A method for developing a resonant acoustic sensor

Abstract

The invention discloses a method for developing a resonant acoustic sensor, and relates to the technical field of sensor development. The specific frequency of a target sensor is calculated; the structure of the target sensor is designed according to the static and dynamic characteristics of a piezoelectric crystal; the designed structure of the target sensor is evaluated and corrected through modeling and physical field simulation analysis; and the purpose of reducing the development difficulty and the R&D cost of the sensor is achieved through the design and simulation of the piezoelectric structure and the mechanical structure.

Description

Technical Field

[0001] The present invention relates to the technical field of sensor development, and more particularly to a method for developing a resonant acoustic sensor. Background Art

[0002] Acoustic emission sensors (AE Sensors) are often used to monitor various types of structures such as pressure vessels and storage tanks because they can receive acoustic emission signals inside materials or structures. The performance of the acoustic emission sensor directly determines the accuracy of the detection results. At present, the most commonly used sensor in the detection of acoustic emission signals is the resonant acoustic emission sensor, which is also the basis of the sensor designed in this paper. This paper uses a single-ended sensor with a simpler structure to reduce the size of the sensor to a greater extent.

[0003] As an important part of the acoustic emission detection system, the performance of the acoustic emission sensor has an important impact on the overall detection accuracy of the system. Most of the sensors currently used in engineering use piezoelectric elements as sensing elements, and the most commonly used sensor elements are quartz, lithium niobate, etc. They have higher response sensitivity and more stable performance, and are currently the piezoelectric materials commonly used in acoustic emission sensors.

[0004] The site for detecting metal pipe leakage is generally outdoors, and the surrounding noise is inevitable during detection. The frequency band of low-frequency sensors currently on the market is relatively wide, which affects the accuracy of the detection signal. Traditional acoustic emission sensors are relatively expensive and easy to damage, which also limits the promotion and use of acoustic emission technology. Therefore, reducing the cost of sensor research and development and reducing the difficulty of sensor development are issues that technical personnel in this field urgently need to solve. Summary of the invention

[0005] In view of this, the present invention provides a method for developing a resonant acoustic sensor, so as to reduce the difficulty of developing the sensor and reduce the cost of developing the sensor.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for developing a resonant acoustic sensor, the method comprising the following steps:

[0008] Calculate the specific frequency of the target sensor;

[0009] Designing the structure of the target sensor according to the static and dynamic characteristics of the piezoelectric crystal;

[0010] Evaluate and modify the structure of the designed target sensor through modeling and physical field simulation analysis;

[0011] A genetic algorithm is selected to perform multi-parameter model optimization on the sensor, and the target sensor is compared with an existing resonant acoustic emission sensor to verify the performance of the target sensor.

[0012] The method for calculating the specific frequency of the target sensor:

[0013] On the basis of the existing narrow-band acoustic sensor, the specific frequency of the target sensor is calculated, the resonance point is found within the frequency range, and the frequency of the acoustic sensor model is limited by using the characteristics of the vocal cord protrusion distribution to retain the signal frequency within the range.

[0014] The specific steps of the method for designing the structure of the target sensor are:

[0015] Establishing a piezoelectric structural dynamics model of the target sensor, and obtaining a resonant structure using sound pressure level distribution based on a theory based on orthogonal experiments;

[0016] Use AutoCAD and SolidWorks software to draw a narrow-band acoustic sensor model with a resonant structure;

[0017] The mechanical structure of the target sensor is designed based on numerical analysis.

[0018] The piezoelectric structure design method includes a piezoelectric structure design method and a mechanical structure design method.

[0019] The specific steps of the design method of the piezoelectric structure of the target sensor are:

[0020] Calculate the natural frequency f of the sensor 0 , and then calculate the natural frequencies of each influencing factor of the model stiffness;

[0021] Compare each calculated natural frequency with f 0 For comparison, when the influence of a certain stiffness factor is ignored, the calculated natural frequency is similar to f 0 If the difference is less than 1%, the neglected stiffness influencing factor is ignored in the simplified dynamic model; based on the series relationship between the influencing factors, the force conditions of the sensor components are analyzed to determine the stiffness of each component, and the empirical formula of the tangential contact stiffness is obtained by fitting the influence relationship between the normal contact stiffness and the tangential contact stiffness of the piezoelectric structure, and the natural frequency relationship of the sensor is determined in conjunction with the contact fractal theory;

