A method and device for obtaining an azimuth angle based on a rotational speed signal

Abstract

The application provides a kind of azimuth acquisition method and device based on rotational speed signal, for the possible existence of azimuth signal in helicopter flight test, such as unable to measure, measurement failure or failure, etc., according to the rotational speed signal of rotor, the azimuth of the test data of rotor is restored.When the azimuth measurement fails, the restored data can be directly used for data processing and analysis, and when the azimuth measurement data is lost or there is a false signal, the restored data can be used to calibrate and correct it, reducing the impact of measurement failure on subsequent work.

Description

Technical Field

[0001] This invention belongs to the field of flight test technology, specifically relating to a method and apparatus for obtaining azimuth angle based on rotation speed signal. Background Technology

[0002] To assess the strength and vibration characteristics of a helicopter structure, it is necessary to measure the load and vibration of its key structures and parts. The load on the helicopter structure mainly comes from the motion of the rotor system, which has obvious periodic characteristics. That is, every time the rotor rotates, the airflow field flowing through the blades changes once, causing the blades to deform, vibrate and alternating stress over time. At the same time, this change is transmitted to other structures. Therefore, damage assessment or harmonic analysis of helicopter structures is mostly based on the blade azimuth angle.

[0003] The azimuth angle of a helicopter rotor blade is the position signal of the rotor blade during helicopter flight, which includes the time taken for the blade to rotate once. When assessing damage to the helicopter structure, a load separation cycle is required to separate the steady-state load from the dynamic load in the measured data. The separation cycle is based on the azimuth angle signals of the main rotor and tail rotor.

[0004] When performing whole-cycle harmonic analysis on structural loads or vibrations, the azimuth angle signal is used to decompose N loads or vibration data in each rotation cycle of the main propeller, tail propeller, transmission, or fuselage into trigonometric series.

[0005] In traditional propeller blade azimuth signal measurement, a light-emitting plate is usually attached to the propeller blade, and a laser generator and receiver are fixed on the machine body. During operation, the laser generator continuously emits laser light. When the light-emitting plate on the propeller blade passes over the laser, the receiver system receives the reflected laser signal, generates a digital pulse signal, and records it.

[0006] In actual flight measurements, due to rotor speed fluctuations, blade swing and torsional motion, weather, and measurement factors, the azimuth angle measurement of the blades has a certain probability of failure. It is also common for measurement signals to be lost within a certain period of time or for multiple false pulses to be triggered within one rotation cycle, which affects the implementation of structural damage calculation or harmonic analysis or the accuracy of the results. Summary of the Invention

[0007] This invention provides a method and apparatus for obtaining azimuth angle based on rotational speed signal. By utilizing the rotational speed signal of the rotor system, it reconstructs or calibrates the azimuth angle signal during measurement to address missing or incorrect information. This improves the accuracy of signal processing and analysis for load, vibration, and other parameters, and also avoids data processing issues caused by missing azimuth angles.

[0008] The first aspect of this invention provides a method for obtaining azimuth angle based on rotational speed signal, comprising:

[0009] Step 1: Obtain the speed signal array Fv[Rate1*T], where Rate1 is the sampling rate of the speed signal and T is the measurement time of the speed signal;

[0010] Step 2: Iterate sequentially through the array Fv[Rate1*T], find the first index i0 of Fv[Rate1*T] that is greater than 0, and continue the sequential traversal to find the index i1 of Fv[Rate1*T] that is 0 again; <i0<i1<Rate1*T;

[0011] Step 3: Interpolate the data from sequence number i0 to i1 in array Fv[Rate1*T] according to the preset interpolation coefficient m to obtain array Fvx[n1]; n1 = (i1-i0)*m;

[0012] Step 4: Obtain the week number corresponding to every two adjacent numbers in the array Fvx[n1] d[i] = 0.5*a[i]*t1*t1 + Fvx[i]*t1; i = 0, 1, 2, ..., n1-1; a[i] = (Fvx[i+1] - Fvx[i]) / t1; t1 = 1 / (Rate1*m);

[0013] Step 5: Accumulate d[i] in ascending order of i to obtain sum[i]. Determine the value of i when sum[i] reaches an integer each time. Correct the azimuth measurement signal based on the value of i when sum[i] reaches an integer each time.

