Optimizing Simulation Design Methods for Air-Coupled Ultrasonic Sensors

Abstract

The present invention relates to the technical field of air-coupled ultrasonic sensors, and specifically to a simulation design method for optimizing air-coupled ultrasonic sensors. To address the high preparation cost and time-consuming nature of conventional optimization methods for air-coupled ultrasonic sensors, a new simulation design method for optimizing air-coupled ultrasonic sensors is provided, comprising the following steps: 1) establishing Leach equivalent circuit models of different piezoelectric composite materials and performing simulation optimization to obtain the optimal piezoelectric composite material; 2) establishing a lossless transmission line model of a first matching layer based on the equivalent circuit model corresponding to the optimal piezoelectric composite material and performing simulation analysis to obtain the optimal first matching layer; and 3) establishing a lossless transmission line model of a second matching layer based on the circuit model corresponding to the optimal first matching layer and performing simulation analysis to obtain the optimal second matching layer. This design method is low-cost and time-consuming.

Description

Technical Field

[0001] The present invention relates to the technical field of air-coupled ultrasonic sensors, and in particular to a design method of an air-coupled ultrasonic sensor, specifically to a simulation design method for optimizing an air-coupled ultrasonic sensor. Background Art

[0002] Air-coupled ultrasonic testing technology is non-contact and requires no coupling agent. It is particularly suitable for automated testing in applications where coupling agents are unsuitable, such as composite materials, multi-layer adhesives, and lithium batteries. It has broad application prospects in the aerospace, automotive, and lithium battery industries. Air-coupled ultrasonic sensors are key components in testing systems, performing acoustic-to-electrical or electrical-to-acoustic energy conversion. Their performance directly impacts detection accuracy.

[0003] The main components that affect the detection performance of air-coupled ultrasonic sensors are the piezoelectric composite material, the first matching layer, and the second matching layer. To create the optimal air-coupled ultrasonic sensor, different combinations of piezoelectric composite materials, first matching layers composed of epoxy resin and glass microbeads in different ratios, and second matching layers formed of foam materials with different expansion ratios must be prepared and repeatedly tested and analyzed to determine the optimal combination, thereby producing the optimal air-coupled ultrasonic sensor. Traditional optimization design methods for air-coupled ultrasonic sensors involve preparing different combinations of physical objects and then testing and analyzing them separately. However, repeated testing and analysis of different physical combinations consumes a large amount of material and may produce a large amount of waste, resulting in increased production costs. Furthermore, the process of preparing different sensor combinations and repeatedly testing and analyzing them after preparation is time-consuming, seriously affecting product development progress and leading to a significant decline in product market competitiveness. Summary of the Invention

[0004] In order to solve the problems of high preparation cost and long time consumption in the traditional optimization design method of air-coupled ultrasonic sensors, the present invention provides a new simulation design method for optimizing air-coupled ultrasonic sensors.

[0005] The present invention is achieved by adopting the following technical solutions:

[0006] The simulation design method for optimizing the air-coupled ultrasonic sensor includes the following steps:

[0007] 1) Optimization of piezoelectric composite materials: a. According to the different piezoelectric composite materials used, the parameters used in establishing the corresponding Leach equivalent circuit model are obtained, namely the center frequency f of the air-coupled sensor, static capacitance C0, piezoelectric constant h, transmission line inductance L, transmission line capacitance C, transmission line resistance R, the center frequency of the air-coupled sensor Static capacitance Piezoelectric constant Transmission line inductance L = Aρ, transmission line capacitance Transmission line resistance R = Lwtanδ m , where d is the known thickness of the piezoelectric composite material, c is the known acoustic velocity of the piezoelectric composite material, and ε S is the known relative clamped dielectric constant, A is the known cross-sectional area of ​​the piezoelectric composite material perpendicular to the direction of acoustic wave propagation, h is the known piezoelectric constant, and e is the known 33 is the known short-circuit elastic constant, ρ is the known density of the piezoelectric composite material, w is the known angular frequency of the piezoelectric composite material, and tanδ m =1 / Qe and is called the dielectric loss factor, where Qe is the known electrical quality factor; b. establishing Leach equivalent circuit models of different piezoelectric composite materials based on the above parameters, thereby forming different first equivalent circuit models; c. performing simulation analysis on the different established first equivalent circuit models, and the piezoelectric composite material corresponding to the first equivalent circuit model with the largest signal amplitude is the optimal piezoelectric composite material;

