Method for detecting and evaluating repairing state of sheet metal shape righting curved surface of aircraft skin

Abstract

The invention provides an aircraft skin metal plate shape righting curved surface repairing state detection and evaluation method, and relates to the technical field of aircraft skin repairing. An actual space coordinate set of pixel points in a repairing area and an actual space coordinate set of pixel points in a peripheral area are obtained through a binocular camera device; based on the actual space coordinate set of the pixel points in the peripheral area, fitting the theoretical space coordinate of each pixel point in the restoration area, obtaining the theoretical space coordinate set of all the pixel points in the restoration area, calculating the distance between each pixel point in the actual space coordinate set of the restoration area and the corresponding point in the theoretical space coordinate set, and calculating the distance between each pixel point in the restoration area and the corresponding point in the theoretical space coordinate set; if the number of the pixel points with the distances within the preset range meets the preset requirement and the maximum distance does not exceed the preset value, the restoration is qualified; the method solves the problem that the aircraft skin repair state cannot be evaluated, and is suitable for detection and evaluation of the aircraft skin sheet metal shape righting curved surface repair state.

Description

Technical Field

[0001] This invention relates to the field of aircraft skin repair technology, and in particular to a method for detecting and evaluating the repair status of aircraft skin sheet metal straightening surfaces. Background Technology

[0002] During aircraft manufacturing, stress concentration during assembly and external forces can cause dents and deformations in the aircraft skin. Conventional repair methods involve hammering the dented area using sheet metal straightening to restore the skin to its original curvature. While existing sheet metal straightening techniques can eliminate visible dents, the lack of standardized reference points means that repair personnel rely on their experience and subjective judgment to remove these defects. Scientific evaluation of the repaired skin's condition is difficult. The repeated occurrence of repaired skin failing inspection, leading to rework and scrap, results in significant waste of human resources and spare parts. Summary of the Invention

[0003] The technical problem solved by this invention is to provide a method for detecting and evaluating the repair status of aircraft skin sheet metal straightening surfaces, thereby solving the problem that the repair status of existing aircraft skin cannot be evaluated.

[0004] The technical solution adopted by this invention to solve the above-mentioned technical problems is: a method for detecting and evaluating the repair status of aircraft skin sheet metal straightening surfaces, comprising the following steps: S1. Photograph the repaired area using a binocular camera device. and its surrounding areas To obtain the pixel coordinates and corresponding depth values ​​of the field of view of the binocular camera device; S2. Using the intrinsic parameter matrix of the binocular camera device, the pixel coordinates and corresponding depth values ​​are converted into spatial coordinates to obtain the repair area. The set of actual spatial coordinates of the middle pixels and surrounding areas The set of actual spatial coordinates of the middle pixels ; S3, based on surrounding area The actual spatial coordinates of pixels in Fit the repair area The theoretical spatial coordinates of each pixel are used to obtain the set of theoretical spatial coordinates of all pixels in the repair area. ; S4, Calculate the repair area actual spatial coordinate set Each pixel in the set of theoretical space coordinates The distance to the corresponding point in the middle; S5. If the number of pixels within the preset distance meets the preset requirements and the maximum distance does not exceed the preset value, the repair is successful; if the number of pixels within the preset distance does not meet the preset requirements or the maximum distance exceeds the preset value, the repair is unsuccessful.

[0005] Furthermore, in S2, the formula for converting pixel coordinates and their corresponding depth values ​​into spatial coordinates is: ,in, Represents pixels The actual spatial coordinates, Represents pixels The corresponding depth value, It is the inverse of the intrinsic parameter matrix. Represents pixels The pixel coordinates.

[0006] Furthermore, in S3, the least squares method is used to fit the actual spatial coordinates of the pixels in the surrounding area to a B-spline surface. The fitting formula is as follows: ,in, Represents pixels Theoretical spatial coordinates Represents the control point vector. express B-spline basis functions in the direction, express The order control parameter of the B-spline basis functions in the direction. express B-spline basis functions in the direction, express The order control parameter of the B-spline basis function in the direction.

[0007] Furthermore, in S4, the formula for calculating distance is: ,in, Indicates distance, Distance calculation symbol, Represents pixels The actual spatial coordinates, Represents pixels Theoretical spatial coordinates.

