Electromagnetic tomography system and imaging method based on flexible conformal probe

Abstract

The application discloses an electromagnetic tomography system and imaging method based on a flexible fitting probe, and the system comprises a probe module, which is arranged in a flexible base structure, wherein a detection coil array and a soft body adsorption module are arranged on the flexible base structure, and the soft body adsorption module is used for controlling the probe to be adsorbed to the surface of a measured structure; a channel switching module, which is connected with the probe module, adopts an excitation-receiving cross channel control structure, is used for performing path distribution on an excitation channel and a receiving channel, and is used for configuring different excitation-receiving coil combinations; a lock-in amplification module, which is connected with the channel switching module, is used for acquiring detection signals; and an upper computer, which is connected with the probe module, the channel switching module and the lock-in amplification module, is used for sending adsorption and channel switching control instructions and receiving lock-in outputs. The application realizes stable attachment through flexible fitting and soft body adsorption, improves a signal-to-noise ratio through lock-in synchronous demodulation, and realizes high-sensitivity electromagnetic tomography detection.

Description

An electromagnetic tomography system and imaging method based on a flexible bonding probe Technical Field

[0001] This invention relates to the field of nondestructive testing and structural health monitoring technology, and in particular to an electromagnetic tomography system and imaging method based on a flexible bonding probe. Background Technology

[0002] Steel structures, as a commonly used load-bearing structural form in modern civil engineering, are widely used in critical infrastructure such as high-rise buildings, bridges, factories, port facilities, and offshore platforms. During long-term service, steel structures are susceptible to corrosive media, alternating loads, and fatigue effects, which can lead to corrosion thinning, crack propagation, fatigue damage, and other defects, resulting in a decline in structural load-bearing capacity and durability. After sudden events such as typhoons, earthquakes, and explosions, the inability to promptly and accurately assess the damage status and hidden defects of steel structures will affect the reliability of subsequent maintenance, reinforcement plan development, and remaining life assessment.

[0003] Electromagnetic tomography (EMT), as a non-destructive testing method, can reconstruct and analyze the changes in conductivity distribution of the measured structure based on electromagnetic response information, thus showing great promise in the field of metal structure defect detection. However, most existing EMT probes adopt rigid coil array structures with fixed shapes, making it difficult to fit complex curvatures or irregular surfaces. In curved components, nodal regions, or scenarios with limited local space, the distance between the probe and the measured surface is prone to change, leading to unstable electromagnetic coupling conditions, which in turn introduces decreased measurement consistency and imaging errors.

[0004] To improve probe attachment stability, existing solutions often employ magnetic attraction or adhesive adhesion for fixation. However, these methods may affect the local electromagnetic field distribution and, in field operations, may lead to problems such as insufficient consistency in repositioning, surface residue, or high requirements for the surface conditions being measured, reducing the repeatability and engineering adaptability of the detection. Furthermore, engineering sites are often accompanied by electromagnetic interference, power frequency noise, and environmental vibrations, which can easily affect the detection signal and reduce the signal-to-noise ratio. Existing systems still have shortcomings in multi-channel rapid switching acquisition, synchronization, and miniaturized integration, making it difficult to meet the flexible deployment and high-reliability imaging detection requirements of complex curved steel structures. Summary of the Invention

[0005] To address the problems of existing electromagnetic tomography (EMT) probes in the detection of complex curved metal structures, such as difficulties in bonding, interference from electromagnetic fields in the fixing method, insufficient consistency in repeated positioning, and low signal-to-noise ratio and insufficient imaging stability caused by noise interference at the engineering site, this invention provides an electromagnetic tomography system and imaging method based on a flexible bonding probe. The aim is to improve the bonding stability and data acquisition consistency of the electromagnetic tomography probe, and enhance the ability to extract low signal-to-noise ratio signals and improve imaging quality.

[0006] This invention provides an electromagnetic tomography system based on a flexible bonding probe, comprising:

[0007] The probe module is constructed using a flexible substrate structure, on which a detection coil array and a soft adsorption module are mounted. The detection coil array includes multiple coil units, which can be selectively configured as excitation coils or receiving coils to achieve electromagnetic excitation and response signal acquisition. The soft adsorption module is used to control the flexible probe to adhere to the surface of the structure being measured.

[0008] A channel switching module is connected to the probe module. The channel switching module adopts an excitation-reception cross-channel control structure to allocate paths between the excitation channel and the receiving channel of the detection coil array, so as to configure different excitation-reception coil combinations for the coil unit.

