KR20170124279A - Method and Apparatus for DEMON Processing in order that Removal of External Target Noise When measuring underwater radiated noise - Google Patents

Abstract

The present invention relates to an underwater radiated noise signal processing technique. More particularly, the present invention relates to a method and apparatus for compensating azimuths for a plurality of targets and applying a cross correlation method to obtain cross spectrum energy and performing a root mean square (RMS) to separate and/or detect the envelope signals of an external target and a desired target.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing method and apparatus capable of eliminating external target noise when measuring underwater radiated noise,

[0001] The present invention relates to a technique for processing underwater radiated noise, and more particularly, to a method and apparatus for compensating azimuths of a plurality of targets and obtaining a cross spectrum energy by applying a cross correlation technique, square method for separating and / or detecting an envelope signal of an external target and a desired target.

If the propeller cavitation radiated noise signal generated in a trap or underwater high - speed maneuvering target is daemon signaled, information such as propeller shaft speed, wing speed and shaft number can be identified and distinguished.

Conventional daemon signal processing generally converts a signal input to a hydrophone into a digital signal according to a predetermined sampling rate through an A / D (Analog / Digital) processor. The signal is then passed through a bandpass filter to eliminate DC bias and high ambient noise in the low frequency band.

The signal passed through the bandpass filter is transformed into a signal having an instantaneous intensity and an instantaneous phase value by transforming a signal having a real value to a complex number through a Hilbert transform. The root mean square (RMS) value is obtained by substituting this value into a value representing the envelope size of the entire measurement signal. Finally, because of the Fast Fourier Transform (FFT) process, it is possible to know the characteristics of the signal periodically appearing over the broadband, such as the cavitation noise of the propeller.

However, there is an increasing demand for quantitative test evaluation of target underwater radiated noise analysis. However, if there is a target outside the measurement target during the test evaluation, and if the DEMON signal processing is performed using the conventional technique, information of the unwanted external target noise will appear simultaneously. Such external target noise information leads to ambiguity in signal analysis. Therefore, it is necessary to provide objective and precise test evaluation support by signal separation of radiated noise of each target.

As prior art documents showing such a target detection technique, Korean Patent Laid-open Publication No. 10-2007-0031941 (title of invention: target detection method), Korean Patent Registration No. 10-1303192 (title of invention: passive sonar system and its daemon Processing improvement technique).

Korean Patent Laid-Open No. 10-2007-0031941 relates to a target detection method by entropy (energy) determination when a plurality of targets exist. In particular, the time segment of the received signal undergoes a linear transformation process to determine the entropy of the transformed received signal, so as to detect a target emitting a broadband noisy low-energy signal, .

Korean Patent Laid-Open No. 10-2007-0031941 and the present invention have a common point in that a target is detected when a plurality of targets exist. However, the present invention enables target separation by detecting orientation to a plurality of targets using phase correlation.

On the other hand, Korean Patent Registration No. 10-1303192 discloses a daemon processing technique in which a sonar system is used to improve the processing of a daemon. In this case, the influence of the tonal signal frequency on the radiation noise collected by the sensor can be eliminated. The above-mentioned Korean Patent Registration No. 10-1303192 and the present invention have a common feature on a daemon processing enhancement technique.

However, the present invention compensates azimuth values for a plurality of targets and acquires cross spectrum energy by applying a cross correlation technique, thereby performing an RMS process, thereby separating and detecting an envelope signal of an external target and a desired target Is possible.

The above prior art attempts to solve the difficulty of analyzing the target signal due to the influx of the external target noise in the underwater acoustic measurement. Therefore, when two or more hydrophones are used, the target signal to be measured can be more clearly analyzed by separating the propeller noise of each target.

1. Korean Patent Publication No. 10-2007-0031941 2. Korean Patent Registration No. 10-1303192 (2013.08.28)

1. Kim, Jin-Seok, "A Robust Daemon Processing Technique for Tonal Signal Interference", Journal of the Acoustical Society of Korea, Vol 31, No 6 (August 2012) pp.384-390

The present invention provides a signal processing method and apparatus capable of separating and / or detecting an envelope signal of an external target and a desired target when two or more hydrophones are used, It has its purpose.

The present invention provides a signal processing method capable of separating and / or detecting an envelope signal of an external target and a desired target when two or more hydrophones are used.

