Device and method for large deformation measurement and material property estimation of beam-shaped polymer materials using stereo camera

Abstract

The present invention relates to a device and a method for large deformation measurement and material property estimation of beam-shaped polymer materials using a stereo camera and, more specifically, to a device and a method for large deformation measurement and material property estimation of beam-shaped polymer materials using a stereo camera, the device comprising: a fixing unit for fixing an end of an object; a linear stage for applying tension to a wire embedded in the object fixed to the fixing unit in a gravity direction; a load cell for measuring the tension applied to the wire; a stereo camera for photographing a deformation curve by deforming the object in accordance with the tension applied to the wire; a data collection unit for collecting tension data measured from the load cell; and a controller for controlling at least one of the linear stage or the stereo camera.

Description

Device and method for measuring large deformation and estimating physical properties of beam-shaped polymer materials using a stereo camera

[0001] The present invention relates to a device and method for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera.

[0002] Endoscopes, catheters, medical robots, and various types of continuum robots are formed from viscoelastic materials, such as polymers, that are highly deformable, to steer the position of their distal ends in a beam-like shape, with some bending. These steering devices apply tension to embedded wires, creating a bending moment, thereby causing the beam to bend.

[0003] To determine the degree of large deformation of these steering devices, various testing methods have been used. First, a typical tensile tester applies tensile force to a material to determine its mechanical properties. This allows for measurements of tensile strength, yield point, elongation, and area shrinkage. However, because it cannot measure large deformation, bending strength cannot be directly measured and must be estimated using a formula. Even for beams with the same cross-sectional area and Young's modulus, bending strength can vary. Therefore, it is difficult to obtain accurate bending strength from Young's modulus and cross-sectional area obtained through a tensile test.

[0004] Furthermore, these steering devices can be formed into multiple sections with different polymers in a beam shape. Therefore, it is impossible to obtain the bending strength for each section through a simple tensile test using the above-mentioned general tensile tester. To overcome the technical limitations of the above-mentioned tensile tester, a large deformation tensile tester exists. However, the large deformation tensile test directly damages the steering devices in order to measure the bending strength for each section of the steering devices composed of multiple sections, and like a general tensile tester, it has the technical limitation of not being able to derive the accurate bending strength from the Young's modulus.

[0005] Furthermore, a single section of these steering devices may be formed by combining multiple materials, such as a main material formed from a single polymer, a wire formed from steel, and a secondary material formed from another type of polymer. In this case, neither the general tensile tester nor the large deformation tensile tester described above can accurately measure the bending strength of a single section. This is because, even if the Young's modulus and cross-sectional area are the same, the bending strength can vary depending on how the various materials are arranged within the beam.

[0006] Therefore, there is an urgent need in this technical field for a device and method that can measure large deformations of steering devices that form a single section with multiple materials and have multiple single sections, such as endoscopes, catheters, medical robots, and various types of continuum robots, and derive material properties such as bending strength without direct damage.

[0007] The present invention is intended to solve the above problems, and the purpose is to obtain a device and method for measuring large deformation of a beam-shaped polymer material and estimating material properties by using a stereo camera that outputs the bending strength of an object by using tension data applied to a wire of an object measured from a load cell and a deformation curve of the object photographed from a stereo camera, in order to measure large deformation of steering devices such as endoscopes, catheters, medical robots, and various types of continuum robots, and to derive material properties such as bending strength without direct damage.

[0008] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the art from the description of the present invention.

[0009] In order to achieve the above object, the present invention provides a device for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera, comprising: a fixing unit for fixing an end of an object; a linear stage for applying tension in the direction of gravity to a wire embedded in an object fixed to the fixing unit; a load cell for measuring tension applied to the wire; a stereo camera for photographing a deformation curve as the object is deformed according to the tension applied to the wire; a data collection unit for collecting tension data measured from the load cell; and a controller for controlling at least one of the linear stage and the stereo camera.

[0010] In order to achieve the above object, the present invention provides a method for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera, comprising: a tension data acquisition step in which tension data for tension applied to a wire embedded in an object are acquired by at least one processor; an image acquisition step in which a deformation curve image of the object photographed by the stereo camera is acquired by the at least one processor; an image processing step in which the deformation curve image is processed by the at least one processor and coordinates for the deformation curve are acquired; a moment calculation step in which a bending moment applied to the object is calculated by the at least one processor using the tension data; a curvature calculation step in which the coordinates for the deformation curve are used to calculate the curvature of the deformation curve; and a modeling step in which a bending strength model for the object is generated by the at least one processor and material property coefficients of the bending strength model are derived by using the bending moment and the curvature of the deformation curve.

[0011] As described above, according to the present invention, it is possible to measure large deformations of sections of steering devices formed of polymer materials in the form of beams, such as endoscopes, catheters, medical robots, and various types of continuum robots, and to derive material properties representing bending strength without direct damage.

[0012] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the detailed description and the description of the claims.

[0013] Figure 1 is a configuration diagram of a device for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera.

[0014] FIG. 2 is a drawing showing an object before being bent (a) and an object after being bent (b) according to one embodiment of the present invention.

[0015] FIG. 3 is a configuration diagram of a device for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera according to an embodiment of the present invention.

[0016] Figure 4 is a drawing showing an image processing process (a)-(c) according to one embodiment of the present invention.

[0017] FIG. 5 is a drawing showing two-dimensional coordinates of a plurality of marking points according to one embodiment of the present invention.

[0018] Figure 6 is a drawing showing the entire deformation curve (a) and the second stiffness section (b) according to one embodiment of the present invention.

[0019] Figure 7 is a drawing showing the curvature (a) and the moment (b) at which stress relaxation occurs according to one embodiment of the present invention.

[0020] FIG. 8 is a drawing showing a bending moment calculated from a moment calculation unit and a result moment calculated from a modeling unit according to one embodiment of the present invention.

[0021] Figure 9 is a flow chart of a method for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera of the present invention.

[0022] Fig. 10 is a flowchart of a method for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera according to an embodiment of the present invention.

[0023] The terms used in this specification have been selected from widely used, current terms, taking into account the functions of the present invention. However, these terms may vary depending on the intentions of those skilled in the art, precedents, the emergence of new technologies, etc. Furthermore, in certain cases, terms may be arbitrarily selected by the applicant, and in such cases, their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this invention should not be defined simply as names, but rather based on their inherent meanings and the overall content of the present invention.

