Limited space toxic gas gradient detection system and method based on unmanned aerial vehicle

Abstract

According to the limited space toxic gas gradient detection system and method based on the unmanned aerial vehicle, a multi-sensor integration module is installed at the bottom of an unmanned aerial vehicle platform and comprises a hydrogen sulfide electrochemical sensor, an oxygen optical sensor, a positioning module and a laser radar; the controller is connected with the unmanned aerial vehicle platform, the multi-sensor integration module and the communication module. And the data processing terminal is connected with the controller through wireless communication. The method comprises the following steps: generating a two-dimensional vertical plane model of a vertical detection plane based on LiDAR data, dividing the two-dimensional vertical plane model into a plurality of detection point locations arranged in a matrix manner, and collecting space coordinate information, hydrogen sulfide gas concentration data and oxygen concentration data of each detection point location; and on the basis of the detection data, hydrogen sulfide and oxygen concentration data of all horizontal layers in the vertical direction are calculated by using a Kriging interpolation algorithm. According to the system and the method, high-precision gradient detection operation of toxic gas in the vertical direction in a limited space can be automatically realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of intelligent detection of toxic gases, and specifically relates to a gradient detection system and method for toxic gases in confined spaces based on unmanned aerial vehicles (UAVs). Background Art

[0002] In industries such as chemical engineering and municipal engineering, the working conditions in confined spaces are frequent. These spaces usually have poor ventilation and complex environments, making it easy to accumulate toxic and harmful gases, especially hydrogen sulfide. Due to its relatively large mass, hydrogen sulfide is prone to accumulate at the bottom of confined spaces, forming a concentration gradient distribution from top to bottom. In recent years, hydrogen sulfide poisoning accidents have occurred frequently. The main reason is that before entering the confined space, the practitioners only conduct single-point sampling and detection at the entrance or shallow positions, ignoring the gradient change of hydrogen sulfide concentration in the space, resulting in the inability to accurately assess the risk of high-concentration areas in the deep part. Most of the existing gas detection devices are handheld single-point measurement equipment, lacking the ability to continuously detect in the vertical direction of the space. At the same time, the method of manual sampling in high-risk areas not only has low efficiency but also poses great safety risks. In addition, the distribution of obstacles in confined spaces is complex, and traditional detection path planning is difficult to meet the requirements of dynamic obstacle avoidance, resulting in incomplete data collection. Moreover, the existing technologies can neither construct a gas concentration gradient distribution model nor delimit a safe operation restricted area based on real-time data, seriously restricting the safety guarantee ability of confined space operations. In recent years, although some gas detection devices based on UAVs have emerged, these devices have the following deficiencies: low sensor integration, unable to detect multiple gases simultaneously; fixed detection step size, lacking an adaptive sampling mechanism, and prone to missed detection in areas with sudden changes in gas concentration gradient; unable to generate a high-precision gas concentration distribution map by combining the space structure and gas diffusion model. Therefore, there is an urgent need to develop a system and method that can efficiently, safely, and accurately detect the gradient distribution of toxic gases in confined spaces. Summary of the Invention

[0003] Aiming at the problems existing in the above-mentioned prior art, the present invention provides a gradient detection system and method for toxic gases in confined spaces based on UAVs. The system has a simple structure, low manufacturing cost, high automation degree, and high safety factor. It can automatically achieve high-precision gradient detection of toxic gases in the vertical direction in confined spaces, without the need for operators to personally enter high-risk areas to perform detection operations. It can solve the technical problem that traditional single-point detection cannot identify deep dangerous areas, and can significantly improve the efficiency and safety of toxic gas detection in confined spaces; the method has a simple implementation process and high automation degree. It can achieve high-precision gradient detection of toxic gases in the vertical direction in confined spaces, and can obtain the hydrogen sulfide gas concentration data and oxygen concentration data of all horizontal layers in the vertical direction.

[0004] To achieve the above object, the present invention provides a limited space toxic gas gradient detection system based on an unmanned aerial vehicle, comprising an unmanned aerial vehicle platform, a multi-sensor integration module, a communication module, a controller, and a data processing terminal;

[0005] The multi-sensor integration module is installed at the bottom of the unmanned aerial vehicle platform, and includes a hydrogen sulfide electrochemical sensor, an oxygen optical sensor, a positioning module, and a lidar;

[0006] The communication module is installed on the unmanned aerial vehicle platform;

[0007] The controller is installed on the unmanned aerial vehicle platform and is respectively connected to the unmanned aerial vehicle platform, the multi-sensor integration module, and the communication module;

[0008] The data processing terminal is installed in the control center and is connected to the controller through wireless communication.

[0009] Furthermore, in order to facilitate the acquisition of spatial coordinate information at different detection points, the multi-sensor integration module further includes a positioning module.

[0010] Furthermore, to ensure the detection accuracy, the measuring range of the hydrogen sulfide electrochemical sensor is 0 - 100 ppm, the measurement accuracy is 0.01 ppm, and the response time ≤ 5 s; the model of the lidar is LiDAR.

[0011] As a preference, the controller is a PLC controller.

