MEMS optical fiber surface-mounted strain gauge

Abstract

An MEMS optical fiber surface-mounted strain gauge, configured to be fixed on the surface of an object to be measured to measure the strain of the object under a particular loading condition. The strain gauge is provided with a left side fixing part (1), a right side fixing part (2) and a quadrilateral structure (3) arranged between the left side fixing part (1) and the right side fixing part (2). The quadrilateral structure (3) is connected to the left side fixing part (1) and the right side fixing part (2) by means of diagonal connection parts, a collimator (41) is provided on a first edge (31) of the quadrilateral structure (3), a blazed grating (51) is provided on a second edge (32) of the quadrilateral structure (3), and the first edge (31) and the second edge (32) are two adjacent edges in the quadrilateral structure (3). The deformation of the quadrilateral structure (3) is monitored by means of the change of the angle between the adjacent edges.

Description

A MEMS optical fiber surface strain gauge Technical Field

[0001] The present invention relates to the technical field of displacement measurement, and in particular to a MEMS optical fiber surface strain gauge. Background Art

[0002] Strain measurement technology is widely used in various fields, including industry, military, aviation, navigation, and communications. Existing strain measurement techniques use strain sensors to measure the strain of monitored objects. These sensors are typically fixed to the surface of the object being measured using glue, welding, or bolts. When strain occurs on the surface, the strain is transmitted to the strain sensor, causing the output signal to change, thereby measuring the strain. Common commercially available strain gauges include electronic strain gauges, vibrating wire strain gauges, and fiber Bragg grating (FBG) strain gauges. Electronic strain gauges measure strain using internal resistance strain gauges. Vibrating wire strain gauges measure strain by changing the natural frequency of the vibrating wire when subjected to external strain. Fiber Bragg grating (FBG) strain gauges measure strain by changing the reflected wavelength of the grating when subjected to external tension. These technologies have the following drawbacks: 1. Poor long-term stability. Electronic strain gauges, vibrating wire strain gauges, and fiber Bragg gratings (FBGs) can all experience creep and drift over time, degrading sensor performance. 2. Resistance strain gauges and vibrating wire strain gauges are active devices and susceptible to electromagnetic interference. 3. Fiber Bragg grating (FBG) strain gauges are limited by the amount of fiber Bragg grating tension, resulting in low resolution and poor accuracy.

[0003] Chinese authorized patent CN115560682B discloses a displacement measurement device having a top support beam and two vertical support beams, wherein a blazed grating chip and a collimation unit are respectively fixed to the vertical support beam and the top support beam, and small displacements are measured by measuring small angles. However, in this document, the corner points set at the connection positions of the top support beam and the two vertical support beams may have inconsistent structures. For example, the notch tolerances of the corner points are different, resulting in different tilt angles and inconsistent deformation of the two vertical support beams under the action of external forces, resulting in inaccurate small displacement measurements. Moreover, in this displacement measurement device, since the two vertical support beams are fixedly connected by the lower corner points, when the top support beam is subjected to a small lateral load or vibration, a bending moment around the lower fixed corner point is generated on the top support beam, making the measurement structure very unstable. The angles between the vertical support beam and the top support beam are constantly changing, which is not conducive to stable displacement measurement. Chinese patent CN206514980U discloses a dual fiber Bragg grating soil pressure sensor. A stretched fiber Bragg grating is disposed inside a parallelogram. When the parallelogram deforms, the wavelength of the light inside the grating changes. The strain is calculated based on the wavelength, and then the pressure of the diaphragm is calculated based on the strain. The fiber Bragg grating of this sensor will experience creep and drift during long-term use. The fiber Bragg grating strain gauge is limited by the amount of fiber Bragg grating stretch, resulting in low resolution and poor accuracy.

[0004] Summary of the Invention

[0005] In order to overcome at least one of the problems in the prior art, the present invention provides a MEMS optical fiber surface strain gauge capable of performing precise measurement.

