KR101580493B1 - Target signal classification method of active sonar - Google Patents

Target signal classification method of active sonar Download PDF

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KR101580493B1
KR101580493B1 KR1020150127055A KR20150127055A KR101580493B1 KR 101580493 B1 KR101580493 B1 KR 101580493B1 KR 1020150127055 A KR1020150127055 A KR 1020150127055A KR 20150127055 A KR20150127055 A KR 20150127055A KR 101580493 B1 KR101580493 B1 KR 101580493B1
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South Korea
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contact
speed
standard deviation
moving direction
target
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KR1020150127055A
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Korean (ko)
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서익수
한동석
장은정
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국방과학연구소
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
    • G01S15/50—Systems of measurement, based on relative movement of the target
    • G01S15/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
    • G01S15/582—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of interrupted pulse-modulated waves and based upon the Doppler effect resulting from movement of targets

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Acoustics & Sound (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)

Abstract

The present invention relates to a method of classifying a target signal of an active sonar capable of classifying an active sonar or a target signal using a standard deviation information of a moving direction and speed of a target in a multi-state sonar system, Measuring a Doppler shift frequency of the target, and calculating a moving direction and a speed of the reflector as a target candidate; Calculating a standard deviation of the calculated reflector moving direction and speed; Assigning to each contact a score indicative of targetability using the calculated standard deviation of the direction of movement and speed and the number of returns belonging to each contact; And classifying the target signal based on the total score assigned to each contact.

Description

{TARGET SIGNAL CLASSIFICATION METHOD OF ACTIVE SONAR}

The present invention relates to a method of classifying a target signal of an active sonar capable of classifying an active sonar or target signal using a standard deviation information of a moving direction and speed of a target in a multi-state sonar system.

Sonar is the way to detect underwater targets. The basic concept of a sonar is to process the received sound signal in the water to obtain information about the target. Sonar can be divided into passive sonar and active sonar depending on the use of sound source. The active sonar is divided into a single-state sonar, a dual-state sonar, and a multi-state sonar, depending on the number of sound sources and receivers. In the present invention to be described later, a multi-state sonar using one or more sound sources and two or more receivers is considered.

In a multi - state sonar, the receiver generally processes the sound signal to obtain two pieces of information. One is the distance from the source to the target and the azimuth of the target from the receiver. Through this information, the position of the target can be known. In the active sonar, the sound signal received by the receiver contains not only the target signal but also undesired noise and reverberation signals.

Therefore, sonar uses an algorithm that properly classifies the location of the target to be searched, the unwanted noise, and the reverberation signal. The classification algorithm classifies the signals into a set based on the similarity of the positions of the sound signals collected by a plurality of receivers, reduces the number of unwanted noise and reverberation signals by considering one group of the classified set as a single signal, Lt; / RTI > into a target signal.

However, most conventional classification algorithms do not provide a method for distinguishing whether a classified signal is a target signal or not, and if there are a large number of signals belonging to the classified set, it is assumed that there is a target at a position indicated by the set.

Accordingly, it is an object of the present invention to provide a method for accurately classifying a target signal of an active sonar using a standard deviation information of a direction and speed of a signal in a multi-state sonar system.

According to another aspect of the present invention, there is provided a method of classifying a target signal of an active sonar according to an embodiment of the present invention, comprising: measuring a Doppler transition frequency of all two possible returns in one contact, Calculating; Calculating a standard deviation of the calculated reflector moving direction and speed; Assigning to each contact a score indicative of targetability using the calculated standard deviation of the direction of movement and speed and the number of returns belonging to each contact; And classifying the target signal based on the total score assigned to each contact.

The contacts represent a set of signals classified by position similarity, and the returns represent signals belonging to each contact.

The moving direction and speed of the reflector can be calculated by a simultaneous equations solution method after substituting the measured Doppler shift frequency into the Doppler shift frequency equation.

In the step of assigning a score to the contact, a score is given to each item of the number of returns belonging to the contact, the standard deviation item of the moving direction, and the standard deviation item of the moving speed for each contact.

The step of assigning a score to the contact can give a score in proportion to the case that the standard deviation of the movement direction and the contact is small and the number of returns in the contact is large.

The step of classifying the target signal determines that the higher the total score assigned to each contact is, the more likely the return in the contact is the target signal.

The target signal classification method of active sonar according to an embodiment of the present invention may further include removing the contact when the standard deviation of the speed and the moving direction of the reflector calculated from the returns in each contact is equal to or greater than a threshold value have.

The step of removing the contact may remove the contact when the moving direction and the speed standard deviation both exceed the threshold or remove the contact when one of the moving direction and the speed standard deviation exceeds a threshold value .

The present invention calculates a Doppler shift frequency of each signal classified as a set based on the similarity of positions, calculates a standard deviation of a moving direction and a speed of the reflector using the calculated Doppler shift frequency, It is possible to accurately distinguish the target signal by assigning a score indicating the possibility of the target to each signal set based on the number of returns in the signal set.

