Method and device for measuring out-of-plane deformation of plate-type structure based on monocular vision and medium

Abstract

The invention discloses a monocular vision-based plate-type structure out-of-plane deformation measurement method and device and a storage medium. The method comprises the following steps of: shooting a plate plane of a plate-type structure through a camera to obtain two frames of images before and after deformation of the plate-type structure; constructing an image deformation function under out-of-plane deformation of the plate type structure based on a camera imaging principle; grid division is carried out on the imaging plane of the plate-type structure, an interpolation shape function of each grid is constructed based on a finite element interpolation method, and finite element interpolation expression of full-field out-of-plane displacement of the plate-type structure is constructed in combination with deformation parameters of the plate-type structure; then combining an image deformation function to construct a digital image related objective function containing deformation parameters of the plate-type structure; and performing minimum value solving on the digital image related objective function to obtain deformation parameters of the plate type structure, and further obtaining full-scene out-of-plane deformation data of the plate type structure. The method has the advantages of being simple, efficient and the like, and meanwhile measurement of whole-scene out-of-plane deformation data of the plate type structure is achieved.

Description

Technical Field

[0001] This invention relates to the field of deformation measurement, and more particularly to a method, apparatus, and medium for measuring out-of-plane deformation of plate structures based on monocular vision. Background Technology

[0002] In engineering applications, contact measurement methods such as accelerometers, displacement gauges, and strain gauges are commonly used to obtain deformation or vibration information of plate structures. However, this traditional contact measurement method requires mounting several contact sensors on the plate structure. Due to the structural characteristics of plate structures, the installation of contact sensors is time-consuming and labor-intensive, and measurements are limited to certain local locations, resulting in a limited number of measurement points and an inability to provide comprehensive deformation response information of the structure. Furthermore, this contact measurement method introduces additional mass into the plate structure, making it difficult to apply to certain patent-sensitive, small-sized, or rotating plate structures. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, one of the objectives of this invention is to provide a method for measuring out-of-plane deformation of plate structures based on monocular vision, which can solve the problems of high difficulty and incomplete data measurement in the existing methods for measuring out-of-plane deformation of plate structures.

[0004] The second objective of this invention is to provide an out-of-plane deformation measurement device for plate structures based on monocular vision, which can solve the problems of high difficulty and incomplete data measurement in existing methods for measuring out-of-plane deformation data of plate structures.

[0005] The third objective of this invention is to provide a computer-readable storage medium that can solve the problems of high difficulty and incomplete data measurement in existing methods for measuring out-of-plane deformation data of plate structures.

[0006] One of the objectives of this invention is achieved through the following technical solution:

[0007] A method for measuring out-of-plane deformation of plate structures based on monocular vision, the method comprising:

[0008] Image acquisition steps: The plate surface of the plate structure is photographed by a camera to obtain two frames of images before and after the plate structure is deformed; wherein, the optical axis of the camera is perpendicular to the plate surface of the plate structure, and a speckle patch is attached to the plate surface;

[0009] Relationship construction steps: Based on the camera imaging principle, construct the homography transformation relationship from out-of-plane deformation of the plate structure to image motion, and then obtain the image deformation function under out-of-plane deformation of the plate structure according to the homography transformation relationship from out-of-plane deformation of the plate structure to image motion;

[0010] The steps for constructing the finite element interpolation representation are as follows: Based on the image, the imaging plane of the plate structure is obtained, and the imaging plane of the plate structure is meshed; and based on the finite element interpolation method, the interpolation shape function of each mesh is constructed, and combined with the deformation parameters of the plate structure, the finite element interpolation representation of the overall out-of-field displacement of the plate structure is constructed.

[0011] Objective function construction steps: Based on the finite element interpolation expression of the full-plane out-of-plane displacement of the plate structure and the image deformation function under the out-of-plane deformation of the plate structure, construct a digital image correlation objective function containing the deformation parameters of the plate structure;

[0012] Calculation steps: The deformation parameters of the plate structure are obtained by minimizing the objective function related to the digital image. Then, the overall out-of-field deformation data of the plate structure are obtained based on the deformation parameters of the plate structure and the finite element interpolation expression of the overall out-of-field displacement of the plate structure.

