Unmanned aerial methane concentration laser wide-range scanning device and three-dimensional reconstruction measurement method

Abstract

The application discloses a kind of unmanned aerial methane concentration laser wide-range scanning device and three-dimensional reconstruction measurement method, device includes unmanned aerial vehicle, front side laser methane detection module and rear side laser methane detection module fixedly installed at the bottom of unmanned aerial vehicle, two detection modules are arranged in front and back along the direction of flight of unmanned aerial vehicle and coplanar, laser emitting unit and laser receiving unit are configured;During the flight of unmanned aerial vehicle, same spatial position is successively scanned and covered;By angle-concentration correlation algorithm fusion double-angle time sequence detection data, the actual concentration three-dimensional space distribution of methane gas in detection area is obtained by reconstruction calculation.The application can solve the problems of two-dimensional detection limitation, low three-dimensional detection efficiency, poor data correlation, insufficient accuracy and lack of accident emergency capability in existing methane detection technology, and can realize efficient and accurate three-dimensional detection of methane gas concentration in target area, while having the ability to judge the diffusion trend after leakage accident.

Description

Technical Field

[0001] This invention belongs to the field of gas detection and UAV application technology, specifically relating to a UAV-borne laser wide-area scanning device for methane concentration and a three-dimensional reconstruction measurement method. Background Technology

[0002] Methane, a gas possessing both high calorific value and a strong greenhouse effect, is widely used and emitted in industrial production (such as oil and gas extraction and chemical synthesis), urban gas supply, and landfill disposal. Data shows that methane's greenhouse potential is more than 28 times that of carbon dioxide, and its leakage not only causes severe energy waste but also risks explosions, poisoning, and other safety accidents, posing a dual threat to ecological sustainability and human life and property safety. Therefore, achieving accurate detection and spatial distribution mapping of methane gas concentration, especially obtaining concentration gradient information in three-dimensional space, has become a core technological requirement for leak tracing, risk warning, and environmental compliance management, possessing irreplaceable application value in scenarios such as oil and gas fields, long-distance natural gas pipelines, chemical industrial parks, and landfills.

[0003] Existing methane detection technologies are mainly divided into three categories: traditional fixed-point monitoring, manual inspection, and drone-borne detection. Among them, fixed-point monitoring relies on the sensor layout of pre-set monitoring stations, which has the disadvantages of limited coverage, many blind spots, and difficulty in adapting to complex terrain. Manual inspection requires staff to carry portable detection equipment to carry out on-site operations, which is not only inefficient and has a long detection cycle, but also prone to safety hazards when operating in high-risk areas (such as confined spaces and around high-pressure pipelines). With the rise of drone technology, the detection method of drones equipped with methane detection modules has gradually become the industry mainstream. However, the existing technology still has significant shortcomings: First, most drones are equipped with single-point detection modules, which can only acquire discrete single-point concentration data on the flight path and cannot form a regionalized spatial distribution of concentration. Second, although some unidirectional scanning detection modules (such as vertical downward scanning) can achieve two-dimensional plane coverage, they lack angular differentiation detection design in the vertical direction, making it difficult to capture the concentration gradient at different height levels. They can only output two-dimensional concentration distribution results and cannot meet the needs of three-dimensional spatial detection. Third, a few technical solutions that attempt to achieve three-dimensional detection by adjusting the drone's flight altitude have problems such as low detection efficiency, lack of spatial correlation of detection data at different height levels, and difficulty in guaranteeing the accuracy of concentration calculation. Moreover, multiple take-off and landing flights can easily lead to uneven overlap of detection areas, data redundancy or omissions, and cannot meet the needs of efficient inspection of large-scale areas. Summary of the Invention

[0004] The purpose of this invention is to provide an unmanned aerial vehicle (UAV)-borne laser wide-area scanning device for methane concentration and a three-dimensional reconstruction measurement method, which can solve the problems of limitations in two-dimensional detection, low efficiency of three-dimensional detection, poor data correlation, insufficient accuracy and lack of emergency response capability in existing methane detection technologies. It can achieve efficient and accurate three-dimensional detection of methane gas concentration in the target area, and at the same time has the ability to judge the diffusion trend after a leakage accident.

