CN115833651A - Vibration energy collecting device based on defect topological metamaterial beam - Google Patents

Abstract

The invention discloses a vibration energy collection device based on a defect topological metamaterial beam, which mainly solves the problems of poor anti-interference ability and low output power of the existing metamaterial vibration energy collection device. The scheme includes: a topological metamaterial beam, local defects, piezoelectric elements and energy harvesting circuits. The topological metamaterial beam consists of two sub-beams, A-beam and B-beam. The A beam consists of four class I units and the B beam consists of four class II units. Through the structural design of type I unit cells and type II unit cells, the topological metamaterial beams appear in the boundary state at the junction of beam A and beam B, and the vibration energy is collected at the boundary, and the piezoelectric element and energy harvesting circuit are used to Vibrational energy is converted into electrical energy. The purpose of setting local defects at the boundary is to improve the vibration energy collection efficiency. The invention has the characteristics of strong anti-interference and high output power, and has the ability to efficiently and stably collect environmental vibration energy.

Description

A Vibration Energy Harvesting Device Based on Defect Topological Metamaterial Beams

technical field

The invention belongs to the technical field of energy collection, and relates to a vibration energy collection device, in particular to a vibration energy collection device based on defect topological metamaterial beams, which has high anti-interference ability and high output power.

Background technique

With the continuous development of wireless sensing technology and MEMS technology, the scale of use of wireless sensors and small portable electronic devices is increasing. At present, most of the energy supply technologies for wireless sensors and small portable electronic devices are based on battery technology, mainly including fuel cells and thin film batteries. This technology has the characteristics of mature production process, high energy density, and simple use, but the service life of traditional batteries is limited relative to the life of working equipment. In some applications, replacing or charging batteries is a high cost. , sometimes an impossible task. At the same time, a large number of discarded batteries will also bring serious pollution to the environment. Therefore, it is necessary to study new energy supply technologies to adapt to the development of microelectronic devices.

In the natural environment, vibration is ubiquitous, such as the driving of vehicles, the work of machines, etc. Harvesting ambient vibration energy to power wireless sensors or small electronic devices has been extensively studied and has specific applications. At present, there are three ways to convert vibration energy into electrical energy: electromagnetic induction, electrostatic effect and piezoelectric effect, among which piezoelectric energy harvesting technology has received more attention. The main reason is that compared with the other two types of conversion mechanisms, piezoelectric energy harvesting technology has the advantages of simple structure, high energy density, and easy integration with micro-devices. However, the traditional piezoelectric energy harvesting device is very sensitive, and it is easy to damage the piezoelectric sheet under severe vibration, thereby affecting its energy harvesting function, and some structural defects may seriously affect its energy harvesting efficiency.

Acoustic metamaterials are man-made composite materials that are precisely manipulated. In recent years, as an artificial material that can periodically modulate sound waves and has a vocal band gap, it has gradually become a new medium for energy harvesting. From the perspective of energy harvesting, compared with natural materials, the unique physical properties of metamaterials, including local resonance bandgap, local defect immunity, and elastic wave concentration, have the potential for energy harvesting. At present, studies on acoustic metamaterial vibration energy harvesters have shown that metamaterials have significantly better energy collection effects on elastic waves than traditional piezoelectric energy harvesting devices. However, energy harvesting systems based on metamaterial structures are very sensitive to defects (such as structural damage and fatigue), and local defects will significantly affect the effect of energy harvesting, and even lose the energy harvesting function in severe cases. Therefore, localized defects may lead to a significant reduction in the output power of metamaterial energy harvesting systems, thereby reducing the energy harvesting efficiency. Therefore, how to improve the robustness of metamaterial energy harvesting technology is a key problem that needs to be solved urgently.

In recent years, topological metamaterials have great application prospects in the efficient transmission and regulation of waves due to their topological protection and insensitivity to local defects, and have gradually become a hot research field. Among them, the boundary states of topological edge bodies have attracted extensive attention of scholars. Topologically protected boundary states are immune to lattice defects, which are important for the stable propagation and concentration of elastic waves. Therefore, the boundary states of topological metamaterials are a very promising solution for robust and reliable vibrational energy harvesting.

