Helicopter mountain flight simulation and flight strategy design method and related device

Abstract

The invention discloses a helicopter mountain flight simulation and flight strategy design method and related devices, and relates to the field of aerodynamics and computational fluid mechanics of rotorcrafts, the method comprises the following steps: establishing a mountain terrain model and a mountain wind environment model and carrying out numerical simulation to obtain flow field velocity distribution and turbulence energy distribution of a whole watershed; a real mountain environment is provided for follow-up helicopter mountain flight simulation, interference and response characteristics encountered by a helicopter in mountain flight can be predicted more accurately, a mountain wind environment model can simulate fluctuating wind and average wind, and the inflow velocity of a whole-basin flow field changing along with time and height is provided; flight strategy research in a complex mountain environment is carried out through rotor aerodynamic loads, full-aircraft response characteristics and driver control loads, a helicopter flight simulation technology based on environment-helicopter-pilot multi-factor coupling is formed, and the flight performance and safety of a helicopter in the complex environment are improved.

Description

Technical Field

[0001] The present application relates to the fields of aerodynamics and computational fluid dynamics of rotorcraft, and in particular to a method and related devices for simulating mountain flight and designing flight strategies of helicopters. Background Art

[0002] In emergency situations and general-purpose flights, helicopters are widely used as a major air transport to quickly transfer personnel and equipment in rugged mountainous areas. However, during mountain flight, unstable turbulent wind fields may occur depending on the characteristics of the terrain and weather. Since helicopters have slow navigation speeds and low flight altitudes, their own energy reserves are relatively low during missions. When affected by unstable flow fields, they will produce complex and disordered oscillations in the flight Euler angles and airspeed. Ultimately, it is difficult for the helicopter to maintain and restore normal flight attitude, resulting in dangerous conditions. Therefore, conducting helicopter flight simulation research in mountainous environments can predict mountain flight hazards and improve the survivability of helicopters in mountains. Safe flight strategies can guide helicopters to take off and land in complex mountainous terrain.

[0003] Current research on helicopter-environment interference in helicopter mountain flight simulation and flight strategy design methods focuses more on the blocking effect of scaled obstacles on the rotor flow field, or uses a simple constant speed as the wind field input to analyze the rotor load characteristics under interference. These studies cannot accurately reflect the unsteady interference and response characteristics caused by large mountain turbulence on helicopters in real atmospheric environments, making it difficult to further develop flight strategy design during mountain flight. Summary of the invention

[0004] The purpose of this application is to provide a helicopter mountain flight simulation and flight strategy design method and related devices, which can simulate the real mountain environment, provide real mountain shape and transient flow field distribution, accurately predict the interference and response characteristics encountered by the helicopter in actual flight, and carry out flight strategy research in complex mountain environments based on the rotor aerodynamic load, the whole machine response characteristics and the pilot's control load, thereby improving the flight performance and safety of the helicopter in complex environments.

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

[0006] In a first aspect, the present application provides a helicopter mountain flight simulation and flight strategy design method, comprising:

[0007] Construct a mountain terrain model based on mountain terrain elevation data;

[0008] Constructing a mountain wind environment model, wherein the mountain wind environment model is used to process the actual average wind speed at different heights of the wind profile using a harmonic synthesis method to obtain a pulsating wind speed that changes with time at the corresponding height, and to obtain an inflow velocity of the flow field of the entire basin based on the pulsating wind speed and the actual average wind speed; the actual average wind speed is a variable value calculated based on the standard average wind speed at a standard reference height and a ground roughness index;

[0009] Numerical simulation is performed on the mountain terrain model and the mountain wind environment model to obtain the flow field velocity distribution and turbulent kinetic energy distribution of the entire basin;

[0010] According to the flight mission of the helicopter, the flight path of the helicopter is planned by using the path optimization algorithm;

[0011] The cost of simulating the helicopter flying on each of the flight paths by using a helicopter flight dynamics model is calculated according to an evaluation function, wherein the evaluation function is a function determined according to a risk loss and a path cost, the risk loss is a variable value calculated according to a current position of the helicopter and a position of a dangerous area, the path cost is a variable value calculated according to a current position of the helicopter and a position of a next flight node, and the dangerous area is an area determined according to the flow field velocity distribution and the turbulent kinetic energy distribution;

[0012] Calculating the safety level of each of the flight paths according to the full-machine response characteristics output by the helicopter flight dynamics model;

[0013] Calculating the pilot control load of each of the flight paths according to the control variable time history output by the helicopter flight dynamics model;

[0014] A helicopter mountain flight strategy is determined based on the cost, the safety level and the pilot control load.

[0015] 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 mountain flight simulation and flight strategy design method described in the first aspect above.

[0016] 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 mountain flight simulation and flight strategy design method described in the first aspect above.

[0017] 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 mountain flight simulation and flight strategy design method described in the first aspect above.

