A Real-time Measurement Method and Device for the Structural Deformation of a Bender Based on Monocular Vision

Abstract

The present invention provides a method and device for real-time measurement of the structural deformation of a bender based on monocular vision, including: S1, camera calibration based on a checkerboard background; S2, installing the bender and setting the recognition line; S3, photographing the initial state of the bender; S4, photographing the bender in the state to be measured; S5, extracting the initial state rectangular coordinate curve f s (x) and the position rectangular coordinate curve f e (x) in the state to be measured; S6, calculating the end deflection w max of the bender; S7, calculating the curvature f e (x) at the i-th coordinate point on the curve f K (x i ); S8, converting the plane rectangular coordinate curvature parameter into the axial distance coordinate curvature y’ ki ; S9, calculating the local deformation curvature of the bender structure; S10, calculating the integral of the local deformation curvature to obtain the deformation rotation angle θ b‑f of the bender. The method and device for real-time measurement of the structural deformation of the bender according to the present invention have the advantages of simple structure, easy operation and implementation, and accurate measurement.

Description

Technical Field

[0001] The present invention relates to the technical field of anti-bending device measurement, and in particular to a real-time measurement method and device for anti-bending device structural deformation based on monocular vision. Background Art

[0002] Bend guards are effective bend protection devices for flexible ducts and cables, widely used in offshore wind power, oil and gas development, and other marine resource development applications. Installed at the ends of flexible ducts and cables, they prevent excessive bending stiffness and, consequently, bending failure. Therefore, testing the bending deformation of bend guards under load, particularly real-time measurement of their bending deformation, is a key test method for verifying their performance.

[0003] At present, the measurement of bending deformation of bend preventers is mainly based on the combination of laser displacement sensors and fiber Bragg grating sensors. For example, when testing the end deflection and axial position curvature, a laser displacement sensor is arranged at the free end of the bend preventer before applying a load, and a fiber Bragg grating sensor is attached to its neutral layer; these two sensors are respectively connected to a dedicated acquisition device to measure the end deflection and axial position curvature data during the test; in addition, the current curvature measurement is also based on the contact measurement of fiber Bragg grating; the fiber Bragg grating needs to be bonded before the test, so the pre-test debugging is relatively complicated, and the test requires a special fiber Bragg grating signal demodulation device, which is expensive to use; similarly, although the end deflection measurement can be measured non-contactly by a laser displacement sensor, it requires specific tooling to fix it at the end of the bend preventer, and the installation and debugging are also relatively troublesome. In addition, this type of measurement method based on laser displacement sensors and fiber Bragg grating sensors also has the problems of low measurement accuracy and high operational difficulty.

[0004] Therefore, providing a device and method with simple structure, convenient installation and debugging, low cost, easy implementation, and accurate measurement, which can measure the structural deformation of the anti-bending device in real time is one of the technical problems that technical personnel in this field urgently need to solve. Summary of the Invention

[0005] The present invention designs a real-time measurement method and device for the structural deformation of a bending stabilizer based on monocular vision to overcome the technical problems of existing devices and methods for measuring the structural deformation of a bending stabilizer, such as complex installation and adjustment, high cost of use, and low measurement accuracy.

[0006] To solve the above problems, the present invention discloses a real-time measurement method for deformation of a bending stabilizer structure based on monocular vision, the measurement method comprising the following steps:

[0007] S1, obtaining a checkerboard background image placed directly behind the fixed stretching device through a camera, and performing calibration based on the checkerboard background using a built-in program of the camera;

[0008] S2. Install the anti-bending device onto the fixed stretching device, fix one end to make it the fixed end, and use the other end as the free end that can deform under the action of the stretching device. At the same time, set an identification line on the anti-bending device.

[0009] S3. Start the camera and take a picture of the initial state of the anti-bending device structure.

[0010] S4. Start the stretching device, use the stretching device to pull the free end of the anti-bending device to make it bend and deform for the anti-bending device bending structure test. At the same time, use the camera to take pictures of its deformation state in the measured state.

