Method and apparatus for estimating leaked gas concentration

Abstract

The present invention provides a leak gas concentration estimation method and leak gas concentration estimation device that can be performed even when it is difficult to image the location of the leaked gas, and that can easily estimate the concentration of the leaked gas. [Solution] The leak gas concentration estimation method comprises: an association information acquisition step of acquiring association information relating the permeability, thickness, and concentration of the leak gas; a permeability acquisition step of imaging the leak gas along a first direction intersecting the direction of gas ejection and acquiring the permeability of the leak gas from the acquired image; a thickness acquisition step of imaging the leak gas along a second direction intersecting the first direction with the direction of gas ejection as the axis and acquiring the thickness of the leak gas from the acquired image; and a concentration estimation step of estimating the concentration of the leak gas from the permeability of the leak gas acquired in the permeability acquisition step and the thickness of the leak gas acquired in the thickness acquisition step, based on the association information.

Description

Technical Field

[0001] The present disclosure relates to a method for estimating the concentration of leaked gas leaking from a detection target and a device for estimating the concentration of leaked gas.

Background Art

[0002] In Patent Document 1, an estimated value of a gas concentration feature amount (light absorption rate) corresponding to time-series image inspection data is calculated using an inference model, and based on the relationship between the light absorption rate and the product of the gas concentration and thickness, an invention for obtaining the product of the gas concentration and thickness from the light absorption rate corresponding to an infrared image is disclosed. It is difficult to distinguish whether a low-concentration gas exists with a thickness or a high-concentration gas exists with a thin thickness from the product of the gas concentration and thickness.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 2, measures are taken to separate whether the decrease in luminance due to the gas imaged by the detection device (camera) is due to the influence of the gas concentration or the influence of the gas thickness. For this purpose, it is necessary to measure the gas jet outlet diameter. For example, when the detection target is a pipe, there are many cases where the pipes are intricately arranged, it is difficult to visually recognize the gas jet outlet or measure the outlet diameter, and there is a risk that it will be difficult to calculate the concentration.

[0005] In view of the circumstances described above, at least one embodiment of this disclosure aims to provide a leak gas concentration estimation method and a leak gas concentration estimation device that can be implemented even when it is difficult to image the location of the leak gas and can easily estimate the concentration of the leak gas. [Means for solving the problem]

[0006] A leak gas concentration estimation method according to at least one embodiment of this disclosure is: A method for estimating the concentration of leaked gas, which is gas leaked from an object to be detected, A relationship information acquisition step involves acquiring relationship information that associates the permeability of the gas, the thickness of the gas, and the concentration of the gas. A transmittance acquisition step involves imaging the leaked gas along a first direction intersecting the ejection direction of the leaked gas, and obtaining the transmittance of the leaked gas from the acquired image, A thickness acquisition step involves imaging the leaked gas along a second direction that intersects the first direction with respect to the ejection direction of the leaked gas as the axis, and obtaining the thickness of the leaked gas from the acquired image. The system includes a concentration estimation step, which estimates the concentration of the leaked gas based on the permeability of the leaked gas obtained in the permeability acquisition step and the thickness of the leaked gas obtained in the thickness acquisition step, based on the association information.

[0007] The leak gas concentration estimation device according to at least one embodiment of the present disclosure is A leak gas concentration estimation device for estimating the concentration of leaked gas, which is gas leaking from an object to be detected, An association information acquisition unit acquires association information relating the permeability of the gas, the thickness of the gas, and the concentration of the gas. A transmittance acquisition unit that acquires the transmittance of the leaked gas from an image captured of the leaked gas along a first direction intersecting the ejection direction of the leaked gas, A thickness acquisition unit that acquires the thickness of the leaked gas from an image of the leaked gas captured along a second direction intersecting the first direction with respect to the ejection direction of the leaked gas as the axis, The system includes a concentration estimation unit that estimates the concentration of the leaked gas based on the permeability of the leaked gas obtained by the permeability acquisition unit and the thickness of the leaked gas obtained by the thickness acquisition unit, based on the association information. [Effects of the Invention]

[0008] According to at least one embodiment of this disclosure, a method and apparatus for estimating leaked gas concentration are provided that can be implemented even when it is difficult to image the location of the leaked gas, and that can easily estimate the concentration of the leaked gas. [Brief explanation of the drawing]

[0009] [Figure 1] This is a flowchart of a leak gas concentration estimation method according to one embodiment of the present disclosure. [Figure 2] This is an explanatory diagram illustrating a method for acquiring captured images in a leak gas concentration estimation method according to one embodiment of the present disclosure. [Figure 3] This is an explanatory diagram for describing the first captured image. [Figure 4] This is an explanatory diagram for describing the second image. [Figure 5] This graph illustrates the boundary between the leaked gas and the surrounding gas. [Figure 6] This graph illustrates the boundary between the leaked gas and the surrounding gas. [Figure 7] This graph illustrates the boundary between the leaked gas and the surrounding gas. [Figure 8] This graph shows the relationship between the permeability, thickness, and concentration of the target gas. [Figure 9] This graph shows the relationship between the thickness of the target gas and the coefficient k. [Figure 10] This graph shows the relationship between the thickness of the target gas and the coefficient b. [Figure 11]It is a schematic perspective view of an imaging device and a calibration plate. [Figure 12] It is an explanatory diagram for explaining the adjustment of the sensitivity of the imaging device using the calibration plate. [Figure 13] It is an explanatory diagram for explaining the adjustment of the sensitivity of the imaging device using the calibration plate. [Figure 14] It is an explanatory diagram for explaining the transfer device in one embodiment of the present disclosure. [Figure 15] It is an explanatory diagram for explaining the transfer device in one embodiment of the present disclosure. [Figure 16] It is a schematic configuration diagram of a leakage gas concentration estimation device according to one embodiment of the present disclosure.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, but are merely illustrative examples.

