Event estimation system

Abstract

To improve the capability of event estimation based on an optical signal received from an optical fiber.SOLUTION: An event estimation system for estimating an event in a predetermined observation target includes an optical fiber-carrying sensor including a long core material and an optical fiber extending in a longitudinal direction of the core material, the optical fiber being provided so as to be located inside or on a circumferential surface of the core material and being provided on the observation target, and an event estimation device configured to estimate the event on the basis of an optical signal output from the optical fiber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an event estimation system. [Background technology]

[0002] A technology is known that detects breakage of a sewer pipe by detecting backscattered light generated inside an optical fiber that is arranged axially in a portion of a sewer pipe having a sewer flow path through which sewage flows, which is located above the normal water level (see, for example, patent document). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-186911 Summary of the Invention [Problem to be solved by the invention]

[0004] When estimating a predetermined event based on an optical signal received from an optical fiber, it is desirable to improve the capability of estimating the event.

[0005] In consideration of the above-mentioned problems, an object of the present invention is to improve the capability of event estimation based on an optical signal received from an optical fiber. [Means for solving the problem]

[0006] (1) One aspect of the present invention that solves the above-mentioned problems is an event estimation system that estimates an event in a specified object of observation, which has a long core material and an optical fiber extending in the longitudinal direction of the core material, and the optical fiber is attached so that it is located inside or on the circumferential surface of the core material, and is equipped with an optical fiber-carrying sensor that is provided on the object of observation, and an event estimation device that estimates the event based on an optical signal output from the optical fiber.

[0007] (2) One aspect of the present invention is the event estimation system described in (1), wherein the object of observation is a structure made of ground soil, and the event may be an event based on strain occurring in the optical fiber.

[0008] (3) One aspect of the present invention is the event estimation system described in (2), in which the optical fiber sensor is buried in the structure as backfill soil, and the core material is a resin pipe having an outer diameter of 35 to 50 mm and a thickness of 3 to 8 mm, and may be JIS K7161 and have a rigidity modulus of 750 MPa or more and 2500 MPa or less.

[0009] (4) One aspect of the present invention is the event estimation system according to (3), wherein the backfill soil may have an N value of 5 or more and 15 or less.

[0010] (5) One aspect of the present invention is the event estimation system described in (2), wherein the optical fiber sensor is embedded in the structure consisting of the road subgrade and roadbed, and the core material is a resin pipe having an outer diameter of 50 to 75 mm and a thickness of 6 to 10 mm, and conforms to JIS K7161 and a rigidity modulus of 1000 MPa or more and 4500 MPa or less.

[0011] (6) One aspect of the present invention is the event estimation system described in (5), wherein the structure consisting of the road subgrade and roadbed may have an N value of 8 or more and 20 or less, or a bearing capacity coefficient K of 50 MPa / m or more.

[0012] (7) One aspect of the present invention is the event estimation system described in (2), wherein the optical fiber sensor is embedded in the structure as fill soil, and the core material is a resin pipe having an outer diameter of 23 mm to 37 mm and a thickness of 2.0 to 5.0 mm, and conforms to JIS K7161 and may have a modulus of rigidity of 100 MPa or more and 1500 MPa or less.

[0013] (8) One aspect of the present invention is the event estimation system described in (7), wherein the fill soil may have an N value of 2 or more and 10 or less, or 85% or more of the maximum dry density.

[0014] (9) One aspect of the present invention is an event estimation system described in any one of (1) to (8), wherein the core material may have a shear wave velocity that differs by 100 m / s or less from the shear wave velocity of the structure being observed, as measured by JGS 0544-2020, a method for measuring soil shear wave velocity using the bender element method.

[0015] (10) One aspect of the present invention is an event estimation system according to any one of (1) to (9), wherein the optical fiber-carrying sensor is JIS K7161 and has a modulus of rigidity of 100 MPa or more and 4500 or less.

