A machine vision-based sensor for detecting maximum tensile and compressive strain.

Abstract

This invention discloses a machine vision-based maximum tensile and compressive strain detection sensor, belonging to the field of civil engineering structural safety inspection technology. It aims to measure the maximum tensile and compressive strain of a structure within a certain deformation range for tensile and compressive strain detection. The technical solution includes: an encapsulated structure connecting a first fixed support, a second fixed support, and a limiting device; both the maximum tensile strain displacement sensing structure and the maximum compressive strain displacement sensing structure are externally connected to the limiting device; both internally have damping and reference probes; and a camera is located at the bottom of a microscope. The sleeve in this invention can only move in one direction, allowing direct measurement of the maximum tensile and compressive strain values, making operation simple and convenient. Data is acquired using a digital camera and digital signals, resulting in a simple structure, low cost, and strong electromagnetic interference resistance. Different camera modules or smartphone cameras can be used to collect sensor data from the same measuring point. The sensor's built-in sensing structure and encapsulation structure are simple, durable, and easy to use.

Description

Technical Field

[0001] This invention relates to the field of civil engineering structural safety testing technology, specifically to a maximum tensile and compressive strain detection sensor based on machine vision. Background Technology

[0002] Strain is a crucial parameter reflecting the structural state, playing a vital role in assessing the mechanical properties, failure behavior, crack propagation, and residual stress of structural components. Among these parameters, the maximum strain value is of paramount importance, as it is often compared with existing theoretical values ​​to analyze and determine the structural safety status. Therefore, obtaining strain information of structures under load, especially the maximum strain value, is of significant research value.

[0003] Existing strain sensors include resistance strain gauges, fiber optic sensors, and vibrating wire strain gauges. However, these sensors obtain maximum tensile and compressive strain values ​​primarily by establishing continuous strain monitoring systems and selecting extreme values ​​from long-term monitoring results. Long-term monitoring generates a large amount of data, making data analysis and processing cumbersome, and data transmission and recording difficult. If the strain of a specific structure is measured discontinuously, only the current strain value at the time of measurement can be obtained. For structures under dynamic loads, this makes it impossible to obtain information on the maximum tensile and compressive strain that may occur outside of the measurement times, potentially exceeding the strain values ​​measured at each time. Currently, there is no low-cost, convenient technique for detecting the maximum tensile and compressive strain parameters of a structure.

[0004] To address the challenge of acquiring maximum tensile and compressive strain information of structures at low cost, this invention provides a machine vision-based maximum tensile and compressive strain detection sensor that is easy to use, highly accurate, and low in measurement cost. It can directly measure and record the maximum strain value that occurs in a structure over a period of time. Summary of the Invention

[0005] To address the limitations of existing strain sensing technologies, such as the difficulty in achieving low-cost strain acquisition and the cumbersome data analysis and processing, as well as the challenges in transmission and recording large amounts of data generated during long-term monitoring, this invention proposes a novel machine vision-based maximum tensile and compressive strain detection sensor. Its key feature is that the displacement corresponding to the maximum tensile and compressive strain change within the strain sensing gauge is converted into a displacement that can be measured visually using a microscope through a maximum tensile and compressive displacement sensitive structure, thereby achieving strain measurement within the sensing gauge. This sensor achieves a strain resolution of 10-1. -6 This sensor is capable of directly measuring and recording the maximum strain value of a structure over a period of time. It has a simple structure and is easy to install, which can reduce the cost of maximum tensile and compressive strain detection and broaden the application prospects of maximum tensile and compressive strain detection in actual structures.

