High-altitude carbon fiber cable detection system and detection method

Abstract

The present invention relates to a high-altitude carbon fiber cable detection system and detection method. The high-altitude carbon fiber cable detection system includes a high-altitude carrying unit, a detection unit, a channel switching unit, an excitation signal amplification unit, a phase-locked amplifier unit, a main control unit, and an image reconstruction unit. The high-altitude carrying unit is used to carry the detection unit, so that the carbon fiber cable in the air can be detected. The high-altitude carrying unit can directly realize the placement and detachment of the detection unit, without the need for manual disassembly and installation, thereby improving the safety and convenience of the detection. After image reconstruction, a damage distribution image on the radial cross section of the inspected carbon fiber cable is obtained. The C-shaped frame of the detection unit can detect the notch position that cannot be detected before rotation by rotating. After image fusion, a complete damage distribution image on the radial cross section of the inspected carbon fiber cable is obtained.

Description

Technical Field

[0001] The present invention relates to a carbon fiber cable detection technology, in particular to a high-altitude carbon fiber cable detection system and detection method. Background Art

[0002] Cables are core load-bearing components of ultra-large equipment and long-span bridges, and their health plays a crucial role in the safety of the entire structure. However, as they age, their surfaces inevitably harden and become damaged by ultraviolet radiation and external impacts. Internally, vibrations from wind and rain cause friction in the strands, leading to wear and breakage. This can seriously impact the safe operation of cables, necessitating effective inspection and testing technology to regularly inspect the cables internally and externally to ensure equipment safety.

[0003] The choice of material also significantly impacts cable performance. In recent years, the rise of carbon fiber composite cables has demonstrated significant advantages in addressing span, lifespan, and wind and rain vibration resistance. These cables hold great potential for application in ultra-large structures, such as amusement rides and cableways, where fatigue and corrosion resistance are crucial. Furthermore, with continued technological advancements, the performance of carbon fiber composites continues to improve, and their cost decreases, their application is expected to continue to rise.

[0004] Currently, there is no nondestructive testing technology specifically designed for high-altitude carbon fiber cables. Existing testing methods primarily involve manually climbing the cable with a handheld tester and inspecting it from top to bottom. This compromises operator safety and prevents observation of the cable's internal conditions. Nondestructive testing technologies for carbon fiber composites, based on acoustic emission, optical fiber, and microwave technologies, have been extensively researched. However, these technologies require direct contact with the structure being tested and are susceptible to external influences, making them unsuitable for real-time testing at high altitudes.

[0005] Electromagnetic detection techniques have proven effective in detecting defects in carbon fiber composite materials. Chinese patent CN 109444255 A proposes a method for diagnosing defects in carbon fiber reinforced composite materials. This method uses an eddy current detector to obtain impedance information for defect diagnosis. However, this method requires a scanning table and is not suitable for scanning large structures or high-altitude components in use. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-altitude carbon fiber cable detection system and detection method to solve the problem that the existing cable detection technology cannot perform non-destructive detection of high-altitude carbon fiber cables.

[0007] The present invention is implemented as follows: a high-altitude carbon fiber cable detection system includes the following parts.

[0008] The high-altitude carrying unit is used to carry the detection unit for high-altitude flight.

[0009] The detection unit is installed on the high-altitude carrying unit and includes a C-shaped frame that can rotate around its own center of circle. A plurality of coils are arranged in an array on the C-shaped frame for generating an excitation magnetic field and detecting the induced potential signal generated by the carbon fiber cable.

[0010] The channel switching unit is used to transmit the excitation signal generated by the lock-in amplifier unit to a certain coil or transmit the induced potential signal detected by the coil to the lock-in amplifier unit.

[0011] The excitation signal amplifying unit is used to amplify the excitation signal generated by the lock-in amplifier unit and transmit it to the channel switching unit.

[0012] The lock-in amplifier unit is used to generate the excitation signal and receive and process the induced potential signal.

