阅读说明：本技术 通过飞行试验辨识飞机气动焦点的方法 (Method for identifying aerodynamic focus of airplane through flight test ) 是由 李亚东 陶晶 管德会 王木国 项松 赵为平 张彦 周国庆 梅莉 李英 陈占伟 于 2021-06-10 设计创作，主要内容包括：本发明公开了一种通过飞行试验辨识飞机气动焦点的方法,包括如下步骤：测量飞机的重量；联调测试系统；通过前重心飞行试验和后重心飞行试验,分别获得辨识飞机气动焦点所需的前重心数据和后重心数据；采用公式辨识飞机的气动焦点。该辨识飞机气动焦点的方法,简单可靠,能够准确辨识气动焦点的相对位置,进而指导飞机的重心前后限位置,对飞机的结构配置起到关键作用。(The invention discloses a method for identifying an aerodynamic focus of an airplane through a flight test, which comprises the following steps: measuring the weight of the aircraft; a joint debugging test system; respectively obtaining front gravity center data and rear gravity center data required by identifying the aerodynamic focus of the airplane through a front gravity center flight test and a rear gravity center flight test; and identifying the aerodynamic focus of the airplane by adopting a formula. The method for identifying the aerodynamic focus of the airplane is simple and reliable, can accurately identify the relative position of the aerodynamic focus, further guides the front and rear limit positions of the gravity center of the airplane, and plays a key role in the structural configuration of the airplane.)

1. The method for identifying the aerodynamic focus of the airplane through the flight test is characterized by comprising the following steps of:

s1: measuring the weight m of the airplane;

s2: a joint debugging test system;

s3: through preceding focus flight test and back focus flight test, obtain respectively and discern required preceding focus data of aircraft aerodynamic focus and back focus data, preceding focus data includes the focus front limit position of the aircraft of primary electionAirplane elevator deflection angle delta corresponding to airplane during flat flight₁Airplane elevator deflection angle delta corresponding to the airplane during pulling and lifting₂And longitudinal overload n_y1The rear center of gravity data comprises the rear limit position of the center of gravity of the initially selected airplaneAirplane elevator deflection angle delta corresponding to airplane during flat flight₃Airplane elevator deflection angle delta corresponding to the airplane during pulling and lifting₄And longitudinal overload n_y2Wherein the aircraft elevator yaw angle δ is obtained₁And aircraft elevator yaw angle delta₃The horizontal flight speeds of the corresponding airplanes are the same;

s4: identifying aerodynamic focus of an aircraft using equation (1)

In the formula (1), the reaction mixture is,is the relative position of the aerodynamic focus of the aircraft,for the pitch damping derivative of an aircraft, μ ═ 2m/ρ Sb_ADenotes the relative density of the aircraft, m denotes the weight of the aircraft, ρ denotes the atmospheric density, S denotes the wing reference area, b_ARepresenting the mean aerodynamic chord length, Δ δ, of the aircraft_z1、Δδ_z2Representing elevator deviation value, Δ δ_z1＝δ₁-δ₂，Δδ_z2＝δ₃-δ₄，Δn_y1、Δn_y2Indicating longitudinal overload increment, Δ n_y1＝n_y1-1，Δn_y2＝n_y2-1，Andrespectively representing the fore limit position and the rear limit position of the gravity center of the initially selected airplane.

2. A method of identifying aerodynamic focus of an aircraft by flight testing as claimed in claim 1, wherein: in the step S3, obtaining the front gravity center data required for identifying the aerodynamic focus of the aircraft through the front gravity center flight test specifically includes the following steps:

front limit position of gravity center of primary selected airplaneSetting the horizontal flying speed V of the airplane and measuring the deflection angle delta of the elevator of the airplane₁；

Maintaining the front limit position of the aircraft center of gravity for initial selectionAnd quickly pulling up the aircraft elevator and measuring the deflection angle delta of the aircraft elevator without changing the set horizontal flying speed V of the aircraft₂And longitudinal overload n_y1。

3. A method of identifying aerodynamic focus of an aircraft by flight testing as claimed in claim 2, wherein: in the step S3, obtaining the rear center-of-gravity data required for identifying the aerodynamic focus of the aircraft through a rear center-of-gravity flight test specifically includes the following steps:

center of gravity rear limit position of primary selection airplaneSetting the horizontal flying speed V of the airplane and measuring the deflection angle delta of the elevator of the airplane₃The set horizontal flying speed V of the airplane is the same as the horizontal flying speed V set in the front gravity center flying test;

maintaining the rear limit position of the aircraft center of gravity for initial selectionAnd quickly pulling up the aircraft elevator and measuring the deflection angle delta of the aircraft elevator without changing the set horizontal flying speed V of the aircraft₄And longitudinal overload n_y2。

Technical Field

The invention relates to the field of aviation, and particularly provides a method for identifying an aerodynamic focus of an airplane through an aerial level flight and pull-up flight test.