[0006] To achieve the above objectives, this invention discloses a maximum tensile and compressive strain detection sensor based on machine vision. The technical solution includes a first fixed support, a reference probe, a microscope, a camera, a second fixed support, damping, a maximum tensile strain displacement-sensitive structure, a maximum compressive strain displacement-sensitive structure, a limiting device, and a packaging structure. This sensor is used only to measure maximum tensile and compressive strain, and can conveniently, directly, and clearly record the maximum deformation value of a structure over a period of time. The left and right ends of the packaging structure are respectively connected to the first and second fixed supports, and the limiting device is located inside. An opening is provided at the top. The exterior of both the maximum tensile strain displacement-sensitive structure and the maximum compressive strain displacement-sensitive structure are connected to the limiting device. The damping and the reference probe are located inside both the maximum tensile strain displacement-sensitive structure and the maximum compressive strain displacement-sensitive structure. The camera is located at the bottom of the microscope, and the camera's position corresponds to the opening. The microscope is used to magnify the relative displacement of a tiny visual target corresponding to the strain change within the gauge length of the strain sensor by tens of times, obtaining a small field-of-view image of the visual target displacement change for subsequent... The system continues to use a camera for visual data acquisition and processing, obtaining the displacement changes caused by the maximum tensile and compressive strains within the sensing gauge length, thereby obtaining the maximum tensile and compressive strains within the sensing gauge length. The function of the maximum tensile strain displacement sensitive structure is to convert the displacement change caused by the maximum tensile strain between the two ends of the strain sensing gauge length into the relative displacement change between visual targets at local positions. Dividing the obtained relative displacement change by the sensor's sensing gauge length yields the maximum tensile strain within the sensing gauge length. Similarly, the function of the maximum compressive strain displacement sensitive structure is to convert the displacement change caused by the maximum compressive strain between the two ends of the strain sensing gauge length into the relative displacement change between visual targets at local positions. Dividing the obtained relative displacement change by the sensor's sensing gauge length yields the maximum compressive strain within the sensing gauge length. The camera's function is to acquire image and video information of the relative position changes of the visual targets. The limiting device is used to reduce the positional fixing error of the internal components of the sensor and facilitate the placement of the internal components, while ensuring the stability of the maximum tensile and compressive strain displacement sensitive structures. The encapsulation structure encapsulates and protects the main components of the sensor, and the fixed support fixes the sensor to the object being measured to generate synchronous strain changes.

[0007] As a preferred embodiment of the present invention, the maximum tensile strain displacement sensitive structure includes a reference probe, a reference scale, a tensile strain mark point, a tensile strain sleeve, and a tensile strain sliding probe. The reference probe is connected to the first fixed support, and one end is fixed with the reference scale. The reference scale is marked with a tiny visual target, which is rectangular or circular in shape. This target is a visual target with known geometric dimensions and is used to establish the correspondence between the pixel displacement measured by the camera and the actual displacement. The tensile strain sleeve contains the tensile strain sliding probe, and a damper is provided in the gap between the two. The damper can be made of a material with damping properties such as rubber or plush to increase friction, ensure stable sliding of the probe in the sleeve, and maintain a stable position when the sensor is placed vertically. The tensile strain sleeve is connected to the second fixed support. The tensile strain mark point is located at one end of the tensile strain sliding probe, and the tensile strain mark point is marked with a tiny visual target. The target is rectangular or circular in shape. In the initial state, both the reference probe and the tensile strain sliding probe have hook-like structures, and these hook-like structures are in contact with each other. When the maximum elongation displacement occurs, the hook-like structures on the reference probe and the tensile strain sliding probe hook together. The hook-like structure fixed at one end of the reference probe pulls the hook-like structure fixed at one end of the tensile strain sliding probe to the position corresponding to the maximum elongation displacement. When a displacement less than the maximum elongation occurs, the hook-like structures on the reference probe and the tensile strain sliding probe cannot contact each other until a new maximum elongation displacement occurs, at which point the tensile strain sliding probe will be moved to the position corresponding to the new maximum elongation, thus achieving the measurement of the maximum elongation and its corresponding maximum tensile strain. When a compressive displacement occurs, there is a reserved space between the reference probe and the tensile strain sliding probe, preventing contact and thus avoiding interference with the measurement results.

