CN113324632B - Optical fiber weighing sensor - Google Patents
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- CN113324632B CN113324632B CN202011248832.7A CN202011248832A CN113324632B CN 113324632 B CN113324632 B CN 113324632B CN 202011248832 A CN202011248832 A CN 202011248832A CN 113324632 B CN113324632 B CN 113324632B
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- 238000005303 weighing Methods 0.000 title claims abstract description 107
- 239000013307 optical fiber Substances 0.000 title claims abstract description 54
- 239000000835 fiber Substances 0.000 claims abstract description 171
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- 230000005484 gravity Effects 0.000 claims description 20
- 241000755266 Kathetostoma giganteum Species 0.000 claims description 16
- 230000035945 sensitivity Effects 0.000 claims description 15
- 238000005259 measurement Methods 0.000 claims description 8
- 239000002360 explosive Substances 0.000 abstract description 6
- 230000000694 effects Effects 0.000 description 8
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- 238000010586 diagram Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000010276 construction Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 229910001315 Tool steel Inorganic materials 0.000 description 1
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- 238000005452 bending Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
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- 239000008358 core component Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
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- 238000001514 detection method Methods 0.000 description 1
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- 230000003287 optical effect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01G—WEIGHING
- G01G3/00—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances
- G01G3/12—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing
- G01G3/125—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing wherein the weighing element is an optical member
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
- G01L1/242—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre
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Abstract
The invention relates to an optical fiber weighing sensor, which comprises a cover plate, a weighing main body and an optical fiber grating sensor, and belongs to the technical field of sensing. The cover plate comprises a positioning screw hole and a spherical support column, a wire outlet hole, a deformation groove, a positioning hole and the like are formed in the weighing main body, the upper fiber grating and the lower fiber grating are orthogonally arranged in an optical fiber fixing groove of the cantilever beam, and the function of preventing unbalance loading can be achieved. When an object to be detected is placed on the cover plate, the cover plate is stressed to press the cantilever beam downwards through the spherical support, the cantilever beam sinks to generate strain in the axial direction, so that the characteristic wavelength of the fiber grating is changed, and the change of the characteristic wavelength of the fiber grating is monitored by using the grating demodulator to monitor the change of the characteristic wavelength of the fiber grating, so that the change of the object to be detected can be monitored. The invention has simple structure, thinner thickness, can prevent unbalance loading, is easy to adjust, integrates the advantages of the fiber bragg grating, and can be applied to the strong electromagnetic interference and flammable and explosive environments to realize weighing.
Description
Technical Field
The invention belongs to the technical field of sensing, and relates to an optical fiber weighing sensor.
Background
Nowadays, weighing sensors are increasingly used. The load cell is called a core component in the electronic weighing apparatus. With the rapid development of science and technology, electronic weighing apparatus assembled by weighing sensors have been widely used in various industries. Particularly, with the continuous improvement of the automation degree of the industrial production process, the weighing sensor becomes a necessary device in the process control, and the weighing sensor is applied to the weighing of large tanks, reaction kettles, bins and the like, the measurement and control of crane scales, truck scales and the like, the batching system for mixing and distributing various raw materials, and even the daily life weight of people.
A load cell is essentially a device that converts a weight signal into a measurable electrical signal output. The sensor is used by considering the actual working environment of the sensor, which is important for correctly selecting the weighing sensor, and the sensor is related to the normal work, the safety and the service life of the sensor, and even the reliability and the safety of the whole weighing apparatus.
At present, the known weighing sensor is mainly based on an electromagnetic technology, and the sensor generally has a complex structure and cannot be applied to weight detection in strong electromagnetic interference and flammable and explosive environments, such as oil and gas storage and transportation, military marshes and the like.
For example, a weighing sensor disclosed in publication No. CN110132382A is a sensor based on electromagnetic technology, which cannot be directly applied to flammable and explosive environments and is complicated in structure.
For example, the optical fiber weighing sensor disclosed in publication No. CN202255574U utilizes springs and elastic sheets to transfer strain, so as to convert the weight signal into a measurable signal, but the spring structure has a large thickness, and is not suitable for use in some space-limited environments.
For example, an arch-shaped optical fiber weighing sensor disclosed in CN202010371618.4, which adopts the force-bearing mode of an arch structure to generate strain. The strain generated by the arch structure is influenced by friction force, the influence of the friction force needs to be reduced in a corresponding mode, and the fiber grating needs to be protected and fixed by the spring piece, so that the structure is more complex. The existence of the spring pieces reduces the generation of strain, and the sensitivity of the sensor is also reduced, and if the arched structure does not move horizontally, the strain generated by the upper spring piece and the lower spring piece is not equal, so that the sensitivity of the two fiber bragg grating sensors is different.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides the optical fiber weighing sensor, the cantilever beam type structure is stressed to generate strain, the cantilever beam is suspended without being influenced by friction, the upper surface and the lower surface of the strain generated by the bending of the cantilever beam are equal in size and opposite in positive and negative, the optical fiber grating sensor is directly fixed in the optical fiber fixing groove, the protection and the fixation of the spring piece are not needed, the sensitivity can be increased, and the structure is simplified. The sensor has the advantages of simple structure, convenient manufacture and use, thinner thickness and application in flammable and explosive environments.