[0008] 2) Optimization of the first matching layer: a. Based on the different first matching layers used, the parameters used to establish the corresponding lossless transmission line model are obtained, namely, the first lossless transmission line signal frequency f1, the first normalized length Nl1, and the first impedance Z1. The first lossless transmission line signal frequency is determined according to the lossless transmission line theory. First normalized length a) establishing a lossless transmission line model of the first matching layer based on the first equivalent circuit model corresponding to the optimal piezoelectric composite material according to the above parameters, thereby forming a second equivalent circuit model; c) performing simulation analysis on the established second equivalent circuit model; the first matching layer corresponding to the second equivalent circuit model with the largest signal amplitude is the optimal first matching layer;

[0009] 3) Optimization of the second matching layer: a. Based on the different second matching layers used, the parameters used to establish the corresponding lossless transmission line model are obtained, namely, the second lossless transmission line signal frequency f2, the second normalized length Nl2, and the second impedance Z2. The second lossless transmission line signal frequency is determined based on the lossless transmission line theory. Second normalized length a. The second impedance Z2=ρ2c2s2, where c2 is the acoustic velocity of the second matching layer, l2 is the thickness of the second matching layer, LEN2 is the length of the transmission line of the second matching layer, ρ2 is the density of the second matching layer material, and s2 is the cross-sectional area of ​​the second matching layer perpendicular to the direction of sound wave propagation. b. Based on the above parameters, a lossless transmission line model of the second matching layer is established on the basis of the second equivalent circuit model corresponding to the optimal first matching layer, thereby forming a third equivalent circuit model. c. The established third equivalent circuit model is simulated and analyzed. The second matching layer corresponding to the third equivalent circuit model with the largest signal amplitude is the optimal second matching layer, thereby completing the simulation design of the optimized air-coupled ultrasonic sensor.

[0010] The beneficial effects of the present invention are as follows: the method cleverly optimizes the air-coupled ultrasonic sensor by analyzing the signal amplitude after establishing an equivalent circuit model for simulation, without consuming a large amount of materials or generating a large amount of waste. At the same time, the method of the present invention can sequentially optimize the design of the piezoelectric composite material, the first matching layer, and the second matching layer, without the need to assemble all of them into physical objects and then conduct repeated testing and analysis. This method is time-saving and effectively improves the progress of product development. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0013] Figure 1 The simulation waveforms are shown when the glass bead model, microsphere weight ratio, and diluent ratio are BR20-20-15, BR40-20-0, and BR60-20-0, respectively, as the first matching layer.

[0014] Figure 2 This is a first equivalent circuit model diagram in a specific embodiment;

[0015] Figure 3 is a second equivalent circuit model diagram in a specific embodiment;

[0016] Figure 4 The third equivalent circuit model diagram in the specific embodiment

[0017] Figure 5 This is the simulation waveform of the air-coupled ultrasonic sensor designed with optimal parameters;

[0018] Figure 6 This is the actual test waveform of the air-coupled ultrasonic sensor designed with optimal parameters;

[0019] Figure 7 Application of optimized air-coupled ultrasonic sensor in defect detection. DETAILED DESCRIPTION

[0020] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0021] In the description, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance. It should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood broadly. For example, they can refer to fixed connections, removable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms based on specific circumstances.

[0022] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all the embodiments.

