Wireless passive piezoelectric ultrasonic thickness measurement method and ultrasonic thickness measurement system thereof

Abstract

This invention belongs to the field of oil and gas pipeline inspection technology, and particularly relates to a wireless passive piezoelectric ultrasonic thickness measurement method and its ultrasonic thickness measurement system. This thickness measurement method, while ensuring relay coupling efficiency, cancels signal crosstalk caused by direct coupling between the excitation coil and the receiving coil through reverse-phase winding of the sub-coil, effectively improving the detection accuracy and result stability of oil and gas pipeline wall thickness. The thickness measurement method includes: determining the structural configuration of the wireless passive piezoelectric ultrasonic thickness measurement system; performing decoupling operations on the excitation coil and the receiving coil; determining the spatial arrangement and magnetic field distribution characteristics of the excitation coil and the receiving coil, and calculating the relay coupling region and structural parameters of the detection coil; determining the coupling parameters of the linear frequency modulated chirp signal used in the excitation process of the excitation coil, and generating the linear frequency modulated chirp signal; receiving the ultrasonic echo signal transmitted back by the detection coil, and performing pulse compression processing on the ultrasonic echo signal.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas pipeline inspection technology, and particularly relates to a wireless passive piezoelectric ultrasonic thickness measurement method and its ultrasonic thickness measurement system. Background Technology

[0002] As crucial infrastructure in the oil and gas energy sector, the structural integrity of oil and gas pipelines directly impacts the stable operation of oil and gas transportation. However, oil and gas pipelines operate under harsh conditions of high temperature, high pressure, and highly corrosive media, making them highly susceptible to localized corrosion. This corrosion can lead to thinning of the cladding or base layer, potentially causing leaks, pipe bursts, and other major safety accidents. Therefore, high-precision and highly reliable non-destructive wall thickness testing of oil and gas pipelines has become a core requirement for ensuring their safety.

[0003] Among existing ultrasonic non-destructive thickness measurement technologies, piezoelectric ultrasonic thickness measurement technology has been widely used due to its advantages of high transduction efficiency, small probe size, and simple and stable ultrasonic excitation. For example, the patent document titled "A Wireless Ultrasonic Measurement System and its Construction Method," application number CN202411805260.6, describes the following technical solution: A wireless ultrasonic measurement system and its construction method, wherein the measurement system includes a sensing module and a detection module; the sensing module includes a piezoelectric layer on the surface of the object to be detected, a first lead-out electrode structure, a first ground electrode structure, a first insulating plate, and a sensing coil; the first insulating plate has a first opening; the first lead-out electrode structure includes a first lead-out electrode at the top of the piezoelectric layer and a second lead-out electrode in the first opening; the first ground electrode structure includes a first ground electrode and a second ground electrode; the second lead-out electrode and the second ground electrode are respectively connected to the first lead-out electrode and the first ground electrode; the sensing coil is disposed at the top of the first insulating plate. The detection system of this technical solution uses an insulating plate to isolate the sensing coil away from the surface of the object being detected. This facilitates the generation of a non-zero induced voltage Uind by the sensing coil, thereby enhancing the signal of the receiving coil and enabling non-contact ultrasonic signal reception at a distance of up to 20mm.

[0004] However, further research revealed that existing technologies, including the aforementioned solutions, generally employ a design where the excitation coil and receiving coil are directly coupled. This results in severe cross-coupling issues in the three-coil system of wireless ultrasonic thickness measurement, leading to significant crosstalk between signals. Directly adding a shielding layer to suppress crosstalk inevitably attenuates the relay magnetic field in the detection coil, causing insufficient ultrasonic excitation power and consequently reducing thickness measurement accuracy. Therefore, it is imperative for those skilled in the art to further optimize existing wireless piezoelectric ultrasonic thickness measurement technology to fundamentally resolve the contradiction between signal crosstalk and energy transmission efficiency. Summary of the Invention

[0005] This invention provides a wireless passive piezoelectric ultrasonic thickness measurement method and system. The method, while ensuring relay coupling efficiency, uses reverse-phase winding of the sub-coil to counteract signal crosstalk caused by direct coupling of the magnetic fields between the excitation and receiving coils, effectively improving the accuracy and stability of oil and gas pipeline wall thickness detection.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: This invention provides a wireless passive piezoelectric ultrasonic thickness measurement method, comprising the following steps: Step S1: Based on the thickness measurement requirements, determine the structural configuration of the wireless passive piezoelectric ultrasonic thickness measurement system required for the wireless passive piezoelectric ultrasonic thickness measurement method; Step S2: To reduce the direct coupling of the excitation signal to the receiving coil, a decoupling operation is performed on the excitation coil and the receiving coil; Step S3: To ensure effective coupling between the detection coil, excitation coil, and receiving coil, determine the spatial arrangement and magnetic field distribution characteristics of the excitation coil and receiving coil, and calculate the relay coupling region and structural parameters of the detection coil. Step S4: Determine the coupling parameters of the linear frequency modulated chirp signal used in the excitation process of the excitation coil, and generate the linear frequency modulated chirp signal; Step S5: Receive the ultrasonic echo signal transmitted back by the detection coil and perform pulse compression processing on the ultrasonic echo signal; The ultrasonic echo signal after pulse compression can be used for wireless passive piezoelectric ultrasonic thickness measurement.

[0007] Preferably, step S2 specifically includes: Assume the excitation coil consists of i anti-phase excitation sub-coils connected in series. The receiving coil is composed of j anti-phase sub-coils connected in series. If the configuration is such that the excitation coil and the receiving coil obtained from the decoupling operation satisfy the following conditions: ; in, To the maximum decoupling error, The residual error between the normalized total mutual inductance of the excitation coil and the receiving coil must satisfy: ; The equivalent total mutual inductance between the excitation coil and the receiving coil is determined by any excitation sub-coil in the excitation coil. and any receiving sub-coil in the receiving coil It is obtained by superimposing the inductance of each pair of elements; ,satisfy: ; In the formula, The mutual inductance between the i-th excitation sub-coil in the excitation coil and the j-th receiving sub-coil in the receiving coil satisfies: ; in, For exciter coil Number of turns, For receiving sub-coil Number of turns; For exciter coil The effective area, For receiving sub-coil The effective area; For exciter coil With receiver sub-coil The center distance between them; For exciter coil With receiver sub-coil Orientation correction factor between them.

