Metamaterial vibration energy collector based on anti-spiral acoustic black hole structure

Abstract

The invention discloses a metamaterial vibration energy collector based on an anti-spiral acoustic black hole structure, which comprises the anti-spiral acoustic black hole structure, an extended mass block and a piezoelectric structure, and is characterized in that the anti-spiral acoustic black hole structure comprises an ABH beam and an extended beam, the ABH beam is bent into an Archimedes spiral shape, and the thickness of the ABH beam is gradually reduced from the starting point end to the terminal end of the spiral; the extension beam extends outwards from the terminal of the ABH beam, and the thickness of the extension beam is the same as the minimum thickness of the ABH beam; the piezoelectric structure is arranged on the expansion beam, and the expansion mass block is combined with the tail end of the expansion beam. According to the invention, the conventional idea that a large-size acoustic black hole needs to be adopted for coping with low-frequency vibration traditionally is broken through, the method is suitable for a space-limited scene, a longer effective wave propagation path is realized in the same space, the energy focusing or dissipation effect is enhanced, the performance of capturing low and medium-frequency vibration is realized while the high-frequency performance is maintained, and the method is suitable for large-scale application. And efficient energy collection is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration energy harvesting, and particularly relates to a metamaterial vibration energy harvester based on an anti-spiral acoustic black hole structure. Background Art

[0002] The rapid popularity of Internet of Things (IoT) networks and intelligent sensing systems - especially in demanding environments such as wearable electronics, aerospace systems, and industrial condition monitoring - has exposed the severe limitations of traditional battery technologies, including limited service life, maintenance complexity, and poor sustainability. Therefore, vibration energy harvesting (VEH) technology, which can achieve autonomous operation by converting ambient mechanical energy, has now become a forefront research direction for sustainable power solutions. However, effectively harvesting broadband, low-amplitude vibration energy remains a formidable challenge, especially in miniaturized applications where power density and spectral adaptability are crucial.

[0003] Contemporary VEH technologies mainly employ three transduction mechanisms: electromagnetic (Faraday induction), electrostatic (capacitive coupling), and piezoelectric (strain-polarization coupling) principles. Although electromagnetic systems show effectiveness in low-frequency, large-displacement excitations, their practical applications are vulnerable to high mass density and electromagnetic interference sensitivity. Although electrostatic collectors have the advantage of a compact structure, their operation relies on an external polarization voltage source, and their insufficient power density also makes it difficult to meet the requirements of industrial applications. In contrast, piezoelectric transduction utilizes the direct piezoelectric effect to convert mechanical strain into charge displacement, making it the preferred choice for self-powered microsystems.

[0004] Traditional piezoelectric collectors generally adopt cantilever beam structures, flexible designs, or multi-stage composite architectures, but their practical application efficacy is limited by the ultra-narrow working bandwidth caused by the linear resonance mechanism (at a reference frequency of 1000 Hz, the effective bandwidth is usually less than 10 Hz). This limitation significantly weakens the adaptability of the energy harvesting system to the broadband vibration spectrum and time-varying dynamics in actual working conditions. However, the latest progress in acoustic black hole (ABH) structures has achieved a paradigmatic breakthrough. Its unique waveguide design not only breaks through the frequency band limitations of traditional methods but also realizes sub-wavelength focusing and precise positioning of flexural wave energy in a wide frequency domain.

[0005] Existing acoustic black hole structure designs are usually over 500 millimeters to minimize reflections caused by truncation. For example, a metamaterial beam vibration energy harvester combining an acoustic black hole disclosed in Chinese Patent CN118413131A includes a vibration structure, a main beam, an additional acoustic black hole beam, and a piezoelectric structure, where the length of the main beam exceeds 550 millimeters, resulting in low space efficiency and severely restricting the miniaturization and integration requirements of wearable devices.

[0006] Although the traditional acoustic black hole structure exhibits excellent energy focusing characteristics in the field of high-frequency vibration control, its performance in the medium and low frequency bands has significant limitations. When the cut-off frequency is low, long-wavelength vibration waves are difficult to be effectively compressed and focused due to insufficient waveguide paths caused by limited physical dimensions, resulting in a sharp attenuation of the energy density in the low-frequency region (such as 100 - 1500 Hz). This phenomenon is directly manifested as a dispersed stress distribution at the piezoelectric conversion end and a reduced strain energy density, thereby weakening the collection efficiency of low-frequency vibration energy.

