Aircraft structural rigidity-based equivalent test bench for automatic drilling equipment and design method

Abstract

The invention discloses an equivalent test bed for automatic hole making equipment based on aircraft structural rigidity and a design method, which are suitable for an aircraft assembly hole making process and serve as a guide scheme for structural design of a hole making test tool rest and a test plate. All hole sites of the flight machine hole-making molded surface are subjected to rigidity partitioning in sequence through a pressure foot module in an end effector of hole-making equipment; based on the structural mechanics special-shaped beam plate shell structure equivalent model, carrying out equivalent analysis of a flat plate structure on the measurement information of the aircraft product rigidity; according to a theoretical analysis result, carrying out structure recombination on a hole-making test tool table or a test flat plate; and calibrating the rigidity of the test flat plate subjected to structure correction through a pressure foot module in an end effector of the drilling equipment, completing verification, and verifying the accuracy of the structure design. According to the invention, theoretical guidance can be provided for the design of the test tool table and the selection and matching of the test plate, the test process of the test tool table can truly restore the flight machine drilling working condition, and the effectiveness of the test result is improved.

Description

Technical Field

[0001] The present invention relates to the field of, but is not limited to, automated hole-making technology, and in particular to an equivalent test bench and design method for automated hole-making equipment based on aircraft structural stiffness. Background Art

[0002] Aircraft assembly hole making is a crucial step in the overall aircraft manufacturing process, involving the assembly of components with different structures and functions into a single unit through mechanical connection, welding, gluing, and other methods. Rivets and bolts are commonly used connection methods in aircraft assembly, and both require the machining of connection holes in the connected components. With technological advancements, hole making technology has evolved from traditional manual operations to automation and digitization, significantly improving production efficiency and processing quality. At the same time, modern aircraft utilize a large number of difficult-to-machine materials such as composite materials and titanium alloys, and the widespread use of these materials presents challenges to hole making technology.

[0003] Due to the complex structural characteristics of aircraft structures, the hole-making locations are widely distributed in the heterogeneous laminated hole-making conditions formed by various connecting components and material combinations. Since the aircraft's hole-making products exhibit weak rigidity characteristics, there are differences in the structural strength of different hole locations, resulting in differences in the local deformation of the hole-making area caused by the clamping force and cutting force during the hole-making process, which ultimately leads to certain fluctuations in the hole-making quality, especially the countersink accuracy is difficult to meet quality requirements. Therefore, in order to restore the processing difficulties of the product working conditions and fully verify the various functions and execution parameters of the hole-making process, it is necessary to develop a test platform that can accurately restore the product's structural working conditions, so that the test process of the test tool bench can more realistically restore the aircraft's hole-making conditions, improve the validity of the test results, and improve the hole-making accuracy. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides an equivalent test bench and design method for automatic hole-making equipment based on aircraft structural stiffness, so as to solve the problem in the prior art that the test conditions are difficult to restore the actual conditions in the production line, resulting in low accuracy of the test results.

[0005] A first aspect of the present invention provides a method for designing an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness, comprising:

[0006] S1, using the pressure foot module in the end effector of the hole making equipment to measure the stiffness and partition all the hole positions of the aircraft hole-making surface product in turn;

[0007] S2: Restructure the hole-making test bench or test plate according to the preset equivalent analytical formula to complete the design of the equivalent test bench for the automatic hole-making equipment; the preset equivalent analytical formula is obtained based on the equivalent model of the special-shaped beam-plate-shell structure in structural mechanics;

[0008] S3, calibrate the stiffness of the equivalent test bench after structural reorganization through the pressure foot module in the end effector of the hole-making equipment, complete the verification, and verify the accuracy of the structural design.

[0009] Optionally, the S1 stiffness measurement and partitioning process includes the following steps:

[0010] S11, extracting the load-displacement signal during the process by applying a gradient compression force to the product surface multiple times;

[0011] S12, fitting the linear model between load variables and displacement variables based on linear regression analysis;

[0012] S13, based on the independent variable slope K in the above linear model, the stiffness coefficient of the current hole position;

[0013] S14, the hole positions with the same stiffness coefficient K value are regarded as the stiffness uniform area.

