Piezoelectric-flexoelectric composite acceleration sensor for tunnel micro-vibration detection

Abstract

The invention belongs to the technical field of tunneling advanced geological forecast. The piezoelectric-flexoelectric composite acceleration sensor comprises an edge mass block, a central mass block, piezoelectric ceramics, a charge amplification circuit, a central column, a sensor base and a piezoelectric ceramic supporting base, the edge mass block is in a step shape and is provided with a through hole, the center mass block penetrates through the through hole to be fixedly connected with the center of the piezoelectric ceramic, the edge mass block is fixedly connected with the top of the supporting base, and when vibration is transmitted, the edge mass block enables the piezoelectric ceramic to bend and sense bending charges, and the center mass block enables the ceramic to compress and sense piezoelectric charges; the charge amplification circuit collects charges and converts the charges into analog voltage data to obtain acceleration. Through the piezoelectric-flexoelectric composite effect and the special structural design, high sensitivity and wide band are considered, and the tunnel micro-vibration detection fineness is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel excavation advanced geological prediction, and particularly relates to a piezoelectric-flexoelectric composite acceleration sensor for tunnel micro-vibration detection. BACKGROUND

[0002] The statements in this section merely provide background technology related to the present application and do not necessarily constitute prior art.

[0003] With the rapid development of underground engineering technology, tunnels, mines and underground energy engineering are evolving towards 'deeper burial depth, higher ground stress and more complex geological environment'. The risk of disasters such as fault fracture zone, water and mud inrush, rock burst has significantly increased, making advanced geological prediction a key link to ensure safety and efficiency. Among many detection methods, the seismic wave method has become one of the most widely used advanced prediction methods for tunnel boring machine construction tunnels due to its high interface imaging accuracy and long detection distance.

[0004] With the development of seismic wave method and tunnel advanced detection technology, vibration observation for underground engineering is moving from 'available' to 'fine inversion', which puts forward higher requirements for sensors in terms of wide frequency band, low noise and low energy weak signal detection. In existing tunnel vibration sensors, piezoelectric type is widely used due to its compact structure and strong environmental resistance. However, different piezoelectric structures have obvious advantages and disadvantages in terms of bandwidth and sensitivity: compression type sensors often rely on pre-tightening force and force transmission chain, and the structure has strong coupling with assembly state, but due to its strong coupling state, it is difficult to sense small vibrations; shear type sensors have good acceleration, but their output is easily limited by factors such as packaging stiffness under ultra-low frequency micro-vibration; bending / beam (cantilever) structure can improve sensitivity through strain amplification, but its equivalent stiffness is low, which is not conducive to flatness for wide frequency measurement; it is difficult to simultaneously realize 'high sensitivity' and 'wide frequency band' in the same device. SUMMARY

[0005] In order to solve the problems in the prior art, the present application provides a piezoelectric-flexoelectric composite acceleration sensor for tunnel micro-vibration detection, which utilizes piezoelectric effect and flexoelectric effect through split mass and trapezoidal ceramic sheet support structure, increases ceramic strain, improves induced charge quantity, and realizes 'high sensitivity' and 'wide frequency band' at the same time.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions: A piezoelectric-flexoelectric composite acceleration sensor for tunnel micro-vibration detection, comprising: an edge mass block, a center mass block, a piezoelectric ceramic, a charge amplification circuit, a center column, a sensor base and a piezoelectric ceramic support base. The top of the piezoelectric ceramic support base is a hollow ring structure, and the bottom of the piezoelectric ceramic support base is a frustum with an inverted trapezoidal cross-section. The piezoelectric ceramic is fixed to the inner bottom of the hollow ring structure. The edge mass block is stepped and is fixedly connected to the top of the hollow ring structure. A through hole for placing the central mass block is opened at the center of the edge mass block, and the charge amplification circuit is arranged on the top of the edge mass block. After passing through the through hole, the central mass block is fixedly connected to the center of the piezoelectric ceramic with conductive adhesive. The central column includes a coaxial upper central column and a lower central column. The cross-sectional area of ​​the upper central column is smaller than that of the lower central column. The bottom of the inverted trapezoidal structure is connected to the upper central column, and the lower central column is connected to the sensor base. When the vibration is transmitted to the accelerometer, the edge mass block acts on the edge of the piezoelectric ceramic, causing the piezoelectric ceramic to flex and deform, inducing flexural charge. The center mass block acts on the center of the piezoelectric ceramic, causing the piezoelectric ceramic to compress and induce piezoelectric charge. The induced flexural charge and piezoelectric charge are collected by the charge amplification circuit, and all the collected charges are converted into corresponding analog voltage data. The acceleration data is obtained based on the analog voltage data.

