A method for shape detection control compensation of aircraft frame skin butt joint
By using a standard strip plate with positive and negative fitting and a camera measurement method, the step difference problem when mating skins of different thicknesses was solved, and precise control and efficient repair of skin mating were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- AVIC XIAN AIRCRAFT IND GRP CO LTD
- Filing Date
- 2026-04-29
- Publication Date
- 2026-07-14
AI Technical Summary
In existing technologies, when connecting metals and composite skins of different thicknesses, there is a problem of excessive step difference, resulting in poor connection accuracy and a large workload.
Using standard tape plates with positive and negative mating, and by setting marking lines and spline normals, combined with CAD models and camera measurements, the seam gap is precisely controlled, and precise mating is achieved through trimming or padding.
It improved the accuracy and coordination of skin docking, reduced the workload, and enabled precise control of skin docking for large aircraft.
Smart Images
Figure CN122379833A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to, but is not limited to, the field of large aircraft skin docking technology, and particularly to a shape detection, control and compensation method for docking of aircraft frame skin. Background Technology
[0002] During aircraft assembly and docking, there are numerous processes for controlling the step difference and gap between the mating seams of the skin panels. Generally, the thickness accuracy of the two mating skin panels, which are machined, is almost the same, and the shape difference and gap accuracy at the seam are easy to control. However, in actual assembly, due to the extensive use of composite structures that cannot be completely replaced, there are objectively situations where skin panels manufactured with two different materials and processes are mated. One skin is a machined metal skin, whose machining thickness accuracy can generally be controlled to around 0.2mm. The other skin is a composite skin. The molding of composite skin involves a semi-liquefied resin to curing process, and the thickness accuracy is generally around 7% to 12% of the thickness. Taking the current international highest of 7% and the thickness of a certain area of a large aircraft panel of 40mm as an example, the thickness error is 2.8mm. Moreover, the thickness error is generally positive, that is, thickening. Therefore, there is a maximum step difference of 2.6mm to 3.0mm when mating skin panels of the two materials.
[0003] Currently, the assembly process of two materials with different thicknesses of skin generally adopts two measures to handle the difference in thickness: trimming and shimming. That is, trimming and matching the thickness of the composite skin in the mating area, or shimming to compensate for the thickness of the metal skin in the mating area. This generally results in poor transition and accuracy of the mating, as well as a large workload. Summary of the Invention
[0004] The purpose of this invention is to provide a shape detection, control and compensation method for the docking of skin on an aircraft frame, so as to solve the problems of poor transition and docking accuracy, as well as large workload, in the existing docking methods for skins of two materials with different thicknesses.
[0005] The technical solution of this invention is as follows: This invention provides a shape detection, control, and compensation method for skin docking on an aircraft frame, comprising: Step 1: According to the theory of mating skin 2, set at least one marker line 6 perpendicular to the mating skin 11 along the entire length of the two skins at the seam 11. Step 2: Set up a standard strip plate group for docking based on the mark line 6 and the seam 11, including the positive docking standard strip plate 7 and the negative docking standard strip plate 8 with positive and negative interaction, and solve the measured edge section profile of the seam position of the positive docking standard strip plate 7 and the docking skin 2, and construct the theoretical CAD profile mathematical model of the positive docking standard strip plate 7 and the docking skin 2. Step 3: Based on the net edge of the mating skin 2, the theoretical edge of the object skin 3, the marker line 6 and the spline normal 9, the positive mating standard strip plate 7 is positioned and fixed, and the negative mating standard strip plate 8 is initially positioned and fixed. Step 4: By moving the object skin 3 to the docking skin 2 in a one-way approach docking translation, the anti-dock standard strip plate 8 is finally positioned and fixed by the interlocking teeth. Step 5: After the object skin 3 is removed and translated relative to the docking skin 2, the seam edge is marked on the outer surface of the object skin 3, and the clean edge of the object skin 3 is trimmed and polished. Step 6: Using the clean edge of the mating skin 2 and the clean edge of the object skin 3 after trimming, the mark line 6, and the spline normal line 9 as a comprehensive reference, position and fix the positive mating standard strip plate 7 and the negative mating standard strip plate 8 on the outer surface of the mating skin 2 and the object skin 3 respectively. Step 7: By setting up a camera 15 between the mating skin 2 and the object skin 3, take pictures of the cross-sectional profile of the standard mating strip 7 and the mating skin 2 at the seam 11, and construct the image CAD profile mathematical model. Step 8: Based on the theoretical CAD contour mathematical model, the detection difference of the cross-sectional contour of the joint position of the mating skin 2 is calculated by comparing the image CAD contour mathematical model; and the mating skin 2 is trimmed or / and padded based on the detection difference.
[0006] Optionally, in the above-described shape detection control compensation method for the mating of the skin on an aircraft frame, the number of marker lines 6 set in step 1 is set according to the length of the seam 11. The marking line 6 is set in one of the following ways: by using a locator located at a corresponding position on the upper-level component, the marking line 6 is drawn on the skin outline using a washable, fine-tipped, soft pencil; or, According to the locator, attach the easy-tear sticker with marking line 6 to the skin outline and align the marking line 6 on the sticker with the locator.