[0008] Preferably, step S3 specifically includes: Assume the detection coil consists of a detection sub-coil With detection sub-coil The configuration involves the mutual inductance between the detection coil and the excitation coil. ,satisfy: Mutual inductance between the detection coil and the receiving coil ,satisfy: ; Mutual inductance between the detection coil and the excitation coil Mutual inductance between the detection coil and the receiving coil By deriving the equivalent mutual inductance, we obtain the following: , ; Define the relay coupling capability of the detection coil as: ;in, satisfy: ; The mutual inductance between the detection coil and the excitation coil derived by substituting into the equivalent mutual inductance Mutual inductance between the detection coil and the receiving coil ,get: ; When the parameters of the detection coil, excitation coil, and receiving coil are fixed, the above formula can be transformed into: ; Further analysis of the size variation of the detection coil: when the size of the detection coil is too small, Get smaller , Get smaller Less than When the detection coil size is too large, Increased, but center distance Get bigger , Get smaller Less than ; Therefore, it is calculated that the relay coupling capability is optimal when the outer contour dimensions of the detection coil are the same as those of the receiving coil and the excitation coil, the number of turns of the detection coil is equal to the number of turns of the receiving coil and the excitation coil, and the detection coil is wound in reverse phase.

[0009] Preferably, step S4 specifically includes the following steps: Step S41: Based on the relay coupling capability of the detection coil and the equivalent total mutual inductance between the excitation coil and the receiving coil The excitation amplitude adjustment coefficient is calculated. ,satisfy: ; Where λ is the excitation end adjustment coefficient; Step S42: Calculate the excitation center frequency of the linear frequency modulated chirp signal. ,satisfy: ; in, The equivalent inductance formed by the coupling of the excitation coil, receiving coil, and detection coil, The equivalent capacitance formed by the coupling of the excitation coil, the receiving coil, and the detection coil; Step S43: Determine the excitation bandwidth of the linear frequency modulated chirp signal. ,satisfy: ; Where μ is the proportionality coefficient; Q is the combined quality factor of the excitation coil, receiving coil, and detection coil. Step S44: Adjust the excitation amplitude according to the calculated value. The excitation center frequency of the linear frequency modulated chirp signal and the excitation bandwidth of the linear frequency modulated chirp signal A linear frequency modulated chirp signal is generated. ; in, satisfy: ; In the formula, For linear frequency modulated chirp signals The starting frequency satisfies: ; For linear frequency modulated chirp signals The termination frequency satisfies: .

[0010] Preferably, step S5 specifically includes the following steps: Step S51: Based on the relay coupling capability of the detection coil and the equivalent total mutual inductance between the excitation coil and the receiving coil Determine the compression gain coefficient ,satisfy: ; in, This is the adjustment coefficient; Step S52: Determine the matched filter time width ,satisfy: ; in, is the proportionality coefficient; Q is the combined quality factor of the excitation coil, receiving coil, and detection coil. The excitation center frequency of the linearly frequency-modulated chirp signal; Step S53: Based on linear frequency modulated chirp signal The matched filter transfer function is constructed. ;in, satisfy: ; Step S54: Calculate the ultrasonic echo signal after pulse compression processing, satisfying: ; in, To receive the ultrasonic echo signal transmitted back by the detection coil.

[0011] On the other hand, the present invention also provides a wireless passive piezoelectric ultrasonic thickness measurement system, which is designed by the aforementioned wireless passive piezoelectric ultrasonic thickness measurement method.

[0012] This invention provides a wireless passive piezoelectric ultrasonic thickness measurement method and system. The wireless passive piezoelectric ultrasonic thickness measurement method includes the following steps: Step S1: Determine the structural configuration of the wireless passive piezoelectric ultrasonic thickness measurement system required for the thickness measurement based on the thickness measurement requirements; Step S2: Perform decoupling operations on the excitation coil and the receiving coil to reduce direct coupling of the excitation signal to the receiving coil; Step S3: Determine the spatial arrangement and magnetic field distribution characteristics of the excitation coil and the receiving coil to ensure effective coupling between the detection coil, excitation coil, and receiving coil, and calculate the relay coupling region and structural parameters of the detection coil; Step S4: Determine the coupling parameters of the linear frequency modulated chirp signal used in the excitation process of the excitation coil, and generate the linear frequency modulated chirp signal; Step S5: Receive the ultrasonic echo signal transmitted back by the detection coil, and perform pulse compression processing on the ultrasonic echo signal; the ultrasonic echo signal after pulse compression processing can then be used for wireless passive piezoelectric ultrasonic thickness measurement.

[0013] The wireless passive piezoelectric ultrasonic thickness measurement method and its ultrasonic thickness measurement system, possessing the above-mentioned characteristics, have at least the following technical advantages compared to existing technologies: 1. The wireless passive piezoelectric ultrasonic thickness measurement method provided by the present invention effectively reduces the signal crosstalk problem caused by the direct coupling of the excitation coil and the receiving coil through the decoupling design of the excitation coil and the receiving coil; and effectively suppresses the deformation of the excitation signal during the thickness measurement process, enhances the distinguishability of the echo signal of the oil and gas pipeline wall thickness, and improves the detection accuracy and stability of the oil and gas pipeline wall thickness.

[0014] 2. The wireless passive piezoelectric ultrasonic thickness measurement system provided by the present invention can be used for long-term fixed-point thickness measurement after the design of each structural unit of the thickness measurement system (including excitation coil, detection coil, receiving coil, signal generator, signal receiver, and piezoelectric ultrasonic transducer) is completed, without the need for preparatory work such as removing the cladding layer, which significantly improves the applicability and work efficiency of oil and gas pipeline wall thickness detection.

