A helicopter level flight performance test method and device

Abstract

The present invention provides a method and device for testing the level flight performance of a helicopter, the method comprising: determining the series n of the polynomial #imgabs0# describing the speed-torque curve; determining the series n and the maximum reference speed V according to the series n and the maximum reference speed V pef , determine the test flight speed point set; test flight, obtain the torque corresponding to each test flight speed point; according to the torque corresponding to each test flight speed point, obtain the coefficients of each term in the polynomial to obtain the speed-torque curve; wherein k is an integer from 0 to n, x indicates the speed, f(x) indicates the torque; a(k) is the coefficient of each term in the polynomial, #imgabs1# According to the Weierstrass approximation theorem, a series approximation method is used to approximate the level flight speed-torque continuous function curve. Only a few speed points need to be tested to determine the level flight speed-torque curve with high precision, which greatly saves the time cost and cost cost of the test flight.

Description

Technical Field

[0001] The invention belongs to the technical field of helicopter flight test, and in particular relates to a method and device for testing the level flight performance of a helicopter. Background Art

[0002] Helicopter test flight is a key link in the helicopter design process and an important step for the designed product to move from theory to practical use. Foreign experience shows that the test flight link accounts for more than half of the entire helicopter upgrade development cycle, and the cost accounts for 30%-50%. In order to ensure the smooth progress of helicopter test flights, a set of scientific, reasonable, simple and efficient test flight plans and methods are indispensable. Among them, the helicopter level flight performance test flight mainly verifies the helicopter's maximum level flight speed Vmax, maximum cruising speed Vcmax, level flight required torque and fuel consumption curve, etc. The commonly used test flight method is to fly back and forth at a certain speed interval at a specified altitude, scan each speed point between the minimum and maximum level flight speeds, and obtain the final speed-torque curve.

[0003] Since the flying speed of helicopters is between 0-300km / h (some high-speed helicopters even exceed 300km / h), the speed range is large and multiple speed points need to be divided for test flight. The traditional test flight uses a minimum speed interval of 20km / h, so at least 12 speed points need to be flown (excluding low-speed sections), and finally the least squares method is used to directly fit the data using a polynomial.

[0004] The accuracy of this method is positively correlated with the number of test flight speed points. If too few speed points are selected, the test results will be inaccurate and it will be difficult to draw conclusions. Too many speed points will extend the test time, and as fuel consumption increases, the error in the test results will gradually increase. Therefore, how to reasonably balance the relationship between the test cost and the accuracy of the test results is the main problem to be solved in the level flight performance test process. Summary of the invention

[0005] The invention provides a method and device for testing the level flight performance of a helicopter, which solves the problem that the prior art cannot balance the test cost and the accuracy of the test result.

[0006] The present invention provides a helicopter level flight performance test method, comprising:

[0007] Determine the polynomial that describes the speed-torque curve The number of series n;

[0008] According to the number of stages n and the maximum reference speed V pef , determine the test flight speed point set;

[0009] Perform a test flight at each test flight speed point in the test flight speed point set to obtain the torque corresponding to each test flight speed point;

[0010] According to the torque corresponding to each test flight speed point, the coefficients of each term in the polynomial are obtained to obtain a speed-torque curve;

[0011] Wherein, k is an integer from 0 to n, x indicates speed, f(x) indicates torque; a(k) is the coefficient of each term in the polynomial,

[0012] Optionally, the step number n and the maximum reference speed V pef , determine the test flight speed point set, including:

[0013] According to the number of stages n and the maximum reference speed V pef , using the formula Determine n+1 test flight speed points V k ;

[0014] According to the maximum reference speed V pef , determine a test flight speed point V n+2 ;

[0015] Set n+1 test flight speed points V k and test flight speed point V n+2 Combine them to get the test flight speed point set.

[0016] Optionally, the maximum reference speed V pef Determined according to the helicopter's maximum level flight speed Vmax or maximum cruising speed Vcmax.

[0017] Optionally, obtaining the coefficients of each term in the polynomial according to the torque corresponding to each test flight speed point includes:

[0018] For each test flight speed point V k And the corresponding torque is normalized;

[0019] The normalized test flight speed points V k and the corresponding torque, and (0, 0) are substituted into the polynomial to establish a system of equations, and the system of equations is solved to obtain the coefficients of each term in the polynomial.

[0020] Optionally, for each test flight speed point V k Before the corresponding torque is normalized, the helicopter level flight performance test method further includes:

[0021] According to Weierstrass approximation theorem, for each test flight speed point V k And the corresponding torque is used for coordinate transformation;

[0022] Correspondingly, after obtaining the coefficients of each term in the polynomial, the helicopter level flight performance test flight method further includes:

[0023] Substitute the acquired coefficients of each term into the polynomial, perform an inverse transformation of the coordinate transformation, and obtain a speed-torque curve.