[0007] In one optional implementation of the present invention, a housing and a connector are also included. The connector is fixed to the top of the housing. The edge mass block, the center mass block, the piezoelectric ceramic and the charge amplification circuit are all arranged inside the housing. The housing is fixedly connected to the sensor base.

[0008] As a further limitation of the present invention, the nozzle, outer shell, piezoelectric ceramic support base, central column, and sensor base are made of titanium alloy, and the edge mass block and central mass block are made of tungsten-nickel-copper alloy.

[0009] In one alternative implementation of the present invention, the charge amplification circuit is ring-shaped and only contacts the edge mass block, and is bonded by insulating adhesive.

[0010] In one optional implementation of the present invention, the total equivalent stiffness K is: ,in, This represents the bending stiffness of the piezoelectric ceramic support base; Represents the compressive stiffness of the central column; Represents the bending stiffness of piezoelectric ceramics; The contact stiffness represents the annular contact stiffness between the edge mass block and the piezoelectric ceramic support base, the normal contact stiffness between the central column and the piezoelectric ceramic support base, and the contact stiffness between the piezoelectric ceramic and the central mass block.

[0011] As a further limitation of the present invention, the bending stiffness of the piezoelectric ceramic support base is... for: , Represents the mass of the edge mass block. Represents the acceleration of the edge mass block. Let r be the deflection at radius r. Represents the maximum deflection. It is the edge mass block that is accelerating. Inertial force under action, The radius of the top surface of the frustum of the piezoelectric ceramic support base; Central column compressive stiffness for: ,in, The Young's modulus of the upper central column. This represents the cross-sectional area of ​​the upper central column. The height of the upper central column, The Young's modulus represents the lower central column. This represents the cross-sectional area of ​​the lower central column. The height of the lower central column; piezoelectric ceramic bending stiffness for: , This represents the radius of the piezoelectric ceramic.

[0012] As a further limitation of the present invention, the total equivalent mass for: ,in, This represents the equivalent mass of the piezoelectric ceramic support base. Represents the equivalent mass of the upper central pillar. Represents the equivalent mass of the lower central column. This represents the sum of the masses of the edge mass block and the center mass block.

[0013] As a further limitation of the present invention, the equivalent mass of the piezoelectric ceramic support base... for: ; Equivalent mass of the upper central pillar for: ; Equivalent mass of the lower central column for: ; in, This represents the cross-sectional area of ​​the lower central column. The height of the lower central column. This represents the cross-sectional area of ​​the upper central column. The height of the upper central column, The equivalent cross-sectional area of ​​the frustum representing the piezoelectric ceramic support base. This represents the height of the frustum of the piezoelectric ceramic support base.

[0014] In one alternative implementation of the invention, flexural charge for: ,in, , , It is the flexural constant of the material. It is the radius of the piezoelectric ceramic. It is the radius of the upper central pillar. It is the Poisson's ratio of piezoelectric ceramics. It is the edge mass block that is accelerating. Inertial force under action, , It is the mass of the edge mass block. , It is the Young's modulus of piezoelectric ceramics. It refers to the thickness of the piezoelectric ceramic. It is the Poisson's ratio of piezoelectric ceramics.

