Flaw detection device and flaw detection method

Abstract

To highly accurately detect the presence of a flaw of a steel plate deck.SOLUTION: This flaw detection device comprises: a magnetic flux generation unit generating a magnetic flux on a steel plate deck; a magnetic sensor 140 measuring the intensity of a magnetic field generated in the steel plate deck; a distance sensor 150 measuring the distance between the sensor 150 and the surface of a pavement laminated on the steel plate deck; a transmission unit causing an electromagnetic wave from the surface of the pavement to enter the transmission unit; a reception unit receiving each of the reflected wave of S-polarized light and the reflected wave of P-polarized light which are based on the incident electromagnetic wave; a dielectric constant calculation unit 310 calculating the dielectric constant of the pavement on the basis of the received reflected waves of S-polarized light and P-polarized light; a thickness estimation unit 312 estimating the thickness of the pavement on the basis of the calculated dielectric constant; and a correction unit 320 correcting the intensity of the magnetic field measured by the magnetic sensor, on the basis of the distance measured by the distance sensor and the estimated thickness of the pavement.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a flaw detection device and a flaw detection method.

Background Art

[0002] Roads such as highways and bridges are composed of a steel floor slab and a pavement such as asphalt laminated on the upper surface of the steel floor slab. The steel floor slab may be damaged, such as cracked, due to aging fatigue caused by vehicles passing over the pavement.

[0003] As a technique for inspecting the damage of the steel floor slab, an ultrasonic flaw detection method is used. However, in the ultrasonic flaw detection method, the probe must be brought into contact with the steel floor slab side, that is, directly under the road. Therefore, it was necessary to construct a scaffold or the like under the road.

[0004] Therefore, as a technique for inspecting the damage of the steel floor slab from above the road, an eddy current flaw detection method (for example, Patent Document 1) or a magnetic flux leakage flaw detection method (MFL) has been studied.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the above magnetic flux leakage flaw detection method, when the distance between the steel floor slab and the magnetic sensor varies, the strength of the magnetic field measured by the magnetic sensor varies regardless of the presence or absence of a flaw. For this reason, there is a risk of erroneously detecting a location without a flaw as having a flaw or failing to detect a location where a flaw actually exists.

[0007] Therefore, in the inspection of the steel floor slab using the magnetic flux leakage flaw detection method, there is a demand for the development of a technique capable of accurately detecting flaws.

[0008] In view of such problems, an object of the present disclosure is to provide a flaw detection device and a flaw detection method capable of highly accurately detecting the presence or absence of flaws in a steel floor slab.

Means for Solving the Problems

[0009] To solve the above problems, a flaw detection device according to an aspect of the present disclosure includes a magnetic flux generation unit that generates a magnetic flux in a steel floor slab, a magnetic sensor that measures the strength of a magnetic field generated in the steel floor slab, a distance sensor that measures the distance between the surface of a paving body laminated on the steel floor slab, and a transmission unit that Inside the fitting body incident electromagnetic waves, a receiving unit that receives a reflected wave of S-polarized light and a reflected wave of P-polarized light based on the incident electromagnetic waves, a relative dielectric constant calculation unit that calculates the relative dielectric constant of the paving body based on the received reflected wave of S-polarized light and the reflected wave of P-polarized light, a thickness estimation unit that estimates the thickness of the paving body based on the calculated relative dielectric constant, and a correction unit that corrects the strength of the magnetic field measured by the magnetic sensor based on the distance measured by the distance sensor and the estimated thickness of the paving body.

[0010] Further, the relative dielectric constant calculation unit may calculate the relative dielectric constant of the paving body based on the phase difference between the reflected wave of S-polarized light and the reflected wave of P-polarized light, the amplitude reflectivity of S-polarized light, and the amplitude reflectivity of P-polarized light.

[0011] Further, at least the magnetic flux generation unit, the magnetic sensor, the distance sensor, the transmission unit, and the receiving unit may be integrally fixed and include a moving unit that can move on the paving body.

[0012] Further, the correction unit may correct the strength of the magnetic field measured by the magnetic sensor based on correction information in which the strength of the magnetic field generated in a steel floor slab without flaws is associated with the distance between the magnetic sensor and the steel floor slab.

[0013] To solve the above problems, a flaw detection method according to one aspect of the present disclosure includes a step of a magnetic flux generation unit provided on a pavement laminated on a steel floor slab generating magnetic flux in the steel floor slab, a step of a magnetic sensor provided on the pavement measuring the strength of the magnetic field generated in the steel floor slab, a step of a distance sensor provided on the pavement measuring the distance between the surface of the pavement and the magnetic sensor, and a step of irradiating electromagnetic waves from the surface of the pavement Inside the fitting body a step of irradiating electromagnetic waves, a step of receiving a reflected wave of S-polarized light and a reflected wave of P-polarized light based on the incident electromagnetic waves, a step of calculating the relative permittivity of the pavement based on the received reflected wave of S-polarized light and reflected wave of P-polarized light, a step of estimating the thickness of the pavement based on the calculated relative permittivity, and a step of correcting the strength of the magnetic field measured by the magnetic sensor based on the distance between the surface of the pavement and the magnetic sensor obtained by performing the step of measuring the distance and the thickness of the pavement obtained by performing the step of estimating.

Advantages of the Invention

[0014] According to the present disclosure, it is possible to highly accurately detect the presence or absence of defects in a steel floor slab.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in such embodiments are merely examples for ease of understanding, and do not limit the present disclosure unless otherwise specified. In the present specification and drawings, elements having substantially the same functions and configurations are denoted by the same reference numerals, and redundant descriptions are omitted, and elements not directly related to the present disclosure are not shown.

[0017] FIG. 1 is a diagram for explaining a road 10 that is a flaw detection target of the flaw detection device 100 according to the present embodiment. In FIG. 1 of the present embodiment and FIGS. 2, 3, 4B, and 4C described later, the X-axis (horizontal direction, road width direction), Y-axis (horizontal direction, road length direction), and Z-axis (vertical direction) that intersect perpendicularly are defined as shown in the figure.

