CN115186221A - Rotor blade-vortex interference noise extraction method and system - Google Patents

Abstract

The invention provides a method and a system for extracting rotor blade-vortex interference noise, which belong to the field of aircraft noise analysis, and the method for extracting the rotor blade-vortex interference noise comprises the following steps: determining high-frequency noise, paddle-vortex interference length and paddle-vortex interference distance in total noise of a rotor wing of an on-site helicopter; determining a plurality of mode maxima in the high-frequency noise and determining the average strength of the paddle-vortex interference and the average strength of the high-frequency noise; determining a plurality of initial paddle-vortex interference intervals in the high-frequency noise according to the average strength of the paddle-vortex interference, the average strength of the high-frequency noise and the sound pressure in the high-frequency noise; determining a plurality of final paddle-vortex interference intervals according to the maximum sound pressure value in each initial paddle-vortex interference interval and the paddle-vortex interference interval; determining a plurality of paddle-vortex interference centers according to the maximum of the sound pressure in each final paddle-vortex interference interval; and determining the final paddle-vortex interference noise in the high-frequency noise according to each paddle-vortex interference center and the paddle-vortex interference length, so that the reliability of the paddle-vortex interference noise is improved.

Description

A method and system for extracting rotor-vortex interference noise

technical field

The invention relates to the field of aircraft noise analysis, in particular to a method and system for extracting rotor propeller-vortex interference noise.

Background technique

Due to the unique flight performance of helicopters, they are widely used in military and civilian missions, but at the same time they also generate high levels of noise composed of different noise types, such as propeller-vortex noise, thickness noise, and load noise. Among them, the propeller-vortex interference noise generated by the rotor is a more important component. The propeller-vortex interference noise is a kind of high-frequency aerodynamic noise. It always appears at the same time as high-frequency noise and low-frequency aerodynamic noise with a very wide frequency band. Not only affects the comfort of passengers, but also increases the work intensity of the pilot and the maintenance cost of the helicopter, and the propeller-vortex interference noise is also one of the main limitations of the helicopter's operation in urban areas.

At present, the combination of wavelet theory and deep neural network is generally used to extract the propeller-vortex interference noise, but this method is based on a purely theoretical aerodynamic noise model, and the propeller-vortex interference signal is constructed based on a pure theoretical method without considering the interference of the experimental environment. The interference ability is not strong, and the theoretical construction process is quite complicated, so it is difficult to directly apply to engineering.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method and system for extracting rotor propeller-vortex interference noise, which can improve the reliability of propeller-vortex interference noise.

For achieving the above object, the present invention provides the following scheme:

A method for extracting rotor-vortex interference noise, comprising:

Obtain the total rotor noise of the on-site helicopter and the occurrence time of the propeller-vortex interference in the total rotor noise;

The total noise of the rotor is filtered by the interlaced projection algorithm to determine the high-frequency noise; the high-frequency noise includes a plurality of sampling points and the sound pressure at each sampling point;

According to the occurrence time of the propeller-vortex interference and the sampling frequency of the total noise of the rotor, determine the propeller-vortex interference length;

Determine the propeller-vortex interference distance according to the rotor speed, the number of propeller blades of the helicopter and the sampling frequency of the total noise of the rotor;

determining a plurality of modulo maxima in the high-frequency noise; each modulo maxima is a sound pressure whose sound pressure in the high-frequency noise is greater than a set threshold;

According to the maximum value of each mode, determine the average intensity of propeller-vortex interference;

Determine the average intensity of high-frequency noise according to the sound pressure at each sampling point in the high-frequency noise;

According to the average intensity of the propeller-vortex interference, the average intensity of the high-frequency noise, and the sound pressure at each sampling point in the high-frequency noise, determining a plurality of initial propeller-vortex interference intervals in the high-frequency noise;

According to the maximum value of sound pressure in each initial propeller-vortex interference interval and the propeller-vortex interference spacing, determine a plurality of final propeller-vortex interference intervals;

According to the maximum value of the sound pressure in each final propeller-vortex interference interval, multiple propeller-vortex interference centers are determined;

According to each propeller-vortex interference center and the propeller-vortex interference length, the final propeller-vortex interference noise is determined in the high-frequency noise.

Optionally, determine the paddle-vortex interference length:

n _BVI ≈t _BVI /f _sr ;

Among them, n _BVI is the length of the propeller-vortex interference, t _BVI is the occurrence time of the propeller-vortex interference, and f _sr is the sampling frequency of the total rotor noise.

Optionally, according to the rotor speed, the number of blades of the helicopter, and the sampling frequency of the total noise of the rotor, the paddle-vortex interference spacing is determined, specifically including:

Determine the propeller-vortex interference period according to the rotor speed and the number of propeller blades of the helicopter;

According to the propeller-vortex interference period and the sampling frequency of the total noise of the rotor, the propeller-vortex interference distance is determined.

Optionally, the following formula is used to determine the propeller-vortex disturbance period:

T _BVI =60/n _{r br} ;

Among them, T _BVI is the propeller-vortex interference period, n _r is the rotor speed, and _br is the number of propeller blades.

Optionally, the following formula is used to determine the propeller-vortex interference spacing:

N _BVI =T _BVI /f _sr ;

Among them, N _BVI is the propeller-vortex interference distance, T _BVI is the propeller-vortex interference period, and f _sr is the sampling frequency of the total rotor noise.