[0013] Furthermore, the image acquisition step includes: when fixing the camera in front of the plate plane of the plate structure, first calibrating the camera parameters using the Zhang Zhengyou method to obtain the camera's intrinsic parameter matrix, and ensuring that the intrinsic parameter matrix satisfies the following formula:

[0014] z c x = KX c ;

[0015] Among them, X c =[x c y c , z c ] T Let G be the coordinates of any point on the plate plane of the plate structure in the camera coordinate system;

[0016] x = [x, y, 1] T Let X be any point X on the plate plane of the plate structure in the camera coordinate system. c Coordinates mapped to the image plane coordinate system during the imaging process;

[0017] K is the intrinsic parameter matrix;

[0018] T represents the vector transpose.

[0019] Furthermore, the relationship construction steps specifically include:

[0020] Step 1: Based on the principle that the plate plane of the plate structure will not pass through the camera focus, the coordinate transformation relationship of any point on the plate plane of the plate structure before and after deformation is constructed by introducing a normal vector;

[0021] Step 2: Based on the camera imaging principle and coordinate transformation relationship, construct the coordinate transformation relationship of any point in the imaging plane of the plate structure before and after deformation, and then obtain the image deformation function of the plate structure under out-of-plane deformation based on the coordinate transformation relationship of any point in the imaging plane of the plate structure before and after deformation.

[0022] Furthermore, the coordinate transformation relationship of any point on the plate plane of the plate structure before and after deformation in step one is specifically as follows:

[0023]

[0024] Where I is a third-order identity matrix;

[0025] X′ c =X c +T c ;X c =[x c y c , z c =l] T Let be the coordinates of any point on the plate plane of the plate structure before deformation in the camera coordinate system;

[0026] l is the distance from the camera's focal point to the plane of the plate structure;

[0027] X′ c =[x′ c y′ c Z′ c ] T In the camera coordinate system, this represents the coordinates of a point on the deformed plate plane of the deformed plate structure.

[0028] T c Let T be the displacement vector. c =[0, 0, w] T And w is outside the plane (or Z) c (Axial) displacement components;

[0029] n c Let n be the normal vector, and n be the normal vector. c = [0, 0, 1 / l],

[0030] The coordinate transformation relationship of any point in the imaging plane of the plate structure before and after deformation in step two is as follows:

[0031]

[0032] z' c x'=KX' c ;

[0033] z′ c =l+w;

[0034] The image deformation function under out-of-plane deformation of the plate structure is as follows:

[0035]

[0036] Wherein, (W(x; w) is the image deformation function under out-of-plane deformation of the plate structure.

[0037] Furthermore, the finite element interpolation expression construction step specifically includes:

[0038] Mesh division steps: Based on the images captured by the camera, the imaging plane of the plate structure is obtained, and the imaging plane is divided into multiple rectangular mesh units according to the set mesh size;

[0039] Interpolation expression construction steps: Interpolate each rectangular mesh element according to the finite element interpolation method to obtain the finite element interpolation expression of each rectangular mesh element. Then, based on the finite element interpolation expressions of multiple rectangular mesh elements and the deformation parameters of the plate structure, construct the finite element interpolation expression of the full-field out-of-field displacement of the plate plane of the plate structure.

[0040] The finite element interpolation expression for the overall out-of-field displacement of the plate plane of the plate structure is given by the following formula:

[0041] w(x c y c )=N(x c y c )p;

[0042] N(x c y c )=[N i N Xi N Yi [i = 1, 2, ..., n];

[0043] p = [w i θ Xi θ Yi [i = 1, 2, ..., n];

[0044]

[0045]

[0046] Where w(x) c y c ) is the overall out-of-field deformation function of the plate structure;

[0047] N(x c yc ) is the interpolation shape function for all points on the plate plane of the plate structure;

[0048] p represents the deformation parameter of the plate structure, including the displacement and rotation degrees of freedom of all points on the plate plane of the plate structure; w i θ Xi θ Yi These are the displacement of node i in the rectangular mesh element, the rotation angle of node i around the x-axis, and the rotation angle of node i around the y-axis, respectively. The value of i ranges from [1, 4].

[0049] n is the number of rectangular grid cells;

[0050] a and b are half the length and half the width of a rectangular grid cell;

[0051] N i N Xi N Yi These are three interpolation shape functions at node i of a rectangular grid cell of the plate structure, respectively;

[0052] (X o y o ( ) represents the coordinates of the center point of the rectangular grid cell in the camera coordinate system;

[0053] (x ci y ci Let be the coordinates of node i within the rectangular grid cell in the camera coordinate system.

