CN104573264A - Method for simulating low-attitude wind shear area crossing of aircraft - Google Patents

Abstract

A method for simulating the passage of an aircraft through a region of low-altitude wind shear. It can accurately simulate the state changes of aircraft passing through the wind shear area, and at the same time, it can also well support flight simulation of various models. It uses the FlightGear platform to simulate a standard flight scene, records the flight control parameters and flight dynamic parameters in this scene, and establishes a low-altitude wind shear field through the Fluent software to obtain wind speed data in the wind shear area, and then comprehensively forms the FlightGear platform control data. Simulate the state of aircraft passing through the low-altitude wind shear region. The present invention utilizes flight control parameters under FlightGear standard flight and wind speed data in the wind shear area as the experimental information source to carry out the simulation experiment of the aircraft passing through the low-altitude wind shear area. The flight parameter analysis of crossing the storm core under the control operation has the advantages of strong flexibility and high fidelity.

Description

Method of Simulating Aircraft Crossing Low-altitude Windshear Region

technical field

The invention belongs to the technical field of flight simulation, in particular to a method for simulating an aircraft passing through a low-altitude wind shear region.

Background technique

Wind shear refers to the drastic change of wind speed or wind direction between two points in the atmosphere with a short distance, which will cause the aircraft track to deviate, and in severe cases may cause the aircraft to lose stability. According to statistics, from 1950 to 2000, there were 39 aviation accidents caused by wind shear, resulting in more than 400 casualties. However, low-altitude wind shear occurs in the airspace below 600 meters, and has the characteristics of short time, small scale, and high intensity, which brings a series of difficulties such as detection, forecasting, air traffic control, and flight, and is not easy to solve. Aeronautical Meteorological Problems. Therefore, it is of great significance to conduct ground flight experiments and data analysis under low-altitude wind shear combined with flight simulators for the study of countermeasures.

FlightGear is an open source flight simulator. The project started in 1997. The main goal is to create a cutting-edge flight simulator framework for academic research, and it can also be extended to flight training, virtual simulation, and flight simulation games. It supports global 3D real scenes, more than 20,000 runways, more than 400 types of aircraft, cross-platform, multi-person joint flight, various open flight data models and other functions. FlightGear has a variety of high-precision flight dynamics models, and has a powerful application data interface. At the same time, FlightGear's unique attribute management mechanism - "attribute tree" provides a simple and complete flight data acquisition channel for flight simulation data analysis under wind shear, increasing the flexibility and practicability of the platform. In view of its open source and flexible data interface, choosing FlightGear as the simulation platform is helpful for the development of low-altitude wind shear research.

Scholars at home and abroad have done a lot of research on the integration of low-altitude wind shear and flight simulators. In the summer of 1983, the Joint Airport Weather Studies (JAWS) project used Doppler radar observations to record about 70 microburst events, analyzed the typical airflow data, and organized them into a specific form It was used in the research of flight simulators; subsequently, Michael Ivan proposed a real-time microburst mathematical model based on the vortex ring method based on the data provided by JAWS, which provided a modeling basis for flight simulation under low-altitude wind shear . Domestically, Gao Zhenxing et al. established a three-dimensional model of low-altitude microbursts, built a high-precision flight dynamics model based on the modeling data of Boeing747-100B aircraft, and based on the two, analyzed the impact of large aircraft passing through low-altitude microbursts and Research on the dynamic response of atmospheric turbulence; Zhang Ran used Simulink to establish a large-scale aircraft full-envelope six-degree-of-freedom nonlinear model under low-altitude wind shear, and carried out real-time simulation, research on reactive wind shear detection algorithms, and aircraft crossing Control law design for approach with windshear. To sum up, most studies are based on simulation platforms such as Simulink and Matlab. Although the simulation accuracy is high, it is limited to a single model. If it is necessary to explore the response of multiple models, it is necessary to re-model the flight dynamics, which is cumbersome and time-consuming. for a long time.

Contents of the invention

In order to solve the above problems, the object of the present invention is to provide a method for simulating aircraft passing through low-altitude windshear regions that can be applied to various types of aircraft.