[0011] S5. Extract the initial state rectangular coordinate curve f s (x) and the measured state position rectangular coordinate curve f e (x);

[0012] S6. Calculate the end deflection w max ;

[0013] S7. Calculate the curvature f e (x) at the i-th coordinate point on the curve f K (x i );

[0014] S8. Convert the plane rectangular coordinate curvature parameter into the axial distance coordinate curvature y’ ki ;

[0015] S9. Solve the difference between the two sets of axial distance coordinate curvatures to obtain the local deformation curvature of the anti-bending device structure.

[0016] S10. Calculate the integral of the local deformation curvature to obtain the deformation rotation angle θ b-f .

[0017] Furthermore, in the step S2, the identification line is located on the neutral layer of the anti-bending device structure.

[0018] Furthermore, in the step S3, the camera is a monocular camera.

[0019] Furthermore, in the step S5, make the fixed end of the anti-bending device coincide with the origin O of the rectangular coordinate system, and the free end of the anti-bending device moves upward under the action of the stretching device, so that the identification line is always in the first quadrant of the rectangular coordinate system during the test.

[0020] Furthermore, in the step S6, the end deflection w max = f e (x max ) - f s (x max ), where fe (x max ) is the ordinate corresponding to the maximum abscissa in the coordinate set formed by the rectangular coordinate curve f e (x), and f s (x max ) is the ordinate corresponding to the maximum abscissa in the coordinate set formed by the initial state rectangular coordinate curve f s (x).

[0021] Furthermore, in the step S7, the curvature f K (x i ) is calculated according to the following formula:

[0022]

[0023] where i refers to the number of the i-th coordinate point on the curve f e (x), and the value range of i is i = 1, 2,..., n; x i is the abscissa of the i-th coordinate point on the curve f e (x); y i is the ordinate of the i-th coordinate point on the curve f e (x).

[0024] Furthermore, in the step S8, the axial distance coordinate curvature y’ ki is calculated according to the following formula:

[0025]

[0026] where x’ i is the independent variable of the i-th coordinate point in the axial distance coordinate system, y’ ki is the dependent variable of the i-th coordinate point in the axial distance coordinate system, and the value of y’ ki is the curvature corresponding to this coordinate point.

[0027] Furthermore, in the step S10, the deflection prevention device deformation angle θ b-f is calculated according to the following formula:

[0028]

[0029] where θ b-f is the rotation angle of a certain section in the deflection prevention device, b is the number of the starting point of this section, f is the number of the ending point of this section, x’ f , x’ b are the abscissas of the corresponding coordinate points in the axial distance coordinate system.

[0030] A real-time measurement device for the structural deformation of a bending preventer based on monocular vision. The measurement device is used for the real-time measurement method of the structural deformation of the bending preventer described above. The measurement device includes:

[0031] A fixed stretching device, which is used to fixedly install the bending preventer and can drive the bending preventer to generate deformation;

[0032] A background board, which is arranged directly behind the fixed stretching device, and a checkerboard is arranged on the background board;

[0033] A camera, which is arranged directly in front of the fixed stretching device and is used to photograph the deformation state of the bending preventer.

[0034] Furthermore, the fixed stretching device includes:

[0035] A fixed tripod, which is used to fixedly install the fixed end of the bending preventer;

[0036] A connecting flange, which connects the fixed tripod and the fixed end of the bending preventer to install the bending preventer on the fixed tripod;

[0037] A stretching device, which is located on the opposite side of the fixed tripod. The stretching device is connected to the free end of the bending preventer to drive the bending preventer to bend and deform.

[0038] The real-time measurement method and device for the structural deformation of the bending preventer based on monocular vision described in this application have the advantages of simple structure, convenient installation and debugging, low cost, easy implementation, simple operation and accurate measurement. Description of the Drawings

[0039] Figure 1 It is a schematic structural diagram of the real-time measurement device for the structural deformation of the bending preventer based on monocular vision described in the present invention;

[0040] Figure 2 It is a schematic structural diagram of the bending preventer described in the embodiment of the present invention;

[0041] Figure 3 It is a schematic flow diagram of the real-time measurement method for the structural deformation of the bending preventer based on monocular vision described in the present invention;

[0042] Figure 4 It is a photo of the identification line on the neutral layer in the initial state and the measured state described in the embodiment of the present invention;

[0043] Figure 5 It is a local deformation curvature change diagram of the bending preventer structure described in the embodiment of the present invention.