[0008] As a preferred embodiment of the present invention, the maximum compressive strain displacement sensing structure includes a reference probe, a reference marker, compressive strain marker points, a compressive strain sleeve, and a compressive strain sliding probe. The reference probe is connected to the first fixed support, and one end is fixed with the reference marker. The reference marker is marked with a tiny visual target, which is rectangular or circular in shape. This target is a visual target with known geometric dimensions and is used to establish the correspondence between the pixel displacement measured by the camera and the actual displacement. The compressive strain sleeve contains the compressive strain sliding probe, and a damping material, such as rubber or plush, with damping properties is provided in the gap between the two to increase friction and ensure stable sliding of the probe in the sleeve. This ensures that the probe can be stably maintained in the correct position when the sensor is placed vertically. The compressive strain sleeve is connected to the second fixed support. The compressive strain marker is located at one end of the compressive strain sliding probe. The compressive strain marker contains a tiny visual target, which may be rectangular or circular in shape. The maximum elongation displacement between the first fixed support and the second fixed support is the displacement of the compressive strain marker. When the sensor is in its initial state, the end of the reference probe is in direct contact with the compressive strain sliding probe. When the maximum compressive displacement occurs, the reference probe pushes the compressive strain sliding probe to the position corresponding to the maximum compressive displacement. When a displacement less than the maximum compressive displacement occurs, the reference probe and the compressive strain sliding probe cannot contact each other until a new maximum compressive displacement occurs, at which point the compressive strain sliding probe will be moved to the position corresponding to the new maximum compressive displacement, thus achieving the measurement of the maximum compressive displacement and its corresponding maximum compressive strain.

[0009] As a preferred embodiment of the present invention, the microscope has a field of view with a diameter of 5 mm and a magnification of 20x. The microscope's field of view contains a clear image of the reference mark ruler and the compressive strain mark point or the reference mark ruler and the tensile strain mark point. The microscope can be used in conjunction with a camera module or a smartphone camera according to the functional requirements of the detection.

[0010] As a preferred embodiment of the present invention, the camera is a camera module with a light source or a smartphone camera, thereby detecting the maximum tensile and compressive strain.

[0011] As a preferred embodiment of the present invention, the encapsulation structure includes an inner encapsulation sleeve and an outer encapsulation sleeve; one end of the inner encapsulation sleeve and the reference probe are fixed to the object under test by the first fixing support; one end of the outer encapsulation sleeve is fixed to the object under test by the second fixing support; the outer diameter of the inner encapsulation sleeve is smaller than the inner diameter of the outer encapsulation sleeve, ensuring smooth relative movement of the inner and outer sleeves.

[0012] As a preferred embodiment of the present invention, the limiting device includes a limiting platform and a limiting hole. The limiting platform only allows the reference probe to pass through and to extend and retract only in the longitudinal direction of the sensor, while restricting the movement of the reference probe in two dimensions in the transverse direction of the sensor to reduce the bending deformation of the reference probe within the sensor. The limiting hole connects the maximum tensile strain displacement sensitive structure and the maximum compressive strain displacement sensitive structure. The limiting hole contains the compressive strain sleeve and the tensile strain sleeve, and is used to fix and support the compressive strain sleeve and the tensile strain sleeve, ensuring that the compressive strain sliding probe and the tensile strain sliding probe can only move in the longitudinal direction of the sensor. The limiting platform and the limiting hole work together to ensure that the reference mark ruler and the tensile strain mark point are on the same horizontal plane as the compressive strain mark point. The limiting platform and the limiting hole are fixed to the inner side of the encapsulation inner sleeve.

[0013] As a preferred technical solution of the present invention, the maximum displacement change divided by the distance between the first fixed support and the second fixed support is the maximum tensile strain or the maximum compressive strain within the measurement gauge length range. The deformation of the structure causes the two fixed supports fixedly connected to it to move and displace. The two fixed supports cause the reference probe and the reference mark ruler to generate relative maximum tensile or compressive displacement changes with the tensile strain mark point on the tensile strain sliding probe or the compressive strain mark point on the compressive strain sliding probe, respectively.

