A magnetic deflection type elastic boundary tri-stable piezoelectric energy harvesting device

Abstract

The application relates to the technical field of piezoelectric energy collection, and discloses a magnetic deflection type elastic boundary three-stable piezoelectric energy collection device, which comprises a pair of horizontally symmetric transverse cantilever beam assemblies, a pair of longitudinally symmetric longitudinal cantilever beam assemblies, and a pair of symmetric magnet-spring devices arranged in each longitudinal cantilever beam assembly; wherein the transverse cantilever beam assembly adopts double magnets to realize reverse deflection and reduce the depth of a potential well; the magnet-spring device of the longitudinal cantilever beam assembly generates horizontal displacement during vibration, forms an elastic boundary, generates a variable potential well, and further reduces the depth of the potential well. Compared with a traditional three-stable piezoelectric energy collector, the application only needs smaller external energy input, can realize that the cantilever beam crosses the potential well at a stable balance position, causes large-amplitude vibration, makes the piezoelectric element generate large deformation, generates a large amount of electric charges on the surface of the piezoelectric element, and thus has higher energy collection efficiency.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric energy harvesting technology, specifically to a magnetically deflected elastic boundary tristable piezoelectric energy harvesting device. Background Technology

[0002] Piezoelectric energy harvesting devices utilize the piezoelectric effect to deform piezoelectric materials and generate electrical energy. Due to their advantages such as high force-electric coupling effect and energy density, they are of great significance in meeting the energy needs of devices such as wireless sensor networks and MEMS.

[0003] Early piezoelectric energy harvesting devices were mostly based on single-degree-of-freedom mass-spring-damped linear systems, but their operating bandwidth was very narrow. Their power generation performance was optimal when the external excitation frequency matched the system's natural frequency. However, when the external excitation frequency deviated significantly from the system's natural frequency, the power generation performance was greatly reduced. Therefore, researchers proposed using nonlinear magnetic forces to change the system's stiffness, thereby obtaining a wider operating bandwidth.

[0004] Analysis of various nonlinear magnetic piezoelectric energy acquisition data reveals that the main focus is on the analysis of "potential wells" and "steady states." In the potential energy curve, a "potential well" refers to the spatial range where the potential energy is locally lower than the surrounding area, resembling a "trap" that confines the system to a certain spatial range. The stable equilibrium position is the location where the potential energy reaches a local minimum, corresponding to the lowest point of the potential well. The "potential well depth" refers to the difference between the potential energy value at the stable equilibrium position and the potential energy value at the adjacent potential energy peak. "Tristable state" represents that the system has three stable equilibrium positions within its operating displacement range. For potential well and steady-state studies, most scholars control the depth and width of the potential well by studying the spacing of the magnets, including horizontal and vertical distances. The depth of the potential well represents the amount of energy required for the piezoelectric beam to make large-amplitude reciprocating motions across the potential well, while the width of the potential well is related to the displacement amplitude of the piezoelectric beam making large-amplitude reciprocating motions across the potential well. Traditional methods of adjusting the magnet spacing, such as increasing the magnet spacing, can indeed reduce the depth of the potential well, i.e., reduce the external energy input required for the piezoelectric beam to cross the potential well. However, this also reduces the width of the potential well, meaning its displacement amplitude will be greatly reduced, and the output voltage will also be significantly reduced. Therefore, the main technical drawback of existing nonlinear magnetic piezoelectric energy harvesting devices is that large vibration amplitudes and high output voltages require a large external vibration energy input. In addition, the traditional method of fixing external magnets also results in a large potential well depth for the piezoelectric energy harvesting device, which means that a large amount of external energy needs to be absorbed to achieve a nonlinear jumping mechanism across the potential well at multiple stable equilibrium positions, thereby obtaining a wider operating frequency band.