[0044] Description of the Reference Numerals:

[0045] 1. Fixed tripod; 2. Connecting flange; 3. Background plate; 4. Camera; 5. Anti-bending device; 51. Anti-bending device insert; 52. Anti-bending device body; 6. Identification line; 7. Stretching device. DETAILED DESCRIPTION

[0046] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0047] like Figures 1 to 3 As shown, a real-time measurement method for deformation of a bending stabilizer structure based on monocular vision is provided, and the measurement method comprises the following steps:

[0048] S1, obtaining a checkerboard background image placed directly behind the fixed stretching device through a camera, and performing calibration based on the checkerboard background using a built-in program of the camera;

[0049] S2, installing the anti-bending device on the fixed stretching device so that one end is fixed as a fixed end and the other end is a free end capable of being deformed under the action of the stretching device, and setting an identification line on the anti-bending device;

[0050] S3, starting the camera and photographing the initial state of the anti-bending device structure;

[0051] S4, starting the stretching device, pulling the free end of the anti-bending device through the stretching device to bend and deform the free end of the anti-bending device to perform a bending structure test of the anti-bending device, and simultaneously using a camera to capture the deformation state of the anti-bending device under the test state;

[0052] S5, extracting the initial rectangular coordinate curve f of the identification line s (x) and the measured state position rectangular coordinate curve f e (x);

[0053] S6, calculate the end deflection w of the anti-bending device max ;

[0054] S7, calculation curve f e The curvature f at the i-th coordinate point on (x) K (x i );

[0055] S8, convert the plane rectangular coordinate curvature parameter into the axial distance coordinate curvature y' ki ;

[0056] S9, solving the difference between the two sets of axial distance coordinate curvatures to obtain the local deformation curvature of the anti-bending device structure;

[0057] S10, calculate the local deformation curvature integral to obtain the bending stabilizer deformation angle θ b-f .

[0058] Specifically, calibrating the camera based on the checkerboard is an existing technical means in the measurement field, and its detailed process will not be elaborated here.

[0059] Preferably, in the step S2, the recognition line is located on the structural neutral layer of the anti-bending device.

[0060] More preferably, in the step S2, the recognition line is a high-contrast line with an obvious difference in color from the surface of the anti-bending device.

[0061] As some embodiments of the present application, in the step S2, the recognition line can be set on the anti-bending device by means of painting, pasting, etc.

[0062] Preferably, in the step S3, the camera is a monocular camera.

[0063] As some embodiments of the present application, in the step S4, start the stretching device, and use the stretching device to pull the free end of the anti-bending device to make it bend and deform for the bending structure test of the anti-bending device, and at the same time use the camera to take pictures of its deformation state in the measured state, and use it for subsequent calculation of the structural deformation of the anti-bending device.

[0064] As other embodiments of the present application, in the step S4, start the stretching device, and use the stretching device to pull the end of the anti-bending device to make it bend and deform for the bending structure test of the anti-bending device, and at the same time use the camera to take pictures of the deformation state of the anti-bending device at a set time interval, and then select the pictures at specific moments or states for subsequent calculation of the structural deformation of the anti-bending device.

[0065] Further, in the step S5, as Figure 4 shown, make the fixed end of the anti-bending device coincide with the origin O of the rectangular coordinate system, and the free end of the anti-bending device moves upward under the action of the stretching device, so that the recognition line is always in the first quadrant of the rectangular coordinate system during the test.

[0066] Further, in the step S6, the end deflection w of the anti-bending device max = f e (x max ) - f s (x max ), where x max is the maximum abscissa in the coordinate set formed by the initial state rectangular coordinate curve f s (x) or the measured state position rectangular coordinate curve f e (x); f e (x max ) is the measured state position rectangular coordinate curve f e(x) The ordinate corresponding to the maximum abscissa in the formed coordinate set, f s (x max ) is the initial state rectangular coordinate curve f s (x). The ordinate corresponding to the maximum abscissa in the formed coordinate set.

[0067] Furthermore, in the step S7, the curvature f K (x i ) is calculated according to the following formula:

[0068]

[0069] where i refers to the number of the i-th coordinate point on the curve f e (x), and the value range of i is i = 1, 2,..., n; x i is the abscissa of the i-th coordinate point on the curve f e (x); y i is the ordinate of the i-th coordinate point on the curve f e (x).