[0008] Furthermore, the method for detecting and evaluating the repair status of aircraft skin sheet metal straightening surfaces also includes eliminating internal stress on the repaired aircraft skin.

[0009] Furthermore, stress relief includes the following steps: S501. Fix the vibrator to the rigid frame at the edge of the repair area and attach the accelerometer to the center of the repair area. S502: Control the vibrator to perform linear frequency sweep within a preset frequency range, and the acceleration sensor monitors the vibration response in real time. S503. Plot the vibration frequency versus acceleration amplitude curve and identify the resonance peaks and their corresponding frequencies. S504. Based on the resonance peak and its corresponding frequency and amplitude, set the frequency and amplitude of the exciter, perform steady-state vibration treatment, and monitor the resonance frequency drift value and acceleration amplitude change value. When the resonance frequency drift value is greater than or equal to 2Hz and the acceleration amplitude change value is greater than or equal to 5%, and is maintained for more than 1 minute, the internal stress elimination is completed.

[0010] Furthermore, the frequency range of the exciter is set to ±5Hz of the frequency corresponding to the maximum amplitude of the resonance peak, and the amplitude range of the exciter is set to 90% to 95% of the maximum amplitude of the resonance peak.

[0011] Furthermore, the method for detecting and evaluating the repair status of aircraft skin sheet metal straightening curved surfaces also includes displaying unqualified pixels for unqualified aircraft skin. The unqualified pixels are pixels whose actual spatial coordinates are not within a preset range and pixels whose actual spatial coordinates are more than a preset value.

[0012] The beneficial effects of this invention: This invention provides a method for detecting and evaluating the repair status of aircraft skin sheet metal straightening surfaces, which uses a binocular camera device to capture images of the repair area. and its surrounding areas The pixel coordinates and corresponding depth values ​​of the field of view of the binocular camera device are obtained. Then, using the intrinsic parameter matrix of the binocular camera device, the pixel coordinates and corresponding depth values ​​are converted into spatial coordinates, thereby obtaining the repair area. The set of actual spatial coordinates of the middle pixels and surrounding areas The set of actual spatial coordinates of the middle pixels Based on the surrounding area The actual spatial coordinates of pixels in Fit the repair area The theoretical spatial coordinates of each pixel are used to obtain the set of theoretical spatial coordinates of all pixels in the repair area. Calculate the repair area actual spatial coordinate set Each pixel in the set of theoretical space coordinates The repair is considered successful if the number of pixels within the preset distance range meets the preset requirements and the maximum distance does not exceed the preset value; otherwise, the repair is considered unsuccessful. This solves the problem of the inability to assess the repair status of existing aircraft skin panels. For successfully repaired aircraft skin panels, internal stress relief is also performed to ensure the long-term reliability of the repaired panels. Attached Figure Description

[0013] Figure 1 This is a flowchart illustrating a method for detecting and evaluating the repair status of aircraft skin sheet metal straightening surfaces provided by the present invention. Figure 2 This is a schematic diagram of the repair area and its surrounding area captured by the binocular camera device provided by the present invention, wherein, Indicates the area to be repaired. This indicates the area surrounding the area to be repaired. Detailed Implementation

[0014] This invention addresses the problem of the inability to assess the repair status of existing aircraft skin panels by providing a method for detecting and assessing the repair status of corrective curved surfaces on aircraft skin panels, enabling troubleshooting personnel to accurately determine whether the aircraft skin panel repair is up to standard.

[0015] like Figure 1 As shown, the present invention provides a method for detecting and evaluating the repair status of aircraft skin sheet metal straightening surfaces, comprising the following steps:

[0016] S1. Photograph the repaired area using a binocular camera device. and its surrounding areas This allows us to obtain the pixel coordinates and corresponding depth values ​​of the field of view of the binocular camera device.

[0017] Specifically, the restoration area and its surrounding area are photographed using a binocular camera device, such as... Figure 2 As shown, Indicates the area to be repaired. This indicates the area surrounding the area to be repaired.

[0018] S2. Using the intrinsic parameter matrix of the binocular camera device, the pixel coordinates and corresponding depth values ​​are converted into spatial coordinates to obtain the repair area. The set of actual spatial coordinates of the middle pixels and surrounding areas The set of actual spatial coordinates of the middle pixels .