Background

For statically stable aircraft, the relative position between the aerodynamic focus and the center of gravity directly affects the flight performance of the aircraft. Specifically, the closer the relative positions of the two are, the smaller the stability margin is, which leads to the deterioration of the stability of the body and seriously affects the flight safety; on the contrary, if the relative position of the two is farther, the stability margin is larger, the following performance of the airplane is poor, the aerodynamic load is increased, and meanwhile, the trim resistance is also increased, so that the cruising economy of the airplane is influenced.

At present, the aerodynamic focus of an airplane is obtained through wind tunnel test data identification, a model of a wind tunnel test is a rigid body, the deformation amount is extremely small in the test process, the obtained focus is the focus of the rigid body airplane, the airplane in flight is an elastic body, the airplane can deform in the flight process, and the position of the focus can deviate. The authenticity of the focus has a crucial effect on the distribution of the position of the center of gravity of the aircraft, and if the aircraft determines the front and rear limit positions of the center of gravity according to the rigid body focus, the danger coefficient is increased, so that how to acquire the real aerodynamic focus in order to accurately determine the front and rear limit positions of the center of gravity becomes a problem to be solved urgently.

Disclosure of Invention

In view of the above, the present invention provides a method for identifying an aerodynamic focus of an aircraft through a flight test to obtain a relative position of a real aerodynamic focus.

The technical scheme provided by the invention is as follows: the method for identifying the aerodynamic focus of the airplane through the flight test comprises the following steps:

s1: measuring the weight m of the airplane;

s2: a joint debugging test system;

s3: through preceding focus flight test and back focus flight test, obtain respectively and discern required preceding focus data of aircraft aerodynamic focus and back focus data, preceding focus data includes the focus front limit position of the aircraft of primary electionAirplane elevator deflection angle delta corresponding to airplane during flat flight₁Airplane elevator deflection angle delta corresponding to the airplane during pulling and lifting₂And longitudinal overload n_y1The rear center of gravity data comprises the rear limit position of the center of gravity of the initially selected airplaneAirplane elevator deflection angle delta corresponding to airplane during flat flight₃Airplane elevator deflection angle delta corresponding to the airplane during pulling and lifting₄And longitudinal overload n_y2Wherein the aircraft elevator yaw angle δ is obtained₁And aircraft elevator yaw angle delta₃The horizontal flight speeds of the corresponding airplanes are the same;

s4: identifying aerodynamic focus of an aircraft using equation (1)

In the formula (1), the reaction mixture is,is the relative position of the aerodynamic focus of the aircraft,for the pitch damping derivative of an aircraft, μ ═ 2m/ρ Sb_ADenotes the relative density of the aircraft, m denotes the weight of the aircraft, ρ denotes the atmospheric density, S denotes the wing reference area, b_ARepresenting the mean aerodynamic chord length, Δ δ, of the aircraft_z1、Δδ_z2Representing elevator deviation value, Δ δ_z1＝δ₁-δ₂，Δδ_z2＝δ₃-δ₄，Δn_y1、Δn_y2Indicating longitudinal overload increment, Δ n_y1＝n_y1-1，Δn_y2＝n_y2-1，Andrespectively representing the fore limit position and the rear limit position of the gravity center of the initially selected airplane.

Preferably, in S3, the obtaining of the front center-of-gravity data required for identifying the aerodynamic focus of the aircraft through the front center-of-gravity flight test specifically includes the following steps:

front limit position of gravity center of primary selected airplaneSetting the horizontal flying speed V of the airplane and measuring the deflection angle delta of the elevator of the airplane₁；

Maintaining the front limit position of the aircraft center of gravity for initial selectionAnd quickly pulling up the aircraft elevator and measuring the deflection angle delta of the aircraft elevator without changing the set horizontal flying speed V of the aircraft₂And longitudinal overload n_y1。

Further preferably, in S3, the obtaining of the rear gravity center data required for identifying the aerodynamic focus of the aircraft through the rear gravity center flight test specifically includes the following steps:

center of gravity rear limit position of primary selection airplaneSetting the horizontal flying speed V of the airplane and measuring the deflection angle delta of the elevator of the airplane₃The set horizontal flying speed V of the airplane is the same as the horizontal flying speed V set in the front gravity center flying test;

maintaining the rear limit position of the aircraft center of gravity for initial selectionAnd quickly pulling up the aircraft elevator and measuring the deflection angle delta of the aircraft elevator without changing the set horizontal flying speed V of the aircraft₄And longitudinal overload n_y2。

The method for identifying the aerodynamic focus of the airplane through the flight test is simple and reliable, can accurately identify the relative position of the aerodynamic focus, further guides the front and rear limit positions of the gravity center of the airplane, and plays a key role in the structural configuration of the airplane.

