A helicopter flexible beam actual load replacement analysis method

Abstract

The application discloses a helicopter flexible beam actual load substitution analysis method, comprising the following steps: considering that the flexible beam root actual measured load data is effective in the initial flight test, using the effective time period corresponding to the effective flight test data of the flexible beam root actual measured load, performing spectrum analysis on the flexible beam root profile actual measured load and the airfoil section profile actual measured load on the same piece of tail rotor blade at preset interval time in the effective time period of the effective flight test data, so as to obtain the amplitude of the flexible beam root profile actual measured load and the airfoil section profile actual measured load corresponding to the tail rotor rotating speed frequency respectively; combining the amplitude of each time point in the effective time period to form two groups of data columns; a scatter plot of the two groups of data columns can be drawn, a plurality of correlation formulas of the two groups of data columns are obtained through linear fitting, the correlation formula with the optimal correlation between the airfoil section profile actual measured load and the flexible beam root profile actual measured load on the same piece of tail rotor blade is selected as the basis for calculating the flexible beam root profile actual measured load, and the flexible beam root profile actual measured load in the whole flight process can be obtained based on the airfoil section profile actual measured load of the tail rotor blade.

Description

TECHNICAL FIELD

[0001] The present application relates to, but is not limited to, the technical field of helicopter structure strength design, and in particular to a helicopter flexible beam actual measurement load substitution analysis method. BACKGROUND

[0002] The tail rotor of the bearingless configuration of the helicopter is a commonly used configuration of the tail rotor of the helicopter at present, has simple structure and good maintainability, and mainly has the following characteristics: a flexible beam is used to replace the flap hinge, the lag hinge and the pitch hinge in the previous configuration, and the flap, the lag and the pitch functions of the tail rotor are realized through deformation of the flexible beam.

[0003] The strength design of the flexible beam is a key factor for safe flight of the tail rotor, and it is particularly important to measure the load of the flexible beam through the actual measurement method due to the extremely complex load and the difficulty in obtaining reliable load through calculation. In the process of flight of the helicopter, in order to realize the flap, the lag and the pitch movement of the tail rotor blade, the flexible beam will produce large deformation, which causes the load strain gauge at the root of the flexible beam to be damaged frequently, and it is difficult to guarantee the monitoring and testing requirements of the test flight. SUMMARY

[0004] The purpose of the present application is to solve the above problems, and the helicopter flexible beam actual measurement load substitution analysis method is provided to solve the existing strength design method of the flexible beam in the tail rotor of the bearingless configuration. In order to realize the flap, the lag and the pitch movement of the tail rotor blade, it is required that the flexible beam produces large deformation, thereby causing the load strain gauge at the root of the flexible beam to be damaged frequently, and it is difficult to guarantee the monitoring and testing requirements of the test flight.

[0005] The technical scheme of the present application is as follows: in the first aspect, the helicopter flexible beam actual measurement load substitution analysis method provided by the embodiments of the present application comprises:

[0006] Step 1: obtaining the actual measurement load effective test flight data of the flexible beam root section and the corresponding effective time period;

[0007] Step 2: performing spectrum analysis on the actual measurement load of the flexible beam root section and the actual measurement load of the airfoil section on the tested tail rotor blade in the effective time period of the actual measurement load effective test flight data of the flexible beam root section with a preset interval time, respectively, to obtain the amplitude of the flexible beam root section and the airfoil section corresponding to the tail rotor speed frequency;

[0008] Step 3: combining the amplitudes in the effective time period to form two groups of data columns, obtaining the correlation formula of the two groups of data columns through linear fitting, and obtaining a plurality of correlation formulas of the actual measurement load of the flexible beam root section and the actual measurement load of the airfoil section;

[0009] Step 4, select the correlation formula of the optimal correlation between the measured load of the airfoil section of the tail rotor blade and the measured load of the flexible beam root section, and use it to calculate the measured load of the flexible beam root section.

[0010] Optionally, in the helicopter flexible beam measured load replacement analysis method described above, the step 1 comprises:

[0011] According to the flight speed and flight height of the performance parameters of the helicopter flight test data, the flight state is divided, and the time period corresponding to the helicopter flexible beam root measured load and the airfoil section measured load effective at the same time in each flight state is recorded.

