Helicopter low-noise flight path design method and related device

Abstract

The invention discloses a helicopter low-noise flight path design method and a related device, and relates to the technical field of helicopter path planning, and the method comprises the steps: adding the accumulated sound exposure level of a local or specific region into an evaluation function of a path optimization algorithm, and improving the weight of the accumulated sound exposure level. Therefore, a path capable of effectively reducing the noise level of the target area or the whole area is selected, and the influence of noise on the surrounding environment is reduced to the maximum extent.

Description

Technical Field

[0001] The present application relates to the technical field of helicopter trajectory planning, and in particular to a method for designing a low-noise flight trajectory for a helicopter and related devices. Background Art

[0002] As an aircraft that can take off and land vertically and fly at low altitude, helicopters have a wide range of uses in military and civilian applications. However, strong noise has always been an important limiting factor for the further application of rotorcraft, with helicopters as a typical example. During flight in urban areas, the noise generated by the frequent maneuvers of helicopters between buildings will not only affect residents, greatly limiting its application in civilian applications, but also easily lead to helicopters being discovered by the enemy in the military, causing unnecessary casualties. Therefore, helicopter noise reduction has always been a focus of research in the development of helicopter technology.

[0003] At present, for global obstacle avoidance and path finding of helicopters in complex terrains such as urban areas, the shortest path is usually selected with the distance between the current node and the target point and the starting point as the main component. However, for different flight mission requirements, the shortest path selected in this way can ensure the fastest arrival at the destination, but the shortest path is not necessarily the path with the lowest noise. Summary of the invention

[0004] The purpose of this application is to provide a helicopter low-noise flight trajectory design method and related devices, which can be used to design a helicopter low-noise flight trajectory and minimize the impact of noise on the surrounding environment.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] In a first aspect, the present application provides a method for designing a low-noise flight trajectory of a helicopter, comprising:

[0007] According to the flight mission requirements of the helicopter, obtain the map data of the target area, helicopter performance parameters, flight constraints, and the starting and ending positions of the flight path;

[0008] Performing rasterization processing on the map data to obtain a rasterized map, wherein the rasterized map includes an obstacle grid and a feasible area grid;

[0009] Based on the helicopter performance parameters, the flight constraints, the starting position and the end position of the flight path, the optimal flight path of the helicopter is determined in the rasterized map using a path optimization algorithm, wherein an evaluation function of the path optimization algorithm is a function determined according to a cumulative sound exposure level, an actual cost from the starting position to a current node, and an estimated cost from the current node to the end position, the cumulative sound exposure level is a variable value calculated according to the current node noise information received by a ground noise observation point, the node corresponding to the minimum of the evaluation function is determined as the optimal node, the optimal node is a node on the optimal flight path, and each grid in the rasterized map represents each of the nodes.

[0010] In a second aspect, the present application provides a computer device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the helicopter low-noise flight trajectory design method described above.

[0011] In a third aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the helicopter low-noise flight trajectory design method described above.

[0012] In a fourth aspect, the present application provides a computer program product, including a computer program, which, when executed by a processor, implements the helicopter low-noise flight trajectory design method described above.

[0013] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0014] The present application provides a method and related device for designing a low-noise flight trajectory for a helicopter. By adding the cumulative sound exposure level of a local or specific area to the evaluation function of a path optimization algorithm and increasing its weight, a path that can effectively reduce the noise level in the target area or the overall area is selected, thereby minimizing the impact of noise on the surrounding environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 This is an application environment diagram of a helicopter low-noise flight trajectory design method in Example 1 of the present application;

[0017] Figure 2 A schematic diagram of a flow chart of a method for designing a low-noise flight trajectory of a helicopter provided in Example 1 of the present application;

[0018] Figure 3 This is a schematic diagram of a two-dimensional grid map in Example 1 of the present application;

[0019] Figure 4 This is a schematic diagram of the obstacle expansion processing in the grid map in Example 1 of the present application;

[0020] Figure 5 This is a schematic diagram of the 0-1 matrix map in Example 1 of the present application;