[0018] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0019] The present application provides a method and related devices for helicopter mountain flight simulation and flight strategy design. By establishing a mountain terrain model and a mountain wind environment model and performing numerical simulation, the flow field velocity distribution and turbulent kinetic energy distribution of the entire basin are obtained, thereby providing a real mountain environment for subsequent helicopter mountain flight simulation, and thus being able to more accurately predict the interference and response characteristics encountered by the helicopter during mountain flight. Among them, the mountain wind environment model can simulate pulsating wind and average wind, and provide an inflow velocity of the entire basin flow field that changes with time and altitude; the flight strategy in a complex mountain environment is studied through the rotor aerodynamic load, the whole machine response characteristics and the pilot's control load, forming a helicopter flight simulation technology based on the "environment-helicopter-pilot" multi-factor coupling, which improves the flight performance and safety of the helicopter in a complex environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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.

[0021] Figure 1 This is an application environment diagram of a helicopter mountain flight simulation and flight strategy design method in Example 1 of the present application;

[0022] Figure 2 A schematic diagram of a flow chart of a helicopter mountain flight simulation and flight strategy design method provided in Example 1 of the present application;

[0023] FIG3( a ) is a schematic diagram of the variation of the pulsating wind speed with time in Example 1 of the present application;

[0024] FIG3( b ) is a schematic diagram of the power spectrum density of the fluctuating wind in Example 1 of the present application;

[0025] Figure 4 This is a schematic diagram of the process of numerically simulating a mountain terrain model and a mountain wind environment model in Example 1 of the present application;

[0026] Figure 5 A schematic diagram of the process of constructing a helicopter flight dynamics model in Example 1 of the present application;

[0027] Figure 6 A schematic diagram of the process of constructing a bare-metal flight dynamics model in Example 1 of the present application;

[0028] Figure 7Schematic diagram of the collective distance control feature in Example 1 of the present application;

[0029] Figure 8 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] In order to make the above-mentioned objects, 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.

[0032] Example 1

[0033] The helicopter mountain flight simulation and flight strategy design method provided in the embodiment of the present application can be applied to Figure 1In the application environment shown, the terminal 102 communicates with the server 104 through a network. The data storage system can store 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 mountain terrain elevation data, the standard average wind speed at the standard reference height and the ground roughness index to the server 104. After receiving the mountain terrain elevation data, the standard average wind speed at the standard reference height and the ground roughness index, the server 104 constructs a mountain terrain model according to the mountain terrain elevation data; constructs a mountain wind environment model according to the standard average wind speed at the standard reference height and the ground roughness index; performs numerical simulation on the mountain terrain model and the mountain wind environment model to obtain the flow field velocity distribution and turbulent kinetic energy distribution of the entire basin; plans the flight path of the helicopter using a path optimization algorithm according to the flight mission of the helicopter; calculates the cost of the helicopter flying on each of the flight paths according to the evaluation function using the helicopter flight dynamics model to simulate the cost; calculates the safety level of each of the flight paths according to the full machine response characteristics output by the helicopter flight dynamics model; calculates the driver control load of each of the flight paths according to the control amount time history output by the helicopter flight dynamics model; determines the helicopter mountain flight strategy according to the cost, the safety level and the driver control load. The server 104 can feed back the obtained helicopter mountain flight strategy to the terminal 102. In addition, in some embodiments, the helicopter mountain flight simulation and flight strategy 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 mountain flight simulation and flight strategy design method to process the mountain terrain elevation data, the standard average wind speed at the standard reference height, and the ground roughness index, or the server 104 can obtain the mountain terrain elevation data, the standard average wind speed at the standard reference height, and the ground roughness index from the data storage system, and use the helicopter mountain flight simulation and flight strategy design method to process it.

[0034] 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, and the portable wearable devices may be smart watches, smart bracelets, head-mounted devices, etc. The server 104 may be implemented by an independent server or a server cluster consisting of multiple servers, or may be a cloud server.

[0035] In an exemplary embodiment, a method for simulating helicopter mountain flight and designing flight strategies is provided, which is used to accurately analyze the environmental interference flow field of a helicopter flying in a mountainous area, design the trajectory of the helicopter during mountainous flight based on the aerodynamic load interference and the overall response characteristics of the helicopter during mountainous flight, and conduct in-depth evaluation of the helicopter's performance limitations and the pilot's control load to obtain a safe flight strategy for the helicopter's mountainous flight. The method is executed by a computer device, which 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 for explanation, and the steps include the following steps 201 to 208.

[0036] in:

[0037] Step 201, constructing a mountain terrain model according to mountain terrain elevation data.

[0038] Step 202, constructing a mountain wind environment model, wherein the mountain wind environment model is used to process the actual average wind speed at different heights of the wind profile using a harmonic synthesis method to obtain a pulsating wind speed that changes with time at the corresponding height, and obtain the inflow velocity of the flow field in the entire basin based on the pulsating wind speed and the actual average wind speed; the actual average wind speed is a variable value calculated based on the standard average wind speed at the standard reference height and the ground roughness index.

[0039] Step 203 , numerically simulate the mountain terrain model and the mountain wind environment model to obtain the flow field velocity distribution and turbulent kinetic energy distribution of the entire basin.