Contents of the invention

The invention discloses a vibration energy collection device based on a defect topology metamaterial beam, which mainly solves the problems of poor anti-interference ability and low output power of the existing metamaterial vibration energy collection device. In order to achieve the above object, embodiments of the present invention adopt the following technical solutions:

A vibration energy harvesting device based on a defect topological metamaterial beam, comprising: a topological metamaterial beam, a defect part, a piezoelectric element, and an energy harvesting circuit; The A beam is composed of four type I units, and the B beam is composed of four type II units.

The type I unit cell is composed of five cuboids with the same width, all of which are W _c , and the total length of the type I unit cell is L=30mm. The lengths of the first cuboid to the fifth cuboid are respectively: l ₁ , l ₂ , l ₃ , l ₄ , l ₅ , the lengths of the first segment and the fifth segment are the same (i.e. l ₁ = l ₅ ), the first The lengths of the second segment and the fourth segment are exactly the same and constant (ie l ₂ =l ₄ ), so the length of the third segment can be l ₃ =L−2l ₁ −2l ₂ . The heights of the first section, the third section and the fifth section are all the same, denoted by h _a ; and the heights of the second section and the fourth section are the same, denoted by h _b .

第一段与第五段的长度相同(即

)，第二段与第四段的长度完全相同且为定值(即

)，因此第三段的长度为

第一段、第三段和第五段的高度均相同，用h_a表示；而第二段和第四段的高度相同，用h_b表示。The type II unit cell is composed of five sections of the same width, all of which are cuboids of W _c . The total length of the type II unit cell is the same as that of the type I unit cell, both of which are L=30mm. The lengths of the first section of cuboid to the fifth section of cuboid are respectively:

The first and fifth paragraphs have the same length (i.e.

), the length of the second segment and the fourth segment are exactly the same and are fixed values (ie

), so the length of the third segment is

The heights of the first section, the third section and the fifth section are all the same, denoted by h _a ; while the heights of the second and fourth sections are the same, denoted by h _b .

宽度等于拓扑超材料梁的宽度W_c；缺陷高度不超过h_a。缺陷的程度主要是通过改变缺陷的尺寸实现的，例如增加缺陷的高度或者长度。The defective part is located on the upper surface of the junction of the left half of the A beam and the right half of the B beam. The length, width and height of the defective part are l _c , W _c , and h _{c ,} respectively. The length of the defect does not exceed

The width is equal to the width W _c of the topological metamaterial beam; the defect height does not exceed h _a . The degree of defect is mainly achieved by changing the size of the defect, such as increasing the height or length of the defect.

The piezoelectric part is mainly composed of a piezoelectric element and an energy harvesting circuit. The piezoelectric element is located on the other side of the defective part (6). The length, width, and height of the piezoelectric element are l _d , W _d , and h _{d ,} respectively. Through the design of the type I unit cell and the type II unit cell, the topological metamaterial beam is at the junction of the left half of the A beam and the right half of the B beam (that is, the fifth section of the type I unit cell and the type II unit cell Paragraph 1) Boundary state can appear, and the vibration energy can be collected at the boundary, and the vibration energy can be converted into electrical energy through the piezoelectric element and the energy harvesting circuit, wherein the energy harvesting circuit can be a resistor or other complex circuits. .

The present invention provides a vibration energy harvesting device based on defect topological metamaterial beams. When the topological metamaterial beams vibrate under external excitation, the bending deformation of the beams will also deform the piezoelectric sheet. The piezoelectric sheet converts mechanical energy into electrical energy through the piezoelectric effect and provides it to the load circuit. When the load circuit is a resistance, the electric energy of the piezoelectric sheet will be consumed; when the load circuit is an energy storage circuit, the electric energy will be stored in the circuit. Through the structural design of type I unit cell and type II unit cell, the topological properties of type I unit cell and type II unit cell can be made different, so as to ensure that the boundary of the entire topological metamaterial beam can appear at the junction of A beam and B beam state, the vibration energy is collected at the boundary, and the vibration energy is converted into electrical energy through piezoelectric elements and energy harvesting circuits. Since the defect topological metamaterial beam has topological protection characteristics and efficient energy gathering characteristics, the present invention has the characteristics of strong anti-interference and high output power, and has the ability to efficiently and stably collect environmental vibration energy.

