Cover box design method for protruding structure of oil tank leakage area

Abstract

The invention discloses a cover box design method for a protruding structure of an oil tank leakage area, relates to the technical field of oil tank leakage detection, and aims at solving the technical problems that an existing sealing cover box is poor in sealing performance and low in design efficiency. The cover box design method for the oil tank leakage area protruding structure comprises the steps that characteristic parameters of the oil tank leakage area protruding structure are obtained; determining a cover box avoiding size according to the characteristic parameters; dynamically planning a cutting path based on the reverse reconstruction model of the oil tank, and processing a framework according to the avoiding size of the cover box; the processed framework is attached to the to-be-detected protruding structure, and heat treatment shaping is carried out; performing temperature activation and form locking on the attached framework; according to the technical scheme, the cover box design method for the protruding structure of the oil tank leakage area is provided.

Description

Technical Field

[0001] The present invention relates to the technical field of oil tank leakage detection, and more particularly to a method for designing a cover box for a convex structure in an oil tank leakage area. Background Art

[0002] In the aviation industry, leak detection of aircraft fuel tanks is crucial. With the continuous advancement of aircraft design and manufacturing, the fuel tank area of ​​modern aircraft has become increasingly complex and crucial for maintaining safety and improving flight performance. Therefore, ensuring the proper sealing of fuel tanks has become a crucial task.

[0003] Existing technologies face challenges and shortcomings in testing sealing covers in leaking fuel tank areas. When sealing and plugging leaking areas in aircraft wing fuel tanks, it is necessary to design and manufacture dedicated sealing inspection covers for sealing tests based on the spatial structure of each location requiring sealing inspection. The structural conditions at each location are inconsistent, requiring the covers to be matched and installed one by one. Operators must accurately identify and confirm the shape and installation position of each sealing tool and perform precise installation to ensure the sealing effect, resulting in low efficiency. Furthermore, existing sealing covers all achieve contact sealing with the aircraft fuel tank structure through a rigid structure plus a rubber interlayer. The design of the sealing layer has not been evaluated through specific parameter studies, resulting in an inability to guarantee sealing. Clearly, existing sealing covers have technical issues with poor sealing and low design efficiency. Summary of the Invention

[0004] The present invention aims to provide a method for designing a cover box for a raised structure in a fuel tank leakage zone, thereby resolving the technical problems of poor sealing and low design efficiency of existing sealing cover boxes.

[0005] The present invention provides a method for designing a cover box for a raised structure in a leakage area of ​​a fuel tank, comprising: Obtain characteristic parameters of the convex structure in the leakage area of ​​the fuel tank; determining the cover box avoidance size according to the characteristic parameters; Dynamic planning of the cutting path is performed based on the reverse reconstruction model of the fuel tank, and the skeleton is processed according to the avoidance size of the cover box; the processed skeleton is fitted to the protruding structure to be inspected, and heat treated to finalize the shape; The bonded skeleton is temperature activated and shape locked.

[0006] Compared with the prior art, in the cover box design method for the raised structure in the leakage area of ​​the fuel tank of the present invention, after obtaining the characteristic parameters of the raised structure in the leakage area of ​​the fuel tank, the cover box avoidance size is determined according to the characteristic parameters; further, the cutting path is dynamically planned based on the inverse reconstruction model of the fuel tank, and the skeleton is processed according to the cover box avoidance size; the processed skeleton is fitted to the raised structure to be detected and heat-treated to shape it; after temperature activation and shape locking of the fitted skeleton, a cover box for the raised structure in the leakage area of ​​the fuel tank is designed. In the above technical solution of the present invention, the cover box avoidance structure can be defined based on the size and position of protrusions such as fuel tank bolts and long stringers. Using shape memory alloys, the "shrink-lock" property of the temperature-controlled triggered memory alloy is utilized to generate a cover box skeleton that can avoid various special structures of the fuel tank. The designed cover box has good sealing performance and the entire design process is highly efficient. Based on the above technical solution, an airtight soft film that can self-repair in a damaged state can be attached to the skeleton using fluorescent positioning, and the overall sealing performance of the cover box can be controlled by the pressure inside the airtight soft film, further achieving airtight fitting in complex areas of the fuel tank. The above technical solution of the present invention solves the technical problems of poor sealing performance and low design efficiency of existing sealed cover boxes.

[0007] Furthermore, in the cover box design method for the raised structure in the oil tank leakage area of ​​the present invention, determining the cover box avoidance size includes: The bolts on the fuel tank are defined as round hole structures, and the long stringers and reinforcement ribs are defined as strip structures; The radial avoidance and length extension of the cover box are: , ;in, Indicates the radial avoidance of the cover box, represents the safety factor, represents the sealing contact force, represents the elastic modulus of the airtight soft film, represents the film thickness, Indicates the length extension, Indicates the ultimate tensile rate of the soft film, Indicates the original length of the structure.

[0008] Furthermore, in the cover box design method for the raised structure in the oil tank leakage area of ​​the present invention, the skeleton processing according to the cover box avoidance size includes: Obtaining nickel-titanium alloy wire and removing the oxide layer on its surface; Based on the inverse reconstruction model and the avoidance structure, the cutting path of the nickel-titanium alloy wire is dynamically planned, with the spacing between adjacent cutting segments as a constraint condition. The objective function is: ;in, Indicates the cutting angle, Indicates the dwell time at the corner; By improving the ant colony algorithm to optimize the path, the alloy skeleton is processed by laser cutting; And / or, the temperature of the heat treatment is 550-750°C.