[0009] A lock-in amplifier module, connected to the channel switching module, is used to acquire the detection signal, and perform synchronous demodulation and low-pass filtering on the detection signal based on a reference signal to extract the response component with the same frequency as the reference signal, and output the in-phase component and quadrature component or complex amplitude and phase results. Where X represents the in-phase component, i represents the imaginary unit, and Y represents the quadrature component;

[0010] The host computer is connected to the probe module, the channel switching module, and the lock-in amplification module, respectively. It is used to send adsorption commands to the probe module, send configuration commands to the channel switching module, and receive the synchronous demodulation and low-pass filtering results output by the lock-in amplification module. It also performs data processing and image reconstruction based on the electromagnetic tomography algorithm.

[0011] Furthermore, the flexible substrate structure is made of a flexible polymer material, which includes one of polyimide and silicone.

[0012] Furthermore, the detection coil array is integrated inside the flexible substrate structure, and the coil units are arranged at equal intervals along the row and column directions in a matrix.

[0013] Furthermore, the soft adsorption module includes multiple flexible vacuum suction cup units disposed on the flexible substrate structure, and a vacuum pump connected to each of the flexible vacuum suction cup units.

[0014] Furthermore, the flexible vacuum suction cup unit includes a negative pressure cavity, and the flexible vacuum suction cup unit and the flexible substrate structure are integrally formed, with the negative pressure cavity integrated inside the flexible substrate structure.

[0015] Furthermore, the channel switching module includes a multi-channel control switch module, which is electrically connected to each of the coil units respectively, for receiving channel switching instructions issued by the host computer, and realizing channel switching of the coil unit between the excitation channel and the receiving channel according to the channel switching instructions.

[0016] Furthermore, the lock-in amplifier module includes a synchronous reference signal input terminal, a quadrature regulator, a low-pass filter, and a DC amplification and output circuit.

[0017] This invention also provides an electromagnetic tomography method based on a flexible bonding probe, applied to the electromagnetic tomography system based on a flexible bonding probe as described above. The method includes:

[0018] The flexible bonding probe is attached to the surface of the structure being tested by a soft adsorption module.

[0019] The path allocation of the excitation channel and the receiving channel of the probe coil array is performed by the channel switching module in order to configure different excitation-receiver coil combinations;

[0020] A lock-in amplifier module generates or outputs a reference signal synchronized with the electromagnetic excitation, driving the selected excitation path to perform electromagnetic excitation and synchronously acquiring the corresponding detection signal. Then, based on the reference signal, the detection signal is synchronously demodulated and low-pass filtered to extract the response component with the same frequency as the reference signal, and outputs the in-phase component, quadrature component, or complex amplitude and phase result. Where X represents the in-phase component, i represents the imaginary unit, and Y represents the quadrature component;

[0021] Based on the results of the synchronous demodulation and low-pass filtering, the conductivity distribution map is reconstructed using an electromagnetic tomography algorithm to identify regions with abnormal conductivity.

[0022] Furthermore, channel switching and polling are performed between different excitation-receiver coil combinations according to a preset timing sequence to collect multiple rounds of detection signals.

[0023] Furthermore, the detection signal is synchronously demodulated and low-pass filtered based on the reference signal to extract the response component with the same frequency as the reference signal, and outputs in-phase and quadrature components or complex amplitude and phase results. The process includes: inputting a reference signal through a synchronous reference signal input terminal, and inputting the reference signal and the probe signal to an orthogonal regulator; performing coherent multiplication processing on the reference signal and the probe signal by the orthogonal regulator to obtain a product signal containing the target frequency component; using a low-pass filter to filter out high-frequency interference terms from the product signal, retaining the DC component with the same frequency as the reference signal; and outputting an in-phase component X and an orthogonal component Y based on the DC component to form a complex amplitude-phase result reflecting the structural conductivity variation characteristics. .

[0024] Compared with the prior art, the present invention has at least the following beneficial effects:

[0025] (1) The flexible bonding probe with flexible substrate structure can adapt to the curved surface, corner and local concave and convex areas of the steel structure surface, reduce the measurement fluctuation caused by the spacing change due to poor bonding, and improve the consistency of detection.

[0026] (2) The soft adsorption module enables the attachment and fixation of non-magnetic and non-colloidal materials, improving the consistency of repeated positioning and reducing the impact on the local electromagnetic field distribution, thereby improving the imaging stability;

[0027] (3) The channel switching module enables controllable configuration and polling acquisition of the excitation-receiving coil combination, thereby improving data acquisition efficiency and coverage.

