Double-cantilever-beam piezoelectric vibration energy collector based on annular steady state

Abstract

The invention discloses a double-cantilever-beam piezoelectric vibration energy collector based on an annular steady state, which comprises a piezoelectric transducer, an elastic cantilever beam, a magnet and a base, after the piezoelectric transducer is mounted on the elastic cantilever beam to form a double-layer composite cantilever beam, the magnet is mounted at the free end of the double-layer composite cantilever beam, nonlinear coupling is carried out through repulsive magnetic force, and the piezoelectric transducer is connected with the base. The two-dimensional annular potential well structure with the adjustable potential well is formed, and the energy collector can easily trigger large-amplitude inter-well movement through the potential well structure. Through the nonlinear coupling induced internal resonance effect, inter-well energy transfer and two-dimensional potential well modulation are realized, and vibration energy can be efficiently captured in a broadband without a large amount of energy input or a complex structure. According to the design, the collection efficiency of low-frequency, low-intensity and multi-direction environment vibration energy in a wide working bandwidth is good.

Description

Technical Field

[0001] This invention belongs to the technical field of piezoelectric energy harvesting of topological phononic crystals, and relates to a technology based on potential well modulation and magnetic coupling internal resonance. It mainly relates to a double cantilever beam piezoelectric vibration energy harvester based on toroidal steady state. Background Technology

[0002] With the rapid development of IoT technology, wearable devices have enormous application potential in various aspects of daily life, such as smart bracelets, biosensors, and smart clothing. While advancements in microelectronics and sensing technologies are driving devices towards miniaturization and low power consumption, the widespread adoption of wearable electronic devices poses a significant challenge to energy supply. Because wearable devices need to operate continuously or for extended periods, consuming substantial amounts of electricity, frequent battery replacements and recharging are necessary. Furthermore, the widespread use of traditional batteries is exacerbating environmental pollution. These factors collectively limit the development of wearable electronic devices. Therefore, developing sustainable and environmentally friendly new power supply methods has become a key direction for promoting the development of wearable technology.

[0003] Vibration, as a continuous and ubiquitous source of environmental energy, has been extensively studied and used to support low-power and small devices. Harvesting vibration energy from environmental vibrations has become a key research direction for solving the problem of sustainable power supply for wearable devices. On the one hand, traditional linear piezoelectric energy harvesters and one-dimensional nonlinear piezoelectric energy harvesters are inefficient at harvesting low-frequency, low-intensity vibrations. On the other hand, environmental vibrations originate from different directions and have a wide frequency band, while traditional piezoelectric energy harvesters are highly dependent on the direction of the vibration source and have a narrow operating frequency band. Therefore, developing energy harvesters with low-frequency, low-intensity, multi-directional energy harvesting capabilities and wide-bandwidth response characteristics is an important direction for improving the practical application efficiency of energy harvesting technology. Summary of the Invention

[0004] This invention addresses the problems of low harvesting efficiency and narrow operating bandwidth of low-frequency, low-intensity, and multi-directional environmental vibration energy in existing technologies. It provides a toroidal steady-state-based double cantilever beam piezoelectric vibration energy harvester, comprising a piezoelectric transducer, an elastic cantilever beam, a magnet, and a base. The piezoelectric transducer is mounted on the elastic cantilever beam to form a double-layer composite cantilever beam, and a magnet is installed at its free end. Nonlinear coupling is achieved through repulsive magnetic force, forming a two-dimensional toroidal potential well structure with adjustable potential wells. This potential well structure allows the energy harvester to easily trigger large-amplitude inter-well movements. This invention achieves inter-well energy transfer and two-dimensional potential well modulation through the internal resonance effect induced by the nonlinear coupling, efficiently capturing vibration energy over a wide frequency band without requiring large energy inputs or complex structures. The design of this invention exhibits good harvesting efficiency for low-frequency, low-intensity, and multi-directional environmental vibration energy over a relatively wide operating bandwidth.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a piezoelectric vibration energy harvester based on a ring steady state, comprising a piezoelectric transducer, an elastic cantilever beam, a magnet and a base;

[0006] The system comprises two elastic cantilever beams, each containing a piezoelectric transducer. The two elastic cantilever beams stand opposite each other symmetrically, forming a double-layer composite piezoelectric cantilever beam. Two single-layer piezoelectric cantilever beams are symmetrically combined, with the sides containing the piezoelectric transducers facing each other to ensure consistency in restoring force and output voltage during vibration. Each free end of the double-layer composite piezoelectric cantilever beam is equipped with a magnet, and the two cantilever beams are orthogonally mounted on the base. The magnets at each free end generate repulsive magnetic force to achieve nonlinear coupling, forming a ring-shaped trap structure with adjustable depth in a two-dimensional plane to achieve multi-directional, low-frequency, wide-bandwidth vibration energy harvesting. By introducing the internal resonance mechanism generated by nonlinear coupling, the system's natural frequency is effectively reduced, thereby improving the response capability to low-frequency vibration energy and energy harvesting efficiency.