[0011] (Leakage Gas Concentration Estimation Method) FIG. 1 is a flowchart of a leakage gas concentration estimation method according to one embodiment of the present disclosure. FIG. 2 is an explanatory diagram for explaining a method of acquiring an imaging image in the leakage gas concentration estimation method according to one embodiment of the present disclosure. The leakage gas concentration estimation method and the leakage gas concentration estimation device 1 according to some embodiments are methods (devices) for estimating the concentration of leakage gas, which is the gas leaked from the detection target 2.

[0012] Inside the detection target 2, there is a gas to be detected (target gas). The detection target 2 may be a tank that stores the target gas, an internal combustion engine that uses the target gas as fuel, or a pipe through which the target gas flows. Further, the detection target 2 may be a structure including two or more of the above tank, the above internal combustion engine, or the above pipe.

[0013] A leak gas concentration estimation method according to several embodiments, as shown in Figure 1, comprises an association information acquisition step S10, a transmittance acquisition step S20, a thickness acquisition step S30, and a concentration estimation step S40. In the embodiment shown in Figure 1, the leak gas concentration estimation method further comprises an ejection direction identification step S50, a transfer step S60, and a sensitivity adjustment step S70.

[0014] (Step to obtain related information) In the association information acquisition step S10, association information is acquired in which the permeability GP of the target gas, the thickness GT of the target gas, and the concentration GC of the target gas are linked. Preferably, the association information is created before the leak gas concentration estimation method is performed. Acquiring the association information in the association information acquisition step S10 means making the association information available for reference.

[0015] The above-mentioned association information shows the correspondence between the permeability GP, thickness GT, and concentration GC of the target gas. It is sufficient if, when permeability GP and thickness GT are used as input information, the corresponding concentration GC can be obtained as output information. This association information may include lists, tables, maps, functions, machine learning models, intensity analysis models, etc., that show the correspondence between the input and output information. This association information may also be created based on numerical analysis results.

[0016] (Transparency acquisition step) In the transmittance acquisition step S20, the leaked gas is imaged along a first direction D1 (see Figure 2) that intersects the ejection direction SD of the leaked gas, and the transmittance GP of the leaked gas is acquired from the acquired image. The transmittance acquisition step S20 includes a first imaging step S21 in which the leaked gas is imaged along the first direction D1 using an imaging device 3 configured to image the leaked gas, and a transmittance detection step S22 in which the transmittance GP of the leaked gas is detected from the first acquired image, which is the acquired image acquired in the first imaging step S21. In the transmittance detection step S22, information extraction (digital image processing) of brightness values ​​(feature quantities) for each region (e.g., pixels) into which the first acquired image is divided into multiple sections is performed.

[0017] The imaging device 3 is a camera (in the illustrated example, an infrared camera) capable of detecting the wavelength range of the target gas. The target gas can be any gas that has infrared absorption properties. Examples of target gases include ammonia gas, methane gas, and carbon dioxide.

[0018] As shown in Figure 2, the leaked gas LG is ejected from the leak point of the object being detected 2 along the ejection direction SD, forming a gas cloud GCL. The gas cloud GCL is defined by the boundary B between the leaked gas LG that defines the gas cloud GCL and the surrounding gas (e.g., air) which is the ambient gas AG. The gas cloud GCL has a central axis CL that extends along the ejection direction SD.

[0019] Figure 3 is an explanatory diagram for illustrating the first captured image. Figures 5 to 7 are graphs illustrating the boundary B between the leaked gas LG and the surrounding gas (environmental gas AG). As shown in Figure 3, the first captured image includes the leaked gas LG, the environmental gas AG, and at least a portion of the boundary B in the direction of emission, forming the gas cloud GCL. The first captured image reflects the light absorption characteristics of the gas. Specifically, as shown in Figure 5, the brightness value (pixel brightness) of the region where the leaked gas LG is captured in the first captured image is smaller than the brightness value of the region where the environmental gas AG is captured in the first captured image.

[0020] Transmittance GP is an indicator of whether light can be transmitted and seen (whether the image sensor of imaging device 3 can receive light) even when absorbed by the gas. Transmittance GP is the reciprocal of the light absorption rate by the gas, and is 0 when all light is absorbed by the gas, and 1 when there is no effect of light absorption by the gas.

[0021] In the transmittance detection step S22, the ratio (GB1 / GB2) of the brightness value GB of the area where the leaked gas LG is captured in the first captured image to the brightness value GB of the area where the environmental gas AG is captured in the first captured image (e.g., GB2 in Figure 5) is calculated, and the calculated ratio is detected as the transmittance GP of the leaked gas LG. The brightness value of the area where the leaked gas LG is captured in the first captured image used in calculating the above ratio may be the average of the brightness values ​​of the pixel with the minimum brightness value in the first captured image and the pixels surrounding that pixel. The brightness value of the area where the environmental gas AG is captured in the first captured image used in calculating the above ratio may also be the average of the brightness values ​​of the pixels included in that area.