[0005] To achieve the above objectives, the present invention provides an unmanned aerial vehicle (UAV)-borne methane concentration laser wide-area scanning device, comprising an UAV and a ground control terminal. The UAV is equipped with a wireless communication module for data interaction with the ground control terminal. A laser methane detection module is installed on the bottom of the UAV. The laser methane detection module includes a front laser methane detection module and a rear laser methane detection module arranged in a front-to-back manner along the flight direction of the UAV and located on the same vertical plane. Both the front and rear laser methane detection modules are equipped with a laser emitting unit and a laser receiving unit. The laser beam emitted by the laser emitting unit of the front laser methane detection module tilts forward to form a front fan-shaped scanning area, and the laser beam emitted by the laser emitting unit of the rear laser methane detection module tilts backward to form a rear fan-shaped scanning area. The front fan-shaped scanning area forms an angle of 30° to 90° with the horizontal plane, and the angle between the front fan-shaped scanning area and the rear fan-shaped scanning area is 30° to 150°. The drone is equipped with a GPS positioning module and a data processing module. The data processing module is connected to the front laser methane detection module, the rear laser methane detection module, and the GPS positioning module, respectively, to receive laser detection data and positioning information, and to calculate the three-dimensional concentration distribution of methane gas.

[0006] As a further aspect of the present invention: the laser emitting unit includes a laser generator, a galvanometer driving assembly and a rotating galvanometer. The direction of the single laser beam emitted by the laser generator is perpendicular to the forward direction of the UAV, and the optical axis of the single laser beam is coplanar with the center of the mirror surface of the rotating galvanometer. The galvanometer driving assembly drives the rotating galvanometer to reciprocate and deflect, thereby scanning the single laser beam to form a fan-shaped scanning area of ​​0° to 120°.

[0007] As a further aspect of the present invention: the laser receiving unit includes a laser detector and a signal conditioning module. The detection field of the laser detector covers the laser beam scanning area and directly receives the laser signal after being scattered by methane gas. The signal conditioning module is electrically connected to the laser detector, processes the laser signal to form a detection electrical signal for data calculation, and transmits the electrical signal to the data processing module in real time.

[0008] To achieve the above-mentioned objectives, the present invention also provides a method for wide-area reconstruction measurement of methane concentration using laser on a UAV, based on the aforementioned wide-area scanning device for methane concentration using laser, comprising the following steps: The system controls the drone to fly along the target area, and the GPS positioning module collects the drone's three-dimensional coordinate information in real time. The front and rear laser methane detection modules are activated, and the two modules simultaneously and rapidly scan the area below the drone. As the drone flies forward, the same spatial position is first scanned by the front laser methane detection module, and then scanned by the rear laser methane detection module as the drone moves forward, achieving dual-angle coverage. The laser receiving unit receives the laser signal scattered by methane gas in real time, processes it to form a detection electrical signal, and transmits it to the data processing module. The data processing module uses an angle-concentration correlation algorithm to fuse and calculate the dual-angle detection data, obtain the actual methane gas concentration value at each detection location, and bind the concentration value with the corresponding three-dimensional coordinates to form a "location-concentration" spatial dataset. The ground control terminal receives the flight path and methane detection information of the UAV, and integrates the flight path and methane detection information according to the time axis to generate a methane concentration distribution map and a three-dimensional concentration spatial distribution map of the inspection area.

