A shear force measuring sensor and measuring module based on white light phase shifting interference principle

Abstract

A shear force measuring sensor and measuring module based on white light phase shift interference principle, having a first mounting seat, a second mounting seat and an elastic body, the elastic body comprising a deformation holder with a parallelogram structure, the deformation holder comprising at least two horizontal frames and at least two vertical frames, the horizontal frames being provided with uniform deformation corner points on the surfaces adjacent to the vertical frames; two vertical frames are fixedly connected with the first mounting seat and the second mounting seat respectively, one of the two vertical frames is fixedly provided with a reflection surface mounting cantilever, and the other is fixedly provided with a collimator mounting cantilever, at least one reflection surface is mounted on the horizontal surface of the reflection surface mounting cantilever, and at least one collimator is mounted on the collimator mounting cantilever, the collimator being mounted vertically relative to the horizontal direction, the reflection surface being correspondingly provided with the collimator, and at least one white light interference cavity being formed between the collimator and the reflection surface.

Description

Technical Field

[0001] This invention relates to the field of force measurement technology, specifically to a shear force measurement sensor based on the principle of white light phase-shifting interference. It is suitable for deformation monitoring of components such as shafts and beams that are mainly subjected to shear forces, and can accurately measure the shear force on the components through calibration. Background Technology

[0002] Currently, in the engineering field, two mainstream and widely used measurement methods have emerged for detecting shear force and shear stress in mechanical structures and load-bearing components: pin-type shear force sensor technology and strain gauge technology bonded to the component surface. Both technologies can achieve indirect or direct acquisition of structural shear loads and are widely used in engineering machinery, bridge construction, automation equipment, structural mechanics testing, and other fields. However, in actual long-term industrial monitoring, complex composite load conditions, non-destructive testing, and general-purpose adaptation scenarios, both existing technologies have inherent technical defects, as follows: For example, the pin-type shear force sensor technology disclosed in CN213085335U replaces the original hinge pin of the equipment with a dedicated sensing pin 20. A pure shear deformation sensitive zone is constructed by machining symmetrical weakening grooves and hollow structures on the pin body. Strain gauges are then mounted within this sensitive zone to form a Wheatstone bridge. Based on the correspondence between shear deformation and the bridge signal, the overall shear force borne by the pin's cross-section is calibrated and obtained. This technology eliminates the need for complex post-processing data conversion and can directly output shear force values, making it suitable for overall load monitoring of various hinge nodes, rotary connections, and heavy-duty support pins. However, this technology has significant inherent drawbacks: firstly, it is highly dependent on structural modifications, limiting its application scenarios and versatility. Secondly, this solution requires complete disassembly and replacement of the original standard pin, necessitating custom-made sensors based on the diameter, length, and load level of the pin being measured. It cannot adapt to different specifications and types of load-bearing components and is unsuitable for non-removable, online, non-stop monitoring scenarios. Secondly, to form a stable, purely shear-sensitive region, the pin body needs to be slotted, thinned, and hollowed out, which destroys the original integrated mechanical structure of the pin, easily leading to stress concentration and significantly reducing the pin's fatigue resistance, impact resistance, and torsional resistance. Under alternating heavy loads and long-term working conditions, there is a safety risk of cracking and failure. Thirdly, the measurement dimension is singular; it can only detect the overall resultant force and obtain the total shear load of the pin cross-section. It cannot detect the local shear stress distribution, local micro-deformation, and stress concentration of the component, nor can it identify potential local damage to the component. Fourthly, the applicable scenarios are limited; it is only suitable for pin-type hinge structures and cannot be applied to shear testing of conventional load-bearing components such as plates, beams, shells, and thin-walled irregular parts. Fifthly, it is greatly affected by temperature changes. Temperature changes generate prestress on the strain gauge group of the sensor, leading to large errors in the measurement results. At the same time, when using strain gauges as measurement sensors, resistance strain gauges are prone to lattice creep and fatigue micro-cracks under long-term stress. When exposed to moisture oxidation and corrosion, the resistance continues to change, causing zero-point drift.