[0022] (Thickness acquisition step) In the thickness acquisition step S30, as shown in Figure 2, the leaked gas is imaged along a second direction D2 that intersects the first direction D1 with respect to the ejection direction SD of the leaked gas (the central axis CL of the gas cloud GCL), and the thickness GT of the leaked gas is acquired from the acquired image. The thickness acquisition step S30 includes a second imaging step S31 in which the imaging device 3 images the leaked gas along the second direction D2, and a thickness detection step S32 in which the thickness GT of the leaked gas is detected from the second acquired image, which is the acquired image acquired in the second imaging step S31. In the thickness detection step S32, information extraction (digital image processing) of brightness values ​​(feature quantities) is performed for each region (e.g., pixels) into which the second acquired image is divided into multiple sections.

[0023] The imaging device 3 that captures the second image may be the same as or different from the imaging device 3 that captures the first image. As shown in Figure 2, the angle (circumferential angle) between the first direction D1 and the second direction D2 with respect to the ejection direction SD of the leaked gas (the central axis CL of the gas cloud GCL) is defined as θ. This angle θ preferably satisfies the condition 30°≦θ≦150°, and more preferably 60°≦θ≦120°, in order to properly detect the thickness GT of the leaked gas. Furthermore, it is more preferable that the angle θ is around 90°, i.e., satisfies the condition 80°≦θ≦100°.

[0024] Figure 4 is an explanatory diagram illustrating the second captured image. As shown in Figure 4, the second captured image includes the leaked gas LG, the environmental gas AG, and at least a portion of the boundary B in the direction of emission, which form the gas cloud GCL. The second captured image reflects the light absorption characteristics of the gas. Specifically, as shown in Figure 5, the brightness value (pixel brightness) of the region where the leaked gas LG is captured in the second captured image is smaller than the brightness value of the region where the environmental gas AG is captured in the second captured image.

[0025] In the thickness detection step S32, boundary B in the second captured image is identified. The method for identifying boundary B will be explained using Figures 5 to 7 as examples. Figure 5 shows a graph with the position in the image on the horizontal axis and the brightness value GB of the image on the vertical axis. As shown in Figure 5, there is an area around boundary B where the change in brightness value exceeds a predetermined amount (edge ​​area). In the illustrated embodiment, an area is identified as an edge area when the ratio GB2 / GB1 of the brightness value GB1 of the area on the leaking gas LG side adjacent to the area suspected to be an edge area to the brightness value GB2 of the area on the environmental gas AG side adjacent to the area suspected to be an edge area is greater than or equal to a predetermined value (for example, 3).

[0026] Boundary B can be identified by differentiating (first derivative, second derivative) the luminance value in the edge region. Figure 6 shows a graph with the horizontal axis representing the position in the image and the vertical axis representing the first derivative of the luminance value in the image. Figure 7 shows a graph with the horizontal axis representing the position in the image and the vertical axis representing the second derivative of the luminance value in the image. As shown in Figure 6, boundary B may be defined as the vertex P1 of the first derivative of the luminance value that forms a Gaussian distribution in the edge region. Alternatively, boundary B may be defined as the zero intersection P2 of the second derivative of the luminance value in the edge region shown in Figure 7.

[0027] In the second image, the length between boundaries B in a direction perpendicular to the leak gas ejection direction SD (the central axis CL of the gas cloud GCL) can be detected as the thickness of the leak gas LG in the second image. By using the distance between the imaging device 3 and the leak gas (object to be imaged) at the time of capturing the second image, the thickness of the leak gas LG in the second image can be converted to the actual thickness GT of the leak gas LG. The imaging device 3 for capturing the second image is configured to acquire the distance between the imaging device 3 and the leak gas (object to be imaged), and the distance between the imaging device 3 and the leak gas (object to be imaged) may be acquired by the imaging device 3. Alternatively, the distance between the imaging device 3 and the leak gas (object to be imaged) may be acquired using a measuring instrument for measuring distance, such as a laser rangefinder, instead of the imaging device 3.

[0028] Specifically, the size of one pixel in the second image is determined as the product of the spatial resolution of the imaging device 3 (mrad, or instantaneous field of view) and the distance between the imaging device 3 and the leaked gas (the object being leaked). Then, the actual thickness GT of the leaked gas LG is determined as the product of the size of one pixel in the second image and the thickness of the leaked gas LG in the second image.

[0029] (Concentration estimation step) In the concentration estimation step S40, the concentration GC of the leaked gas is estimated based on the association information obtained in the association information acquisition step S10, using the permeability GP of the leaked gas obtained in the permeability acquisition step S20 and the thickness GT of the leaked gas obtained in the thickness acquisition step S30.

[0030] According to the leaked gas concentration estimation method, the permeability GP and thickness GT of the leaked gas can be obtained from the captured image of the leaked gas. Then, based on the correlation information showing the relationship between the permeability GP, thickness GT, and concentration GC of the leaked gas, the concentration GC of the leaked gas can be estimated from the permeability GP and thickness GT obtained from the captured image. In the leaked gas concentration estimation method, it is not necessary to image the leak location from the object 2 from which the leaked gas is detected, and the concentration GC of the leaked gas can be estimated if the leaked gas can be imaged. Therefore, it can be applied even when it is difficult to image the leak location, and the estimation of the concentration GC of the leaked gas can be easily performed.

[0031] Figure 8 is a graph showing the relationship between the permeability GP, thickness GT, and concentration GC of the target gas. In Figure 8, the concentration GC of the target gas is shown on the horizontal axis and the permeability GP of the target gas is shown on the vertical axis. Approximation curves C1, C2, and C3 for each thickness GT are shown in this graph. Approximation curve C1 shows the relationship between concentration GC and permeability GP when the thickness GT of the target gas is a first predetermined value. Approximation curve C2 shows the relationship between concentration GC and permeability GP when the thickness GT of the target gas is a second predetermined value which is thicker than the first predetermined value. Approximation curve C3 shows the relationship between concentration GC and permeability GP when the thickness GT of the target gas is a third predetermined value which is thicker than the second predetermined value.