[0054] Furthermore, the formula for the digital image correlation objective function is as follows:

[0055]

[0056] Where f(x) and g(x) are the brightness distribution functions of the images before and after the deformation of the plate structure, respectively;

[0057] Ω represents the image region where the plate plane of the plate structure is located before deformation.

[0058]

[0059]

[0060] x′=W(x;N(x c y c )p);

[0061] X c =lK -1 x.

[0062] Furthermore, the calculation steps specifically include: obtaining the deformation parameters of the plate structure by minimizing the objective function related to the digital image using the Gauss-Newton iteration method, and then obtaining the full-field out-of-field deformation data of the plate structure based on the deformation parameters of the plate structure and the finite element interpolation expression of the full-field out-of-field displacement of the plate structure.

[0063] Furthermore, the calculation step of obtaining the deformation parameters of the plate structure by minimizing the objective function related to the digital image using the Gauss-Newton iteration method specifically includes:

[0064] Step 1: Set the initial deformation parameter to zero, and set the change amount of the deformation parameter of the plate to be tested, so as to gradually update and obtain the deformation parameter of the plate structure after deformation.

[0065] Where, p←p+Δp;

[0066] Δp is the change in the deformation parameter;

[0067] Step 2: Calculate the brightness and sensitivity of the deformed image;

[0068] Wherein, the expression for image brightness is g(W(x); N(x) c y c The Taylor expansion of (p+Δp) is performed as follows:

[0069]

[0070] in,

[0071] x′=(W(x;N(x c y c )p);

[0072]

[0073] Step 3: Substitute the expression for image brightness into the digital image correlation objective function using the linear least squares method to obtain the change in the deformation parameters of the plate structure. Determine whether the convergence condition is met based on the change in the deformation parameters of the plate structure. If yes, the iteration terminates. The deformation parameters of the plate structure are obtained based on the change in the deformation parameters of the plate structure, the original deformation parameters of the plate plane, and p←p+Δp. If not, return to step 2.

[0074] The second objective of this invention is achieved by the following technical solution.

[0075] An out-of-plane deformation measurement device for plate structures based on monocular vision includes a memory and a processor. The memory stores an out-of-plane deformation measurement program for plate structures that runs on the processor. The out-of-plane deformation measurement program for plate structures is a computer program. When the processor executes the out-of-plane deformation measurement program for plate structures, it implements the steps of the out-of-plane deformation measurement method for plate structures based on monocular vision, as one of the objectives of this invention.

[0076] The third objective of this invention is achieved by the following technical solution.

[0077] A computer-readable storage medium storing an out-of-plane deformation measurement program for a plate structure, the out-of-plane deformation measurement program for the plate structure being a computer program, wherein when the out-of-plane deformation measurement program for the plate structure is executed by a processor, it implements the steps of an out-of-plane deformation measurement method for a plate structure based on monocular vision, as one of the objectives of this invention.

[0078] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0079] This invention utilizes homography and camera imaging models, with out-of-plane displacement as the basic variable, to establish the correspondence between points in the images before and after deformation. This effectively overcomes the limitation of traditional monocular vision measurement methods, which can only measure in-plane deformation, and also avoids the difficulties in matching and synchronous control of multi-view vision. This invention is simple and efficient. Furthermore, this invention introduces finite element interpolation of plate structures to obtain full-scale out-of-plane deformation information of plate structures, making the deformation information more comprehensive and effectively supporting structural stress measurement and condition assessment. Attached Figure Description

[0080] Figure 1 A flowchart of the out-of-plane deformation measurement method for plate structures based on monocular vision provided by the present invention;

[0081] Figure 2 A schematic diagram showing the positional relationship between the plate structure and the camera provided by the present invention;

[0082] Figure 3 A schematic diagram of the grid division of the imaging plane provided by the present invention;

[0083] Figure 4 for Figure 3 A schematic diagram showing the dimensions and nodal degrees of freedom of a rectangular mesh cell;

[0084] Figure 5 for Figure 1 The flowchart for step S5 in the process. Detailed Implementation

[0085] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0086] Example 1

[0087] To address the shortcomings of traditional contact measurement methods, this invention provides a method for measuring out-of-plane deformation of plate structures based on monocular vision. This method employs a non-contact measurement approach to measure the full out-of-plane deformation information of the plate structure's deformation or vibration. Specifically, as... Figure 1 As shown, the present invention provides a preferred embodiment of a method for measuring out-of-plane deformation of a plate structure based on monocular vision, comprising:

[0088] Step S1: During the vibration of the plate structure, the plate plane of the plate structure is photographed by a camera to obtain two frames of images before and after the deformation of the plate structure; the optical axis of the camera is perpendicular to the plate plane of the plate structure, and speckle patches are attached to the plate plane.