[0006] A MEMS fiber optic surface strain gauge capable of precise measurement, used for being fixed on the surface of a measured object to measure the strain of the object under corresponding load conditions, comprising a left fixing portion, a right fixing portion and a quadrilateral structure arranged between the left fixing portion and the right fixing portion, and fixedly connected to the measured object via the left fixing portion and the right fixing portion, the quadrilateral structure being connected to the left fixing portion and the right fixing portion via a diagonal connecting portion, for example, the quadrilateral structure being connected to the left fixing portion and the right fixing portion via a lower left position and an upper right position, or being fixedly connected to the left fixing portion and the right fixing portion via an upper left position and a lower right position; the quadrilateral structure having two horizontal sides and two vertical sides, the two horizontal sides being of equal length, the two vertical sides being of equal length, a collimator arranged on a first side of the quadrilateral structure and a blazed grating arranged on a second side of the quadrilateral structure, the first side and the second side being two adjacent sides in the quadrilateral structure. When the object under test is deformed under the action of the corresponding load, the distance between the left fixed part and the right fixed part changes accordingly, and the quadrilateral is deformed through the corresponding force acting on the diagonal connection part of the quadrilateral, and tends to change towards a parallelogram. Therefore, the four corners of the quadrilateral are generated by the angle change corresponding to the strain of the object under test. The angle change between adjacent sides causes the angle between the collimator and the blazed grating to change, thereby realizing the monitoring of the deformation of the quadrilateral structure, and then obtaining the strain between the left fixed part and the right fixed part based on the calculation of the quadrilateral deformation.

[0007] In an optional embodiment, by adjusting the distance ratio between two adjacent sides of the quadrilateral structure, adjusting the change between the two corresponding adjacent sides at the same distance, and utilizing the adjustment of the angle change between the adjacent sides of the quadrilateral structure, the sensitivity of the strain gauge can be adjusted. Preferably, the ratio of the vertical side to the horizontal side is set in the range of 1:1 to 1:3, so that the best measurement range and sensitivity can be obtained when the object being measured produces corresponding strain.

[0008] In an optional embodiment, the left fixing part is provided with a left connecting hole, and the right fixing part is provided with a right connecting hole. The left fixing part and the right fixing part are fixedly connected to the object to be measured by cooperating with the left connecting hole and the right connecting hole through connecting devices such as bolts and pins in the prior art.

[0009] Preferably, four corner points are formed at the connection between the horizontal side and the vertical side, and a deformation structure is formed at the corner points. Preferably, the deformation structure is an arc-shaped groove. By utilizing the deformation structure set at the corner points, stress concentration at the corner point position can be prevented when the quadrilateral structure is deformed under force. At the same time, the inclination angle of the quadrilateral during the deformation process can be increased, and the accuracy of the angle measurement of the blazed grating can be increased, thereby improving the accuracy of the strain measurement.

[0010] In an optional implementation, the arc-shaped groove is tangent to the surface of the horizontal edge, and the line connecting the centers of the two horizontally opposite grooves is parallel to the length direction of the horizontal edge. The inner wall of the arc-shaped groove is used to achieve elastic deformation to prevent stress concentration during the deformation process of the quadrilateral structure, which may cause irreversible damage.

[0011] In an optional embodiment, the collimator is fixed to the horizontal edge via a collimator bracket, to which the collimator bracket is fixedly connected, and the collimator is mounted on the collimator bracket; the blazed grating is fixed to a vertical edge adjacent to the horizontal edge via a chip fixing rod, to which the chip fixing rod is fixedly connected, and to which the blazed grating is mounted. The blazed grating is used to reflect incident light from the collimator, and fixing it to the vertical edge causes the blazed grating to change position when the vertical edge tilts slightly. Therefore, positioning the blazed grating on the vertical edge keeps the collimator stationary, thereby reducing the impact of deformation on the collimator and its disturbance on the measurement results.

[0012] In a preferred embodiment, a weakening structure and a U-shaped groove are provided on the left or right fixing portion adjacent to one side of the blazed grating. The weakening structure is formed between the diagonal connecting portion and the left or right connecting hole. The thickness of the weakening structure is less than that of the left or right fixing portion, and the weakening structure is arranged at the middle position along the thickness direction. The U-shaped groove surrounds the left or right connecting hole and penetrates the left or right fixing portion along the thickness direction. A portion of the weakening structure in the vertical direction penetrates to form a portion of the U-shaped groove. Two U-shaped grooves are provided and are symmetrically arranged along the line connecting the left and right connecting holes. When the angle between the working surface of the blazed grating and the incident light of the collimator changes, the output signal (reflected light wavelength) will change. When the angle between the incident light of the collimator and the plane perpendicular to the working surface of the blazed grating changes, the reflected signal will be lost. When torsion occurs, signal loss will also occur. To minimize spectral loss caused by structural deformation during installation, a weakened structure and a U-shaped groove are machined into the left or right connecting hole. These structures absorb deformation caused by uneven mounting surfaces during strain gage installation, preventing this deformation from being transmitted to the quadrilateral structure. When the strain gage is subjected to left-right tensile and compressive loads, the deformation is primarily absorbed by the quadrilateral structure. However, when the strain gage is subjected to bending moments perpendicular to the paper surface or torque generated by surface irregularities of the measured object, the deformation of the weakened structure and the U-shaped groove absorbs this load, preventing it from acting on the parallelogram structure and causing spectral degradation (within a certain range; exceeding this reasonable range may damage the strain gage). This structure reduces strain gage installation requirements and increases its adaptability.