[0007] In summary, there is an urgent need in this field for a compact broadband energy harvester that can be applied to energy collection in space-constrained applications while achieving enhanced high-efficiency energy collection in the medium and low frequencies. Summary of the Invention

[0008] In view of the deficiencies of the existing technology, the present invention provides a metamaterial vibration energy harvester based on an anti-helical acoustic black hole structure.

[0009] To achieve the above object, the technical solution of the present invention is as follows:

[0010] A metamaterial vibration energy harvester based on an anti-helical acoustic black hole structure, which includes an anti-helical acoustic black hole structure, an extended mass block, and a piezoelectric structure; the anti-helical acoustic black hole structure includes an ABH beam and an extended beam; the ABH beam is bent into an Archimedean spiral shape configuration, and the thickness gradually decreases from the starting end to the terminal end of the spiral; the extended beam extends outward from the terminal end of the ABH beam, and the thickness is the same as the minimum thickness of the ABH beam; the piezoelectric structure is disposed on the extended beam, and the extended mass block is combined with the end of the extended beam.

[0011] Optionally, the Archimedean spiral shape of the ABH beam is described as r = a + bθ, where the initial radius a and the pitch parameter b define the Archimedean spiral geometry, and θ = 0.

[0012] Optionally, the thickness h(x) of the ABH beam follows the form of a power-law with an exponent along the x-direction h(x) = ax n (n≥2) to make the thickness transition smooth enough.

[0013] Optionally, the anti-helical acoustic black hole structure further includes a non-ABH beam, the non-ABH beam is connected to the starting end of the ABH beam, and the thickness is the same as the thickness of the starting end of the ABH beam.

[0014] Optionally, the thickness variation formula of the anti-helical acoustic black hole structure is

[0015]

[0016] where h0 corresponds to the uniform thickness of the non-ABH beam, and h t corresponds to the minimum thickness of the extended beam, and l1, l ABH and l2 correspond to the lengths of the non-ABH beam, ABH beam, and extended beam respectively.

[0017] Optionally, the widths of the non-ABH beam, ABH beam, and extended beam are uniform.

[0018] Optionally, the extended mass block is combined with the end of the extended beam by mechanical connection or integral molding, and the center of gravity of the extended mass block coincides with the end of the waveguide path of the anti-helical acoustic black hole structure.

[0019] Optionally, the piezoelectric structure is a piezoelectric ceramic patch attached to the back of the extended beam.

[0020] Optionally, the length of the piezoelectric ceramic patch is less than half of the minimum operating wavelength of the terminal.

[0021] Optionally, the piezoelectric structure is provided with an external electrode, and the external electrode is electrically connected to a load integrated on a wiring board.

[0022] The beneficial effects of the present invention are as follows:

[0023] 1. Through the design of the helical acoustic black hole structure, the present invention "compresses" the wave propagation path of the traditional linear or planar acoustic black hole into a smaller space, breaking through the conventional idea of using large-sized acoustic black holes to deal with low-frequency vibrations. It is not only applicable to space-limited scenarios, but also realizes a longer effective wave propagation path in the same space, enhancing the energy focusing or dissipation effect.

[0024] 2. By arranging the acoustic black hole in an anti-helical layout, the present invention not only significantly weakens the size dependence on the energy harvesting terminal (l2), but also endows the terminal with modular expansion compatibility. The previous helical acoustic black hole structure has high space requirements for the installation of internal components, but the reverse configuration greatly improves the space efficiency and facilitates integration with complex vibration energy harvesting systems without affecting the energy conversion performance.

[0025] 3. By integrating a mass block in the piezoelectric space to form a cantilever piezoelectric structure, not only can targeted frequency band enhancement be achieved,

[0026] but also the resonance frequency of the system can be precisely adjusted, the stress distribution on the piezoelectric sheet can be optimized, and the strain energy can be maximized.

