Method for determining the suitability of airborne suspension reliability tests based on vibration tests

Abstract

The application provides a method for determining adaptability of airborne suspension reliability test based on vibration test, which comprises the following steps: determining vibration stress V1 and duration T1 of weak position in airborne suspension vibration test process, and determining vibration stress V2 and duration T2 of weak position in airborne suspension reliability test; determining the frequency band F1 with minimum margin in which vibration stress V1 covers vibration stress V2; performing vibration equivalence on vibration stress V1 and duration T1 in frequency band F1 to obtain TY1; performing vibration equivalence on vibration stress V2 and duration T2 in frequency band F1 to obtain TY2; if TY1 is not less than TY2, it is predicted that the airborne suspension can meet the requirements of airborne suspension reliability test after airborne suspension vibration test. The application can determine the adaptability of airborne suspension reliability test by comparing vibration stresses of typical frequency bands according to the weak position of airborne suspension in vibration test and reliability test.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of reliability test, and relates to a method for determining adaptability of airborne suspension reliability test based on vibration test. BACKGROUND

[0002] The airborne suspension generally needs to be subjected to vibration test and reliability test before flight test. The vibration cumulative time of the reliability test is long, but sometimes only one airborne suspension can be used for test due to test fund, if the airborne suspension expires during the test, the test cannot be completed, in order to avoid this situation, the design margin needs to be increased, which causes the design cost to increase. Whether to increase the design margin is mainly based on the judgment of the adaptability of the aircraft reliability test. SUMMARY

[0003] The purpose of the application is to at least solve one of the problems in the prior art.

[0004] To this end, the application provides a method for determining adaptability of airborne suspension reliability test based on vibration test, which can determine the adaptability of the airborne suspension reliability test by comparing the vibration stresses of typical frequency bands according to the weak positions of the airborne suspension in the vibration test and the reliability test of the airborne suspension.

[0005] The technical solution of the application is:

[0006] A method for determining adaptability of airborne suspension reliability test based on vibration test, the specific steps of the determination method are:

[0007] Step 1, according to the weak position A1 on the airborne suspension, the vibration stress V1 and the duration T1 of the weak position A1 during the airborne suspension flight vibration test, and the vibration stress V2 and the duration T2 of the weak position A1 during the airborne suspension flight reliability test of multiple different vibration magnitudes are determined respectively; wherein the maximum vibration magnitude of the weak position A1 during the airborne suspension flight reliability test is Vmax';

[0008] Step 2, determine the frequency band F1 with the minimum margin of vibration stress V1 covering vibration stress V2;

[0009] Step 3, vibration equivalent is performed on the vibration stress V1 and the duration T1 of the airborne suspension flight vibration test in the frequency band F1 to determine the equivalent time TY1=(V1 / Vmax') of the maximum vibration magnitude Vmax' of the airborne suspension flight reliability test 4 ×T1;

[0010] Vibration stress V2 and duration T2 of airborne suspension flying reliability test in frequency band F1 are vibrationally equivalent, to determine the equivalent time TY2=(V2 / Vmax')×T2 of the maximum vibration level Vmax' of airborne suspension flying reliability test. 4

[0011] If TY1 is not less than TY2, it is predicted that the airborne suspension can meet the flying reliability test requirements after flying vibration test, that is, a new airborne suspension can pass the flying reliability test; if TY1 is less than TY2, it cannot be predicted whether the airborne suspension can meet the flying reliability test requirements after flying vibration test.

[0012] Further, in step three, if TY1 is less than TY2, it cannot be predicted whether the airborne suspension can meet the flying reliability test requirements after flying vibration test, the equivalent time of the airborne suspension self-flying vibration test is increased, and then it is judged, which is specifically:

[0013] Step 1, determine the vibration stress V3 and duration T3 of the weak position A1 in the airborne suspension self-flying vibration test process;

[0014] Step 2, vibrationally equivalent vibration stress V3 and duration T3 in frequency band F1 to determine the equivalent time TY3=(V3 / Vmax')×T3 of the maximum vibration level Vmax' of airborne suspension flying reliability test. 4

[0015] If the sum of TY1 and TY3 is not less than TY2, it is predicted that the airborne suspension can meet the flying reliability test requirements after flying vibration test and self-flying vibration test, that is, a new airborne suspension can pass the flying reliability test; if the sum of TY1 and TY3 is less than TY2, it cannot be predicted whether the airborne suspension can meet the flying reliability test requirements according to the vibration test.

[0016] Further, when it is predicted that the airborne suspension can meet the flying reliability test requirements after flying vibration test, the limiting method of flying reliability test is determined:

[0017] Step 1), the weak position A1 is determined as the limiting point position of airborne suspension flying reliability test;

[0018] Step 2), the limiting strategy of the limiting point position A1 of airborne suspension flying reliability test is determined, which is that the vibration acceleration power spectrum at the limiting point position A1 cannot exceed (TY1 / TY2) times of V2. 1 / 4

[0019] ​​​Further, when it is predicted that the airborne suspension can meet the requirements of the flight reliability test through the flight vibration test and the autonomous flight vibration test, the limiting method of the flight reliability test is determined:

[0020] Step 1), determining the weak position A1 as the limiting point position of the flight reliability test of the airborne suspension;

[0021] Step 2), determining the limiting strategy of the limiting point position A1 of the flight reliability test of the airborne suspension, and the limiting strategy is that the vibration acceleration power spectrum at the limiting point position A1 cannot exceed ((TY1+TY3) / TY2) of V2 1 / 4 times.

[0022] Further, when it is not possible to predict whether the requirements of the flight reliability test can be met according to the vibration test of the airborne suspension, the number requirement of the airborne suspension for the flight reliability test is further determined, that is, the total flight reliability test time is shared by increasing the number of airborne suspensions, so that the airborne suspensions after the number is increased can pass the flight reliability test;

[0023] Wherein, when the number requirement of the airborne suspension for the flight reliability test is determined, the calculation result of TY2 / (TY1+TY3) is rounded up as the number requirement of the airborne suspension for the flight reliability test.

