Nonlinear five-steady-state electromagnetic vibration energy collector and induced electromotive force calculation method thereof

Abstract

The invention discloses a nonlinear five-steady-state electromagnetic vibration energy collector which comprises a base, annular magnets, rectangular sleeves, rectangular magnets, springs and coils, and the nonlinear five-steady-state electromagnetic vibration energy collector is obtained by adjusting the geometric dimensions and magnetization intensity of the annular magnets and the rectangular magnets, the distance between the annular magnets, the vertical distance between the annular magnets and the rectangular magnets and the rigidity of the springs. And the collector is in a five-stable state. When the collector is subjected to external excitation in the horizontal direction, the rectangular magnet in the sleeve vibrates left and right, so that the magnetic flux of the coil is changed, and induced electromotive force is generated. On one hand, the complexity of structural design, dynamic simulation and analysis, installation and debugging and the like of the multistable collector is simplified, and a new thought and a new technical method are provided for design of the nonlinear multistable electromagnetic vibration energy collector; on the other hand, the invention provides a calculation method for the induced electromotive force of the nonlinear five-steady-state electromagnetic vibration energy collector, and a foundation is laid for manufacturing and application of the collector.

Description

Technical Field

[0001] The present invention belongs to the field of new energy collection technology, and particularly relates to a non-linear five-stable state device that utilizes the electromagnetic induction law to collect vibration energy and convert it into electrical energy. Background Art

[0002] In recent years, with the continuous progress and development of the Internet of Things technology, low-power wireless sensor networks and mobile electronic devices used to sense and collect signals such as sound, light, force, and heat have been everywhere. However, any sensor and electronic device requires continuous power supply to operate. Traditional batteries have a limited service life, and when the electrical energy stored in them is exhausted, they need to be charged or replaced in a timely manner. In addition, if discarded batteries are not properly disposed of, they will cause great pollution to the environment. To make up for the deficiencies of traditional batteries, finding a new type of environmentally friendly and pollution-free power source has become an important solution. Energy harvesters can collect renewable energy such as light energy, thermal energy, wind energy, rain energy, and vibration energy in the environment and convert it into electrical energy to power sensors or electronic devices. They can not only meet the power supply requirements in some special environments, such as deep sea, desert, inside bridges, nuclear reactors, volcanic craters, etc., but also are environmentally friendly and pollution-free. Among the above renewable energies, vibration energy is widely present in production and life, such as machine operation, transportation, human movement, etc. Therefore, vibration energy harvesters have attracted extensive attention from scientific researchers.

[0003] According to the working principle, vibration energy harvesters are mainly divided into electrostatic, piezoelectric, triboelectric, and electromagnetic types. Among them, electromagnetic vibration energy harvesters work based on Faraday's law of electromagnetic induction. They have the advantages of simple structure, small size, no need for an external power supply, and easy integration, and have become a research hotspot in recent years. Electromagnetic vibration energy harvesters can be divided into linear and non-linear structures. The linear structure only has a large output power near the natural frequency, and its working bandwidth is narrow, only suitable for narrowband excitation environments. However, in many application scenarios, the frequency of the vibration source is not single, but complex and variable, such as airplanes, vehicles, wind towers, construction sites, etc. The non-linear structure can well expand the working bandwidth of the energy harvester, thereby improving the working efficiency of the energy harvester under broadband excitation. The non-linear structure usually realizes it by means of special interaction forces between magnets. According to the number of stable states, the system can be divided into bistable, tristable, and quadristable. Under certain conditions, the increase in the number of stable states of the system can increase the distance between the two outer stable states, so that the system can achieve a larger amplitude of transition motion under the same excitation conditions, and thus obtain a better power generation effect.

