Apparatus and method for aircraft cabin section inner surface corrosion defect detection

Abstract

The application is a device and method for detecting surface corrosion defects in an aircraft cabin section. The SRI7140 three-dimensional laser profilometer continuously outputs line profile data. The upper computer system constructs a three-dimensional point cloud according to the movement position corresponding to each line profile, and sequentially performs three-dimensional point cloud preprocessing, local health reference surface fitting, signed height residual calculation, suspected corrosion area screening and local review. For the suspected corrosion area with consistent review results, after determining the independent corrosion area, the corrosion maximum depth, corrosion average depth, corrosion projection area and corrosion volume loss are calculated, and the corrosion area position, projection boundary, type, three-dimensional appearance and quantitative parameters can be output. A folding telescopic tension compensation mechanism is arranged above the telescopic arm, so that the telescopic elastic tension rod is elongated synchronously with the extension of the telescopic arm, and a reverse compensation torque is formed through the moving table, so as to reduce the overall elastic deformation of the reconfigurable flexible mechanical arm and the measurement posture deviation of the profilometer.

Description

Technical Field

[0001] This invention relates to the field of corrosion detection technology, and more specifically, to an apparatus and method for detecting corrosion defects on the inner surface of aircraft cabin sections. Background Technology

[0002] As a crucial structural component of an aircraft, the cabin section bears immense lift and loads during takeoff. Its primary manufacturing materials are aluminum alloys and magnesium alloys. Aircraft located in coastal areas, operating for extended periods in environments characterized by high temperatures, high humidity, and salt spray, experience severe corrosion of their cabin structures. This corrosion typically manifests as pitting, spalling, and crack-like corrosion morphologies on the inner surfaces of the cabin sections. Furthermore, corrosion is a prevalent and wear-and-tear failure in older aircraft, characterized by its wide distribution and deep penetration. These corrosion phenomena pose a serious threat to flight safety. At best, it increases flight noise, affecting passenger comfort; at worst, it can lead to cabin structure failure, weakened cabin sealing, and malfunctions in the cabin's electrical system, potentially triggering major safety incidents.

[0003] Currently, the main methods for detecting corrosion on the internal surfaces of aircraft cabins include manual visual inspection, industrial endoscopy, ultrasonic testing, eddy current testing, and traditional image processing. Among these, manual visual inspection is the most basic. Inspectors directly observe key areas such as the skin, fasteners, and welds on the internal surface of the cabin with the naked eye or simple magnifying tools, relying on experience to judge the presence and severity of corrosion. This method is a contact-based manual inspection, highly subjective, and prone to missing minor pitting corrosion or corrosion inside bolt holes. Furthermore, it cannot quantitatively analyze key parameters such as corrosion depth and area. In addition, the cabin space is confined and poorly lit, making operation difficult and inefficient. Industrial endoscopy involves inserting a probe-equipped inspection device through the cabin inspection port, transmitting internal images to an external display screen for visual inspection. However, its field of view is limited by the probe diameter and length, easily creating blind spots on complex curved surfaces or narrow areas. It also only provides two-dimensional images, unable to obtain three-dimensional dimensional data of the corroded area, resulting in weak quantitative analysis capabilities. Simultaneously, precise control of the probe's attitude is required, demanding extremely high operator skills. Ultrasonic testing utilizes the propagation characteristics of ultrasonic waves in metallic materials to identify material defects caused by corrosion through reflected signals. This method typically requires pre-cleaning the test surface and applying a coupling agent, making it cumbersome and environmentally polluting within the compartment. It also has poor adaptability to non-planar areas such as flanges and joint corners, and its accuracy in identifying localized corrosion such as pitting and spalling is low. Eddy current testing uses high-frequency alternating current to create an alternating magnetic field, identifying corrosion defects by utilizing changes in induced eddy currents within the metal. Its effective detection range is mostly limited to the surface and near the surface. The results of this method are usually displayed as electrical signals such as impedance changes, amplitude changes, or phase changes, which are not intuitive and require the inspector to interpret them based on probe scanning position and experience. In the inner surface areas of the compartment around structures such as rivets, fasteners, joints, and holes, probe posture, lift-off distance, surface curvature, and adjacent metal components can all affect the detection signal, easily leading to difficulties in signal interpretation. Furthermore, eddy current testing cannot directly output complete three-dimensional morphology, actual boundaries, depth, area, and volume parameters of corrosion defects, which is detrimental to defect location, determination of grinding areas, and re-inspection comparison during subsequent maintenance. Traditional image processing methods acquire images through cameras and extract corrosion features using algorithms such as edge detection and threshold segmentation. These methods are extremely sensitive to lighting conditions. Uneven lighting within the compartment can lead to high image noise, making it difficult to distinguish the corrosion area from the background. Furthermore, they can only process two-dimensional information and cannot accurately identify multiple types of corrosion.

[0004] The detection technologies disclosed in the relevant patents mostly revolve around the optimization of traditional methods: Patent application publication number CN109658389A discloses a method for binarizing corrosion images, which improves the Otsu algorithm to optimize the grayscale image processing effect of corrosion morphology and reduce noise interference, but it still relies on two-dimensional images and cannot obtain three-dimensional corrosion data, and has high requirements for image quality; Chinese patent application publication number CN118446987A discloses a visual detection method for corrosion on the inner surface of a compartment in a narrow and confined space, which improves the detection accuracy by improving the YOLOv5s model, but it still belongs to the category of two-dimensional machine vision detection, mainly relying on image grayscale, color, texture and edge features to identify corrosion areas. The confined space inside aircraft compartments is prone to interference from localized shadows, reflections, uneven brightness, and shadows and seam textures caused by structures such as rivets. Changes in lighting directly affect the image feature extraction results, leading to insufficient stability in distinguishing between corroded areas and the metallic background. At the same time, two-dimensional images can only obtain the position and outline of the corroded area in the image plane, and cannot directly obtain the height difference of the corroded depression relative to the inner surface of the compartment. Therefore, it is difficult to achieve three-dimensional quantitative detection of corrosion depth, area, and volume.

[0005] Existing structured light inspection platforms mainly include online line laser contour inspection platforms, desktop surface structured light 3D scanning platforms, handheld 3D scanning platforms, circular structured light internal surface inspection platforms, and robot-mounted structured light scanning platforms. These platforms are primarily used for inspecting open surfaces, regular planes, regular curved surfaces, pipe inner surfaces, or production line parts. Aircraft cabin inspection requires access through dimensionally limited inspection holes. The internal space is long and enclosed, with rivets, fasteners, seams, reinforcing ribs, and holes distributed around its inner surface, creating localized obstructions. Furthermore, the inner surface is an irregular and complex curved surface, making it difficult for ordinary structured light platforms to completely cover and scan it. When a robot is mounted on a structured light beam, it is further affected by the weight of the inspection head, cable tension, and end-effector deflection, leading to changes in the measurement distance and the incident angle of the line structured light. Therefore, existing structured light inspection platforms cannot be directly applied to corrosion inspection of aircraft cabin inner surfaces.

[0006] Therefore, there is a need to invent a novel three-dimensional structured light device and method for detecting corrosion on the inner surface of aircraft cabin sections, which can perform high-precision three-dimensional detection of corrosion on the inner surface of cabin sections, simultaneously acquire the two-dimensional morphology and three-dimensional dimensional parameters of corrosion, effectively resist the influence of cabin lighting interference and structural complexity, so as to meet engineering requirements such as quantitative corrosion assessment and maintenance accuracy control. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide an apparatus and method for detecting corrosion defects on the inner surface of aircraft cabin sections.

[0008] The technical solution of the present invention to solve the aforementioned technical problem is: In a first aspect, the present invention provides an apparatus for detecting corrosion defects on the inner surface of an aircraft cabin section. The apparatus includes an SRI7140 three-dimensional laser profile measuring instrument (1), a reconfigurable flexible robotic arm (2), an Ethernet communication module (3), a host computer system (4), an omnidirectional mobile positioning platform (5), and a folding telescopic tension compensation mechanism (6). The omnidirectional mobile positioning platform (5) is used to carry the apparatus and move and position it to the outside of the inspection port of the aircraft cabin section to be tested. The reconfigurable flexible robotic arm (2) is used to carry the SRI7140 three-dimensional laser profile measuring instrument (1) through the inspection port into the interior of the aircraft cabin section to be tested, and to adjust the SRI7140 three-dimensional laser profile measuring instrument (1). 1) The detection position and detection posture; the folding telescopic tension compensation mechanism (6) is set above the outside of the telescopic arm (22) of the reconfigurable flexible robotic arm (2) to form a reverse compensation torque when the telescopic arm (22) extends; the Ethernet communication module (3) is connected to the SRI7140 three-dimensional laser profile measuring instrument (1), the controller of the reconfigurable flexible robotic arm (2) and the host computer system (4) respectively; the host computer system (4) is used to send acquisition instructions and motion instructions, receive line profile data and motion feedback information, construct three-dimensional point cloud according to the line profile data and its corresponding motion position, and complete the scanning path generation, corrosion defect identification, corrosion parameter calculation and detection result output.