[0012] As a preference, the data processing terminal is an industrial computer.

[0013] In the present invention, a drone platform is used as the carrier of the multi-sensor integration module. At the same time, the actions of the drone platform are controlled by a controller, which facilitates the flexible adjustment of the detection position. Furthermore, it can facilitate the detection of the toxic gas concentration data at any detection point within the two-dimensional vertical plane, significantly improving the continuous detection ability in the vertical direction of the space. By integrating a hydrogen sulfide electrochemical sensor, an oxygen optical sensor, a positioning module, and a lidar in the multi-sensor integration module, on the one hand, the hydrogen sulfide concentration and oxygen concentration at different detection points can be synchronously detected. Thus, the hydrogen sulfide concentration and oxygen concentration data at different detection points within the entire detection range can be comprehensively sensed. Furthermore, it is beneficial to construct the hydrogen sulfide and oxygen concentrations of all horizontal layers in the vertical direction using the detection data at each detection point, greatly improving the safety guarantee ability during the operation in a confined space. On the other hand, the lidar can also be used to perform laser scanning detection within the confined space, which is beneficial to construct a two-dimensional vertical plane model based on the laser scanning detection data. Thus, it is convenient to generate the hydrogen sulfide and oxygen concentration distribution curves within different height ranges in the confined space by combining the hydrogen sulfide and oxygen concentration data of all horizontal layers in the vertical direction in the subsequent process. At the same time, it is convenient to construct a heat map of the gas concentration distribution on the two-dimensional plane in the confined space in the subsequent process, so as to more effectively guide the detection actions of subsequent personnel entering the detection operation environment to ensure the personal safety of the operators. By connecting the data processing terminal to the controller through wireless communication, it is convenient to receive the detection data sent by the controller and to perform efficient and accurate analysis and processing of the detection data using the data processing terminal.

[0014] The system has a simple structure, low manufacturing cost, high automation degree, and high safety factor. It can automatically achieve high-precision gradient detection of toxic gases in the vertical direction within a confined space, without the need for operators to personally enter high-risk areas to perform detection operations, solving the technical problem that traditional single-point detection cannot identify deep dangerous areas, significantly improving the efficiency and safety of toxic gas detection in confined spaces, and providing reliable safety guarantees for operators.

[0015] The present invention also provides a method for gradient detection of toxic gases in a confined space based on a drone. A system for gradient detection of toxic gases in a confined space based on a drone is adopted, including the following steps:

[0016] Step 1: First, select a vertical detection plane in the confined space to be detected, control the drone platform to hover at the midpoint of the top of the vertical detection plane, then use the lidar to emit laser pulses into the confined space and measure the reflection time, and generate LiDAR data. Then, send the LiDAR data to the controller;

[0017] Step 2: The controller generates a two-dimensional vertical plane model of the vertical detection plane based on the LiDAR data. Then, the two-dimensional vertical plane model is divided into multiple detection planes from top to bottom at equal vertical step distances. Next, multiple detection points 1 are divided from left to right at equal horizontal step distances on each detection plane, thereby forming a number of multiple detection points 1 arranged in a matrix on the two-dimensional vertical plane model;

[0018] Step 3: Control the UAV platform to sequentially traverse each detection plane from top to bottom. At the same time, traverse each detection point 1 from left to right on each detection plane, and make the UAV platform hover at each detection point 1 for a set detection time;

[0019] During the detection process of each detection point 1, use the positioning module to collect the spatial coordinate information of the current detection point 1 and send it to the controller. Use the hydrogen sulfide electrochemical sensor to collect the hydrogen sulfide gas concentration signal of the current detection point 1 in real time and send it to the controller. Use the oxygen optical sensor to collect the oxygen concentration signal of the current detection point 1 in real time and send it to the controller; obtain the hydrogen sulfide gas concentration data of the current detection point 1 according to the hydrogen sulfide gas concentration signal of the current detection point 1, obtain the oxygen concentration data of the current detection point 1 according to the oxygen concentration signal of the current detection point 1, and record and store the data;

[0020] After completing the detection operations on two detection planes, compare the hydrogen sulfide gas concentration data and oxygen concentration data in adjacent two detection planes. When the change rate of the hydrogen sulfide gas concentration data > 3 ppm / 0.5 m or the oxygen concentration gradient difference > 5% VOL / 0.5 m, re-divide the remaining undetected area, reduce both the vertical step distance and the horizontal step distance to half of the original, thereby forming a number of detection points 2 arranged in a matrix on the remaining undetected area, and continue the detection operations on the number of detection points 2 in the above-mentioned manner;

[0021] During the movement of the UAV platform, use the lidar to collect the obstacle signals on the flight path and send them to the controller. The controller generates an obstacle avoidance path based on the dynamic path planning algorithm, combines the obstacle signals and the position of the target detection point 1, and then controls the UAV platform to fly to the target detection point 1 according to the obstacle avoidance path;

[0022] After completing the detection operations on the entire vertical detection plane, the controller sends the spatial coordinate information of each detection point, the hydrogen sulfide gas concentration data of each detection point, and the oxygen concentration data of each detection point to the data processing terminal located in the control center through the communication module;