The signal processing method includes:

(a) converting radiated noise measurement data measured from a plurality of external targets into a radiated noise digital signal using a plurality of underwater acoustic filters;

(b) applying a band-pass filter to the radiated noise digital signal in a cavitation frequency band and performing windowing according to the plurality of underwater acoustic listening periods;

      (c) generating phase correlation data by applying a phase correlation technique to calculate an external target number and a time delay in the test zone;

      (d) detecting a peak value in the phase correlation data and generating movement data by compensating individual time delays for the plurality of external targets according to the number of peak values;

      (e) applying and averaging the cross-correlation technique to the moving data;

      (f) calculating an RMS (Root Means Square) on the result of applying the cross-correlation technique to calculate an envelope size for the plurality of external targets; And

      (g) extracting the desired propulsion system information of the corresponding external target by taking Fast Fourier Transform (FFT) on the effective value.

In this case, the cavitation frequency band may be 3 to 10 kHz.

In addition, the windowing may be performed using a hanning window.

The step (d) may further include comparing the number of the peak values with a reference value; Detecting an orientation of individual noises for the plurality of external targets if the comparison result is greater than a reference value and calculating an individual time delay value of the plurality of external targets grasped to be free from interference from noise effects; And compensating for a corresponding underwater acoustic anechoic transducer generating a time delay by the time delay value.

The step (f) includes the step of determining an operation range when calculating the effective value.

In the step (f), a phase correlation technique is applied for noise isolation of the plurality of external targets, and then compensation is performed on the corresponding underwater acoustic echo signal by a time delay of a plurality of external targets detected, and a cross correlation technique is applied Thereby obtaining a cross spectrum.

Further, the calculation of the effective value may be performed on the result of the cross spectrum.

및

(여기서,

는 두 수중 음향 청음기간 위상 상관 적용 결과이며,

는 외부 표적 s개에 따른 시간 지연값을 나타내고,

는 s개의 표적으로부터 두 수중 음향 청음기까지 전파되는 소음의 지연시간 차이이며,

는 음속

와 수중 음향 청음기 간격

에 따른 표적들의 방위를 나타낸다.Further, the time delay value and the azimuth can be expressed by the following equations

And

(here,

Is the result of application of phase correlation between two underwater acoustic hearing periods,

Represents the time delay value according to the number of external targets s,

Is the difference in the delay time of the noise propagated from the s targets to the two underwater acoustic eaves,

Speed

And underwater acoustics

≪ / RTI >

(여기서,

는 m만큼 시간지연이 발생한

수중 음향 청음기 신호에 식별된

값만큼 시간지연을 보상한 후, 외부 표적의 소음 영향이 없는 에너지 구간 P만큼의 범위에 상호 상관관계 적용 결과를 나타내며, P는 신호 분리를 위한 상관관계 최소 범위이며 수신기의 셈플링 레이트 또는 시험환경에 따라 그 값이 달라진다. 본 특허에서는 P 값을 0.05초로 고정 하는 것을 특징으로 할 수 있다.Further, the application and the averaging of the correlation technique can be expressed by Equation

(here,

Lt; RTI ID = 0.0 > m <

Identified underwater acoustic echo signal

P is the minimum correlation range for the signal separation and is the receiver's sampling rate or the test environment. The value is changed according to the value. In this patent, the P value is fixed to 0.05 seconds.

On the other hand, another embodiment of the present invention includes a plurality of underwater acoustic filters for measuring a plurality of external targets and generating measured radiation noise measurement data; An AD (Analog Digital) converter for converting the radiation noise measurement data into a radiation noise digital signal; Applying a band pass filter, which is a cavitation frequency band, to the radiated noise digital signal, performing windowing according to the plurality of underwater acoustic listening periods, calculating a phase correlation technique to calculate the number of external targets and time delay in the test zone A peak calculating unit for generating phase correlation data by detecting a peak value in the phase correlation data; A compensation unit for compensating individual time delays for the plurality of external targets according to the number of the calculated peak values to generate movement data; Calculating a Root Means Square (RMS) on the result of applying the cross-correlation technique to apply and averify the cross-correlation technique to the movement data and to calculate an envelope size for the plurality of external targets; And a daemon signal calculation unit for taking a fast Fourier transform (FFT) on the rms value and extracting a desired propulsion system information of a corresponding external target. In the measurement of underwater radiated noise, external target noise can be removed A signal processing method can be provided.