[0022] According to the relationship between the area of ​​the piezoelectric sheet and the mass block of the piezoelectric structure, the minimum mass block volume and the corresponding piezoelectric sheet area are first calculated, and then substituted into the dynamic model for calculation to obtain the law of change of the natural frequency of the sensor with the area of ​​the piezoelectric sheet; the area of ​​the piezoelectric sheet is selected on the basis of ensuring the natural frequency and size requirements of the sensor;

[0023] The thickness of the piezoelectric sheet is determined according to the stiffness of the sheet and the degree of bending when it is vibrated;

[0024] According to the values ​​calculated by the theoretical model of piezoelectric structural dynamics, the size of the piezoelectric crystal and the contact area between the piezoelectric sheet and the contact surface are controlled;

[0025] The method of gradually increasing the thickness of the piezoelectric sheet is adopted, and the thickness of the sheet is compared with the natural frequency of the sensor, and then the thickness of the sheet is selected.

[0026] The specific steps of the mechanical structure design method are:

[0027] A cantilever beam is used to separate the direct contact between the base and the piezoelectric element; the structure is modified based on the cantilever beam type acoustic sensor structure foundation to determine the structural form;

[0028] According to the frequency performance requirements, the volume and mass of the mass block are determined; according to the fit between the piezoelectric sheet and the mass block, the contact area between the mass block and the piezoelectric sheet and the thickness of the mass block are determined;

[0029] Determine the connection method between the piezoelectric sheet and the mass block according to the reserved space for inserting the conductive sheet in the structure;

[0030] The form of the base is determined based on the signal acquisition error caused by the vibration amplitude when the sensor is excited, the relationship between the base thickness and the natural frequency, and the factors of the invalid strain of the isolation shell;

[0031] Analyze the acoustic sensor's reception of sound waves by judging the charge sensitivity and voltage sensitivity;

[0032] The insulation resistance of the insulating sleeve is designed and calculated according to the insulation requirements of the insulating sleeve to determine the outer diameter of the insulating sleeve.

[0033] The modeling and physical field simulation analysis method includes a piezoelectric structure modeling and physical field simulation analysis method, and a piezoelectric structure and mechanical structure coupling simulation analysis method.

[0034] The specific steps of the piezoelectric structure modeling and physical field simulation analysis method are:

[0035] The multi-physics field coupling software Comsol Multiphysics is used to establish a model of the piezoelectric structure of the acoustic sensor. The vibration deformation, potential change and mechanical deformation form of the sensor piezoelectric structure under excitation conditions are obtained through finite element modal analysis. The gap between the designed model and the ideal performance is determined in the simulated physical field.

[0036] The coupling simulation analysis method of the piezoelectric structure and the mechanical structure:

[0037] The mechanical structure and piezoelectric structure of the sensor are electromechanically coupled, and the frequency range of the sensor is obtained through simulation verification.

[0038] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a method for developing a resonant acoustic sensor, thereby achieving the following beneficial effects:

[0039] 1. The frequency of the acoustic sensor model is limited by utilizing the characteristics of the distribution of vocal cord protrusions, thereby increasing the sensitivity of the model to receive signals within a specific frequency range, while other frequencies cannot receive signals, thereby ensuring the sensitivity and anti-interference performance of the target sensor.

[0040] 2. Through the design and simulation of piezoelectric structure and mechanical structure, the goal of reducing the difficulty of sensor development and the cost of sensor research and development can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0042] Figure 1 The accompanying drawing is a schematic structural diagram of the present invention.

[0043] Figure 2 The attached figure is a schematic diagram of the variation of the natural frequency with the number of piezoelectric sheets.

[0044] Figure 3 The accompanying drawing is a schematic diagram of the mass block form of the resonant piezoelectric acoustic sensor of the present invention.

[0045] Figure 4 The accompanying drawing is a schematic diagram of the charge extraction method of the sensor of the present invention.

[0046] Figure 5 The accompanying drawing is a schematic diagram of the base form of the piezoelectric sensor of the present invention.

[0047] Figure 6 The accompanying drawing is a schematic diagram of the mesh division of the piezoelectric structure of the present invention.

[0048] Figure 7 The accompanying drawing is a schematic diagram of the grid division of the sensor mechanical structure of the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Embodiment 1:

[0051] A method for developing a resonant acoustic sensor comprises the following steps:

[0052] The narrowband acoustic sensor model with a resonant structure was drawn using AutoCAD and SolidWorks software, and the model was numerically simulated in COMSOL Multiphysics software to obtain a preliminary sensor model and judge its performance. The resonant structure of the sensor was reasonably designed to ensure that the sensor met the requirements of engineering use.