[0005] Therefore, in order to overcome the shortcomings of existing technologies, it is urgent to improve existing nonlinear magnetic piezoelectric energy harvesting devices and propose a piezoelectric energy harvesting device with a smaller potential well depth, which has a wider operating frequency band under the same magnitude of external force. Summary of the Invention

[0006] The technical problem to be solved by this invention is to propose a piezoelectric energy harvesting device with a smaller potential well depth, which has a wider operating frequency band under the same magnitude of external force.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A magnetically deflected elastic boundary tristable piezoelectric energy harvesting device includes: a pair of horizontally symmetrically arranged transverse cantilever beam assemblies, a pair of longitudinally symmetrically arranged longitudinal cantilever beam assemblies, and a pair of symmetrically arranged magnet-spring devices in each longitudinal cantilever beam assembly. The transverse cantilever beam assembly uses a dual-magnet reverse deflection method to change the magnetic field distribution and thus reduce the depth of the potential well; the magnet-spring device of the longitudinal cantilever beam assembly will generate horizontal displacement during vibration, forming an elastic boundary and generating a variable potential well.

[0009] Furthermore, a pair of transverse cantilever beam assemblies includes transverse cantilever beam assembly 1 and transverse cantilever beam assembly 2 3; The transverse cantilever beam assembly 1 includes a first transverse cantilever beam 11, a first piezoelectric element 12, a first bar magnet 14, and a second bar magnet 15; The first bar magnet 14 and the second bar magnet 15 are located at the free end of the first transverse cantilever beam 11 and can be deflected in opposite directions along the axis of the first transverse cantilever beam 11, respectively; the first piezoelectric element 12 is located at the root of the first transverse cantilever beam 11. The same applies to the transverse cantilever beam assembly 2.3.

[0010] Furthermore, a pair of longitudinal cantilever beam assemblies includes longitudinal cantilever beam assembly 1 2 and longitudinal cantilever beam assembly 2 4; The longitudinal cantilever beam assembly 2 includes a first longitudinal cantilever beam 21, a left magnet-spring device 1 and a right magnet-spring device 1 symmetrically arranged at the free end of the first longitudinal cantilever beam 21, and a third piezoelectric element 22 located at the root of the first longitudinal cantilever beam 21. The same applies to longitudinal cantilever beam assembly 2.4.

[0011] Furthermore, the left-side magnet-spring device includes a horizontally placed first shaft 23A, a first annular magnet 24A, and a first spring 25A; The first spring 25A and the first annular magnet 24A are sleeved on the first shaft 23A, and one end of the first shaft 23A is fixedly connected to the first longitudinal cantilever beam 21. The two ends of the first spring 25A are fixedly connected to the first annular magnet 24A and the first longitudinal cantilever beam 21, respectively. The first annular magnet 24A can slide on the first shaft 23A. The magnet-spring device on the right works in the same way.

[0012] Furthermore, the annular magnet in the magnet-spring device has the same polarity as the bar magnet in the lateral cantilever beam assembly.

[0013] Furthermore, the first piezoelectric element 12 is a two-layer piezoelectric element, located on both sides of the root of the first transverse cantilever beam 11, and the polarization directions of the two piezoelectric elements are opposite, and the electric fields generated are in the same direction. A wire is led out from the upper surface of the upper layer and the lower surface of the lower layer, and then the two wires are connected to the load or energy storage circuit to complete the extraction of charge. The same applies to the piezoelectric elements in the transverse cantilever beam assembly 2 and the pair of longitudinal cantilever beam assemblies.

[0014] Furthermore, the transverse cantilever beam assembly 1 includes a first triangular prism block 13; the first triangular prism block 13 is fixedly located at the free end of the first transverse cantilever beam 11, and a first bar magnet 14 and a second bar magnet 15 are attached to the first triangular prism block 13.

[0015] Furthermore, when the first transverse cantilever beam 11 vibrates vertically, the first bar magnet 14 and the second bar magnet 15 will exert a magnetic force on the first ring magnet 24A and the third ring magnet 44A, causing the first ring magnet 24A and the third ring magnet 44A to slide horizontally along the first shaft 23A and the third shaft 43A respectively, resulting in the compression and stretching of the first spring 25A and the third spring 45A. The vertical vibration process of the transverse cantilever beam assembly 2 3 is similar; among them, the third annular magnet 44A, the third shaft 43A, and the third spring 45A belong to the components of the left magnet-spring device 2 in the longitudinal cantilever beam assembly 2 4.