[0016] (11) One aspect of the present invention is an event inference system according to any one of (1) to (10), wherein the optical fiber-carrying sensor has two or more optical fibers, and the event inference device outputs two or more detection results obtained by detecting at least one of vibration and sound as a detection target, corresponding to each optical signal of the two or more optical fibers, and makes an inference regarding the specified event based on the two or more detection results. [Effects of the Invention]

[0017] According to the present invention, it is possible to obtain an effect that the capability of inferring an event based on an optical signal received from an optical fiber is improved. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of an event estimation system according to an embodiment of the present invention. [Figure 2] 1 is a diagram illustrating an example of the configuration of an optical fiber sensor according to an embodiment of the present invention. [Figure 3] FIG. 2 is a diagram showing an example of shear wave velocity data for each soil type in this embodiment. [Figure 4] 10A and 10B are diagrams illustrating another example of the configuration of the optical fiber sensor according to the present embodiment. [Figure 5]FIG. 2 is a diagram illustrating an example of a functional configuration of an event inference device according to the present embodiment. [Figure 6] 10 is a flowchart illustrating an example of a processing procedure executed by the event estimation device according to the present embodiment in response to event estimation. [Figure 7] FIG. 1 is a diagram illustrating a specific example of an event estimation system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] <Embodiment> FIG. 1 shows an example of the overall configuration of an event estimation system according to this embodiment. The event estimation system shown in the figure includes an optical fiber sensor 20 and an event estimation device 300.

[0020] The optical fiber-carrying sensor 20 is arranged in a predetermined manner in the event estimation environment ENV. The event estimation environment ENV is an environment in which an event to be estimated by the event estimation system occurs. The optical fiber-carrying sensor 20 is a sensor that detects vibrations and sounds generated in response to the event to be estimated as changes in an optical signal. The optical fiber-carrying sensor 20 arranged in the event estimation environment ENV is connected to the event estimation device 300 via the end of the optical fiber.

[0021] The event estimation device 300 is a device that estimates an event to be estimated by using an optical signal input from the optical fiber sensor 20. In the figure, the event estimation device 300 is shown as being configured as a single device, but it may also be configured as, for example, a plurality of devices in which predetermined functions are distributed.

[0022] An example of the configuration of the optical fiber held sensor 20 of this embodiment will be described with reference to Fig. 2. The optical fiber held sensor 20 shown in the figure has a cylindrical resin tube 21 and an optical fiber 22 extending in the axial direction (pipe axis) O1 of the resin tube 21 within a cylindrical wall 21A of the resin tube 21. In this embodiment, the resin tube 21 is a core material.

[0023] A plurality of optical fibers 22 may be provided inside the tube wall 21A. When bending displacement is detected using the optical fibers 22, at least two are required, and when twisting or flattening displacement is detected, four or more are preferred. In order to ensure the mechanical strength of the resin tube 21, the number of optical fibers 22 is preferably 20 or less, and more preferably 8 or less. The optical fiber 22 is preferably located within 25% of the thickness of the cylindrical wall 21A from the center bisecting position toward the surface, thereby preventing the optical fiber 22 from being exposed to the outside of the resin tube 21 and being damaged.

[0024] As shown in FIG. 2, the four optical fibers 22 are positioned at 90° intervals around the tube axis 2 in a cross section perpendicular to the axis O1. Furthermore, the four optical fibers 22 are arranged in a spiral shape centered on the axis O1. Therefore, in a side view, the optical fibers 22 are inclined at an angle greater than 0 degrees and less than 90 degrees relative to the axis O1 in the circumferential direction of the resin tube 21. The spiral pitch P of the optical fibers 22 is preferably 50 mm or more and 2000 mm or less, more preferably 100 mm or more and 500 mm or less, and even more preferably 300 mm or more and 400 mm or less. If the spiral pitch P is equal to or greater than the above upper limit, the measurement accuracy can be improved without excessively increasing the length of the optical fibers 22. If the spiral pitch P is equal to or less than the above upper limit, the measurement accuracy can be further improved.

[0025] The optical fiber held sensor 20 of this embodiment has a folded portion 222 and a folded portion 223 that protrude from one end edge of the resin tube 21 in the longitudinal direction (direction of the axis O1). The folded portion 222 is a member in which the optical fiber 22a and the optical fiber 22b protruding from one longitudinal end edge of the resin pipe 21 are connected to each other outside the resin pipe 21 (in the direction of the axis O1 away from the resin pipe 21). The optical fiber 22a and the optical fiber 22b are adjacent to each other in the circumferential direction of the resin pipe 21. The folded portion 223 is a member in which the optical fiber 22c and the optical fiber 22d protruding from one end edge of the resin pipe 21 are connected to each other outside the resin pipe 21. The optical fiber 22c and the optical fiber 22d are adjacent to each other in the circumferential direction of the resin pipe 21. That is, in this embodiment, the optical fiber 22 protrudes from the resin tube 21 at one end in the direction of the axis O1, and has folded portions 222, 223 outside the resin tube 21 in which an arbitrary optical fiber 22 is connected to another arbitrary optical fiber 22 adjacent to the arbitrary optical fiber 22 in the circumferential direction of the resin tube 21, which is the core material.

