Method for compiling vibration environment spectrum of airborne equipment of jet aircraft

Abstract

The invention discloses a method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft. The method comprises the following steps of: (1) dividing a region: dividing the whole aircraft into regions according to the structural characteristics of the aircraft, the equipment installation density, the airborne equipment installation mode and the vibration condition of each test point; (2) task state division: measuring and obtaining vibration actual measurement data of each task section of the airplane, and performing typical task state division on each actual measurement task section; (3) constructing a power spectrum envelope curve of each measuring point under a given confidence coefficient; (4) constructing spectral pattern conclusions of all measuring points in each region; (5) establishing a vibration environment prediction model; (6) calculating the root-mean-square value of the upper limit spectrum of the acceleration power spectrum of each region: obtaining the root-mean-square value of the upper limit spectrum of the acceleration power spectrum of each region by using the rising spectrum, the falling spectrum and the straight spectrum; and (7) compiling a random vibration test spectrum: obtaining a vibration environment condition random vibration standard spectrum as a vibration test condition after obtaining the root mean square values of the vibration predicted upper limit spectrum and the acceleration upper limit spectrum of each region. The method solves the problem that the vibration environment of the airborne equipment is difficult to truly reflect according to a standard method for compiling the vibration environment spectrum of the airborne equipment.

Description

Technical Field

[0001] The invention relates to the technical field of aircraft vibration environment engineering, and in particular to a method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft. Background Art

[0002] In order to ensure the safety and reliability of airborne equipment in a vibration environment during the use of a certain type of aircraft in my country, it is necessary to compile a suitable vibration environment spectrum to evaluate the function and durability of airborne equipment. The purpose of the vibration test of airborne equipment is different from that of the functional test. It is mainly to determine the structural integrity of the airborne equipment under the long-term action of the predetermined vibration environment conditions. At present, the compilation of the vibration environment spectrum of domestic aircraft is mostly based on standards. The standards are basically derived from foreign standards. In essence, it is equivalent to using the test conditions of foreign aircraft to inspect the airborne equipment of Chinese aircraft. However, there are great differences between Chinese and foreign aircraft in structure, strength, mission profile and environmental profile during the use of aircraft. The use of vibration environment spectrum compiled based on standards for assessment may lead to a significant increase in the weight and cost of airborne equipment, and it is difficult to accurately evaluate the true life of its structure, which cannot meet the needs of model development and finished product development. Summary of the invention

[0003] The purpose of the present invention is to provide a method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft. The present invention solves the problem that the method for compiling a vibration environment spectrum of airborne equipment in accordance with the standard is difficult to truly reflect the vibration environment of the aircraft airborne equipment.

[0004] Technical solution: A method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft, comprising the following steps:

[0005] (1) Area division: The whole aircraft is divided into zones according to the structural characteristics of the aircraft, the density of equipment installation, the installation method of airborne equipment, and the vibration conditions of each test point;

[0006] (2) Mission status division: Measure and obtain the actual vibration data of each mission profile of the aircraft, and divide each measured mission profile into typical mission states;

[0007] (3) Construct the power spectrum envelope curve at each measuring point with a given confidence level;

[0008] (4) Construct a spectrum summary of all measurement points in each region;

[0009] (5) Establish a vibration environment prediction model;

[0010] (6) Calculate the RMS value of the upper limit spectrum of the acceleration power spectrum in each region: Use the rising spectrum, the falling spectrum, and the flat spectrum to obtain the RMS value of the upper limit spectrum of the acceleration power spectrum in each region;

[0011] (7) Preparation of random vibration test spectrum: After obtaining the root mean square value of the predicted upper limit spectrum of vibration and the upper limit spectrum of acceleration in each area, the random vibration specification spectrum of the vibration environment conditions is obtained as the vibration test condition.

