Low-altitude environment operation risk assessment method considering the impact of eVTOL aircraft crashes

Abstract

This invention discloses a low-altitude environment operation risk assessment method considering the impact of eVTOL aircraft crashes. Belonging to the field of aircraft risk assessment, it constructs an operation risk model that considers the spatial distribution of buildings within the city and ground personnel, vehicles, or small multi-rotor UAVs that may be injured after an aircraft crash. By calculating the total risk of each cell in the airspace grid, and removing grids occupied by buildings and trackpoints below the equivalent safety level, a safe airspace environment is obtained. This allows the eVTOL aircraft to be controlled to fly within the reserved safe airspace environment, significantly improving the practicality and accuracy of three-dimensional track planning for eVTOL aircraft when considering urban environments.

Description

Technical Field

[0001] This invention relates to the field of aircraft risk assessment technology, and in particular to a method for assessing operational risks in low-altitude environments that takes into account the impact of eVTOL aircraft crashes. Background Technology

[0002] Cities, as environments for people's production and life, have a high density of buildings, people, and vehicles. Because electric vertical takeoff and landing (eVTOL) aircraft have the potential for accidental crashes, posing a threat to the safety of ground buildings, people, and vehicles, and may also collide with small multi-rotor drones, urban air traffic trajectory planning must meet obstacle avoidance requirements while also considering operational risks. Traditional trajectory planning only considers obstacle avoidance, resulting in significant deviations in actual flight; therefore, ensuring a safe distance between aircraft and obstacles is crucial. Summary of the Invention

[0003] This invention provides a method for assessing operational risks in low-altitude environments that takes into account the impact of eVTOL aircraft crashes, improving the practicality and accuracy of three-dimensional trajectory planning for eVTOL aircraft when considering urban environments.

[0004] This invention provides a method for assessing operational risks in low-altitude environments considering the impact of eVTOL aircraft crashes, comprising the following steps: establishing a ground personnel risk model and a ground vehicle risk model based on the spatial distribution of buildings within a city, and establishing an air collision risk model based on the aircraft's flight information; dividing the aircraft's flight airspace into grids to obtain multiple airspace grid units, calculating the total crash risk within each airspace grid unit based on the ground personnel risk model, the ground vehicle risk model, and the air collision risk model; and filtering the total crash risk within each airspace grid unit to remove airspace grid units that do not meet safety conditions, thereby obtaining a safe airspace environment.

[0005] In one embodiment of the present invention, after obtaining a safe airspace environment, the method further includes: performing hierarchical airspace planning in the safe airspace environment to form an urban low-altitude airspace environment based on operational risks.

[0006] In one embodiment of the present invention, a risk model for ground-based personnel is established based on the spatial distribution of buildings within a city, including:

[0007] The number of people, M, who determined the area where the aircraft crashed:

[0008] M = ρ P A = ρ P πr 2

[0009] Where, ρ PLet A be the population density of the crash site, A be the area of ​​the crash site, and r be the radius of the crash site.

[0010] Determine the ground fatality rate P caused by an aircraft crash. p :

[0011]

[0012] Among them, c s Let α be the shading coefficient, and c be the shading coefficient. s The impact kinetic energy when = 0.5, β is c s The impact kinetic energy at →0, E imp The kinetic energy of an aircraft impacting the ground;

[0013] The ground personnel risk model for aircraft impacting ground personnel is as follows:

[0014] R p (p ijk )=λMP p (p ijk )

[0015] Where λ is the probability of the aircraft crashing, p ijk (x,y,z) represents the coordinates of the center point of the grid in the i-th layer, j-th column, and k-th layer.

[0016] In one embodiment of the present invention, a ground vehicle risk model is established based on the spatial distribution of buildings within a city, including:

[0017] Determine the probability P of an aircraft-vehicle collision. v :

[0018]

[0019] Among them, S v S is the projected area of ​​the vehicle. r Let N be the road area, N be the number of vehicles, k be the traffic density, and w be the traffic density. r For road width, l r Where k is the road length and k is the traffic density;

[0020] The ground vehicle risk model for aircraft impacting ground vehicles is as follows:

[0021] R v (p ijk )=λNP v (p ijk )

[0022] Where λ is the probability of the aircraft crashing, p ijk (x,y,z) represents the coordinates of the center point of the grid in the i-th layer, j-th column, and k-th layer.

