Design method of vibration energy harvesting device, wireless sensor

Abstract

The present invention discloses a design method of a vibration energy harvesting device, including: the vibration energy harvesting device includes: a floating slider, a first piezoelectric sheet, a second piezoelectric sheet, a first spring, a second spring and an interdigital electrode group, and the design method includes: constructing a vibration model of the floating slider; obtaining the motion displacement of the floating slider under different damping conditions according to the vibration model; constructing a force deformation analysis model of the first piezoelectric sheet or the second piezoelectric sheet; obtaining the deformation and bending moment at any point on the first piezoelectric sheet or the second piezoelectric sheet according to the force deformation analysis model; and determining the relevant parameters of the floating slider, the first piezoelectric sheet, the second piezoelectric sheet, the first spring and the second spring in combination with the output current and voltage. The present invention designs the relevant parameters of the floating slider, the first piezoelectric sheet, the second piezoelectric sheet, the first spring and the second spring according to the power requirements of the wireless sensor, so as to ensure that the vibration energy harvesting device can meet the use requirements of self-power supply.

Description

Technical Field

[0001] The invention belongs to the technical field of power generation devices, and in particular relates to a design method of a vibration energy harvesting device and a wireless sensor. Background Art

[0002] The wireless sensor system is to complete the predetermined sensing monitoring task by deploying sensors with sensing, storage, wireless communication and other functions in the target monitoring area. At present, traditional wireless sensors are powered by batteries, which will bring many problems such as difficulty in battery replacement and environmental pollution. On the other hand, the energy collected by some existing energy harvesting devices cannot meet the self-power supply of wireless sensors after being converted into electrical energy. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0004] To this end, the present invention proposes a design method for a vibration energy harvesting device, which has the advantage of being able to design a wireless sensor that meets the requirements of self-power supply.

[0005] The design method of the vibration energy harvesting device according to the embodiment of the present invention includes: the vibration energy harvesting device includes: a floating slider, the floating slider generates vibration according to the vibration energy received; a first piezoelectric sheet, the first piezoelectric sheet is arranged on one side of the floating slider; a second piezoelectric sheet, the second piezoelectric sheet is arranged on the side of the floating slider away from the first piezoelectric sheet; a first spring, the first spring elastically connects the floating slider and the first piezoelectric sheet together; a second spring, the second spring elastically connects the floating slider and the second piezoelectric sheet together; an interdigitated electrode group, the interdigitated electrode group is sleeved on the outer peripheral surface of the floating slider, the floating slider When the slider vibrates, the floating slider and the interdigitated electrode group generate friction to generate electricity, and the first piezoelectric sheet and the second piezoelectric sheet generate deformation to generate electricity; the design method includes: step one, constructing a vibration model of the floating slider; step two, obtaining the motion displacement of the floating slider under different damping conditions according to the vibration model; step three, constructing a force-deformation analysis model of the first piezoelectric sheet or the second piezoelectric sheet; step four, obtaining the deformation and bending moment at any point on the first piezoelectric sheet or the second piezoelectric sheet according to the force-deformation analysis model; step five, determining the relevant parameters of the floating slider, the first piezoelectric sheet, the second piezoelectric sheet, the first spring, and the second spring in combination with the output current and voltage.

[0006] According to one embodiment of the present invention, based on the vibration model in step 1, the motion differential equation of the floating slider is obtained as follows:

[0007]

[0008] Where x is the displacement of the floating slider, t is the time, m is the mass of the floating slider, g is the gravity coefficient of the floating slider, k1 and k2 are the stiffness coefficients of the first spring and the second spring respectively, c1 and c2 are the damping coefficients of the first spring and the second spring respectively, δ st =mg / (k1+k2).

[0009] According to an embodiment of the present invention, in step 2, according to the motion differential equation of the floating slider, the motion displacement of the floating slider in three damping situations is obtained as follows:

[0010] For the case of small damping, when When:

[0011]

[0012] Where A and θ are integral constants, which are determined by the initial position and velocity of the floating slider;

[0013] For the critical damping case, when When:

[0014]

[0015] Where C1 and C2 are integral constants, which are determined by the initial position and velocity of the floating slider;

[0016] For the case of large damping, when When:

[0017]

[0018] Where C1 and C2 are integral constants, which are determined by the initial position and velocity of the floating slider.

