A device for calibrating the size of dike leakage by unmanned aerial vehicle thermal imaging

Abstract

The application discloses a device for unmanned aerial vehicle thermal imaging dike leakage size quantitative calibration, which comprises a device body, the top surface of the device body is provided with a passive size calibration array and a thermal feature simulation unit, the passive size calibration array comprises a plurality of first materials and second materials arranged at intervals, the infrared radiation emissivity of the first material is less than 0.1, the difference between the infrared radiation emissivity of the first material and the infrared radiation emissivity of the second material is not less than 0.5, the thermal feature simulation unit comprises a temperature control panel and a temperature control module, the temperature control module is attached to the bottom surface of the temperature control panel and is used for controlling the temperature change of the temperature control panel. The application can form a scale with extremely high contrast in the thermal imaging picture, establish clear boundaries and temperature references which are not affected by soil thermal diffusion, improve the calculation accuracy of the leakage area and length, and reduce the detection error rate.

Description

Technical Field

[0001] This invention relates to a calibration device, and more particularly to a device for quantitative calibration of the dimensions of seepage in dikes using thermal imaging from unmanned aerial vehicles (UAVs). Background Technology

[0002] During the flood season, using drones equipped with thermal infrared cameras to inspect dikes for seepage (piping, soil erosion, etc.) has become an important flood control method. The principle is to use the temperature difference between the seeping water and the surrounding dry soil to form abnormal color spots on the thermal imaging map.

[0003] However, existing detection technologies mainly focus on "qualitative" detection, that is, determining where the leak is, but they face significant difficulties in "quantitative" analysis (that is, measuring the specific area, length, and width of the leak area):

[0004] Perspective distortion: Embankments are usually slopes, and the drone's shooting angle is not perpendicular to the slope, resulting in trapezoidal distortion in the image.

[0005] Uncertainty in scale: Fluctuations in the drone's flight altitude (relative altitude) cause the ground resolution (GSD) of the image to change constantly, making it difficult to calculate the actual area directly from pixels.

[0006] Thermal diffusion blurring: Due to soil capillary action, the thermal characteristics of the actual seepage edge are gradual, resulting in blurred boundaries on infrared images and making it difficult to define the size.

[0007] Current technology lacks a device that can be used for quantitative calibration of UAV thermal imaging to assist in the quantitative determination of dike seepage dimensions. Summary of the Invention

[0008] To address the shortcomings of the existing technology, this invention provides a device for quantitative calibration of the size of seepage in dikes using UAV thermal imaging. This device solves the problems of uncertain image scale due to flight altitude fluctuations and blurred seepage boundaries caused by soil thermal diffusion when using existing UAV thermal imaging to detect seepage in dikes.

[0009] The technical solution of this invention is as follows:

[0010] A device for quantitative calibration of the dimensions of seepage in dikes using thermal imaging from unmanned aerial vehicles (UAVs) includes a device body. The top surface of the device body is provided with a passive dimension calibration array and a thermal characteristic simulation unit. The passive dimension calibration array includes several spaced-apart first and second materials. The infrared emissivity of the first material is less than 0.1, and the difference between the infrared emissivity of the first material and the infrared emissivity of the second material is not less than 0.5. The thermal characteristic simulation unit includes a temperature control panel and a temperature control module. The temperature control module is attached to the bottom surface of the temperature control panel and is used to control the temperature change of the temperature control panel.

[0011] Furthermore, the device body is equipped with a temperature sensor and a controller. The temperature sensor is used to detect the ground temperature and send it to the controller. The controller is electrically connected to the temperature control module and controls the operation of the temperature control module so that the temperature of the temperature control panel and the ground temperature maintain a preset temperature difference.

[0012] Furthermore, the temperature control module is a semiconductor cooling / heating module, the cold end of the semiconductor cooling / heating module is attached to the temperature control panel, the hot end of the semiconductor cooling / heating module is provided with a heat dissipation device, and the controller has a first control mode and a second control mode; the first control mode: the cold end of the semiconductor cooling / heating module is cooled, and the second control mode: the cold end of the semiconductor cooling / heating module is heated.

[0013] Furthermore, in order to solve the problem that perspective distortion caused by the imaging of the embankment slope affects the measurement of leakage, the device body is equipped with an attitude sensing unit and a data transmission unit. The attitude sensing unit is used to detect the pitch angle and roll angle of the device body, and the data transmission unit is used to transmit the pitch angle and roll angle data to the outside world.