[0015] 3. The wireless passive piezoelectric ultrasonic thickness measurement method provided by this invention, compared with the existing wired piezoelectric ultrasonic thickness measurement technology, solves the adverse effects of complex construction environments such as high altitude, narrow space and high temperature on the reliability of thickness measurement results; it only requires the cooperation of excitation coil and detection coil to realize inductively coupled wireless signal transmission, ensuring the safety and reliability of the oil and gas pipeline wall thickness detection process. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the following drawings: Figure 1 This is a schematic diagram of the structure of the excitation coil and the receiving coil cooperating with each other in a wireless passive piezoelectric ultrasonic thickness measurement system based on the wireless passive piezoelectric ultrasonic thickness measurement method provided by the present invention. Figure 2 for Figure 1 The diagram shows the structure of the excitation coil in the wireless passive piezoelectric ultrasonic thickness measurement system. Figure 3 for Figure 1 The diagram shows the structure of the receiving coil in the wireless passive piezoelectric ultrasonic thickness measurement system. Figure 4 A schematic diagram of the reverse winding of the excitation coil; Figure 5 This is a schematic diagram of the reverse winding of the receiving coil; Figure 6 This is a schematic diagram of the detection coil in a wireless passive piezoelectric ultrasonic thickness measurement system based on the wireless passive piezoelectric ultrasonic thickness measurement method provided by this invention. Figure 7(a) is a schematic diagram of the reverse winding of the detection coil; Figure 7(b) is a schematic diagram of the current flow of the detection coil shown in Figure 7(a); Figure 8(a) shows the magnetic field distribution generated by the first excitation sub-coil on the effective area of ​​the first receiving sub-coil and the second receiving sub-coil of the receiving coil after the excitation coil is energized; Figure 8(b) shows the magnetic field distribution generated by the second excitation sub-coil on the effective area of ​​the first and second receiving sub-coils of the receiving coil after the excitation coil is energized; Figure 9 A schematic diagram showing the induced current generated by the magnetic field of the excitation coil in the detection coil; Figure 10 A schematic diagram showing the induced current generated in the receiving coil by the magnetic field of the detection coil; Figure 11 This is a schematic diagram of the simulation of the three-coil structure of a wireless passive piezoelectric ultrasonic thickness measurement system using ANSYS Maxwell electromagnetic simulation software. Figure 12 This is a schematic diagram of a traditional three-coil power transmission structure. Figure 13(a) is a schematic diagram of the time-domain waveform of the excitation signal used in the first simulation experiment; Figure 13(b) is a schematic diagram of the original output signal of piezoelectric ultrasonic thickness measurement based on the first simulation experiment using a traditional three-coil power transmission structure. Figure 13(c) is a schematic diagram of the amplified echo signal from Figure 13(b); Figure 13(d) is a schematic diagram of the original output signal of the wireless passive piezoelectric ultrasonic thickness measurement system obtained by using the wireless passive piezoelectric ultrasonic thickness measurement method provided by the present invention based on the first simulation experiment. Figure 13(e) is a schematic diagram of the amplified echo signal from Figure 13(d); Figure 13(f) is a schematic diagram of the time-domain waveform of the excitation signal used in the second simulation experiment; Figure 13(g) is a schematic diagram of the original output signal of piezoelectric ultrasonic thickness measurement based on the second simulation experiment using a traditional three-coil power transmission structure; Figure 13(h) is a schematic diagram of the amplified echo signal from Figure 13(g); Figure 13(i) is a schematic diagram of the original output signal of the wireless passive piezoelectric ultrasonic thickness measurement system obtained by using the wireless passive piezoelectric ultrasonic thickness measurement method provided by the present invention based on the second simulation experiment. Figure 13(j) is a schematic diagram of the amplified echo signal from Figure 13(i); Figure 14 This is a flowchart illustrating the wireless passive piezoelectric ultrasonic thickness measurement method provided by the present invention.

[0017] Figure label: 1. Excitation coil; 101. First excitation sub-coil; 102. Second excitation sub-coil; 2. Receiving coil; 201. First receiving sub-coil; 202. Second receiving sub-coil; 3. Detection coil; 301. First detection sub-coil; 302. Second detection sub-coil; 4. Simulation modeling of the excitation coil; 401. Simulation modeling of the first excitation sub-coil; 402. Simulation modeling of the second excitation sub-coil; 5. Simulation modeling of the receiving coil; 501. Simulation modeling of the first receiving sub-coil; 502. Simulation modeling of the second receiving sub-coil; 6. Simulation modeling of the detection coil; 601. Simulation modeling of the first detection sub-coil; 602. Simulation modeling of the second detection sub-coil; 7. Excitation coil in a traditional three-coil power transmission structure; 8. Receiving coil in a traditional three-coil power transmission structure; 9. Detection coil in a traditional three-coil power transmission structure. Detailed Implementation

[0018] This invention provides a wireless passive piezoelectric ultrasonic thickness measurement method and system. The method, while ensuring relay coupling efficiency, uses reverse-phase winding of the sub-coil to counteract signal crosstalk caused by direct coupling of the magnetic fields between the excitation and receiving coils, effectively improving the accuracy and stability of oil and gas pipeline wall thickness detection.

[0019] like Figure 14As shown, the present invention provides a wireless passive piezoelectric ultrasonic thickness measurement method, comprising the following steps: Step S1: Based on the thickness measurement requirements, determine the structural composition of the wireless passive piezoelectric ultrasonic thickness measurement system required for the wireless passive piezoelectric ultrasonic thickness measurement method. The wireless passive piezoelectric ultrasonic thickness measurement system includes an excitation coil, a detection coil, a receiving coil, a signal generator, a signal receiver, and a piezoelectric ultrasonic transducer.

[0020] In implementing the wireless passive piezoelectric ultrasonic thickness measurement method provided by this invention, the structural configuration of the wireless passive piezoelectric ultrasonic thickness measurement system needs to be determined first according to the thickness measurement requirements. Specifically, the wireless passive piezoelectric ultrasonic thickness measurement system includes at least an excitation coil, a detection coil, a receiving coil, a signal generator, a signal receiver, and a piezoelectric ultrasonic transducer.

[0021] Step S2: To reduce the direct coupling of the excitation signal to the receiving coil, a decoupling operation is performed on the excitation coil and the receiving coil.

[0022] Based on step S1, further implement step S2. It is worth noting that, in order to reduce the direct coupling of the excitation signal to the receiving coil, the coupling magnetic fields between the excitation coil and the receiving coil need to be as symmetrical and destructive as possible. Preferably, this can be achieved by using at least one of the following design methods: spatially orthogonal arrangement, anti-phase winding, or differential structure.

[0023] In a preferred embodiment of the present invention, step S2 specifically includes: Assume the excitation coil consists of i anti-phase excitation sub-coils connected in series. The receiving coil is composed of j anti-phase sub-coils connected in series. If the configuration is such that the excitation coil and the receiving coil obtained from the decoupling operation satisfy the following conditions: ; in, To the maximum decoupling error, The residual error between the normalized total mutual inductance of the excitation coil and the receiving coil must satisfy: .

[0024] The equivalent total mutual inductance between the excitation coil and the receiving coil is determined by any excitation sub-coil in the excitation coil. and any receiving sub-coil in the receiving coil It is obtained by superimposing the two pairs of inductances.

[0025] ,satisfy: ; In the formula, The mutual inductance between the i-th excitation sub-coil in the excitation coil and the j-th receiving sub-coil in the receiving coil satisfies: .

[0026] in, For exciter coil Number of turns, For receiving sub-coil Number of turns; For exciter coil The effective area, For receiving sub-coil The effective area; For exciter coil With receiver sub-coil The center distance between them; For exciter coil With receiver sub-coil Orientation correction factor between them.

[0027] It should be noted that, as shown in the aforementioned formula, the mutual inductance between the i-th excitation sub-coil in the excitation coil and the j-th receiving sub-coil in the receiving coil is determined by the number of turns, area, distance, and relative direction of the excitation and receiving sub-coils. The total mutual inductance between the excitation and receiving coils is further obtained by superimposing multiple sub-mutual inductances. Therefore, step S2, by quantifying the decoupling effect between the excitation channel of the excitation coil and the receiving channel of the receiving coil, can ultimately obtain the decoupling design requirements that need to be achieved between the excitation and receiving coils.

[0028] Step S3: To ensure effective coupling between the detection coil, excitation coil, and receiving coil, determine the spatial arrangement and magnetic field distribution characteristics of the excitation coil and receiving coil, and calculate the relay coupling region and structural parameters of the detection coil.

[0029] Based on completing step S2, further implement step S3. It should be noted that, in order to realize the detection coil as a relay coupling structure and ensure effective coupling between it and the excitation and receiving coils, the relay coupling region and structural parameters of the detection coil need to be further designed as follows.