[0023] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0024] 1) Optimization of piezoelectric composite materials: a. The piezoelectric composite materials used are 1-3 type, 2-2 type, and 2-3 type piezoelectric composite materials. According to the different piezoelectric composite materials selected, the parameters used in establishing the corresponding Leach equivalent circuit model are obtained, namely the center frequency f of the air-coupled sensor, static capacitance C0, piezoelectric constant h, transmission line inductance L, transmission line capacitance C, transmission line resistance R, the center frequency of the air-coupled sensor Static capacitance Piezoelectric constant Transmission line inductance L = Aρ, transmission line capacitance Transmission line resistance R = Lwtanδ m , where d is the known thickness of the piezoelectric composite material, c is the known acoustic velocity of the piezoelectric composite material, and ε Sis the known relative clamped dielectric constant, A is the known cross-sectional area of ​​the piezoelectric composite material perpendicular to the direction of acoustic wave propagation, h is the known piezoelectric constant, and e is the known 33 is the known short-circuit elastic constant, ρ is the known density of the piezoelectric composite material, w is the known angular frequency of the piezoelectric composite material, and tanδ m =1 / Qe and is called the dielectric loss factor, where Qe is the known electrical quality factor; b. Leach equivalent circuit models of different piezoelectric composite materials are established based on the above parameters, thereby forming different first equivalent circuit models; c. Simulation analysis is performed on the first equivalent circuit models corresponding to the three different models, and it is concluded that the piezoelectric composite material corresponding to the first equivalent circuit model with the largest signal amplitude is the type 1-3 piezoelectric composite material, which is the optimal piezoelectric composite material;

[0025] 2) Optimization of the first matching layer: a. Use glass bead model, microsphere weight ratio, and diluent ratio of BR20-20-15, BR40-20-0, and BR60-20-0 as the first matching layer. The parameters used in the corresponding lossless transmission line model are obtained based on the different first matching layers selected, namely the first lossless transmission line signal frequency f1, the first normalized length Nl1, and the first impedance Z1. The first lossless transmission line signal frequency is determined based on the lossless transmission line theory. First normalized length The first impedance Z1=ρ1c1s1, where c1 is the known acoustic velocity of the first matching layer, l1 is the known thickness of the first matching layer, LEN1 is the known length of the transmission line of the first matching layer, ρ1 is the known density of the first matching layer material, and s1 is the known cross-sectional area of ​​the first matching layer perpendicular to the direction of acoustic wave propagation. b. Based on the above parameters, a lossless transmission line model of the first matching layer is established on the basis of the first equivalent circuit model corresponding to the optimal piezoelectric composite material to form a second equivalent circuit model. c. The second equivalent circuit models corresponding to the three first matching layers are simulated and analyzed respectively. The simulation waveforms of the second equivalent circuit models corresponding to the three first matching layers are shown in FIG. Figure 1 As shown, the first matching layer corresponding to the second equivalent circuit model with the largest signal amplitude is the first matching layer of BR20-20-15, which is the optimal first matching layer;

[0026] 3) Optimization of the second matching layer: a. Use foam materials with 5 times the foaming rate, 10 times the foaming rate, and 15 times the foaming rate as the second matching layer. According to the different second matching layers selected, the parameters used to establish the corresponding lossless transmission line model are obtained, namely, the second lossless transmission line signal frequency f2, the second normalized length Nl2, and the second impedance Z2. The second lossless transmission line signal frequency is determined according to the lossless transmission line theory. Second normalized length b. A second impedance Z2 = ρ2c2s2, where c2 is the known acoustic velocity of the second matching layer, l2 is the known thickness of the second matching layer, LEN2 is the known length of the second matching layer transmission line, ρ2 is the known density of the second matching layer material, and s2 is the known cross-sectional area of ​​the second matching layer perpendicular to the direction of sound wave propagation. b. Based on the above parameters, a lossless transmission line model of the second matching layer is established on the basis of the second equivalent circuit model corresponding to the optimal first matching layer, thereby forming a third equivalent circuit model. c. Simulation analysis is performed on the three third equivalent circuit models corresponding to the second matching layer, and it is concluded that the third equivalent circuit model with the largest signal amplitude corresponds to a second matching layer composed of a foam material with a foaming ratio of 10 times, which is the optimal second matching layer.