[0027] Other features and beneficial effects of the present invention will be described in the subsequent specification, and some of them will become obvious from the specification or be understood by implementing the present invention. Brief Description of the Drawings

[0028] Figure 1 Schematic diagram of the overall structure of the vibration energy harvester disclosed in Embodiment 1 of the present invention;

[0029] Figure 2 Schematic diagram of the structure of the anti-spiral acoustic black hole structure of the vibration energy harvester disclosed in Embodiment 1 of the present invention;

[0030] Figure 3 Schematic diagram of the parameter at another angle of the vibration energy harvester disclosed in Embodiment 1 of the present invention;

[0031] Figure 4 Installation schematic diagram of the piezoelectric structure of the vibration energy harvester disclosed in Embodiment 1 of the present invention;

[0032] Figure 5 Schematic diagram of the structure of the traditional linear ABH beam energy harvester of Comparative Example 1;

[0033] Figure 6 Schematic diagram of the comparison of the piezoelectric power harvesting performance in the medium and low frequency bands of Embodiment 1 of the present invention and Comparative Example 1;

[0034] Among them, the reference numerals in the figure are: 1, extended mass block, 2, piezoelectric structure, 3, anti-spiral acoustic black hole structure, 301, non-ABH beam, 302, ABH beam, 303, extended beam. Detailed implementation manners

[0035] The present invention will be further explained and described in detail below in conjunction with specific embodiments, which are explanations of the present invention rather than limitations. It should be noted that the following embodiments are only used to illustrate the present invention and do not limit the technical solutions described in the present invention. All technical solutions and their improvements that do not deviate from this scope should be included in the scope of the claims of the present invention.

[0036] Reference Figures 1 to 3, the vibration energy harvester of the metamaterial based on the anti-helical acoustic black hole structure in the embodiment includes an extended mass block 1, a piezoelectric structure 2, and an anti-helical acoustic black hole structure 3. The anti-helical acoustic black hole structure 3 is composed of a non-ABH beam 301, an ABH beam 302, and an extended beam 303. The ABH beam 302 is bent into an Archimedean spiral shape configuration, and its thickness gradually decreases from the starting end to the terminal end of the spiral. The extended beam 303 extends outward from the terminal end and has the minimum thickness of the ABH beam 302. The non-ABH beam 301 is connected to the starting end and has the maximum thickness of the ABH beam 302. The piezoelectric structure 2 is covered under the extended beam 303 of the anti-helical acoustic black hole structure 3, and its electrodes are connected to the load integrated on the wiring board through copper foil and wires. The extended mass block 1 is combined with the end of the extended beam 303 by mechanical connection or integral molding, so that the center of gravity of the extended mass block 1 coincides with the end of the waveguide path of the anti-helical acoustic black hole structure 3, thereby ensuring that the inertial force directly acts on the strain concentration area of the piezoelectric structure 2.

[0037] The ABH beam 302 is bent into an Archimedean spiral shape by a thin plate with a thickness distributed according to the power law h(x) = ax n (n≥2), and is specifically described as r = a + bθ, where the initial radius a = 30 mm and the pitch parameter b = 10 / π mm define the Archimedean spiral geometry. θ = 0 defines the maximum thickness at the starting point of the spiral, and the spiral curvature radius gradually increases from the inside to the outside. When the wave enters the area of the ABH beam 302, the wavelength reaches the maximum value, while the bending radius reaches the minimum value, making the anti-helical ABH beam 302 exhibit a higher wavelength-to-curvature radius ratio in the initial area, resulting in more obvious wavefront distortion. The anti-helical structure realizes the equivalent extension of the wave propagation path (the total effective length l ABH = 400 mm) through the Archimedean spiral equation r(θ) = a + bθ, and at the same time, the transverse projection size is reduced by 77.3% (the straight beam is 440 mm), which can make long-wavelength low-frequency waves (100 - 1500 Hz) experience multiple reflections and focusing in the spiral path, significantly improving the energy density. The anti-helical structure not only maintains the performance equivalent to the classical spiral design but also releases the space at the piezoelectric end.

[0038] The extended beam 303 is a straight structure with a uniform thickness. It extends outward in a way tangent to the terminal end of the ABH beam 302 and realizes a smooth transition, and further increases the energy collection efficiency in the medium and low frequency range by extending the end structure l2. Due to the manufacturing limitations and truncation effects of the actual ABH beam 302, the energy concentration always occurs near the truncated end point rather than the ideal end point. Extending l2 can redistribute the stress to the piezoelectric patch, thereby significantly improving the energy conversion efficiency in this range.

