A spherical micro-displacement sensing head based on fiber Bragg grating

Abstract

This invention discloses a spherical shell-type micro-displacement sensing head based on a fiber Bragg grating (FBG). The invention includes: an outer spherical shell with a transverse annular groove and a vertical annular groove on its inner surface, the bottom of which forms a locally sensitive deformation zone; an inner sphere rotatably placed inside the outer spherical shell and having an annular protrusion that mates with the groove, so that when the probe is subjected to force, the annular protrusion forces the locally sensitive deformation zone to undergo tangential / circumferential tensile or compressive deformation; and a fiber Bragg grating sensing assembly, the fiber Bragg grating embedded in the groove and fixed along the groove's length, used to convert the deformation into wavelength changes, thereby achieving micro-displacement detection. This invention, through the mating design of the outer spherical shell groove and the inner spherical annular grating, forms a locally sensitive deformation zone, enabling the FBG embedded in the groove area to accurately sense minute deformations, avoiding signal interference caused by deformation of traditional integral structures.

Description

Technical Field

[0001] This utility model relates to the field of precision measurement technology, specifically to a ball-joint fiber optic sensing head for high-precision micro-displacement detection in a coordinate measuring machine. Background Technology

[0002] Coordinate measuring machines (CMMs) are widely used in high-precision measurement fields such as aerospace and precision mold manufacturing, and are the core equipment for measuring the geometric quantities of minute parts. The ball joint probe, as a key sensing component, has a structural design that directly determines its measurement sensitivity, stability, and reliability.

[0003] Existing ball joint probes often employ rigid connections or complex sensor combinations, resulting in problems such as complex structures, high costs, and slow response. Alternatively, the deformation sensing area of ​​the ball joint probe may be poorly designed, leading to insufficient accuracy in detecting minute displacements and failing to meet the demands of precision measurement. While the probe structure disclosed in Chinese patent CN211085181U simplifies the mechanical design, its low integration of the sensor and structure limits its measurement sensitivity to overall deformation interference, preventing the achievement of μm-level accuracy.

[0004] In recent years, fiber Bragg grating (FBG) sensing technology has been gradually applied to precision measurement due to its advantages such as high sensitivity, resistance to electromagnetic interference, and small size. However, in existing probes, FBGs are mostly used as integral strain sensing elements, which are easily affected by the overall deformation of the structure, resulting in poor signal stability and limited accuracy improvement. Utility Model Content

[0005] To address the issues of low integration between existing probe structures and FBG sensors, and insufficient accuracy in micro-displacement detection, this invention proposes a ball-joint fiber optic sensing probe. Through the cooperative design of the outer spherical shell groove and the inner spherical ring, a localized sensitive deformation zone is formed, enabling the FBG embedded in the groove area to accurately sense minute deformations and significantly improve measurement sensitivity.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This utility model includes:

[0008] The outer spherical shell has at least one transverse annular groove and at least one vertical annular groove on its inner surface, and the bottom of the groove forms a localized sensitive deformation zone.

[0009] The inner sphere is rotatably placed inside the outer spherical shell and is provided with an annular protrusion that can cooperate with the groove so that when the probe is subjected to force, the annular protrusion can force the local sensitive deformation area to produce tangential / circumferential tensile or compressive deformation.

[0010] A fiber Bragg grating sensing component, wherein the fiber Bragg grating is embedded in the groove and fixed along the length of the groove, is used to convert the deformation into a wavelength change to realize micro-displacement detection.

[0011] Furthermore, the transverse annular groove is a rectangular annular groove distributed around the equator of the outer spherical shell, and the vertical annular groove is a trapezoidal annular groove distributed along the meridian of the outer spherical shell. The two intersect to divide the inner surface of the spherical shell into four quadrant regions.

[0012] Furthermore, the fiber Bragg grating sensing component includes four sets of fiber Bragg gratings, which are respectively embedded in the horizontal annular groove and the vertical annular groove.

[0013] Furthermore, the fiber Bragg grating is bonded and fixed to the sidewall of the groove using UV-cured adhesive to avoid installation stress interference.