[0013] The main control unit is connected to the channel switching unit, the lock-in amplifier unit and the image reconstruction unit, and is used to control the channel switching unit, the lock-in amplifier unit and the image reconstruction unit.

[0014] and an image reconstruction unit, which is used to reconstruct an image of the conductivity distribution on the radial cross section of the inspected carbon fiber cable using the induced potential signal data obtained through the detection through an image reconstruction algorithm.

[0015] The detection unit includes a shell and a C-shaped frame and a driving element arranged in the shell. A plurality of coils are evenly arranged around the center of the circle on the inner circle of the C-shaped frame. The C-shaped frame is slidably connected to the shell bracket. The C-shaped frame is driven by the driving element to rotate around the center of the circle of the C-shaped frame.

[0016] An arc-shaped slide groove is provided on the C-shaped frame, and the center of the slide groove coincides with the center of the C-shaped frame. A plurality of pulleys are provided on the shell, and the pulleys are installed in the slide groove.

[0017] Driven teeth are arranged on the outer ring of the C-shaped frame, the driving element is a stepping motor, and a driving wheel is arranged on the rotating shaft of the stepping motor, and the driving wheel is meshed with the driven teeth.

[0018] The high-altitude carrying unit includes a drone, a connecting device is provided on the drone, and the detection unit is provided on the connecting device.

[0019] The present invention also discloses a high-altitude carbon fiber cable detection method, which is implemented based on the above-mentioned high-altitude carbon fiber cable detection system, and the steps are as follows.

[0020] a. Use the high-altitude carrying unit to carry the detection unit to the location to be tested, and put the C-frame of the detection unit on the carbon fiber cable.

[0021] b. The control unit controls the lock-in amplifier unit to generate an excitation signal, and controls the channel switching unit to pass the excitation signal into any one of the N coils in the detection unit, so that the coil generates an alternating excitation magnetic field.

[0022] c. The channel switching unit sequentially selects the other N-1 coils in the N coils in the detection unit to detect their induced potential signals, and sends the induced potential signals to the lock-in amplifier unit through the channel switching unit.

[0023] d. The phase-locked amplifier unit demodulates the amplitude and phase shift relative to the excitation signal from the detected induced potential signal, and sends the processed results to the main control unit.

[0024] e. Repeat steps b to d until all N coils generate overexcitation magnetic fields, and obtain a set of N×(N-1)×2 detection data.

[0025] f. Using the obtained test data, an image reconstruction algorithm is used to reconstruct the conductivity distribution on the radial cross section of the inspected carbon fiber cable to obtain a damage distribution image on the radial cross section of the inspected carbon fiber cable before rotation.

[0026] g. Rotate the C-frame of the detection unit 90° and repeat steps b to f to obtain a damage distribution image on the radial cross section of the rotated carbon fiber cable being tested.

[0027] h. Perform image fusion on the damage distribution images on the radial cross section of the inspected carbon fiber cable before and after rotation, process the fused images, obtain object field characteristic parameters, and quantitatively analyze the radial cross section damage of the inspected carbon fiber cable.

[0028] The image reconstruction algorithm includes the following steps.

[0029] S1. Obtain the boundary voltage value U and sensitivity matrix based on the detection data, and derive G through the linear equation U = SG, where S is the normalized sensitivity matrix and G is the normalized conductivity distribution vector, which represents the image grayscale value in image reconstruction.

[0030] S2. Establish the objective function of the Tikhonov regularization algorithm:

[0031]

[0032] Derivative the above formula and set the derivative to 0, solve the extreme point of the objective function, and get

[0033] G=(S TS+αI) -1 S T U

[0034] Where α is the regularization parameter and I is the identity matrix.