[0019] According to one embodiment of the present invention, the current I and the voltage V1 outputted by the frictional power generation between the floating slider and the interdigital electrode group are respectively:

[0020]

[0021]

[0022] Among them, the raised area of ​​the floating slider is A, the charge density is σ, the motion displacement of the floating slider is x, and ε is the dielectric constant of the material.

[0023] According to one embodiment of the present invention, the other one is determined according to any two of the mass m of the floating slider, the stiffness coefficients k1 and k2 of the first spring and the second spring, and the damping coefficients c1 and c2 of the first spring and the second spring.

[0024] According to one embodiment of the present invention, based on the disk elastic deformation theory and the force deformation analysis model in step three, the deformation and bending moment of any point on the first piezoelectric sheet or the second piezoelectric sheet are obtained:

[0025]

[0026]

[0027]

[0028] Among them, r, θ are radial coordinates and circumferential coordinates respectively, w is the deformation, and D is the bending strength E is the elastic modulus of the material, μ is Poisson’s ratio, t is the plate thickness, M is the bending moment, and Q is the normal pressure.

[0029] According to one embodiment of the present invention, when the first piezoelectric sheet or the second piezoelectric sheet generates deformation and generates electricity, the generated charge Q, voltage V2, i.e., stored energy E are respectively:

[0030] Q=d 33 WA2

[0031]

[0032]

[0033] Among them, the piezoelectric constant d of the piezoelectric piece is 33 , the force W acting on the surface of the piezoelectric film, the area A2 where the piezoelectric film applies the force, the thickness h of the piezoelectric film, the capacitance C of the external capacitor p ;

[0034] Combined with the deformation and bending moment of any point on the first piezoelectric sheet or the second piezoelectric sheet, according to the thickness h of the piezoelectric sheet, the piezoelectric constant d of the piezoelectric sheet 33 , and the area A2 where the piezoelectric film applies force determines the other one.

[0035] According to an embodiment of the present invention, there is a gap between the outer peripheral surface of the floating slider and the interdigital electrode group, and the ratio of the gap to the radius of the floating slider is 0.2%-0.4%.

[0036] According to one embodiment of the present invention, the interdigitated electrode group includes: a first interdigitated electrode and a second interdigitated electrode, the interdigitated fingers of the second interdigitated electrode are arranged alternately with the interdigitated fingers of the first interdigitated electrode; a plurality of annular grooves are provided on the outer peripheral surface of the floating slider, the plurality of annular grooves are evenly arranged along the axial direction of the floating slider, the width of the annular grooves is equal to the sum of the distance between two adjacent interdigitated fingers and the width of one interdigitated finger, and the distance between two adjacent interdigitated grooves is equal to the width of the annular grooves.

[0037] According to one embodiment of the present invention, a wireless sensor uses the above-mentioned vibration energy harvesting device to harvest vibration energy to achieve self-power supply.

[0038] The beneficial effect of the present invention is that the present invention combines the frictional power generation effect and the piezoelectric effect, and converts the received vibration energy into electrical energy through the vibration energy harvesting device, thereby realizing the self-power supply of the wireless sensor, without the need to replace the battery, and is more environmentally friendly and reliable. The relevant parameters of the floating slider, the first piezoelectric sheet, the second piezoelectric sheet, the first spring, and the second spring are designed according to the power requirements of the wireless sensor to ensure that the vibration energy harvesting device can meet the use requirements of self-power supply.

