Adjustable frequency vibration energy harvesting device based on magnetic field modulation

Abstract

The application discloses a frequency-adjustable vibration energy collection device based on magnetic field modulation, which comprises a packaging shell, a frequency-adjusting component arranged on the upper portion of the packaging shell, a vibration beam arranged in the middle portion of the packaging shell, a permanent magnet arranged on the lower surface of the vibration beam and a coil arranged on the bottom of the packaging shell; the vibration beam and the permanent magnet constitute a vibration energy collector, and vibration energy in the environment is converted into relative movement between the coil and the permanent magnet so as to output electric energy. The position of the magnetic component of the soft magnetic material in the frequency-adjusting component is adjusted, the magnetic field distribution and the magnetic field force characteristics of the permanent magnet in the energy collector are changed, and the accurate adjustment of the resonance frequency of the device is realized. In addition, the soft magnetic material has excellent magnetic shielding characteristics, so that the magnetic field cross-interference in and outside the energy collector can be effectively reduced, the applicable environment and the environmental stability of the energy collector are greatly improved, and the accurate frequency adjustment process of the vibration energy collector is ensured while the mutual influence of the external interference and the internal magnetic field of the device is reduced.

Description

Technical Field

[0001] This invention relates to the field of vibration energy harvesting technology, specifically to frequency adjustment technology for vibration energy harvesting devices, and particularly to a frequency-adjustable vibration energy harvesting device based on magnetic field modulation. Background Technology

[0002] Vibration energy harvesting technology is a technique that converts vibration energy from the environment into electrical energy to power electronic products. Currently, most vibration energy harvesting devices are resonant devices, characterized by maximum output power when the device's resonant frequency matches the ambient vibration frequency; the output power drops sharply when the frequency deviates from the resonant frequency. However, in practical applications, ambient vibration frequencies are random and non-adjustable, and the device's resonant frequency can easily shift due to errors in design, manufacturing, and assembly. Therefore, to achieve a match between the device's resonant frequency and the ambient vibration frequency, a resonant frequency adjustment design for the device is essential.

[0003] The resonant frequency of the device is mainly adjusted by regulating the system's mass or stiffness. Mass adjustment typically involves increasing or decreasing the size or position of the mass block; however, since the mass block is a movable component, this method is inconvenient and lacks precision. Stiffness adjustment can be achieved by modifying the parameters of various components, such as the geometric parameters of the vibration-collecting beam, the mass of the vibration-collecting unit, the stress on the vibration-collecting beam, and the magnetic force on the permanent magnet of the vibration-collecting unit.

[0004] In the field of energy harvesting technology, existing patents have addressed the issue of altering the resonant frequency of a device by adjusting the parameters of the vibration-harvesting beam. Patent 201210551994.7 proposes a method for fabricating an electromagnetic energy harvester using micro-nano fabrication technology, adjusting the resonant frequency by changing the thickness and length of the vibrating plate and the folded beam. Patent 202010067919.8 proposes an integrated, nonlinearly cascaded, multi-degree-of-freedom vibration energy harvester, increasing the operating bandwidth of the harvester by independently changing the parameters of the inner and outer oscillators, thereby adjusting the spacing between two nonlinear modes and the bandwidth characteristics of a single nonlinear mode. However, these methods involve combining multiple energy harvesting devices with different parameters, resulting in discontinuous operating bandwidth and failing to truly achieve adjustment of the device's resonant frequency.

[0005] Existing patents have introduced permanent magnet materials into energy harvesters, utilizing nonlinear principles to expand the device's operating bandwidth. Patents 201711211951.3 and 201721612390.3 propose a multi-directional broadband energy harvester using a curved beam, utilizing the magnetic force between the piezoelectric beam magnet and the curved beam magnet to harvest broadband vibration energy. Patent 201611024248.7 proposes an amplitude amplification and superposition vibration energy harvesting device, using the magnetic force between the magnet fixed at the end of the cantilever beam and the fixed magnet to make the system a bistable nonlinear system, thus increasing the device's operating bandwidth. Patent 201821788962.8 proposes a novel piezoelectric vibration energy harvester, utilizing the magnetic force between a moving magnet and a fixed magnet to adapt the device to vibration environments of various frequencies. Patent 201610962588.8 proposes a nonlinear eddy-induced vibration energy harvester with force-electric-fluid coupling, increasing the device's operating bandwidth by introducing nonlinear magnetic force. All of the above patents introduce magnetic force through permanent magnet materials and expand the working bandwidth of the device by utilizing nonlinear characteristics. However, the nonlinearity caused by permanent magnet materials is relatively large, resulting in problems such as low frequency tuning accuracy and inability to adjust the device frequency to the specified frequency.