[0023] Step 4: The data processing terminal summarizes the spatial coordinate information of each detection point, the hydrogen sulfide gas concentration data and the oxygen concentration data of each detection point, and obtains the hydrogen sulfide gas concentration data and the oxygen concentration data at different detection points on the two-dimensional vertical plane model. At the same time, based on the hydrogen sulfide gas concentration data and the oxygen concentration data at different detection points, the hydrogen sulfide gas concentration data and the oxygen concentration data of all horizontal layers in the vertical direction of the confined space are calculated by using the Kriging interpolation algorithm according to formula (1), and the hydrogen sulfide and oxygen concentration distribution curves in different height ranges within the confined space are generated. At the same time, a heat map of the gas concentration distribution on the two-dimensional plane in the confined space is constructed. Then, in combination with the hydrogen sulfide and oxygen concentration distribution curves and the gas concentration distribution heat map in different height ranges, a red restricted area and a green safety area in the vertical direction of the confined space are demarcated on the two-dimensional vertical plane model;

[0024]

[0025] In the formula, C(Z0) pre is the predicted concentration value at any position Z0 in the vertical direction, d(Z i , Z0) is the vertical distance between the known point Z i and the interpolation point Z0 to be interpolated, where Z i is the detection point above the position where Z0 is located; is the absolute value of the concentration gradient at the known point Z i ; α is the gradient sensitivity coefficient, which is dynamically adjusted according to the hydrogen sulfide / oxygen concentration threshold.

[0026] Furthermore, in order to effectively divide the high-concentration hydrogen sulfide and low-oxygen restricted area and the safe operation area, in Step 4, the demarcation method of the red restricted area and the green safety area in the vertical direction of the confined space is as follows:

[0027] Taking 19.5% oxygen concentration and 7 ppm hydrogen sulfide concentration as the critical values, the red area and the green area are marked in the vertical direction. When the oxygen concentration content in any area is lower than 19.5% or the hydrogen sulfide concentration is greater than 7 ppm, it is demarcated as the red restricted area and the red area is displayed on the two-dimensional vertical plane model. At the same time, the area coordinates are marked in the red area. When the oxygen concentration content in any area is higher than or equal to 19.5% or the hydrogen sulfide concentration is lower than or equal to 7 ppm, it is demarcated as the green safety area and the green area is displayed on the two-dimensional vertical plane model. Taking 19.5% oxygen concentration and 7 ppm hydrogen sulfide concentration as the critical values to demarcate the red restricted area and the green safety area can maximize the safety factor of the operators and greatly reduce the risk of poisoning accidents.

[0028] The present invention overcomes the deficiencies of the prior art and provides a method for detecting toxic gas gradients in confined spaces based on drones. This method conducts detection operations at different detection points by using drones as carriers of multi-sensor integration modules, significantly enhancing the continuous detection capabilities in the vertical and horizontal directions of the space. Compared with traditional single-point detection, it can comprehensively capture the spatial distribution changes of gas concentrations, avoid the risk of missed judgment, and significantly improve the detection efficiency and safety. At the same time, there is no need for personnel to enter high-risk areas to perform detection operations in person, with a high safety factor. By integrating a positioning module, a hydrogen sulfide electrochemical sensor, an oxygen optical sensor, and a lidar in the multi-sensor integration module, the multi-sensor integration module can have multiple detection functions, and can conveniently collect the spatial coordinates, hydrogen sulfide gas concentration, and oxygen gas concentration of different detection points. At the same time, LiDAR data within the confined space can also be obtained, and then a two-dimensional vertical plane model of the vertical detection plane can be generated based on the LiDAR data. Further, the vertical detection plane can be divided into a grid based on the two-dimensional vertical plane model to obtain a number of detection points arranged in a matrix. Detection operations are carried out one by one for each detection point to obtain the spatial coordinates, hydrogen sulfide gas concentration, and oxygen gas concentration of a number of detection points. At the same time, when the change rate of hydrogen sulfide gas concentration data in adjacent detection planes > 3 ppm / 0.5 m or the oxygen concentration gradient difference > 5% VOL / 0.5 m, the subsequent vertical step and horizontal step are automatically modified to half of the previous ones. Thus, by dynamically adjusting the step, the detection density in the abnormal area is significantly improved, the accumulation of hydrogen sulfide at the bottom can be accurately captured, and the risk of high-concentration areas in the deep part can be accurately evaluated, solving the problem of deep missed detection in traditional single-point detection. On this basis, based on the hydrogen sulfide gas concentration and oxygen gas concentration of a number of detection points at different depths, the interpolation algorithm can be used to calculate the hydrogen sulfide gas concentration data and oxygen concentration data of all horizontal layers in the vertical direction, and generate the hydrogen sulfide and oxygen concentration distribution curves within different height ranges in the confined space. At the same time, a heat map of the gas concentration distribution of the two-dimensional plane in the confined space is constructed. Then, combined with the hydrogen sulfide and oxygen concentration distribution curves and the gas concentration distribution heat map within different height ranges, a red restricted area and a green safety area in the vertical direction of the confined space are demarcated on the two-dimensional vertical plane model. In addition, in order to accurately detect the vertical gradient of the toxic gas concentration and accurately demarcate the dangerous area, the present invention also innovates in the interpolation calculation process. The traditional Kriging method relies on the semi-variogram to calculate weights, and the present invention innovatively adjusts the gradient-sensitive weights through the attenuation term It directly incorporates the influence of the concentration gradient, simplifies the calculation process and the amount of calculation, and improves the calculation efficiency. In the high-gradient area (near the toxic gas leakage point), the gradient term automatically reduces the weight of the distant points and preferentially relies on the adjacent data, meeting the requirements of adaptive sampling and facilitating the acquisition of more accurate calculation results. At the same time, according to the continuous detection requirements in the spatial vertical direction, the present invention innovatively focuses in the vertical direction and only needs to calculate the vertical distance d(Z i , Z0), ignoring the horizontal direction differences, adapting to the vertical layer interpolation scenario. At the same time, it is beneficial to further reduce the calculation process and the amount of calculation and further improve the calculation efficiency. Moreover, the present invention innovatively adopts dynamic coefficient adaptation: the coefficient α can be adjusted according to the gradient thresholds of hydrogen sulfide (3 ppm / 0.5 m) or oxygen (5% VOL / 0.5 m) to achieve parametric adaptation, which is conducive to constructing a more accurate complete gas concentration gradient distribution model. By demarcating the red restricted area and the green safety area in the vertical direction of the limited space on the two-dimensional vertical plane model, the annotation of the concentration mutation area can be realized, effectively breaking through the limitations of traditional modeling, providing real-time visual decision support for the operators, effectively guiding the actions of the subsequent personnel during the detection operation, being beneficial to ensuring the safety of the operators, and greatly reducing the accident risk in the subsequent operation process. During the movement of the UAV platform, the lidar is used to collect the obstacle signals on the flight path, and the controller generates the obstacle avoidance path based on the dynamic path planning algorithm, enabling the UAV to have the ability of real-time obstacle avoidance, ensuring the continuity and safety of the detection process, and effectively coping with various complex environments.