[0039] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0042] Figure 1 is a schematic diagram of the three-dimensional structure of the vibration energy harvesting device according to the present invention;

[0043] Figure 2 is a schematic diagram of a half-section structure of a vibration energy harvesting device according to the present invention;

[0044] Figure 3 is a schematic diagram of the working principle of the vibration energy harvesting device according to the present invention;

[0045] Figure 4 is a vibration model of a floating slider in a vibration energy harvesting device according to the present invention;

[0046] Figure 5 A stress deformation analysis model of the first piezoelectric sheet or the second piezoelectric sheet in the vibration energy harvesting device according to the present invention;

[0047] Reference numerals:

[0048] The first cover 10 , the first piezoelectric sheet 20 , the housing 30 , the first spring 40 , the first interdigital electrode 50 , the floating slider 60 , the second interdigital electrode 70 , the second spring 80 , the second piezoelectric sheet 90 , and the second cover 100 . DETAILED DESCRIPTION

[0049] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0050] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0051] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0052] The design method of the vibration energy harvesting device according to the embodiment of the present invention is described in detail below with reference to the accompanying drawings.

[0053] like Figures 1 to 3As shown, the design method of the vibration energy harvesting device according to the embodiment of the present invention includes: the vibration energy harvesting device includes: a floating slider 60, a first piezoelectric sheet 20, a second piezoelectric sheet 90, a first spring 40, a second spring 80 and an interdigital electrode group, the floating slider 60 vibrates according to the vibration energy received; the first piezoelectric sheet 20 is arranged on one side of the floating slider 60; the second piezoelectric sheet 90 is arranged on the side of the floating slider 60 away from the first piezoelectric sheet 20; the first spring 40 elastically connects the floating slider 60 and the first piezoelectric sheet 20 together; the second spring 80 elastically connects the floating slider 60 and the second piezoelectric sheet 90 together; the interdigital electrode group is sleeved on the outer peripheral surface of the floating slider 60, when the floating slider vibrates, the floating slider 60 and the interdigital electrode group generate friction to generate electricity, and the first piezoelectric sheet 20 and the second piezoelectric sheet 90 are deformed to generate electricity.

[0054] The vibration energy harvesting device also includes: a shell 30, which is a circular tube. A accommodating cavity is formed inside the shell 30. The interdigitated electrode group is arranged on the inner wall of the shell 30. The floating slider 60 is located in the middle position of the accommodating cavity. The first piezoelectric sheet 20 and the second piezoelectric sheet 90 are both circular pieces. The first piezoelectric sheet 20 and the second piezoelectric sheet 90 are respectively located at the two ends of the shell 30.

[0055] According to one embodiment of the present invention, there is a gap between the outer circumference of the floating slider 60 and the interdigital electrode group, and the ratio of the gap to the radius of the floating slider 60 is 0.2%-0.4%. In other words, if the gap between the outer circumference of the floating slider 60 and the interdigital electrode group is too large, the power generation efficiency will be reduced, while if the gap is too small, the floating slider 60 will be difficult to move. The gap is more suitable to be 0.2%-0.4% of the radius of the floating slider 60.

[0056] According to one embodiment of the present invention, the interdigital electrode group includes: a first interdigital electrode 50 and a second interdigital electrode 70, both of which are arranged on the inner wall of the housing 30, and the interdigital electrodes of the second interdigital electrode 70 are arranged in an interlaced manner with the interdigital electrodes of the first interdigital electrode 50. Because the housing 30 in this embodiment is a round tube, the first interdigital electrode 50 and the second interdigital electrode 70 are installed on the inner wall of the housing 30, and in the present invention, the first interdigital electrode 50 and the second interdigital electrode 70 are fixed to the housing 30 by a copper coating or tin coating process, then the interdigital electrode group composed of the first interdigital electrode 50 and the second interdigital electrode 70 is also formed into a round tube structure, and the first interdigital electrode 50 and the second interdigital electrode 70 are located in the middle of the housing 30, so that the interdigital motor group corresponds to the floating slider 60, and the first interdigital electrode 50 and the second interdigital electrode 70 are made of copper material.

[0057] Furthermore, if Figure 2 and Figure 3As shown, a plurality of annular grooves are formed on the outer peripheral surface of the floating slider 60, and the plurality of annular grooves are evenly arranged along the axial direction of the floating slider 60. The width of the annular grooves is equal to the sum of the distance between two adjacent interdigits and the width of one interdigit, and the distance between two adjacent annular grooves is equal to the width of the annular grooves, that is, an annular protrusion is formed between two adjacent annular grooves, and the width of the annular protrusion is equal to the width of the annular groove. The floating slider 60 is made of dielectric material, preferably ceramic; the width of the annular groove and the distance between two adjacent annular grooves are designed in coordination with the interdigits, so that the floating slider 60 can switch between adjacent interdigits in time when reciprocating, thereby improving the efficiency of friction power generation.