[0014] Furthermore, the device body is equipped with telescopic outriggers.

[0015] Furthermore, the infrared emissivity of the second material is greater than 0.95.

[0016] Furthermore, the first material is polished aluminum foil or stainless steel strip, and the second material is a black matte material.

[0017] Furthermore, the surface of the temperature control panel is coated with a coating that has an infrared emissivity greater than 0.95.

[0018] Furthermore, the passive dimensional calibration array is arranged around the thermal characteristic simulation unit, and the periphery of the thermal characteristic simulation unit is covered with a thermal insulation layer. The thermal insulation layer reduces the temperature influence of the thermal characteristic simulation unit on the passive dimensional calibration array when the temperature changes.

[0019] Furthermore, the thermal characteristic simulation unit is provided with a variable diameter aperture mechanism, which covers the temperature control panel and changes the aperture diameter to change the exposed area of ​​the temperature control panel.

[0020] The advantages of the technical solution provided by this invention are as follows:

[0021] By setting up a passive dimension calibration array with known physical dimensions and utilizing the property of low-emissivity materials to reflect cold background radiation from the sky, a scale with extremely high contrast is formed in the thermal imaging image without the need for power supply. This provides real-time geometric constraints for thermal imaging, eliminates scale errors caused by fluctuations in the drone's flight altitude, and assists in the accurate calculation of leakage area and length. Furthermore, by combining the passive dimension calibration array with a temperature-controllable thermal feature simulation unit to generate a temperature difference comparison with the environment, a clear boundary and temperature reference unaffected by soil heat diffusion are established within the field of view, significantly reducing the detection false positive rate. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the device used for quantitative calibration of seepage dimensions in dikes using UAV thermal imaging, as described in this embodiment.

[0023] Figure 2 This is a structural diagram of the top surface of the device body.

[0024] Figure 3 This is a schematic diagram of the thermal characteristic simulation unit.

[0025] Figure 4 This is a schematic diagram of the working scenario of a device used for quantitative calibration of the size of seepage in dikes using drone thermal imaging.

[0026] Figure 5 This is an electrical principle block diagram of a device used for quantitative calibration of dike seepage dimensions using UAV thermal imaging. Detailed Implementation

[0027] The present invention will be further described below with reference to embodiments. It should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention. After reading this description, any modifications of this description in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0028] Please combine Figure 1 As shown, the first embodiment of the present invention relates to a device for quantitative calibration of the size of seepage in dikes by thermal imaging of unmanned aerial vehicles, which includes a device body 1. The device body 1 can be made into a rectangular box structure. A passive size calibration array 2 and a thermal feature simulation unit 3 are provided on the top surface of the device body 1.

[0029] like Figure 2As shown, the passive size calibration array 2 is composed of several spaced-apart first materials 201 and second materials 202. The infrared emissivity of the first material 201 is less than 0.1, and the difference between the infrared emissivity of the first material 201 and the second material 202 is not less than 0.5. In this embodiment, the first material 201 is a polished aluminum foil strip, with a magnet bonded to its back side, allowing it to adhere to the top surface of the iron device body 1. Alternatively, a polished stainless steel strip can also be used as the first material 201. In this embodiment, the second material 202 is a black ABS plastic sheet with an infrared emissivity of 0.95. Similarly, a magnet is bonded to the back side of the black ABS plastic sheet, allowing it to adhere to the top surface of the iron device body 1. The magnetic adsorption method allows for convenient adjustment of the shape formed by the first material 201 and the second material 202. Specifically, they can be arranged in a straight line or spaced apart in the longitudinal and transverse directions to form physical dimension references along different axes. In some other embodiments, the first material 201 and the second material 202 can also be made into rings of different diameters and arranged coaxially, or formed into multiple grid-like arrangements. This passive dimension calibration array 2, through the alternation of the low-infrared emissivity first material 201 and the high-infrared emissivity second material 202, utilizes the characteristic of the low-infrared emissivity first material 201 reflecting the cold background radiation of the sky, to form stripes with extremely high contrast in the thermal imaging image without the need for power supply. By making the width of the first material 201 and the second material 202 into specific sizes, such as 5cm or 10cm, the stripes form a scale that can clearly indicate the physical length, thereby providing standard geometric constraints for calculating the leakage area and length based on thermal imaging images collected by UAVs, and improving calculation accuracy.