The beneficial effect of the present invention compared with prior art is:

The invention applies the topological metamaterial to the piezoelectric vibration energy collection technology to realize the vibration energy collection with defect immune function. The research results are expected to provide a theoretical basis and design basis for topological metamaterial piezoelectric vibration energy harvesting systems, and provide a new method for further realizing stable and reliable vibration energy harvesting.

Description of drawings

Fig. 1 is a possible structural schematic diagram provided by the embodiment of the present invention;

Figure 2 is a size parameter diagram of a type I unit cell;

Figure 3 is a size parameter diagram of a type II unit cell;

Fig. 4 is a schematic diagram of local defects and the position and size of the piezoelectric sheet;

Fig. 5 is a unit structure dispersion relation energy band diagram;

Figure 6 shows the law of influence of element length on the dispersion relationship;

Figure 7 is a diagram of the transfer characteristics and energy harvesting voltage of defect-free topological metamaterials;

Figure 8 is a diagram of the transfer characteristics and energy harvesting voltage of the defective topological metamaterial;

Among them, 1-topological metamaterial beam, 2-left half A beam, 3-right half B beam, 4-type I unit cell, 5-type II unit cell, 6-local defect, 7-piezoelectric element, 8- Energy Harvesting Circuit.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. Hereinafter, embodiments of the present invention will be described in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention. Those skilled in the art can understand that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It should also be understood that terms such as those defined in commonly used dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless defined as herein explain.

This embodiment specifically provides a vibration energy harvesting device based on a defect-containing metamaterial beam, as shown in Figure 1, which includes: the present invention includes a topological metamaterial beam 1, a beam A in the left half of the topological metamaterial beam 1 2. The right half of the B-beam 3 , the local defect 6 , the piezoelectric part 7 and the energy harvesting circuit 8 . Specifically: the topological metamaterial beam 1 includes a base and a left half A beam 2 and a right half B beam 3 fixed on the base; the leftmost end of the left half A beam 2 is connected to the base, and the right half B beam The rightmost end of the beam 3 is a free end; the left half A beam 2 and the right half B beam 3 both include four unit structures, and the left half A beam 2 and the right half B beam 3 have different unit structures , the left half A beam 2 includes four type I unit cells, and the right half B beam 3 includes four type II unit cells, as shown in FIG. 1 .

The type I unit cell 4 is composed of five cuboids with the same width, all of which are W _c , and the total length L of the type I unit cell 4 is 30mm. The lengths of the first cuboid to the fifth cuboid are respectively: l ₁ , l ₂ , l ₃ , l ₄ , l ₅ , the lengths of the first segment and the fifth segment are the same (i.e. l ₁ = l ₅ ), the first The lengths of the second segment and the fourth segment are exactly the same and constant (ie l ₂ =l ₄ ), so the length of the third segment is l ₃ =L−2l ₁ −2l ₂ . The heights of the first section, the third section and the fifth section are all the same, denoted by h _a ; and the heights of the second section and the fourth section are the same, denoted by h _b . The specific dimensions are shown in Figure 2. The specific size values of the above parameters in this embodiment are shown in Table 1.

Table 1. Class I unit cell size table

第一段与第五段的长度相同(即

)，第二段与第四段的长度完全相同且为定值(即

)，因此第三段的长度为

第一段、第三段和第五段的高度均相同，用h_a表示；而第二段和第四段的高度相同，用h_b表示。具体尺寸如图3所示。本实施例中以上参数具体尺寸值如表2所示。The class II unit cell 5 is composed of five cuboids with the same width, all of which are W _c . The total length of the class II unit cell 5 is the same as that of the class I unit cell 4 , both of which are L=30mm. The lengths of the first section of cuboid to the fifth section of cuboid are respectively:

The first and fifth paragraphs have the same length (i.e.