[0058] According to one embodiment of the present invention, the housing 30 has an upper stepped hole, the first piezoelectric sheet 20 is disposed in the upper stepped hole, the first spring 40 is disposed in the accommodating cavity, the side of the first piezoelectric sheet 20 facing the floating slider 60 is connected to one end of the first spring 40, and the other end of the first spring 40 is connected to the floating slider 60. Preferably, the upper stepped hole is covered with a first cover 10, and the first cover 10 is used to open or close the upper stepped hole.

[0059] That is to say, the upper stepped hole at the upper end of the shell 30 can connect the accommodating cavity and the outside of the shell 30, and the step surface of the upper stepped hole can limit the installation of the first piezoelectric sheet 20, and the first cover 10 and the shell 30 are detachably connected by bolts, which is convenient for the installation and disassembly of the first piezoelectric sheet 20.

[0060] On this basis, the housing 30 is provided with a lower stepped hole, the second piezoelectric sheet 90 is arranged in the lower stepped hole, the second spring 80 is arranged in the accommodating cavity, the side of the second piezoelectric sheet 90 facing the floating slider 60 is connected to one end of the second spring 80, and the other end of the second spring 80 is connected to the floating slider 60. Preferably, a second cover 100 is provided on the upper cover of the lower stepped hole, and the second cover 100 is detachably connected to the housing 30 by bolts, and the second cover 100 is used to open or close the lower stepped hole. In this embodiment, the composition structure of the second spring 80, the second piezoelectric sheet 90 and the second cover 100 is the same as the composition structure of the first spring 40, the first piezoelectric sheet 20 and the first cover 10, and is symmetrical with respect to the floating slider 60.

[0061] The material of the piezoelectric sheet can be selected from PVDF and its copolymer (film), polypropylene (pp), etc., which are light in weight, soft in texture, easy to process and have a wide frequency response.

[0062] Furthermore, the diameter of the first spring 40 and the diameter of the second spring 60 are both smaller than the diameter of the floating slider 60. Furthermore, the central axis of the first spring 40, the central axis of the second spring 60 and the central axis of the interdigital electrode group are collinear. This design avoids the first spring 40 and the second spring 60 from contacting the interdigital electrode group. At the same time, when the floating slider 60 moves upward in the interdigital electrode group, the first piezoelectric sheet 20 is compressed and the second piezoelectric sheet 90 is pulled. When the floating slider 60 moves downward in the interdigital electrode group, the first piezoelectric sheet 20 is pulled and the second piezoelectric sheet 90 is compressed, so that the present invention can effectively collect vibration energy.

[0063] like Figure 3 As shown, as the floating slider 60 moves up and down after receiving vibration energy, the annular protrusion on the outer peripheral surface of the floating slider 60 gradually leaves the first interdigital electrode 50 and approaches the second interdigital electrode 70. The negative charge on the surface of the floating slider 60 gradually accumulates positive charge on the second interdigital electrode 70, forming a transient current between two adjacent interdigits. Next, when the annular protrusion on the floating slider 60 is aligned with the interdigits on the second interdigital electrode 70, a new electrostatic equilibrium is formed, similar to the initial state. Subsequently, the floating slider 60 performs an opposite movement, thereby generating an opposite current. Obviously, when the floating slider 60 repeatedly vibrates up and down, the direction of the current will change periodically, thereby generating an alternating current between the first interdigital electrode 50 and the second interdigital electrode 70.