[0021] Figure 6 A schematic diagram of the process flow of the trajectory design in Example 1 of the present application;

[0022] Figure 7 This is a schematic diagram of an 8-neighborhood search direction diagram in Example 1 of the present application;

[0023] Figure 8 A schematic diagram of the spatial positioning of the secondary sound radiation ball in Example 1 of the present application;

[0024] Fig. 9 Schematic diagram of the secondary sound radiation model in Example 1 of the present application;

[0025] Fig.10 is a schematic diagram of a two-dimensional linear interpolation method in Example 1 of the present application;

[0026] FIG11( a ) is a schematic diagram of the initial path before smoothing by the Floyd method;

[0027] FIG11( b ) is a schematic diagram of the path obtained after processing in step (1) of the Floyd method;

[0028] FIG11( c ) is a schematic diagram of the path obtained after processing in step (2) of the Floyd method;

[0029] Fig.12 A schematic diagram of the structure of a computer device provided in Example 2 of the present application. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] Research has found that changing the flight attitude and trajectory can achieve the purpose of noise reduction, which is the mainstream means of helicopter maneuvering flight noise reduction. Due to the presence of many unevenly distributed obstacles in complex terrain such as urban areas, helicopters need to avoid various obstacles while considering noise reduction.

[0032] Although the global obstacle avoidance pathfinding method for complex terrains such as urban areas is relatively mature, in general, in order to quickly find the shortest path to the destination, the evaluation function generally uses the distance between the current node and the target point and the starting point as the main component. However, this calculation method can only ensure that the shortest path is selected. For different flight mission requirements, the path that can reach the destination the fastest is not necessarily the path with the lowest noise. Moreover, even if noise information is considered in the noise reduction pathfinding of UAVs in urban areas, the relevant solution is to represent the UAV with a sphere containing the corresponding noise information. Assuming that it flies in the building at a uniform speed, the sphere only considers the change of direction, and uses the sphere to calculate the local noise as another component of the evaluation function, so as to complete the pathfinding from the starting point to the end point while ensuring a low noise level throughout the flight. When the helicopter is in different maneuvering states during urban flight, the size and directionality of the noise will also change. This is one of the reasons why trajectory noise reduction is feasible. Therefore, it is not possible to directly calculate the local noise with a fixed sound radiation sphere.

[0033] The helicopter low-noise flight trajectory design method provided in this embodiment can plan a path that effectively reduces the noise level in the target area or the overall area. It considers the maneuvering state and noise characteristics of the helicopter to construct a dynamically changing secondary sound radiation model to calculate the local noise. It can more accurately determine the size and directionality of the noise in different maneuvering states when the helicopter is flying in the urban area, so as to more accurately evaluate and optimize its flight path, thereby minimizing the impact of noise on the surrounding environment while ensuring flight safety and efficiency.

[0034] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0035] Example 1

[0036] The helicopter low-noise flight trajectory design method provided in the embodiment of the present application can be applied to Figure 1In the application environment shown. Among them, the terminal 102 communicates with the server 104 through the network. The data storage system can store the data that the server 104 needs to process. The data storage system can be set up separately, integrated on the server 104, or placed on the cloud or other servers. The terminal 102 can send the map data of the target area, the helicopter performance parameters, the flight constraints, the starting position and the end position of the flight path to the server 104. After receiving the map data of the target area, the helicopter performance parameters, the flight constraints, the starting position and the end position of the flight path, the server 104 rasterizes the map data to obtain a rasterized map; based on the helicopter performance parameters, the flight constraints, the starting position and the end position of the flight path, the path optimization algorithm is used to determine the optimal flight path of the helicopter in the rasterized map. The server 104 can feedback the obtained optimal flight path to the terminal 102. In addition, in some embodiments, the helicopter low-noise flight trajectory design method can also be implemented independently by the server 104 or the terminal 102. For example, the terminal 102 can directly use the helicopter low-noise flight trajectory design method to process the map data of the target area, helicopter performance parameters, flight constraints, and the starting and ending positions of the flight path. The server 104 can also obtain the map data of the target area, helicopter performance parameters, flight constraints, and the starting and ending positions of the flight path from the data storage system and use the helicopter low-noise flight trajectory design method to process them.

