Method for obtaining component overload based on full-aircraft drop test acceleration

Abstract

The application belongs to the field of aircraft drop test, and is a method for obtaining the overload of a component based on the acceleration of a full aircraft drop test. The vertical acceleration time history and the touchdown sink speed in the full aircraft drop test are obtained first. The vertical acceleration time history is filtered to obtain the acceleration. The acceleration is integrated to obtain the vertical speed time history. The absolute maximum of the vertical speed time history is taken as the measured drop speed. Whether the relative error between the measured drop speed and the touchdown sink speed is greater than 2% is judged to determine whether it is the required filtering frequency. If yes, the vertical acceleration time history of the concerned component is extracted, and low-pass filtering is performed to obtain the overload of the concerned component. The method provides input for the design of a carrier-based aircraft structure and airborne equipment, is simple and stable, and can effectively remove the influence of high-order elastic modes and high-frequency interference signals.

Description

Technical Field

[0001] This application belongs to the field of aircraft drop test, and specifically relates to a method for obtaining component overload based on the acceleration of a full-aircraft drop test. Background Technology

[0002] In full-aircraft drop tests, accelerometers are installed at various components of the test machine to measure the dynamic response time history at those locations. The overload of the components is then obtained through data processing. Drop tests are impact processes that excite higher-order elastic modal responses in the airframe, and the acceleration measurement data is also superimposed with high-frequency interference signals. However, the overload that is of concern in the design of components or airborne equipment is only related to the rigid body modes and lower-order elastic modes of the airframe. Therefore, how to process the acceleration data to obtain the overload of the components is a problem that needs to be solved in full-aircraft drop tests. Summary of the Invention

[0003] The purpose of this application is to provide a method for obtaining component overload based on the acceleration of a full-aircraft drop test, so as to solve the problem that acceleration data in the prior art can excite high-order elastic mode data and superimpose high-frequency interference signals, making it difficult to process.

[0004] The technical solution of this application is: a method for obtaining component overload based on full-aircraft drop test acceleration, comprising: conducting a full-aircraft drop test and obtaining the vertical acceleration time history a at the aircraft's center of gravity. c (t) and the sinking speed upon contact; set the low-pass filter frequency f0 for a c (t) is low-pass filtered to obtain the acceleration a. f (t); will a f Integrate v(t) once over time t to obtain the vertical velocity time history v(t); calculate the measured drop velocity v based on v(t). t ; calculate v t The relative error R between V and V; determine whether the relative error R is not greater than 2%. If so, determine the low-pass filter frequency f. c =f0, proceed to the next step; if not, reset the low-pass filter frequency f0 and repeatedly obtain the relative error R until the relative error R is no greater than 2%; extract the vertical acceleration time history a at the component of interest. i (t); with f c As a low-pass filter frequency, for a i (t) The acceleration a is obtained after filtering. j (t); calculate a j The maximum value of (t) is max{a j (t)} serves as the upper limit g for the overload of the component of concern. u Minimum value min{a j (t)} serves as the lower limit g for the overload of the component of concern.l .

[0005] Preferably, numerical integration is used for a. f Integrate (t) over time t.

[0006] Preferably, the absolute maximum value of v(t) is taken as the measured drop velocity v. t .

[0007] This application discloses a method for obtaining component overload based on acceleration from a full-aircraft drop test. The method first acquires the vertical acceleration time history and the ground contact sinking velocity from the full-aircraft drop test. The vertical acceleration time history is then filtered to obtain the acceleration, and the acceleration is integrated to obtain the vertical velocity time history. The absolute maximum value of the vertical velocity time history is then used as the measured drop velocity. The relative error between the measured drop velocity and the ground contact sinking velocity is determined to be greater than 2% to determine if it is the required filtering frequency. If so, the vertical acceleration time history of the component of interest is extracted, and after low-pass filtering, the overload magnitude of the component of interest can be obtained. This provides input for the design of carrier-based aircraft structures and airborne equipment. The method is simple and stable, and can effectively remove the influence of higher-order elastic modes and high-frequency interference signals. Attached Figure Description

[0008] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0009] Figure 1 This is a schematic diagram of the overall process of this application;

[0010] Figure 2 This is a schematic diagram of the time history of vertical acceleration at the center of gravity of the aircraft in this application;

[0011] Figure 3 This is a schematic diagram of the time history of vertical acceleration at the center of gravity of the aircraft after low-pass filtering according to this application.

[0012] Figure 4 The vertical velocity time history at the center of gravity of the aircraft in this application;

[0013] Figure 5 The vertical acceleration time history at the horizontal stabilizer of the aircraft in this application;

[0014] Figure 6 This is the time history of the vertical acceleration at the horizontal stabilizer of the aircraft after low-pass filtering in this application. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings.

[0016] A method for obtaining component overload based on the acceleration of a full-aircraft drop test includes the following steps:

[0017] Step S100: Conduct a full-aircraft drop test and obtain the vertical acceleration time history a at the aircraft's center of gravity. c (t) and the sinking velocity V upon contact with the ground.

[0018] Step S200, set the low-pass filter frequency f0, for a c (t) is low-pass filtered to obtain the acceleration a. f (t).

[0019] Step S300, a f Integrating (t) once over time t yields the vertical velocity time history v(t), i.e., v t =max{|v(t)|}.

[0020] Step S400: Calculate the measured drop velocity v based on v(t). t .

[0021] Step S500, calculate v t The relative error R between V and V is: R = |(vt-V)| / V.