[0015] piezoelectric charge for: , denoted as ρ, which is the piezoelectric coefficient of the material.

[0016] As a further limitation of the present invention, obtaining acceleration data based on analog voltage data includes: calculating the total charge. for: The charge amplification circuit collects all the charges. Convert to corresponding analog voltage data, and then use the analog voltage data and acceleration... The relationship determines the acceleration under the current vibration. .

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention innovatively designs a split mass structure, which allows for the decoupled application of pressure and flexural force. The central mass block applies a force perpendicular to the sensitive element for piezoelectric effect induction of charge, while the surrounding mass blocks apply a force acting on the edge of the supporting base for flexural effect induction of charge. This achieves the combined application of piezoelectric and flexural effects. At the same time, the central mass block structure transforms the equivalent stiffness from pure bending stiffness to bending-compression stiffness, thereby improving the equivalent stiffness and increasing the resonant frequency.

[0018] This invention innovatively designs a trapezoidal support base. The trapezoidal support base structure made of TC4 material is produced by laser cutting. The thicker middle structure allows the center of the base to effectively support the sensor structure and make effective use of the piezoelectric effect. The thinner sides allow the support base to undergo greater deformation, increasing the deformation of the sensitive element, thereby amplifying the flexural effect and increasing the amount of induced charge.

[0019] This invention innovatively designs a method for calculating the total equivalent stiffness and equivalent mass of a sensor, defines the stiffness, mass parameters, and contact stiffness of each component, standardizes the calculation logic of flexural charge and piezoelectric charge, and establishes the conversion relationship between total charge and analog voltage data and acceleration data. It solves the problems of unclear calculation of sensor mechanical properties and induced charge, and lack of unified logic in the correlation between total charge and acceleration data. It overcomes the shortcomings of existing technologies, such as difficulty in accurately calculating sensor performance and inability to effectively guarantee detection accuracy, and improves the accuracy of sensor mechanical property calculation, the standardization of induced charge calculation, and the reliability of charge-to-acceleration data conversion.

[0020] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 A schematic diagram of the structure of a piezoelectric-flexoelectric composite accelerometer for detecting tunnel micro-vibrations provided as an exemplary embodiment of the present invention; Figure 2 A schematic diagram of the equivalent working principle of a sensor provided as an exemplary embodiment of the present invention; Figure 3 A circuit connection diagram is provided for an exemplary embodiment of the present invention; Among them, 1. connector; 2. outer shell; 3. charge amplification circuit; 4. edge mass block; 5. center mass block; 6. piezoelectric ceramic; 7. piezoelectric ceramic support base; 8. center column; 8-1. upper center column; 8-2. lower center column; 9. sensor base. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0025] As mentioned in the background technology, to meet the needs of tunnel construction environment and broadband weak signal acquisition, it is urgent to optimize frequency response and broadband consistency from the perspective of sensing structure and encapsulation coupling mechanism, and improve the ability to finely characterize complex wave field changes. Currently, there are still some difficulties in achieving broadband high-sensitivity detection of tunnel micro-vibrations: the resonant frequency of the sensor is affected by the equivalent stiffness of the system; the greater the stiffness, the higher the resonant point. Different structures have significantly different equivalent stiffnesses. Finding a sensing structure with high equivalent stiffness is an important method to improve the resonant frequency. Furthermore, the number of induced charges in the sensitive element is affected by the stress-strain gradient; the greater the stress and the greater the strain gradient, the more induced charges are. Therefore, this implementation proposes a piezoelectric-flexoelectric composite accelerometer for tunnel micro-vibration detection, such as... Figure 1 As shown, it includes: a connector 1, a housing 2, a charge amplification circuit 3, an edge mass block 4, a center mass block 5, a piezoelectric ceramic 6, a piezoelectric ceramic support base 7, a center column 8, and a sensor base 9.