[0039] The non-ABH beam 301 has a straight structure and a uniform thickness. It extends outward in a way that is tangent to the starting end of the ABH beam 302 and achieves a smooth transition. Its function is to provide a foundation support part with a uniform thickness for the anti-helical acoustic black hole structure. As the starting section of the structure, the non-ABH beam 301 is usually directly connected to a fixed end (such as a support frame or a vibration source) to ensure the stable installation of the entire ABH beam and the extended beam. Its uniform thickness provides the necessary rigidity and strength, avoiding the overall structure being fragile due to the tapered design of the ABH beam. The vibration wave enters the tapered region of the ABH beam 302 from the uniform section of the non-ABH beam 301. This transition section optimizes the wave transmission path through a smooth geometric connection (such as the starting point of the power-law distribution), reducing reflection or energy loss, and ensuring that the vibration energy efficiently enters the ABH region.

[0040] Combined with Figure 4 , the piezoelectric structure 2 is a PZT-5H piezoelectric ceramic attached to the extended beam 303 of the anti-helical acoustic black hole structure 3. The electrodes are connected to a 10 kΩ load resistor through copper foil. The piezoelectric structure 2 converts mechanical strain into charge output through the direct piezoelectric effect. To minimize the charge cancellation caused by the simultaneous deformation of peaks and valleys, the length of the piezoelectric patch must be kept below half of the minimum operating wavelength at the terminal. If the length of the piezoelectric patch exceeds half of the wavelength, waves will form tensile and compressive deformations simultaneously at different positions of the patch (i.e., the coexistence of wave peaks and valleys), resulting in the cancellation of positive and negative charges and significantly reducing the output voltage and energy conversion efficiency. When the length of the piezoelectric patch is less than half of the minimum operating wavelength, it can ensure that the vibration wave phases are consistent within the area covered by the patch, maximizing the efficiency of converting strain energy into charge.

[0041] The extended mass block 1 is fixedly installed in the end region of the extended beam 303. By adding a mass block, the system resonance is reduced to match the low-frequency vibrations in the environment. The inertial force of the extended mass block 1 causes the strain energy to concentrate on the piezoelectric structure 2, achieving a peak power enhancement of 83.7% and a valley power amplification of 53 times through geometric impedance matching.

[0042] Example 1

[0043] The structure of the metamaterial vibration energy harvester based on the anti-helical acoustic black hole structure in Example 1 is as described above. The anti-helical acoustic black hole structure 3 uses metallic iron, and the geometric parameters, material parameters, and piezoelectric ceramic sheet parameters are shown in Table 1, Table 2, and Table 3 respectively.

[0044] Table 1 Geometric parameters of the vibration energy harvester

[0045]

[0046] Among them, h0 represents the thickness of the non-ABH beam 301, h t represents the thickness of the extended beam 303, h mrepresents the thickness of the extended mass block, l1 represents the length of the non-ABH beam 301, l ABH represents the effective length of the ABH beam 302, l2 represents the length of the extended beam 303, l3 represents the length of the extended mass block, and B represents the width of the vibration energy harvester.

[0047] Table 2 Material parameters of the vibration energy harvester

[0048]

[0049] Table 3 Piezoelectric ceramic sheet parameters

[0050]

[0051] where l p represents the length of the piezoelectric ceramic sheet, h p represents the thickness of the piezoelectric ceramic sheet, and B represents the width of the piezoelectric ceramic sheet.

[0052] Comparative Example 1

[0053] This comparative example provides a traditional linear ABH beam energy harvester, as Figure 5 shown. Its energy harvesting efficiency is consistent with the established benchmark of similar configurations. The difference from Example 1 is that it is a linear ABH beam without spiral curling and extended mass blocks, and the remaining geometric parameters, material parameters, and piezoelectric ceramic sheet parameters are the same.

[0054] Compare the piezoelectric power harvesting performance of the metamaterial vibration energy harvester based on the anti-spiral acoustic black hole and cantilever beam in Example 1 and the traditional linear ABH beam energy harvester in Comparative Example 1.