Optionally, according to the average intensity of the propeller-vortex interference, the average intensity of the high-frequency noise, and the sound pressure at each sampling point in the high-frequency noise, a plurality of initial propellers are determined in the high-frequency noise. - Eddy interference interval, which includes:

According to the average intensity of the propeller-vortex interference and the average intensity of the high-frequency noise, a constant is determined; wherein, the constant satisfies the following conditions: m _n c > m _L , c∈(0,1), c is a constant, m _n is the average intensity of propeller-vortex interference, and m _L is the average intensity of high-frequency noise;

According to the average propeller-vortex interference intensity, the constant, and the sound pressure at each sampling point in the high-frequency noise, a plurality of initial propeller-vortex interference intervals are determined; wherein, within the i-th initial propeller-vortex interference interval The sound pressure of satisfies the following conditions: |f(x)|≥m _n c, x∈[l _ia , l _ib ], [l _ia , l _ib ] is the ith initial propeller-vortex interference interval, and l _ia is the ith The starting sampling point of the i initial propeller-vortex interference interval, l _ib is the ending sampling point of the ith initial propeller-vortex interference interval, and f(x) is the sampling point x in the ith initial propeller-vortex interference interval The sound pressure of , | | is the modulo operation.

Optionally, determining a plurality of final propeller-vortex interference intervals according to the maximum sound pressure in each initial paddle-vortex interference interval and the paddle-vortex interference interval, specifically including:

According to the maximum sound pressure in each initial propeller-vortex interference interval, determine the distance between two adjacent initial propeller-vortex interference intervals;

If the distance between two adjacent initial propeller-vortex interference intervals is less than or equal to half of the propeller-vortex interference interval, the initial propeller-vortex interference with the smaller maximum sound pressure in the two adjacent initial propeller-vortex interference intervals Intervals are discarded to obtain multiple final propeller-vortex interference intervals.

Optionally, the following formula is used to determine the distance between the ith initial propeller-vortex interference interval and the jth initial propeller-vortex interference interval:

d _ij = |argmax|f(x ^* )|-argmax|f(y ^* )||, x ^* ∈ [l _ia , l _ib ], y ^* ∈ [l _ja , l _jb ];

Among them, d _ij is the distance between the i-th initial propeller-vortex interference interval and the j-th initial propeller-vortex interference interval, f(x ^* ) is the sound pressure at the sampling point x ^* , and f(y ^* ) is the sampling point The sound pressure at y ^* , argmax|f(x ^* )| is the sampling point corresponding to the maximum sound pressure in the ith initial propeller-vortex interference interval, argmax|f(y ^* )| is the jth initial propeller - The sampling point corresponding to the maximum sound pressure in the vortex interference interval, [l _ia , l _ib ] is the ith initial propeller-vortex interference interval, [l _ja , l _jb ] is the jth initial propeller-vortex interference interval , i≠j.

Optionally, according to each propeller-vortex interference center and the propeller-vortex interference length, the final propeller-vortex interference noise is determined in the high-frequency noise, specifically including:

According to each propeller-vortex interference center and the propeller-vortex interference length, multiple propeller-vortex interference occurrence intervals are determined; the kth propeller-vortex interference occurrence interval is [w _k -n _BVI /2, wk+n _BVI / 2], where w _k is the k-th propeller-vortex interference center, n _BVI is the propeller-vortex interference length;

The signal outside the occurrence interval of the propeller-vortex interference in the high-frequency noise is assigned as 0, and the final propeller-vortex interference noise is obtained.

For achieving the above object, the present invention also provides the following scheme:

A rotor-vortex interference noise extraction system, comprising:

The signal acquisition unit is used to acquire the total rotor noise of the on-site helicopter and the occurrence time of the propeller-vortex interference in the total rotor noise;

A high-frequency noise determination unit, connected with the signal acquisition unit, is used to filter the total noise of the rotor by using an interleaved projection algorithm to determine the high-frequency noise; the high-frequency noise includes a plurality of sampling points and a signal at each sampling point. Sound pressure;

an interference length determination unit, connected with the signal acquisition unit, for determining the length of the propeller-vortex interference according to the occurrence time of the propeller-vortex interference and the sampling frequency of the total noise of the rotor;

an interference distance determination unit, connected with the signal acquisition unit, for determining the paddle-vortex interference distance according to the rotating speed of the rotor, the number of propeller blades of the helicopter and the sampling frequency of the total noise of the rotor;

A modulus maximum value determination unit, connected with the high-frequency noise determination unit, is used for determining a plurality of modulus maximum values in the high-frequency noise; Sound pressure at a certain threshold;

an interference average intensity determination unit, connected with the mode maximum value determination unit, and used for determining the average propeller-vortex interference intensity according to each mode maximum value;

a high-frequency noise average intensity determination unit, connected to the high-frequency noise determination unit, and configured to determine the high-frequency noise average intensity according to the sound pressure at each sampling point in the high-frequency noise;

The initial interval determination unit is connected with the interference average intensity determination unit, the high frequency noise average intensity determination unit and the high frequency noise determination unit, and is used for determining the average intensity of the paddle-vortex interference, the high frequency noise average intensity and the the sound pressure at each sampling point in the high-frequency noise, and determine a plurality of initial propeller-vortex interference intervals in the high-frequency noise;

The final interval determination unit is connected to the initial interval determination unit and the interference distance determination unit, and is used for determining a plurality of final intervals according to the maximum value of sound pressure in each initial paddle-vortex interference interval and the paddle-vortex interference distance Propeller-vortex interference range;

an interference center determination unit, connected to the final interval determination unit, for determining a plurality of propeller-vortex interference centers according to the maximum value of the sound pressure in each final propeller-vortex interference interval;

An interference noise determination unit, connected with the interference center determination unit and the interference length determination unit, and used for determining the final propeller in the high-frequency noise according to each propeller-vortex interference center and the propeller-vortex interference length - Eddy disturbance noise.