[0014] Optionally, the data with sequence numbers i0 to i1 in the array Fv[Rate1*T] are interpolated according to a preset interpolation coefficient m to obtain the array Fvx[n1], which includes:

[0015] Fvx[i*m+j]=(1-delt)*Fv[i+i0]+delt*Fv[i+i0+1];

[0016] Where: delt = j / m; i = 0, 1, 2, ..., i1-i0-1; j = 0, 1, 2, ..., m-1.

[0017] Optional, interpolation coefficient m = 30.

[0018] Optionally, the rotational speed signal array Fv[Rate1*T] is a rotor rotational speed signal array.

[0019] Optionally, when used to obtain the azimuth angle of the drive shaft, the method further includes:

[0020] After obtaining the array Fvx[n1], multiply the values ​​in the array Fvx[n1] by Nz / Nr;

[0021] Where Nz is the rated speed of the drive shaft and Nr is the rated speed of the rotor.

[0022] A second aspect of the present invention provides an azimuth angle acquisition device based on a rotational speed signal, comprising:

[0023] The speed signal array acquisition module is used to acquire the speed signal array Fv[Rate1*T], where Rate1 is the sampling rate of the speed signal and T is the measurement time of the speed signal;

[0024] The valid data acquisition module is used to sequentially traverse the array Fv[Rate1*T], find the first sequence number i0 of Fv[Rate1*T] that is greater than 0, continue sequential traversal, and find the sequence number i1 of Fv[Rate1*T] that is 0 again; <i0<i1<Rate1*T;

[0025] The interpolation module is used to interpolate the data with sequence numbers i0 to i1 in the array Fv[Rate1*T] according to the preset interpolation coefficient m to obtain the array Fvx[n1]; n1=(i1-i0)*m;

[0026] The week number acquisition module is used to obtain the week number corresponding to every two adjacent numbers in the array Fvx[n1]: d[i] = 0.5*a[i]*t1*t1 + Fvx[i]*t1; i = 0, 1, 2, ..., n1-1; a[i] = (Fvx[i+1] - Fvx[i]) / t1; t1 = 1 / (Rate1*m);

[0027] The correction module is used to accumulate d[i] in ascending order of i to obtain sum[i], determine the value of i when sum[i] reaches an integer each time, and correct the azimuth measurement signal based on the value of i when sum[i] reaches an integer each time.

[0028] Optionally, the interpolation module is specifically used for interpolation according to the following formula:

[0029] Fvx[i*m+j]=(1-delt)*Fv[i+i0]+delt*Fv[i+i0+1];

[0030] Where: delt = j / m; i = 0, 1, 2, ..., i1-i0-1; j = 0, 1, 2, ..., m-1.

[0031] Optional, interpolation coefficient m = 30.

[0032] Optionally, the rotational speed signal array Fv[Rate1*T] is a rotor rotational speed signal array.

[0033] Optionally, the week number retrieval module is also used for:

[0034] When used to obtain the drive shaft azimuth angle, after obtaining the array Fvx[n1], the value in the array Fvx[n1] is multiplied by Nz / Nr;

[0035] Where Nz is the rated speed of the drive shaft and Nr is the rated speed of the rotor.

[0036] This invention provides a method and apparatus for acquiring azimuth angle based on rotor speed signals. Addressing potential issues such as unmeasurable, erroneous, or failed azimuth angle signals during helicopter flight testing, it reconstructs the azimuth angle of rotor and other test data based on rotor speed signals. When azimuth angle measurement fails, the reconstructed data can be directly used for data processing and analysis. When azimuth angle measurement data is missing or contains false signals, it can be calibrated and corrected based on the reconstructed data, reducing the impact of measurement errors on subsequent work. This invention utilizes the rotor system's rotational speed signal to correct or reconstruct errors or mistakes in the measurement of blade azimuth angle signals. It can also be used to construct the azimuth angle of the drive shaft, improving the accuracy of load, vibration, and other signal processing and analysis while avoiding the impact of measurement errors. It has been successfully applied in the processing and analysis of flight test data for various ZXX models. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the main rotor azimuth angle signal (with some omissions in measurement) and rotation speed signal of the present invention;

[0038] Figure 2 This is a schematic diagram illustrating the calculation principle of the blade azimuth angle based on the helicopter rotor speed signal of this invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0041] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0042] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0043] like Figure 1 and 2 As shown, the present invention provides a method and apparatus for obtaining azimuth angle based on rotational speed signal.