[0064] The present invention utilizes the vibration energy of the equipment environment itself to drive the floating slider 60 and the interdigital electrode group to produce relative movement, and generates electricity through friction between the floating slider 60 and the interdigital electrode group to provide power for the wireless sensor, thereby realizing self-power supply, and no need to replace batteries, thus meeting environmental protection requirements; the present invention converts the pressure generated by the floating slider 60 into electrical energy by setting the first piezoelectric sheet 20 and the second piezoelectric sheet 90, and combines the piezoelectric effect with the friction nano-power generation effect to jointly improve the power generation effect; at the same time, the present invention does not require the sliding permanent magnet, fixed permanent magnet and coil structure in the traditional electromagnetic induction, and has a simple structure. It can be used at high temperatures, solving the problem that the traditional battery-driven wireless vibration sensor cannot be used at high temperatures.

[0065] The design method of the present invention includes: constructing a vibration model of the floating slider 60; obtaining the movement displacement of the floating slider 60 under different damping conditions according to the vibration model; constructing a force-deformation analysis model of the first piezoelectric sheet 20 or the second piezoelectric sheet 90; obtaining the deformation and bending moment at any point on the first piezoelectric sheet 20 or the second piezoelectric sheet 90 according to the force-deformation analysis model; and determining the relevant parameters of the floating slider 60, the first piezoelectric sheet 20, the second piezoelectric sheet 90, the first spring 40, and the second spring 80 in combination with the output current and voltage.

[0066] like Figure 4As shown, the vibration models of the floating slider 60 in the up and down directions are equivalent to the vibration model in one direction, and the motion differential equation of the floating slider 60 is obtained as follows:

[0067]

[0068] Wherein, x is the movement displacement of the floating slider 60, t is the time, m is the mass of the floating slider 60, g is the gravity coefficient of the floating slider 60, k1 and k2 are the stiffness coefficients of the first spring 40 and the second spring 80, c1 and c2 are the damping coefficients of the first spring 40 and the second spring 80, δ st =mg / (k1+k2).

[0069] According to the motion differential equation of the floating slider 60, the motion displacement of the floating slider 60 in three damping situations is obtained as follows:

[0070] For the case of small damping, when When:

[0071]

[0072] Where A and θ are integral constants, which are determined by the initial position and velocity of the floating slider 60;

[0073] For the critical damping case, when When:

[0074]

[0075] Where C1 and C2 are integral constants, which are determined by the initial position and speed of the floating slider 60;

[0076] For the case of large damping, when When:

[0077]

[0078] C1 and C2 are integral constants, which are determined by the initial position and speed of the floating slider 60 .

[0079] Furthermore, since the present invention needs to power the wireless sensor, the normal operation of the wireless sensor requires a certain amount of power. Therefore, when designing, the output current I and the output voltage V1 need to be greater than or equal to the preset value. The current I and the output voltage V1 generated by the friction power generation between the floating slider 60 and the interdigital electrode group are respectively,

[0080]

[0081]

[0082] The raised area of ​​the floating slider 60 is A, the charge density is σ, the movement displacement of the floating slider 60 is x, and ε is the dielectric constant of the material.

[0083] In summary, the other one is determined based on the preset values ​​of the output current I and the output voltage V1, and any two of the mass m of the floating slider 60, the stiffness coefficients k1 and k2 of the first spring 40 and the second spring 80, and the damping coefficients c1 and c2 of the first spring 40 and the second spring 80. That is to say, when the mass m of the floating slider 60, the stiffness coefficients k1 and k2 of the first spring 40 and the second spring 80 are known, we can determine the value of c1+c2, and then the sum of the damping coefficients of the first spring 40 and the second spring 80 can be determined. In this application, the first spring 40 and the second spring 80 use springs with the same parameters, so k1=k2, c1=c2.

[0084] like Figure 5 As shown, q is the distributed stress on the disk, R is the radius of the disk, and according to the disk elastic deformation theory, the deformation and bending moment at any point on the disk are:

[0085]

[0086]

[0087]

[0088] According to the above formula and the stress-deformation analysis model in step 3, the deformation and bending moment of any point on the first piezoelectric sheet 20 or the second piezoelectric sheet 90 are obtained:

[0089]

[0090]

[0091]

[0092] Among them, r, θ are radial coordinates and circumferential coordinates respectively, w is the deformation, and D is the bending strength E is the elastic modulus of the material, μ is Poisson’s ratio, t is the plate thickness, M is the bending moment, and Q is the normal pressure.