[0007] Optionally, in the above-described method for shape detection, control, and compensation of mating of aircraft frame skins, the positive mating standard strip 7 in step 2 is disposed on the mating skin 2, and the negative mating standard strip 8 is disposed on the object skin 3; the method for solving the measured edge cross-sectional profile of the joint position between the positive mating standard strip 7 and the mating skin 2 in step 2 includes: At the seam edge position of the standard strip plate 7 corresponding to the mating skin 2, no less than 5 spline normals 9 are set according to the principle of equal spacing to divide the edge section of the standard strip plate 7 into multiple normal regions. The measured length of each spline normal 9 and the length of the inner contour line of the adjacent spline normal 9 on the edge section of the standard strip plate 7 are measured and recorded. Based on the measured length of each spline normal 9 and the length of the inner contour line of the adjacent spline normal 9 on the edge section of the standard strip plate 7, the measured edge section contour of the standard strip plate 7 is solved by fitting CAD drawing. The methods for constructing the theoretical CAD contour mathematical model in step 2 include: Based on the marker line 6 and spline normal line 9 determined in steps 1 and 2, and their measured data, a theoretical CAD profile mathematical model integrating the edge section profile of the orthogonal standard strip plate 7 and the joint position section profile of the orthogonal skin 2 is constructed.
[0008] Optionally, in the above-described method for shape detection, control, and compensation of skin mating on an aircraft frame, The standard strip assembly set in step 2 is a long thin plate assembly 12 with the thickness of the skin section at the seam 11 of the mating skin 2 and the object skin 3 as the reference thickness. A toothed structure 13 in the form of interlocking comb teeth is set at the mark line 6. Along the entire length of the seam 11 of the standard strip assembly, the edge of the skin seam on the mating side or the object side is used as the edge reference surface of the positive and negative standard strips. Multiple interlocking comb teeth-like structures 13 are set at intervals on the edge reference surface, which are equidistant from each other and have gaps. Both the positive and negative standard strips use the mark line 6 as the longitudinal position reference and the seam 11 as the edge reference.
[0009] Optionally, in the above-described method for shape detection, control, and compensation of skin mating on an aircraft frame, in step 2, The comb teeth in the mating standard strip plate group are arranged in an alternating manner: the tooth-like structures 13 on both sides of the positive mating standard strip plate 7 and the negative mating standard strip plate 8 are closely attached to the corresponding tooth-like structures 13 on the opposite mating standard strip plate in an alternating manner. Each mating standard strip plate has a reference shoulder 14 located between adjacent tooth-like structures 13 at the edge reference position for positioning the mating standard strip plate. The length of the toothed structure 13 in each standard strip plate is set according to the sum of the distance dimensions of the object skin 3 and its components before they are moved into place and the gap between the seams.
[0010] Optionally, in the above-described method for shape detection, control, and compensation of skin mating on an aircraft frame, step 3 includes: Step 31: Using the skin shape and clear edge of the mating skin 2, the mark line 6, and the spline normal line 9 as a comprehensive benchmark, the standard strip plate 7 for mating is positioned and fixed. Step 32: With the object skin 3 far away from the docking skin 2, the anti-dock standard strip plate 8 is initially positioned and fixed using the skin shape, theoretical edge, mark line 6, and spline normal line 9 of the object skin 3 as a comprehensive reference.
[0011] Optionally, in the above-described method for shape detection, control, and compensation of skin mating on an aircraft frame, step 4 includes: Step 41: The object skin 3 and its components are moved in a one-way approach to the docking skin 2 until the toothed structure 13 of the anti-dating standard strip plate 8 is fully aligned and in contact with the reference shoulder 14 of the positive docking standard strip plate 7. Step 42: Using the positive mating standard strip plate 7 as a reference, the negative mating standard strip plate 8 and the positive mating standard strip plate 7 are coordinated and fixed with interlocking comb teeth.
[0012] Optionally, in the above-described method for shape detection, control, and compensation of skin mating on an aircraft frame, step 5 includes: Step 51: The object skin 3 and its components are moved in a one-way retraction and translation to the mating skin 2 until the toothed structure 13 of the positive mating standard strip 7 and the negative mating standard strip 8 are completely disengaged. Step 52: Using the reference shoulder 14 of the positive butt standard belt plate 7 and the negative butt standard belt plate 8 as the edge reference, scribing the seam edge on the outer surface of the butt skin 2 and the object skin 3 before trimming the seam gap uniformity. Step 53: Remove the orthogonal standard strip plate 7 and the anti-orthogonal standard strip plate 8, and trim and polish the clean edge of the object skin 3 according to the scribing lines.
[0013] Optionally, in the above-described method for shape detection, control, and compensation of skin mating on an aircraft frame, step 7 includes: Step 71: Set up a camera at a position away from the clean edge of the mating skin and close to the object skin to take pictures of the cross-sectional profile of the standard strip edge of the mating seam and the cross-sectional profile of the mating seam of the mating skin. Step 72: Based on the edge section profile of the standard strip plate 7 and the joint position section profile of the mating skin 2 extracted from the photos taken by camera 15, construct the image CAD profile mathematical model.
[0014] Optionally, in the above-described method for shape detection, control, and compensation of skin mating on an aircraft frame, step 8 includes: Step 81: Based on the theoretical CAD contour mathematical model, the overlapping line of the cross-sectional contour of the joint position of the standard strip plate 7 and the joint skin 2 in the image CAD contour mathematical model is used as the main weight benchmark. The edge cross-sectional contour of the standard strip plate 7, the marker line 6, and the spline normal line 9 are used as the secondary weight benchmarks for comparison. By comparing with the image CAD contour mathematical model, the detection difference of the cross-sectional contour of the joint position of the joint skin 2 is solved. Step 82: Based on the detection difference, if the image CAD contour mathematical model protrudes from the theoretical CAD contour mathematical model, it is determined to be trimmed; if the image CAD contour mathematical model is lower than the theoretical CAD contour mathematical model, it is determined to be padded. Step 83: Trim and / or pad the mating skin 2; Among them, for each interval that is determined to be trimmed, grinding is performed according to the detection difference of the interval and the interval corresponding to the extension line 10. For independent or multiple consecutive intervals identified as requiring padding, the overlapping line of the cross-sectional profile of the butt joint of the standard strip plate 7 and the butt skin 2 is used as the straight line reference for development. The mark line 6 and the spline normal 9 are used as the vertical line reference for development. The detection difference is used as the numerical basis for the vertical line reference. A pad thickness profile for this interval is developed and fitted. The width of the pad is determined based on the width of the connection area between the butt skin 2 and the butt frame 1. A compensation pad is then manufactured to compensate for the connection position between the butt skin 2 and the frame 1.