[0028] (4) By extracting the same frequency response component through synchronous demodulation and low-pass filtering of the lock-in amplifier module, the signal-to-noise ratio of the detection signal and the distinguishability of the weak defect response are improved, thereby enhancing the reconstruction quality and engineering adaptability of electromagnetic tomography. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. It should be understood that the drawings shown below are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0030] Figure 1 is a schematic diagram of the overall structure of an electromagnetic tomography system based on a flexible bonding probe provided in an embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of the probe module in an electromagnetic tomography system based on a flexible bonding probe provided in an embodiment of the present invention;

[0032] Figure 3 is a schematic diagram of the flexible bonding probe provided in the embodiment of the present invention being attached to the surface of the planar structure being measured;

[0033] Figure 4 is a schematic diagram of the flexible bonding probe provided in the embodiment of the present invention being attached to the surface of the cylindrical curved structure being measured;

[0034] Figure 5 is a schematic diagram of the cross-sectional structure of the coil unit in the flexible bonding probe provided in an embodiment of the present invention;

[0035] Figure 6 is a three-dimensional structural diagram of the coil unit in the flexible bonding probe provided in an embodiment of the present invention;

[0036] Figure 7 is a schematic diagram of the flexible vacuum suction cup unit in the flexible bonding probe provided in an embodiment of the present invention;

[0037] Figure 8 is a block diagram of the synchronous demodulation and low-pass filtering principle of the phase-locked amplification module in the electromagnetic tomography system provided in the embodiment of the present invention;

[0038] Figure 9 is a flowchart illustrating an electromagnetic tomography method based on a flexible bonding probe provided in an embodiment of the present invention.

[0039] Figure 10 is a functional block diagram of an electromagnetic tomography system based on a flexible bonding probe provided in an embodiment of the present invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0042] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0043] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0044] Please refer to Figure 1 below. Figure 1 is a schematic diagram of the overall structure of an electromagnetic tomography system based on a flexible bonding probe provided in an embodiment of the present invention. The system includes:

[0045] The probe module 100 adopts a flexible substrate structure. The flexible substrate structure is provided with a detection coil array 101 and a soft adsorption module 102. The detection coil array 101 includes multiple coil units, which can be selectively configured as excitation coils or receiving coils to realize electromagnetic excitation and response signal acquisition. The soft adsorption module 102 is used to control the flexible probe to adsorb onto the surface of the structure under test.

[0046] The channel switching module 200 is connected to the probe module 100. The channel switching module 200 adopts an excitation-reception cross-channel control structure to allocate the excitation channel and the receiving channel of the detection coil array 101 to configure different excitation-reception coil combinations for the coil unit.

[0047] The lock-in amplifier module 300, connected to the channel switching module 200, is used to acquire the detection signal and perform synchronous demodulation and low-pass filtering on the detection signal based on the reference signal to extract the response component with the same frequency as the reference signal, and output the in-phase component and quadrature component or complex amplitude and phase result. Where X represents the in-phase component, i represents the imaginary unit, and Y represents the quadrature component;

[0048] The host computer 400 is connected to the probe module 100, the channel switching module 200, and the lock-in amplification module 300, respectively. It is used to send adsorption commands to the probe module 100, send configuration commands to the channel switching module 200, and receive the synchronous demodulation and low-pass filtering results output by the lock-in amplification module 300, and perform data processing and imaging reconstruction based on the electromagnetic tomography algorithm.

[0049] In this embodiment, the electromagnetic tomography system integrates a probe coil array 101, a soft adsorption module 102, a channel switching module 200, and a lock-in amplification module 300, constructing a multifunctional integrated detection platform that adapts to complex structural morphologies and possesses stable adhesion and anti-interference capabilities. The probe employs a flexible substrate structure, capable of adapting to curved surfaces, corners, and local uneven areas on steel structures, achieving effective adhesion without the need for rigid probe alignment or grinding. Simultaneously, the soft adsorption module 102 allows for the firm adsorption of the flexible probe onto the tested metal surface without the use of magnets or colloids, effectively improving signal acquisition stability. Furthermore, combined with the signal extraction mechanism of the controllable channel switching module 200 and the lock-in amplification module 300, the system can accurately extract weak co-frequency response components in complex environments, improving imaging stability and defect identification resolution.

[0050] The electromagnetic tomography system provided in this embodiment can flexibly fit the surface of the steel structure to be tested and achieve high-sensitivity electromagnetic imaging detection. It is particularly suitable for non-destructive testing and condition identification of potential hazards such as corrosion and cracks in engineering structures such as bridges, towers, steel beams, and pipelines.

[0051] In one embodiment, the flexible substrate structure is made of a flexible polymer material, which includes at least one of polyimide and silicone.