[0024] Further, when it is not possible to predict whether the requirements of the flight reliability test can be met according to the vibration test of the airborne suspension, the life time of the airborne suspension during the flight reliability test is further determined, and then the airborne suspension is replaced after the life time, or the subsequent failure is not regarded as a responsible failure;

[0025] Wherein, the method for determining the life time of the airborne suspension during the flight reliability test is:

[0026] Step (1), determining the maximum vibration equivalent time TYP of a single test profile of the flight reliability test TYP=(VP / Vmax') 4 ×TP;

[0027] Step (2), determining the whole cycle number N2 of the life time, and N2 is the calculation result of (TY1+TY3) / TYP rounded down;

[0028] Step (3), determining the remaining equivalent time Tr=TY1+TY3-TYP*N2;

[0029] Step (4), determining the cycle number N3 corresponding to the remaining equivalent time:

[0030] According to the vibration application sequence of the single test profile of the hanging flight reliability test, the equivalent vibration time of each vibration stress is calculated and accumulated in turn, and when the accumulated equivalent vibration time first exceeds Tr, the last vibration stress stage of the accumulated is recorded as T4 at the starting time of the corresponding single reliability test profile; the equivalent vibration ratio of Tr and the last vibration stress stage is recorded as Tu, the time corresponding to Tu is added to T4, and the ratio of (T4+Tu) to the duration of the single hanging flight reliability test profile is determined as N3.

[0031] Step (5), determining the time to life: the duration of the single test profile of the N2+N3 hanging flight reliability tests is taken as the time to life.

[0032] Further, in step one, the process of determining the vibration stress V1 and the duration T1 of the weak position A1 in the airborne suspension hanging flight vibration test is as follows:

[0033] Step a, collect the vibration test information required in the development process of the airborne suspension, including the vibration conditions, test time and control point position of the airborne suspension hanging flight vibration test;

[0034] Step b, according to the airborne suspension cabin section where the weak position A1 is located and the vibration conditions of the airborne suspension hanging flight vibration test collected in step a, determine the vibration stress V1 and the duration T1 of the airborne suspension cabin section where the weak position A1 is located.

[0035] Further, in step one, the process of determining the vibration stress V2 and the duration T2 of the weak position A1 in the airborne suspension hanging flight reliability test of multiple different vibration levels is as follows:

[0036] Step A, collect the test profile data of the airborne suspension hanging flight reliability test:

[0037] The test profile data includes: the vibration test conditions VP of each vibration level in the airborne suspension reliability test profile and the vibration duration TP of a single cycle; wherein the vibration test conditions VP of each vibration level include the maximum vibration Vmax, the weighted vibration Vint, the minimum vibration Vmin and the continuous vibration Vc; the vibration duration TP of a single cycle includes TP1, TP2, TP3 and TP4 corresponding to the vibration test conditions VP of each vibration level;

[0038] Step B, collect the test scheme data of the airborne suspension hanging flight reliability test;

[0039] The test scheme data includes: the test cycle number N and the control mode, and the control mode determines that the vibration level applied at the geometric center of the airborne suspension is the reference vibration level;

[0040] Step C, determine the vibration cumulative time TN in the airborne suspension hanging flight reliability test:

[0041] The airborne suspension hanging flight reliability test has multiple vibration levels, respectively maximum vibration Vmax, weighted vibration Vint, minimum vibration Vmin, and continuous vibration Vc, and the vibration cumulative times TN1, TN2, TN3, and TN4 corresponding to the four vibration levels are determined; wherein TN1=TP1*N, TN2=TP2*N, TN3=TP3*N, and TN4=TP4*N.

[0042] Step D, according to the airborne suspension cabin section where the weak position A1 is located and the test scheme data collected in step B, the vibration stress V2 and the duration T2 of the airborne suspension cabin section where the weak position A1 is located are determined.

[0043] According to the vibration level applied by the geometric center of the airborne suspension determined in step B as the reference vibration level, the vibration level at the weak position A1 of the airborne suspension A is increased based on the reference vibration level, so that the vibration stress V2 includes the maximum vibration Vmax', the weighted vibration Vint', the minimum vibration Vmin', and the continuous vibration Vc', and the duration T2 includes TN1, TN2, TN3, and TN4 corresponding to the maximum vibration Vmax', the weighted vibration Vint', the minimum vibration Vmin', and the continuous vibration Vc'.

[0044] Further, the frequency band F1 in step two is: the frequency band corresponding to the minimum difference between the acceleration power spectrum density of the vibration stress V1 and the acceleration power spectrum density of the vibration stress V2 is determined as F1.

[0045] Further, the TY2=TN1+(Vint' / Vmax') 4 ×TN2+(Vmin' / Vmax') 4 ×TN3+(Vc' / Vmax') 4 ×TN4.

[0046] By applying the above technical solution, the present application has the following beneficial effects:

[0047] (1) Considering that the fatigue damage caused by vibration in the reliability test is the main reason for the failure of the test piece, the present application first proposes a specific method for predicting whether the airborne suspension can meet the hanging flight reliability test requirements after passing the vibration test by comparing the vibration test conditions of the airborne suspension with the reliability test conditions,

[0048] That is, by using the vibration test of the airborne suspension and the predicted value of the reliability test, the airborne suspension is predicted whether it can meet the requirements of the flight reliability test after the vibration test, and then the adaptability of the airborne suspension reliability test is determined, the method is suitable for the airborne suspension of long time flight, the test pieces (i.e. airborne suspension) can be produced according to the reliability test product (i.e. airborne suspension) determined by the evaluation before the flight reliability test is implemented, when the number of flight reliability test pieces is insufficient, the life time of the test product can be determined in advance, which provides a basis for determining whether the test failure is a responsible failure, and the airborne suspension product can be improved in design to enhance the adaptability of the product to the flight reliability test, so as to reduce the demand for the number of test pieces, and then reduce the test cost. The present application fills the gap of determining the number of flight reliability test pieces, optimizing the test limit scheme, and determining the life time by comparing the flight vibration conditions of the airborne suspension with the reliability test conditions, and can be popularized to the flight reliability test of various airborne suspensions.

[0049] (2) The present application first proposes a method for comparing the vibration test conditions of the airborne suspension with the reliability test conditions, when the airborne suspension can meet the requirements of the flight reliability test after the vibration test, the limit method of the flight reliability test is determined, which can provide a reasonable limit strategy for the implementation of the flight reliability test, and ensure that the airborne suspension can complete the test without unreasonable excessive test during the implementation of the reliability test, and then the expected number of airborne suspensions can complete the flight reliability test.