[0003] Regarding the surface-mounted strain gauge testing technology for structural components, US4509610A discloses a weighing device that adhesively attaches a bidirectional strain gauge 6 to the surface of a quadrilateral measuring mechanism. The shear deformation generated on the surface of the quadrilateral measuring mechanism under load drives the resistance change of the strain gauge. Shear strain is separated through bridging calculations, and the local shear stress and shear force on the component surface are calculated using material mechanics formulas. This technology requires no modification to the original structure, is low-cost, and widely adaptable, making it a common method for short-term structural mechanical testing and stress detection of steel structures. However, this technology also has significant limitations: First, the measurement accuracy is highly dependent on the manual patching process, resulting in extremely poor consistency. The surface grinding, cleaning, adhesive layer thickness, bonding angle, and curing environment during patching directly affect strain transfer efficiency, easily leading to problems such as incomplete adhesion, delamination, and uneven adhesive layers, resulting in large measurement errors and poor batch consistency, failing to meet high-precision measurement requirements. Second, it has poor environmental adaptability, suitable only for short-term testing and unable to perform long-term online monitoring. Exposed strain gauges and adhesive layers are susceptible to corrosion from factors such as humidity, oil, dust, alternating high and low temperatures, and mechanical friction, leading to aging, debonding, and failure. They also exhibit significant temperature drift and mechanical creep, compromising long-term operational stability. Thirdly, they lack resistance to combined load interference. When components are simultaneously subjected to tensile, compressive, bending, torsional, and shear loads, conventional shear strain measurement signals are easily affected by bending normal stress and axial stress, resulting in a significant decrease in shear signal separation accuracy and measurement accuracy. Furthermore, another embodiment in US4509610A (…) Figure 5 The document describes a quadrilateral force measuring mechanism. Two opposite sides of the quadrilateral extend into corresponding cantilever arms. Force sensors 23 installed on the cantilever arms measure the corresponding strain, thereby reflecting the displacement and deformation generated on both sides of the quadrilateral for force calculation. This technical solution requires converting the gravity applied to the weighing support 34 into the deformation of the cantilever 40 through the connecting rod 24. Therefore, when calculating the corresponding weight, it is necessary to consider not only factors such as the quadrilateral shear modulus, but also the elastic modulus and Poisson's ratio of the connecting rod and the cantilever 40. As a result, the force calculation becomes complicated due to the intermediate connecting rod, which has an adverse effect on high-precision force measurement. At the same time, the force measuring mechanism is greatly affected by temperature changes. Temperature changes generate prestress on the sensor, resulting in a large error in the measurement results.

[0004] Furthermore, in the applicant's prior art, CN117928695A discloses a MEMS fiber optic cantilever load cell, which uses a blazed grating and a collimator on two adjacent faces of a quadrilateral mechanism to measure weight. However, this device uses bending moment to deform the quadrilateral mechanism and measures angle changes by using the blazed grating and collimator on the two adjacent faces. However, the working principle of the blazed grating requires the collimator to be fixed at approximately a 45-degree angle to the blazed grating chip, which has high angle requirements. At the same time, the sensor structure is complex and costly. In addition, fixing the collimator requires soldering and attaching the chip requires the introduction of adhesive. These processes are uncontrollable factors for the temperature coefficient of the sensor and are greatly affected by temperature changes. It is impossible to guarantee the consistency of the sensor due to temperature effects, resulting in large errors in the measurement results.