[0016] Furthermore, when the first longitudinal cantilever beam 21 vibrates horizontally, initially due to inertia, the first spring 25A and the second spring 25B are compressed and stretched respectively. The springs store energy, and under the action of both, the first annular magnet 24A and the second annular magnet 24B will slide horizontally along the shaft. During the sliding process, the first annular magnet 24A and the second annular magnet 24B will be subjected to the magnetic forces of the first bar magnet 14 and the third bar magnet 34 respectively. The horizontal vibration process of the second longitudinal cantilever beam 41 in the longitudinal cantilever beam assembly 2 is similar; among them, the second annular magnet 24B and the second spring 25B belong to the components of the right magnet-spring device 1.

[0017] Furthermore, by adjusting the opposite deflection angle between the first bar magnet 14, the second bar magnet 15 and the axis of the first transverse cantilever beam 11, and similarly adjusting the bar magnets and transverse cantilever beam in the transverse cantilever beam assembly 3, the potential energy curve can be adjusted to maintain the existence of three potential wells and with the goal of reducing the depth of the potential wells.

[0018] Compared with the prior art, the beneficial effects of the present invention are: In this invention, two magnets at the free end of the transverse cantilever beam deflect in opposite directions about the beam's axis. The deflection angle is determined by analyzing the cantilever beam's potential energy curve, aiming to maintain three potential wells with a reduced depth. During vibration, the potential energy difference between the highest and lowest points of the potential wells is smaller, requiring less energy for the transverse cantilever beam to cross the potential well constraints. By using the opposite deflection of the two magnets, this invention reduces the potential well depth in the potential energy curve, enabling large-amplitude reciprocating vibrations across multiple stable equilibrium positions with less external excitation, thus improving the device's energy harvesting efficiency.

[0019] This invention introduces a magnet-spring boundary. During vibration, the horizontal sliding of the magnet and the compression and stretching of the spring cause the magnetic potential energy and elastic potential energy terms in the system's potential energy to change continuously, and the potential well depth in the potential energy curve also changes continuously, thereby generating a variable potential well. Moreover, the potential well depth is shallower, which further improves the energy harvesting efficiency of the device.

[0020] The present invention has a simple structure and installation, stable working performance, and excellent power generation performance. It can collect vibration energy from multiple directions simultaneously and can be widely used for vibration energy collection in various mechanical and building structures to power the corresponding structural health monitoring system. It solves the problem of the lack of a piezoelectric energy collection device with a smaller potential well depth in the existing technology.

[0021] Compared with traditional tristable piezoelectric energy harvesters, this invention requires only a smaller external energy input to enable the cantilever beam to pass over the potential well at a stable equilibrium position, causing large-amplitude vibrations and large deformation of the piezoelectric element, generating a large amount of charge on its surface, thereby achieving higher energy harvesting efficiency. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a magnetically deflected elastic boundary tristable piezoelectric energy harvesting device according to an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of a magnet-spring device according to an embodiment of the present invention.

[0024] Figure 3 This is a comparison diagram of the potential energy curves of the present invention and a conventional device in an embodiment of the present invention.

[0025] Figure 4(a) is a schematic diagram of the frequency domain output characteristics of TPEH under the same excitation amplitude in an embodiment of the present invention.

[0026] Figure 4(b) is a schematic diagram of the frequency domain output characteristics of DTPEH under the same excitation amplitude in an embodiment of the present invention.

[0027] Figure 4(c) is a schematic diagram of the frequency domain output characteristics of DTPEH-EB under the same excitation amplitude in an embodiment of the present invention. Detailed Implementation

[0028] To facilitate understanding of the technical solution of the present invention by those skilled in the art, the technical solution of the present invention will now be further described in conjunction with the accompanying drawings.