[0037] The terminal 102 may be, but is not limited to, various desktop computers, laptop computers, smart phones, tablet computers, IoT devices, and portable wearable devices. The IoT devices may be smart speakers, smart TVs, smart air conditioners, smart vehicle-mounted devices, etc. The portable wearable devices may be smart watches, smart bracelets, head-mounted devices, etc. The server 104 may be implemented as an independent server or a server cluster consisting of multiple servers, or may be a cloud server.

[0038] In an exemplary embodiment, a method for designing a low-noise flight trajectory of a helicopter is provided. The method is executed by a computer device, and can be executed by a computer device such as a terminal or a server alone, or by a terminal and a server together. In the embodiment of the present application, the method is applied to Figure 1 The server 104 in the example is used as an example to illustrate the method, which includes the following steps 201 to 208. Among them:

[0039] Step 201, according to the flight mission requirements of the helicopter, obtain map data of the target area, helicopter performance parameters, flight constraints, and the starting position and end position of the flight path;

[0040] Step 202, rasterizing the map data to obtain a rasterized map;

[0041] Step 203: Based on the helicopter performance parameters, the flight constraints, the starting position and the end position of the flight path, an optimal flight path of the helicopter is determined in the rasterized map using a path optimization algorithm, wherein an evaluation function of the path optimization algorithm is a function determined according to a cumulative sound exposure level, an actual cost from the starting position to the current node, and an estimated cost from the current node to the end position; the cumulative sound exposure level is a variable value calculated according to the current node noise information received by a ground noise observation point; a node corresponding to a minimum of the evaluation function is determined as an optimal node; the optimal node is a node on the optimal flight path; and each grid in the rasterized map represents each of the nodes.

[0042] In order to make those skilled in the art more aware of the specific implementation process of the helicopter low-noise flight trajectory design method based on steps 201 to 203, a specific description is given below.

[0043] like Figure 2 As shown in the figure, the general process of the design method of low-noise helicopter flight trajectory in urban areas includes:

[0044] 1. Urban environment modeling and initialization.

[0045] This embodiment mainly adopts the grid method to model the urban environment, uses the C++ program to rasterize the extracted map data file and output a 0-1 matrix file, and matlab reads the 0-1 matrix file.

[0046] 1.1 Rasterization of map data.

[0047] When the static environment is known, the grid method divides the environment into equally divided grids and distinguishes the areas with black grids and white grids. The black grids represent obstacles such as buildings, while the white grids represent passable areas.

[0048] Ignoring factors such as terrain height, assume that the selected urban area (i.e., target area) is a rectangle consisting of a×b square grids, where:

[0049]

[0050] Among them, x max and max are the length and width of the selected rectangular area, and L is the side length of each grid cube. The resulting two-dimensional grid map (i.e., gridded map) is as follows: Figure 3 shown.

[0051] 1.2 Obstacle expansion.

[0052] In complex terrain, not every obstacle is a regular rectangle, and the helicopter may collide with the edge of the obstacle during the pathfinding process. Therefore, it is necessary to expand it. That is, if the obstacle does not occupy a grid, the size of the obstacle is expanded outward and calculated as an environmental obstacle grid to ensure that the mobile aircraft does not collide with the obstacle. Figure 4 As shown, Figure 4 The left part of the figure is the actual shape of the obstacle in the two-dimensional plane. Figure 4 The right part of the figure is the actual shape of the obstacle after expansion in the grid map.

[0053] 1.3 0-1 matrix processing of the grid.

[0054] When writing code, storing the coordinates of the four vertices of each obstacle and participating in the calculation will consume a lot of time and resources, so it is necessary to simplify the relative position of each grid to reduce the amount of data involved in the calculation. One method is to simplify the position of each grid into the coordinates (x_mid, y_mid) of the center of the grid for storage, and another method is to convert the map into a 0-1 matrix and convert the 0-1 matrix back into actual map coordinates after finding a low-noise trajectory. This embodiment selects the 0-1 matrix method to reduce the amount of data required for obstacle judgment in the later stage.