[0093] According to one embodiment of the present invention, since the present invention needs to power the wireless sensor, the normal operation of the wireless sensor requires a certain amount of power. Therefore, when designing, the generated charge Q, voltage V2, that is, the stored energy E, all need to be greater than or equal to the preset value. When the first piezoelectric sheet 20 or the second piezoelectric sheet 90 generates deformation and generates electricity, the generated charge Q, voltage V2, that is, the stored energy E are respectively:

[0094] Q=d 33WA2

[0095]

[0096]

[0097] Among them, the piezoelectric constant d of the piezoelectric piece is 33 , the force W acting on the surface of the piezoelectric film, the area A2 where the piezoelectric film applies the force, the thickness h of the piezoelectric film, the capacitance C of the external capacitor p ;

[0098] In the present invention, the first piezoelectric sheet 20 and the second piezoelectric sheet 90 are piezoelectric sheets with the same parameters. The force W acting on the surface of the piezoelectric sheet is determined by the mass m of the floating slider 60, the initial position and speed of the movement, and the area A2 where the force of the piezoelectric sheet is applied. In the calculation, the present application will equate the force W acting on the surface of the piezoelectric sheet and the area A2 where the force of the piezoelectric sheet is applied to the cross-sectional area of ​​the entire piezoelectric sheet and the uniformly distributed force received, and combine the deformation and bending moment received at any point on the first piezoelectric sheet 20 or the second piezoelectric sheet 90, according to the thickness h of the piezoelectric sheet, the piezoelectric constant d of the piezoelectric sheet 33 , and the area A2 where the piezoelectric film applies force determines the other one.

[0099] The present invention also discloses a wireless sensor, which uses the above-mentioned vibration energy harvesting device to harvest vibration energy to achieve self-power supply. The wireless sensor is provided with a rectifier circuit, which is connected to the first interdigital electrode 50, the second interdigital electrode 70, the first piezoelectric sheet 20 and the second piezoelectric sheet 90, so as to effectively utilize the electric energy converted from the vibration energy. The vibration energy harvesting device can be installed at a location with large vibration, such as a bearing seat of an equipment, a truss of a bridge, etc.

[0100] The beneficial effect of the present invention is that the present invention combines the frictional power generation effect and the piezoelectric effect, and converts the received vibration energy into electrical energy through the vibration energy harvesting device, thereby realizing the self-power supply of the wireless sensor, without the need to replace the battery, and is more environmentally friendly and reliable. The relevant parameters of the floating slider 60, the first piezoelectric sheet 20, the second piezoelectric sheet 90, the first spring 40, and the second spring 80 are designed according to the power requirements of the wireless sensor to ensure that the vibration energy harvesting device can meet the use requirements of self-power supply.

[0101] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0102] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A design method for a vibration energy harvesting device, characterized in that: The vibration energy harvesting device comprises: A floating slider (60), wherein the floating slider (60) vibrates according to the vibration energy received; A first piezoelectric sheet (20), the first piezoelectric sheet (20) being arranged on one side of the floating slider (60); a second piezoelectric sheet (90), the second piezoelectric sheet (90) being arranged on a side of the floating slider (60) away from the first piezoelectric sheet (20); a first spring (40), wherein the first spring (40) elastically connects the floating slider (60) and the first piezoelectric sheet (20); a second spring (80), wherein the second spring (80) elastically connects the floating slider (60) and the second piezoelectric sheet (90); an interdigital electrode group, the interdigital electrode group being sleeved on the outer peripheral surface of the floating slider (60), and when the floating slider vibrates, friction between the floating slider (60) and the interdigital electrode group is generated to generate electricity, and the first piezoelectric sheet (20) and the second piezoelectric sheet (90) are deformed to generate electricity; The design method comprises: Step 1: construct a vibration model of the floating slider (60); Step 2: obtain the movement displacement of the floating slider (60) under different damping conditions according to the vibration model; Step 3: construct a force-deformation analysis model of the first piezoelectric sheet (20) or the second piezoelectric sheet (90); Step 4: obtain the deformation and bending moment at any point on the first piezoelectric sheet (20) or the second piezoelectric sheet (90) according to the force-deformation analysis model; Step 5: determine the relevant parameters of the floating slider (60), the first piezoelectric sheet (20), the second piezoelectric sheet (90), the first spring (40), and the second spring (80) in combination with the output current and voltage; According to the vibration model in step 1, the motion differential equation of the floating slider (60) is obtained as follows: in, is the movement displacement of the floating slider (60), For time, is the mass of the floating slider (60), is the gravity coefficient of the floating slider (60), and are the stiffness coefficients of the first spring (40) and the second spring (80), respectively, and are the damping coefficients of the first spring (40) and the second spring (80), respectively, .