[0050] (3) The present application first proposes a method for comparing the vibration test conditions of the airborne suspension with the reliability test conditions, when the airborne suspension cannot be predicted whether it can meet the requirements of the flight reliability test according to the vibration test, the method for determining the number of airborne suspensions required for the flight reliability test is determined, which provides a reasonable basis for the production preparation of the product by further determining the number of airborne suspensions required for the flight reliability test.

[0051] (4) The present application first proposes a method for comparing the vibration test conditions of the airborne suspension with the reliability test conditions, when the airborne suspension cannot be predicted whether it can meet the requirements of the flight reliability test according to the vibration test, the method for determining the life time of the airborne suspension in the flight reliability test is determined, which provides a basis for timely replacement of test pieces and failure judgment of life time by determining the life time of the product in the flight reliability test. BRIEF DESCRIPTION OF DRAWINGS

[0052] The accompanying drawings, which are included to provide a further understanding of the embodiments of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:

[0053] Figure 1 Flowchart of the process of the present application. DETAILED DESCRIPTION

[0054] It should be noted that the embodiments and features of the application herein disclosed can be used in any combination, without mutual limitation, unless the context implies otherwise. The embodiments presented herein are described below with reference to the accompanying drawings. The description is made with reference to the accompanying drawings, in which:

[0055] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0056] The relative arrangement of parts and steps, numerical expressions, and numerical values set forth in the examples are not intended to limit the scope of the application unless specifically so stated. It should be understood that the size, shapes and proportions of the parts shown in the drawings are not necessarily to scale. Techniques, methods, and devices known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered as part of the description of the application. In all examples shown and discussed herein, any specific value should be interpreted as merely an example, and not as a limitation. Thus, other examples of the exemplary embodiments can have different values. It should be noted that like reference numerals and letters refer to like items in the following drawings, and thus, once an item is defined in one drawing, it need not be discussed further in subsequent drawings.

[0057] Example 1:

[0058] For the calculation of airborne suspension hanging flight reliability test conditions, GJB899A stipulates the method for establishing the flight reliability test profile of airborne weapons and combined external hanging and its equipment, which is the main method for determining the reliability test conditions of airborne suspension at present. In the implementation of airborne suspension hanging flight reliability test, the calculated vibration conditions are taken as the vibration conditions of the geometric center of airborne suspension, and the vibration levels of each part of airborne suspension are controlled according to the linear relationship of head-3dB and tail+3dB along the length direction of airborne suspension.

[0059] The airborne suspension hanging flight vibration test includes hanging flight vibration durability test and hanging flight vibration function test. The vibration test conditions are determined according to relevant standards or model development experience. Different vibration test conditions are proposed for different cabin sections, generally two to three vibration test conditions. In recent years, the hanging flight life of airborne suspension is getting higher and higher, and the corresponding hanging flight vibration durability test time is getting longer and longer. The cumulative vibration test time in reliability test does not change much, and the hanging flight vibration level has coverage for the reliability vibration spectrum type, which provides the basis for evaluating the adaptability of airborne suspension reliability test according to the environmental test results.

[0060] Based on these technical foundations, the embodiment proposes a method for determining the adaptability of airborne suspension reliability test based on vibration test. According to the weak position of airborne suspension in vibration test (i.e. airborne suspension hanging flight vibration test and airborne suspension self-flight vibration test) and reliability test, the adaptability of airborne suspension reliability test is analyzed and determined by comparing the vibration stress of typical frequency band. See the attached Figure 1 The specific steps of the determination method are as follows:

[0061] Firstly, collect the vibration test information required in the development process of airborne suspension, including the vibration conditions, test time and control point position of airborne suspension hanging flight vibration test, and the vibration conditions, test time and control point position of airborne suspension self-flight vibration test.

[0062] Secondly, determine the weak position A1 in the process of airborne suspension hanging flight reliability test. In this embodiment, the direct connection between the cabin section of airborne suspension and the front and rear vibration clamps is selected as the weak position.

[0063] Thirdly, determine the vibration stress V1 (including frequency and acceleration power spectral density) and duration T1 of the weak position A1 in the process of airborne suspension hanging flight vibration test. The specific process is as follows: according to the cabin section of airborne suspension where the weak position A1 is located and the vibration conditions of airborne suspension hanging flight vibration test collected in the first step, the vibration stress V1 and duration T1 of the cabin section of airborne suspension where the weak position A1 is located are determined.

[0064] The fourth step is to collect test profile data of the airborne suspension hanging flight reliability test;

[0065] The test profile data includes vibration test conditions VP of each vibration level in the airborne suspension hanging flight reliability test profile and vibration duration TP of a single cycle; wherein the vibration test conditions VP of each vibration level includes maximum vibration Vmax, weighted vibration Vint, minimum vibration Vmin and continuous vibration Vc; the vibration duration TP of a single cycle includes TP1, TP2, TP3 and TP4 corresponding to the vibration test conditions VP of each vibration level;

[0066] The fifth step is to collect test scheme data of the airborne suspension hanging flight reliability test;

[0067] The test scheme data includes test cycle number N and control mode, and the control mode determines that the vibration level applied by the geometric center of the airborne suspension is the reference vibration level;

[0068] The sixth step is to determine vibration cumulative time TN in the airborne suspension hanging flight reliability test:

[0069] Since the airborne suspension hanging flight reliability test has multiple vibration levels, there are four vibration levels in the embodiment, which are maximum vibration Vmax, weighted vibration Vint, minimum vibration Vmin and continuous vibration Vc, and vibration cumulative times TN1, TN2, TN3 and TN4 corresponding to the four vibration levels are determined; wherein TN1=TP1*N, TN2=TP2*N, TN3=TP3*N and TN4=TP4*N,

[0070] The seventh step is to determine vibration stress V2 and duration T2 of the weak position A1 in the airborne suspension hanging flight reliability test, and the specific process is: according to the airborne suspension cabin section where the weak position A1 is located and the test scheme data collected in the fifth step, the vibration stress V2 and duration T2 of the airborne suspension cabin section where the weak position A1 is located are determined;