[0023] In one embodiment of the present invention, the aircraft is regarded as a cuboid collision box, and the collision between the aircraft and the flying vehicle is the process of the flying vehicle intruding into the collision box. An air collision risk model is established based on the aircraft's flight information, including:

[0024] Determine the probability P of a collision between two aircraft. U :

[0025]

[0026] Among them, V e V represents the volume swept by the collision box during aircraft flight, and V represents the volume of the airspace environment.

[0027] The mid-air collision risk model for an aircraft crash affecting other aircraft is as follows:

[0028] R U (p ijk )=λUP U =λρ U VP U

[0029] Where λ is the probability of the aircraft crashing, and U and ρ U These refer to the number and density of aircraft, respectively.

[0030] In one embodiment of the present invention, the total fall risk within each airspace grid cell is calculated based on the ground personnel risk model, the ground vehicle risk model, and the air collision risk model, including:

[0031] p ijk The total risk R within the spatial grid cell containing (x,y,z) is R pijk for:

[0032] R pijk =ω1R p (pi jk )+ω2R v (p ij k)+ω3R U (p ijk )

[0033] Where ω1, ω2, and ω3 are the weighting coefficients for ground personnel risk, ground vehicle risk, and air collision risk, respectively, and ω1 + ω2 + ω3 = 1, R p (p ijk R is a risk model for ground personnel. v (p ijk R is a risk model for ground vehicles. U (p ijk () is a mid-air collision risk model.

[0034] In one embodiment of the present invention, the safety conditions are that the flight area is free of obstacles or is a non-no-fly zone, and the total risk of crash within the airspace grid cell is less than an acceptable risk level.

[0035] In one embodiment of the present invention, hierarchical airspace planning is performed in the safe airspace environment, including dividing the flight zones into multiple levels according to flight altitude.

[0036] The low-altitude environment operation risk assessment method considering the impact of eVTOL aircraft crashes in this invention constructs an operation risk model that considers the spatial distribution of buildings within the city and ground personnel, vehicles, or small multi-rotor UAVs that may be injured after an aircraft crash. By calculating the total risk of each cell in the airspace grid and eliminating grids occupied by buildings and trackpoints below the equivalent safety level, a safe airspace environment is obtained, which greatly improves the practicality and accuracy of three-dimensional track planning for eVTOL aircraft when considering urban environments.

[0037] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0038] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0039] Figure 1 A flowchart of a low-altitude environment operation risk assessment method considering the impact of eVTOL aircraft crashes, provided according to an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram illustrating the impact of an aircraft crash on a small multi-rotor drone, provided according to an embodiment of the present invention.

[0041] Figure 3 This is a schematic diagram of the framework for a low-altitude environment operation risk assessment method that considers the impact of eVTOL aircraft crashes, according to an embodiment of the present invention.

[0042] Figure 4 This is a plan view of the outline of a section of buildings in a city, provided according to an embodiment of the present invention.

[0043] Figure 5 This is another three-dimensional outline of a city building provided according to an embodiment of the present invention;

[0044] Figure 6 A schematic diagram of a gridded urban airspace environment (external) provided according to an embodiment of the present invention;

[0045] Figure 7A schematic diagram of a gridded urban airspace environment (internal) provided according to an embodiment of the present invention;

[0046] Figure 8 A schematic diagram of an urban airspace environment (external) after risk assessment, provided according to an embodiment of the present invention;

[0047] Figure 9 A schematic diagram of an urban airspace environment (interior) after risk assessment, provided according to an embodiment of the present invention;

[0048] Figure 10 This is a schematic diagram illustrating the total risk of different combinations of weighting coefficients according to embodiments of the present invention;