2. The design method of the vibration energy harvesting device according to claim 1, characterized in that: In step 2, according to the differential equation of motion of the floating slider (60), the motion displacements of the floating slider (60) in three damping situations are obtained as follows: For the case of small damping, when When: in and is an integral constant determined by the initial position and velocity of the floating slider (60); For the critical damping case, when When: in and is an integral constant determined by the initial position and velocity of the floating slider (60); For the case of large damping, when When: in and is an integral constant determined by the initial position and velocity of the floating slider (60).

3. The design method of the vibration energy harvesting device according to claim 2, characterized in that: The current output by the frictional power generation between the floating slider (60) and the interdigital electrode group and the output voltage They are respectively, Wherein, the raised area of ​​the floating slider (60) is A, and the charge density is , the displacement of the floating slider (60) is , is the dielectric constant of the material.

4. The design method of the vibration energy harvesting device according to claim 3, characterized in that: According to the floating slider (60) quality , the stiffness coefficients of the first spring (40) and the second spring (80) and , the damping coefficients of the first spring (40) and the second spring (80) and Any two of the determine the other.

5. The design method of the vibration energy harvesting device according to claim 1, characterized in that: According to the disk elastic deformation theory and the force deformation analysis model in step three, the deformation and bending moment at any point on the first piezoelectric sheet (20) or the second piezoelectric sheet (90) are obtained: in, are radial coordinates and circumferential coordinates respectively, is the deformation amount, The bending strength , is the elastic modulus of the material, is Poisson's ratio, is the plate thickness, is the bending moment, Is positive pressure.

6. The design method of the vibration energy harvesting device according to claim 5, characterized in that: When the first piezoelectric sheet (20) or the second piezoelectric sheet (90) generates deformation and generates electricity, the generated electric charge ,Voltage , i.e. energy storage They are: Among them, the piezoelectric constant of the piezoelectric piece is , the force acting on the surface of the piezoelectric piece , the area where the piezoelectric force is applied , piezoelectric sheet thickness , the capacitance of the external capacitor ; Combined with the deformation and bending moment at any point on the first piezoelectric sheet (20) or the second piezoelectric sheet (90), according to the thickness of the piezoelectric sheet , the piezoelectric constant of the piezoelectric piece , the area where the piezoelectric force is applied One of the two determines the other.

7. The design method of the vibration energy harvesting device according to claim 1, characterized in that: There is a gap between the outer peripheral surface of the floating slider (60) and the interdigital electrode group, and the ratio of the gap to the radius of the floating slider (60) is 0.2%-0.4%.

8. The design method of the vibration energy harvesting device according to claim 7, characterized in that: The interdigitated electrode group comprises: a first interdigitated electrode (50) and a second interdigitated electrode (70), wherein the interdigitated fingers of the second interdigitated electrode (70) are arranged in an interdigitated manner with the interdigitated fingers of the first interdigitated electrode (50); a plurality of annular grooves are provided on the outer peripheral surface of the floating slider (60), wherein the plurality of annular grooves are evenly arranged along the axial direction of the floating slider (60), wherein the width of the annular grooves is equal to the sum of the distance between two adjacent interdigitated fingers and the width of one interdigitated finger, and the distance between two adjacent interdigitated grooves is equal to the width of the annular groove.

9. A wireless sensor, characterized in that: The vibration energy harvesting device as described in any one of claims 1 to 8 is used to harvest vibration energy to achieve self-power supply.

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