[0029] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0030] Please see Figure 1 , 2 As shown, this invention discloses a piezoelectric energy harvesting device with a magnetically deflected elastic boundary tristable state, comprising: a pair of horizontally symmetrically arranged transverse cantilever beam assemblies and a pair of vertically symmetrically arranged longitudinal cantilever beam assemblies. Each longitudinal cantilever beam assembly contains a pair of symmetrical magnet-spring devices. The transverse cantilever beam assemblies employ a dual-magnetic-reverse deflection method to alter the magnetic field distribution, thereby reducing the depth of the potential well. The magnet-spring devices of the longitudinal cantilever beam assemblies generate horizontal displacement during vibration, forming an elastic boundary and creating a variable potential well.

[0031] In one embodiment of the present invention, a pair of transverse cantilever beam assemblies and a pair of longitudinal cantilever beam assemblies are located inside the housing 5 and are fixedly connected to the housing 5 at their roots. The pair of transverse cantilever beam assemblies includes transverse cantilever beam assembly 1 and transverse cantilever beam assembly 2 3.

[0032] The transverse cantilever beam assembly 1 includes a first transverse cantilever beam 11, a first piezoelectric element 12, a first triangular prism block 13, a first bar magnet 14, and a second bar magnet 15. The first bar magnet 14 and the second bar magnet 15 are located at the free ends of the first transverse cantilever beam 11 and are deflected at a certain angle in the opposite direction along the axis of the first transverse cantilever beam 11. The first piezoelectric element 12 consists of two layers, located on both sides of the root of the transverse cantilever beam 11, with opposite polarization directions. The electric fields generated by the two layers are in the same direction. A wire is led out from the upper surface of the upper layer and the lower surface of the lower layer, respectively, to increase the output voltage in series. Then, the two wires are connected to a load or energy storage circuit to complete the charge extraction.

[0033] The first bar magnet 14 and the second bar magnet 15 are attached to the first triangular prism block 13, which is fixed at the free end of the first transverse cantilever beam 11. This not only better ensures the symmetry of the installation of the first bar magnet 14 and the second bar magnet 15 and the accuracy of the deflection angle, but also facilitates adjustment and disassembly. The magnitude of the deflection angle is determined by analyzing the potential energy curve of the cantilever beam assembly, with the goal of maintaining the existence of three potential wells and reducing the depth of the potential wells. The depth of the potential wells represents the energy required for the cantilever beam assembly to perform large-amplitude reciprocating vibrations across the constraints of the potential wells.

[0034] In this embodiment, the second transverse cantilever beam assembly 3 is similarly configured to the first transverse cantilever beam assembly 1, including a second transverse cantilever beam 31, a second piezoelectric element 32, a second triangular prism block 33, a third bar magnet 34, and a fourth bar magnet 35. The third bar magnet 34 and the fourth bar magnet 35 are located at the free end of the second transverse cantilever beam 31 and are respectively deflected at a certain angle in the opposite direction along the axis of the second transverse cantilever beam 31. The second piezoelectric element 32 is also configured in two layers, located on both sides of the root of the second transverse cantilever beam 31. The second triangular prism block 33 is fixedly located at the free end of the second transverse cantilever beam 31, and the third bar magnet 34 and the fourth bar magnet 35 are attached to the second triangular prism block 33.

[0035] In one embodiment of the present invention, a pair of longitudinal cantilever beam assemblies includes a first longitudinal cantilever beam assembly 2 and a second longitudinal cantilever beam assembly 4. The first longitudinal cantilever beam assembly 2 includes a first longitudinal cantilever beam 21, a left magnet-spring device 1 and a right magnet-spring device 1 symmetrically arranged at the free end of the first longitudinal cantilever beam 21, and a third piezoelectric element 22 located at the root of the first longitudinal cantilever beam 21.

[0036] In this embodiment, the longitudinal cantilever beam assembly 2 4 is similar, that is, the longitudinal cantilever beam assembly 2 4 includes a second longitudinal cantilever beam 41, a left magnet-spring device 2 and a right magnet-spring device 2 symmetrically arranged at the free end of the second longitudinal cantilever beam 41, and a fourth piezoelectric element 42 located at the root of the second longitudinal cantilever beam 41.