[0024] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0025] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Fig. 1 is a configuration diagram of a device for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera. Fig. 2 is a diagram showing an object (10) (a) before being bent and an object (10) (b) after being bent according to an embodiment of the present invention. Fig. 3 is a configuration diagram of a device for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera according to an embodiment of the present invention.

[0026] Fig. 4 is a diagram showing an image processing process (a)-(c) according to an embodiment of the present invention. Fig. 5 is a diagram showing two-dimensional coordinates of a plurality of marking points according to an embodiment of the present invention. Fig. 6 is a diagram showing an entire deformation curve (a) and a second stiffness section (14b)(b) according to an embodiment of the present invention.

[0027] Fig. 7 is a diagram showing a curvature (a) and a moment (b) at which a stress relaxation phenomenon occurs according to an embodiment of the present invention. Fig. 8 is a diagram showing a bending moment calculated from a moment calculation unit (912) and a resultant moment calculated from a modeling unit (914) according to an embodiment of the present invention.

[0028] Fig. 9 is a flow chart of a method for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera according to the present invention. Fig. 10 is a flow chart of a method for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera according to an embodiment of the present invention.

[0029]

[0030] Device for measuring large deformation and estimating material properties of beam-shaped polymer materials using a stereo camera

[0031] Referring to FIG. 1, the device for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera of the present invention includes a fixing unit (100) for fixing an end of an object (10), a linear stage (200) for applying tension in the direction of gravity to a wire (11) embedded in the object (10) fixed to the fixing unit (100), a load cell (300) for measuring tension applied to the wire (11), a stereo camera (400a, 400b) for photographing a deformation curve as the object (10) is deformed according to the tension applied to the wire (11), a data collection unit (500) for collecting tension data measured from the load cell (300), and a controller (600) for controlling at least one of the linear stage (200) and the stereo camera (400a, 400b).

[0032] The object (10) referred to in the present invention is part or all of a steering device such as an endoscope, a catheter, a medical robot, and various types of continuum robots. The object (10) is made of a polymer material in the form of a beam, and has a wire (11) built in therein. When an external force is applied to the wire (11) in a wire-driven manner, the object (10) bends.

[0033] At this time, the object (10) may include a plurality of rigid sections having the same rigidity in the longitudinal direction or having different rigidities. Referring to one embodiment of Fig. 2, the object (10) may include the first rigid section (14a) and the second rigid section (14b). The first rigid section (14a) is a section adjacent to one end (12) fixed to the fixing member (100), and may be a high-rigidity section having relatively high rigidity and thus less bending. The second rigid section (14b) is a section adjacent to the other end (13), and may be a low-rigidity section having relatively low rigidity and thus more bending.

[0034] Next, the fixing member (100) can vertically fix one end (12) from the upper surface. In addition, the fixing member (100) can fully support the object (10) even if the object (10) is bent due to tension applied to the wire in the direction of gravity by the linear stage (200).

[0035] Meanwhile, the fixed part (100) is characterized in that a wire (11) exposed from one end (12) passes through it. And the penetrated wire (11) can be directly connected to the linear stage (200). For example, the load cell (300) can be arranged on the upper side of the linear stage (200). And the load cell (300) can be connected to the wire (11) that passes through it. And the linear stage (200) can operate in the up-and-down direction to pull the wire (11) in the direction of gravity or slowly release the wire (11) in the direction opposite to gravity. Accordingly, the object (10) can be bent or straightened depending on the rigidity. And the load cell (300) can measure the tension applied to the wire (11) and output tension data expressed numerically.

[0036] Next, the stereo camera (400a, 400b) is composed of two cameras with a constant pixel count, and can be arranged in parallel at a distance of several millimeters (mm). At this time, the stereo camera (400a, 400b) can be installed with the pixel count and the distance between the two cameras appropriately selected according to the size of the object (10) and the required precision. In addition, the deformation curve can be repeatedly photographed at preset shooting cycles.

[0037] In addition, the stereo camera (400a, 400b) can be directly connected to the computer device (900) by wire or wirelessly to transmit a deformation curve image in which the deformation curve is photographed to the computer device (900) in real time. Alternatively, the stereo camera (400a, 400b) can transmit a deformation curve image in which the deformation curve is photographed to the computer device (900) in real time via the connected controller (600). Alternatively, the stereo camera (400a, 400b) can further include a memory and store the deformation curve image in the memory. In addition, by connecting the memory to the computer device (900), the computer device (900) can obtain a deformation curve image for the object (10).

[0038] Next, the data acquisition unit (500) may most preferably be a DAQ (Data Acquisition) board. The data acquisition unit (500) may acquire tension data measured in analog or digital format from the load cell (300) and store the data as much as the storage capacity allows. In addition, it may be connected to a computer device (900) via wired or wireless means to provide previously stored tension data.

[0039] Next, the controller (600) is connected to the linear stage (200) so as to be able to communicate with it via wire or wirelessly, and can control the up and down movement of the linear stage (200). In addition, the controller (600) is connected to the stereo camera (400a, 400b) so as to be able to communicate with it via wire or wirelessly, and can set the shooting cycle of the stereo camera (400a, 400b).

[0040] Next, the device for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera of the present invention further includes a plurality of marking points (700) displayed on the surface in the longitudinal direction of an object (10) fixed to the fixing member (100), and the stereo camera (400a, 400b) is characterized in that it outputs each of the plurality of marking points (700) as three-dimensional coordinates so as to be able to digitize the deformation curve.

[0041] In addition, the device for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera of the present invention further includes a graph paper (800) for displaying a plurality of coordinate system reference points (810a, 810b, 810c, 810d) for transforming a coordinate system of three-dimensional coordinates output from the stereo camera (400a, 400b), and the stereo camera (400a, 400b) is characterized in that it compares the coordinates of the plurality of coordinate system reference points (810a, 810b, 810c, 810d) output from the stereo camera (400a, 400b) with the coordinates of the actual plurality of coordinate system reference points (810a, 810b, 810c, 810d), and if the difference is within a preset error range, it is determined that the accuracy of the stereo camera (400a, 400b) is secured.

[0042] Referring to an embodiment of FIG. 3, the plurality of marking points (700) may be displayed at arbitrary intervals on the surface of the object (10) facing the stereo camera (400a, 400b) so as to be displayed on the deformation curve image. The plurality of marking points (700) may be spaced at the same interval or spaced at different intervals. The graph paper (800) may be arranged to face the stereo camera (400a, 400b) at the rear side of the object (10) fixed to the fixing member (100). That is, the stereo camera (400a, 400b), the object (10) fixed to the fixing member (100), and the graph paper (800) are arranged in that order.