[0013] In a preferred embodiment, the peripheral portions of the left connecting hole and the right connecting hole have the same thickness and are greater than the thickness of the left fixing portion and the right fixing portion, so that the peripheral portions extend out of the left fixing portion and the right fixing portion, so that when the MEMS fiber optic surface strain gauge is installed, only the peripheral portions of the left connecting hole and the right connecting hole are in contact with the surface of the object to be measured, thereby reducing the contact area between the MEMS fiber optic surface strain gauge and the object to be measured, reducing the potential strain of the strain gauge caused by the unevenness of the installation surface of the object to be measured, and improving the strain measurement accuracy.

[0014] It can be seen from the above technical solution that the MEMS optical fiber surface strain gauge of the present application improves the accuracy of strain measurement, increases the anti-interference and anti-vibration performance of the strain gauge, improves the stability of the strain gauge during measurement, reduces the surface requirements for strain gauge installation, increases its adaptability, and avoids the defects of strain measurement in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are provided for a better understanding of the present invention and are not intended to limit the present invention.

[0016] FIG1 is a schematic structural diagram of a MEMS optical fiber surface strain gauge according to an embodiment of the present invention;

[0017] FIG2 is a side view of FIG1;

[0018] FIG3 is a schematic diagram of a strain gauge subjected to tension and compression loads;

[0019] 1-left fixing part, 11-left connecting hole, 2-right fixing part, 21-right connecting hole, 22-weak structure, 23-U-shaped groove, 3-quadrilateral structure, 31-horizontal edge, 32-vertical edge, 33-corner point, 41-collimator, 42-collimator bracket, 51-blazed grating, 52-chip fixing rod, 6-peripheral part. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. The terms used herein are merely for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," and the like as used herein indicate the presence of the described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0021] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0022] Certain embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings, some, but not all, of which embodiments are shown. Indeed, the various embodiments of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.

[0023] The present invention provides a MEMS fiber optic surface strain gauge capable of precise measurement, which is used to be fixed on the surface of a measured object to measure the strain of the object under corresponding load conditions. As shown in FIG1 , the gauge comprises a left-side fixing portion 1, a right-side fixing portion 2, and a quadrilateral structure 3 arranged between the left-side fixing portion 1 and the right-side fixing portion 2, and is fixedly connected to the measured object through the left-side fixing portion 1 and the right-side fixing portion 2. The quadrilateral structure 3 is connected to the left-side fixing portion 1 and the right-side fixing portion 2 through a diagonal connection portion. For example, the quadrilateral structure in FIG1 is connected to the left-side fixing portion 1 and the right-side fixing portion 2 through a lower left position and an upper right position, or is fixedly connected to the left-side fixing portion 1 and the right-side fixing portion 2 through an upper left position and a lower right position; the quadrilateral structure has two horizontal sides 31 and two vertical sides 32, the two horizontal sides 31 are equal in length, and the two vertical sides 32 are equal in length, a collimator 41 is arranged on a first side of the quadrilateral structure, and a blazed grating 51 is arranged on a second side of the quadrilateral structure, and the first side and the second side are two adjacent sides in the quadrilateral structure 3. When the object under test is deformed under the action of the corresponding load, the distance between the left fixed part and the right fixed part 2 changes accordingly, and the quadrilateral is deformed through the corresponding force acting on the diagonal connection part of the quadrilateral, and tends to change towards a parallelogram. Therefore, the four corners of the quadrilateral are generated by the angle change corresponding to the strain of the object under test. The angle change between adjacent sides causes the angle between the collimator 41 and the blazed grating 51 to change, thereby realizing the monitoring of the deformation of the quadrilateral structure 3, and then obtaining the strain between the left fixed part 1 and the right fixed part 2 based on the calculation of the quadrilateral deformation.