), the length of the second segment and the fourth segment are exactly the same and are fixed values (ie

), so the length of the third segment is

The heights of the first section, the third section and the fifth section are all the same, denoted by h _a ; while the heights of the second and fourth sections are the same, denoted by h _b . The specific dimensions are shown in Figure 3. The specific size values of the above parameters in this embodiment are shown in Table 2.

Table 2. Class II unit cell size table

Through the structural design of type I unit cell 4 and type II unit cell 5, the topological properties of type I unit cell 4 and type II unit cell 5 can be made different, so that the entire topological metamaterial beam 1 is in the left half of A beam 2 and Boundary states can appear at the junction of the right half of the B-beam 3, the vibration energy is collected at the boundary, and the vibration energy is converted into electrical energy through the piezoelectric element (7) and the energy harvesting circuit 8.

The defective part 6 is shown in FIG. 1 , and it is located on the upper surface of the junction of the left half A beam 2 and the right half B beam 3 . The specific dimensions of the defects are shown in Figure 4, and the length, width and height of the defects are l _c , W _c , and h _c , respectively. The defect sizes used in this embodiment are shown in Table 3.

Table 3. Dimensions of defective parts

The piezoelectric part is mainly composed of a piezoelectric element 7 and an energy harvesting circuit 8. The piezoelectric element 7 is located on the other side of the defective part 6. The specific dimensions of the piezoelectric element 7 are shown in Figure 4. The length of the piezoelectric element is The width and height are l _d , W _d , and h _{d ,} respectively. The piezoelectric element 7 is connected to an external energy harvesting circuit 8, and the energy harvesting circuit 8 can be a resistor or other complex circuits. The piezoelectric sheet used in this embodiment is PZT-5H, and the specific dimensions are shown in Table 4.

Table 4. Dimensions of Piezoelectric Elements

In the present invention, the topological metamaterial vibration energy harvesting device with defects composed of topological metamaterial beam 1, local defect 6, piezoelectric element 7, and energy harvesting circuit 8, compared with the existing metamaterial vibration energy harvesting device, this The invention has the characteristics of strong anti-interference and high output power, and has the ability to efficiently and stably collect environmental vibration energy.

A vibration energy harvesting device based on defect topological metamaterial beams, characterized in that the design method of the device is:

S1: Use COMSOL finite element software to establish the model of the unit structure, set the structure size and material parameters, and the material of the beam in the present invention is structural steel.

)和第四段(l₄和

)微结构的长度不变，计算第三段微结构长度(l₃或

)对整个单元结构色散关系的影响规律，其中L＝30mm，注意：第一段和第五段的长度依然保持一致，且随着第三段长度的变化而变化。S2: Apply periodic boundary conditions to unit structure 4 of beam A and unit structure 5 of beam B, keep the total unit length L, height and width W _c unchanged, and keep the second section (l ₂ and

) and the fourth paragraph (l ₄ and

) the length of the microstructure is constant, calculate the length of the third microstructure (l ₃ or

) on the influence law of the dispersion relation of the whole unit structure, where L=30mm, note: the length of the first section and the fifth section are still consistent, and change with the length of the third section.

