An Unmanned Aerial Vehicle Control Method for Spraying Flame Retardant

Abstract

The present invention discloses a method for controlling an unmanned aerial vehicle (UAV) that sprays a flame retardant, belonging to the field of UAV fire extinguishing, including: obtaining a distance-thermal imaging image that fuses the fire field temperature and distance, and positioning the bottom of the fire field based on the DEM terrain data of the target fire extinguishing area; calculating the height of the fire field, and constructing a relationship model between the height and width of the fire field for calculating the burning diameter of the fire field and determining the coverage range of the flame retardant spray; calculating the injection pressure and total spray volume of the UAV control nozzle for spraying the flame retardant according to the height and horizontal distance of the UAV from the bottom of the fire field; calculating the reaction force on the UAV during the flame retardant spraying process, constructing an attitude correction equation of the UAV, and correcting the attitude of the UAV. The present invention can achieve high-precision control of flame retardant spraying and the attitude of the UAV, significantly improving the accuracy and effectiveness of flame retardant spraying, and can be applied to various complex fire scenarios such as forests, grasslands, and cities.

Description

Technical Field

[0001] The present invention relates to the field of drone fire extinguishing, and particularly to a method for controlling a drone for spraying flame retardant. Background Art

[0002] With the development of society and the progress of technology, drones are beginning to be used for fire extinguishing to cope with large-area and long-distance fires. Especially for fires in complex terrains such as alpine forests and grasslands where it is difficult for firefighters to extinguish the fire, using drones to carry flame retardant for high-altitude spraying has natural fire extinguishing advantages. Drone fire extinguishing is carried out from an aerial path, with high fire extinguishing efficiency and the ability to handle large-area fires at multiple points.

[0003] However, in dealing with complex fire scene situations, how to achieve precise control of the flame retardant spraying process and the drone cruising process is a technical difficulty in drone fire extinguishing. In the prior art, during the process of using a drone to spray flame retardant for fire extinguishing, precise identification and assessment of the fire scene cannot be achieved, and spraying control for different fire scenes cannot be carried out, resulting in inaccurate spraying at the ignition point, inaccurate spraying amount, excessive spraying amount wasting flame retardant and reducing the fire extinguishing ability of the drone, and too little spraying amount failing to achieve the fire extinguishing effect. Moreover, the reaction force during the spraying process will affect the attitude of the drone, resulting in a large spraying positioning error during secondary spraying. Summary of the Invention

[0004] In view of the above deficiencies in the prior art, the present invention provides a method for controlling a drone for spraying flame retardant, which realizes precise control and positioning of the flame retardant spraying by using high-precision identification of the fire scene, calculation and evaluation of fire scene parameters, and reduces the influence of the spraying process on the attitude of the drone.

[0005] In order to achieve the above invention object, the technical solution adopted by the present invention is as follows:

[0006] Provide a method for controlling a drone for spraying flame retardant, which includes:

[0007] Step S1: The drone obtains a distance-thermal imaging image that fuses the fire scene temperature and distance, and calculates the positioning coordinates of the bottom of the fire scene based on the DEM terrain data of the target fire extinguishing area, as well as the direction angles and field of view angles of laser ranging and infrared thermal imaging, so as to achieve the positioning of the fire scene;

[0008] Step S2: Calculate the height of the fire scene, and construct a relationship model between the height and width of the fire scene for calculating the burning diameter of the fire scene to determine the coverage range of the flame retardant spraying;

[0009] Step S3: According to the height and horizontal distance of the drone from the bottom of the fire scene, construct a control model for the flame retardant spraying, and calculate the injection pressure and total spraying amount of the control nozzle of the drone for spraying the flame retardant;

[0010] Step S4: Based on the cruising altitude of the drone, calculate the reaction force on the drone during the flame retardant spraying process using the height and horizontal distance of the drone from the bottom of the fire field, construct an attitude correction equation for the drone, and correct the attitude of the drone.