[0009] Furthermore, in the method for designing a cover box for a raised structure in a fuel tank leakage area of ​​the present invention, the temperature activation and shape locking of the bonded skeleton includes: The skeleton is heated using a resistance wire array, and after heating, the grid of the skeleton contracts to form a preset avoidance structure; The power of the resistance wire is controlled to make its target critical temperature 65~75℃. The control process is expressed as: ; in, represents the power variation function over time, represents the proportional gain coefficient, represents the instantaneous error, represents the integral gain coefficient, Indicates time The instantaneous error at time, represents the differential gain coefficient, Indicates the temperature setting value, Indicates the actual temperature value.

[0010] Furthermore, in the method for designing a cover box for a convex structure in a fuel tank leakage area of ​​the present invention, the step of obtaining characteristic parameters of the convex structure in the fuel tank leakage area includes: Install a rotating camera bracket inside the oil tank to scan the leak location; collecting and preprocessing point cloud data of the convex structure of the oil tank leakage area, and reconstructing the oil tank leakage area to obtain a three-dimensional model; The characteristic parameters of the convex structure in the oil tank leakage area are obtained according to the three-dimensional model.

[0011] Furthermore, in the method for designing a cover box for a convex structure in a fuel tank leakage area of ​​the present invention, the step of obtaining characteristic parameters of the convex structure in the fuel tank leakage area according to the three-dimensional model includes: Determine the special surface. In the three-dimensional model, the auxiliary surface includes the fillet surface, inner fillet surface and chamfer surface existing in the three-dimensional model; the small surface is a surface with a small geometric area and less geometric information; the area S of the current surface and the overall area S of the three-dimensional model are used to calculate the surface area. sum As the judgment criterion, when the ratio is less than the threshold e, the corresponding surface is judged as a small surface, and both the auxiliary surface and the small surface are determined as special surfaces; Face set definition, determine the specific face f of the 3D model s, add all specific faces to the specific face set V s , the other faces are determined as general faces f m , add all general faces to the general face set V m , the adjacent face set of the face is determined as V n ; All surfaces of the three-dimensional model are traversed to obtain feature parameters.

[0012] Furthermore, in the method for designing a cover box for a raised structure in a fuel tank leakage area of ​​the present invention, traversing all surfaces of the three-dimensional model to obtain characteristic parameters includes: Traverse all faces of the 3D model, and traverse the specific face set V according to the specific face, general face, specific face set, general face set and adjacent face set. s A specific face f in s , the adjacent face set V of its face n If there are other specific faces f s , then the two specific faces f s Add to a list and put two specific faces f s The adjacent face set V of the face n Merger; wherein: If the adjacent face set V of the new face n There are still certain aspects in s , then continue to add to the list until the adjacent face set V of the face n There is no specific face in s ; All specific faces in the list f s and general noodles m and its adjacent face set V n The combined features are exported; the exported surface features are compared with the raised structures in the test area of ​​the fuel tank, and the geometric dimensions and position coordinates of the raised structures that need to be avoided are marked to complete the feature parameter extraction; The raised structure of the oil tank to be tested area includes bolts, long beams and reinforcing ribs.

[0013] Furthermore, in the method for designing a cover box for a raised structure in a fuel tank leakage area of ​​the present invention, after temperature activation and shape locking of the skeleton, the method further includes: A self-repairing airtight soft film is used to attach the airtight soft film to the frame through fluorescent alignment, and the sealing of the cover box is adjusted by pressure control.

[0014] Furthermore, in the method for designing a cover box for a raised structure in a fuel tank leakage area of ​​the present invention, the self-repairable airtight soft film is attached to the frame by fluorescent alignment, and the sealing of the cover box is adjusted by pressure control, including: An airtight soft film is attached to the skeleton, and a UV fluorescent marking layer is simultaneously covered on the outside of the skeleton. The position of the marking point is aligned with the edge of the avoidance hole, and the deformation error of the marking point is compensated based on bilinear interpolation. The coordinate correction formula is: , ; in, Indicates the corrected coordinate, Indicates the value before correction coordinate, represents the correction weight parameter, express The deformation error of the direction, Indicates the corrected coordinate, Indicates the value before correction coordinate, express Directional deformation error; Place the cover box on the raised surface of the tank's leaking area, turn on the UV light, and visually or with a camera to capture the position of the marking point and the reference point on the tank surface. If the deviation is greater than 0.5mm, adjust the cover box manually or with a robotic arm until the fluorescent marking points coincide. Connect a vacuum pump to reduce the pressure inside the cavity. The minimum pressure difference required for bonding is: ;in, Indicates the minimum pressure difference required for bonding. represents the contact force, Indicates the contact area between the cover box and the fuel tank, represents the friction coefficient, Indicates the pre-tightening force of the cover box on the fuel tank.