(取

)。为了提高能量收集效率，构造拓扑边界态，通过分别设置l₃＝2mm和

来设计I类单胞4和II类单胞5。取左半部分A梁2和右半部分B梁3单元数均为10。通过仿真得到该无缺陷拓扑超材料的传递率。图7给出了无缺陷拓扑超材料传递率和位移响应分布。首先，在传递率图中观察到带隙，并且在带隙内部观察到拓扑边界态。根据该拓扑超材料的传递率图像和位移响应分布图，在带隙内有两个共振峰，但只有f＝2620Hz的共振峰是边界态。为了说明这些特性，绘制了位移分布，如图7所示。当f＝2620Hz时，A梁2和B梁3的连接处出现边界态，弹性波集中在此处，此时能量收集效率最高。本实施例中所采用的外接电路电阻R＝10MΩ，计算禁带区域内的电压分布，如图7(e)所示。由图7(e)可知，当f＝2620Hz时，电压最大，为365V。S3: Based on the influence law of the microstructure unit length on the dispersion relationship, the mode flip curve can be obtained, as shown in Figure 7. Wherein, the position where the two curves intersect is the mode inversion point, and the corresponding length is the critical length l ₀ , as shown in Fig. 7, in the structure shown in this paper, l ₀ =8mm. According to the law of the effect of unit length on the dispersion relationship, with the increase of l ₃ , the band gap is closed and reopened. When l ₃ <8mm, the part with larger first-order modal deformation of the unit cell structure is concentrated in the middle part, as The anti-symmetric structure, the larger part of the second-order mode deformation is concentrated at both ends, which is a symmetrical structure; when l ₃ >8mm, the symmetry of the first-order mode and the second-order mode is reversed, and the unit cell structure The larger part of the first-order modal deformation is concentrated at both ends, which is a symmetrical structure, and the larger part of the second-order modal deformation is concentrated in the middle area, which is an anti-symmetric structure. The microstructure corresponding to l ₃ >l ₀ has different topological properties from the microstructure corresponding to l ₃ <l ₀ . In order to ensure that A-beam 2 and B-beam 3 have different topological properties, in the structure shown in this paper, the length of the third section of type I unit cell 4 is selected l ₃ < l ₀ (l ₃ = 2mm), and the type II unit cell 4 is selected The length of the third section of cell 5

(Pick

). In order to improve the energy collection efficiency and construct the topological boundary state, by setting l ₃ =2mm and

To design class I unit cell 4 and class II unit cell 5. Take the left half A beam 2 and the right half B beam 3 with 10 units. The transmissibility of the defect-free topological metamaterial is obtained by simulation. Figure 7 presents the distribution of the transmissibility and displacement response of the defect-free topological metamaterial. First, a band gap is observed in the transmissibility diagram, and topological boundary states are observed inside the band gap. According to the transmissibility image and displacement response distribution diagram of this topological metamaterial, there are two resonance peaks in the band gap, but only the resonance peak at f=2620Hz is a boundary state. To illustrate these properties, the displacement distribution is plotted, as shown in Fig. 7. When f=2620Hz, a boundary state appears at the junction of A-beam 2 and B-beam 3, where elastic waves are concentrated, and the energy collection efficiency is the highest at this time. The external circuit resistance R=10MΩ used in this embodiment calculates the voltage distribution in the forbidden band region, as shown in FIG. 7( e ). It can be seen from Fig. 7(e) that when f=2620Hz, the voltage is the largest, which is 365V.

来设计I类单胞4和II类单胞5。设置如图4所示的局部缺陷6，具体尺寸见表3。取左半部分A梁2和右半部分B梁3单元数均为10。通过仿真得到该拓扑超材料的传递率。图7给出了带缺陷拓扑超材料传递率和位移响应分布。首先，在传递率图中观察到带隙，并且在带隙内部观察到拓扑边界态。根据该拓扑超材料的传递率图像和位移响应分布图，在带隙内有两个共振峰，但只有f＝2532Hz的共振峰是边界态。为了说明这些特性，绘制了位移分布，如图8所示。当f＝2532Hz时，A梁2和B梁3的连接处出现边界态，弹性波集中在此处，此时能量收集效率最高。与无缺陷的拓扑超材料压电能量收集器相同，本实施例中所采用的外接电路电阻R＝10MΩ，计算此时禁带区域内的电压分布，如图8(e)所示。由图8(e)可知，当f＝2532Hz时，电压最大，为532V。S4: To improve energy harvesting efficiency, construct topological boundary states with defects. Set l ₃ =2mm and