[0089] Specifically, this invention employs a visual measurement method to measure the deformation of a plate structure. This method primarily uses speckle patterns to match and estimate deformation parameters. Specifically, before measuring the plate structure, speckle patterns are sprayed onto or attached to the surface of the plate structure. These speckle patterns can be generated and printed using the open-source software Speckle Generator, and parameters such as the diameter, density, and degree of variation of the speckle patterns can be adjusted directly within the software as needed. By attaching speckle patterns to the plate surface, the image captured by the camera exhibits distinction between light and dark areas, thereby enabling the monitoring of deformation on the plate surface.

[0090] After the speckle pattern is arranged on the plate structure, the camera is fixed with its optical axis perpendicular to the plane of the plate structure. Two frames of images are taken before and after the plate structure deforms, such as... Figure 2 As shown, the camera coordinate system is a coordinate system O constructed with the camera's focal point as the center. c X c Y c Z c The captured image is an imaging plane, and the imaging plane coordinate system is a coordinate system oxy constructed with the center point of the imaging plane as the center; the plate plane also has a corresponding coordinate system XOY.

[0091] In addition, before shooting, the parameters of the camera are calibrated using Zhang Zhengyou's method to obtain the camera's intrinsic parameter matrix K, and K satisfies formula (1):

[0092] z c x = KX c (1);

[0093] In the formula, X c =[x c y c , z c ] T This refers to the camera coordinate system O c X c Y c Z c In this context, the coordinates of any point on the plane of the plate structure are given.

[0094] x = [x, y, 1] T In camera coordinate system O c X c Y c Z c In the process of imaging, any point on the plate plane of the plate structure is mapped to the coordinates in the two-dimensional imaging plane coordinate system oxy.

[0095] K is the intrinsic parameter matrix, which is generally related to the camera focal length, skew coefficient, optical center offset, etc.

[0096] T represents the vector transpose.

[0097] Step S2: Based on the camera imaging model, construct the homography transformation relationship between the out-of-plane deformation of the plate structure and the image motion, and then derive the image deformation function under the out-of-plane deformation of the plate structure according to the homography transformation relationship.

[0098] Specifically, in the camera coordinate system O c X c Y c Z c middle:

[0099] Let the initial coordinates of any point A on the plane of the slab structure be: X c =[x c y c , z c =l] T ;

[0100] The distance from the camera's focal point to the plane of the plate structure is l;

[0101] After deformation, the coordinates of point A become: X′ c =[x′ c y′ c , z′ c ] T ;

[0102] The displacement vector is T c .

[0103] Then, in the camera coordinate system, the coordinates of any point on the plate plane of the plate structure before and after deformation both satisfy formula (2):

[0104] X′ c =Z c +T c (2).

[0105] Since the plate structure only undergoes out-of-plane displacement, the displacement vector T c =[0, 0, w] T And w is outside the plane (or Z) c (Axis) displacement components, and Z′ c =l+w.

[0106] Furthermore, since the camera's optical axis is perpendicular to the plane of the plate structure, the plane of the plate structure will not pass through the camera's focal point. Therefore, a normal vector n can be introduced. c = [0, 0, 1 / l], so that formula (3) holds, specifically:

[0107]

[0108] Therefore, by combining formulas (2) and (3), we obtain formula (4), which is as follows:

[0109]

[0110] Where I is a third-order identity matrix.

[0111] Simultaneously, the movement of a point in the camera coordinate system will also cause the movement of points on the imaging plane. Therefore, when the coordinates X of any point within the plate plane of the plate structure in the camera coordinate system change, the position of the point will also change. c When the coordinate in the corresponding imaging plane coordinate system is x, then after the plate structure is deformed, the coordinate of that point in the plate plane of the plate structure in the camera coordinate system is X′. c The coordinates in the corresponding imaging plane system become x′, and the two satisfy the following formula:

[0112] z′ c x′=KX′ c ;

[0113]

[0114] Meanwhile, by combining equation (4) and formula (1), the homography transformation relationship of the imaging plane coordinates of the plate structure before and after deformation is obtained, as shown in formula (5):

[0115]

[0116] Meanwhile, to simplify the above formula, x′ is expressed as a function of w and x, then formula (5) can be simplified to formula (6):

[0117]

[0118] Among them, w (x；w) This is the image deformation function for out-of-plane deformation of a plate structure.