[0004] Traditional multi-stable systems are usually realized by means of the magnetic force between rectangular (or cylindrical) and rectangular (or cylindrical) magnets. In general, the traditional bistable system requires at least two magnets, the traditional tristable system requires at least three magnets, and the traditional quadri-stable system requires at least four magnets. It can be seen that for each additional stable point in the system, one more magnet needs to be introduced. The increase in the number of magnets increases the structural parameters of the system, and also increases the difficulty of system dynamics analysis and structural optimization, making the installation and debugging of the prototype more complicated. Therefore, the current research on nonlinear multi-stable electromagnetic vibration energy harvesters has only stayed at the quadri-stable state, and no one has yet proposed a five-stable electromagnetic vibration energy harvester and a calculation method for its induced electromotive force. Summary of the invention Summary of the invention

[0006] In order to make up for the technical defects of the traditional multi-stable electromagnetic vibration energy harvester and fill the blank of the five-stable electromagnetic vibration energy harvester, the purpose of the present invention is to propose a nonlinear five-stable electromagnetic vibration energy harvester and determine its induced electromotive force calculation method. The energy harvester can achieve the five-stable technical characteristics with only three magnets.

[0007] The technical solution of the present invention includes the structure of the energy harvester and the calculation steps for determining the induced electromotive force of the harvester.

[0008] The nonlinear five-stable electromagnetic vibration energy harvester includes: two annular magnets, a rectangular magnet, two springs, a coil, a base, and a rectangular sleeve. The technical solution of the structure is: the shape of the base is "匚", and the top and bottom surfaces of the base are perpendicular to the side of the base. The rectangular magnet is placed in the middle position inside the rectangular sleeve and is symmetrically supported by two springs; in the initial state, the two annular magnets are placed on the top surface of the base with the center of the rectangular magnet as the symmetrical point. The coil is wound in the middle position of the outer surface of the rectangular sleeve, and the rectangular sleeve is fixed to the side of the base. By adjusting the geometric dimensions and magnetization strength of the annular magnet and the rectangular magnet, the distance between the two annular magnets, the vertical distance between the annular magnet and the rectangular magnet, and the stiffness of the two springs, the energy harvester is in a five-stable state.

[0009] The working principle of the nonlinear five-stable electromagnetic vibration energy harvester is: when it is stimulated by external excitation in the horizontal direction, the rectangular magnet inside the rectangular sleeve will vibrate left and right, which will cause the magnetic flux of the coil to change. According to Faraday's law of electromagnetic induction, when the magnetic flux of the coil changes, an induced electromotive force will be generated.

[0010] The technical key of the present invention is that the two magnets on the top surface of the base are annular magnets, and the magnet inside the rectangular cylinder sleeve is a rectangular magnet; in the initial state, the two annular magnets on the top surface of the base are placed symmetrically with the center of the rectangular magnet as the symmetry point; only three magnets are used to make the energy harvesting system in a five-stable state, so as to achieve the five-stable state transition motion. Generally speaking, the increase in the number of stable states can expand the working bandwidth of the energy harvester, thereby improving the energy harvesting efficiency. When harvesting broadband energy in the harvesting environment, the reason why the single-stable energy harvester has a lower working efficiency than the multi-stable energy harvester is that the single-stable energy harvester only has one stable state section and can only oscillate back and forth in one potential well near the resonance frequency, and the energy collection frequency band is narrow. Of course, the efficiency of collecting vibration energy in the collection environment is low. The multi-stable harvester can well expand the working bandwidth of the energy harvester, thereby improving the working efficiency of the energy harvester under broadband excitation. However, for traditional multi-stable harvesters, while introducing more stable state points, more rectangular (or cylindrical) magnets must also be introduced. The increase in the number of magnets not only increases the structural parameters of the system, but also increases the difficulty of system dynamics analysis and structural optimization, making the manufacturing and installation of the prototype more complex. The present invention only uses three magnets, but achieves the five-stable state characteristics that the traditional multi-stable harvester configuration requires five magnets. In addition, based on Faraday's law of electromagnetic induction, the present invention gives a calculation method for the induced electromotive force of the non-linear five-stable electromagnetic vibration energy harvester.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: Compared with the traditional five-stable structure using five magnets, this energy harvester only needs to use three magnets. By adjusting the geometric dimensions and magnetization intensities of the annular magnet and the rectangular magnet, the distance between the two annular magnets, the vertical distance between the annular magnet and the rectangular magnet, and the stiffness of the two springs, the five-stable state technical characteristics can be achieved. On the one hand, the present invention simplifies the complexity of the structural design, dynamic simulation, dynamic analysis, installation and debugging, etc. of the multi-stable harvester, and provides new ideas and technical methods for the design of the non-linear multi-stable electromagnetic vibration energy harvester; on the other hand, the present invention gives a calculation method for the induced electromotive force of the non-linear five-stable electromagnetic vibration energy harvester, laying a foundation for the manufacture and application of the harvester. Brief Description of the Drawings