[0014] The beneficial effects of this invention are as follows: Through the ingenious design of the device, the sleeve can only move in one direction, enabling simultaneous detection of tensile and compressive strain. That is, within the allowable range, the maximum tensile and compressive strain value of the structure over a period of time can be directly measured, simplifying the cumbersome monitoring and data processing processes and making data acquisition, recording, analysis, and transmission particularly convenient. The use of a digital camera for data acquisition results in a simple data acquisition and analysis system, especially since it can utilize smartphone cameras for data acquisition, leading to low cost. Based on digital signal acquisition, the sensor has strong anti-electromagnetic interference capabilities. For temporary maximum tensile and compressive strain detection, different camera modules or smartphone cameras can be used to collect sensor data at the same measuring point to obtain the maximum tensile and compressive strain. The sensor's built-in sensitive structure and sensor packaging structure are simple, durable, and easy to use. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention (front view).

[0016] Figure 2 This is a top view of the structure of the present invention;

[0017] Figure 3 This is a structural schematic diagram of the AA cross-section view of the present invention;

[0018] Figure 4 This is a structural schematic diagram of the BB cross-section of the present invention;

[0019] Figure 5 This is a structural schematic diagram of the visual detection area of ​​the present invention.

[0020] In the figure: 1. First fixed support; 2. Inner encapsulation sleeve; 3. Outer encapsulation sleeve; 4. Reference probe; 5. Limiting platform; 6. Microscope; 7. Reference marker ruler; 8. Camera; 9. Hook-shaped structure; 10. Compressive strain marker point; 11. Tensile strain marker point; 12. Compressive strain sleeve; 13. Tensile strain sleeve; 14. Compressive strain sliding probe; 15. Tensile strain sliding probe; 16. Limiting hole; 17. Second fixed support; 18. Damping. Detailed Implementation Example

[0021] like Figures 1 to 5As shown, this invention discloses a maximum tensile and compressive strain detection sensor based on machine vision. The technical solution includes a first fixed support 1, a reference probe 4, a microscope 6, a camera 8, a second fixed support 17, a damper 18, a maximum tensile strain displacement sensing structure, a maximum compressive strain displacement sensing structure, a limiting device, and a packaging structure. This sensor is only used to measure maximum tensile and compressive strain, and can conveniently, directly, and clearly record the maximum deformation value of a structure over a period of time. The left and right ends of the packaging structure are respectively connected to the first fixed support 1 and the second fixed support 17. The limiting device is located inside, and an opening is provided at the top. The exterior of both the maximum tensile strain displacement sensing structure and the maximum compressive strain displacement sensing structure are connected to the limiting device. The damper 18 and the reference probe 4 are located inside both the maximum tensile strain displacement sensing structure and the maximum compressive strain displacement sensing structure. The camera 8 is located at the bottom of the microscope 6, and the camera 8 corresponds to the opening. The microscope 6 is used to magnify the relative displacement of a tiny visual target corresponding to the strain change within the gauge length of the strain sensor by tens of times, obtaining a microscopic field-of-view map of the target displacement change. This allows for subsequent visual data acquisition and processing using a camera to obtain the displacement changes caused by the maximum tensile and compressive strain within the sensing gauge length, thereby obtaining the maximum tensile and compressive strain within the sensing gauge length. The function of the maximum tensile strain displacement sensitive structure is to convert the displacement change caused by the maximum tensile strain between the two ends of the strain sensing gauge length into the relative displacement change between the visual targets at local locations. Dividing the obtained relative displacement change by the sensor's sensing gauge length yields the maximum tensile strain within the sensing gauge length. The function of the maximum compressive strain displacement sensitive structure is to convert the displacement change caused by the maximum compressive strain between the two ends of the strain sensing gauge length into the relative displacement change between the visual targets at local locations. The displacement change is converted into the relative displacement change between visual targets at local positions. Dividing the obtained relative displacement change by the sensor's sensing gauge length yields the maximum compressive strain within the sensing gauge length. The camera 8 is used to collect images and videos of the relative position changes of the visual targets. The limiting device is used to reduce the position fixing error of the internal components of the sensor and facilitate the placement of the internal components, while ensuring the stability of the displacement-sensitive structure with maximum tensile and compressive strain. The encapsulation structure encapsulates and protects the main components of the sensor. The fixed support fixes the sensor to the object being measured to generate synchronous strain changes.