[0012] Optionally, in the helicopter flexible beam measured load replacement analysis method described above, the step 2 comprises:

[0013] Step 21, in each flight state, the flexible beam root section measured load and the airfoil section measured load of the tested tail rotor blade are respectively analyzed at a preset interval time in the effective time period, and the measured load of the flexible beam root section and the airfoil section at each influencing frequency in each flight state is obtained. The tail rotor speed frequency is the dominant frequency in the influencing frequency.

[0014] Step 22, for each effective time period, the amplitude of the flexible beam root section measured load and the airfoil section measured load corresponding to the tail rotor speed frequency at the same time in the corresponding flight state is extracted.

[0015] Optionally, in the helicopter flexible beam measured load replacement analysis method described above, the step 3 comprises:

[0016] Step 31, the amplitudes of the flexible beam root section measured load and the airfoil section measured load corresponding to the tail rotor speed frequency at the same time in the corresponding flight state are combined to form two data columns, and the scatter plot of the two data columns is drawn, and the correlation formula of the two data columns is obtained by linear fitting.

[0017] Step 32, for each section position on the same tail rotor blade, the correlation formula of the flexible beam root section measured load and the airfoil section measured load corresponding to each section position is obtained, so as to obtain a plurality of correlation formulas corresponding to a plurality of section positions in the same tail rotor blade.

[0018] Optionally, in the helicopter flexible beam measured load replacement analysis method described above, the step 4 comprises:

[0019] Step 41, select the correlation formula of the optimal correlation between the airfoil section measured load and the flexible beam root section measured load on the same tail rotor blade.

[0020] Optionally, the helicopter flexible beam measured load replacement analysis method as described above further comprises:

[0021] Step 42, in the selected optimal correlation formula of the plurality of tail rotor blades, an optimal correlation formula for calculating the measured load of the flexible beam root section is selected.

[0022] Optionally, in the helicopter flexible beam measured load replacement analysis method as described above, the optimal correlation formula selected in step 4 is selected in the following manner:

[0023] Through linear fitting, the correlation formula of the two groups of data is obtained, and the optimal correlation formula is selected according to the fitting variance of the correlation formula. The closer the fitting variance value is to 1, the better the linear fitting degree is.

[0024] Optionally, the helicopter flexible beam measured load replacement analysis method as described above further comprises:

[0025] Step 5, the optimal correlation formula selected in step 4 is used to obtain the measured load of the flexible beam root section in the entire flight process according to the measured load of the airfoil section.

[0026] In a second aspect, the embodiments of the present application further provide a computer readable storage medium, comprising: a memory and a processor;

[0027] The memory is configured to save executable instructions;

[0028] The processor is configured to implement the helicopter flexible beam measured load replacement analysis method as described in any one of the above when executing the executable instructions saved by the memory.

[0029] The helicopter flexible beam measured load replacement analysis method provided by the embodiments of the present application is as follows: the measured load of the flexible beam root section is obtained according to the measured load of the airfoil section of the tail rotor blade; generally, in the initial flight test, the measured load data of the flexible beam root section is effective, the effective time period corresponding to the effective flight test data of the measured load of the flexible beam root section and the measured load of the airfoil section of the same tail rotor blade is selected, and the spectrum analysis is performed on the measured load of the flexible beam root section and the measured load of the airfoil section at a preset interval of time in the effective time period, so as to obtain the amplitude corresponding to the tail rotor speed frequency of the measured load of the flexible beam root section and the measured load of the airfoil section, respectively; the amplitudes at each time point in the effective time period are combined to form two groups of data; a scatter plot of the two groups of data can be drawn, a plurality of correlation formulas of the two groups of data are obtained through linear fitting, the correlation formula with the optimal correlation between the measured load of the airfoil section and the measured load of the flexible beam root section of the same tail rotor blade is selected as the basis for calculating the measured load of the flexible beam root section, and the measured load of the flexible beam root section in the entire flight process can be obtained based on the measured load of the airfoil section of the tail rotor blade.

[0030] The helicopter flexible beam actual load replacement analysis method provided by the embodiment of the present application has high universality and engineering application value. BRIEF DESCRIPTION OF DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the technical solutions of the present application, and constitute a part of the specification, and are used together with the embodiments of the present application to explain the technical solutions of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0032] Figure 1 A flowchart of a helicopter flexible beam actual load replacement analysis method provided by the embodiment of the present application is shown in the figure.