[0055] Figure 3 The grid (0-1 matrix map) obtained by simplifying the two-dimensional grid map shown in Figure 5 As shown, 1 represents an obstacle and 0 represents a passable area.

[0056] The conversion formula between the center coordinates (x0, y0) of the obstacle grid on the real map and the coordinates (x, y) of the 0-1 matrix element with M rows and N columns is as follows:

[0057]

[0058] 2. Pathfinding calculation (low-noise flight trajectory design).

[0059] After completing the environment modeling, trajectory design starts from the starting point. The calculation process is as follows: Figure 6 As shown, the specific steps include:

[0060] The specific steps are as follows:

[0061] Step 2.1: Use the C++ program to rasterize the extracted map data file and output a 0-1 matrix file, which is then read by MATLAB. The obstacle and feasible area grid coordinates are then stored in the Close and Open lists respectively.

[0062] Step 2.2: Input the parameters required for pathfinding calculation, including the starting position, the end position, helicopter performance parameters, flight constraints, etc., and store the starting position in the Close list.

[0063] Step 2.3: Start pathfinding from the starting point.

[0064] Step 2.3.1: Take the current node as the parent node P, and in two-dimensional space, select the nodes in the neighborhood in the Open list as candidate child nodes p i .

[0065] Grid-based pathfinding algorithms usually find paths in a two-dimensional plane in the form of 8 or 16 neighborhoods. Figure 7 This is a schematic diagram of the 8-neighborhood search direction used in this embodiment. The center point is the parent node P, and the eight surrounding nodes are child nodes p i .

[0066] Before pathfinding begins, the coordinates (x, y) of the starting point in the two-dimensional grid are given. When planning a path, the starting point is the current node (parent node) in the cycle, and the nodes to be selected around it (neighborhood) are child nodes p i When the optimal child node is selected according to the evaluation function and recorded as p best After that, p best Add to the path already found, the current cycle is completed, p best As the parent node of the next cycle, select the next p from its neighborhood best , until you find the end.

[0067] Step 2.3.2: Calculate each candidate child node p according to the evaluation function i The optimal child node (the node with the lowest cost) is selected and stored in the path list and the Close list, and this child node p is used as the new parent node P. Steps 2.3.1-2.3.2 are repeated until the parent node P is the end point.

[0068] 2.3.2.1 Improvement of evaluation function.

[0069] In the commonly used pathfinding algorithms, taking the A* algorithm as an example, there are two main aspects of the improvement method, one is to improve the search neighborhood, and the other is to improve the evaluation function. This embodiment aims to generate a helicopter flight trajectory that can reduce urban noise, and adds noise as one of the evaluation criteria in the evaluation function as an improvement.

[0070] The traditional A* algorithm uses Manhattan distance and other factors as the main components of the evaluation function to quickly find the shortest path to the target point. However, such a path is not necessarily the path with the least noise impact, so the cumulative sound exposure level C(n) is added to the evaluation function as an improvement. The improved evaluation function is:

[0071] f(n)=w1*g(n)+w2*h(n)+w3*C(n)(3);

[0072] In the formula, C(n) is the local noise level. In actual situations, the weight coefficient can be adjusted according to different mission requirements. f(n) represents the estimated cost of reaching the target state from the initial state via the state node n in the grid map. g(n) is the actual cost from the initial state to node n in the state space. h(n) is the estimated cost of the best path from the state node n to the target state. w1, w2, and w3 are weight coefficients. In actual situations, they can be adjusted according to different mission requirements. Adding C(n) as part of the evaluation function can effectively find a low-noise flight path that can quickly reach the target location.

[0073] 2.3.2.2 Calculation of cumulative sound exposure level.

[0074] A helicopter will continuously generate noise during flight, and when pathfinding is performed in the grid, the evaluation function needs to be calculated for the eight child nodes of the current neighborhood. Therefore, it is unrealistic to calculate the sound exposure level in the urban area after global pathfinding. Therefore, this embodiment chooses to use the cumulative sound exposure level of the local area to participate in the calculation of the evaluation function.