[0022] As a preferred embodiment of the present invention, the maximum tensile strain displacement sensitive structure includes a reference probe 4, a reference mark 7, a tensile strain mark 11, a tensile strain sleeve 13, and a tensile strain sliding probe 15. The main body of the reference probe 4 is made of a high-stiffness material with a rectangular cross-section of 12 mm × 4 mm, and the tensile strain sliding probe 15 is made of a high-stiffness material with a circular cross-section of 3 mm in diameter. The reference probe 4 is connected to the first fixed support 1, and one end is fixed with the reference mark 7. The reference mark 7 is marked with a small visual target in a rectangular shape. This target is a visual target with known geometric dimensions and is used to establish the correspondence between the pixel displacement measured by the camera and the actual displacement. The tensile strain sleeve 13 houses the tensile strain sliding probe 15, and a damper 18 is provided in the gap between the two. The damper 18 is made of rubber to increase friction, ensure stable sliding of the probe in the sleeve, and maintain stable position when the sensor is placed vertically. The tensile strain sleeve 13 is connected to the second fixed support 17. The tensile strain mark 11 is located at the tensile strain... At one end of the strain sliding probe 15, a small, circular visual target is marked in the tensile strain mark point 11. In the initial state, both the reference probe 4 and the tensile strain sliding probe 15 are equipped with hook-shaped structures 9, and the two hook-shaped structures 9 are in contact with each other. When the maximum elongation displacement occurs, the hook-shaped structures 9 on the reference probe 4 and the tensile strain sliding probe 15 hook each other, and the hook-shaped structure 9 fixed at one end of the reference probe 4 pulls the hook-shaped structure 9 fixed at one end of the tensile strain sliding probe 15 to move. The reference probe 4 and the hook structure 9 on the tensile strain sliding probe 15 cannot contact each other when a displacement less than the maximum elongation occurs. The tensile strain sliding probe 15 will only be moved to the position corresponding to the new maximum elongation when a new maximum elongation displacement occurs, thus realizing the measurement of the maximum elongation and its corresponding maximum tensile strain. When a compressive displacement occurs, there is a reserved space between the reference probe 4 and the tensile strain sliding probe 15 so they do not contact each other and thus do not interfere with the measurement results.

[0023] As a preferred embodiment of the present invention, the maximum compressive strain displacement sensitive structure includes a reference probe 4, a reference mark 7, a compressive strain mark 10, a compressive strain sleeve 12, and a compressive strain sliding probe 14. The main body of the reference probe 4 is made of a high-stiffness material with a 12 mm × 4 mm rectangular cross-section, and the compressive strain sliding probe 14 is made of a high-stiffness material with a 3 mm diameter circular cross-section. The reference probe 4 is connected to the first fixed support 1, and one end is fixed with the reference mark 7. The reference mark 7 is marked with a small visual target, which is circular in shape and has known geometric dimensions. This target is used to establish the correspondence between the pixel displacement measured by the camera and the actual displacement. The compressive strain sleeve 12 houses the compressive strain sliding probe 14, and a damping 18, such as a plush material, is provided in the gap between the two to increase friction and ensure the probe... The compressive strain sleeve 12 is connected to the second fixed support 17 and slides stably within the sleeve, maintaining the correct position when the sensor is placed vertically. The compressive strain mark 10 is located at one end of the compressive strain sliding probe 14, and the compressive strain mark 10 is marked with a tiny visual target in a rectangular shape. When the sensor is in its initial state, the reference probe 4 is in direct contact with the compressive strain sliding probe 14. When the maximum compressive displacement occurs, the reference probe 4 pushes the compressive strain sliding probe 14 to the position corresponding to the maximum compressive displacement. When a displacement less than the maximum compressive displacement occurs, the reference probe 4 does not contact the compressive strain sliding probe 14 until a new maximum compressive displacement occurs, at which point the compressive strain sliding probe 14 will be moved to the position corresponding to the new maximum compressive displacement, thereby realizing the measurement of the maximum compressive displacement and its corresponding maximum compressive strain.