[0040] Step 204, planning the flight path of the helicopter using a path optimization algorithm according to the flight mission of the helicopter.

[0041] Step 205, calculating the cost of the helicopter flying on each of the flight paths by simulating the helicopter flight dynamics model according to the evaluation function, wherein the evaluation function is a function determined according to the risk loss and the path cost, the risk loss is a variable value calculated according to the current position of the helicopter and the position of the danger zone, the path cost is a variable value calculated according to the current position of the helicopter and the position of the next flight node, and the danger zone is an area determined according to the flow field velocity distribution and the turbulent kinetic energy distribution.

[0042] Step 206, calculating the safety level of each of the flight paths according to the overall helicopter response characteristics output by the helicopter flight dynamics model.

[0043] Step 207, calculating the pilot control load of each flight path according to the control variable time history output by the helicopter flight dynamics model.

[0044] Step 208, determining the helicopter mountain flight strategy based on the cost, the safety level and the pilot control load.

[0045] This embodiment aims at the mission requirements of helicopter flight in mountainous areas, breaks through the key technologies of multidisciplinary coupling modeling and flight safety design of helicopter flight, and provides helicopter flight simulation technology based on the multi-factor coupling of "environment-helicopter-pilot" and a comprehensive flight strategy design technology with boundary constraints and control load evaluation. By implementing the above steps 201 to 208, a man-machine-environment coupled flight analysis model (mountain terrain model, mountain wind environment model and helicopter flight dynamics model) is established, and the velocity field, vorticity and turbulent kinetic energy distribution in the mountain environment are analyzed, and attention is paid to the transient flow field velocity distribution of the rotor in the mountain environment. It is possible to simulate the influence of real mountain environmental factors such as terrain undulations, mountain disturbances, wind speed and wind direction changes on the helicopter when flying in the mountains, and accurately predict the response characteristics of the helicopter after experiencing unsteady aerodynamic force and torque changes during flight, thereby overcoming the technical defect of the related technology that "it is impossible to accurately reflect the unsteady interference and response characteristics of the helicopter caused by large mountain disturbances in the real atmospheric environment"; based on the rotor aerodynamic load, the whole machine response characteristics and the pilot's control load, the flight strategy research in the complex mountain environment is carried out, and the helicopter flight simulation technology based on the multi-factor coupling of "environment-helicopter-pilot" is formed, which improves the flight performance and safety of the helicopter in the complex environment and provides a guide for the safe flight of the helicopter.

[0046] In order to make those skilled in the art more aware of the specific process of the helicopter mountain flight simulation and flight strategy design method provided by this embodiment, a specific explanation is given below.

[0047] According to the requirements of helicopter mountain flight missions, this embodiment applies CFD (Computational Fluid Dynamics) and flight dynamics analysis methods to the research of helicopter mountain flight simulation and flight strategy design. Based on the unsteady RANS equations (Unsteady Reynolds-Averaged Navier-Stokes Equations, unsteady Reynolds-averaged Navier-Stokes equations, referred to as unsteady RANS equations), a numerical simulation method for mountain environmental wind fields is established, and a helicopter flight mechanics model coupled with environmental wind field characteristics is established. The mountain wind field characteristics, helicopter control response characteristics analysis and flight strategy research are carried out. Figure 2 The specific plan is as follows:

[0048] The first step is environment modeling.

[0049] (1.1) Establish a mountain terrain model (i.e. Figure 2 Mountain model in ).

[0050] In order to establish a real mountain environment, first collect the mountain terrain elevation data, then project the longitude and latitude coordinate system corresponding to the mountain terrain elevation data into the Mercator coordinate system through the longitude belt number and Gaussian projection technology, and form point cloud data according to the converted terrain surface (longitude, latitude, elevation) data points. Finally, reverse modeling is performed to fit the surface according to the scattered point data (scattered points are terrain surface sampling points, which can form point cloud data when arranged in a specified format) to form a terrain surface, and stretch the terrain surface to obtain a relatively rough real terrain, thereby forming a mountain terrain model that can be used for numerical simulation to provide the geometric terrain data required for CFD calculations.

[0051] (1.2) Establish a mountain wind environment model (i.e. Figure 2 wind field model in ).

[0052] The wind environment is composed of average wind and pulsating wind. The average wind profile is described according to the exponential law (the law of wind speed changing with height can be described by an exponential function), and the profile wind speed is taken as the average wind speed at the corresponding height (the average wind speed increases with the increase of height, and the average wind speed is 10m / s in Figure 3(a) as an example). For the exponential wind profile, the law of average wind speed changing along the height is expressed as follows:

[0053]

[0054] In the formula, Z0 and are the standard reference height and the reference average wind speed at the standard reference height, respectively. According to the national standard wind force level classification, the height of 10m is used as the average wind reference height; Z and are the actual average wind speed at any height and at any height respectively; α is the ground roughness index.

[0055] The pulsating wind speed time history is generated by the harmonic synthesis method (Figure 3(a) is a schematic diagram of the pulsating wind speed, and the pulsating wind speed fluctuates around 10m / s over time).