[0037] In this embodiment, the third piezoelectric element 22 and the fourth piezoelectric element 42 are both configured in two layers. The configuration of the second piezoelectric element 32, the third piezoelectric element 22, and the fourth piezoelectric element 42 is the same as that of the first piezoelectric element 12. The polarization directions of the two layers of piezoelectric elements are opposite, and the electric fields they generate are in the same direction. A wire is led out from the upper surface of the upper layer and the lower surface of the lower layer, respectively. Then, the two wires are connected to the load or energy storage circuit to complete the extraction of charge.

[0038] In this embodiment, the left magnet-spring device includes a horizontally placed first shaft 23A, a first annular magnet 24A, and a first spring 25A.

[0039] In this embodiment, the first spring 25A and the first annular magnet 24A are sleeved on the first shaft 23A, and one end of the first shaft 23A is fixedly connected to the first longitudinal cantilever beam 21. The two ends of the first spring 25A are fixedly connected to the first annular magnet 24A and the first longitudinal cantilever beam 21, respectively. The first annular magnet 24A can slide on the first shaft 23A.

[0040] In this embodiment, the right magnet-spring device is similar to the left magnet-spring device, that is, the right magnet-spring device includes a second shaft 23B, a second annular magnet 24B, and a second spring 25B. The second spring 25B and the second annular magnet 24B are sleeved on the second shaft 23B, and one end of the second shaft 23B is fixedly connected to the first longitudinal cantilever beam 21. The two ends of the second spring 25B are fixedly connected to the second annular magnet 24B and the first longitudinal cantilever beam 21, respectively. The second annular magnet 24B can slide on the second shaft 23B.

[0041] In this embodiment, the left magnet-spring device 2 and the right magnet-spring device 2 are configured in the same way as the left magnet-spring device 1 and the right magnet-spring device 1.

[0042] The left-side magnet-spring device includes a third shaft 43A, a third annular magnet 44A, and a third spring 45A. The right-side magnet-spring device includes a fourth shaft 43B, a fourth annular magnet 44B, and a fourth spring 45B. The third shaft 43A and the fourth shaft 43B are located on both sides of the second longitudinal cantilever beam 41 and are fixedly connected to it. The third annular magnet 44A and the third spring 45A are sleeved on the third shaft 43A, and the two ends of the third spring 45A are fixedly connected to the third annular magnet 44A and the second longitudinal cantilever beam 41, respectively. The third annular magnet 44A can slide on the third shaft 43A. The fourth annular magnet 44B and the fourth spring 45B are sleeved on the fourth shaft 43B, and the two ends of the fourth spring 45B are fixedly connected to the fourth annular magnet 44B and the second longitudinal cantilever beam 41, respectively. The fourth annular magnet 44B can slide on the fourth shaft 43B.

[0043] In one embodiment of the present invention, the transverse and longitudinal cantilever beams are made of beryllium bronze, the magnets are made of neodymium iron boron, the triangular prism blocks are made of PETG, and the shafts are made of acrylic rods. More specifically, the magnets in the transverse cantilever beam assembly are bar magnets, which are easy to fix and adjust the angle, while the magnets in the longitudinal cantilever beam assembly are hollow cylindrical magnets, i.e., ring magnets, with the inner diameter of the hole being substantially the same as the diameter of the shaft, allowing the ring magnets to slide horizontally along the shaft with low friction.

[0044] In this embodiment, the annular magnet in the magnet-spring device has the same polarity as the bar magnet in the opposite position, that is, the annular magnet and the bar magnet have the same polarity facing each other. Specifically, the first bar magnet 14 and the first annular magnet 24A have the same polarity facing each other, the second bar magnet 15 and the third annular magnet 44A have the same polarity facing each other, the third bar magnet 34 and the second annular magnet 24B have the same polarity facing each other, and the fourth bar magnet 35 and the fourth annular magnet 44B have the same polarity facing each other.