[0012] Appendix Figure 1 It is the main structural schematic view of the present invention.

[0013] Appendix Figure 2 It is the side structural schematic view of the present invention.

[0014] Appendix Figure 3 It is the influence of the spring stiffness change on the system potential energy.

[0015] Appendix Figure 4The influence of the length change of the rectangular magnet on the system potential energy.

[0016] Appendix Figure 5 The influence of the width change of the rectangular magnet on the system potential energy.

[0017] Appendix Figure 6 The influence of the thickness change of the rectangular magnet on the system potential energy.

[0018] Appendix Figure 7 The influence of the outer radius change of the annular magnet on the system potential energy.

[0019] Appendix Figure 8 The influence of the inner radius change of the annular magnet on the system potential energy.

[0020] Appendix Figure 9 The influence of the thickness change of the annular magnet on the system potential energy.

[0021] Appendix Figure 10 The influence of the distance change between two annular magnets on the system potential energy.

[0022] Appendix Figure 11 The influence of the surface perpendicular distance change between the annular magnet and the rectangular magnet on the system potential energy.

[0023] Appendix Figure 12 The influence of the magnetization intensity of the rectangular magnet on the system potential energy.

[0024] Appendix Figure 13 The influence of the magnetization intensity of the annular magnet on the system potential energy. Specific implementation manners

[0025] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and through embodiments. It should be noted that although the accompanying drawings of the specification describe the embodiments, the implementation manners are merely illustrative and not restrictive. Without departing from the spirit of the present invention and the scope protected by the claims, the materials and dimensional parameters of each component can also be changed, and these all fall within the protection scope of the present invention.

[0026] The technical solutions include the structure of the non-linear five-stable electromagnetic vibration energy harvester and the calculation method of the induced electromotive force of the harvester.

[0027] Nonlinear five-stable electromagnetic vibration energy harvester, whose structure is as follows: The base 5 is in the shape of a "C", and both the top and bottom surfaces of the base are perpendicular to the side surface of the base. Two annular magnets 1-1 and 1-2 are fixed on the top surface of the base. Two springs 3-1 and 3-2 are provided at both ends of the rectangular sleeve 6. The rectangular magnet 2 is placed inside the rectangular sleeve and is symmetrically supported by two springs. The two annular magnets are placed on the top surface of the base with the center of the rectangular magnet as the symmetry point. The N poles of the two annular magnets face downwards, and the N pole of the rectangular magnet faces upwards. The coil 4 is wound around the middle position of the outer surface of the rectangular sleeve, and the rectangular sleeve is fixed on the side surface of the base. By adjusting the geometric dimensions and magnetization intensities of the annular magnets and the rectangular magnet, the distance between the two annular magnets, the vertical distance between the annular magnet and the rectangular magnet, and the stiffness of the two springs, the energy harvester is in a five-stable state.

[0028] The five-stable state of the nonlinear five-stable electromagnetic vibration energy harvester is determined by the following calculation steps:

[0029] (1) According to the Biot-Savart law, calculate the magnetic induction intensity B(x, y, z) at any point P(x, y, z) in space by the following formula:

[0030]

[0031]