[0035] S3. Correct the error of the gray value conductivity distribution vector. The corrected formula of Tikhonov regularization algorithm is:

[0036] G c =(S T S+αI) -1 S T (U+μΔU)

[0037] Among them, G c is the grayscale value after correction, μ is the error correction parameter, and ΔU is the difference between the detected boundary voltage value and the actual voltage value set during excitation.

[0038] S4. Use the least squares method to solve the error correction parameter μ and construct the least squares function F(μ) about μ:

[0039] F(μ)=||S(S T S+αI) -1 S T (U+μΔU)-U|| 2

[0040] Derivative the above formula, and set the derivative to 0, solve for μ and get

[0041]

[0042] S5. Perform relative tolerance judgment on the corrected grayscale value. The judgment formula is:

[0043] |G c -G f |≤ε

[0044] Among them, G f represents the grayscale value of the original image model, and ε represents the pre-calculated relative tolerance value; if the above formula is true, the corrected grayscale value image is directly output; if not, the regularization parameter α and the error correction parameter μ are changed, and steps S1 to S5 are repeated until the judgment conditions are met to obtain an accurate grayscale value image.

[0045] In step h, the damage distribution image on the radial cross-section of the inspected carbon fiber cable before rotation is taken as the source image A, and the damage distribution image on the radial cross-section of the inspected carbon fiber cable after rotation is taken as the source image B. Feature values ​​of source image A and source image B are extracted at multiple angles and then fused to obtain a fused distribution image R with complete damage characteristics.

[0046] The present invention uses a high-altitude mounting unit equipped with a detection unit to detect carbon fiber cables at high altitudes. The C-shaped frame of the detection unit can be placed at any position on the carbon fiber cables at high altitudes, thereby quickly detecting the locations that need to be detected. The high-altitude mounting unit can directly realize the placement and detachment of the detection unit, eliminating the need for manual disassembly and installation, thereby improving the safety and convenience of detection. After image reconstruction, a damage distribution image on the radial cross-section of the inspected carbon fiber cables is obtained. The C-shaped frame of the detection unit can be rotated to detect the position of the gap that could not be detected before rotation. After image fusion, a complete damage distribution image on the radial cross-section of the inspected carbon fiber cables is obtained.

[0047] The present invention meets the demand for rapid, non-contact detection of carbon fiber cables, realizes visualization of internal broken wires and other damage defects, can use a computer to achieve remote control of detection, avoids the risks of high-altitude operations, and realizes inspection and detection of large-scale high-altitude structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a structural diagram of the high-altitude carbon fiber cable detection system of the present invention.

[0049] Figure 2 It is a schematic diagram of the present invention when testing a carbon fiber cable.

[0050] Figure 3 It is a structural diagram of the detection unit of the present invention.

[0051] Figure 4 It is a schematic diagram of the high-altitude carbon fiber cable detection process of the present invention.

[0052] Figure 5 This is a comparison diagram between the image reconstruction algorithm of the present invention and the existing algorithm.

[0053] In the figure: 1. High-altitude carrying unit; 2. Detection unit; 3. Channel switching unit; 4. Excitation signal amplification unit; 5. Phase-locked amplifier unit; 6. Main control unit; 7. Image reconstruction unit; 8. Carbon fiber cable; 1-1. UAV; 1-2. Connecting device; 2-1. Shell; 2-2. C-frame; 2-3. Coil; 2-4. Slide; 2-5. Pulley; 2-6. Driven gear; 2-7. Driving wheel; 2-8. Magnetic shielding layer. DETAILED DESCRIPTION

[0054] like Figure 1 、 Figure 2 As shown, the high-altitude carbon fiber cable 8 detection system of the present invention includes a high-altitude carrying unit 1, a detection unit 2, a channel switching unit 3, an excitation signal amplification unit 4, a phase-locked amplifier unit 5, a main control unit 6 and an image reconstruction unit 7.