Technical scheme
An optical fiber weighing sensor comprises a cover plate 1, a weighing main body 2 and an optical fiber grating 3; the fiber bragg grating 3 comprises a lower fiber bragg grating 31 and an upper fiber bragg grating 32; the weighing body 2 comprises a supporting outer wall 27, a cantilever beam structure 24 and a strain tank 25; the cantilever beam structure 24 is arranged in the supporting outer wall 27, the cantilever beam structure 24 is provided with a strain groove 25, and the cantilever beam structure 24 is divided into four centrally symmetrical cantilever beams which are respectively positioned in four main directions on the same horizontal plane in the supporting outer wall 12, and the height of the cantilever beam structure 24 is larger than the maximum displacement of the cantilever beam structure 24 under the maximum load vertically downwards; the two lower fiber gratings 31 and the two upper fiber gratings 32 are orthogonally arranged at the center of the cantilever beam structure, and the cover plate 1 is connected with the center of the weighing main body 2 through four spherical pillars 11; when a heavy object with the gravity of F is placed on the cover plate 1, the cantilever beam structure 24 is pressed downwards, the force is transmitted to the cantilever beam structure 24, the cantilever beam structure 24 bends downwards to generate vertical displacement and simultaneously can be slightly bent to generate transverse displacement, the transverse displacement can pull the upper fiber bragg grating 32 and the lower fiber bragg grating 31 to generate axial strain, and the weight measurement is realized.
The front end of the cantilever beam structure, namely the part close to the center of the circular ring, is of a strip-shaped rectangular structure, and the tail end of the cantilever beam structure 24 is gradually widened to be of an axe-shaped structure.
The end of the cantilever structure 24 is formed in a straight configuration by digging out 4 squares.
The strip-shaped rectangular structure of the cantilever beam structure 24 is positioned in a long rectangular groove in the middle of the weighing main body 2.
The strain groove 25 is a circular groove and is located on the upper and lower surfaces of the tail end of the cantilever beam structure 24, so that the cantilever beam structure 24 and the support outer wall 27 are connected into a whole.
The strain groove 25 is a circular groove strip-shaped groove.
The cover plate 1 and the weighing main body 2 are both circular and have the same radius.
The positioning hole 22 on the cover plate 1 is coaxial with the positioning screw hole 12 on the weighing main body 2, and the diameter of the positioning hole is larger than that of the positioning screw hole 12; when the cover plate 1 sinks, the flat head screw sinks together with the cover plate 1. The function of fixing the weighing body 2 and the cover plate 1 is realized without influencing the sinking of the cantilever structure 24, namely, without influencing the sensitivity, namely, the measurement. The measuring result is not influenced while the fixing effect is achieved.
The fiber bragg grating is arranged at the tail end of a cantilever beam structure 24 of the weighing main body 2, and the upper fiber bragg grating 32 is fixed in fiber fixing grooves on the upper surfaces of a cantilever beam 242 and a cantilever beam 244 in a two-point adhesion mode; the lower fiber grating 31 is fixed in the fiber fixing grooves on the lower surfaces of the cantilever beams 241 and 243 in a two-point adhesion manner; the upper fiber grating 32 and the lower fiber grating 31 are arranged orthogonally; when a heavy object with the gravity of F is placed on the cover plate 1, the cover plate 1 is forced to press the cantilever structure 24, when the tail end of the cantilever structure 24 descends, a microbending is generated to pull the fiber grating 3 transversely, so that the wavelength of the fiber grating 3 is changed, the wavelength of the fiber grating 3 is in a linear relation with the strain, namely the linear relation with the gravity F in a use range, and the strain = η F is provided, wherein η is a mechanical sensitivity coefficient for converting the gravity into the transverse strain by the structure.
The optical fiber device with the grating 3 having the grid structure includes but is not limited to: fiber bragg gratings, tilted fiber bragg gratings, or long-period fiber gratings.
Advantageous effects
The invention provides an optical fiber weighing sensor which comprises a cover plate, a weighing main body and an optical fiber grating sensor and belongs to the technical field of sensing. The cover plate comprises a positioning screw hole and a spherical support column, a wire outlet hole, a deformation groove, a positioning hole and the like are formed in the weighing main body, the upper fiber grating and the lower fiber grating are orthogonally arranged in an optical fiber fixing groove of the cantilever beam, and the function of preventing unbalance loading can be achieved. When an object to be detected is placed on the cover plate, the cover plate is stressed to press the cantilever beam downwards through the spherical support, the cantilever beam sinks to generate strain in the axial direction, so that the characteristic wavelength of the fiber grating is changed, and the change of the characteristic wavelength of the fiber grating is monitored by using the grating demodulator to monitor the change of the characteristic wavelength of the fiber grating, so that the change of the object to be detected can be monitored. The invention has simple structure, thinner thickness, can prevent unbalanced loading, is easy to adjust, integrates the advantages of the fiber bragg grating and can be applied to weighing in strong electromagnetic interference and flammable and explosive environments.