[0026] In this implementation, preferably, the top of the piezoelectric ceramic support base 7 is a hollow ring structure, and the bottom of the piezoelectric ceramic support base 7 is a frustum with an inverted trapezoidal cross-section (the cross-section here passes through the longitudinal section of the central axis of the frustum). The support base is fixed on a precision lathe and the frustum is cut out by a picosecond laser. The piezoelectric ceramic 6 is fixed to the inner bottom of the hollow ring structure. The edge mass block 4 is stepped (divided into multiple layers, integrally molded, with the cross-sectional area of ​​the upper layer being larger than that of the lower layer, preferably a coaxial cylinder, with the area of ​​the upper cylinder being larger than that of the lower cylinder). The edge mass block 4 is fixedly connected to the top of the hollow ring structure (preferably by laser welding). A through hole for placing the central mass block 5 is opened at the center of the edge mass block 4, and the charge amplification circuit 3 is arranged on the top of the edge mass block 4.

[0027] In this implementation, preferably, the central mass block 5 passes through the through hole and is fixedly connected to the center of the piezoelectric ceramic 6 by conductive adhesive. The central column 8 includes an upper central column 8-1 and a lower central column 8-2 that are coaxial. The cross-sectional area of ​​the upper central column 8-1 is smaller than that of the lower central column 8-2. The bottom of the inverted trapezoidal structure is connected to the upper central column 8-1 (preferably by bolt fastening), and the lower central column 8-2 is connected to the sensor base 9 (preferably by bolt fastening).

[0028] In this implementation, preferably, the connector 1 is fixed to the top of the housing 2 (preferably by laser welding), the edge mass block 4, the center mass block 5, the piezoelectric ceramic 6 and the charge amplification circuit 3 are all arranged inside the housing 2, and the housing 2 is fixedly connected to the sensor base 9 (preferably by laser welding).

[0029] In this implementation, preferably, the nozzle 1, the outer shell 2, the piezoelectric ceramic support base 7, the central column 8, and the sensor base 9 are made of TC4 titanium alloy, the edge mass block 4 and the central mass block 5 are made of tungsten nickel copper alloy, and the piezoelectric ceramic 6 is PZT-5A.

[0030] In this implementation, preferably, the charge amplification circuit 3 is ring-shaped, and the charge amplification circuit 3 only contacts the edge mass block 4 and is bonded by insulating adhesive.

[0031] In this invention, the outer shell 2 and other structures are made of TC4 titanium alloy, which is laser-cut. As an alternative design, other materials with low density and high structural rigidity, such as aluminum alloy, can be used instead. The piezoelectric ceramic 6 in this invention is made of PZT-5A. As an alternative design, other lead-containing or lead-free piezoelectric materials, such as PZT-5H and KNN-based ceramics, can be used instead. In this invention, the mass block is a cylinder and the ceramic sheet is a circular thin sheet. As an alternative design, the mass block can be designed as a prism, cube, or other shape that can apply inertial force, and the ceramic sheet can be designed as a square thin sheet or other shape that can sense force.

[0032] The equivalent working principle of the sensor is as follows Figure 2 As shown (the spring is equivalent to the inertial force of the mass block acting on the piezoelectric ceramic. Due to the existence of inertia, when the force is removed, the mass block will continue to vibrate with reduced amplitude, analogous to the stretching and contraction of the spring), when the vibration is transmitted to the acceleration sensor, the edge mass block 4 acts on both ends of the piezoelectric ceramic 6, causing the piezoelectric ceramic 6 to flex and deform, inducing flexural charge. The center mass block 5 acts on the center of the piezoelectric ceramic 6, causing the piezoelectric ceramic 6 to compress and be subjected to force, inducing piezoelectric charge. The induced flexural charge and piezoelectric charge are collected by the charge amplification circuit 3, and all the collected charges are converted into corresponding analog voltage data. The acceleration data is obtained based on the analog voltage data.