[0005] In summary, based on the problems of structural damage, low versatility, and single measurement dimension of existing measurement sensors, and the defects of surface patch strain detection technology such as strong process dependence, poor long-term stability, and large influence of temperature on measurement results, a novel shear force detection structure and technical solution is proposed to solve many technical pain points in the existing technology. Summary of the Invention

[0006] In order to overcome at least one of the many problems of corresponding measurement sensors in the prior art, the present invention proposes a shear force measurement sensor and measurement module based on the principle of white light phase-shifting interference.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a shear force measurement sensor based on the principle of white light phase-shifting interference, comprising a first mounting base, a second mounting base, and an elastic body. The elastic body includes a deformation retainer with a parallelogram structure. The deformation retainer includes at least two horizontal frames and two vertical frames. The surfaces of the horizontal frames adjacent to the vertical frames are provided with deformation corner points. The deformation corner points are grooves, notches, or other shapes. The grooves and notches are arc-shaped, triangular, or other shapes that facilitate deformation of the deformation retainer. The two vertical frames are fixedly connected to the first and second mounting bases, respectively. A reflector mounting cantilever is fixedly mounted on one of the two vertical frames, and a collimator mounting cantilever is fixedly mounted on the other. At least one reflector is mounted on the horizontal surface of the reflector mounting cantilever, and at least one collimator is mounted on the collimator mounting cantilever. The collimator is mounted perpendicular to the horizontal direction, and the reflector and the collimator are correspondingly arranged. At least one white light interference cavity is formed between the collimator and the reflector. Through the above structure, the first and second mounting bases are rigidly fixedly connected to the reflecting surface and collimator, respectively. When the shear force measuring sensor is installed on the object under test, i.e., connected to the object under test through the first and second mounting bases, the object under test deforms after being subjected to shear force. The two vertical frames generate a height difference in the vertical direction, causing the reflecting surface and collimator to displace in the vertical direction. The distance between the reflecting surface and collimator changes. By demodulating this distance using the principle of white light interference, the magnitude of the shear force applied to the object under test can be obtained. In this invention, the construction of the white light interference cavity only requires ensuring the parallelism of the coaxial and collimating end faces and the reflecting end face. This can be easily achieved by grinding a standard fiber optic ferrule into a PC surface. The construction process uses riveting, laser welding, etc., making the overall process more mature and controllable. Moreover, it directly measures the deformation of the elastic body without the need for intermediate structures such as connecting rods, thus achieving more accurate measurement of shear force.

[0008] In a further preferred embodiment, the reflector mounting cantilever includes a first cantilever and a second cantilever, both of which are fixed with a reflector. The collimator mounting cantilever has a "T"-shaped structure, and at least two collimators (or four, six, or other even numbers) are mounted at the ends of the collimator mounting cantilever. At least two collimators are mounted at both ends of the horizontal side of the "T"-shaped structure and are correspondingly positioned to the reflector on the reflector mounting cantilever, forming an even number of white light interference cavities between the collimators and the reflector. By setting an even number of white light interference cavities, the demodulated distance is averaged, reducing random errors during the measurement process.

[0009] In a further preferred embodiment, the projections of the even number of white light interference cavities onto the horizontal plane are located on both sides of the deformation retainer. By symmetrically arranging the white light interference cavities, measurement errors caused by processing defects or material inhomogeneities in the elastomer can be reduced, thereby improving the accuracy of shear force measurement.

[0010] Preferably, the reflector mounting cantilever includes a first cantilever and a second cantilever, which are fixedly connected to the same vertical frame. The first cantilever is located at the upper part of the vertical frame, and the second cantilever is located at the bottom of the vertical frame. The collimator mounting cantilever is fixedly connected to the middle of the opposite vertical frame. The vertical projection of the collimator mounting arm is located between the first and second cantilever. With this structural arrangement, an even number of white light interference cavities are located on the upper and lower sides of the collimator mounting cantilever and on the left and right sides of the deformation retainer. When subjected to external shear force, the deformation retainer deforms, causing one of the multiple white light interference cavities to increase in length and another to decrease in length. This setting can eliminate measurement errors caused by temperature changes. When the measured object experiences a change in cavity length due to shear force, one cavity length increases while the other decreases. The shear force can be calculated by subtracting the two cavity lengths, or by subtracting the cavity lengths of two sets of even-numbered white light interference cavities located on the upper and lower sides. However, if the change in the cavity lengths of the two sets of sensitive structures is caused by changes in ambient temperature, the cavity lengths of the two sets of white light interference cavities on the upper and lower sides will either increase simultaneously (temperature rise) or decrease simultaneously (temperature decrease). Subtracting the cavity lengths of the two sets of cavity lengths can eliminate the cavity length changes caused by temperature changes, thereby eliminating the temperature influence on the measured structure.