[0052] This embodiment employs a flexible coil array substrate structure, enabling the flexible probe to adhere to steel structure surfaces with varying curvatures or localized unevenness, thus adapting to different testing scenarios. Existing electromagnetic tomography probes often utilize rigid coil array designs, making it difficult to achieve stable adhesion to curved, undulating, or locally uneven steel structure surfaces. This can lead to variations in the distance between the probe and the measured surface, resulting in unstable electromagnetic coupling conditions and consequently, problems such as fluctuating detection signals, blurred image edges, and localized reconstruction distortion. These structural limitations severely restrict the probe's applicability to actual engineering structures such as bridge steel pipes, bent steel plates, and towers. Especially when inspecting cylindrical or irregular components, achieving high-precision adhesion measurement is challenging, potentially leading to misjudgments or omissions of critical damage such as structural corrosion and cracks, thereby affecting the completeness of the inspection and the reliability of structural safety assessments.

[0053] To address the problems of poor surface fit, numerous blind spots, and weak repeatability of existing electromagnetic tomography probes, this embodiment combines the continuous deformation characteristics of flexible materials to design a flexible coil array substrate structure. As shown in Figure 2, the flexible substrate structure is equipped with a detection coil array 101 and a soft adsorption module 102. The flexible substrate structure can conform to the geometry of the target surface (e.g., steel pipes, bent plates, grooves, etc.), thereby improving adhesion consistency and effective coverage area. It is particularly suitable for engineering structure inspection scenarios with non-flat or irregularly shaped metal interfaces. The flexible substrate structure is made of flexible polymer material and integrates multiple equally spaced coil units. The coil units are arranged in a matrix, such as a 4×8 matrix or a 6×6 matrix, to balance flexible bending capability with array sampling coverage capability.

[0054] Each coil unit can be selectively configured as an excitation coil or a receiving coil under the control of the channel switching module 200, realizing the multiplexing of excitation and reception functions and dynamic switching of excitation-receiver coil combinations. During use, the flexible bonding probe can be attached to the surface of the metal structure under test by the soft adsorption module 102, without the need for magnetic or adhesive adhesion fixation, thus reducing the potential impact on the surface of the structure under test and the local electromagnetic field distribution. At the same time, the host computer 400 can selectively enable or disable the coil units according to the needs of the detection area to achieve imaging scanning or local data acquisition enhancement in a specified area. Figure 3 shows the working state of the flexible bonding probe attached to the surface of the structure under test on a planar surface, and Figure 4 shows the working state of the flexible bonding probe attached to the surface of the structure under test on a cylindrical curved surface. Through the bonding deformation of the flexible substrate structure and the stable attachment of the soft adsorption, the signal drift caused by the fluctuation of the bonding gap can be reduced, the acquisition consistency and imaging reconstruction stability can be improved, thereby enhancing the ability to identify surface defects of complex steel structures.

[0055] In addition, the detection coil array 101 is integrated inside the flexible substrate structure, and the coil units are arranged at equal intervals along the row and column directions and in a matrix arrangement.

[0056] As shown in Figures 5 and 6, the coil units in the detection coil array 101 are distributed in a matrix within the flexible substrate structure, and each coil unit has two wires 1011 leading out for electrical connection. The wires 1011 of each coil unit converge into the channel switching module 200, and are electrically connected to the lock-in amplifier module 300 by the channel switching module 200. Under the control of the host computer 400, the channel switching module 200 is used to switch any coil unit to the excitation drive end as an excitation coil, or to the receiving front end as a receiving coil. Unselected coil units remain disconnected to reduce the influence of parasitic loops and channel crosstalk on the detection signal.

[0057] In one embodiment, referring to FIG7, the soft adsorption module 102 includes a plurality of flexible vacuum suction cup units 1021 disposed on the flexible substrate structure, and a vacuum pump 1022 connected to each of the flexible vacuum suction cup units 1021.

[0058] Specifically, the flexible vacuum suction cup unit 1021 includes a negative pressure chamber. The flexible vacuum suction cup unit 1021 and the flexible substrate structure are integrally formed, and the negative pressure chamber is integrated inside the flexible substrate structure. The vacuum pump 1022 includes an air intake channel 10221 and an air outlet channel 10222, used to suction or depressurize the negative pressure chamber to achieve adsorption and release control.

