JPH0360393B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for tracking a target sound source in a sonar. [Prior Art] Conventionally, as a method for tracking a target sound source in a sonar, a standby beam is formed using a standby beam former for signals from a receiver array, and the output power of the standby beam is maximized. The beam output in the direction of the maximum value is analyzed by frequency analysis, etc., and it is determined whether the signal from the target sound source is included. There is a method of tracking the target sound source by interpolating the standby beam output power in the surrounding directions and outputting the direction of the maximum value as the estimated direction of the target sound source. FIG. 2 is a block diagram of a device for tracking a target sound source in a sonar as described above. In the figure, 10 is a receiver array;
11 ₁ , 11 ₂ ..., 11 _k ..., 11 _K are wave receiving elements, 2
0 is standby beam former, 21 ₁ , 21 ₂
..., 21 _k , ..., 21 _K are time delay compensators, 22 ₁ ,
22 ₂ ,..., 22 _k ,..., 22 _K are fixed coefficient filters, 23 is an adder, 30 is a power detector, 40 is a maximum point detector, 41 is a first multiplexer, 4
2 is an analysis processor, 43 is a judgment classifier, 44 is a beam direction selector, 50 is a second multiplexer, 5
1 is an interpolator, 52 is a maximum point detector, and 60 is an output terminal. Further, α _o (n=1, 2, ..., N) is a vector expressed in the main axis direction of N beams formed by the standby beam former 20, and S ( α _o ) is a standby beam output signal in the vector α _o direction. , P
( α _o ) is the standby beam output signal power in the α _o direction,
α _l (l=1, 2, ..., L) is a vector α _o indicating the direction of the L maximum values detected by the maximum point detector.
, S( α _l ) is the output signal of the standby beam in the vector α _l direction, α _p is a vector indicating the direction in which the target sound source is determined to exist among the vector α _l directions, α _n (m=1, 2,...,M)
is a vector that includes the vector α _p direction and indicates the beam main axis direction of the beam output signal power necessary for interpolation selected from the vector α _o , and P ( α _n ) is the standby beam output signal power in the vector α _n direction. , α is a continuous vector value indicating the direction, P( α^ )
is the output signal of the interpolator 51, and α is the direction vector α that maximizes the output signal P( α ). FIG. 3 is a geometrical explanation of the receiver array and the target direction when the receiver array 10 is assumed to be a three-dimensional array. In the same figure, X, Y, Z
are the coordinate axes of the orthogonal coordinate system, O is the origin of the coordinate system, T is the target direction, θx, θy, and θz are the directional cosine angles of the target direction T with respect to the coordinates X, Y, and Z, respectively, 1
1 _k is the k-th element of the receiver array 10, P _k
is the position vector of the kth element in the rectangular coordinate system. In FIG. 3, the signal received by the k-th element 11 _k is the signal received at the origin O and the reference value τ _k =−P _k ^T · α /C (k=1, 2, . . . , K). (1) Subject to delays. However, C is the propagation speed of the signal, the subscript T is the vector rotation value, and the receiver array 10
When is a three-dimensional array, α = [αx, αy, αz] ^T , αx = cosθx, αy = cosθy, αz = cosθz (2). k-th receiving element 11 _k of the receiver array 10
The signal received by the k-th delay compensator 21
k, the main axis direction of the standby beam is α _o (n
= 1, 2, ..., N), then D _k ( α _o ) = P _k ^T · α _o /C (k = 1, 2, ..., K, n = 1, 2, ...,
N) (3) After receiving the time delay compensation and passing through the k-th fixed coefficient filter _22k having the desired transfer characteristic, the filter output signals of k=1, 2, . . . The adder 23 adds them together, and N standby beam outputs S( α _o ) (n=1, 2, . . . , N) (4) are output as output signals of the standby beam former 20 . However, the increment width Δ α in the principal axis direction α _o of N standby beams = [Δαx, Δαy, Δαz] ^T
, Δαx = Δcosθ, Δαy = Δcosθy, Δαz = Δcosθz are the Nyquist step widths determined by the array aperture, that is, the array width in the ) taken below. The power detector 30 detects the power P( _αo ) of the output signal S( _αo ) of the standby beamformer.
Output. The local maximum point detector 40 detects L directions with a large value of P( α _o ) that are likely to contain a signal from the target sound source, and calculates a vector α _l (l
= 1, 2, ..., L). The first multiplexer 41 selects a beam output signal in the direction of the vector α _l from among the N standby beam output signals S ( α _o ), and outputs it as an output signal S ( α _l ). The analysis processor 42 performs processing such as frequency analysis on the output signal S ( α _l ), and the judgment classifier 43
It is determined whether or not the signal from the target sound source is included, and the determination classifier 43 outputs the principal axis direction α _p of the beam that includes the signal from the target sound source. The beam direction selector 44 selects M directions from α _o including the principal axis direction α _p necessary for interpolation, and α _n
Output as (1, 2,...,M). The second multiplexer 50 outputs outputs P(α _n ) of M directions, which are the outputs of the beam direction selector 44, from the power P( α _o ), which is the output of the power detector 30.