[0009] As a further aspect of the present invention: a methane concentration threshold is set, and when the methane concentration in the detection area exceeds the set threshold, the ground control terminal outputs an alarm signal.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a fixed installation of front and rear dual-laser methane detection modules and a bidirectional fan-shaped scanning design with differentiated angles. By using a sequential dual-angle scanning method, it achieves two laser coverage detections at the same detection position. Combined with the angle-concentration correlation algorithm preset in the data processing module, the dual-angle detection data is fused and processed, which can effectively eliminate the environmental interference that single-angle detection is susceptible to and significantly improve the accuracy of methane concentration detection. The laser emitting unit of this invention, through the cooperation of the galvanometer driving component and the rotating galvanometer, deflects and scans a single laser beam at high speed to form a large-angle fan-shaped scanning area. It can achieve large-area, high-density spatial coverage detection without the need for multiple take-off and landing and back-and-forth flights of the UAV. Combined with the three-dimensional flight trajectory of the UAV, it generates three-dimensional distribution information of methane gas concentration, which solves the problem of low efficiency of traditional three-dimensional detection and takes into account both efficient inspection of large-scale areas and fine detection of abnormal areas. In this invention, the laser emitting unit and the laser receiving unit are independent of each other. The laser detector directly faces the ground to receive the gas scattered signal, which effectively avoids optical path interference and signal attenuation, and improves the stability and effectiveness of signal reception. The invention has no complex moving parts in its overall structure, is highly reliable and adaptable, and is compatible with mainstream industrial-grade drone platforms on the market. It can simultaneously meet multiple needs such as large-scale area efficient inspection, precise location of leak points, three-dimensional presentation of concentration gradients, and judgment of gas diffusion range, diffusion path and development trend after a leak accident. It has high engineering practical value and promotion prospects. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of the UAV-borne methane concentration laser wide-area scanning device of the present invention; Figure 2 This is a schematic diagram of the internal structure of the laser methane detection module of the present invention; Figure 3 This is a schematic diagram of the operation of the UAV performing lateral scanning along the flight direction according to the present invention; Figure 4 This is a schematic diagram of the UAV performing forward scanning according to the present invention.

[0012] In the diagram: 1. UAV, 2. Laser methane detection module, 3. Ground control terminal, 4. Target inspection area, α, angle between the emitted laser and the horizontal plane, β, angle between the front and rear fan-shaped scanning areas, θ, angle of the fan-shaped scanning range; 21. Front laser methane detection module; 22. Rear laser methane detection module; 201. Laser emitting unit; 202. Laser receiving unit; 2011, Laser generator; 2012, Galvanometer drive assembly; 2013, Rotating galvanometer; 2021, Laser detector; 2022, Signal conditioning module. Detailed Implementation

[0013] The invention will now be further described with reference to the accompanying drawings.

[0014] like Figures 1 to 4 As shown, the UAV-borne methane concentration laser wide-area scanning device includes a UAV 1 and a ground control terminal 3. The UAV 1 includes the UAV body and a power system module, a control module, a wireless communication module and a GPS positioning module installed on the UAV body.

[0015] The power system module provides stable flight power for the UAV, meeting the needs of large-area, long-distance outdoor inspection operations; the GPS positioning module provides real-time three-dimensional position information for the UAV, enabling precise spatial positioning of the detection points and providing a basis for three-dimensional matching of methane concentration data; the wireless communication module enables real-time communication between the UAV and the ground control terminal 3, realizing bidirectional transmission and reception of detection data, flight status data, and control commands between the UAV and the ground control terminal 3; and the control module enables the UAV to fly stably according to the commands of the ground control terminal 3.

[0016] The drone 1 is equipped with a laser methane detection module 2 at its bottom. Preferably, the laser methane detection module 2 can be fixedly installed at the bottom of the drone 1 by a mounting bracket. The laser methane detection module 2 includes a front laser methane detection module 21 and a rear laser methane detection module 22 arranged in the same vertical plane along the flight direction of the drone 1. Both the front laser methane detection module 21 and the rear laser methane detection module 22 are equipped with a laser emitting unit 201 and a laser receiving unit 202.

[0017] Furthermore, the laser emitting unit 201 includes a laser generator 2011, a galvanometer driving assembly 2012, and a rotating galvanometer 2013. The direction of the single laser beam emitted by the laser generator 2011 is perpendicular to the forward direction of the UAV 1, and the optical axis of the single laser beam is coplanar with the center of the mirror surface of the rotating galvanometer 2013. The galvanometer driving assembly 2012 drives the rotating galvanometer 2013 to reciprocate and deflect, thereby scanning the single laser beam to form a fan-shaped scanning area of ​​0° to 120°. This structure is simple, has a fast response, and can realize left and right lateral scanning during the flight of the UAV 1.

[0018] Furthermore, the laser receiving unit 202 includes a laser detector 2021 and a signal conditioning module 2022. The detection field of the laser detector 2021 covers the laser beam scanning area and directly receives the laser signal after being scattered by methane gas. The signal conditioning module 2022 is electrically connected to the laser detector 2021 and performs filtering, amplification and photoelectric conversion processing on the received laser signal to form a detection electrical signal for data calculation, and transmits the electrical signal to the data processing module in real time.