[0029] The implementation process of this method is simple and has a high degree of automation. It innovatively realizes the high-precision gradient detection operation of toxic gases in the vertical direction within a limited space, can obtain the hydrogen sulfide gas concentration data and oxygen concentration data of all horizontal layers in the vertical direction, solves the problems of missed judgment of gradient risk in traditional single-point detection and low efficiency of manual sampling, realizes the three-dimensional dynamic assessment of toxic gases in a limited space and the accurate definition of safety areas, and has the characteristics of high efficiency, safety and strong engineering applicability, and can provide reliable safety guarantees for the operators. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the detection operation of toxic gases in a limited space based on the UAV of the present invention;

[0031] Figure 2 It is a schematic diagram of the distribution of each detection point in the vertical direction within the limited space of the present invention;

[0032] Figure 3 It is a schematic diagram of the range of the two-dimensional plane model in the vertical direction constructed based on the lidar (LiDAR) data of the present invention;

[0033] Figure 4 Schematic diagram of the assembly of the multi-sensor integration module and the UAV platform in the present invention;

[0034] Figure 5 is Figure 4 top view of;

[0035] Figure 6 Schematic diagram of the structure of the multi-sensor integration module in the present invention;

[0036] Figure 7 Principle block diagram of the system control part in the present invention;

[0037] Figure 8 Schematic diagram of the gas concentration distribution curve (height-concentration contrast curve) in the present invention.

[0038] In the figure: 1. UAV platform; 2. Multi-sensor integration module, 2-1. Hydrogen sulfide electrochemical sensor, 2-2. Oxygen optical sensor, 2-3. Positioning module, 2-4. Lidar, 2-5. Positioning module; 3. Confined space. Specific implementation mode

[0039] The present invention will be further described below with reference to the accompanying drawings.

[0040] As Figures 1 to 7 shown, the present invention provides a confined space toxic gas gradient detection system based on a UAV, including a UAV platform 1, a multi-sensor integration module 2, a communication module, a controller and a data processing terminal;

[0041] The multi-sensor integration module 2 is installed at the bottom of the UAV platform 1, and includes a hydrogen sulfide electrochemical sensor 2-1, an oxygen optical sensor 2-2, a positioning module 2-3 and a lidar 2-4;

[0042] The communication module is installed on the UAV platform 1;

[0043] The controller is installed on the UAV platform 1 and is respectively connected to the UAV platform 1, the multi-sensor integration module 2 and the communication module;

[0044] The data processing terminal is installed in the control center and is connected to the controller through wireless communication.

[0045] As a preference, a power supply module is further included, and the power supply module is used for power supply.

[0046] In order to facilitate the acquisition of spatial coordinate information at different detection points, the multi-sensor integration module 2 further includes a positioning module 2-3.

[0047] To ensure the detection accuracy, the measurement range of the hydrogen sulfide electrochemical sensor 2-1 is 0-100 ppm, the measurement accuracy is 0.01 ppm, and the response time ≤ 5 s; the model of the lidar 2-4 is LiDAR.