Drawings

The invention is described in further detail below with reference to the following figures and embodiments:

FIG. 1 is a flow chart of a method for identifying an aerodynamic focus of an aircraft through a flight test according to the present invention;

FIG. 2 is a measurement curve of horizontal flight speed, elevator deflection angle and longitudinal overload of an RX4E four-seat electric aircraft during horizontal flight and pulling-up flight in a front center-of-gravity flight test;

fig. 3 is a measurement curve of the horizontal flight speed, the elevator deflection angle and the longitudinal overload of the RX4E four-seat electric aircraft during the horizontal flight and the pulling-up flight in the rear center-of-gravity flight test.

Detailed Description

The invention will be further explained with reference to specific embodiments, without limiting the invention.

As shown in fig. 1, the present invention provides a method for identifying an aerodynamic focus of an aircraft through a flight test, comprising the following steps:

s1: measuring the weight m of the airplane:

before the aircraft carries out a flight test, in order to determine the technical state during the air flight test, the weight of the aircraft is actually measured on the ground, instruments and equipment used for measurement are required to have qualified marks within the qualified valid period of verification, and the weighing precision is not lower than: plus or minus 0.1 percent, and the range of the weighed quantity is about 2/3 of the maximum weighing range;

s2: a joint debugging test system;

the test system includes flying parameter record appearance, airborne data acquisition system, ground data processing system and ground monitoring system, specifically includes: on-board: RXAP100 data recorder, GPS antenna, voltage and current transducer, absolute value rotary encoder, speed sensor, airspeed, data transmission antenna, temperature and pole force sensor, etc. The method comprises the following steps of (1) positioning on the ground: GCS ground station, dual-frequency dual-star antenna, data transmission antenna. The RXAP100 data recorder integrates a high-precision IMU combined module, a high-precision dynamic and static pressure sensor, a high-precision magnetic sensor and a high-precision differential GPS positioning module. The speed measurement precision error is not more than 0.05kts, the longitudinal overload measurement precision error is not more than 0.2%, and the rudder deflection angle measurement error is not more than 0.2%;

s3: through preceding focus flight test and back focus flight test, obtain respectively and discern required preceding focus data of aircraft aerodynamic focus and back focus data, preceding focus data includes the focus front limit position of the aircraft of primary electionAirplane elevator deflection angle delta corresponding to airplane during flat flight₁Airplane elevator deflection angle delta corresponding to the airplane during pulling and lifting₂And longitudinal overload n_y1The rear center of gravity data comprises the rear limit position of the center of gravity of the initially selected airplaneAirplane elevator deflection angle delta corresponding to airplane during flat flight₃Airplane elevator deflection angle delta corresponding to the airplane during pulling and lifting₄And longitudinal overload n_y2Wherein the aircraft elevator yaw angle δ is obtained₁And aircraft elevator yaw angle delta₃The horizontal flight speeds of the corresponding airplanes are the same;

the method comprises the following steps of obtaining front gravity center data required by identifying an aerodynamic focus of an airplane through a front gravity center flight test:

front limit position of gravity center of primary selected airplaneSetting the horizontal flying speed V of the airplane and measuring the deflection angle delta of the elevator of the airplane₁；

Maintaining the front limit position of the aircraft center of gravity for initial selectionAnd quickly pulling up the aircraft elevator and measuring the deflection angle delta of the aircraft elevator without changing the set horizontal flying speed V of the aircraft₂And longitudinal overload n_y1；

The method comprises the following steps of obtaining rear gravity center data required by identifying an aerodynamic focus of an airplane through a rear gravity center flight test:

center of gravity rear limit position of primary selection airplaneSetting the horizontal flying speed V of the airplane and measuring the deflection angle delta of the elevator of the airplane₃The set horizontal flying speed V of the airplane is the same as the horizontal flying speed V set in the front gravity center flying test;

maintaining the rear limit position of the aircraft center of gravity for initial selectionAnd quickly pulling up the aircraft elevator and measuring the deflection angle delta of the aircraft elevator without changing the set horizontal flying speed V of the aircraft₄And longitudinal overload n_y2；

S4: identifying aerodynamic focus of an aircraft using equation (1)