[0030] In a preferred embodiment of the present invention, step S3 specifically includes: Assume the detection coil consists of a detection sub-coil With detection sub-coil The configuration involves the mutual inductance between the detection coil and the excitation coil. ,satisfy: Mutual inductance between the detection coil and the receiving coil ,satisfy: ; Mutual inductance between the detection coil and the excitation coil Mutual inductance between the detection coil and the receiving coil By deriving the equivalent mutual inductance, we obtain the following: , ; Define the relay coupling capability of the detection coil as: ;in, satisfy: ; The mutual inductance between the detection coil and the excitation coil derived by substituting into the equivalent mutual inductance Mutual inductance between the detection coil and the receiving coil ,get: .

[0031] When the parameters of the detection coil, excitation coil, and receiving coil are fixed, the above formula can be transformed into: .

[0032] Further analysis of the size variation of the detection coil: when the size of the detection coil is too small, Get smaller , Get smaller Less than When the detection coil size is too large, Increased, but center distance Get bigger , Get smaller Less than .

[0033] Therefore, it is calculated that the relay coupling capability is optimal when the outer contour dimensions of the detection coil are the same as those of the receiving coil and the excitation coil, the number of turns of the detection coil is equal to the number of turns of the receiving coil and the excitation coil, and the detection coil is wound in reverse phase.

[0034] The above calculations show that the relay coupling capability of the detection coil... The number of turns, area, and relative position of the detection coil to the excitation / receiving sub-coil are all determined by the detection coil itself. It's important to note that when the detection coil is too small, the insufficient effective coupling area reduces its relay coupling capability; conversely, when the detection coil is too large, the increased center-to-center distance between the detection sub-coils weakens the cross-coupling and main coupling terms, ultimately leading to a decrease in the detection coil's relay coupling capability.

[0035] Step S4: Determine the coupling parameters of the linear frequency modulated chirp signal used in the excitation process of the excitation coil, and generate the linear frequency modulated chirp signal.

[0036] Based on step S3, step S4 is further implemented. It is worth noting that since there are at least three coil link structures between the piezoelectric transducer and the signal generator, the presence of these coil link structures will distort the obtained excitation signal, thus adversely affecting the piezoelectric ultrasonic thickness measurement results. Therefore, during the excitation of the excitation coil, it is necessary to anticipate the aforementioned coil link structure and correct the transmitted signal in reverse to obtain a more ideal excitation waveform at the transducer end.

[0037] In a preferred embodiment of the present invention, step S4 specifically includes the following steps: Step S41: Based on the relay coupling capability of the detection coil and the equivalent total mutual inductance between the excitation coil and the receiving coil The excitation amplitude adjustment coefficient is calculated. ,satisfy: .

[0038] Where λ is the excitation end adjustment coefficient.

[0039] One point that needs further explanation is that the excitation amplitude adjustment coefficient is first adaptively adjusted. This can achieve the following effects: when the relay coupling capability η of the detection coil increases, the excitation energy is improved; when the equivalent total mutual inductance between the excitation coil and the receiving coil increases, the excitation energy is increased. When the absolute value of increases, it suppresses direct crosstalk caused by excessive excitation.

[0040] Step S42: Calculate the excitation center frequency of the linear frequency modulated chirp signal. ,satisfy: .

[0041] in, The equivalent inductance formed by the coupling of the excitation coil, receiving coil, and detection coil, This is the equivalent capacitance formed by the coupling of the excitation coil, the receiving coil, and the detection coil.

[0042] Based on completing step S41, step S42 is further implemented. Specifically, this involves adjusting the excitation center frequency of the linearly frequency-modulated chirp signal. Calculations are performed to achieve adaptive adjustment of the excitation center frequency of the chirp signal; the purpose of this is to ensure consistent transmission frequency bands and improve the transmission efficiency of wireless energy. Step S43: Determine the excitation bandwidth of the linear frequency modulated chirp signal. ,satisfy: .

[0043] Where μ is the proportionality coefficient; Q is the combined quality factor of the excitation coil, receiving coil, and detection coil.

[0044] Based on completing step S42, step S43 is further implemented. Specifically, this involves adjusting the excitation bandwidth of the linear frequency modulated chirp signal. Calculations are performed to achieve adaptive adjustment of the excitation bandwidth. Specifically, when the system bandwidth is narrow (i.e., higher than the combined quality factor of the excitation coil, receiving coil, and detection coil), the frequency sweep range of the chirp signal is reduced; conversely, when the system bandwidth is wide (i.e., lower than the combined quality factor of the excitation coil, receiving coil, and detection coil), the frequency sweep range of the chirp signal is increased.

[0045] Step S44: Adjust the excitation amplitude according to the calculated value. The excitation center frequency of the linear frequency modulated chirp signal and the excitation bandwidth of the linear frequency modulated chirp signal A linear frequency modulated chirp signal is generated. .

[0046] in, satisfy: .

[0047] In the formula, For linear frequency modulated chirp signals The starting frequency satisfies: ; For linear frequency modulated chirp signals The termination frequency satisfies: .

[0048] Based on step S43, step S44 is further implemented. It should be noted that the linear frequency modulated chirp signal generated in this step is not a fixed-output chirp signal. This linear frequency modulated chirp signal must possess at least the following characteristics: (1) Adaptively adjust the excitation amplitude using the coil mutual inductance parameters MTD, MDR, and MTR; (2) The excitation center frequency is determined by using the equivalent inductance and equivalent capacitance of the three coils together; (3) The bandwidth of the chirp signal is adaptively determined using the quality factor Q.

[0049] Step S5: Receive the ultrasonic echo signal transmitted back by the detection coil and perform pulse compression processing on the ultrasonic echo signal; the ultrasonic echo signal after pulse compression processing can be used for wireless passive piezoelectric ultrasonic thickness measurement.

[0050] Based on completing step S4, step S5 is further implemented. It is worth noting that although the aforementioned steps can ensure direct coupling between the excitation coil and the detection coil, further research revealed that the excitation coil and the detection coil cannot achieve a completely decoupled state (i.e., mutual inductance is 0). At this point, a small amount of residual crosstalk will still appear, which needs to be further suppressed, i.e., residual crosstalk adaptive cancellation.

[0051] In a preferred embodiment of the present invention, step S5 specifically includes the following steps: Step S51: Based on the relay coupling capability of the detection coil and the equivalent total mutual inductance between the excitation coil and the receiving coil Determine the compression gain coefficient ,satisfy: .

[0052] in, This is the adjustment coefficient.

[0053] First, by calculating the compression gain coefficient This allows for adaptive adjustment of the compression gain. The purpose of this is to improve the effective echo compression output when the relay capability is strong, while suppressing the synchronous enhancement of crosstalk peaks when crosstalk is high.

[0054] Step S52: Determine the matched filter time width ,satisfy: .