[0024] As a preferred embodiment of the present invention, the microscope 6 has a field of view with a diameter of 5 mm and a magnification of 20x. The microscope 6 has a clear image of the reference mark 7 and the compressive strain mark 10 or the reference mark 7 and the tensile strain mark 11 within its field of view. The microscope 6 can be used in conjunction with a camera module or a smartphone camera according to the functional requirements of the detection.

[0025] As a preferred technical solution of the present invention, the camera 8 is a camera module with a light source or a smartphone camera, used to acquire images of the position changes of the reference mark ruler 7 and the tensile and compressive strain mark points, and then to detect the maximum tensile and compressive strain.

[0026] As a preferred embodiment of the present invention, the encapsulation structure includes an inner encapsulation sleeve 2 and an outer encapsulation sleeve 3; one end of the inner encapsulation sleeve 2 and the reference probe 4 are fixed to the object under test by the first fixing support 1; one end of the outer encapsulation sleeve 3 is fixed to the object under test by the second fixing support 17; the outer diameter of the inner encapsulation sleeve 2 is smaller than the inner diameter of the outer encapsulation sleeve 3, ensuring smooth relative movement of the inner and outer sleeves.

[0027] As a preferred embodiment of the present invention, the limiting device includes a limiting platform 5 and a limiting hole 16. The limiting platform 5 only allows the reference probe 4 to pass through and to move only in the longitudinal direction of the sensor, while restricting the movement of the reference probe 4 in two dimensions in the transverse direction of the sensor to reduce the bending deformation of the reference probe 4 within the sensor. The limiting hole 16 connects the maximum tensile strain displacement sensitive structure and the maximum compressive strain displacement sensitive structure. The limiting hole 16 contains the compressive strain sleeve 12 and the tensile strain sleeve 13. The limiting hole 16 is used to fix and support the compressive strain sleeve 12 and the tensile strain sleeve 13, ensuring that the compressive strain sliding probe 14 and the tensile strain sliding probe 15 can only move in the longitudinal direction of the sensor. The limiting platform 5 and the limiting hole 16 work together to ensure that the reference mark 7 and the tensile strain mark 11 are on the same horizontal plane as the compressive strain mark 10. The limiting platform 5 and the limiting hole 16 are fixed to the inner side of the encapsulation inner sleeve 2.

[0028] As a preferred technical solution of the present invention, the maximum displacement change divided by the distance between the first fixed support 1 and the second fixed support 17 is the maximum tensile strain or maximum compressive strain within the measurement gauge length range. The deformation of the structure causes the two fixed supports fixedly connected to it to move and displace. The two fixed supports cause the reference probe 4 and the reference mark 7 to produce relative maximum tensile or compressive displacement changes with the tensile strain mark point 11 on the tensile strain sliding probe 15 or the compressive strain mark point 10 on the compressive strain sliding probe 14, respectively.