[0119] Step S3: Divide the imaging plane of the plate structure before deformation into rectangular meshes, and construct the interpolation shape function of each mesh based on the finite element interpolation method. Then, combine the deformation parameters of the plate structure to construct the finite element interpolation expression of the overall out-of-field displacement of the plate structure.

[0120] Preferably, the grid size is set based on experience, such as... Figure 3 As shown, the grid size can be set to 100 pixels in the corresponding image.

[0121] This invention employs thin-plate finite element interpolation to establish a displacement function to describe the overall out-of-field deformation function w(x) of a plate structure. c y c Specifically, based on each of the above rectangular grid cells, such as Figure 4 As shown, each rectangular grid cell has a node i, and three degrees of freedom are defined: w i θ Xi θ Yi These represent: the displacement of node i, the rotation angle of node i around the x-axis, and the rotation angle of node i around the y-axis, respectively. Furthermore, since a rectangular mesh element has four nodes, the value range of i is [1, 4].

[0122] by Figure 4 Taking a rectangular grid cell as an example, any point (x) within this rectangular grid cell c ,y c The displacement interpolation value at point ) is:

[0123]

[0124] in,

[0125]

[0126] a and b are half the length and half the width of a rectangular grid cell;

[0127] N i N Xi N Yi These are the three interpolation shape functions at node i of a rectangular grid cell in a plate structure.

[0128] (xo y o () represents the coordinates of the center point of the rectangular grid cell;

[0129] (x ci y ci ) represents the coordinates of node i in the rectangular grid cell.

[0130] Based on the above method, interpolation is performed on each rectangular mesh element to obtain the finite element interpolation expression of each rectangular mesh element. Then, combined with the deformation parameters of the plate structure, the expression of any point (x) on the plate plane of the plate structure can be obtained. c y c The finite element interpolation expression at () is also the finite element interpolation expression of the overall off-field displacement of the plate structure, specifically as follows:

[0131] w(x c y c )=N(x c y c )p (8).

[0132] Where N(x) c y c )=[N i N Xi N Yi [i = 1, 2, ..., n];

[0133] p = [w i θ Xi θ Yi , i = 1, 2, ..., n).

[0134] n is the number of nodes in the rectangular grid of the imaging plane. From the rectangular grid unit above, we know that there are 4 nodes, so n = 4.

[0135] N(x c y c ) is an interpolation shape function that includes all points.

[0136] p is the deformation parameter of the plate structure, which includes the displacement and rotation degrees of freedom of all points.

[0137] According to formula (8), the problem of finding the deformation parameters of the plate structure is transformed into solving formula (8).

[0138] Step S4: Construct a digital image correlation objective function containing the deformation parameters of the plate structure based on the finite element interpolation expression of the overall out-of-plane displacement of the plate structure and the image deformation function under the out-of-plane deformation of the plate structure.

[0139] Specifically, an out-of-plane deformation function based on deformation parameters is established based on formulas (6) and (8), as shown in formula (9):

[0140] x′=W(x;N(x c y c )p) (9).

[0141] Because x c y c It is the camera coordinate X c Therefore, combining formula (1), we obtain formula (10):

[0142] X c =lK -1 x (10).

[0143] At the same time, x c y c It is also a function of x.

[0144] Based on the zero-mean normalization principle, a digital image correlation objective function containing the deformation parameters of the plate structure is constructed, as shown in formula (11):

[0145]

[0146] Where f(x) and g(x) are the image brightness distribution functions before and after the deformation of the plate plane of the plate structure, respectively;

[0147] Ω represents the image region where the plate plane is located within the imaging plane coordinate system before the deformation of the plate structure.

[0148]

[0149] Furthermore, |Ω| represents the total number of pixels within the image region Ω. The total number of pixels can be directly obtained from the pixel count within the image region.

[0150] Therefore, the problem of determining the deformation parameter p of the plate structure in this invention is transformed into making the objective function C ZNSSD (p) The smallest problem.

[0151] Step S5: The deformation parameters of the plate structure are obtained by minimizing the objective function related to the digital image. The overall out-of-field deformation data of the plate structure are obtained based on the deformation parameters of the plate structure and the finite element interpolation expression of the overall out-of-field displacement of the plate structure.