According to the specific embodiment provided by the present invention, the present invention discloses the following technical effects: first extract high-frequency noise from the total rotor noise of the helicopter on site, and then determine the propeller-vortex interference occurrence time and the sampling frequency of the total rotor noise. Vortex interference length; determine the propeller-vortex interference distance according to the rotor speed, the number of propeller blades of the helicopter and the sampling frequency of the total rotor noise; determine multiple mode maxima in high-frequency noise; determine the propeller-vortex interference according to the maximum value of each mode Average intensity of interference; determine the average intensity of high-frequency noise according to the sound pressure at each sampling point in the high-frequency noise; according to the average intensity of propeller-vortex interference, the average intensity of high-frequency noise and the sound pressure at each sampling point in Determine multiple initial propeller-vortex interference intervals in the high-frequency noise; determine multiple final propeller-vortex interference intervals according to the maximum sound pressure in each initial propeller-vortex interference interval and the propeller-vortex interference distance; according to each final propeller-vortex interference interval The maximum value of the sound pressure in the interference interval determines multiple propeller-vortex interference centers; according to each propeller-vortex interference center and the propeller-vortex interference length, the final propeller-vortex interference noise is determined in the high-frequency noise. Using the total rotor noise of the helicopter site, the propeller-vortex interference noise is extracted under the condition of environmental noise interference, which improves the reliability of the propeller-vortex interference noise.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative labor.

Fig. 1 is the flow chart of the rotor propeller-vortex interference noise extraction method of the present invention;

Fig. 2 is the overall schematic diagram of the rotor propeller-vortex interference noise extraction process of the present invention;

Figure 3 is a schematic diagram of the total noise of the rotor;

Figure 4 is a schematic diagram of low frequency noise;

Figure 5 is a schematic diagram of high frequency noise;

Figure 6 is a schematic diagram of the spacing and length of the propeller-vortex interference noise;

7 is a schematic diagram of extracting propeller-vortex interference noise from high-frequency noise;

8 is a schematic diagram of a modulus maximum point;

Figure 9 is a schematic diagram of the propeller-vortex interference interval;

Figure 10 is a schematic diagram of the center point of the propeller-vortex interference noise;

Figure 11 is a schematic diagram of the final propeller-vortex interference noise;

FIG. 12 is a schematic diagram of a staggered projection algorithm;

13 is a schematic diagram of the module structure of the rotor-vortex interference noise extraction system of the present invention.

Symbol Description:

Signal acquisition unit-1, high frequency noise determination unit-2, interference length determination unit-3, interference distance determination unit-4, modulus maximum value determination unit-5, interference average intensity determination unit-6, high frequency noise average intensity A determination unit-7, an initial interval determination unit-8, a final interval determination unit-9, an interference center determination unit-10, and an interference noise determination unit-11.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The purpose of the present invention is to provide a method and system for extracting rotor-vortex interference noise. By using the total rotor noise at the helicopter site, the rotor-vortex interference noise is extracted under the condition of environmental noise interference, which improves the performance of the rotor-vortex interference noise. Reliability of disturbing noise.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

As shown in Figure 1 and Figure 2, the method for extracting rotor propeller-vortex interference noise of the present invention includes:

S1: Obtain the total rotor noise of the on-site helicopter and the occurrence time of the propeller-vortex interference in the total rotor noise. In this embodiment, the total noise of the rotor is the total noise in the microphone, and FIG. 3 is a schematic diagram of the total noise.

S2: Use an interlaced projection algorithm to filter the total noise of the rotor to determine high-frequency noise. The high-frequency noise includes a plurality of sampling points and the sound pressure at each sampling point. Specifically, the interlaced projection algorithm first separates the low-frequency noise from the total rotor noise, and subtracts the low-frequency noise from the total rotor noise to obtain the high-frequency noise. The low-frequency noise and the high-frequency noise are shown in Figures 4 and 5. In this embodiment, assuming that the length of the high-frequency noise signal is L, and the sound pressure of the high-frequency noise signal at the r-th point is f(r), the high-frequency noise signal is

S3: Determine the length of the propeller-vortex interference according to the occurrence time of the propeller-vortex interference and the sampling frequency of the total noise of the rotor.

Specifically, the occurrence time t _BVI of the propeller-vortex interference noise can be estimated by the total noise of the microphone, and then according to the occurrence time of the propeller-vortex interference and the sampling frequency of the total noise of the rotor, it is estimated that each propeller-vortex interference noise is at high Length in frequency noise: n _BVI ≈t _BVI /f _sr . Among them, the sampling frequency of the microphone is known, and the sampling interval is known. Calculate the number of sampling points of any propeller-vortex interference noise. The product of the sampling interval and the number of points existing in the propeller-vortex interference noise is the estimated propeller-vortex interference noise. time of occurrence.

S4: Determine the propeller-vortex interference distance according to the rotational speed of the rotor, the number of propeller blades of the helicopter, and the sampling frequency of the total noise of the rotor.

Specifically, the propeller-vortex interference period is determined according to the rotational speed of the rotor and the number of propeller blades of the helicopter. According to the propeller-vortex interference period and the sampling frequency of the total noise of the rotor, the propeller-vortex interference distance is determined. The propeller-vortex interference period is determined by the formula T _BVI =60/n _{r br} , where T _BVI is the propeller-vortex interference period, n _r is the rotational speed of the rotor, and _br is the number of propeller blades. The propeller-vortex interference spacing is determined by the formula N _BVI =T _BVI /f _sr , where N _BVI is the propeller-vortex interference spacing, as shown in Fig. 6 .

Since the propeller-vortex interference noise has obvious characteristics, such as periodic appearance, the intensity is obviously higher than that of broadband noise such as turbulent noise and electromagnetic interference noise, so steps S5-S11 of the present invention are based on the characteristics of the propeller-vortex interference noise. The propeller-vortex interference noise is determined in the noise, as shown in Figure 7.