[0009] The reconfigurable flexible robotic arm (2) includes a base rotation joint (21), a telescopic arm (22), a swing arm (23), and a rotation attitude joint (24); the base rotation joint (21) is used to adjust the overall orientation of the reconfigurable flexible robotic arm (2); the telescopic arm (22) is used to extend and retract along the longitudinal direction of the aircraft compartment to be tested; the swing arm (23) and the rotation attitude joint (24) are used to adjust the detection attitude; the SRI7140 three-dimensional laser profile measuring instrument (1) is fixed to the end of the rotation attitude joint (24) by a rigid clamp, and its detection window faces the inner surface of the aircraft compartment to be tested; The folding telescopic tension compensation mechanism (6) includes a fixed platform (61), a movable platform (62), and a telescopic elastic tension rod (63). The fixed platform (61) is located at the top of one end of the telescopic arm (22) near the base rotation joint (21), and the movable platform (62) is located at the top of one end of the telescopic arm (22) near the swing arm (23). The two ends of the telescopic elastic tension rod (63) are connected to the fixed platform (61) and the movable platform (62) respectively. When the telescopic arm (22) extends, the movable platform (62) moves synchronously with the end of the telescopic arm (22), and the telescopic elastic tension rod (63) extends accordingly, applying the reverse compensation torque to the telescopic arm (22) through the movable platform (62). When the telescopic arm (22) is in a fully retracted state, the folding telescopic tension compensation mechanism (6) is retracted above the telescopic arm (22).

[0010] The vertical distance between the lower edge of the retractable elastic tension rod (63) and the upper surface of the telescopic arm (22) is defined as the vertical clearance. The vertical net distance It is 10–30 mm.

[0011] Further, let the extension length of the telescopic arm (22) relative to the fully retracted state be... The folding telescopic tension compensation mechanism (6) extends to a length of The reverse compensation torque formed at that time is The reconfigurable flexible robotic arm (2) extends to a length of The overall downward torque at that time is The reverse compensation torque and the overall droop torque satisfy the following: in, The compensation coefficient represents the proportion of the reverse compensation torque to the overall drooping torque, and .

[0012] The device is used to measure the corrosion status of the inner surface of aircraft compartments in real time under scenarios such as maintenance and periodic inspection, and achieves high-precision corrosion depth monitoring. It is compatible with corrosion detection of the inner surface of metals such as aluminum alloy and titanium alloy in aircraft compartments, and does not require surface pretreatment or coupling agent.

[0013] Secondly, the present invention provides a method for detecting corrosion defects on the inner surface of an aircraft cabin section, employing a device including an SRI7140 three-dimensional laser profile measuring instrument (1), a reconfigurable flexible robotic arm (2), an Ethernet communication module (3), a host computer system (4), an omnidirectional mobile positioning platform (5), and a folding telescopic tension compensation mechanism (6). The reconfigurable flexible robotic arm (2) includes a base rotation joint (21), a telescopic arm (22), a swing arm (23), and a rotational attitude joint (24). The method includes the following steps: Step 1: Position the device outside the inspection hole of the aircraft section to be tested, determine the coordinate transformation parameters between the SRI7140 three-dimensional laser profile measuring instrument (1), the reconfigurable flexible robotic arm (2) and the aircraft section to be tested, and use the physical coordinate system of the section as the unified reference coordinate system for the positioning of the corrosion area. Step 2: Determine the detection area boundary of the inner surface of the aircraft cabin section to be tested, divide the detection area into mutually parallel and partially overlapping scanning bands, generate an initial full-coverage scanning path, and set the compensation parameters of the folding telescopic tension compensation mechanism (6). Step 3: The reconfigurable flexible robotic arm (2) carries the SRI7140 three-dimensional laser profile measuring instrument (1) to collect line profile data according to the initial full-coverage scanning path. The host computer system (4) constructs the initial full-coverage original three-dimensional point cloud based on the line profile data and its corresponding motion position, checks the integrity of the initial full-coverage original three-dimensional point cloud, and performs local supplementary scanning on the incomplete areas of the point cloud. Step 4: Perform statistical filtering, fine registration, fusion, voxel downsampling, and smoothing on the initial full-coverage original 3D point cloud and the locally supplemented scanned point cloud in sequence to obtain the preprocessed 3D point cloud; Step 5: Fit a local health reference plane to the preprocessed 3D point cloud to predict the surface height when no corrosion occurs. Screen suspected corrosion areas based on the inward indentation depth of the point cloud points relative to the local health reference plane. Perform local verification scans on the suspected corrosion areas. Point cloud points in the suspected corrosion areas with consistent verification results whose inward indentation depth exceeds a preset initial screening threshold are identified as corrosion points. Based on the spatial adjacency relationship between the point cloud points, the corrosion points are aggregated into independent corrosion areas. Calculate the corrosion parameters of each independent corrosion area and determine the corrosion type to generate detection results.

[0014] Further, in step two, the lateral width of the detection area is denoted as... The effective measurement width of the SRI7140 three-dimensional laser profile measuring instrument (1) is denoted as... Let the step size coefficient be denoted as The range of values ​​for the step size coefficient is: ; Lateral step size between adjacent scan bands for: Overlap width between adjacent scan bands for: when At that time, the number of scan strips required to complete full coverage of the detection area. for: in, Indicates rounding up; when the lateral width of the detection area is not greater than the effective measurement width, the number of scan bands... The value is 1.

[0015] Further, in step three, scanning is performed sequentially according to the scanning tape number. When collecting each line contour, the corresponding scanning tape number, timestamp, and real-time extension amount of the telescopic arm (22) are recorded. The angles of the base rotation joint (21), the swing angle of the swing arm (23), and the angle of the rotation attitude joint (24), which are locked during the collection of this scanning tape, are associated with and saved with the scanning tape number. The sampling points of each line contour are converted to the physical coordinate system of the compartment according to the coordinate transformation parameters obtained in step one. If a point cloud point exists and its height value is within the preset height threshold range, it is recorded as a valid point. The number of valid point cloud points in the area used to check the integrity of the point cloud is recorded as... The theoretical number of sampling points determined based on the sampling parameters is denoted as... effective point ratio for: Among them, when When this occurs, the corresponding region is determined to be an incomplete region of the point cloud; let... and The scan is indexed and satisfies When the incomplete point cloud region is located only within a single scan band, the center line of that scan band is used as the local supplementary scan center line; when the incomplete point cloud region spans two or more scan bands, the two scan bands with the smallest and largest numbers are respectively denoted as... and The lateral positions of the centerlines of the two are respectively denoted as and The lateral position of the center line of the local supplementary scan for: One or more local supplementary scan bands are generated based on the local supplementary scan center line, so that the local supplementary scan range covers all scan bands involved in the incomplete area of ​​the point cloud, thereby obtaining a local supplementary scan point cloud.

[0016] Furthermore, in step five, highly continuous point cloud points are selected from the preprocessed 3D point cloud, and the local health reference surface is fitted using the least squares method: in, , The planar coordinates of the selected point cloud points. For the local health reference plane at The predicted height at that location and These respectively represent the local health reference plane along... direction and Rate of change of height in direction This represents the predicted height at the local coordinate origin; Let the physical coordinate system of the compartment be... The positive axis points from the bulkhead material towards the interior space. For the point cloud point index, the first The coordinates of the point cloud points are as follows Its signed height residual relative to the local health reference surface for: Corresponding inward concavity depth for: The preset initial screening threshold is determined in advance based on the height residual fluctuation range of the local health reference surface and the minimum corrosion depth of concern; when the inward indentation depth of the point cloud point exceeds the preset initial screening threshold and its connectivity reaches the preset minimum area, the corresponding area is marked as the suspected corrosion area. The local verification scan covers the scan band containing the suspected corrosion area and uses the same acquisition parameters as the initial full-coverage scan. When the suspected corrosion area is located within a single scan band, the center line of that scan band is used as the center line of the local verification scan. When the suspected corrosion area spans two or more scan bands, the two scan bands with the smallest and largest numbers are respectively denoted as... and The lateral positions of the centerlines of the two are respectively denoted as and The lateral position of the center line of the local verification scan for: When the lateral range of the suspected corrosion area exceeds the effective measurement width of a verification scan band, the verification scan bands are added to both sides according to the lateral step distance in step two, based on the local verification scan center line, until the suspected corrosion area is covered. Compare the spatial location, local three-dimensional morphology, and maximum depression depth of the suspected corrosion area in the initial scan and the local verification scan; when the results of the two valid scans are consistent within a preset repeatability range, the suspected corrosion area is retained; when the point cloud of the local verification scan is incomplete, a local supplementary scan is performed according to step three, and this local verification scan is not included in the consistency comparison; when the difference between the results of the two valid scans exceeds the preset repeatability range, another local verification scan is performed; if the results of multiple valid scans are still inconsistent, the corresponding area is marked as a data inconsistency area to be verified. For the suspected corrosion areas with consistent verification results, highly continuous point cloud points are selected to fit the local healthy reference surface. The inward concavity depth of each point cloud point is calculated according to the calculation method of the signed height residual and the inward concavity depth. Point cloud points whose inward concavity depth exceeds the preset initial screening threshold are identified as corrosion points.