[0024] In an optional embodiment, by adjusting the distance ratio between two adjacent sides of the quadrilateral structure, adjusting the change between the two corresponding adjacent sides at the same distance, and utilizing the adjustment of the angle change between the adjacent sides of the quadrilateral structure, the sensitivity of the strain gauge can be adjusted. Preferably, the ratio of the vertical side 32 to the horizontal side 31 is set in the range of 1:1 to 1:3, so that the best measurement range and sensitivity can be obtained when the object to be measured generates corresponding strain.

[0025] In an optional embodiment, the left fixing part 1 is provided with a left connecting hole 11, and the right fixing part 2 is provided with a right connecting hole 21. The left fixing part 1 and the right fixing part 2 are fixedly connected to the object to be measured by cooperating with the left connecting hole 11 and the right connecting hole 21 through connecting devices such as bolts and pins in the prior art.

[0026] Preferably, four corner points 33 are formed at the connection between the horizontal side 31 and the vertical side, and a deformation structure is formed at the corner points 33. Preferably, the deformation structure is an arc-shaped groove. By utilizing the deformation structure set at the corner points 33, when the quadrilateral structure is deformed by force, stress concentration at the corner points 33 is prevented. At the same time, the inclination angle of the quadrilateral during the deformation process can be increased, and the accuracy of the angle measurement of the blazed grating 51 is increased, thereby improving the accuracy of the strain measurement.

[0027] In an optional implementation, the arc-shaped groove is tangent to the surface of the horizontal edge 31, and the line connecting the centers of the two horizontally opposite grooves is parallel to the length direction of the horizontal edge 31. The inner wall of the arc-shaped groove is used to achieve elastic deformation to prevent stress concentration during the deformation process of the quadrilateral structure 3, which may cause irreversible damage.

[0028] In an optional embodiment, the collimator 41 is fixed to the horizontal edge 31 via a collimator bracket 42, the collimator 41 is connected to an optical fiber (not shown), the collimator 41 bracket is fixedly connected to the horizontal edge 31, and the collimator 41 is mounted on the collimator bracket 42; the blazed grating 51 is fixed to the vertical edge 32 adjacent to the horizontal edge 31 via a chip fixing rod 52, the chip fixing rod 52 is fixedly connected to the vertical edge 32, and the blazed grating 51 is mounted on the chip fixing rod 52. The blazed grating 51 is used to reflect the incident light of the collimator 41 and fix it to the vertical edge 32. When the vertical edge 32 is slightly tilted, the position of the blazed grating 51 changes. Therefore, the blazed grating 51 is set on the vertical edge 32 to keep the collimator 41 fixed and unchanged, thereby reducing the influence of the deformation disturbance on the collimator 41 on the measurement result.

[0029] In a preferred embodiment, a weakening structure 22 and a U-shaped groove 23 are provided on the left fixing portion 1 or the right fixing portion 2 adjacent to the blazed grating 51, wherein the weakening structure 22 is formed between the diagonal connecting portion and the left connecting hole 11 or the right connecting hole 21, and the thickness of the weakening structure 22 is less than the thickness of the left fixing portion 1 or the right fixing portion 2, and the weakening structure 22 is arranged in the middle position along the thickness direction; the U-shaped groove 23 surrounds the left connecting hole 11 or the right connecting hole 21 and penetrates the left fixing portion 1 or the right fixing portion 2 along the thickness direction, and a portion of the weakening structure 22 in the vertical direction is penetrated to form a portion of the U-shaped groove 23, and two U-shaped grooves 23 are provided and are symmetrically arranged along the line connecting the left connecting hole 11 and the right connecting hole 21. When the angle between the working surface of the blazed grating 51 and the incident light from the collimator 41 changes, the output signal (the wavelength of the reflected light) will change. When the angle between the incident light from the collimator 41 and the plane perpendicular to the working surface of the blazed grating 51 changes, the reflected signal will be lost. Twisting will also cause signal loss. To minimize spectral loss that may result from structural installation deformation, a weakening structure 22 and a U-shaped groove 23 are machined in the left connecting hole 11 or the right connecting hole 21. These two structures can absorb structural deformation caused by uneven mounting surfaces during strain gauge installation, preventing this deformation from being transmitted to the quadrilateral structure 3. As shown in FIG3 , when the strain gauge is subjected to left-right tensile and compressive loads, the deformation is primarily absorbed by quadrilateral structure 3 . When subjected to a bending moment perpendicular to the paper surface caused by an uneven surface of the measured object, or when subjected to torque as a whole, the deformation of weak structure 22 and U-shaped groove 23 absorbs this load, preventing the load from acting on parallelogram structure 3 and causing spectral degradation (within a certain range; exceeding a reasonable range may damage the strain gauge). This structure can reduce the strain gauge installation requirements and increase its adaptability.