[0018] As shown in FIG. 1, the road 10 is composed of a steel floor slab 20 and a paving body 30. The steel floor slab 20 is a floor slab composed of steel members. The steel floor slab 20 supports the vertical load from the vehicle. The steel floor slab 20 includes a deck plate 40, a main girder web 42, a vertical stiffener 44, a transverse rib 46, and a U-rib 48.

[0019] The deck plate 40 is a steel plate extending in a substantially horizontal direction. The main girder web 42 is a steel plate that stands vertically downward from the deck plate 40 and extends in the extending direction of the road 10. The vertical stiffener 44 is a steel plate provided on the main girder web 42. The upper surface of the vertical stiffener 44 is welded to the deck plate 40. The transverse rib 46 is a steel plate that stands vertically downward from the deck plate 40 and extends in the width direction of the road 10. The transverse rib 46 is connected to the main girder web 42. The U-rib 48 is a steel plate having a U-shaped vertical cross section. The U-rib 48 is welded to the deck plate 40 so as to extend in the extending direction of the road 10.

[0020] The paving body 30 is laminated on the deck plate 40. The paving body 30 is composed of asphalt or the like.

[0021] Due to the aging fatigue caused by the passage of vehicles on the paving body 30, cracks or other damages may occur in the welded parts between the deck plate 40 and the U-rib 48, and the welded parts between the deck plate 40 and the vertical stiffener 44 in the steel floor slab 20. The cracks progress from the welded part toward the deck plate 40.

[0022] Therefore, the flaw detection device 100 shown in FIG. 2 below inspects the presence or absence of damages in the steel floor slab 20 from above the paving body 30. In the present embodiment, the flaw detection device 100 inspects the presence or absence of damages while scanning the road 10 in the passing direction of the vehicle (in the Y-axis direction in FIG. 1, the extending direction of the road 10, that is, the extending direction of the U-rib 48).

[0023] [Flaw Detection Device 100] FIG. 2 is a diagram for explaining the flaw detection device 100 according to the present embodiment. Note that FIG. 2 is a view of the vehicle 110 constituting the flaw detection device 100 according to the present embodiment as seen from vertically below.

[0024] As shown in FIG. 2, the flaw detection device 100 includes a vehicle 110, an encoder 120, a magnetic flux generation unit 130, a magnetic sensor 140, a distance sensor 150, an electromagnetic wave transmission and reception device 160, and a control unit 200.

[0025] An encoder 120, a magnetic flux generation unit 130, a magnetic sensor 140, a distance sensor 150, an electromagnetic wave transceiver 160, and a control unit 200 are integrally fixed to the lower surface 112 of the vehicle 110 (mobile body). The vehicle 110 moves (travels) on the pavement 30 when inspecting the presence or absence of damage on the steel floor slab 20. In this embodiment, the encoder 120, the magnetic flux generation unit 130, the magnetic sensor 140, and the distance sensor 150 are provided at the rear part of the vehicle 110. Also, the electromagnetic wave transceiver 160 is provided at the front part of the vehicle 110.

[0026] The encoder 120 acquires path information indicating the distance of the path traveled by the magnetic sensor 140. The path information acquired by the encoder 120 is output to the control unit 200.

[0027] The magnetic flux generation unit 130 applies a magnetic field to the steel floor slab 20 and generates a magnetic flux in the horizontal direction (XY direction in FIG. 2) on the steel floor slab 20. In this embodiment, the magnetic flux generation unit 130 is composed of a first magnet 132 and a second magnet 134. The first magnet 132 and the second magnet 134 are, for example, permanent magnets. The first magnet 132 is provided on the vehicle 110 such that the N pole faces the road 10. The second magnet 134 is provided on the vehicle 110 such that the S pole faces the road 10. The first magnet 132 and the second magnet 134 are provided on the vehicle 110 in parallel in a direction (X-axis direction in FIG. 2) orthogonal (intersecting) to the moving direction of the vehicle 110 (the extending direction of the U rib 48, Y-axis direction in FIG. 2).

[0028] The magnetic sensor 140 is provided between the first magnet 132 and the second magnet 134. The magnetic sensor 140 measures the strength of the magnetic field (magnetic field) generated in the steel floor slab 20. In this embodiment, the magnetic sensor 140 converts the strength of the magnetic field [A / m] into voltage [V] and outputs it to the control unit 200.

[0029] FIG. 3 is a diagram for explaining the measurement of the strength of the magnetic field by the magnetic sensor 140. In FIG. 3, the solid arrow indicates the magnetic field. In FIG. 3, the dashed arrow indicates the magnetic flux. In FIG. 3, the dash-dotted arrow indicates the leakage magnetic flux.

[0030] As shown in FIG. 3, a magnetic flux is generated in the steel floor slab 20 (deck plate 40) by the magnetic fields applied by the first magnet 132 and the second magnet 134. Here, if there is a defect such as a crack between the first magnet 132 and the second magnet 134, a leakage magnetic flux is generated. Then, the magnetic sensor 140 measures the strength of the magnetic field in which the leakage magnetic flux is added to the magnetic flux generated in the steel floor slab 20.

[0031] On the other hand, if there is no defect such as a crack between the first magnet 132 and the second magnet 134, no leakage magnetic flux is generated. Therefore, the magnetic sensor 140 measures the strength of the magnetic field corresponding to the magnetic flux generated in the steel floor slab 20 (without the leakage magnetic flux added).

[0032] Returning to FIG. 2 for explanation, the distance sensor 150 is provided near the magnetic sensor 140 (for example, at a location within 20 mm from the magnetic sensor 140). The distance sensor 150 is, for example, an optical sensor or a lidar.