[0030] Please combine Figure 3As shown, the thermal characteristic simulation unit mainly includes a temperature control panel 301 and a temperature control module 302. The temperature control panel 301 is made into a regular geometric shape, such as a rectangle or a circle, to generate a thermal radiation reference with a specific temperature difference and shape. The thermal characteristic simulation unit 301 can be set in the middle of the top surface of the device body 1, and the passive size calibration array 2 is arranged around the thermal characteristic simulation unit 302. The temperature control panel 301 is a metal plate, and its top surface serves as a thermal radiation emitting surface. In this embodiment, the temperature control panel 301 is made of a 3mm thick aviation aluminum plate with good thermal conductivity. The surface of the temperature control panel 301 is also sprayed with a matte black paint with an emissivity of 0.96 to radiate uniform thermal infrared signals outward. The temperature control module 302 is attached to the bottom surface of the temperature control panel 301. The temperature control module 301 includes a heating element that uses a flexible polyimide (PI) heating film or a carbon crystal heating plate as a heat source and a temperature controller. The temperature controller controls the operation of the heating element according to the set temperature, so that the temperature of the temperature control panel 301 changes to create a temperature difference with the ground temperature. This temperature difference is usually 5 to 10°C. For example, when the ground temperature is 10°C, the temperature control panel 301 is heated to reach 20°C.

[0031] In this embodiment, the power supply for the thermal feature simulation unit 3 can be either a battery pack built into the device body 1 or an external mobile power supply. The battery pack or mobile power supply constitutes the power module 4. The principle of calibration using the device for quantitative calibration of dike seepage dimensions using UAV thermal imaging in this embodiment is as follows: Figure 4 As shown, the device A is placed on the back slope B of the dike that needs to be inspected. The power module 4 is turned on to make the thermal feature simulation unit 3 work until the temperature control panel 301 is heated to the predetermined temperature. Then, the drone C performs thermal imaging inspection to detect the damp or seepage areas D on the dike surface to determine the leakage situation.

[0032] A temperature control panel 301 with a defined temperature difference from the ambient surface temperature and a regular shape, along with a passive dimensional calibration array 2 as a dimensional marker, provides a physically accurate and temperature-contrast-strong "artificial target." This target provides a mapping reference for the seepage boundary caused by soil heat diffusion in three aspects, thereby achieving the purpose of accurate correction and quantitative assessment of the seepage area size:

[0033] First, a pixel-to-space scaling mapping can be established. Due to the dynamic changes in the drone's altitude, focal length, and shooting angle, the distance represented by one pixel in a thermal imaging image can vary. The temperature control panel 301, with its regular shape, and the passive size calibration array 2, can determine the size of the temperature control panel 301 by identifying its boundaries within the same image. This allows for the calculation of the ground sampling interval (GSD) under the current operating conditions, thereby transforming the blurry leakage "spots" into true "physical dimensions."

[0034] Secondly, the extraction threshold for "boundary temperature" can be determined. The reason why the seepage boundary is blurred is that it is impossible to determine at what threshold point the temperature drops to in the thermal imaging image to be considered the "edge of water". However, by using the temperature difference between the temperature control panel 301 and the surface temperature, a temperature difference similar to that between the dry soil pile of the dike and the actual seepage water (wet area) can be simulated. In subsequent measurements, the edge of the actual seepage water can be inferred by comparing the "diffusion edge" performance of the temperature control panel 301 in the thermal imaging image. For example, if it is known that the edge of the temperature control panel 301 occupies 3 transition pixels in the thermal imaging image, then the actual seepage area can be "de-blurred" and corrected by using a deconvolution algorithm or an edge detection operator.

[0035] Third, environmental impact compensation: the temperature control panel 301 serves as a reference source, and its image in the thermal imaging generally reflects the impact of current solar radiation, atmospheric humidity, and wind speed on infrared detection. Therefore, in subsequent measurements, it is equivalent to providing a zero-point calibration that already includes compensation for environmental factors.

[0036] For example, based on the above, the algorithm in quantitative measurement can clearly state that, under the current drone flight altitude and environment, one pixel in the thermal imaging image represents 5 centimeters, and the diffusion width corresponding to a 5°C decrease in temperature is 2 pixels. With this mathematical relationship, edge extraction and size correction can be performed on the blurred leakage hot spots, thereby achieving quantitative calibration.