[0011] Further, step S1 includes:

[0012] Step S11: Retrieve the DEM terrain data of the target fire extinguishing area. The drone carries the flame retardant and reaches above the fire field. Use a laser rangefinder and an infrared thermal imager to obtain a distance-thermal imaging image that fuses the fire field temperature and distance, and obtain the temperature data and distance data of each pixel in the distance-thermal imaging image, where is the pixel number; and distance data , is the pixel number;

[0013] Step S12: Set the fire field temperature threshold, compare the temperature data with the fire field temperature threshold. If, then determine that the pixel is a fire field pixel. If, then determine that the pixel is a non-fire field pixel; , compare the temperature data with the fire field temperature threshold . If , then determine that the pixel is a fire field pixel. If , then determine that the pixel is a non-fire field pixel;

[0014] Step S13: Delete the non-fire field pixels in the distance-thermal imaging image, retain the fire field pixels, and obtain the distance data corresponding to each fire field pixel; ;

[0015] Step S14: Take the current cruising point of the drone as the coordinate origin, establish a three-dimensional coordinate system, and obtain the coordinates of the terrain positioning point below the drone in the three-dimensional coordinate system based on the cruising altitude of the drone; based on the coordinates of the current cruising point of the drone in the DEM terrain data, use the coordinates as the coordinate system conversion basis, where is the elevation of the terrain positioning point; obtain the coordinates of the terrain positioning point below the drone in the three-dimensional coordinate system based on the cruising altitude of the drone ; based on the coordinates of the current cruising point of the drone in the DEM terrain data , use the coordinates as the coordinate system conversion basis, is the elevation of the terrain positioning point;

[0016] Step S15: Calculate the coordinates of the terrain point at the bottom of the fire field in the three-dimensional coordinate system using the azimuth angle and field of view angle of the laser rangefinder and infrared thermal imager carried on the drone; β and field of view angle α calculate the coordinates of the terrain point at the bottom of the fire field in the three-dimensional coordinate system ;

[0017] ;

[0018] where, is the distance data corresponding to the bottommost fire field pixel, is the horizontal azimuth angle of the laser rangefinder and the infrared thermal imager in the three-dimensional coordinate system;

[0019] Step S16: Use the coordinates and the coordinates to calculate the coordinates of the terrain points at the bottom of the fire scene within the DEM terrain data ;

[0020] ;

[0021] Step S17: Locate the fire scene according to the coordinates within the DEM terrain data, and feedback the current ignition point of the fire scene to the control center.

[0022] Furthermore, Step S2 includes:

[0023] Step S21: Calculate the height of the fire scene according to the relative height of the fire scene pixels at the top compared to the fire scene pixels at the bottom in the distance-thermal imaging image H ;

[0024] ;

[0025] wherein, is the pixel coordinate of the fire scene pixel at the top, is the pixel coordinate of the fire scene pixel at the bottom, is the proportionality coefficient between the pixel coordinate and the actual distance;

[0026] Step S22: Use the height of the fire scene to calculate the burning diameter of the fire scene;

[0027] Step S23: Take the coordinates of the terrain points at the bottom of the fire scene as the center point for spraying the flame retardant, and take the coverage radius of the flame retardant as , and generate the coverage range of the flame retardant spraying with the center point of the flame retardant spraying as the center.

[0028] Furthermore, the calculation method of the burning diameter R is:

[0029] ;

[0030] wherein, is the burning rate of the combustibles at the fire occurrence location, is the air density, g is the gravitational acceleration, u is the wind speed around the fire scene, is the characteristic wind speed, , is the combustion range.

[0031] Further, step S3 includes:

[0032] Step S31: The drone controls the angle of the flame retardant spray nozzle to point to the terrain point at the bottom of the fire scene. According to the height of the drone from the bottom of the fire scene and the horizontal distance , a control model for flame retardant spraying is constructed , and the injection pressure for the drone to control the nozzle to spray the flame retardant is calculated p ;

[0033] Step S32: According to the rated spraying intensity of the nozzle , considering the attenuation of the spraying intensity within the coverage of the flame retardant spraying, the total spraying amount is calculated Q .

[0034] Further, the control model for flame retardant spraying is:

[0035] ;

[0036] wherein, is the injection pressure based on the vertical injection velocity component, is the injection pressure based on the horizontal injection velocity component, is the density of the flame retardant, represents taking the maximum value, is the velocity coefficient of the injection velocity.

[0037] Further, the method for calculating the total spraying amount Q is;

[0038] ;

[0039] wherein, is the spraying intensity attenuation coefficient, is the natural constant, is the rated spraying intensity.