According to the present invention, it is possible to solve the difficulty of analyzing the target signal due to the inflow of the external target noise during the underwater acoustical measurement, and the hardware and the signal processing are simple, so that it can be configured at low cost.

Another advantage of the present invention is that it can be usefully used in places where it is difficult to carry out marine experiments without the influx of noise of an external target in the measurement of underwater acoustics like the Korean sea area.

FIG. 1 is a flowchart illustrating a signal processing process capable of removing an external target noise during measurement of underwater radiated noise according to an embodiment of the present invention.
Fig. 2 is a conceptual diagram of the signal processing shown in Fig. 1. Fig.
FIG. 3 is a graph of a simulation result when the signal processing process of FIG. 1 is applied.
4 is a block diagram of a signal processing apparatus capable of removing an external target noise during measurement of underwater radiated noise according to another embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Like reference numerals are used for similar elements in describing each drawing.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. The term "and / or" includes any combination of a plurality of related listed items or any of a plurality of related listed items.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Should not.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout.

FIG. 1 is a flowchart illustrating a signal processing process capable of removing an external target noise during measurement of underwater radiated noise according to an embodiment of the present invention. Referring to FIG. 1, a radiated noise digital signal is generated by A / D (analog / digital) conversion of radiation noise measurement data measured from an underwater acoustic horn to perform signal processing for eliminating rotational component of external target shafts ).

Next, the mechanical noise source of the targets is removed and band pass filtering is performed at 3 to 10 kHz, which is the cavitation frequency band, to obtain envelope data of the shaking rotation component. A hanning window according to the distribution between the underwater acoustic eavesquaters is performed to reduce the side lobe of the signal and to collect the signal of the desired band (step S110).

Next, a phase correlation technique is applied to calculate the number of targets and time delay in the test zone (step S120).

The phase correlation technique is similar to the following equation and uses only phase information without using amplitude information, so it is not affected by the target noise magnitude and calculation speed is fast.

는 두 수중 음향 청음기간 위상 상관 적용 결과이며, N은 표적의 개수이다.

는 s개의 표적으로부터 두 수중 음향 청음기까지 전파되는 소음의 지연시간 차이고, 표적에 따른

는 서로 독립적인 성격을 가진다. h1,h2는 수중 음향 청음기를 나타내며, IFT는 역 푸리에 변환을 나타내며, (^*)는 complex-conjugate를 나타낸다.here,

Is the result of applying phase correlation between two underwater acoustic perception periods, and N is the number of targets.

Is the delay time difference of the noise propagated from the s target to the two underwater acoustic eavesdroppers,

Are independent of each other. h1 and h2 denote an underwater acoustic horn, IFT denotes an inverse Fourier transform, and ( ^* ) denotes a complex-conjugate.

Next, it is determined whether the number of peak values (i.e., the number of peaks) exceeds a reference value (for example, "1") by applying the following equation to the phase correlation technique result (step 130).

값 중 threshold 보다 큰 첨두값을 찾아낸다. 첨두값의 개수(즉 피크수)가 1이 넘지 않으면 NO 과정으로 단계 S150으로 넘어가고, 그렇지 않으면 YES 과정으로 단계 S140으로 넘어간다.here,

Finds a peak value that is greater than the threshold value. If the number of peak values (i.e., the number of peaks) does not exceed 1, the process proceeds to step S150. Otherwise, the process proceeds to step S140.

If the number of the peak values exceeds 1 in step S140, the time delay value and / or orientation for each external target is calculated as follows (step S140).

는 외부 표적 s개에 따른 시간 지연값을 나타낸다.

는 개별 외부 표적의

, 음속

와 수중 음향 청음기 간격

에 따른 표적들의 방위를 나타내고, 이를 이용하여 외부 표적을 식별한다(단계 S150).here,

Represents the time delay value according to the number of external targets s.

Of the individual external targets

, Sound speed

And underwater acoustics

And identifies an external target using this (step S150).