[0037] Another embodiment of the present invention provides a device for quantitative calibration of levee seepage dimensions using UAV thermal imaging. Multiple telescopic legs 5 are provided on the device body. When the telescopic legs 5 are manually telescopic, a spirit level (not shown, but at any position on the top surface) can be provided on the top surface of the device body 1. This allows for manual adjustment of each telescopic leg 5 to ensure the top surface of the device body is level, providing a horizontal reference for quantitative measurement. The ends of the telescopic legs 5 are equipped with universal adaptive foot pads for support on uneven levee slopes. Preferably, a leveling base 6 with electrically operated telescopic legs can also be used. The leveling base 6 is a prior art device used to support the device body 1. An attitude sensing unit 7 (such as an IMU or inclinometer) is installed inside the device body 1 to detect the attitude of the top surface of the device body 1. Please refer to... Figure 5As shown, the device body 1 also includes a main control unit 8 and a data transmission unit 9, with the main control unit 8 acting as a controller. The data transmission unit 9 is equipped with a transmitting antenna 901, which is mounted on the top surface of the device body 1. The quantitative calibration device is placed on the slope of the embankment. The attitude sensing unit 7 detects the pitch and roll angles of the device body 1 and transmits them to the main control unit 8. The main control unit 8 then transmits the pitch and roll angle data externally (such as to a drone or ground station) via the data transmission unit 9 using 4G / LoRa or other methods. In addition, the main control unit 8 controls the leveling base 6 to maintain a horizontal position on the top surface of the device body 1 through the motor drive circuit 10. The attitude sensing unit 7 records the slope and tilt angle data in real time, providing geometric parameters for subsequent image processing and effectively correcting trapezoidal projection distortion caused by non-perpendicular shooting angles.

[0038] Please combine Figure 3 As shown, in this embodiment, the thermal characteristic simulation unit 3 uses a semiconductor cooling / heating module as the temperature control module 302. The cold end of the semiconductor cooling / heating module is attached to the bottom surface of the temperature control panel 301, and the hot end of the semiconductor cooling / heating module is equipped with a heat dissipation device, which includes a heat sink 302a and a cooling fan 302b. The main control unit 8 acts as a controller, controlling the current direction of the semiconductor cooling / heating module through the TEC drive circuit 11, thereby changing the control mode and power of the semiconductor cooling / heating module. The semiconductor cooling / heating module has a first control mode and a second control mode. In the first control mode, the cold end of the semiconductor cooling / heating module cools, reducing the temperature of the temperature control panel, and the heat generated at the hot end is dissipated through the heat dissipation device. In the second control mode, the cold end of the semiconductor cooling / heating module heats, and the generated heat is used to raise the temperature of the temperature control panel.

[0039] The device body 1 is also equipped with a temperature sensor 12, which is used to detect the surface temperature and send it to the main control unit. Specifically, the temperature sensor 12 is an infrared thermometer (not shown) installed at the bottom of the device body 1. The main control unit 8 receives the surface temperature measured by the temperature sensor 12 and then controls the cold end of the semiconductor cooling / heating module to cool or heat, so that the temperature of the temperature control panel 301 is maintained at a preset temperature difference (5-10°C) with the surface temperature. The device body 1 can be configured to operate the semiconductor cooling / heating module in different modes. Specifically, in summer, when the sun shines directly, the surface and the inside of the dike usually absorb a lot of heat. At this time, because the temperature of groundwater or deep water is much lower than that of the sun-heated surface, the seepage of the dike is often a "cold source". The semiconductor cooling / heating module works in the first control mode, lowering the temperature of the temperature control panel 301 to simulate "cold" seepage, forming a cold point that is colder than the surface, thus improving the sensitivity of the UAV in capturing the boundary of low-temperature targets in summer. Conversely, in winter, the surface temperature is lower due to atmospheric influence, while the groundwater temperature remains relatively constant. At this time, the temperature of water seeping from deep within the ground is often higher than the frozen surface temperature. The semiconductor cooling / heating module then operates in the second control mode, and the temperature control panel 301 heats up to simulate hot spots with temperatures higher than the surface temperature, thereby improving the drone's sensitivity in capturing the boundaries of high-temperature targets in winter environments.