[0040] Further, step S4 includes:

[0041] Step S41: Based on the cruising altitude of the drone , the drone controls the nozzle to point to the bottom of the fire scene and controls the spraying amount Q and the injection pressure p of the flame retardant to extinguish the fire on the fire scene;

[0042] Step S42: Calculate the horizontal reaction force on the drone during the flame retardant spraying according to the height of the drone from the bottom of the fire scene and the horizontal distance ​ and the vertical reaction force ;

[0043] ;

[0044] Among them, is the mass flow rate during the flame retardant spraying process;

[0045] Step S43: Based on the horizontal reaction force and the vertical reaction force Construct the attitude correction equation for the drone during the flame retardant spraying process;

[0046] ;

[0047] Among them, are the angular velocities around the x , y , z axes respectively, are the moments of inertia around the x , y , z axes respectively, are respectively x , y , z the reaction forces in the directions, and satisfy , the resultant force of is equal to the horizontal reaction force , and satisfy , is the position coordinate of the reaction point on the drone relative to the centroid of the drone during the flame retardant spraying process;

[0048] Step S44: During the process of the drone spraying the flame retardant, correct the attitude of the drone according to the attitude correction equation to ensure the accuracy of the flame retardant spraying process.

[0049] The beneficial effects of the present invention are as follows: This solution uses infrared imaging technology and laser ranging technology to locate and identify the fire scene, calculate the height and combustion diameter data of the fire scene, which are used to locate the spraying of the flame retardant and determine the spraying range. While ensuring the fire extinguishing effect, it avoids excessive spraying of the flame retardant, resulting in waste of the flame retardant, realizes the precise calculation of the spraying amount and spraying pressure of the flame retardant, and at the same time, the calculated flame retardant spraying control data can be used for the attitude correction of the drone, reducing the influence on the attitude of the drone during the flame retardant spraying process. The present invention can achieve high-precision control of the flame retardant spraying and the attitude of the drone, significantly improving the accuracy and effectiveness of the flame retardant spraying, and can be applied to various complex fire scenes such as forests, grasslands, and cities. Description of the Drawings

[0050] Figure 1 It is a flowchart of a control method for a drone spraying a flame retardant.

[0051] Figure 2 It is a schematic diagram of the space between a fire scene and a drone. Specific embodiments

[0052] The following describes the specific embodiments of the present invention to facilitate those skilled in the art of this technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of this technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0053] As Figure 1 shown, a control method for a drone spraying a flame retardant includes:

[0054] S1: The drone obtains a distance-thermal imaging image that fuses the fire scene temperature and distance, and calculates the positioning coordinates of the bottom of the fire scene based on the DEM terrain data of the target fire extinguishing area, as well as the direction angles β and field of view angles α of laser ranging and infrared thermal imaging to achieve the positioning of the bottom of the fire scene. Step S1 specifically includes:

[0055] Step S11: Retrieve the DEM terrain data of the target fire extinguishing area. The drone carries the flame retardant and reaches above the fire scene. Use a laser rangefinder and an infrared thermal imager to obtain a distance-thermal imaging image that fuses the fire scene temperature and distance, and obtain the temperature data and distance data , where is the pixel number;

[0056] The temperature data represents the temperature at which the combustible corresponding to each pixel in the distance-thermal imaging image burns, and the distance data represents the straight-line distance from the position of the combustible corresponding to each pixel in the distance-thermal imaging image to the drone. During the fusion of the fire scene temperature and distance, ensure that the measurement range of the laser rangefinder is the same as the imaging range of the infrared thermal imager, that is, the pixels of the laser distance image and the infrared temperature image correspond in position.

[0057] During the flight of the drone, the positioning coordinates are fed back to the DEM terrain data in real time. The coordinates of the drone flight positioning are converted into the DEM terrain data space, and the positioning of the fire scene is achieved by using the fire scene data obtained by the drone. Through the DEM terrain data, the terrain elevation and plane coordinate data in the target fire extinguishing area can be reflected.

[0058] Step S12: Set the fire ground temperature threshold , compare the temperature data with the fire ground temperature threshold . If , then determine that the pixel n is a fire ground pixel. If , then determine that the pixel is a non-fire ground pixel;

[0059] Step S13: Delete the non-fire ground pixels in the distance-thermal imaging image, retain the fire ground pixels, and obtain the distance data corresponding to each fire ground pixel d , the distance data d represents the straight-line distance from different positions to the fire ground;

[0060] Step S14: Take the current cruising position of the UAV as the coordinate origin to establish a three-dimensional coordinate system, as Figure 2 shown. According to the cruising altitude of the UAV, obtain the coordinates of the terrain positioning point below the UAV in the three-dimensional coordinate system ; Based on the coordinates of the current cruising position of the UAV in the DEM terrain data, use the coordinates as the basis for coordinate transformation, is the elevation of the terrain positioning point;

[0061] In this embodiment, during the coordinate transformation process, the unit coordinate scale of the three-dimensional coordinate system is the same as that in the DEM terrain data, and the directions of the coordinate axes are the same, which facilitates the coordinate transformation between different coordinate systems and avoids the positioning error caused by the differences between coordinate systems.