[0033] Figure 2 A position diagram of a flexible beam root section and a tail rotor blade airfoil section in the helicopter flexible beam actual load replacement analysis method provided by the embodiment of the present application is shown in the figure.

[0034] Figure 3 A time-domain curve diagram of the flexible beam root section actual load on the tail rotor blade at a typical moment in the embodiment of the present application is shown in the figure.

[0035] Figure 4 A frequency-domain curve diagram of the flexible beam root section actual load on the tail rotor blade at a typical moment in the embodiment of the present application is shown in the figure.

[0036] Figure 5 A frequency-domain curve diagram of the flexible airfoil section actual load on the tail rotor blade at a typical moment in the embodiment of the present application is shown in the figure.

[0037] Figure 6 A correlation diagram of the flexible beam root section actual load and the tail rotor blade airfoil section actual load in the embodiment of the present application is shown in the figure.

[0038] Figure 7 A result diagram of the flexible beam root section actual load in a typical flight obtained by the method provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0039] The accompanying drawings are used to provide a further understanding of the technical solutions of the present application, and constitute a part of the specification, and are used together with the embodiments of the present application to explain the technical solutions of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0040] It has been explained in the foregoing background art that the tail rotor of the bearingless configuration of the helicopter is the configuration commonly used for the tail rotor of the helicopter at present, and the strength design of the flexible beam is a key factor to ensure the safe flight of the tail rotor. In view of the existing strength design mode of the flexible beam in the tail rotor of the bearingless configuration, in order to realize the flapping, oscillation and pitch motion of the tail rotor blade, a larger deformation of the flexible beam is required, thereby causing the load strain gauge at the root of the flexible beam to be frequently damaged, and it is difficult to ensure the monitoring and testing requirements of the test flight.

[0041] In view of the above problems, the strength design mode of the flexible beam of the previous type is as follows: the flexible beam root section load is derived from the tail rotor shaft section load by measuring the tail rotor shaft load, and since the correlation coefficient between the tail rotor shaft load and the flexible beam load changes with the flight state, there is a large difference between the flexible beam root load derived by this mode and the actual load, and it is necessary to obtain the load of the flexible beam by a more reliable mode.

[0042] In view of the test requirement of the flexible beam load, the helicopter flexible beam actual load replacement analysis method provided by the embodiment of the present application is based on the force transmission of the tail rotor load, combines the characteristics of the flexible beam root load and the airfoil section load of the tail rotor blade, and proposes to derive the flexible beam root load based on the airfoil section load of the tail rotor blade, thereby forming a helicopter flexible beam actual load replacement analysis method.

[0043] The design idea of the helicopter flexible beam actual load replacement analysis method provided by the embodiment of the present application is as follows:

[0044] On the one hand, the direct source of the flexible beam root load is the aerodynamic load and the inertial load of the airfoil section of the tail rotor blade, and theoretically the flexible beam root load and the same airfoil section load of the tail rotor blade have a certain proportional relationship;

[0045] On the other hand, the frequency component of the flexible beam root load is relatively single, and the frequency component of the tail rotor speed dominates the load. Therefore, the method of deriving the flexible beam root section load from the airfoil section load of the tail rotor blade is feasible and reliable.

[0046] The present application provides the following specific embodiments which can be combined with each other, and the same or similar concepts or processes can not be described in some embodiments.

[0047] Figure 1 The flowchart of the helicopter flexible beam actual load replacement analysis method provided by the embodiment of the present application is shown in FIG. Figure 1 As shown in the figure, the helicopter flexible beam actual load replacement analysis method provided by the embodiment of the present application includes the following steps:

[0048] Step 1, obtaining the effective test flight data of the flexible beam root actual load and the corresponding effective time period.

[0049] Step 2, the measured load of the flexible beam root section and the measured load of the airfoil section are respectively subjected to spectrum analysis at preset interval time within the effective time period of the effective flight test data, and the amplitude of the measured load of the flexible beam root section and the measured load of the airfoil section corresponding to the tail rotor speed frequency is obtained.