[0055] Where ρ is the proportionality coefficient; Q is the combined quality factor of the excitation coil, receiving coil, and detection coil. The excitation center frequency of the linear frequency modulated chirp signal is denoted as .

[0056] Based on completing step S51, further implement step S52. Specifically, calculate the matched filter time width. This enables adaptive adjustment of the matched filter's bandwidth. The aim is to increase the bandwidth for high-Q systems, which have longer ringing times, while decreasing it for low-Q systems, which have faster responses.

[0057] Step S53: Based on linear frequency modulated chirp signal The matched filter transfer function is constructed. ;in, satisfy: .

[0058] Step S54: Calculate the ultrasonic echo signal after pulse compression processing, satisfying: .

[0059] in, To receive the detected ultrasonic echo signal transmitted back by the detection coil.

[0060] On the basis of completing step S52, steps S53 and S54 are further implemented. It should be noted that the matched filter transfer function constructed through this step S53 can ultimately calculate the pulse compression output (i.e., the ultrasonic echo signal output after pulse compression processing). Through the above pulse compression processing, the detection signal-to-noise ratio and time-domain resolution of the weak interface echo signal of the oil and gas pipeline are further improved.

[0061] Finally, to facilitate the understanding of the present invention by those skilled in the art, a set of three-coil structures of the wireless passive piezoelectric ultrasonic thickness measurement system calculated based on the foregoing steps is further provided herein, and an explanation is made based on this. Among them, as shown in Figure 1 shown, the designed excitation coil, receiving coil and detection coil preferably adopt a planar coil structure, and the excitation coil and the receiving coil are directly decoupled. The detection coil serves as part of the relay coupling coil structure and is coupled to the excitation coil and the receiving coil respectively.

[0062] Furthermore, the excitation coil is made up of two square excitation sub-coils with the same structure connected in series diagonally. The current between the first excitation sub-coil and the second excitation sub-coil is continuous and the directions are opposite. Specifically, refer to Figure 2 shown. The receiving coil is selected to be composed of two square receiving sub-coils with the same structure connected in series diagonally. The current between the first receiving sub-coil and the second receiving sub-coil is continuous and the directions are opposite. Preferably, the excitation coil and the receiving coil are set with the same structure and arranged in a plane orthogonal manner, and the two together form a "field" character structure. Specifically, it can be referred to Figure 3 shown.

[0063] Furthermore, refer to Figure 4 shown, the winding starting point of the excitation coil is set at the innermost end of the first excitation sub-coil. The wire starts to wind from this position from the inside to the outside and forms a multi-turn continuous coil structure in a counterclockwise direction along the square direction. When the wire reaches the outermost side of the first excitation sub-coil, it starts to enter the outermost side of the second excitation sub-coil and winds from the outside to the inside, forming a multi-turn continuous coil structure in a clockwise direction along the square direction until it reaches the innermost end point of the second excitation sub-coil, thus forming an excitation coil structure composed of two square excitation sub-coils with the same structure connected in series diagonally.

[0064] Similarly, refer to Figure 5As shown, the winding starting point of the receiving coil is selected and set at the innermost end of the first receiving sub-coil. The wire starts to wind from this position from the inside to the outside, and successively forms a multi-turn continuous coil structure in a clockwise direction along the square direction. When the wire reaches the outermost side of the first receiving sub-coil, it starts to enter the outermost side of the second receiving sub-coil and winds from the outside to the inside, successively forming a multi-turn continuous coil structure in a counterclockwise direction along the square direction until reaching the end point at the innermost end of the second receiving sub-coil, thereby forming a receiving coil structure composed of two square receiving sub-coils with the same structure connected in series diagonally.

[0065] And, referring to as Figure 6 shown, the detection coil is selected to be composed of two rectangular detection sub-coils with the same structure connected in series symmetrically. Among them, the first detection sub-coil and the second detection sub-coil are adjacent and symmetrically arranged, and the current between the sub-coils is continuous and in opposite directions. Among them, as shown in Fig. 7(a), the winding starting point of the detection coil is located at the innermost end of the first detection sub-coil. The wire starts to wind from this position from the inside to the outside, and successively forms a multi-turn continuous coil structure in a counterclockwise direction along the rectangular direction. When the wire reaches the outermost side of the first detection sub-coil, it starts to enter the outermost side of the second detection sub-coil and winds from the outside to the inside, successively forming a multi-turn continuous coil structure in a clockwise direction along the rectangular direction until reaching the end point at the innermost end of the second detection sub-coil, thereby forming a detection coil structure composed of two rectangular detection sub-coils with the same structure connected in series. Further referring to Fig. 7(b), the current flows counterclockwise in the first detection sub-coil, and the current flows clockwise in the second detection sub-coil.

[0066] Based on the above settings, the preferred embodiments of the number of turns, inner diameter and turn pitch of the first detection sub-coil and the second detection sub-coil are obtained, that is, their structural parameters satisfy 15 turns, a turn pitch of 0.2 mm, and a wire width of 0.2 mm. It should be noted that the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed can be specifically divided into an upper and a lower layer structure. Among them, the upper layer structure is the excitation coil and the receiving coil, and the two are arranged in a plane orthogonal manner, jointly forming a "field" - shaped structure; the lower layer structure is the detection coil. The upper layer structure and the lower layer structure are placed parallel to each other and centered. It should be noted that here the outer contour side lengths of the first excitation sub-coil, the second excitation sub-coil, the first receiving sub-coil and the second receiving sub-coil are preferably 20 mm, and the outer contour side length of the "field" - shaped structure is 40 mm; the long sides of the first detection sub-coil and the second detection sub-coil are preferably 40 mm, the short sides are preferably 20 mm, and the square outer contour side length of the detection coil is 40 mm.

[0067] Further analysis is made on the direct decoupling effect of the excitation coil and the receiving coil in the three-coil structure of the above-mentioned wireless passive piezoelectric ultrasonic thickness measurement system, as well as the relay coupling effect between the detection coil and the excitation coil, and between the detection coil and the receiving coil.

[0068] It is worth noting that during the power transmission process of the three-coil structure, when a high-frequency alternating current is applied to the excitation coil, an alternating magnetic field is generated in the space around it. The alternating magnetic field passes through the detection coil and generates a changing magnetic flux, thereby inducing a current in the detection coil. The piezoelectric transducer excites ultrasonic bulk waves to measure thickness through the piezoelectric effect. The receiving coil mainly responds to the effective echo signal generated by the detection coil through the interface and bottom surface of the oil and gas pipeline being measured, rather than the direct crosstalk signal from the excitation coil. This improves the distinguishability of the weak interface echo of the oil and gas pipeline and the reliability of the detection results, thereby improving the accuracy and stability of the oil and gas pipeline wall thickness detection.