[0152] Preferably, the present invention uses the Gauss-Newton iterative method to solve the digital image correlation objective function C. ZNSSD The minimum value of (p) is used to obtain the deformation parameters of the plate structure. Then, based on the deformation parameters of the plate structure and the finite element interpolation of the overall out-of-field displacement of the plate structure, the overall out-of-field deformation data of the plate structure are obtained.

[0153] Specifically, such as Figure 5 As shown, step S5 further includes:

[0154] Step S51: Set the initial deformation parameters of the plate plane of the plate structure.

[0155] Specifically, before deformation, the plate structure has not undergone deformation, so its initial deformation parameter is set to 0.

[0156] Step S52: Based on the set change in deformation parameters, gradually update the new deformation parameters on the basis of the current deformation. That is, when the plate structure is deformed, its deformation parameter is set to p, and when deformation is performed on the basis of this deformation, the change in deformation parameters is set to Δp. Then, the new deformation parameters can be gradually updated and obtained, that is: p←p+Δp.

[0157] Step S53: Improve the image brightness of the imaging plane of the deformed plate structure.

[0158] Specifically, for g(W(x); N(x) c y c Perform Taylor expansion on (p+Δp) to obtain formula (16):

[0159]

[0160] in,

[0161] x′=W(x;N(x c y c )p);

[0162]

[0163] Step S54: Substitute the calculated image brightness of the imaging plane of the plate structure into the digital image correlation objective function using the linear least squares method to obtain the change in the deformation parameters of the plate structure.

[0164] That is, by substituting formula (16) into formula (11), the minimum value of formula (11) is obtained by using the linear least squares method, specifically:

[0165]

[0166] That is:

[0167]

[0168] H is the Hessian matrix.

[0169] Step S55: Determine whether the convergence condition is met based on the change in the deformation parameters of the plate structure. If not, return to step S52; if yes, proceed to step S56.

[0170] That is, when the calculated result does not meet the convergence condition, return to step S52 to update the deformation parameters again based on the calculated change, and then execute steps S53, S54 and S55; until the calculation result meets the convergence condition, the loop ends.

[0171] Step S56: Based on the change in the deformation parameters of the plate structure and the previous calculation of the plate plane of the plate structure, the deformation parameters of the plate structure are obtained.

[0172] Specifically, when If the convergence condition is met, the iteration terminates, and the final deformation parameter p of the plate structure is obtained by p←p+Δp. Here, ||p|| represents the L2 norm of the vector.

[0173] Step S57: Substitute the deformation parameters of the plate structure into the finite element interpolation expression of the overall out-of-field displacement of the plate structure to obtain the overall out-of-field deformation data of the plate structure.

[0174] That is, by substituting the calculated deformation parameters into formula (8), the overall off-site deformation data w(x) of the plate structure can be obtained. c ,y c ).

[0175] This invention establishes a correspondence between points in the images before and after deformation by using an imaging plane model with out-of-plane displacement as the basic variable. This effectively overcomes the limitation of traditional monocular vision methods, which can only measure deformation within the plane of the plate, and also avoids the matching and synchronization control difficulties of multi-view vision. This invention is simple and efficient. Furthermore, this invention introduces finite element interpolation for plate structures to measure the full-scale out-of-plane deformation information of the plate structure, enabling rapid and accurate measurement of the full-scale out-of-plane deformation information of the plate structure.

[0176] Example 2

[0177] Based on Embodiment 1, the present invention provides Embodiment 2, an out-of-plane deformation measurement device for plate structures based on monocular vision, including a memory and a processor. The memory stores an out-of-plane deformation measurement program for plate structures that runs on the processor. The out-of-plane deformation measurement program for plate structures is a computer program. When the processor executes the out-of-plane deformation measurement program for plate structures, it implements the steps of the out-of-plane deformation measurement method for plate structures based on monocular vision provided in Embodiment 1.

[0178] Example 3

[0179] Based on Embodiment 1, the present invention also provides Embodiment 3, a computer-readable storage medium storing an out-of-plane deformation measurement program for a plate structure. The out-of-plane deformation measurement program for the plate structure is a computer program, and when the out-of-plane deformation measurement program for the plate structure is executed by a processor, it implements the steps of the monocular vision-based out-of-plane deformation measurement method for plate structures provided in Embodiment 1.