[0027] The following is a detailed verification of the optimal piezoelectric composite material, the optimal first matching layer, and the optimal second matching layer selected above:

[0028] 1) Establishing the Leach equivalent circuit model of the piezoelectric composite material: a. Based on the selected optimal 1-3 type piezoelectric composite material, the parameters used in establishing the Leach equivalent circuit model of the piezoelectric composite material are obtained, namely, the center frequency f of the air-coupled sensor is 231 kHz, the static capacitance C0 is 0.1966 nF, and the piezoelectric constant h is 2.68×10 9 , transmission line inductance L = 1.46H, transmission line capacitance C = 55nF, transmission line resistance R = 4260Ω; b, establish the Leach equivalent circuit model of the piezoelectric composite material according to the above parameters, thereby forming a first equivalent circuit model, such as Figure 2 As shown;

[0029] 2) Establishing an infinite transmission line model of the first matching layer based on the Leach equivalent circuit model of the piezoelectric composite material: a. Based on the first matching layer selected with the optimal glass microbead model, microbead weight ratio, and diluent ratio of BR20-20-15, the parameters used to establish the lossless transmission line model are obtained, namely, the first lossless transmission line signal frequency f1 = 635 kHz, the first normalized length Nl1 = 0.5, and the first impedance Z1 = 382 Ω; b. Based on the above parameters, establishing the lossless transmission line model of the first matching layer based on the Leach equivalent circuit model of the piezoelectric composite material, forming a second equivalent circuit model, such as Figure 3 As shown;

[0030] 3) Establishing a lossless transmission line model of the second matching layer based on the Leach equivalent circuit model of the piezoelectric composite material and the lossless transmission line model of the first matching layer: a. Obtaining the parameters used to establish the lossless transmission line model based on the selected optimal second matching layer with a foaming ratio of 10 times, namely, the second lossless transmission line signal frequency f2 = 396 kHz, the second normalized length Nl2 = 0.5, and the second impedance Z2 = 13 Ω; b. Establishing a lossless transmission line model of the second matching layer based on the Leach equivalent circuit model of the piezoelectric composite material and the lossless transmission line model of the first matching layer according to the above parameters, thereby forming a third equivalent circuit model, such as Figure 4 As shown;

[0031] 4) Simulation analysis: The third equivalent circuit model is simulated. The signal amplitude of the waveform during simulation is 1165mV. Figure 5 As shown;

[0032] 5) The optimal 1-3 type piezoelectric composite material, the optimal first matching layer with the glass microbead model, microbead weight ratio and diluent ratio of BR20-20-15, and the optimal second matching layer composed of a foam material with a foaming ratio of 10 times were physically combined to prepare an air-coupled ultrasonic sensor and the signal amplitude was tested. The test signal amplitude was 1187mV, as shown in FIG. Figure 6 shown.

[0033] From the above verification, it can be seen that the error between the signal amplitude of the simulation test and the signal amplitude of the test after the physical combination preparation is 1.85%, and the test structures of the two are well consistent, which verifies the effectiveness of the design method of the present invention.