[0069] Further referencing Figures 8(a) and 8(b), which show the magnetic field distribution generated over the effective area of ​​the receiving coil after the excitation coil is energized, respectively. and The currents in the first and second excitation coils are shown, respectively. Solid dots and solid crosses describe the directions of the magnetic fields generated by the first and second excitation coils. A dot indicates the magnetic field direction is perpendicular to the paper and outwards, while a cross indicates the magnetic field direction is perpendicular to the paper and inwards. As shown in Figure 8(a), after the excitation coil is energized, the first excitation coil generates a first excitation magnetic field on the effective area of ​​the receiving coil. This includes the excitation magnetic field generated by the first excitation sub-coil over the effective area of ​​the first receiving sub-coil. The excitation magnetic field generated by the first excitation sub-coil on the effective area of ​​the second receiving sub-coil and obtain As shown in Figure 8(b), the second excitation sub-coil generates a second excitation magnetic field on the effective area of ​​the receiving coil. This includes the excitation magnetic field generated by the second excitation sub-coil over the effective area of ​​the first receiving sub-coil. The excitation magnetic field generated by the second excitation sub-coil on the effective area of ​​the second receiving sub-coil and obtain .

[0070] Since the excitation coil and receiving coil in the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system obtained in the aforementioned steps are orthogonally arranged in plane and have the same structural dimensions, the excitation magnetic field is within the effective area of ​​the first receiving sub-coil. and The magnetic field strengths are almost equal and opposite in direction, that is... Within the effective area of ​​the second receiving sub-coil, the excitation magnetic field is... and The magnetic field strengths are almost equal and opposite in direction, that is... ,so ,Right now Therefore, the first excitation magnetic field is obtained. Second excitation magnetic field Regarding the geometric symmetry axis of the first exciter coil and the second exciter coil If they are symmetrical and their magnetic field strengths are almost equal but opposite in direction, then... Therefore, the magnetic field lines generated by the first excitation sub-coil and the second excitation sub-coil on the effective area of ​​the first receiving sub-coil cancel each other out. Simultaneously, the magnetic field lines generated by the first excitation sub-coil and the second excitation sub-coil on the effective area of ​​the second receiving sub-coil also cancel each other out, thus achieving a decoupling effect where the signals from the excitation coil and the receiving coil cancel each other out.

[0071] like Figure 9 As shown, when a high-frequency alternating current is applied to the excitation coil, since the first and second excitation sub-coils are connected diagonally in series with opposite winding directions, the two excitation currents are in opposite directions. Therefore, the induced currents generated by the two excitation sub-coils in the detection coil are respectively... and The directions are also opposite, which matches the structural characteristics of the first and second detection sub-coils being symmetrically connected in series and with opposite winding directions. Therefore, the total induced current of the detection coils satisfies: .

[0072] like Figure 10 As shown, when the ultrasonic signal is reflected from the bottom and interface of the oil and gas pipeline to the piezoelectric transducer, a high-frequency alternating current is applied to the detection coil based on the principle of the inverse piezoelectric effect. At this time, the first and second detection sub-coils are symmetrically connected in series with opposite winding directions, and the two detection currents are in opposite directions. Therefore, the induced currents generated by the two detection sub-coils in the receiving coil are respectively... and The directions are also opposite, which matches the structural characteristics of the first and second receiving sub-coils connected diagonally in series with opposite winding directions. Therefore, the total induced current of the receiving coils satisfies: .

[0073] Based on the above analysis of the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system, it can be found that: the magnetic fields generated by the excitation sub-coil of the excitation coil cancel each other out in the receiving coil area, achieving a decoupling effect; at the same time, the detection coil maximizes the coupling area of ​​magnetic flux, ensuring relay efficiency; therefore, for the above structural design, it can effectively suppress crosstalk signals and improve the amplitude of the echo signal.

[0074] Based on this, the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed above was further simulated using ANSYS Maxwell electromagnetic simulation software, with reference to... Figure 11 As shown. Specifically, the coupling between the detection coil, excitation coil, and receiving coil in the three-dimensional eddy current field is as follows: the mutual inductance between the excitation coil and the receiving coil is... The mutual inductance between the excitation coil and the detection coil is The mutual inductance between the detection coil and the receiving coil is Simulation analysis reveals that the mutual inductance among the three coils satisfies: , , The results show that the mutual inductance between the excitation coil and the receiving coil... The value is much smaller than the specified value, indicating that the decoupling effect between the excitation coil and the receiving coil is excellent. The mutual inductance between the excitation coil and the detection coil... Mutual inductance between the detection coil and the receiving coil All values ​​were higher than the corresponding specified values, indicating that the detection coil played a good relay coupling role.

[0075] Furthermore, the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed above and the traditional three-coil power transmission structure were respectively applied to the piezoelectric ultrasonic nondestructive testing for the detection of oil and gas pipeline wall thickness, and the experimental results were compared as follows.

[0076] In the traditional three-coil power transmission structure, three identical square coils are placed coaxially and parallel, such as... Figure 12 As shown. Specifically, the experiment used two methods for measuring the thickness of oil and gas pipelines: The first method involved exciting a 10-cycle Hanning window weighted sinusoidal pulse signal, without much processing of the output signal, and observing the comparison results between the designed wireless passive piezoelectric ultrasonic thickness measurement system with the traditional three-coil power transmission structure. The second method involved exciting a 25-cycle Hanning window weighted linear frequency modulated pulse signal, and performing pulse compression processing on the output signal, again observing the comparison results between the designed wireless passive piezoelectric ultrasonic thickness measurement system with the traditional three-coil power transmission structure.

[0077] In piezoelectric ultrasonic thickness measurement of oil and gas pipelines, the acoustic impedance difference between some composite materials, such as stainless steel and low-alloy steel, is too small, resulting in high ultrasonic wave transmittance and low reflectance. When ultrasonic waves enter the composite metal, very little is reflected at the interface. In previous thickness measurement experiments using traditional three-coil power transmission structures, the weak interface echo signals were often submerged in noise and difficult to detect. Therefore, further signal processing methods using pulse compression are needed to improve the output signal-to-noise ratio.

[0078] Assume the transfer function of the matched filter is The impulse response is Input signal .in, For a valid signal, Gaussian noise, effective signal The spectrum signal is , Let be the noise power spectral density. , It is the sum of the effective signal and noise at output. Wherein, It is the output signal after the input valid signal has been processed by the pulse compression method. This process can be expressed by the following formula: ; The power spectral density of the output Gaussian white noise is equal to the noise power spectral density in the input signal multiplied by the integral of the square of the modulus of the matched filter transfer function in the frequency domain. The expression for the noise power in the signal is: ; Therefore, in At time , the signal-to-noise ratio of the output signal It can be expressed as follows: ; According to the Cauchy-Schwarz inequality: ; The above inequality applies if and only if The equality holds when k is an arbitrary constant. Since conjugate is indicated, we have: ; Further releases: ; In the above formula, for The energy if and only if The above equation can only be considered equal when the following condition is met, at which point the output signal has the maximum signal-to-noise ratio.