[0033] When the flaw detection device 100 scans the road 10 (the vehicle 110 moves on the road 10), one or more wheels 114 constituting the vehicle 110 get stuck in the recesses such as ruts formed in the pavement 30 or ride over the protrusions formed in the pavement 30, so that the distance between the lower surface 112 of the vehicle 110 and the surface of the pavement 30, that is, the distance between the magnetic sensor 140 and the surface of the pavement 30 varies. Therefore, the distance sensor 150 measures the distance between the surface of the pavement 30 (the surface of the road 10) and the distance sensor 150 (the distance in the Z-axis direction in FIG. 2, indicated by H in FIG. 3). The distance sensor 150 measures the distance between a predetermined reference point on the main body of the distance sensor 150 and the surface of the pavement 30. As described above, the distance sensor 150 is integrally fixed to the lower surface 112 of the vehicle 110 with the magnetic sensor 140 and is provided near the magnetic sensor 140. Therefore, the distance sensor 150 measures the height H from the pavement 30 to the magnetic sensor 140. Information (distance information) indicating the distance measured by the distance sensor 150 is output to the control unit 200.

[0034] The electromagnetic wave transmitting and receiving device 160 transmits electromagnetic waves and receives, respectively, the reflected waves of S polarization and the reflected waves of P polarization based on the transmitted electromagnetic waves.

[0035] FIG. 4 is a diagram for explaining the electromagnetic wave transmitting and receiving device 160 according to the present embodiment. FIG. 4A is a functional block diagram of the electromagnetic wave transmitting and receiving device 160. FIG. 4B is a diagram for explaining the antenna 170 that constitutes the electromagnetic wave transmitting and receiving device 160. FIG. 4C is a diagram for explaining the arrangement of a plurality of 162.

[0036] As shown in FIG. 4A, the electromagnetic wave transmitting and receiving device 160 includes a plurality of antennas 170 (denoted as 170a to 170g in FIG. 4A), a transmitting unit 180, and a receiving unit 190.

[0037] As shown in FIG. 4B, the antenna 170 is, for example, a Vivaldi antenna. The antenna 170 includes a plate portion 172 and two main bodies 174. The plate portion 172 is a rectangular flat plate. The plate portion 172 is made of an insulator (for example, resin).

[0038] The main body 174 includes an extending portion 176 and a gradually increasing portion 178. The extending portion 176 has a rod shape extending in the Z-axis direction in FIG. 4B. The gradually increasing portion 178 is a plate that is continuous from the end of the extending portion 176 and extends in the X-axis direction in FIG. 4B. The tip 178b of the gradually increasing portion 178 extends in the Z-axis direction in FIG. 4B. The gradually increasing portion 178 has a shape in which the width in the Z-axis direction gradually increases from the base end 178a continuous with the extending portion 176 toward the tip 178b. The main body 174 is made of metal (for example, copper).

[0039] In the antenna 170, a plate portion 172 is provided between one main body 174 and the other main body 174. Also, the two main bodies 174 are provided on the plate portion 172 such that the positions of the extending portions 176 of one main body 174 and the extending portions 176 of the other main body 174 in the X-axis direction and the Z-axis direction in FIG. 4B are substantially equal. Further, the two main bodies 174 are provided on the plate portion 172 such that the positions of the tips 178b of the increasing portions 178 of one main body 174 and the tips 178b of the increasing portions 178 of the other main body 174 in the X-axis direction in FIG. 4B are different. That is, one main body 174 and the other main body 174 are provided on the plate portion 172 so as to be inverted with respect to each other. By including the plate portion 172, the antenna 170 can easily secure a clearance (clearance in the Y-axis direction in FIG. 4B) between one main body 174 and the other main body 174. Note that if a uniform clearance is provided between one main body 174 and the other main body 174, the plate portion 172 may be omitted.

[0040] As shown in FIG. 4C, the antennas 170a to 170d are fixed to the lower surface 112 of the vehicle 110 with a predetermined first interval therebetween. The antennas 170a to 170d are fixed to the lower surface 112 of the vehicle 110 such that the in-plane direction is the X-axis direction in FIG. 4C.

[0041] The antennas 170e to 170g are fixed to the lower surface 112 of the vehicle 110 with a predetermined second interval therebetween. The antennas 170e to 170g are fixed to the lower surface 112 of the vehicle 110 such that the in-plane direction is the Y-axis direction in FIG. 4C. That is, the in-plane directions of the antennas 170a to 170d and the antennas 170e to 170g are orthogonal to each other. The antennas 170a to 170d and the antennas 170e to 170g are provided with different positions in the Y-axis direction in FIG. 4C.

[0042] Also, the distance between the antenna 170a and the antenna 170e, the distance between the antenna 170b and the antenna 170f, and the distance between the antenna 170c and the antenna 170g are the above-mentioned first interval.

[0043] Returning to FIG. 4A for explanation, the transmitting unit 180 causes electromagnetic waves (for example, with a frequency of 1 MHz or more and 10 GHz or less) to enter the paving body 30 from the surface of the paving body 30 through the antennas 170a, 170b, and 170c. The receiving unit 190 receives, through the antennas 170b, 170c, and 170d, a reflected wave of P-polarized light based on the electromagnetic waves incident on the paving body 30 by the transmitting unit 180. Further, the receiving unit 190 receives, through the antennas 170e, 170f, and 170g, a reflected wave of S-polarized light based on the electromagnetic waves incident on the paving body 30 by the transmitting unit 180.

[0044] Specifically, the transmitting unit 180 causes electromagnetic waves to enter the paving body 30 from the surface of the paving body 30 through the antenna 170a, and the receiving unit 190 receives, through the antenna 170b, a reflected wave of P-polarized light reflected by the steel floor slab 20. Similarly, the transmitting unit 180 causes electromagnetic waves to enter the paving body 30 from the surface of the paving body 30 through the antenna 170b, and the receiving unit 190 receives, through the antenna 170c, a reflected wave of P-polarized light reflected by the steel floor slab 20. The transmitting unit 180 causes electromagnetic waves to enter the paving body 30 from the surface of the paving body 30 through the antenna 170c, and the receiving unit 190 receives, through the antenna 170d, a reflected wave of P-polarized light reflected by the steel floor slab 20.