[0043] Since the present invention is to measure the large deformation of the object (10) using the stereo camera (400a, 400b), adjustment of the stereo camera (400a, 400b) is essential.

[0044] First, the stereo cameras (400a, 400b) can be calibrated. Conventional calibration techniques can be used to calibrate the stereo cameras (400a, 400b). Specifically, considering the experimental environment, the stereo cameras (400a, 400b) can be calibrated by photographing a checkerboard having a preset square size from various distances and angles while the spacing and composition of the stereo cameras (400a, 400b) are fixed. The size of the squares of the checkerboard can be appropriately selected depending on the shooting precision.

[0045] In addition, the stereo camera (400a, 400b) can perform coordinate system transformation using the plurality of marking points (700) indicated on the object (10) and the plurality of coordinate system reference points (810) indicated on the graph paper (800). The plurality of coordinate system reference points (810) may include a second coordinate system reference point (810b) positioned on a vertical line with respect to the first coordinate system reference point (810a), a third coordinate system reference point (810c) positioned on a horizontal line, and a fourth coordinate system reference point (810d) positioned on a diagonal line.

[0046] That is, the stereo camera (400a, 400b) can compare the coordinates of the measured first to fourth coordinate system reference points (810a, 810b, 810c, 810d) with the coordinates of the real first to fourth coordinate system reference points (810a, 810b, 810c, 810d) and determine that the shooting accuracy is secured if the difference is within a preset error range.

[0047] For example, the above stereo cameras (400a, 400b) can calculate the distance error using the following [Mathematical Formula 1]. If the error range is ±4 mm, the stereo cameras (400a, 400b) can be judged as not having secured accuracy if the error exceeds the ±4 mm range, and can be judged as having secured accuracy if the error is within the ±4 mm range.

[0048]

[0049] Here, (x m , y m , z m ) are the coordinates of the first to fourth coordinate system reference points (810a, 810b, 810c, 810d) measured from the stereo camera (400a, 400b), and (x a , y a , za ) are the coordinates of the first to fourth coordinate system reference points (810a, 810b, 810c, 810d).

[0050] In addition, since the stereo cameras (400a, 400b) are initially set with one camera (400a) as the origin of the coordinate system, it is necessary to transform the coordinate system of the three-dimensional coordinates using the first to fourth coordinate system reference points (810a, 810b, 810c, 810d). For example, the stereo cameras (400a, 400b) can be set so that the starting point of the object (10) or the point where the object (10) is fixed to the fixing member (100) becomes the origin coordinate (0,0,0).

[0051] Next, the device for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera of the present invention further includes a computer device (900) including a memory (920) and at least one processor (910), and the computer device (900) is characterized in that it outputs the bending strength of the object (10) using the tension data collected from the data collection unit (500) and the deformation curve image of the object (10) captured by the stereo camera (400a, 400b).

[0052] The above at least one processor (910) may include an image processing unit (911), a moment calculation unit (912), a curvature calculation unit (913), a stiffness section coordinate setting unit (914), and a modeling unit (915).

[0053] First, the image processing unit (911) can process the deformation curve image and obtain coordinates for the deformation curve.

[0054] In image processing, the image processing unit (911) can further acquire a reference image in which the object (10) does not exist through the stereo camera (400a, 400b). Here, the deformation curve image refers to a left deformation curve image and a right deformation curve image, and the reference image also refers to a left reference image and a right reference image.

[0055] In addition, the image processing unit (911) can display the background of the deformation curve image in black by excluding the reference image from the deformation curve image. Then, only the deformation curve of the object (10) can be displayed.

[0056] Referring to an embodiment of (a) in Fig. 4, the image processing unit (911) can detect the maximum edge, which is located at the extreme edge, from the deformation curve image from which the reference image is excluded using an edge detection technique. Referring to an embodiment of (b) in Fig. 4, the image processing unit (911) can determine the center line of the object (10) from the maximum edge. In addition, the image processing unit (911) can restore the color of the object (10) to distinguish the plurality of marking points (700).

[0057] At this time, the image processing unit (911) can easily identify the starting point of the maximum edge at the bottom of the image, and accordingly, can set the direction from the starting point to the ending point of the maximum edge. When the direction of the target object (10) is set, the image processing unit (911) can assign a number to each marking point according to the set direction. The image processing unit (911) can distinguish each section by utilizing the number and positions of a plurality of marking points (700) displayed on the target object (10). Since a marking point is necessarily displayed at the end point of each section, the sections of the target object (10) can be distinguished.

[0058] Referring to an embodiment of (c) of FIG. 4, the plurality of marking points (700) can be ordered as first to sixth marking points (700a, 700b, 700c, 700d, 700e, 700f) in the order adjacent to the lower part of the image. That is, the fifth marking point (700e) to the sixth marking point (700f) are recognized as the other end (13) where the wire (11) of the object (10) is not connected and thus there is no bending, and therefore there is no need to check the physical properties. In addition, the first rigid section (14a) and the second rigid section (14b) can be distinguished based on the third marking point (700c).

[0059] And the image processing unit (911) can generate two-dimensional coordinates from the three-dimensional coordinates for the plurality of marking points (700). The three-dimensional coordinates for the plurality of marking points (700) can be generated by utilizing the pixel values ​​generated from the left deformation curve image and the pixel values ​​generated from the right deformation curve image by the stereo cameras (400a, 400b). However, since the object (10) is actually bent two-dimensionally, not three-dimensionally, the image processing unit (911) can generate two-dimensional coordinates by deleting the z-axis data from the three-dimensional coordinates. Referring to one embodiment of FIG. 5, two-dimensional coordinates for the plurality of marking points (700) displayed on the xy plane are displayed.

[0060] Next, the moment calculation unit (912) can calculate the bending moment applied to the object using the tension data.

[0061] The above moment calculation unit (912) can calculate the bending moment using the following [Mathematical Formula 2].

[0062]

[0063] Here, M is the bending moment, T is the tension data, and r is the distance from the central axis of the object (10) to the wire (11).

[0064] Next, the curvature calculation unit (913) can calculate the curvature of the deformation curve using the two-dimensional coordinates for the deformation curve.

[0065] In addition, the curvature calculation unit (913) may include a stiffness section coordinate setting unit (9131) that sets start coordinates and end coordinates that indicate each end of an arbitrary stiffness section, and calculates the curvature for an arbitrary stiffness section using the start coordinates and end coordinates, thereby calculating the curvature for each stiffness section of the object (10).