[0055] Figure 6 Shows the comparison of the piezoelectric power harvesting performance of Example 1 and Comparative Example 1. The results show that the metamaterial vibration energy harvester based on the anti-spiral acoustic black hole and cantilever beam reduces the projected axial length by 77% while maintaining broadband efficiency. In the range of 100 - 1500 Hz, the average power of the SABH-ETMS is 2.7×10 -3 W, which is 14.2 times higher than the traditional design (1.9×10 - 4 W). It is worth noting that the peak power output (7.1×10 -2 W) appears at 304 Hz. Compared with the traditional linear ABH (3.1×10 -3 W at 800 Hz), the low-frequency response is enhanced, and the peak power increases by 22.9 times. Compared with the traditional linear ABH beam energy harvester, the energy harvester proposed in the example expands the working bandwidth and enhances the ability to harvest medium and low-frequency vibration energy.

[0056] The metamaterial vibration energy harvester based on the antihelical acoustic black hole structure proposed by the present invention has significantly better performance in capturing medium and low frequency vibrations than traditional linear ABH beams. While maintaining the high frequency performance (the power output is flat at >1500 Hz), the average power output in the medium and low frequency bands is increased by 14.2 times, the power density in the 200 - 600 Hz band is increased by 1000%, the peak power is increased by 22.9 times, and the space efficiency is also better (the lateral dimension is reduced by 77%).

[0057] The above are only the specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantive modification of the present invention using this concept shall fall within the scope of infringement of the protection scope of the present invention.

Claims

1. A metamaterial vibration energy harvester based on an anti-helical acoustic black hole structure, characterized in that: It includes an anti-helical acoustic black hole structure, an extended mass block, and a piezoelectric structure; the anti-helical acoustic black hole structure includes an ABH beam and an extended beam; the ABH beam is bent into an Archimedean spiral shape configuration, and its thickness gradually decreases from the starting end to the terminal end of the spiral; the extended beam extends outward from the terminal end of the ABH beam, and its thickness is the same as the minimum thickness of the ABH beam; the piezoelectric structure is disposed on the extended beam, and the extended mass block is combined with the end of the extended beam.

2. The vibration energy harvester of the metamaterial based on the anti-helical acoustic black hole structure according to claim 1, characterized in that: The Archimedean spiral shape of the ABH beam is described as r = a + bθ, where the initial radius a and the pitch parameter b define the Archimedean spiral geometry, and θ = 0.

3. The metamaterial vibration energy harvester based on the anti-helical acoustic black hole structure according to claim 1, wherein: The thickness h(x) of the ABH beam follows the form h(x) = axn (n ≥ 2) varying along the x-direction according to a power-law with an exponent. n (n ≥ 2) varies.

4. The vibration energy harvester of the metamaterial based on the anti-helical acoustic black hole structure according to claim 1, characterized in that: The anti-helical acoustic black hole structure further includes a non-ABH beam, which is connected to the starting end of the ABH beam, and its thickness is the same as the thickness of the starting end of the ABH beam.

5. The metamaterial vibration energy harvester based on the anti-helical acoustic black hole structure according to claim 4, characterized in that: The thickness variation formula of the anti-helical acoustic black hole structure is where h0 corresponds to the uniform thickness of the non-ABH beam, and h t corresponds to the minimum thickness of the extended beam, and l1, l ABH and l2 respectively correspond to the lengths of the non-ABH beam, the ABH beam, and the extended beam.

6. The metamaterial vibration energy harvester based on the anti-spiral acoustic black hole structure according to claim 4, characterized in that: The widths of the non-ABH beam, the ABH beam, and the extended beam are uniform.

7. The vibration energy harvester of the metamaterial based on the antihelical acoustic black hole structure according to claim 1, characterized in that: The extended mass block is combined with the end of the extended beam by mechanical connection or integral molding, and the center of gravity of the extended mass block coincides with the end of the waveguide path of the anti-helical acoustic black hole structure.

8. The metamaterial vibration energy harvester based on the anti-helical acoustic black hole structure according to claim 1, characterized in that: The piezoelectric structure is a piezoelectric ceramic patch, which is attached to the back of the extended beam.

9. The metamaterial vibration energy harvester based on the anti-spiral acoustic black hole structure according to claim 8, characterized in that: The length of the piezoelectric ceramic patch is less than half of the minimum operating wavelength of the terminal.

10. The metamaterial vibration energy harvester based on the anti-helical acoustic black hole structure according to claim 1, characterized in that: The piezoelectric structure is provided with an external electrode, and the external electrode is electrically connected to a load integrated on a wiring board.

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