S5: Determine a plurality of modulo maxima in the high-frequency noise. The maximum value of each mode is the sound pressure in the high-frequency noise whose sound pressure is greater than the set threshold, as shown in FIG. 8 . That is to find some points with larger values in the high-frequency noise signal, the purpose is to determine the strength of the propeller-vortex interference noise.

本发明将第g个模极大值记为M_g＝|f(x_g)|。Specifically, find a finite number of modulo maxima points (x ₁ , x ₂ ,..., x _n ) in high-frequency noise, n<<L, and maximize the product of these n modulo maxima, that is, satisfy

In the present invention, the g-th modulus maximum value is denoted as M _g =|f(x _g )|.

确定桨-涡干扰平均强度。其中，m_n为桨-涡干扰平均强度，n为模极大值的数量。S6: According to the maximum value of each mode, determine the average intensity of propeller-vortex interference. Specifically, using the formula

Determine the mean strength of the paddle-vortex disturbance. where m _n is the average intensity of the propeller-vortex interference, and n is the number of modulo maxima.

确定高频噪声平均强度。其中，m_L为高频噪声平均强度，L为高频噪声的长度，f(x_i)为高频噪声中采样点x_i处的声压。S7: Determine the average intensity of high-frequency noise according to the sound pressure at each sampling point in the high-frequency noise. Specifically, using the formula

Determines the average intensity of high frequency noise. Among them, m _L is the average intensity of high-frequency noise, L is the length of high-frequency noise, and f( _xi ) is the sound pressure at the sampling point _xi in the high-frequency noise.

S8: Determine a plurality of initial propeller-vortex interference intervals in the high-frequency noise according to the average intensity of the propeller-vortex interference, the average intensity of the high-frequency noise, and the sound pressure at each sampling point in the high-frequency noise , as shown in Figure 9.

Specifically, the constant is first determined according to the average intensity of the propeller-vortex interference and the average intensity of the high-frequency noise. Wherein, the constant satisfies the following conditions: m _n c>m _L , c∈(0,1), c is a constant, m _n is the average intensity of propeller-vortex interference, and m _L is the average intensity of high-frequency noise. Generally take c=0.1～0.5. In fact, the value of c has no effect on the result of the algorithm, but it can reduce the number of iterations required for convergence.

Steps S6-S8 roughly estimate the average intensity of the propeller-vortex interference noise and the average intensity of the high-frequency signal in the high-frequency noise signal, and estimate the value of the constant c, which provides a basis for narrowing the range where the propeller-vortex interference noise exists.

I为初始桨-涡干扰区间的总数。Then, according to the average intensity of the propeller-vortex interference, the constant, and the sound pressure at each sampling point in the high-frequency noise, a plurality of initial propeller-vortex interference intervals are determined. That is to search for the high-frequency noise signal with a large sound pressure amplitude range, and narrow the range where the propeller-vortex interference noise exists. Among them, the sound pressure in the ith initial propeller-vortex interference interval satisfies the following conditions: |f(x)|≥m _n c, x∈[l _ia , l _ib ], [l _ia , l _ib ] is the ith initial propeller-vortex interference interval, l _ia is the starting sampling point of the ith initial propeller-vortex interference interval, l _ib is the end sampling point of the ith initial propeller-vortex interference interval, f(x) is the ith initial propeller-vortex interference interval The sound pressure at the sampling point x in the initial propeller-vortex interference interval, || is the modulo operation. Further, the interval

I is the total number of initial propeller-vortex interference intervals.

S9: According to the maximum value of sound pressure in each initial propeller-vortex interference interval and the propeller-vortex interference interval, determine a plurality of final propeller-vortex interference intervals.

的距离d_ij为两个区间的声压最大值所在时刻差的模。采用以下公式，确定第i个初始桨-涡干扰区间与第j个初始桨-涡干扰区间的距离：Specifically, according to the maximum value of sound pressure in each initial propeller-vortex interference interval, the distance between two adjacent initial propeller-vortex interference intervals is determined. In this embodiment, according to the characteristic of the periodic appearance of propeller-vortex interference noise, it can be inferred that any two intervals in which propeller- _vortex interference noise occurs are periodic. , l _ib ], [l _ja , l _jb ],

The distance d _ij is the modulus of the time difference of the maximum sound pressure of the two intervals. The following formula is used to determine the distance between the ith initial propeller-vortex interference interval and the jth initial propeller-vortex interference interval:

d _ij = |argmax|f(x ^* )|-argmax|f(y ^* )||, x ^* ∈ [l _ia , l _ib ], y ^* ∈ [l _ja , l _jb ];

Among them, d _ij is the distance between the i-th initial propeller-vortex interference interval and the j-th initial propeller-vortex interference interval, f(x ^* ) is the sound pressure at the sampling point x ^* , and f(y ^* ) is the sampling point The sound pressure at y ^* , argmax|f(x ^* )| is the sampling point corresponding to the maximum sound pressure in the ith initial propeller-vortex interference interval, argmax|f(y ^* )| is the jth initial propeller - The sampling point corresponding to the maximum sound pressure in the vortex interference interval, [l _ia , l _ib ] is the ith initial propeller-vortex interference interval, [l _ja , l _jb ] is the jth initial propeller-vortex interference interval .