In order to achieve the above object, the method for simulating aircraft provided by the invention to pass through the low-altitude windshear region includes the following steps carried out in order:

(1) S1 stage of recording flight control parameters and flight power parameters under standard flight conditions;

(2) Modeling of low-altitude wind shear field to obtain the S2 stage of wind speed data in the wind shear area;

(3) according to the flight control parameter under the standard flight condition that step (1) obtains and the wind shear regional wind speed data that step (2) obtains, form the S3 stage of FlightGear platform control data comprehensively;

(4) according to the comprehensive control data that step (3) obtains, control FlightGear platform simulation aircraft to pass through the S4 stage of the flight dynamic parameter of low altitude wind shear zone;

(5) According to the flight dynamic parameters under the standard flight conditions obtained in step (1) and the flight dynamic parameters obtained in step (4) through the wind shear region, the S5 stage of real-time comparison of flight data is formed.

In step (1), the method for recording flight control parameters and flight dynamic parameters under the described standard flight conditions is based on the FlightGear platform simulation standard flight scene, using the JSBSim flight dynamics model of the platform, 3D visual system and complete Model library, control the aircraft through external input devices including external joystick, mouse, and keyboard to generate a set of flight control parameters and flight power parameters under standard flight, and record these two parameters to the flight in csv format in the log file.

In step (2), the low-altitude wind shear field is modeled, and the method of obtaining wind speed data in the wind shear area is to use Fluent software to build a microburst simulation physics based on the characteristics of the microburst wind field data. Model, the model adopts structured grid division, and uses the velocity inlet boundary condition to set the velocity and scalar of the flow inlet boundary, and then simulates the wind speed data in the low-altitude wind shear area.

In step (3), the described flight control parameters under the standard flight conditions obtained according to step (1) and the wind shear area wind speed data obtained by step (2), the method of comprehensively forming the FlightGear platform control data is to build data The communication platform integrates the flight control parameters under standard flight obtained in step (1) and the wind speed data in the wind shear area obtained in step (2) into FlightGear platform control data, and publishes it in UDP data format.

In step (4), the comprehensive control data obtained according to step (3), the method of controlling FlightGear platform simulation aircraft to cross the flight dynamic parameters of the low-altitude wind shear zone is to receive step ( 3) The integrated FlightGear platform control data enables the FlightGear platform to simulate the flight scene of the aircraft affected by low-altitude wind shear interference under the original standard flight control parameters, and generate corresponding flight dynamic parameters.

In step (5), the flight dynamic parameters under the standard flight conditions obtained according to step (1) and the flight dynamic parameters obtained by step (4) through the wind shear region form a real-time comparison method of flight data It is the flight power parameter under the standard flight obtained according to step (1) and the flight power parameter under the low-altitude wind shear condition obtained by step (4), utilizes the scripting language Nasal and Canvas of FlightGear to generate the visual output of the real-time comparison of flight data, Complete the analysis of the impact of low-altitude wind shear on flight.

The method for simulating aircraft crossing the low-altitude wind shear region provided by the invention can accurately simulate the state change of the aircraft passing through the wind shear region, and can also well support flight simulation of various models. This method uses the FlightGear platform to simulate a standard flight scene, records the flight control parameters and flight dynamic parameters in this scene, and establishes a low-altitude wind shear field through the Fluent software, obtains the wind speed data in the wind shear area, and then comprehensively forms the FlightGear platform Control data to simulate the state of the aircraft passing through the low-altitude wind shear region. The inventive method utilizes FlightGear standard flight control parameters and the wind speed data in the windshear region as the experimental information source to carry out the simulation experiment of the aircraft crossing the low-altitude windshear region. It can be applied to flight training under low-altitude wind shear and flight parameter analysis of aircraft crossing the storm core under uncontrolled operation, and has the advantages of strong flexibility and high fidelity.

