Target velocity vector display system, target velocity vector display method, and program

Abstract

To determine a target rate vector and make the vector displayable even when a transmission machine side cannot receive a reflection signal from a target in a bistatic / multi-statics system.SOLUTION: The present invention relates to a target rate vector display system for receiving a transmission signal reflected by a target, by a reception array in a position different from a transmission source of the transmission signal, determining the target rate vector, and displaying the vector in the display device. For each plural partial arrays formed by virtually dividing the reception array, the Doppler coefficient based on the target movement is estimated. On the basis of the Doppler coefficient estimated for each partial arrays, the target rate vector is determined.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a target speed vector display system, a target speed vector display method, and a program. [Background technology]

[0002] Generally, a form of active sonar in which the transmitting sound source (transmitter, etc.) and the receiving sensor (receiver) are located in different locations is called "bistatic sonar" or "multistatic sonar." It is also sometimes called "bistatic active sonar" or "multistatic active sonar." While it is often said that a system with one receiving sensor is bistatic, and that a system with multiple sensors (not limited to two) is multistatic, there is sometimes no clear distinction between the two. Therefore, hereinafter, we will refer to them as "bistatic / multistatic sonar."

[0003] In active sonar, which transmits sound waves and detects the echoes from the target, it is extremely important to determine and display the target's line-of-sight velocity. The same is true for bi-multi sonar. However, it is not possible to determine the target's line-of-sight velocity from the signal received by the receiving sensor alone. This point will be explained with reference to Figure 1.

[0004] 1, a sound source is mounted in the transmitter 11, and a receiving sensor in which a plurality of acoustic elements are arranged in an array is mounted in the receiver 10. The acoustic elements convert the received sound waves into electrical signals and output them.

[0005] The velocity of the transmitter 11 (the magnitude of the velocity vector 14) is v s , The velocity of target 12 (the magnitude of velocity vector 15) is v t , The angle formed by the velocity vector 14 of the transmitter 11 with respect to the line 16 connecting the target 12 and the transmitter 11 is θs, the angle formed by the velocity vector 15 of the target 12 is α, Let the speed of sound be c.

[0006] If the transmitter 11 transmits a pulsed continuous wave (PCW) with a constant frequency of fc, the frequency of the sound wave received by the transmitter 11 is f s is given by the following equation (1) due to the Doppler effect. TIFF0007749966000001.tif10150…(1)

[0007] That is, if the velocity component of the transmitter 11 relative to the direction of the target 12 from the transmitter 11 is v1 (for example, a positive value when approaching the target 12), and the velocity component of the target 12 relative to the direction of the transmitter 11 is v2 (a positive value when moving away from the transmitter 11), the frequency f1 of the wave received by the target 12 from the transmitter 11 is TIFF0007749966000002.tif9150…(2) Conversely, when the sound wave reflected by the target 12 is received by the transmitter 11, the direction from the target 12 (the wave source) to the transmitter 11 is taken as positive, and the velocity component of the target in that direction is v1', and the velocity component of the transmitter 11 is v2'. The frequency f s teeth, TIFF0007749966000003.tif11150…(3) Given.

[0008] In the above equation (3), substituting v1'=-v2 and v2'=-v1 into equation (3) and substituting equation (2) into f1 gives the following equation (4). TIFF0007749966000004.tif10150…(4)

[0009] From FIG. 1, the velocity component of the transmitter 11 when the direction from the transmitter 11 to the target 12 is positive is: v1 = -v S cosθ S , velocity component of target 12: v2 = -v t Substituting cosα into equation (4) yields equation (1) above.

[0010] The frequency f on the right side of the above equation (1) cThe coefficient multiplied by this is called the “Doppler coefficient.” The Doppler coefficient η of the sound wave received by the transmitter 11 is given by the following equation (5): TIFF0007749966000005.tif10150…(5)

[0011] For any function waveform f(t), the Doppler effect on the received waveform appears as f(ηt) multiplied by the Doppler coefficient η over time. For example, suppose the transmitted waveform is LFM (Linear Frequency Modulation), where the frequency changes linearly. TIFF0007749966000006.tif9150…(6)

[0012] The angular frequency ω of the transmitted signal at time t is TIFF0007749966000007.tif9150…(7) and it increases linearly from ω0 at t=0 to ω0+μL at t=L, and this frequency change is repeated with a repetition period of L.