[0071] According to the reference vibration level applied by the geometric center of the airborne suspension determined in the fifth step, the vibration level at the weak position A1 of the airborne suspension A is adjusted on the basis of the reference vibration level, so that the vibration stress V2 includes maximum vibration Vmax', weighted vibration Vint', minimum vibration Vmin' and continuous vibration Vc', and the duration T2 includes TN1, TN2, TN3 and TN4 corresponding to the maximum vibration Vmax', the weighted vibration Vint', the minimum vibration Vmin' and the continuous vibration Vc' one by one;

[0072] The eighth step is to determine the frequency band F1 with the minimum margin in which the vibration stress V1 covers the vibration stress V2, and the specific process is as follows: the vibration stress V1 covers the vibration stress V2 in the whole frequency band, and the frequency band corresponding to the minimum difference between the acceleration power spectrum density of the vibration stress V1 and the acceleration power spectrum density of the vibration stress V2 is determined as F1;

[0073] The ninth step is to first predict whether the airborne suspension meets the requirements of the flight reliability test, and the specific process is as follows:

[0074] The vibration stress V1 and the duration T1 of the airborne suspension flight vibration test in the frequency band F1 are subjected to vibration equivalence, and the equivalent time TY1 of the maximum vibration level Vmax' of the airborne suspension flight reliability test is determined as TY1=(V1 / Vmax') 4 ×T1;

[0075] The vibration stress V2 and the duration T2 of the airborne suspension flight reliability test in the frequency band F1 are subjected to vibration equivalence, and the equivalent time TY2 of the maximum vibration level Vmax' of the airborne suspension flight reliability test is determined as TY2=(V2 / Vmax') 4 ×T2;

[0076] In this embodiment, since the flight reliability test has four vibration levels, the equivalent time is calculated respectively, and then TY2=TN1+(Vint' / Vmax') 4 ×TN2+(Vmin' / Vmax') 4 ×TN3+(Vc' / Vmax') 4 ×TN4;

[0077] If TY1 is not less than TY2, it is predicted that the airborne suspension can meet the requirements of the flight reliability test after passing the flight vibration test, that is, a new airborne suspension can pass the flight reliability test; if TY1 is less than TY2, it is not possible to predict whether the airborne suspension can meet the requirements of the flight reliability test after passing the flight vibration test, and the tenth step is jumped to for further judgment.

[0078] The tenth step is to determine the vibration stress V3 and the duration T3 of the weak position A1 in the airborne suspension autonomous flight vibration test, and the specific process is as follows: according to the airborne suspension cabin section where the weak position A1 is located and the vibration conditions of the airborne suspension autonomous flight vibration test collected in the first step, the vibration stress V3 and the duration T3 of the airborne suspension cabin section where the weak position A1 is located are determined.

[0079] The eleventh step is to secondly predict whether the airborne suspension meets the requirements of the reliability test, and the specific process is as follows:

[0080] Within frequency band F1, the vibration stress V3 and duration T3 are subjected to vibration equivalent analysis to determine the equivalent time TY3 = (V3 / Vmax') for the maximum vibration magnitude Vmax' in the reliability test of the airborne suspended object. 4 ×T3;

[0081] If the sum of TY1 and TY3 is not less than TY2, it is expected that after the airborne suspension passes the attached flight vibration test and the autonomous flight vibration test, the airborne suspension design can meet the requirements of the attached flight reliability test, that is, a new airborne suspension can pass the attached flight reliability test; if the sum of TY1 and TY3 is less than TY2, it is impossible to predict whether the requirements of the attached flight reliability test are met based on the vibration test of the airborne suspension (including the attached flight vibration test and the autonomous flight vibration test).

[0082] In one embodiment, once it is anticipated that the airborne suspension will meet the requirements for flight reliability testing after passing vibration tests (i.e., by passing a flight-on-hook vibration test or by passing both a flight-on-hook vibration test and an autonomous flight vibration test), the limiting methods for flight reliability testing can be further determined:

[0083] Step 1: Determine the weak point A1 as the limiting point location for the reliability test of the airborne suspended object during flight;

[0084] Step 2: Determine the limiting strategy for the limiting point location A1 of the airborne suspended object flight reliability test. The limiting strategy is as follows:

[0085] When the airborne suspended object is expected to pass the airborne vibration test, the vibration acceleration power spectrum at the limiting point A1 must not exceed (TY1 / TY2) of V2. 1 / 4 When the airborne suspended object is expected to pass the attached flight vibration test and the autonomous flight vibration test, the vibration acceleration power spectrum at the limit point A1 must not exceed ((TY1+TY3) / TY2) of V2. 1 / 4 times.

[0086] In one embodiment, when it is impossible to predict whether the requirements for flight reliability testing are met based on the vibration test of the airborne suspension, the quantity requirement of the airborne suspension for flight reliability testing can be further determined. That is, the total flight reliability testing time can be distributed by increasing the quantity of airborne suspension, so that the increased number of airborne suspensions can pass the flight reliability testing.

[0087] When determining the quantity requirement of airborne suspension for the flight reliability test, the calculation result of TY2 / (TY1+TY3) is rounded up (i.e., rounded to the nearest integer) as the quantity requirement of airborne suspension for the flight reliability test.

[0088] In another embodiment, when it is unable to predict whether the suspension reliability test requirements are met according to the airborne suspension vibration test, the life time of the airborne suspension during the suspension reliability test is further determined, and then the airborne suspension is replaced after the life time, or the subsequent failure is not regarded as a responsibility failure;

[0089] The method for determining the life time of the airborne suspension during the suspension reliability test comprises the following steps:

[0090] Step one, determining the maximum vibration equivalent time TYP of a single test profile (i.e. a single cycle) of the suspension reliability test;

[0091] The equivalent time TYP corresponding to the maximum vibration level Vmax' of the suspension reliability test is determined as TYP=(VP / Vmax') 4 ×TP

[0092] In this embodiment, since the suspension reliability test has four vibration levels, the equivalent times are calculated respectively, TYP1=TP1, TYP2=(Vint' / Vmax') 4 ×TP2, TYP3=(Vmin' / Vmax') 4 ×TP3, TYP4=(Vc' / Vmax') 4 ×TP4, and TYP=TYP1+TYP2+TYP3+TYP4.