[0056] A zero-mean Gaussian stationary random process is used to simulate the fluctuating wind speed.

[0057] The Davenport spectrum is used to describe the fluctuating wind speed, and the expression is:

[0058]

[0059] In the formula, S(ω l ) is the spectral density matrix generated by the corresponding fluctuating wind speed power spectrum, such as the fluctuating wind power spectrum density shown in Figure 3(b); k is the ground roughness coefficient; U0 is the average wind speed (m / s); x = 1200ω / U0; ω lis the frequency of the lth data, which is specified as 0.001~6Hz here; the frequency increment Δω=0.001; the number of data collection points N=6000.

[0060] For S(ω l ) performs Cholesky decomposition, the expression is:

[0061] S(ω l )=H(ω l )H * (ω l ) T ;

[0062] Among them, H(ω l ) is the lower triangular matrix of the lth data; H * (ω l ) T is H(ω l ) is the conjugate transpose of .

[0063] The time history of the pulsating component in the wind speed can be further expressed by the following formula:

[0064]

[0065] Where, u(t) is the fluctuating wind speed at time t; N is the total number of data collected in the frequency domain; l is an integer increasing from 1 to N; Δω is the frequency increment; is a random number between 0 and 2π; |H(ω l )| is the modulus of the above lower triangular matrix.

[0066] The fluctuating wind speed is superimposed on the actual average wind speed to obtain the wind speed time history of the wind environment at a specified height. When the height change causes the actual average wind speed to change, the corresponding synthetic wind speed time history can be used to obtain the flow field inlet wind speed of the entire basin as the CFD inlet boundary condition.

[0067] The second step is wind field simulation.

[0068] The geometry and inflow velocity obtained in the first step are input into the CFD calculation program, and numerical simulation calculations are carried out to obtain the flow field velocity distribution and turbulent kinetic energy distribution. The flow field velocity distribution and turbulent kinetic energy distribution can be used to divide the dangerous area of ​​trajectory design on the one hand, and on the other hand, the coupling between the environment and the helicopter is realized by inputting the flow field velocity into the flight dynamics model, and the interference of the environment on the helicopter is introduced.

[0069] The specific process of obtaining the wind speed and turbulent kinetic energy distribution characteristics in a large-scale mountain environment through CFD simulation is as follows: Figure 4 As shown, including:

[0070] 1) Read the configuration, which describes the initial parameters of the flow field and the solution control parameters.

[0071] Read the configuration file: discretize the terrain geometry into an unstructured grid domain. The configuration file is organized in JSON format, which describes each grid block and file name, flow field initial parameters (flow field inflow velocity), solution control parameters (space / time discrete format and turbulence model of each block grid setting), solution control parameters (unsteady time step, maximum calculation iteration step, etc.), post-processing and output settings.

[0072] 2) Read the grid file and discretize the terrain geometry model into an unstructured grid form that can be used by CFD.

[0073] 3) Flow field initialization: Use the exponential mean wind profile to directly assign values ​​to the global flow field, thus reducing the convergence time of subsequent calculations.

[0074] 4) Flow field solution: According to the solution configuration of the corresponding grid block, the space / time discrete format and turbulence model are selected to perform iterative calculations.

[0075] The terrain surface is set as the wall surface, other boundaries are set as free flow conditions, and the velocity input uses the flow field inflow velocity obtained in the second step. Perform CFD simulation, and when the calculation converges, the distribution characteristics of velocity, pressure, density, turbulent kinetic energy, etc. in the flow field can be obtained.

[0076] 5) Output and post-processing: output the wind speed and turbulent kinetic energy at the grid points in the calculation domain for subsequent analysis.

[0077] The third step is flight dynamics modeling.

[0078] A helicopter flight dynamics model is constructed to study the helicopter's response characteristics during mountain flight. Figure 5 As shown, the helicopter flight dynamics model includes the flight dynamics bare metal model (i.e. Figure 5 The helicopter flight dynamics bare metal model in ), helicopter flight control model and pilot model.

[0079] The spatial position and yaw angle of the corresponding trajectory of the mission profile are input into the pilot model, and the pilot's control behavior is simulated through a transfer function with a pilot gain to obtain the driving control variables (total pitch, lateral and longitudinal cyclic pitch change, and tail rotor collective pitch) and input them into the flight dynamics bare-metal model; the flight control model decouples the four channels (vertical, lateral, longitudinal, and heading) of the flight dynamics bare-metal model and responds to each state variable; the actual spatial position obtained by integrating the speed over time is fed back to the pilot model together with the yaw angle, eventually forming a closed loop.

[0080] On the basis of the bare-metal flight dynamics model, inner and outer loop cascade control is added to achieve attitude holding and trajectory tracking. The inner loop control uses the helicopter flight control model to stabilize the attitude of the entire aircraft, and the outer loop control uses the pilot model to track the trajectory. The cooperation of the inner and outer loops can achieve the specific trajectory flight of the aircraft.