[0019] Specifically, the formula for converting pixel coordinates and their corresponding depth values ​​into spatial coordinates is as follows: ,in, Represents pixels The actual spatial coordinates, Represents pixels The corresponding depth value, It is the inverse of the intrinsic parameter matrix. Represents pixels Pixel coordinates, obtain The actual spatial coordinates of each pixel in the image form the repair area. The set of actual spatial coordinates of the middle pixels and obtain The actual spatial coordinates of each pixel in the image, and the surrounding area. The set of actual spatial coordinates of the middle pixels .

[0020] S3, based on surrounding area The actual spatial coordinates of pixels in Fit the repair area The theoretical spatial coordinates of each pixel are used to obtain the set of theoretical spatial coordinates of all pixels in the repair area. .

[0021] Specifically, the least squares method is used to fit the actual spatial coordinates of the pixels in the surrounding area to a B-spline surface. The fitting formula is as follows: ,in, Represents pixels Theoretical spatial coordinates Represents the control point vector. express B-spline basis functions in the direction, express The order control parameter of the B-spline basis functions in the direction. express B-spline basis functions in the direction, express The order control parameter of the B-spline basis function in the direction.

[0022] S4, Calculate the repair area actual spatial coordinate set Each pixel in the set of theoretical space coordinates The distance to the corresponding point in the middle.

[0023] Specifically, the formula for calculating distance is: ,in, Indicates distance, Distance calculation symbol, Represents pixels The actual spatial coordinates, Represents pixels The theoretical spatial coordinates are used to calculate the distance corresponding to each pixel.

[0024] S5. If the number of pixels within the preset distance meets the preset requirements and the maximum distance does not exceed the preset value, the repair is successful; if the number of pixels within the preset distance does not meet the preset requirements or the maximum distance exceeds the preset value, the repair is unsuccessful.

[0025] Specifically, the overall repair status is verified by the number of pixels within a preset range that meet the preset requirements, and the local repair status is verified by the maximum distance not exceeding the preset value.

[0026] Specifically, internal stress relief is performed on the repaired aircraft skin. Internal stress relief includes the following steps:

[0027] S501. Fix the vibrator to the rigid frame at the edge of the repair area and attach the accelerometer to the center of the repair area.

[0028] S502: Control the vibrator to perform linear frequency sweep within a preset frequency range (50 Hz to 500 Hz), and the acceleration sensor monitors the vibration response, i.e. the acceleration amplitude, in real time.

[0029] S503. Plot the vibration frequency versus acceleration amplitude curves and identify the resonance peaks and their corresponding frequencies.

[0030] S504. Based on the resonance peak and its corresponding frequency and amplitude, set the frequency and amplitude of the exciter, perform steady-state vibration treatment, and monitor the resonance frequency drift value and acceleration amplitude change value. When the resonance frequency drift value is greater than or equal to 2Hz and the acceleration amplitude change value is greater than or equal to 5%, and is maintained for more than 1 minute, the internal stress elimination is completed.

[0031] The frequency range of the exciter is set to ±5Hz of the frequency corresponding to the maximum amplitude of the resonance peak, and the amplitude range of the exciter is set to 90% to 95% of the maximum amplitude of the resonance peak. The first threshold can be 5Hz.

[0032] In this invention, internal stress relief employs a cold-working process, preventing new thermal deformation or oxidation of the skin due to heating. This perfectly maintains the surface curvature achieved in the previous process. The entire process is typically completed within 20 minutes, with low energy consumption. The stress relief effect is determined by objective data changes in resonance frequency and amplitude, eliminating the uncertainty of human experience-based judgment. This forms an integrated automated workstation for "detection-evaluation-stress relief," significantly improving the overall quality and efficiency of aircraft skin repair.

[0033] Specifically, for aircraft skin that has failed repair, the system displays defective pixels. These defective pixels are those where the distance between the actual and theoretical spatial coordinates is outside a preset range, and those where the distance exceeds a preset value. This is to guide troubleshooting personnel in performing secondary repairs.

[0034] This invention can compare the repaired coordinates of the actual deformed and dented locations of the skin with the theoretical coordinates (coordinates before deformation), enabling pixel-level quantitative evaluation. Skin that meets the preset repair criteria is then sent to subsequent processing steps without rework. For skin that does not meet the criteria, it can pinpoint the precise coordinate-level locations and quantitatively display the deviation direction and value for each coordinate position, allowing the repaired skin to achieve millimeter-level repair accuracy. Compared to existing visual judgment, this greatly improves the reliability and efficiency of inspection and evaluation, and avoids the uncontrollability of relying on subjective human factors.