[0017] Furthermore, based on the spatial adjacency relationship between point cloud points, the eroded points are aggregated into the independent eroded regions; let... For indexing eroded regions, the first... The set of indexes of point cloud points contained in an independent erosion region is denoted as . ,use The method extracts the first The projected boundaries of individual corrosion regions on the local health reference plane are denoted as... The The method is used to obtain the actual non-convex projected boundary of the independent corrosion region, avoiding incorrect connection of boundary depressions or adjacent independent corrosion regions; the first Number of point cloud points contained in an individual corrosion region for: The first Maximum corrosion depth of each independent corrosion zone for: Average corrosion depth for: Corrosion Projected Area for: Let the first The weight of the projected area of ​​each point cloud point on the local health reference plane is: Then the corrosion volume loss for: Corrosion center location for: in, Determined based on point cloud sampling interval or local grid area; For the first The coordinate vectors of the corrosion points in the physical coordinate system of the compartment.

[0018] Furthermore, the projected boundary The perimeter is recorded as The first The boundary roundness of each independent corrosion zone for: in, The closer it is to 1, the stronger the projection boundary. The closer it is to a circle; Establish the projection boundary within the local health reference plane. The minimum area circumscribed rectangle is denoted by its long side and short side as follows. and , extension ratio Used to characterize the first The extent to which an independent corrosion zone extends in a single direction is: Given relative depth coefficient ,and Deep area proportion This indicates that the inward depression depth of the corrosion point is not less than The proportion of point cloud points is as follows: in, This is an indicator function that takes the value 1 if the condition is true, and 0 otherwise.

[0019] The first The corrosion type of each independent corrosion zone is denoted as Pitting corrosion, exfoliation, and crack corrosion are respectively denoted as... , and The corrosion type is determined according to the following formula: in, The threshold for the crack-like corrosion extension ratio. This represents the upper limit of roundness for crack-like corrosion. This represents the upper limit of the pitting projection area. This is the lower limit for pitting roundness. The upper limit of the proportion of pitting corrosion deep area; the above threshold is determined based on the detection specifications, the material type of the aircraft compartment and the statistical results of the three types of corrosion samples pre-marked, and is stored in the host computer system (4); For the first type of corrosion determined to be crack-like corrosion Each independent eroded region will define the projected boundary. Upper The discrete boundary points are denoted as... , to project the boundary The total number of discrete boundary points included is denoted as Among all the discrete boundary points, select the two boundary points with the largest Euclidean distance, and normalize the direction of the line connecting the two points to obtain the unit vector of the main extension direction. The unit normal vector of the local health reference surface is denoted as... ,Will and The cross product result, after normalization, yields a unit vector perpendicular to the main extension direction within the local health reference plane. The length of the crack-like corrosion. and maximum width They are respectively: in, This represents the transpose of a vector.

[0020] Furthermore, the method of the present invention for detecting corrosion defects on the inner surface of aircraft compartments can be used for corrosion surveys of aircraft compartments, verification of repair effects after maintenance, and prediction of potential corrosion hazards after compartment assembly, providing data support for compartment structural safety assessment and intelligent maintenance decision-making.

[0021] The object of the present invention is the inner surface of an aircraft cabin section, and the object of the inspection is the corrosion defects on the inner surface; rivets, fasteners, seams and holes are only used to characterize the complex structural environment of the inner surface of the cabin section and its surrounding inspection area, and are not considered as independent inspection objects.

[0022] The present invention also protects a computer-readable storage medium having a computer program stored thereon that, when executed by a processor, can implement the steps of the method.

[0023] Furthermore, the processor can output a detection report, which includes information on the aircraft section under test and the detection area, scanning parameters, overall three-dimensional morphology, corrosion area number, corrosion area projection boundary, corrosion center location, corrosion type, maximum corrosion depth, average corrosion depth, corrosion projection area, corrosion volume loss, crack corrosion length and maximum width, local three-dimensional morphology map, corrosion depth distribution map, and information on the area to be reviewed.

[0024] Compared with the prior art, the beneficial effects of the present invention are: 1. Capable of three-dimensional quantitative detection of corrosion defects on the inner surface of aircraft compartments. Traditional visual inspection and industrial endoscopy rely primarily on personnel observing corrosion contours and surface conditions, making it difficult to directly obtain parameters such as corrosion depth, area, and volume. While traditional two-dimensional image inspection methods can identify the location and contour of corrosion areas within the image plane, they cannot reflect the true depth of corrosion defects relative to the inner surface of the compartment. This invention utilizes an SRI7140 3D laser contour measuring instrument to continuously output line contour data. The host computer system constructs a 3D point cloud based on the motion positions corresponding to each line contour and sequentially performs 3D point cloud preprocessing, local health reference surface fitting, signed height residual calculation, suspected corrosion area screening, and local verification. For suspected corrosion areas with consistent verification results, after further processing to form independent corrosion areas, the maximum corrosion depth, average corrosion depth, corrosion projected area, and corrosion volume loss are calculated. For crack-like corrosion areas, the crack length and maximum width are further calculated. Thus, this invention can output the location, projected boundary, type, 3D morphology, and quantitative parameters of corrosion areas, providing a basis for determining the repair scope and subsequent re-inspection.

[0025] 2. The test results are more intuitive, making it easier to locate defects and make repair decisions.

[0026] Ultrasonic testing typically requires cleaning the test surface and applying coupling agent. The confined space inside the cabin makes probe placement and coupling difficult. Eddy current testing results usually manifest as changes in electrical signals such as impedance, amplitude, or phase, requiring operators to interpret them based on probe scanning position and experience. The results are less intuitive than 3D point clouds and cannot directly provide the true boundaries, depth, and volume of the corroded area. This invention uses an omnidirectional mobile positioning platform to move the testing device to the aircraft cabin section under test. A reconfigurable flexible robotic arm carries an SRI7140 3D laser profilometer into the cabin and collects line profile data along the scanning path. The host computer system then displays the point cloud, calculates corrosion depth, corrosion projected area, and corrosion volume loss. Thus, the test results are no longer limited to signal curves, 2D images, or manual records, but instead generate a 3D morphological map of the corroded area, its projected boundary, center position, and quantitative parameters. This allows maintenance personnel to visually see the location, extent, and degree of corrosion, facilitating the determination of repair scope and comparison for re-inspection.

[0027] 3. Capable of corrosion detection in the confined space of an aircraft cabin.

[0028] Aircraft cabin interiors suffer from limitations such as restricted access port sizes, narrow and elongated internal spaces, difficulty in manual entry, and obstructions from internal structures. Fixed inspection platforms and manually operated handheld inspection equipment struggle to achieve continuous coverage inspections. This invention utilizes an omnidirectional mobile positioning platform for external movement and positioning of the inspection device. A reconfigurable flexible robotic arm then carries the SRI7140 3D laser profilometer into the cabin through the access port. A base rotation joint adjusts the overall orientation, a telescopic arm extends and retracts along the cabin's depth, and a swing arm and rotational attitude joint adjust the inspection posture, enabling the SRI7140 3D laser profilometer to continuously scan the inspection area. This reduces the risk of missed inspections due to difficulties in manual entry and blind spots in two-dimensional vision.

[0029] 4. It can reduce the impact of end-effector posture offset on measurement results during the telescopic scanning process of a reconfigurable flexible robotic arm.

[0030] During inspection inside the compartment, the end-effector load formed by the SRI7140 3D laser profilometer, rigid fixture, swing arm, rotary attitude joint, and connecting cables acts on the reconfigurable flexible robotic arm, causing elastic deformation. The bending deflection of the telescopic arm is particularly significant, ultimately leading to a shift in the end-effector position and orientation. This shift alters the measurement distance between the SRI7140 3D laser profilometer and the interior surface of the compartment, as well as the incident angle of the line structured light, affecting the positional consistency and high repeatability of the line profile data. This invention incorporates a folding telescopic tension compensation mechanism above the telescopic arm, allowing the retractable elastic tension rod to extend synchronously with the telescopic arm. A counter-compensation torque is generated via a moving stage to reduce the overall elastic deformation of the reconfigurable flexible robotic arm and the measurement attitude deviation of the SRI7140 3D laser profilometer.

[0031] 5. It can improve the integrity of the three-dimensional point cloud on the inner surface of the surrounding compartments of complex structures.

[0032] The inner surfaces of aircraft compartments contain rivets, fasteners, seams, holes, and partially obstructed areas. Structural protrusions, obstructions, localized reflections, or inappropriate measurement orientation can all cause continuous gaps in line contour data. To improve the integrity of the 3D point cloud, this invention divides the detection area into parallel and partially overlapping scanning zones. After the initial scan, the integrity of the point cloud is determined based on the distribution of invalid height values ​​and the proportion of valid points in the contour height matrix. For incomplete point cloud areas, the host computer system generates a local supplementary scanning path based on its associated scanning zone number; if necessary, the swing arm and rotation attitude joint are adjusted to change the measurement orientation of the SRI7140 3D laser profile measuring instrument. The locally supplemented scanning point cloud and the initial 3D point cloud are saved separately and fused after fine registration, thereby reducing the impact of local gaps on the inner surfaces of the complex structure's surrounding compartments on the projection boundary, depth variation, and overall morphology calculation of the corroded area.