[0059] In existing electromagnetic tomography (EMT) systems, probe attachment methods primarily rely on magnetic attraction, colloidal adhesion, or rigid pressing. These methods are insufficiently adaptable to non-ferromagnetic surfaces and may affect the local electromagnetic field distribution during attachment, introducing measurement errors. Furthermore, rigid pressing makes it difficult to achieve uniform adhesion on irregular or uneven surfaces, easily leading to localized air gaps and fluctuations in the attachment spacing, resulting in signal drift, decreased data consistency, and imaging distortion. Especially in high-altitude, curved, or vertical detection scenarios, traditional attachment methods may also cause probe slippage or partial detachment, affecting detection stability and repeatability.

[0060] Therefore, this embodiment includes a soft adsorption module 102, enabling the flexible bonding probe to achieve stable adhesion to curved metal surfaces without relying on magnets or colloids. This soft adsorption module 102 is particularly suitable for various irregularly shaped structural surfaces such as bridge steel pipes, curved guardrails, and tower cylinders, providing stable adhesion boundary conditions for electromagnetic tomography. The soft adsorption module 102 can be positioned on the back of the probe and consists of multiple flexible vacuum suction cup units 1021. These flexible vacuum suction cup units 1021 can be made of materials such as flexible silicone, possessing strong edge sealing and a deformable central cavity. A micro-electric vacuum pump 1022 draws suction from the negative pressure cavity to create a negative pressure adsorption force, allowing the flexible bonding probe to adhere tightly to the surface of the metal structure being measured. When the detection position needs to be changed, the adsorption is released by depressurization.

[0061] In practical applications, multiple flexible vacuum suction cup units 1021 can be activated individually or simultaneously to form a negative pressure matrix for multi-point collaborative attachment, thereby stably attaching the flexible bonding probe to the surface of the target metal structure. During the attachment process, the host computer 400 can send an adsorption control command to the soft adsorption module 102, causing the vacuum pump 1022 to evacuate the negative pressure chamber, establishing the target negative pressure within a preset time and completing the overall adsorption. When the detection task ends or the detection position needs to be changed, the host computer 400 can send a release command to depressurize the negative pressure chamber and release the adsorption, achieving non-destructive detachment of the flexible bonding probe. Since the flexible vacuum suction cup unit 1021 is a soft structure, the adsorption process does not require rigid pressure, which reduces the risk of scratching the tested structure and avoids potential electromagnetic disturbances caused by magnetic attachment, thereby improving the attachment stability and the consistency of detection signal acquisition, and further enhancing the stability and repeatability of imaging reconstruction.

[0062] In one embodiment, the channel switching module 200 includes a multi-channel control switch module, which is electrically connected to each of the coil units. The multi-channel control switch module is used to receive channel switching instructions issued by the host computer 400 and to allocate paths for the excitation channel and receiving channel of the coil unit according to the channel switching instructions, thereby realizing the role switching of the coil unit between the excitation coil and the receiving coil and the configuration of different excitation-receiver coil combinations.

[0063] In existing electromagnetic tomography (EMT) systems, channel switching often relies on manual plugging and unplugging or fixed connections, which is complex and inefficient. This makes it difficult to achieve rapid polling acquisition of high-density excitation-receiver combinations, resulting in insufficient data coverage, limited reconstruction resolution, and impacted defect identification accuracy. Furthermore, the rigidity of channel configuration reduces the system's adaptability to different target structures and detection areas, increasing on-site deployment and adjustment costs. By introducing a matrix-style channel switching structure, this embodiment can automatically complete the rapid switching of multi-channel configurations and excitation / receiver paths under the control of a host computer, thereby improving imaging data acquisition efficiency and system automation.

[0064] To achieve efficient combined excitation and reception of multi-coil arrays under limited hardware resources, this embodiment provides a matrix-type channel switching and data acquisition circuit structure to improve the automation level and spatial resolution in electromagnetic tomography. The circuit adopts an excitation-reception cross-channel control structure, where each coil unit has the capability for excitation and reception multiplexing. Through a programmable channel switching module 200, any coil unit can be selectively configured as either an excitation or reception end at any time, thereby achieving dynamic reconstruction of the dynamic excitation-reception coil combination path. Each coil unit is connected to a multi-channel control switch module via wires 1011. This multi-channel control switch module can form a programmable channel switching matrix based on multi-channel analog switches. Under the control of the host computer 400, it establishes electrical connection paths between selected excitation coils and selected reception coils as needed, and disconnects and isolates unselected coil channels to reduce parasitic loops and channel crosstalk.