[0032] In the formula, B B1o (x, y, z) is the magnetic induction intensity at any point in space due to the magnetized current on the outer surface of the annular magnet 1-1; B B1i (x, y, z) is the magnetic induction intensity at any point in space due to the magnetized current on the inner surface of the annular magnet 1-1; B B2o (x, y, z) is the magnetic induction intensity at any point in space due to the magnetized current on the outer surface of the annular magnet 1-2; B B2i (x, y, z) is the magnetic induction intensity at any point in space due to the magnetized current on the inner surface of the annular magnet 1-2; μ 0 is the vacuum magnetic permeability, μ 0 = 4π×10 -7 H / m (henry / meter); M B1 、M B2 are the magnetization intensities of the annular magnets 1-1 and 1-2 respectively, and their unit is A / m (ampere / meter); t B1 、t B2 are the thicknesses of the annular magnets 1-1 and 1-2 respectively, and their unit is m (meter); φ B1o 、φ B2o are the outer diameters of the annular magnets 1-1 and 1-2 respectively, and their unit is m; φ B1i 、φ B2iare the inner diameters of the annular magnets 1-1 and 1-2 respectively, with the unit of m; s is the distance between the two annular magnets, with the unit of m; l is the thickness integration variable; θ is the angle integration variable; i, j, k are the unit vectors in the x, y, and z directions; B i (x, y, z), B j (x, y, z), B k (x, y, z) are the magnetic induction intensity components in the x, y, and z directions at any point in space for the two annular magnets, and their units are all T (Tesla).

[0033] (2) According to the magnetization current theory, the non-linear magnetic force F between the two annular magnets and the rectangular magnet placed in the sleeve is calculated by the following formula i :

[0034]

[0035] In the formula, M A is the magnetization intensity of the rectangular magnet 2, with the unit of A / m; t A , w A , l A are the thickness, width, and length of the rectangular magnet 2 respectively, with the unit of m; a is the surface perpendicular distance between the annular magnet and the rectangular magnet, with the unit of m; F i has the unit of N (Newton).

[0036] (3) Calculate the system potential energy V according to the following formula

[0037]

[0038] In the formula, K is the stiffness of the two springs, with the unit of N / m (Newton per meter); the unit of V is J (Joule).

[0039] Using MATLAB software to perform numerical simulations on equations (1) to (7), the potential energy images of the system under different structural parameters can be obtained. Based on the potential energy images of the system, the system parameters for achieving the five-stable state can be obtained.

[0040] As an example of the five-stable system (just a name), it can be set that the size of the annular magnet 1-1 is φ B1o 25 mm × φ B1i 10 mm × t B1 2.75 mm, and the magnetization intensity M B1 is 7.5×10 5 A / m; the size of the annular magnet 1-2 is φ B2o 25 mm × φ B2i 10 mm × t B2 2.75 mm, and the magnetization intensity M B2 is 7.5×105 A / m; The dimensions of the rectangular magnet are l A 10 mm × w A 8 mm × t A 3 mm, and the magnetization intensity M A is 9.5 × 10 5 A / m; The stiffness K of the two springs is 7 N / m; The distance s between the two ring magnets is 28.2 mm; The surface perpendicular distance a between the ring magnet and the rectangular magnet is 6 mm.

[0041] Appendix Figure 3 To ensure that the other above parameters remain unchanged, when the stiffness K of the two springs is set to 3 N / m, 9 N / m, 15 N / m, and 21 N / m, the potential energy images of the system are shown. The concave points in the figure are the steady-state points of the system, representing the positions where the energy of the system is the smallest in the steady-state section.

[0042] Appendix Figure 4 To ensure that the other above parameters remain unchanged, when the length l of the rectangular magnet is set A to 5 mm, 10 mm, 15 mm, and 20 mm, the potential energy images of the system are shown.

[0043] Appendix Figure 5 To ensure that the other above parameters remain unchanged, when the width w of the rectangular magnet is set A to 4 mm, 8 mm, 12 mm, and 16 mm, the potential energy images of the system are shown.

[0044] Appendix Figure 6 To ensure that the other above parameters remain unchanged, when the thickness t of the rectangular magnet is set A to 1 mm, 3 mm, 5 mm, and 7 mm, the potential energy images of the system are shown.

[0045] Appendix Figure 7 To ensure that the other above parameters remain unchanged, when the outer radius r of the ring magnet is set o to 6.5 mm, 8.5 mm, 10.5 mm, and 12.5 mm, the potential energy images of the system are shown.