[0045] Also, the transmitting unit 180 causes electromagnetic waves to enter the paving body 30 from the surface of the paving body 30 through the antenna 170a, and the receiving unit 190 receives, through the antenna 170e, a reflected wave of S-polarized light reflected by the steel floor slab 20. Similarly, the transmitting unit 180 causes electromagnetic waves to enter the paving body 30 from the surface of the paving body 30 through the antenna 170b, and the receiving unit 190 receives, through the antenna 170f, a reflected wave of S-polarized light reflected by the steel floor slab 20. The transmitting unit 180 causes electromagnetic waves to enter the paving body 30 from the surface of the paving body 30 through the antenna 170c, and the receiving unit 190 receives, through the antenna 170g, a reflected wave of S-polarized light reflected by the steel floor slab 20.

[0046] FIG. 5 is a functional block diagram of the flaw detector 100 according to the present embodiment. As shown in FIG. 5, the control unit 200 includes a differential amplifier 210, an A / D converter 220, a central control unit 230, a memory 240, and a display device 250.

[0047] The intensity of the magnetic field (voltage value) measured by the magnetic sensor 140 is input to the differential amplifier 210, converted by the A / D converter 220, and input to the central control unit 230. The differential amplifier 210 amplifies the intensity of the magnetic field (voltage value) measured by the magnetic sensor 140.

[0048] The A / D converter 220 performs AD conversion on the path information acquired by the encoder 120, the voltage value amplified by the differential amplifier 210, the distance information measured by the distance sensor 150, and the reflected waves of S-polarized light and P-polarized light received by the receiving unit 190 of the electromagnetic wave transmitting and receiving device 160. The AD-converted path information, voltage value, distance information, and the reflected waves of S-polarized light and P-polarized light are output to the central control unit 230.

[0049] The central control unit 230 is composed of a semiconductor integrated circuit including a CPU (Central Processing Unit). The central control unit 230 reads out a program, parameters, etc. for operating the CPU from the ROM. The central control unit 230 manages and controls the entire flaw detector 100 in cooperation with a RAM as a work area and other electronic circuits.

[0050] The memory 240 is composed of a ROM, a RAM, a flash memory, an HDD, etc. The memory 240 stores programs and various data used by the central control unit 230. In the present embodiment, the memory 240 stores correction information described later.

[0051] The display device 250 is composed of a liquid crystal display, an organic EL (Electro Luminescence) display, etc.

[0052] In this embodiment, the central control unit 230 functions as a relative permittivity calculation unit 310, a thickness estimation unit 312, a distance calculation unit 314, a distance determination unit 316, a selection unit 318, a correction unit 320, and a damage determination unit 322.

[0053] The relative permittivity calculation unit 310 calculates the relative permittivity εr of the pavement 30 based on the phase difference Δ between the reflected wave of the S polarization and the reflected wave of the P polarization received by the receiving unit 190, the amplitude reflectivity r s of the S polarization, and the amplitude reflectivity r p of the P polarization.

[0054] First, the relative permittivity calculation unit 310 calculates the phase difference Δ, the amplitude reflectivity r s of the S polarization, and the amplitude reflectivity r p of the P polarization from the reflected wave of the S polarization and the reflected wave of the P polarization received by the receiving unit 190 (ellipsometry).

[0055] Then, the relative permittivity calculation unit 310 calculates the relative permittivity εr of the pavement 30 using the following formulas (1) to (4).

Equation

[0056] The thickness estimation unit 312 estimates the thickness D of the pavement 30 based on the calculated relative permittivity εr using the following formula (5). D = (dt × c) / (2 × √εr) … Equation (5) In the above formula (5), dt is the time from when the electromagnetic wave is transmitted by the transmitting unit 180 until the reflected wave is received by the receiving unit 190. c is the speed of light.

[0057] The distance calculation unit 314 adds the distance H from the distance sensor 150 to the surface of the pavement 30 measured by the distance sensor 150 and the thickness D of the pavement 30 estimated by the thickness estimation unit 312 (the distance from the surface of the pavement 30 to the steel floor slab 20, see FIG. 3) to calculate the estimated distance L from the magnetic sensor 140 to the steel floor slab 20 (see FIG. 3).

[0058] The distance determination unit 316 determines, for each of the plurality of magnetic sensors 140, whether the estimated distance L estimated by the distance calculation unit 314 is a reference distance. The reference distance is a predetermined distance, for example, 120 mm.

[0059] The selection unit 318 selects correction information according to the estimated distance L.

[0060] FIG. 6 is a diagram for explaining the result of simulating the relationship between the distance between the steel floor slab 20 and the magnetic sensor 140 and the strength of the magnetic field measured by the magnetic sensor 140. FIG. 6A is a diagram for explaining the relationship between the distance between the steel floor slab 20 and the magnetic sensor 140 and the strength of the magnetic field measured by the magnetic sensor 140. FIG. 6B is a partial enlarged view of FIG. 6A. In FIGS. 6A and 6B, the vertical axis indicates the strength of the magnetic field [A / m]. In FIGS. 6A and 6B, the horizontal axis indicates the distance [mm] between the steel floor slab 20 and the magnetic sensor 140. Also, in FIG. 6A, the solid line indicates the strength of the magnetic field at a non-defective location. In FIGS. 6A and 6B, the broken line indicates the strength of the magnetic field at a defective location.

[0061] As shown in FIG. 6A, when the distance between the steel floor slab 20 (deck plate 40) and the magnetic sensor 140 is about 1 to 2 mm, the difference in the strength of the magnetic field between the case with a defect and the case without a defect is as large as about 2000 [A / m].

