  FIG. 25 , where first and second magnets  108  and  110  are shown attached to bottom and top surfaces  98  and  96 , respectively, of second mechanical spring  82 . This represents another configuration of device  10  where only one mechanical spring is employed and one or more grids of composite structures. As will be described more fully herein, this double mass configuration of second mechanical spring  82  uncovered a non-linear characteristic response of device  10  above 50 Hz that is not present in conventional devices. 
         [0068]    Referring to  FIG. 26 , where a cross section view of device  10  shows static magnetic energy available for electromagnetic transduction. 
         [0069]    Referring to  FIGS. 27-28 , four different configurations of device  10  were tested with first housing  12  attached to a shaker table. Electrical outputs from wires  82  and  84  of three composite structures  180  of second housing  32  were connected to a data logger and the results are shown in  FIGS. 27 and 28 . The four different configurations are labeled and described as follows: (i) the presence of first and second magnets  108  and  110  secured to first and second mechanical springs  80  and  82 , respectively; (ii) the presence of only second magnet  110  secured to second mechanical spring  82 ; (iii) the absence of first and second magnets  108  and  110  and first and second mechanical springs  80  and  82 ; and (iv) the presence of only first and second magnets  110  secured to second mechanical spring  82 . In each of the above configurations, only three out of the eighteen cavities of first and second grids  110  and  112  were populated with the composite structure representing seventeen percent of the total capacity of device  10  in the piezoelectric mode. Unlike conventional energy harvesting devices, the real time data of device  10  demonstrate the harvesting of energy by device  10  in large bandwidths across wide ranges of frequencies, for example, a band width of 50 Hz at a low frequency region ( FIG. 27 ), and significantly larger bandwidths within a frequency range of 50 Hz to 350 Hz, differing in width according to configurations ( FIG. 28 ). Examples are given below in Tables 1 and 2 of performance parameters as extracted from  FIGS. 27 and 28  for device  10  at seventeen percent (17%) of its total capacity. Circuitry for extraction of energy from the piezoelectric mode comprises high input impedance and low output impedance. Real power was dissipated across less than ten ohms. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Frequency below 50 Hz (Linear Character) 
               
             
          
           
               
                 Data Labels 
                   
                   
                   
               
               
                 (Configuration) 
                 Peak Frequency (Hz) 
                 Voltage (V) 
                 Bandwidth (Hz) 
               
               
                   
               
             
          
           
               
                 (i) 
                 7.02 
                 217.44 
                 50 
               
               
                 (ii) 
                 14.04 
                 73.85 
                 50 
               
               
                 (iii) 
                 21.97 
                 41.15 
                 50 
               
               
                 (iv) 
                 4.12 
                 157.50 
                 50 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Frequency above 50 Hz and below 350 Hz (Non-Linear Character) 
               
             
          
           
               
                 Data Labels 
                   
                   
                 Bandwidth 
               
               
                 (Configuration) 
                 Peak Frequency (Hz) 
                 Voltage (V) 
                 (Hz) 
               
               
                   
               
               
                 (i) 
                 281.68 
                 34.95 
                 225 
               
               
                 (ii) 
                 193.18 
                 27.02 
                 127 
               
               
                 (iii) 
                 Not Applicable 
                 Not Applicable 
                 Not Applicable 
               
               
                 (iv) 
                 131.07 
                 14.31 
                  80 
               
               
                   
               
             
          
         
       
     