[0050] As shown in Figure 2 The position diagram of the flexible beam root section and the airfoil section of the tail rotor blade in the helicopter flexible beam measured load substitution analysis method provided by the embodiment of the application is shown.

[0051] Step 3, the amplitudes within the effective time period are combined to form two groups of data columns, the correlation formula of the two groups of data columns is obtained through linear fitting, and a plurality of correlation formulas of the measured load of the flexible beam root section and the measured load of the airfoil section are obtained;

[0052] Step 4, the correlation formula with the best correlation between the measured load of the airfoil section and the measured load of the flexible beam root section is selected, and is used to calculate the measured load of the flexible beam root section.

[0053] In an implementation manner of the embodiment of the application, the implementation manner of the above step 1 may, for example, include:

[0054] In the scientific research flight process of a certain type of aircraft, the flight states are divided according to the flight speed and flight height in the performance parameters of the helicopter flight test data, and the effective time period corresponding to the simultaneously effective measured load of the flexible beam root section and the measured load of the airfoil section under each flight state is recorded.

[0055] In an implementation manner of the embodiment of the application, the implementation process of the above step 2 may include:

[0056] Step 21, within the effective time period of the load of each flight state, the measured load of the flexible beam root section and the measured load of the airfoil section on the tested tail rotor blade are respectively subjected to spectrum analysis at preset interval time, and the measured load of the flexible beam root section and the measured load of the airfoil section on the tested tail rotor blade under each influencing frequency in each flight state is obtained, and the tail rotor speed frequency is the dominant frequency in the influencing frequency.

[0057] Step 22, for each effective time period, the amplitude of the measured load of the flexible beam root section and the measured load of the airfoil section corresponding to the tail rotor speed frequency at the same time corresponding to the flight state is extracted.

[0058] Through comparative analysis, the frequency component of the flexible beam root section load is relatively single, and the tail rotor speed frequency component (1Ωt) absolutely dominates in the load.

[0059] In an implementation form of the step 3, the step 3 can include, for example:

[0060] In the step 31, the amplitude of the flexible beam root section measured load and the airfoil section measured load corresponding to the tail rotor speed frequency at the same moment of time for each flight state are combined to form two data series, and a scatter plot of the two data series is drawn, and a correlation formula of the two data series is obtained through linear fitting.

[0061] In the step 31, the amplitude of the flexible beam root section measured load and the airfoil section measured load corresponding to the tail rotor speed frequency at the same moment of time for each flight state are combined to form two data series, and a scatter plot of the two data series is drawn, and a correlation formula of the two data series is obtained through linear fitting.

[0062] In the step 32, for each section position on the same tail rotor blade, a correlation formula corresponding to the flexible beam root section measured load and the airfoil section measured load at each section position is obtained, thereby obtaining a plurality of correlation formulas corresponding to a plurality of section positions in the same tail rotor blade.

[0063] In an implementation form of the step 4, the step 4 can include, for example:

[0064] On the same tail rotor blade, a correlation formula with the best correlation between the airfoil section measured load and the flexible beam root section measured load is selected.

[0065] On the other hand, among the selected optimal correlation formulas of the plurality of tail rotor blades, an optimal correlation formula for calculating the flexible beam root section measured load is selected.

[0066] In an implementation form of the step 4, the step 4 can include, for example:

[0067] Through linear fitting, a correlation formula of the two data series is obtained, and according to the fitting variance of the correlation formula, an optimal correlation formula is selected, and the closer the fitting variance value is to 1, the better the linear fitting degree is.

[0068] Further, the helicopter flexible beam measured load replacement analysis method provided by the embodiment of the application can further include:

[0069] In the step 5, the optimal correlation formula selected in the step 4 is used to obtain the flexible beam root section measured load during the entire flight process according to the airfoil section measured load.