[0065] The channel switching module 200 described in this embodiment supports a combined dynamic switching mechanism for excitation and reception channels, enabling excitation-reception combined polling scanning of arrays such as 4×8, 6×6, or larger. While ensuring electrical isolation, it works in conjunction with a preset timing excitation and synchronous acquisition mechanism to achieve high-coverage imaging data acquisition. The channel switching module 200, in conjunction with the lock-in amplifier module 300, can perform channel-by-channel synchronous demodulation and output of inductive signals under different excitation-reception combinations. The output data corresponding to each combination is archived according to channel number and sent to the host computer 400 for subsequent electromagnetic tomography reconstruction.

[0066] Compared with manual plugging or fixed connection methods, this matrix channel control structure can reduce hardware wiring complexity and on-site switching operations, improve array scalability, and enhance the system's configuration flexibility and automated acquisition capabilities under different structural morphologies and detection areas.

[0067] In one embodiment, the lock-in amplifier module 300 includes a synchronization reference signal input terminal, a quadrature regulator, a low-pass filter, and a DC amplification and output circuit.

[0068] In electromagnetic tomography, the amplitude of the induced signal from the receiving coil (i.e., the detection signal) is generally small and easily affected by multiple factors such as the electromagnetic environment of the construction site, sensor noise, and cable coupling. This often results in the target feature signal being submerged in background noise, thus affecting the stability of image reconstruction and the accuracy of defect identification. Conventional broadband amplification or filtering methods are prone to introducing out-of-band noise or gain drift when extracting weak responses at specific frequencies, making it difficult to achieve stable and selective signal extraction.

[0069] Therefore, this embodiment employs a signal processing structure based on the reference phase-locked loop principle. It uses a reference input synchronized with the excitation signal to perform phase-sensitive demodulation of the probe signal, extracting the in-phase response component consistent with the excitation frequency. A low-pass filter suppresses asynchronous components, thereby improving the extractability and anti-interference capability of the in-phase response component. The phase-locked amplification module 300 consists of a synchronous reference signal input terminal, a quadrature regulator, a low-pass filter, and DC amplification and output circuits, enabling stable output of the in-phase component X and quadrature component Y, or complex amplitude and phase results, for imaging reconstruction under complex operating conditions. This is to improve the discernibility of weak defect responses.

[0070] During operation, the excitation signal generated by the system's excitation source remains synchronized with the phase-locked reference signal, wherein the reference signal... The induced signal received by the receiving channel serves as the reference input to the phase-locked amplifier module 300 and is used as the signal to be measured. Input is to the phase-locked loop amplifier module 300. The two signals undergo synchronous demodulation processing in the quadrature regulator, specifically... and Perform coherent multiplication to obtain a product signal containing the target's same-frequency information. In the process of multiple excitation-receiver combined polling detection, the lock-in amplifier module 300 maintains synchronous operation with the corresponding excitation signal during each round of excitation and acquisition, so as to improve the consistency of data in different rounds and suppress the influence of asynchronous noise on the detection signal.

[0071] As shown in Figure 8, the signal to be measured With reference signal The input is fed into a quadrature regulator, which performs coherent multiplication on the two signals and outputs a product signal containing the target's same-frequency information. Subsequently, the product signal enters the low-pass filter module, which filters out high-frequency terms and asynchronous interference components, retains the DC component with the same frequency as the reference frequency, and obtains the in-phase component X and the quadrature component Y, forming a complex amplitude-phase output. X, Y, or It can be used to characterize the electromagnetic response features under different excitation-receiver coil combinations, and further serve as input data for electromagnetic tomography reconstruction. The demodulated results can be displayed and stored by the host computer 400 for imaging reconstruction and result analysis.

[0072] In one embodiment, the system can be coordinated and driven by an FPGA control module, including but not limited to: generation of reference signals and their quadrature components, synchronous timing control of excitation and acquisition, channel switching and demodulation process management, and interface output and buffer management of demodulated data.

[0073] It should also be noted that the lock-in amplification module 300 described in this embodiment is used for the extraction of the same frequency component of weak sensing signals. It can improve the signal-to-noise ratio and output stability of the detection signal in scenarios where the conductivity difference is slight or the target response is weak, thereby improving the stability of electromagnetic tomography reconstruction and the reliability of defect identification.

[0074] Figure 9 is a flowchart illustrating an electromagnetic tomography method based on a flexible bonding probe according to an embodiment of the present invention. The method is applied to the electromagnetic tomography system based on a flexible bonding probe as described above, and specifically includes steps S101 to S104.

[0075] Step S101: The flexible bonding probe is attached to the surface of the structure being tested by the soft adsorption module 102.