[0062] On the other hand, as the distance between the steel floor slab 20 and the magnetic sensor 140 increases, the leakage magnetic flux decays, so the difference in the strength of the magnetic field between the case with a defect and the case without a defect becomes smaller.

[0063] Also, regardless of the presence or absence of a flaw, until the distance between the steel floor plate 20 and the magnetic sensor 140 becomes about 100 mm, the magnetic field strength gradually increases as the distance increases. When the distance exceeds 100 mm, the magnetic field strength gradually decreases as the distance increases. That is, when the distance between the steel floor plate 20 and the magnetic sensor 140 fluctuates, the magnetic field strength fluctuates regardless of the presence or absence of a flaw.

[0064] Here, when the flaw detection device 100 scans the road 10 (the vehicle 110 moves on the road 10), one or more wheels 114 constituting the vehicle 110 may get stuck in a recess such as a rut formed in the pavement 30 or ride over a protrusion formed in the pavement 30, and the distance between the lower surface 112 of the vehicle 110 and the surface of the pavement 30 may fluctuate. In this case, even if the thickness of the pavement 30 is constant, the distance between the surface of the pavement 30 and the magnetic sensor 140 fluctuates, and the distance between the magnetic sensor 140 and the steel floor plate 20 fluctuates. Also, when the thickness of the pavement 30 fluctuates due to wear of the pavement 30 by the running of the vehicle or an increase in the thickness of the pavement 30 due to repair of the pavement 30, even if the distance between the surface of the pavement 30 and the magnetic sensor 140 is constant, the distance between the magnetic sensor 140 and the steel floor plate 20 fluctuates. As described above, when the distance between the magnetic sensor 140 and the steel floor plate 20 fluctuates, the magnetic field strength fluctuates. Then, there is a risk of misdetecting a non-flawed portion as a flaw or failing to detect a portion where a flaw actually exists.

[0065] Therefore, the central control unit 230 creates correction information corresponding to the distance between the magnetic sensor 140 and the steel floor plate 20 and stores it in the memory 240 in advance. The correction information is information in which the magnetic field strength when there is no flaw in the steel floor plate 20 is associated with the distance between the magnetic sensor 140 and the steel floor plate 20. The correction information is, for example, an approximate formula (linear function) of a curve showing the relationship between the magnetic field strength when there is no flaw and the distance from the steel floor plate 20, as shown in FIG. 6B. In the present embodiment, the memory 240 stores first correction information, second correction information, and third correction information as correction information.

[0066] The first correction information is an approximate formula of the curve showing the magnetic field strength when the distance from the steel floor slab 20 is 80 mm or more and less than 100 mm, as indicated by the dashed line in FIG. 6B.

[0067] The second correction information is an approximate formula of the curve showing the magnetic field strength when the distance from the steel floor slab 20 is 100 mm or more and less than 120 mm, as indicated by the dash-dotted line in FIG. 6B.

[0068] The third correction information is an approximate formula of the curve showing the magnetic field strength when the distance from the steel floor slab 20 is 120 mm or more, as indicated by the double-dashed line in FIG. 6B.

[0069] And the selection unit 318 selects the corresponding correction information from the first correction information, the second correction information, and the third correction information based on the estimated distance L of the magnetic sensor 140. Specifically, when the estimated distance L of the magnetic sensor 140 is 80 mm or more and less than 100 mm, the selection unit 318 selects the first correction information. When the estimated distance L of the magnetic sensor 140 is 100 mm or more and less than 120 mm, the selection unit 318 selects the second correction information. When the estimated distance L of the magnetic sensor 140 exceeds 120 mm, the selection unit 318 selects the third correction information.

[0070] Returning to FIG. 5 for explanation, the correction unit 320 corrects the magnetic field strength measured by the magnetic sensor 140 based on the estimated distance L of the magnetic sensor 140 estimated by the distance calculation unit 314. In the present embodiment, the correction unit 320 corrects the magnetic field strength measured by the magnetic sensor 140 based on the correction information selected by the selection unit 318. For example, the correction unit 320 normalizes the magnetic field strength measured by the magnetic sensor 140 with a reference distance of 1 based on the correction information selected by the selection unit 318.

[0071] For example, when the second correction information is selected, that is, when the estimated distance L of the magnetic sensor 140 is 100 mm or more and less than 120 mm, the strength of the magnetic field measured by the magnetic sensor 140 becomes greater than the strength of the magnetic field measured at the reference distance. Therefore, the correction unit 320 corrects (multiplies) the strength of the magnetic field measured by the magnetic sensor 140 with a correction coefficient less than 1 calculated based on the second correction information (magnetic field strength × correction coefficient). Specifically, the correction unit 320 first substitutes the estimated distance L of the magnetic sensor 140 into the second correction information (linear function) to calculate the correction coefficient. Then, the correction unit 320 multiplies the calculated correction coefficient by the strength of the magnetic field measured by the magnetic sensor 140. When the reference distance (120 mm) is substituted into the second correction information, the correction coefficient becomes 1.

[0072] Similarly, when the third correction information is selected, that is, when the estimated distance L of the magnetic sensor 140 exceeds 120 mm, the strength of the magnetic field measured by the magnetic sensor 140 becomes less than the strength of the magnetic field measured at the reference distance. Therefore, the correction unit 320 corrects the strength of the magnetic field measured by the magnetic sensor 140 with a correction coefficient greater than 1 calculated based on the third correction information (magnetic field strength × correction coefficient). Specifically, the correction unit 320 first substitutes the estimated distance L of the magnetic sensor 140 into the third correction information (linear function) to calculate the correction coefficient. Then, the correction unit 320 multiplies the calculated correction coefficient by the strength of the magnetic field measured by the magnetic sensor 140. When the reference distance (120 mm) is substituted into the third correction information, the correction coefficient becomes 1.