[0032] In several embodiment of the leak gas concentration estimation method, the association information described above includes a relationship between the transmittance GP of the target gas and the concentration GC of the target gas for each target gas thickness GT, obtained by imaging target gases with different conditions for the target gas thickness GT and concentration GC, and acquiring the transmittance GP of the target gas for each condition.

[0033] In creating the above relational equation, the target gas is imaged with constant thickness GT and concentration GC conditions, and the transmittance GP of the target gas is detected from the image using the same method as in transmittance detection step S22. Then, the transmittance GP of the target gas is detected from the image of the target gas after changing at least one of the thickness GT or concentration GC conditions. By repeating this process, the relational equation (graph) shown in Figure 8 can be created.

[0034] In the leak gas concentration estimation method according to this embodiment, the relational expression showing the relationship between the transmittance GP, thickness GT, and concentration GC of the target gas, which is the target of concentration GC estimation, was obtained from the results of actually imaging the target gas. By using the above relational expression to estimate the concentration GC of the leak gas, the estimated concentration GC of the leak gas will be relatively accurate as it reflects the actual relationship described above.

[0035] In some embodiments of the leak gas concentration estimation method, the above-described relation includes an exponential function where the concentration GC of the target gas is the independent variable x and the permeability GP of the target gas is the dependent variable y. The relation shown in Figure 8 (approximation curves C1, C2, C3) is expressed by the following equation (1). y = k × exp(bx) ... Equation (1) In equation (1), k and b are coefficients.

[0036] Figure 9 is a graph showing the relationship between the thickness GT of the target gas and the coefficient k. In Figure 9, the thickness GT of the target gas is on the horizontal axis and the coefficient k is on the vertical axis. As shown in Figure 9, the coefficient k decreases as the thickness GT of the target gas increases, and the relationship between the thickness GT of the target gas and the coefficient k can be represented by an approximate straight line.

[0037] Figure 10 is a graph showing the relationship between the thickness GT of the target gas and the coefficient b. In Figure 10, the thickness GT of the target gas is on the horizontal axis and the coefficient b is on the vertical axis. As shown in Figure 10, the coefficient b decreases as the thickness GT of the target gas increases, and the relationship between the thickness GT of the target gas and the coefficient b can be represented by an approximate straight line.

[0038] Even when the thickness GT of the leaked gas differs from the approximate curves C1, C2, and C3, the concentration GC can be estimated from the permeability GP and thickness GT of the leaked gas using the above-mentioned relational equations.

[0039] The inventors have found that the above relation can be accurately approximated by an exponential function in which the concentration GC of the target gas is the independent variable x and the permeability GP of the target gas is the dependent variable y. By using the above exponential function relation (Equation (1)) to estimate the concentration GC of the leaked gas, the estimated concentration GC of the leaked gas can be obtained with relatively high accuracy.

[0040] In some embodiments of the leak gas concentration estimation method, a discharge direction identification step S50 is included, as shown in Figure 1. The discharge direction identification step S50 is performed before the transmittance acquisition step S20 and the thickness acquisition step S30. In the discharge direction identification step S50, the detection area 20 including the object to be detected 2 is imaged, and the discharge direction SD of the leak gas is identified from the captured image. In the discharge direction identification step S50, information extraction (digital image processing) of brightness values ​​(feature quantities) is performed for each region (e.g., pixels) into which the captured image taken in the discharge direction identification step S50 is divided into multiple sections.

[0041] The imaging device 3 that captures the image in the ejection direction identification step S50 may be the same as or different from the imaging device 3 that captures the first or second image. The image captured in the ejection direction identification step S50 includes at least a portion of the leaked gas LG, environmental gas AG, and boundary B that form the gas cloud GCL in the ejection direction. Information regarding the presence or absence of leaked gas can be obtained from the brightness value of the image captured in the ejection direction identification step S50. In addition, the shape of the gas cloud GCL can be identified from the brightness value of the image captured in the ejection direction identification step S50, and the ejection direction SD of the leaked gas and the central axis CL of the gas cloud GCL can be identified from the shape of the gas cloud GCL.

[0042] In one embodiment, during the ejection direction identification step S50, the imaging device 3 is moved around the gas cloud GCL by a transport device 5 or the like. Then, in the image captured during the ejection direction identification step S50, the imaging device 3 is moved to a position where the area of ​​the gas cloud GCL at a certain distance from the gas cloud GCL is minimized. The imaging direction D3 (see Figure 2) of the imaging device 3 moved to the position where the area of ​​the gas cloud GCL at a certain distance from the gas cloud GCL is minimized is in the opposite direction to the ejection direction SD of the leaked gas and in the direction of the extension of the central axis CL of the gas cloud GCL. Therefore, the ejection direction SD of the leaked gas and the central axis CL of the gas cloud GCL can be identified from the imaging direction of the imaging device 3.

[0043] By identifying the emission direction SD of the leaked gas from the captured image of the detection area 20, the emission direction SD of the leaked gas can be easily determined. By identifying the emission direction SD of the leaked gas in the emission direction determination step S50, the position of the imaging device 3 that images the leaked gas in the transmittance acquisition step S20 and the thickness acquisition step S30 can be made appropriate, resulting in more accurate transmittance GP and thickness GT of the leaked gas obtained from the captured image.