[0029] The working principle of this invention: The measurement principle of this microscopic visual strain sensor is to detect the relative displacement changes of the microscopic visual targets by observing and tracking the reference mark ruler 7 on the reference probe 4, which is fixedly connected to the inner sleeve 2, and the microscopic visual targets of the compressive strain mark point 10 on the compressive strain sliding probe 14 and the tensile strain mark point 11 on the tensile strain sliding probe 15, which are fixedly connected to the outer sleeve 3. The inner sleeve 2 is connected to the first fixed support 1, and the outer sleeve 3 is connected to the second fixed support 17. The two fixed supports are fixedly connected to the object. Deformation of the object causes the two fixed supports to undergo expansion and contraction displacement, which in turn causes the two fixed supports to undergo relative displacement of the tensile and compressive sliding probes and the reference mark ruler 7, respectively. In the initial state, the reference probe 4 and the compressive strain sliding probe 14 are in contact. When the maximum compressive displacement occurs, the reference probe 4 pushes the compressive strain sliding probe 14 to the position corresponding to the maximum compressive displacement. When the small... When the displacement of maximum compression occurs, the reference probe 4 and the compressive strain sliding probe 14 cannot make contact until a new maximum compression displacement occurs, at which point the compressive strain sliding probe 14 will be moved to the position corresponding to the new maximum compression, thus realizing the measurement of the maximum compression and its corresponding maximum compressive strain. In the process of generating the tensile strain relative displacement, in the initial state of the sensor, the hook-shaped structure 9 on the upper part of the reference probe 4 and the hook-shaped structure 9 on the tensile strain sliding probe 15 are in contact. When the maximum elongation displacement occurs, the hook-shaped structure 9 fixed to one end of the reference probe 4 pulls the hook-shaped structure 9 fixed to one end of the tensile strain sliding probe 15 to the position corresponding to the maximum elongation displacement. When a displacement less than the maximum elongation occurs, the hook-shaped structure 9 on the reference probe 4 and the tensile strain sliding probe 15 cannot make contact until a new maximum elongation displacement occurs, at which point the tensile strain sliding probe 15 will be moved to the position corresponding to the new maximum elongation, thus realizing the measurement of the maximum elongation and its corresponding maximum tensile strain.Simultaneously, when compressive displacement occurs, reference probe 4 and tensile strain sliding probe 15 do not come into contact due to sufficient reserved space, thus avoiding interference with the measurement results; the distance moved between the initial and final states of the tensile strain marker point 11, a tiny visual target, is the maximum tensile displacement between the two supports. Subtracting the measured maximum tensile displacement from the strain sensor length yields the maximum tensile strain within the measurement distance range; the maximum compressive strain is obtained similarly, thereby enabling the measurement of the maximum tensile and compressive strain values ​​generated by structural deformation over a period of time; the limiting platform 5 only allows reference probe 4 to pass through, restricting its movement in two dimensions along the horizontal axis and allowing it to only extend and retract along the longitudinal axis of the sensor, thus reducing the impact on the reference probe 4. The bending deformation within the sensor, and the limiting hole 16, are used to fix and support the compressive strain sleeve 12 and the tensile strain sleeve 13, ensuring that the compressive strain sliding probe 14 and the tensile strain sliding probe 15 can only move in the longitudinal direction of the sensor. The limiting platform 5 and the limiting hole 16 work together to ensure that the reference mark 7 and the tensile strain mark 11 are on the same horizontal plane as the compressive strain mark 10. The microscope 6 and the camera 8 cooperate to acquire image data of the sensor displacement and to detect the maximum tensile and compressive strain. The damping 18 can increase friction to ensure that the compressive strain sliding probe 14 slides stably in the compressive strain sleeve 12 and the tensile strain sliding probe 15 slides stably in the tensile strain sleeve 13, and can be stably maintained in the correct position when the sensor is placed vertically.

[0030] The circuit connection involved in this invention is a common method used by those skilled in the art, and technical inspiration can be obtained through a limited number of experiments. It is common knowledge.

[0031] Components not described in detail in this article are existing technologies.

[0032] While the specific embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and modifications or variations without creative effort are still within the protection scope of the present invention.