[0053] Embodiment 2:

[0054] Using MATLAB software, programming is performed based on orthogonal experiments. By calculating specific frequencies, the resonance point is found within the frequency range, and the frequency of the acoustic sensor model is limited by the distribution characteristics of the vocal cord protrusions, thereby improving the sensitivity of the model.

[0055] Embodiment 3:

[0056] Design of dynamic model of piezoelectric structure of sensor

[0057] The sensor dynamics theoretical model is simplified, and the natural frequency relationship of the sensor is determined by fitting the influence relationship between the normal contact stiffness and the tangential contact stiffness of the piezoelectric structure.

[0058] The calculated minimum mass volume is 4.02 mm 3 , the piezoelectric sheet area is 4.32mm 2 , the area of ​​the piezoelectric sheet is equal to the area of ​​the mass block, and the law of change of the natural frequency of the sensor with the area of ​​the piezoelectric sheet is obtained, such as Figure 2 As shown. The area of ​​the piezoelectric sheet is selected to be 4.5mm based on the natural frequency of the sensor. 2 The size of the piezoelectric structure is set to 3.6 mm × 1.2 mm × 0.35 mm. The piezoelectric structure of the sensing unit in parallel is designed to make the sound absorption effect of the sensor as close to 100% as possible.

[0059] Embodiment 4:

[0060] Design of dynamic model of sensor mechanical structure

[0061] The sensor structure design uses a cantilever beam to separate the base from the direct contact with the piezoelectric element, and determines the symmetrical structure.

[0062] Furthermore, the form of the mass block is determined by increasing the contact area between the mass block and the piezoelectric sheet and reducing the thickness of the mass block, such as Figure 3 shown.

[0063] Further, the piezoelectric sheet is directly connected to the mass block, and the two ends of the electrode are connected to the left and right ends of the central column, such as Figure 4 As shown, the charge is drawn out.

[0064] When further designing the base, a double-layer lamination method is used to alleviate the problem, such as Figure 5 Shown is the designed sensor mount.

[0065] The outer diameter of the insulating sleeve is further determined by designing and calculating the insulation resistance, and the sensor installation is more convenient by keeping the piezoelectric sheet through hole and the center column through hole consistent with the outer diameter of the insulating sleeve.

[0066] Embodiment 5:

[0067] Piezoelectric structure modeling and physical field simulation analysis methods:

[0068] After importing the sensor 3D model into COMSOL Multiphysics and selecting the sensor material, the sensor unit is meshed to achieve finite element meshing.

[0069] Different density division methods are adopted for different regions, and the boundary conditions are controlled for solution. The maximum unit size of the piezoelectric sheet and the insulating sheet is set to 83.5 μm, and the minimum unit size is set to 6.48 μm. The mesh division results are shown in the figure below. Figure 6 shown.

[0070] Based on the research on piezoelectric materials, AT-cut quartz was selected as the piezoelectric material for the piezoelectric structure, and the piezoelectric structure size of the sensor was designed to be 3.6mm×1.2mm×0.35mm.

[0071] Embodiment 6:

[0072] Sensor Coupling Simulation

[0073] The piezoelectric structure and mechanical structure of the sensor were designed respectively, and the sensor was coupled using the model to verify the coupling effect of the sensor.

[0074] The finite element simulation method is further used to calculate and verify it to ensure the natural frequency of the acoustic emission sensor. Mechanical damping is added to the sensor model, and the piezoelectric coefficient of the sensor material under different parameters is set to obtain the frequency of the sensor.

[0075] By analyzing the variation of sensor frequency through theoretical calculation and finite element simulation, the obtained sensor frequency range is basically between 40KHz and 70KHz, but the sensitivity is slightly different. Since the sensitivity of the sensor will be disturbed by the external environment during actual use, the sensitivity of theoretical calculation is higher than that of finite element simulation.

[0076] The numerical simulation method is further used to simulate and verify the electromechanical force. After the mechanical structure and piezoelectric structure of the sensor are coupled and contacted, the whole is discretized, and the two approximate numerical calculation methods of difference method and variation method are combined to deal with more complex physical field coupling problems. The three-dimensional model of the sensor is imported into COMSOL Multiphysics software for meshing, and the results are as follows Figure 7 shown.

[0077] The size of the sensor's mechanical structure was further determined to be 20mm×20mm×22mm. The sensor's mechanical structure and piezoelectric structure were electromechanically coupled, and the frequency range of the sensor was verified to be 40KHz to 70KHz through simulation.