[0046] Appendix Figure 8 To ensure that the other above parameters remain unchanged, when the inner radius r of the ring magnet is set i to 2 mm, 5 mm, 8 mm, and 11 mm, the potential energy images of the system are shown.

[0047] Appendix Figure 9 To ensure that the other above parameters remain unchanged, when the thickness t of the ring magnet is set B1 (t B1 = t B2 ) to 1 mm, 3 mm, 5 mm, and 7 mm, the potential energy images of the system are shown.

[0048] Appendix Figure 10 To ensure that the above other parameters remain unchanged, the potential energy images of the system are shown when the distance s between the two annular magnets is set to 28 mm, 32 mm, 36 mm, and 40 mm.

[0049] Appendix Figure 11 To ensure that the above other parameters remain unchanged, the potential energy images of the system are shown when the surface vertical distance a between the annular magnet and the rectangular magnet is set to 4 mm, 6 mm, 8 mm, and 10 mm.

[0050] Appendix Figure 12 To ensure that the above other parameters remain unchanged, set the magnetization intensity M of the rectangular magnet A to 7.5×10 5 A / m, 9.5×10 5 A / m, 1.15×10 6 A / m, 1.35×10 6 A / m, and the potential energy images of the system are shown.

[0051] Appendix Figure 13 To ensure that the above other parameters remain unchanged, set the magnetization intensity M of the annular magnet B1 (M B1 = M B2 ) to 5.5×10 5 A / m, 7.5×10 5 A / m, 9.5×10 5 A / m, 1.15×10 6 A / m, and the potential energy images of the system are shown.

[0052] It can be seen from the appendix Figures 3 to 13 that the stiffness of the two springs, the geometric dimensions and magnetization intensities of the annular magnet and the rectangular magnet, the distance between the two annular magnets, and the vertical distance between the annular magnet and the rectangular magnet all affect the stable state of the system. Taking the appendix Figure 3 as an example, when the stiffness K of the two springs is 3 N / m, the system has only one stable state point. Therefore, to implement the five-stable system embodiment, it is necessary to comprehensively adjust the stiffness of the two springs, the geometric dimensions and magnetization intensities of the annular magnet and the rectangular magnet, the distance between the two annular magnets, and the vertical distance between the annular magnet and the rectangular magnet.

[0053] The calculation method of the induced current I of the non-linear five-stable electromagnetic vibration energy harvester is determined by the following formula:

[0054]

[0055] Wherein, P is the external excitation force, and its unit is N; M is the mass of the rectangular magnet, and its unit is kg (kilogram); η is the system damping, and its unit is N·s / m (Newton·second / meter); γ is the electromagnetic coupling coefficient, and its unit is N / A (Newton / Ampere); R is the total resistance of the system, and its unit is Ω (Ohm).

[0056] The electromagnetic coupling coefficient γ can be obtained by the following formula:

[0057]

[0058] φ = N∫∫B i dxdy (11)

[0059] Wherein, φ is the magnetic flux of the coil, and its unit is T·m 2 (Tesla·meter 2 ); N is the number of turns of the coil.

[0060] Therefore, the induced electromotive force U of the nonlinear five-stable electromagnetic vibration energy harvester can be obtained from Equations (8) to (11):

[0061] U = RI (12)

[0062] Wherein, the voltage of the induced electromotive force is V (Volt).

Claims

1. A nonlinear five-stable electromagnetic vibration energy harvester, comprising a base, two annular magnets, a rectangular sleeve, a rectangular magnet, two springs, and a coil, characterized in that: The shape of the base (5) is "匚", the top and bottom surfaces of the base are perpendicular to the side surface of the base, two annular magnets (1-1), (1-2) are fixed on the top surface of the base, two springs (3-1), (3-2) are provided at both ends of the rectangular cylinder sleeve (6), the rectangular magnet (2) is placed inside the rectangular sleeve and is symmetrically supported by two springs, the two annular magnets are placed on the top surface of the base with the center of the rectangular magnet as the symmetry point, the N poles of the two annular magnets face downwards, the N pole of the rectangular magnet faces upwards, the coil (4) is wound around the middle position of the outer surface of the rectangular cylinder sleeve, and the rectangular cylinder sleeve is fixed on the side surface of the base; by adjusting the geometric dimensions and magnetization intensities of the annular magnet and the rectangular magnet, the distance between the two annular magnets, the vertical distance between the annular magnet and the rectangular magnet, and the stiffness of the two springs, the energy harvester is in a five-stable state.