[0014] Furthermore, the outer spherical shell is formed by the joining of an upper hemisphere and a lower hemisphere, with eight M3 threaded holes evenly distributed on the edges of the two hemispheres, which are fastened with stainless steel screws to form a detachable integral structure.

[0015] Furthermore, the outer spherical shell is provided with flanges with mounting holes at the top and bottom for rigid connection with the measuring arm of the coordinate measuring machine.

[0016] Furthermore, the outer shell material is nylon glass fiber composite material, and the inner sphere material is 316L stainless steel, in order to balance lightweight and wear and corrosion resistance.

[0017] Furthermore, a threaded hole is formed at the center of the inner sphere, which is connected to one end of the measuring rod via a self-locking thread. The other end of the measuring rod is fixed with a zirconia ceramic measuring ball, which is used to contact the workpiece being measured and transmit displacement.

[0018] Furthermore, the bottom of the groove is provided with a 0.1 mm thick elastic buffer layer to absorb the initial impact stress, so as to smooth the deformation transmission and protect the fiber Bragg grating.

[0019] Furthermore, the rectangular annular groove has a width of 2 mm, a depth of 1 mm, and a length of 40 mm; the trapezoidal annular groove has a width of 1.5 mm, a depth of 1.2 mm, and a length of 50 mm.

[0020] This utility model can bring the following beneficial effects:

[0021] The ball-joint fiber optic sensing head involved in this utility model forms a localized sensitive deformation zone through the matching design of the outer spherical shell groove and the inner spherical ring. This allows the FBG embedded in the groove area to accurately sense minute deformations, avoiding signal interference caused by deformation of the traditional overall structure.

[0022] The passive, interference-resistant, and high-precision characteristics of FBG enable the probe to detect displacements at the μm level, significantly improving sensitivity; its simple structure and low cost make it easy to mass-produce and assemble; its high integration, with FBG directly embedded in local grooves, provides strong signals and strong resistance to electromagnetic interference, making it suitable for high-precision measurements in complex industrial environments. Attached Figure Description

[0023] Figure 1 This is a structural schematic diagram of an embodiment of this application.

[0024] Figure 2 This is a schematic diagram of the inner sphere unit in an embodiment of this application.

[0025] Figure 3 This is a cross-sectional view of the outer spherical shell unit according to an embodiment of this application.

[0026] Figure 4 This is a top view of the outer spherical shell unit according to an embodiment of this application.

[0027] Figure 5 This is a cross-sectional view of a spherical micro-displacement sensing head based on a fiber Bragg grating according to an embodiment of this application.

[0028] Reference numerals: 1. Upper horizontal ring; 2. Lower horizontal ring; 3. Left vertical ring; 4. Right vertical ring; 5. Inner sphere; 6. Measuring rod; 7. Measuring ball; 8. Outer spherical shell; 9. Threaded hole; 10. Left vertical annular groove; 11. Right vertical annular groove; 12. Upper horizontal annular groove; 13. Lower horizontal annular groove. Detailed Implementation

[0029] The present invention will be further explained below with reference to the embodiments and accompanying drawings. The following embodiments are only used to illustrate the present invention, but are not intended to limit the scope of implementation of the present invention.

[0030] This embodiment proposes a ball-joint type fiber optic sensing head, referencing... Figure 1 and Figure 2 It includes an upper horizontal ring 1, a lower horizontal ring 2, a left vertical ring 3, a right vertical ring 4, an inner sphere 5, and an outer spherical shell 8.

[0031] The outer spherical shell 8 is formed by the joining of two hemispherical shells, and its inner surface is provided with an upper horizontal annular groove 12, a left vertical annular groove 10, a right vertical annular groove 11, and a lower horizontal annular groove 13, which intersect to form four hollowed-out groove areas, as shown in the figure. Figure 3 , Figure 4 and Figure 5The outer surface of the inner sphere 5 is provided with an upper horizontal ring 1, a lower horizontal ring 2, a left vertical ring 3, and a right vertical ring 4 that match the groove; one end of the measuring rod 6 is connected to the inner sphere 5, and the other end is connected to the measuring ball 7; the FBG sensing component is set in the lower horizontal annular groove 13, the upper horizontal annular groove 12, the left vertical annular groove 10, and the right vertical annular groove 11 of the outer spherical shell 8, and the two hemispherical shells are fixed by threaded holes 9.