[0066] The coordinates for the deformation curve mentioned in the present invention are two-dimensional coordinates for the plurality of marking points (700) generated from the image processing unit (911).

[0067] Most preferably, the plurality of marking points (700) may include points indicating the starting point of each section. For example, the starting point of the second rigid section (14b) is the third marking point (700c). The rigid section coordinate setting unit (9131) may recognize the area from the origin in the graph indicating the two-dimensional coordinates to the third marking point (700c) as the first rigid section (14a), and may recognize the area from the third marking point (700c) to the fifth marking point (700e) as the second rigid section (14b). In addition, the area from the fifth marking point (700e) to the sixth marking point (700f) may be recognized as the other end (13) where the wire (11) of the object (10) is not connected, so there is no bending, and therefore, there is no need to check the physical properties.

[0068] At this time, the curvature calculation unit (913) can perform curvature calculation even if only one marking point is placed in a section including the origin. The curvature calculation unit (913) can perform curvature calculation even if only two marking points are placed in a section not including the origin. However, since the minimum number of marking points that can approximate a circle is three, the number of marking points (700) per section may be three according to one embodiment of the present invention. That is, the number of marking points placed in a section is not limited to a specific number.

[0069] Referring to an example of (a) in Fig. 6, as described above, the start coordinate of the first rigid section (14a) is (0,0), and the end coordinate is (x) which is the two-dimensional coordinate of the third marking point (700c). p ,y p ) is. The above curvature calculation unit (913) is the end coordinate (x p ,y p ) can be substituted into [Mathematical Formula 3] to calculate the curvature of the first rigid section (14a).

[0070]

[0071] Here, ρ is the curvature of the first rigid section (14a), R is the radius of the first rigid section (14a), and x, y are the two-dimensional coordinates of the third marking point (700c) (x p , y p ) can be substituted.

[0072] In addition, as described above, the starting coordinate of the second rigid section (14b) is the two-dimensional coordinate of the third marking point (700c) (x p ,y p ), and the end coordinate is the two-dimensional coordinate of the fifth marking point (700e) (x d ,y d) is. However, it is difficult to directly derive the radius of the second rigid section (14b) connected to the first rigid section (14a) from the graph shown in (a) of Fig. 6. Therefore, coordinate transformation is required using the angle (θ) of the second rigid section (14b) with respect to the first rigid section (14a).

[0073] The above rigid section coordinate setting unit (9131) can calculate the angle (θ) of the second rigid section (14b) with respect to the first rigid section (14a) using the following [Mathematical Formula 4].

[0074]

[0075] Here, L P is the length of the first rigid section (14a), and R P is the radius of the first rigid section (14a).

[0076] Referring to an example of (b) of Fig. 6, the rigid section coordinate setting unit (9131) sets the two-dimensional coordinates of the third marking point (700c) (x p ,y p ) is converted to the origin, and the two-dimensional coordinates of the fifth marking point (700e) are (x) as shown in [Mathematical Formula 5] below. d ,y d ) to (x 2d ,y 2d ) can be converted into each.

[0077]

[0078] And, the above curvature calculation unit (913) (x 2d ,y 2d ) can be substituted into x and y of the above [Mathematical Formula 3], respectively, to calculate the curvature of the second rigid section (14b).

[0079] Meanwhile, for example, the object (10) includes a first rigid section (14a) and a second rigid section (14b), but may include more rigid sections. The rigid section coordinate setting unit (9131) may transform the end coordinates of each rigid section into the [Mathematical Formula 4] to the [Mathematical Formula 5] as many times as the number of rigid sections excluding the first rigid section, and the curvature calculation unit (913) may calculate the curvature of each rigid section by substituting the transformed coordinates into the [Mathematical Formula 3].

[0080] Therefore, the present invention has a remarkable effect of being able to measure the section-by-section large deformation of the target object (10) formed of a beam-shaped polymer material by including a curvature calculation unit (913).

[0081] Next, the modeling unit (914) can create a bending strength model for the object (10) and derive the material property coefficients of the bending strength model using the bending moment and the curvature of the deformation curve.

[0082] The viscoelastic cantilever mentioned in the present invention refers to a beam in which one end is fixed and the other end is not supported, i.e., a cantilever. The fixed body (10) has one end (12) fixed to the fixed part (100) and the other end (13) is not fixed and is configured to be bendable, so it can be determined to be a viscoelastic cantilever. A viscoelastic cantilever can generally experience a stress relaxation phenomenon. Referring to an embodiment of FIG. 7, the stress relaxation phenomenon refers to a phenomenon in which the bending moment is not constant as the curvature is constant, but rather the bending moment gradually decreases over time despite the curvature being constant.

[0083] According to one embodiment of the present invention, the modeling unit (914) determines that the object (10) is a viscoelastic cantilever that receives a constant bending moment according to its length, and generates the bending strength model using the following [Mathematical Formula 6] that reflects the stress relaxation phenomenon that occurs in the viscoelastic cantilever. The following [Mathematical Formula 6] can be used when the stress relaxation phenomenon is linear.

[0084]

[0085] Here, M(t) is the resulting moment with respect to time (t), EI(t-τ) is the relaxation function of the stress-strain relationship, ρ(τ) is the curvature of the strain curve, and τ is the time constant.

[0086] In addition, the modeling unit (914) is characterized by calculating the relaxation function (EI(t-τ)) of the stress-strain relationship using the following [Mathematical Formula 7].

[0087]

[0088] Here, k0, k1, k2, τ1, and τ2 are material property coefficients.

[0089] According to another embodiment of the present invention, the modeling unit (914) is characterized in that it generates the bending strength model using the following [Mathematical Formula 8] that reflects the stress relaxation phenomenon occurring in an elastic cantilever. The following [Mathematical Formula 8] can be used when the stress relaxation phenomenon is nonlinear.

[0090]

[0091] Here, M(t) is the resulting moment with respect to time (t), g(t) is the stress relaxation property, and M ρ (ρ) is the nonlinearity of the bending moment in the curvature of the above deformation curve, ρ is the curvature of the above deformation curve, and τ is the time constant.

[0092] In addition, the modeling unit (914) is characterized by calculating the stress relaxation property (g(t)) using the following [Mathematical Formula 9].

[0093]

[0094] Here, A0, A1, A2, τ1, and τ2 are material property coefficients.

[0095] And the above modeling unit (914) uses the following [Mathematical Formula 10] to calculate the nonlinearity (M) of the bending moment in the curvature of the deformation curve. ρ It is characterized by calculating (ρ)).