         [0070]    Unlike conventional devices, within the alternating voltage wave form produced by the device of the present invention are a series of wide bandwidths of over the linear region of the wave form and wider bandwidths of energy available over the non-linear region of the wave form. The availability of energy over both the linear and non-linear portions of the waveform at larger bandwidths makes it possible to extract significantly more useful power than conventional energy harvesters. 
         [0071]    Referring to  FIG. 29 , where device  10  is shown having a one piece housing. Fabrication of a one piece housing may be accomplished by current three dimensional (3-D) printing processes or other futurely developed technologies. 
         [0072]    Referring to  FIGS. 30 and 31 , where device  10  is shown having a two piece housing. A two piece housing allows for each modular use of separate cores or grids to produce energy. Two piece housing may be accomplished by current machining processes or three dimensional (3-D) printing processes or other futurely developed technologies. 
         [0073]    Referring to  FIGS. 32-34 , where a conductor panel assembly  250  is removably mounted to an open end of device  10  to provide electromagnetic transduction independent of the output from the piezoelectric materials. Conductor panel assembly  250  generally comprises a frame  252 , helical wires  290 ,  292 ,  294 , and  296  freely mounted to frame  252 , and first and second conductors  302  and  304  electrically connected with helical wires  290 ,  292 ,  294 , and  296  to provide a low impedance AC output. Movements of helical wires  290 ,  292 ,  294  and/or  296  within the static or changing magnetic fields of first and second magnets  108  and  110  (and the static magnetic field of fixed magnets  186  of composite structures  162 ,  164 ,  166 ,  168 ,  170 ,  172 ,  174 ,  176  and  178 ) induces a current into helical wires  290 ,  292 ,  294 , and  296  that is output across first and second conductors  302  and  304 . 
         [0074]    Referring to  FIGS. 35-39 , frame  252  comprises a wall  254  having an outside surface  256  and an inside surface  258 , a left side wall  260 , a right side wall  262 , and a top side wall  264 . Frame  252  further comprises a boss  266  extending upward from inside surface  258  at the innermost end of left sidewall  260 , right side wall  262 , and top side wall  24 . Frame  252  further comprises an opening  269  that in the embodiment is square shaped and sized to match the open face portion of device  10 . Frame  252  further comprises a lower coil cavity  270 , a lower coil cavity  272 , a lower coil cavity  274 , and a lower coil cavity  276 . Frame  252  further comprises an upper coil cavity  278 , upper coil cavity  280 , an upper coil cavity  282 , and an upper coil cavity  284 . Frame  252  further comprises a lower conductor cavity  286  and a upper conductor cavity  288 . Conductors  302  and  304  are secured within lower conductor cavity  286  and upper conductor cavity  288 , respectively, by conventional means such as adhesive. End portions  298  and  300  of helical wire  290  are secured to lower and upper coil cavity  270  and  278 , respectively, by conventional means such as adhesive. End portions  298  and  300  of helical wire  290  are electrically connected to first and second conductors  302  ad  304  by conventional soldering operations. End portions  298  and  300  of helical wire  292  are secured to lower and upper coil cavity  272  and  280 , respectively, by conventional means such as adhesive. End portions  298  and  230  of helical wire  292  are electrically connected to first and second conductors  302  ad  304  by conventional soldering operations. End portions  298  and  300  of helical wire  294  are secured to lower and upper coil cavity  274  and  282 , respectively, by conventional means such as adhesive. End portions  298  and  300  of helical wire  294  are electrically connected to first and second conductors  302  ad  304  by conventional soldering operations. End portions  298  and  300  of helical wire  296  are secured to lower and upper coil cavity  274  and  284 , respectively, by conventional means such as adhesive. End portions  298  and  300  of helical wire  296  are electrically connected to first and second conductors  302  ad  304  by conventional soldering operations. Each of helical wires  290 ,  292 ,  294 , and  296  may be any type of highly conductive wire or helical coil. For example, each of helical wires  290 ,  292 ,  294 , and  296  may be copper micro coils having a thickness of 58 gauge and an outside diameter of about 1 mm available from Benatav Ltd., 16 Zvi-Bergman Street, Petach-Tikva, 4927973, Israel (www.benatav.com). 