Description of drawings

Fig. 1 is the flow chart of the method for simulating an aircraft passing through a low-altitude windshear region provided by the present invention;

Figure 2 is a physical model diagram of a microburst simulation;

Fig. 3 is a flow field velocity vector distribution diagram: (a) v ₀ =30ft/s; (b) v ₀ =50ft/s;

Fig. 4 is a diagram of the operation interface of the data communication platform;

Figure 5 is a schematic diagram of the working principle of the FlightGear-based low-altitude windshear flight simulation platform;

Fig. 6 is a real-time comparison monitoring interface diagram of flight data;

Figure 7 is a curve diagram of B777-200ER flight parameters through the storm: (a) altitude change curve; (b) pitch angle change curve; (c) airspeed change curve.

Detailed ways

The method for simulating an aircraft passing through a low-altitude wind shear region provided by the present invention will be described in detail below in conjunction with the accompanying drawings and specific examples.

Fig. 1 is a flowchart of a method for simulating an aircraft passing through a low-altitude wind shear region provided by the present invention.

As shown in Figure 1, the method for simulating aircraft provided by the present invention to pass through the low-altitude windshear region comprises the following steps carried out in order:

(1) S1 stage of recording flight control parameters and flight power parameters under standard flight conditions:

Use the JSBSim flight dynamics model of the FlightGear platform, 3D visual system and complete model library to simulate the standard flight scene, and control the aircraft through external input devices (such as external joystick, mouse, keyboard, etc.) to simulate the standard flight scene, and generate a Set the flight control parameters and flight power parameters under standard flight, and record these two parameters into the flight log file in csv format.

The flight control parameters mainly include left and right engine throttle, elevator, rudder, aileron deflection and trim, landing gear status, flap position, etc. The flight experiment can be carried out by using the above-mentioned flight control parameters instead of the manual control mode. The specific meaning of each control parameter is as follows:

1) Left and right engine throttle: This information reflects the speed of the left and right engines. Increasing the throttle will increase the power of the aircraft, accelerate or climb, and vice versa, it will decelerate or decrease;

2) The amount of deflection and trim of the elevator, rudder, and aileron: the pitch of the aircraft is controlled by the deflection and trim of the elevator, the heading of the aircraft is controlled by the deflection and trim of the rudder, and the deflection and trim of the aileron are used to control the pitch of the aircraft. control the roll of the aircraft;

3) Landing gear state: This state reflects whether the aircraft is properly retracting and retracting the landing gear during taxiing, takeoff, landing, taxiing and cruising;

4) Flap gear: the flap can be deflected downward or (and) slide backward (forward), and the lift of the aircraft in flight can be controlled by the flap gear.

The flight dynamic parameters mainly include the flight airspeed, the three attitude angles along the coordinate axis of the aircraft body, and the longitude, latitude and flight altitude that characterize the spatial position of the aircraft. When analyzing the influence of aircraft passing through the center of the storm, the changes in flight airspeed, pitch angle and flight altitude are the key analysis parameters due to the significant change in longitudinal performance.

(2) Modeling of the low-altitude wind shear field, and the S2 stage of obtaining wind speed data in the wind shear area:

In order to simulate the influence of aircraft by wind shear disturbance, it is first necessary to build a realistic and reliable wind shear model. The concept of microburst (Microbust) was first proposed by Japanese meteorologist Fujita in 1981, that is, a downdraft airflow caused by convection with a wind speed higher than 34 knots, and its radially divergent outer flow field The horizontal scale does not exceed 4 kilometers. According to the statistical analysis of actual microburst wind field strength and spatial scale, microbursts usually occur below 500 meters, accompanied by horizontal and radial divergent airflows in the range of about 3 kilometers.

According to the wind field data characteristics of the typical microburst model released by JAWS, the present invention uses the Fluent software computational fluid dynamics software to build a microburst simulation physical model as shown in Figure 2. The entrance above the container has a width of 2,000 feet and a height of 1,500 feet; the lower rectangular area has a height of 6,000 feet and a width of 16,000 feet. The fluid rushes down from the inlet at 30 ft/s and 50 ft/s respectively, and hits the ground in a rectangular area to form a radially divergent flow field.

Due to the regular shape of the built model, the structured grid is used, that is, the two-dimensional planar quadrilateral grid division, which can provide a grid division quality as high as 0.9. The mesh size is 50 feet by 50 feet, and the total number of meshes for the entire model is 43858.