[0024] Optional, the value of n is 3 or 4.

[0025] Another aspect of the present invention further provides a helicopter level flight performance test device, comprising:

[0026] Series acquisition module to determine the polynomial describing the speed-torque curve The number of series n;

[0027] The test flight speed point set acquisition module is used to obtain the maximum reference speed V according to the level n pef , determine the test flight speed point set;

[0028] A torque acquisition module, used to perform a test flight at each test flight speed point in the test flight speed point set, and obtain the torque corresponding to each test flight speed point;

[0029] A speed-torque curve acquisition module, used to obtain the coefficients of each term in the polynomial according to the torque corresponding to each test flight speed point, so as to obtain a speed-torque curve;

[0030] Wherein, k is an integer from 0 to n, x indicates speed, f(x) indicates torque; a(k) is the coefficient of each term in the polynomial,

[0031] Optionally, the test flight speed point set acquisition module is specifically used to:

[0032] According to the number of stages n and the maximum reference speed V pef , using the formula Determine n+1 test flight speed points V k ;

[0033] According to the maximum reference speed V pef , determine a test flight speed point V n+2 ;

[0034] Set n+1 test flight speed points V k and test flight speed point V n+2 Combine them to get the test flight speed point set.

[0035] The present invention provides a method and device for testing the level flight performance of a helicopter. According to the Weirstrass Theorem, a series approximation method is used to perform function approximation on a level flight speed-torque continuous function curve. The method only needs to perform a test flight at 5 speed points at least to determine the level flight speed-torque curve with high precision, thereby greatly saving the time cost and expense cost of the test flight. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic diagram of a flow chart of a helicopter level flight performance test method provided by the present invention;

[0037] Figure 2 A schematic diagram of normalization and coordinate transformation provided by the present invention;

[0038] Figure 3 A schematic diagram of a speed-torque curve when n=3 provided by the present invention;

[0039] Figure 4 This is a schematic diagram of the speed-torque curve when n=4 provided by the present invention. DETAILED DESCRIPTION

[0040] The present invention is explained below with reference to the accompanying drawings.

[0041] The present invention adopts a series approximation method to perform function approximation on the level flight speed-torque continuous function curve according to the Weirstrass Theorem. The method can determine the level flight speed-torque curve with high precision by performing a test flight at least at 5 speed points, thus greatly saving the time cost and expense cost of the test flight.

[0042] Reference Figure 1-4 As shown, the main idea of ​​the present invention is as follows: the method first determines the polynomial series of the curve type based on the characteristics of the speed-torque curve, then designs the speed points and performs test flights according to the required accuracy requirements, and finally calculates the values ​​of various unknown coefficients based on the speed points and the corresponding test flight torque to obtain the final speed-torque curve.

[0043] The main steps of the present invention include:

[0044] S1. Determine the series n of the approximation function according to the following polynomial series, for example, n=3:

[0045]

[0046] in,

[0047] S2, according to the maximum reference speed V of the horizontal axis of the coordinate pef (usually Vmax or a value greater than Vmax), determine the test flight speed point V k And conduct test flight to obtain a set of V k -Q k (Torque) Relationship:

[0048]

[0049] S3. When n=3, there are 5 test flight speed points, which are And add a V pef , where the maximum speed V pef It should be around Vcmax or Vmax.

[0050] S4. Since x∈(0,1), the data obtained from the test flight is normalized:

[0051]

[0052]

[0053] Because f nor (0) = 0, f nor (1) = 0. In order to make it conform to the polynomial function approximation rule, it is necessary to perform coordinate transformation before normalization. The change process and formula refer to Figure 2 .

[0054] In order to satisfy f nor (0) = 0, f nor (1)=0, when x nor =0, the corresponding speed is V k = 0, that is, at this time, a hover test data is still needed as an auxiliary input, or a ground-out hover is performed at the beginning of this sortie (level flight performance test subject); when x nor =1, the corresponding speed is V k =V pef , which is the maximum speed point of the test flight.

[0055] S4. Solve the equation based on the normalized data that meets the conditions obtained by transformation to obtain the coefficient a(k) of each monomial in the polynomial, and then obtain the normalized speed-torque curve.

[0056] The final speed-torque curve is obtained by inverse transformation of the coordinate change process in step 3, and the relevant parameters of level flight performance, such as long-flight speed, long-flight speed, maximum level flight speed and fuel consumption, are obtained accordingly. The accuracy analysis of this method is shown in Tables 1 and 2 below.