[0096]

[0097] Here, a and b are material property coefficients, and ρ is the curvature of the deformation curve.

[0098] The material property coefficients mentioned in the present invention represent the bending strength of the object (10) formed of a beam-shaped polymer material, and according to one embodiment of the present invention, they are k0, k1, k2, τ1, τ2 in the above [Mathematical Formula 7], or A0, A1, A2, τ1, τ2 in the above [Mathematical Formula 9] and a, b in the above [Mathematical Formula 10].

[0099] In each material property coefficient, τ1 and τ2 are time constants, and k0, k1, k2, A0, A1 and A2 are coefficients that affect the shape of the resulting moment (M(t)) graph versus time (t) according to the stress relaxation phenomenon, and in particular, A0 is a coefficient that determines the maximum instantaneous drop during the stress relaxation phenomenon, and A1 and A2 are coefficients that affect the long-term and short-term stress relaxation phenomena, respectively. As a and b increase, the nonlinearity of the bending moment in the curvature of the deformation curve may increase.

[0100] At this time, the modeling unit (914) may further include a material property coefficient tuning unit (9141) in which the material property coefficient is tuned by optimizing the resulting moment derived by substituting the curvature of the deformation curve into the [Mathematical Formula 6] to match the bending moment calculated from the moment calculation unit (912).

[0101] According to one embodiment of the present invention, since the object (10) is composed of one rigid section, the curvature for one rigid section can be derived from the curvature calculation unit (913). Accordingly, the modeling unit (914) can calculate the resulting moment (M(t)) for time (t) for one rigid section by substituting the curvature for one rigid section into [Mathematical Formula 6] or [Mathematical Formula 8].

[0102] According to another embodiment of the present invention, since the object (10) is composed of a plurality of rigid sections, the curvature for each rigid section can be derived from the curvature calculation unit (913). For example, the object (10) may include a first rigid section (14a) having relatively high rigidity and a second rigid section (14b) having relatively low rigidity. Accordingly, a curvature graph according to time, such as the embodiment of Fig. 7 (a), can be created for each section. On the other hand, a moment graph according to time, such as the embodiment of Fig. 7 (b), does not change according to the section and can be created as one. The above material property coefficient tuning unit (9141) can tune the material property coefficients for each section by substituting the curvature for each section in the form of (a) of FIG. 7 into [Mathematical Expression 6] or [Mathematical Expression 8], respectively, so that the resulting moment is optimized to match the bending moment calculated from the moment calculation unit (912). That is, the modeling unit (914) can calculate the resulting moment (M(t)) for each section's time (t) by substituting the respective curvatures for the first stiffness section (14a) and the second stiffness section (14b) calculated from the curvature calculation unit (913) into [Mathematical Expression 6] or [Mathematical Expression 8].

[0103] Referring to an embodiment of FIG. 8, the moment calculation unit (912) can obtain tension data for time and calculate the bending moment (M) for time using the above [Mathematical Expression 2]. That is, the bending moment for time calculated from the moment calculation unit (912) is an experimental value. The modeling unit (914) can calculate the result moment (M(t)) for time in which the stress relaxation phenomenon is reflected by inputting the curvature for time derived from the curvature calculation unit (913) into the above [Mathematical Expression 6] or the above [Mathematical Expression 8]. That is, the result moment (M(t)) for time calculated from the modeling unit (914) is a simulation value. However, although the simulation value has the shape of the experiment value, there is bound to be a difference.

[0104] Accordingly, the present invention includes the above-described property coefficient tuning unit (9141), so that the above-described property coefficient can be tuned to reduce this difference. In addition, there is a remarkable effect of being able to determine the bending strength of the object (10) through the tuned property coefficient.

[0105]

[0106] A method for measuring large deformation and estimating material properties of beam-shaped polymer materials using a stereo camera

[0107] The method for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera of the present invention can be implemented by having at least one processor (910) in a computer device (900) read the memory (920). The memory (920) can record a program that performs the method for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera of the present invention. The at least one processor (910) can include the image processing unit (911), the moment calculation unit (912), the curvature calculation unit (913), and the modeling unit (914) mentioned in the device for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera of the present invention.

[0108] Referring to FIG. 9, the method for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera of the present invention comprises: a tension data acquisition step (S500) in which tension data for tension applied to a wire (11) embedded in an object (10) is acquired by at least one processor (910); an image acquisition step (S600) in which a deformation curve image of the object (10) photographed from a stereo camera (400a, 400b) is acquired by the at least one processor (910); an image processing step (S700) in which the deformation curve image is processed by the at least one processor (910) and coordinates for the deformation curve are acquired; a moment calculation step (S800) in which a bending moment applied to the object (10) is calculated by using the tension data by the at least one processor (910); and a curvature calculation step in which the curvature of the deformation curve is calculated by using the coordinates for the deformation curve by the at least one processor (910). A bending strength model for the object (10) is generated by the operation step (S900) and the at least one processor (910), and a modeling step (S1000) is included in which the bending moment and the curvature of the deformation curve are used to derive the material property coefficients of the bending strength model. The method for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera of the present invention is not limited to the described step order and may be changed or performed simultaneously.

[0109] Meanwhile, referring to an embodiment of FIG. 10, the method for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera of the present invention may further include a tension data measuring step (S100) in which tension applied to a wire (11) embedded in an object (10) is measured by a load cell (300), a tension data storing step (S200) in which tension data measured from the load cell (300) is collected by a data collecting unit (500), a camera adjusting step (S300) in which the stereo cameras (400a, 400b) are adjusted to improve the precision and accuracy of the image and coordinates output from the stereo cameras (400a, 400b), and a photographing step (S400) in which the object (10) is deformed according to the tension applied to the wire (11) and a deformation curve is photographed by the adjusted stereo cameras (400a, 400b). there is.

[0110] More specifically, the tension data measuring step (S100) and the tension data storing step (S200) can obtain tension data for the time applied to the object (10).

[0111] Next, in the camera adjustment step (S300), a checkerboard having a preset square size is photographed from various distances and angles while the spacing and composition of the stereo cameras (400a, 400b) are fixed in consideration of the experimental environment, thereby allowing calibration of the stereo cameras (400a, 400b). The size of the squares of the checkerboard can be appropriately selected depending on the precision.