For flow inlet and outlet, Fluent software provides ten types of boundary elements: velocity inlet, pressure inlet, mass inlet, pressure outlet, pressure far field, mass outlet, air inlet, inlet fan, air outlet and exhaust fan. The present invention selects the velocity inlet boundary condition for defining the velocity and scalar of the flow inlet boundary, and provides the following information required for the velocity inlet boundary condition:

1) Velocity magnitude and direction or velocity components. The data used in the experiment of the present invention are the fluids flowing vertically downward at 30 ft/s and 50 ft/s respectively;

2) Temperature (for energy calculations). Calculated according to the temperature drop of 6K per kilometer, the corresponding fluid temperature at the inlet of 9000 feet is about 280K, so the present invention sets the inlet gas temperature to 280K.

3) The container wall for building the model is set as a static (stationary) non-slide (non-slide) wall surface, which is thermally insulated and has no radiation.

The present invention utilizes the above-mentioned physical model and simulation parameter settings to obtain the velocity vector distribution diagram of the flow field as shown in FIG. 3 .

It can be seen from Figure 3 that the vortex center of the flow field appears at about 3000 feet, and clearly presents three areas—the downdraft area in the center of the flow field, the symmetrically distributed central vortex core area, and the area near the bottom of the container. No rotating flow area. The locations and ranges of each region are in line with the JAWS model, which proves that the overall distribution of the simulation results is in line with the real situation. In addition, in terms of the local velocity vector, the average wind velocity in the key characteristic area of the simulated flow field at v ₀ =30ft/s was counted and compared with the typical microburst of JAWS. The results are shown in Table 1.

Table 1

The fluid velocity vector in the vortex core area shows a tendency of increasing rotation, which is in line with reality. The wind speed in the central axis downdraft area at the height of the center of the vortex core is about 10 m/s (about 33 ft/s), and the average wind speed in the near-ground irrotational flow area is about 13 m/s (about 40 ft/s). All of them are highly consistent with the JAWS data, which verifies the correctness and usability of the built model and the data generated by using the model.

(3) According to the flight control parameters under the standard flight conditions obtained in step (1) and the wind speed data in the wind shear area obtained in step (2), the S3 stage of the FlightGear platform control data is formed comprehensively:

In order to accurately study the influence of low-altitude wind shear on uncontrolled and fixed-rudder flight, it is necessary to ensure that the wind field data is a single variable for standard flight and flight through the low-altitude wind shear area. Ordinary manual flight control cannot guarantee that the control volume of the two flight experiments is exactly the same. It is necessary to use flight control parameters instead of manual operation for flight experiments to achieve stable data-driven flight and accurate flight scene reproduction. Therefore, in order to simulate the state of the aircraft passing through the low-altitude wind shear region, it is necessary to integrate the flight control parameters obtained in step (1) under standard flight and the wind speed data in the wind shear region obtained in step (2) to form comprehensive FlightGear platform control data.

In order to obtain comprehensive FlightGear platform control data, the present invention uses C# to build a data communication platform that integrates data receiving, data recording and data sending functions. The platform first reads the flight log file in csv format formed in step (1) to obtain the flight control parameters under standard flight, then receives the wind speed data in the wind shear area generated in step (2), and combines the flight control parameters under standard flight Then get the integrated FlightGear platform control data, and release it in UDP data format.

Figure 4 is the operation interface diagram of the data communication platform. The left side is the data sending area, which can control the aircraft by controlling the scroll bar, or realize the data driving of the aircraft by loading the flight control parameter file in csv format; the upper right is the data display area, which is used for The loaded csv data is fully displayed; the data receiving area on the lower right can display the flight data sent back by FlightGear in real time.