[0006] Existing patents have incorporated permanent magnet materials into energy harvesters, combined with mechanical adjustment components, to achieve resonant frequency adjustment. Patent 202110557821.5 proposes a tunable broadband piezoelectric-electromagnetic composite power generation device with an elastic amplifier, using a motor-driven frequency modulation device to adjust the device's resonant frequency. However, this proposed solution suffers from drawbacks such as a large frequency modulation device and high energy consumption. Patent 202010759431.1 proposes a centrifugal distance optimization matching method for a bistable energy harvester, optimizing the effective harvesting bandwidth of the bistable energy harvester by adjusting the centrifugal distance of the magnets installed at the end of the cantilever beam. While this patent analyzes the impact of centrifugal distance on the device's bandwidth, the distance adjustment steps are complex and only applicable to environments with a fixed frequency. Patent 201910398485.7 proposes a miniature antimagnetic levitation vibration energy harvester and harvesting method for rail transit, adjusting the resonant frequency of the device by changing the height of the lifting permanent magnet to alter the magnetic force on the suspended permanent magnet. The limitations of this patent are that it does not provide the relationship between the adjustment distance and the resonant frequency, making it impossible to flexibly and conveniently adjust the resonant frequency. Furthermore, it does not consider the impact of external interference on the device or the interference of the device's internal magnetic field on the external environment, and its actual operational reliability needs further investigation.

[0007] In summary, frequency modulation technology based on permanent magnet materials can effectively adjust the resonant frequency of energy harvesting devices, but it still has the following shortcomings: Since the magnetic force is inversely proportional to the distance between magnets, the nonlinearity is significant, resulting in low frequency modulation accuracy, high difficulty, and poor controllability; the permanent magnets in the device are easily affected by external magnetic fields or ferromagnetic materials, usually requiring high-performance magnetic shielding packaging, which in turn can significantly change the device characteristics due to interference with the magnetic field distribution; the permanent magnets in the device can generate magnetic fields, which can affect the external application environment, thus limiting the application scenarios. Summary of the Invention

[0008] To overcome the shortcomings of the prior art, the present invention aims to provide a frequency-adjustable vibration energy harvesting device based on magnetic field modulation. By adjusting the position of the soft magnetic frequency modulation component, the magnetic field distribution and magnetic force characteristics of the permanent magnet in the energy harvester are changed, thereby achieving accurate adjustment of the device's resonant frequency. In addition, since the soft magnetic material has excellent magnetic shielding characteristics, it can effectively reduce crosstalk between the internal and external magnetic fields of the energy harvester, significantly improve the applicability and environmental stability of the energy harvester, ensure the accuracy of the vibration energy harvester's frequency adjustment process, and reduce the mutual influence between external interference and the internal magnetic field of the device.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] The frequency-adjustable vibration energy harvesting device based on magnetic field modulation includes an encapsulation shell 5, a frequency modulation component 1 is provided on the upper part of the encapsulation shell 5, a vibration pickup beam 2 is provided in the middle of the encapsulation shell 5, a permanent magnet 3 is provided on the lower surface of the vibration pickup beam 2, and a coil 4 is provided at the bottom of the encapsulation shell 5.

[0011] The frequency modulation component 1 includes a cover plate 12 that serves as the top cover of the encapsulation shell 5. A frequency modulation screw 11 is disposed through the center of the cover plate 12. A bolt 15 is disposed on the cover plate 12. A magnetic component 13 is sleeved on the bolt 15. The bottom end of the frequency modulation screw 11 contacts the upper surface of the magnetic component 13. A spring 14 is sleeved on the bolt 15 located below the magnetic component 13. A nut 16 is installed at the end of the bolt 15.

[0012] The magnetic component 13 is made of soft magnetic material.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] This invention uses a soft magnetic material to make a frequency tuning mechanism. By adjusting the position of the soft magnetic frequency tuning mechanism, the distribution of the magnetic field around the permanent magnet in the vibration energy harvester is changed and the magnetic force acting on it is changed, thereby changing the resonant frequency of the device.

[0015] 1. Although both soft magnetic materials and permanent magnet materials can change the magnetic field distribution generated by the permanent magnet in the energy harvester, smaller permanent magnet materials can generate larger magnetic forces. The frequency modulation method based on permanent magnet materials has significant nonlinearity problems, low frequency modulation accuracy, and difficulty in accurately adjusting the device's resonant frequency to the target frequency. The present invention is based on the frequency modulation method of soft magnetic materials, which has a low degree of nonlinearity, improves the frequency modulation accuracy of the device, and enhances the device's environmental adaptability.