[0015] The beneficial effects of this invention are as follows: This invention provides a shape detection, control, and compensation method for the mating of aircraft frame skins, specifically addressing the measurement, fitting, and determination of the thickness dimensions of skin trimming and / or shim addition during the mating process of aircraft frame skins. This invention addresses the difficulty in precisely controlling the shape difference and gap at the seam position during the mating process of large aircraft skins. It employs positive and negative mating standard strips with alternating positive and negative fits to control the gap, and uses photometric measurement to fit and determine the trimming data and / or shim dimensions and structure. The shape detection, control, and compensation method provided by this invention, combined with photometric data analysis, achieves precise detection and control of the mating shape of large aircraft frame skins. Compared to the purely positive and negative sample-coordinated skin mating and fitting method, it introduces data coordination, resulting in higher coordination accuracy and significantly improved segmented and step-by-step coordination feasibility. This invention is applicable to the shape detection and control process of mating of frame skins for various aircraft components and has universal applicability to the mating of frame skins or sheet metal. Attached Figure Description
[0016] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of the present invention and do not constitute a limitation on the technical solutions of the present invention.
[0017] Figure 1 This is an isometric view of the assembly of the skin on the aircraft frame in an embodiment of the present invention; Figure 2 An axonometric view illustrating the implementation principle of the shape detection, control, and compensation method for docking the upper skin of an aircraft frame provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the combined structure of the docking standard strip plate group in the shape detection control compensation method provided by the present invention; Figure 4 This is a schematic diagram of the disassembled structure of the docking standard strip plate group in the shape detection control compensation method provided by the present invention; Figure 5 This is a schematic diagram illustrating the principle of the padding and fitting method in the shape detection control compensation method provided by the present invention; Figure 6 This is a schematic diagram illustrating the principle of photographic measurement of skin deviation structure in the shape detection control compensation method provided by the present invention.
[0018] Explanation of reference numerals in the attached figures: 1. Frame; 2. Butt skin; 3. Object skin; 4. Shim; 5. Repair area; 6. Marker line; 7. Positive butt standard strip plate; 8. Negative butt standard strip plate; 9. Spline normal; 10. Extension line; 11. Butt joint; 12. Long thin plate assembly; 13. Toothed structure; 14. Reference shoulder; 15. Camera. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.
[0020] As explained in the background section, the current assembly process for butt joints of skins made of two different thicknesses generally employs two methods to address the step difference: trimming and shimming. Specifically, existing butt joint assembly methods mainly include the following: 1. Using a feeler gauge to inspect the skin with a step difference in the butt joint area, and then ignoring, adding liquid shims, or adding hard shims based on the inspection results; 2. Using measured data to inspect the fit of the outer shape assembly, and returning the skin thickness exceeding the butt joint thickness step difference to the machining center for sacrificial layer compensation processing; 3. Performing theoretical data inspection and compensation processing on both butt joint skins in their respective pre-processing stages until their thicknesses are essentially consistent according to theoretical data. The shimming method is time-consuming, labor-intensive, and has poor transition characteristics; the compensation processing method based on measured data involves rework and has generally low accuracy; and the theoretical inspection and compensation processing in the pre-processing stages are difficult to simultaneously account for the influence of assembly process factors and involve a large workload.
[0021] The existing skin docking assembly method described above is insufficient to meet the requirements for rapid and precise docking of skins between large aircraft components and parts, which involves steps and gaps. There is an urgent need to research a more precise and faster new technology and solution to address the repair or shim compensation issues when there are large manufacturing errors in the two thicknesses.
[0022] Based on the above requirements, the present invention provides a shape detection, control and compensation method for the docking of the skin on the aircraft frame, specifically for measuring, fitting and determining the thickness of the skin trimming or padding during the docking process of the skin on the aircraft frame.
[0023] The present invention provides the following specific embodiments, which can be combined with each other. For the same or similar concepts or processes, they may not be described again in some embodiments.
[0024] Figure 1 This is a flowchart illustrating a shape detection, control, and compensation method for skin docking on an aircraft frame, provided by an embodiment of the present invention. Figure 1 As shown, the shape detection, control, and compensation method for aircraft frame skin docking provided by the present invention includes the following steps: Step 1: According to the theory of mating skin 2, set at least one marker line 6 perpendicular to the mating skin 11 along the entire length of the two skins at the seam 11. In this step, one or more marker lines can be set according to the actual length of the actual seam 11.