Select and output. The interpolator 51 outputs the output P
Interpolation is performed on ( α _n ) and an output P ( α ) is output. The maximum checker 52 determines the direction α in which the output P( α ) is maximum, and outputs the direction α to the output terminal 60 as the estimated direction α^ of the target sound source. In the example of FIG. 2, it is assumed that the receiver array is three-dimensional, but the same can be applied even if the receiver array 10 is a planar array or a linear array. [Problems to be Solved by the Invention] In the tracking method in the sonar described above, a non-adaptive beam former (hereinafter simply referred to as "standby") is used as a standby beamformer.
CBF) or adaptive beam formers (hereinafter simply referred to as "standby ABF") are used. However, when using the standby CBF, if there is an unsteady interference signal from other than the target sound source in the signal received by the receiver array 10, the signal-to-noise ratio at the beam output signal S ( α _o ), that is, S /
There is a drawback that N (S: signal power in the beam main axis direction, N: signal power from a direction other than the beam main axis direction) is low, and estimation accuracy is poor if the direction of the target sound source is estimated using the beam output signal. On the other hand, when using a standby ABF, signals arriving from directions other than the main axis of the beam are treated as noise and can be removed even if the characteristics are unknown or unsteady, so the beam output signal S( α _o ) can be obtained, but the filter 22
Since it is necessary to adaptively change the transmission characteristics of ₁ to 22 _K , a digital filter is generally used as the filter 22 _{k .}
If the order of is J, then the number of coefficients that need to be changed at each update time is I (I = K × J), and N × I coefficients are calculated at each update time in the standby ABF. Is required. For this reason, the amount of processing per unit time increases in proportion to the increase in the number N of standby beams and the number I of variable coefficients, and there is a drawback that the hardware scale increases in order to realize real-time processing. The present invention has been made in view of the above-mentioned points, and eliminates the above-mentioned problems and limits the number of beams formed by the standby ABF as much as possible. An object of the present invention is to provide a tracking method in a sonar that increases estimation accuracy by using a beam output signal at ABF with a high S/N for azimuth estimation. [Means for Solving the Problems] In order to solve the above problems, the present invention receives a signal from a target sound source with a receiver array, and applies a beam former to the output signal of the receiver array. In a sonar system that forms a standby beam and tracks the target sound source using the standby beam output signal, the standby beam is formed by a standby CBF, and the approximate direction of the target sound source is determined using the beam output of the standby CBF. ,
Form a beam with an adaptive beam former (hereinafter referred to as ABF) in the minimum direction necessary for interpolation including the direction,
This is a tracking method that obtains a beam output signal with a high S/N ratio and uses the beam output signal to accurately determine the direction of the target sound source. [Operation] By configuring as above, the standby
Find the approximate target sound source direction using CBF, and use the information on the target sound source direction to determine the signal-to-noise ratio (S/N) at the beam output only for the minimum direction necessary for interpolation.
Since a beam is formed with a high adaptive beam former and the beam output signal of the adaptive beam former is used to estimate the direction of the target sound source, the direction of the target sound source can be estimated with high accuracy. [Example] An example of the present invention will be described below with reference to FIG. In this figure, parts given the same reference numerals as those in FIG. 2 indicate the same or equivalent parts. 31 is a second power detector, 70 is ABF, 71 ₁ , 71 ₂ ,..., 71 _k ,
..., 71 _K is the second time delay compensator, 72 ₁ , 72
₂ ,...,72 _k ,...,72 _K are variable coefficient filters,
73 is a second adder, and 74 is a coefficient calculator.
In addition, Sa ( α _n ) is the beam output signal of the ABF70 in the α _n direction, Pa ( α _n ) is the power of the beam output signal when the main axis of the beam is in the α _n direction, and P _a ( α ) is the beam output power P The signal power obtained by interpolating _a ( α _n ),
α^ _a is the value of the direction α of the signal where the power P _a ( α ) is maximum, and is the estimated direction of the target sound source in this embodiment. In FIG. 1, a beam direction selector 44 selects M beam directions to be used for interpolation calculations in the vicinity of the direction _{α p, based on information about the approximate direction α p} of the target sound source selected by the judgment classifier 43. α _n (m=
1, 2, ..., M), and the second of the ABF70 is determined.
output to the time delay compensators 71 ₁ to 71 _K. Second
The time delay compensators 71 ₁ to 71 _K perform time delay compensation corresponding to each of the M directions α _n given by the beam direction selector 44, similarly to the first time delay compensators _{21 1} to 21 _K. This is applied to the output signals of the wave receiving elements 11 ₁ to 11 _K. Variable coefficient filter 72 ₁
~72 _K is the second time delay compensator 71 ₁ ~71 _K
This is an adaptive filter that passes the signal after time delay compensation, and is similar to the fixed coefficient filter 22.