[0044] Figure 11 is a schematic perspective view of the imaging device 3 and the calibration plate 4. Figures 12 and 13 are explanatory diagrams illustrating the adjustment of the sensitivity of the imaging device 3 using the calibration plate 4. Figure 12 shows the image obtained when acquiring the relationship described above. This image includes a calibration plate image 41 obtained by imaging the calibration plate 4 included in the imaging range 30. Figure 13 shows the image obtained by imaging without adjusting the sensitivity of the imaging device 3 using the calibration plate 4. This image includes a calibration plate image 42 obtained by imaging the calibration plate 4 included in the imaging range 30.

[0045] External factors, such as ambient light (sunlight) and the surrounding environment (temperature, etc.), may cause the overall brightness value of the captured image to increase or decrease. The surface of the calibration plate 4 that is imaged by the imaging device 3 has been treated to reduce its brightness, such as by applying black paint. The calibration plate image 41 shown in Figure 11 and the calibration plate image 42 shown in Figure 12 are images of the same calibration plate 4 with the same brightness, but the brightness of the calibration plate image has changed due to the influence of external factors.

[0046] In some embodiments of the leak gas concentration estimation method, a sensitivity adjustment step S70 is included, as shown in Figure 1. The sensitivity adjustment step S70 is performed before imaging in the first imaging step S21 (transmittance acquisition step S20). In the sensitivity adjustment step S70, the sensitivity (temperature observation range) of the imaging device 3 configured to image the leak gas in the transmittance acquisition step S20 is adjusted based on the calibration plate image 41 obtained by imaging the calibration plate 4 included in the imaging range 30 when acquiring the above-mentioned relational expression, and the calibration plate image 42 obtained by imaging the calibration plate 4 included in the imaging range 30 when imaging in the transmittance acquisition step S20. The calibration plate 4 that is the target of imaging in the calibration plate image 41 and the calibration plate image 42 only needs to have the same brightness, and is not limited to being the same.

[0047] In the sensitivity adjustment step S70, the brightness value of the calibration plate image 41 acquired during imaging to obtain the above relational expression is used as the reference value, and the sensitivity (temperature observation range) of the imaging device 3 can be adjusted within the dynamic range of the imaging device 3 so that the brightness value of the calibration plate image 42 acquired during imaging in the transmittance acquisition step S20 matches the reference value. By performing this sensitivity adjustment of the imaging device 3, the influence of external factors can be suppressed from the image acquired during imaging, and by making the brightness value of the image appropriate as a comparison target, the estimated leak gas concentration GC becomes more accurate.

[0048] Furthermore, the sensitivity adjustment step S70 may be performed not only before imaging in the first imaging step S21 (transmittance acquisition step S20), but also before imaging in the thickness detection step S32 (thickness acquisition step S30) and before imaging in the ejection direction identification step S50.

[0049] In several embodiments of the leak gas concentration estimation method, as shown in Figure 11, the calibration plate 4 described above is supported by the imaging device 3 so as to be included in the imaging range 30. In the embodiment shown in Figure 11, the calibration plate 4 is supported by the imaging device 3 via a support member 43, one end of which is connected to the calibration plate 4 and the other end of which is connected to the imaging device 3.

[0050] By supporting the calibration plate 4 in the imaging device 3 so that it is included in the imaging range 30, the image captured by the imaging device 3 will always include the calibration plate image. As a result, there is no need to prepare the calibration plate 4 when imaging with the imaging device 3, making it possible to easily perform the sensitivity adjustment step S70.

[0051] In some embodiments of the leak gas concentration estimation method, a transfer step S60 is included, as shown in Figure 1. In the transfer step S60, the imaging device 3 is transferred by the transfer device 5. The transfer in the transfer step S60 moves the imaging device 3 to the imaging position before imaging in each step of the leak gas concentration estimation method (first imaging step S21, thickness detection step S32, ejection direction identification step S50) (and before the sensitivity adjustment step S70). By transferring the imaging device 3 with the transfer device 5, imaging in the leak gas concentration estimation method becomes possible without using multiple imaging devices 3.

[0052] Figures 14 and 15 are explanatory diagrams illustrating a transfer device 5 in one embodiment of the present disclosure. In the embodiment shown in Figure 14, the transfer device 5 includes a plurality (four in the illustrated example) of wire members 51 that suspend and support the imaging device 3. Each of the plurality of wire members 51 is supported by a corresponding support column 52 so as to be able to adjust the length of the wire member 51 from the support column 52 to the imaging device 3. The plurality of support columns 52 are arranged at a distance from each other. By suspending and supporting the imaging device 3 with a plurality of wire members 51, the position and height of the imaging device 3 can be easily changed, thus easily accommodating imaging from multiple directions in the leak gas concentration estimation method.

[0053] In the embodiment shown in Figure 15, the transport device 5 includes a self-propelled mobile body 50 equipped with an imaging device 3. The mobile body 50 is capable of traveling around the object to be detected 2 on the floor surface where the object to be detected 2 is installed. The mobile body 50 may be configured to receive information (signals) from other devices (in the illustrated example, a leak gas concentration estimation device 1) via wired or wireless communication, and may travel in accordance with the information (signals) received from the other devices, or it may travel on the floor surface according to a predetermined travel route, and when leak gas is detected using the imaging device 3, it may be configured to change the travel route to a predetermined travel route for leak gas detection, specifically, a travel route that passes through the imaging positions of each step (first imaging step S21, thickness detection step S32, ejection direction identification step S50) in the leak gas concentration estimation method by the imaging device 3. By moving the mobile body 50 equipped with the imaging device 3, imaging by the imaging device 3 becomes possible over a relatively wide area.