[0007] As an improvement to this invention, a side clamping device is also included. This side clamping device is adjustablely mounted on the base and is used to adjust the horizontal distance between the two magnets to control the shape of the potential well, thereby achieving adjustability of the potential well structure. The two cantilever beams are orthogonally arranged in space, with their centers aligned, forming a symmetrical structure in a two-dimensional plane, thus achieving a highly efficient response to vibrations in any direction within the two-dimensional plane.

[0008] As another improvement of the present invention, the width of the piezoelectric transducer is the same as the width of the elastic cantilever beam, and it is fixedly installed on the substrate of the elastic cantilever beam. The fixed installation method includes, but is not limited to, bolt fastening, epoxy resin bonding and welding, to ensure structural strength and energy conversion efficiency.

[0009] As another improvement of the present invention, the number of piezoelectric transducers in each elastic cantilever beam is not unique, but at least two are provided, located on the elastic cantilever beam substrate near the free end and on the other end near the fixed end, respectively, in order to improve the energy conversion efficiency.

[0010] As another improvement of the present invention, the magnet is a cylindrical N35 magnet, the distance between the two magnets is 16-20 mm, and the two magnets are nonlinearly magnetically coupled by repulsive force to form an adjustable potential well structure.

[0011] As a further improvement of the present invention, the cylindrical magnet has a radius of 5 mm and a height of 10 mm, and the piezoelectric transducer is specifically located 5 mm from the fixed end and the free end of the elastic substrate.

[0012] As a further improvement of the present invention, the system potential well is switched between a linear monostable state and a nonlinear toroidal steady state by adjusting the horizontal distance between the two magnets. The relationship between the magnet distance D and the radius r of the toroidal potential well equilibrium position is as follows:

[0013]

[0014] in, Let be the magnetic dipole moment of each of the two magnets. The equivalent concentrated stiffness at the free end of the double-layer piezoelectric cantilever beam;

[0015] when After the value increases to a critical value, that is... At this point, the system equilibrium state exhibits a monostable state; when The equilibrium state of the system is a toroidal steady state.

[0016] Compared with existing technologies, the present invention has the following advantages: It provides a toroidal steady-state double cantilever beam piezoelectric vibration energy harvester. By introducing a nonlinear internal resonance effect and a potential well modulation mechanism, and utilizing the pre-set repulsive magnetic force between magnets to achieve nonlinear mechanical coupling, a two-dimensional toroidal potential well structure with dynamically adjustable potential well depth and shape is formed. This structure, through repulsive magnetic coupling, causes the double cantilever beams to rotate significantly around the central potential barrier under low-intensity vibration excitation, breaking through the energy threshold limitation of traditional nonlinear systems that require crossing the potential barrier. Based on the internal resonance effect induced by nonlinear coupling, energy exchange between the two beams and dynamic modulation of the cantilever beam stiffness are achieved, significantly widening the operating bandwidth of the system under small excitation. Its two-dimensional toroidal potential well design maintains almost the same high energy conversion efficiency for vibrations in any direction within the plane, eliminating the direction dependence of traditional directional piezoelectric energy harvesters, and exhibiting excellent harvesting performance, especially for low-frequency, low-intensity, multi-directional vibration energy, over a wide frequency range. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the double cantilever beam piezoelectric vibration energy harvester based on the ring steady state of the present invention;

[0018] Figure 2 This is a schematic diagram of the piezoelectric single-crystal structure in the double cantilever beam piezoelectric vibration energy harvester based on ring steady state of the present invention;

[0019] Figure 3 This is a schematic diagram of the mechanical and lumped parameter model of the double cantilever beam piezoelectric vibration energy harvester based on the ring steady state of the present invention;

[0020] Figure 4 This is a schematic diagram of the potential energy trajectory of the double cantilever beam piezoelectric vibration energy harvester based on ring steady state according to the present invention;

[0021] Figure 5 This is a schematic diagram of the voltage frequency domain response numerical simulation results of the double cantilever beam piezoelectric vibration energy harvester based on ring steady state in the test example of the present invention;