[0081] The whole aircraft attitude stability is achieved through PID; the gain coefficient is introduced to gradually convert the position, speed, angle, and angular acceleration deviations, and finally the relationship between the angular acceleration deviation and the driver's correction control is established through the transfer function to achieve the output of the desired control amount from the input of the predetermined trajectory. The response characteristics can be obtained by outputting the control amount to the flight dynamics bare machine model, and the driver continuously corrects the error between the actual state and the expectation to form a closed loop.

[0082] Since the CFD calculation results are stored on unstructured grid points, they need to be interpolated and stored in a structured manner before the wind field data is coupled, and the wind field file containing the scattered point position coordinates and three-way wind speed information is provided to the component aerodynamic model. In the component aerodynamic model, the wind speed at the aerodynamic center of the component is obtained by position interpolation (such as u in the vertical tail aerodynamic model). wind 、v wind 、w wind ), thereby achieving the coupling of the ambient wind field and the bare-machine model of flight dynamics.

[0083] So far, the helicopter flight dynamics model has been established ( Figure 2 The points in the attached figure of the third step are aerodynamic calculation points). By inputting the specified trajectory, the control quantity and state quantity (i.e. the response characteristics of the entire aircraft) of the helicopter in a complex wind field can be fed back in real time.

[0084] like Figure 6 As shown, the construction process of the flight dynamics bare metal model includes:

[0085] (1) Based on the helicopter's configuration parameters (size, mass, shape, etc., including the radius, rotation speed, airfoil parameters, number of blades, inclination angle, center of gravity, mass of the rotor and tail rotor; the center of gravity, length, and frontal area of ​​the fuselage, horizontal tail, and vertical tail), the aerodynamic models of each component are established, including the rotor aerodynamic model, tail rotor aerodynamic model, fuselage aerodynamic model, vertical tail aerodynamic model, and horizontal tail aerodynamic model. When modeling the rotor, the blades are divided into several micro-segments, and the first-order flapping of the blades is retained. The rotor downwash speed is calculated through dynamic inflow, and the flow field velocity obtained by CFD is interpolated and superimposed on the micro-segment center and the aerodynamic center of other helicopter components according to the position, so as to realize the coupling of CFD and flight dynamics model. The component aerodynamic model is used to calculate the aerodynamic force and torque at the aerodynamic center position of the corresponding component according to the helicopter motion state parameters and the flow field velocity distribution. Specifically, by considering the mutual interference between components, combining the lift and drag coefficients of each component in the wind tunnel test, introducing the influence of ambient wind speed, and interpolating the aerodynamic force and torque of each component at its aerodynamic center.

[0086] Before establishing the aerodynamic models of each component, the coordinate transformation relationship between the components must be established first.

[0087] An inertial coordinate system is established based on the earth plane and fixed on the ground. The body coordinate system is obtained based on the attitude angle, and the wind axis system is determined according to the body angle of attack and sideslip angle. The rotor calculation needs to consider the motion state of a single blade, so the hub coordinate system is obtained based on the longitudinal installation angle and the lateral installation angle of the hub. On this basis, the azimuth angle is introduced to establish the rotor rotation coordinate system, and finally the blade coordinate system is obtained based on the blade flapping motion state. If the tail rotor axis is not perpendicular to the longitudinal plane of the fuselage, it is also necessary to establish a transformation relationship between the tail rotor coordinate system and the body coordinate system through the tail rotor inclination angle. The above transformation relationship is formed into a matrix, and the conversion between any coordinate systems can be achieved by multiplying the vector and the matrix.

[0088] (2) Determine the dynamic equation at the center of gravity of the helicopter based on the aerodynamic forces and moments of the aerodynamic models of all the components.

[0089] The aerodynamic forces and moments of all components are integrated to the center of gravity of the entire machine through coordinate transformation.

[0090] (3) A bare-machine flight dynamics model is formed based on the six-degree-of-freedom rigid body motion equation and the dynamic equation.

[0091] The bare metal model of helicopter flight dynamics can be obtained by combining the blade flapping motion equation and the helicopter six-degree-of-freedom rigid body dynamics equation. Through this model, the flight attitude, speed, power consumption, etc. can be calculated according to the helicopter's operation.

[0092] The following is the specific process of establishing the vertical tail aerodynamic model:

[0093] (a) Establish the transformation relationship from the wind axis system to the body coordinate system.

[0094] Wind axis origin O W Located at the aerodynamic center of the helicopter's aerodynamic components, X W Axis along the flight speed direction, Z W The axis is located in the symmetry plane of the aircraft and points downward perpendicular to the flight speed. W The axis is determined by the right-hand rule. Wind axis S W With the body coordinate system S B The conversion relationship between the helicopter angle of attack α and the sideslip angle β s From the wind axis S W To the body coordinate system S B The coordinate transformation matrix is:

[0095]

[0096] (b) Establish the vertical tail aerodynamic model.