[0054] (Leak gas concentration estimation device) Figure 16 is a schematic diagram of a leak gas concentration estimation device 1 according to one embodiment of the present disclosure. In some embodiments of the leak gas concentration estimation device 1, as shown in Figure 16, the device comprises an association information acquisition unit 101, a transmittance acquisition unit 102, a thickness acquisition unit 103, and a concentration estimation unit 104. The leak gas concentration estimation device 1 receives captured images (image data), such as a first captured image and a second captured image, from the aforementioned imaging device 3 via information transmission means such as wired communication or wireless communication. The captured images (image data) sent from the imaging device 3 are stored in the storage device 13 of the leak gas concentration estimation device 1.

[0055] In the illustrated embodiment, the leaked gas concentration estimation device 1 includes an electronic control unit 10 for estimating the concentration GC of the leaked gas. The leaked gas concentration estimation device 1 may be configured as a microcomputer including an input device 11 (input interface), an output device 12 (output interface), a storage device 13 (memory such as ROM or RAM, external storage device, etc.), and an arithmetic unit 14 (CPU), as shown in Figure 16. The electronic control unit 10 may realize each operation of the leaked gas concentration estimation device 1 (for example, association information acquisition unit 101, transmittance acquisition unit 102, thickness acquisition unit 103, concentration estimation unit 104, etc.) by the CPU operating (for example, performing calculations on data) according to instructions of a program loaded into the main memory of the above-mentioned memory.

[0056] The association information acquisition unit 101 is configured to acquire the association information described above. The association information acquisition unit 101 may acquire the association information stored in the storage device 13, or it may acquire the association information from outside the leak gas concentration estimation device 1.

[0057] In the illustrated embodiment, the leak gas concentration estimation device 1 receives the output (image data) from the imaging device 3 as input to the storage device 13 and the arithmetic unit 14 via the input device 11. The storage device 13 stores the output from the imaging device 3. The arithmetic unit 14 is configured to execute various controls according to the control program stored in the storage device 13.

[0058] The transmittance acquisition unit 102 is configured to perform the transmittance detection step S22 described above. That is, the transmittance acquisition unit 102 is configured to acquire the transmittance GP of the leaked gas from the first captured image. The thickness acquisition unit 103 is configured to perform the thickness detection step S32 described above. That is, the thickness acquisition unit 103 is configured to acquire the thickness GT of the leaked gas from the second captured image. The concentration estimation unit 104 is configured to perform the concentration estimation step S40 described above. That is, the concentration estimation unit 104 is configured to estimate the concentration GC of the leaked gas from the transmittance GP of the leaked gas acquired by the transmittance acquisition unit 102 and the thickness GT of the leaked gas acquired by the thickness acquisition unit 103, based on the association information acquired by the association information acquisition unit 101.

[0059] The leaked gas concentration estimation device 1 can obtain the permeability GP and thickness GT of the leaked gas from an image of the leaked gas. Based on correlation information showing the relationship between the permeability GP, thickness GT, and concentration GC of the leaked gas, it can estimate the concentration GC of the leaked gas from the permeability GP and thickness GT obtained from the image. The leaked gas concentration estimation device 1 does not require an image of the leak location from the object 2 to be detected by the leaked gas; it can estimate the concentration GC of the leaked gas if an image of the leaked gas is available. Therefore, it can be applied even when it is difficult to image the leak location, and it can easily estimate the concentration GC of the leaked gas.

[0060] In this specification, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" shall not only describe such arrangements strictly, but also describe states of relative displacement with tolerances or angles or distances that allow for the same function to be achieved. For example, expressions such as "identical," "equal," and "homogeneous" that describe things being in an equal state not only describe a state of being strictly equal, but also describe a state in which there is a tolerance or a difference that is sufficient to achieve the same function. Furthermore, in this specification, expressions describing shapes such as quadrilaterals and cylindrical shapes shall not only represent geometrically precise quadrilaterals and cylindrical shapes, but also shapes that include uneven surfaces, chamfered surfaces, etc., to the extent that the same effect can be achieved. Furthermore, in this specification, the expressions “equipment,” “includes,” or “possess” of a component are not exclusive expressions that exclude the existence of other components.

[0061] This disclosure is not limited to the embodiments described above, but also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate.

[0062] The contents described in some of the embodiments above can be understood, for example, as follows:

[0063] 1) A method for estimating the leaked gas concentration according to at least one embodiment of the present disclosure is: A method for estimating the concentration of leaked gas, which is gas leaked from an object to be detected (2), The association information acquisition step (S10) involves acquiring association information that associates the permeability (GP) of the gas, the thickness (GT) of the gas, and the concentration (GC) of the gas. A transmittance acquisition step (S20) is performed to image the leaked gas along a first direction (D1) intersecting the ejection direction (SD) of the leaked gas, and to obtain the transmittance (GP) of the leaked gas from the acquired image, A thickness acquisition step (S30) is performed to image the leaked gas along a second direction (D2) that intersects the first direction (D1) with respect to the ejection direction (SD) of the leaked gas as the axis, and to obtain the thickness (GT) of the leaked gas from the acquired image, The system includes a concentration estimation step (S40) which estimates the concentration (GC) of the leaked gas from the permeability (GP) of the leaked gas obtained in the permeability acquisition step (S20) and the thickness (GT) of the leaked gas obtained in the thickness acquisition step (S30), based on the association information.