According to the optical fiber weighing sensor, a weight signal in the vertical direction is converted into a transverse strain change, and then the optical fiber grating is used for outputting an electric signal through the optical fiber grating signal processor, and a displacement signal in the vertical direction is converted into a transverse strain signal of the optical fiber grating, so that the sensor has an ultrathin thickness and can be applied to a specific space environment. Under overweight condition, the cover plate can contact with the weighing main body to prevent the cantilever beam from continuously deforming, and the function of overrun protection is achieved. The two fiber gratings which are orthogonally arranged can prevent unbalance loading, the temperature influence can be compensated by installing a temperature sensor, and the sensitivity can be adjusted by changing the thickness of the cantilever beam strain groove according to the requirement. Because the optical fiber sensor transmits information by using light waves, and the optical fiber is an electrically insulated and corrosion-resistant transmission medium, the optical fiber weighing sensor can be applied to weighing in strong electromagnetic interference and flammable and explosive environments, and has the advantages of simple structure and easy processing.
Drawings
FIG. 1 is the overall structure diagram of the novel optical fiber weighing sensor in embodiment 1
FIG. 2 is a sectional view of the whole structure of the novel optical fiber weighing sensor in embodiment 1
FIG. 3 is a cover plate structure diagram of the novel optical fiber weighing sensor
FIG. 4 is a diagram of the weighing main body of the novel optical fiber weighing sensor in embodiment 1
Fig. 5 is a graph showing a relationship between a force load and a change in a center wavelength of optical characteristics of a fiber grating of a sensor, which is obtained through simulation measurement in embodiment 1 of the present invention.
FIG. 6 is the weighing body structure of example 2
FIG. 7 is a view showing the structure of the weighing main body in example 3
FIG. 8 is a view showing the structure of the weighing main body in example 4
In the drawings: 1. the optical fiber grating sensor comprises a cover plate, 11 spherical pillars, 12 positioning screw holes, 2 weighing main bodies, 21 wire outlet holes, 22 positioning holes, 23 wear-resistant pieces, 24 cantilever beam structures, 241 first cantilever beams, 242 second cantilever beams, 243 third cantilever beams, 244 fourth cantilever beams, 25 strain tanks, 26 optical fiber fixing grooves, 27 supporting outer walls, 28 rectangular notches, 3 optical fiber gratings, 31 lower optical fiber gratings and 32 upper optical fiber gratings.
Detailed Description
The invention will now be further described with reference to the following examples, and the accompanying drawings:
the technical scheme of the invention provides a novel optical fiber weighing sensor structure which comprises a cover plate, a weighing main body and an optical fiber grating.
The cover plate comprises a positioning screw hole and a spherical support, and the spherical support is fixed with the cover plate through structural fixing glue. The cover plate is placed on the weighing body through the spherical support.
The weighing main body comprises a supporting outer wall and cantilever beams, the supporting outer wall is annular, the four cantilever beams are located in four main directions on the same horizontal plane in the annular supporting outer wall and keep a certain height with the ground, and the specific height is larger than the vertical downward maximum displacement of the cantilever beams under the maximum load.
The cantilever beam comprises a strain groove, a positioning hole, an optical fiber fixing groove and a wear-resistant sheet.
The strain groove connects the cantilever beam structure with the supporting outer wall, the thickness of the cantilever beam is reduced by the part with the strain groove, strain is concentrated in the strain groove, and the rectangular part of the cantilever beam can generate larger deformation by the strain groove, so that larger strain is generated.
The positioning hole is positioned at the tail end of the cantilever beam rectangular structure, is coaxial with the positioning screw hole in the cover plate and is larger than the positioning screw hole in aperture, and the flat-head screw penetrates through the positioning hole in the weighing main body and is screwed at the positioning screw hole of the cover plate.
The wear-resistant sheet material is made of abrasive tool steel and is in contact with the spherical support, and the concave pits in the wear-resistant sheet play a role in fixing the spherical support.
The optical fiber fixing groove is positioned at the front end of the cantilever beam and used for fixing the optical fiber grating.
The fiber bragg grating is divided into an upper fiber bragg grating and a lower fiber bragg grating, the upper fiber bragg grating is fixed in the fiber fixing groove on the upper surface of the cantilever beam in a two-point sticking mode, the lower fiber bragg grating is fixed in the fiber fixing groove on the lower surface of the cantilever beam in a two-point sticking mode, and the upper fiber bragg grating and the lower fiber bragg grating are arranged in an orthogonal mode.