[0016] 2. Frequency modulation methods based on permanent magnet materials are easily affected by external interference and can also cause interference to the external environment, making them difficult to apply in applications with spatial magnetic fields or those sensitive to magnetic fields (such as power, aerospace, and rail transportation). This invention utilizes a soft magnetic material-based magnetic component 13, whose force on the permanent magnet 3 in the vibration pickup component is similar to the attraction between opposite magnetic poles. This effectively reduces the mass of the vibration pickup component, increasing the resonant frequency of the device. The attraction between the magnetic component 13 and the permanent magnet 3 in the vibration pickup component causes an upward displacement of the vibration pickup component, generating tensile or compressive stress on the vibration pickup beam 2, thus changing the resonant frequency of the device. This frequency modulation method ensures that the internal magnetic field of the device is not affected by the external environment and does not interfere with the external environment. This has decisive significance for the high reliability and strong safety of the device in practical applications. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the adjustable frequency vibration energy harvesting device based on magnetic field modulation of the present invention.

[0018] Figure 2 This is a schematic diagram of the frequency modulation component used for magnetic field modulation in this invention.

[0019] Figure 3 This is a diagram showing the effect of the frequency modulation component on the magnetic field distribution obtained by finite element simulation in this invention.

[0020] Figure 4 This is a device assembly diagram of the adjustable frequency vibration energy harvesting device of the present invention.

[0021] Figure 5 This is a test result diagram of the prototype of the present invention. Detailed Implementation

[0022] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0023] Figure 1 , Figure 4This is a schematic diagram of the present invention. The adjustable frequency vibration energy harvesting device based on magnetic field modulation includes an encapsulated shell 5. A frequency modulation component 1 is disposed on the upper part of the encapsulated shell 5. A vibration pickup beam 2 is disposed in the middle inside the encapsulated shell 5, a permanent magnet 3 is disposed on the lower surface of the vibration pickup beam 2, and a coil 4 is disposed at the bottom of the encapsulated shell 5. The vibration pickup beam 2, permanent magnet 3, and coil 4 constitute a vibration energy harvester. The vibration pickup beam 2 and permanent magnet 3 constitute the vibration pickup component of the vibration energy harvester. When the external environment vibrates, the vibration pickup beam 2 drives the permanent magnet 3 to vibrate together, while the coil 4 remains relatively stationary with respect to the shell. Therefore, there is relative motion between the coil 4 and the permanent magnet 3, converting the vibration energy in the environment into relative motion between the coil 4 and the permanent magnet 3, thereby outputting electrical energy. The encapsulated shell 5 serves to fix and protect the frequency modulation component 1 based on magnetic field modulation and the vibration energy harvester.

[0024] Reference Figure 2 The frequency modulation component 1 includes a cover plate 12 serving as the upper cover of the encapsulation shell 5. A frequency modulation screw 11 is disposed through the center of the cover plate 12, and a bolt 15 is disposed on the cover plate 12. A magnetic component 13 is sleeved on the bolt 15. The bottom end of the frequency modulation screw 11 contacts the upper surface of the magnetic component 13. A spring 14 is sleeved on the bolt 15 located below the magnetic component 13, and a nut 16 is installed at the end of the bolt 15. By rotating the frequency modulation screw 11, the magnetic component 13 moves up and down, thereby changing the vertical height of the magnetic component 13, thereby changing the magnetic field distribution in the vibration energy harvester and the magnetic force on the permanent magnet 3, thus realizing the adjustment of the resonant frequency of the device. The magnetic component 13 is made of soft magnetic material and permanent magnet material. When the magnetic component 13 is made of soft magnetic material, it can also effectively shield the magnetic field generated by the permanent magnet 3, avoiding cross-interference with the external environment. In addition, the compressed spring 14 can provide sufficient force to keep the magnetic component 13 at different heights, improving the stability of the frequency adjustment of the device. The structural diagram of this typical implementation can be modified as needed, such as changing the position of each bolt, the position of the spring, the shape of the cover plate, the connection method and position, etc. The frequency tuning screw can also be replaced by other similar linear motion mechanisms.

[0025] Figure 3This diagram illustrates the effect of different materials used in the frequency modulation component on the magnetic field distribution, obtained through finite element simulation. The magnetic component 13 is made of either soft magnetic material or permanent magnet material, with the permanent magnet 3 providing both attractive and repulsive magnetic forces. Without the magnetic component 13, the magnetic field generated by the permanent magnet 3 of the vibration energy harvester is distributed in the surrounding air, with magnetic field lines pointing from the N pole to the S pole. When the magnetic component 13 is made of soft magnetic material, the path of the magnetic field lines generated by the permanent magnet 3 changes; the magnetic field lines that originally passed through the air are now confined to the magnetic component 13, resulting in almost no magnetic field lines in the air on the side of the soft magnetic component 13 away from the permanent magnet. If the magnetic component 13 is made of permanent magnet material, it possesses both attractive and repulsive magnetic forces, and the path of the magnetic field lines generated by the permanent magnet 3 also changes. However, magnetic field lines are still distributed in the air on the side of the permanent magnet component 13 away from the permanent magnet 3.

