Airplane aerodynamic data correction method based on parameter identification

Abstract

The invention discloses an aircraft pneumatic data correction method based on parameter identification, which comprises the following steps: in a fixed wing mode, an aircraft stably and flatly flies at a certain fixed speed, and test flight data is recorded; in the fixed wing mode, on the basis of the first step, tail thrust is closed, gliding is kept at the stable speed, and test flight data are recorded; in the fixed wing mode, the flight speed is changed, and the steps 1-2 are repeated; and processing data according to a kinematics equation of the airplane to obtain an airplane lift-drag coefficient and tail thrust aerodynamic data, so as to correct the model. According to the method, the flight mechanics mathematical model is corrected by adopting a parameter identification method, the tail thrust model with interference can be accurately identified, and a basic guarantee is provided for control system design, aircraft simulation and flight quality evaluation of an aircraft.

Description

Technical Field

[0001] The invention relates to the field of aviation technology, and in particular to an aircraft aerodynamic data correction method based on parameter identification. Background Art

[0002] Electric vertical take-off and landing aircraft (eVtol) has the characteristics of vertical take-off and landing, strong maneuverability, and environmental protection and energy saving. It has shown broad prospects in urban transportation. eVtol can take off and land vertically like a helicopter, and can also fly at high speed like a fixed-wing aircraft. Therefore, there will inevitably be interference in the structure and aerodynamic layout, which will bring challenges to flight mechanics modeling. However, accurate flight dynamics mathematical models are not only the prerequisite for the design and correction of aircraft control systems, but also an important basis for aircraft ground simulation and flight quality evaluation. Therefore, identifying accurate aerodynamic parameters and correcting the aerodynamic model are of great significance to improving aircraft performance.

[0003] At present, the main methods for obtaining eVtol aerodynamic data are CFD calculation and wind tunnel test. The former is based on theoretical numerical calculation, the process is complicated and the error is large, and the latter uses wind tunnel experimental test, which is very expensive. In terms of parameter identification, there are technologies for aerodynamic parameter identification of fixed-wing aircraft, but the engine thrust line is often used as a known condition; although there are also technologies for multi-rotor parameter identification, they are often in a low-speed flight state and do not consider the aerodynamic characteristics of the fuselage. Summary of the invention

[0004] The purpose of the present invention is to provide an aircraft aerodynamic data correction method based on parameter identification to solve the problems mentioned in the background technology. To achieve the above purpose, the present invention provides the following technical solution: an aircraft aerodynamic data correction method based on parameter identification, comprising the following steps:

[0005] Step 1: In fixed-wing mode, the aircraft flies steadily at a fixed speed and records the test flight data;

[0006] Step 2: In fixed-wing mode, based on step 1, turn off the tail thrust, maintain a stable glide speed, and record the test flight data;

[0007] Step 3: In fixed-wing mode, change the flight speed and repeat steps 1 to 2;

[0008] Step 4: Process the data according to the aircraft's kinematic equations to obtain the aircraft's lift-drag coefficient and tail thrust aerodynamic data, thereby correcting the model.

[0009] Preferably, the kinematic equation of the aircraft in step 4 is:

[0010]

[0011] Among them, m is the aircraft mass, v is the aircraft flight speed, h is the flight altitude, T is the tail thrust, D is the aircraft drag, L is the aircraft lift, α is the aircraft angle of attack, σ is the tail thrust installation angle, γ is the track inclination angle, and g is the acceleration of gravity.

[0012] Preferably, the expressions of tail thrust, aircraft lift and aircraft drag are:

[0013] T=ρπR 4 *ω 2 *C T (λ)

[0014] L=ρv 2 S*C L (α)

[0015] D=ρv 2 S*C D (α)

[0016] λ=v / (ωR)

[0017] Where ρ is the air density, R is the radius of the tail propeller, ω is the speed of the propeller, and C T is the tail thrust coefficient, λ is the inflow ratio, S is the aircraft reference area, C L is the aircraft lift coefficient, C D is the aircraft drag coefficient.

[0018] Preferably, in step 4, the data is processed according to the kinematic equation of the aircraft to obtain the lift-drag coefficient and tail thrust aerodynamic data of the aircraft, so that the specific content of the correction model is:

[0019] When the aircraft glides at different speeds, T = 0, and γ is only related to the flight speed, so equation (1) can be simplified to

[0020] ρv 2 S*C D (α) = mgsin(-γ)

[0021] Simplify formula (2) to

[0022] ρv 2 S*C L (α) = mgcos(-γ)

[0023] According to different gliding speeds, C D ~α, C L ~α data;

[0024] When the aircraft flies level at different speeds, γ=0, (1) is simplified to

[0025] πR 4ω 2 C T (λ)*cos(α+σ)=v 2 S*C D (α)

[0026] According to different level flight speeds, obtain C T ~λ data,

[0027] Obtained C D (α), C L (α), C T (λ) is the result of parameter identification, thereby correcting the model.