The fiber bragg grating comprises Fiber Bragg Gratings (FBGs), TFBG, LPFG and other optical fiber devices with a grid structure, and is characterized in that when broadband light passes through the fiber bragg grating, light waves carrying grid structure characteristic information can be reflected or transmitted, and the light waves have corresponding characteristic wavelengths; when the temperature of the fiber grating changes or axial strain is generated, the characteristic wavelength of the fiber grating will change.
The variation of the characteristic wavelength of the fiber bragg grating reflects the external force acting value of the cantilever beam component at the stress end.
The supporting outer wall is of an annular structure, four wire outlet holes are formed in the outer wall, and an included angle of 45 degrees is formed between the four wire outlet holes and the axial direction of the cantilever beam, so that optical fiber routing is facilitated.
The cover plate is placed on the cantilever beams through the spherical support, the fiber grating sensors are fixed in the fiber fixing grooves of the two opposite cantilever beams, namely, the two fiber gratings are orthogonally arranged on the 4 cantilever beams, and the cover plate and the weighing main body are fixed together through flat-head screws on the positioning holes. When the fiber grating hanging device works, the cover plate is stressed to press the cantilever beam arm, and the fiber grating can be transversely pulled when the cantilever beam arm descends, so that the wavelength of the fiber grating is changed. The cover plate is arranged above the weighing main body, h is determined according to the weighing range, and the cover plate is in contact with the weighing main body when the weighing range is exceeded, so that the ultralimit protection effect can be achieved.
Referring to fig. 1 to 4, a conventional optical fiber load cell in embodiment 1 of the present invention has the following structure: the cover plate 1 is of a disc-shaped structure, and the cover plate 1 is provided with a positioning screw hole 12 for mounting a corresponding fixing screw. 4 spherical pillars 11 are fixed in the groove of the cover plate 1 by structural adhesive, the pillars 11 are spherical, so that the stress direction of the weighing main body 2 can be kept on an axis passing through the spherical center of the spherical pillars 11, the influence of unbalance loading is reduced, and the selected material of the spherical pillars 11 is as wear-resistant as possible and has a smooth surface. The cover plate 1 is placed on the weighing main body 2 through four spherical supports 11, the radius of the weighing main body 2 is the same as that of the cover plate 1, the wear-resistant pieces 23 on the weighing main body 2 are in contact with the spherical supports 11, and the pits in the wear-resistant pieces 23 fix the spherical supports 11. It has 4 wire holes 21 to open on the support outer wall 27 of main part 2 of weighing, is 45 degrees contained angles with cantilever structure 24 in the horizontal plane, makes things convenient for optic fibre to walk the line, and cantilever structure 24 front end is close to the ring central point promptly and widens gradually for strip rectangle structure cantilever structure 24 end and be axe shape structure, has guaranteed the intensity of structure, and the arc portion makes structure surface stress distribution more even with the terminal tangency of rectangle structure, has better structural strength. The strain groove 25 is located on the upper surface and the lower surface of the tail end of the cantilever beam structure 24, the cantilever beam structure 24 is connected with the supporting outer wall 27, the whole strain groove 25 is a circular ring-shaped groove, the thickness of the cantilever beam structure 24 is reduced by the strain groove 25, strain is concentrated on the strain groove, the rectangular part of the cantilever beam 24 can generate larger deformation and further generate larger strain, the strain groove is wider, the thickness is thinner, the strain is easier to generate, and the sensitivity is improved. The upper fiber grating 32 is fixed in the fiber fixing grooves 26 on the upper surfaces of the second cantilever beam 242 and the fourth cantilever beam 244 by two-point adhesion, the lower fiber grating 31 is fixed in the fiber fixing grooves 26 on the lower surfaces of the first cantilever beam 241 and the third cantilever beam 243 by two-point adhesion, and the upper fiber grating 32 and the lower fiber grating 31 are orthogonally arranged. The weighing main body 2 is provided with 4 positioning holes 22 which are coaxial with the positioning screw holes 12 on the cover plate 1, and the diameter of the positioning holes 22 is larger than that of the positioning screw holes 12. The flat-head screw is screwed at the positioning screw hole 12 through the positioning hole 22 from bottom to top, and the flat head is clamped at the lower surface of the weighing main body 2. When the cover plate 1 sinks, the flat head screw sinks together with the cover plate 1. The function of fixing the weighing body 2 and the cover plate 1 is achieved without affecting the sinking of the cantilever structure 24, i.e. without affecting the sensitivity, i.e. the measurement. The measuring result is not influenced while the fixing effect is achieved.
When a heavy object with the gravity F is placed on the cover plate 1, the spherical pillar 11 presses down the cantilever structure 24, and transmits the force to the cantilever structure 24, and due to the existence of the thickness of the cantilever, when the cantilever structure 24 bends downward, the upper surface generates positive strain, and the lower surface generates negative strain, i.e., transverse displacement is generated. The strained channel portion reduces the thickness of the cantilevered beam structure 24, making it easier for the cantilevered beam structure to bend downward. The lateral displacement pulls the upper fiber grating 32 and the lower fiber grating 31 within the fiber-securing groove 26 to create axial strain.