[0093] Step two, determining the whole cycle number N2 of the life time:

[0094] The calculation result of (TY1+TY3) / TYP is rounded down as the whole cycle number N2 included in the life time;

[0095] Step three, determining the remaining equivalent time Tr:

[0096] TY1+TY3-TYP*N2 is taken as the remaining equivalent time Tr;

[0097] Step four, determining the cycle number N3 corresponding to the remaining equivalent time:

[0098] According to the vibration application sequence of the single test profile of the suspension reliability test, the equivalent vibration times of the vibration stresses are calculated and accumulated in sequence, and when the accumulated equivalent vibration time exceeds Tr for the first time, the last vibration stress stage of the accumulated is recorded as T4 at the starting time of the corresponding single reliability test profile; Tr and the equivalent vibration proportion of the last vibration stress stage are recorded as Tu, the time corresponding to Tu is added to T4, and the ratio of (T4+Tu) to the duration of the single suspension reliability test profile is determined as N3.

[0099] Step five, determine the life time: the duration of single test profile of N2+N3 airborne suspension reliability test is taken as the life time.

[0100] Embodiment 2

[0101] This embodiment provides an application example of the adaptive determination method of airborne suspension reliability test based on vibration test on the basis of embodiment 1, and the specific steps of the application example are as follows:

[0102] First step, collect the vibration test information required in the development process of airborne suspension, including the vibration conditions, test time, control point position of airborne suspension flight vibration test, and the vibration conditions, test time, control point position of autonomous flight vibration test of airborne suspension;

[0103] Second step, determine the weak position A1 in the process of airborne suspension flight reliability test, and the direct connection between the cabin section of airborne suspension and the front and rear vibration clamps is selected as the weak position in this embodiment.

[0104] Third step, determine the vibration stress V1 and the duration T1 of the weak position A1 in the process of airborne suspension flight vibration test, and the specific process is as follows: according to the cabin section of airborne suspension where the weak position A1 is located and the vibration conditions of airborne suspension flight vibration test collected in the first step, the vibration stress V1 of the cabin section of airborne suspension where the weak position A1 is located is determined as shown in Table 1, and the duration T1 is 15h.

[0105] Table 1

[0106]

[0107] Fourth step, collect the test profile data of airborne suspension flight reliability test.

[0108] The vibration test conditions VP of each value in the flight airborne suspension reliability test profile, and the power spectral density corresponding to each value of the vibration test conditions VP are shown in Table 2. In this embodiment, the vibration test conditions VP of each value include the maximum vibration Vmax and the weighted vibration Vint; the vibration duration of a single cycle corresponding to the maximum vibration Vmax and the weighted vibration Vint is TP1 and TP2 respectively, and the specific corresponding values are shown in the first to third columns of Table 3.

[0109] Table 2

[0110]

[0111] Table 3

[0112]

[0113] Step 5, collect the test scheme data of the airborne suspension hanging flight reliability test; the test scheme data includes: test cycle number N and control mode;

[0114] Test cycle number N = 40;

[0115] Control mode: the input value of the vibration stress in the reliability test is 0 dB at the geometric center of the airborne suspension, -3 dB at the head, and +3 dB at the tail. The vibration level of the airborne suspension is linearly distributed. The vibration level at the control point is determined by calculating the distance between the control point and the geometric center of the airborne suspension. The vibration level applied at the geometric center of the airborne suspension is the reference vibration level, which is the acceleration power spectral density W0 in Table 3. The acceleration power spectral density at the geometric center of the airborne suspension and the vibration duration of a single cycle are shown in columns 1-3 of Table 3.

[0116] Step 6: determine the vibration cumulative time TN in the airborne suspension hanging flight reliability test:

[0117] This embodiment has two vibration levels. The vibration cumulative time TN1 and TN2 corresponding to each vibration level are determined, TN1 = TP1 * N, TN2 = TP2 * N. The total duration in column 4 of Table 3 is shown in detail.

[0118] Step 7, determine the vibration stress V2 and duration T2 at the weak position A1 in the airborne suspension hanging flight reliability test. The specific process is: according to the airborne suspension cabin section where the weak position A1 is located and the test scheme data collected in step 5, the vibration stress V2 and duration T2 of the airborne suspension cabin section where the weak position A1 is located are determined.

[0119] In this embodiment, the vibration level at the geometric center of the airborne suspension in the airborne suspension hanging flight reliability test is the maximum vibration Vmax and the weighted vibration Vint, respectively. Therefore, the vibration stress V2 at the weak position A1 of the airborne suspension is 0.8 dB (corresponding to 1.2 times power spectral density amplification) of the reference vibration level. The vibration stress V2 at the weak position A1 of the airborne suspension includes the maximum vibration Vmax' and the weighted vibration Vint'. The acceleration power spectral density corresponding to the maximum vibration Vmax' and the weighted vibration Vint' is 1.2 times the power spectral density of the maximum vibration Vmax and the weighted vibration Vint. The duration T2 at the weak position A1 of the airborne suspension is the total duration corresponding to the maximum vibration Vmax' and the weighted vibration Vint', which is equal to TN1 and TN2 in Table 3. Details are shown in Table 4.

[0120] Table 4

[0121]

[0122] The eighth step is to determine the frequency band F1 with the minimum margin that the vibration stress V1 covers the vibration stress V2. The specific process is as follows: the vibration stress V1 covers the vibration stress V2 in the whole frequency band, and the frequency band corresponding to the minimum difference between the acceleration power spectral density of the vibration stress V1 and the acceleration power spectral density of the vibration stress V2 is determined as F1. In the vibration stress V1 (i.e., Table 1) of the embodiment, the frequency is divided into three frequency bands, i.e., a 20-220 Hz frequency band, a 220-300 Hz frequency band, and a 300-2000 Hz frequency band;

[0123] (1) The acceleration power spectral density corresponding to the 20-220 Hz frequency band is 0.02 g 2 / Hz, and the difference between the acceleration power spectral density corresponding to the 20-220 Hz frequency band of the vibration stress V2 (i.e., Table 2) and the acceleration power spectral density corresponding to the 20-220 Hz frequency band of the vibration stress V1 is as follows:

[0124]

[0125]

[0126] When W0=0.01 g 2 / Hz, the minimum value of formula (1) is 0.01 g 2 / Hz corresponding to 200-220 Hz; when W0=0.004 g 2 / Hz, the minimum value of formula (1) is 0.016 g 2 / Hz corresponding to 200-220 Hz.