[0014] Optionally, the equivalent model of the special-shaped beam-plate-shell structure based on structural mechanics in S2 is:

[0015] According to the rectangular cross-section plate with fixed supports on four sides, the test condition is to apply a concentrated load at the center of the test plate surface. The maximum sinking deflection is

[0016] Where F is the compressive load applied during the test; w is the maximum opposite side length of the test plate, i.e. the length and width of the test plate; the calculation formula for the bending stiffness D is Wherein, E is the elastic modulus of the test plate material; h is the thickness of the test plate; ν is the Poisson's ratio of the test plate material;

[0017] The structural stiffness K is the slope coefficient in the expression of the concentrated load F and the change in deflection Δm, that is,

[0018] Optionally, the structural form of the product structure equivalent object in S2 includes:

[0019] Structural forms of the test bench: rectangular lattice type, rectangular truss type, portal type, bridge type, cantilever type;

[0020] Test plate structure forms: plates made of a single material, plates made of multiple materials.

[0021] Optionally, the structural reorganization process of the test bench and the single material test plate in S2 includes:

[0022] To ensure that the stiffness of the test plate is equivalent to that of the product, the width of the testable area of the test bench can be adjusted to be approximately equal to the width of the test plate; or the thickness of the test plate can be adjusted.

[0023] If the size of the testable area in the test bench is used as the design target, the thickness h of the test plate is consistent with the thickness of the stiffness equivalent area in the product. Based on the stiffness calculation model, the width of the testable area in the test bench can be obtained as follows: K is the stiffness of a certain area of the product;

[0024] If the thickness of the test plate is used as the design target, the length and width of the test plate are based on the inherent size of the testable area in the test bench. Based on the stiffness calculation model, the thickness of the test plate can be obtained as K is the stiffness of a certain area of the product.

[0025] Optionally, the structural reorganization process of the test bench and the multi-material superimposed test plate in S2 includes:

[0026] The materials of the multi-material superposition test plate include material A, material B, and material C; the length and width of the various materials remain consistent after superposition, that is, the length of material A is b A = length b of material B B = length b of material C C ; Width of material A c A = Width c of material B B = width c of material C C ; The elastic modulus of material A, material B, and material C are: E A 、E B 、E C ;

[0027] If the size of the testable area in the test bench is used as the design target, the thickness h of the test plates of materials A, B, and C respectively should be consistent with the thickness of the stiffness equivalent area in the product. Based on the stiffness calculation model, the width of the testable area in the test bench can be obtained as follows: If the test plate size b>c, then w=b A =b B =b C , if the test plate size b <c,w=c A =c B =c C ; where h A is the plate thickness of material A, h B h is the plate thickness of material B; C is the plate thickness of material C; E′ is the equivalent stiffness of the multi-material composite test plate, E′=αE, α is the equivalent coefficient, and the value range is [0, 1]; K is the stiffness of a certain area of the product; ν′=δν, δ is the equivalent coefficient, and the value range is [0, 1].

[0028] If the thickness of the test plate is used as the design target, the length and width of the test plate are based on the inherent size of the testable area in the test bench. Based on the stiffness calculation model, the thickness of the test plate of material A can be obtained as The thickness of the test plate of material B is The thickness of the test plate of material A is K B =βK A , K C =γK A ;;β and γ are equivalent coefficients, and their value range is [0, 1]; K is the stiffness of a certain area of the product.

[0029] Optionally, the method for verifying the structural equivalent design results of the test bench in S3 includes the following sub-steps:

[0030] S31, by applying a gradient compression force to the surface of the test plate after the test bench is clamped multiple times, and extracting the load-displacement signal during the process;

[0031] S32, fitting the linear model between load variables and displacement variables based on linear regression analysis;

[0032] S33, based on the independent variable slope K′ in the above linear model, is the stiffness coefficient of the current test plate;

[0033] S34, compare the numerical value of the stiffness coefficient K′ with the numerical value of the measured stiffness K of the product. When K′=K is satisfied, the structural equivalence is considered to be completed; if K′≠K, calculate |K′-K|=a, and compensate a to the initial calculated value K, that is, K=K+a. Based on this calculation criterion, loop through the contents of S1 and S2 until K′=K is satisfied, and the structural equivalence is considered to be completed.