[0034] In order to fully demonstrate the effectiveness of the air-coupled ultrasonic sensor designed by the simulation design method of the present invention, the air-coupled ultrasonic sensor designed by the simulation design method of the present invention is used to detect defects in composite materials. The signal amplitude after detection is as follows: Figure 7 As shown, the detection signal amplitude at penetration position 1 is 261mV, and the detection signal amplitude at penetration position 2 is 52mV. However, it is well known to those skilled in the art that when a signal passes through a defect, energy is reflected and transmitted, and the signal amplitude decreases. Therefore, by comparing the signal amplitudes, it can be determined that the composite material has a defect at position 2. If the performance of the designed air-coupled ultrasonic sensor itself is poor, the detection signal amplitude at the penetration defect position will be very weak or even undetectable. Therefore, it can be seen that the air-coupled ultrasonic sensor designed by the simulation design method of the present invention can be used for defect detection.

[0035] The above description is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions have been made with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents; and such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments, and they should all be included in the scope of protection of the claims.

Claims

1. A simulation design method for optimizing an air-coupled ultrasonic sensor, characterized in that: The steps include: 1) Optimization of piezoelectric composite materials: a. According to the different piezoelectric composite materials used, the parameters used in establishing the corresponding Leach equivalent circuit model are obtained, namely the center frequency f of the air-coupled sensor, static capacitance C0, piezoelectric constant h, transmission line inductance L, transmission line capacitance C, transmission line resistance R, the center frequency of the air-coupled sensor Static capacitance Piezoelectric constant Transmission line inductance L = Aρ, transmission line capacitance Transmission line resistance R = Lwtanδ m , where d is the known thickness of the piezoelectric composite material, c is the known acoustic velocity of the piezoelectric composite material, and ε S is the known relative clamped dielectric constant, A is the known cross-sectional area of ​​the piezoelectric composite material perpendicular to the direction of acoustic wave propagation, h is the known piezoelectric constant, and e is the known 33 is the known short-circuit elastic constant, ρ is the known density of the piezoelectric composite material, w is the known angular frequency of the piezoelectric composite material, and tanδ m =1 / Qe and is called the dielectric loss factor, where Qe is the known electrical quality factor; b. establishing Leach equivalent circuit models of different piezoelectric composite materials based on the above parameters, thereby forming different first equivalent circuit models; c. performing simulation analysis on the different established first equivalent circuit models, and the piezoelectric composite material corresponding to the first equivalent circuit model with the largest signal amplitude is the optimal piezoelectric composite material; 2) Optimization of the first matching layer: a. Based on the different first matching layers used, the parameters used to establish the corresponding lossless transmission line model are obtained, namely, the first lossless transmission line signal frequency f1, the first normalized length Nl1, and the first impedance Z1. The first lossless transmission line signal frequency is determined according to the lossless transmission line theory. First normalized length a) establishing a lossless transmission line model of the first matching layer based on the first equivalent circuit model corresponding to the optimal piezoelectric composite material according to the above parameters, thereby forming a second equivalent circuit model; c) performing simulation analysis on the established second equivalent circuit model; the first matching layer corresponding to the second equivalent circuit model with the largest signal amplitude is the optimal first matching layer; 3) Optimization of the second matching layer: a. Based on the different second matching layers used, the parameters used to establish the corresponding lossless transmission line model are obtained, namely, the second lossless transmission line signal frequency f2, the second normalized length Nl2, and the second impedance Z2. The second lossless transmission line signal frequency is determined based on the lossless transmission line theory. Second normalized length a. The second impedance Z2=ρ2c2s2, where c2 is the acoustic velocity of the second matching layer, l2 is the thickness of the second matching layer, LEN2 is the length of the transmission line of the second matching layer, ρ2 is the density of the second matching layer material, and s2 is the cross-sectional area of ​​the second matching layer perpendicular to the direction of sound wave propagation. b. Based on the above parameters, a lossless transmission line model of the second matching layer is established on the basis of the second equivalent circuit model corresponding to the optimal first matching layer, thereby forming a third equivalent circuit model. c. The established third equivalent circuit model is simulated and analyzed. The second matching layer corresponding to the third equivalent circuit model with the largest signal amplitude is the optimal second matching layer, thereby completing the simulation design of the optimized air-coupled ultrasonic sensor.

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