[0028] The technical effects and advantages of the present invention are as follows: the present invention adopts a gradually decoupled identification method, the flight test method is simple, the flight test data is easy to obtain, the data processing does not involve complex algorithms, and the method is easy to implement; the present invention adopts a parameter identification method to correct the flight mechanics mathematical model, and can more accurately identify the tail thrust model under interference, providing a basic guarantee for the control system design, aircraft simulation and flight quality evaluation of the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0030] The present application is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technical personnel in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0031] Example

[0032] like Figure 1 As shown, a method for correcting aircraft aerodynamic data based on parameter identification includes the following contents:

[0033] (1) In fixed-wing mode, the aircraft flies steadily at a fixed speed and records the flight test data;

[0034] (2) In fixed-wing mode, based on step 1, turn off the tail thrust, maintain a stable glide speed, and record the test flight data;

[0035] (3) In fixed-wing mode, change the flight speed and repeat steps 1 to 2;

[0036] (4) Process the data according to the aircraft's kinematic equation, where the aircraft's kinematic equation is:

[0037]

[0038] Among them, m is the mass of the aircraft, v is the flight speed of the aircraft, h is the flight altitude, T is the tail thrust, D is the aircraft drag, L is the aircraft lift, α is the aircraft angle of attack, σ is the tail thrust installation angle, γ is the track inclination angle, and g is the acceleration of gravity;

[0039] The tail thrust is related to the rotation speed and the incoming flow velocity, and the lift resistance is related to the incoming flow velocity (dynamic pressure) and the angle of attack, that is:

[0040] T=ρπR 4 *ω 2 *C T (λ)

[0041] L=ρv 2 S*C L (α)

[0042] D=ρv 2 S*C D (α)

[0043] λ=v / (ωR)

[0044] Where ρ is the air density, R is the radius of the tail propeller, ω is the speed of the propeller, and C T is the tail thrust coefficient, λ is the inflow ratio, S is the aircraft reference area, C L is the aircraft lift coefficient, C D is the aircraft drag coefficient;

[0045] When the aircraft glides at different speeds, T = 0, and γ is only related to the flight speed, so equation (1) can be simplified to

[0046] ρv 2 S*C D (α) = mgsin(-γ)

[0047] Simplify formula (2) to

[0048] ρv 2 S*C L (α) = mgcos(-γ)

[0049] According to different gliding speeds, C D ~α, C L ~α data;

[0050] When the aircraft flies level at different speeds, γ=0, (1) is simplified to

[0051] πR 4 ω 2 C T (λ)*cos(α+σ)=v 2S*C D (α)

[0052] According to different level flight speeds, obtain C T ~λ data,

[0053] Obtained C D (α), C L (α), C T (λ) is the result of parameter identification, thereby correcting the model.

[0054] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for correcting aircraft aerodynamic data based on parameter identification, characterized in that: The following steps are involved: Step 1: In fixed-wing mode, the aircraft flies steadily at a fixed speed and records the test flight data; Step 2: In fixed-wing mode, based on step 1, turn off the tail thrust, maintain a stable glide speed, and record the test flight data; Step 3: In fixed-wing mode, change the flight speed and repeat steps 1 to 2; Step 4: Process the data according to the aircraft's kinematic equations to obtain the aircraft's lift-drag coefficient and tail thrust aerodynamic data, thereby correcting the model.

2. The aircraft aerodynamic data correction method based on parameter identification according to claim 1, characterized in that: The kinematic equation of the aircraft in step 4 is: Among them, m is the aircraft mass, v is the aircraft flight speed, h is the flight altitude, T is the tail thrust, D is the aircraft drag, L is the aircraft lift, α is the aircraft angle of attack, σ is the tail thrust installation angle, γ is the track inclination angle, and g is the acceleration of gravity.

3. The aircraft aerodynamic data correction method based on parameter identification according to claim 2, characterized in that: The expressions for tail thrust, aircraft lift and aircraft drag are: T=ρπR 4 *oh 2 *C T (l) L=ρv 2 S*C L (a) D=ρv 2 S*C D (a) λ=v / (ωR) Where ρ is the air density, R is the radius of the tail propeller, ω is the speed of the propeller, and C T is the tail thrust coefficient, λ is the inflow ratio, S is the aircraft reference area, C L is the aircraft lift coefficient, C D is the aircraft drag coefficient.

4. The aircraft aerodynamic data correction method based on parameter identification according to claim 3 is characterized in that: In step 4, the data is processed according to the aircraft's kinematic equation to obtain the aircraft's lift-drag coefficient and tail thrust aerodynamic data, so that the specific content of the correction model is: When the aircraft glides at different speeds, T = 0, and γ is only related to the flight speed, so equation (1) can be simplified to pv 2 S*C D (a)=mgsin(-γ) Simplify formula (2) to pv 2 S*C L (a)=mgcos(-γ) According to different gliding speeds, C D ~α, C L ~α data; When the aircraft flies level at different speeds, γ=0, (1) is simplified to pR 4 oh 2 C T (λ)*cos(α+σ)=v 2 S*C D (a) According to different level flight speeds, obtain C T ~λ data, Obtained C D (α), C L (α), C T (λ) is the result of parameter identification, thereby correcting the model.

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