[0012] In the aforementioned method for compiling the vibration environment spectrum of airborne equipment of a jet aircraft, in step (1), the zones include: fuselage zone, wing zone, horizontal tail zone, vertical tail zone, landing gear zone, engine vicinity zone and engine zone; the fuselage zone is divided into three parts: the front 1 / 4 zone, the middle 1 / 2 zone and the rear 1 / 4 zone; the wing zone is divided into two parts: the inner 1 / 3 zone and the outer 2 / 3 zone.

[0013] In the aforementioned method for compiling the vibration environment spectrum of airborne equipment of a jet aircraft, in step (2), typical mission states are divided into: ground takeoff, takeoff acceleration, climb, air cruise, air combat, circling and descent, and ground landing.

[0014] In the above-mentioned method for compiling the vibration environment spectrum of the jet aircraft airborne equipment, step (3) is specifically as follows:

[0015] The Corey-Duquet method is used to directly perform fast Fourier transform on the original vibration data to obtain the acceleration power spectrum density; all spectral line values ​​under the corresponding mission state of each test point in all flight sorties are extracted as sample values, and the spectral line value with the required confidence level is taken as the inductive vibration power spectrum envelope curve of a single test point.

[0016] In the above-mentioned method for compiling the vibration environment spectrum of jet aircraft airborne equipment, the sample values ​​are extracted based on equations (1) to (3):

[0017] According to formula (1), the feature samples Each spectral line corresponds to Take the mean variance estimate

[0018]

[0019] According to formula (2), the average of adjacent spectral lines With variance Calculate the statistic F n (k,k+1) and t n (k,k+1)

[0020]

[0021] Assuming that the PSDs of adjacent spectral lines k and k+1 of the characteristic sample belong to the same population, then F n (k,k+1) is subject to the degree of freedom (Q p -1,Q p -1) of the F distribution, t n(k,k+1) is subject to 2 degrees of freedom (Q p -1) central t distribution;

[0022]

[0023] Under a given confidence level (1-α), if equation (3) holds, the assumption holds and the PSDs of adjacent spectral lines k and k+1 of the feature sample belong to the same population, otherwise they do not belong to the same population.

[0024] In the aforementioned method for compiling the vibration environment spectrum of airborne equipment of a jet aircraft, the stationarity, ergodicity, periodicity and normality of the vibration data are tested before the original vibration data is processed to confirm that the vibration data to be summarized is an ergodic random signal.

[0025] In the above-mentioned method for compiling the vibration environment spectrum of the jet aircraft airborne equipment, step (4) is specifically as follows:

[0026] On the basis of the confidence power envelope spectrum required by each region, the power spectrum envelope values ​​of all measuring points in each region are used to obtain the summarized spectrum of the corresponding region according to equations (1) to (3). The characteristic value points on the spectrum are selected, and the multi-line spectrum obtained by connecting each characteristic point in turn in the power spectrum diagram is the summarized regional vibration power spectrum.

[0027] In the aforementioned method for compiling the vibration environment spectrum of airborne equipment of a jet aircraft, step (5) is specifically as follows: conducting a vibration and flight parameter correlation analysis, then conducting a flight state analysis, and finally establishing a vibration environment prediction model;

[0028] Vibration and flight parameter correlation analysis: Analyze the correlation between dynamic pressure and engine speed and the vibration of each channel of the aircraft to determine the key factors affecting the vibration of different areas of the aircraft;

[0029] Flight state analysis: Analyze the maximum dynamic pressure in the design limit state and the maximum dynamic pressure in actual flight according to the flight envelope and typical mission profile of the jet aircraft, establish a prediction model of vibration magnitude and dynamic pressure, and predict the vibration magnitude in the limit state;

[0030] Establish a vibration environment prediction model: calculate the vibration root mean square value of the power spectrum density in the frequency range of 15 to 2000 Hz;

[0031] A linear fitting prediction model is established for the vibration root mean square value and dynamic pressure. The linear fitting prediction formula is:

[0032] V=k*q+b (4)

[0033] Where V is the root mean square value of vibration, q is the dynamic pressure;

[0034] Through linear regression calculation, the values ​​of equation k and b are obtained, and then the predicted model equation of the relationship between the vibration root mean square value and the dynamic pressure is obtained;

[0035] According to the fitting formula of the relationship between the root mean square value of vibration and the dynamic pressure, the dynamic pressure of the aircraft in the limit state is substituted into the corresponding fitting formula to obtain the estimated value of the root mean square value of vibration, thereby obtaining the upper limit spectrum of the estimated acceleration power spectrum of each area of ​​the whole aircraft.