The fiber bragg grating 3 comprises fiber bragg gratings, inclined fiber bragg gratings, long-period fiber bragg gratings and other fiber devices with a grid structure, and is characterized in that when broadband light passes through the fiber bragg grating 3, the broadband light can reflect or project light waves carrying characteristic information of the grid structure, the light waves have corresponding characteristic wavelengths, and when the temperature of the fiber bragg grating 3 changes or axial strain is generated, the characteristic wavelengths of the fiber bragg grating 3 change. The wavelength of the fiber grating 3 in the structure has a linear relationship with strain, i.e. the fiber grating is in a linear relationship with gravity F in a use range, and has a value of delta lambda = eta F, wherein eta is a mechanical sensitivity coefficient for converting gravity into transverse strain by the structure.
Fig. 5 is a graph showing the relationship between the external force F and the variation Δ λ of the characteristic wavelength of the fiber grating 3 according to the simulation measurement of the conventional sensor of this embodiment. As can be seen from fig. 6, the external force F has a good linear relationship with the characteristic wavelength variation Δ λ of the fiber grating 3, and the sensitivities are almost equal.
The cantilever structure 24 is lowered to cause the upper fiber grating 32 to be axially compressed to generate a negative strain, and the lower fiber grating 31 is axially stretched to generate a positive strain, which are substantially equal in magnitude. Let the weight measured by the fiber grating 32 be F a The weight measured by the lower fiber grating 31 is F b Then the measured weight is F a +F b The effect of the offset load can be prevented by orthogonally arranging the fiber gratings 3 and adopting such an algorithm.
Fig. 6 shows a structure of a weighing main body 2 of a conventional optical fiber weighing sensor in embodiment 2 of the invention, and a structure of a cover plate 1 in embodiment 2 is shown in fig. 3. The optical fiber load cell structure of example 2 was as follows except that the position of the strain gage was changed from the end of the cantilever beam to the middle.
The cover plate 1 is of a disc-shaped structure, and the cover plate 1 is provided with a positioning screw hole 12 for mounting a corresponding fixing screw. 4 spherical pillars 11 are fixed in the groove of the cover plate 1 through structural glue. The use of a spherical shape for the support 11 allows the load-bearing direction of the weighing body 2 to be maintained on an axis passing through the centre of the sphere of the spherical support 11, so as to reduce the effect of unbalance loading, the material chosen for the spherical support 11 being as wear-resistant as possible and having a smooth surface. The cover plate 1 is placed on the weighing main body 2 through four spherical supports 11, the radius of the weighing main body 2 is the same as that of the cover plate 1, the wear-resistant pieces 23 on the weighing main body 2 are in contact with the spherical supports 11, and the pits in the wear-resistant pieces 23 fix the spherical supports 11. It has 4 wire holes 21 to open on the support outer wall 27 of main part 2 of weighing, is 45 degrees contained angles with cantilever structure 24 in the horizontal plane, makes things convenient for optic fibre to walk the line, and cantilever structure 24 front end is close to the ring central point promptly and is strip rectangle structure, and cantilever structure 24 end widens gradually and is axe shape structure, and the tangent messenger structure surface stress distribution of arc portion and rectangle structure end is more even, has better structural strength. The cantilevered beams 241, 242, 243, 244 are separated by rectangular gaps 28. The strain groove 25 is positioned on the upper surface and the lower surface of the middle part of the cantilever beam structure 24, the whole strain groove 25 is a strip-shaped groove, the thickness of the cantilever beam structure 24 is reduced by the part with the strain groove 25, and strain is concentrated on the strain groove 25, so that the rectangular part of the cantilever beam 24 can generate larger transverse displacement. The upper fiber grating 32 is fixed in the fiber fixing grooves 26 on the upper surfaces of the second cantilever beam 242 and the fourth cantilever beam 244 in a two-point bonding manner, the lower fiber grating 31 is fixed in the fiber fixing grooves 26 on the lower surfaces of the first cantilever beam 241 and the third cantilever beam 243 in a two-point bonding manner, and the upper fiber grating 32 and the lower fiber grating 31 are orthogonally arranged. The weighing main body 2 is provided with 4 positioning holes 22 which are coaxial with the positioning screw holes 12 on the cover plate 1, and the diameter of each positioning hole 22 is larger than that of each positioning screw hole 12. The flat-head screw is screwed at the positioning screw hole 12 through the positioning hole 22 from bottom to top, and the flat head is clamped at the lower surface of the weighing main body 2. When the cover plate 1 sinks, the flat head screw sinks together with the cover plate 1. Therefore, the weighing device can play a role in fixing the weighing main body 2 and the cover plate 1, and cannot influence the strain generated by sinking of the cantilever beam structure 24, and the bottom of the cantilever beam structure 24 adopts an axe-shaped structure, so that the strength of the structure is ensured.