을 시간지연 신호에 보상하여 생성된 이동 데이터에 다음 수학식과 같이 상호 상관 관계 기법 적용 및 평균화를 실시한다(단계 S160)Next, the time delay value for the identified individual noise

Is applied to the movement data generated by compensating the time delay signal, and a cross correlation technique is applied and averaged as shown in the following equation (step S160)

는 m만큼 시간지연이 발생한

수중 음향 청음기 신호에 식별된

값만큼 시간지연을 보상한 후, 외부 표적의 소음 영향이 없는 에너지 구간 P만큼의 범위에 상호 상관관계 적용 결과를 나타내며, P는 신호 분리를 위한 상관관계 최소 범위이며 수신기의 셈플링 레이트 또는 시험환경에 따라 그 값이 달라진다. 본 특허에서는 P 값을 0.05초로 고정 하는 것을 특징으로 할 수 있다.here,

Lt; RTI ID = 0.0 > m <

Identified underwater acoustic echo signal

P is the minimum correlation range for the signal separation and is the receiver's sampling rate or the test environment. The value is changed according to the value. In this patent, the P value is fixed to 0.05 seconds.

Next, in order to obtain the envelop size of the external target, the result of the above equation is continuously stored, and the root mean square (RMS) is calculated using the following equation (step S170).

의 RMS값을

에 입력하며, 연산 범위

의 크기는 P와 동일하게 설정한다.Here, the cross correlation result

The RMS value of

And the operation range

Is set to be equal to P.

Next, in order to calculate a desired DEMON signal of an external target, Fast Fourier Transform (FFT) is performed on the result of Equation (5) and then propulsion system information (i.e., propulsion system signal) is extracted (Step S180 ).

Fig. 2 is a signal processing conceptual diagram 200 shown in Fig. In particular, FIG. 2 illustrates the concept of underwater radiated noise measurement using, for example, two sets of underwater acoustic horns (H1, H2) for two targets.

First, a target signal is received at the first and second underwater acoustic equipments H1 and H2 as shown in the following equation (210).

은 수중 음향 청음기 두 조(H1,H2) 주위의 독립적인 주변 소음이며,

는 표적으로부터의 방사소음 감쇄 정도이다. 그리고

는 표적의 시간지연 정보가 포함된 신호이다.here,

Is an independent ambient noise around the two sets of hydrophone equipments (H1, H2)

Is the degree of radiated noise attenuation from the target. And

Is a signal including time delay information of the target.

및

수중 음향 청음기에 수신된 신호를 나타낸 것이다. 이때 각 수중 음향 청음기의 신호는 표적과 수중 청음기 간의 거리에 따라 달라진다(220, 230).Next, the underwater acoustic emission noise from each target

And

The signal received at the underwater acoustic horn is shown. At this time, the signal of each underwater acoustic filter depends on the distance between the target and the hydrophone (220, 230).

을 나타내며, 표적 B의 첨두값은

을 나타낸다(240).Next, we show the relative time delay of each target after applying a phase correlation to the two sets of underwater acoustic eavesdroppers. The peak value of target A is

, And the peak value of the target B is

(240).

만큼 보상후 두 수중 음향 청음기의 상호 상관 관계를 적용한 것이고 원하는 표적 에너지 구간과 외부 표적 소음 에너지 구간을 나타낸다.Next, (250) represents the time delay of the desired target noise

, And the desired target energy interval and the external target noise energy interval, respectively.

FIG. 3 is a simulation result graph 300 when the signal processing process of FIG. 1 is applied. Referring to FIG. 3, the first graph 310 shows the result of processing the existing DEMON signal, and it is difficult to distinguish the A and B target signals.

Alternatively, the second graph 320 using the proposed DEMON signal processing may show the DEMON signal processing result after acquiring the energy section of the desired target, and the third graph 330 may show the DEMON signal processing result of the external target .

4 is a block diagram of a signal processing apparatus 400 capable of removing external target noise in the measurement of underwater radiated noise according to another embodiment of the present invention. 4, the signal processing apparatus 400 includes first through n-th underwater acoustic echo filters 410-1 through 410-n for measuring the first through n-th targets 401-1 through 401- 410-n), a signal processing unit 420 for processing the radiation noise measurement data to calculate a daemon signal, and the like.

The signal processing unit 420 may include an AD (analog to digital) converter 421 for converting the radiation noise measurement data into a radiation noise digital signal, a band pass filter as a cavitation frequency band for the radiation noise digital signal, A phase correlation method is applied to calculate the number of external targets and a time delay in the test region by performing windowing according to a distribution of a listening period and generating peak correlation data by detecting a peak value in the phase correlation data, A compensating unit 423 for compensating individual time delays for the plurality of external targets according to the number of calculated peak values to generate moving data, applying a cross-correlation technique to the moving data, and averaging , To calculate the envelope size for the plurality of external targets, A calculation unit 424 for calculating a root mean square (RMS), and a daemon signal calculation unit 425 for taking a fast Fourier transform (FFT) on the effective value and extracting the desired propulsion system information of the corresponding external target, And the like.