[0048] As a preference, the controller is a PLC controller.

[0049] As a preference, the data processing terminal is an industrial computer.

[0050] In the present invention, a drone platform is used as the carrier of the multi-sensor integration module. Meanwhile, the actions of the drone platform are controlled by the controller, which can facilitate the flexible adjustment of the detection position. Furthermore, it can facilitate the detection of the toxic gas concentration data at any detection point in the two-dimensional vertical plane, significantly improving the continuous detection ability in the vertical direction of space. By integrating a hydrogen sulfide electrochemical sensor, an oxygen optical sensor, a positioning module, and a lidar in the multi-sensor integration module, on the one hand, the hydrogen sulfide concentration and oxygen concentration at different detection points can be synchronously detected. Thus, the hydrogen sulfide concentration and oxygen concentration data at different detection points within the entire detection range can be comprehensively sensed. Furthermore, it is beneficial to use the detection data at each detection point to construct the hydrogen sulfide and oxygen concentrations at all horizontal layers in the vertical direction, greatly improving the safety guarantee ability during the confined space operation. On the other hand, it can also perform laser scanning detection on the confined space through the lidar, which is beneficial to construct a two-dimensional vertical plane model based on the laser scanning detection data. Thus, it is convenient to generate the hydrogen sulfide and oxygen concentration distribution curves within different height ranges in the confined space by combining the hydrogen sulfide and oxygen concentration data at all horizontal layers in the vertical direction. Meanwhile, it is convenient to construct a heat map of the gas concentration distribution on the two-dimensional plane in the confined space subsequently, so as to more effectively guide the detection actions of subsequent personnel entering the detection operation environment to ensure the personal safety of the operators. By connecting the data processing terminal to the controller through wireless communication, it is convenient to receive the detection data sent by the controller and to perform efficient and accurate analysis and processing of the detection data using the data processing terminal.

[0051] The system has a simple structure, low manufacturing cost, high automation degree, and high safety factor. It can automatically realize the high-precision gradient detection operation of toxic gases in the vertical direction within the confined space, without the need for operators to personally enter the high-risk area to perform the detection operation, solving the technical problem that traditional single-point detection cannot identify deep dangerous areas, significantly improving the efficiency and safety of toxic gas detection in the confined space, and providing reliable safety guarantee for the operators.

[0052] The present invention also provides a method for detecting the gradient of toxic gases in a confined space based on an unmanned aerial vehicle, using a system for detecting the gradient of toxic gases in a confined space based on an unmanned aerial vehicle, including the following steps:

[0053] Step 1: First, select a vertical detection plane in the confined space 3 to be detected, control the unmanned aerial vehicle platform 1 to hover at the midline of the top of the vertical detection plane, then use the lidar 2-4 to emit laser pulses into the confined space 3 and measure the reflection time, and generate LiDAR data. Then, send the LiDAR data to the controller;

[0054] Step 2: The controller generates a two-dimensional vertical plane model of the vertical detection plane based on the LiDAR data, then divides the two-dimensional vertical plane model into multiple detection planes (A horizontal detection plane, B horizontal detection plane, C horizontal detection plane, D horizontal detection plane, E horizontal detection plane, F horizontal detection plane, and G horizontal detection plane) from top to bottom at equal vertical step distances, and then divides each detection plane into multiple detection points one from left to right at equal horizontal step distances, thereby forming a number of multiple detection points one arranged in a matrix on the two-dimensional vertical plane model;

[0055] Step 3: Control the unmanned aerial vehicle platform 1 to traverse each detection plane one by one from top to bottom. At the same time, traverse each detection point one from left to right on each detection plane, and make the unmanned aerial vehicle platform 1 hover at each detection point for a set detection time;

[0056] During the detection process of each detection point one, use the positioning module 2-3 to collect the spatial coordinate information of the current detection point one and send it to the controller, use the hydrogen sulfide electrochemistry sensor 2-1 to collect the hydrogen sulfide gas concentration signal of the current detection point one in real time and send it to the controller, use the oxygen optical sensor 2-2 to collect the oxygen concentration signal of the current detection point one in real time and send it to the controller; obtain the hydrogen sulfide gas concentration data of the current detection point one according to the hydrogen sulfide gas concentration signal of the current detection point one, obtain the oxygen concentration data of the current detection point one according to the oxygen concentration signal of the current detection point one, and record and store the data;

[0057] After completing the detection operations of two detection planes, compare the hydrogen sulfide gas concentration data and oxygen concentration data in two adjacent detection planes. When the change rate of the hydrogen sulfide gas concentration data > 3 ppm / 0.5 m or the oxygen concentration gradient difference > 5% VOL / 0.5 m, perform secondary division on the remaining undetected area, reduce both the vertical step distance and the horizontal step distance to half of the original, thereby forming a number of detection points two arranged in a matrix on the remaining undetected area, and continue to perform detection operations on the number of detection points two in the above manner;