[0064] According to method 1) above, the permeability (GP) and thickness (GT) of the leaked gas can be obtained from the captured image of the leaked gas. Then, based on the correlation information showing the relationship between the permeability (GP), thickness (GT), and concentration (GC) of the leaked gas, the concentration (GC) of the leaked gas can be estimated from the permeability (GP) and thickness (GT) of the leaked gas obtained from the captured image. In the leaked gas concentration estimation method, it is not necessary to image the leak location from the object (2) from which the leaked gas is detected, and if the leaked gas can be imaged, the concentration (GC) of the leaked gas can be estimated. Therefore, it can be applied even when it is difficult to image the leak location, and the estimation of the concentration (GC) of the leaked gas can be easily performed.

[0065] 2) In some embodiments, the method for estimating the leaked gas concentration described in 1) above, The aforementioned association information is, The method includes a relationship between the transmittance of the gas and the concentration of the gas for each gas thickness, obtained by imaging the gas under different conditions of thickness and concentration, and acquiring the transmittance of the gas for each condition.

[0066] According to method 2) above, the relational equation showing the relationship between the permeability, thickness, and concentration of the target gas, which is the target of concentration estimation, is obtained from the results of actually imaging the target gas. By using the above relational equation to estimate the concentration of the leaked gas, the estimated concentration of the leaked gas will be relatively accurate as it reflects the actual relationship described above.

[0067] 3) In some embodiments, the method for estimating the leaked gas concentration described in 2) above, The aforementioned relation includes an exponential function with the gas concentration as the independent variable and the gas permeability as the dependent variable.

[0068] The inventors have found that the above relation can be accurately approximated by an exponential function with gas concentration as the independent variable and gas permeability as the dependent variable. By using the relation expressed by the exponential function above to estimate the concentration of leaked gas, the estimated concentration of leaked gas can be obtained with relatively high accuracy.

[0069] 4) In some embodiments, the method for estimating the leaked gas concentration described in 2) or 3) above, The system further includes a sensitivity adjustment step (S70) to adjust the sensitivity of the imaging device (3) configured to image the leaked gas in the transmittance acquisition step (S20), based on a calibration plate image (41) obtained by imaging the calibration plate (4) included in the imaging range (30) when acquiring the aforementioned relational expression, and a calibration plate image (42) obtained by imaging the calibration plate (4) included in the imaging range (30) when acquiring the transmittance acquisition step (S20).

[0070] According to method 4) above, the brightness value of the entire captured image may increase or decrease due to the influence of external factors, namely ambient light (sunlight) and the surrounding environment (temperature, etc.). In the sensitivity adjustment step (S70), the brightness value of the calibration plate image (41) acquired during imaging to obtain the above relational expression is used as the reference value, and the sensitivity (temperature observation range) of the imaging device (3) can be adjusted within the dynamic range so that the brightness value of the calibration plate image (42) acquired during imaging in the transmittance acquisition step (S20) matches the reference value. By performing this sensitivity adjustment of the imaging device (3), the influence of external factors can be suppressed from the captured image acquired during imaging, and by making the brightness value of the captured image (3) an appropriate comparison target, the estimated leak gas concentration (GC) becomes more accurate.

[0071] 5) In some embodiments, the method for estimating the leaked gas concentration described in 4) above, The calibration plate (4) is supported by the imaging device (3) so as to be included in the imaging range (30).

[0072] According to the method described in 5) above, by supporting the calibration plate (4) in the imaging device (3) so that it is included in the imaging range (30), the image captured by the imaging device (3) will always include the calibration plate image (42). As a result, there is no need to prepare the calibration plate (4) when imaging with the imaging device (3), making it possible to easily perform the sensitivity adjustment step (S70).

[0073] 6) In some embodiments, the method for estimating the leaked gas concentration described in any of 1) to 5) above, The system further includes a step (S50) of identifying the ejection direction of the leaked gas by imaging the detection area (20) including the object to be detected (2) and identifying the ejection direction (SD) of the leaked gas from the captured image.

[0074] According to the method described in 6) above, the direction of gas ejection (SD) of the leaked gas can be easily determined by identifying it from the captured image of the detection area (20). By determining the direction of gas ejection (SD) of the leaked gas in the ejection direction determination step (S50), the position of the imaging device (3) that images the leaked gas in the transmittance acquisition step (S20) and the thickness acquisition step (S30) can be made appropriate, and the transmittance (GP) and thickness (GT) of the leaked gas that can be obtained from the captured image will be more accurate.

[0075] 7) In some embodiments, the method for estimating the leaked gas concentration described in any of 1) to 6) above, The transfer step (S60) further includes transferring an imaging device (3) configured to image the leaked gas using a transfer device (5), The transfer device (5) includes a plurality of wire members (51) that suspend and support the imaging device (3).

[0076] According to the method described in 7) above, by transporting the imaging device (3) with the transport device (5), imaging in the leak gas concentration estimation method becomes possible without using multiple imaging devices (3). By suspending and supporting the imaging device (3) with multiple wire members (51), the position and height of the imaging device (3) can be easily changed, thus easily accommodating imaging from multiple directions in the leak gas concentration estimation method.

[0077] 8) In some embodiments, the method for estimating the leaked gas concentration described in any of 1) to 6) above, The transfer step (S60) further includes transferring an imaging device (3) configured to image the leaked gas using a transfer device (5), The transport device (5) includes a self-propelled vehicle (50) on which the imaging device (3) is mounted.