[0022] Figure 6 This is a schematic diagram of the voltage frequency domain response experimental results of the double cantilever beam piezoelectric vibration energy harvester based on ring steady state in the test examples of this invention;

[0023] In the figure: 1. Piezoelectric transducer, 2. Substrate, 3. Magnet, 4. Elastic cantilever beam, 5. Side clamping device, 6. Base. Detailed Implementation

[0024] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0025] Example 1

[0026] A piezoelectric vibration energy harvester based on a toroidal steady-state double cantilever beam, such as Figure 1 As shown, it includes a piezoelectric transducer 2, an elastic cantilever beam 4, a magnet 3, and a base 6;

[0027] Two elastic cantilever beams 4 are provided, each containing a piezoelectric transducer 1. The two elastic cantilever beams 4 stand opposite each other symmetrically, forming a double-layer composite piezoelectric cantilever beam. Each free end of the double-layer composite piezoelectric cantilever beam is equipped with a magnet 3, and the two elastic cantilever beams 4 are orthogonally mounted on the base 6. The magnets 3 at each free end generate repulsive magnetic force to achieve nonlinear coupling, forming a two-dimensional ring-shaped potential well structure with adjustable potential well. A side clamping device 5 is also included, which is used to orthogonally and movably mount the two elastic cantilever beams 4 on the base 6. By adjusting the distance between the two elastic cantilever beams 4, the horizontal distance between the two magnets 3 is controlled, making the potential well structure adjustable.

[0028] like Figure 1 As shown, the side clamping devices 5 on both sides respectively fix two mutually orthogonal double-layer piezoelectric cantilever beam structures, referred to as beam A and beam B. The double-layer piezoelectric cantilever beam includes a piezoelectric transducer 1 fixed to an elastic substrate 2, the elastic substrate 2, and a magnet 3 fixed to the free end. In this embodiment, the dimensions of the elastic substrate 2 are... The dimensions of the rectangular piezoelectric transducer 1 are: ,

[0029] The piezoelectric transducer 3 is fixed 5mm from both the fixed and free ends of the elastic substrate 2. Due to the symmetrical vibration mode, its output capability is significantly improved. Furthermore, assembling the sides with the piezoelectric transducer 1 facing each other ensures the consistency of the restoring force experienced by the double-layer composite cantilever beam during vibration. The width of the piezoelectric transducer 3 on the substrate 2 is the same as that of the elastic substrate 2, and they completely overlap during fixing. Figure 2 This is a schematic diagram of the piezoelectric single-crystal structure of the toroidal steady-state double cantilever piezoelectric vibration energy harvester of the present invention. During the assembly of the double-layer piezoelectric composite cantilever beam, it is connected to the outside environment through bolt fastening, epoxy resin bonding, or welding to ensure structural strength and energy conversion efficiency. Two independent electrode leads are welded to the upper and lower surfaces of the piezoelectric transducer 1 for connection to the input ports of other extended circuits. An N35 cylindrical magnet 3 with a radius of 5mm and a height of 10mm is fixed to the free end of the double-layer piezoelectric cantilever beam. The magnets 3 of the two beams are coupled by repulsive force, allowing the potential energy between the two beams to be exchanged through magnetic coupling. The two elastic cantilever beams 4 are aligned at their centers and placed orthogonally to each other during installation, extending the potential well from one-dimensional space to two-dimensional space.

[0030] In this embodiment, the dimensions of the side clamping device 5 are: The dimensions of the rigid base 6 are Two symmetrical rectangular slots, each 5mm wide, are made on the left and right sides of the rigid base 6 to serve as guide rails. Two 3mm diameter threaded holes are made on the bottom of the side clamping devices 5, corresponding to the guide rail positions, to accommodate screws or other fixing parts for mounting the side clamping devices 5 onto the rigid base 6, allowing for free adjustment of their left and right positions. One slot is removed from the center of the two side clamping devices 5. The vertical holes are used to fix the double-layer cantilever beams to the side clamping device 5 with parts such as washers and screws, and can adjust the vertical position to ensure the alignment of the two side clamping devices 5. At the same time, the side clamping device 5 can adjust the distance between the two elastic cantilever beams 4 to control the horizontal distance between the two magnets 3, making the two-dimensional annular trap adjustable.

[0031] The collector of this invention introduces a magnet to make the system potential well ring-shaped. During vibration, the two elastic cantilever beams 4 can generate large-amplitude motion around the central potential barrier along the ring-shaped potential well. At the same time, the excitation conditions for triggering large-amplitude motion are reduced, and vibration energy in any direction in the two-dimensional plane can be collected. By introducing an internal resonance mechanism, the resonant frequency of the system is reduced, which enables the collector to improve the collection efficiency of low-frequency vibration energy.