[0026] The optical fiber sensor 20 has a folded portion 229 that protrudes from the other end edge of the resin tube 21 in the longitudinal direction. The folded portion 229 is a member in which optical fibers 22g and 22h protruding from the other longitudinal edge of the resin wall portion 24 are connected to the outside of the resin tube 21 (in the direction away from the resin tube 21 in the direction of the axis O1). The optical fibers 22g and 22h are adjacent to each other in the circumferential direction of the resin tube 21. The optical fibers 22g and 22h protrude from the other longitudinal edge of the resin tube 21. The optical fiber end 22e and the optical fiber end 22f do not form a folded portion. The optical fiber end 22e is connected to the event estimation device 300.

[0027] In this embodiment, one optical fiber is folded back to form folded portions 222, 223, and 229, and optical fiber ends 22e and 22f are protruded from the other edge, thereby positioning four optical fibers 22 within the resin tube 21.

[0028] As described below, the thickness of the cylindrical wall 21A and the outer diameter R of the cylindrical wall 11A may be determined according to the shear wave velocity and rigidity of the resin pipe 21. As an example, the outer diameter R is preferably set in the range of 20 mm to 60 mm.

[0029] The cylindrical wall 21A may be made of, for example, a resin composition containing the resin (A), ceramic, or the like. Examples of the resin (A) include polyolefin resins, polyvinyl chloride resins, acrylamide-butadiene-styrene resins (ABS), polyamide resins, and silicone resins. Examples of polyolefin resins include polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, and ethylene-α-olefin copolymer. Examples of vinyl chloride resins include chlorinated vinyl chloride and propylene vinyl chloride copolymer. An example of the polyamide resin is so-called nylon 66. These resins (A) may be used alone or in combination of two or more.

[0030] The optical fiber 22 has a core, a cladding, and a coating layer, and generates scattered light such as Brillouin scattering or Raman scattering due to distortion or temperature of the core when discontinuous pump light such as laser light is incident on the core. An optical fiber composed of a core and a cladding can be suitably used as this type of optical fiber 22. Examples of materials for the core and cladding include plastic and quartz glass.

[0031] Examples of optical fibers include an optical fiber strand having a primary coating around the cladding, an optical fiber core having a secondary coating around the primary coating, and an optical fiber cord having a reinforcing material around the secondary coating and an outer jacket covering the reinforcing material.

[0032] Examples of materials for the primary coating include ultraviolet curable resin, polyamide, fluororesin, polyimide, and polyethylene. Examples of materials for the secondary coating include flame-retardant polyester elastomers and polyimides. Examples of the material for the reinforcing material include glass fiber, carbon fiber, and aramid fiber. Examples of materials for the outer jacket include flame-retardant polyolefins such as flame-retardant polyethylene, flame-retardant cross-linked polyolefins such as flame-retardant cross-linked polyethylene, and heat-resistant vinyl.

[0033] The type of optical fiber 22 is not particularly limited and can be selected depending on the detection target (such as strain, vibration, or sound), the detection method, the type of scattered light used during detection, etc. For example, at least one type of optical fiber selected from the group consisting of a single-mode optical fiber, a multi-mode optical fiber, and a polarization-maintaining optical fiber can be used.

[0034] When a plurality of optical fibers 22 are arranged in the optical fiber-carrying sensor 20, the plurality of optical fibers 22 may be the same type of optical fiber or different types of optical fibers.

[0035] When detecting vibrations or sounds according to this embodiment, Brillouin scattered light, Rayleigh scattered light, or the like can be preferably used as scattered light, and a single-mode optical fiber is preferably used because a sharp peak can be obtained. Alternatively, Raman scattered light or the like can be used as scattered light, or a multi-mode optical fiber can be used.

[0036] The outer diameter of the optical fiber 22 is preferably 125 to 2000 μm, more preferably 150 to 1000 μm. When the outer diameter of the optical fiber 22 is equal to or greater than the above lower limit, the strength can be further increased.

[0037] In this embodiment, the optical fiber sensor 20 is buried under a road RD (an example of an observation target). That is, the optical fiber sensor 20 is installed with its periphery in contact with a substance such as soil. The resin pipe 21, which is the core material of the optical fiber sensor 20 installed in this state, is configured to have a shear wave velocity equivalent to that of the surrounding objects. By making the shear wave velocity of the resin tube 21 equivalent to the shear wave velocity of the material surrounding the optical fiber-carrying sensor 20, it becomes possible to ignore the peculiar vibration transmission in the resin tube 21 when transmitting vibrations from the material surrounding the optical fiber-carrying sensor 20 (hereinafter also referred to as "surrounding material") to the optical fiber 22, thereby improving detection accuracy.