[0015] Furthermore, in the method for designing a cover box for a raised structure in a leakage area of ​​a fuel tank of the present invention, after determining the minimum pressure difference required for the fitting, the method further includes: Based on the minimum pressure difference, a safety margin of 3 to 5 times is set, the airtight soft film is sunken to fit the tank surface, and the pressure fluctuation rate in the cavity is maintained at less than or equal to 3 kPa / minute; Check the coverage of the cover box on the raised structure of the fuel tank leakage area. If it meets the requirements, turn off the heating element, wait for the frame to cool to below 40°C to restore its flexible state, and remove the cover box that meets the requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1A schematic flow chart of a method for designing a cover box according to the present invention; Figure 2 This is a schematic diagram of the three-dimensional reconstruction regional model of the complex area of ​​the fuel tank in the present invention; Figure 3 This is a schematic diagram of the 3D reconstruction process of the complex area of ​​the fuel tank in the present invention; Figure 4 Schematic diagram of the coverage degree of the cover box on the leakage area of ​​the fuel tank in the present invention. DETAILED DESCRIPTION

[0017] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0019] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined. "Several" means one or more, unless otherwise specifically defined.

[0020] Existing technologies face challenges and shortcomings in testing sealing covers in leaking fuel tank areas. When sealing and plugging leaking areas in aircraft wing fuel tanks, it is necessary to design and manufacture dedicated sealing inspection covers for sealing tests based on the spatial structure of each location requiring sealing inspection. The structural conditions at each location are inconsistent, requiring the covers to be matched and installed one by one. Operators must accurately identify and confirm the shape and installation position of each sealing tool and perform precise installation to ensure the sealing effect, resulting in low efficiency. Furthermore, existing sealing covers all achieve contact sealing with the aircraft fuel tank structure through a rigid structure plus a rubber interlayer. The design of the sealing layer has not been evaluated through specific parameter studies, resulting in an inability to guarantee sealing. Clearly, existing sealing covers have technical issues with poor sealing and low design efficiency.

[0021] In order to solve the above technical problems, the present invention provides a method for designing a cover box for a raised structure in a fuel tank leakage area, comprising: Obtain characteristic parameters of the convex structure in the leakage area of ​​the fuel tank; determining the cover box avoidance size according to the characteristic parameters; Dynamic planning of the cutting path is performed based on the reverse reconstruction model of the fuel tank, and the skeleton is processed according to the avoidance size of the cover box; the processed skeleton is fitted to the protruding structure to be inspected, and heat treated to finalize the shape; The bonded skeleton is temperature activated and shape locked.

[0022] Under the condition of adopting the above-mentioned technical scheme, in the cover box design method for the raised structure in the leakage area of ​​the fuel tank of the present invention, compared with the prior art, after obtaining the characteristic parameters of the raised structure in the leakage area of ​​the fuel tank, the cover box avoidance size is determined according to the characteristic parameters; further, the cutting path is dynamically planned based on the inverse reconstruction model of the fuel tank, and the skeleton is processed according to the cover box avoidance size; the processed skeleton is fitted to the raised structure to be detected and heat-treated to shape it; after temperature activation and shape locking of the fitted skeleton, a cover box for the raised structure in the leakage area of ​​the fuel tank is designed. In the above technical solution of the present invention, the cover box avoidance structure can be defined based on the size and position of protrusions such as fuel tank bolts and long stringers. Using shape memory alloys, the "shrink-lock" property of the temperature-controlled triggered memory alloy is utilized to generate a cover box skeleton that can avoid various special structures of the fuel tank. The designed cover box has good sealing performance and the entire design process is highly efficient. Based on the above technical solution, an airtight soft film that can self-repair in a damaged state can be attached to the skeleton using fluorescent positioning, and the overall sealing performance of the cover box can be controlled by the pressure inside the airtight soft film, further achieving airtight fitting in complex areas of the fuel tank. The above technical solution of the present invention solves the technical problems of poor sealing performance and low design efficiency of existing sealed cover boxes.

[0023] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with specific examples, but the content of the present invention is not limited to the following examples.

[0024] Example 1 This embodiment provides a method for designing a cover box for a raised structure in a fuel tank leakage area, including: S100, obtaining characteristic parameters of the convex structure in the oil tank leakage area; Furthermore, the content of step S100 includes: Install a rotating camera bracket inside the oil tank to scan the leak location; collecting and preprocessing point cloud data of the convex structure of the oil tank leakage area, and reconstructing the oil tank leakage area to obtain a three-dimensional model; Acquire characteristic parameters of the convex structure in the oil tank leakage area according to the three-dimensional model; Furthermore, the step of obtaining characteristic parameters of the protrusion structure in the oil tank leakage area according to the three-dimensional model includes: Determine the special surface. In the three-dimensional model, the auxiliary surface includes the fillet surface, inner fillet surface and chamfer surface existing in the three-dimensional model; the small surface is a surface with a small geometric area and less geometric information; the area S of the current surface and the overall area S of the three-dimensional model are used to calculate the surface area. sum As the judgment criterion, when the ratio is less than the threshold e, the corresponding surface is judged as a small surface, and both the auxiliary surface and the small surface are determined as special surfaces; Face set definition, determine the specific face f of the 3D model s , add all specific faces to the specific face set V s , the other faces are determined as general faces f m , add all general faces to the general face set V m , the adjacent face set of the face is determined as V n ; Traversing all faces of the three-dimensional model to obtain feature parameters; Furthermore, traversing all faces of the three-dimensional model to obtain feature parameters includes: Traverse all faces of the 3D model, and traverse the specific face set V according to the specific face, general face, specific face set, general face set and adjacent face set. s A specific face f in s , the adjacent face set V of its face n If there are other specific faces f s , then the two specific faces f s Add to a list and put two specific faces f s The adjacent face set V of the face n Merger; wherein: If the adjacent face set V of the new face n There are still certain aspects in s , then continue to add to the list until the adjacent face set V of the face n There is no specific face in s ; All specific faces in the list f s and general noodles m and its adjacent face set V n The combined features are exported; the exported surface features are compared with the raised structures in the test area of ​​the fuel tank, and the geometric dimensions and position coordinates of the raised structures that need to be avoided are marked to complete the feature parameter extraction; The raised structure of the oil tank to be tested area includes bolts, long beams and reinforcing ribs.