The term "part" and the like described in Fig. 4 means a unit for processing at least one function or operation, which may be implemented by a combination of hardware and / or software.

400: signal processing device
401-1 to 401-n: first to n-th targets
410-1 to 410-n: first to n-th underwater acoustic gasses
420: Signal processor
421: AD converter
422: peak calculation unit
423:
424:
425: Daemon signal calculation unit

Claims (9)

(a) converting radiated noise measurement data measured from a plurality of external targets into a radiated noise digital signal using a plurality of underwater acoustic filters;
(b) applying a band-pass filter, which is a cavitation frequency band, to the radiated noise digital signal and performing windowing according to the plurality of underwater acoustic listening periods;
(c) generating phase correlation data by applying a phase correlation technique to calculate an external target number and a time delay in the test zone;
(d) detecting a peak value in the phase correlation data and generating movement data by compensating individual time delays for the plurality of external targets according to the number of peak values;
(e) applying and averaging the cross-correlation technique to the moving data;
(f) calculating an RMS (Root Means Square) on the result of applying the cross-correlation technique to calculate an envelope size for the plurality of external targets; And
(g) extracting the desired propulsion system information of the corresponding external target by taking Fast Fourier Transform (FFT) for the effective value;
Wherein the signal processing method is capable of removing an external target noise in the measurement of underwater radiated noise. The method according to claim 1,
Wherein the cavitation frequency band is 3 to 10 kHz, and the windowing is performed using a hanning window.
The method according to claim 1,
The step (d)
Comparing the number of the peak values with a reference value;
Detecting individual noise orientations for the plurality of external targets if the comparison result is greater than a reference value and calculating an individual time delay value of the plurality of external targets grasped to be free from interference from noise effects; And
And compensating for the underwater acoustic horn generating time delay by the time delay value.
The method according to claim 1,
Wherein the step (f) includes the step of determining an operation range when calculating the effective value.
The method according to claim 1,
In the step (f), a phase correlation technique is applied for noise isolation of the plurality of external targets, and then the corresponding underwater acoustic aneuryser is delayed by time delays of the plurality of external targets, And a cross spectrum is obtained by applying a signal to the signal processing method.
6. The method of claim 5,
Wherein the calculation of the effective value is taken with respect to the result of the cross spectrum.
The method according to claim 1,
Wherein the time delay value and the azimuth are calculated using Equation

And

(here,

Is the result of application of phase correlation between two underwater acoustic hearing periods,

Represents the time delay value according to the number of external targets s,

Is the difference in the delay time of the noise propagated from the s target to the two underwater acoustic eaves,

Of the individual external targets

, Sound speed

And underwater acoustics

Wherein the target signal is calculated using the signal of the target signal.
8. The method of claim 7,
The interrelationship technique application and averaging are performed using Equation

(here,

Lt; RTI ID = 0.0 > m <

Identified underwater acoustic echo signal

P is the minimum correlation range for the signal separation and is the receiver's sampling rate or the test environment. The value is changed according to the value. In this patent, the P value is fixed to 0.05 seconds. A plurality of underwater acoustic ceilters for measuring a plurality of external targets and generating measured radiation noise measurement data;
An AD (Analog Digital) converter for converting the radiation noise measurement data into a radiation noise digital signal;
Applying a band pass filter, which is a cavitation frequency band, to the radiated noise digital signal, performing windowing according to the plurality of underwater acoustic listening periods, calculating a phase correlation technique to calculate the number of external targets and time delay in the test zone A peak calculating unit for generating phase correlation data by detecting a peak value in the phase correlation data;
A compensation unit for compensating individual time delays for the plurality of external targets according to the number of the calculated peak values to generate movement data;
Calculating a Root Means Square (RMS) on the result of applying the cross-correlation technique to apply and averify the cross-correlation technique to the movement data and to calculate an envelope size for the plurality of external targets; And
A daemon signal calculation unit for taking a Fast Fourier Transform (FFT) on the RMS value and extracting propulsion system information of a desired external target;
Wherein the signal processing method is capable of removing an external target noise in the measurement of underwater radiated noise.

Images