[0019] The laser beam emitted by the laser emitting unit 201 of the front laser methane detection module 21 is tilted forward to form a front fan-shaped scanning area, and the laser beam emitted by the laser emitting unit 201 of the rear laser methane detection module 22 is tilted backward to form a rear fan-shaped scanning area. The front fan-shaped scanning area forms an angle of 30° to 90° with the horizontal plane. Figure 3 As shown in the diagram, the angle α between the front and rear sector scanning areas is 30° to 150°. Figure 3The β angle shown in the figure makes the front and rear fan-shaped scanning areas form an effective overlapping coverage area below the UAV 1; the 3D reconstruction effect is optimal when the β angle is close to 90°.

[0020] When UAV 1 flies forward, the same spatial position is first covered by the front fan-shaped scanning area, and then covered by the rear fan-shaped scanning area as UAV 1 flies, realizing sequential dual-angle scanning of the same detection position; and the overlapping part of the two fan-shaped scanning areas needs to cover the potential high methane concentration area.

[0021] The UAV 1 is equipped with a data processing module, which is communicatively connected to the front laser methane detection module 21, the rear laser methane detection module 22, and the GPS positioning module. It receives laser detection data and positioning information, and calculates the three-dimensional concentration distribution of methane gas. The calculated three-dimensional concentration distribution can be used for routine methane leak monitoring and location, and can also be used to assess the gas diffusion range, diffusion path, and diffusion trend after a leak occurs.

[0022] A wide-area laser reconstruction measurement method for methane concentration on a UAV, based on the aforementioned wide-area laser scanning device for methane concentration on a UAV, includes the following steps: Control the UAV 1 to fly along the target area, and the GPS positioning module collects the three-dimensional coordinate information of the UAV 1 in real time; The front laser methane detection module 21 and the rear laser methane detection module 22 are activated, and the two modules simultaneously and quickly scan the area below the UAV 1. As the UAV 1 flies forward, the same spatial position is first scanned by the front laser methane detection module 21, and then scanned by the rear laser methane detection module 22 as the UAV 1 moves forward, achieving dual-angle coverage. The laser receiving unit 202 receives the laser signal scattered by methane gas in real time, processes it to form a detection electrical signal and transmits it to the data processing module. The data processing module uses an angle-concentration correlation algorithm to fuse and calculate the dual-angle detection data, eliminate environmental interference, obtain the actual methane gas concentration value at each detection location, and bind the concentration value with the corresponding three-dimensional coordinates to form a "location-concentration" spatial dataset. Ground control terminal 3 receives the flight path and methane detection information of UAV 1, and integrates the flight path and methane detection information according to the time axis to generate a methane concentration distribution map and three-dimensional concentration spatial distribution of the inspection area.

[0023] In order to achieve rapid early warning and location of methane leaks, the ground control terminal 3 is further configured with a methane concentration threshold. When the methane concentration in the detection area exceeds the set threshold, the ground control terminal 3 outputs an alarm signal.

[0024] In a specific implementation of this invention, the steps are as follows: Step 1: Before UAV 1 takes off to perform the inspection mission, the staff imports the on-site map of the target inspection area 4 through the ground control terminal 3. Based on the terrain and facility distribution of the inspection area, the staff plans the three-dimensional flight path of UAV 1 to ensure that no area is missed during detection. At the same time, the staff completes the setting of various parameters through the ground control terminal 3: setting the angle α between the emitted laser of the front laser methane detection module and the horizontal plane, the angle β between the front and rear fan-shaped scanning areas, and the fan-shaped scanning range angle θ of the front laser methane detection module 21 and the rear laser methane detection module 22 to ensure that the overlapping area angle of the two fan-shaped scanning areas is not less than 10°; setting the emission wavelength of the laser emitter to match the characteristic absorption wavelength of methane molecules; setting the methane concentration alarm threshold; and completing the communication debugging of UAV 1, laser methane detection module and ground control terminal 3 to ensure that the modules are connected normally and the data transmission is smooth.