[0033] 6. Capable of generating inspection procedures and reports for on-site aircraft maintenance.

[0034] This invention connects an SRI7140 3D laser profile measuring instrument, a reconfigurable flexible robotic arm, and a host computer system via an Ethernet communication module. The SRI7140 3D laser profile measuring instrument outputs line profile data, and the reconfigurable flexible robotic arm system provides feedback on the base rotation joint angle, telescopic arm extension, swing arm swing angle, rotational attitude joint angle, movement speed, and operating status. The host computer system constructs a 3D point cloud based on the line profile data and corresponding movement positions, and sequentially performs point cloud integrity control, statistical filtering, fine registration, fusion, voxel downsampling, smoothing, suspected corrosion area screening, local verification, corrosion type determination, and quantitative parameter calculation. The inspection report includes information on the aircraft section under test and the inspection area, scanning parameters, overall 3D morphology, corrosion area number, corrosion area projection boundary, corrosion center location, corrosion type, maximum corrosion depth, average corrosion depth, corrosion projection area, corrosion volume loss, crack corrosion length and maximum width, local 3D morphology map, corrosion depth distribution map, and information on areas to be verified. Compared with manual recording, two-dimensional photography, and single signal interpretation, this invention can uniformly save three-dimensional morphological data and quantitative results during the detection process, which facilitates the confirmation of corrosion location, determination of repair scope, and subsequent re-inspection and comparison. Attached Figure Description

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments. Figure 1 This is an overall structural diagram of the device for detecting corrosion defects on the inner surface of aircraft cabin sections according to the present invention; Figure 2 This is a schematic diagram of the device for detecting corrosion defects on the inner surface of aircraft cabin sections according to the present invention. Figure 3 This is a flowchart illustrating the working process of the device for detecting corrosion defects on the inner surface of aircraft cabin sections according to the present invention. Figure 4 This is a flowchart illustrating the steps of the three-dimensional detection method for corrosion defects on the inner surface of aircraft compartments according to the present invention.

[0036] Figure 5 This is a schematic diagram of the folding telescopic tension compensation mechanism of the present invention in its initial folded state and its working state after entering the compartment.

[0037] Figure 6 This is a schematic diagram of the reconfigurable flexible robotic arm structure of the present invention.

[0038] In the figure: 1. SRI7140 3D laser profile measuring instrument; 2. Reconfigurable flexible robotic arm; 3. Ethernet communication module; 4. Host computer system; 5. Omnidirectional mobile positioning platform; 6. Folding telescopic tension compensation mechanism; 61. Fixed platform; 62. Movable platform; 63. Telescopic elastic tension rod; 21. Base rotation joint; 22. Telescopic arm; 23. Swing arm; 24. Rotational posture joint. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0040] The device for detecting corrosion defects on the inner surface of aircraft cabin sections according to the present invention includes an SRI7140 three-dimensional laser profile measuring instrument 1, a reconfigurable flexible robotic arm 2, an Ethernet communication module 3, a host computer system 4, an omnidirectional mobile positioning platform 5, and a folding telescopic tension compensation mechanism 6.

[0041] Specifically, the omnidirectional mobile positioning platform 5 is used to move the overall detection device to the location of the aircraft compartment to be tested; the reconfigurable flexible robotic arm 2 is used to carry the SRI7140 3D laser profile measuring instrument 1 into the compartment and adjust the detection position and attitude; the folding telescopic tension compensation mechanism 6 is used to generate a reverse compensation torque during the telescopic scanning process to reduce the overall elastic deformation of the reconfigurable flexible robotic arm 2 and the measurement attitude deviation of the SRI7140 3D laser profile measuring instrument 1. The Ethernet communication module 3 connects the controllers of the SRI7140 3D laser profile measuring instrument 1 and the reconfigurable flexible robotic arm 2 to the host computer system 4, and is used to transmit acquisition commands, line profile data, path and motion commands, as well as the joint angles, extension amount of the telescopic arm 22, end pose and operating status fed back by the reconfigurable flexible robotic arm 2. During the scanning process, the SRI7140 3D laser profile measuring instrument 1 outputs line profile data, and the host computer system 4 constructs a 3D point cloud based on the line profile data and its corresponding motion position, and completes the scanning path generation, data processing and detection result output.

[0042] Example 1 This embodiment illustrates the structural composition, installation relationship, communication relationship, and working principle of the folding telescopic tension compensation mechanism 6 of the detection device. The detection device includes an SRI7140 three-dimensional laser profile measuring instrument 1, a reconfigurable flexible robotic arm 2, an Ethernet communication module 3, a host computer system 4, an omnidirectional mobile positioning platform 5, and a folding telescopic tension compensation mechanism 6.

[0043] The SRI7140 3D laser profile measuring instrument 1 employs line laser triangulation, continuously outputting line profile data during the scanning process. The SRI7140 3D laser profile measuring instrument 1 is fixed to the end of the rotational attitude joint 24 using a dedicated rigid fixture, with the detection window facing the inner surface of the aircraft compartment under test; the length direction of the inner surface of the compartment is defined as... Direction, width direction is Direction, surface normal is direction, The positive axis points from the bulkhead material to the interior space. Each line profile output by the SRI7140 3D laser profile measuring instrument 1 is used to characterize the measured height of each sampling position within the measurement line range. Subsequently, the host computer system 4 combines the corresponding motion positions to construct a 3D point cloud.

[0044] The omnidirectional mobile positioning platform 5 is used to move the overall inspection device to the outside of the compartment inspection hole and lock it at a position that meets the requirements for the reconfigurable flexible robotic arm 2 to extend. The reconfigurable flexible robotic arm 2 is used to carry the SRI7140 3D laser profile measuring instrument 1 into the compartment through the compartment inspection hole. The base rotation joint 21 is used to adjust the overall orientation, the telescopic arm 22 is used to extend and retract along the longitudinal direction of the compartment, the swing arm 23 is used to adjust the end face orientation, and the rotation attitude joint 24 is used to further adjust the inspection attitude of the SRI7140 3D laser profile measuring instrument 1.

[0045] After the base rotation joint 21, swing arm 23 and rotation posture joint 24 complete the detection direction and posture adjustment and remain locked, the telescopic arm 22 performs the extension or retraction movement, so that the SRI7140 three-dimensional laser profile measuring instrument 1 completes the acquisition of line profile data while maintaining the detection posture.

[0046] Ethernet communication module 3 connects to the controller of SRI7140 3D laser profile measuring instrument 1, the reconfigurable flexible robotic arm 2, and the host computer system 4. The host computer system 4 sends acquisition commands to SRI7140 3D laser profile measuring instrument 1 and receives line profile data through Ethernet communication module 3. At the same time, it sends motion commands to the reconfigurable flexible robotic arm 2 and receives the angle of the base rotation joint 21, the extension amount of the telescopic arm 22, the swing angle of the swing arm 23, the angle of the rotational posture joint 24, the end effector pose, the motion speed, and the running status.

[0047] The host computer system 4 consists of an industrial control computer, 3D analysis software, and data storage unit. It is used for issuing instructions, receiving line contour data and motion feedback information, constructing 3D point clouds, storing data, and displaying detection status.

[0048] The folding telescopic tension compensation mechanism 6 is installed on the upper outer side of the telescopic arm 22, without changing the internal structure of the telescopic arm 22, and is not connected to the swing arm 23, the rotational attitude joint 24, or the SRI7140 three-dimensional laser profile measuring instrument 1. The folding telescopic tension compensation mechanism 6 includes a fixed platform 61, a movable platform 62, and a telescopic elastic tension rod 63; the fixed platform 61 is located at the top of the end of the telescopic arm 22 near the base rotational joint 21, the movable platform 62 is located at the top of the end of the telescopic arm 22 near the swing arm 23, and the telescopic elastic tension rod 63 connects the fixed platform 61 and the movable platform 62.

[0049] When the telescopic arm 22 is retracted, the mechanism is folded above the telescopic arm 22, and a vertical clearance is maintained between the lower edge of the retractable elastic tension rod 63 and the upper surface of the telescopic arm 22. , The clearance is 10–30 mm, preferably 15–20 mm. This range takes into account dynamic safety clearance, support stiffness, and compensation force transmission efficiency. If the telescopic arm is too small, deflection, assembly errors, or vibrations may cause the retractable elastic tension rod to come into contact with or interfere with the telescopic arm. When the height is too large, the support height of the fixed platform and the moving platform relative to the telescopic boom increases, making the connection points more prone to bending deformation. This causes some of the tensile force to be consumed by the deformation of the support structure, thereby reducing the effective reverse compensation torque transmitted to the telescopic boom and decreasing the compensation stability. This preferred range also ensures that the overall outline of the device meets the access requirements of the compartment maintenance openings.