[0073] Also, when the first correction information is selected, that is, when the estimated distance of the magnetic sensor 140 is 80 mm or more and less than 100 mm, the correction unit 320 corrects (multiplies) the magnetic field strength measured by the magnetic sensor 140 with a correction coefficient calculated based on the first correction information (magnetic field strength × correction coefficient). Specifically, the correction unit 320 first substitutes the estimated distance L of the magnetic sensor 140 into the first correction information (linear function) to calculate the correction coefficient. Then, the correction unit 320 multiplies the calculated correction coefficient by the magnetic field strength measured by the magnetic sensor 140.

[0074] FIG. 7 is a diagram for explaining the correction by the correction unit 320. FIG. 7A is a diagram for explaining the magnetic field strength measured by the magnetic sensor 140. FIG. 7B is a diagram for explaining the corrected value after correction by the correction unit 320. In FIGS. 7A and 7B, the solid line indicates the result of scanning the non-defective range. In FIGS. 7A and 7B, the dashed line indicates the result of scanning the defective range.

[0075] As described above, when the distance between the steel floor slab 20 and the magnetic sensor 140 fluctuates, even at a non-defective location, the magnetic field strength fluctuates due to the distance fluctuation. Therefore, as shown in FIG. 7A, when the distance from the steel floor slab 20 fluctuates, the converted voltage value [V] of the magnetic field strength measured by the magnetic sensor 140 fluctuates regardless of the presence or absence of defects. Thus, it is impossible to distinguish whether the voltage value fluctuation is due to distance fluctuation or defect fluctuation.

[0076] On the other hand, as shown by the solid line in FIG. 7B, when there is no defect, when the correction unit 320 corrects the magnetic field strength measured by the magnetic sensor 140, the fluctuation due to the distance is eliminated. As a result, the corrected voltage value (corrected value) [V] is maintained within a predetermined fluctuation range. Therefore, as shown by the dashed line in FIG. 7B, the corrected value at the defective location protrudes from the fluctuation range.

[0077] The damage determination unit 322 determines the presence or absence of damage based on whether the correction value is within a predetermined determination range. The determination range is a predetermined voltage range based on a threshold value. The threshold value is determined by the strength of the magnetic field in the case of no damage at the reference distance. Also, the determination range is calculated by experiments or simulations and set based on the correction value in the case of damage of a predetermined size. The determination range may be equal to the above-described variation range or may be larger than the variation range.

[0078] When the correction value is within the determination range, the damage determination unit 322 determines that there is no damage. On the other hand, when the correction value is outside the determination range, the damage determination unit 322 determines that there is damage.

[0079] Also, in the present embodiment, when the distance determination unit 316 determines that the distance is not the reference distance, the damage determination unit 322 determines the presence or absence of damage based on the correction value corrected by the correction unit 320. Also, when the distance determination unit 316 determines that the distance is the reference distance, the damage determination unit 322 determines the presence or absence of damage based on the strength of the magnetic field (voltage value) input from the A / D converter 220 without being corrected by the correction unit 320.

[0080] [Flaw detection method] Subsequently, a flaw detection method for detecting flaws in the road 10 using the flaw detection device 100 will be described. FIG. 8 is a flowchart showing the processing flow of the flaw detection method according to the present embodiment. As shown in FIG. 8, the flaw detection method according to the present embodiment includes an end determination step S110, a signal acquisition step S120, a relative permittivity calculation step S130, a thickness estimation step S140, a distance calculation step S150, a distance determination step S160, a selection step S170, a correction step S180, a storage step S190, a movement step S200, a damage determination step S210, an image generation step S220, and an image display step S230. Hereinafter, each step will be described.

[0081] [End determination step S110] The central control unit 230 determines whether or not the scanning of a predetermined flaw detection range has been completed. As a result, if it is determined that the scanning of the flaw detection range has not been completed (NO in S110), the central control unit 230 transfers the process to the signal acquisition step S120. On the other hand, if it is determined that the scanning of the flaw detection range has been completed (YES in S110), the central control unit 230 transfers the process to the flaw determination step S210.

[0082] [Signal acquisition step S120] The encoder 120 acquires path information. The magnetic sensor 140 measures the strength of the magnetic field based on the magnetic flux generated in the steel floor plate 20 by the magnetic flux generation unit 130. The distance sensor 150 measures the distance between the distance sensor 150 and the surface of the pavement 30. The receiving unit 190 of the electromagnetic wave transmission / reception device 160 receives the reflected wave of S polarization and the reflected wave of P polarization based on the electromagnetic wave incident from the surface of the pavement 30 by the transmitting unit 180, respectively. The path information, the strength of the magnetic field (voltage value), the distance information, and the reflected wave of S polarization and the reflected wave of P polarization are output to the control unit 200.

[0083] [Relative permittivity calculation step S130] The relative permittivity calculation unit 310 calculates the relative permittivity εr of the pavement 30 using the above formulas (1) to (4) based on the reflected wave of S polarization and the reflected wave of P polarization acquired in the signal acquisition step S120.

[0084] [Thickness estimation step S140] The thickness estimation unit 312 estimates the thickness D of the pavement 30 using the above formula (5) based on the relative permittivity εr of the pavement 30 calculated in the relative permittivity calculation step S130.

[0085] [Distance calculation step S150] The distance calculation unit 314 calculates the estimated distance L between the magnetic sensor 140 and the steel floor plate 20 based on the distance information (distance H) acquired in the signal acquisition step S120 and the thickness D of the pavement 30 estimated in the thickness estimation step S140.

[0086] [Distance determination step S160] The distance determination unit 316 determines whether the estimated distance L of the magnetic sensor 140 calculated in the distance calculation step S150 corresponds to the reference distance. As a result, if it is determined that it does not correspond to the reference distance (NO in S160), the central control unit 230 transfers the process to the selection step S170. On the other hand, if it is determined that it corresponds to the reference distance (YES in S160), the central control unit 230 transfers the process to the storage step S190.