Claims

1. A maximum tensile / compressive strain detection sensor based on machine vision, characterized in that: The device includes a first fixed support (1), a reference probe (4), a microscope (6), a camera (8), a second fixed support (17), a damper (18), a maximum tensile strain displacement sensitive structure, a maximum compressive strain displacement sensitive structure, a limiting device, and a packaging structure. The left and right ends of the packaging structure are respectively connected to the first fixed support (1) and the second fixed support (17). The limiting device is provided inside the packaging structure, and an opening is provided at the top. The exterior of the maximum tensile strain displacement sensitive structure and the exterior of the maximum compressive strain displacement sensitive structure are both connected to the limiting device. The damper (18) and the reference probe (4) are provided inside the maximum tensile strain displacement sensitive structure and the interior of the maximum compressive strain displacement sensitive structure. The camera (8) is provided at the bottom of the microscope (6), and the camera (8) and the opening are positioned correspondingly. The maximum tensile strain displacement sensitive structure includes a reference probe (4), a reference mark (7), a tensile strain mark (11), a tensile strain sleeve (13), and a tensile strain sliding probe (15). The reference probe (4) is connected to the first fixed support (1), and one end is fixed with the reference mark (7). The reference mark (7) is marked with a small visual target to calibrate the correspondence between pixels and the actual displacement. The tensile strain sleeve (13) contains the tensile strain sliding probe (15), and the damping (18) is provided in the gap between the two. The tensile strain sleeve (13) is connected to the second fixed support (17). The tensile strain mark (11) is located at one end of the tensile strain sliding probe (15), and the tensile strain mark (11) is marked with a small visual target. When the sensor is in the initial state, the reference probe (4) and the tensile strain sliding probe (15) are connected. Each probe is provided with a hook-shaped structure (9), and the two hook-shaped structures (9) are in contact with each other; when the maximum elongation displacement occurs, the reference probe (4) hooks with the hook-shaped structure (9) on the tensile strain sliding probe (15); when the displacement is less than the maximum elongation, the reference probe (4) and the hook-shaped structure (9) on the tensile strain sliding probe (15) cannot contact each other; when the compressive displacement occurs, there is a reserved space between the reference probe (4) and the tensile strain sliding probe (15), and they do not contact each other; The maximum compressive strain displacement sensing structure includes a reference probe (4), a reference mark (7), a compressive strain mark (10), a compressive strain sleeve (12), and a compressive strain sliding probe (14). The reference probe (4) is connected to the first fixed support (1), and one end is fixed with the reference mark (7). The reference mark (7) is marked with a tiny visual target to calibrate the correspondence between pixels and the actual displacement. The compressive strain sleeve (12) contains the compressive strain sliding probe (14), and a damper (18) is provided in the gap between the two. The compressive strain sleeve (12) is connected to the second fixed support (17). The compressive strain mark (10) is located at one end of the compressive strain sliding probe (14), and the compressive strain mark (10) is marked with a tiny visual target. When the sensor is in the initial state, the end of the reference probe (4) is in direct contact with the compressive strain sliding probe (14). When the maximum compressive displacement occurs, the reference probe (4) pushes the compressive strain sliding probe (14). Move to the position corresponding to the maximum compressive displacement; when a displacement less than the maximum compressive displacement occurs, the reference probe (4) does not contact the compressive strain sliding probe (14).

2. The maximum tensile and compressive strain detection sensor based on machine vision according to claim 1, characterized in that: The microscope (6) has a field of view geometry diameter of 5 mm and a magnification of 20 times. The microscope (6) can be used in conjunction with a camera module or a smartphone camera.

3. The maximum tensile and compressive strain detection sensor based on machine vision according to claim 1, characterized in that: The camera (8) is a camera module with a light source for supplemental lighting or a smartphone camera.

4. The maximum tensile and compressive strain detection sensor based on machine vision according to claim 1, characterized in that: The encapsulation structure includes an inner encapsulation sleeve (2) and an outer encapsulation sleeve (3); one end of the inner encapsulation sleeve (2) and the reference probe (4) is fixed to the object under test by the first fixed support (1); one end of the outer encapsulation sleeve (3) is fixed to the object under test by the second fixed support (17); the outer diameter of the inner encapsulation sleeve (2) is smaller than the inner diameter of the outer encapsulation sleeve (3).

5. The maximum tensile and compressive strain detection sensor based on machine vision according to claim 4, characterized in that: The limiting device includes a limiting platform (5) and a limiting hole (16); the limiting platform (5) only allows the reference probe (4) to pass through and only makes telescopic movements in the longitudinal direction of the sensor, and restricts the movement of the reference probe (4) in two dimensions in the transverse direction of the sensor; the limiting hole (16) connects the maximum tensile strain displacement sensitive structure and the maximum compressive strain displacement sensitive structure, and the limiting platform (5) and the limiting hole (16) are fixed to the inside of the inner sleeve (2) of the package.

6. The maximum tensile and compressive strain detection sensor based on machine vision according to claim 1, characterized in that: The maximum displacement change divided by the distance between the first fixed support (1) and the second fixed support (17) is the maximum tensile strain or maximum compressive strain within the gauge length range.

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