[0011] In a preferred embodiment, the optical fiber at the end of the collimator is led out through the cable outlet of the first mounting base for signal output.

[0012] This invention also relates to a measurement module, wherein a first disc bracket is disposed at a first mounting base and the elastic body, and the first disc bracket is fixedly connected to the first mounting base; a second disc bracket is disposed at a second mounting base and the elastic body, and the second disc bracket is fixedly connected to the second mounting base; a protective shell is supported by the first disc bracket and the second disc bracket, and is welded to the first disc bracket and the second disc bracket. The protective shell provides sealed protection for the measurement module.

[0013] Preferably, the protective housing is filled with an inert gas, which ensures that the refractive index of the gas inside the measurement module remains stable even when the ambient temperature changes, further reducing the impact of temperature changes on the cavity length and improving the measurement accuracy and stability of the measurement module and sensor.

[0014] Further features of the invention will be apparent from the accompanying drawings and descriptions. The features and combinations thereof mentioned above in the specification, as well as those mentioned below in the description of the drawings and / or shown separately in the drawings, may be applied not only to the given combinations, but also to other combinations or individually. Attached Figure Description

[0015] Figure 1 This is a structural view of the shear force measuring sensor of the present invention; Figure 2 This is a structural view of a shear force measuring sensor according to another embodiment of the present invention; Figure 3 This is an axonometric view of a shear force measuring sensor structure according to another embodiment of the present invention; Figure 4 This is a top view of the shear force measuring sensor structure according to another embodiment of the present invention; Figure 5 This is a simulation diagram of a deformation according to another embodiment of the present invention; Figure 6 This is a structural view of the measurement module of the present invention.

[0016] Figure label: 1-Shear force measuring sensor, 11-First mounting base, 111-First disc bracket, 12-Second mounting base, 121-Second disc bracket, 13-Deformation retainer, 131-Vertical frame, 132-Horizontal frame, 133-Reflector mounting cantilever, 1331-First cantilever, 1332-Second cantilever, 134-Collider mounting cantilever, 14-Reflector, 15-Collider, 16-Protective housing. Detailed Implementation

[0017] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0018] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0019] Certain embodiments of this disclosure will be described more fully below with reference to the accompanying drawings, some of which, but not all, will be shown. In fact, various embodiments of this disclosure may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to enable this disclosure to meet applicable legal requirements.

[0020] This invention adopts the following technical solution: a shear force measurement sensor 1 based on the principle of white light phase-shifting interference, such as... Figure 1 As shown, the device includes a first mounting base 11, a second mounting base 12, and an elastic body. The elastic body includes a deformation retainer 13 with a parallelogram structure. The deformation retainer 13 includes at least two horizontal frame edges 132 and at least two vertical frame edges 131. The surfaces of the horizontal frame edges 132 adjacent to the vertical frame edges 131 are provided with deformation corner points. The deformation corner points can be grooves, notches, or other shapes. The grooves and notches can be arc-shaped, triangular, or other shapes. Any other structure that facilitates the deformation of the deformation retainer is acceptable. Figure 1 Only the deformed corner point with the arc-shaped groove is shown; the two vertical frames 131 are fixedly connected to the first mounting base 11 and the second mounting base 12 respectively. One of the two vertical frames 131 is fixedly mounted with a reflector mounting cantilever 133, and the other is fixedly mounted with a collimator mounting cantilever 134. At least one reflector 14 is mounted on the horizontal surface of the reflector mounting cantilever 133. At least one collimator 15 is mounted on the collimator mounting cantilever 134. The collimator 15 is mounted vertically relative to the horizontal direction. The reflector 14 and the collimator 15 are correspondingly arranged. At least one white light interference cavity is formed between the collimator 15 and the reflector 14. Figure 1 Only one white light interference cavity is given in the original text, but multiple white light interference cavities can be provided in other embodiments to improve the accuracy of the measurement results. With the above structure, the first mounting base 11 and the second mounting base 12 are rigidly fixedly connected to the reflecting surface 14 and the collimator 15, respectively. When the shear force measuring sensor is installed on the object to be measured, that is, connected to the object to be measured through the first mounting base 11 and the second mounting base 12, the object to be measured will deform after being subjected to shear force. The two vertical frame 131 will generate a height difference in the vertical direction, which will cause the reflecting surface 14 and the collimator 15 to be displaced in the vertical direction. The distance between the reflecting surface 14 and the collimator 15 will change. By demodulating this distance according to the principle of white light interference, the magnitude of the shear force applied to the object to be measured can be obtained. In this invention, the construction of the white light interference cavity only requires ensuring the parallelism of the coaxial and collimated end faces and the reflecting surface. This can be easily achieved by grinding the standard fiber ferrule into a physical contact end face (PC surface). The construction process uses riveting, laser welding, etc., making the overall process more mature and controllable. Furthermore, it allows for direct measurement of elastic body deformation without the need for intermediate structures such as connecting rods, thus enabling more accurate measurement of shear force.