[0062] Step S15: Use the direction angles β and field of view angles α of the laser rangefinder and infrared thermal imager carried on the UAV to calculate the coordinates of the terrain point at the bottom of the fire in the three-dimensional coordinate system ;

[0063] ;

[0064] Among them, is the distance data corresponding to the bottommost fire ground pixel, is the horizontal azimuth angle of the laser rangefinder and infrared thermal imager in the three-dimensional coordinate system;

[0065] Step S16: Use the coordinates and the coordinates to calculate the coordinates of the terrain point at the bottom of the fire in the DEM terrain data ;

[0066] ;

[0067] Step S17: Locate the fire scene according to the coordinates within the DEM terrain data and feed back the current ignition point of the fire scene to the control center.

[0068] Step S2: Calculate the height of the fire scene, and construct a relationship model between the height and width of the fire scene to calculate the burning diameter of the fire scene and determine the coverage range of the flame retardant spraying. Step S2 specifically includes:

[0069] Step S21: Calculate the height of the fire scene according to the relative height of the fire scene pixels at the top compared to the fire scene pixels at the bottom in the distance-thermal imaging image H ;

[0070] ;

[0071] wherein, is the pixel coordinate of the fire scene pixel at the top, is the pixel coordinate of the fire scene pixel at the bottom,

[0072] is the proportionality coefficient between the pixel coordinate and the actual distance.

[0073] When the present invention fuses the temperature data and distance data of the pixels in the distance-thermal imaging image, since the upper part of the fire scene is the flame part and the laser can penetrate the flame, the distance data of the upper part pixels of the distance-thermal imaging image is an untrue distance value, while the lower part is the combustible or combustion area, and the distance data is the true distance value. When calculating the height data of the fire scene, the calculation is based on the distance data of the bottom pixels.

[0074] Step S22: Use the height of the fire scene to calculate the burning diameter of the fire scene ; In this embodiment, when calculating the burning diameter of the fire scene, the burning effect of the fire scene is equivalent to a standard experimental model, considering the influence of the wind field and ignoring the influence of other natural conditions to reduce the calculation difficulty. After verification, the fire scene height and the width model of the combustible burning in this embodiment are sufficient to meet the requirements of the flame retardant spraying evaluation, and the fire extinguishing effect of the drone spraying the flame retardant meets the requirements.

[0075] ;

[0076] wherein, is the burning rate of the combustible at the fire occurrence location, is the air density, g is the acceleration due to gravity, u is the wind speed around the fire scene, is the characteristic wind speed, , is the combustion range, and the combustion range is determined according to the terrain where the fire occurs. If it occurs indoors, the maximum straight-line distance in the indoor space is taken as the combustion range . If it occurs in the mountainous area, the straight-line distance between the fire occurrence location and the nearest obstacle is taken as the combustion range ;

[0077] Step S23: Take the terrain point coordinates at the bottom of the fire scene as the center point for spraying the flame retardant. The coverage radius of the flame retardant is taken as 2 R , and a coverage range for spraying the flame retardant is generated with the center point of the flame retardant spraying as the center of the circle

[0078] Step S3: According to the height and horizontal distance of the UAV from the bottom of the fire scene, construct a control model for spraying the flame retardant, and calculate the injection pressure and total spraying amount of the UAV-controlled nozzle for spraying the flame retardant. Step S3 specifically includes:

[0079] Step S31: The UAV controls the angle of the flame retardant spraying nozzle to point to the terrain point at the bottom of the fire scene. According to the height of the UAV from the bottom of the fire scene and the horizontal distance , construct a control model for spraying the flame retardant , and calculate the injection pressure of the UAV-controlled nozzle for spraying the flame retardant p ;

[0080] ;

[0081] Among them, is the injection pressure based on the vertical injection velocity component, is the injection pressure based on the horizontal injection velocity component, is the density of the flame retardant, represents taking the maximum value, is the velocity coefficient, and the highest value of the velocity coefficient is taken as 0.97, and generally 0.95 is taken;

[0082] Step S32: According to the rated spraying intensity of the nozzle , considering the attenuation of the spraying intensity within the coverage range of the flame retardant spraying, calculate the total spraying amount Q ;

[0083] ;

[0084] Among them, is the spraying intensity attenuation coefficient, is the natural constant, is the rated spraying intensity. Since the nozzle is aimed at the center of the spraying coverage, it is considered in the calculation process of this embodiment that there will be no attenuation of the spraying intensity at the center of the coverage of the flame retardant spraying. Based on this, the spraying intensity follows a Gaussian distribution, that is, the closer to the spraying center point, the higher the spraying intensity, and the farther the distance, the lower it is. The spraying intensity represents the spraying amount per unit area per unit time.