[0127] (2) The acceleration power spectral density corresponding to the 220-300 Hz frequency band is 0.007 g 2 / Hz, and the difference between the acceleration power spectral density corresponding to the 220-300 Hz frequency band of Table 2 and the acceleration power spectral density corresponding to the 220-300 Hz frequency band of the vibration stress V1 is as follows:

[0128] 0.007-W0 or W0-0.007 Formula (2)

[0129] When W0=0.01 g 2 / Hz, formula (2) is 0.003 g 2 / Hz; when W0=0.004 g 2 / Hz, formula (2) is 0.003 g 2 / Hz.

[0130] (3) The acceleration power spectral density corresponding to the 300-2000 Hz frequency band is 0.015 g 2 / Hz, and the difference between the acceleration power spectral density corresponding to the 300-2000 Hz frequency band of Table 2 and the acceleration power spectral density corresponding to the 300-2000 Hz frequency band of the vibration stress V1 is as follows:

[0131] 0.015-W0 Formula (3)

[0132] When W0=0.01 g 2 ​Hz, formula (2) is 0.005g 2 Hz; when W0=0.004g 2 Hz, formula (3) is 0.011g 2 Hz;

[0133] Therefore, according to the calculation result, the minimum value 0.003g 2 Hz of the difference is selected as F1 corresponding to the frequency band of 220-300Hz;

[0134] The ninth step is to first predict whether the airborne suspension meets the requirements of the airborne reliability test, and the specific process is as follows:

[0135] The vibration stress V1 and the duration T1 of the airborne suspension in the airborne vibration test in the frequency band of 220-300Hz are vibrationally equivalent, and the equivalent time TY1=(V1 / Vmax') of the maximum vibration level Vmax' of the airborne suspension reliability test is determined. 4 ×T1= (0.007 / 0.012) 4 ×15*60=104min.

[0136] The vibration stress V2 and the duration T2 of the airborne suspension reliability test are vibrationally equivalent, and the equivalent time TY2=(V2 / Vmax') of the maximum vibration level Vmax' of the airborne suspension reliability test is determined. 4 ×T2, since the reliability test has two vibration levels, TY2=TN1+(Vint' / Vmax') 4 ×TN2=40+(0.0048 / 0.012) 4 ×4800=162.88min;

[0137] The results show that TY1 is less than TY2, and it is not possible to predict whether the airborne suspension can meet the requirements of the airborne reliability test after the airborne vibration test, and the tenth step is jumped to for further judgment.

[0138] The tenth step is to determine the vibration stress V3 and the duration T3 of the weak position A1 in the airborne suspension during the autonomous flight vibration test, and the specific process is as follows: according to the airborne suspension cabin section where the weak position A1 is located, and the vibration conditions of the airborne suspension autonomous flight vibration test collected in the first step, the V3 of the F1 frequency band of the airborne suspension cabin section where the weak position A1 is located is determined to be 0.03g 2 / Hz, and the duration T3 is 2min, as shown in Table 5.

[0139] Table 5

[0140] Frequency Hz Power spectral density g 2 / Hz 20～400 0.03

[0141] The tenth step is to predict whether the airborne suspension meets the reliability test requirements for the second time, and the specific process is as follows:

[0142] The vibration stress V3 and the duration T3 are vibrationally equivalent in the frequency band F1 to determine the equivalent time TY3 of the maximum vibration level Vmax' of the weak position A1 corresponding to the airborne suspension flight reliability test = (V3 / Vmax') 4 × T3 = (0.03 / 0.012) 4 × 2 = 78 min.

[0143] The results show that the sum of TY1 and TY3 (104+78=182 min) is not less than TY2 (162.88 min), so it is predicted that the airborne suspension can meet the flight reliability test requirements after passing the flight vibration test and the autonomous flight vibration test, that is, one new airborne suspension can be used to pass the subsequent flight reliability test.

[0144] In one embodiment, when it is predicted that the airborne suspension can meet the flight reliability test requirements after passing the vibration test (i.e., passing the flight vibration test or passing the flight vibration test and the autonomous flight vibration test), the limiting method of the flight reliability test can be further determined:

[0145] Step one, the weak position A1 is determined as the limiting point position of the airborne suspension flight reliability test;

[0146] Step two, the limiting strategy of the limiting point position A1 of the airborne suspension flight reliability test is determined, and the limiting strategy is that the vibration acceleration power spectrum at the limiting point position A1 cannot exceed ((TY1+TY3) / TY2) of V2 1 / 4 = (182 / 162.88) 1 / 4 = 1.03 times.

[0147] In one embodiment, when it is not possible to predict whether the airborne suspension meets the flight reliability test requirements according to the vibration test of the airborne suspension, the number requirement of the airborne suspension for the flight reliability test can be further determined, that is, the number of airborne suspensions is increased so that the airborne suspensions after the number is increased can pass the flight reliability test; taking TY2=162.88 min and TY2 / (TY1+TY3)=1.2 as an example, that is, assuming TY1+TY3=135.73 mm, which is less than TY2 (162.88 min);

[0148] Wherein, when determining the quantity requirement of airborne suspension of the flight reliability test, the result of TY2 / (TY1+TY3) is rounded up (i.e. rounding up to the larger one), and the result is 2, i.e. the quantity requirement of airborne suspension of the flight reliability test is 2, and the total number of airborne suspension of the flight reliability test is 2.

[0149] In another embodiment, when it is unable to predict whether the flight reliability test requirement is met according to the airborne suspension vibration test, the life time of the airborne suspension in the flight reliability test process can be further determined, and then the airborne suspension is replaced after the life time, or the subsequent failure is not regarded as a responsibility failure;

[0150] Taking TY2=162.88min and TY2 / (TY1+TY3)=1.2 as an example:

[0151] Step one, determining the maximum vibration equivalent time TYP of a single test profile (i.e. a single cycle) of the flight reliability test;

[0152] For multiple vibration levels (see Table 6) included in a single test profile of the flight reliability test, the equivalent time is calculated respectively:

[0153] Table 6

[0154]

[0155] TYP1=TP1=1min

[0156] TYP2=(Vint' / Vmax') 4 ×TP2=(0.0048 / 0.012) 4 ×120=3.07min

[0157] TYP=TYP1+TYP2=4.07min;

[0158] Step two, determining the whole cycle number N2 of the life time:

[0159] Calculating (TY1+TY3) / TYP=162.88 / 1.2 / 4.07=33.35; the calculation result is 33.35, and the whole cycle number N2=33 is rounded down as the life time.