[0055] The high-altitude carrying unit 1 is used to carry the detection unit 2 for high-altitude flight. The high-altitude carrying unit 1 is generally a drone 1-1, but can also be other aircraft. The position and movement trajectory of the detection unit 2 can be remotely controlled, so that a predetermined position or area on the high-altitude carbon fiber cable 8 can be detected.

[0056] like Figure 3 As shown, the detection unit 2 is mounted on the high-altitude carrying unit 1 and moves with the high-altitude carrying unit 1. The detection unit 2 includes a housing, a C-shaped frame 2-2 disposed within the housing, and a driving element. A plurality of coils 2-3 are evenly arranged around the center of the inner circle of the C-shaped frame 2-2. The C-shaped frame 2-2 is slidably connected to the housing bracket and is driven by the driving element to rotate around the center of the C-shaped frame 2-2.

[0057] The outer shell is fixed to the aerial mounting unit 1 via a connecting device 1-2. A C-shaped frame 2-2 is mounted within the outer shell. An arc-shaped chute 2-4 is provided on the C-shaped frame 2-2, with the center of the chute 2-4 coinciding with the center of the C-shaped frame 2-2. A plurality of pulleys 2-5 are provided on the housing 2-1. These pulleys 2-5 are distributed in an arc shape on the housing 2-1, with the center of the arc coinciding with the center of the C-shaped frame 2-2. The pulleys 2-5 are mounted within the chute 2-4 and can move along the chute 2-4. Driven by a drive element, the pulleys 2-5 and the chute 2-4 cooperate to enable the C-shaped frame 2-2 to rotate about its own center.

[0058] A driven tooth 2-6 is provided on the outer ring of the C-type frame 2-2, and the driving element is a stepper motor. A driving wheel 2-7 is provided on the rotating shaft of the stepper motor. The driving wheel 2-7 is engaged with the driven tooth 2-6. The stepper motor drives the rotation of the C-type frame 2-2 through the transmission of the driving wheel 2-7 and the driven wheel.

[0059] A magnetic shielding layer 2-8 is also provided on the outer side of the C-shaped frame 2-2 for shielding the magnetic field generated by the coil 2-3 to prevent the magnetic field from affecting other surrounding components.

[0060] The coil 2-3 is fixed on the inner ring of the C-shaped frame 2-2, and the coil 2-3 array is evenly arranged at equal angles around the imaging area, wherein each coil 2-3 is wound with multiple turns of copper wire, and the specific size of the coil 2-3 depends on the size of the imaging area.

[0061] When receiving an excitation signal, the coil 2-3 can generate an alternating excitation magnetic field. At the same time, the coil 2-3 can also be used as a detection element for the induced potential signal generated by the carbon fiber cable 8. The detection unit 2 has a total of several coils 2-3. When one of the coils 2-3 is used to generate an excitation magnetic field, the excitation magnetic field it generates acts on the carbon fiber cable 8 being tested. Since the carbon fiber cable 8 has electrical conductivity / magnetic permeability, it will change the distribution of the excitation magnetic field. The remaining coils 2-3 can act as detection elements to detect the induced potential signal for subsequent processing.

[0062] Channel switching unit 3 is connected to the array of coils 2-3 of detection unit 2, as well as to the lock-in amplifier unit 5 and the signal amplification unit. Channel switching unit 3 switches coils 2-3 to either detection elements or excitation elements, transmitting the excitation signal generated by the lock-in amplifier unit 5 to a specific coil 2-3 or transmitting the induced potential signal detected by coil 2-3 to the lock-in amplifier unit 5.

[0063] The excitation signal amplifying unit 4 is located between the channel switching unit 3 and the lock-in amplifier unit 5 , and is used to amplify the excitation signal generated by the lock-in amplifier unit 5 and transmit the amplified signal to the channel switching unit 3 .

[0064] The lock-in amplifier unit 5 can generate an excitation signal, receive the induced potential signal transmitted to the lock-in amplifier unit 5 via the excitation signal amplification unit 4, and demodulate the amplitude and phase shift relative to the excitation signal from the induced potential signal.