[0038] In this embodiment, the shear wave velocity of the resin pipe 21 does not need to strictly match the shear wave velocity of the surrounding material. In other words, the shear wave velocity of the resin pipe 21 may have an error within a range that allows the transmission of anomalous vibrations in the resin pipe 21 to be negligible, based on the shear wave velocity of the surrounding material. In this way, by providing a certain tolerance range for the shear wave velocity to be set in the resin pipe 21, even in cases where it is difficult to match the shear wave velocity to that of the surrounding material due to constraints such as the material or size of the resin pipe 21, the resin pipe 21 can be used as a resin pipe having a shear wave velocity equivalent to that of the surrounding material.

[0039] Specifically, in this embodiment, the resin pipe 21 is made to have a shear wave velocity equivalent to that of the soil around the optical fiber sensor 20 buried under the road RD. The procedure for setting the shear wave velocity of the resin pipe 21 is to first identify the shear wave velocity of the material surrounding the optical fiber held sensor 20. Then, taking into consideration conditions such as the material and size of the resin pipe 21, a value may be determined that falls within a certain range of error using the identified shear wave velocity of the material as a reference.

[0040] Furthermore, as described above, the shear wave velocity of the surrounding material, which serves as a reference for determining the shear wave velocity of the resin pipe 21, may be determined by actually measuring it. In this case, data on shear wave velocity for each soil type that has been obtained as actual results from previous measurements may be used.

[0041] Figure 3 shows an example of shear wave velocity data for each soil type. The shear wave velocity data in this figure shows the shear wave velocity Vs corresponding to the N value. In the shear wave velocity data in this figure, lines L1 to L4 show shear wave velocity data for four different soil types. Specifically, line L1 shows shear wave velocity data for the upper alluvial sand layer, line L2 shows shear wave velocity data for the upper alluvial clay layer, line L3 shows shear wave velocity data for the diluvial sandy soil layer, and line L4 shows shear wave velocity data for the diluvial clay layer. For example, to determine the shear wave velocity of the resin pipe 21, the person in charge determines the soil quality and measures the N value at the location where the optical fiber sensor 20 is buried. By comparing the shear wave velocity data of the determined soil quality with the measured N value, the person in charge can identify the shear wave velocity corresponding to the soil quality of the surrounding material.

[0042] For example, the shear wave velocity of the resin pipe 21 can be set by the physical properties of the resin pipe 21, such as the mass, Young's modulus, and Poisson's ratio. For example, the relationship between shear wave velocity Vs, mass ρ, Young's modulus E, and Poisson's ratio ν is expressed by the following equation 1.

[0043]

number

[0044] The person in charge may select the material of the resin pipe 21, determine the outer diameter R of the resin pipe 21, the thickness of the cylindrical wall 21A of the resin pipe 21, etc. so as to obtain a combination of mass, Young's modulus, and Poisson's ratio that will cause the resin pipe 21 to have the desired shear wave velocity.

[0045] In this embodiment, it is preferable that the rigidity of the resin tube 21, which is the core material of the optical fiber sensor 20, is small. The small rigidity of the resin tube 21 makes it possible to increase the amplitude of the transmitted vibration, thereby improving the detection sensitivity. As a specific example, it is preferable that the resin pipe 21 has a Young's modulus of about 100 to 100 MPa.

[0046] From the above explanation, it can be said that in this embodiment, it is preferable that the resin pipe 21 has low rigidity and a shear wave velocity equivalent to that of the surrounding material. Therefore, the procedure for determining the physical properties (mass, Young's modulus, Poisson's ratio) of the resin pipe 21 may be to first determine the Young's modulus in the range of 100 to 100 MPa, and then determine the mass and Poisson's ratio that will allow the resin pipe 21 to have a shear wave velocity equivalent to that of the surrounding material.

[0047] A method for manufacturing the optical fiber sensor of this embodiment will be described. A polyolefin resin composition containing only the above resin (A) and an optical fiber 22 are supplied to a mold, and an extrusion molded body in which the resin tube and the optical fiber 22 are integrally molded is taken up using a take-up machine installed downstream of the mold, thereby obtaining the optical fiber-supported sensor 20 shown in Figure 2.