[0050] When the telescopic arm 22 is in the retracted state, the folding telescopic tension compensation mechanism 6 retracts above the telescopic arm 22; when the telescopic arm 22 extends outward, the moving platform 62 moves synchronously with the end of the telescopic arm 22, and the retractable elastic tension rod 63 extends accordingly, generating a gradually increasing tension. This tension forms a counter-compensating torque at the telescopic arm 22 through the moving platform 62, which is used to reduce the overall elastic deformation of the reconfigurable flexible robotic arm 2 caused by the end load and the measurement posture deviation of the SRI7140 three-dimensional laser profile measuring instrument 1.

[0051] set up The extension length of the telescopic arm 22 relative to its fully retracted state. The extension length of the telescopic arm 22 is Given the self-weight torque of the body at that time, the overall downward torque of the reconstructed flexible robotic arm 2 is: (1) in The reconfigurable flexible robotic arm 2 extends to a length of The overall downward torque at that time For the quality of the SRI7140 3D laser profile measuring instrument 1, For the mass of the rigid fixture, The equivalent total mass of the swing arm 23, the rotational attitude joint 24, and the follower cable; , , The extension lengths are respectively The horizontal distance from the center of gravity of the above three parts to the pivot of the support end of the telescopic boom 22. It is the acceleration due to gravity. The reverse compensation torque generated by the folding telescopic tension compensation mechanism 6 is: (2) in, The folding telescopic tension compensation mechanism 6 has an extension length of... The reverse compensating torque formed at that time The initial preload of the retractable elastic tension rod 63, Its axial equivalent stiffness. This represents the elongation relative to the initial state. The angle between the axis of the retractable elastic tension rod 63 and the axis of the telescopic arm 22. The horizontal lever arm is the distance from the force-bearing point of the moving platform 62 to the pivot of the support end of the telescopic arm 22. The reverse compensation torque and the overall droop torque satisfy the following: (3) in, The compensation coefficient represents the proportion of the reverse compensation torque to the overall droop torque, and its value ranges from [value missing]. The initial value is preferably 0.8 to 0.9. When the SRI7140 3D laser profile measuring instrument 1 still exhibits a continuous downward measurement posture deviation, increase... When the end effector of the reconfigurable flexible robotic arm 2 exhibits upward displacement, springback, or reciprocating oscillation, reduce... .

[0052] After the detection device is in place and communication is established, the host computer system 4 sends motion commands to the reconfigurable flexible robotic arm 2, causing the SRI7140 3D laser profile measuring instrument 1 to reach the position to be measured and adjust to the detection posture; during the movement of the telescopic arm 22, the folding telescopic tension compensation mechanism 6 unfolds synchronously and forms a reverse compensation torque, the SRI7140 3D laser profile measuring instrument 1 continuously outputs line profile data, the reconfigurable flexible robotic arm 2 synchronously feeds back the corresponding movement position, and the host computer system 4 constructs a 3D point cloud based on this.

[0053] Example 2 A three-dimensional structured light detection method for corrosion of aircraft cabin interior surfaces first acquires the boundary of the detection area. Then, overlapping scan bands and scan paths are generated. The SRI7140 three-dimensional laser profilometer 1 outputs line profile data, and the host computer system 4 constructs a three-dimensional point cloud based on the motion position. The system then sequentially performs point cloud integrity control, three-dimensional point cloud preprocessing, screening of suspected corrosion areas, local verification, and corrosion parameter calculation.

[0054] The detection method uses the aforementioned detection device, and the specific steps are as follows: Step 1: Calibration of the physical coordinate system of the compartment Before inspection, the omnidirectional mobile positioning platform 5 was fixed to the outside of the aircraft compartment inspection port, and the SRI7140 three-dimensional laser profilometer 1 was mounted on the rotational attitude joint 24 using a rigid clamp. The physical coordinate system of the compartment was used as a unified reference coordinate system to represent the location of the corrosion area.

[0055] At least six, preferably at least nine, uniformly distributed, non-collinear, and corrosion-free reference points are selected on the inner surface of the aircraft compartment to be tested. The positions of these reference points in the physical coordinate system of the compartment are determined based on the CAD 3D model of the aircraft compartment or the actual dimensions of the compartment. Combining the positions of these reference points acquired by the SRI7140 3D laser profile measuring instrument 1 and the end effector pose of the reconfigurable flexible robotic arm 2, the fixed installation relationship between the SRI7140 3D laser profile measuring instrument 1 and the rotational attitude joint 24, as well as the coordinate relationship between the base of the reconfigurable flexible robotic arm 2 and the aircraft compartment, are determined. These relationships form coordinate transformation parameters, which describe the positional and orientational relationships between the corresponding components and the aircraft compartment. During the scanning process, the host computer system 4 calculates the position and attitude of the SRI7140 3D laser profile measuring instrument 1 in real time using the kinematic model of the reconfigurable flexible robotic arm 2, based on the angle of the base rotational joint 21, the extension amount of the telescopic arm 22, the swing angle of the swing arm 23, and the angle of the rotational attitude joint 24, and converts the acquired line contour data to the physical coordinate system of the compartment. The kinematic model is based on the angles or extensions of the base rotation joint 21, telescopic arm 22, swing arm 23, and rotational attitude joint 24 to calculate the geometric relationship between the position and attitude of the SRI7140 three-dimensional laser profile measuring instrument 1.

[0056] When the base rotation joint 21, telescopic arm 22, swing arm 23, and rotation attitude joint 24 are in normal movement, only the real-time position and attitude of the SRI7140 3D laser profile measuring instrument 1 change, and no recalibration is required. When the SRI7140 3D laser profile measuring instrument 1 is re-clamped, the rotation attitude joint 24 is repaired or re-zeroed, or the position of the omnidirectional moving positioning platform 5 relative to the aircraft compartment changes, the corresponding coordinate transformation parameters are re-determined. Step 1 outputs the coordinate transformation parameters for subsequent 3D point cloud construction, point cloud registration, and erosion area positioning.

[0057] Step 2: Determine the boundary of the detection area and generate the scanning path After completing the calibration of the physical coordinate system and installation relationship of the cabin section in step 1, determine the boundary of the detection area on the inner surface of the aircraft cabin section to be tested, divide the initial scanning zone, and set the compensation parameters of the folding telescopic tension compensation mechanism 6.

[0058] When a CAD 3D model matching the aircraft section to be tested is available, the 3D analysis software extracts the boundary of the detection area from the CAD 3D model; when a CAD 3D model is not available, the operator sets the boundary of the detection area in the host computer system 4 according to the actual size of the section.

[0059] For the horizontal width of the detection area The effective measurement width of the SRI7140 3D laser profile measuring instrument is greater than 1. In this case, the detection area is divided into several parallel and partially overlapping scanning bands.

[0060] Lateral step size between adjacent scan bands for: (4) in, The step size factor is used. If the step size factor is too large, the overlap area between adjacent scan bands decreases, potentially causing local missed scans and affecting point cloud registration; if the step size factor is too small, it increases the number of scan bands, data redundancy, and detection time. The value range of the step size factor is... In this embodiment, it is preferred that... .

[0061] The overlap width between adjacent scan bands is: (5) when hour, This means that a coverage area of ​​25% of the effective measurement width is reserved between adjacent scan bands to ensure continuous coverage of the detection area and to provide a data basis for the fine registration of the three-dimensional point cloud of subsequent adjacent scan bands.

[0062] when At that time, the number of scan strips required to complete full coverage of the detection area is: (6) in, For the number of scan strips, Indicates rounding up. When At that time, set a scanning band.

[0063] The host computer system 4 generates scanning bands sequentially from one side of the detection area to the other side of the detection area according to the lateral step distance, and numbers them in sequence. The scan strip number is used to record the data acquisition order and determine the point cloud registration relationship between adjacent scan strips.

[0064] The start and end positions of each scan band are determined by the intersection of the center line of the scan band and the boundary of the detection area.

[0065] The host computer system 4 records the lateral position of the center line of each scan band and saves the center line position with the corresponding scan band number as the basis for subsequent local scan path positioning.

[0066] The host computer system 4 calculates the target rotation angle and extension amount required for the base rotation joint 21, telescopic arm 22, swing arm 23 and rotation attitude joint 24 to reach the corresponding positions based on the start position, end position and number sequence of each scanning strip.

[0067] The generated scanning path should ensure that each motion unit can reach the start and end positions of the scanning strip, and avoid motion interference between the SRI7140 3D laser profile measuring instrument 1, the reconfigurable flexible robotic arm 2 and the connecting cables and the internal structure of the aircraft cabin.

[0068] A single scanning band is planned to be moved in a straight line from the starting position to the ending position by the telescopic arm 22; the transition path between adjacent scanning bands is used to move the SRI7140 3D laser profile measuring instrument 1 to the starting position of the next numbered scanning band.

[0069] Step 2 outputs the detection area boundary, scanning band number and centerline position, uniform step distance coefficient, lateral step distance, overlap width, start and end positions of each scanning band, target rotation angle and extension of each motion unit, and compensation parameters of the folding telescopic tension compensation mechanism 6.

[0070] Step 3: Line contour data acquisition, 3D point cloud construction and integrity control The host computer system 4 controls the reconfigurable flexible robotic arm 2 to carry the SRI7140 3D laser profile measuring instrument 1 to complete the initial scan and construct a 3D point cloud based on the scanning path generated in step 2.