When a heavy object with the gravity F is placed on the cover plate 1, the spherical pillar 11 presses down the cantilever structure 24 to transmit the force to the cantilever structure 24, and the thickness of the cantilever structure 24 is reduced by the portion with the strain groove, so that the cantilever structure is easier to bend downwards. The cantilever structure 24 bends downward while the upper surface thereof generates positive strain, and the lower surface thereof generates negative strain, i.e. lateral displacement, which pulls the upper fiber grating 32 and the lower fiber grating 31 in the fiber fixing groove 26 to generate axial strain.
The fiber grating 3 comprises fiber bragg gratings, inclined fiber bragg gratings, long-period fiber gratings and other fiber devices with a grid structure, and is characterized in that when broadband light passes through the fiber grating 3, light waves carrying grid structure characteristic information can be reflected or projected, the light waves have corresponding characteristic wavelengths, and when the temperature of the fiber grating 3 changes or axial strain is generated, the characteristic wavelengths of the fiber grating 3 change. The wavelength of the fiber grating 3 in the structure has a linear relationship with strain, i.e. the fiber grating is in a linear relationship with gravity F in a use range, and has a value of delta lambda = eta F, wherein eta is a mechanical sensitivity coefficient for converting gravity into transverse strain by the structure.
Fig. 7 shows a weighing main body 2 structure of a conventional optical fiber weighing sensor in embodiment 3 of the invention, and fig. 3 shows a cover plate 1 structure of embodiment 3. The construction of the optical fiber load cell of embodiment 3 is as follows, except that the construction of the cantilever beam 24 is changed.
The cover plate 1 is of a disc-shaped structure, and the cover plate 1 is provided with a positioning screw hole 12 for mounting a corresponding fixing screw. 4 spherical pillars 11 are fixed in the groove of the cover plate 1 through structural glue. The use of a spherical shape for the support 11 allows the load-bearing direction of the weighing body 2 to be maintained on an axis passing through the centre of the sphere of the spherical support 11, so as to reduce the effect of unbalance loading, the material chosen for the spherical support 11 being as wear-resistant as possible and having a smooth surface. The cover plate 1 is placed on the weighing main body 2 through four spherical supports 11, the radius of the weighing main body 2 is the same as that of the cover plate 1, the wear-resistant pieces 23 on the weighing main body 2 are in contact with the spherical supports 11, and the pits in the wear-resistant pieces 23 fix the spherical supports 11. It has 4 wire holes 21 to open on the support outer wall 27 of main part 2 of weighing, is 45 degrees contained angles with cantilever beam structure 24 in the horizontal plane, makes things convenient for optic fibre to walk the line, and cantilever beam structure 24 front end is close to the ring central point promptly and is strip rectangle structure, and cantilever beam structure 24 is terminal to become the linear type structure through digging 4 square parts to the 3 kinds of fiber grating who make up with it have been changed. The remainder is the same as described in example 1. The strain groove 25 is positioned on the upper surface and the lower surface of the tail end of the cantilever beam structure 24, the cantilever beam structure 24 is connected with the supporting outer wall 27, the whole strain groove 25 is a circular ring-shaped groove, the thickness of the cantilever beam structure 24 is reduced by the strain groove 25, and strain is concentrated on the strain groove to enable the rectangular part of the cantilever beam 24 to generate larger vertical displacement. The upper fiber grating 32 is fixed in the fiber fixing grooves 26 on the upper surfaces of the second cantilever beam 242 and the fourth cantilever beam 244 in a two-point bonding manner, the lower fiber grating 31 is fixed in the fiber fixing grooves 26 on the lower surfaces of the first cantilever beam 241 and the third cantilever beam 243 in a two-point bonding manner, and the upper fiber grating 32 and the lower fiber grating 31 are orthogonally arranged. The weighing main body 2 is provided with 4 positioning holes 22 which are coaxial with the positioning screw holes 12 on the cover plate 1, and the diameter of each positioning hole 22 is larger than that of each positioning screw hole 12. The flat head screw is screwed at the position of the positioning screw hole 12 through the positioning hole 22 from bottom to top, and the flat head is clamped at the lower surface of the weighing main body 2. When the cover plate 1 sinks, the flat head screw sinks together with the cover plate 1. Therefore, the function of fixing the weighing body 2 and the cover plate 1 can be achieved, and the strain generated by the sinking of the cantilever beam structure 24 cannot be influenced.
When a heavy object with the gravity of F is placed on the cover plate 1, the spherical pillar 11 presses down the cantilever structure 24, so that the force is transmitted to the cantilever structure 24, and the cantilever structure 24 bends downward to generate vertical displacement while the thickness of the cantilever structure 24 is reduced by the strain groove, so that the cantilever structure is easier to bend downward. The upper surface of the cantilever structure 24 is positively strained while the lower surface is negatively strained, i.e. a lateral displacement is generated, and the lateral displacement pulls the upper fiber grating 32 and the lower fiber grating 31 in the fiber fixing groove 26 to generate an axial strain.