[0160] Step three, determining the remaining equivalent time Tr:

[0161] Calculating TY1+TY3-TYP*N2=162.88 / 1.2-4.07*33=1.42;

[0162] The calculation result is 1.42, and the remaining equivalent time Tr=1.42min.

[0163] Step four, determine the cycle number N3 corresponding to the remaining equivalent time:

[0164] Table 7 Vibration application sequence of single hang test profile

[0165] Vibration timing Vibration type Equivalent vibration time 30 min No vibration 60 min Weighted vibration Vint 1.53 5 min 1 min Maximum vibration Vmax 1 min 60 min Weighted vibration Vint 1.53 5 min

[0166] According to the vibration application sequence of the single test profile of the hang test (see Table 7), the equivalent vibration time of each vibration stress is calculated and accumulated in turn, and when the accumulated equivalent vibration time first exceeds Tr, the last vibration stress stage accumulated at the starting time of the corresponding single reliability test profile is recorded as T4;

[0167] That is, if Tr is less than or equal to the equivalent vibration time of the first weighted vibration 1.535 min, the end of 30 min without vibration will be the starting time, if Tr is greater than the equivalent vibration time of the first weighted vibration 1.535 min and less than or equal to the equivalent vibration time of the first weighted vibration 1.535 min + the equivalent vibration time of the maximum vibration 1 min, the end of 60 min of the first weighted vibration will be the starting time, if Tr is greater than the equivalent vibration time of the first weighted vibration 1.535 min + the equivalent vibration time of the maximum vibration 1 min and less than or equal to the equivalent vibration time of the first weighted vibration 1.535 min + the equivalent vibration time of the maximum vibration 1 min + the equivalent vibration time of the second weighted vibration 1.535 min, the end of 1 min of the maximum vibration will be the starting time;

[0168] Therefore, in this embodiment, Tr = 1.42 min is less than the equivalent vibration time of the first weighted vibration (1.535 min), so the end of 30 min without vibration in the above table is taken as the starting time, that is, T4 = 30 min;

[0169] The equivalent vibration ratio of Tr and the last vibration stress stage is 1.42 / 1.535, and the vibration time corresponding to this stage is 1.42 / 1.535*60 = 55.505 min, and the ratio of (T4+55.505) = 85.505 to the duration of the single hang test profile (30+60+1+60 = 131 min) is 0.652, which is determined as N3.

[0170] Step twenty: determine the life time. The duration of the single test profile of the N2+N3 hang test reliability test (131 min) is taken as the life time, that is, the life time is (33+0.652)*131 / 60 = 74.47 h.

[0171] For purposes of the description hereinafter, the terms "upper", "lower", "right", "left", "rear", "front", "vertical" and "horizontal" as can be perceived herein relative to the accompanying drawings refer to the orientation of the components being described. However, it is to be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device described herein relative to the other device or structure is inverted, then a spatially relative term such as "above" can be interpreted as meaning "below" or "below" can be interpreted as meaning "above". The device can also be oriented in other ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. The devices can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0172] In addition, it should be pointed out that the use of "first", "second" and the like words to define parts, only for the convenience of the corresponding parts to be distinguished, as no further declaration, the above words have no special meaning, therefore can not be understood as limiting the scope of the present application.

[0173] The preferred embodiments of the present application have been described above with the aid of drawing only and are not limited to those preferred embodiments, and can be modified in various ways by those skilled in the art without departing from the spirit and technical scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the scope of the present application.

Claims

1. A method for determining adaptability of airborne suspension reliability testing based on vibration testing, characterized in that, The specific steps of the determination method are as follows: Step 1: According to the weak position A1 on the airborne suspension, the vibration stress V1 and the duration T1 of the weak position A1 during the airborne suspension flight vibration test are determined respectively, and the vibration stress V2 and the duration T2 of the weak position A1 during the airborne suspension flight reliability test of multiple different vibration levels are determined; wherein the maximum vibration level of the weak position A1 during the airborne suspension flight reliability test is Vmax'; Step 2: The frequency band F1 with the minimum margin of the vibration stress V1 covering the vibration stress V2 is determined; Step three, the vibration stress V1 and the duration T1 of the airborne suspension hanging flight vibration test in the frequency band F1 are vibrationally equivalent, and the equivalent time TY1=(V1 / Vmax')×T1 of the corresponding maximum vibration level Vmax' of the airborne suspension hanging flight reliability test is determined. 4 ×T1; The vibration stress V2 and the duration T2 of the airborne suspension hanging flight reliability test in the frequency band F1 are vibrationally equivalent, and the equivalent time TY2 = (V2 / Vmax') × T2 of the corresponding maximum vibration level Vmax' of the airborne suspension hanging flight reliability test is determined. 4 ×T2; If TY1 is not less than TY2, it is predicted that the airborne suspension can meet the requirements of the flight reliability test after the flight vibration test, that is, a new airborne suspension can pass the flight reliability test; if TY1 is less than TY2, it cannot be predicted whether the airborne suspension can meet the requirements of the flight reliability test after the flight vibration test.

2. The method of claim 1, wherein the method further comprises: In step three, if TY1 is less than TY2, it cannot be predicted whether the airborne suspension can meet the requirements of the flight reliability test after the flight vibration test, the equivalent time of the airborne suspension flight vibration test is increased, and then the judgment is made, which is specifically as follows: Step 1: The vibration stress V3 and the duration T3 of the weak position A1 during the airborne suspension flight vibration test are determined; Step 2, vibration stress V3 and duration T3 are vibrationally equivalent in frequency band F1 to determine the equivalent time TY3 = (V3 / Vmax') x T3 of the maximum vibration level Vmax' of airborne suspension hanging flight reliability test 4 ×T3; If the sum of TY1 and TY3 is not less than TY2, it is predicted that the airborne suspension can meet the requirements of the flight reliability test after the flight vibration test and the flight vibration test, that is, a new airborne suspension can pass the flight reliability test; if the sum of TY1 and TY3 is less than TY2, it cannot be predicted whether the airborne suspension can meet the requirements of the flight reliability test according to the vibration test of the airborne suspension.