Since it is not certain that there are propeller-vortex interference signals in each initial propeller-vortex interference interval, and some initial propeller-vortex interference intervals may contain other high-frequency noises, the present invention periodically appears according to the propeller-vortex interference noise. , the propeller-vortex interference spacing N _BVI can be estimated in advance. If the distance between the two initial propeller-vortex interference intervals is much smaller than the propeller-vortex interference interval N _BVI , that is, d _ij ≤N _BVI /2, it is determined that there is at most one propeller-vortex interference in the two initial propeller-vortex interference intervals Noise, and possibly a paddle-vortex interference noise at all. At this time, the interval with a relatively large modulus value of the sound pressure is selected, and the other interval is discarded. If there is propeller-vortex interference noise, it must be in the interval corresponding to the point with the largest signal modulus value. If the interval is continuously rounded between two adjacent intervals, the distance between the intervals will continue to increase. According to the periodic characteristics of the propeller-vortex interference noise, it can be determined that the distance d _ij >N _BVI /2 in all adjacent intervals Then the final propeller-vortex interference interval can be obtained. Make sure that there is only one propeller-vortex interference noise in each interval, and the number of remaining intervals is the number of propeller-vortex interference noise.

S10: Determine multiple propeller-vortex interference centers according to the modulo maximum value of the sound pressure in each final propeller-vortex interference interval, as shown in Figure 10. Accurate positioning of propeller-vortex interference noise is achieved. Specifically, the time coordinates corresponding to the modulo maximum value |f(x)| of the sound pressure in each final propeller-vortex interference interval (l _ka , l _kb ) are obtained. That is, w _k =argmin|f(w)|,w∈(l _ka ,l _kb ). w _k is also the coordinate of the k-th propeller-vortex interference noise center, f(w) is the sound pressure at the sampling point w, and the coordinates of all propeller-vortex interference noise centers can be obtained by traversing all final propeller-vortex interference intervals .

S11: According to each propeller-vortex interference center and the propeller-vortex interference length, determine the final propeller-vortex interference noise in the high-frequency noise, as shown in FIG. 11 .

Specifically, according to each propeller-vortex interference center and the propeller-vortex interference length, a plurality of propeller-vortex interference occurrence intervals are determined. The occurrence interval of the k-th propeller-vortex interference is [w _k -n _BVI /2,w _k +n _BVI /2], where w _k is the k-th propeller-vortex interference center, and n _BVI is the length of the propeller-vortex interference .

其中，K(t)为桨-涡干扰噪声中t时刻的声压。The signal outside the occurrence interval of the propeller-vortex interference in the high-frequency noise is assigned as 0, and the final propeller-vortex interference noise is obtained. which is

Among them, K(t) is the sound pressure at time t in the propeller-vortex interference noise.

In addition, the abscissa in FIGS. 3-5 and 8-11 is the sampling time, and the ordinate is the sound pressure.

The present invention first uses wavelet theory to separate high-frequency and low-frequency noise, and then extracts the propeller-vortex interference noise from the high-frequency noise according to the inherent characteristics of the propeller-vortex interference noise of the helicopter rotor. Considering the feasibility of the project, according to the propeller-vortex interference noise The vortex interference noise signal has the particularity that the existence time is short and the intensity is much higher than that of ordinary noise. The propeller-vortex interference noise is directly extracted from the acoustic signal of the rotor experimental site microphone. The extraction algorithm is simple and reliable, and has the ability of engineering application. The reliability of the propeller-vortex interference noise, and then the helicopter is improved according to the propeller-vortex interference noise to accurately reduce the propeller-vortex interference noise of the rotor, reduce the pilot's work intensity and the maintenance cost of the helicopter.

Further, in step S2, the interlaced projection algorithm of Mallat is used to determine the high-frequency noise in the total noise of the rotor, and the interlaced projection algorithm is a filtering algorithm in wavelet analysis, as shown in Figure 12, and the details are as follows:

Note that the binary wavelet transform of h(t) is WT _h (j, t), and h(t) is a hypothetical low-frequency noise signal, which is an unknown quantity. The constraints on the set {h(t); h(t)∈L ² (R)} are:

Condition 1: Corresponding to each scale j, at all the abscissas (t _{j, n} ) _n∈Z of the modulo maxima, there is |WT _h (j, t _{j, n} )|=|WT _f (j, t _j,n )|. Among them, WT _f (j, t _{j, n} ) is the wavelet transform of the noise f, j is the scaling parameter, and t _{j, n} is the translation parameter.

Condition 2: Corresponding to each scale j, the local extrema of WT _h (j, t) should be located at the abscissa (t _{j, n} ) _n∈Z of the modulo maxima.

where L ² (R) is the space in which all square-integrable noise signals reside; Z is the set of integers.

Let V be the space composed of the binary wavelet transforms of all functions on the L ² (R) space, K be the space composed of the sequence g _j (t), and g _j (t) satisfies:

对比

序列g_j(t)应是某一个序列的小波变换。再令Γ是空间K上的一个闭包，其中的元素g_j(t)满足g_j(t_j，n)＝WT_f(j，t_j，n)，

和

均为中间变量，即代指等式后面的结果。Obviously,

Compared

The sequence g _j (t) should be the wavelet transform of a certain sequence. Let Γ be a closure on space K, and the element g _j (t) in it satisfies g _j (t _{j, n} )=WT _f (j, t _{j, n} ),

and

Both are intermediate variables, that is, refer to the result after the equation.

Alternatively, it can be expressed more completely as

Γ={{g _j (t)}∈K|g _j (t _j,n )=WT _f (j,t _j,n ),j,n∈Z}.

In this way, the wavelet transform satisfying condition 1 should be an element in the space Λ=V∩Γ. The task now turns into finding the elements in Λ such that their norm is the smallest. What accomplishes this is the alternating projection of V and Γ.

是空间V和Γ之间的交替投影算子，

是P的n次迭代，则对任一序列X＝{g_j(t)}_j∈Z∈K，可以证明，有

P_Λ是总噪声在空间Λ上的投影算子。其中，P_V是投影算子，表示噪声在y空间上的投影，P_Γ是也是投影算子，表示噪声在Γ空间上的投影。make

is the alternate projection operator between spaces V and Γ,

is n iterations of P, then for any sequence X={g _j (t)} _{j∈Z ∈K} , it can be proved that there is

P _Λ is the projection operator of the total noise on space Λ. Among them, P _V is the projection operator, which represents the projection of the noise on the y space, and P _Γ is also the projection operator, which represents the projection of the noise on the Γ space.