[0112] In addition, the camera adjustment step (S300) may perform coordinate system transformation using the plurality of marking points (700) indicated on the object (10) and the plurality of coordinate system reference points (810) indicated on the graph paper (800). The plurality of coordinate system reference points (810) may include a second coordinate system reference point (810b) positioned on a vertical line with respect to the first coordinate system reference point (810a), a third coordinate system reference point (810c) positioned on a horizontal line, and a fourth coordinate system reference point (810d) positioned on a diagonal line.

[0113] In addition, in the camera adjustment step (S300), the coordinates of the measured first to fourth coordinate system reference points (810a, 810b, 810c, 810d) and the coordinates of the actual first to fourth coordinate system reference points (810a, 810b, 810c, 810d) are compared, and if the difference is within a preset error range, it can be determined that the shooting accuracy is secured.

[0114] For example, the camera adjustment step (S300) may calculate the distance error using the above [Mathematical Formula 1]. If the error range is ±4 mm, the camera adjustment step (S300) may be judged as not ensuring accuracy if the error exceeds the ±4 mm range, and may be judged as ensuring accuracy if the error is within the ±4 mm range. In the above [Mathematical Formula 1], (x m , y m , z m ) are the coordinates of the first to fourth coordinate system reference points (810a, 810b, 810c, 810d) measured from the stereo camera (400a, 400b), and (x a , y a , z a ) are the coordinates of the first to fourth coordinate system reference points (810a, 810b, 810c, 810d).

[0115] In addition, since the camera adjustment step (S300) is initially set to the origin of the coordinate system, the first to fourth coordinate system reference points (810a, 810b, 810c, 810d) are used to transform the three-dimensional coordinate system. For example, the camera adjustment step (S300) may be performed to transform the coordinate system so that the starting point of the object (10) or the point where the object (10) is fixed to the fixing member (100) becomes the three-dimensional origin coordinate (0,0,0).

[0116] Next, in the above-described photographing step (S400), a plurality of marking points (700) displayed on the surface in the longitudinal direction of the object (10) fixed to the fixing member (100) can be output as three-dimensional coordinates so that the deformation curve is digitized.

[0117] The present invention is completed when all of the tension data required from the tension data measurement step (S100) and the tension data storage step (S200) are collected, and all of the deformation curve images required from the photographing step (S400) are photographed, and then the next step can be performed.

[0118] Next, in the image processing step (S700), a reference image in which the object (10) does not exist can be further acquired from the photographing step (S400). Here, the deformation curve image collectively refers to two images, a left deformation curve image and a right deformation curve image, and the reference image collectively refers to two images, a left reference image and a right reference image.

[0119] In addition, in the image processing step (S700), the background of the deformation curve image can be displayed in black by excluding the reference image from the deformation curve image. Then, only the deformation curve of the object (10) can be displayed.

[0120] Referring to an embodiment of (a) in Fig. 4, the image processing step (S700) may use an edge detection technique to detect the maximum edge located at the extreme edge from the deformation curve image from which the reference image is excluded. Referring to an embodiment of (b) in Fig. 4, the image processing step (S700) may determine the center line of the object (10) from the maximum edge. In addition, the image processing step (S700) may restore the color of the object (10) so that the plurality of marking points (700) may be distinguished.

[0121] At this time, in the image processing step (S700), the starting point of the maximum edge can be easily identified at the bottom of the image, and accordingly, the direction from the starting point to the end point of the maximum edge can be set. In the image processing step (S700), when the direction of the target object (10) is set, a number can be assigned to each marking point (700) according to the direction. In the image processing step (S700), each section can be distinguished by utilizing the number and positions of a plurality of marking points (700) displayed on the target object (10). Since a marking point must be displayed at the end point of each section, the sections of the target object (10) can be distinguished.

[0122] Referring to an embodiment of (c) of FIG. 4, the image processing step (S700) may determine the order of the first to sixth marking points (700a, 700b, 700c, 700d, 700e, 700f) in the order adjacent to the lower part of the image. That is, the sixth marking point (700f) is recognized as the other end (13) of the object (10). In addition, the first rigid section (14a) and the second rigid section (14b) may be distinguished based on the third marking point (700c).

[0123] And the image processing step (S700) can generate two-dimensional coordinates from the three-dimensional coordinates for the plurality of marking points (700). Since the object (10) is actually bent two-dimensionally rather than three-dimensionally, the image processing step (S700) can generate two-dimensional coordinates by deleting the z-axis data from the three-dimensional coordinates. Referring to one embodiment of Fig. 5, two-dimensional coordinates for a plurality of marking points (700) displayed on the xy plane are displayed.

[0124] Next, in the moment calculation step (S800), the bending moment can be calculated using the above [Mathematical Formula 2]. In the above [Mathematical Formula 2], M is the bending moment, T is the tension data, and r is the distance from the central axis of the object (10) to the wire (10).

[0125] Next, in the curvature calculation step (S900), the curvature of the deformation curve can be calculated using two-dimensional coordinates for a plurality of marking points (700) forming the deformation curve generated from the image processing step (S700).

[0126] According to one embodiment of the present invention, since the object (10) is composed of one rigid section, the curvature for one rigid section can be derived. The plurality of marking points (700) can include first to third marking points (700A, 700b, 700c). Then, in the curvature calculation step (S900), the origin is set as the starting coordinate for one rigid section in the graph of the two-dimensional coordinates generated from the image processing step (S700), and the coordinates of the third marking point (700c) are (x p ,y p ) can be set as the end coordinate for one rigid section.

[0127] And the above curvature calculation step (S900) is the end coordinate of one rigid section (x p ,yp ) is substituted into the above [Mathematical Expression 3], the curvature of one rigid section can be calculated. In the above [Mathematical Expression 3], ρ is the curvature of one rigid section, R is the radius of one rigid section, and x and y are the two-dimensional coordinates of the third marking point (700c) (x p , y p ) can be substituted.

[0128] According to another embodiment of the present invention, the object (10) may include a plurality of rigid sections having different rigidities, and the curvature calculation step (S900) is characterized in that the start coordinate and the end coordinate indicating each end of an arbitrary rigid section are set, and the start coordinate and the end coordinate are used to calculate the curvature for an arbitrary rigid section, thereby calculating the curvature for each rigid section of the object (10).

[0129] Referring to an embodiment of Fig. 2, the object (10) may include the first rigid section (14a) and the second rigid section (14b). The first rigid section (14a) is a section adjacent to one end (12) fixed to the fixing member (100), and may be a high-rigidity section having relatively high rigidity and thus less bending. The second rigid section (14b) is a section adjacent to the other end (13), and may be a low-rigidity section having relatively low rigidity and thus more bending.