[0036] In the above-mentioned method for compiling the vibration environment spectrum of the jet aircraft airborne equipment, the calculation of step (6) is as shown in equations (5) to (8):

[0037]

[0038] A2=W0Δf=W0(f1-f b ) (6)

[0039]

[0040] Where: A1 is the acceleration spectrum density curve W(f) and frequency f b -f a The area enclosed by the axis; A2 is the acceleration spectral density value W0 and the frequency f1-f b A3 is the area enclosed by the acceleration spectral density curve W(f) and the frequency f2-f1 axis; m=N / 3, N is the slope of the spectrum line;

[0041]

[0042] G RMS is the total RMS value of random vibration acceleration.

[0043] In the above-mentioned method for compiling the vibration environment spectrum of the jet aircraft airborne equipment, if N=3 and m=1, the descent spectrum calculation formula is adopted.

[0044] Beneficial effects: The present invention provides a method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft, which utilizes the measured data of vibration during the test flight, summarizes and processes the measured data, and obtains the vibration test spectrum of each area of ​​the aircraft as the design input of the adaptability of the airborne design environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is the envelope curve of the Y-axis vibration function rate spectrum of each state of a certain measuring point in the vicinity of the engine;

[0046] Figure 2 It is the inductive spectrum curve diagram of the vibration power spectrum in the vicinity of the engine;

[0047] Figure 3 Estimated upper limit spectrum for vibration near the engine;

[0048] Figure 4 It is the acceleration power spectrum curve;

[0049] Figure 5 This is the test vibration spectrum. DETAILED DESCRIPTION

[0050] Example 1. A method for compiling a vibration environment spectrum of a jet aircraft onboard equipment, see Figure 1-Figure 5 ,include:

[0051] (1) Division of regions: Based on the structural characteristics of the aircraft, the density of equipment installation, and the installation method of onboard equipment, the vibration conditions of each test point are used to divide the entire aircraft into different regions: the fuselage is divided into three parts, the front 1 / 4 area, the middle 1 / 2 area, and the rear 1 / 4 area; the wing is divided into two parts, the inner 1 / 3 area and the outer 2 / 3 area; the horizontal tail and the vertical tail; the landing gear area, the area near the engine, and the engine area; the subsequent analysis and summary of the measured vibration data are carried out according to the above-mentioned divisions.

[0052] (2) Mission status classification: Measure and obtain the actual vibration data of each mission profile of the aircraft, and classify each measured mission profile into typical mission states: ground (take-off), take-off acceleration, climb, air cruise, air combat, circling and descent, and ground (landing).

[0053] (3) Power spectrum envelope at each measurement point with a given confidence level

[0054] Before data processing, the basic characteristics of vibration data such as stationarity, ergodicity, periodicity and normality need to be tested to confirm that the vibration data to be summarized is a random signal with ergodicity. The Cooley-Tukey method is used to directly perform fast Fourier transform on the original vibration data to obtain the acceleration power spectrum density. According to formulas (1) to (3), all spectral line values ​​under the corresponding mission state of each test point in all flight sorties are taken as sample values, and the spectral line value with the required confidence level is taken as the envelope curve of the summarized vibration power spectrum of a single test point. For example, the envelope curve of the Y-axis vibration power spectrum of a certain measuring point in the vicinity of the engine is shown in Figure 1 .