Thus, the alternating projection between spaces V and Γ converges to the orthogonal projection of space Λ. At the beginning of the iteration, g _j (t) = 0 is selected, then the norm of the elements converged to the space Λ is close to zero after the alternate projection, and the reconstruction of the signal binary wavelet transform coefficient is realized.

Then use the reconstructed binary wavelet coefficients to perform inverse transformation to separate the low-frequency noise, and subtract the low-frequency noise from the total noise to obtain all the high-frequency noise (including the propeller-vortex interference noise).

As shown in FIG. 13 , the rotor-vortex interference noise extraction system of the present invention includes: a signal acquisition unit 1, a high-frequency noise determination unit 2, an interference length determination unit 3, an interference distance determination unit 4, a modulus maximum value determination unit 5, Interference average strength determination unit 6 , high frequency noise average strength determination unit 7 , initial interval determination unit 8 , final interval determination unit 9 , interference center determination unit 10 , and interference noise determination unit 11 .

Wherein, the signal acquisition unit 1 is used to acquire the total rotor noise of the on-site helicopter and the occurrence time of the propeller-vortex interference in the total rotor noise.

The high-frequency noise determination unit 2 is connected to the signal acquisition unit 1, and the high-frequency noise determination unit 2 is used to filter the total noise of the rotor by using an interleaved projection algorithm to determine the high-frequency noise; the high-frequency noise includes a plurality of samples point and the sound pressure at each sampling point.

The interference length determination unit 3 is connected to the signal acquisition unit 1, and the interference length determination unit 3 is configured to determine the propeller-vortex interference length according to the occurrence time of the propeller-vortex interference and the sampling frequency of the total noise of the rotor.

The interference distance determination unit 4 is connected to the signal acquisition unit 1, and the interference distance determination unit 4 is used for determining the propeller-vortex interference distance according to the rotating speed of the rotor, the number of propeller blades of the helicopter and the sampling frequency of the total noise of the rotor.

Specifically, the interference distance determination unit 4 includes: an interference period determination module and a distance determination module.

Among them, the interference period determination module is used to determine the propeller-vortex interference period according to the rotor speed and the number of propeller blades of the helicopter.

The distance determination module is connected with the signal acquisition unit 1 and the interference period determination module, and the distance determination module is used for determining the propeller-vortex interference distance according to the propeller-vortex interference period and the sampling frequency of the total noise of the rotor.

The modulus maximum value determination unit 5 is connected to the high frequency noise determination unit 2, and the modulus maximum value determination unit 5 is used for determining a plurality of modulus maximum values in the high frequency noise. The maximum value of each mode is the sound pressure in the high-frequency noise whose sound pressure is greater than the set threshold.

The average interference intensity determination unit 6 is connected to the mode maximum value determination unit 5, and the average interference intensity determination unit 6 is configured to determine the average propeller-vortex interference intensity according to each mode maximum value.

The high-frequency noise average intensity determination unit 7 is connected to the high-frequency noise determination unit 2, and the high-frequency noise average intensity determination unit 7 is configured to determine the high-frequency noise average intensity according to the sound pressure at each sampling point in the high-frequency noise .

The initial interval determination unit 8 is connected with the interference average intensity determination unit 6, the high frequency noise average intensity determination unit 7 and the high frequency noise determination unit 2, and the initial interval determination unit 8 is used for The average intensity of the high-frequency noise and the sound pressure at each sampling point in the high-frequency noise are determined, and a plurality of initial propeller-vortex interference intervals are determined in the high-frequency noise.

Specifically, the initial interval determination unit 8 includes a constant determination module and an interval determination module.

Among them, the constant determination module, the average interference intensity determination unit 6 and the high frequency noise average intensity determination unit 7, the constant determination module is used for determining the constant according to the average intensity of the propeller-vortex interference and the average intensity of the high frequency noise. Wherein, the constant satisfies the following conditions: m _n c > m _L , c∈(0,1), c is a constant, m _n is the average intensity of propeller-vortex interference, and m _L is the average intensity of high-frequency noise.

The interval determination module is connected with the constant determination module, the interference average intensity determination unit 6 and the high-frequency noise determination unit 2, and the interval determination module is used to determine the average intensity of the propeller-vortex interference, the constant and each sample in the high-frequency noise The sound pressure at the point is used to determine multiple initial propeller-vortex interference intervals. Among them, the sound pressure in the ith initial propeller-vortex interference interval satisfies the following conditions: |f(x)|≥m _n c, x∈[l _ia , l _ib ], [l _ia , l _ib ] is the ith initial propeller-vortex interference interval, l _ia is the starting sampling point of the ith initial propeller-vortex interference interval, l _ib is the end sampling point of the ith initial propeller-vortex interference interval, f(x) is the ith initial propeller-vortex interference interval The sound pressure at the sampling point x in the initial propeller-vortex interference interval, | | is the modulo operation.

The final interval determination unit 9 is connected to the initial interval determination unit 8 and the interference distance determination unit 4, and the final interval determination unit 9 is used to determine the maximum value of sound pressure in each initial paddle-vortex interference interval and the paddle-vortex interference interval. Interference spacing to determine multiple final propeller-vortex interference intervals.

Specifically, the final interval determination unit 9 includes: a distance determination module and an interval selection module.

The distance determination module is connected to the initial interval determination unit 8, and the distance determination module is used to determine the distance between two adjacent initial paddle-vortex interference intervals according to the maximum sound pressure in each initial paddle-vortex interference interval.