[0071] The host computer system 4 is based on the scanning tape number. The scanning is performed sequentially. Before acquiring the current scan strip, the reconfigurable flexible robotic arm 2 moves to the starting position of the scan strip; after acquisition begins, the base rotation joint 21, the swing arm 23 and the rotation attitude joint 24 remain locked, and the telescopic arm 22 performs linear motion from the starting position to the ending position of the scan strip.

[0072] The SRI7140 3D laser profile measuring instrument 1 continuously outputs line profile data during the movement of the telescopic arm 22.

[0073] The host computer system 4 records the scan tape number, the timestamp of each line contour, and the real-time extension of the telescopic arm 22 at the corresponding acquisition time. It also records the base rotation joint 21 angle, swing arm 23 swing angle, and rotation posture joint 24 angle that remain locked during the acquisition of this scan tape.

[0074] The timestamp is used to establish the relationship between each line profile and its corresponding extension amount, so as to determine the actual position of each line profile in the physical coordinate system of the compartment and avoid point cloud misalignment caused by the mismatch between the line profile data and the movement position.

[0075] After completing the current scan strip, pause data acquisition and control the reconfigurable flexible robotic arm 2 to move to the starting position of the next numbered scan strip, until data acquisition of all scan strips is completed.

[0076] The discrete locations in a single line profile that have a defined lateral position and a measured height value are defined as sampling points.

[0077] For each scan strip, the host computer system 4 arranges the height coordinates of each sampling point into a contour height matrix according to the acquisition order of the line contour. : (7) in, For the column index of sampling points in a single line profile, This is the row index for the line contours acquired sequentially along the scanning direction. Indicates the first The first line in the outline The measured height values ​​at each sampling location.

[0078] No. The horizontal coordinates of each sampling location are: (8) in, The horizontal coordinate of the starting sampling position of the line contour. This represents the horizontal physical spacing between adjacent sampling points.

[0079] No. The first line in the outline The homogeneous coordinates of the sampling points in the SRI7140 3D laser profile measuring instrument 1 coordinate system are: (9) Among them, superscript Indicates the coordinate system of the SRI7140 3D laser profilometer; symbol " "" indicates homogeneous coordinates.

[0080] Based on the coordinate transformation relationship obtained in step 1 and the... The real-time extension amount of the telescopic arm 22 corresponding to the line contour is used to convert the sampling points to the physical coordinate system of the compartment: (10) Among them, superscript Indicates the physical coordinate system of the compartment. Indicates the collection of the first When defining the outline, the transformation matrix is ​​used to convert the SRI7140 3D laser profile measuring instrument from the 1 coordinate system to the physical coordinate system of the compartment.

[0081] After coordinate transformation, each sampling point forms a point cloud in the physical coordinate system of the compartment. Each scan band forms a three-dimensional point cloud with a scan band number, and all scan bands form the initial three-dimensional point cloud set.

[0082] The host computer system 4 removes invalid height values ​​(when the height exceeds the preset height threshold) output by the SRI7140 3D laser profile measuring instrument 1, and checks the integrity of the 3D point cloud corresponding to each scanning band according to the distribution of invalid height values ​​in the profile height matrix.

[0083] In the 3D point cloud of all scanned areas, if a point exists and its height value is within the preset height threshold range, it is considered a valid point; otherwise, it is recorded as an invalid point. When the proportion of valid points is less than 80%, the area is determined to be an incomplete point cloud area.

[0084] The effective point ratio is calculated as follows: (11) in, The effective point ratio, For the effective number of point cloud points, This represents the theoretical number of sampling points determined based on the sampling parameters.

[0085] set up and The scan is indexed and satisfies When the incomplete point cloud region is located only within a single scan band. When the point cloud is incomplete, the center line of the scan band is used as the center line of the local supplementary scan; when the incomplete area of ​​the point cloud spans two or more scan bands, the two scan bands with the smallest and largest numbers are respectively denoted as... and ,and At this point, the lateral position of the center line of the local supplementary scan is: (12) in, To supplement the lateral position of the scan centerline in a localized area, and These represent the lateral positions of the center line of the outermost scan band spanned by the incomplete region.

[0086] One or more local supplementary scan bands are generated based on the local supplementary scan center line, so that the local supplementary scan range covers all scan bands involved in the incomplete area of ​​the point cloud, and a local supplementary scan point cloud is obtained. The local supplementary scan point cloud and the initial three-dimensional point cloud are saved separately.

[0087] Step 4: 3D point cloud preprocessing The host computer system 4 performs statistical filtering, fine registration, fusion, voxel downsampling and smoothing on the initial 3D point cloud and the locally supplemented scanned point cloud output in step 3 in sequence to obtain a preprocessed 3D point cloud with unified coordinates, controlled noise and the ability to retain erosion boundaries and depth changes.

[0088] Statistical filtering is used to remove isolated outliers generated during the acquisition process. The host computer system 4 identifies outliers based on the distance relationship between each point cloud point and its local neighboring points. The neighborhood range and the judgment threshold are determined based on the point cloud sampling interval and the minimum corrosion morphology size to be retained, so as to avoid accidentally deleting valid point cloud points at corrosion boundaries.

[0089] Step 3 has transformed the point clouds of each scan strip to the physical coordinate system of the compartment. To correct the slight positional deviations that still exist after the coordinate transformation, the host computer system 4 uses the overlapping areas of adjacent scan strips to perform iterative nearest-point fine registration, and iteratively corrects the rotational and translational deviations between the point clouds. After the fine registration is completed, the point clouds of each scan strip are merged in order of scan strip number, and the locally supplemented scan point clouds are merged into the corresponding incomplete point cloud areas to form a fused three-dimensional surface in the same physical coordinate system of the compartment.

[0090] To reduce the number of point clouds and subsequent computational load, the host computer system 4 divides the three-dimensional space into voxels of the same size and uses the average coordinates of the point cloud points within each voxel as representative points to complete voxel downsampling; subsequently, smoothing is performed on locally continuous surfaces. The voxel size, smoothing neighborhood, and processing intensity are determined based on the point cloud sampling interval and the minimum erosion morphology size to be retained. Smoothing is performed only on locally continuous surfaces, and the smoothing neighborhood must not cross positions where the local surface height is discontinuous.

[0091] Step 5: Screening of suspected corrosion areas, local verification, quantitative calculation, and output of test results. The host computer system 4 selects highly continuous point cloud points from the preprocessed 3D point cloud and uses the least squares method to fit the local healthy reference surface: (13) in, , The planar coordinates of the selected point cloud points. For local health benchmarks The predicted height at that location and These represent the local health reference planes along... direction and Rate of change of height in direction This represents the predicted height at the local coordinate origin. The local health reference plane is used to predict the surface height when no corrosion has occurred, avoiding the influence of the tilt of the test surface on the determination of corrosion depth.

[0092] set up For point cloud point indexing, the first The coordinates of the point cloud points are: Its signed height residual relative to the local health reference surface is: (14) in, z q Indicates the first q The height of each point cloud point; When the point cloud points are recessed relative to the local health baseline and facing the interior of the bulkhead It is a positive value. The corresponding [number]th [value]. The erosion depth of each point cloud point is: (15) When the inward indentation depth of a point cloud point exceeds a preset initial screening threshold, and its connectivity reaches a preset minimum area, the region is marked as a suspected corrosion region. The preset initial screening threshold is predetermined based on the height residual fluctuation range of the local health reference surface and the minimum corrosion depth of concern.

[0093] The host computer system 4 records the location, boundary range, and associated scan zone number of the suspected corrosion area in the physical coordinate system of the compartment, which is used to generate a local verification scan path.

[0094] When the suspected corrosion area is located in a single scan band During the internal process, the scanning belt was used. The center line is used as the center line for local verification scanning.

[0095] When a suspected corrosion area spans two or more scanning bands, the two scanning bands with the lowest and highest numbers among those spanned are still respectively recorded as... and The horizontal position of the center line of the local verification scan is: (16) in, This refers to the horizontal position of the center line of the local verification scan.

[0096] The local verification scan area covers the scan band where the suspected corrosion area is located. When the lateral range of the suspected corrosion area exceeds the effective measurement width of a verification scan band, the verification scan band is added to both sides according to the step distance specified in step 2, based on the verification scan center line, until the suspected corrosion area is completely covered.

[0097] The local verification scan uses the same acquisition parameters as the initial scan, so that the suspected corrosion area is located in the middle of the verification scan range as much as possible, reducing the influence of the scan edge and point cloud splicing position on the corrosion morphology.

[0098] The local verification scan point cloud is first transformed to the physical coordinate system of the compartment based on the coordinate transformation relationship obtained in step 1, and then processed using the statistical filtering and fine registration methods in step 4.

[0099] The host computer system 4 compares the spatial location, projected boundary shape, inward concavity direction, local three-dimensional morphology, and maximum concavity depth of the suspected corrosion area in the initial scan and local verification scan.