[0097] In the body coordinate system S B The coordinates of the aerodynamic center of the droop tail are (x V ,y V ,z V ), considering the influence of wind field, rotor and fuselage on the vertical tail, the velocity components of the aerodynamic center of the vertical tail relative to the inflow are:

[0098]

[0099] Among them, u V 、v V 、w V K is the velocity component of the aerodynamic center of the vertical tail relative to the inflow velocity; QV is the dynamic pressure loss coefficient at the vertical tail; u wind 、v wind 、w wind is the velocity component of the relative motion velocity of the aerodynamic center of the vertical tail caused by the wind field; p, q, r are the velocity components of the angular velocity of the helicopter; x V ,y Z 、z V is the position of the vertical tail relative to the helicopter's center of gravity; u ITF 、v ITF 、w ITF is the velocity component caused by the rotor and fuselage wake.

[0100] The vertical tail angle of attack and sideslip angle can be calculated from the velocity component. By interpolating the wind tunnel test data (based on the wind axis system), the vertical tail aerodynamic force and moment coefficient under the flight state can be determined. After coordinate transformation, the vertical tail aerodynamic force and moment under the body coordinate system are finally obtained as follows:

[0101]

[0102] In the formula, F XV 、F YV 、F ZV are the aerodynamic forces in the three coordinate axis directions in the body coordinate system; L V 、M V 、N V They represent the rolling moment, pitching moment and yaw moment generated by the vertical tail respectively; C LV , C DV is the vertical tail lift and drag coefficient obtained by interpolation of wind tunnel test data; S V is the vertical tail area; q V For dynamic pressure.

[0103] The dynamic equations of the helicopter's center of gravity movement and its rotation around the center of gravity are established based on the aerodynamic forces and torques of each component. The dynamic equations are combined with the blade flapping motion equations to form a flight dynamics model.

[0104] The dynamic equations of the helicopter's center of gravity movement and its rotation around the center of gravity are:

[0105]

[0106]

[0107] Among them, u, v, and w are three-dimensional velocities; are the three-dimensional velocity derivatives; p, q, r are the three-dimensional angular velocities; is the three-dimensional angular velocity derivative; m is the mass; F XYZ is a three-dimensional force; I (where I ** is the moment of inertia, which is a design parameter) and ω * denote the cross product matrix of the inertia matrix and the angular velocity, respectively, and

[0108]

[0109] Combining the blade flapping motion equation with the six-degree-of-freedom rigid body motion equation, we can get the flight dynamics bare machine model, which is simplified as follows:

[0110]

[0111] Among them, t is time; U is the control quantity, including collective pitch, lateral cyclic pitch change, longitudinal cyclic pitch change, and tail rotor collective pitch; X is the state quantity, including speed, angular velocity and attitude angle; is the helicopter state derivative; W wind is the flow field velocity, including horizontal velocity component, lateral velocity component and vertical velocity component.

[0112] The fourth step is trajectory design.

[0113] According to the velocity distribution and turbulent kinetic energy distribution of the flow field obtained in the second step, the environmental danger zone is divided according to the vertical velocity mean square error and turbulent kinetic energy limit conditions; for specific flight missions, the obstacle avoidance conditions are considered first, and the danger factor is introduced into the A* algorithm according to the distance from the danger zone. The flight trajectory is designed based on the total range and danger as the criteria. The specific process includes:

[0114] 1) Preliminary division of dangerous areas. When designing trajectories, the mountain terrain model is first converted into a basic map, and then the velocity distribution and turbulent kinetic energy distribution of the flow field are analyzed. The standard deviation of the vertical velocity of the environment exceeds 1.75m / s, and the turbulent kinetic energy is greater than 4.59m 2 / s 2 The area is divided into dangerous areas and added to the map as obstacles, so that the trajectory can be avoided directly. Figure 2 In the attached figure of step 4, the undulating ground is the basic map and the cylindrical area is the danger area.

[0115] 2) Design of helicopter mountain flight trajectory. For specific flight missions, obstacle avoidance conditions are considered first. Combined with the wind field environment, based on intelligent algorithms, different starting and ending positions are found at the minimum cost to obtain a short-distance, low-risk flight path. The A* algorithm is used for trajectory planning. The cost function g(h) represents the cost of the driving path from the starting point to the current position. According to the characteristics of the mountainous environment, risk loss is introduced according to the distance from the danger zone (center of the cylinder):

[0116] g(n)=α(2-R)+βL;

[0117] Where α and β are the weight coefficients of route risk and navigation distance, respectively, α+β=1; R is the comprehensive risk of the current location, the maximum risk of wind speed and turbulent kinetic energy are both 1; L is the distance between the current step grids.

[0118] The heuristic function h(n) represents the future path cost. To avoid falling into the local optimum, the Euclidean distance is used:

[0119]

[0120] In the formula, x n ,y n 、z n is the current position coordinate; x g ,y g 、z g is the target position coordinate.

[0121] In order to take into account both search speed and efficiency, the weight coefficient is adjusted dynamically:

[0122]

[0123] Where d(n) is the distance from the current node to the end point; d(s) is the distance from the start point to the end point.

[0124] Finally, the evaluation function is obtained:

[0125] f(n)=g(n)+w(n)×h(n).

[0126] Step 5: Trajectory evaluation.