[0070] Furthermore, in the step S8, the axial distance coordinate curvature y’ ki is calculated according to the following formula:

[0071]

[0072] where x’ i is the independent variable of the i-th coordinate point in the axial distance coordinate system, y’ ki is the dependent variable of the i-th coordinate point in the axial distance coordinate system, and the value of y’ ki is the curvature corresponding to this coordinate point.

[0073] Furthermore, in the step S10, the deformation angle θ of the anti-bending device b-f is calculated according to the following formula:

[0074]

[0075] where θ b-f is the rotation angle of a certain section in the anti-bending device, b is the number of the starting point of this section, f is the number of the ending point of this section, x’ f , x’ b are the abscissas of the corresponding coordinate points in the axial distance coordinate system for the two.

[0076] In addition, as Figures 1 to 2 shown, the present application also provides a real-time measurement device for the structural deformation of an anti-bending device based on monocular vision. The measurement device includes:

[0077] A fixed stretching device, which is used to fixedly install the anti-bending device 5 and can drive the anti-bending device 5 to deform;

[0078] A background board 3, which is arranged directly behind the fixed stretching device, and a checkerboard is arranged on the background board 3;

[0079] A camera 4, which is arranged directly in front of the fixed stretching device and is used to photograph the deformation state of the anti-bending device 5.

[0080] Furthermore, the fixed stretching device at least includes a fixing device for fixing one end of the anti-bending device 5 and a stretching device 7 for stretching the other end of the anti-bending device 5.

[0081] As some embodiments of the present application, the fixed stretching device includes:

[0082] A fixed tripod 1, which is used to fixedly install the fixed end of the anti-bending device 5;

[0083] A connecting flange 2, which connects the fixed tripod 1 and the fixed end of the anti-bending device 5 to install the anti-bending device 5 on the fixed tripod 1;

[0084] A stretching device 7, which is located on the opposite side of the fixed tripod 1, and the stretching device 7 is connected to the free end of the anti-bending device 5 to drive the anti-bending device 5 to bend and deform.

[0085] Furthermore, an identification line 6 is arranged on the neutral layer of the structure of the anti-bending device 5.

[0086] Preferably, the camera 4 is a monocular camera.

[0087] As some embodiments of the present application, the specific structure of the anti-bending device 5 is as Figure 2 shown, including: an anti-bending device insert 51 and an anti-bending device main body 52. Among them, the anti-bending device insert 51 is arranged axially in the anti-bending device main body 52, and a connecting bolt group is arranged on the anti-bending device insert 51, and the connecting bolt group can be connected to the connecting flange 2; the anti-bending device main body 52 is a variable cross-section beam structure, the outer diameter of its cross-section changes along the axial direction, and at the same time any cross-section of it is a concentric circle, Figure 2 A structure of a three-section anti-bending device main body 52 is given. The anti-bending device main body 52 is prepared from a uniform polymer material. Therefore, the neutral layer of its structure coincides with its geometric center line, that is, the identification line 6 should be pasted at the middle position of the vertical height on the outside of the anti-bending device 5.

[0088] The following uses specific embodiments to illustrate the real-time measurement method for the structural deformation of the anti-bending device based on monocular vision described in the present application:

[0089] Embodiment 1

[0090] A real-time measurement method for deformation of a bending stabilizer structure based on monocular vision: the measurement method comprises the following steps:

[0091] S1, using a camera to acquire an image of a checkerboard background directly behind the fixed stretching device, and using the camera's built-in program to perform calibration based on the checkerboard background. At the same time, the camera's position change and the camera's own optical distortion are corrected based on the known checkerboard size.