(4) according to the comprehensive control data that step (3) obtains, control FlightGear platform simulation aircraft to pass through the S4 stage of the flight dynamic parameter of low altitude wind shear zone;

In order to utilize the comprehensive control data that step (3) obtains to control FlightGear platform simulation aircraft to cross the state of low-altitude wind shear zone, the data communication platform that the present invention utilizes step (2) to build is data sending end, by the UDP data interface that FlightGear reserves Receive the FlightGear platform control data synthesized in step (3), so that the FlightGear platform simulates the flight scene where the aircraft is affected by low-altitude wind shear interference under the original standard flight control parameters, and generates corresponding flight dynamic parameters.

Figure 5 is a schematic diagram of the working principle of the FlightGear-based low-altitude windshear flight simulation platform. It can be seen from Figure 5 that, as described in step (1), the aircraft is controlled by an external input device to generate a set of flight control parameters and flight control parameters under standard flight conditions. Power parameters, and record them into the flight log file in csv format, and then use the data communication platform to send the comprehensive control data obtained in step (3) back to FlightGear to control the flight of the aircraft through the UDP data interface.

The flight control parameters and wind speed data input from FlightGear will access and rewrite the attribute tree, and the internal flight dynamics model will return the calculation result to the attribute tree after solving. As shown in Figure 5, the data acquisition function reads the values of each target attribute on the attribute tree according to the sampling time set by the user and records them in the flight log file in csv format to form the flight dynamic parameters for crossing the wind shear area, and the steps (1) The generated flight dynamic parameters under standard flight are similar, mainly including flight airspeed, three attitude angles along the coordinate axis of the body, and parameters such as longitude, latitude and flight altitude representing the spatial position of the aircraft.

(5) according to the flight power parameter under the standard flight condition that step (1) obtains and the flight power parameter that crosses the wind shear region that step (4) obtains, form the S5 stage of the real-time comparison of flight data:

FlightGear provides high-fidelity 2D and 3D cockpits for various aircraft types, including various instrument displays such as main flight display and navigation display. This type of display only provides current flight parameter display and a few predictions of future data, and cannot provide an intuitive historical trend of flight data. In order to show the influence of flight operation and external environment on flight parameters more intuitively, the present invention carries out secondary development to FlightGear, uses the scripting language Nasal of XML language, FlightGear and Canvas image rendering to develop a new graphical user interface, and steps ( 1) The flight dynamic parameters obtained under the standard flight conditions and the flight dynamic parameters obtained in step (4) through the wind shear region are reflected into real-time drawn parameter curves using Canvas and displayed on the development interface. It can realize the visual output of real-time comparison of flight data, and complete the analysis of the impact of low-altitude wind shear on flight.

As shown in Figure 6, it is a graphical user interface designed by the present invention, and the attribute parameters represented by the curves of each color, such as the check box on the left side of the canvas, set the text, which can be set in the attribute tree by clicking the Properties button. This function allows observers to observe the change trend of flight parameters more intuitively, or conduct comparative analysis on some specific related parameters when needed.

Experimental results

The method for simulating aircraft passing through the low-altitude windshear region provided by the present invention can be further illustrated by the following experiments.

Taking Boeing777-200ER as an example, many landing experiments were carried out by using the low-altitude wind shear model established by the present invention and the FlightGear data communication platform. Compared with the standard flight experiment, the flight experiment under low-altitude wind shear disturbance, except the wind field, the rest of the parameters are consistent, achieving the purpose of single variable control.

According to the Boeing777-200 flight manual, the flight parameters are set as follows:

1) Sliding angle: γ=-3°;

2) Flap position: flap=30°;

3) Flight speed: use the minimum safe landing speed. In the current flap position, the stall speed of the aircraft is 125kt; in order to ensure a certain safety margin, the landing speed is set to 132kt.

According to the above flight parameters, the flight altitude, pitch angle and airspeed curves shown in Figure 7(a), 7(b) and 7(c) are obtained.

It can be seen from Figure 7(a) that when the aircraft enters the windward area, the increase in relative speed leads to an increase in lift, and then enters the downwind area in a short period of time. The aircraft lift drops sharply, making the flight trajectory lower than the standard glide curve, and finally ahead of the standard flight path. The trace landed. It can be seen from Figure 7(b) that the pitch angle of the aircraft increases to 5° when it enters the windward area, and then decreases rapidly after entering the downwind area, that is, the aircraft dives for a certain period of time. The sharp drop in altitude increases the kinetic energy of the aircraft, that is, the flight speed increases. At this time, the aircraft regains a part of the lost lift and gradually stabilizes. In Fig. 7(c), since the aircraft has just entered the windward area, both lift and airspeed will increase, and when entering the downdraft area and downwind area, the airspeed will drop suddenly due to the decrease of lift force.