The present invention has the effect of greatly reducing the clutter signal by removing the set when the standard deviation of the speed and direction of movement of each set exceeds a preset threshold value.

1 shows the positional relationship between a receiver and a target when the reflector is a target;
2 is a flowchart illustrating a method of classifying a target signal of an active sonar according to an embodiment of the present invention.

In the present invention, the Doppler information of each signal (contact signal) classified as a set is calculated based on the similarity of positions, and a set of possible targets is presented by assigning a score indicating that each set is a target, We propose a method to remove the signal.

The present invention refers to a set of signals classified as similarity of positions as a contact and a signal belonging to each contact as a return.

In the present invention, the direction and velocity of the reflector are searched using Doppler information of the return in the contact. Assume that there are N returns in one contact. Since the N returns are signals that have been reflected from one reflector, it is assumed that the direction of movement and the speed of return are the same.

Fig. 1 shows the positional relationship between the receiver and the target receiving the i-th and j-th return (i, j ∈ {1, 2, ..., N), i ≠ j) when the reflector is the target.

It is assumed in FIG. 1 that the position of the sound source and the receiver are known precisely. θ H represents the moving direction of the reflector, and θ TS represents the angle between the vector 10 indicating the traveling direction of the reflector and the line 11 connecting the sound source and the reflector. Here, the subscript H denotes heading, T denotes a target candidate reflector, S denotes a source, and R denotes a receiver. Further, θ TRi and θ TRj are the angles formed by the horizontal line 12 in the right direction of the reflector and the lines 13 and 14 connecting the receiver and the reflector respectively receiving the i-th and j-th returns. β i and β j represent angles formed by the line 11 connecting the source-reflector and the lines 13 and 14 connecting the i and j receiver-reflectors, respectively. Since β i , β j , θ TRi and θ TRj know the position of the sound source and the receiver and the position of the return, they can be known through calculation.

Therefore, the i-th and j-th returns in the contact (signal set) are shifted by the Doppler frequency

Figure 112015087303540-pat00001
,
Figure 112015087303540-pat00002
) Can be expressed by the following Equation (1).

[Equation 1]

Figure 112015087303540-pat00003

Where c is the speed of the underwater sound waves,

Figure 112015087303540-pat00004
The center frequency of the transmission signal,
Figure 112015087303540-pat00005
Is the speed of the reflector. Then, the angle? TS and the moving direction? H of the reflector have the relationship represented by the following equation (2).

&Quot; (2) "

Figure 112015087303540-pat00006

Therefore, obtaining the angle? TS is similar to finding the moving direction? H of the reflector. In the above equation (1)

Figure 112015087303540-pat00007
,
Figure 112015087303540-pat00008
,
Figure 112015087303540-pat00009
And β i , β j , c are known or known values through calculation.

Therefore, in the equation (1), the unknown angle &thetas; TS and the reflector speed

Figure 112015087303540-pat00010
) Can be solved by solving the simultaneous equations,
Figure 112015087303540-pat00011
. In this way, for every combination of i-th and j-th returns in {1,2, ..., N)
Figure 112015087303540-pat00012
, The number of combinations is N
Figure 112015087303540-pat00013
Dogs.

If all returns belonging to one contact (signal combination) are signals reflected from one reflector, all

Figure 112015087303540-pat00014
Will have a small value. Conversely, if all returns are reflected from different reflectors, or are reflected from noise, then their standard deviation will have a large value.

Therefore, the present invention is not limited to the return combination

Figure 112015087303540-pat00015
And then scoring the contact for the likelihood of being a target based on the calculated standard deviation. Of the total of K contacts,
Figure 112015087303540-pat00016
Wow
Figure 112015087303540-pat00017
The standard deviation of
Figure 112015087303540-pat00018
to be.

In other words, it is generally considered that a contact with a large number of contacts belonging to a contact is likely to be a target in the location-based clutter classification algorithms. In the present invention, the number of returns in the contact and the standard deviation (

Figure 112015087303540-pat00019
) Is small, it is likely that the target is more likely to be a target.

In the present invention, there are three items that score a contact: the number of returns belonging to the contact, the standard deviation of the direction of movement

Figure 112015087303540-pat00020
) And the standard deviation of the traveling speed (
Figure 112015087303540-pat00021
)to be. Contact is small
Figure 112015087303540-pat00022
,
Figure 112015087303540-pat00023
The moving direction and the speed item score
Figure 112015087303540-pat00024
Wow
Figure 112015087303540-pat00025
And the highest number of returns, the number of returns
Figure 112015087303540-pat00026
The highest score.

Item score value Sum result The maximum score K is given to the contact having the largest value and the score is given to the remaining contacts by applying a ratio to the contact. Here, the subscripts r, h, and v indicate return, heading, and velocity, respectively.

The total score is the sum of the three points

Figure 112015087303540-pat00027
, And the maximum score is K, the higher the score, the more likely it is the target signal. That is, the higher the score, the greater the likelihood that there is a relatively large return, or a small standard deviation of the target's moving direction and speed, which is likely to be the target.