[0092] S2, installing the anti-bending device on the fixed stretching device so that one end is fixed as a fixed end and the other end is a free end capable of being deformed under the action of the stretching device, and setting an identification line on the anti-bending device;

[0093] S3, starting the camera and photographing the initial state of the anti-bending device structure so as to later analyze the process variation such as the end deflection during the anti-bending device test;

[0094] S4, starting the stretching device, pulling the free end of the anti-bending device through the stretching device to bend and deform the free end of the anti-bending device to perform a bending structure test of the anti-bending device, and simultaneously using a camera to capture the deformation state of the anti-bending device under the test state;

[0095] S5, take the axial direction of the anti-bending device as the X axis, the radial direction perpendicular to the X axis as the Y axis, and the Y axis is consistent with the stretching direction, extract the initial state rectangular coordinates of the identification line on the neutral layer and the measured state rectangular coordinates, and obtain the initial state rectangular coordinate curve f of the identification line s (x) and the measured state position rectangular coordinate curve f e (x); When extracting the position coordinates, the starting point is selected on the end face of the bend limiter at the fixed end of the connecting flange, and the ending point is selected at the end of the free end of the bend limiter; In addition, when extracting the rectangular coordinates of the initial state of the identification line on the neutral layer and the rectangular coordinates of the measured state, 1 / 10 of the inner diameter d1 of the bend limiter can be selected as the reference spacing of the points. In order to increase the measurement accuracy of the cross-section mutation or other positions that need to be paid attention to, d1 / 50 can be used as the point spacing to encrypt the local area. The coordinate curves of the initial state and the measured state extracted according to the above method are as follows Figure 4 As shown, the initial rectangular coordinate curve is f s (x), the measured state rectangular coordinate curve is f e (x);

[0096] S6, calculate the end deflection w of the anti-bending device max , end deflection w max The difference between the two curves obtained in the previous step and the farthest points on the axis. The specific formula is: w max =f e (x max )-f s (x max), where x max is the maximum abscissa in the coordinate set formed by the initial state rectangular coordinate curve f s (x) or the measured state position rectangular coordinate curve f e (x); f e (x max ) is the ordinate corresponding to the maximum abscissa in the coordinate set formed by the measured state position rectangular coordinate curve f e (x), and f s (x max ) is the ordinate corresponding to the maximum abscissa in the coordinate set formed by the initial state rectangular coordinate curve f s (x).

[0097] S7. Calculate the curvature f e (x) at the i-th coordinate point on the curve, specifically selecting the Euclidean geometry method considering the trigonometric function non-linearity. The curvature f K (x i ) is calculated according to the following formula: K (x i )

[0098]

[0099] where i refers to the number of the i-th coordinate point on the curve f e (x), and the value range of i is i = 1, 2,..., n; x i is the abscissa of the i-th coordinate point on the curve f e (x); y i is the ordinate of the i-th coordinate point on the curve f e (x).

[0100] S8. Convert the plane rectangular coordinate curvature parameter into the axial distance coordinate curvature y' ki . The axial distance coordinate curvature y' ki is calculated according to the following formula:

[0101]

[0102] where x' i is the independent variable of the i-th coordinate point in the axial distance coordinate system, y' ki is the dependent variable of the i-th coordinate point in the axial distance coordinate system, and the value of y' ki is the curvature corresponding to this coordinate point.

[0103] S9. Solve the difference between the two sets of axial distance coordinate curvatures to obtain the local deformation curvature of the bender structure. The specific result is as Figure 5 shown. Usually, the curvature deformation result can be analyzed in segments according to the bender structure characteristics, Figure 5Taking three sections as an example, first check whether the deformation curvature of each section exceeds the design range.

[0104] S10. Calculate the integral of the local deformation curvature to obtain the deformation angle θ of the anti-bending device b-f , and the deformation angle θ of the anti-bending device b-f is calculated according to the following formula:

[0105]

[0106] where θ b-f is the rotation angle of a certain section in the anti-bending device, b is the number of the starting point of this section, f is the number of the ending point of this section, and x’ f , x’ b are the abscissas of the corresponding coordinate points of the two in the axial distance coordinate system.