         [0075]    Device  10  may also include additional ways of harvesting energy using a piezoelectric block  180 . Specifically, deflection of the two unfixed parts  90  and  92  of first and second mechanical springs  80  and  82 , respectively, act as fixed-fixed spring beams upon which one or more piezoelectric blocks  180  may be attached. 
         [0076]    Referring to  FIGS. 2 and 40 , energy harvester device  10  comprises screws  190 ,  192 ,  198 , and  200  for fastening left and right sidewalls  52  and  66  to first housing  12  and fasteners  194 ,  196 ,  202  and  204  for fastening left and right sidewalls  52  and  66  to second housing  32 . Energy harvester device  10  has multiple degrees of freedom, including mechanical spring  80  carrying magnet  108 . The mechanical resonant frequency of the mechanical spring  80  of energy harvester device  10  may be adjusted or tuned by tightening or loosening at least one of screws  190 ,  192 ,  194 ,  196 ,  198 ,  200 ,  202  and  204  without changing the mass either magnet  108  or spring  80 . 
         [0077]    Referring to  FIG. 41 , a frequency response spectra or graph is shown for tuning down or tuning up of the mechanical natural resonant frequencies of energy harvester  10 . In this example, energy harvester device  10  was configured with only second magnet  110  secured to second mechanical spring  82  and one (1) composite structure  180  buried in second grid  114  and second housing  32 . Electrical outputs from wires  82  and  84  of one composite structure  180  were connected to a data logger. The vibrating environment was a random noise spectrum generated by a conventional shaker. Tuning was performed by tightening (stiffening) or loosening (softening) of mechanical spring  80  using clockwise or anti-clockwise turning of screw  190  by relatively small amounts. A blue line  4102  represents the output response of the piezoelectric devices to a very stiff device  10  where all the screws are tightened as tight as possible. A purple line  4104  represents the output response of the piezoelectric devices when screw  190  is loosened by very small amount (one-quarter revolution). An orange line  4106  represents the output response of the piezoelectric devices when screw  190  is loosened by more than one revolution. As shown, a series of three peaks occur for lines  4102 ,  4104 , and  4106  at about the same frequency, namely, 29 Hz, and represent the output response of the coupled mechanical resonance with the vibration source. A second series of three peaks tuned to frequencies of about 198 Hz, 360 Hz, and 400 Hz represent the first natural resonant frequency caused by vertical translation of second magnet  110  and mechanical spring  82 . A third series of peaks tuned to frequencies of about 275 Hz, 907 Hz and 1028 Hz represent natural resonant frequencies caused by a first flexure of second magnet  110  and mechanical spring  82 . A fourth series of peaks tuned to frequencies of about flat (nil peak), 1204 Hz and 1302 Hz represent natural resonant frequencies caused by a second flexure of second magnet  110  and mechanical spring  82 .  FIG. 41  is only an example as turning of the screw by multiple revolutions shifts down the natural resonant frequency to even much lower frequencies below 120 Hz. A minimum amplification factor of 18.4 dB for the frequency range shown in  FIG. 41  was obtained for tuning around the natural resonant frequencies of energy harvester  10 . This represents a low total damping ratio and mechanical losses. Screws  190 ,  192 ,  194 ,  196 ,  198 ,  200 ,  202  and/or  204  of energy harvester  10  may be tightened or loosened without creating significant mechanical losses to the device. 
         [0078]    Referring to  FIGS. 42 and 43 , there has been little study on how to adjust or tune the electromagnetic natural resonant frequency of an energy harvester operating in an electromagnetic environment.  FIG. 42  shows an electromagnetic natural resonant frequency tuning circuit  320  connected between the outputs of energy harvester device  10  and a conventional charge-to-voltage converter  340  such as those produced by DJB Instruments, Meggitts (Endevco Corporation). Tuning circuit  320  allows the electromagnetic natural resonant frequency of energy harvester  10  to be tuned electronically without changing the mechanical natural resonant frequencies of the energy harvester device  10 . As shown by  FIG. 43 , tuning circuit  320  comprises a variable dissipative element such as a variable resistor between the outputs of energy harvester device  10  and the input of charge-to-voltage converter  340 . 