[0100] When two valid scan results are consistent within a preset repeatability range, the suspected corrosion area is retained. When the point cloud of the local verification scan is incomplete, a local supplementary scan is performed according to the method in step 3. This local verification scan is not included in the consistency comparison. If the point cloud is still incomplete after the local supplementary scan, the corresponding area is marked as an area with incomplete point cloud to be verified. When the difference between two valid scan results is significant, another local verification scan is performed. If the results of multiple valid scans are still inconsistent, the area is marked as an area with inconsistent data to be verified.

[0101] For suspected corrosion areas with consistent verification results, a local healthy reference surface is fitted with highly continuous point cloud points, and the inward concavity depth of each point cloud point is calculated according to the aforementioned signed height residual and corrosion depth calculation method.

[0102] In the suspected corrosion area where the verification results are consistent, point cloud points with an inward indentation depth exceeding the aforementioned preset initial screening threshold are defined as corrosion points.

[0103] Based on the spatial adjacency relationships between point cloud points, consecutive corrosion points are aggregated into independent corrosion regions. Set as the erosion region index, and set the first... The set of point cloud indexes contained in a given eroded region is represented as follows: The number of point cloud points contained in the eroded region. for: (17) in, This indicates the number of elements in the set.

[0104] use The method extracts the projected boundary of the corroded region on the local healthy reference plane. Used to obtain the actual non-convex boundary of the corroded area, avoiding incorrect connection of boundary depressions or adjacent corroded areas.

[0105] For independent corrosion areas with consistent verification results, the quantitative corrosion parameters and classification features used for corrosion type determination are calculated sequentially, as follows: The corrosion zone is divided into pitting corrosion, exfoliation corrosion, and fissure corrosion. First, the maximum corrosion depth, average corrosion depth, projected corrosion area, volumetric corrosion loss, and corrosion center location are calculated for each corrosion zone. Then, [further details are needed]. The projected boundary forms classification characteristics such as boundary perimeter, boundary roundness, elongation ratio, and deep area proportion. Among them, pitting corrosion is a localized, concentrated, and compact pit-shaped material loss; spalling is a continuous sheet-like material loss with a large projected area or irregular boundaries; and crack-like corrosion is a narrow and elongated material loss extending along a specific direction.

[0106] Areas with incomplete point clouds and inconsistent data that need to be reviewed will retain their original markings and be displayed separately in the detection results.

[0107] No. The maximum corrosion depth of each corrosion zone is: (18) The average corrosion depth is: (19) The projected area of ​​the corroded region on the local healthy reference plane is: (20) in, For the first The projected area of ​​each corrosion zone.

[0108] Let the first The weight of the projected area of ​​each point cloud on the local health reference plane is: Then the corrosion volume loss for: (twenty one) in, Determined based on point cloud sampling interval or local grid area, used to represent the first... The actual surface area corresponding to each point cloud point.

[0109] The location of the corrosion center is: (twenty two) in, For the first The coordinates of each corrosion point in the physical coordinate system of the compartment. For the first The number of point cloud points contained in each eroded region. This is the center of the corroded area.

[0110] Regarding the aforementioned Calculate its The circularity of the projected boundary. The perimeter of the projected boundary is denoted as... Boundary roundness is denoted as . The closer the value is to 1, the closer the erosion projection boundary is to a circle. The calculation formula is: (twenty three) Construct a minimum-area bounding rectangle within the local health reference plane, and denote its long side and short side as . and elongation ratio The formula used to characterize the extent to which a corrosion zone extends in a single direction is: (twenty four) Given relative depth coefficient ,and Shenzhen area percentage Indicates corrosion depth is not less than The proportion of points in the point cloud is calculated using the following formula: (25) in, This is an indicator function that takes the value 1 if the condition is true, and 0 otherwise.

[0111] The corrosion type is denoted as ,in, , and These represent pitting corrosion, exfoliation, and fissure corrosion, respectively. Fissure corrosion is first identified based on elongation ratio and boundary roundness. Pitting corrosion is then identified based on corrosion projection area, boundary roundness, and the proportion of deep areas. The remaining corrosion areas are classified as exfoliation. Specifically: (26) in, The threshold for the crack-like corrosion extension ratio. This represents the upper limit of roundness for crack-like corrosion. This represents the upper limit of the pitting projection area. This is the lower limit for pitting roundness. This represents the upper limit of the proportion of deep pitting corrosion. The above thresholds are determined based on the testing specifications, the type of aircraft cabin material, and the statistical results of three types of pre-labeled corrosion samples, and are stored in the host computer system.

[0112] For pitting and flaking, output the corrosion type and the aforementioned quantitative corrosion parameters; for crack corrosion, further calculate the crack corrosion length and maximum width.

[0113] For areas identified as crack-like corrosion, The projected boundary is denoted as ,Will Upper The discrete boundary points are denoted as... ,in , This represents the total number of discrete boundary points included in the projected boundary. From all discrete boundary points, the two boundary points with the largest Euclidean distance are selected, and the direction of the line connecting these two points is normalized to obtain the unit vector of the main extension direction. The unit normal vector of the local health reference surface is denoted as... ;Will and The cross product result is normalized to obtain a unit vector perpendicular to the main extension direction within the local health reference plane. The maximum projected range along the two directions mentioned above (the main extension direction and the direction perpendicular to the main extension direction) is defined as the crack corrosion length. and maximum width The formula for its calculation is: (27) superscript This represents the transpose of a vector.

[0114] The host computer system 4 establishes a three-dimensional topography model of the inner surface of the aircraft compartment under test based on the preprocessed three-dimensional point cloud output in step 4, and maps the boundaries, corrosion types, corrosion center locations and maximum corrosion depths of each corrosion area to the three-dimensional model.

[0115] Corrosion depth distribution maps are generated based on the corrosion depth of each point cloud point, and local three-dimensional topographic maps and height profile maps are generated for each corrosion area to show the concave shape of the corrosion area relative to the local healthy reference surface.

[0116] The inspection report includes information on the aircraft section to be tested and the inspection area, scanning parameters, overall three-dimensional morphology, corrosion area number, corrosion area boundary, corrosion center location, corrosion type, maximum corrosion depth, average corrosion depth, corrosion projected area, corrosion volume loss, crack corrosion length, maximum crack corrosion width, local three-dimensional morphology map, corrosion depth distribution map, and information on areas to be reviewed.

[0117] The host computer system 4 saves the inspection report as an electronic inspection record, which is used for confirming the corrosion location, determining the scope of maintenance, and comparing the results of subsequent re-inspections.

[0118] Example 3 This embodiment provides an apparatus and method for detecting corrosion defects on the inner surface of aircraft cabin sections, in conjunction with the attached... Figure 1-6 The specific installation sequence and location of the device are as follows: Step 1: Omnidirectional mobile positioning platform 5 is in place The omnidirectional mobile positioning platform 5 is moved to a stable bearing surface outside the aircraft compartment inspection hole, so that the extension direction of the reconfigurable flexible robotic arm 2 is adapted to the compartment inspection hole and inspection area.

[0119] The specific locking position of the omnidirectional mobile positioning platform 5 is determined based on the size of the compartment inspection hole, the depth of the detection area inside the compartment, the effective extension length of the reconfigurable flexible robotic arm 2, and the movement range of each moving component. Before positioning, the distance from the compartment inspection hole to the detection area is measured and recorded, and the position of the omnidirectional mobile positioning platform 5 is adjusted according to the actual reach of the reconfigurable flexible robotic arm 2.

[0120] After the position adjustment is completed, the omnidirectional mobile positioning platform 5 is locked, and the reconfigurable flexible robotic arm 2 is controlled to extend and adjust its attitude at a low speed. It is confirmed that the base rotation joint 21, telescopic arm 22, swing arm 23, rotation attitude joint 24, SRI7140 three-dimensional laser profile measuring instrument 1 and connecting cables do not interfere with the edge of the compartment inspection hole and the internal structure of the compartment during the movement.

[0121] Step 2: Installation and inspection of measuring instrument and compensation mechanism Following the installation relationship described in Example 1, check the rigid fixture connection status between the SRI7140 3D laser profilometer 1 and the rotational attitude joint 24, confirming that the detection window faces the inner surface of the aircraft section to be measured. In the initial scanning posture, adjust the distance between the SRI7140 3D laser profilometer 1 and the local surface to be measured to approximately 140 mm (reference measurement distance), ensuring that the bending radius of the connecting cable is not less than 30 mm. Check the connection status of the fixed stage 61, the moving stage 62, and the retractable elastic tension rod 63; with the telescopic arm 22 fully retracted, measure the vertical clearance between the lower edge of the retractable elastic tension rod 63 and the upper surface of the telescopic arm 22, ensuring it remains within the range of 10–30 mm, preferably 15–20 mm, and record the actual measurement value.

[0122] Step 3: Install and connect the communication equipment to the host computer Secure the Ethernet communication module 3 to the side of the omnidirectional mobile positioning platform 5 or to a dedicated bracket outside the compartment, ensuring it is located outside the movement area of ​​the reconfigurable flexible robotic arm 2. Place the host computer system 4 in a stable, easily operable, and observable location outside the compartment. The installation distance between the Ethernet communication module 3 and the host computer system 4 is determined based on the actual length of the shielded Ethernet cable used and the available operating space. The cable arrangement should allow for connection and protection margins and must not enter the movement area of ​​the reconfigurable flexible robotic arm 2. After installation, record the positions of the Ethernet communication module 3 and the host computer system 4 relative to the compartment inspection holes, as well as the actual cable lengths. Then, connect the SRI7140 3D laser profile measuring instrument 1, the controller of the reconfigurable flexible robotic arm 2, and the host computer system 4 via the Ethernet communication module 3. Complete the power connection according to the power supply requirements of each component, and check the communication and power interfaces for looseness.