[0130] The above multiple marking points (700) include first to sixth marking points (700a, 700b, 700c, 700d, 700e, 700f), and at least one of these may be a point indicating a starting point of each section. For example, the starting point of the second rigid section (14b) is the third marking point (700c). In the above curvature calculation step (S900), the third marking point (700c) may be recognized as the first rigid section (14a) from the origin in the graph indicating the two-dimensional coordinates, and the fifth marking point (700e) from the third marking point (700c) may be recognized as the second rigid section (14b). And, from the fifth marking point (700e) to the sixth marking point (700f), the wire (11) of the object (10) is not connected, so there is no bending, and it can be recognized as the other end (13) that does not need to check the physical properties.

[0131] Referring to one embodiment of (a) of Fig. 6, as described above, the start coordinate of the first rigid section (14a) is (0,0), and the end coordinate is (x) which is the two-dimensional coordinate of the third marking point (700c). p ,y p ) is. The above curvature calculation step (S900) is the end coordinate (x p ,y p ) is substituted into the above [Mathematical Expression 3], the curvature of the first rigid section (14a) can be calculated. In the above [Mathematical Expression 3], ρ is the curvature of the first rigid section (14a), R is the radius of the first rigid section (14a), and x, y are the two-dimensional coordinates of the third marking point (700c) (x p , y p ) can be substituted.

[0132] In addition, the starting coordinate of the second rigid section (14b) is the two-dimensional coordinate of the third marking point (700c) (x p ,y p ) and the end coordinate is the two-dimensional coordinate of the fifth marking point (700e) (x d,y d ) is. However, it is difficult to directly derive the radius of the second rigid section (14b) connected to the first rigid section (14a) from the graph shown in (a) of Fig. 6. Therefore, coordinate transformation is required using the angle (θ) of the second rigid section (14b) with respect to the first rigid section (14a).

[0133] The above curvature calculation step (S900) can calculate the angle (θ) of the second rigid section (14b) with respect to the first rigid section (14a) using the above [Mathematical Formula 4]. In the above [Mathematical Formula 4], L P is the length of the first rigid section (14a), and R P is the radius of the first rigid section (14a).

[0134] Looking at one embodiment of (b) of Fig. 6, the curvature calculation step (S900) calculates the two-dimensional coordinates of the third marking point (700c) (x p ,y p ) is converted to the origin, and the two-dimensional coordinates of the sixth marking point (700f) are (x) using the above [Mathematical Formula 5]. d ,y d ) is (x 2d ,y 2d ) can be converted into (x 2d ,y 2d ) are substituted into x and y of the above [Mathematical Formula 3], respectively, so that the curvature of the second rigid section (14b) can be calculated.

[0135] For example, the object (10) includes only the first rigid section (14a) and the second rigid section (14b), but may include more rigid sections. In the curvature calculation step (S900), the start coordinates of each rigid section can be converted to the origin as many times as the number of rigid sections excluding the first rigid section, and the end coordinates of each rigid section can be coordinate-converted to [Mathematical Expression 4] to [Mathematical Expression 5]. In addition, in the curvature calculation step (S900), the curvature of each rigid section can be calculated by substituting the converted end coordinates into [Mathematical Expression 3].

[0136] Next, the modeling step (S1000) is characterized in that the object (10) is determined to be a viscoelastic cantilever that receives a constant bending moment along its length, and the bending strength model is generated using the above [Mathematical Expression 6] that reflects the stress relaxation phenomenon that occurs in the viscoelastic cantilever. The above [Mathematical Expression 6] can be used when the stress relaxation phenomenon is linear. In the above [Mathematical Expression 6], M(t) is a resultant moment for time (t), EI(t-τ) is a relaxation function of the stress-strain relationship, ρ(τ) is a curvature of the deformation curve, and τ is a time constant.

[0137] And the above modeling step (S1000) is characterized in that the relaxation function (EI(t-τ)) of the stress-strain relationship is calculated using the above [Mathematical Formula 7]. In the above [Mathematical Formula 7], k0, k1, k2, τ1, and τ2 are material property coefficients.

[0138] According to another embodiment of the present invention, the modeling step (S1000) is characterized in that the bending strength model is generated by the above [Mathematical Formula 8] that reflects the stress relaxation phenomenon occurring in the elastic cantilever. The above [Mathematical Formula 8] can be used when the stress relaxation phenomenon is nonlinear. In the above [Mathematical Formula 8], M(t) is the resulting moment with respect to time (t), g(t) is the stress relaxation property, and Mρ (ρ) is the nonlinearity of the bending moment in the curvature of the above deformation curve, ρ is the curvature of the above deformation curve, and τ is the time constant.

[0139] And the above modeling step (S1000) is characterized in that the stress relaxation property (g(t)) is calculated using the above [Mathematical Formula 9]. In the above [Mathematical Formula 9], A0, A1, A2, τ1, and τ2 are material property coefficients.

[0140] And the above modeling step (S1000) uses the above [Mathematical Formula 10] to determine the nonlinearity (M) of the bending moment in the curvature of the deformation curve. ρ (ρ)) is calculated. In the above [Mathematical Formula 10], a and b are property coefficients, and ρ is the curvature of the deformation curve.

[0141] The material property coefficients mentioned in the present invention represent the bending strength of the object (10) formed of a beam-shaped polymer material, and according to one embodiment of the present invention, they are k0, k1, k2, τ1, τ2 in the above [Mathematical Formula 7], or A0, A1, A2, τ1, τ2 in the above [Mathematical Formula 9] and a, b in the above [Mathematical Formula 10].

[0142] In each material property coefficient, τ1 and τ2 are time constants, and k0, k1, k2, A0, A1 and A2 are coefficients that affect the shape of the resulting moment (M(t)) graph versus time (t) according to the stress relaxation phenomenon, and in particular, A0 is a coefficient that determines the maximum instantaneous drop during the stress relaxation phenomenon, and A1 and A2 are coefficients that affect the long-term and short-term stress relaxation phenomena, respectively. As a and b increase, the nonlinearity of the bending moment in the curvature of the deformation curve may increase.

[0143] At this time, the modeling step (S1000) is characterized in that the material property coefficient is tuned by optimizing the resulting moment derived by substituting the curvature of the deformation curve into the [Mathematical Formula 6] so that it matches the bending moment calculated from the moment calculation step (S900).