[0025] Step 2: Set up a standard strip plate group for docking based on the mark line 6 and the seam 11, including the positive docking standard strip plate 7 and the negative docking standard strip plate 8 with positive and negative interaction, and solve the measured edge section profile of the seam position of the positive docking standard strip plate 7 and the docking skin 2, and construct the theoretical CAD profile mathematical model of the positive docking standard strip plate 7 and the docking skin 2. Step 3: Based on the net edge of the mating skin 2, the theoretical edge of the object skin 3, the marker line 6 and the spline normal 9, the positive mating standard strip plate 7 is positioned and fixed, and the negative mating standard strip plate 8 is initially positioned and fixed. Step 4: By moving the object skin 3 to the docking skin 2 in a one-way approach docking translation, the anti-dock standard strip plate 8 is finally positioned and fixed by the interlocking teeth. Step 5: After the object skin 3 is removed and translated relative to the docking skin 2, the seam edge is marked on the outer surface of the object skin 3, and the clean edge of the object skin 3 is trimmed and polished. Step 6: Using the clean edge of the mating skin 2 and the clean edge of the object skin 3 after trimming, the mark line 6, and the spline normal line 9 as a comprehensive reference, position and fix the positive mating standard strip plate 7 and the negative mating standard strip plate 8 on the outer surface of the mating skin 2 and the object skin 3 respectively. Step 7: By setting up a camera 15 between the mating skin 2 and the object skin 3, take pictures of the cross-sectional profile of the standard mating strip 7 and the mating skin 2 at the seam 11, and construct the image CAD profile mathematical model. Step 8: Based on the theoretical CAD contour mathematical model, the detection difference of the cross-sectional contour of the joint position of the mating skin 2 is calculated by comparing the image CAD contour mathematical model; and the mating skin 2 is trimmed or / and padded based on the detection difference.
[0026] In one implementation of this invention, the number of marker lines 6 set in step 1 is determined based on the length of the seam 11; the marker lines 6 can be set in the following manner: Method 1: Using the locator set at the corresponding position of the upper group component, draw the marking line 6 on the skin outline with a washable fine-tipped soft pencil; Method 2: Using the locator set at the corresponding position of the upper group component, attach an easy-tear sticker with marking line 6 to the skin outline, and align the marking line 6 on the sticker with the locator.
[0027] In one implementation of this invention, the positive mating standard strip 7 in step 2 is disposed on the mating skin 2, and the negative mating standard strip 8 is disposed on the object skin 3; the method for solving the measured edge cross-sectional profile of the joint position between the positive mating standard strip 7 and the mating skin 2 in step 2 includes: At the seam edge position of the standard strip plate 7 corresponding to the mating skin 2, no less than 5 spline normals 9 are set according to the principle of equal spacing to divide the edge section of the standard strip plate 7 into multiple normal regions. The measured length of each spline normal 9 and the length of the inner contour line of the adjacent spline normal 9 on the edge section of the standard strip plate 7 are measured and recorded. Based on the measured length of each spline normal 9 and the length of the inner contour line of the adjacent spline normal 9 on the edge section of the standard strip plate 7, the measured edge section contour of the standard strip plate 7 is solved by fitting through CAD drawing. In addition, the extension line of the spline normal 9 on the mating skin 2 is the extension line 10.
[0028] In addition, the specific methods for constructing the theoretical CAD contour mathematical model in step 2 include: Based on the marker line 6 and spline normal line 9 determined in steps 1 and 2, and their measured data, a theoretical CAD profile mathematical model is constructed that integrates the edge section profile of the standard strip plate 7 and the section profile of the joint position of the mating skin 2. The theoretical CAD profile mathematical model constructed in step 2 is used to obtain the detection difference of the section profile of the joint position of the mating skin 2 by comparing the image CAD profile mathematical model in subsequent steps.
[0029] Furthermore, in this implementation, the docking standard strip plate group set in step 2 is a long thin plate assembly 12 with the thickness of the skin section at the joint 11 position of the docking skin 2 and the object skin 3 as the reference thickness. A toothed structure 13 in the form of interlocking comb teeth is set at the position of the mark line 6. Along the entire length of the joint 11 of the docking standard strip plate group, the edge of the skin joint on the docking side or the object side is used as the edge reference surface of the positive and negative docking standard strip plates. Multiple toothed structures 13 in the form of interlocking comb teeth with gaps are set at intervals on the edge reference surface. Both the positive and negative docking standard strip plates take the mark line 6 as the longitudinal position reference and the joint 11 as the edge reference.
[0030] In addition, the comb teeth in the standard strip plate group in step 2 are arranged in the following manner: the tooth-like structures 13 on both sides of the positive and negative standard strip plates 7 and 8 are arranged in an alternating manner and closely adhere to the corresponding tooth-like structures 13 on the opposite side of the standard strip plates. Each standard strip plate has a reference shoulder 14 located between adjacent tooth-like structures 13 at the edge reference position for positioning the standard strip plate. In specific implementation, the length of the tooth-like structure 13 in each standard strip plate is set according to the sum of the distance dimensions of the object skin 3 and its components before the docking translation and the seam gap.
[0031] In one implementation of this invention, step 3 may include: Step 31: Using the skin shape and clear edge of the mating skin 2, the mark line 6, and the spline normal line 9 as a comprehensive benchmark, the standard strip plate 7 for mating is positioned and fixed. Step 32: With the object skin 3 far away from the docking skin 2, the anti-dock standard strip plate 8 is initially positioned and fixed using the skin shape, theoretical edge, mark line 6, and spline normal line 9 of the object skin 3 as a comprehensive reference.
[0032] In one implementation of this invention, step 4 may include: Step 41: The object skin 3 and its components are moved in a one-way approach to the docking skin 2 until the toothed structure 13 of the anti-dating standard strip plate 8 is fully aligned and in contact with the reference shoulder 14 of the positive docking standard strip plate 7. Step 42: Using the positive mating standard strip plate 7 as a reference, the negative mating standard strip plate 8 and the positive mating standard strip plate 7 are coordinated and fixed with interlocking comb teeth.