[0045] In one embodiment of the present invention, when the first transverse cantilever beam 11 vibrates vertically, it drives the first bar magnet 14 and the second bar magnet 15 to vibrate. The first annular magnet 24A and the third annular magnet 44A are continuously subjected to their magnetic forces. When the resultant magnetic force of the first bar magnet 14 and the second bar magnet 15 is a repulsive force, the first annular magnet 24A and the third annular magnet 44A will slide to the right along the shaft (towards the longitudinal cantilever beam) and compress the first spring 25A and the third spring 45A respectively, storing energy. When the repulsive force is less than the elastic restoring force of the spring, the spring gradually recovers and releases energy, and the first annular magnet 24A and the third annular magnet 44A will slide to the left along the shaft. When the combined magnetic force of the first bar magnet 14 and the second bar magnet 15 is an attractive force, the first ring magnet 24A and the third ring magnet 44A will slide to the left along the shaft, stretching the first spring 25A and the third spring 45A respectively. The springs store energy. When the attractive force is less than the elastic restoring force of the springs, the springs gradually recover and release energy, and the first ring magnet 24A and the third ring magnet 44A will slide to the right along the shaft. The magnetic potential energy curve in the system's potential energy changes continuously with the horizontal displacement of the first ring magnet 24A and the third ring magnet 44A. At the same time, the elastic potential energy in the system's potential energy also changes continuously with the compression and stretching of the springs, causing the total potential energy curve of the system to change continuously, thus generating a variable potential well. This potential well has a smaller potential well depth, and the cantilever beam can more easily cross the potential well to make large-amplitude vibrations. The first piezoelectric element 12 attached to the surface of the first transverse cantilever beam 11 is more likely to undergo large deformations and generate more charge, thus having higher energy harvesting efficiency; the same applies to the vertical vibration of the transverse cantilever beam assembly 3.

[0046] In one embodiment of the present invention, when the first longitudinal cantilever beam 21 vibrates horizontally, initially, due to inertia, the first spring 25A and the second spring 25B are compressed and stretched respectively, storing energy. Subsequently, under the action of the springs, the first annular magnet 24A and the second annular magnet 24B slide horizontally along the shaft. During the leftward sliding of the first annular magnet 24A, it is mainly subjected to the repulsive force of the first bar magnet 14, which in turn causes the first annular magnet 24A to slide to the right. During the rightward sliding of the second annular magnet 24B (away from the direction of the first longitudinal cantilever beam 21), it is mainly subjected to the repulsive force of the third bar magnet 34, which in turn causes the second annular magnet 24B to slide to the left. The first annular magnet 24A is subjected to the magnetic force of the first bar magnet 14 and the elastic force of the first spring 25A. The second annular magnet 24B is subjected to the magnetic force of the third bar magnet 34 and the elastic force of the second spring 25B. The first spring 25A is subjected to the force of the first annular magnet 24A and the force of the first longitudinal cantilever beam 21. The second spring 25B is subjected to the force of the second annular magnet 24B and the force of the first longitudinal cantilever beam 21. The magnetic potential energy and elastic potential energy in the system's potential energy change continuously with vibration. The horizontal vibration process of the longitudinal cantilever beam assembly 4 is similar.

[0047] Please see Figure 3As shown, in one embodiment of the present invention, the first transverse cantilever beam 11, together with the first piezoelectric element 12, the first bar magnet 14, and the second bar magnet 15, under the action of the first annular magnet 24A, the third annular magnet 44A, the first spring 25A, and the third spring 45A, constitute a magnetically deflected tri-stable piezoelectric energy harvester with an elastic boundary (DTPEH-EB). Compared with the total potential energy of a conventional tri-stable piezoelectric energy harvester (TPEH), the magnetically deflected tri-stable piezoelectric energy harvester (DTPEH) has a smaller potential well depth. This means that the DTPEH needs to absorb less external energy to cross the potential well and perform large-amplitude reciprocating motion. This is due to the deflection of the first bar magnet 14 and the second bar magnet 15, which changes the distribution of the magnetic field. On the other hand, comparing the potential energy curves of DTPEH and DTPEH-EB reveals that after introducing the elastic boundary, during the vibration process, the first spring 25A and the third spring 45A repeatedly store and release energy, which further reduces the potential well depth of the piezoelectric beam, thus achieving a better energy harvesting effect; the same applies to other cantilever beam components.