[0032] Example 2

[0033] As described in Example 1, in the ring-steady-state-based double cantilever beam piezoelectric vibration energy harvester, the distance between the two opposing magnets 3 can be adjusted by adjusting the fixed position of the side clamping device 5 on the base 6, making the two-dimensional ring-shaped trap adjustable. Therefore, a mechanical and lumped parameter model of the ring-steady-state-based double cantilever beam piezoelectric vibration energy harvester is established, such as... Figure 3 As shown. By calculating the concentrated mass, concentrated stiffness, and mechanical damping of each double-layer piezoelectric cantilever beam, it is equivalent to a typical cantilever beam, whose mechanical model is a typical spring-mass-damped system.

[0034] In this embodiment, the potential well of the double cantilever beam piezoelectric vibration energy harvester based on toroidal steady-state is adjustable. Adjusting the distance between the magnets 3 between the two beams allows the system potential well to switch between linear monostable and nonlinear toroidal steady-state. The relationship between the magnet distance D and the radius r of the toroidal potential well equilibrium position is as follows:

[0035]

[0036] in, Let be the magnetic dipole moment of each of the two magnets. The equivalent concentrated stiffness at the free end of the double-layer piezoelectric cantilever beam.

[0037] The above formula is After the value increases to a critical value, that is... At this point, the system equilibrium state exhibits a monostable state; when The system's equilibrium state exhibits a toroidal steady state. The critical value in this embodiment is 22.2 mm.

[0038] The schematic diagram showing the relationship between the trajectories of beams A and B in the two-dimensional plane and the system potential energy of the double cantilever piezoelectric vibration energy harvester based on ring steady state is shown below. Figure 4 As shown, the combined motion of beams A and B is in the circumferential direction around the bottom of the potential well. Furthermore, beams A and B move around the potential barrier at the center of the potential well; therefore, the energy harvester does not need to collect a large amount of mechanical energy from the outside to overcome the barrier. Under relatively small excitation, compared to traditional linear piezoelectric vibration energy harvesters or one-dimensional nonlinear piezoelectric vibration energy harvesters, this toroidal steady-state-based double cantilever beam piezoelectric vibration energy harvester, by introducing nonlinear internal resonance and utilizing the principle of potential well modulation, generates a large-amplitude rotational motion around the central potential barrier in two-dimensional space. This allows it to generate a large voltage output under low-intensity conditions, without needing to absorb a large amount of mechanical energy from the outside, and significantly broadens the operating frequency band.

[0039] Test case

[0040] The invention's circular steady-state double cantilever beam piezoelectric vibration energy harvester was subjected to numerical simulation experiments and shaking table tests, yielding the following results: Figure 5 and Figure 6 As shown, Figure 5 This is a schematic diagram of the frequency domain voltage response of the collector in numerical simulation.

[0041] The state control equations of the energy harvester were imported into MATLAB, and its frequency response in the 5-15 Hz frequency range was solved using the Runge-Kutta method. The excitation size used in the numerical simulation was 0.5 g, and the distance between the two magnets was 18 mm. A schematic diagram of the frequency domain voltage response of the numerical simulation experiment of the toroidal steady-state double cantilever piezoelectric vibration energy harvester is shown below. Figure 5 As shown, the peak voltage output of beam A is 75.84V, and the operating bandwidth is 3.0Hz. Due to the strong nonlinear coupling between beam A and beam B via magnetic force, beam B will also generate significant vibration and voltage output in the y-direction. The peak voltage output of beam B is 57.83V. This indicates that both beams of the toroidal steady-state-based double cantilever beam piezoelectric vibration energy harvester can generate large voltage output and wide operating bandwidth under low-intensity excitation.

[0042] The energy harvester was mounted on a vibration table, and an actual energy harvesting test was conducted using the same excitation magnitude and magnet spacing as in the numerical simulation experiment. A MATLAB program on a PC was used to output a swept frequency signal, which was amplified by a power amplifier and then output to the vibration table, thereby causing the energy harvester to vibrate. Simultaneously with the vibration, the output of the piezoelectric transducer patch on the beam of the energy harvester was connected to a data acquisition card. The acquired data was processed to obtain a schematic diagram of the experimental frequency domain voltage response of the toroidal steady-state-based double cantilever beam piezoelectric vibration energy harvester, as shown in the figure. Figure 6 As shown, the maximum peak-to-peak voltage output of beam A is 129.7V with a working bandwidth of 7.1Hz, while the peak voltage output of beam B is 115.3V with a working bandwidth of 6.7Hz. This further demonstrates that the piezoelectric vibration energy harvester based on ring steady state has a large voltage output and a wide working frequency range in practical applications.