It has an order of about ₁ to 22 _K. Each coefficient of the variable coefficient filters 72 ₁ to 72 _K is calculated by the coefficient adder 74 and updated sequentially. The second time delay compensators 71 ₁ to 71 _K configure the ABF 70 in the beam direction α _n (m=1, 2, . . . , M).
Each time a delay amount corresponding to one direction α _n is generated,
The outputs of the variable coefficient filters 72 ₁ to 72 _K are added in the second adder 73, _and
A beam output signal S _a ( α _n ) of the ABF 70 is output. By repeating this operation for each α _n of m = 1, 2, ..., M, output signals S _a ( α _n ) of M ABF70s (m = 1, 2, ..., M) are obtained. .
The second power detector 31 calculates the power of the output signal of the ABF 70 for each α _n direction and calculates the power P _a
( α _n ) (m=1, 2, ..., M).
The interpolator 51 uses the output P _a ( α _n ) (m=1,
2 _, . Similar to the maximum point detector 52 in FIG. 2, the maximum point detector 52 determines the direction α in which the interpolated signal P _a ( α ) is maximum , and outputs this α as the estimated value α^ _a of the direction of the target sound source to the output terminal. Output to 60. In addition, the ABF7
The coefficient calculator 74 calculates each coefficient of the variable coefficient filters 72 _{1 to} 72 _{K of} 0 _.
α _n in each direction so as to maximize the S/N of ( α _n ).
Calculate for (m=1, 2,...,M). That is, assuming that the order of each of the variable coefficient filters 72 ₁ to 72 _K is J, the coefficient calculator 74 calculates a total of M×I (I=K×J) coefficients at each update time. become. The variable coefficient filter 7 maximizes the signal-to-noise ratio, that is, S/N.
As a method _for adaptively updating the coefficients of 2 ₁ to 72 _K , for example, _an LMS algorithm (B.
Widrow et al.: Adaptive Noise Canceling
Principles and Applications, Proc. IEEE, 63,
1975, P1692-1716). In addition, the ABF70 may be of a different configuration than the example shown in Fig. 1 (for example, LJ
GRIFFITHS: An Alternative Approach to
Linearly Constrained Adaptive
Beamforming, IEEE.Trans, Antennas &
Propag. 30-1, 1982, P27-34) is also used. [Effects of the Invention] As described above, according to the present invention, the approximate target sound source direction is obtained using the standby CBF, and the beam output is performed only in the minimum direction required for interpolation using information on the target sound source direction. The signal-to-noise ratio (S/
Since a beam is formed with a high adaptive beam former (N) and the beam output signal of the adaptive beam former is used to estimate the direction of the target sound source,
The beam is shaped to form a traditional ABF
The beam output of the standby CBF with a low signal-to-noise ratio can be improved without significantly increasing the amount of processing required for forming (that is, the number of coefficients calculated per update time can be reduced from N×I to M×I). An excellent effect can be obtained in that the direction of the target sound reduction can be estimated with higher accuracy than the direction estimation using the method.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a tracking device in a sonar according to the present invention, FIG. 2 is a diagram showing the configuration of a tracking device in a conventional sonar,
FIG. 3 is a geometric explanatory diagram regarding the receiver array and the target direction when the receiver array is assumed to be a three-dimensional array. In the figure, 10... Receiver array, 11 ₁ to 11K
... Receiving element, 20 ... Standby beam former, 21 ₁ ~ 21 _K ... Time delay compensator, 22 ₁ ~
22 _K ... Fixed coefficient filter, 23... Adder,
30...First power detector, 31...Second power detector, 40...Maximum point detector, 41...First multiplexer, 42...Analysis processor, 43
... Judgment classifier, 44 ... Beam direction selector, 5
0... second multiplexer, 51... interpolator,
52... Maximum point detector, 60... Output terminal.

Claims (1)

[Claims] 1. A signal from a target sound source is received by a receiver array, and a beam signal is applied to the output signal of the receiver array.
In a sonar system that forms a standby beam by a former and tracks the target sound source using the standby beam output signal, a non-adaptive beam former that forms the standby beam and an adaptive beam that forms a beam in a specified direction. - Using a former, find the approximate target sound source direction from the beam output of the non-adaptive beam former that forms the portable beam, and use the information on the target sound source direction as the specified direction,
Select the direction around the target sound source direction required for interpolation,
A tracking method in a sonar, characterized in that a beam is formed in the direction using the adaptive beam former, and the beam output is used to estimate the direction of the target sound source.