[0048] Please refer to Figures 4(a), 4(b), and 4(c), which show the frequency domain output characteristics of TPEH, DTPEH, and DTPEH-EB under the same excitation amplitude. It can be seen that DTPEH-EB has a wider operating frequency band, that is, the magnetic deflection type elastic boundary tristable piezoelectric energy harvesting device proposed in this invention has a higher energy harvesting efficiency.

[0049] In one embodiment of the present invention, in order to make the present invention easier to design and use, the potential energy curve is dynamically adjusted. The following is an example of the vibration of a single first transverse cantilever beam 11, and the formula for calculating its total potential energy during the vibration process is given. These are the strain energy stored by the bending deformation of the first transverse cantilever beam 11 and the first piezoelectric element 12 at its root, the magnetic potential energy of the first bar magnet 14 and the second bar magnet 15 in the superimposed magnetic field of the first ring magnet 24A and the third ring magnet 44A, and the elastic potential energy of the first spring 25A and the third spring 45A.

[0050] Total potential energy: ; In the formula, For total potential energy, For strain energy, It is elastic potential energy. It is magnetic potential energy.

[0051] Among them, strain energy: ; In the formula, The bending stiffness of the composite beam consisting of the first transverse cantilever beam 11 and the first piezoelectric element 12 is given. The axial direction of the beam. , The lengths of the first transverse cantilever beam 11 and the first piezoelectric element 12 are given. For the displacement of the free end of the first transverse cantilever beam 11, The bending stiffness of the first transverse cantilever beam 11 is given.

[0052] Elastic potential energy: ; In the formula, , These are the elastic stiffnesses of the first spring and the third spring, respectively. , This represents the sliding displacement of the first and third springs.

[0053] Magnetic potential energy:

[0054] in: ; In the formula, , , , The magnetization intensities of the first bar magnet, the second bar magnet, the first ring magnet, and the third ring magnet are respectively. , , , The volumes of the first bar magnet, the second bar magnet, the first ring magnet, and the third ring magnet are respectively. The vacuum permeability; Let be the rotation angle at the free end of the first transverse cantilever beam, which can be expressed as the first derivative of the deflection, i.e. ; The angle by which the first and second bar magnets deflect relative to the axis of the transverse cantilever beam is given. The initial horizontal distance between the bar magnet and the ring magnet is denoted as . It is half the length of the first bar magnet and the second bar magnet; It is half the width of the first bar magnet and the second bar magnet; Let be the initial vertical distance between the axis of the transverse cantilever beam and the annular magnet. For time.

[0055] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0056] The above embodiments are merely examples of implementation methods of the invention. The scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A piezoelectric energy harvesting device with magnetic deflection-type elastic boundary tristable state, characterized in that, include: A pair of horizontally symmetrical cantilever beam assemblies, a pair of longitudinally symmetrical cantilever beam assemblies; and, in each longitudinal cantilever beam assembly, a pair of symmetrical magnet-spring devices are provided. Among them, the transverse cantilever beam assembly uses a double magnet to deflect in opposite directions to change the distribution of the magnetic field, thereby reducing the depth of the potential well; the magnet-spring device of the longitudinal cantilever beam assembly will generate horizontal displacement during vibration, forming an elastic boundary and generating a variable potential well. A pair of transverse cantilever beam assemblies includes transverse cantilever beam assembly one (1) and transverse cantilever beam assembly two (3); transverse cantilever beam assembly one (1) includes a first transverse cantilever beam (11), a first piezoelectric element (12), a first bar magnet (14), and a second bar magnet (15); The first bar magnet (14) and the second bar magnet (15) are located at the free end of the first transverse cantilever beam (11) and can be deflected in the opposite direction along the axis of the first transverse cantilever beam (11); the first piezoelectric element (12) is located at the root of the first transverse cantilever beam (11); The same applies to the transverse cantilever beam assembly two (3); A pair of magnet-spring devices includes a left magnet-spring device 1 and a right magnet-spring device 1; the left magnet-spring device 1 includes a horizontally placed first shaft (23A), a first annular magnet (24A), and a first spring (25A); A first spring (25A) and a first annular magnet (24A) are sleeved on a first shaft (23A), and one end of the first shaft (23A) is fixedly connected to a first longitudinal cantilever beam (21). The two ends of the first spring (25A) are fixedly connected to the first annular magnet (24A) and the first longitudinal cantilever beam (21) respectively. The first annular magnet (24A) can slide on the first shaft (23A). The magnet-spring device on the right works in the same way; The ring magnet in the magnet-spring device has the same polarity as the bar magnet in the transverse cantilever beam assembly.