[0048] 2, the optical fiber is positioned so as to be attached to the inside of the cylindrical wall of a cylindrical resin pipe. However, the present invention is not limited to this, and the optical fiber may be positioned so as to be attached to the outside of the cylindrical wall (i.e., the outer circumferential surface of the resin pipe). In the above-described embodiment, the core material is a cylindrical resin tube, but the present invention is not limited to this. The core material may not be cylindrical (i.e., hollow) but may be solid. When the core material is solid, the optical fiber may be located within the core material or may be located on the outer periphery of the core material.

[0049] 4, a configuration example of an optical fiber sensor 20A in which the core material is solid and the optical fiber is located on the outer periphery of the core material will be described. The optical fiber sensor 20A can be used in place of the optical fiber sensor 20 in the event inference system of this embodiment. Alternatively, when the event inference system of this embodiment is provided with multiple optical fiber sensors, the optical fiber sensor 20 and the optical fiber sensor 20A may be mixed among the multiple optical fiber sensors. 4, the same parts as those in FIG. 2 are denoted by the same reference numerals and the description thereof will be omitted, and the differences from the optical fiber sensor 20 in FIG. 1 will be mainly described.

[0050] The optical fiber sensor 20A has a long rod-shaped core material 121 and an optical fiber 22 located on the outer circumferential surface of the core material 121. The optical fiber 22 forms a spiral around an axis O2. The spiral pitch P2 of the spiral formed by the optical fiber 22 is the same as the spiral pitch P.

[0051] The core material 121 is a straight rod-shaped solid member. By making the core material 121 a solid member, the rigidity of the optical fiber held sensor 20A can be further increased, and the displacement detection accuracy can be further improved. The outer diameter R2 of the core material 121 is the same as the outer diameter R of the resin pipe 21. Examples of materials for the core 121 include a resin composition containing the resin (B), ceramic, metal, glass, and the like. Resin (B) is the same as resin (A).

[0052] The optical fiber 22 is fixed in close contact with the outer circumferential surface of the core material 121. Examples of methods for fixing the optical fiber 22 to the outer circumferential surface of the core material 121 include adhesion, fusion, and tape attachment.

[0053] The rigidity of the core material 121 may be the same as that of the resin pipe 21 .

[0054] The optical fiber sensor 20A can be manufactured, for example, by winding the optical fiber 22 around the core material 121 and bonding it with an adhesive.

[0055] As a specific example, the core material (resin pipe 21, core material 121) in this embodiment may have a shear wave velocity that differs by 100 m / s or less from the shear wave velocity of the structure being observed, as measured by the soil shear wave velocity measurement method using the bender element method in JGS 0544-2020. The shear wave velocity of such a core material may be determined based on tolerances associated with ground conditions, etc. The optical fiber sensors 20 and 20A may be made to comply with JIS K7161 and have a modulus of rigidity of 100 MPa or more and 4500 or less.

[0056] Furthermore, the specifications of the optical fiber sensor 20 may be determined so as to suit the structure to be observed in which the optical fiber sensor 20 is buried. Below, examples will be given of specifications of the optical fiber sensor 20 that suit the cases where the structure to be observed is backfill soil (an example of ground soil), a structure consisting of a road subgrade and roadbed, and embankment soil (an example of ground soil). The order of ground strength, from strongest to weakest, is the structure consisting of a road subgrade and roadbed, backfill soil, and embankment degree. The embankment degree includes, for example, embankments, general embankments, etc.

[0057] First, a case where the structure to be observed is backfill soil will be described. In the case of backfill soil, the optical fiber sensor 20 may be buried when backfilling a trench or hole that has been excavated, for example. When the optical fiber sensor 20 is buried in backfill soil, the core material (resin pipe 21, core material 121) is preferably made of resin with an outer diameter of 35 to 50 mm and a thickness of 3 to 8 mm, and has a Young's modulus (rigidity modulus, tensile elastic modulus) of 750 MPa to 2500 MPa in accordance with JIS K7161. In addition, with these specifications, it is preferable that the backfill soil has an N value of 5 to 15.

[0058] Furthermore, when the optical fiber sensor 20 is embedded in a structure consisting of a road subgrade and roadbed, it is preferable that the core material (resin pipe 21, core material 121) is made of resin with an outer diameter of 50 to 75 mm and a thickness of 6 to 10 mm, and conforms to JIS K7161 and has a modulus of rigidity of 1000 MPa to 4500 MPa. Furthermore, in the case of such specifications, it is preferable that the structure consisting of a road subgrade and roadbed has an N value of 8 to 20, or a bearing capacity coefficient K of 50 MPa / m or more.