[0033] In one implementation of this invention, step 5 may include: Step 51: The object skin 3 and its components are moved in a one-way retraction and translation to the mating skin 2 until the toothed structure 13 of the positive mating standard strip 7 and the negative mating standard strip 8 are completely disengaged. Step 52: Using the reference shoulder 14 of the positive butt standard belt plate 7 and the negative butt standard belt plate 8 as the edge reference, scribing the seam edge on the outer surface of the butt skin 2 and the object skin 3 before trimming the seam gap uniformity. Step 53: Remove the orthogonal standard strip plate 7 and the anti-orthogonal standard strip plate 8, and trim and polish the clean edge of the object skin 3 according to the scribing lines.
[0034] It should be noted that steps 1 to 5 above are the process of trimming and polishing the clean edge of the object skin 3. By repeating steps 31 to 53, the gap between the mating skin 2 and the object skin 3 is within the gap tolerance control range.
[0035] In one implementation of this invention, step 7 may include: Step 71: At a position far from the clean edge of the mating skin 2 and close to the object skin 3, set up camera 15 to take pictures of the cross-sectional profile of the edge of the standard strip plate 7 at the seam 11 and the cross-sectional profile of the seam position of the mating skin 2. Step 72: Based on the edge section profile of the standard strip plate 7 and the joint position section profile of the mating skin 2 extracted from the photos taken by camera 15, construct the image CAD profile mathematical model.
[0036] In one implementation of this invention, step 8 may include: Step 81: Based on the theoretical CAD contour mathematical model, the overlapping line of the cross-sectional contour of the joint position of the standard strip plate 7 and the joint skin 2 in the image CAD contour mathematical model is used as the main weight benchmark. The edge cross-sectional contour of the standard strip plate 7, the marker line 6, and the spline normal line 9 are used as the secondary weight benchmarks for comparison. By comparing with the image CAD contour mathematical model, the detection difference of the cross-sectional contour of the joint position of the joint skin 2 is solved. Step 82: Based on the detection difference, if the image CAD contour mathematical model protrudes from the theoretical CAD contour mathematical model, it is determined to be trimmed; if the image CAD contour mathematical model is lower than the theoretical CAD contour mathematical model, it is determined to be padded. Step 83: Trim and / or pad the mating skin 2; Among them, for each interval that is determined to be trimmed, grinding is performed according to the detection difference of the interval and the interval corresponding to the extension line 10. For independent or multiple consecutive intervals identified as requiring padding, the overlapping line of the cross-sectional profile of the butt joint of the standard strip plate 7 and the butt skin 2 is used as the straight line reference for development. The mark line 6 and the spline normal 9 are used as the vertical line reference for development. The detection difference is used as the numerical basis for the vertical line reference. A pad thickness profile for this interval is developed and fitted. The width of the pad is determined based on the width of the connection area between the butt skin 2 and the butt frame 1. A compensation pad is then manufactured to compensate for the connection position between the butt skin 2 and the frame 1.
[0037] It should be noted that steps 6 to 9 of the present invention are for trimming and / or padding of the docking skin 2. All steps 7 to 9 are repeated until the shape of the docking skin 2 reaches the theoretical tolerance range.
[0038] This invention provides a method for shape detection, control, and compensation in aircraft frame skin mating. Specifically, it addresses the measurement, fitting, and determination of the thickness dimensions of skin trimming and / or shim addition during the mating process of aircraft frame skin. This invention solves the problem of precise control over the shape step and gap at the seam position during the mating of large aircraft skins. It employs positive and negative mating standard strips with alternating positive and negative fits to control the gap, and uses photometric measurement to fit and determine the trimming data and / or shim dimensions and structure. The shape detection, control, and compensation method provided by this invention, combined with photometric data analysis, achieves precise detection and control of the mating shape of large aircraft frame skins. Compared to the purely positive and negative sample-coordinated skin mating and fitting method, it introduces data coordination, resulting in higher coordination accuracy and significantly improved segmented and step-by-step coordination feasibility. This invention is applicable to the shape detection and control process of mating skins on various aircraft component frames and has universal applicability to the mating of frame skins or sheet metal.
[0039] The following examples illustrate the implementation of the shape detection, control, and compensation method for docking the upper skin of an aircraft frame provided by the present invention.
[0040] Implementation Example See Figure 1 The aircraft frame skin mating involves connecting two aircraft components via a structural frame 1. Frame 1 has two flanges at the mating location to connect the skin and reinforcing stringers of the two components respectively. Typically, one flange of frame 1 is used to assemble the skin and stringers of one of the components. Figure 1The skin on one side of the assembly component is the mating skin 2; the skin and stringer of another frameless assembly component are assembled on the frame 1 using the mating skin 2, and the skin on this frameless assembly component is the target skin 3. In the current mating assembly method, since the mating skin 2 and the target skin 3 are manufactured through two manufacturing or forming processes with at least four steps, and assembled through two assembly processes with three steps, there will inevitably be a shape step error between the mating skin 2 and the target skin 3 at the joint position when assembled on the frame 1. This is especially true for aircraft fuselage sections composed of multiple skins, where the shape step error accumulates significantly, thus requiring trimming or shim compensation for the shape step error at the joint position during the mating assembly process. The focus of this invention is to use a more accurate and convenient detection method to determine the shim 4 and the repair area 5, thereby achieving a precise trimming and shim-addition skin mating assembly process.
[0041] See Figures 2-6 The diagram illustrates the docking process of the shape detection and control compensation method for skin docking on an aircraft frame, provided in this embodiment of the invention. This method is used to accurately determine the trimming amount and / or shim amount of the skin during the skin docking process. The steps for determining the trimming amount and / or shim amount during skin docking include: Step 1: According to the theory of the mating skin 2, mark the two skins on both sides of the seam position with a perpendicular line 6 to the seam 11; and according to the length of the seam 11, one or more mark lines 6 can be set.