[0065] The main control unit 6 is connected to the channel switching unit 3 , the lock-in amplifier unit 5 and the image reconstruction unit 7 , and controls the channel switching unit 3 , the lock-in amplifier unit 5 and the image reconstruction unit 7 via the main control unit 6 .

[0066] The image reconstruction unit 7 is connected to the main control unit 6. The main control unit 6 transmits the data processed by the phase-locked amplifier unit 5 to the image reconstruction unit 7. The image reconstruction unit 7 reconstructs the conductivity distribution on the radial section of the inspected carbon fiber cable 8 through an image reconstruction algorithm.

[0067] In addition to the detection unit 2, the channel switching unit 3, the excitation signal amplifying unit 4, the excitation signal amplifying unit 4, and the phase-locked amplifier unit 5 can also be carried on the high-altitude carrying unit 1. The main control unit 6 is wirelessly connected to the channel switching unit 3 and the phase-locked amplifier unit 5 via Ethernet, which can realize remote control and information transmission.

[0068] The present invention uses a high-altitude mounting unit 1 equipped with a detection unit 2 to detect carbon fiber cables 8 at high altitudes. The C-shaped frame 2-2 of the detection unit 2 can be placed at any position on the carbon fiber cables 8 at high altitudes, thereby quickly detecting the position that needs to be detected. The detection unit 2 can be directly placed in and out of position through the high-altitude mounting unit 1, without the need for manual disassembly and installation, thereby improving the safety and convenience of detection. After image reconstruction, a damage distribution image on the radial cross-section of the inspected carbon fiber cables 8 is obtained. The C-shaped frame 2-2 of the detection unit 2 can be rotated to detect the position of the gap that could not be detected before the rotation. After subsequent image fusion, a complete damage distribution image on the radial cross-section of the inspected carbon fiber cables 8 can be obtained.

[0069] The present invention meets the demand for rapid and non-contact detection of carbon fiber cables 8, realizes visualization of internal broken wires and other damage defects, can use a computer to achieve remote control of detection, avoids the risk of high-altitude operations, and realizes inspection and detection of ultra-large high-altitude structures.

[0070] like Figure 4 As shown, the present invention also discloses a high-altitude carbon fiber cable 8 detection method, which is implemented based on the above-mentioned high-altitude carbon fiber cable 8 detection system, and the steps are as follows.

[0071] a. Use the high-altitude carrying unit 1 to carry the detection unit 2 to move to the position to be detected, and put the C-frame 2-2 of the detection unit 2 on the carbon fiber cable 8.

[0072] b. The control unit controls the lock-in amplifier unit 5 to generate an excitation signal, and controls the channel switching unit 3 to pass the excitation signal into any one coil 2-3 of the N coils 2-3 in the detection unit 2, so that the coil 2-3 generates an alternating excitation magnetic field.

[0073] c. The channel switching unit 3 sequentially selects the other N-1 coils 2-3 of the N coils 2-3 in the detection unit 2 to detect their induced potential signals, and sends the induced potential signals to the lock-in amplifier unit 5 through the channel switching unit 3.

[0074] d. The phase-locked amplifier unit 5 demodulates the amplitude and phase shift relative to the excitation signal from the detected induced potential signal and sends the processed result to the main control unit 6.

[0075] e. Repeat steps b to d until all N coils 2-3 generate overexcitation magnetic fields, and obtain a set of N×(N-1)×2 detection data.

[0076] f. Using the obtained test data, an image reconstruction algorithm is used to reconstruct the conductivity distribution on the radial cross section of the inspected carbon fiber cable 8 to obtain a damage distribution image on the radial cross section of the inspected carbon fiber cable 8 before rotation.

[0077] g. Rotate the C-frame 2-2 of the detection unit 2 by 90° and repeat steps b to f to obtain a damage distribution image on the radial cross section of the rotated carbon fiber cable 8 being tested.