[0044] The algorithm of this invention is implemented using a computer programming language. Based on the rotor speed data measured in flight, it generates discretized blade azimuth angle data with matching time and sampling rate according to the specific processing requirements of measurement parameters such as load and vibration.

[0045] 1) Modify the flight measurement machine on the helicopter to measure flight parameters (including main rotor speed Nr) and rotor load (or fuselage vibration) parameters;

[0046] 2) Determine the measurement sampling rate Rate1 for flight parameters and Rate2 for rotor load (or fuselage vibration) parameters;

[0047] 3) Conduct flight measurements according to the requirements of the test flight mission, continuously record the process data of each parameter changing over time during each takeoff and landing, and ensure that the measurement time of each parameter is synchronized;

[0048] Note: Rotor speed Nr is a slow variable, measured in revolutions per minute (rpm). It is often measured together with flight parameters such as speed, altitude, flight attitude, and control. The sampling rate Rate1 during flight measurements is generally below 100Hz. The rotor speed Nr of traditional helicopter configurations ranges from hundreds to thousands of revolutions per minute.

[0049] Rotor loads require measurement accuracy of at least 6th to 10th order harmonics. Therefore, the sampling rate Rate2 for load measurement often exceeds 1000Hz. Airframe vibrations are related to the rotor's passing frequency or the rotation frequency of the drive shaft, so the sampling rate is even higher.

[0050] 4) The time interval between two adjacent measurement points of rotor speed is t0 = 1. / Rate1, which is generally tens of milliseconds. During this time period, it is assumed that the rotor speed changes linearly.

[0051] 5) Obtain the total time length T of the flight takeoff and landing measurements to be processed;

[0052] 6) Based on the sampling rate Rate1 and measurement time T of the flight parameters, dynamically allocate a floating-point array Fv[n] in the computer memory. The array size n = Rate1 * T. Assign the rotor speed measurement data of the complete flight take-off and landing to the array Fv[i] in time order, i = 1, 2, 3 ... Rate1 * T;

[0053] 7) In the data of a helicopter flight takeoff and landing, starting from the starting point of the rotor speed measurement data, sequentially traverse the array Fv, find the first sequence number i0 of the rotor speed array that is greater than 0, continue to sequentially traverse, and find the sequence number i1 of the rotor speed value in the array when it becomes 0 again.

[0054] Note: From engine start-up, flight to engine shutdown, the rotor speed of a helicopter follows the sequence of 0 to operating speed, and then back to 0.

[0055] 8) Select the rotational speed interpolation factor m = 30. After considering the interpolation factor, the time interval between two adjacent measurement points of the rotor speed is t1 = 1. / Rate1 / m;

[0056] Note: The accuracy of azimuth calculation increases with the increase of the m value, but the improvement in accuracy is limited when the m value is too high.

[0057] 9) Dynamically allocate a floating-point array Fvx[n1] in computer memory, with an array size n1 = (i1 - i0) * m, to store the interpolated rotor speed values. Allocate a dynamic floating-point array Top[k] to store the sequence number of the calculated azimuth angle results.

[0058] Considering the fluctuation of rotor speed during takeoff and landing, the array size k is the rounded value of T*Nr / 60.*1.1.

[0059] 10) Using linear interpolation, m rotational speed values ​​are interpolated between adjacent rotational speed array values ​​Fy[i0+j] and Fy[i1+j+1]. The interpolation step size delt is (t1*j) / t0. The interpolated rotor speeds are assigned to the array Fvx[n1] in sequence according to formula (1).