The fiber grating 3 comprises fiber bragg gratings, inclined fiber bragg gratings, long-period fiber gratings and other fiber devices with a grid structure, and is characterized in that when broadband light passes through the fiber grating 3, light waves carrying grid structure characteristic information can be reflected or projected, the light waves have corresponding characteristic wavelengths, and when the temperature of the fiber grating 3 changes or axial strain is generated, the characteristic wavelengths of the fiber grating 3 change. The wavelength of the fiber grating 3 in the structure has a linear relationship with strain, i.e. the fiber grating is in a linear relationship with gravity F in a use range, and has a value of delta lambda = eta F, wherein eta is a mechanical sensitivity coefficient for converting gravity into transverse strain by the structure.
Fig. 8 shows a structure of a weighing main body 2 of a conventional optical fiber weighing sensor in embodiment 4 of the invention, and a structure of a cover plate 1 in embodiment 4 is shown in fig. 3. The optical fiber load cell structure of embodiment 4 is as follows, except that the structure of the cantilever beam 24 is changed.
The cover plate 1 is of a disc-shaped structure, and the cover plate 1 is provided with a positioning screw hole 12 for mounting a corresponding fixing screw. 4 spherical pillars 11 are fixed in the groove of the cover plate 1 through structural glue. The use of a spherical shape for the support 11 allows the load-bearing direction of the weighing body 2 to be maintained on an axis passing through the centre of the sphere of the spherical support 11, so as to reduce the effect of unbalance loading, the material chosen for the spherical support 11 being as wear-resistant as possible and having a smooth surface. The cover plate 1 is placed on the weighing main body 2 through four spherical pillars 11, the radius of the weighing main body 2 is the same as that of the cover plate 1, the wear-resistant pieces 23 on the weighing main body 2 are in contact with the spherical pillars 11, and the pits on the wear-resistant pieces 23 play a role in fixing the spherical pillars 11. It has 4 wire holes 21 to open on the support outer wall 27 of main part 2 of weighing, is 45 degrees contained angles with cantilever beam structure 24 in the horizontal plane, makes things convenient for the optic fibre to walk the line. The cantilever structure 24 is formed by digging out 4 long rectangular parts in the middle of the weighing main body 2, the front end of the cantilever structure 24, namely the part close to the center of the circular ring, is of a strip-shaped rectangular structure, the type of the fiber grating 3 combined with the cantilever structure is changed, and the rest parts are the same as the described embodiment 1. The strain groove 25 is positioned on the upper surface and the lower surface of the tail end of the cantilever beam structure 24, the cantilever beam structure 24 is connected with the supporting outer wall 27, the whole strain groove 25 is a circular ring-shaped groove, the thickness of the cantilever beam structure 24 is reduced by the strain groove 25, and strain is concentrated on the strain groove to enable the rectangular part of the cantilever beam 24 to generate larger vertical displacement. The upper fiber grating 32 is fixed in the fiber fixing grooves 26 on the upper surfaces of the second cantilever beam 242 and the fourth cantilever beam 244 by two-point adhesion, the lower fiber grating 31 is fixed in the fiber fixing grooves 26 on the lower surfaces of the first cantilever beam 241 and the third cantilever beam 243 by two-point adhesion, and the upper fiber grating 32 and the lower fiber grating 31 are orthogonally arranged. The weighing main body 2 is provided with 4 positioning holes 22 which are coaxial with the positioning screw holes 12 on the cover plate 1, and the diameter of each positioning hole 22 is larger than that of each positioning screw hole 12. The flat-head screw is screwed at the positioning screw hole 12 through the positioning hole 22 from bottom to top, and the flat head is clamped at the lower surface of the weighing main body 2. When the cover plate 1 sinks, the flat head screw sinks together with the cover plate 1. Thus, the weighing body 2 and the cover plate 1 can be fixed, and the strain generated by the sinking of the cantilever beam structure 24 can not be influenced.
When a heavy object with the gravity F is placed on the cover plate 1, the spherical pillar 11 presses down the cantilever structure 24 to transmit the force to the cantilever structure 24, and the part of the cantilever structure 24 bent downward and provided with the strain groove reduces the thickness of the cantilever structure 24, so that the cantilever structure is easier to bend downward. The cantilever structure 24 bends downward while the upper surface thereof generates positive strain, and the lower surface thereof generates negative strain, i.e. lateral displacement, which pulls the upper fiber grating 32 and the lower fiber grating 31 in the fiber fixing groove 26 to generate axial strain.