[0049] Figure 11 This is a risk-assessed urban airspace environmental plan diagram provided by an embodiment of the present invention when h=100m;

[0050] Figure 12 This is a risk-assessed urban airspace environmental plan diagram provided by an embodiment of the present invention when h=160m;

[0051] Figure 13 This is a risk-assessed urban airspace environmental plan for h=220m provided according to an embodiment of the present invention. Detailed Implementation

[0052] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0053] To reduce the impact of accidental aircraft crashes, this invention analyzes the sources of risk in urban air traffic operations, including ground personnel, ground vehicles, and small multi-rotor drones, and establishes risk models for ground personnel, ground vehicles, and aerial collisions, respectively. The urban airspace is gridded, and the risk level is determined based on the total collision risk of personnel, vehicles, and small multi-rotor drones in each unit. Based on the risk level, a distribution map of urban low-altitude operational risks is drawn, forming an urban low-altitude airspace environment model based on operational risks.

[0054] To address the operational risks posed by aircraft crashes, this invention sets the following assumptions for a low-altitude environment operational risk assessment model that considers the impact of eVTOL aircraft crashes:

[0055] (1) Consider three risk sources: ground personnel, vehicles and small multi-rotor drones;

[0056] (2) The density of ground personnel, vehicles and small multi-rotor UAVs is uniformly distributed;

[0057] (3) The impact of aircraft noise on the low-altitude environment was not considered;

[0058] (4) The flight speed of small multi-rotor UAVs is constant.

[0059] Considering the practicality of eVTOL aircraft operation in urban low-altitude airspace, the model variables set in this invention are shown in Table 1.

[0060] Table 1 Model Parameters and Variables

[0061]

[0062]

[0063] Figure 1 This is a flowchart illustrating a low-altitude environment operation risk assessment method that considers the impact of eVTOL aircraft crashes, according to an embodiment of the present invention.

[0064] like Figure 1 As shown, the low-altitude environment operational risk assessment method considering the impact of eVTOL aircraft crashes includes the following steps:

[0065] In step S101, a ground personnel risk model and a ground vehicle risk model are established based on the spatial distribution of buildings within the city, and an air collision risk model is established based on the flight information of aircraft.

[0066] When performing 3D trajectory planning for eVTOL aircraft, the urban airspace environment is complex. It is necessary to avoid obstacles distributed throughout the city while also considering operational risks. Therefore, this invention utilizes the objective function value of a low-altitude environment operational risk assessment model that considers the impact of eVTOL aircraft crashes to accurately quantify the risk value of each airspace grid, determine its risk level, and generate a 3D spatial risk distribution map. This invention adds the risk of mid-air collisions between eVTOL aircraft and small multi-rotor UAVs to the objective function.

[0067] In one embodiment of the invention, an aircraft may lose control or power during flight and crash, resulting in injury to people on the ground. The number of people in the aircraft crash zone is:

[0068] M = ρ P A = ρ P πr 2

[0069] Where, ρ P Let A be the population density of the crash site, A be the area of ​​the crash site, and r be the radius of the crash site.

[0070] During an aircraft crash, the vertical force is:

[0071]

[0072] Among them, R I It is the drag coefficient related to the aircraft model, ρ A It is air density, v z It is the vertical speed of the aircraft.

[0073] The acceleration of the aircraft is:

[0074]

[0075] Among them, F g For gravity, m e For the mass of the aircraft, m p Let g be the mass of the passenger, and g be the acceleration due to gravity.

[0076] The speed at which the aircraft hit the ground was:

[0077]

[0078] Where h' represents the height of the aircraft above the ground personnel.

[0079] The kinetic energy of an aircraft impacting the ground is:

[0080]

[0081] Trees and buildings can mitigate the impact of an aircraft crashing onto the ground, thanks to the shielding factor c. s The buffering effect is represented by the values ​​shown in Table 2. Under the same kinetic energy, the better the shielding effect, the lower the mortality rate of personnel on the ground.