[0059] Furthermore, when the optical fiber sensor 20 is buried in the banking soil, the core material (resin pipe 21, core material 121) is preferably a resin pipe with an outer diameter of 23 mm to 37 mm and a thickness of 2.0 to 5.0 mm, and has a rigidity of 100 MPa to 1500 MPa in accordance with JIS K7161. Furthermore, in the case of such specifications, it is preferable that the banking soil has an N value of 2 to 10, or 85% or more of the maximum dry density.

[0060] An example of the configuration of the event inference device 300 of this embodiment will be described with reference to FIG. In the following description, an example will be given in which the event estimation device 300 is connected to one optical fiber sensor 20. Also, an example will be given in which one optical fiber sensor 20 has four optical fibers 22 each individually arranged in a spiral shape.

[0061] The event inference device 300 in the figure includes a detection unit 301, an inference unit 302, and a storage unit 303. The functions of the event inference device 300 in the figure may be realized by executing a CPU (Central Processing Unit) program included in the event inference device 300 as hardware.

[0062] The detection unit 301 detects a predetermined detection item used for event estimation by utilizing an optical signal received from the optical fiber 22. The detection unit 301 in the figure is connected to optical fiber ends 22e (22e-1, 22e-2, 22e-3, 22e-4) of each of the four optical fibers 22. In other words, the detection unit 301 is connected to each of the four optical fibers 22 provided in one optical fiber-held sensor 20.

[0063] The detecting unit 301 inputs pulsed light from the optical fiber end 22e into each of the four connected optical fibers 22. Scattered light generated as the input pulsed light is transmitted through the optical fiber 22 returns to the input side as return light via the same optical fiber 22. The detecting unit 301 receives the return light as an optical signal.

[0064] For example, in the event estimation environment ENV, vibrations and sounds occur in response to the occurrence of an event to be estimated. The occurrence of such vibrations and sounds affects the scattered light transmitted through the optical fiber 22 via the ground or air, and also affects the return light received by the detection unit 301. In other words, the return light changes in response to the vibrations and sounds occurring in the event estimation environment ENV.

[0065] The detection unit 301 detects vibrations and sounds occurring in the event estimation environment ENV based on changes in the received return light. Specifically, the detection unit 301 may detect amplitude patterns, frequency patterns, etc. of the vibrations and sounds.

[0066] The detection unit 301 may perform the above-described vibration and sound detection individually for each of the four optical signals received from the four optical fibers 22. In this case, the detection unit 301 obtains four detection results corresponding to the same detection target. The detection unit 301 outputs the four detection results DT (DT-1, DT-2, DT-3, DT-4) to the estimation unit 302. The detection unit 301 may store the detection result DT in the storage unit 303.

[0067] The estimation unit 302 estimates the event to be estimated based on the detection result DT. The estimation unit 302 in the figure may estimate the event to be estimated using four detection results DT. In this case, the estimation unit 302 may estimate the event using a result (integrated detection result) obtained by integrating the four detection results DT (DT-1, DT-2, DT-3, DT-4). Alternatively, the estimation unit 302 may estimate the event using one or more detection results DT that are determined to have high reliability among the four detection results DT (DT-1, DT-2, DT-3, DT-4).

[0068] The estimation unit 302 may use a trained model for event estimation. Such a trained model is constructed, for example, by having a learning device perform learning using training data that associates detection results with events that occur in response to the detection results.

[0069] The estimation unit 302 may store the estimation result for the event (event estimation result) in the storage unit 303. Furthermore, the estimation unit 302 may output the event estimation result, for example, to an external display or printer. Furthermore, data obtained by the estimation unit 302 in association with the event estimation result and the corresponding detection result DT may be used as training data for constructing a trained model of the estimation unit 302.

[0070] An example of a processing procedure executed by the event estimation device 300 in response to event estimation will be described with reference to the flowchart of FIG. Step S100 : In the event estimation device 300 , the detection unit 301 receives an optical signal from each of the optical fibers 22 .

[0071] Step S102: The detection unit 301 detects a detection item such as vibration or sound using the optical signal received in step S100. The detection unit 301 outputs the detection result DT obtained by detecting the detection item to the estimation unit 302.

[0072] Step S104 : The estimation unit 302 acquires the detection result output by the detection unit 301 .

[0073] Step S106: The estimation unit 302 performs estimation regarding the phenomenon to be estimated using the detection result acquired in step S104. The estimation unit 302 may store the estimation result in the storage unit 303 as described above, or may output the estimation result to the outside.