[0087] [Selection step S170] The selection unit 318 selects the corresponding correction information from among the first correction information, the second correction information, and the third correction information based on the estimated distance L of the magnetic sensor 140 calculated in the distance calculation step S150.

[0088] [Correction step S180] The correction unit 320 corrects the strength (voltage value) of the magnetic field acquired in the signal acquisition step S120 based on the correction information selected in the selection step S170.

[0089] [Storage step S190] When the central control unit 230 determines that it is the reference distance in the distance determination step S160, it stores the strength (voltage value) of the magnetic field acquired in the signal acquisition step S120 in the memory 240 in association with the path information.

[0090] On the other hand, when the central control unit 230 determines that it is not the reference distance in the distance determination step S160, it stores the corrected value corrected in the correction step S180 in the memory 240 in association with the path information.

[0091] [Movement step S200] The vehicle 110 constituting the flaw detection device 100 moves from the first position where the signal acquisition step S120 was executed this time to the second position within a predetermined time. The second position is a position where the position in the moving direction of the vehicle 110 (Y-axis direction in FIG. 2) is different from the first position.

[0092] [Defect determination step S210] The flaw determination unit 322 compares the magnetic field strength (voltage value) and the correction value with the determination range in all of the flaw detection ranges held in the memory 240 to determine the presence or absence of flaws.

[0093] [Image generation step S220] The central control unit 230 generates a flaw detection result image indicating the position of a flaw in the flaw detection range based on the presence or absence of a flaw and the path information in all of the flaw detection ranges stored in the memory 240.

[0094] [Image display step S230] The central control unit 230 causes the display device 250 to display the flaw detection result image. FIG. 9 is a diagram for explaining an example of the flaw detection result image. As shown in FIG. 9, for example, the result image 252 is an image in which the locations of flaws are indicated in black in a frame on a rectangle where the vertical axis indicates the road width [m] of the flaw detection range and the horizontal axis indicates the road length [m] of the flaw detection range.

[0095] As described above, the flaw detection device 100 and the flaw detection method using the same according to the present embodiment include the distance sensor 150, the relative permittivity calculation unit 310, the thickness estimation unit 312, the distance calculation unit 314, and the correction unit 320. Thereby, even if the vehicle 110 tilts during scanning and the distance H between the magnetic sensor 140 and the surface of the pavement 30 fluctuates, or the thickness D of the pavement 30 fluctuates, the flaw detection device 100 can accurately detect the presence or absence of flaws in the steel floor slab 20.

[0096] Also, as described above, the thickness estimation unit 312 estimates the thickness D of the pavement 30 based on the relative permittivity εr of the pavement 30 calculated by the relative permittivity calculation unit 310. The relative permittivity εr of the pavement 30 varies depending on, for example, the material of the pavement 30, the water content of the pavement 30, and chemicals (such as salts) sprayed for preventing road surface freezing. Therefore, the flaw detection device 100 can calculate the relative permittivity εr of the pavement 30 when performing flaw detection by the flaw detection device 100 by including the receiving unit 190 and the relative permittivity calculation unit 310. Thereby, the thickness estimation unit 312 can accurately estimate the thickness D of the pavement 30 when performing flaw detection by the flaw detection device 100.

[0097] Also, as described above, the electromagnetic wave transmitting / receiving device 160 includes a plurality of antennas 170. Thereby, the relative permittivity calculation unit 310 can calculate the relative permittivity εr of the pavement 30 with high accuracy.

[0098] Also, as described above, in the flaw detection device 100, the magnetic flux generation unit 130, the magnetic sensor 140, the distance sensor 150, and the electromagnetic wave transmitting / receiving device 160 are integrally fixed to the vehicle 110. Therefore, since the relative positional relationship among the magnetic flux generation unit 130, the magnetic sensor 140, the distance sensor 150, and the electromagnetic wave transmitting / receiving device 160 is fixed, the flaw detection device 100 can perform flaw detection with high accuracy.

[0099] Also, as described above, the correction unit 320 corrects the strength of the magnetic field based on the correction information. Thereby, the correction unit 320 can reduce the processing load required for correction.

[0100] Also, as described above, the flaw detection method using the flaw detection device 100 repeats from the end determination step S110 to the movement step S200. That is, the flaw detection device 100 detects the presence or absence of a flaw in a time-division manner according to the running of the vehicle 110. Thereby, the flaw detection device 100 can comprehensively detect all areas on the road 10 where the vehicle 110 has traveled.

[0101] As described above, the embodiments have been described with reference to the accompanying drawings. Needless to say, the present disclosure is not limited to the above embodiments. It is obvious that those skilled in the art can conceive of various modification examples or correction examples within the scope described in the claims, and it is naturally understood that those also belong to the technical scope of the present disclosure.

[0102] For example, in the above-described embodiment, the case where the electromagnetic wave transmitting and receiving device 160 includes a plurality of antennas 170 arranged in an array was taken as an example. However, the electromagnetic wave transmitting and receiving device 160 only needs to include at least one antenna 170 for incident S-polarized electromagnetic waves, at least one antenna 170 for receiving reflected S-polarized waves, at least one antenna 170 for incident P-polarized electromagnetic waves, and at least one antenna 170 for receiving reflected P-polarized waves.

[0103] Also, in the above-described embodiment, the case where the antenna 170 is a Vivaldi antenna was taken as an example. However, there is no limitation on the type of the antenna 170 as long as the transmitting unit 180 can make electromagnetic waves incident from the surface of the pavement 30 and the receiving unit 190 can receive the reflected S-polarized wave and the reflected P-polarized wave based on the incident electromagnetic waves respectively. For example, the antenna 170 may be a quad-ridge horn antenna or a bowtie antenna.