[0058] During the movement of the UAV platform 1, the lidars 2-4 are used to collect obstacle signals on the flight path and send them to the controller. The controller generates an obstacle avoidance path based on the dynamic path planning algorithm, combining the obstacle signals and the position of the target detection point 1, and then controls the UAV platform 1 to fly to the target detection point 1 according to the obstacle avoidance path;

[0059] After completing the detection operation of the entire vertical detection plane, the controller sends the spatial coordinate information of each detection point, the hydrogen sulfide gas concentration data of each detection point, and the oxygen concentration data of each detection point to the data processing terminal located in the control center through the communication module;

[0060] Step 4: The data processing terminal correspondingly summarizes the spatial coordinate information of each detection point, the hydrogen sulfide gas concentration data of each detection point, and the oxygen concentration data received, to obtain the hydrogen sulfide gas concentration data and oxygen concentration data at different detection points on the two-dimensional vertical plane model. At the same time, based on the hydrogen sulfide gas concentration data and oxygen concentration data at different detection points, the kriging interpolation algorithm is used according to formula (1) to calculate the hydrogen sulfide gas concentration data and oxygen concentration data of all horizontal layers in the vertical direction of the confined space 3, and generate the hydrogen sulfide and oxygen concentration distribution curves in different height ranges within the confined space 3. At the same time, a heat map of the gas concentration distribution of the two-dimensional plane in the confined space 3 is constructed. Then, combining the hydrogen sulfide and oxygen concentration distribution curves and the gas concentration distribution heat map in different height ranges, a red restricted area and a green safe area in the vertical direction of the confined space 3 are demarcated on the two-dimensional vertical plane model;

[0061]

[0062] In the formula, C(Z0) pre is the predicted concentration value at any position Z0 in the vertical direction, d(Z i , Z0) is the vertical distance between the known point Z i and the interpolation point Z0, where Z i is the detection point above the position where Z0 is located; is the absolute value of the concentration gradient at the known point Z i ; α is the gradient sensitivity coefficient, which is dynamically adjusted according to the hydrogen sulfide / oxygen concentration threshold. Preferably, the gradient sensitivity coefficient of hydrogen sulfide is 0.5, and the gradient sensitivity coefficient of oxygen is 0.3.

[0063] In order to effectively divide the high-concentration hydrogen sulfide and low-oxygen restricted area and the safe operation area, in Step 4, the demarcation method of the red restricted area and the green safe area in the vertical direction of the confined space (3) is as follows:

[0064] Such as Figure 8As shown, with an oxygen concentration of 19.5% and a hydrogen sulfide concentration of 7 ppm as the critical values, the red area and the green area are marked vertically. When the oxygen concentration in any area is lower than 19.5% or the hydrogen sulfide concentration is greater than 7 ppm, it is classified as a red restricted area, and the red area is displayed on the two-dimensional vertical plane model. At the same time, the area coordinates are marked in the red area. When the oxygen concentration in any area is higher than or equal to 19.5% or the hydrogen sulfide concentration is lower than or equal to 7 ppm, it is classified as a green safety area, and the green area is displayed on the two-dimensional vertical plane model. By using 19.5% oxygen concentration and 7 ppm hydrogen sulfide concentration as the critical values to divide the red restricted area and the green safety area, the safety factor of the operators can be maximally ensured, and the risk of poisoning accidents can be greatly reduced.