[0021] In a further preferred embodiment, the reflective surface mounting cantilever 133 includes a first cantilever 1331 and a second cantilever 1332, both of which are fixed with the reflective surface 14. Figure 2Each cantilever in the design has one reflecting surface; in other embodiments, multiple reflecting surfaces may be provided. The collimator mounting cantilever 134 has a "T"-shaped structure, and at least two collimators 15 are mounted at the end of the collimator mounting cantilever 134, or there may be four, six, or other even numbers. At least two collimators 15 are mounted at both ends of the horizontal side of the "T"-shaped structure and are correspondingly arranged with the reflecting surfaces 14 on the reflecting surface mounting cantilever 133, forming an even number of white light interference cavities between the collimators 15 and the reflecting surfaces 14. By setting an even number of white light interference cavities, the demodulated distance is averaged, which can reduce random errors in the measurement process.

[0022] In a further preferred embodiment, the projection of the white light interference cavity onto the horizontal plane is located on both sides of the deformation retainer 13. By using symmetrically arranged white light interference cavities, measurement errors caused by processing defects in the elastomer, such as inconsistent processing of deformation corners, or material inhomogeneity can be reduced, thereby improving the accuracy of shear force measurement.

[0023] Preferably, the reflective surface mounting cantilever 133 includes a first cantilever 1331 and a second cantilever 1332, such as Figure 2-4 As shown, the first cantilever 1331 and the second cantilever 1332 are fixedly connected to the same vertical frame 131, with the first cantilever 1331 located at the bottom of the vertical frame 131 and the second cantilever 1332 located at the top of the vertical frame 131. The collimator mounting cantilever 134 is fixedly connected to the middle of the opposite vertical frame 131. The vertical projection of the collimator mounting arm is located between the first cantilever 1331 and the second cantilever 1332. Through this structural arrangement, an even number of white light interference cavities are located on the upper and lower sides of the collimator mounting cantilever 134 and on the left and right sides of the deformation retainer 13. Under the action of external shear force, such as... Figure 5 As shown, the deformation cage 13 deforms, causing one of the multiple white light interference cavities to increase in length and another to decrease in length. This arrangement can eliminate measurement errors caused by temperature changes. When the measured object experiences shear force, causing a change in the length of the white light interference cavities, one cavity length increases and the other decreases. The shear force can be calculated by subtracting the lengths of the two cavities, or by subtracting the lengths of the two sets of cavities located on the upper and lower sides of an even number of white light interference cavities. However, if the change in the lengths of the two sets of sensitive structure cavities is caused by changes in ambient temperature, the lengths of the two sets of white light interference cavities on the upper and lower sides will either increase simultaneously (temperature rise) or decrease simultaneously (temperature decrease). Subtracting the lengths of the two sets of cavities can eliminate the change in cavity length caused by temperature changes, thereby eliminating the temperature influence on the measurement structure.