[0127] (5.1) Each flight path is simulated according to the helicopter flight dynamics model, and the output is the response characteristics of the entire aircraft.

[0128] (5.2) Calculating the safety level of each flight path based on the overall aircraft response characteristics output by the helicopter flight dynamics model.

[0129] Helicopter safety boundary limitation analysis: The established flight dynamics model is used to track the flight path, and the engine power, helicopter state quantity, and control quantity time history under different flight trajectories are calculated. The safety of the selected trajectory is evaluated based on the helicopter safety boundary (i.e., the safety threshold is set corresponding to the response characteristics of the entire aircraft, such as the helicopter control safety criterion threshold shown in Table 1).

[0130] Table 1 shows the helicopter operation safety criteria thresholds

[0131]

[0132] (5.3) Calculate the pilot control load for each flight path based on the time history of the control variable output by the helicopter flight dynamics model, such as Figure 7 Collective handling characteristics shown.

[0133] For the maneuvering time history, when the correction is too frequent, it may be difficult for the driver to complete the specified task during the maneuver, and the driver load under the specified maneuvering requirements needs to be further evaluated. The rapidity is a time-domain-based method that can measure the change in the driver's control amplitude during the maneuvering process. The calculation method is:

[0134]

[0135] Among them, J A is the control speed index; δ(t) is the control time course; δ(t0) is the reference control amount; δ min , δ max are the minimum and maximum manipulation formations, t0, t f are the start and end time of the flight mission, respectively, and Δt is the discrete time step of the numerical simulation. The larger the control amplitude, the more serious the defect of the flight strategy.

[0136] The driver cutoff frequency is a frequency domain-based method that can accurately identify the frequency components in the signal and can be obtained by manipulating the power spectral density G of the input time history. δδ (ω) Calculate the root mean square of the rod signal in the entire frequency domain:

[0137]

[0138] Where ω is the angular frequency (rad / s), S(ω) is the power spectrum density of the manipulated variable, and if more high-frequency signals are identified, it means that the manipulation is difficult.

[0139] (5.4) Determine the helicopter mountain flight strategy (i.e., safe flight trajectory) based on the cost, the safety level, and the pilot control load.

[0140] After completing the analysis in steps (5.3) and (5.4), if the loads of both the human and the aircraft are within the limit, the designed trajectory is safe and reliable; if it does not meet the safety limit, the location where the limit is exceeded will be added as an obstacle area, and the trajectory will be redesigned. Taking into account the terrain restrictions, environmental wind speed restrictions, full aircraft control and power restrictions, and pilot load restrictions, the safe flight boundary (the area remaining in the environment after removing obstacles) is delineated, and a better trajectory recommendation is given until a flight strategy that meets the safe flight boundary restrictions is finally obtained.

[0141] The advantages of this embodiment are: it is the first attempt in China to conduct relevant research on helicopter flight strategies in complex mountainous environments. In response to the demand for safe helicopter flight in mountainous environments, the mountainous terrain environment and wind environment modeling and analysis are carried out according to the characteristics of mountainous wind fields. The helicopter flight dynamics calculation can be realized by establishing a helicopter flight dynamics model and a pilot model, forming a helicopter flight simulation technology based on the multi-factor coupling of "environment-helicopter-pilot". In the face of the problems of rotor load changes and control failure caused by turbulent wind fields in complex mountainous environments, a safe flight boundary that considers restrictions on control, power and other factors is constructed; and on this basis, a human-in-the-loop simulation of the mountain wind field navigation mission is carried out, and a low-load flight path plan for the pilot is formed by evaluating the pilot's control load, and a mountain flight strategy design technology is formed based on boundary restrictions and the pilot's control load.

[0142] The present application also provides an application scenario, which applies the above-mentioned helicopter mountain flight simulation and flight strategy design method. Specifically: The helicopter mountain flight simulation and flight strategy design method provided in this embodiment can be applied in the preparation scenario of emergency rescue missions. The preparation scenario of emergency rescue missions includes a flight environment assessment link, a flight simulation link, and a strategy optimization link. The helicopter mountain flight simulation and flight strategy design method provided in this embodiment is a key technology in the flight simulation link. This method can help pilots make quick and accurate decisions in actual rescue missions and improve the success rate and safety of missions.

[0143] Example 2

[0144] This embodiment provides a computer device, which may be a server or a terminal. Its internal structure diagram may be as follows: Figure 8 As 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 mountain flight simulation and flight strategy 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 mountain flight simulation and flight strategy design method provided in Example 1 is implemented.

[0145] Those skilled in the art will understand that Figure 8 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.

[0146] Example 3

[0147] 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 mountain flight simulation and flight strategy design method provided in Example 1 is implemented.

[0148] Example 4

[0149] This embodiment provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the helicopter mountain flight simulation and flight strategy design method provided in Embodiment 1 is implemented.

[0150] Example 5

[0151] This embodiment provides a computer program product, including a computer program, which, when executed by a processor, implements the helicopter mountain flight simulation and flight strategy design method provided in Embodiment 1.

[0152] 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.

[0153] 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).