[0060] Fvx[i*m+j]=(1.-delt)*Fv[i+i0]+delt*Fv[i+i0+1] (1)

[0061] In the formula: i = 0, 1, 2, ..., i1-i0-1; j = 0, 1, 2, ..., 29.

[0062] 11) Starting from the first rotational speed value in the Fvx array, calculate the acceleration value a[i] between two adjacent rotor rotational speed values ​​Fvx[i] and Fvx[i+1] in a loop according to formula (2), where a[i] is a double-precision floating-point array;

[0063] a[i]=(Fvx[i+1]-Fvx[i]) / t1 (2)

[0064] In the formula: i = 0, 1, 2, ..., i1-i0-1;

[0065] 12) Calculate the number of revolutions d[i] of the rotor when the rotor speed changes from Fvx[i] to Fvx[i+1] using formula (3). The number of revolutions d[i] is a double-precision floating-point array less than 1.

[0066] d[i]=1. / 2.*a[i]*t1*t1+Fvx[i]*t1 (3)

[0067] In the formula: i = 0, 1, 2, ..., i1-i0-1.

[0068] 13) Initialize the double-precision floating-point variables s and ds to 0, and calculate the number of revolutions the rotor has made by accumulating i from 0 to n1-1 in a loop: s = d[i] + ds;

[0069] 14) Establish the condition s>=1 for determining that the rotor completes one full rotation;

[0070] Note: When s = 1, the rotor completes a full rotation. In actual calculations, the probability that s is exactly equal to 1 is very small. Therefore, s >= 1 is used as the condition for determining one rotation.

[0071] 15) When s>1, calculate the number of extra revolutions s-1 of the rotor, assign the result to ds for the cumulative calculation of the next rotation cycle, and assign s to 0.

[0072] 16) The variable k is initially assigned a value of 0. In the loop calculation from step 11) to step 15), when the judgment condition of step 14) is met, that is, when the rotor rotates a full revolution, the azimuth sequence number corresponding to the rotor load (or fuselage vibration) measurement data is calculated using formula (4) and stored in the array Top[k]. At the same time, the value of k is increased by 1.

[0073] Top[k]=INT((i-ds / d[i])*Rate1 / (Rate0*m))+ INT(i0 / rate0*rate1) (4)

[0074] In the formula: i = 0, 1, 2, ..., i1-i0-1; m is the interpolation coefficient; k = 0, 1, 2, ...; INT() is the integer part of the formula.

[0075] 17) Calculate repeatedly until the condition in step 14) no longer appears, then end the calculation and obtain an array Top[k] of azimuth angle results during takeoff and landing, where k is the total number of azimuth angle sequence numbers;

[0076] 18) When the rotor system lacks azimuth test data, Top[k] is directly used for the separation of dynamic and static load quantities, or for whole-cycle harmonic analysis of load (or fuselage vibration); when the rotor system has azimuth test data, Top[k] is used to fill in the gaps or remove redundant points in the possible loss or false signals of the azimuth measurement data.

[0077] 19) The azimuth angle of the drive shaft is difficult to measure. It can be calculated and constructed according to the above steps. In step 8), when calculating Fvx[i*m+j] by speed interpolation, the interpolation result is multiplied by 1.*Nz / Nr, where Nz is the speed of the drive shaft. Other steps remain unchanged.

[0078] The above description is merely a further embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and concept of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A method for obtaining azimuth angle based on rotational speed signal, characterized in that, include: Step 1: Obtain the speed signal array Fv[Rate1*T], where Rate1 is the sampling rate of the speed signal and T is the measurement time of the speed signal; Step 2: Iterate sequentially through the array Fv[Rate1*T], find the first index i0 of Fv[Rate1*T] that is greater than 0, and continue the sequential iteration to find the index i1 of Fv[Rate1*T] that is 0 again; <i0<i1<Rate1*T; Step 3: Interpolate the data from sequence number i0 to i1 in array Fv[Rate1*T] according to the preset interpolation coefficient m to obtain array Fvx[n1]; n1 = (i1-i0)*m; Step 4: Obtain the week number corresponding to every two adjacent numbers in the array Fvx[n1]: d[i] = 0.5*a[i]*t1*t1 + Fvx[i]*t1; i = 0, 1, 2, ..., n1-1; a[i] = (Fvx[i+1] - Fvx[i]) / t1; t1 = 1 / (Rate1*m); Step 5: Accumulate d[i] in ascending order of i to obtain sum[i]. Determine the value of i when sum[i] reaches an integer each time. Correct the azimuth measurement signal based on the value of i when sum[i] reaches an integer each time.