[0079] Right now ; Meanwhile, its transmission characteristics Its impulse response can also be used. To indicate that at this time: ; The output signal after the above processing It can be expressed as follows: ; The above process constitutes the entire numerical calculation process for pulse compression. Through the above calculations, it can be concluded that the most fundamental principle of pulse compression is to cross-correlate the received signal with the excitation signal, then output their matching degree, highlighting weak interface echo signals from the noise wave, thereby improving the signal-to-noise ratio of the output signal.

[0080] In the thickness measurement simulation experiment, standard stainless steel / low-alloy steel composite plates were used as the experimental materials. The base material was Q345R low-alloy steel with a measured thickness of 3.5 mm, and the cladding material was corrosion-resistant S31603 stainless steel with a measured thickness of 15 mm. In the experiment, the square coil size in the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed earlier was kept consistent with the coil size in the traditional three-coil power transmission structure, thus ensuring that the experimental results were not affected by irrelevant variables.

[0081] Based on the first simulation experiment, a 10-cycle Hanning window weighted sinusoidal pulse signal was used as the excitation source, and the output signal was not processed in large quantities. The comparison results between the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed above and the traditional three-coil power transmission structure were observed. Specifically, the time-domain waveform of the excitation signal is shown in Figure 13(a). The original output signal of the piezoelectric ultrasonic thickness measurement using the traditional three-coil power transmission structure is shown in Figure 13(b), and its echo signal is magnified and observed in Figure 13(c). The original output signal of the piezoelectric ultrasonic thickness measurement using the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed in this invention is shown in Figure 13(d), and its echo signal is magnified and observed in Figure 13(e). Comparing Figure 13(b) and Figure 13(d) representing the original output signals, it can be seen that the excitation signal waveform in Figure 13(d) is more ideal, indicating that the decoupling effect between the excitation coil and the receiving coil in the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed in this invention is better, effectively reducing the signal crosstalk caused by the direct coupling of the two coils and significantly suppressing the deformation of the excitation signal. Comparing Figures 13(c) and 13(e), which show magnified observations of the echo signal, it can be seen that there is obvious interface echo information in the time-domain waveform of Figure 13(e), while there is none in Figure 13(c). Furthermore, subsequent calculations show that the error between the calculated thickness and the measured thickness of the oil and gas pipeline is less than the specified error, confirming the existence of the interface echo and verifying that the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed in this invention is more reliable.

[0082] In summary, the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed in this invention allows for the direct observation of effective interface echo information from the original output signal during piezoelectric ultrasonic thickness measurement, enabling further calculation of the thickness of the base layer and cladding of oil and gas pipelines. In contrast, the traditional three-coil power transmission structure cannot directly observe the interface echo from the original output signal. This further proves that the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed in this invention improves the output signal-to-noise ratio and enhances the distinguishability and detection reliability of weak interface echoes from oil and gas pipelines.

[0083] Based on the second simulation experiment, a 25-cycle Hanning window weighted linear frequency modulated pulse signal was used to excite the output signal, and pulse compression processing was performed. The comparison results between the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed in this invention and the traditional three-coil power transmission structure were observed. Specifically, the time-domain waveform of the excitation signal is shown in Figure 13(f), the center frequency of the excitation signal is 5MHz, and the bandwidth is 6MHz. The original output signal of the piezoelectric ultrasonic thickness measurement using the traditional three-coil power transmission structure is shown in Figure 13(g), and its pulse compression processing and magnification are shown in Figure 13(h). The original output signal of the piezoelectric ultrasonic thickness measurement using the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed in this invention is shown in Figure 13(i), and its pulse compression processing and magnification are shown in Figure 13(j). Comparing Figures 13(g) and 13(i), which represent the original output signals, it can be seen that the excitation signal waveform in Figure 13(i) is more ideal, while the excitation signal waveform in Figure 13(g) is severely distorted. This indicates that the excitation coil and receiving coil in the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed in this invention have a better decoupling effect, effectively reducing the signal crosstalk caused by the direct coupling of the two coils and significantly suppressing the degree of distortion of the excitation signal. Subsequent calculations showed that the error between the calculated thickness and the measured thickness of the oil and gas pipeline was less than the specified error, confirming the existence of interface echo and verifying the feasibility of the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed in this invention. Comparing Figures 13(h) and 13(j), which represent pulse compression processing and magnified observation, although effective interface echo signals can be observed in both, the interface echo signal in Figure 13(j) has a larger amplitude and is easier to observe than that in Figure 13(h). Furthermore, the excitation signal in Figure 13(j) before the first interface echo is much less distorted than that in Figure 13(h), where the excitation signal is severely distorted, and part of it has begun to submerge the first interface echo signal. Calculations show that, for interface echo signals, the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed in this invention improves the signal-to-noise ratio by approximately 5.24 dB compared to the traditional three-coil power transmission structure. This further demonstrates that the three-coil structure of the wireless passive piezoelectric ultrasonic thickness measurement system designed in this invention improves the output signal-to-noise ratio, enhances the distinguishability and detection reliability of weak interface echoes from oil and gas pipelines, and improves the accuracy and stability of oil and gas pipeline wall thickness detection.

[0084] On the other hand, the present invention also provides a wireless passive piezoelectric ultrasonic thickness measurement system, which is designed by the aforementioned wireless passive piezoelectric ultrasonic thickness measurement method.

[0085] This invention provides a wireless passive piezoelectric ultrasonic thickness measurement method and system. The wireless passive piezoelectric ultrasonic thickness measurement method includes the following steps: Step S1: Determine the structural configuration of the wireless passive piezoelectric ultrasonic thickness measurement system required for the thickness measurement based on the thickness measurement requirements; Step S2: Perform decoupling operations on the excitation coil and the receiving coil to reduce direct coupling of the excitation signal to the receiving coil; Step S3: Determine the spatial arrangement and magnetic field distribution characteristics of the excitation coil and the receiving coil to ensure effective coupling between the detection coil, excitation coil, and receiving coil, and calculate the relay coupling region and structural parameters of the detection coil; Step S4: Determine the coupling parameters of the linear frequency modulated chirp signal used in the excitation process of the excitation coil, and generate the linear frequency modulated chirp signal; Step S5: Receive the ultrasonic echo signal transmitted back by the detection coil, and perform pulse compression processing on the ultrasonic echo signal; the ultrasonic echo signal after pulse compression processing can then be used for wireless passive piezoelectric ultrasonic thickness measurement.

[0086] The wireless passive piezoelectric ultrasonic thickness measurement method and its ultrasonic thickness measurement system, possessing the above-mentioned characteristics, have at least the following technical advantages compared to existing technologies: 1. The wireless passive piezoelectric ultrasonic thickness measurement method provided by the present invention effectively reduces the signal crosstalk problem caused by the direct coupling of the excitation coil and the receiving coil through the decoupling design of the excitation coil and the receiving coil; and effectively suppresses the deformation of the excitation signal during the thickness measurement process, enhances the distinguishability of the echo signal of the oil and gas pipeline wall thickness, and improves the detection accuracy and stability of the oil and gas pipeline wall thickness.