[0034] Optionally, the aircraft assembly hole making system has an adjustable and controllable hardware sensing module, including:

[0035] The hole-making end effector has the functions of normal measurement and normal posture adjustment. It adjusts the end effector posture according to the measured normal information of the product surface so that the center axis of the pressure foot is perpendicular to the product surface and the angle is within the range of 90°±1°.

[0036] The hole-making end effector is equipped with a pressure foot module, which adjusts the pressure foot to fit the surface of the hole-making product according to the preset pressing force value. The pressure value is 10-3000N.

[0037] The hole-making end effector has the function of measuring the distance in the pressing direction of the pressure foot. The sensor module in the hole-making end effector collects the distance moved by the pressure foot from the coordinate origin after pressing the product surface, and then obtains the deformation displacement of the hole-making area.

[0038] A second aspect of the present invention provides an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness, which is designed and manufactured using the design method for an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness as described in any one of the first aspects.

[0039] Beneficial Effects of the Invention: In the field of automated hole drilling in aircraft assembly, to improve the accuracy of test results obtained within a test platform and enhance product hole drilling precision, this invention proposes a design method for an equivalent test bench for automated hole drilling equipment based on aircraft structural stiffness. This method uses a hole drilling end effector to monitor the product hole drilling conditions in real time, using the measured data as the basis for test platform design. This establishes an equivalent relationship between the test process and the machining conditions, enabling relatively accurate mapping and migration of test data to the product. This method provides a design method for highly customized test conditions based on product requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a flow chart of a design method for an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness;

[0041] Figure 2 A three-dimensional structural diagram of the end effector of the hole-making system for aircraft assembly;

[0042] Figure 3 This is the three-dimensional structure diagram of the test bench;

[0043] Figure 4 Data matrix for designing dimensions of the test bench;

[0044] Description of reference numerals:

[0045] 1. End effector of the aircraft assembly hole-making system; 2. Pressure foot drive cylinder; 3. Pressure foot grating scale; 4. Industrial camera; 5. Pressure foot mechanism; 6. Pressure foot nose piece; 7. Laser rangefinder; 8. Borescope calibration ring gauge; 9. Spindle tool; 10. Borescope; 11. Test fixture; 12. Test plate; 13. Test bench test area. DETAILED DESCRIPTION

[0046] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection of the present invention.

[0047] The features and illustrative embodiments of various aspects of the present invention will be described in detail below. In the detailed description below, many specific details are proposed in order to provide a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is in no way limited to any specific arrangement and method proposed below, but rather encompasses any improvements, replacements, and modifications to structures, methods, and devices without departing from the spirit of the present invention. In the accompanying drawings and the following description, well-known structures and techniques are not shown to avoid unnecessary ambiguity in the present invention.

[0048] In the description of the present invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "up," "down," "left," "right," "vertical," "horizontal," "inside," and "outside" are based on the directions or positional relationships described in the accompanying drawings and are intended only to facilitate and simplify the description of the present invention and should not be construed as limiting the present invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is intended to distinguish between objects and is not limited to this order, and should not be construed as indicating or implying relative importance.

[0049] In the description of the present invention, it should be noted that, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly, and may refer to direct connection or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of these terms in the present invention.

[0050] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other, and the embodiments can refer to and quote each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0051] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0052] The present invention provides a method for designing an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness, comprising the following steps:

[0053] The rigidity of all hole positions on the aircraft hole-making surface is divided into zones in sequence by the pressure foot module in the end effector of the hole-making equipment.

[0054] Based on the equivalent model of special-shaped beam-plate-shell structure in structural mechanics, the measured information of aircraft product stiffness is used to perform equivalent analysis of flat plate structure;

[0055] Restructure the hole-making test bench or test plate according to the theoretical analysis results;

[0056] The stiffness of the test plate after structural modification is calibrated through the pressure foot module in the end effector of the hole-making equipment to complete the verification and verify the accuracy of the structural design.

[0057] Figure 1 A flow chart of a method for designing an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness provided in an embodiment of the present disclosure. A certain product is taken as the object to be holed, and there are multiple hole-making positions on its outer surface. The local stiffness analysis method provided by the present invention requires the end effector 1 to move to a certain hole-making position and perform normal posture adjustment. The database is accumulated according to the method of collecting deformation displacement by multiple pressing, and a data matrix of pressing force-product deformation displacement is established. A univariate regression equation with pressing force as the dependent variable and product deformation as the independent variable is established by linear regression analysis, and the unknown stiffness coefficient K is solved to determine the stiffness of the hole position. The analysis process is repeated until the stiffness distribution of all hole-making positions in the product is obtained.