[0040] In this embodiment, to simulate leak points of different sizes, the thermal characteristic simulation unit 3 is equipped with a variable diameter aperture mechanism 13. The variable diameter aperture mechanism 13 covers the temperature control panel 301 and is used to shield and control the exposed area of ​​the temperature control panel 301. The variable diameter aperture mechanism 13 is a prior art structure, which is equipped with a micro motor 1301 controlled by the main control unit 8 to drive the blade 1302 to change the aperture diameter, thereby adjusting the exposed area of ​​the temperature control panel 301 and changing the area of ​​the temperature control panel 301 that can be photographed. For example, it can vary within a circular range with a diameter of 20cm to 5cm. By changing the area of ​​the thermal radiation region photographed by the temperature control panel 301, it is convenient to correct the size of all blurred leak targets in complex field environments through post-processing. In addition, in order to control the thermal impact of the temperature change of the temperature control panel 301 on the surrounding passive size calibration array 2, the thermal characteristic simulation unit 3 has an outer shell 303, and the inner wall of the outer shell 303 is wrapped with aerogel or polyurethane foam material to form a heat insulation layer (not shown).

Claims

1. A device for quantitative calibration of seepage dimensions in dikes using thermal imaging from unmanned aerial vehicles (UAVs), characterized in that, The device includes a main body, the top surface of which is provided with a passive size calibration array and a thermal characteristic simulation unit. The passive size calibration array includes several first materials and second materials arranged at intervals. The infrared emissivity of the first material is less than 0.1, and the difference between the infrared emissivity of the first material and the infrared emissivity of the second material is not less than 0.

5. The thermal characteristic simulation unit includes a temperature control panel and a temperature control module. The temperature control module is attached to the bottom surface of the temperature control panel and is used to control the temperature change of the temperature control panel.

2. The device for quantitative calibration of seepage dimensions in dikes using UAV thermal imaging according to claim 1, characterized in that, The device body is equipped with a temperature sensor and a controller. The temperature sensor is used to detect the ground temperature and send it to the controller. The controller is electrically connected to the temperature control module and controls the operation of the temperature control module to maintain a preset temperature difference between the temperature of the temperature control panel and the ground temperature.

3. The device for quantitative calibration of seepage dimensions in dikes using UAV thermal imaging according to claim 2, characterized in that, The temperature control module is a semiconductor cooling / heating module. The cold end of the semiconductor cooling / heating module is attached to the temperature control panel, and the hot end of the semiconductor cooling / heating module is equipped with a heat dissipation device. The controller has a first control mode and a second control mode. The first control mode is: the cold end of the semiconductor cooling / heating module is cooled; the second control mode is: the cold end of the semiconductor cooling / heating module is heated.

4. The device for quantitative calibration of seepage dimensions in dikes using UAV thermal imaging according to claim 1, characterized in that, The device body is equipped with an attitude sensing unit and a data transmission unit. The attitude sensing unit is used to detect the pitch angle and roll angle of the device body, and the data transmission unit is used to transmit the pitch angle and roll angle data to the outside world.

5. The device for quantitative calibration of seepage dimensions in dikes using UAV thermal imaging according to claim 4, characterized in that, The device body is equipped with telescopic support legs.

6. The device for quantitative calibration of seepage dimensions in dikes using UAV thermal imaging according to claim 1, characterized in that, The infrared emissivity of the first material is less than 0.1, and the infrared emissivity of the second material is greater than 0.

95.

7. The device for quantitative calibration of seepage dimensions in dikes using UAV thermal imaging according to claim 1, characterized in that, The first material is polished aluminum foil or stainless steel strip, and the second material is a black matte material.

8. The device for quantitative calibration of seepage dimensions in dikes using UAV thermal imaging according to claim 1, characterized in that, The surface of the temperature control panel is coated with a coating that has an infrared emissivity greater than 0.

95.

9. The device for quantitative calibration of seepage dimensions in dikes using UAV thermal imaging according to claim 1, characterized in that, The passive dimensional calibration array is arranged around the thermal characteristic simulation unit, and the thermal characteristic simulation unit is covered with a thermal insulation layer.

10. The device for quantitative calibration of seepage dimensions in dikes using UAV thermal imaging according to claim 1, characterized in that, The thermal characteristic simulation unit is equipped with a variable diameter aperture mechanism, which covers the temperature control panel. The variable diameter aperture mechanism changes the aperture diameter to change the exposed area of ​​the temperature control panel.

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