[0055] The vibration spectrum is matched to the characteristic sample The frequency bands are divided according to the distribution of the characteristic sample PSD along the frequency axis, and the adjacent spectral lines correspond to Perform parameter hypothesis test. Merge adjacent spectral lines belonging to the same population into the same frequency band to form H1 frequency bands. The spectral line numbers of the two end points of the h frequency band are k. h1 , k h2 (h=1,2…,H1), the number of spectral lines is N h =k h2 -k h1 +1. In the band Approximately follows a normal distribution.

[0056] According to formula (1), the feature samples Each spectral line corresponds to Take the mean variance estimate

[0057]

[0058] According to formula (2), the average of adjacent spectral lines With variance Calculate the statistic F n (k,k+1) and t n (k,k+1)

[0059]

[0060] Assuming that the PSDs of adjacent spectral lines k and k+1 of the characteristic sample belong to the same population, then F n (k,k+1) is subject to the degree of freedom (Q p -1,Q p -1) of the F distribution, t n (k,k+1) is subject to 2 degrees of freedom (Q p -1) of the central t distribution.

[0061] Under a given confidence level (1-α), if equation (3) holds, the assumption holds and the PSDs of adjacent spectral lines k and k+1 of the feature sample belong to the same population, otherwise they do not belong to the same population.

[0062]

[0063] (4) Spectral summary of all measurement points in each area

[0064] Based on the power envelope spectrum of the confidence level required in each area, the power envelope values ​​of all measuring points in each area are used to obtain the summarized spectrum of the area according to formulas (1) to (3). Select the characteristic value points on the spectrum, and connect the characteristic points in turn in the power spectrum spectrum diagram to obtain the multi-line spectrum, which is the summarized regional vibration power spectrum. For example, the summarized spectrum of the vibration power spectrum near the engine is shown in Figure 2 .

[0065] (5) Establish a vibration environment prediction model

[0066] Since actual flight tests are difficult to cover the aircraft's extreme flight conditions, it is impossible to directly summarize the vibration environment test conditions based on the measured data. It is necessary to establish a vibration environment prediction model to calculate the vibration value under the extreme state as the value of the environmental vibration function test. In order to establish a vibration environment prediction model, it is necessary to first conduct a vibration and flight parameter correlation analysis, then conduct a flight state analysis, and finally establish a vibration environment prediction model.

[0067] 1) Analysis of the correlation between vibration and flight parameters: The vibration environment of equipment installed on jet aircraft mainly comes from the excitation of the aircraft structure by engine noise and the aerodynamic turbulence on the external structure of the aircraft, and the corresponding flight state parameters are dynamic pressure and engine speed. Therefore, the correlation between dynamic pressure and engine speed and the vibration of each channel of the aircraft is analyzed to determine the key factors affecting the vibration of different areas of the aircraft.

[0068] 2) Flight status analysis

[0069] Through the correlation analysis between vibration and flight parameters, it is determined that dynamic pressure is the key factor of vibration. It is necessary to analyze the maximum dynamic pressure of the design limit state and the maximum dynamic pressure of the measured flight according to the flight envelope and typical mission profile of the jet aircraft. Because the measured samples have not yet covered the limit state in the flight envelope, it is necessary to establish a prediction model of vibration magnitude and dynamic pressure to predict the vibration magnitude under the limit state.

[0070] 3) Establish a vibration environment prediction model

[0071] For the vibration power spectrum of each area and each flight state of the whole aircraft, according to the recommended values ​​of the environmental test conditions for jet aircraft in the standard, the frequency range of power spectrum density analysis is selected as 15 to 2000 Hz, so the vibration root mean square value of the power spectrum density in the frequency range of 15 to 2000 Hz is calculated.