[0078] According to the method described in 8) above, by transporting the imaging device (3) with the transport device (5), imaging in the leak gas concentration estimation method becomes possible without using multiple imaging devices (3). By moving the mobile body (50) equipped with the imaging device (3), imaging by the imaging device (3) becomes possible over a relatively wide area.

[0079] 9) A leak gas concentration estimation device (1) according to at least one embodiment of the present disclosure is: A leak gas concentration estimation device (1) for estimating the concentration of leaked gas, which is gas leaked from an object to be detected (2), An association information acquisition unit (101) acquires association information relating the permeability (GP) of the gas, the thickness (GT) of the gas, and the concentration (GC) of the gas. A transmittance acquisition unit (102) acquires the transmittance (GP) of the leaked gas from an image captured of the leaked gas along a first direction (D1) intersecting the ejection direction (SD) of the leaked gas, A thickness acquisition unit (103) acquires the thickness of the leaked gas from an image of the leaked gas captured along a second direction (D2) that intersects the first direction (D1) with respect to the ejection direction (SD) of the leaked gas as the axis, The system includes a concentration estimation unit (104) that estimates the concentration (GC) of the leaked gas from the permeability (GP) of the leaked gas obtained by the permeability acquisition unit (102) and the thickness (GT) of the leaked gas obtained by the thickness acquisition unit (103), based on the association information.

[0080] According to the configuration in 9) above, the permeability (GP) and thickness (GT) of the leaked gas can be obtained from the captured image in which the leaked gas is captured. Then, based on the correlation information showing the relationship between the permeability (GP), thickness (GT), and concentration (GC) of the leaked gas, the concentration of the leaked gas can be estimated from the permeability (GP) and thickness (GT) of the leaked gas obtained from the captured image. The leaked gas concentration estimation device (1) does not require an image of the leak location from the object (2) in which the leaked gas is detected, and the concentration (GC) of the leaked gas can be estimated if there is an image in which the leaked gas is captured. Therefore, it can be applied even when it is difficult to capture the leak location, and the estimation of the concentration (GC) of the leaked gas can be easily performed. [Explanation of Symbols]

[0081] 1. Leaked gas concentration estimation device 2. Objects to be detected 3. Imaging device 4 Calibration plate 5 Transfer device

Claims

1. A method for estimating the concentration of leaked gas, which is gas leaked from an object to be detected, A relationship information acquisition step involves acquiring relationship information that associates the permeability of the gas, the thickness of the gas, and the concentration of the gas. A transmittance acquisition step involves imaging the leaked gas along a first direction intersecting the ejection direction of the leaked gas, and obtaining the transmittance of the leaked gas from the acquired image. A thickness acquisition step involves imaging the leaked gas along a second direction that intersects the first direction with respect to the ejection direction of the leaked gas as the axis, and obtaining the thickness of the leaked gas from the acquired image. The system includes a concentration estimation step which estimates the concentration of the leaked gas from the permeability of the leaked gas obtained in the permeability acquisition step and the thickness of the leaked gas obtained in the thickness acquisition step, based on the association information. Method for estimating leaked gas concentration.

2. The aforementioned association information is, The following is a relationship between the transmittance of the gas and the concentration of the gas for each gas thickness, obtained by imaging the gas under different conditions of thickness and concentration, and acquiring the transmittance of the gas for each condition. The method for estimating the concentration of leaked gas according to claim 1.

3. The aforementioned relation includes an exponential function with the gas concentration as the independent variable and the gas permeability as the dependent variable. The method for estimating the concentration of leaked gas according to claim 2.

4. The invention further includes a sensitivity adjustment step, which adjusts the sensitivity of the imaging device configured to image the leaked gas in the transmittance acquisition step, based on a calibration plate image obtained by imaging a calibration plate included in the imaging range during imaging to acquire the aforementioned relational expression, and a calibration plate image obtained by imaging a calibration plate included in the imaging range during imaging in the transmittance acquisition step. The method for estimating the concentration of leaked gas according to claim 2 or 3.

5. The calibration plate is supported by the imaging device so as to be included in the imaging range. The method for estimating the concentration of leaked gas according to claim 4.

6. The system further includes a step of determining the ejection direction, which involves imaging a detection area including the object to be detected and determining the ejection direction of the leaked gas from the captured image. A method for estimating the concentration of leaked gas according to any one of claims 1 to 3.

7. The system further includes a transfer step of transferring an imaging device configured to image the leaked gas using a transfer device, The transfer device includes a plurality of wire members that suspend and support the imaging device. A method for estimating the concentration of leaked gas according to any one of claims 1 to 3.

8. The system further includes a transfer step of transferring an imaging device configured to image the leaked gas using a transfer device, The transport device includes a self-propelled vehicle equipped with the imaging device. A method for estimating the concentration of leaked gas according to any one of claims 1 to 3.

9. A leak gas concentration estimation device for estimating the concentration of leaked gas, which is gas leaking from an object to be detected, An association information acquisition unit acquires association information relating the permeability of the gas, the thickness of the gas, and the concentration of the gas. A transmittance acquisition unit acquires the transmittance of the leaked gas from an image captured of the leaked gas along a first direction intersecting the ejection direction of the leaked gas, A thickness acquisition unit acquires the thickness of the leaked gas from an image of the leaked gas captured along a second direction intersecting the first direction with respect to the ejection direction of the leaked gas as the axis, The system includes a concentration estimation unit that estimates the concentration of the leaked gas from the permeability of the leaked gas obtained by the permeability acquisition unit and the thickness of the leaked gas obtained by the thickness acquisition unit, based on the association information. Leaked gas concentration estimation device.

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