[0058] For example, according to the above measurement method, the pressure foot is fitted to the product with a pressure of 100N. At this time, the displacement information collected by the grating ruler is 20mm relative to the origin, and this displacement distance is calibrated as 0 point. The product is pressed again with a pressure of 200N, and the displacement information collected by the grating ruler is 20.01mm. At this time, the deformation increment is 0.01mm. After the product is pressed with a pressure gradient of 100N for many times, the deformation displacement information is recorded. The pressure-product deformation displacement database is thus accumulated, and the regression equation of a certain stiffness partition formed by fitting is F=659.815Δx+6.533. The slope of the equation is the stiffness K, and the intercept is the fitting residual term. In short, the stiffness K of this area is 659.815N / mm. This reciprocation is repeated until all the hole-making positions in the product are partitioned. The stiffness coefficient K of a certain stiffness partition is extracted as 1000N / mm, and this stiffness value is used as the design basis for the test bench size.

[0059] According to the stiffness calculation formula of rectangular cross-section plate The relationship between the test plate dimensions must satisfy Eh 3 =4.92×10 5 ×w 2 (1-ν 2 ).

[0060] For example, taking aluminum alloy as an example, the elastic modulus E is 70 GPa, and the Poisson's ratio ν is 0.33, then the test plate size must meet h 3 =6.27×10 -6 w 2 It is known that the maximum width of the test area of the test bench is 200mm, that is, the maximum width w of the test plate is 200mm, then the thickness of the test plate should meet Thickness h is 6.30×10 -3 m, i.e. 6.30mm. If the thickness of the test plate h is known to be 5mm, the maximum width of the test area of the test bench should meet The maximum width w is 0.14m, that is, the maximum width of the test plate is 140mm.

[0061] For example, taking a test plate made of a composite material of carbon fiber and an aluminum alloy as an example, the elastic modulus E1 of the aluminum alloy is 70 GPa, the elastic modulus E2 of the carbon fiber composite is 450 GPa, and the equivalent elastic modulus coefficient α after lamination is 0.56. Therefore, the elastic modulus E of the laminated test plate is α(E1+E2), that is, E is 291.2 GPa. The Poisson's ratio ν of the aluminum alloy is 0.33, the Poisson's ratio ν of the carbon fiber composite is 0.1, and the equivalent Poisson's ratio coefficient δ after lamination is 0.4. Therefore, the elastic modulus ν of the laminated test plate is δ(ν1+ν2), that is, ν is 0.17. It can be obtained that the size of the test plate needs to meet h 3 =1.64×10 -6 w 2 It is known that the maximum width of the test area of the test bench is 200mm, that is, the maximum width w of the test plate is 200mm, then the thickness of the test plate should meet h=h1+h2,h2=βh1 The equivalent thickness coefficient β of carbon fiber composite material is 0.21, so the thickness h is 4×10 -3 m, based on the above relationship, the thickness h1 of the aluminum alloy test plate is 3.31mm, and the thickness h2 of the carbon fiber composite material test plate is 0.69mm. If the total thickness h of the composite test plate is 5mm, of which the thickness h1 of the aluminum alloy test plate is 4.13mm and the thickness h2 of the carbon fiber composite material test plate is 0.86mm, then the maximum width of the test area of the test bench should meet The maximum width w is 0.27m, that is, the maximum width of the test plate is 270mm.

[0062] After equivalent calculations, the structural design of the test bench and test plate was preliminarily completed. The stiffness of the test plate surface area after it was clamped in the test bench was measured. The measurement method was consistent with the calibration of the local stiffness of the product. The end effector was moved to the surface of the test plate and adjusted in the normal direction. A database was accumulated by collecting deformation displacements through multiple compactions, and a data matrix of compaction force and product deformation displacement was established. A linear regression analysis method was used to establish a univariate regression equation with compaction force as the dependent variable and product deformation as the independent variable. The unknown stiffness coefficient K′ was solved to determine the stiffness of the test plate. The difference a between the test plate K′ and the aircraft product K was calculated. If a was within the range [0-100], the test plate and aircraft product were considered equivalent in structural stiffness, and the test was completed. If a was not within the specified range, the difference a was compensated to within the initially calculated stiffness K. The test bench and test plate dimensions were iterated until the test requirements were met.