[0075] In the path-finding algorithm based on the grid method and the 8-neighborhood, the path has been discretized into multiple path segments connecting different grids. The cumulative sound exposure level when the helicopter flies to the sth path segment is sel(s), and the sound exposure level of the sth segment is L E (s), the calculation model is:

[0076]

[0077] In the formula, t s (s) is the time it takes for the helicopter to arrive at the starting point of the path, t e (s) is the time it takes for the helicopter to reach the end of the path, i.e. the starting point of the next path. s (t) is the instantaneous sound pressure at a specific ground noise observation point at that moment, P ref is the reference sound pressure value.

[0078] For different purposes or mission requirements, ground noise observation points can be fixed at specific locations or certain locations to study the noise impact in a specific area. During the helicopter flight, the location of the noise receiving point may also change as the helicopter moves.

[0079] For fast pathfinding, the noise evaluation function can also be simplified. For example, the calculation formula of C(n) can be simplified to:

[0080]

[0081] Where i is the i-th path; n is the total number of path segments (including the paths that have been found plus the n-th path currently being judged); t e (i) is the time it takes for the sound pressure level generated at the end of the i-th path to reach the receiving point; t s (i) is the time it takes for the sound pressure level generated at the starting point of the i-th path to reach the receiving point; p i (t) is the sound pressure level of the i-th path propagated by the receiving point at time t. s to e The accumulation of is a simplification of formula (5), and the second accumulation of i=1:n is C(n), which is a simplification of formula (4).

[0082] The calculation process of the instantaneous sound pressure at the ground noise observation point is the sound exposure level calculation process based on the secondary sound radiation sphere method.

[0083] The main improvement of the trajectory design method of this embodiment is that the noise calculation part is added to the evaluation function. Considering the calculation efficiency and other issues, this method adopts a rotor noise radiation model that combines the point sound source concept and the directional characteristics of rotor noise propagation. The secondary sound radiation ball replaces the actual blade sound source to transmit the noise information of the rotor and calculate the local sound exposure level on the ground. The specific process of the sound exposure level calculation model of a helicopter at a certain trajectory point is as follows:

[0084] (1) According to the helicopter state and spatial position information, the inverse simulation method is used to calculate the spatial position parameters, motion parameters and rotor noise characteristic parameters of the control vector of each control point on the helicopter flight trajectory.

[0085] During the unsteady flight of a helicopter, its flight state is constantly changing, that is, the flight state at the starting point and the end point of each discrete trajectory segment is also different. For this reason, a control point is set in the middle of each discrete trajectory segment, and a corresponding control vector is assigned to each control point. The control vector contains information such as the helicopter's spatial position and flight parameters, which are used for the subsequent selection and positioning of the sound radiation ball and the calculation of noise. The control vector includes: t: the time when the helicopter moves to the control point; (x, y, z): the helicopter's spatial position parameters (in a two-dimensional grid map, it is the grid center coordinate position (x, y), and in a three-dimensional grid map, it is (x, y, z)); γ eff : helicopter equivalent flight trajectory angle, and α tpp Used together for positioning the acoustic radiation ball; dV / dt: helicopter flight acceleration; (μ, α tpp ): The helicopter advance ratio and rotor disc inclination angle are also the characteristic parameters of the secondary acoustic radiation sphere, which can be directly used for the selection of the secondary acoustic radiation sphere at each discrete segment control point.

[0086] (2) Select the starting point of the flight trajectory, select the corresponding secondary sound radiation sphere according to the rotor noise characteristic parameters at the starting point, and perform spatial positioning and azimuth positioning of the secondary sound radiation sphere according to parameters such as spatial position.

[0087] (μ,α tpp ) is used to determine the corresponding secondary sound radiation sphere.

[0088] (x, y, z) (generally (x, y) in a two-dimensional grid map), α tpp With γ eff These three parameters are used to locate the spatial position of the sound radiation ball. Figure 8 shown.

[0089] After the sound radiation model is determined, it needs to be placed in the correct spatial position and the direction of the sound radiation ball adjusted according to the azimuth of the aircraft (i.e. the orientation of the aircraft). This ensures that the simulated sound wave propagation path is consistent with the actual situation, thereby more accurately predicting and analyzing the rotor noise generated by the aircraft during flight.