[0154] 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.

[0155] 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.

[0156] 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 helicopter mountain flight simulation and flight strategy design method, characterized in that: The helicopter mountain flight simulation and flight strategy design method comprises: Construct a mountain terrain model based on mountain terrain elevation data; Constructing a mountain wind environment model, wherein the mountain wind environment model is used to process the actual average wind speed at different heights of the wind profile using a harmonic synthesis method to obtain a pulsating wind speed that changes with time at the corresponding height, and to obtain an inflow velocity of the flow field of the entire basin based on the pulsating wind speed and the actual average wind speed; the actual average wind speed is a variable value calculated based on the standard average wind speed at a standard reference height and a ground roughness index; Numerical simulation is performed on the mountain terrain model and the mountain wind environment model to obtain the flow field velocity distribution and turbulent kinetic energy distribution of the entire basin; According to the flight mission of the helicopter, the flight path of the helicopter is planned by using the path optimization algorithm; The cost of simulating the flight of the helicopter on each of the flight paths based on the helicopter flight dynamics model is calculated according to an evaluation function, wherein the evaluation function is a function determined according to a risk loss and a path cost, the risk loss is a variable value calculated according to a current position of the helicopter and a position of a dangerous area, the path cost is a variable value calculated according to the current position of the helicopter and a position of a next flight node, and the dangerous area is an area determined according to the flow field velocity distribution and the turbulent kinetic energy distribution; Calculating the safety level of each of the flight paths according to the full-machine response characteristics output by the helicopter flight dynamics model; Calculating the pilot control load of each of the flight paths according to the control variable time history output by the helicopter flight dynamics model; A helicopter mountain flight strategy is determined based on the cost, the safety level and the pilot control load.

2. The helicopter mountain flight simulation and flight strategy design method according to claim 1 is characterized in that: The calculation formula of the pulsating wind speed is: S(ω l )=H(ω l )H * (oh l ) T ; Among them, S(ω l ) is the spectral density matrix generated by the corresponding fluctuating wind speed power spectrum; k is the ground roughness coefficient; U0 is the actual average wind speed; x = 1200ω l / U0;ω l is the frequency of the lth data; H(ω l ) is the lower triangular matrix of the lth data; H * (ω l ) T is H(ω l ) is the conjugate transpose of ; u(t) is the fluctuating wind speed at time t; N is the total number of data collected in the frequency domain; l is an integer increasing from 1 to N; Δω is the frequency increment; Is a random number.

3. The helicopter mountain flight simulation and flight strategy design method according to claim 1 is characterized in that: The expression of the evaluation function is: f(n)=g(n)+w(n)×h(n); g(n)=α(2-R)+βL; Among them, f(n) is the function value of the evaluation function; g(n) is the value of risk loss; w(n) is the weight coefficient; h(n) is the value of path cost; R is the comprehensive risk of the current location; L is the distance between the current step grids; α and β are the weight coefficients of route risk and navigation distance respectively; x n ,y n 、z n is the current position coordinate; x g ,y g 、z g is the target position coordinate; d(n) is the distance from the current node to the end point; d(s) is the distance from the starting point to the end point.

4. The helicopter mountain flight simulation and flight strategy design method according to claim 1, characterized in that: The helicopter flight dynamics model includes a flight dynamics bare metal model; the specific construction process of the flight dynamics bare metal model includes: Establishing a component aerodynamic model according to the configuration parameters of the helicopter, wherein the component aerodynamic model includes a rotor aerodynamic model, a tail rotor aerodynamic model, a fuselage aerodynamic model, a vertical tail aerodynamic model and a horizontal tail aerodynamic model, and the component aerodynamic model is used to calculate the aerodynamic force and moment at the aerodynamic center position of the corresponding component according to the helicopter motion state parameters and the flow field velocity distribution; Determine the dynamic equation at the center of gravity of the helicopter according to the aerodynamic forces and moments of the aerodynamic models of all the components; A bare-machine flight dynamics model is constructed based on the six-degree-of-freedom rigid body motion equation and the dynamics equation at the center of gravity of the entire helicopter.

5. The helicopter mountain flight simulation and flight strategy design method according to claim 4 is characterized in that: The expression of the bare metal model of flight dynamics is: Among them, t is time; U is the control quantity; X is the helicopter state quantity; is the helicopter state derivative; W wind is the flow field velocity.

6. The helicopter mountain flight simulation and flight strategy design method according to claim 1, characterized in that: The expression of the operation rapidity index in the driver's control load is: Among them, J A is the control speed index; δ(t) is the control time course; δ(t0) is the reference control amount; δ min , δ max are the minimum and maximum manipulation formations respectively; t0, t f are the start and end time of the flight mission respectively; Δt is the discrete time step of the numerical simulation.

7. 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 mountain flight simulation and flight strategy design method according to any one of claims 1 to 6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the helicopter mountain flight simulation and flight strategy design method described in any one of claims 1 to 6 is implemented.

9. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the helicopter mountain flight simulation and flight strategy design method described in any one of claims 1 to 6 is implemented.

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