[0078] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0079] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for developing a resonant acoustic sensor, characterized in that: The method for developing the resonant acoustic sensor comprises the following steps: Calculate the specific frequency of the target sensor; Designing the structure of the target sensor according to the static and dynamic characteristics of the piezoelectric crystal; Evaluate and modify the structure of the designed target sensor through modeling and physical field simulation analysis; Selecting a genetic algorithm to optimize a multi-parameter model of the sensor, comparing the target sensor with an existing resonant acoustic emission sensor, and verifying the performance of the target sensor; The method for calculating the specific frequency of the target sensor: Based on the existing narrow-band acoustic sensor, the resonance point is found within the frequency range by calculating the specific frequency of the target sensor, and the frequency of the acoustic sensor model is limited by using the characteristics of the vocal cord convex distribution to retain the signal frequency within the range. The specific steps of the method for designing the structure of the target sensor are: Establishing a piezoelectric structural dynamics model of the target sensor, and obtaining a resonant structure using sound pressure level distribution based on a theory based on orthogonal experiments; Use AutoCAD and SolidWorks software to draw a narrow-band acoustic sensor model with a resonant structure; Designing a mechanical structure of the target sensor based on numerical analysis; The piezoelectric structure design method includes a piezoelectric structure design method and a mechanical structure design method; The specific steps of the design method of the piezoelectric structure of the target sensor are: Calculate the natural frequency of the sensor f 0, and then calculate the natural frequency of each factor affecting the model stiffness; Each calculated natural frequency is compared with f 0, when the influence of a certain stiffness factor is ignored, the calculated natural frequency is f 0 difference is less than 1%, then the neglected stiffness influencing factors are ignored in the simplified dynamic model; based on the series relationship between the influencing factors, the force conditions of the sensor components are analyzed to determine the stiffness of each component, and the empirical formula of the tangential contact stiffness is obtained by fitting the influence relationship between the normal contact stiffness and the tangential contact stiffness of the piezoelectric structure, and the natural frequency relationship of the sensor is determined in conjunction with the contact fractal theory; According to the relationship between the area of ​​the piezoelectric sheet and the mass block of the piezoelectric structure, the minimum mass block volume and the corresponding piezoelectric sheet area are first calculated, and then substituted into the dynamic model for calculation to obtain the law of change of the natural frequency of the sensor with the area of ​​the piezoelectric sheet; the area of ​​the piezoelectric sheet is selected on the basis of ensuring the natural frequency and size requirements of the sensor; The thickness of the piezoelectric sheet is determined according to the stiffness of the sheet and the degree of bending when it is vibrated; According to the values ​​calculated by the theoretical model of piezoelectric structural dynamics, the size of the piezoelectric crystal and the contact area between the piezoelectric sheet and the contact surface are controlled; The thickness of the piezoelectric sheet is gradually increased, and the thickness of the sheet is compared with the natural frequency of the sensor to select the thickness of the sheet. The specific steps of the mechanical structure design method are: A cantilever beam is used to separate the direct contact between the base and the piezoelectric element; the structure is modified based on the cantilever beam type acoustic sensor structure foundation to determine the structural form; According to the frequency performance requirements, the volume and mass of the mass block are determined; according to the fit between the piezoelectric sheet and the mass block, the contact area between the mass block and the piezoelectric sheet and the thickness of the mass block are determined; Determine the connection method between the piezoelectric sheet and the mass block according to the reserved space for inserting the conductive sheet in the structure; The form of the base is determined based on the signal acquisition error caused by the vibration amplitude when the sensor is excited, the relationship between the base thickness and the natural frequency, and the factors of the invalid strain of the isolation shell; Analyze the acoustic sensor's reception of sound waves by judging the charge sensitivity and voltage sensitivity; Design and calculate the insulation resistance of the insulating sleeve according to the insulation requirements of the insulating sleeve to determine the outer diameter of the insulating sleeve; The modeling and physical field simulation analysis methods include piezoelectric structure modeling and physical field simulation analysis methods, and piezoelectric structure and mechanical structure coupling simulation analysis methods; The specific steps of the piezoelectric structure modeling and physical field simulation analysis method are: The multi-physics coupling software Comsol Multiphysics is used to establish a model of the piezoelectric structure of the acoustic sensor. The vibration deformation, potential change and mechanical deformation form of the piezoelectric structure of the sensor under excitation conditions are obtained through finite element modal analysis. The gap between the designed model and the ideal performance is determined in the simulated physical field. The coupling simulation analysis method of the piezoelectric structure and the mechanical structure: The mechanical structure and piezoelectric structure of the sensor are electromechanically coupled, and the frequency range of the sensor is obtained through simulation verification.

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