[0072] According to the relationship between vibration value and dynamic pressure in the military standard, there is a strong linear correlation between the vibration root mean square value and the dynamic pressure. Therefore, a linear fitting prediction model is established for the vibration root mean square value and the dynamic pressure. The linear fitting prediction formula is:

[0073] V=k*q+b (4)

[0074] Among them, V is the vibration root mean square value, and q is the dynamic pressure. Through linear regression calculation, the values ​​of equations k and b are obtained, and then the predicted model equation of the relationship between the vibration root mean square value and the dynamic pressure is obtained.

[0075] According to the fitting formula of the relationship between the vibration root mean square value and the dynamic pressure, the dynamic pressure of the aircraft limit state is substituted into the corresponding fitting formula to obtain the estimated value of the vibration root mean square value, thereby obtaining the upper limit spectrum of the acceleration power spectrum of each area of ​​the whole aircraft, see Figure 3 .

[0076] (6) Calculate the RMS value of the upper limit spectrum of the acceleration power spectrum in each region

[0077] The calculation process of the RMS value of the upper limit spectrum of the acceleration power spectrum in each region of the rising spectrum, the falling spectrum and the flat spectrum is as shown in equations (5) to (8). Figure 4 .

[0078]

[0079] A2=W0Δf=W0(f1-f b ) (6)

[0080]

[0081] Where: A1 is the acceleration spectrum density curve W(f) and frequency f b -f a The area enclosed by the axis; A2 is the acceleration spectral density value W0 and the frequency f1-f b The area enclosed by the axis; A3 is the area enclosed by the acceleration spectrum density curve W(f) and the frequency f2-f1 axis; m = N / 3, N is the slope of the spectrum. If N = 3, then when m = 1, the following descent spectrum calculation formula must be used:

[0082]

[0083]

[0084] G RMS For Figure 4 The area enclosed by each spectral line shown is the total RMS value of random vibration acceleration.

[0085] (7) Random vibration test spectrum compilation

[0086] The root mean square value G of the upper limit spectrum of acceleration power in each region RMS and Figure 5 The data in is input and calculated by using formula (5) to formula (8) Figure 5 The acceleration spectral density value W in Figure 5 As a random vibration test spectrum.

Claims

1. A method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft, characterized in that: The steps include: (1) Area division: The whole aircraft is divided into zones according to the structural characteristics of the aircraft, the density of equipment installation, the installation method of airborne equipment, and the vibration conditions of each test point; (2) Mission status division: Measure and obtain the actual vibration data of each mission profile of the aircraft, and divide each measured mission profile into typical mission states; (3) Construct the power spectrum envelope curve at each measuring point with a given confidence level; (4) Construct a spectrum summary of all measurement points in each region; (5) Establish a vibration environment prediction model; (6) Calculate the RMS value of the upper limit spectrum of the acceleration power spectrum in each region: Use the rising spectrum, the falling spectrum, and the flat spectrum to obtain the RMS value of the upper limit spectrum of the acceleration power spectrum in each region; (7) Preparation of random vibration test spectrum: After obtaining the root mean square value of the predicted upper limit spectrum of vibration and the upper limit spectrum of acceleration in each area, the random vibration specification spectrum of the vibration environment conditions is obtained as the vibration test condition.

2. The method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft according to claim 1, characterized in that: In step (1), the partitions include: fuselage area, wing area, horizontal tail area, vertical tail area, landing gear area, engine vicinity area and engine area; the fuselage area is divided into 3 parts: front 1 / 4 area, middle 1 / 2 area and rear 1 / 4 area; the wing area is divided into 2 parts: inner 1 / 3 area and outer 2 / 3 area.

3. The method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft according to claim 1, characterized in that: In step (2), typical mission states are divided into: ground takeoff, takeoff acceleration, climbing, air cruising, air combat, circling and descending, and ground landing.

4. The method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft according to claim 1, characterized in that: Step (3) is as follows: The Corey-Duquet method is used to directly perform fast Fourier transform on the original vibration data to obtain the acceleration power spectrum density; all spectral line values ​​under the corresponding mission state of each test point in all flight sorties are extracted as sample values, and the spectral line value with the required confidence level is taken as the inductive vibration power spectrum envelope curve of a single test point.