The interval selection module is connected to the distance determination module and the interference distance determination unit 4, and the interval selection module is used to select the adjacent two initial propeller-vortex interference intervals if the distance between them is less than or equal to half of the propeller-vortex interference interval. In the two initial propeller-vortex interference intervals, the initial propeller-vortex interference interval with the smaller maximum sound pressure is discarded to obtain multiple final propeller-vortex interference intervals.

The interference center determination unit 10 is connected to the final interval determination unit 9, and the interference center determination unit 10 is configured to determine a plurality of propeller-vortex interference centers according to the maximum value of the sound pressure in each final propeller-vortex interference interval.

The interference noise determination unit 11 is connected to the interference center determination unit 10 and the interference length determination unit 3, and the interference noise determination unit 11 is used for determining the maximum value at the high Determine the final propeller-vortex interference noise from the frequency noise.

Specifically, the interference noise determination unit 11 includes an occurrence interval determination module and a final noise determination module.

Wherein, the occurrence interval determination module is connected with the interference center determination unit 10 and the interference length determination unit 3, and the occurrence interval determination module is used for determining a plurality of propeller-vortex interference centers according to each propeller-vortex interference center and the propeller-vortex interference length Interference occurrence interval. The occurrence interval of the kth propeller-vortex interference is [w _k -n _BVI /2, w _k +n _BVI /2], where w _k is the kth propeller-vortex interference center, and n _BVI is the propeller-vortex interference length .

The final noise determination module is connected with the occurrence interval determination module, and the final noise determination module is used for assigning a value of 0 to the signal outside the occurrence interval of the propeller-vortex interference in the high-frequency noise to obtain the final propeller-vortex interference noise.

Compared with the prior art, the rotor-vortex interference noise extraction system of the present invention has the same beneficial effects as the above-mentioned rotor-vortex interference noise extraction method, which will not be repeated here.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant part can be referred to the description of the method.

The principles and implementations of the present invention are described herein using specific examples. The descriptions of the above embodiments are only used to help understand the method and the core idea of the present invention; meanwhile, for those skilled in the art, according to the present invention There will be changes in the specific implementation and application scope. In conclusion, the contents of this specification should not be construed as limiting the present invention.

Claims (10)