[0090] (3) Select a ground noise observation point, determine the corresponding secondary sound radiation point according to the position of the ground noise observation point and the spatial position of the trajectory control point, and use the two-dimensional linear interpolation method to calculate the noise information of the radiation point. Finally, map the corresponding noise radiation information to the ground noise observation point. The secondary sound radiation model and the two-dimensional linear interpolation method are as follows: Fig. 9 and Fig.10 shown.

[0091] According to the noise attenuation formula of point sound source, the noise level received by the ground noise observation point is:

[0092] L(r)=L(ro)-Ageometry(7);

[0093] Where L(r) represents the noise sound pressure level received by the ground noise observation point, L(r o ) represents the noise pressure level of the secondary sound source radiation point; r represents the distance from the ground noise observation point to the center of the hub, r o Indicates the radius of the secondary sound radiation sphere. geometry Represents spherical propagation loss. As the distance increases, the noise sound pressure level attenuation is:

[0094] Ageometry = 20 lg (r / ro) (8).

[0095] (4) Loop through the ground noise observation points to calculate the noise of the rotor on all ground observation points when the helicopter is at a certain trajectory control point, and then perform noise post-processing according to specific requirements.

[0096] Different post-processing methods can be used according to different requirements. When there is only one ground noise observation point, the sound exposure level sel of the ground noise observation point can be calculated, and when there are multiple ground noise observation points, the sound exposure levels of different ground noise observation points can be calculated separately, and finally the average processing is performed.

[0097] (5)The calculation is completed.

[0098] 3. Path smoothing.

[0099] This embodiment uses the Floyd method to remove redundant optimal nodes in the optimal flight path, and then uses a B-spline curve to smooth the optimal path after removing the nodes to obtain a smoothed optimal path.

[0100] Floyd smoothing is mainly divided into two core steps: one is to merge all nodes on the same straight line; the other is to eliminate the nodes. The specific steps are as follows:

[0101] (1) For the initial path (i.e., the optimal flight path) shown in Figure 11(a), starting from the starting point, if there are three or more adjacent nodes on the same line, then the middle nodes are removed and only the first and last nodes of each collinear line are retained. The retained nodes are added to the new list in sequence to obtain the path shown in Figure 11(b).

[0102] (2) Start from the starting point of the new list. Take the line connecting the current node p and the adjacent node p+1 as an alternative path. If the alternative path satisfies the maximum turning angle constraint and avoids obstacles, delete the p+1 node, and continue to connect the p node with the p+2 node for judgment; otherwise, keep the p+1 node and add the p node and the p+1 node to the path list. Repeat the step of "taking the line connecting the current node p and the adjacent node p+1 as an alternative path" until the current node is the last node, and obtain the path shown in Figure 11(c).

[0103] 4. Export flight trajectory data.

[0104] The generated smoothing optimal path is transmitted to the inverse simulation program to obtain the maneuvering state data of the smoothing optimal path, which is stored together with the smoothing optimal path data to generate a complete flight trajectory data file.

[0105] 5. Noise calculation and analysis.

[0106] The generated complete flight trajectory data file is transferred to the ground noise calculation program to generate the sound exposure level contour map and the sound pressure-time history map and analyze them.

[0107] The helicopter low-noise flight trajectory design method provided in this embodiment has the following advantages:

[0108] 1) Realize low-noise pathfinding for helicopters in complex terrain.

[0109] The evaluation function of the commonly used pathfinding algorithm takes the A* algorithm as an example. The evaluation function is as follows:

[0110] f(n)=g(n)+h(n)(9);

[0111] Where f(n) is the estimated cost of reaching the target state from the initial state via the state node n in the grid map, g(n) is the actual cost from the initial state to the node n in the state space, and h(n) is the estimated cost of the best path from the state node n to the target state. When the shortest path to the target point is obtained in the shortest time, g(n) and h(n) are usually expressed in Manhattan distance, Euclidean distance and diagonal distance. For different flight requirements, g(n) and h(n) may also include other information, such as fuel consumption.