         [0079]    Referring to  FIGS. 44 and 45 , a frequency response spectra or graph is shown for tuning down or tuning up of the electromagnetic natural resonant frequency of energy harvester  10 . In this example, energy harvester device  10  was configured with only second magnet  110  secured to second mechanical spring  82  and one (1) composite structure  180  buried in second grid  114  and second housing  32 . Electrical outputs from wires  82  and  84  of composite structure  180  was connected to charge-to-voltage converter  340  by tuning circuit  320 . The electromagnetic environment was generated by radiations from AC power cords of electrical instruments and operating machineries. Tuning was performed by changing the value of the variable resistor of tuning circuit  320 . As shown in both  FIGS. 44 and 45 , a red line  4402  is the measured output response from charge-to-voltage converter  340  with the variable resistor of tuning circuit  320  set to 1 ohm. As shown in  FIG. 44 , a black line  4404  is the measured output response from charge-to-voltage converter  340  with the variable resistor of tuning circuit  320  set to 3 ohms. As shown in  FIG. 44 , a blue line  4406  is the measured output response from charge-to-voltage converter  340  with the variable resistor of tuning circuit  320  set to 5 ohms. As shown in  FIG. 44 , a pink line  4408  is the measured output response from charge-to-voltage converter  340  with the variable resistor of tuning circuit  320  set to 7 ohms. As shown in  FIG. 44 , a green line  4410  is the measured output response from charge-to-voltage converter  340  with the variable resistor of tuning circuit  320  set to 9 ohms. As shown in  FIG. 45 , a black line  4502  is the measured output response from charge-to-voltage converter  340  with the variable resistor of tuning circuit  320  set to 10 ohms. As shown in  FIG. 45 , a blue line  4504  is the measured output response from charge-to-voltage converter  340  with the variable resistor of tuning circuit  320  set to 100 ohms. As shown in  FIG. 45 , a pink line  4506  is the measured output response from charge-to-voltage converter  340  with the variable resistor of tuning circuit  320  set to 1000 ohms. As shown in  FIG. 45 , a green line  4508  is the measured output response from charge-to-voltage converter  340  with the variable resistor of tuning circuit  320  set to 10,000 ohms. A first peak measured at about 29 Hz represents the coupled mechanical resonance of vibration source; the second peak tuned around to different frequencies represents electromagnetic resonant frequency caused by electromagnetic waves from the environment; and the third peak remaining unchanged in frequency position at ca 400 Hz represents first natural resonant frequency caused by vertical translation of second magnet  110  and mechanical spring  82 . When the EM resonant frequency is tuned down to the lower frequency region, minimum quality factor drops and flattens out to 0 dB at extremely low frequencies. As shown in the table below, the electromagnetic natural frequency of energy harvester device  10  varied from 145.26 Hz with the resistance of tuning circuit  320  set at 1 ohm to 3.66 Hz with the resistance of tuning circuit  320  set at 10,000 ohms: 
         [0000]                                                              Electromagnetic Natural           Resistance (Ohms)   Frequency                                        1   145.26           3   127.56           5   114.14           7   104.37           9   96.43           10   93.38           100   35.40           1000   11.60           10000   3.66                        
The present invention allows the tuning of the electromagnetic resonance caused by electromagnetic waves that are mutually coupled to vibration frequency response of energy harvester device  10  without changing natural resonant frequencies of energy harvester device  10 . Tunability is over 150%, highest performance when compared with conventional tuning methods for energy harvesting as described in background of the invention.
 
         [0080]    The above description is intended primarily for purposes of illustration. This invention may be embodied in several other forms or carried out in other ways without departing from the spirit or scope of the invention. Modifications and variations still within the spirit or scope of the invention as claimed will be readily obvious to those of skill in the art.