[0085] Step S4: Based on the cruising altitude of the UAV, and using the height and horizontal distance of the UAV from the bottom of the fire scene, calculate the reaction force on the UAV during the flame retardant spraying process, construct an attitude correction equation for the UAV, and correct the flight attitude of the UAV. Step S4 specifically includes:

[0086] Step S41: Based on the cruising altitude of the UAV , the UAV controls the nozzle to point to the bottom of the fire scene and controls the spraying amount Q and injection pressure p of the flame retardant to extinguish the fire at the fire scene;

[0087] Step S42: Calculate the horizontal reaction force and vertical reaction force on the UAV during the flame retardant spraying process according to the height and horizontal distance of the UAV from the bottom of the fire scene;

[0088] ;

[0089] wherein, is the mass flow rate during the flame retardant spraying process;

[0090] Step S43: Based on the horizontal reaction force and vertical reaction force construct an attitude correction equation for the UAV during the flame retardant spraying process;

[0091] ;

[0092] wherein, are the angular velocities about the x , y , z axes respectively, are the moments of inertia about the x , y , z axes respectively, are the reaction forces in the x , y , z directions respectively, and satisfy , the resultant force of which is equal to the horizontal reaction force , and satisfy , is the position coordinate of the reaction point on the UAV relative to the centroid of the UAV during the flame retardant spraying process;

[0093] Step S44: During the process of the UAV spraying the flame retardant, correct the flight attitude of the UAV according to the attitude correction equation to ensure the accuracy of the flame retardant spraying process.

[0094] The present invention uses infrared imaging technology and laser ranging technology to locate and identify a fire scene, calculate the height and burning diameter data of the fire scene, which are used to locate the spraying of the flame retardant and determine the spraying range. While ensuring the fire extinguishing effect, it avoids excessive spraying of the flame retardant, resulting in waste of the flame retardant, realizes the precise calculation of the spraying amount and spraying pressure of the flame retardant, and at the same time, the calculated flame retardant spraying control data can be used for UAV attitude correction to reduce the influence on the UAV attitude during the flame retardant spraying process. The present invention can achieve high-precision control of flame retardant spraying and UAV attitude, significantly improve the accuracy and effectiveness of flame retardant spraying, and can be applied to various complex fire scenarios such as forests, grasslands, and cities.

Claims

1. A method for controlling a drone for spraying flame retardants, characterized in that: include: Step S1: The UAV obtains a distance-thermal imaging image that integrates the temperature and distance of the fire scene, calculates the positioning coordinates of the bottom of the fire scene based on the DEM terrain data of the target fire extinguishing area, and the direction angle and field angle of the laser ranging and infrared thermal imaging, and realizes the positioning of the fire scene; Step S2: Calculate the height of the fire scene and construct a relationship model between the height and width of the fire scene to calculate the burning diameter of the fire scene and determine the coverage of the flame retardant spraying; Step S3: construct a control model for spraying flame retardant according to the height and horizontal distance of the drone from the bottom of the fire scene, and calculate the injection pressure and total spraying volume of the nozzle controlled by the drone to spray flame retardant; Step S4: Based on the cruising altitude of the UAV, the height and horizontal distance of the UAV from the bottom of the fire scene are used to calculate the reaction force on the UAV during the spraying of the flame retardant, and the attitude correction equation of the UAV is constructed to correct the attitude of the UAV; The step S1 comprises: Step S11: retrieve the DEM terrain data of the target fire extinguishing area, and use the UAV to carry the flame retardant to reach the fire scene. Use the laser rangefinder and infrared thermal imager to obtain the distance-thermal imaging image that integrates the temperature and distance of the fire scene, and obtain the temperature data of each pixel in the distance-thermal imaging image. and distance data , Number the pixels; Step S12: Setting the fire scene temperature threshold , compare temperature data Fire temperature threshold The size of , then determine the pixel is the fire scene pixel, if , then determine the pixel are non-fire pixels; Step S13: Delete the non-fire scene pixels in the distance-thermal imaging image, retain the fire scene pixels, and obtain the distance data corresponding to each fire scene pixel ; Step S14: Using the current cruising point of the drone as the coordinate origin, establish a three-dimensional coordinate system based on the drone's cruising altitude. Get the coordinates of the terrain positioning point under the drone in the three-dimensional coordinate system ; Based on the coordinates of the current cruising point of the drone in the DEM terrain data , the coordinates As the basis for coordinate system transformation, is the elevation of the terrain location point; Step S15: Using the laser rangefinder and infrared thermal imager on the drone to measure the direction of the β and field of view α Calculate the coordinates of the terrain points at the bottom of the fire scene in the three-dimensional coordinate system ; ； in, is the distance data corresponding to the bottom fire pixel, is the horizontal azimuth of the laser rangefinder and infrared thermal imager in the three-dimensional coordinate system; Step S16: Using coordinates With coordinates Calculate the coordinates of the terrain points at the bottom of the fire scene within the DEM terrain data ; ； Step S17: Based on the coordinates in the DEM terrain data Locate the fire scene and provide feedback to the control center on the current ignition point.