[0057] Table 1 Approximation error results of polynomial series function when n=3

[0058] <![CDATA[x nor原始值 ]]> 0.111111 0.333333 0.555556 0.777778 <![CDATA[f nor Original Value]]> -0.04157 -0.16542 -0.19243 -0.13229 f(x) -0.04157 -0.16542 -0.19243 -0.13229 error(%) 2.67077E-15 -1.34228E-15 -5.19266E-15 2.09805E-15

[0059] Table 2 Approximation error results of polynomial series function when n=4

[0060] <![CDATA[X nor原始值 ]]> 1 / 11 3 / 11 5 / 11 7 / 11 9 / 11 <![CDATA[f nor Original Value]]> -0.02999545 -0.13822 -0.19403 -0.17793 -0.11487 f(x) -0.02999545 -0.13822 -0.19403 -0.17793 -0.11487 error(%) 2.31332E-16 -1E-15 1.29E-15 -1.9E-15 3.14E-15

[0061] The method of the present invention is used to test the level flight performance of a helicopter. Only a small number of speed points need to be tested. Combined with semi-theoretical curve function analysis, a high-precision speed-power curve of the level flight performance of the helicopter can be obtained and the level flight performance can be obtained. In a test flight, the traditional least squares fitting method requires at least a dozen speed points to give a conclusion, while the method only needs to fly 5-6 speed points. While the time spent is reduced by more than 50% compared with the traditional method, the test flight cost is greatly saved. In addition, due to the reduction of the test flight time, the test flight deviation caused by fuel consumption is also reduced accordingly, which improves the accuracy of the results.

Claims

1. A helicopter level flight performance test method, characterized in that: include: Determine the polynomial that describes the speed-torque curve The number of series n; According to the number of stages n and the maximum reference speed V pef , determine the test flight speed point set; Perform a test flight at each test flight speed point in the test flight speed point set to obtain the torque corresponding to each test flight speed point; According to the torque corresponding to each test flight speed point, the coefficients of each term in the polynomial are obtained to obtain a speed-torque curve; Wherein, k is an integer from 0 to n, x indicates speed, f(x) indicates torque; a(k) is the coefficient of each term in the polynomial, According to the number of stages n and the maximum reference speed V pef , determine the test flight speed point set, including: According to the number of stages n and the maximum reference speed V pef , using the formula Determine n+1 test flight speed points V k ; According to the maximum reference speed V pef , determine a test flight speed point V n+2 ; Set n+1 test flight speed points V k and test flight speed point V n+2 Combine them to get the test flight speed point set.

2. The method according to claim 1, characterized in that The maximum reference speed V pef Determined according to the helicopter's maximum level flight speed Vmax or maximum cruising speed Vcmax.

3. The method according to claim 1, characterized in that The step of obtaining the coefficients of each term in the polynomial according to the torque corresponding to each test flight speed point includes: For each test flight speed point V k And the corresponding torque is normalized; The normalized test flight speed points V k and the corresponding torque, and (0, 0) are substituted into the polynomial to establish a system of equations, and the system of equations is solved to obtain the coefficients of each term in the polynomial.

4. The method according to claim 3, characterized in that For each test flight speed point V k Before the corresponding torque is normalized, the method further includes: According to Weierstrass approximation theorem, for each test flight speed point V k And the corresponding torque is used for coordinate transformation; Correspondingly, after obtaining the coefficients of each term in the polynomial, the method further includes: Substitute the acquired coefficients of each term into the polynomial, perform an inverse transformation of the coordinate transformation, and obtain a speed-torque curve.

5. The method according to claim 1, characterized in that The value of n is 3 or 4.

6. A helicopter level flight performance test device, characterized in that: include: Series acquisition module to determine the polynomial describing the speed-torque curve The number of series n; The test flight speed point set acquisition module is used to obtain the maximum reference speed V according to the level n pef , determine the test flight speed point set; A torque acquisition module, used to perform a test flight at each test flight speed point in the test flight speed point set, and obtain the torque corresponding to each test flight speed point; A speed-torque curve acquisition module, used to obtain the coefficients of each term in the polynomial according to the torque corresponding to each test flight speed point, so as to obtain a speed-torque curve; Wherein, k is an integer from 0 to n, x indicates speed, f(x) indicates torque; a(k) is the coefficient of each term in the polynomial, The test flight speed point set acquisition module is specifically used for: According to the number of stages n and the maximum reference speed V pef , using the formula Determine n+1 test flight speed points V k ; According to the maximum reference speed V pef , determine a test flight speed point V n+2 ; Set n+1 test flight speed points V k and test flight speed point V n+2 Combine them to get the test flight speed point set.

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