[0082] Table 2. Shading Coefficient c s The value of

[0083]

[0084] The fatality rate for ground personnel resulting from an aircraft crash is:

[0085]

[0086] Where α and β are c s =0.5 (ground personnel mortality rate is 50%) and c s →Impact kinetic energy at 0.

[0087] The risk model for aircraft impacting ground personnel is as follows:

[0088] R p (p ijk )=λMPp (p ijk )

[0089] Where λ is the probability of the aircraft crashing.

[0090] In embodiments of the present invention, an aircraft may lose control or power during flight and crash, colliding with a ground vehicle. The probability of an aircraft colliding with a vehicle is:

[0091]

[0092] Among them, S v and S r These represent the projected area of ​​the vehicle and the road area, respectively, where N is the number of vehicles, k is the traffic density, and w r and l r These refer to the road width and length, respectively.

[0093] The risk model for aircraft impacting ground vehicles is as follows:

[0094] R v (p ijk )=λNP v (p ijk )

[0095] In an embodiment of the invention, an aircraft may lose control or power during flight and crash, colliding with a small multi-rotor drone performing a logistics delivery task below. A spatial Cartesian coordinate system is established with the aircraft's center as the origin O'. The collision process is simplified to the small multi-rotor drone intruding into the aircraft's collision box, where the collision box's length, width, and height are e, respectively. l e w e h ,like Figure 2 As shown.

[0096] The relative velocities of the aircraft and the small multi-rotor UAV in the O'x'y' plane and the z' axis are respectively:

[0097]

[0098] v rz' =v A sinθ-v B sinγ

[0099] Among them, v A v B Let θ and γ be the velocities of the aircraft and the small multi-rotor UAV, respectively; let θ and γ be the angles between the velocities of the two aircraft and the O'x'y' plane, respectively; and let ε be the angle between the velocities of the two aircraft. γ and ε are respectively located in... And [0,π] are uniformly distributed.

[0100] The relative speed and average relative speed of the two aircraft are as follows:

[0101]

[0102]

[0103] Assuming the aircraft flies along the x-axis, the volume swept by the collision box is:

[0104]

[0105] The probability of a collision between the two aircraft is:

[0106]

[0107] Where V represents the volume of the airspace environment.

[0108] The risk model for aircraft impacting small multi-rotor drones is as follows:

[0109] R U (p ijk )=λUP U =λρ U VP U

[0110] Where U and ρ U These refer to the number and density of small multi-rotor drones, respectively.

[0111] In step S102, the flight airspace of the aircraft is divided into grids to obtain multiple airspace grid cells. The total crash risk within each airspace grid cell is calculated based on the ground personnel risk model, the ground vehicle risk model, and the air collision risk model.

[0112] Each spatial grid cell includes the three types of risks mentioned above. The total risk of each spatial grid cell is obtained by summing the three risk values.

[0113] p ijk The total risk value of the spatial grid containing (x,y,z) is:

[0114] R pijk =ω1R p (p ijk )+ω2R v (p ijk )+ω3R U (p ijk )

[0115] Wherein, ω1, ω2, and ω3 are the weighting coefficients for ground personnel risk, ground vehicle risk, and air collision risk, respectively, and ω1+ω2+ω3=1.

[0116] In step S103, the total fall risk within each airspace grid cell is screened, and airspace grid cells that do not meet the safety conditions are removed to obtain a safe airspace environment.

[0117] By taking the steps described above, the total risk value of each grid is obtained. The total fall risk within each airspace grid cell is then filtered to obtain a safe airspace environment where flight is permitted.

[0118] In embodiments of the present invention, the safety conditions are that the flight area is free of obstacles or is a non-no-fly zone, and the total risk of crash within the airspace grid cell is less than an acceptable risk level.

[0119] Specifically, risk is defined as the product of the probability of an accident occurring and the severity of its consequences. The selection criteria for the airspace grid are as follows:

[0120]

[0121] Where R represents the acceptable risk level.

[0122] In one embodiment of the present invention, such as Figure 3 As shown, after obtaining a safe airspace environment, the process also includes: conducting hierarchical airspace planning within the safe airspace environment to form an urban low-altitude airspace environment based on operational risks.