[0076] Step S102: Use the channel switching module 200 to allocate the paths of the excitation channel and the receiving channel of the probe coil array 101 to configure different excitation-receiver coil combinations;

[0077] Step S103: Generate or output a reference signal synchronized with the electromagnetic excitation using the lock-in amplifier module 300, and drive the selected excitation path to perform electromagnetic excitation, synchronously acquiring the corresponding detection signal. Then, based on the reference signal, perform synchronous demodulation and low-pass filtering on the detection signal to extract the response component with the same frequency as the reference signal, and output the in-phase component and quadrature component or complex amplitude and phase result. Where X represents the in-phase component, i represents the imaginary unit, and Y represents the quadrature component;

[0078] Specifically, the detection signal is synchronously demodulated and low-pass filtered based on the reference signal to extract the response component with the same frequency as the reference signal, and the in-phase component, quadrature component, or complex amplitude-phase result is output. ,include:

[0079] A reference signal is input through the synchronous reference signal input terminal, and the reference signal and the detection signal are input to the quadrature regulator;

[0080] The orthogonal regulator performs coherent multiplication processing on the reference signal and the detection signal to obtain a product signal containing the target's same-frequency information;

[0081] A low-pass filter is used to filter out high-frequency terms and asynchronous interference components from the product signal, while retaining the DC component with the same frequency as the reference signal.

[0082] Based on the DC component, the in-phase component X and the quadrature component Y are output, forming a complex amplitude-phase result that reflects the characteristics of structural conductivity variation. ;

[0083] Step S104: Based on the results of the synchronous demodulation and low-pass filtering, the conductivity distribution map is reconstructed using an electromagnetic tomography algorithm to identify abnormal conductivity regions.

[0084] Furthermore, the electromagnetic tomography method based on the flexible bonding probe also includes: switching and polling channels between different excitation-receiver coil combinations according to a preset timing sequence to acquire multiple rounds of detection signals.

[0085] This embodiment, based on the aforementioned electromagnetic tomography system with a flexible bonding probe, employs a flexible bonding structure combining a probe coil array 101 and a soft adsorption module 102. Combined with the synchronous demodulation processing of the lock-in amplification module 300 and the electromagnetic tomography reconstruction algorithm, it achieves stable acquisition and imaging reconstruction of weak electromagnetic response signals. Specifically, referring to Figure 10, the system operation process may include:

[0086] (1) After the system starts, the host computer 400 sends an adsorption control command to the soft adsorption module 102 to make the flexible bonding probe attach to the surface of the structure to be tested and make the attachment area cover the area to be tested.

[0087] (2) The host computer 400 sends a channel switching command to the channel switching module 200, and the channel switching module 200 completes the path allocation of the excitation channel and the receiving channel, and configures the excitation-receiving coil combination for the current round;

[0088] (3) The lock-in amplifier module 300 generates or outputs a reference signal that is synchronized with the electromagnetic excitation and drives the selected excitation path to perform electromagnetic excitation on the structure under test; at the same time, it synchronously acquires the induced signal returned by the selected receiving coil.

[0089] (4) The lock-in amplifier module 300 performs synchronous demodulation and low-pass filtering on the induced signal based on the reference signal, extracts the same-frequency response component, outputs the in-phase component X and the quadrature component Y, and forms a complex amplitude-phase result reflecting the structural conductivity change characteristics. ;

[0090] (5) The system performs channel switching polling between different excitation-receiving coil combinations according to a preset timing sequence, repeating steps (2) to (4) to obtain detection data under multiple rounds and different combinations;

[0091] (6) The host computer 400 receives X, Y or ... of each round The data is processed and an electromagnetic tomography algorithm is executed to reconstruct the image, resulting in a conductivity distribution map. By analyzing the conductivity distribution map, abnormal conductivity areas are identified, enabling the location and visualization of defects such as corrosion and cracks.

[0092] This embodiment utilizes a channel switching module 200 to achieve programmable combination configuration of multiple excitation / reception paths. Through synchronous timing coordination with the lock-in amplifier module 300, it enables polling acquisition of excitation and response signals and extraction of co-frequency components. In the signal link, the lock-in amplifier module 300 integrates reference signal synchronization, quadrature demodulation, and low-pass filtering to improve the signal-to-noise ratio and output stability of weak induced signals under complex electromagnetic interference environments. This meets the requirement for stable imaging data in detecting minor surface damage (such as early corrosion and hidden cracks) on steel structures. The system has a modular structure, adaptable to flexible probes of different array sizes and deployment methods, facilitating configuration expansion based on the size and structural morphology of the detection area.