[0024] In a preferred embodiment, the optical fiber at the end of the collimator 15 is led out through the cable outlet of the first mounting base 11 for signal output.

[0025] The present invention also relates to a measurement module, such as Figure 6 As shown, a first disc bracket 111 is provided at the first mounting base 11 and the elastic body, and the first disc bracket 111 is fixedly connected to the first mounting base 11; a second disc bracket 121 is provided at the second mounting base 12 and the elastic body, and the second disc bracket 121 is fixedly connected to the second mounting base 12; the protective shell 16 is supported by the first disc bracket 111 and the second disc bracket 121, and is fixedly connected to the first disc bracket 111 and the second disc bracket 121. The protective shell 16 provides sealed protection for the measuring module.

[0026] Preferably, the protective housing 16 is filled with inert gas. The protective housing 16 is a stainless steel corrugated pipe, and it is welded to the first disc support 111 and the second disc support 121. This ensures the stability of the gas refractive index inside the measurement module even when the ambient temperature changes, further reducing the impact of temperature changes on the cavity length and improving the measurement accuracy and stability of the measurement module and sensor.

Claims

1. A shear force measurement sensor based on the principle of white light phase-shifting interference, comprising a first mounting base, a second mounting base, and an elastic body, wherein the elastic body includes a deformation retainer with a parallelogram structure, characterized in that, The deformation retainer includes at least two horizontal frames and at least two vertical frames. The surfaces of the horizontal frames adjacent to the vertical frames are provided with consistent deformation corner points. The two vertical frames are fixedly connected to a first mounting base and a second mounting base, respectively. A reflector mounting cantilever is fixedly mounted on one of the two vertical frames, and a collimator mounting cantilever is fixedly mounted on the other. At least one reflector is mounted on the horizontal surface of the reflector mounting cantilever, and at least one collimator is mounted on the collimator mounting cantilever. The collimator is mounted perpendicular to the horizontal direction, and the reflector is correspondingly arranged with the collimator. At least one white light interference cavity is formed between the collimator and the reflector. The reflector mounting cantilever includes a first cantilever and a second cantilever, both of which are fixed with a reflector. The collimator mounting cantilever has a "T"-shaped structure, with at least two collimators mounted at both ends of the horizontal side of the "T"-shaped structure, forming at least two white light interference cavities between the collimators and the reflector.

2. The shear force measuring sensor based on the white light phase-shifting interference principle as described in claim 1, characterized in that, The projections of at least two of the white light interference cavities onto the horizontal plane are located on both sides of the deformation retainer.

3. The shear force measuring sensor based on the white light phase-shifting interference principle according to any one of claims 1-2, characterized in that, The reflector mounting cantilever includes a first cantilever and a second cantilever, which are fixedly connected to the same vertical frame. The first cantilever is located at the bottom of the vertical frame, and the second cantilever is located at the top of the vertical frame. The collimator mounting cantilever is fixedly connected to the middle of the opposite vertical frame. The vertical projection of the collimator mounting arm is located between the first and second cantilever, such that at least two white light interference cavities are located on the upper and lower sides of the collimator mounting cantilever and on the left and right sides of the deformation retainer.

4. The shear force measuring sensor based on the white light phase-shifting interference principle as described in claim 1, characterized in that, The optical fiber at the end of the collimator is led out through the cable outlet hole of the first mounting base.

5. A measurement module comprising a shear force measuring sensor as described in any one of claims 1-4, wherein a first disc bracket is provided at the first mounting base and the elastic body, the first disc bracket being fixedly connected to the first mounting base; a second disc bracket is provided at the second mounting base and the elastic body, the second disc bracket being fixedly connected to the second mounting base; and a protective housing is supported by the first disc bracket and the second disc bracket, and is fixedly connected to the first disc bracket and the second disc.

6. The measurement module according to claim 5, characterized in that, The protective outer shell is filled with inert gas.

7. The measurement module according to claim 5 or 6, characterized in that, The protective outer shell is made of stainless steel corrugated pipe.

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