[0074] In the event inference system of this embodiment configured as described above, an event is inferred based on an optical signal from an optical fiber 22 arranged in the longitudinal direction of a core material such as a resin pipe 21. Because a core material such as a resin pipe 21 has a certain degree of rigidity, it is possible to transmit external energy such as vibrations and sounds to the optical fiber 22 with low loss. As a result, the detection accuracy of the detection items in the event inference device 300 is improved, and the accuracy of event inference is also improved. In other words, the configuration of this embodiment improves the ability to infer events.

[0075] Moreover, in this embodiment, the optical fiber 22 is spirally arranged around the axis O1 in the optical fiber sensor 20. The optical fiber 22 may be arranged linearly along the axis O1 in the cylindrical wall 21A, for example. However, by arranging the optical fiber 22 spirally as in this embodiment, the length of the optical fiber present per unit length of the resin pipe 21 can be increased compared to when the optical fiber 22 is arranged linearly. This makes it possible to increase the spatial resolution in measurement, thereby improving the detection accuracy by the detection unit 301 and the estimation accuracy by the estimation unit 302.

[0076] Furthermore, since the optical fiber 22 is provided in a spiral shape, the optical fiber 22 is arranged around the circular cylindrical wall 21A, and therefore it is possible to perform sensing with uniform sensitivity to vibrations, sounds, and the like coming from all directions (360° directions) around the axis O1, causing changes in the returned light. This makes it possible to obtain a large amount of information about the items detected by the detection unit 301, and to obtain good event estimation results.

[0077] Furthermore, the trained model used by the estimation unit 302 for event estimation can be constructed using training data that associates patterns of detection results output by the detection unit 301 with events that occur corresponding to the patterns of the detection results. In this case, estimation accuracy can be improved by using the patterns of detection results in the training data that the detection unit 301 detects using the optical signal obtained by the optical fiber-held sensor 20 of this embodiment in which the optical fiber 22 is spirally arranged.

[0078] Furthermore, by improving estimation accuracy as described above and enabling sensing in all directions, it becomes possible to relax or eliminate restrictions on what can be detected and what events can be estimated, thereby improving event estimation capabilities in this respect as well.

[0079] A specific example of the event estimation system of this embodiment will be described with reference to Fig. 7. In Fig. 7, the same parts as in Fig. 1 are given the same reference numerals and the description thereof will be omitted. In the event estimation system shown in the figure, an optical fiber sensor 20 is buried under a road RD along which a vehicle CR such as an automobile passes. The optical fiber 22 in the optical fiber sensor 20 thus installed changes the return light in response to vibrations and sounds generated as the vehicle CR passes over the road RD. In the event estimation device 300, the detection unit 301 uses the received return light to detect vibrations and sounds generated in response to a vehicle passing over the road RD, and outputs the obtained detection result DT to the estimation unit 302. The estimation unit 302 estimates the passing status of the vehicle CR on the road RD based on the input detection result DT. Specifically, the estimation unit 302 may estimate the speed of each vehicle CR passing the road RD, the type of each vehicle CR passing the road RD (for example, passenger car, freight vehicle, motorcycle, etc.), the weight and size of each vehicle CR passing the road RD, the unevenness of the road RD, the status of objects such as luggage falling onto the road RD, etc. Furthermore, information on the estimation result by the estimation unit 302 may be stored in the storage unit 303. Furthermore, information on the estimation result by the estimation unit 302 may be output to an external computer device, printer, or the like.

[0080] In the event estimation system of this embodiment, the items (detection items) that the detection unit 301 detects are not limited to vibrations and sounds. For example, the detection unit 301 may be configured to detect temperature, strain, dynamic pressure, etc. Based on the detection results of such detection items, the estimation unit 302 may estimate a predetermined event that has a correlation with temperature, strain, dynamic pressure, displacement, vibration frequency, vibration acceleration, etc.

[0081] The detection unit 301 may divide the optical signals of the plurality of optical fibers 22 provided in one optical fiber sensor 20 into a plurality of groups and detect different detection items for each group. As a specific example, the detection unit 301 may detect vibrations using the optical signals of two of the four optical fibers 22 divided into a predetermined group, and detect sound using the optical signals of the remaining two optical fibers 22 divided into another group. In addition, in response to the detection unit 301 detecting a plurality of different detection items, the estimation unit 302 may estimate a plurality of different events by selecting and using a predetermined detection item from the plurality of detection items.

[0082] It should be noted that a plurality of optical fiber-held sensors 20 may be connected to the event estimation device 300. In this case, the event estimation device 300 may estimate the same event by using optical signals received from each of the optical fibers 22 arranged in the plurality of optical fiber-held sensors 20. Alternatively, the plurality of connected optical fiber-held sensors 20 may be divided into a plurality of groups, and the event estimation device 300 may estimate different events corresponding to each group.