[0025] S200, determining a cover box avoidance dimension according to the characteristic parameters; Furthermore, in step S200, the process of determining the cover box avoidance size is as follows: The bolts on the fuel tank are defined as round hole structures, and the long stringers and reinforcement ribs are defined as strip structures; The radial avoidance and length extension of the cover box are: , ;in, Indicates the radial avoidance of the cover box, represents the safety factor, represents the sealing contact force, represents the elastic modulus of the airtight soft film, represents the film thickness, Indicates the length extension, Indicates the ultimate tensile rate of the soft film, Indicates the original length of the structure.

[0026] S300: Dynamically planning a cutting path based on the reverse reconstruction model of the fuel tank, processing the skeleton according to the cover box avoidance size; fitting the processed skeleton to the protruding structure to be inspected, and performing heat treatment to finalize the shape; Furthermore, the skeleton processing according to the cover box avoidance size includes: Obtaining nickel-titanium alloy wire and removing the oxide layer on its surface; Based on the inverse reconstruction model and the avoidance structure, the cutting path of the nickel-titanium alloy wire is dynamically planned, with the spacing between adjacent cutting segments as a constraint condition. The objective function is: ;in, Indicates the cutting angle, Indicates the dwell time at the corner; By improving the ant colony algorithm to optimize the path, the alloy skeleton is processed by laser cutting; The heat treatment setting temperature is 550-750°C. For example, the heat treatment setting temperature is 550°C, 650°C or 750°C.

[0027] S400, temperature activation and shape locking of the bonded skeleton; Furthermore, the content of step S400 includes: The skeleton is heated using a resistance wire array, and after heating, the grid of the skeleton contracts to form a preset avoidance structure; The power of the resistance wire is controlled to make its target critical temperature 65~75℃. The control process is expressed as: ; in, represents the power variation function over time, represents the proportional gain coefficient, represents the instantaneous error, represents the integral gain coefficient, Indicates time The instantaneous error at time, represents the differential gain coefficient, Indicates the temperature setting value, Indicates the actual temperature value.

[0028] S500 uses a self-repairing airtight soft film, which is attached to the frame through fluorescent alignment, and the sealing of the cover box is adjusted by pressure control; Furthermore, the content of step S500 includes: An airtight soft film is attached to the skeleton, and a UV fluorescent marking layer is simultaneously covered on the outside of the skeleton. The position of the marking point is aligned with the edge of the avoidance hole, and the deformation error of the marking point is compensated based on bilinear interpolation. The coordinate correction formula is: , ; in, Indicates the corrected coordinate, Indicates the value before correction coordinate, represents the correction weight parameter, express The deformation error of the direction, Indicates the corrected coordinate, Indicates the value before correction coordinate, express Directional deformation error; Place the cover box on the raised surface of the tank's leaking area, turn on the UV light, and visually or with a camera to capture the position of the marking point and the reference point on the tank surface. If the deviation is greater than 0.5mm, adjust the cover box manually or with a robotic arm until the fluorescent marking points coincide. Connect a vacuum pump to reduce the pressure inside the cavity. The minimum pressure difference required for bonding is: ;in, Indicates the minimum pressure difference required for bonding. represents the contact force, Indicates the contact area between the cover box and the fuel tank, represents the friction coefficient, Indicates the pre-tightening force of the cover box on the fuel tank; Based on the minimum pressure difference, a safety margin of 3 to 5 times is set, the airtight soft film is sunken to fit the tank surface, and the pressure fluctuation rate in the cavity is maintained at less than or equal to 3 kPa / minute; Check the coverage of the cover box on the raised structure of the fuel tank leakage area. If it meets the requirements, turn off the heating element, wait for the frame to cool to below 40°C to restore its flexible state, and remove the cover box that meets the requirements.