[0030] In a preferred embodiment, the thickness of the peripheral portion 6 of the left connecting hole 11 and the right connecting hole 21 is the same, as shown in Figure 2, and is greater than the thickness of the left fixing portion 1 and the right fixing portion 2, so that the peripheral portion 6 extends out of the left fixing portion 1 and the right fixing portion 2, so that when the MEMS fiber optic surface strain gauge is installed, only the peripheral portion 6 of the left connecting hole 11 and the right connecting hole 21 contacts the surface of the object to be measured, reducing the contact area between the MEMS fiber optic surface strain gauge and the object to be measured, reducing the potential strain of the strain gauge caused by the unevenness of the installation surface of the object to be measured, and improving the strain measurement accuracy.

Claims

1. A MEMS fiber optic surface strain gauge, used to be fixed on the surface of a measured object to measure the strain of the object under corresponding load conditions, comprising a left fixing portion, a right fixing portion, and a quadrilateral structure disposed between the left and right fixing portions, and fixedly connected to the measured object via the left and right fixing portions; characterized in that: The quadrilateral structure is connected to the left fixing part and the right fixing part through a diagonal connecting part. The quadrilateral structure has two horizontal sides and two vertical sides. The lengths of the two horizontal sides are equal, and the lengths of the two vertical sides are equal. A collimator is arranged on the first side of the quadrilateral structure and a blazed grating is arranged on the second side of the quadrilateral structure. The first side and the second side are two adjacent sides in the quadrilateral structure.

2. The MEMS optical fiber surface strain gauge according to claim 1, wherein: The measurement sensitivity can be adjusted by adjusting the distance ratio between two adjacent sides of the quadrilateral structure.

3. The MEMS optical fiber surface strain gauge according to claim 2, characterized in that: Set the ratio of vertical to horizontal width to 1:1 to 1:

3.

4. The MEMS optical fiber surface strain gauge according to claim 1, wherein: The left fixing part is provided with at least one left connecting hole, and the right fixing part is provided with at least one right connecting hole. The left connecting hole and the right connecting hole cooperate to fix the left fixing part and the right fixing part to the object to be measured.

5. The MEMS optical fiber surface strain gauge according to claim 1, wherein: Four corner points are formed at the connection points between the horizontal side and the vertical side, and deformation structures are formed at the corner points.

6. The MEMS optical fiber surface strain gauge according to claim 5, characterized in that: The deformation structure is an arc-shaped groove.

7. The MEMS optical fiber surface strain gauge according to claim 6, characterized in that: The arc-shaped groove is tangent to the surface of the horizontal side, and the line connecting the centers of the two horizontally opposite grooves is parallel to the length direction of the horizontal side.

8. The MEMS optical fiber surface strain gauge according to claim 1, wherein: The collimator is fixed to the horizontal edge through a collimator bracket, the collimator bracket is fixedly connected to the horizontal edge, and the collimator is mounted on the collimator bracket; the blazed grating is fixed to the vertical edge adjacent to the horizontal edge through a chip fixing rod, the chip fixing rod is fixedly connected to the vertical edge, and the blazed grating is mounted on the chip fixing rod.

9. The MEMS optical fiber surface strain gauge according to claim 2, characterized in that: A weakening structure and a U-shaped groove are provided on the left fixing portion or the right fixing portion adjacent to the blazed grating side, wherein the weakening structure is formed between the diagonal connecting portion and the left connecting hole or the right connecting hole, and the thickness of the weakening structure is less than the thickness of the left fixing portion or the right fixing portion, and the weakening structure is arranged in the middle position along the thickness direction; the U-shaped groove surrounds the left connecting hole or the right connecting hole and penetrates the left fixing portion or the right fixing portion along the thickness direction.

10. The MEMS optical fiber surface strain gauge according to claim 4, characterized in that: The outer peripheral portions of the left connecting hole and the right connecting hole have the same thickness and are greater than the thickness of the left fixing portion and the right fixing portion.

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