[0087] 2. The wireless passive piezoelectric ultrasonic thickness measurement system provided by the present invention can be used for long-term fixed-point thickness measurement after the design of each structural unit of the thickness measurement system (including excitation coil, detection coil, receiving coil, signal generator, signal receiver, and piezoelectric ultrasonic transducer) is completed, without the need for preparatory work such as removing the cladding layer, which significantly improves the applicability and work efficiency of oil and gas pipeline wall thickness detection.

[0088] 3. The wireless passive piezoelectric ultrasonic thickness measurement method provided by this invention, compared with the existing wired piezoelectric ultrasonic thickness measurement technology, solves the adverse effects of complex construction environments such as high altitude, narrow space and high temperature on the reliability of thickness measurement results; it only requires the cooperation of excitation coil and detection coil to realize inductively coupled wireless signal transmission, ensuring the safety and reliability of the oil and gas pipeline wall thickness detection process.

[0089] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A wireless passive piezoelectric ultrasonic thickness measurement method, characterized in that, It includes the following steps: Step S1: Based on the thickness measurement requirements, determine the structural configuration of the wireless passive piezoelectric ultrasonic thickness measurement system required for the wireless passive piezoelectric ultrasonic thickness measurement method; Step S2: To reduce the direct coupling of the excitation signal to the receiving coil, a decoupling operation is performed on the excitation coil and the receiving coil; Step S3: To ensure effective coupling between the detection coil, excitation coil, and receiving coil, determine the spatial arrangement and magnetic field distribution characteristics of the excitation coil and receiving coil, and calculate the relay coupling region and structural parameters of the detection coil. Step S4: Determine the coupling parameters of the linear frequency modulated chirp signal used in the excitation process of the excitation coil, and generate the linear frequency modulated chirp signal; Step S5: Receive the ultrasonic echo signal transmitted back by the detection coil and perform pulse compression processing on the ultrasonic echo signal; Among them, the ultrasonic echo signal after pulse compression processing can be used for wireless passive piezoelectric ultrasonic thickness measurement. Step S4 specifically includes the following steps: Step S41: Based on the relay coupling capability of the detection coil and the equivalent total mutual inductance between the excitation coil and the receiving coil The excitation amplitude adjustment coefficient is calculated. ,satisfy: ; in, This is the adjustment coefficient for the excitation end; Step S42: Calculate the excitation center frequency of the linear frequency modulated chirp signal. ,satisfy: ; in, The equivalent inductance formed by the coupling of the excitation coil, receiving coil, and detection coil, The equivalent capacitance formed by the coupling of the excitation coil, the receiving coil, and the detection coil; Step S43: Determine the excitation bandwidth of the linear frequency modulated chirp signal. ,satisfy: ; Where μ is the proportionality coefficient; Q is the combined quality factor of the excitation coil, receiving coil, and detection coil. Step S44: Adjust the excitation amplitude according to the calculated value. The excitation center frequency of the linear frequency modulated chirp signal and the excitation bandwidth of the linear frequency modulated chirp signal A linear frequency modulated chirp signal is generated. ; in, satisfy: ; In the formula, For linear frequency modulated chirp signals The starting frequency satisfies: ; For linear frequency modulated chirp signals The termination frequency satisfies: .

2. The wireless passive piezoelectric ultrasonic thickness measurement method according to claim 1, characterized in that, Step S2 specifically includes: Assume the excitation coil consists of i anti-phase excitation sub-coils connected in series. The receiving coil is composed of j anti-phase sub-coils connected in series. If the configuration is such that the excitation coil and the receiving coil obtained from the decoupling operation satisfy the following conditions: ; in, To the maximum decoupling error, The residual error between the normalized total mutual inductance of the excitation coil and the receiving coil must satisfy: ; The equivalent total mutual inductance between the excitation coil and the receiving coil is determined by any excitation sub-coil in the excitation coil. and any receiving sub-coil in the receiving coil It is obtained by superimposing the pairwise mutual inductances; ,satisfy: ; In the formula, The mutual inductance between the i-th excitation sub-coil in the excitation coil and the j-th receiving sub-coil in the receiving coil satisfies: ; in, For exciter coil Number of turns, For receiving sub-coil Number of turns; For exciter coil The effective area, For receiving sub-coil The effective area; For exciter coil With receiver sub-coil The center distance between them; For exciter coil With receiver sub-coil Orientation correction factor between them.

3. The wireless passive piezoelectric ultrasonic thickness measurement method according to claim 2, characterized in that, Step S3 specifically includes: Assume the detection coil consists of a detection sub-coil With detection sub-coil The configuration involves the mutual inductance between the detection coil and the excitation coil. ,satisfy: Mutual inductance between the detection coil and the receiving coil ,satisfy: ; Mutual inductance between the detection coil and the excitation coil Mutual inductance between the detection coil and the receiving coil By deriving the equivalent mutual inductance, we obtain the following: , ; Define the relay coupling capability of the detection coil as: ;in, satisfy: ; The mutual inductance between the detection coil and the excitation coil derived by substituting into the equivalent mutual inductance Mutual inductance between the detection coil and the receiving coil ,get: ; When the parameters of the detection coil, excitation coil, and receiving coil are fixed, the above formula can be transformed into: ; Further analysis was conducted on the dimensional changes of the detection coil: When the detection coil size is too small Get smaller , Get smaller Less than When the detection coil size is too large, Increased, but center distance Get bigger , Get smaller Less than ; Therefore, it is calculated that the relay coupling capability is optimal when the outer contour dimensions of the detection coil are the same as those of the receiving coil and the excitation coil, the number of turns of the detection coil is equal to the number of turns of the receiving coil and the excitation coil, and the detection coil is wound in reverse phase.

4. The wireless passive piezoelectric ultrasonic thickness measurement method according to claim 1, characterized in that, Step S5 specifically includes the following steps: Step S51: Based on the relay coupling capability of the detection coil and the equivalent total mutual inductance between the excitation coil and the receiving coil Determine the compression gain coefficient ,satisfy: ; in, This is the adjustment coefficient; Step S52: Determine the matched filter time width ,satisfy: ; Where ρ is the proportionality coefficient; Q is the combined quality factor of the excitation coil, receiving coil, and detection coil. The excitation center frequency of the linearly frequency-modulated chirp signal; Step S53: Based on linear frequency modulated chirp signal The matched filter transfer function is constructed. ;in, satisfy: ; Step S54: Calculate the ultrasonic echo signal after pulse compression processing, satisfying: ; in, To receive the ultrasonic echo signal transmitted back by the detection coil.

5. A wireless passive piezoelectric ultrasonic thickness measurement system, characterized in that, The wireless passive piezoelectric ultrasonic thickness measurement system is designed based on the wireless passive piezoelectric ultrasonic thickness measurement method as described in any one of claims 1-4.

Images