[0022] Step S600: Determine if the relative error R is not greater than 2%. If so, determine the low-pass filter frequency f. c =f0, proceed to the next step. If not, repeat steps S200-S600, reset the low-pass filter frequency f0, and repeatedly obtain the relative error R until the relative error R is no greater than 2%.

[0023] Step S700: Extract the vertical acceleration time history a at the component of interest. i (t).

[0024] Step S800, with f c As a low-pass filter frequency, for a i (t) The acceleration a is obtained after filtering. j (t).

[0025] Step S900, calculate a j The maximum value of (t) is max{a j (t)} serves as the upper limit g for the overload of the component of concern. u Minimum value min{a j (t)} serves as the lower limit g for the overload of the component of concern. l That is, g u =max{a j (t)}、g l =min{aj (t)}.

[0026] This application first obtains the vertical acceleration time history and the ground contact sinking velocity during the full-scale drop test. After filtering the vertical acceleration time history, the acceleration is obtained. After integrating the acceleration, the vertical velocity time history is obtained. Then, the absolute maximum value of the vertical velocity time history is taken as the measured drop velocity. By judging whether the relative error between the measured drop velocity and the ground contact sinking velocity is greater than 2%, it is determined whether it is the required filtering frequency. If so, the vertical acceleration time history of the component of interest is extracted, and after low-pass filtering, the overload magnitude of the component of interest can be obtained. This provides input for the design of carrier-based aircraft structure and airborne equipment. The method is simple and stable and can effectively remove the influence of high-order elastic modes and high-frequency interference signals.

[0027] As one specific implementation method, the following is an illustration using a concrete example:

[0028] Step 1:

[0029] Extracting the time history of vertical acceleration at the aircraft's center of gravity during the full-scale drop test (a) c (t), see Figure 2 The sinking velocity upon contact with the ground, determined by the high-speed camera, is V = 3.5 m / s.

[0030] Step Two:

[0031] Set the low-pass filter frequency f0 = 15Hz for a c (t) is low-pass filtered, here using a Butterworth filter, and the acceleration a is obtained after processing. f (t), see Figure 3 .

[0032] Step 3:

[0033] Numerical integration is employed, specifically the trapezoidal rule, to integrate a. f Integrating (t) once over time t yields the vertical velocity time history v(t), see [link to relevant documentation]. Figure 4 .

[0034] Step Four:

[0035] Calculate the absolute maximum value of v(t) as the measured drop velocity v. t ,Depend on Figure 4 It can be known that v t = 3.687 m / s.

[0036] Step 5:

[0037] Calculate v t The relative error between V and R: R = |(v t -V)| / V=5.34%.

[0038] Step Six:

[0039] If the relative error R is greater than 2%, steps two through six need to be repeated until the required filter frequency is obtained. Table 1 shows the measured drop velocity v corresponding to different low-pass filter frequencies f0 during the iteration process. t And the relative error R. It can be seen that when f0 = 5Hz, the relative error R = 0.15%, which is no greater than 2%, meeting the requirements. Therefore, the low-pass filter frequency f is determined. c =5Hz.

[0040] Table 1. Parameter values ​​for the iterative process

[0041] Iteration order <![CDATA[f0Hz]]> <![CDATA[v t m / s]]> R 1 15 3.687 5.34％ 2 10 3.642 4.06％ 3 5 3.505 0.15％

[0042] Step Seven:

[0043] Extracting the vertical acceleration time history at the horizontal tail a i (t), see Figure 5 .

[0044] Step 8:

[0045] Using 5Hz as the low-pass filter frequency, for a i (t) The acceleration a is obtained after filtering. j (t), see Figure 6 .

[0046] Step Nine:

[0047] Calculate a j The maximum value of (t) is max{a j (t)}、Minimum value min{a j (t)} serves as the upper limit g for the overload of the component of concern. u Lower limit g l .Depend on Figure 6 It can be known that g u =2.848g, g l = -1.405g.

[0048] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for obtaining component overload based on the acceleration of a full-aircraft drop test, characterized in that, include: A full-aircraft drop test was conducted to obtain the time history of the vertical acceleration at the aircraft's center of gravity. c (t) and the ground subsidence velocity V; Set the low-pass filter frequency f0 for a c (t) is low-pass filtered to obtain the acceleration a. f (t); a f Integrating (t) once over time t yields the vertical velocity time history v(t); Calculate the measured drop velocity v based on v(t). t ; Calculate v t The relative error R between V and V; Determine if the relative error R is no greater than 2%. If so, determine the low-pass filter frequency f. c =f0, proceed to the next step; if not, reset the low-pass filter frequency f0 and repeatedly obtain the relative error R until the relative error R is no greater than 2%; Extracting the vertical acceleration time history at the component of interest a i (t); f c As a low-pass filter frequency, for a i (t) The acceleration a is obtained after filtering. j (t); Calculate a j The maximum value of (t) is max{a j (t)} serves as the upper limit g for the overload of the component of concern. u Minimum value min{a j (t)} serves as the lower limit g for the overload of the component of concern. l .

2. The method for obtaining component overload based on the acceleration of a full-aircraft drop test as described in claim 1, characterized in that: Numerical integration method is used for a f Integrate (t) over time t.

3. The method for obtaining component overload based on the acceleration of a full-aircraft drop test as described in claim 1, characterized in that: The absolute maximum value of v(t) is taken as the measured drop velocity v. t .

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