[0070] The helicopter flexible beam measured load replacement analysis method provided by the embodiment of the present application, the overall scheme is to obtain the flexible beam root section measured load according to the tail rotor blade airfoil section profile measured load; generally in the initial flight test, the flexible beam root section measured load data is effective, the effective time period corresponding to the effective flight test data of the flexible beam root section measured load is used, the flexible beam root section measured load and the airfoil section profile measured load on the same tail rotor blade are respectively subjected to spectrum analysis at a preset interval time within the effective time period, so that the amplitude corresponding to the tail rotor speed frequency of the flexible beam root section measured load and the airfoil section profile measured load is respectively obtained; the amplitudes of each time point within the effective time period are combined to form two data columns; a scatter plot of the two data columns can be drawn, a plurality of correlation formulas of the two data columns are obtained through linear fitting, the correlation formula with the optimal correlation between the airfoil section profile measured load and the flexible beam root section measured load on the same tail rotor blade is selected as the basis for calculating the flexible beam root section measured load, and the flexible beam root section measured load in the whole flight process can be obtained based on the tail rotor blade airfoil section profile measured load.

[0071] The related application examples show that the helicopter flexible beam measured load replacement analysis method provided by the embodiment of the present application can obtain the real flexible beam root section measured load, ensures the flexible beam measured load flight test and safety monitoring requirements, provides accurate and reliable measured load data for the flexible beam strength design, can more accurately carry out the flexible beam strength design, and has high universality and engineering application value.

[0072] The helicopter flexible beam measured load replacement analysis method provided by the embodiment of the present application is schematically described below through a specific application example.

[0073] Application example

[0074] In order to prove the applicability and effectiveness of the helicopter flexible beam measured load replacement analysis method provided by the embodiment of the present application, the method provided by the present application is used to determine the flexible beam load replacement analysis method by analyzing the typical flight cycle measured data of a certain type of aircraft through scientific research flight. The specific implementation manner is as follows:

[0075] S1: In the process of scientific research flight of a certain type of aircraft, the performance parameters of flight data are divided into flight states, and the corresponding time periods are recorded;

[0076] S2: In the effective time period corresponding to the effective flight test data of the flexible beam root section measured load, the flexible beam root section measured load and the tail rotor blade airfoil section profile measured load are respectively subjected to spectrum analysis;

[0077] S3: Through the spectrum analysis in S2, the tail rotor speed frequency (1Ωt) corresponding to the flexible beam root section measured load and the tail rotor blade airfoil section measured load, and the load amplitude of other frequencies 2Ωt, 3Ωt, 4Ωt, 5Ωt corresponding to the flight state are obtained respectively;

[0078] S4: Through the comparative analysis of the flexible beam root section measured load amplitude and the airfoil section measured load amplitude corresponding to each frequency, it is concluded that the tail rotor speed frequency (1Ωt) is absolutely dominant in the load. Figure 3 It is a time domain curve schematic diagram of the flexible beam root section measured load on the tail rotor blade at a typical moment in the embodiment of the application. Figure 4 It is a frequency domain curve schematic diagram of the flexible beam root section measured load on the tail rotor blade at a typical moment in the embodiment of the application. Figure 5 It is a frequency domain curve schematic diagram of the flexible airfoil section measured load on the tail rotor blade at a typical moment in the embodiment of the application.

[0079] S5: Based on the corresponding load amplitude of each flight state, two groups of data series of the flexible beam root section measured load and the airfoil section measured load are formed, and the scatter plot of the two groups of data is drawn.

[0080] S6: Through linear fitting, the correlation formula of the two groups of data is derived as follows:

[0081] y = 2.6089x - 2.575;

[0082] R 2 = 0.9963;

[0083] Wherein, y represents the flexible beam root section measured load;

[0084] x represents the tail rotor blade airfoil section measured load;

[0085] R 2 represents the fitting variance, which is used to represent the linear fitting degree, and the correlation formula when R 2 = 1 is the optimal correlation formula. Figure 6 It is a schematic diagram of the correlation relationship between the flexible beam root section measured load and the tail rotor blade airfoil section measured load in the embodiment of the application.

[0086] S7: According to the optimal correlation formula obtained in S6, the flexible beam root section measured load in the whole flight process is obtained based on the airfoil section measured load.

[0087] Figure 7 It is a result schematic diagram of the flexible beam root section measured load in a typical flight obtained by using the method provided in the embodiment of the application.

[0088] Although the present application has been described with reference to the above embodiments, the contents are only the embodiments for facilitating the understanding of the present application, and are not intended to limit the present application. Any modification and change in the form and details of the embodiments can be made by any person skilled in the art without departing from the spirit and scope of the present application. The patent protection scope of the present application shall be subject to the scope defined by the appended claims.