[0029] Example 2 This embodiment provides a method for designing a cover box for a raised structure in a fuel tank leakage area, including: S100, obtaining characteristic parameters of the convex structure in the oil tank leakage area; Further, see Figure 3 , the contents of step S100 include: S101, installation of 3D scanning equipment for confined areas of the fuel tank; for 3D scanning in confined spaces, a rotating camera bracket is installed inside the fuel tank to achieve full-scale scanning of the leak location; S102, acquisition and preprocessing of point cloud data for complex areas. During data acquisition, surface data of an object is recorded as points after being scanned by a scanning device. Each point contains three-dimensional coordinates and other information about the point's attributes. The specific implementation process of data acquisition is as follows: Pre-processing: Place the laser 3D scanner in a stable environment, avoiding strong light and backlight to ensure that the laser 3D scanner results are not affected by external factors; calibrate the laser 3D scanner before scanning to ensure accurate 3D scanning of the 3D data; spray a thin layer of developer on the surface of the workpiece in the oil tank leakage area to better scan the 3D features of the object and make the data more accurate. The camera parameter determination process is as follows: ; Where s represents the scale factor, which is used to scale the three-dimensional space point when projecting it onto the two-dimensional image plane. represents the homogeneous coordinates of a point on the image plane, 、 Respectively represent the horizontal and vertical coordinates of the image plane, K represents the intrinsic parameter matrix of the camera, Represents the external parameter matrix, which describes the rotation and translation relationship between the camera coordinate system and the world coordinate system. 、 、 is the column vector of the rotation matrix, is the translation vector, represents the homogeneous coordinates of a point in a general coordinate system, represents the simplified extrinsic parameter matrix, Represents the homogeneous coordinates of a point on the template plane; ;in, Represents the homography matrix, which describes the projective transformation relationship between two planes. Represents the homography matrix Column vector of , represents the scaling factor, represents the intrinsic parameter matrix of the camera, represents the simplified extrinsic parameter matrix, Represents the external parameter matrix corresponding to The column vector of the direction, Represents the external parameter matrix corresponding to Column vector of direction; According to the properties of the rotation matrix, and ,in, express The transposed vector of Represents the external parameter matrix corresponding to The column vector of the direction, Representing the norm, i.e., the modulus of the vector, each image can obtain the following two basic constraints on the internal parameter matrix: ; ;in, Represents the transposition operator symbol, Represents the homography matrix The first column vector of Represents the homography matrix The second column vector of Represents the intrinsic parameter matrix of the camera; Since the camera has four unknown intrinsic parameters, when the number of captured images is greater than or equal to 3, the K value can be solved linearly and uniquely; 3D scanning and point cloud data extraction: Marking points are attached to the leaking area of ​​the tank to locate the scanning plane; the object in the leaking area of ​​the tank is scanned from multiple angles, and the relative positions of each surface are determined based on the marking points on each surface. The objects are then automatically spliced ​​together to generate a complete scanning engineering file of the physical model; S103, reconstructing the entity of the fuel tank leakage area; reverse modeling quickly and accurately creates a three-dimensional model by processing point cloud data, surface fitting, and patch sketching functions; converting the entity reconstructed by reverse modeling into solid data in STL format, importing it into a 3D printer, setting printing parameters such as material selection, filling material, temperature, support, etc., and printing the solid model of the fuel tank leakage area to obtain a three-dimensional model; S104, obtaining characteristic parameters of the convex structure in the oil tank leakage area according to the three-dimensional model; Furthermore, the step of obtaining characteristic parameters of the protrusion structure in the oil tank leakage area according to the three-dimensional model includes: Determine the special surface. In the three-dimensional model, the auxiliary surface includes the fillet surface, inner fillet surface and chamfer surface existing in the three-dimensional model; the small surface is a surface with a small geometric area and less geometric information; the area S of the current surface and the overall area S of the three-dimensional model are used to calculate the surface area. sum The ratio of is used as the judgment standard, that is, ,When the ratio is less than the threshold e, the corresponding face is judged as a tiny face, and both the auxiliary face and the tiny face are determined as special faces; Face set definition, determine the specific face f of the 3D model s , add all specific faces to the specific face set V s , the other faces are determined as general faces f m , add all general faces to the general face set V m , the adjacent face set of the face is determined as V n ; Traversing all faces of the three-dimensional model to obtain feature parameters; Furthermore, traversing all faces of the three-dimensional model to obtain feature parameters includes: Traverse all faces of the 3D model, and traverse the specific face set V according to the specific face, general face, specific face set, general face set and adjacent face set. s A specific face f in s , the adjacent face set V of its face n If there are other specific faces f s , then the two specific faces f s Add to a list and put two specific faces f s The adjacent face set V of the face n Merger; wherein: If the adjacent face set V of the new face n There are still certain aspects in s , then continue to add to the list until the adjacent face set V of the face n There is no specific face in s ; All specific faces in the list f s and general noodles m and its adjacent face set V n The combined features are exported; the exported surface features are compared with the raised structures in the test area of ​​the fuel tank, and the geometric dimensions and position coordinates of the raised structures that need to be avoided are marked to complete the feature parameter extraction; The raised structure of the oil tank to be tested area includes bolts, long beams and reinforcing ribs.

[0030] S200, determining a cover box avoidance dimension according to the characteristic parameters; Furthermore, in step S200, the process of determining the cover box avoidance size is as follows: The bolts on the fuel tank are defined as round hole structures, and the long stringers and reinforcement ribs are defined as strip structures; The radial avoidance and length extension of the cover box are: , ;in, Indicates the radial avoidance of the cover box, Indicates the safety factor, the safety factor value is 0.1~0.5, represents the sealing contact force, represents the elastic modulus of the airtight soft film, represents the film thickness, Indicates the length extension, Indicates the ultimate tensile rate of the soft film, Indicates the original length of the structure.

[0031] S300: Dynamically planning a cutting path based on the reverse reconstruction model of the fuel tank, processing the skeleton according to the cover box avoidance size; fitting the processed skeleton to the protruding structure to be inspected, and performing heat treatment to finalize the shape; Furthermore, the skeleton processing according to the cover box avoidance size includes: Obtaining nickel-titanium alloy wire and removing the oxide layer on its surface; Based on the inverse reconstruction model and the avoidance structure, the cutting path of the nickel-titanium alloy wire is dynamically planned, with the spacing between adjacent cutting segments as a constraint condition. The objective function is: ;in, Indicates the cutting angle, Indicates the dwell time at the corner; By improving the ant colony algorithm to optimize the path, the alloy skeleton is processed by laser cutting; The heat treatment setting temperature is 550-750°C. For example, the heat treatment setting temperature is 550°C, 650°C or 750°C.