[0065] The present invention overcomes the deficiencies of the prior art and provides a method for detecting toxic gas gradients in confined spaces based on unmanned aerial vehicles (UAVs). This method uses UAVs as carriers for multi-sensor integration modules to conduct detection operations at different detection points, significantly improving the continuous detection capabilities in the vertical and horizontal directions of space. Compared with traditional single-point detection, it can comprehensively capture changes in the spatial distribution of gas concentrations, avoid the risk of missed judgments, and significantly improve detection efficiency and safety. At the same time, there is no need for personnel to personally enter high-risk areas to perform detection operations, resulting in a high safety factor. By integrating a positioning module, a hydrogen sulfide electrochemical sensor, an oxygen optical sensor, and a lidar in the multi-sensor integration module, the multi-sensor integration module can have multiple detection functions, enabling convenient acquisition of the spatial coordinates, hydrogen sulfide gas concentration, and oxygen gas concentration at different detection points. At the same time, LiDAR data within the confined space can be obtained, and then a two-dimensional vertical plane model of the vertical detection plane can be generated based on the LiDAR data. Further, the vertical detection plane can be divided into a grid pattern based on the two-dimensional vertical plane model to obtain a number of detection points arranged in a matrix. Detection operations are carried out one by one for each detection point to obtain the spatial coordinates, hydrogen sulfide gas concentration, and oxygen gas concentration of a number of detection points. At the same time, when the change rate of hydrogen sulfide gas concentration data in adjacent detection planes > 3 ppm / 0.5 m or the oxygen concentration gradient difference > 5% VOL / 0.5 m, the subsequent vertical and horizontal step distances are automatically modified to half of the previous ones. Thus, by dynamically adjusting the step distances, the detection density in abnormal areas is significantly improved, the accumulation of hydrogen sulfide at the bottom can be accurately captured, and the risk of high-concentration areas in the deep part can be accurately evaluated, solving the problem of deep missed detections in traditional single-point detection. On this basis, based on the hydrogen sulfide gas concentration and oxygen gas concentration at a number of detection points at different depths, interpolation algorithms can be used to calculate the hydrogen sulfide gas concentration data and oxygen concentration data for all horizontal layers in the vertical direction, and generate the hydrogen sulfide and oxygen concentration distribution curves within different height ranges in the confined space. At the same time, a heat map of the gas concentration distribution on the two-dimensional plane in the confined space is constructed. Combining the hydrogen sulfide and oxygen concentration distribution curves and the gas concentration distribution heat map within different height ranges, red restricted areas and green safe areas in the vertical direction of the confined space are demarcated on the two-dimensional vertical plane model. In addition, in order to accurately detect the vertical gradient of toxic gas concentrations and accurately demarcate dangerous areas, the present invention also innovates in the interpolation calculation process. Traditional Kriging methods rely on semi-variograms to calculate weights. The present invention innovatively adjusts the gradient-sensitive weights through a decay term Directly incorporate the influence of the concentration gradient, simplify the calculation process and the amount of calculation, and improve the calculation efficiency. In the high-gradient region (near the toxic gas leakage point), the gradient term automatically reduces the weight of the points at a long distance and preferentially relies on the adjacent data, meeting the requirements of adaptive sampling and facilitating the acquisition of more accurate calculation results. At the same time, according to the continuous detection requirements in the vertical direction of space, the present invention innovatively focuses in the vertical direction and only needs to calculate the vertical distance d(Z i , Z0), ignoring the horizontal direction difference, adapting to the vertical layer interpolation scenario. At the same time, it is conducive to further reducing the calculation process and the amount of calculation and further improving the calculation efficiency. Furthermore, the present invention innovatively adopts dynamic coefficient adaptation: the coefficient α can be adjusted according to the gradient threshold of hydrogen sulfide (3 ppm / 0.5 m) or oxygen (5% VOL / 0.5 m) to achieve parametric adaptation, which is conducive to constructing a more accurate complete gas concentration gradient distribution model. By demarcating the red restricted area and the green safety area in the vertical direction of the limited space on the two-dimensional vertical plane model, the annotation of the concentration mutation area can be realized, effectively breaking through the limitations of traditional modeling, providing real-time visual decision support for the operators, effectively guiding the actions of the subsequent personnel during the detection operation, facilitating ensuring the safety of the operators, and greatly reducing the accident risk in the subsequent operation process. During the movement of the UAV platform, the lidar is used to collect the obstacle signals on the flight path, and the controller generates the obstacle avoidance path based on the dynamic path planning algorithm, enabling the UAV to have the ability of real-time obstacle avoidance, ensuring the continuity and safety of the detection process, and effectively coping with various complex environments.

[0066] The implementation process of this method is simple and has a high degree of automation. It innovatively realizes the high-precision gradient detection operation of toxic gases in the vertical direction within a limited space, can obtain the hydrogen sulfide gas concentration data and oxygen concentration data of all horizontal layers in the vertical direction, solves the problems such as the risk of missed judgment of the gradient in traditional single-point detection and the low efficiency of manual sampling, realizes the three-dimensional dynamic assessment of toxic gases in a limited space and the accurate definition of the safety area, and has the characteristics of high efficiency, safety and strong engineering applicability, and can provide reliable safety guarantee for the operators.

Claims

1. A gradient detection system for toxic gases in confined spaces based on drones, comprising a drone platform (1), characterized in that, It also includes a multi-sensor integration module (2), a communication module, a controller, and a data processing terminal; The multi-sensor integration module (2) is installed at the bottom of the UAV platform (1), and it includes a hydrogen sulfide electrochemical sensor (2-1), an oxygen optical sensor (2-2), a positioning module (2-3), and a lidar (2-4); The communication module is installed on the UAV platform (1); The controller is installed on the UAV platform (1), and it is respectively connected to the UAV platform (1), the multi-sensor integration module (2), and the communication module; The data processing terminal is installed in the control center and is connected to the controller through wireless communication.

2. The limited space toxic gas gradient detection system based on an unmanned aerial vehicle according to claim 1, wherein The multi-sensor integration module (2) also includes a positioning module (2-3).

3. The limited space toxic gas gradient detection system based on an unmanned aerial vehicle according to claim 1, wherein, The measuring range of the hydrogen sulfide electrochemical sensor (2-1) is 0-100 ppm, the measurement accuracy is 0.01 ppm, and the response time ≤ 5 s; the model of the lidar (2-4) is LiDAR.

4. The limited space toxic gas gradient detection system based on a drone according to claim 1, characterized in that, The controller is a PLC controller.

5. A gradient detection system for toxic gases in confined spaces based on an unmanned aerial vehicle according to claim 1, characterized in that, The data processing terminal is an industrial computer.