[0025] Step 2: Send a command through the ground control terminal 3 to confirm that the fan-shaped scanning areas of the front laser methane detection module 21 and the rear laser methane detection module 22 are accurately aligned with the predetermined initial detection area. After the initial calibration is completed, the UAV 1 enters the takeoff-ready state.

[0026] Step 3: The staff issues the takeoff command through the ground control terminal 3. The UAV 1 begins automatic inspection along the planned three-dimensional flight trajectory. The ground control terminal 3 monitors the flight status of the UAV 1 in real time, including the flight speed, flight altitude, flight attitude and hovering time, to ensure that the UAV 1 flies stably and completes the inspection operation according to the planned path.

[0027] Step 4: During the flight of UAV 1, the GPS positioning module collects the three-dimensional coordinates of UAV 1 in real time at a preset frequency and transmits the position data to the ground control terminal 3 and the data processing module in real time.

[0028] Step 5: During the inspection of UAV 1, the front laser methane detection module 21 and the rear laser methane detection module 22 are activated simultaneously. The rotating galvanometer 2013 of the laser emitting unit 201 reciprocates within a preset angle range, forming a fan-shaped scanning area by scanning a single laser beam, and simultaneously scanning and detecting the area below UAV 1. When UAV 1 flies forward, the same spatial position is first scanned and covered by the front laser methane detection module 21, and then scanned and covered by the rear laser methane detection module 22, realizing sequential dual-angle coverage detection. The laser receiving unit 202 receives the laser signal after being scattered by methane gas in real time, and after being processed by the signal conditioning module 2022, it forms a detection electrical signal, which is then transmitted to the data processing module.

[0029] Step 6: The data processing module receives the detection electrical signal from the laser detection module and the three-dimensional position information from the GPS positioning module. Using a built-in angle-concentration correlation algorithm, it fuses the sequential dual-angle detection data from the two laser detection modules to eliminate environmental interference errors such as atmospheric scattering and terrain reflection, obtaining the actual methane gas concentration value at each detection location. The concentration value is then bound to the corresponding three-dimensional coordinates to form a "position-concentration" spatial dataset, which is transmitted in real-time to the ground control terminal 3. Specifically, the projection signals acquired from the two angles undergo a one-dimensional Fourier transform to the frequency domain, then are multiplied by a ramp filter to compensate for low-frequency blurring caused by back projection and restore high-frequency edge details. Subsequently, an inverse transform is performed back to the time domain, and finally, the filtered signals are back-projected along each ray direction to the pixel grid and superimposed. This filtered back projection method is used to reconstruct the concentration on different scanning surfaces, obtaining the two-dimensional concentration distribution of each cross-section layer. Finally, inter-layer interpolation forms a three-dimensional concentration field.

[0030] Ground control terminal 3 receives flight path data and "position-concentration" spatial dataset transmitted by UAV 1 in real time. It then fuses the two types of data according to the time axis to generate a methane concentration change map of the inspection area. Staff can use this concentration change map to intuitively view the methane concentration distribution in the detection area, thus realizing the visualization of the detection data.

[0031] Step 7: The ground control terminal 3 performs threshold determination on the real-time methane concentration data. If the detected methane concentration exceeds the initially set alarm threshold, the ground control terminal 3 immediately outputs an audible and visual alarm signal and highlights the abnormal alarm area on the methane concentration change graph to prompt staff to focus on confirming the leak point.

[0032] Step 8: After completing all inspection tasks along the preset flight path, UAV 1 automatically returns to the takeoff point under the control of ground control terminal 3. Staff then shut down and store the equipment. Ground control terminal 3 stores and exports all inspection data, including flight path, 3D location information, methane concentration data, and alarm records. Staff can then review and analyze the data to generate a complete 3D distribution report of methane gas concentration in the target area, providing comprehensive and reliable data support for methane leak mitigation, risk warning, subsequent inspection planning, and accident emergency diffusion assessment.

[0033] This invention achieves three-dimensional detection with a wide scanning range and rapid scanning by using a two-way fan-shaped scanning method with a front laser methane detection module 21 and a rear laser methane detection module 22, and by fusing sequential dual-angle data. It features a simple structure, high precision, and strong applicability, and is suitable for various methane leak monitoring and emergency scenarios such as oil and gas fields, chemical industrial parks, natural gas pipelines, and landfills.