[0032] S400, temperature activation and shape locking of the bonded skeleton; Furthermore, the content of step S400 includes: The skeleton is heated using a resistance wire array, and after heating, the grid of the skeleton contracts to form a preset avoidance structure; The power of the resistance wire is controlled to make its target critical temperature 65~75℃. The control process is expressed as: ; in, represents the power variation function over time, represents the proportional gain coefficient, represents the instantaneous error, represents the integral gain coefficient, Indicates time The instantaneous error at time, represents the differential gain coefficient, Indicates the temperature setting value, Indicates the actual temperature value.

[0033] S500 uses a self-repairing airtight soft film, which is attached to the frame through fluorescent alignment, and the sealing of the cover box is adjusted by pressure control; Furthermore, the content of step S500 includes: An airtight soft film is attached to the skeleton, and a UV fluorescent marking layer is simultaneously covered on the outside of the skeleton. The position of the marking point is aligned with the edge of the avoidance hole, and the deformation error of the marking point is compensated based on bilinear interpolation. The coordinate correction formula is: , ; in, Indicates the corrected coordinate, Indicates the value before correction coordinate, represents the correction weight parameter, express The deformation error of the direction, Indicates the corrected coordinate, Indicates the value before correction coordinate, express Directional deformation error; Furthermore, the preparation process of the airtight soft film may be: The epoxy resin microcapsules were hot-pressed at a temperature of 180°C and a pressure of 10 MPa. Epoxy resin was dispersed into TPU (thermoplastic polyurethane) at a rate of 5 wt%, forming a self-repairing, airtight soft film. When the film is damaged, the epoxy resin is released from the damaged area, completing self-repair under oxygen catalysis. Place the cover box on the raised surface of the tank's leaking area, turn on the UV light, and visually or with a camera to capture the position of the marking point and the reference point on the tank surface. If the deviation is greater than 0.5mm, adjust the cover box manually or with a robotic arm until the fluorescent marking points coincide. Connect a vacuum pump to reduce the pressure inside the cavity. The minimum pressure difference required for bonding is: ;in, Indicates the minimum pressure difference required for bonding. represents the contact force, Indicates the contact area between the cover box and the fuel tank, represents the friction coefficient, Indicates the pre-tightening force of the cover box on the fuel tank; Based on the minimum pressure difference, a safety margin of 3 to 5 times is set, the airtight soft film is sunken to fit the tank surface, and the pressure fluctuation rate in the cavity is maintained at less than or equal to 3 kPa / minute; Check the coverage of the cover box on the raised structure of the fuel tank leakage area. If it meets the requirements, turn off the heating element, wait for the frame to cool to below 40°C to restore its flexible state, and remove the cover box that meets the requirements.

[0034] Example 3 See also Figure 1 This embodiment provides a method for designing a cover box for a raised structure in a fuel tank leakage area, including: S1, 3D reconstruction and feature extraction for the narrow area of ​​the fuel tank leakage; S101, please refer to Figure 3 This embodiment uses a Phantom S210 micro laser scanner (resolution 0.01mm, field of view 70°) with a 4-DOF micro-manipulator (positioning accuracy ±0.03mm). The scanning path adopts spiral progressive coverage (pitch increment 3mm, scanning speed 25mm / s). Titanium dioxide developer (particle diameter 5μm, coverage ≥95%) is sprayed to enhance the surface diffuse reflectivity. A high-precision calibration target sphere (diameter 10mm, position error <0.005mm) is installed as a stitching reference. In S102, multi-view point clouds were aligned and stitched using the ICP algorithm, with a stitching residual RMS of ≤0.02mm. Noise was filtered using statistical outliers (neighborhood radius 3mm, standard deviation threshold 2.0). A complete 3D model was formed using NURBS surface fitting (order 3×3, control point density 12 points / cm²), with a maximum model deviation of ±0.15mm. The reconstructed model was as follows: As shown; S103, the entity reconstructed by reverse modeling is converted into entity data in STL format, imported into the 3D printer, and the parameters are set as shown in Table 1, and the physical object is printed; the 3D printed physical object is compared with the original structure, and the dimensional consistency is ≥99.2% with the three-dimensional coordinate measuring machine (error ±0.01mm). The three-dimensional reverse reconstruction process is as follows As shown; Table 1 3D printing parameter settings

[0035] S104, 3D model special surface definition, model total area S sum =12560mm 2 , set the small face threshold e=0.1% and set the area smaller than 12.56mm 2The faces with the radius of 0.1 mm are defined as tiny faces. Based on curvature mutation detection (curvature change rate > 0.1 mm⁻¹), fillets / chamfers are marked and defined as auxiliary faces. The corresponding special faces, general faces, and adjacent faces are placed in the corresponding face set. All faces of the 3D model are traversed, and if the distance between adjacent special faces is less than 0.1 mm, they are merged into the same feature area. 26 sets of composite features are output, including key avoidance structures such as bolt bosses, long string intersections, and bosses. The positions and sizes of the extracted avoidance features are recorded and compared with the actual sizes. Some comparisons are shown in Table 2.