[0033] When vibration is transmitted to the sensor, due to inertia, the mass will have the same acceleration as the sensed vibration. According to Newton's second law, the accelerated mass will exert a force on the piezoelectric ceramic 6, causing the ceramic to deform. Based on the piezoelectric and flexural effects, when the piezoelectric ceramic 6 is subjected to force and undergoes bending deformation, generating a strain gradient, a large amount of charge will be induced. After the induced charge is collected by the charge amplification circuit 3, it is converted into corresponding analog voltage data for processing. This allows the relationship between acceleration and output charge to be obtained, thus enabling the measurement of acceleration based on the amount of output charge.

[0034] The resonant frequency of this sensor Calculation formula: (1); in, This represents the total equivalent stiffness of the sensor. It represents the total equivalent mass of the sensor.

[0035] piezoelectric ceramic support base 7 bending stiffness for: (2); in, For edge mass block 4, The acceleration of edge mass block 4, The piezoelectric ceramic support base 7 has a radius of Deflection at the point, This represents the radius of the top surface of the frustum of the piezoelectric ceramic support base.

[0036] exist The value is 0 at the location. It is monotonically decreasing within the interval, therefore | |=| | Let be the radius of the upper central pillar.

[0037] Central column 8 compressive stiffness for: (3); in, Represents the Young's modulus of the upper central column 8-1. This represents the cross-sectional area of ​​the upper central column 8-1. The height of the upper central column is 8-1. This represents the Young's modulus of the lower central column 8-2. This represents the cross-sectional area of ​​the lower central column 8-2. The height of the lower central column is 8-2.

[0038] piezoelectric ceramics 6 bending stiffness for: (4); in, For piezoelectric ceramic 6 in radius of Deflection at the point, exist The value is 0 at the location. It is monotonically decreasing within the interval, therefore | |=| |, Represents the radius of the piezoelectric ceramic. This represents the radius of the upper central column.

[0039] Contact stiffness It mainly includes: the annular contact stiffness between the edge mass block 4 and the piezoelectric ceramic support base 7, the normal contact stiffness between the central column and the piezoelectric ceramic support base 7, and the contact stiffness between the piezoelectric ceramic 6 and the central mass block 5.

[0040] Equivalent mass of piezoelectric ceramic support base 7, upper central column 8-1, and lower central column 8-2 The expression is as follows: (5); (6); (7); (8); (9); (10); The volume formula for the bottom frustum of the piezoelectric ceramic support base 7 is: (11); In formula (5) This is the equivalent cross-sectional area of ​​the bottom frustum, corresponding to , The height of the bottom frustum of the piezoelectric ceramic support base. This represents the maximum radius of the bottom frustum. This represents the minimum radius of the bottom frustum.

[0041] The fundamental differential equation for the bending of piezoelectric ceramic 6 is: (12); in, D Let be the bending stiffness constant of piezoelectric ceramic 6. q For load, w For deflection, This represents the stress distribution that varies with the radius. Represents the Laplace operator.

[0042] For axisymmetric problems, the Laplace operator can be expressed in polar coordinates as: (13) ； Because of axial symmetry, all The derivatives of all equations are zero, and the fundamental differential equation for thin plate bending simplifies to: (14) ； After integration, the general solution is obtained: (15); in, This represents the distance from any point on the piezoelectric ceramic 6 to the center point. Since there is no distributed load, there is no particular solution. , , and All are constant coefficients.

[0043] The calculation of this model can be simplified to: a radius of... A circular thin plate (i.e., piezoelectric ceramic 6) with a radius of in the middle. The central column provides support, and the edges of the circular plate are subjected to edge loads perpendicular to the plate surface. Given the effect of the edge mass block under acceleration, calculate the deflection at any point on the circular thin plate.