[0042] In step 1, the marking line 6 is set on the mating skin 2 and the object skin 3. The marking line is drawn on the skin outline with a washable fine-tipped soft pencil by the locator set at the corresponding position of the upper group component, or an easy-tear sticker with marking lines is pasted on the skin outline according to the locator, and the marking line on the sticker is aligned with the locator.
[0043] Step 2: Set up the standard tape plate group for docking based on the mark line 6 and the seam 11, including the positive docking standard tape plate 7 and the negative docking standard tape plate 8 with alternating positive and negative fits; In this step, the standard strip plate 7 for positive mating is set on the mating skin 2, and the standard strip plate 8 for negative mating is set on the object skin 3. At the seam edge position of the standard strip plate 7 corresponding to the mating skin 2, no less than 5 spline normal lines 9 are set according to the principle of equal spacing to divide the edge section of the standard strip plate 7 into multiple normal areas. The measured length of each spline normal line 9 and the length of the inner contour line of the adjacent spline normal line 9 on the edge section of the standard strip plate 7 are measured and recorded. Based on the measured length of each spline normal line 9 and the length of the inner contour line of the adjacent spline normal line 9 on the edge section of the standard strip plate 7, the measured edge section contour of each mating standard strip plate is solved by fitting through CAD drawing.
[0044] In step 2, the standard strip plate assembly is a long thin plate assembly 12 with the thickness of the skin section at the seam 11 of the mating skin 2 and the target skin 3 as the reference thickness. A toothed structure 13 in the form of interlocking comb teeth is set at the mark line 6. Along the entire length of the seam 11 of the standard strip plate assembly, the edge of the skin seam on the mating side or the target side is used as the edge reference for the positive and negative standard strip plates. Multiple interlocking comb teeth-like structures 13 are set at intervals on the edge reference surface, which are equidistant from each other and have gaps. Both the positive and negative standard strip plates use the mark line 6 as the longitudinal position reference and the seam 11 as the edge reference position.
[0045] The interlaced comb pattern in the standard strip plate assembly refers to the following: the tooth-like structures 13 on both sides of the positive and negative standard strip plates 7 and 8 are arranged in an alternating manner and closely adhere to the corresponding tooth-like structures 13 on the opposite side of the standard strip plates. Each standard strip plate has a reference shoulder 14 located between adjacent tooth-like structures 13 at the edge reference position to position the standard strip plate.
[0046] It should be noted that the length of the toothed structure 13 of each standard strip plate is preset according to the sum of the distance and seam gap of the object skin 3 and its components before they are moved into place.
[0047] Step 3: Using the skin shape and clear edge of the mating skin 2, the mark line 6, and the spline normal line 9 as a comprehensive benchmark, position and fix the standard strip plate 7 for mating. The edge of the mating skin 2 in this step specifically refers to the clean edge of the mating skin 2, which is machined to the theoretical dimensions without leaving any allowance.
[0048] Step 4: With the object skin 3 far away from the docking skin 2, the anti-dock standard strip plate 8 is initially positioned and fixed using the skin shape, theoretical edge, mark line 6, and spline normal line 9 of the object skin 3 as a comprehensive reference. The theoretical edge of object skin 3 in this step specifically refers to the actual edge of object skin 3 being equidistantly recessed along the shape to the edge position where the reserved allowance has been removed.
[0049] Step 5: The object skin 3 and its components are moved in a one-way approach to the mating skin 2 until the toothed structure 13 of the anti-mating standard strip plate 8 is fully aligned and in contact with the reference shoulder 14 of the positive mating standard strip plate 7. Step 6: Using the positive mating standard strip plate 7 as a reference, coordinate and fix the negative mating standard strip plate 8 and the positive mating standard strip plate 7 with the interlocking comb teeth. Step 7: The object skin 3 and its components are moved in a one-way retraction and translation to the mating skin 2 until the toothed structure 13 of the positive mating standard strip 7 and the negative mating standard strip 8 are completely disengaged. Step 8: Using the reference shoulder 14 of the positive butt standard belt plate 7 and the negative butt standard belt plate 8 as the edge reference, scribing the seam edge on the outer surface of the butt skin 2 and the object skin 3 before trimming the seam gap uniformity. Step 9: Remove the standard strip plate 7 and the standard strip plate 8, and trim and polish the clean edge of the object skin 3 according to the scribing lines. Step 10: Repeat steps 3 to 9 until the gap between the mating skin 2 and the object skin 3 is within the gap tolerance control range. It should be noted that in this implementation example, the clean edge trimming of the object skin 3 is completed by executing steps 1 to 10 above; the following process is executed in sequence: set the marking lines 6 of the docking skin 2 and the object skin 3 → set the docking standard strip plate group → fix the positive standard strip plate 7 → initially position the negative standard strip plate 8 → translate the object skin 3 to the alignment contact of the docking standard strip plate group → coordinate the positioning of the docking standard strip plate group → remove the object skin 3 → mark the seam of the object skin 3 → trim the edge → repeat the marking and trimming.