[0063] Figure 2 This is a three-dimensional diagram of the end effector of an aircraft assembly drilling system. The end effector 1 is integrated with multiple mechanisms, including a support carrier, a hole position recognition module, a spindle module, a pressure foot module, a drilling module, and a sensor module. The pressure foot module includes a pressure foot mechanism 5, a pressure foot nose piece 6, a pressure foot drive cylinder 2, and a pressure foot grating scale 3; the hole position recognition module includes an industrial camera 4; the sensor module includes a laser rangefinder 7, a borescope 10, and a borescope calibration ring 8; and the drilling module consists of a spindle tool 9.

[0064] The stiffness calibration process relies on the pressure foot to drive the cylinder to push the pressure foot mechanism body out and press the surface of the product to be tested, so that the pressure foot nose is always in contact with the surface of the product to be tested. At this time, the pressure foot grating scale monitoring signal is read to obtain the deformation displacement of the product after compression.

[0065] Figure 3 The three-dimensional structure of the test bench is shown in Figure 1. The test bench consists of a test fixture frame 11 and a test plate 12. The test plate is connected to the test fixture frame using a clamping mechanism. The test bench's testable area 13 is the area where holes can be made and is typically the same width as the test plate.

[0066] Figure 4 The data matrix for the test bench design dimensions is shown in Figure 1. Based on the above calculation process, some common test plate materials and their single-layer dimensions are listed in millimeters.

[0067] The foregoing description shows and describes preferred embodiments of the present invention. As previously mentioned, it should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Instead, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the inventive concept described herein by the teachings above or by techniques or knowledge in the relevant art. Modifications and variations made by those skilled in the art without departing from the spirit and scope of the present invention are intended to be within the scope of the appended claims.

Claims

1. A design method for an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness, characterized in that: include: S1, using the pressure foot module in the end effector of the hole making equipment to measure the stiffness and partition all the hole positions of the aircraft hole-making surface product in turn; S2: Restructure the hole-making test bench or test plate according to the preset equivalent analytical formula to complete the design of the equivalent test bench for the automatic hole-making equipment; the preset equivalent analytical formula is obtained based on the equivalent model of the special-shaped beam-plate-shell structure in structural mechanics; S3, calibrate the stiffness of the equivalent test bench after structural reorganization through the pressure foot module in the end effector of the hole-making equipment, complete the verification, and verify the accuracy of the structural design.

2. The method for designing an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness according to claim 1 is characterized in that: The S1 stiffness measurement and partitioning process includes the following steps: S11, extracting the load-displacement signal during the process by applying a gradient compression force to the product surface multiple times; S12, fitting the linear model between load variables and displacement variables based on linear regression analysis; S13, based on the independent variable slope K in the above linear model, the stiffness coefficient of the current hole position; S14, the hole positions with the same stiffness coefficient K value are regarded as the stiffness uniform area.

3. The method for designing an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness according to claim 1 is characterized in that: The equivalent model of the special-shaped beam-plate-shell structure in S2 based on structural mechanics is: According to the rectangular cross-section plate with fixed supports on four sides, the test condition is to apply a concentrated load at the center of the test plate surface. The maximum sinking deflection is Where F is the compressive load applied during the test; w is the maximum opposite side length of the test plate, i.e. the length and width of the test plate; the calculation formula for the bending stiffness D is Wherein, E is the elastic modulus of the test plate material; h is the thickness of the test plate; ν is the Poisson's ratio of the test plate material; The structural stiffness K is the slope coefficient in the expression of the concentrated load F and the change in deflection Δm, that is, 4. The method for designing an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness according to claim 1 is characterized in that: The structural form of the product structure equivalent object in S2 includes: Structural forms of the test bench: rectangular lattice type, rectangular truss type, portal type, bridge type, cantilever type; Test plate structure forms: plates made of a single material, plates made of multiple materials.