[0112] For low-noise trajectories, the local or specific area sound exposure level sel is added to the evaluation function as a component of the evaluation function, and its weight is increased, so as to select a path that can effectively reduce the noise level of the target area or the overall area. The improved evaluation function is shown in formula (3).

[0113] 2) Rapid noise calculation under complex maneuvering conditions of helicopters is realized.

[0114] The size and directionality of the noise are different in different maneuvering states of the helicopter. The direct calculation method based on the FW-H (FfowcsWilliams-Hawkings) equation is computationally intensive and time-consuming, so a noise calculation method based on a secondary acoustic radiation sphere is used. The characteristic parameters corresponding to the trajectory control points can be obtained through the inverse simulation method, so that the corresponding acoustic radiation sphere can be selected, which can ensure the calculation efficiency and take into account the size and directionality of the noise in different maneuvering states.

[0115] The present application also provides an application scenario, which applies the above-mentioned helicopter low-noise flight trajectory design method. Specifically: The helicopter low-noise flight trajectory design method provided in this embodiment can be applied in helicopter flight scenarios. Helicopter flight scenarios include take-off, cruising, landing, etc. The helicopter low-noise flight trajectory design method provided in this embodiment can be applied to take-off and landing links. By optimizing the flight trajectory, the noise generated by the helicopter during take-off and landing can be significantly reduced, thereby reducing the impact on the surrounding environment and residents. In addition, the design method can also be applied to the cruising link to further improve the overall flight performance of the helicopter and the comfort of passengers. In short, the helicopter low-noise flight trajectory design method provided in this embodiment plays an important role in multiple key links and provides effective technical support for the low-noise flight of helicopters.

[0116] Example 2

[0117] This embodiment provides a computer device, which may be a server or a terminal. Its internal structure diagram may be as follows: Fig.12As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. Among them, the processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store any data in the helicopter low-noise flight trajectory design method. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, the helicopter low-noise flight trajectory design method provided in Example 1 is implemented.

[0118] Those skilled in the art will understand that Fig.12 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0119] Example 3

[0120] This embodiment provides a computer device, including a memory and a processor. The memory stores a computer program. When the processor executes the computer program, the helicopter low-noise flight trajectory design method provided in Example 1 is implemented.

[0121] Example 4

[0122] This embodiment provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the method for designing a low-noise flight trajectory of a helicopter provided in Embodiment 1 is implemented.

[0123] Example 5

[0124] This embodiment provides a computer program product, including a computer program, which, when executed by a processor, implements the helicopter low-noise flight trajectory design method provided in Embodiment 1.

[0125] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0126] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0127] The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a distributed database based on blockchain, etc., but is not limited thereto. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but is not limited thereto.

[0128] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0129] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for designing a low-noise flight trajectory of a helicopter, characterized in that: The helicopter low-noise flight trajectory design method comprises: According to the flight mission requirements of the helicopter, obtain the map data of the target area, helicopter performance parameters, flight constraints, and the starting and ending positions of the flight path; Performing rasterization processing on the map data to obtain a rasterized map; Based on the helicopter performance parameters, the flight constraints, the starting position and the end position of the flight path, the optimal flight path of the helicopter is determined in the rasterized map using a path optimization algorithm, wherein an evaluation function of the path optimization algorithm is a function determined according to a cumulative sound exposure level, an actual cost from the starting position to a current node, and an estimated cost from the current node to the end position, the cumulative sound exposure level is a variable value calculated according to the current node noise information received by a ground noise observation point, the node corresponding to the minimum of the evaluation function is determined as the optimal node, the optimal node is a node on the optimal flight path, and each grid in the rasterized map represents each of the nodes.

2. The method for designing a helicopter low-noise flight trajectory according to claim 1, characterized in that: The calculation expression of the cumulative sound exposure level is: Where sel(s) is the cumulative sound exposure level when the helicopter flies to the sth segment of the path; L E (s) is the sound exposure level of the sth path; t s (s) is the time when the helicopter arrives at the starting point of the sth path; t e (s) is the time when the helicopter reaches the end point of the sth path; P s (t) is the instantaneous sound pressure at a specific observation point on the sth path at time t; P ref is the reference sound pressure.