[0050] Step 11: Using the methods from Step 3 to Step 7, with the clean edge of the mating skin 2 and the clean edge of the object skin 3 after trimming, the mark line 6, and the spline normal line 9 as comprehensive references, the positive mating standard strip plate 7 and the negative mating standard strip plate 8 are positioned and fixed on the outer surfaces of the mating skin 2 and the object skin 3 respectively. Step 12: At a position far from the clean edge of the mating skin 2 and close to the object skin 3, set up camera 15 to take pictures of the cross-sectional profile of the edge of the standard strip plate 7 at the seam 11 and the cross-sectional profile of the seam position of the mating skin 2. Step 13: Based on the edge section profile of the standard strip plate 7 and the joint position section profile of the mating skin 2 extracted from the photos taken by camera 15 in step 12, construct the image CAD profile mathematical model. Step 14: Based on the marker line 6 and spline normal line 9 determined in Step 1 and Step 2, and their measured data, construct a theoretical CAD profile mathematical model that integrates the edge section profile of the orthogonal standard strip plate 7 with the joint position section profile of the orthogonal skin 2. Step 15: Based on the theoretical CAD contour mathematical model, the overlapping line of the cross-sectional contour of the joint position of the standard strip plate 7 and the joint skin 2 in the image CAD contour mathematical model is used as the main weight benchmark. The edge cross-sectional contour of the standard strip plate 7, the marker line 6, and the spline normal line 9 are used as the secondary weight benchmarks for comparison. By comparing with the image CAD contour mathematical model, the detection difference of the cross-sectional contour of the joint position of the joint skin 2 is solved. The detection difference in this step is calculated based on the comparison values of the overlapping line, marker line 6, and spline normal line 9 of the cross-sectional profile of the standard strip plate 7 and the mating skin 2 at the seam position in the image CAD profile mathematical model. The actual fitted cross-sectional profile of the mating skin 2 under the measurement state of the camera 15 is obtained, and the detection difference between the image CAD profile mathematical model and the theoretical CAD profile mathematical model is obtained at the positions of each marker line 6 and spline normal line 9.
[0051] Step 16: Based on the detection difference, if the image CAD contour mathematical model protrudes from the theoretical CAD contour mathematical model, it is determined to be trimmed; if the image CAD contour mathematical model is lower than the theoretical CAD contour mathematical model, it is determined to be padded. Step 17: Trim and / or pad the mating skin 2; When determining the trimming, trimming and grinding are performed directly based on the detection difference and the extension line 10 normal interval to which the difference belongs; When it is determined that a shim needs to be added, the overlapping line of the cross-sectional profile of the joint position of the standard strip plate 7 and the mating skin 2 is used as the straight line reference for each continuous interval, the mark line 6 and the spline normal line 9 are used as the vertical line reference for expansion, and the detection difference is used as the numerical basis of the vertical line reference to expand and fit a shim thickness profile for that interval, and the shim width is based on the width of the connection area between the mating skin 2 and the mating frame 1. Step 18: For the shim addition process in Step 17, based on the shim thickness profile and shim width, process the corresponding compensation shim. Step 19: Based on the compensation shims, compensate for the connection position between the mating skin 2 and the frame 1; Step 20: Repeat steps 12 to 19 until the shape of the mating skin 2 reaches the theoretical tolerance range.
[0052] It should be noted that in this implementation example, by performing steps 11 to 20 above, the thickness is detected by photograph, and the trimming and padding of the mating skin 2 are performed; the following process is executed in sequence: positioning and fixing the mating standard strip plate group → setting the camera to take pictures → image CAD contour mathematical model → comparing and solving the detection difference based on the theoretical CAD contour mathematical model → judgment of trimming and padding → performing trimming and / or padding → for padding, solving the padding unfolding thickness and width → processing the pads and implementing compensation.
[0053] While the embodiments disclosed in this invention are as described above, they are merely illustrative of the embodiments to facilitate understanding of the invention and are not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and variations in the form and details of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.
Claims
1. A method for shape detection, control, and compensation for skin mating on an aircraft frame, characterized in that, include: Step 1: Based on the theory of mating skin, set a marker line perpendicular to the seam on both sides of the skin along the entire length of the seam. Step 2: Set up a set of standard strip plates for butt joints based on the marking lines and seams, including positive butt joint standard strip plates and negative butt joint standard strip plates, solve for the measured edge section profile of the positive butt joint standard strip plate, and construct the theoretical CAD profile mathematical model of the positive butt joint standard strip plate. Step 3: Based on the net edge of the mating skin, the theoretical edge of the object skin, the marker line and the spline normal, position and fix the positive mating standard strip plate, and perform initial positioning and fixation on the negative mating standard strip plate. Step 4: Through unidirectional approach-type docking translation from the object skin to the docking skin, the anti-dating standard strip plate is coordinated and fixed in a comb-tooth pattern for final positioning. Step 5: After removing the object skin, mark the seam edges on the outer surface of the object skin, and trim and grind out the clean edge of the object skin. Step 6: Using the clean edge of the mating skin and the clean edge of the object skin after trimming, the mark line, and the spline normal as references, position and fix the positive mating standard strip plate and the negative mating standard strip plate on the outer surface of the mating skin and the object skin. Step 7: By setting a camera between the mating skin and the object skin, take pictures of the cross-sectional profile of the standard mating strip and the mating skin at the seam position, and construct an image CAD profile mathematical model. Step 8: Based on the theoretical CAD contour mathematical model, the detection difference of the cross-sectional contour at the joint position of the mating skin is calculated by comparing the image CAD contour mathematical model; and the mating skin is trimmed or / and padded based on the detection difference.
2. The shape detection, control, and compensation method for skin docking on an aircraft frame according to claim 1, characterized in that, The number of marker lines set in step 1 is based on the seam length; The marking lines are set in several ways, including: using a locator positioned at a corresponding location on the upper-level component to draw marking lines on the skin outline with a washable, fine-tipped, soft pencil; or... Apply an easy-tear sticker with marking lines to the skin outline according to the locator, and align the marking lines on the sticker with the locator.