[0026] Soft magnetic materials refer to materials whose magnetization occurs at a Hc value of no more than 1000 A / m. The reason soft magnetic materials cause changes in the magnetic field is that, compared to air, they have a high permeability to weak magnetic fields and low magnetic reluctance. Magnetic field lines pass through the low-resistance soft magnetic material, confining those dispersed in air. The difference between soft magnetic materials and permanent magnets in their influence on magnetic field distribution is: 1. Soft magnetic materials result in lower nonlinearity due to frequency modulation, improving the device's frequency modulation accuracy and enhancing its environmental adaptability. 2. Frequency modulation based on soft magnetic materials ensures that the internal magnetic field of the device is not disturbed by the external environment and does not interfere with the external environment, which is crucial for the practical application of the device.

[0027] See Figure 4 The working principle of this invention is as follows: In actual operation, rotating the frequency tuning screw 11 pushes the magnetic component 13 of the soft magnetic material to move up and down, thereby changing the vertical height of the magnetic component 13 and altering the magnetic force on the permanent magnet 3 in the vibration energy harvester, thus adjusting the resonant frequency of the device. The frequency adjustment mechanism of the magnetic component 13 of the soft magnetic material is mainly as follows: First, the force exerted by the magnetic component 13 of the soft magnetic material on the permanent magnet 3 in the vibration pickup component is similar to the attraction between opposite magnetic poles, which is equivalent to reducing the mass of the vibration pickup component, thus increasing the resonant frequency of the device. Second, the attraction between the magnetic component 13 of the soft magnetic material and the permanent magnet 3 of the vibration pickup component causes the vibration pickup component to move upward, generating tensile or compressive stress on the vibration pickup beam 2, causing a change in the resonant frequency of the device. The structure and spatial arrangement of the magnetic component 13 of the frequency tuning component 1 are not limited to the arrangement directly above in the schematic diagram; it can be arranged on top, bottom, side, side ring, fully enclosed by the outer shell, or a combination of several arrangements.

[0028] Figure 5This is a test result diagram of the prototype of the present invention, in which the magnetic component 13 in the frequency modulation component 1 is made of permalloy. As shown by the curves in the diagram, as the adjustment distance H of the permalloy frequency modulation component decreases from 8mm to 2.5mm, the resonant frequency of the device increases from 100Hz to 138Hz, a relative frequency adjustment range of 38%, and the peak-to-peak output voltage of the device decreases from 2.6V to 1.4V. Within the adjustment distance H from 8mm to 4.5mm, the resonant frequency of the device increases from 100Hz to 106Hz, a change of 6Hz; while within the adjustment distance H from 4.5mm to 2.5mm, the resonant frequency of the device increases from 106Hz to 138Hz, a change of 32Hz. This is because the closer the permalloy is to the permanent magnet in the electromagnetic vibration energy harvester, the stronger the attraction between the permalloy and the permanent magnet, and the greater the impact on the resonant frequency of the device. The output voltage of the device decreases as the distance between the permalloy and the permanent magnet approaches. This is because the attraction between the permalloy and the permanent magnet increases the distance between the permanent magnet and the coil surface, and the attraction limits the displacement of the permanent magnet in the vibration pickup component.

Claims

1. A frequency-tunable vibration energy harvesting device based on magnetic field modulation, comprising a housing (5), characterized in that, A frequency modulation component (1) is provided on the upper part of the encapsulation shell (5); a vibration pickup beam (2) is provided in the middle of the encapsulation shell (5); a permanent magnet (3) is provided on the lower surface of the vibration pickup beam (2); and a coil (4) is provided at the bottom of the encapsulation shell (5). The frequency modulation component (1) includes a cover plate (12) that serves as the top cover of the encapsulation shell 5. A frequency modulation screw (11) is provided through the center of the cover plate (12). A bolt (15) is provided on the cover plate (12). A magnetic component (13) is sleeved on the bolt (15). The bottom end of the frequency modulation screw (11) contacts the upper surface of the magnetic component (13). A spring (14) is sleeved on the bolt (15) located below the magnetic component (13). A nut (16) is installed at the end of the bolt (15). The magnetic component (13) is made of soft magnetic material.

Images