[0078] h. Perform image fusion on the damage distribution images on the radial section of the inspected carbon fiber cable 8 before and after rotation, process the fused images, obtain object field characteristic parameters, and quantitatively analyze the radial section damage of the inspected carbon fiber cable 8.

[0079] The image reconstruction algorithm includes the following steps.

[0080] S1. Obtain the boundary voltage value U and sensitivity matrix based on the detection data, and derive G through the linear equation U = SG, where S is the normalized sensitivity matrix and G is the normalized conductivity distribution vector, which represents the image grayscale value in image reconstruction.

[0081] S2. Establish the objective function of the Tikhonov regularization algorithm:

[0082]

[0083] Derivative the above formula and set the derivative to 0, solve the extreme point of the objective function, and get

[0084] G=(S T S+αI) -1 S T U

[0085] Where α is the regularization parameter and I is the identity matrix.

[0086] S3. In order to improve the accuracy of image reconstruction, the error correction of the solved gray value conductivity distribution vector is performed and the correction formula is established:

[0087] G c =G0+ΔG

[0088] and

[0089] ΔG=(S T S+αI) -1 S T μΔU

[0090] Then the modified formula of Tikhonov regularization algorithm is

[0091] G c =(S T S+αI) -1 S T (U+μΔU)

[0092] Among them, G cis the corrected grayscale value, G0 is the grayscale estimation value solved by regularization (i.e., G obtained in step S2), ΔG is the grayscale error value, μ is the error correction parameter, and ΔU is the difference between the detected boundary voltage value and the actual voltage value set during excitation.

[0093] S4. Use the least squares method to solve the error correction parameter μ.

[0094] First, determine the difference ΔU between the detected boundary voltage value and the actual voltage value set during excitation:

[0095] ΔU=U1-U

[0096] =S(G+ΔG)-U

[0097] =S(S T S+αI) -1 S T (U+μΔU)-U

[0098] Where U1 represents the corrected voltage value.

[0099] Use the above formula to construct the least squares function F(μ) about μ:

[0100] F(μ)=||S(S T S+αI) -1 S T (U+μΔU)-U|| 2

[0101] Derivative the above formula, and set the derivative to 0, solve for μ and get

[0102]

[0103] S5. Perform relative tolerance judgment on the corrected grayscale value. The judgment formula is:

[0104] |G c -G f |≤ε

[0105] Among them, G f represents the grayscale value of the original image model, and ε represents the pre-calculated relative tolerance value; if the above formula is true, the corrected grayscale value image is directly output; if not, the regularization parameter α and the error correction parameter μ are changed, and steps S1 to S5 are repeated until the judgment conditions are met to obtain an accurate grayscale value image.

[0106] The present invention performs image reconstruction through an improved Tikhonov regularization algorithm, thereby obtaining a grayscale value image with high accuracy.

[0107] In step h, the damage distribution image on the radial section of the inspected carbon fiber cable 8 before rotation is taken as the source image A, and the damage distribution image on the radial section of the inspected carbon fiber cable 8 after rotation is taken as the source image B. Multiple angle feature values ​​are extracted from the source image A and the source image B, and then fused to obtain a fused distribution image R with complete damage characteristics.

[0108] The specific steps are as follows: first align the reconstructed source image A and source image B, that is, project the two source images at different angles onto the same plane and align them; smooth the source image, that is, perform a convolution operation on the source image, and use convolution layers with convolution kernels of different sizes to extract features from source image A and source image B from multiple angles to obtain extracted eigenvalues ​​LP_1,…,LP_N; fuse the corresponding eigenvalues ​​of the two images using a weighted average fusion rule to obtain fused eigenvalues ​​LP_Fusion_1,…,LP_Fusion_N, and reconstruct the fused eigenvalues ​​to obtain the fused cable damage image R to achieve accurate damage positioning.