3. The shape detection, control, and compensation method for skin docking on an aircraft frame according to claim 1, characterized in that, In step 2, the positive mating standard strip plate is set on the mating skin, and the negative mating standard strip plate is set on the object skin; the method for solving the measured edge section profile of the positive mating standard strip plate in step 2 includes: At the seam edge of the standard strip plate corresponding to the butt skin, no less than 5 spline normals are set according to the principle of equal spacing to divide the edge section of the standard strip plate into multiple normal regions. The measured length of each spline normal and the length of the inner contour line of the adjacent spline normal in the edge section of the standard strip plate are measured and recorded. Based on the measured length of each spline normal and the length of the inner contour line of the adjacent spline normal in the edge section of the standard strip plate, the measured edge section contour of the standard strip plate is solved by fitting CAD drawing. The methods for constructing the theoretical CAD contour mathematical model in step 2 include: Based on the marker lines and spline normals determined in steps 1 and 2, and their measured data, a theoretical CAD profile mathematical model integrating the profile of the edge section of the standard strip plate and the profile of the joint position of the mating skin is constructed.
4. The shape detection, control, and compensation method for docking of the skin on an aircraft frame according to claim 3, characterized in that, The standard strip assembly set in step 2 is a long thin plate assembly with the thickness of the skin section at the seam position of the mating skin and the object skin as the reference thickness. A toothed structure in the form of interlocking comb teeth is set at the mark line position. Furthermore, along the entire length of the seam of the standard strip assembly, the edge of the skin seam on the mating side or the object side is used as the edge reference surface of the positive and negative standard strips. Multiple equidistant interlocking comb teeth-like structures with gaps are set at intervals on the edge reference surface. Both the positive and negative standard strips use the mark line as the longitudinal position reference and the seam as the edge reference.
5. The shape detection, control, and compensation method for skin docking on an aircraft frame according to claim 4, characterized in that, In step 2, The comb teeth in the mating standard strip plate group are arranged in an alternating manner: the tooth-like structures on both sides of the positive mating standard strip plate and the negative mating standard strip plate are closely attached to the tooth-like structures at the corresponding positions of the opposite mating standard strip plate in an alternating manner. Each mating standard strip plate has a reference shoulder at the edge reference position located between adjacent tooth-like structures for positioning the mating standard strip plate. The length of the toothed structure in each standard strip plate is set according to the sum of the distance dimensions of the object skin and its components before they are moved into place and the gap between the seams.
6. The shape detection, control, and compensation method for skin docking on an aircraft frame according to claim 1, characterized in that, Step 3 includes: Step 31: Using the skin shape, clear edge, marking line, and spline normal of the mating skin as a comprehensive benchmark, position and fix the standard strip plate for mating. Step 32: With the object skin far away from the mating skin, the anti-mating standard strip plate is initially positioned and fixed using the object skin's shape, theoretical edge, marking line, and spline normal as a comprehensive reference.
7. The shape detection, control, and compensation method for skin docking on an aircraft frame according to claim 6, characterized in that, Step 4 includes: Step 41: Move the object skin and its components to the mating skin in a one-way approaching motion until the toothed structure of the anti-mating standard strip plate is fully aligned and in contact with the reference shoulder of the positive mating standard strip plate. Step 42: Using the positive mating standard strip plate as a reference, coordinate and fix the negative mating standard strip plate and the positive mating standard strip plate with interlocking comb teeth.
8. The shape detection, control, and compensation method for skin docking on an aircraft frame according to claim 7, characterized in that, Step 5 includes: Step 51: Move the object skin and its components to the mating skin in a one-way retraction and translation until the toothed structure of the positive mating standard strip plate and the negative mating standard strip plate is completely separated. Step 52: Using the reference shoulders of the positive and negative standard belt plates as edge references, scribing the seam edges on the outer surfaces of the mating skin and the object skin before trimming the uniformity of the seam gap. Step 53: Remove the orthogonal and anti-orthogonal standard strip plates, and trim and polish the clean edges of the object skin according to the markings.
9. The shape detection, control, and compensation method for skin docking on an aircraft frame according to claim 1, characterized in that, Step 7 includes: Step 71: Set up a camera at a position away from the clean edge of the mating skin and close to the object skin to take pictures of the cross-sectional profile of the standard strip edge of the mating seam and the cross-sectional profile of the mating seam of the mating skin. Step 72: Based on the extracted cross-sectional profiles of the standard strip edge and the joint seam of the mating skin from the photos taken by the camera, construct the image CAD profile mathematical model.
10. The shape detection, control, and compensation method for skin docking on an aircraft frame according to claim 1, characterized in that, Step 8 includes: Step 81: Based on the theoretical CAD contour mathematical model, the overlapping line of the cross-sectional contour of the butt joint standard strip plate and the butt skin in the image CAD contour mathematical model is used as the main weight benchmark, and the edge cross-sectional contour of the butt joint standard strip plate, the marker line, and the spline normal are used as the secondary weight benchmark. By comparing with the image CAD contour mathematical model, the detection difference of the cross-sectional contour of the butt joint of the skin is solved. Step 82: Based on the detection difference, if the image CAD contour mathematical model protrudes from the theoretical CAD contour mathematical model, it is determined to be trimmed; if the image CAD contour mathematical model is lower than the theoretical CAD contour mathematical model, it is determined to be padded. Step 83: Trim and / or pad the mating skin; Specifically, for each interval where trimming is to be performed, grinding is carried out according to the detection difference of the interval and the intervals corresponding to the extension line. For independent or multiple consecutive intervals identified as requiring padding, the overlapping line of the cross-sectional profile of the butt joint of the standard strip plate and the butt skin is used as the development straight line reference, the mark line and spline normal are used as the development perpendicular line reference, and the detection difference is used as the numerical basis for the perpendicular line reference. A pad thickness profile for this interval is developed and fitted, and the pad width is determined based on the width of the connection area between the butt skin and the butt frame. Compensation pads are then manufactured to compensate for the connection position between the butt skin and the frame.