[0036] Table 2 Comparison of some feature sizes

[0037] S2, shape memory alloy cover box frame design for structural avoidance; S201: Based on the extracted convex structural features of the fuel tank leakage area, define the cover box avoidance structure: define the bolts on the fuel tank area model as circular holes with a hole diameter equal to the bolt diameter + 2 mm (surface glue thickness 2 mm); define the long stringers and reinforcements as strip structures with dimensions equal to the corresponding long stringers or reinforcements, and set the safety factor to 0.1; S202, using nickel-titanium alloy wire (0.5mm diameter, phase transition temperature 68°C) as the material, the nickel-titanium alloy wire was immersed in an electrolyte and treated with a plasma cleaner for 5 minutes to remove the surface oxide layer. Laser cutting was performed at a speed of 1000mm / min, a power of 250W, and a focus offset of ±0.3mm. Heat treatment conditions were 650°C for 15 minutes (in a vacuum environment), followed by water quenching (cooling rate 200°C / s) to form a structure with various irregular protrusions in the narrow area of ​​the aircraft fuel tank leak. In step S203, the skeleton is heated using a resistance wire array (heating rate 4°C / s). The grid shrinks to form a preset avoidance hole (deviation ≤ 0.3mm). The PID (proportional-integral-differential) algorithm is used to adjust the resistance wire power. The target critical temperature is 70°C, and the control equation is: ; in, represents the power variation function over time, represents the proportional gain coefficient, which is set to 1.8 in this embodiment. represents the instantaneous error, Indicates the integral gain coefficient, which is set to 0.03 in this embodiment. Indicates time The instantaneous error at time, represents the differential gain coefficient, which is set to 0.25 in this embodiment. Indicates the temperature setting value, Indicates the actual temperature value, and the temperature stability error is ≤0.5℃.

[0038] S3, self-repairing airtight soft film attachment and pressure control method for cover box; S301: Prepare epoxy resin microcapsules (particle size 20 μm, shell thickness 2 μm) by hot pressing at 180°C and 10 MPa, maintaining a microcapsule integrity rate of >99%. Disperse 5 wt% of epoxy resin into TPU (thermoplastic polyurethane rubber) raw material to form a self-repairing airtight soft film. S302: Attach an airtight soft film to the shape memory alloy skeleton. Simultaneously, cover the outside of the skeleton with a UV fluorescent marking layer (zinc sulfide-based material, marking point diameter 2mm, spacing 50mm, error ±0.1mm). Align the marking point position with the edge of the avoidance hole. S303: Place the cover box over the surface of the printed model of the complex leakage area of ​​the fuel tank, turn on the UV light, and visually or with a camera to capture the position of the marking point and the reference point on the tank surface. The UV marking point overlap accuracy is ±0.3mm, and the positioning is completed by fine-tuning the robot arm (step resolution 0.01mm). Connect a vacuum pump and pump air to reduce the internal pressure. According to the negative pressure adsorption theory, set the initial adsorption pressure to -90kPa and maintain it at -80kPa in a steady state. The soft film is sunken to fit the surface of the tank and the internal pressure fluctuation rate is maintained at ≤3kPa / min. Check the coverage of the cover box on the tank area. As shown, then turn off the heating element, wait for the skeleton to cool to below 40°C to restore its flexible state, remove the cover box that meets the requirements, and complete the overall inspection cover box design.

[0039] Further, combined with Figure 1 As described in the above embodiment 3, the cover box design method of the above embodiment 3 may mainly include three steps, step S1 mainly includes equipment installation, three-dimensional scanning, reverse reconstruction and feature extraction, step S2 mainly includes cover box avoidance size definition, shape memory alloy skeleton chemical engineering, temperature activation and shape locking, step S3 mainly includes airtight soft film preparation, fluorescent alignment and attachment and pressure control of cover box sealing; the above process has been described in detail in embodiments 1 to 3 and will not be repeated here.

[0040] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0041] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for designing a cover box for a raised structure in a fuel tank leakage area, characterized in that: include: Obtain characteristic parameters of the convex structure in the leakage area of ​​the fuel tank; determining the cover box avoidance size according to the characteristic parameters; Dynamic planning of the cutting path is performed based on the reverse reconstruction model of the fuel tank, and skeleton processing is performed according to the avoidance size of the cover box; Fit the processed skeleton to the protruding structure to be tested and heat treat it to finalize the shape; The bonded skeleton is temperature activated and shape locked.

2. The method for designing a cover box for a raised structure in a fuel tank leakage area according to claim 1, characterized in that: The step of determining the cover box avoidance size includes: The bolts on the fuel tank are defined as round hole structures, and the long stringers and reinforcement ribs are defined as strip structures; The radial avoidance and length extension of the cover box are: , ;in, Indicates the radial avoidance of the cover box, represents the safety factor, represents the sealing contact force, represents the elastic modulus of the airtight soft film, represents the film thickness, Indicates the length extension, Indicates the ultimate tensile rate of the soft film, Indicates the original length of the structure.

3. The method for designing a cover box for a raised structure in a fuel tank leakage area according to claim 2, characterized in that: The skeleton processing according to the cover box avoidance size includes: Obtaining nickel-titanium alloy wire and removing the oxide layer on its surface; Based on the inverse reconstruction model and the avoidance structure, the cutting path of the nickel-titanium alloy wire is dynamically planned, with the spacing between adjacent cutting segments as a constraint condition. The objective function is: ;in, Indicates the cutting angle, Indicates the dwell time at the corner; By improving the ant colony algorithm to optimize the path, the alloy skeleton is processed by laser cutting; And / or, the temperature of the heat treatment is 550-750°C.