[0123] Step 4: Initial status check and low-speed trial run After powering on, check the line contour data transmission, base rotation joint 21 angle feedback, telescopic arm 22 extension feedback, swing arm 23 swing angle feedback, rotational attitude joint 24 angle feedback, end effector pose, and operating status. Control the reconfigurable flexible robotic arm 2 to perform a low-speed test run, check the extension and retraction of the telescopic arm 22, the follow-up of the connecting cable, and the unfolding and retraction process of the folding telescopic tension compensation mechanism 6; confirm that there is no motion interference between the retractable elastic tension rod 63 and the telescopic arm 22, that the distance between the SRI7140 3D laser profile measuring instrument 1 and the surface to be measured can be kept near the reference measurement distance, and that the line contour data is continuous and stable.

[0124] Step 5: Execution of detection method and device exit After confirming that the detection device is securely installed, communication is normal, and movement is uninterrupted, and that the line profile data output of the SRI7140 3D laser profile measuring instrument 1 is stable, and that the folding telescopic tension compensation mechanism 6 can normally unfold and retract with the telescopic arm 22, the corrosion defect detection of the aircraft cabin interior surface is completed according to the method described in Example 2. After the detection is completed, the telescopic arm 22 is retracted to restore the folding telescopic tension compensation mechanism 6 to its retracted state. Then, the reconfigurable flexible robotic arm 2 is removed from the cabin inspection hole, and the on-site installation position, installation parameters, trial operation status, and detection results are recorded.

[0125] This application utilizes the line contour data output by the SRI7140 3D laser profilometer. The host computer system constructs a 3D point cloud based on the motion position. Through 3D point cloud preprocessing, local healthy reference surface fitting, signed height residual calculation, suspected corrosion area screening, and local verification, the system obtains detection results such as corrosion area location, projection boundary, type, 3D morphology, maximum depth, average depth, projected area, and volume loss. It combines a reconfigurable flexible robotic arm, a foldable telescopic tension compensation mechanism, overlapping scanning, local supplementary scanning, and 3D point cloud registration and fusion to achieve 3D quantitative detection of corrosion defects on the inner surface of aircraft cabin sections.

[0126] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A device for detecting corrosion defects on the inner surface of aircraft cabin sections, characterized in that, The device includes an SRI7140 3D laser profile measuring instrument (1), a reconfigurable flexible robotic arm (2), an Ethernet communication module (3), a host computer system (4), an omnidirectional mobile positioning platform (5), and a folding telescopic tension compensation mechanism (6). The omnidirectional mobile positioning platform (5) is used to carry the device and move and position the device to the outside of the inspection port of the aircraft section to be tested. The reconfigurable flexible robotic arm (2) is used to carry the SRI7140 3D laser profile measuring instrument (1) through the inspection port into the interior of the aircraft section to be tested, and to adjust the detection position and detection attitude of the SRI7140 3D laser profile measuring instrument (1). The stacked telescopic tension compensation mechanism (6) is set above the outside of the telescopic arm (22) of the reconfigurable flexible robotic arm (2) to generate a reverse compensation torque when the telescopic arm (22) extends; the Ethernet communication module (3) is connected to the SRI7140 three-dimensional laser profile measuring instrument (1), the controller of the reconfigurable flexible robotic arm (2) and the host computer system (4) respectively; the host computer system (4) is used to send acquisition commands and motion commands, receive line profile data and motion feedback information, construct a three-dimensional point cloud based on the line profile data and its corresponding motion position, and complete the scanning path generation, corrosion defect identification, corrosion parameter calculation and detection result output; The reconfigurable flexible robotic arm (2) includes a base rotation joint (21), a telescopic arm (22), a swing arm (23), and a rotation attitude joint (24); the base rotation joint (21) is used to adjust the overall orientation of the reconfigurable flexible robotic arm (2); the telescopic arm (22) is used to extend and retract along the longitudinal direction of the aircraft compartment to be tested; the swing arm (23) and the rotation attitude joint (24) are used to adjust the detection attitude; the SRI7140 three-dimensional laser profile measuring instrument (1) is fixed to the end of the rotation attitude joint (24) by a rigid clamp, and its detection window faces the inner surface of the aircraft compartment to be tested; The folding telescopic tension compensation mechanism (6) includes a fixed platform (61), a movable platform (62), and a telescopic elastic tension rod (63). The fixed platform (61) is located at the top of one end of the telescopic arm (22) near the base rotation joint (21), and the movable platform (62) is located at the top of one end of the telescopic arm (22) near the swing arm (23). The two ends of the telescopic elastic tension rod (63) are connected to the fixed platform (61) and the movable platform (62) respectively. When the telescopic arm (22) extends, the movable platform (62) moves synchronously with the end of the telescopic arm (22), and the telescopic elastic tension rod (63) extends accordingly, applying the reverse compensation torque to the telescopic arm (22) through the movable platform (62). When the telescopic arm (22) is in a fully retracted state, the folding telescopic tension compensation mechanism (6) is retracted above the telescopic arm (22).

2. The apparatus according to claim 1, characterized in that, Let the extension length of the telescopic arm (22) relative to its fully retracted state be... The folding telescopic tension compensation mechanism (6) extends to a length of The reverse compensation torque formed at that time is The reconfigurable flexible robotic arm (2) extends to a length of The overall downward torque at that time is The reverse compensation torque and the overall droop torque satisfy the following: ， in, The compensation coefficient represents the proportion of the reverse compensation torque to the overall drooping torque, and ; The vertical distance between the lower edge of the retractable elastic tension rod (63) and the upper surface of the telescopic arm (22) is defined as the vertical clearance. The vertical net distance It is 10–30 mm.

3. A method for detecting corrosion defects on the inner surface of aircraft cabin sections, characterized in that, The method employs a device including an SRI7140 3D laser profile measuring instrument (1), a reconfigurable flexible robotic arm (2), an Ethernet communication module (3), a host computer system (4), an omnidirectional mobile positioning platform (5), and a folding telescopic tension compensation mechanism (6). The reconfigurable flexible robotic arm (2) includes a base rotation joint (21), a telescopic arm (22), a swing arm (23), and a rotational attitude joint (24). The method includes the following steps: Step 1: Position the device outside the inspection hole of the aircraft section to be tested, determine the coordinate transformation parameters between the SRI7140 three-dimensional laser profile measuring instrument (1), the reconfigurable flexible robotic arm (2) and the aircraft section to be tested, and use the physical coordinate system of the section as the unified reference coordinate system for the positioning of the corrosion area. Step 2: Determine the detection area boundary of the inner surface of the aircraft cabin section to be tested, divide the detection area into mutually parallel and partially overlapping scanning bands, generate an initial full-coverage scanning path, and set the compensation parameters of the folding telescopic tension compensation mechanism (6). Step 3: The reconfigurable flexible robotic arm (2) carries the SRI7140 three-dimensional laser profile measuring instrument (1) to collect line profile data according to the initial full-coverage scanning path. The host computer system (4) constructs the initial full-coverage original three-dimensional point cloud based on the line profile data and its corresponding motion position, checks the integrity of the initial full-coverage original three-dimensional point cloud, and performs local supplementary scanning on the incomplete areas of the point cloud. Step 4: Perform statistical filtering, fine registration, fusion, voxel downsampling, and smoothing on the initial full-coverage original 3D point cloud and the locally supplemented scanned point cloud in sequence to obtain the preprocessed 3D point cloud; Step 5: Fit a local health reference plane to the preprocessed 3D point cloud to predict the surface height when no corrosion occurs. Screen suspected corrosion areas based on the inward indentation depth of the point cloud points relative to the local health reference plane. Perform local verification scans on the suspected corrosion areas. Point cloud points in the suspected corrosion areas with consistent verification results whose inward indentation depth exceeds a preset initial screening threshold are identified as corrosion points. Based on the spatial adjacency relationship between the point cloud points, the corrosion points are aggregated into independent corrosion areas. Calculate the corrosion parameters of each independent corrosion area and determine the corrosion type to generate detection results.

4. The method for detecting corrosion defects on the inner surface of aircraft compartments according to claim 3, characterized in that, In step two, the lateral width of the detection area is denoted as... The effective measurement width of the SRI7140 three-dimensional laser profile measuring instrument (1) is denoted as... Let the step size coefficient be denoted as The range of values ​​for the step size coefficient is: ; Lateral step size between adjacent scan bands for: ， Overlap width between adjacent scan bands for: ， when At that time, the number of scan strips required to complete full coverage of the detection area. for: ， in, Indicates rounding up; when the lateral width of the detection area is not greater than the effective measurement width, the number of scan bands... The value is 1.

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