[0043] Numerical simulations and shaking table tests were conducted for all different combinations of these two parameters, with excitation amplitude ranging from 0.3 to 0.6 g and a growth step of 0.05 g, and magnet spacing ranging from 16 to 20 mm and a growth step of 0.5 mm. The results show superior energy harvesting performance compared to traditional linear piezoelectric vibration energy harvesters or one-dimensional nonlinear piezoelectric vibration energy harvesters. Specifically, the excitation magnitude of the toroidal steady-state-based double cantilever beam piezoelectric vibration energy harvester can be any value within the range of 0.3 to 0.6 g, and the magnet spacing constant can be any value within the range of 16 to 20 mm.

[0044] In summary, this invention introduces nonlinear internal resonance and utilizes the principle of potential well modulation to design a double cantilever beam piezoelectric vibration energy harvester based on a ring-shaped adjustable potential well. Through nonlinear coupling using repulsive magnetic force, a two-dimensional ring-shaped potential well structure with adjustable potential wells is formed. This potential well structure allows the two cantilever beams of the energy harvester to generate large-amplitude rotational motion around the central potential barrier in two-dimensional space without needing to jump over the potential barrier. This enables the generation of a large voltage output under low-intensity conditions without absorbing a large amount of mechanical energy from the outside, and significantly broadens the operating frequency band. Furthermore, since the system's potential well is a two-dimensional ring-shaped potential well, this energy harvester can collect vibrational energy in any direction within a two-dimensional plane without reducing collection efficiency.

[0045] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A double cantilever beam piezoelectric vibration energy harvester based on ring steady-state, characterized in that... It includes a piezoelectric transducer, a flexible cantilever beam, a magnet, and a base; The elastic cantilever beams are provided in two configurations, each containing a piezoelectric transducer. The two elastic cantilever beams stand opposite each other in a symmetrical configuration, forming a double-layer composite piezoelectric cantilever beam. Each free end of the double-layer composite piezoelectric cantilever beam is provided with a magnet, and the two cantilever beams are orthogonally mounted on the base. The magnets at each free end generate repulsive magnetic force to achieve nonlinear coupling, thus forming a two-dimensional ring potential well structure with adjustable potential well.

2. The double cantilever beam piezoelectric vibration energy harvester based on ring steady state as described in claim 1, characterized in that: It also includes a side clamping device, which is used to orthogonally and movably mount two cantilever beams on the base. By adjusting the distance between the two cantilever beams, the horizontal distance between the two magnets can be controlled, making the potential well structure adjustable.

3. The double cantilever beam piezoelectric vibration energy harvester based on ring steady state as described in claim 1, characterized in that: The width of the piezoelectric transducer is the same as the width of the elastic cantilever beam, and it is fixedly installed on the substrate of the elastic cantilever beam. The fixed installation method includes, but is not limited to, bolt fastening, epoxy resin bonding and welding.

4. The double cantilever beam piezoelectric vibration energy harvester based on ring steady state as described in claim 3, characterized in that: The number of piezoelectric transducers in each elastic cantilever beam is not unique, but there are at least two, located on the substrate of the elastic cantilever beam near the free end and on the other end near the fixed end.

5. The double cantilever beam piezoelectric vibration energy harvester based on ring steady state as described in claim 1, characterized in that: The magnet is a cylindrical N35 magnet, and the distance between the two magnets is 16-20 mm.

6. The double cantilever beam piezoelectric vibration energy harvester based on ring steady state as described in claim 4 or 5, characterized in that: The cylindrical magnet has a radius of 5 mm and a height of 10 mm. The piezoelectric transducer is located 5 mm from the fixed end and the free end of the elastic substrate.

7. The double cantilever beam piezoelectric vibration energy harvester based on ring steady state as described in claim 2, characterized in that: The system potential well is switched between a linear monostable state and a nonlinear toroidal steady state by adjusting the horizontal distance between the two magnets. The relationship between the magnet distance D and the radius r of the toroidal potential well equilibrium position is as follows: ； in, Let be the magnetic dipole moment of each of the two magnets. The equivalent concentrated stiffness at the free end of the double-layer piezoelectric cantilever beam; when After the value increases to a critical value, that is... At this point, the system equilibrium state exhibits a monostable state; when The equilibrium state of the system is a toroidal steady state.

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