2. The method for controlling a UAV for spraying flame retardant according to claim 1, characterized in that: The step S2 comprises: Step S21: Calculate the height of the fire scene based on the relative height of the fire scene pixel at the top compared to the fire scene pixel at the bottom in the distance-thermal imaging image. H ; ； in, is the pixel coordinate of the top fire pixel, is the pixel coordinate of the bottom fire pixel, is the proportional coefficient between pixel coordinates and actual distance; Step S22: Using the height of the fire Calculate the burning diameter of the fire ; Step S23: The topographic point coordinates at the bottom of the fire scene As the center point of flame retardant spraying, the coverage radius of flame retardant is The coverage of the flame retardant spraying is generated with the center point of the flame retardant spraying as the center of the circle.

3. The method for controlling a UAV for spraying flame retardant according to claim 2, characterized in that: The burning diameter R The calculation method is: ； in, is the burning rate of combustibles at the fire location, is the air density, g is the acceleration due to gravity, u is the wind speed around the fire scene, is the characteristic wind speed, , The combustion range.

4. The method for controlling a UAV for spraying flame retardant according to claim 2, characterized in that: The step S3 comprises: Step S31: The drone controls the angle of the flame retardant spray nozzle to point to the terrain point at the bottom of the fire scene, and the drone controls the angle of the flame retardant spray nozzle to point to the terrain point at the bottom of the fire scene according to the height of the drone from the bottom of the fire scene. and horizontal distance , build a control model for flame retardant spraying , calculate the injection pressure of the drone controlled nozzle spraying flame retardant p ; Step S32: According to the rated spraying intensity of the nozzle , considering the attenuation of the spraying intensity within the coverage area of ​​the flame retardant spraying, calculate the total spraying amount Q .

5. The method for controlling a UAV for spraying flame retardant according to claim 4, characterized in that: The control model of the flame retardant spraying for: ； in, is the injection pressure based on the vertical injection velocity component, is the injection pressure based on the lateral injection velocity component, is the density of the flame retardant, Indicates taking the maximum value, is the velocity coefficient of the injection velocity.

6. The method for controlling a UAV for spraying flame retardant according to claim 4, characterized in that: The total spraying volume is calculated Q The method is; ； in, is the spray intensity attenuation coefficient, is a natural constant, is the rated spray intensity.

7. The method for controlling a UAV for spraying flame retardant according to claim 4, characterized in that: The step S4 comprises: Step S41: Based on the cruising altitude of the drone The drone controls the nozzle to point to the bottom of the fire and controls the amount of flame retardant sprayed. Q and injection pressure p , extinguish the fire; Step S42: Calculate the height of the drone from the bottom of the fire scene and horizontal distance Calculate the horizontal reaction force on the drone during flame retardant spraying and vertical reaction force ; ； in, is the mass flow rate of flame retardant during spraying; Step S43: Based on the horizontal reaction force and vertical reaction force Construct the attitude correction equation for the UAV during the flame retardant spraying process; ； in, Respectively around x , y , z The angular velocity of the axis, Respectively around x , y , z The moment of inertia of the shaft, They are x , y , z The reaction force in the direction of , The resultant force is equal to the horizontal reaction force , It is the position coordinate of the reaction point on the UAV relative to the mass center of the UAV during the flame retardant spraying process; Step S44: During the process of the UAV spraying the flame retardant, the posture of the UAV is corrected according to the posture correction equation to ensure the accuracy of the flame retardant spraying process.

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