3. The helicopter low-noise flight trajectory design method according to claim 1, characterized in that: The process of obtaining noise information specifically includes: According to the real-time flight status and spatial position information of the helicopter, the control vector of each control point on the helicopter flight path is calculated by the inverse simulation method, wherein the control vector includes the time when the helicopter moves to the control point, spatial position parameters, equivalent flight trajectory angle, flight acceleration, advance ratio and rotor blade inclination angle; Determine a corresponding secondary sound radiation sphere according to the advancement ratio and the inclination angle of the rotor disc of each control point; Determine the spatial position and orientation of the corresponding secondary sound radiation sphere according to the spatial position parameters of each control point, the equivalent flight trajectory angle and the rotor blade disc inclination angle; Determine the secondary sound radiation point on the corresponding target secondary sound radiation sphere according to the position of the ground noise observation point and the spatial position parameters of each of the control points, wherein the target secondary sound radiation sphere is a secondary sound radiation sphere with a determined spatial position and orientation; The noise information of the secondary sound radiation point is calculated by using the two-dimensional linear interpolation method; The noise information received by the ground noise observation point is calculated according to the noise information of the secondary sound radiation point.

4. The method for designing a low-noise helicopter flight trajectory according to claim 3, characterized in that: The expression of noise information is: L(r)=L(ro)-Ageometry; Ageometry = 20lg(r / ro); Where L(r) represents the noise sound pressure level received by the ground noise observation point; L(r o ) represents the noise pressure level of the secondary sound source radiation point; A geometry represents the spherical propagation loss; r represents the distance between the ground noise observation point and the hub center; r o Represents the radius of the secondary sound radiation sphere.

5. The method for designing a low-noise helicopter flight trajectory according to claim 1, characterized in that: The expression of the evaluation function is: f(n)=w1*g(n)+w2*h(n)+w3*C(n); Among them, f(n) is the estimated cost of reaching the target state from the initial state via the state node n in the rasterized map; g(n) is the actual cost from the initial state to node n in the state space; h(n) is the estimated cost from state node n to the target state; C(n) is the cumulative sound exposure level; w1, w2, w3 are weight coefficients.

6. The method for designing a low-noise helicopter flight trajectory according to claim 1, characterized in that: After executing the step of "determining the optimal flight path of the helicopter in the rasterized map by using a path optimization algorithm based on the helicopter performance parameters, the flight constraints, the starting position and the end position of the flight path", the helicopter low-noise flight trajectory design method further includes: The Floyd method is used to remove redundant optimal nodes on the optimal flight path to obtain an optimal path with nodes removed, wherein the redundant optimal nodes include the middle optimal nodes other than the first and last optimal nodes on the target segment and the second optimal node on the potential segment that meets the conditions, the target segment is a segment composed of at least three nodes on the optimal flight path that are collinear, the potential segment refers to a segment composed of two adjacent optimal nodes on the optimal flight path, the condition is that the turning angle of the potential segment meets the maximum turning angle constraint and the potential segment can avoid obstacles, and the second optimal node refers to the optimal node that is relatively backward on the potential segment; The optimal path for removing nodes is smoothed using a B-spline curve to obtain a smoothed optimal path.

7. The method for designing a low-noise helicopter flight trajectory according to claim 6, characterized in that: After executing the step of "using a B-spline curve to smooth the node-removed optimal path to obtain a smoothed optimal path", the helicopter low-noise flight trajectory design method further includes: Performing inverse simulation on the smoothed optimal path to obtain maneuvering state data of the helicopter; A sound exposure level contour map and a sound pressure-time history map are generated according to the smoothing optimal path and the maneuvering state data.

8. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the helicopter low-noise flight trajectory design method according to any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for designing a low-noise flight trajectory of a helicopter according to any one of claims 1 to 7 is implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the method for designing a low-noise flight trajectory of a helicopter according to any one of claims 1 to 7 is implemented.

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