6. A method for detecting the gradient of toxic gases in a confined space based on an unmanned aerial vehicle, which uses a system for detecting the gradient of toxic gases in a confined space based on an unmanned aerial vehicle as described in any one of claims 1 to 5, characterized in that, It includes the following steps: Step 1: First, select a vertical detection plane in the limited space (3) to be detected, control the UAV platform (1) to hover at the midline of the top of the vertical detection plane first, then use the lidar (2-4) to emit laser pulses into the limited space (3) and measure its reflection time, and generate LiDAR data, and then send the LiDAR data to the controller; Step 2: The controller generates a two-dimensional vertical plane model of the vertical detection plane based on the LiDAR data, then divides the two-dimensional vertical plane model into multiple detection planes from top to bottom at equal vertical step distances, and then divides multiple detection points one from left to right at equal horizontal step distances on each detection plane, thereby forming a number of multiple detection points one arranged in a matrix on the two-dimensional vertical plane model; Step 3: Control the UAV platform (1) to traverse each detection plane one by one from top to bottom. At the same time, traverse each detection point one from left to right on each detection plane, and make the UAV platform (1) hover at each detection point one for a set detection time; During the detection of each detection point one, use the positioning module (2-3) to collect the spatial coordinate information of the current detection point one and send it to the controller, use the hydrogen sulfide electrochemical sensor (2-1) to collect the hydrogen sulfide gas concentration signal of the current detection point one in real time and send it to the controller, use the oxygen optical sensor (2-2) to collect the oxygen concentration signal of the current detection point one in real time and send it to the controller; obtain the hydrogen sulfide gas concentration data of the current detection point one according to the hydrogen sulfide gas concentration signal of the current detection point one, obtain the oxygen concentration data of the current detection point one according to the oxygen concentration signal of the current detection point one, and record and store the data; After the detection operations on two detection planes are completed, the hydrogen sulfide gas concentration data and oxygen concentration data in two adjacent detection planes are compared. When the change rate of hydrogen sulfide gas concentration data > 3 ppm / 0.5 m or the oxygen concentration gradient difference > 5% VOL / 0.5 m, the remaining undetected area is re-divided, and both the vertical step distance and the horizontal step distance are reduced to half of the original, so as to form a number of detection points two arranged in a matrix on the remaining undetected area, and then continue the detection operations on the number of detection points two in the above-mentioned manner; During the movement of the UAV platform (1), the lidar (2-4) is used to collect the obstacle signals on the flight path and send them to the controller. The controller generates an obstacle avoidance path based on the dynamic path planning algorithm, combining the obstacle signals and the position of the target detection point one, and then controls the UAV platform (1) to fly to the target detection point one according to the obstacle avoidance path; After the detection operations on the entire vertical detection plane are completed, the controller sends the spatial coordinate information of each detection point, the hydrogen sulfide gas concentration data of each detection point, and the oxygen concentration data of each detection point to the data processing terminal located in the control center through the communication module; Step 4: The data processing terminal correspondingly summarizes the spatial coordinate information of each detection point, the hydrogen sulfide gas concentration data and oxygen concentration data of each detection point received, to obtain the hydrogen sulfide gas concentration data and oxygen concentration data at different detection points on the two-dimensional vertical plane model. At the same time, based on the hydrogen sulfide gas concentration data and oxygen concentration data at different detection points, the hydrogen sulfide gas concentration data and oxygen concentration data of all horizontal layers in the vertical direction of the confined space (3) are calculated using the Kriging interpolation algorithm according to formula (1), and the hydrogen sulfide and oxygen concentration distribution curves in different height ranges within the confined space (3) are generated. At the same time, a heat map of the gas concentration distribution on the two-dimensional plane in the confined space (3) is constructed. Then, combining the hydrogen sulfide and oxygen concentration distribution curves and the gas concentration distribution heat map in different height ranges, a red restricted area and a green safety area in the vertical direction of the confined space (3) are demarcated on the two-dimensional vertical plane model; Where, C(Z0) pre is the predicted concentration value at any position Z0 in the vertical direction, d(Z i , Z0) is the vertical distance between the known point Z i and the interpolation point Z0, where Z i is the detection point above the position where Z0 is located; is the absolute value of the concentration gradient at the known point Z i ; α is the gradient sensitivity coefficient, which is dynamically adjusted according to the hydrogen sulfide / oxygen concentration threshold.

7. A method for detecting the gradient of toxic gases in a confined space based on an unmanned aerial vehicle according to claim 6, characterized in that, In Step 4, the method for demarcating the red restricted area and the green safety area in the vertical direction of the confined space (3) is as follows: Using 19.5% oxygen concentration and 7 ppm hydrogen sulfide concentration as the critical values, the red area and the green area are marked in the vertical direction. When the oxygen concentration content in any area is lower than 19.5% or the hydrogen sulfide concentration is greater than 7 ppm, it is demarcated as a red restricted area and the red area is displayed on the two-dimensional vertical plane model. At the same time, the area coordinates are marked in the red area. When the oxygen concentration content in any area is higher than or equal to 19.5% or the hydrogen sulfide concentration is lower than or equal to 7 ppm, it is demarcated as a green safety area and the green area is displayed on the two-dimensional vertical plane model.

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