[0032] In this embodiment, the outer spherical shell 8 is formed by joining two upper and lower hemispherical shells. The inner surface is provided with two sets of transverse annular grooves and two sets of vertical annular grooves, which intersect to form four quadrant regions: the first quadrant (the intersection of the upper and left sides), the second quadrant (the intersection of the upper and right sides), the third quadrant (the intersection of the lower and left sides), and the fourth quadrant (the intersection of the lower and right sides). The groove edges are provided with a 30° chamfer to reduce stress concentration.

[0033] In a preferred embodiment, the inner sphere 5 is made of 316L stainless steel and has a diameter of 40mm. It has a central hole for connecting to the measuring rod 6. One end of the measuring rod 6 is connected to the central hole of the inner sphere 5 by a thread, and the other end is connected to the measuring ball 7.

[0034] In a preferred embodiment, the FBG sensing component includes four FBGs, which are respectively embedded in the horizontal and vertical grooves and fixed by UV curing adhesive to avoid installation stress interference. Each FBG is bonded to the left and right sidewalls of the groove by UV adhesive.

[0035] In a preferred embodiment, the fixing mechanism includes eight M3 threaded holes located at the edges of the two hemispherical shells, which are fastened by stainless steel screws.

[0036] In a preferred embodiment, flanges are disposed at the top and bottom of the outer spherical shell 8 to facilitate rigid connection with the coordinate measuring machine arm.

[0037] Furthermore, in this embodiment, a 0.1mm thick buffer layer is provided at the bottom of the lower horizontal annular groove 13, the upper horizontal annular groove 12, the left vertical annular groove 10, and the right vertical annular groove 11. When the probe is subjected to force, the buffer layer absorbs the initial impact stress, making the deformation transmission smoother.

[0038] Furthermore, in this embodiment, the outer spherical shell 8 is made of nylon glass fiber composite material to ensure no wear during long-term use.

[0039] Furthermore, in this embodiment, the flange is made of aluminum alloy with anodized surface treatment and mounting hole tolerance H7.

[0040] Furthermore, in this embodiment, the threaded connection between the measuring rod 6 and the inner ball 5 adopts a self-locking thread design to prevent the thread from loosening under vibration environment and ensure long-term measurement stability.

[0041] Furthermore, in this embodiment, the measuring ball 7 is made of zirconia ceramic, which reduces frictional damage when in contact with the workpiece and extends its service life.

[0042] In this embodiment, when the probe is subjected to force, the probe rod 6 causes the inner sphere 5 to rotate slightly or be axially compressed. The inner sphere 5 ring pushes the material of the upper transverse annular groove 12, the left vertical annular groove 10, and the right vertical annular groove 11 of the outer spherical shell 8 to undergo tangential / circumferential stretching. The FBG is stretched / shortened with the deformation of the groove. The displacement is calculated by detecting the Bragg wavelength shift of the FBG.

[0043] In this embodiment, the upper transverse annular groove 12, the lower transverse annular groove 13, the left vertical annular groove 10, and the right vertical annular groove 11 of the outer spherical shell 8 serve as localized sensitive deformation areas. The deformation transmission path is as follows: the probe 7 is subjected to force → the probe 6 drives the inner sphere 5 to move → the inner sphere 5's annular ring fits with the groove through a gap → local elastic deformation of the material in the groove area → FBG strain change → wavelength drift output. This design avoids signal interference caused by deformation of the traditional overall structure, concentrating the deformation in the groove area, thus improving the FBG detection sensitivity by 3 times. FBG wavelength drift detection uses a high-precision spectrometer, which collects the wavelength shift in real time and calculates the strain change to achieve digital output of the displacement.

[0044] In summary, this utility model adopts a ball-joint structure, which forms a localized sensitive deformation zone through the cooperation design of the outer spherical shell groove and the inner spherical ring. This allows the FBG embedded in the groove area to accurately sense minute deformations and achieve μm-level displacement detection, while solving the defects of complex structure, high cost, and slow response.