[0093] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0094] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. An electromagnetic tomography system based on a flexible bonding probe, characterized in that, include: The probe module is set on a flexible substrate structure, and the flexible substrate structure is provided with a detection coil array and a soft adsorption module. The detection coil array includes multiple coil units, which can be selectively configured as excitation coils or receiving coils to achieve electromagnetic excitation and response signal acquisition. The soft adsorption module is used to control the flexible probe to adhere to the surface of the structure under test. The flexible substrate structure is made of a flexible polymer material, which includes one of polyimide and silicone. The detection coil array is integrated inside the flexible substrate structure, and the coil units are arranged in a matrix with equal spacing along the row and column directions. A channel switching module is connected to the probe module. The channel switching module adopts an excitation-reception cross-channel control structure to allocate paths between the excitation and receiving channels of the detection coil array, so as to configure different excitation-reception coil combinations for the coil units. The channel switching module includes a multi-channel control switch module, which is electrically connected to each of the coil units and is used to receive channel switching commands issued by the host computer and realize channel switching between the excitation and receiving channels of the coil units according to the channel switching commands. A lock-in amplifier module, connected to the channel switching module, is used to acquire the detection signal and perform synchronous demodulation and low-pass filtering on the detection signal based on a reference signal to extract the response component with the same frequency as the reference signal, and output the in-phase component, quadrature component, or complex amplitude and phase result. Where X represents the in-phase component, i represents the imaginary unit, and Y represents the quadrature component; the host computer is connected to the probe module, the channel switching module, and the lock-in amplification module, respectively, and is used to send adsorption commands to the probe module, send configuration commands to the channel switching module, and receive the synchronous demodulation and low-pass filtering results output by the lock-in amplification module, and perform data processing and imaging reconstruction based on the electromagnetic tomography algorithm.

2. The electromagnetic tomography system based on a flexible bonding probe according to claim 1, characterized in that, The soft adsorption module includes multiple flexible vacuum suction cup units disposed on the flexible substrate structure, and a vacuum pump connected to each of the flexible vacuum suction cup units.

3. The electromagnetic tomography system based on a flexible bonding probe according to claim 2, characterized in that, The flexible vacuum suction cup unit includes a negative pressure cavity. The flexible vacuum suction cup unit and the flexible substrate structure are integrally formed, and the negative pressure cavity is integrated inside the flexible substrate structure.

4. The electromagnetic tomography system based on a flexible bonding probe according to claim 1, characterized in that, The lock-in amplifier module includes a synchronous reference signal input terminal, a quadrature regulator, a low-pass filter, and a DC amplification and output circuit.

5. An electromagnetic tomography method based on a flexible bonding probe, applied to the electromagnetic tomography system based on a flexible bonding probe as described in any one of claims 1-4, characterized in that, The method includes: controlling the flexible bonding probe to adhere to the surface of the structure under test via a soft adsorption module; using a channel switching module to allocate paths for the excitation and receiving channels of the probe coil array to configure different excitation-receiving coil combinations; using a lock-in amplifier module to generate or output a reference signal synchronized with the electromagnetic excitation, and driving the selected excitation path to perform electromagnetic excitation, synchronously acquiring the corresponding probe signal; then, based on the reference signal, performing synchronous demodulation and low-pass filtering on the probe signal to extract the response component with the same frequency as the reference signal, and outputting the in-phase component and quadrature component or complex amplitude-phase result. Where X represents the in-phase component, i represents the imaginary unit, and Y represents the quadrature component; based on the results of the synchronous demodulation and low-pass filtering, the conductivity distribution map is reconstructed using an electromagnetic tomography algorithm to identify abnormal conductivity regions.

6. The electromagnetic tomography method based on a flexible bonding probe according to claim 5, characterized in that, Also includes: According to a preset timing sequence, the channel is switched and polled between different excitation-receiver coil combinations to collect multiple rounds of detection signals.

7. The electromagnetic tomography method based on a flexible bonding probe according to claim 5, characterized in that, The detection signal is synchronously demodulated and low-pass filtered based on the reference signal to extract the response component with the same frequency as the reference signal, and the in-phase component, quadrature component, or complex amplitude and phase result is output. The process includes: inputting a reference signal through a synchronous reference signal input terminal, and inputting the reference signal and the probe signal to an orthogonal regulator; performing coherent multiplication processing on the reference signal and the probe signal by the orthogonal regulator to obtain a product signal containing the target frequency component; using a low-pass filter to filter out high-frequency interference terms from the product signal, retaining the DC component with the same frequency as the reference signal; and outputting an in-phase component X and an orthogonal component Y based on the DC component to form a complex amplitude-phase result reflecting the structural conductivity variation characteristics. 。

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