[0104] Also, the receiving unit 190 may be provided with a filter such as a wire grid polarizer that can extract the S-polarized component and the P-polarized component from the reflected wave respectively. In any case, there is no limitation on the configuration as long as the receiving unit 190 can receive the reflected S-polarized wave and the reflected P-polarized wave based on the incident electromagnetic waves respectively.

[0105] Also, in the above-described embodiment, the case where the relative permittivity calculation unit 310 calculates the relative permittivity εr of the pavement 30 based on the phase difference Δ between the reflected S-polarized wave and the reflected P-polarized wave, the amplitude reflectivity r s of the S-polarized wave, and the amplitude reflectivity r p of the P-polarized wave was taken as an example. However, there is no limitation on the calculation method as long as the relative permittivity calculation unit 310 can calculate the relative permittivity εr of the pavement 30 based on the received reflected S-polarized wave and reflected P-polarized wave.

[0106] Also, in the above-described embodiment, the case where the control unit 200 is provided in the vehicle 110 was taken as an example. However, the control unit 200 may be provided at a location separated from the vehicle 110.

[0107] Further, in the above embodiment, the case where the magnetic flux generation unit 130 is a permanent magnet has been taken as an example. However, in any case, the magnetic flux generation unit 130 is not limited in configuration as long as it can generate a magnetic flux in a predetermined direction in the steel floor slab 20. For example, the magnetic flux generation unit 130 may be an electromagnet.

[0108] Further, in the above embodiment, the case where the flaw detection device 100 includes the selection unit 318 has been taken as an example. However, the selection unit 318 is not an essential configuration. For example, the central control unit 230 may use an approximate formula (for example, a quadratic function) of a curve showing the relationship between the magnetic field strength in the case of no flaw and the distance from the surface (steel floor slab 20) of the pavement body 30 as correction information. In this case, the correction unit 320 corrects the magnetic field strength (voltage value) based on the distance information and the correction information.

[0109] Further, in the above embodiment, the case where the path information acquired by the encoder 120, the magnetic field strength (voltage value) measured by the magnetic sensor 140, the distance information measured by the distance sensor 150, and the reflected waves of S-polarized light and P-polarized light received by the receiving unit 190 are analog values has been taken as an example. However, any one or more of the path information acquired by the encoder 120, the magnetic field strength (voltage value) measured by the magnetic sensor 140, the distance information measured by the distance sensor 150, and the reflected waves of S-polarized light and P-polarized light received by the receiving unit 190 may be digital values. In addition, when the path information acquired by the encoder 120, the magnetic field strength (voltage value) measured by the magnetic sensor 140, the distance information measured by the distance sensor 150, and the reflected waves of S-polarized light and P-polarized light received by the receiving unit 190 are digital values, the control unit 200 may omit the A / D converter 220.

[0110] The present disclosure can contribute to, for example, Goal 12, "Ensure sustainable consumption and production patterns," of the Sustainable Development Goals (SDGs).

Explanation of Reference Numerals

[0111] 100 Flaw detection equipment 110 Vehicles (Mobile) 130 Magnetic flux generating section 140 Magnetic Sensor 150 Distance Sensor 180 Transmitter 190 Receiving unit 310 Relative permittivity calculation section 312 Thickness Estimation Section 320 Correction Unit

Claims

1. A magnetic flux generation unit that generates magnetic flux in a steel floor plate, A magnetic sensor that measures the strength of the magnetic field generated in the steel floor plate, A distance sensor that measures the distance between the surface of the pavement layer laminated on the steel floor plate, A transmission unit that causes electromagnetic waves to enter the pavement layer from the surface of the pavement layer, A reception unit that receives a reflected wave of S polarization and a reflected wave of P polarization based on the incident electromagnetic wave, A relative permittivity calculation unit that calculates the relative permittivity of the pavement layer based on the received reflected wave of S polarization and the reflected wave of P polarization, A thickness estimation unit that estimates the thickness of the pavement layer based on the calculated relative permittivity, A correction unit that corrects the strength of the magnetic field measured by the magnetic sensor based on the distance measured by the distance sensor and the estimated thickness of the pavement layer, A flaw detection device comprising the above.

2. The relative permittivity calculation unit calculates the relative permittivity of the pavement layer based on the phase difference between the reflected wave of S polarization and the reflected wave of P polarization, the amplitude reflectivity of S polarization, and the amplitude reflectivity of P polarization. The flaw detection device according to Claim 1.

3. The flaw detection device according to Claim 1 or 2, comprising at least a moving unit in which the magnetic flux generation unit, the magnetic sensor, the distance sensor, the transmission unit, and the reception unit are integrally fixed and movable on the pavement layer.

4. The correction unit corrects the strength of the magnetic field measured by the magnetic sensor based on correction information in which the strength of the magnetic field generated in a steel floor plate without damage is associated with the distance between the magnetic sensor and the steel floor plate. The flaw detection device according to any one of Claims 1 to 3.

5. A step in which a magnetic flux generation unit provided on a pavement layer laminated on a steel floor plate generates magnetic flux in the steel floor plate, A step in which a magnetic sensor provided on the pavement layer measures the strength of the magnetic field generated in the steel floor plate, A step in which a distance sensor provided on the pavement layer measures the distance from the surface of the pavement layer, A step of causing electromagnetic waves to enter the pavement layer from the surface of the pavement layer, A step of receiving a reflected wave of S polarization and a reflected wave of P polarization based on the incident electromagnetic wave, A step of calculating the relative permittivity of the pavement layer based on the received reflected wave of S polarization and the reflected wave of P polarization, A step of estimating the thickness of the pavement layer based on the calculated relative permittivity, A step of correcting the strength of the magnetic field measured by the magnetic sensor based on the distance between the surface of the pavement and the magnetic sensor obtained by performing the step of measuring the distance, and the thickness of the pavement obtained by performing the step of estimating. A flaw detection method including the above.

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