From the analysis of the above three flight parameters, it can be seen that under small and medium-scale wind shear, the aircraft can return to a stable flight state by relying on its own stability design when flying without a fixed rudder. However, as the scale of the storm increases and the wind speed gradient increases, flying without a fixed rudder may cause the aircraft to drop too much in altitude and crash directly when encountering a strong tailwind. Therefore, it is necessary to study the recovery method of the response to ensure flight safety.

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Claims (6)

1. simulate the method that aircraft passes through low district, it is characterized in that, the method that described simulation aircraft passes through low district comprises the following step carried out in order:

(1) S1 stage of record-setting flight controling parameters and flying power parameter under Standard Flight condition;

(2) low field modeling, obtains the S2 stage of wind shear region air speed data;

(3) the wind shear region air speed data that the flight controling parameters under the Standard Flight condition obtained according to step (1) and step (2) obtain, the comprehensive S3 stage forming FlightGear platform courses data;

(4) according to the Comprehensive Control data that step (3) obtains, control FlightGear platform simulation aircraft passes through the S4 stage of the flying power parameter in low district;

(5) the flying power parameter of passing through wind shear region that the flying power parameter under the Standard Flight condition obtained according to step (1) and step (4) obtain, forms the S5 stage of comparing in real time of flying quality.

2. simulation aircraft according to claim 1 passes through the method in low district, it is characterized in that: in step (1), under described Standard Flight condition, the method for record-setting flight controling parameters and flying power parameter is based on FlightGear platform emulation Standard Flight scene, utilize the JSBSim flight dynamics model of this platform, 3D visual system and complete type storehouse, by comprising external operating rod, mouse, keyboard is at interior external input device manipulation aircraft, to produce flight controling parameters under one group of Standard Flight and flying power parameter, and by these two kinds of reference records in the Air Diary file of csv form.

3. simulation aircraft according to claim 1 passes through the method in low district, it is characterized in that: in step (2), described low field modeling, the method of acquisition wind shear region air speed data is the feature according to micro handling system wind field data, Fluent software is utilized to build micro handling system emulated physics model, model adopts structured grid to divide, and utilize speed and the scalar of condition setting flowing inlet boundary, speed inlet boundary, and then simulate the air speed data in low region.

4. simulation aircraft according to claim 1 passes through the method in low district, it is characterized in that: in step (3), the wind shear region air speed data that flight controling parameters under the described Standard Flight condition obtained according to step (1) and step (2) obtain, the method of comprehensive formation FlightGear platform courses data builds data communication platform, the controling parameters that flown under Standard Flight step (1) obtained comprehensively becomes FlightGear platform courses data with the wind shear region air speed data that step (2) obtains, and outwards issue with UDP message form.

5. simulation aircraft according to claim 1 passes through the method in low district, it is characterized in that: in step (4), the described Comprehensive Control data obtained according to step (3), the method that control FlightGear platform simulation aircraft passes through the flying power parameter in low district is the FlightGear platform courses data comprehensively become by the UDP message interface step (3) that FlightGear is reserved, FlightGear platform emulation aircraft under primary standard flight controling parameters is made to be subject to the flying scene of low disturbing effect, and generate corresponding flying power parameter.

6. simulation aircraft according to claim 1 passes through the method in low district, it is characterized in that: in step (5), the flying power parameter of passing through wind shear region that flying power parameter under the described Standard Flight condition obtained according to step (1) and step (4) obtain, forming the method compared in real time of flying quality is flying power parameter under the low condition that under the Standard Flight obtained according to step (1), flying power parameter and step (4) obtain, script Nasal and Canvas of FlightGear is utilized to generate the visual output of comparing in real time of flying quality, complete the analysis of low on flight impact.