[0144] According to one embodiment of the present invention, since the object (10) is composed of one rigid section, the curvature for one rigid section can be derived from the curvature calculation step (S900). Accordingly, in the modeling step (S1000), the curvature for one rigid section can be substituted into the above [Mathematical Formula 6] or the above [Mathematical Formula 8] to calculate the resulting moment (M(t)) for time (t).

[0145] According to another embodiment of the present invention, since the object (10) is composed of a plurality of rigid sections, the curvature for each rigid section can be derived from the curvature calculation step (S900). For example, the object (10) may include a first rigid section (14a) having relatively high rigidity and a second rigid section (14b) having relatively low rigidity. Accordingly, a curvature graph according to time, such as the embodiment of Fig. 7 (a), can be created for each section. On the other hand, a moment graph according to time, such as the embodiment of Fig. 7 (b), does not change according to each section and can be created as one. The above modeling step (S1000) is optimized so that the resulting moment derived by substituting the section-wise curvature of the form (a) of Fig. 7 into [Mathematical Formula 6] or [Mathematical Formula 8] respectively matches the bending moment calculated from the moment calculation step (S800), thereby tuning the section-wise material property coefficient.

[0146] Referring to an embodiment of FIG. 8, the moment calculation step (S800) obtains tension data for time from the tension data acquisition step (S500), so that the bending moment (M) for time can be calculated using the [Mathematical Formula 2]. That is, the bending moment for time calculated from the moment calculation step (S800) is an experimental value. The modeling step (S1000) can calculate the result moment (M(t)) for time in which the stress relaxation phenomenon is reflected by inputting the curvature for time derived from the curvature calculation step (S900) into the [Mathematical Formula 6] or the [Mathematical Formula 8]. That is, the result moment (M(t)) for time calculated from the modeling step (S1000) is a simulation value. However, although the simulation value has the shape of the experimental value, there is bound to be a difference.

[0147] Therefore, the modeling step (S1000) of the present invention can tune the material property coefficients to reduce such differences. In addition, there is a remarkable effect in that the bending strength of the object (10) can be determined through the tuned material property coefficients.

[0148]

[0149] Embodiments may be implemented in hardware, software, firmware, middleware, microcode, hardware description language, or any combination thereof. When implemented in software, firmware, middleware, or microcode, program code or code segments that perform the necessary tasks may be stored on a computer-readable storage medium and executed by one or more processors.

[0150] Aspects of the subject matter described herein may be described in the general context of computer-executable instructions, such as program modules or components, being executed by a computer. Typically, program modules or components include routines, programs, objects, and data structures that perform particular tasks or implement particular data formats. Aspects of the subject matter described herein may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media, including memory storage devices.

[0151] Although the embodiments described above have been described by way of limited examples and drawings, those skilled in the art will appreciate that various modifications and variations can be made based on the above description. For example, appropriate results can be achieved even if the described techniques are performed in a different order than described, and / or components of the described systems, structures, devices, circuits, etc. are combined or combined in a different manner than described, or are replaced or substituted with other components or equivalents.

[0152] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims described below.

Claims

1. A fixing part that fixes the end of the object; A linear stage that applies tension in the direction of gravity to a wire embedded in an object fixed to the above-mentioned fixture; A load cell that measures the tension applied to the above wire; A stereo camera that photographs a deformation curve of the object as it deforms according to the tension applied to the wire; A data collection unit that collects tension data measured from the load cell; and A device for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera, the device including a controller for controlling at least one of the linear stage and the stereo camera.

2. In paragraph 1, Further comprising a plurality of marking points displayed on the surface in the longitudinal direction of the object fixed to the above-mentioned fixing member; The above stereo camera, A device for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera, characterized in that the plurality of marking points are each output as three-dimensional coordinates so that the deformation curve can be digitized.

3. In paragraph 2, Further comprising a graph paper displaying a plurality of coordinate system reference points for coordinate system transformation of the three-dimensional coordinates output from the stereo camera; The above stereo camera, A device for measuring large deformation and estimating physical properties of a beam-shaped polymer material using a stereo camera, characterized in that the accuracy of the stereo camera is determined to be secured if the coordinates of a plurality of coordinate system reference points output from the stereo camera are compared with the coordinates of a plurality of actual coordinate system reference points and the difference is within a preset error range.

4. In paragraph 1, memory; and A computer device further comprising at least one processor; The above computer device, A device for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera, characterized in that it outputs the bending strength of the object using tension data collected from the data collection unit and a deformation curve image of the object captured by the stereo camera.

5. A tension data acquisition step in which tension data regarding tension applied to a wire embedded in a target object is acquired by at least one processor; An image acquisition step in which a deformation curve image of the object captured from a stereo camera is acquired by at least one processor; An image processing step in which the deformation curve image is processed by at least one processor and coordinates for the deformation curve are obtained; A moment calculation step in which the tension data is used to calculate a bending moment applied to the object by at least one processor; A curvature calculation step in which the curvature of the deformation curve is calculated using coordinates for the deformation curve by at least one processor; and A method for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera, comprising a modeling step in which a bending strength model for the object is generated by at least one processor, and the bending moment and the curvature of the deformation curve are used to derive material property coefficients of the bending strength model.

6. In paragraph 5, The above object is, Contains multiple stiffness sections with different stiffnesses, The above curvature calculation step is, A method for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera, characterized in that the start and end coordinates indicating each end of an arbitrary stiffness section are set, and the curvature for an arbitrary stiffness section is calculated using the start and end coordinates, thereby calculating the curvature for each stiffness section of the object. In paragraph 7.5, The above modeling steps are: The above object is judged to be a viscoelastic cantilever that receives a constant bending moment along its length, A method for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera, characterized in that the bending strength model is generated by the following [Mathematical Formula 6] reflecting the stress relaxation phenomenon occurring in a viscoelastic cantilever. [Equation 6] Here, M(t) is the resulting moment with respect to time (t), EI(t-τ) is the relaxation function of the stress-strain relationship, ρ(τ) is the curvature of the strain curve, and τ is the time constant.

8. In paragraph 7, The above modeling steps are: A method for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera, characterized in that the relaxation function (EI(t-τ)) of the stress-strain relationship is calculated using the following [Mathematical Formula 7]. [Equation 7] Here, k0, k1, k2, τ1, and τ2 are material property coefficients.

9. In paragraph 7, The above modeling steps are: A method for measuring large deformation and estimating material properties of a beam-shaped polymer material using a stereo camera, characterized in that the material property coefficient is tuned by optimizing the resulting moment derived by substituting the curvature of the deformation curve into the above [Mathematical Formula 6] to match the bending moment calculated from the moment calculation step.

Images