2. The piezoelectric energy harvesting device of magnetic deflection type elastic boundary tristable state according to claim 1, characterized in that, A pair of longitudinal cantilever beam assemblies includes longitudinal cantilever beam assembly one (2) and longitudinal cantilever beam assembly two (4); The longitudinal cantilever beam assembly (2) includes a first longitudinal cantilever beam (21), a left magnet-spring device and a right magnet-spring device symmetrically arranged at the free end of the first longitudinal cantilever beam (21), and a third piezoelectric element (22) located at the root of the first longitudinal cantilever beam (21). The same applies to longitudinal cantilever beam assembly two (4).

3. The piezoelectric energy harvesting device of magnetic deflection type elastic boundary tristable state according to claim 1, characterized in that, The first piezoelectric element (12) consists of two piezoelectric elements, located on both sides of the root of the first transverse cantilever beam (11), and the polarization directions of the two piezoelectric elements are opposite, and the electric fields generated are in the same direction. A wire is drawn out from the upper surface of the upper layer and the lower surface of the lower layer, and then the two wires are connected to the load or energy storage circuit to complete the extraction of charge. The same applies to the piezoelectric elements in the transverse cantilever beam assembly 2 (3) and the pair of longitudinal cantilever beam assemblies.

4. The piezoelectric energy harvesting device of magnetic deflection type elastic boundary tristable state according to claim 1, characterized in that, The transverse cantilever beam assembly (1) includes a first triangular prism block (13); the first triangular prism block (13) is fixed at the free end of the first transverse cantilever beam (11), and a first bar magnet (14) and a second bar magnet (15) are attached to the first triangular prism block (13).

5. The piezoelectric energy harvesting device of magnetic deflection type elastic boundary tristable state according to claim 2, characterized in that, When the first transverse cantilever beam (11) vibrates vertically, the first bar magnet (14) and the second bar magnet (15) will exert magnetic force on the first ring magnet (24A) and the third ring magnet (44A), causing the first ring magnet (24A) and the third ring magnet (44A) to slide horizontally along the first shaft (23A) and the third shaft (43A) respectively, resulting in the compression and stretching of the first spring (25A) and the third spring (45A); The vertical vibration process of the transverse cantilever beam assembly 2 (3) is similar; among them, the third annular magnet (44A), the third shaft (43A), and the third spring (45A) are components of the left magnet-spring device 2 in the longitudinal cantilever beam assembly 2 (4).

6. The piezoelectric energy harvesting device of magnetic deflection type elastic boundary tristable state according to claim 2, characterized in that, When the first longitudinal cantilever beam (21) vibrates horizontally, initially due to inertia, the first spring (25A) and the second spring (25B) are compressed and stretched respectively. The springs store energy, and under the action of the springs, the first ring magnet (24A) and the second ring magnet (24B) will slide horizontally along the shaft. During the sliding process, the first ring magnet (24A) and the second ring magnet (24B) will be subjected to the magnetic force of the first bar magnet (14) and the third bar magnet (34) respectively. The horizontal vibration process of the second longitudinal cantilever beam (41) in the longitudinal cantilever beam assembly 2 (4) is similar; among them, the second annular magnet (24B) and the second spring (25B) belong to the components of the right magnet-spring device 1.

7. The piezoelectric energy harvesting device of magnetic deflection type elastic boundary tristable state according to claim 2, characterized in that, By adjusting the deflection angles of the first bar magnet (14), the second bar magnet (15) and the axis of the first transverse cantilever beam (11), the bar magnets and transverse cantilever beams in the second transverse cantilever beam assembly (3) are similarly adjusted to maintain the existence of three potential wells and to adjust the potential energy curve with the goal of reducing the depth of the potential wells.

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