In the formula (1), the reaction mixture is,is the relative position of the aerodynamic focus of the aircraft,for the pitch damping derivative of an aircraft, μ ═ 2m/ρ Sb_ADenotes the relative density of the aircraft, m denotes the weight of the aircraft, ρ denotes the atmospheric density, S denotes the wing reference area, b_ARepresenting the mean aerodynamic chord length, Δ δ, of the aircraft_z1、Δδ_z2Representing elevator deviation value, Δ δ_z1＝δ₂-δ₁，Δδ_z2＝δ₄-δ₃，Δn_y1、Δn_y2Indicating longitudinal overload increment, Δ n_y1＝n_y1-1，Δn_y2＝n_y2-1，Andrespectively representing the fore limit position and the rear limit position of the gravity center of the initially selected airplane.

The derivation of equation (1) is given below:

simultaneous equations (2) to (7) to yield equation (8)

μ＝2m/ρSb_A (5)

Δc_y＝Δn_ygc_ypf＝(n_y-1)gc_ypf (6)

And (3) simultaneously establishing equations (2) to (7), and solving the equations to obtain:

in the formulas (2) to (8),for static margin, Δ c_yThe increase in the coefficient of lift is indicated,expressing elevator efficiency, Δ δ_zThe values of the elevator deviation are indicated,the pitch damping derivative of the aircraft is represented,representing dimensionless pitch angle velocity, b_ARepresenting the average aerodynamic chord length of the airplane, V representing the set flat flying speed of the airplane, g representing the gravity acceleration, n_yIndicating a pulling-up longitudinal overload,the position of the center of gravity of the aircraft is indicated,representing the relative position of the aerodynamic focus of the aircraft, m representing the weight of the aircraft, S representing the reference area of the wing, ρ representing the atmospheric density, Δ n_yIndicating longitudinal overload increment, c_ypfRepresenting the lift coefficient of the aircraft when flying flat.

The front limit position of the center of gravity of the aircraft primarily selected in the front center of gravity flight testAircraft elevator deflection angle delta₁Deviation angle delta of airplane elevator₂And longitudinal overload increment Δ n_y1Substituting into the formula (8) to obtain

In the formula, Δ δ_z1＝δ₂-δ₁，Δn_y1＝n_y1-1；

The center of gravity rear limit position of the aircraft primarily selected in the rear center of gravity flight testAircraft elevator deflection angle delta₃Deviation angle delta of airplane elevator₄And longitudinal overload increment Δ n_y2Substituting into the formula (8) to obtain

In the formula, Δ δ_z2＝δ₄-δ₃，Δn_y2＝n_y2-1；

The formula (1) can be obtained by combining the formulas (9) and (10).

The method for identifying the aerodynamic focus of the airplane through the flight test provided by the invention comprises the steps of initially selecting the front limit position and the rear limit position of the gravity center of the airplane, calculating the elevator deviation value and the longitudinal overload of the plane level flight and the plane pull-up at the two positions, and utilizing a formulaThe method can identify the aerodynamic focus of the airplane, the number of the needed parameters is small, the method is easy to implement, and compared with the method of identifying the aerodynamic focus of the airplane by CFD calculation or wind tunnel test, the method can obtain the real relative position of the aerodynamic focus of the airplane.

The following gives the comparison example of the method provided by the invention adopted by the RX4E four-seat electric aircraft and the identification of the aerodynamic focus of the aircraft by adopting a wind tunnel test:

FIG. 2 shows the horizontal flight speed (m/s), the elevator deflection angle (degree) and the longitudinal overload (i.e. the Z-axis acceleration, m/s) of an RX4E four-seat electric aircraft during the horizontal flight and the vertical flight in the front center-of-gravity flight test²) The measurement curve of (2); FIG. 3 shows the horizontal flight speed (m/s), the elevator deflection angle (degree) and the longitudinal overload (i.e. the Z-axis acceleration, m/s) of an RX4E four-seat electric aircraft during the horizontal flight and the vertical flight in the rear center-of-gravity flight test²) The measurement curve of (1).

Table 1 shows the comparison of the results of identifying the aerodynamic focus of an aircraft by the method of the present invention and by the wind tunnel test

TABLE 1 comparison of flight test focus with wind tunnel test focus

The wind tunnel test model is a rigid body and a scaling model, and the deformation of the whole machine is small in the wind tunnel test process. In actual flight, the RX4E four electric airplanes are elastic bodies, and wings, a fuselage and a tail wing of the electric airplanes are all made of carbon fiber composite materials, so that the elastic deformation amount is large in flight, the focus of the electric airplanes is ahead of the focus of the wind tunnel test, and the focus of the electric airplanes in actual flight is the real aerodynamic focus of the airplane.