To design class I unit cell 4 and class II unit cell 5. Set the local defect 6 as shown in Figure 4, and see Table 3 for the specific size. Take the left half A beam 2 and the right half B beam 3 with 10 units. The transmissibility of the topological metamaterial is obtained by simulation. Figure 7 shows the distribution of transmissibility and displacement response of topological metamaterials with defects. First, a band gap is observed in the transmissibility diagram, and topological boundary states are observed inside the band gap. According to the transmissibility image and displacement response distribution diagram of this topological metamaterial, there are two resonance peaks in the band gap, but only the resonance peak at f=2532Hz is a boundary state. To illustrate these properties, the displacement distribution is plotted, as shown in Fig. 8. When f=2532Hz, a boundary state appears at the junction of A-beam 2 and B-beam 3, where elastic waves are concentrated, and the energy collection efficiency is the highest at this time. Similar to the defect-free topological metamaterial piezoelectric energy harvester, the external circuit resistance R=10MΩ used in this embodiment is used to calculate the voltage distribution in the forbidden band region at this time, as shown in Figure 8(e). It can be seen from Fig. 8(e) that when f=2532Hz, the voltage is the largest, which is 532V.

Compared with the defect-free piezoelectric energy harvester, the voltage of the topological metamaterial energy harvesting system with defects is significantly increased by about 46%. Therefore, the energy collection efficiency of the piezoelectric energy harvester containing defects is higher than that of the piezoelectric energy harvester without defects. In addition, compared with the existing metamaterial vibration energy harvesting device, the present invention adds defective parts and has strong resistance With the characteristics of interference and high output power, it has the ability to efficiently and stably collect environmental vibration energy

Finally, it is noted that the above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out Modifications or equivalent replacements, without departing from the spirit and scope of the technical solution, should be included in the scope of the claims of the present invention.

Claims (5)

1. A vibration energy collection device based on a defect topological metamaterial beam, characterized in that, said device comprises a topological metamaterial beam (1), a defective part (6), a piezoelectric part; The topological metamaterial beam (1) includes a base and a left half A beam (2) and a right half B beam (3) fixed on the base; the leftmost end of the left half A beam (2) is connected to the base , the rightmost end of the right half of the B beam (3) is the free end; The left half A beam (2) and the right half B beam (3) both include four unit structures, and the left half A beam (2) and the right half B beam (3) have different unit structures, Described left half A beam (2) comprises four I type unit cells (4); Right half B beam (3) comprises four II type unit cells (5); Described I type unit cell (4) ) is composed of five identical cuboids with a width of _Wc , the total length of the type I unit cell (4) is L=30mm; the lengths of the first cuboid to the fifth cuboid are respectively: l ₁ , l ₂ , l ₃ , l ₄ , l ₅ , the length of the first segment is the same as that of the fifth segment, i.e. l ₁ = l ₅ ; the length of the second segment is exactly the same as that of the fourth segment and is a fixed value, i.e. l ₂ = l ₄ ; The length of the segment is the remaining length after subtracting the length of other segments from the total length, that is, l ₃ =L-2l ₁ -2l ₂ ; the heights of the first segment, the third segment and the fifth segment are all the same, expressed by h _a ; and The height of the second segment and the fourth segment are the same, denoted by h _b ; The class II unit cell (5) is composed of five identical cuboids with a width of _Wc , and the total length of the class II unit cell (5) is the same as that of the class I unit cell (4), both of which are L=30mm; wherein The lengths from one section of cuboid to the fifth section of cuboid are:

The first segment is the same length as the fifth segment, i.e.