The fiber bragg grating 3 comprises fiber bragg gratings, inclined fiber bragg gratings, long-period fiber bragg gratings and other fiber devices with a grid structure, and is characterized in that when broadband light passes through the fiber bragg grating 3, the broadband light can reflect or project light waves carrying characteristic information of the grid structure, the light waves have corresponding characteristic wavelengths, and when the temperature of the fiber bragg grating 3 changes or axial strain is generated, the characteristic wavelengths of the fiber bragg grating 3 change. The wavelength of the fiber grating 3 in the structure has a linear relationship with strain, i.e. the fiber grating is in a linear relationship with gravity F in a use range, and has a value of delta lambda = eta F, wherein eta is a mechanical sensitivity coefficient for converting gravity into transverse strain by the structure.
Claims (9)
1. An optical fiber weighing sensor comprises a cover plate (1), a weighing main body (2) and an optical fiber grating (3); the fiber bragg grating is characterized in that the fiber bragg grating (3) comprises a lower fiber bragg grating (31) and an upper fiber bragg grating (32); the weighing body (2) comprises a supporting outer wall (27), a cantilever beam structure (24) and a strain tank (25); the cantilever beam structure (24) is arranged in the supporting outer wall (27), the cantilever beam structure (24) is provided with a strain groove (25), the cantilever beam structure (24) is divided into four cantilever beams which are centrosymmetric, the four cantilever beams are respectively positioned in the supporting outer wall (27) in four main directions on the same horizontal plane, and the height of the four cantilever beams is greater than the maximum displacement of the cantilever beam structure (24) under the maximum load in the vertical downward direction; the lower fiber bragg grating (31) and the upper fiber bragg grating (32) are orthogonally arranged at the center of the cantilever beam structure, and the cover plate (1) is connected with the center of the weighing main body (2) through four spherical pillars (11); when a heavy object with the gravity of F is placed on the cover plate (1), the cantilever beam structure (24) is pressed downwards, the force is transmitted to the cantilever beam structure (24), the cantilever beam structure (24) bends downwards to generate vertical displacement and simultaneously can be slightly bent to generate transverse displacement, the transverse displacement can pull the upper fiber bragg grating (32) and the lower fiber bragg grating (31) to generate axial strain, and the weight measurement is realized; the fiber bragg grating is arranged at the tail end of a cantilever beam structure (24) of the weighing main body (2), and the upper fiber bragg grating (32) is fixed in fiber fixing grooves on the upper surfaces of the second cantilever beam (242) and the fourth cantilever beam (244) in a two-point sticking mode; the lower fiber grating (31) is fixed in the fiber fixing grooves on the lower surfaces of the first cantilever beam (241) and the third cantilever beam (243) in a two-point adhesion mode; the upper fiber grating (32) and the lower fiber grating (31) are orthogonally arranged; when a heavy object with the gravity of F is placed on the cover plate (1), the cover plate (1) is stressed to press the cantilever structure (24), when the tail end of the cantilever structure (24) descends, a microbend can be generated to transversely pull the fiber grating (3), so that the wavelength of the fiber grating (3) is changed, the wavelength of the fiber grating (3) is in a linear relation with the strain, namely the fiber grating is in a linear relation with the gravity F in a use range, and delta lambda = eta F is provided, wherein eta is a mechanical sensitivity coefficient for converting the gravity into the transverse strain by the structure.
2. The fiber optic load cell of claim 1, wherein: the front end of the cantilever beam structure, namely the part close to the center of the circular ring, is of a strip-shaped rectangular structure.
3. The optical fiber load cell of claim 1 or 2, wherein: the tail end of the cantilever beam structure (24) is in a linear structure by digging 4 square parts.
4. The optical fiber load cell of claim 1, wherein: the strip-shaped rectangular structure of the cantilever beam structure (24) is positioned in a long rectangular groove in the middle of the weighing main body (2).
5. The fiber optic load cell of claim 1, wherein: the strain groove (25) is a circular groove and is positioned on the upper surface and the lower surface of the tail end of the cantilever beam structure (24) to connect the cantilever beam structure (24) and the support outer wall (27) into a whole.
6. The fiber optic load cell of claim 1 or 5, wherein: the strain groove (25) is a circular groove strip-shaped groove.
7. The fiber optic load cell of claim 1 or 2, wherein: the cover plate (1) and the weighing main body (2) are both circular and have the same radius.
8. The fiber optic load cell of claim 1, wherein: the positioning hole (22) on the cover plate (1) is coaxial with the positioning screw hole (12) on the weighing main body (2), and the diameter of the positioning hole is larger than that of the positioning screw hole (12); when the cover plate (1) sinks, the flat-head screw sinks together with the cover plate (1); the cantilever beam structure (24) can not be influenced by sinking when the fixed weighing main body (2) and the cover plate (1) are used, namely, the sensitivity can not be influenced by measurement, and the measuring result can not be influenced when the fixed weighing main body and the cover plate are used for fixing.
9. The optical fiber load cell of claim 1 or 8, wherein: the optical fiber device with the grating (3) of the optical fiber having the grid structure includes but is not limited to: fiber bragg gratings, tilted fiber bragg gratings, or long period fiber gratings.
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