Claims

1. An aircraft skin sheet metal ortho-curvature repair status detection and evaluation method, characterized in that, The method comprises the following steps: S1, taking the repair area by binocular camera device and the surrounding area , obtaining the pixel coordinates and corresponding depth values in the field of view of the binocular camera device; S2, converting the pixel coordinates and the corresponding depth values into space coordinates through an intrinsic matrix of the binocular camera device, so as to obtain the repair region actual space coordinate set of the middle pixel point and the peripheral region actual space coordinate set of the middle pixel point ; S3, based on surrounding area The actual spatial coordinates of pixels in Fit the repair area The theoretical spatial coordinates of each pixel are used to obtain the set of theoretical spatial coordinates of all pixels in the repair area. ; S4, calculating the repair region the actual spatial coordinate set the distance between each pixel point in the actual spatial coordinate set and the corresponding point in the theoretical spatial coordinate set the distance between each pixel point in the actual spatial coordinate set and the corresponding point in the theoretical spatial coordinate set S5, if the number of pixel points within the preset range meets the preset requirement and the maximum distance does not exceed the preset value, the repair is qualified; if the number of pixel points within the preset range does not meet the preset requirement or the maximum distance exceeds the preset value, the repair is unqualified.

2. The method of claim 1, wherein the method further comprises: In S2, the formula for converting pixel coordinates and their corresponding depth values ​​into spatial coordinates is: ,in, Represents pixels The actual spatial coordinates, Represents pixels The corresponding depth value, It is the inverse of the intrinsic parameter matrix. Represents pixels The pixel coordinates.

3. The method of claim 2, wherein the method further comprises: In S3, the least squares method is used to fit the actual spatial coordinates of the pixels in the surrounding area to a B-spline surface. The fitting formula is: ,in, Represents pixels Theoretical spatial coordinates Represents the control point vector. express B-spline basis functions in the direction, express The order control parameter of the B-spline basis functions in the direction. express B-spline basis functions in the direction, express The order control parameter of the B-spline basis function in the direction.

4. The method of claim 3, wherein the method further comprises: In S4, the formula for calculating distance is: ,in, Indicates distance, Distance calculation symbol, Represents pixels The actual spatial coordinates, Represents pixels Theoretical spatial coordinates.

5. The method of claim 1, wherein the method further comprises: determining a repair status of the aircraft skin panel based on the comparison of the first and second sets of data. The method further comprises internal stress relief of the repaired aircraft skin. ​ 6. The method of claim 5, wherein the method further comprises: The internal stress relief comprises the following steps: S501, fixing the exciter on the rigid framework at the edge of the repair area, and adsorbing the acceleration sensor at the center of the repair area; S502, controlling the exciter to perform linear sweep in a preset frequency range, and monitoring the vibration response in real time by the acceleration sensor; S503, drawing a vibration frequency and acceleration amplitude curve, and identifying the resonance peak and the corresponding frequency; S504, setting the frequency and amplitude of the exciter according to the resonance peak, the corresponding frequency and amplitude, performing steady-state vibration processing, and monitoring the resonance frequency drift value and the acceleration amplitude change value, when the resonance frequency drift value is greater than or equal to 2 Hz and the acceleration amplitude change value is greater than or equal to 5%, and the values are maintained for more than 1 minute, the internal stress relief is completed.

7. The method for detecting and evaluating the repair status of aircraft skin sheet metal straightening surfaces according to claim 6, characterized in that, The frequency range of the exciter is set to be the maximum amplitude of the resonance peak ± 5 Hz, and the amplitude range of the exciter is set to be 90% to 95% of the maximum amplitude of the resonance peak.

8. The method for detecting and evaluating the repair status of aircraft skin sheet metal straightening surfaces according to claim 1, characterized in that, The method further comprises displaying unqualified pixel points of the unqualified repaired aircraft skin, wherein the unqualified pixel points are pixel points whose actual spatial coordinates and theoretical spatial coordinates are not within the preset range and pixel points whose actual spatial coordinates and theoretical spatial coordinates exceed the preset value.

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