2 is a flowchart illustrating a method of classifying a target signal of an active sonar according to an embodiment of the present invention.

As shown in FIG. 2, when a plurality of returns are received from the reflector, the controller (not shown) classifies the plurality of returns into at least one contact based on the similarity of the position (S100).

The control unit measures the Doppler transition frequency of all possible two returns in one contact to calculate the moving direction and speed of the reflector as the target candidate (S110), and calculates the standard deviation of the calculated moving direction and speed of the reflector (S120).

The controller classifies the target signals according to the scores given to the respective contacts after assigning a score indicating the target possibility to each contact using the calculated standard deviation items of the moving direction and the speed and the number of return items belonging to the contact (S130) . At this time, the control unit can assign a score in proportion to the moving distance and the standard deviation of the contact and the number of returns in the contact, and the weight can be applied according to the accuracy of each score item.

In addition, the present invention also considers elimination of return corresponding to the clutter signal among the return (signals) of the contact. If the standard deviations of the direction and speed of movement of each contact exceeds a preset threshold value, the clutter of the contact is removed. There are AND and OR methods for removal. The AND method removes the contact by considering it as a clutter if both the moving direction and the speed standard deviation exceed the threshold, and the OR method removes the contact when the value of one of the moving direction and the speed standard deviation exceeds the threshold value .

As described above, according to the present invention, the Doppler shift frequency of each of signals classified into sets is calculated based on the similarity of positions, the standard deviation of the moving direction and speed of the reflector is calculated using the calculated Doppler shift frequency, The target signal can be accurately discriminated by assigning a score indicating the possibility of the target to the signal set. In addition, the present invention has the effect of greatly reducing the clutter signal by removing the set when the standard deviation of the speed and direction of movement of each set exceeds a preset threshold value. Due to this series of operations, the present invention can greatly reduce the false alarm rate.

It will be appreciated that the configurations and methods of the embodiments described above are not to be limited and that the embodiments may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Therefore, it should be understood that the above-described embodiments are to be considered in all respects as illustrative and not restrictive.

10: vector representing the direction of the reflector
11: Line connecting sound source and reflector
12: Horizontal line from the reflector to the right
13, 14: A line connecting the receiver to the reflector that receives the i-th and j-th returns

Claims (8)

Measuring a Doppler transition frequency of two returns in one contact to calculate a moving direction and a speed of a reflector as a target candidate;
Calculating a standard deviation of the calculated reflector moving direction and speed;
Assigning to each contact a score indicative of targetability using the calculated standard deviation of the direction of movement and speed and the number of returns belonging to each contact; And
And classifying the target signals based on a total score assigned to each of the contacts. 2. The connector according to claim 1,
And wherein the return represents a signal belonging to each contact. ≪ Desc / Clms Page number 19 > The method of claim 1, wherein the moving direction and speed of the reflector
Calculating a Doppler shift frequency by substituting the measured Doppler shift frequency into a Doppler shift frequency equation, and then calculating the Doppler shift frequency by a simultaneous equations solution method. 2. The method of claim 1, wherein assigning a score to the contact
A score is assigned to the number of return items belonging to the contact, the standard deviation item of the moving direction, and the standard deviation item of the moving speed for each contact. 2. The method of claim 1, wherein assigning a score to the contact
Wherein the standard deviation of the moving direction and the standard deviation of the moving speed are small and the score is proportionally given in the case where the number of returns in the contact is large. The method of claim 1, wherein classifying the target signal comprises:
And determining that the higher the total score assigned to each contact is, the more likely the returns in the contacts are likely to be the target signals. The method of claim 1, further comprising: removing the contact when the standard deviation of the speed and direction of movement of the reflector calculated from the returns in each contact is greater than or equal to a threshold value . 8. The method of claim 7, wherein removing the contact
Removing the contact when both the moving direction and the speed standard deviation exceed the threshold value or removing the contact when the value of one of the moving direction and the speed standard deviation exceeds a threshold value. Way.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20110031310A (en) * 2008-06-06 2011-03-25 콩스베르그 디펜스 앤드 에어로스페이스 에이에스 Method and apparatus for detection and classification of a swimming object
KR20110046171A (en) * 2009-10-28 2011-05-04 국방과학연구소 Method for estimating target range error and sonar system thereof
KR20110111158A (en) * 2010-04-02 2011-10-10 국방과학연구소 A method for estimating the self propelled decoy's deceiving capability of the sonar system active mode

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20110031310A (en) * 2008-06-06 2011-03-25 콩스베르그 디펜스 앤드 에어로스페이스 에이에스 Method and apparatus for detection and classification of a swimming object
KR20110046171A (en) * 2009-10-28 2011-05-04 국방과학연구소 Method for estimating target range error and sonar system thereof
KR20110111158A (en) * 2010-04-02 2011-10-10 국방과학연구소 A method for estimating the self propelled decoy's deceiving capability of the sonar system active mode

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