[0109] like Figure 5 As shown, the image reconstruction method of the present invention can obtain an image with high resolution and small artifacts, thereby facilitating accurate judgment of the damage distribution on the radial section of the carbon fiber cable 8.

[0110] The present invention utilizes the principle of electromagnetic tomography to detect damage distribution on a radial cross-section of a carbon fiber cable 8. The principle is as follows: an alternating excitation current is passed through the excitation coils 2-3, generating an alternating excitation magnetic field within the measured space. The presence of conductive or magnetic materials in the measured space alters the distribution of the excitation magnetic field, thereby forming a sensitive field for the distribution of the electrical and magnetic permeability of the measured material space. Detection coils 2-3, located at the boundaries of the measured space, acquire magnetic field distribution information, i.e., "projected" data, through electromagnetic induction. By controlling the excitation unit, the excitation scanning direction of the excitation magnetic field is changed, obtaining detection information from multiple projection directions. After acquiring this information through a data processing circuit, an image reconstruction algorithm is used to reconstruct the distribution of the material within the measured space, including distribution images of the conductive and magnetic materials. Finally, an image feature parameter extraction unit is used to obtain the distribution parameters of the object field.

[0111] The beneficial effects of the method of the present invention for high-altitude carbon fiber cable 8 detection are as follows: by imaging the radial cross-section of the carbon fiber cable 8, the size of the damage can be intuitively distinguished, providing an intuitive and reliable basis for quantitative detection of the damage; the innovative "C"-shaped structure can realize detection position control by the drone 1-1, without the need for manual disassembly, reducing the risk in practical applications; using a stepper motor to control the rotation of the "C-type probe", the system collects comprehensive data, is convenient to write programs, and can realize automatic control; it is a non-contact, non-invasive and harmless detection instrument, which avoids wear between the carbon fiber cable 8 and the instrument and extends the service life of the instrument; it can realize remote control of the imaging system, does not require manual high-altitude operations, and improves the safety of detection.

Claims

1. A high altitude carbon fiber cable detection system, characterized in that: include High-altitude carrying unit, used to carry the detection unit for high-altitude flight; The detection unit is installed on the high-altitude carrying unit and includes a C-shaped frame that can rotate around its own center of circle. A plurality of coils are arranged in an array on the C-shaped frame to generate an excitation magnetic field and detect the induced potential signal generated by the carbon fiber cable; A channel switching unit is used to transmit the excitation signal generated by the lock-in amplifier unit to a certain coil or transmit the induced potential signal detected by the coil to the lock-in amplifier unit; an excitation signal amplifying unit, configured to amplify the excitation signal generated by the lock-in amplifier unit and transmit the amplified signal to the channel switching unit; A lock-in amplifier unit, used for generating an excitation signal and receiving and processing an induced potential signal; a main control unit connected to the channel switching unit, the lock-in amplifier unit, and the image reconstruction unit, and configured to control the channel switching unit, the lock-in amplifier unit, and the image reconstruction unit; as well as An image reconstruction unit is used to reconstruct an image of the conductivity distribution on the radial cross section of the inspected carbon fiber cable using the induced potential signal data obtained through the detection through an image reconstruction algorithm; The detection unit includes a housing, a C-shaped frame and a driving element arranged in the housing. A plurality of coils are evenly arranged around the center of the circle on the inner circle of the C-shaped frame. The C-shaped frame is slidably connected to the housing, and the C-shaped frame is driven by the driving element to rotate around the center of the circle of the C-shaped frame.

2. The high altitude carbon fiber cable detection system according to claim 1 is characterized in that: An arc-shaped slide groove is provided on the C-shaped frame, and the center of the slide groove coincides with the center of the C-shaped frame. A plurality of pulleys are provided on the shell, and the pulleys are installed in the slide groove.