4. The method for designing a cover box for a raised structure in a fuel tank leakage area according to claim 3, characterized in that: The temperature activation and shape locking of the bonded skeleton includes: The skeleton is heated using a resistance wire array, and after heating, the grid of the skeleton contracts to form a preset avoidance structure; The power of the resistance wire is controlled to make its target critical temperature 65~75℃. The control process is expressed as: ； in, represents the power variation function over time, represents the proportional gain coefficient, represents the instantaneous error, represents the integral gain coefficient, Indicates time The instantaneous error at time, represents the differential gain coefficient, Indicates the temperature setting value, Indicates the actual temperature value.

5. The method for designing a cover box for a raised structure in a fuel tank leakage area according to claim 4, characterized in that: The step of obtaining characteristic parameters of the convex structure in the oil tank leakage area includes: Install a rotating camera bracket inside the oil tank to scan the leak location; collecting and preprocessing point cloud data of the convex structure of the oil tank leakage area, and reconstructing the oil tank leakage area to obtain a three-dimensional model; The characteristic parameters of the convex structure in the oil tank leakage area are obtained according to the three-dimensional model.

6. The method for designing a cover box for a raised structure in a fuel tank leakage area according to claim 5, characterized in that: The step of obtaining characteristic parameters of the protrusion structure in the oil tank leakage area according to the three-dimensional model includes: Determine the special surface. In the three-dimensional model, the auxiliary surface includes the fillet surface, inner fillet surface and chamfer surface existing in the three-dimensional model; the small surface is a surface with a small geometric area and less geometric information; the area S of the current surface and the overall area S of the three-dimensional model are used to calculate the surface area. sum As the judgment criterion, when the ratio is less than the threshold e, the corresponding surface is judged as a small surface, and both the auxiliary surface and the small surface are determined as special surfaces; Face set definition, determine the specific face f of the 3D model s , add all specific faces to the specific face set V s , the other faces are determined as general faces f m , add all general faces to the general face set V m , the adjacent face set of the face is determined as V n ; All surfaces of the three-dimensional model are traversed to obtain feature parameters.

7. The method for designing a cover box for a raised structure in a fuel tank leakage area according to claim 6, characterized in that: The step of traversing all surfaces of the three-dimensional model to obtain feature parameters includes: Traverse all faces of the 3D model, and traverse the specific face set V according to the specific face, general face, specific face set, general face set and adjacent face set. s A specific face f in s , the adjacent face set V of its face n If there are other specific faces f s , then the two specific faces f s Add to a list and put two specific faces f s The adjacent face set V of the face n Merger; wherein: If the adjacent face set V of the new face n There are still certain aspects in s , then continue to add to the list until the adjacent face set V of the face n There is no specific face in s ; All specific faces in the list f s and general noodles m and its adjacent face set V n The combined features are exported; the exported surface features are compared with the raised structures in the test area of ​​the fuel tank, and the geometric dimensions and position coordinates of the raised structures that need to be avoided are marked to complete the feature parameter extraction; The raised structure of the oil tank to be tested area includes bolts, long beams and reinforcing ribs.

8. The method for designing a cover box for a raised structure in a fuel tank leakage area according to claim 7, characterized in that: After the skeleton is temperature activated and morphologically locked, the method further comprises: A self-repairing airtight soft film is used to attach the airtight soft film to the frame through fluorescent alignment, and the sealing of the cover box is adjusted by pressure control.

9. The method for designing a cover box for a raised structure in a fuel tank leakage area according to claim 8, characterized in that: The self-repairable airtight soft film is attached to the frame by fluorescence alignment, and the sealing of the cover box is adjusted by pressure control, including: An airtight soft film is attached to the skeleton, and a UV fluorescent marking layer is simultaneously covered on the outside of the skeleton. The position of the marking point is aligned with the edge of the avoidance hole, and the deformation error of the marking point is compensated based on bilinear interpolation. The coordinate correction formula is: , ; in, Indicates the corrected coordinate, Indicates the value before correction coordinate, represents the correction weight parameter, express The deformation error of the direction, Indicates the corrected coordinate, Indicates the value before correction coordinate, express Directional deformation error; Place the cover box on the raised surface of the tank's leaking area, turn on the UV light, and visually or with a camera to capture the position of the marking point and the reference point on the tank surface. If the deviation is greater than 0.5mm, adjust the cover box manually or with a robotic arm until the fluorescent marking points coincide. Connect a vacuum pump to reduce the pressure inside the cavity. The minimum pressure difference required for bonding is: ;in, Indicates the minimum pressure difference required for bonding. represents the contact force, Indicates the contact area between the cover box and the fuel tank, represents the friction coefficient, Indicates the pre-tightening force of the cover box on the fuel tank.

10. The method for designing a cover box for a raised structure in a fuel tank leakage area according to claim 9, characterized in that: After determining the minimum pressure difference required for the bonding, the following steps are also included: Based on the minimum pressure difference, a safety margin of 3 to 5 times is set, the airtight soft film is sunken to fit the tank surface, and the pressure fluctuation rate in the cavity is maintained at less than or equal to 3 kPa / minute; Check the coverage of the cover box on the raised structure of the fuel tank leakage area. If it meets the requirements, turn off the heating element, wait for the frame to cool to below 40°C to restore its flexible state, and remove the cover box that meets the requirements.

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