5. The method for designing an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness according to claim 3 is characterized in that: The reorganization process of the test bench and single material test plate structure in S2 includes: To ensure that the stiffness of the test plate is equivalent to that of the product, the width of the testable area of the test bench can be adjusted to be approximately equal to the width of the test plate; or the thickness of the test plate can be adjusted. If the size of the testable area in the test bench is used as the design target, the thickness h of the test plate is consistent with the thickness of the stiffness equivalent area in the product. Based on the stiffness calculation model, the width of the testable area in the test bench can be obtained as follows: K is the stiffness of a certain area of the product; If the thickness of the test plate is used as the design target, the length and width of the test plate are based on the inherent size of the testable area in the test bench. Based on the stiffness calculation model, the thickness of the test plate can be obtained as K is the stiffness of a certain area of the product.

6. The method for designing an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness according to claim 3 is characterized in that: The reorganization process of the test bench and the multi-material superimposed test plate structure in S2 includes: The materials of the multi-material superposition test plate include material A, material B, and material C; the length and width of the various materials remain consistent after superposition, that is, the length of material A is b A = length b of material B B = length b of material C C ; Width of material A c A = Width c of material B B = width c of material C C ; The elastic modulus of material A, material B, and material C are: E A 、E B 、E C ; If the size of the testable area in the test bench is used as the design target, the thickness h of the test plates of materials A, B, and C respectively should be consistent with the thickness of the stiffness equivalent area in the product. Based on the stiffness calculation model, the width of the testable area in the test bench can be obtained as follows: If the test plate size b>c, then w=b A =b B =b C , if the test plate size b <c,w=c A =c B =c C ; where h A is the plate thickness of material A, h B h is the plate thickness of material B; C is the plate thickness of material C; E′ is the equivalent stiffness of the multi-material composite test plate, E′=αE, α is the equivalent coefficient, and the value range is [0, 1]; K is the stiffness of a certain area of the product; ν′=δν, δ is the equivalent coefficient, and the value range is [0, 1]. If the thickness of the test plate is used as the design target, the length and width of the test plate are based on the inherent size of the testable area in the test bench. Based on the stiffness calculation model, the thickness of the test plate of material A can be obtained as The thickness of the test plate of material B is The thickness of the test plate of material A is K B =βK A , K C =γK A ;;β and γ are equivalent coefficients, and their value range is [0, 1]; K is the stiffness of a certain area of the product.

7. The method for designing an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness according to claim 1 is characterized in that: The method for verifying the structural equivalent design results of the test bench in S3 includes the following sub-steps: S31, by applying a gradient compression force to the surface of the test plate after the test bench is clamped multiple times, and extracting the load-displacement signal during the process; S32, fitting the linear model between load variables and displacement variables based on linear regression analysis; S33, based on the independent variable slope K′ in the above linear model, is the stiffness coefficient of the current test plate; S34, compare the numerical value of the stiffness coefficient K′ with the numerical value of the measured stiffness K of the product. When K′=K is satisfied, the structural equivalence is considered to be completed; if K′≠K, calculate |K′-K|=a, and compensate a to the initial calculated value K, that is, K=K+a. Based on this calculation criterion, loop through the contents of S1 and S2 until K′=K is satisfied, and the structural equivalence is considered to be completed.

8. The method for designing an equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness according to claim 1 is characterized in that: The aircraft assembly hole making system has an adjustable and controllable hardware sensing module, including: The hole-making end effector has the functions of normal measurement and normal posture adjustment. It adjusts the end effector posture according to the measured normal information of the product surface so that the center axis of the pressure foot is perpendicular to the product surface and the angle is within the range of 90°±1°. The hole-making end effector is equipped with a pressure foot module, which adjusts the pressure foot to fit the surface of the hole-making product according to the preset pressing force value. The pressure value is 10-3000N. The hole-making end effector has the function of measuring the distance in the pressing direction of the pressure foot. The sensor module in the hole-making end effector collects the distance moved by the pressure foot from the coordinate origin after pressing the product surface, and then obtains the deformation displacement of the hole-making area.

9. An equivalent test bench for automatic hole-making equipment based on aircraft structural stiffness, characterized in that: The invention is designed and manufactured by adopting the design method of an equivalent test bench for automatic hole-making equipment based on aircraft structure stiffness as described in any one of claims 1 to 8.

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