3. The high altitude carbon fiber cable detection system according to claim 1 is characterized in that: Driven teeth are arranged on the outer ring of the C-shaped frame, the driving element is a stepping motor, and a driving wheel is arranged on the rotating shaft of the stepping motor, and the driving wheel is meshed with the driven teeth.

4. The high altitude carbon fiber cable detection system according to claim 1, characterized in that: The high-altitude carrying unit includes a drone, a connecting device is provided on the drone, and the detection unit is provided on the connecting device.

5. A high altitude carbon fiber cable detection method, characterized in that: The high-altitude carbon fiber cable detection system according to any one of claims 1 to 4 is implemented, and the steps include: a. Use the high-altitude carrying unit to carry the detection unit to the location to be tested, and put the C-frame of the detection unit on the carbon fiber cable; b. The control unit controls the lock-in amplifier unit to generate an excitation signal, and controls the channel switching unit to pass the excitation signal into any one of the N coils in the detection unit, so that the coil generates an alternating excitation magnetic field; c. The channel switching unit sequentially selects the other N-1 coils in the detection unit to detect the induced potential signal, and the induced potential signal is fed into the lock-in amplifier unit through the channel switching unit; d. Demodulate the amplitude and phase shift of the induced potential signal from the detected signal through the lock-in amplifier unit, and send the processed result to the main control unit; e. Repeat steps b to d until all N coils have generated an overexcitation magnetic field, obtaining a set of N × (N-1) × 2 detection data. f. Using the obtained test data, the conductivity distribution on the radial cross section of the inspected carbon fiber cable is reconstructed by an image reconstruction algorithm to obtain a damage distribution image on the radial cross section of the inspected carbon fiber cable before rotation; g. Rotate the C-shaped frame of the detection unit 90 degrees and repeat steps b to f to obtain a damage distribution image on the radial cross section of the carbon fiber cable being tested after rotation; h. Perform image fusion on the damage distribution images on the radial cross section of the inspected carbon fiber cable before and after rotation, process the fused images, obtain object field characteristic parameters, and quantitatively analyze the radial cross section damage of the inspected carbon fiber cable.

6. The high altitude carbon fiber cable detection method according to claim 5, characterized in that: The image reconstruction algorithm comprises the following steps: S1. Obtain the boundary voltage value U and sensitivity matrix based on the detection data, and derive G through the linear equation U=SG, where S is the normalized sensitivity matrix and G is the normalized conductivity distribution vector, which represents the image grayscale value in image reconstruction; S2. Establish the objective function of the Tikhonov regularization algorithm: Derivative the above formula and set the derivative to 0, solve the extreme point of the objective function, and get Among them, α is the regularization parameter, I is the identity matrix; S3. Correct the error of the grayscale conductivity distribution vector. The corrected formula after Tikhonov regularization algorithm is: Among them, G c is the grayscale value after correction, μ is the error correction parameter, and ΔU is the difference between the detected boundary voltage value and the actual voltage value set during excitation; S4. Use the least squares method to solve the error correction parameter μ and construct the least squares function F(μ) about μ: Derivative the above formula, and set the derivative to 0, solve for μ and get ； S5. Perform relative tolerance judgment on the corrected grayscale value. The judgment formula is: Among them, G f represents the grayscale value of the original image model, and ε represents the pre-calculated relative tolerance value; if the above formula is true, the corrected grayscale value image is directly output; if not, the regularization parameter α and the error correction parameter μ are changed, and steps S1 to S5 are repeated until the judgment conditions are met to obtain an accurate grayscale value image.

7. The high altitude carbon fiber cable detection method according to claim 5, characterized in that: In step h, the damage distribution image on the radial cross-section of the inspected carbon fiber cable before rotation is taken as the source image A, and the damage distribution image on the radial cross-section of the inspected carbon fiber cable after rotation is taken as the source image B. Feature values ​​of source image A and source image B are extracted at multiple angles and then fused to obtain a fused distribution image R with complete damage characteristics.

Images