Claims

1. A method of helicopter flexible beam real load substitution analysis, characterized in that, The method comprises the following steps: Step 1, obtaining the effective flight test data of the flexible beam root section profile measured load and the corresponding effective time period; Step 2, performing spectrum analysis on the flexible beam root section profile measured load and the airfoil section profile measured load on the tested tail rotor blade at preset interval time within the effective time period of the flexible beam root section profile measured load effective flight test data, and obtaining the amplitude of the flexible beam root section profile measured load and the airfoil section profile measured load corresponding to the tail rotor speed frequency; Step 3, combining the amplitudes within the effective time period to form two groups of data columns, obtaining the correlation formula of the two groups of data columns through linear fitting, and obtaining multiple correlation formulas of the flexible beam root section profile measured load and the airfoil section profile measured load; Step 4, selecting the correlation formula with the best correlation between the airfoil section profile measured load and the flexible beam root section profile measured load on the tail rotor blade to calculate the flexible beam root section profile measured load; The step 3 comprises: Step 31, combining the amplitudes of the flexible beam root section profile measured load and the airfoil section profile measured load corresponding to the tail rotor speed frequency at the same time extracted from the flight state corresponding to each effective time period to form two groups of data columns, and drawing the scatter plot of the two groups of data columns, and obtaining the correlation formula of the two groups of data columns through linear fitting.

2. The helicopter flexible beam load measurement surrogate analysis method of claim 1, wherein, The step 1 comprises: According to the flight speed and flight height in the performance parameters of the helicopter flight test data, the flight states are divided, and the time periods corresponding to the flexible beam root section profile measured load and the airfoil section profile measured load effective under each flight state are recorded.

3. The helicopter flexible beam load measurement surrogate analysis method of Claim 2, wherein, The step 2 comprises: Step 21, within the effective time period of the load effective in each flight state, spectrum analysis is performed on the flexible beam root section profile measured load and the airfoil section profile measured load on the tested tail rotor blade at preset interval time, respectively, to obtain the measured load of the flexible beam root section and the airfoil section under each influencing frequency under each flight state, and the tail rotor speed frequency is the dominant frequency in the influencing frequency; Step 22, for each effective time period, the amplitudes of the flexible beam root section profile measured load and the airfoil section profile measured load corresponding to the tail rotor speed frequency at the same time corresponding to the flight state are extracted.

4. The helicopter flexible beam load measurement surrogate analysis method of Claim 3, wherein, The step 3 further comprises: Step 32, for each profile position on the same tail rotor blade, the correlation formula corresponding to the flexible beam root section profile measured load and the airfoil section profile measured load at each profile position is obtained, so as to obtain multiple correlation formulas corresponding to multiple profile positions in the same tail rotor blade.

5. The helicopter flexible beam load measurement surrogate analysis method of Claim 4, wherein, The step 4 comprises: Step 41, on the same tail rotor blade, the correlation formula with the best correlation between the airfoil section profile measured load and the flexible beam root section profile measured load is selected.

6. The helicopter flexible beam load measurement surrogate analysis method of claim 5, wherein, Further comprising: Step 42, in the selected optimal correlation formulas of multiple tail rotor blades, one optimal correlation formula for calculating the flexible beam root section profile measured load is selected.

7. The helicopter flexible beam measured load substitution analysis method according to claim 6, wherein, The optimal correlation formula in step 4 is selected in the following manner: through linear fitting, the correlation formula of the two groups of data columns is obtained, and according to the fitting variance of the correlation formula, the optimal correlation formula is selected, and the closer the fitting variance value is to 1, the better the linear fitting degree is.

8. The helicopter flexible beam load measurement surrogate analysis method according to any one of claims 1 to 7, characterized in that, Also includes: Step 5, using the optimal correlation formula selected in step 4, the measured load of the flexible beam root section profile is obtained according to the measured load of the airfoil section profile.

9. A computer-readable storage medium, characterized in that, Including: Memory and processor; The memory is configured to save executable instructions; The processor is configured to implement the helicopter flexible beam measured load replacement analysis method in any one of claims 1-8 when executing the executable instructions saved by the memory.

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