[0107] Although the present invention is disclosed as above, the present invention is not limited thereto. In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. A real-time measurement method for the structural deformation of a bending preventer based on monocular vision, characterized in that, The measuring method comprises the steps of: S1, obtaining a checkerboard background image placed directly behind the fixed stretching device through a camera, and performing calibration based on the checkerboard background using a built-in program of the camera; S2, installing the anti-bending device on the fixed stretching device so that one end is fixed as a fixed end and the other end is a free end capable of being deformed under the action of the stretching device, and setting an identification line on the anti-bending device; S3, starting the camera and photographing the initial state of the anti-bending device structure; S4, starting the stretching device, pulling the free end of the anti-bending device through the stretching device to bend and deform the free end of the anti-bending device to perform a bending structure test of the anti-bending device, and simultaneously using a camera to capture the deformation state of the anti-bending device under the test state; S5. Extract the initial state rectangular coordinate curve f s (x) of the recognition line and the rectangular coordinate curve f e (x) of the measured state position; S6. Calculate the end deflection w of the anti-bending device max ; S7, calculate the curvature f e at the i-th coordinate point on the curve f K (x i ), and the curvature f K (x i ) is calculated according to the following formula: Among them, i refers to the serial number of the i-th coordinate point on the curve f e (x), and the value range of i is i = 1, 2, …, n; x i is the abscissa of the i-th coordinate point on the curve f e (x); y i is the ordinate of the i-th coordinate point on the curve f e (x); S8. Convert the plane rectangular coordinate curvature parameter into the axial distance coordinate curvature y’ ki , where the axial distance coordinate curvature y’ ki is calculated according to the following formula: where x’ i is the independent variable of the i-th coordinate point in the axial distance coordinate system, and y’ ki is the dependent variable of the i-th coordinate point in the axial distance coordinate system, and the value of y’ ki is the curvature corresponding to this coordinate point; S9, solving the difference between the two sets of axial distance coordinate curvatures to obtain the local deformation curvature of the anti-bending device structure; S10, calculate the deformation angle θ of the anti-bending device b-f , the deformation angle θ of the anti-bending device b-f is calculated according to the following formula: Among them, θ b-f is the rotation angle of a certain section in the anti-bending device, b is the starting point number of this section, f is the ending point number of this section, x’ f , x’ b is the independent variable of the corresponding coordinate points of the two in the axial distance coordinate system, and y’ k is the dependent variable of the corresponding coordinate points of the two in the axial distance coordinate system.

2. The real-time measurement method for the structural deformation of the anti-bending device according to claim 1, characterized in that In step S2, the identification line is located on the structural neutral layer of the bending stabilizer.

3. The real-time measurement method for the structural deformation of the anti-bending device according to claim 1, characterized in that In step S3, the camera is a monocular camera.

4. The real-time measurement method for the structural deformation of the anti-bending device according to claim 1, wherein In step S5, the fixed end of the anti-bending device is made to coincide with the origin O of the rectangular coordinate system, and the free end of the anti-bending device moves upward under the action of the stretching device, so that the identification line is always in the first quadrant of the rectangular coordinate system during the test.

5. The real-time measurement method for the structural deformation of the anti-bending device according to claim 1, characterized in that In the step S6, the end deflection w of the anti-bending device max = f e (x max ) - f s (x max ), where f e (x max ) is the ordinate corresponding to the maximum abscissa in the coordinate set formed by the rectangular coordinate curve f e (x) in the measured state position, and f s (x max ) is the ordinate corresponding to the maximum abscissa in the coordinate set formed by the rectangular coordinate curve f s (x) in the initial state.

6. A real-time measurement device for the structural deformation of a bending preventer based on monocular vision, characterized in that, The measuring device is used in the real-time measurement method of the anti-bending device structural deformation according to any one of claims 1 to 5, and the measuring device comprises: A fixed stretching device, which is used to fix the anti-bending device (5) and can drive the anti-bending device (5) to produce deformation; A background plate (3) is arranged directly behind the fixed stretching device, and a checkerboard pattern is arranged on the background plate (3); A camera (4) is arranged in front of the fixed stretching device and is used to photograph the deformation state of the anti-bending device (5).

7. The real-time deformation measurement device for the anti-bending structure according to claim 6, characterized in that, The fixed stretching device comprises: A fixed tripod (1) for fixing the fixed end of the anti-bending device (5); A connecting flange (2) connecting the fixed tripod (1) and the fixed end of the anti-bending device (5) for mounting the anti-bending device (5) on the fixed tripod (1); A stretching device (7) is located on the opposite side of the fixed tripod (1), and the stretching device (7) is connected to the free end of the anti-bending device (5) to drive the anti-bending device (5) to undergo bending deformation.

Images