[0045] This embodiment is further configured such that: the upper horizontal annular groove 12 and the lower horizontal annular groove 13 are rectangular annular grooves (groove width 2mm, groove depth 1mm, groove length 40mm), the left vertical annular groove 10 and the right vertical annular groove 11 are trapezoidal annular grooves (groove width 1.5mm, groove depth 1.2mm, groove length 50mm), the two hollowed-out grooves in each quadrant region are parallel and spaced 5mm apart, and a 0.1mm thick buffer layer is set at the bottom of the groove to further optimize the deformation transmission efficiency.

[0046] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

Claims

1. A fiber Bragg grating based spherical shell micro-displacement sensor head, characterized in that: include: The outer spherical shell has at least one transverse annular groove and at least one vertical annular groove on its inner surface, and the bottom of the groove forms a localized sensitive deformation zone. The inner sphere is rotatably placed inside the outer spherical shell and is provided with an annular protrusion that can cooperate with the groove so that when the probe is subjected to force, the annular protrusion can force the local sensitive deformation area to produce tangential / circumferential tensile or compressive deformation. A fiber Bragg grating sensing component, wherein the fiber Bragg grating is embedded in the groove and fixed along the length of the groove, is used to convert the deformation into a wavelength change to realize micro-displacement detection.

2. A fiber Bragg grating based micro-displacement sensor probe in the form of a spherical shell according to claim 1, characterized in that: The transverse annular groove is a rectangular annular groove distributed around the equator of the outer spherical shell, and the vertical annular groove is a trapezoidal annular groove distributed along the meridian of the outer spherical shell. The two intersect to divide the inner surface of the spherical shell into four quadrant regions.

3. A fiber Bragg grating based micro-displacement sensor probe in the form of a spherical shell according to claim 2, characterized in that: The fiber Bragg grating sensing component includes four sets of fiber Bragg gratings, which are respectively embedded in the horizontal annular groove and the vertical annular groove.

4. A fiber Bragg grating based micro-displacement sensor probe in the form of a spherical shell according to claim 3, characterized in that: The fiber Bragg grating is bonded to the sidewall of the groove using UV-cured adhesive to avoid installation stress interference.

5. The optical fiber Bragg grating based spherical shell micro-displacement sensor probe according to claim 1, wherein: The outer spherical shell is formed by the joining of an upper hemisphere and a lower hemisphere. Eight M3 threaded holes are evenly distributed on the edges of the two hemispheres, which are fastened with stainless steel screws to form a detachable integral structure.

6. A fiber Bragg grating based micro-displacement sensor probe in the form of a spherical shell according to any one of claims 1 to 5, characterized in that: The outer spherical shell is provided with flanges with mounting holes at the top and bottom for rigid connection with the measuring arm of the coordinate measuring machine.

7. The optical fiber Bragg grating based spherical shell micro-displacement sensor probe of claim 1, wherein: The outer shell is made of nylon glass fiber composite material, and the inner sphere is made of 316L stainless steel, in order to balance lightweight and wear and corrosion resistance.

8. A fiber Bragg grating based micro-displacement sensor probe in the form of a spherical shell according to claim 1 or 7, characterized in that: The inner sphere has a threaded hole at its center, which is connected to one end of the measuring rod via a self-locking thread. The other end of the measuring rod is fixed with a zirconia ceramic measuring ball, which is used to contact the workpiece being measured and transmit displacement.

9. A spherical shell micro-displacement sensing head based on a fiber Bragg grating according to claim 1 or 2, characterized in that: The bottom of the groove is provided with a 0.1 mm thick elastic buffer layer to absorb the initial impact stress, so as to smooth the deformation transmission and protect the fiber Bragg grating.

10. The optical fiber Bragg grating based spherical shell micro-displacement sensor head of claim 2, wherein: The rectangular annular groove has a width of 2 mm, a depth of 1 mm, and a length of 40 mm; the trapezoidal annular groove has a width of 1.5 mm, a depth of 1.2 mm, and a length of 50 mm.

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