[0180] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for measuring out-of-plane deformation of plate structures based on monocular vision, characterized in that, The method for measuring the out-of-plane deformation of the plate structure includes: Image acquisition steps: The plate surface of the plate structure is photographed by a camera to obtain two frames of images before and after the plate structure is deformed; wherein, the optical axis of the camera is perpendicular to the plate surface of the plate structure, and a speckle patch is attached to the plate surface; Relationship construction steps: Based on the camera imaging principle, construct the homography transformation relationship from out-of-plane deformation of the plate structure to image motion, and then obtain the image deformation function under out-of-plane deformation of the plate structure according to the homography transformation relationship from out-of-plane deformation of the plate structure to image motion; The steps for constructing the finite element interpolation representation are as follows: Based on the image, the imaging plane of the plate structure is obtained, and the imaging plane of the plate structure is meshed; and based on the finite element interpolation method, the interpolation shape function of each mesh is constructed, and combined with the deformation parameters of the plate structure, the finite element interpolation representation of the overall out-of-field displacement of the plate structure is constructed. Objective function construction steps: Based on the finite element interpolation expression of the full-plane out-of-plane displacement of the plate structure and the image deformation function under the out-of-plane deformation of the plate structure, construct a digital image correlation objective function containing the deformation parameters of the plate structure; Calculation steps: The deformation parameters of the plate structure are obtained by minimizing the objective function related to the digital image. Then, the overall out-of-field deformation data of the plate structure are obtained based on the deformation parameters of the plate structure and the finite element interpolation expression of the overall out-of-field displacement of the plate structure.

2. The method for measuring out-of-plane deformation of plate structures based on monocular vision according to claim 1, characterized in that, The image acquisition step includes: when fixing the camera in front of the plate plane of the plate structure, first calibrating the camera parameters using the Zhang Zhengyou method to obtain the camera's intrinsic parameter matrix, and ensuring that the intrinsic parameter matrix satisfies the following formula: z c x = Kx c ; Among them, X c =[x c y c , z c ] T Let G be the coordinates of any point on the plate plane of the plate structure in the camera coordinate system; x = [x, y, 1] T Let X be any point X on the plate plane of the plate structure in the camera coordinate system. c Coordinates mapped to the image plane coordinate system during the imaging process; K is the intrinsic parameter matrix; T represents the vector transpose.

3. The method for measuring out-of-plane deformation of plate structures based on monocular vision according to claim 1, characterized in that, The relationship construction steps specifically include: Step 1: Based on the principle that the plate plane of the plate structure will not pass through the camera focus, the coordinate transformation relationship of any point on the plate plane of the plate structure before and after deformation is constructed by introducing a normal vector; Step 2: Based on the camera imaging principle and coordinate transformation relationship, construct the coordinate transformation relationship of any point in the imaging plane of the plate structure before and after deformation, and then obtain the image deformation function of the plate structure under out-of-plane deformation based on the coordinate transformation relationship of any point in the imaging plane of the plate structure before and after deformation.

4. The method for measuring out-of-plane deformation of plate structures based on monocular vision according to claim 3, characterized in that, The coordinate transformation relationship of any point on the plate plane of the plate structure before and after deformation in step one is as follows: Where I is a third-order identity matrix; X′ c =X c +T c ;X c =[x c y c , z c =l] T Let be the coordinates of any point on the plate plane of the plate structure before deformation in the camera coordinate system; l is the distance from the camera's focal point to the plane of the plate structure; X′ c =[x′ c y′ c , z′ c ] T In the camera coordinate system, this represents the coordinates of a point on the deformed plate plane of the deformed plate structure. T c Let T be the displacement vector. c =[0, 0, w] T And w is outside the plane (or Z) c (Axial) displacement components; n c Let n be the normal vector, and n be the normal vector. c = [0, 0, 1 / l], The coordinate transformation relationship of any point in the imaging plane of the plate structure before and after deformation in step two is as follows: z′ c x′=KX′ c ; With' c =l+w; The image deformation function under out-of-plane deformation of the plate structure is as follows: Wherein, W(x; w) is the image deformation function under the out-of-plane deformation of the plate structure.