Claims

1. A wide-area laser scanning device for methane concentration carried by an unmanned aerial vehicle (UAV), comprising an UAV (1) and a ground control terminal (3), wherein the UAV (1) is equipped with a wireless communication module for data interaction with the ground control terminal (3), characterized in that, The drone (1) is equipped with a laser methane detection module (2) at the bottom. The laser methane detection module (2) includes a front laser methane detection module (21) and a rear laser methane detection module (22) arranged in the same vertical plane along the flight direction of the drone (1). Both the front laser methane detection module (21) and the rear laser methane detection module (22) are equipped with a laser emitting unit (201) and a laser receiving unit (202). The laser beam emitted by the laser emitting unit (201) of the front laser methane detection module (21) tilts forward to form a front fan-shaped scanning area, and the laser beam emitted by the laser emitting unit (201) of the rear laser methane detection module (22) tilts backward to form a rear fan-shaped scanning area. The front fan-shaped scanning area forms an angle of 30° to 90° with the horizontal plane, and the angle between the front fan-shaped scanning area and the rear fan-shaped scanning area is 30° to 150°. The UAV (1) is equipped with a GPS positioning module and a data processing module. The data processing module is connected to the front laser methane detection module (21), the rear laser methane detection module (22), and the GPS positioning module respectively. It receives laser detection data and positioning information and calculates the three-dimensional concentration distribution of methane gas.

2. The UAV-borne methane concentration laser wide-area scanning device according to claim 1, characterized in that, The laser emitting unit (201) includes a laser generator (2011), a galvanometer driving assembly (2012), and a rotating galvanometer (2013). The direction of the single laser beam emitted by the laser generator (2011) is perpendicular to the forward direction of the UAV (1), and the optical axis of the single laser beam is coplanar with the center of the mirror surface of the rotating galvanometer (2013). The galvanometer driving assembly (2012) drives the rotating galvanometer (2013) to reciprocate and deflect, thereby scanning the single laser beam to form a fan-shaped scanning area of ​​0°~120°.

3. The UAV-borne methane concentration laser wide-area scanning device according to claim 1, characterized in that, The laser receiving unit (202) includes a laser detector (2021) and a signal conditioning module (2022). The detection field of the laser detector (2021) covers the laser beam scanning area and directly receives the laser signal after being scattered by methane gas. The signal conditioning module (2022) is electrically connected to the laser detector (2021), processes the laser signal to form a detection electrical signal for data calculation, and transmits the electrical signal to the data processing module in real time.

4. A method for wide-area laser reconstruction measurement of methane concentration on a UAV, characterized in that, The UAV-borne methane concentration laser wide-area scanning device according to any one of claims 1-3 includes the following steps: Control the UAV (1) to fly along the target area, and the GPS positioning module collects the three-dimensional coordinate information of the UAV (1) in real time; The front laser methane detection module (21) and the rear laser methane detection module (22) are activated, and the two modules simultaneously and quickly scan the area below the UAV (1); During the forward flight of the UAV (1), the same spatial position is first scanned by the front laser methane detection module (21), and then scanned by the rear laser methane detection module (22) as the UAV (1) moves forward, thus achieving dual-angle coverage. The laser receiving unit (202) receives the laser signal after it is scattered by methane gas in real time, processes it to form a detection electrical signal and transmits it to the data processing module; The data processing module uses an angle-concentration correlation algorithm to fuse and calculate the dual-angle detection data to obtain the actual methane gas concentration value at each detection location, and binds the concentration value with the corresponding three-dimensional coordinates to form a "location-concentration" spatial dataset. The ground control terminal (3) receives the flight path and methane detection information of the UAV (1), and integrates the flight path and methane detection information according to the time axis to generate a methane concentration distribution map and three-dimensional concentration spatial distribution of the inspection area.

5. The UAV-borne methane concentration laser wide-area reconstruction measurement method according to claim 4, characterized in that, Set a methane concentration threshold. When the methane concentration in the detection area exceeds the set threshold, the ground control terminal (3) outputs an alarm signal.

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