5. The method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft according to claim 4, characterized in that: The sample values ​​are extracted based on equations (1) to (3): According to formula (1), the feature samples Each spectral line corresponds to Take the mean variance estimate According to formula (2), the average of adjacent spectral lines With variance Calculate the statistic F n (k,k+1) and t n (k,k+1) Assuming that the PSDs of adjacent spectral lines k and k+1 of the characteristic sample belong to the same population, then F n (k,k+1) is subject to the degree of freedom (Q p -1,Q p -1) of the F distribution, t n (k,k+1) is subject to 2 degrees of freedom (Q p -1) central t distribution; Under a given confidence level (1-α), if equation (3) holds, the assumption holds and the PSDs of adjacent spectral lines k and k+1 of the feature sample belong to the same population, otherwise they do not belong to the same population.

6. The method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft according to claim 4, characterized in that: Before processing the original vibration data, the stationarity, ergodicity, periodicity and normality of the vibration data are tested to confirm that the vibration data to be summarized are ergodic random signals.

7. The method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft according to claim 5, characterized in that: Step (4) is as follows: Based on the confidence power envelope spectrum required by each region, the power spectrum envelope values ​​of all measuring points in each region are used to obtain the inductive spectrum of the corresponding region according to equations (1) to (3); Select the characteristic value points on the spectrum, and connect the characteristic points in sequence in the power spectrum diagram to obtain a multi-line spectrum, which is the summarized regional vibration power spectrum.

8. The method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft according to claim 1, characterized in that: Step (5) is as follows: conduct a vibration and flight parameter correlation analysis, then conduct a flight status analysis, and finally establish a vibration environment prediction model; Vibration and flight parameter correlation analysis: Analyze the correlation between dynamic pressure and engine speed and the vibration of each channel of the aircraft to determine the key factors affecting the vibration of different areas of the aircraft; Flight state analysis: Analyze the maximum dynamic pressure in the design limit state and the maximum dynamic pressure in actual flight according to the flight envelope and typical mission profile of the jet aircraft, establish a prediction model of vibration magnitude and dynamic pressure, and predict the vibration magnitude in the limit state; Establish a vibration environment prediction model: calculate the vibration root mean square value of the power spectrum density in the frequency range of 15 to 2000 Hz; A linear fitting prediction model is established for the vibration root mean square value and dynamic pressure. The linear fitting prediction formula is: V=k*q+b (4) Where V is the root mean square value of vibration, q is the dynamic pressure; Through linear regression calculation, the values ​​of equation k and b are obtained, and then the predicted model equation of the relationship between the vibration root mean square value and the dynamic pressure is obtained; According to the fitting formula of the relationship between the root mean square value of vibration and the dynamic pressure, the dynamic pressure of the aircraft in the limit state is substituted into the corresponding fitting formula to obtain the estimated value of the root mean square value of vibration, thereby obtaining the upper limit spectrum of the estimated acceleration power spectrum of each area of ​​the whole aircraft.

9. The method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft according to claim 1, characterized in that: The calculation of step (6) is as follows: <h2 style=";text-align:left;direction:ltr">A2 = W0Δf = W0(f1-f<h2 style=";text-align:left;direction:ltr"> b <h2 style=";text-align:left;direction:ltr"> ) (6) Where: A1 is the acceleration spectrum density curve W(f) and frequency f b -f a The area enclosed by the axis; A2 is the acceleration spectral density value W0 and the frequency f1-f b A3 is the area enclosed by the acceleration spectral density curve W(f) and the frequency f2-f1 axis; m=N / 3, N is the slope of the spectrum line; G RMS is the total RMS value of random vibration acceleration.

10. The method for compiling a vibration environment spectrum of airborne equipment of a jet aircraft according to claim 9, characterized in that: If N=3 and m=1, the descent spectrum calculation formula is used.

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