1. a rotor blade-vortex interference noise extraction method, is characterized in that, described rotor blade-vortex interference noise extraction method comprises: Obtain the total rotor noise of the on-site helicopter and the occurrence time of the propeller-vortex interference in the total rotor noise; The total noise of the rotor is filtered by the interlaced projection algorithm to determine the high-frequency noise; the high-frequency noise includes a plurality of sampling points and the sound pressure at each sampling point; According to the occurrence time of the propeller-vortex interference and the sampling frequency of the total noise of the rotor, determine the propeller-vortex interference length; Determine the propeller-vortex interference distance according to the rotor speed, the number of propeller blades of the helicopter and the sampling frequency of the total noise of the rotor; determining a plurality of modulo maxima in the high-frequency noise; each modulo maxima is a sound pressure whose sound pressure in the high-frequency noise is greater than a set threshold; According to the maximum value of each mode, determine the average intensity of propeller-vortex interference; Determine the average intensity of high-frequency noise according to the sound pressure at each sampling point in the high-frequency noise; According to the average intensity of the propeller-vortex interference, the average intensity of the high-frequency noise, and the sound pressure at each sampling point in the high-frequency noise, determining a plurality of initial propeller-vortex interference intervals in the high-frequency noise; According to the maximum value of sound pressure in each initial propeller-vortex interference interval and the propeller-vortex interference spacing, determine a plurality of final propeller-vortex interference intervals; According to the maximum value of the sound pressure in each final propeller-vortex interference interval, multiple propeller-vortex interference centers are determined; According to each propeller-vortex interference center and the propeller-vortex interference length, the final propeller-vortex interference noise is determined in the high-frequency noise. 2. rotor propeller-vortex interference noise extraction method according to claim 1, is characterized in that, adopts following formula, determines propeller-vortex interference length: n _BVI ≈t _BVI /f _sr ; Among them, n _BVI is the length of the propeller-vortex interference, t _BVI is the occurrence time of the propeller-vortex interference, and f _sr is the sampling frequency of the total rotor noise. 3. rotor propeller-vortex interference noise extraction method according to claim 1, is characterized in that, described according to the sampling frequency of rotor rotating speed, the number of propeller blades of helicopter and described rotor total noise, determine propeller-vortex interference spacing, Specifically include: Determine the propeller-vortex interference period according to the rotor speed and the number of propeller blades of the helicopter; According to the propeller-vortex interference period and the sampling frequency of the total noise of the rotor, the propeller-vortex interference distance is determined. 4. rotor propeller-vortex interference noise extraction method according to claim 3, is characterized in that, adopts following formula, determines propeller-vortex interference period: T _BVI =60/n _{r br} ; Among them, T _BVI is the propeller-vortex interference period, n _r is the rotor speed, and _br is the number of propeller blades. 5. rotor propeller-vortex interference noise extraction method according to claim 3, is characterized in that, adopts following formula, determines propeller-vortex interference spacing: N _BVI =T _BVI /f _sr ; Among them, N _BVI is the propeller-vortex interference distance, T _BVI is the propeller-vortex interference period, and f _sr is the sampling frequency of the total rotor noise. 6. The method for extracting rotor propeller-vortex interference noise according to claim 1, characterized in that, according to the average intensity of the propeller-vortex interference, the average intensity of the high-frequency noise, and each sample in the high-frequency noise The sound pressure at the point is determined, and a plurality of initial propeller-vortex interference intervals are determined in the high-frequency noise, specifically including: According to the average intensity of the propeller-vortex interference and the average intensity of the high-frequency noise, a constant is determined; wherein, the constant satisfies the following conditions: m _n c > m _L , c∈(0,1), c is a constant, m _n is the average intensity of propeller-vortex interference, and m _L is the average intensity of high-frequency noise; According to the average propeller-vortex interference intensity, the constant, and the sound pressure at each sampling point in the high-frequency noise, a plurality of initial propeller-vortex interference intervals are determined; wherein, within the i-th initial propeller-vortex interference interval The sound pressure of satisfies the following conditions: |f(x)|≥m _n c, x∈[l _ia , l _ib ], [l _ia , l _ib ] is the ith initial propeller-vortex interference interval, and l _ia is the ith The starting sampling point of the i initial propeller-vortex interference interval, l _ib is the ending sampling point of the ith initial propeller-vortex interference interval, and f(x) is the sampling point x in the ith initial propeller-vortex interference interval The sound pressure, || is the modulo operation. 7. The method for extracting rotor propeller-vortex interference noise according to claim 1, characterized in that, according to the maximum value of sound pressure in each initial propeller-vortex interference interval and the propeller-vortex interference spacing, determine a plurality of The final propeller-vortex interference interval, including: According to the maximum value of sound pressure in each initial propeller-vortex interference interval, determine the distance between two adjacent initial propeller-vortex interference intervals; If the distance between two adjacent initial propeller-vortex interference intervals is less than or equal to half of the propeller-vortex interference interval, the initial propeller-vortex interference with the smaller maximum sound pressure in the two adjacent initial propeller-vortex interference intervals Intervals are discarded to obtain multiple final propeller-vortex interference intervals. 8. rotor propeller-vortex interference noise extraction method according to claim 7, is characterized in that, adopt following formula, determine the distance of the ith initial propeller-vortex interference interval and the jth initial propeller-vortex interference interval: d _ij = |argmax|f(x ^* )|-argmax|f(y ^* )||, x ^* ∈ [l _ia , l _ib ], y ^* ∈ [l _ja , l _jb ]; Among them, d _ij is the distance between the i-th initial propeller-vortex interference interval and the j-th initial propeller-vortex interference interval, f(x ^* ) is the sound pressure at the sampling point x ^* , and f(y ^* ) is the sampling point The sound pressure at y ^* , argmax|f(x ^* )| is the sampling point corresponding to the maximum sound pressure in the ith initial propeller-vortex interference interval, argmax|f(y ^* )| is the jth initial propeller - The sampling point corresponding to the maximum sound pressure in the vortex interference interval, [l _ia , l _ib ] is the ith initial propeller-vortex interference interval, [l _ja , l _jb ] is the jth initial propeller-vortex interference interval , i≠j. 9. The method for extracting rotor propeller-vortex interference noise according to claim 1, characterized in that, according to each propeller-vortex interference center and the propeller-vortex interference length, determine the final value in the high-frequency noise. Propeller-vortex interference noise, including: According to each propeller-vortex interference center and the propeller-vortex interference length, multiple propeller-vortex interference occurrence intervals are determined; the kth propeller-vortex interference occurrence interval is [w _k -n _BVI /2, w _k +n _BVI /2], where w _k is the k-th propeller-vortex interference center, and n _BVI is the propeller-vortex interference length; The signal outside the occurrence interval of the propeller-vortex interference in the high-frequency noise is assigned as 0, and the final propeller-vortex interference noise is obtained. 10. A rotor-vortex interference noise extraction system, wherein the rotor-vortex interference noise extraction system comprises: The signal acquisition unit is used to acquire the total rotor noise of the on-site helicopter and the occurrence time of the propeller-vortex interference in the total rotor noise; A high-frequency noise determination unit, connected with the signal acquisition unit, is used to filter the total noise of the rotor by using an interleaved projection algorithm to determine the high-frequency noise; the high-frequency noise includes a plurality of sampling points and a signal at each sampling point. Sound pressure; an interference length determination unit, connected with the signal acquisition unit, for determining the length of the propeller-vortex interference according to the occurrence time of the propeller-vortex interference and the sampling frequency of the total noise of the rotor; an interference distance determination unit, connected with the signal acquisition unit, for determining the paddle-vortex interference distance according to the rotating speed of the rotor, the number of propeller blades of the helicopter and the sampling frequency of the total noise of the rotor; A modulus maximum value determination unit, connected with the high-frequency noise determination unit, is used for determining a plurality of modulus maximum values in the high-frequency noise; Sound pressure at a certain threshold; an interference average intensity determination unit, connected with the mode maximum value determination unit, and used for determining the average propeller-vortex interference intensity according to each mode maximum value; a high-frequency noise average intensity determination unit, connected to the high-frequency noise determination unit, and configured to determine the high-frequency noise average intensity according to the sound pressure at each sampling point in the high-frequency noise; The initial interval determination unit is connected with the interference average intensity determination unit, the high frequency noise average intensity determination unit and the high frequency noise determination unit, and is used for determining the average intensity of the paddle-vortex interference, the high frequency noise average intensity and the the sound pressure at each sampling point in the high-frequency noise, and determine a plurality of initial propeller-vortex interference intervals in the high-frequency noise; The final interval determination unit is connected to the initial interval determination unit and the interference distance determination unit, and is used for determining a plurality of final intervals according to the maximum value of sound pressure in each initial paddle-vortex interference interval and the paddle-vortex interference distance Propeller-vortex interference range; an interference center determination unit, connected to the final interval determination unit, for determining a plurality of propeller-vortex interference centers according to the maximum value of the sound pressure in each final propeller-vortex interference interval; An interference noise determination unit, connected with the interference center determination unit and the interference length determination unit, and used for determining the final propeller in the high-frequency noise according to each propeller-vortex interference center and the propeller-vortex interference length - Eddy disturbance noise.

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