The length of the second segment is exactly the same as that of the fourth segment and is a constant value, that is

Therefore, the length of the third segment is the remaining length after subtracting the length of other segments from the total length, that is

The heights of the first section, the third section and the fifth section are all the same, represented by h _a ; while the heights of the second section and the fourth section are the same, represented by h _b ; the defective part (6) is located in the left half The junction of the A beam (2) and the right half of the B beam (3), that is, the defect part (6) described on the upper surface of the first section of the type I unit cell (4) and the type II unit cell (5): The length, width and height are respectively l _c , W _c , h _c ; the length l _c of the defective part (6) does not exceed

The width of the defect portion (6) is equal to the width W _c of the topological metamaterial beam; The height h _c of said defective portion (6) does not exceed h _a ; The piezoelectric part includes a piezoelectric element (7) and an energy harvesting circuit (8); the topological metamaterial beam (1) is placed on the left half of the A boundary state appears at the junction of part A beam (2) and the right half of B beam (3), that is, the fifth section of type I unit cell (4) and the first section of type II unit cell (5), and the vibration energy Collected at the boundary, the vibrational energy is converted into electrical energy through piezoelectric elements (7) and energy harvesting circuits (8). 2. a kind of vibration energy harvesting device based on defect topological metamaterial beam according to claim 1, is characterized in that, based on the law of influence of microstructural unit length on dispersion relation, obtains mode flip curve; Mode flip curve The intersecting position in the figure is the mode inversion point, and the corresponding length is the critical length l ₀ . When the left half of beam A (2) and the right half of beam B (3) have different topological characteristics, the I The length of the third section of unit cell (4) l ₃ <l ₀ , the length of the third section of unit cell (5) of type II

3. A kind of vibration energy harvesting device based on defect topological metamaterial beam according to claim 1, characterized in that, the piezoelectric element (7) is located on the other side of the defect part (6), that is, on the left side On the lower surface of the junction of the half A beam (2) and the right half B beam (3), the length, width and height of the piezoelectric element (7) are l _d , W _d , h _d respectively; wherein the piezoelectric element (7 ) is connected to an external energy harvesting circuit (8), and the energy harvesting circuit (8) can be a resistor or other complex circuits. 4. a kind of vibration energy harvesting device based on defect topological metamaterial beam according to claim 1, is characterized in that, when described topological metamaterial beam (1) vibrates under external excitation, topological metamaterial beam The bending deformation of (1) deforms the piezoelectric sheet; the piezoelectric element (7) of the piezoelectric part converts mechanical energy into electrical energy through the piezoelectric effect and provides it to the load circuit; when the load circuit is a resistance, the piezoelectric sheet Electrical energy is consumed; when the load circuit is an energy storage circuit, electrical energy is stored in the circuit. 5. The vibration energy harvesting device based on defect topological metamaterial beams according to any one of claims 1 to 4, characterized in that, the preparation method of the device is: S1: Use COMSOL finite element software to establish a model of the unit structure, and set the structure size and material parameters; S2: Apply periodic boundary conditions to the type I unit cell (4) and type II unit cell (5), keep the total unit length L, height and width W _c constant, keep the second segment l ₂ and

and the fourth paragraph l ₄ and

The length of the microstructure is constant, and the length of the third microstructure is calculated l ₃ or

The law of influence on the dispersion relationship of the entire unit structure; the lengths of the first and fifth segments remain the same, and change with the length of the third segment; S3: Based on the influence law of the length of the microstructure unit on the dispersion relationship, the mode inversion curve is obtained; the position where the two curves intersect is the mode inversion point, and the corresponding length is the critical length l ₀ : for l ₃ <l ₀ In the left half of the unit cell structure, the larger part of the first-order modal deformation is concentrated in the middle of the unit cell, which is an anti-symmetric structure, and the larger part of the second-order modal deformation is concentrated at both ends of the unit cell, which is a symmetrical structure; for In the left half of l ₃ >l ₀ , the larger part of the first-order modal deformation of the unit cell structure is concentrated at both ends of the unit cell, which is a symmetrical structure, and the larger part of the second-order modal deformation is concentrated in the middle of the unit cell, as antisymmetric structure. Therefore, the microstructure corresponding to l ₃ >l ₀ and the microstructure corresponding to l ₃ <l ₀ have different topological properties; the left half of A beam (2) and the right half of B beam (3) have different topological properties Next, select the length of the third section of the type I unit cell (4) l ₃ <l ₀ , and the length of the third section of the type II unit cell (5)

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