2. The nonlinear five-stable-state electromagnetic vibration energy harvester according to claim 1 is characterized in that: The magnetic induction intensity B(x, y, z) of the two annular magnets at any point P(x, y, z) in space is determined by the following formula In the formula, B B1o (x, y, z) is the magnetic induction intensity of the magnetizing current on the outer surface of the ring magnet (1-1) at any point in space; B B1i (x, y, z) is the magnetic induction intensity of the magnetizing current on the inner surface of the ring magnet (1-1) at any point in space; B B2o (x, y, z) is the magnetic induction intensity of the magnetizing current on the outer surface of the annular magnet (1-2) at any point in space; B B2i (x, y, z) is the magnetic induction intensity of the magnetizing current on the inner surface of the annular magnet (1-2) at any point in space; μ0 is the magnetic permeability of vacuum; M B1 、M B2 are the magnetization intensities of the annular magnets (1-1) and (1-2) respectively; t B1 ,t B2 are the thickness of the annular magnets (1-1) and (1-2) respectively; φ B1o ,φ B2o are the outer diameters of the annular magnets (1-1) and (1-2); φ B1i ,φ B2i are the inner diameters of the annular magnets (1-1) and (1-2) respectively; s is the distance between the two annular magnets; l is the thickness integral variable; θ is the angle integral variable; i, j, k are the unit vectors in the x, y, z directions; B i (x,y,z),B j (x,y,z),B k (x, y, z) are the components of the magnetic induction intensity of the two annular magnets in the x, y, and z directions at any point in space.

3. The nonlinear five-stable-state electromagnetic vibration energy harvester according to claim 1 is characterized in that: The non-linear magnetic force between the two annular magnets and the rectangular magnet placed in the sleeve is determined by the following formula Where M A is the magnetization intensity of the rectangular magnet (2); t A 、w A , l A are respectively the thickness, width and length of the rectangular magnet (2); and a is the surface vertical distance between the annular magnets (1-1), (1-2) and the rectangular magnet (2).

4. The nonlinear five-stable-state electromagnetic vibration energy harvester according to claim 1 is characterized in that: The system potential energy V is determined by the following formula In the formula, K is the stiffness of the two springs (3-1), (3-2).

5. The nonlinear five-stable electromagnetic vibration energy harvester according to claim 1 is characterized in that: The induced electromotive force U is determined by the following formula φ=N∫∫B i dxdy (11) U = RI (12) In the formula, P is the external excitation force; M is the mass of the rectangular magnet (2); η is the system damping; γ is the electromagnetic coupling coefficient; R is the total resistance of the system; φ is the magnetic flux of the coil; N is the number of turns of the coil.

6. The nonlinear five-stable-state electromagnetic vibration energy harvester according to claim 1 is characterized in that: When the energy harvester is in the five-stable state, the size of the annular magnet (1-1) is φ B1o 25 mm×φ B1i 10 mm×t B1 2.75 mm, magnetization intensity M B1 7.5×10 5 A / m; the size of the ring magnet (1-2) is φ B2o 25 mm×φ B2i 10 mm×t B2 2.75 mm, magnetization intensity M B2 7.5×10 5 A / m; rectangular magnet (2) size is l A 10 mm×w A 8 mm×t A 3 mm, magnetization intensity M A 9.5×10 5 A / m; the stiffness K of the two springs (3-1) and (3-2) is 7N / m; the distance s between the two annular magnets (1-1) and (1-2) is 28.2mm; the vertical distance a between the two annular magnets (1-1) and (1-2) and the rectangular magnet (2) is 6mm.

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