[0083] Alternatively, a program for implementing the functions of the event estimation device 300 may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed to perform the processing of the event estimation device 300. Here, "loading a program recorded on a recording medium into a computer system and executing it" includes installing the program on a computer system. The term "computer system" here includes hardware such as an operating system and peripheral devices. The term "computer system" may also include multiple computer devices connected via a network, including the Internet, a wide area network (WAN), a local area network (LAN), or a dedicated line. The term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, read-only memory (ROM), and CD-ROMs, as well as storage devices such as hard disk drives (HDDs) and solid-state drives (SDDs) built into a computer system. The recording medium storing the program may be a non-transitory recording medium such as a CD-ROM. The recording medium may also include internal or external recording media accessible from a distribution server for distributing the program. The program code stored on the distribution server's recording medium may be different from the program code executable on a terminal device. In other words, the format in which the program is stored on the distribution server does not matter as long as it can be downloaded from the distribution server and installed in a form that is executable on the terminal device. The program may be divided into multiple parts, each of which may be downloaded at different times and then combined on the terminal device, or each of the divided programs may be distributed by a different distribution server. Furthermore, the term "computer-readable recording medium" also includes a storage medium that stores a program for a certain period of time, such as volatile memory (RAM) within a computer system that serves as a server or client when a program is transmitted over a network. The program may also be a program that realizes part of the above-described functions. Furthermore, the program may be a so-called differential file (differential program) that can realize the above-described functions in combination with a program already stored in the computer system. [Explanation of symbols]

[0084] 20, 20A optical fiber carrying sensor, 21 resin pipe, 22 optical fiber, 22e (22e-1, 22e-2, 22e-3, 22e-4) optical fiber end, 121 core material, 300 event estimation device, 301 detection unit, 302 estimation unit, 303 memory unit

Claims

1. An event inference system that infers an event in a predetermined observation target, A long core material and an optical fiber extending in the longitudinal direction of the core material, an optical fiber sensor attached to the object to be observed, the optical fiber being attached to the core material so as to be positioned inside or on the circumferential surface of the core material; an event estimation device that estimates the event based on the optical signal output from the optical fiber. Event inference system.

2. The observation target is a structure made of ground soil, The event is an event based on strain occurring in the optical fiber. The event inference system according to claim 1 .

3. The optical fiber sensor is embedded in the structure as backfill soil, The core material is a resin pipe having an outer diameter of 35 to 50 mm and a thickness of 3 to 8 mm, and is JIS K7161, and has a modulus of rigidity of 750 MPa or more and 2500 MPa or less. The event inference system according to claim 2 .

4. The backfill soil has an N value of 5 or more and 15 or less. The event inference system according to claim 3 .

5. The optical fiber sensor is embedded in the structure consisting of the roadbed and the roadbed, The core material is a resin pipe having an outer diameter of 50 to 75 mm and a thickness of 6 to 10 mm, and is JIS K7161-compliant and has a modulus of rigidity of 1000 MPa or more and 4500 MPa or less. The event inference system according to claim 2 .

6. The structure consisting of the roadbed and subgrade has an N value of 8 to 20, or a bearing capacity coefficient K of 50 MPa / m or more. The event inference system according to claim 5 .

7. The optical fiber sensor is embedded in the structure as the embankment, The core material is a resin pipe having an outer diameter of 23 mm to 37 mm and a thickness of 2.0 to 5.0 mm, and is JIS K7161-compliant and has a modulus of rigidity of 100 MPa or more and 1500 MPa or less. The event inference system according to claim 2 .

8. The fill soil has an N value of 2 to 10, or 85% or more of the maximum dry density. The event inference system according to claim 7 .

9. The core material has a shear wave velocity that is 100 m / s or less different from the shear wave velocity of the structure being observed, as measured by the soil shear wave velocity measurement method according to JGS 0544-2020, Bender element method. The event inference system according to any one of claims 1 to 8.

10. The optical fiber sensor conforms to JIS K7161 and has a modulus of rigidity of 100 MPa or more and 4500 or less. The event inference system according to any one of claims 1 to 8.

11. The optical fiber sensor has two or more optical fibers, The event estimation device outputs two or more detection results obtained by detecting at least one of vibration and sound as a detection target in response to each of the optical signals from the two or more optical fibers, and makes an estimation regarding the predetermined event based on the two or more detection results. The event inference system according to any one of claims 1 to 8.

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