[0123] Layered airspace planning in a safe airspace environment includes dividing flight zones into multiple levels based on flight altitude.

[0124] Specifically, after completing the risk assessment of the urban airspace environment, the airspace will continue to be divided into layers within the reserved low-risk airspace.

[0125] The first layer: 0-60m is the flight zone, which is used by small multi-rotor drones to perform logistics delivery tasks.

[0126] The second layer: 60-90m is a no-fly zone, used to isolate aircraft from the first and third layers.

[0127] The third layer, from 90 to 270 meters, is the flight zone, providing air transport services for eVTOL aircraft. Based on the different passenger-carrying cruising speeds of the unmanned aerial vehicle (UAV) systems, it is further subdivided into low-speed routes (v≤50m / s), medium-speed routes (50m / s<v<70m / s), and high-speed routes (v≥70m / s). Specifically, 90-120m and 120-150m are used for round-trip flights of low-speed aircraft, 150-180m and 180-210m for round-trip flights of medium-speed aircraft, and 210-240m and 240-270m for round-trip flights of high-speed aircraft.

[0128] The fourth level: 270-300m is a no-fly zone, used to isolate aircraft from the third level.

[0129] The following detailed description of the low-altitude environment operation risk assessment method of the present invention, which takes into account the impact of eVTOL aircraft crashes, is provided through specific embodiments.

[0130] This invention uses building outline data from a certain region for experiments. The simulated scenario includes eight main roads, and the building outlines in the urban area are shown below. Figure 4 As shown in Table 3, the parameters for running the risk assessment model are also shown.

[0131] Table 3 Parameter Setting Table

[0132]

[0133] The selected area is gridded with a resolution of u = 50m, v = 50m, w = 30m, as follows: Figure 6 , Figure 7 As shown. The total risk of each spatial grid is calculated based on the established operational risk assessment model, and the risk level is represented by continuous color bands, with risk values ​​gradually increasing from cool colors to warm colors, such as... Figure 8 , Figure 9 As shown, the operational risk values ​​of the safe airspace environment are all no higher than 7 × 10⁻⁶. -7 .

[0134] To compare the impact of different combinations of weighting coefficients and flight altitude on risk assessment, this invention conducts risk assessments of low-altitude environments under multiple different numerical settings and compares the results.

[0135] (1) Weighting coefficients. Under the condition that the buildings are distributed in the same way, different combinations of weighting coefficients are set and the risk assessment results are analyzed. ω1, ω2, ω3∈[0.1,0.8], Δω=0.1, and ω1+ω2+ω3=1. The results are as follows: Figure 10 As shown in the figure, it can be seen that the smaller the diameter of the point, the lower the total risk; among them, ω1=0.6, ω2=0.2, ω3=0.2 is the optimal combination of weight coefficients, at which the total risk is the lowest.

[0136] (2) Flight Altitude. Under the condition of identical building distribution, different flight altitudes were set, and the risk assessment results were analyzed. The results for h = 100m, 160m, and 220m are as follows: Figures 11-13 As shown, at lower altitudes, the safe zones are more dispersed and the risk is higher; as the altitude increases, the safe zones become interconnected, the risk decreases, and the availability of airspace increases.

[0137] In summary, this invention, based on flight scenarios in urban environments, considers multiple sources of operational risk and utilizes an established operational risk assessment model to evaluate the urban environment. Addressing the issue of insufficient comprehensive consideration of operational risks in previous urban airspace environment studies, this invention includes ground personnel, vehicles, and small multi-rotor UAVs as risk sources, and can employ different combinations of risk sources in different environments. After risk assessment, the operational risk values ​​of the retained safe airspace environments are all no higher than 7 × 10⁻⁶. -7 The model meets the low-risk level of the risk assessment matrix. Addressing the problems of irregular shapes and low efficiency in traditional airspace planning, a stratified approach is adopted based on different aircraft performance characteristics, with further subdivisions according to different directions. This approach is suitable for the actual operation of urban air traffic, and the effectiveness of the model is verified using different combinations of weighting coefficients and flight altitudes.