[0044] The deflection is 0 (fixed boundary conditions). ： (16); The rate of change of deflection is 0 (fixed boundary conditions): (17); When the bending moment is 0 (free boundary condition): (18); in, It is the Poisson's ratio of the material.

[0045] Shear force at time (Free boundary conditions): (19); The above four conditions can be solved as follows: (20); (twenty one); (twenty two) ； Solving for: (twenty three); in, ， It is the Young's modulus of the material. It refers to the thickness of the material. It is the material's Poisson's ratio The amount of charge induced by the flexural effect can be obtained as follows: (twenty four); in, It is the charge induced by the flexural effect. It is the flexural constant of the material. It is the radius of the piezoelectric ceramic 6. It is the radius of the upper central column 8-1. It is the Poisson's ratio of piezoelectric ceramic 6. It is the edge mass block 4 that is accelerating. Inertial force under action, , It is the mass of edge mass block 4.

[0046] make: ; ; Then it can be established and Relationship: (25); The charge induced by the piezoelectric effect is: (26); in, The piezoelectric coefficient of the material is a constant. , It is the mass of the central mass block 5, that is ; (27); As can be seen, under a constant acceleration, the total induced charge increases, realizing piezoelectric-flexoelectric combined induction. The collected charge is then amplified by charge amplifier circuit 3. Convert to corresponding analog voltage data, and then use the analog voltage data and acceleration... The relationship determines the acceleration under the current vibration. Specifically, such as Figure 3 As shown, firstly, the piezoelectric ceramic generates induced charges, which are then transferred to the central mass block via conductive adhesive. Next, the central mass block transmits the charges to a charge amplification circuit via wires, which converts the charges into a voltage signal. Subsequently, the voltage signal is transmitted to the connector via wires, and finally, the connector transmits the voltage signal to the subsequent acquisition and processing stage via wires. This invention enhances the balance between high sensitivity and wide bandwidth of the sensor, avoiding data deviations caused by improper calculations of stiffness, mass, and charge, as well as the inability to accurately characterize tunnel micro-vibrations. This ensures the precision and stability of tunnel micro-vibration detection, providing more reliable technical support for advanced geological prediction of tunnels.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A piezoelectric-flexoelectric composite accelerometer for detecting micro-vibrations in tunnels. Its features are, Includes: edge mass block, center mass block, piezoelectric ceramic, charge amplification circuit, center column, sensor base and piezoelectric ceramic support base; The top of the piezoelectric ceramic support base is a hollow ring structure, and the bottom of the piezoelectric ceramic support base is a frustum with an inverted trapezoidal cross-section. The piezoelectric ceramic is fixed to the inner bottom of the hollow ring structure. The edge mass block is stepped and is fixedly connected to the top of the hollow ring structure. A through hole for placing the center mass block is opened at the center of the edge mass block, and the charge amplification circuit is arranged on the top of the edge mass block. The central mass block passes through the through hole and is fixedly connected to the center of the piezoelectric ceramic by conductive adhesive. The central column includes an upper central column and a lower central column that are coaxial. The cross-sectional area of ​​the upper central column is smaller than that of the lower central column. The bottom of the inverted trapezoidal structure is connected to the upper central column, and the lower central column is connected to the sensor base. When the vibration is transmitted to the acceleration sensor, the edge mass block acts on the edge of the piezoelectric ceramic, causing the piezoelectric ceramic to flex and deform, inducing flexural charge. The center mass block acts on the center of the piezoelectric ceramic, causing the piezoelectric ceramic to compress and induce piezoelectric charge. The induced flexural charge and piezoelectric charge are collected by the charge amplification circuit, and all the collected charges are converted into corresponding analog voltage data. The acceleration data is obtained based on the analog voltage data.

2. The piezoelectric-flexoelectric composite accelerometer for tunnel micro-vibration detection as described in claim 1, characterized in that, It also includes a housing and a connector, with the connector fixed to the top of the housing. The edge mass block, the center mass block, the piezoelectric ceramic and the charge amplification circuit are all arranged inside the housing, and the housing is fixedly connected to the sensor base.