2. The azimuth angle acquisition method based on rotational speed signal according to claim 1, characterized in that, For the data with sequence numbers i0 to i1 in the array Fv[Rate1*T], interpolation is performed according to the preset interpolation coefficient m to obtain the array Fvx[n1], which includes: Fvx[i*m+j]=(1-delt)*Fv[i+i0]+delt*Fv[i+i0+1]; Where: delt = j / m; i = 0, 1, 2, ..., i1-i0-1; j = 0, 1, 2, ..., m-1.

3. The azimuth angle acquisition method based on rotational speed signal according to claim 1, characterized in that, The interpolation coefficient m = 30.

4. The azimuth angle acquisition method based on rotational speed signal according to claim 1, characterized in that, The rotational speed signal array Fv[Rate1*T] is the rotor rotational speed signal array.

5. The azimuth angle acquisition method based on rotational speed signal according to claim 4, characterized in that, When used to obtain the azimuth angle of the drive shaft, the method further includes: After obtaining the array Fvx[n1], multiply the values ​​in the array Fvx[n1] by Nz / Nr; Where Nz is the rated speed of the drive shaft and Nr is the rated speed of the rotor.

6. An azimuth angle acquisition device based on rotational speed signal, characterized in that, include: The speed signal array acquisition module is used to acquire the speed signal array Fv[Rate1*T], where Rate1 is the sampling rate of the speed signal and T is the measurement time of the speed signal; The valid data acquisition module is used to sequentially traverse the array Fv[Rate1*T], find the first sequence number i0 of Fv[Rate1*T] that is greater than 0, continue sequential traversal, and find the sequence number i1 of Fv[Rate1*T] that is 0 again; <i0<i1<Rate1*T; The interpolation module is used to interpolate the data with sequence numbers i0 to i1 in the array Fv[Rate1*T] according to the preset interpolation coefficient m to obtain the array Fvx[n1]; n1=(i1-i0)*m; The week number acquisition module is used to obtain the week number corresponding to every two adjacent numbers in the array Fvx[n1]: d[i] = 0.5*a[i]*t1*t1 + Fvx[i]*t1; i = 0, 1, 2, ..., n1-1; a[i] = (Fvx[i+1] - Fvx[i]) / t1; t1 = 1 / (Rate1*m); The correction module is used to accumulate d[i] in ascending order of i to obtain sum[i], determine the value of i when sum[i] reaches an integer each time, and correct the azimuth measurement signal based on the value of i when sum[i] reaches an integer each time.

7. The azimuth angle acquisition device based on rotational speed signal according to claim 6, characterized in that, The interpolation module is specifically used for interpolation based on the following formula: Fvx[i*m+j]=(1-delt)*Fv[i+i0]+delt*Fv[i+i0+1]; Where: delt = j / m; i = 0, 1, 2, ..., i1-i0-1; j = 0, 1, 2, ..., m-1.

8. The azimuth angle acquisition device based on rotational speed signal according to claim 6, characterized in that, The interpolation coefficient m = 30.

9. The azimuth angle acquisition device based on rotational speed signal according to claim 6, characterized in that, The rotational speed signal array Fv[Rate1*T] is the rotor rotational speed signal array.

10. The azimuth angle acquisition device based on rotational speed signal according to claim 9, characterized in that, The week number acquisition module is also used for: When used to obtain the drive shaft azimuth angle, after obtaining the array Fvx[n1], the value in the array Fvx[n1] is multiplied by Nz / Nr; Where Nz is the rated speed of the drive shaft and Nr is the rated speed of the rotor.

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