[0138] The low-altitude environment operation risk assessment method considering the impact of eVTOL aircraft crashes in this invention constructs an operation risk model based on existing building outline data. This model considers the spatial distribution of buildings within the city and ground personnel, vehicles, or small multi-rotor UAVs that may be injured after an aircraft crash. By calculating the total risk of each unit in the airspace grid, grids occupied by buildings and trackpoints below the equivalent safety level are eliminated. Secondly, within a safe airspace environment after risk assessment, a layered airspace planning method is combined to form an urban low-altitude airspace environment model based on operation risk, improving the practicality and accuracy of three-dimensional track planning for eVTOL aircraft when considering the urban environment.

[0139] The terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0140] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0141] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or N executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of the invention pertain.

Claims

1. A method for assessing operational risks in low-altitude environments considering the impact of eVTOL aircraft crashes, characterized in that, Includes the following steps: Based on the spatial distribution of buildings within the city, establish a risk model for ground personnel and a risk model for ground vehicles; and establish an air collision risk model based on aircraft flight information. The flight airspace of the aircraft is divided into grids to obtain multiple airspace grid cells. The total crash risk in each airspace grid cell is calculated based on the ground personnel risk model, the ground vehicle risk model and the air collision risk model. The total fall risk within each airspace grid cell is screened, and airspace grid cells that do not meet the safety conditions are removed to obtain a safe airspace environment; Layered airspace planning is carried out in the safe airspace environment to form an urban low-altitude airspace environment based on operational risks; A risk model for ground-based personnel is established based on the spatial distribution of buildings within the city, including: The number of people in the area where the aircraft crashed was determined : in, Population density in the crash area, The area of ​​the crash site. The radius of the crash zone; Determine the mortality rate of ground personnel caused by an aircraft crash. : Among them, c s The shading factor is... for The impact kinetic energy at that time for The impact kinetic energy at that time The kinetic energy of an aircraft impacting the ground; The ground personnel risk model for aircraft impacting ground personnel is as follows: in, This represents the probability of an aircraft crashing. These are the coordinates of the center point of the grid in the i-th layer, j-th column, and k-th layer. A risk model for ground vehicles is established based on the spatial distribution of buildings within the city, including: Determine the probability of an aircraft-vehicle collision. : in, This represents the projected area of ​​the vehicle. For road area, For the number of vehicles, For traffic density, For road width, For road length, Traffic density; The ground vehicle risk model for aircraft impacting ground vehicles is as follows: in, This represents the probability of an aircraft crashing. These are the coordinates of the center point of the grid in the i-th layer, j-th column, and k-th layer. The aircraft is considered as a cuboid collision box, and the collision between two aircraft is the process of the aircraft intruding into the collision box. An airborne collision risk model is established based on the aircraft's flight information, including: Determine the probability of collision between aircraft and spacecraft : in, This refers to the volume swept by the collision box during aircraft flight. The volume of the airspace environment; The mid-air collision risk model for an aircraft crash affecting other aircraft is as follows: in, This represents the probability of an aircraft crashing. and These refer to the number and density of aircraft, respectively.

2. The method according to claim 1, characterized in that, The total fall risk within each airspace grid cell is calculated based on the ground personnel risk model, the ground vehicle risk model, and the air collision risk model, including: Total risk within the spatial grid cell for: in, These are the weighting coefficients for ground personnel risk, ground vehicle risk, and air collision risk, respectively. , For ground personnel risk model, For ground vehicle risk models, For mid-air collision risk model.

3. The method according to claim 1, characterized in that, The safety conditions are that the flight area is free of obstacles or is not a no-fly zone, and the total risk of crash within the airspace grid cell is less than an acceptable risk level.

4. The method according to claim 1, characterized in that, Layered airspace planning is carried out in the safe airspace environment, including dividing the flight zones into multiple levels according to flight altitude.

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