3. The piezoelectric-flexoelectric composite accelerometer for tunnel micro-vibration detection as described in claim 2, characterized in that, The nozzle, the outer shell, the piezoelectric ceramic support base, the central column, and the sensor base are made of titanium alloy, while the edge mass block and the central mass block are made of tungsten-nickel-copper alloy.

4. The piezoelectric-flexoelectric composite accelerometer for tunnel micro-vibration detection as described in claim 1, characterized in that, The charge amplification circuit is ring-shaped and only contacts the edge mass block, and is bonded together with insulating adhesive.

5. The piezoelectric-flexoelectric composite accelerometer for tunnel micro-vibration detection as described in claim 1, characterized in that, The total equivalent stiffness K is: ,in, This represents the bending stiffness of the piezoelectric ceramic support base; Represents the compressive stiffness of the central column; Represents the bending stiffness of piezoelectric ceramics; The contact stiffness represents the annular contact stiffness between the edge mass block and the piezoelectric ceramic support base, the normal contact stiffness between the central column and the piezoelectric ceramic support base, and the contact stiffness between the piezoelectric ceramic and the central mass block.

6. The piezoelectric-flexoelectric composite accelerometer for tunnel micro-vibration detection as described in claim 5, characterized in that, piezoelectric ceramic support base bending stiffness for: , Represents the mass of the edge mass block. Represents the acceleration of the edge mass block. To support the maximum radius of the base Deflection at the point, Represents the maximum deflection. It is the edge mass block that is accelerating. Inertial force under action; Central column compressive stiffness for: ,in, The Young's modulus of the upper central column. This represents the cross-sectional area of ​​the upper central column. The height of the upper central column, The Young's modulus represents the lower central column. This represents the cross-sectional area of ​​the lower central column. The height of the lower central column; piezoelectric ceramic bending stiffness for: .

7. The piezoelectric-flexoelectric composite accelerometer for tunnel micro-vibration detection as described in claim 5, characterized in that, Overall equivalent quality for: ,in, This represents the equivalent mass of the piezoelectric ceramic support base. Represents the equivalent mass of the upper central pillar. Represents the equivalent mass of the lower central column. This represents the mass of the edge mass block and the center mass block.

8. The piezoelectric-flexoelectric composite accelerometer for tunnel micro-vibration detection as described in claim 7, characterized in that, Equivalent mass of piezoelectric ceramic support base for: ; Equivalent mass of the upper central pillar for: ; Equivalent mass of the lower central column for: ; in, This represents the cross-sectional area of ​​the lower central column. The height of the lower central column. This represents the cross-sectional area of ​​the upper central column. The height of the upper central column, The equivalent cross-sectional area of ​​the frustum representing the piezoelectric ceramic support base. This represents the height of the frustum of the piezoelectric ceramic support base.

9. The piezoelectric-flexoelectric composite accelerometer for tunnel micro-vibration detection as described in any one of claims 1-8, characterized in that, Flexural charge for: ,in, , , It is the flexural constant of the material. It is the radius of the piezoelectric ceramic. It is the radius of the upper central pillar. It is the Poisson's ratio of piezoelectric ceramics. It is the edge mass block that is accelerating. Inertial force under action, , It is the mass of the edge mass block. , It is the Young's modulus of the material. It refers to the thickness of the piezoelectric ceramic. piezoelectric charge for: , denoted as ρ, which is the piezoelectric coefficient of the material.

10. The piezoelectric-flexoelectric composite accelerometer for tunnel micro-vibration detection as described in claim 9, characterized in that, Acceleration data is obtained based on the simulated voltage data, including: calculating the total charge. for: The charge amplification circuit collects all the charges. Convert to corresponding analog voltage data, and then use the analog voltage data and acceleration... The relationship determines the acceleration under the current vibration. .

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