5. The method for measuring out-of-plane deformation of plate structures based on monocular vision according to claim 1, characterized in that, The specific steps for constructing the finite element interpolation representation include: Mesh division steps: Based on the image captured by the camera, the imaging plane of the plate structure is obtained, and the imaging plane is divided into multiple rectangular mesh units according to the set mesh size; Interpolation expression construction steps: Interpolate each rectangular mesh element according to the finite element interpolation method to obtain the finite element interpolation expression of each rectangular mesh element. Then, based on the finite element interpolation expressions of multiple rectangular mesh elements and the deformation parameters of the plate structure, construct the finite element interpolation expression of the full-field out-of-field displacement of the plate plane of the plate structure. The finite element interpolation expression for the overall out-of-field displacement of the plate plane of the plate structure is given by the following formula: w(x c y c )=N(x c y c )p: N(x c ,y c )=[N i ,N Xi ,N Yi ,i=1,2,…,n]; p=[w i ,the Xi ,the Yi ,i=1,2,…,n]; Where w(x) c y c ) is the overall out-of-field deformation function of the plate structure; N(x c y c ) is the interpolation shape function for all points on the plate plane of the plate structure; p represents the deformation parameter of the plate structure, including the displacement and rotation degrees of freedom of all points on the plate plane of the plate structure; w i θ Xi θ Yi These are the displacement of node i in the rectangular mesh element, the rotation angle of node i around the x-axis, and the rotation angle of node i around the y-axis, respectively. The value of i ranges from [1, 4]. n is the number of rectangular grid cells; a and b are half the length and half the width of a rectangular grid cell; N i N Xi N Yi These are three interpolation shape functions at node i of a rectangular grid cell of the plate structure, respectively; (x o y o ( ) represents the coordinates of the center point of the rectangular grid cell in the camera coordinate system; (x ci y ci Let be the coordinates of node i within the rectangular grid cell in the camera coordinate system.

6. The method for measuring out-of-plane deformation of a plate structure based on monocular vision according to claim 1, characterized in that, The formula for the objective function of digital image correlation is: Where f(x) and g(x) are the brightness distribution functions of the images before and after the deformation of the plate structure, respectively; Ω represents the image region where the plate plane of the plate structure is located before deformation. x′=W(x;N(x c ,y c )p); X c =lK -1 x。 7. The method for measuring out-of-plane deformation of plate structures based on monocular vision according to claim 1, characterized in that, The calculation steps specifically include: obtaining the deformation parameters of the plate structure by minimizing the objective function related to the digital image using the Gauss-Newton iteration method, and then obtaining the full-field out-of-field deformation data of the plate structure based on the deformation parameters of the plate structure and the finite element interpolation expression of the full-field out-of-field displacement of the plate structure.

8. The method for measuring out-of-plane deformation of a plate structure based on monocular vision according to claim 7, characterized in that, The calculation step, which uses the Gauss-Newton iteration method to find the minimum value of the objective function related to the digital image to obtain the deformation parameters of the plate structure, specifically includes: Step 1: Set the initial deformation parameter to zero, and set the change amount of the deformation parameter of the plate to be tested, so as to gradually update and obtain the deformation parameter of the plate structure after deformation. Where, p←p+Δp; Δp is the change in the deformation parameter; Step 2: Calculate the brightness and sensitivity of the deformed image; Wherein, the expression for image brightness is g(W(x); N(x) c y c The Taylor expansion of (p+Δp) is performed as follows: in, x′=W(x;N(x c ,y c )p); Step 3: Substitute the expression for image brightness into the digital image correlation objective function using the linear least squares method to obtain the change in the deformation parameters of the plate structure. Determine whether the convergence condition is met based on the change in the deformation parameters of the plate structure. If yes, the iteration terminates. The deformation parameters of the plate structure are obtained based on the change in the deformation parameters of the plate structure, the original deformation parameters of the plate plane, and p←p+Δp. If not, return to step 2.

9. A monocular vision-based out-of-plane deformation measurement device for plate structures, comprising a memory and a processor, characterized in that, The memory stores an out-of-plane deformation measurement program for a plate structure that runs on a processor. The out-of-plane deformation measurement program for the plate structure is a computer program. When the processor executes the out-of-plane deformation measurement program for the plate structure, it implements the steps of the out-of-plane deformation measurement method for a plate structure based on monocular vision as described in any one of claims 1-8.

10. A computer-readable storage medium storing thereon an out-of-plane deformation measurement program for a plate structure, characterized in that, The out-of-plane deformation measurement program for the plate structure is a computer program. When the out-of-plane deformation measurement program for the plate structure is executed by the processor, it implements the steps of the out-of-plane deformation measurement method for plate structures based on monocular vision as described in any one of claims 1-8.

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