3. The method of claim 1, wherein the method further comprises: When it is predicted that the airborne suspension can meet the requirements of the flight reliability test after the flight vibration test, the limiting method of the flight reliability test is determined: Step 1), the weak position A1 is determined as the limiting point position of the airborne suspension flight reliability test; Step 2), determine the limit strategy of the limit point position A1 of the airborne suspension hanging flight reliability test, which is that the vibration acceleration power spectrum at the limit point position A1 cannot exceed (TY1 / TY2) of V2 1 / 4 times.

4. The method of claim 2, wherein the method further comprises: When it is predicted that the airborne suspension can meet the requirements of the flight reliability test after the flight vibration test and the flight vibration test, the limiting method of the flight reliability test is determined: Step 1), the weak position A1 is determined as the limiting point position of the airborne suspension flight reliability test; Step 2), determining the limiting strategy of the limiting point position A1 of the airborne suspended object flight reliability test, which is that the vibration acceleration power spectrum at the limiting point position A1 cannot exceed ((TY1+TY3) / TY2) of V2 1 / 4 times.

5. The method of claim 2, wherein the method further comprises: When it cannot be predicted whether the airborne suspension can meet the requirements of the flight reliability test according to the vibration test of the airborne suspension, the number requirement of the airborne suspension for the flight reliability test is further determined, that is, the number of airborne suspensions is increased to share the total flight reliability test time, so that the airborne suspension after the number is increased can pass the flight reliability test; When it cannot be predicted whether the airborne suspension can meet the requirements of the flight reliability test according to the vibration test of the airborne suspension, the life time of the airborne suspension during the flight reliability test is further determined, and then the airborne suspension is replaced after the life time, or the subsequent failure is not regarded as a responsible failure; 6. The method of claim 2, wherein the method further comprises: ​ The method for determining the life time of the airborne suspension in the airborne suspension reliability test process is as follows: Step (1), determine the maximum vibration equivalent time TYPof the single test profile of the hang flight reliability test = (VP / Vmax') 4 x TP; Step (2), determining the whole cycle number N2 of the life time, N2 is the calculation result of (TY1+TY3) / TYP, and is rounded down; Step (3), determining the remaining equivalent time Tr=TY1+TY3-TYP*N2; Step (4), determining the cycle number N3 corresponding to the remaining equivalent time: According to the vibration application sequence of a single test profile of the airborne suspension reliability test, the equivalent vibration time of each vibration stress is calculated and accumulated in turn, and when the accumulated equivalent vibration time exceeds Tr for the first time, the last vibration stress stage of the accumulated is recorded as T4 at the starting time of the corresponding single reliability test profile; the equivalent vibration proportion of Tr and the last vibration stress stage is recorded as Tu, the time corresponding to Tu is added to T4, and the ratio of (T4+Tu) to the duration of a single airborne suspension reliability test profile is determined as N3; Step (5), determining the life time: the duration of a single test profile of N2+N3 airborne suspension reliability tests is taken as the life time.

7. The method according to any one of claims 1-5, wherein, In step one, the process of determining the vibration stress V1 and the duration T1 of the weak position A1 in the airborne suspension vibration test process is as follows: Step a, collecting vibration test information required in the development process of the airborne suspension, the vibration test information including vibration conditions, test time and control point position of the airborne suspension vibration test; Step b, according to the airborne suspension cabin section where the weak position A1 is located and the vibration conditions of the airborne suspension vibration test collected in step a, the vibration stress V1 and the duration T1 of the airborne suspension cabin section where the weak position A1 is located are determined.

8. The method of claim 1-5, wherein, In step one, the process of determining the vibration stress V2 and the duration T2 of the weak position A1 in the airborne suspension reliability test of multiple different vibration levels is as follows: Step A, collecting test profile data of the airborne suspension reliability test: The test profile data includes: vibration test conditions VP and vibration duration TP of a single cycle of each vibration level in the airborne suspension reliability test profile; wherein the vibration test conditions VP of each vibration level include maximum vibration Vmax, weighted vibration Vint, minimum vibration Vmin and continuous vibration Vc; the vibration duration TP of a single cycle includes TP1, TP2, TP3 and TP4 corresponding to the vibration test conditions VP of each vibration level; Step B, collecting test scheme data of the airborne suspension reliability test; The test scheme data includes: test cycle number N and control mode, and the control mode determines that the vibration level applied at the geometric center of the airborne suspension is the reference vibration level; Step C, determining the vibration accumulation time TN in the airborne suspension reliability test: The airborne suspension hanging flight reliability test has multiple vibration levels, respectively, maximum vibration Vmax, weighted vibration Vint, minimum vibration Vmin, and continuous vibration Vc, and the vibration cumulative times TN1, TN2, TN3, and TN4 corresponding to the four vibration levels are determined; wherein TN1=TP1*N, TN2=TP2*N, TN3=TP3*N, and TN4=TP4*N; Step D, according to the weak position A1 of the airborne suspension cabin section, and the test scheme data collected in step B, the vibration stress V2 and the duration T2 of the weak position A1 of the airborne suspension cabin section are determined; According to the vibration level applied by the geometric center of the airborne suspension determined in step B as the reference vibration level, the vibration level at the weak position A1 of the airborne suspension A is increased on the basis of the reference vibration level, so that the vibration stress V2 includes the maximum vibration Vmax', the weighted vibration Vint', the minimum vibration Vmin', and the continuous vibration Vc', and the duration T2 includes TN1, TN2, TN3, and TN4 corresponding to the maximum vibration Vmax', the weighted vibration Vint', the minimum vibration Vmin', and the continuous vibration Vc' one by one.

9. The method of claim 1-5, wherein, The frequency band F1 in step two is: the frequency band corresponding to the minimum difference between the acceleration power spectrum density of the vibration stress V1 and the acceleration power spectrum density of the vibration stress V2 is determined as F1.

10. The method of claim 8, wherein the method further comprises: said TY2 = TN1 + (Vint' / Vmax') 4 × TN2 + (Vmin' / Vmax') 4 × TN3 + (Vc' / Vmax') 4 × TN4.

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