[0013] If the time from when the transmitted signal is transmitted until it is reflected by the target 12 and received by the receiver 10 (receiving array) is t0, the waveform of the received signal Sr(t) can be expressed as a waveform in which f(jt) in equation (1) is changed to f(jη(t-t0)) (see Patent Documents 2 and 3). TIFF0007749966000008.tif9150…(8)

[0014] In Patent Document 3, the current received signal waveform S r (t) and from the present time to t A The signal waveform S received just before r (tt A ) TIFF0007749966000009.tif9150…(9) The product of the complex conjugates of S r (t)S r * (tt A ): TIFF0007749966000010.tif11150…(10) Ask for. S in the above equation (10) r (t)S r * (tt A ) is a time-dependent term in the phase of μ η 2 t A t, and the integrated signal has an angular frequency of |μ·η 2 t A Therefore, the signal waveform is constant at S r (t)S r * (tt A ) from the frequency spectrum of |μ·η 2 t A Find the frequency f where |=2πf, and calculate the Doppler coefficient η TIFF0007749966000011.tif14150…(11) I'm looking for it from.

[0015] In addition, in Patent Document 2, the received signal waveform S r Time-differentiated waveform of (t) TIFF0007749966000012.tif9150 and the received signal waveform S r Absolute value of the ratio of (t) R(t)=|S' r (t) / S r (t)| TIFF0007749966000013.tif11150…(12) and fitting the instantaneous frequency of the transmitted waveform to the absolute value R(t) of the ratio between the time-differential waveform and the received waveform using the least squares method or the like to estimate the Doppler shift η.

[0016] From the above equation (5), which is the relational expression of the Doppler coefficient η of the sound wave received by the transmitter 11, the line-of-sight velocity v of the target 12 as seen from the transmitter 11 is t cosα (the projection of the velocity vector 15 onto the line 16 connecting the transmitter 11 and the target 12) is given by the following equation (13). TIFF0007749966000014.tif10150…(13)

[0017] In addition, v s ,v t < <c(v s ,v t is sufficiently smaller than the speed of sound c), then the above equation (5) becomes TIFF0007749966000015.tif16150 TIFF0007749966000016.tif9150 TIFF0007749966000017.tif9150 TIFF0007749966000018.tif10150 TIFF0007749966000019.tif9150…(14)

[0018] From equation (14), the line-of-sight velocity of target 12, v t cosα is calculated (approximated) by the following equation (15). TIFF0007749966000020.tif8150…(15)

[0019] The frequency f1 of the wave received by the target 12 from the transmitter 11 is given by the above equation (2). On the line 17 (Fig. 1) from the target 12 to the receiver 10, if the direction from the target 12 to the receiver 10 is positive, the velocity component of the target 12 in that direction is v2', and the velocity component of the receiver 10 is v3, then the frequency f1 at the receiver 10 receiving the reflected wave from the target 12 is r is given by the following equation (16). TIFF0007749966000021.tif9150…(16)

[0020] In equation (16), Velocity component of the transmitter 11 relative to the direction of the target 12: v1 = -v s cosθ s , Velocity component of target 12 relative to the direction of transmitter 11: v2 = -v t cosα, Velocity component of target 12 relative to the direction of receiver 10: v2' = v tcosβ (in FIG. 1, v t cosβ < 0), Velocity component of the target 12 of the receiver 10 with respect to the direction: v3 = v r cosθ r (in FIG. 1, v r cosθ r < 0), substituting gives the following equation (17). TIFF0007749966000022.tif10150…(17)

[0021] Therefore, the Doppler coefficient ηr of the sound wave received by the receiver 10 is given by the following equation (18). TIFF0007749966000023.tif10150…(18)

[0022] v s , v t , v r << c, the above equation (18) can be approximated as follows. TIFF0007749966000024.tif16150 TIFF0007749966000025.tif9150 TIFF0007749966000026.tif9150 TIFF0007749966000027.tif9150 TIFF0007749966000028.tif9150 TIFF0007749966000029.tif9150…(19)

[0023] Regardless of whether it is equation (18) or equation (19), in addition to v t cosα, v<00(continued on next page)00055>cosβ enters as an unknown variable. Even if the Doppler coefficient η r of the sound wave received by the receiver 10 is obtained by measuring the received signal, etc., and v s cosθ s and v r cosθ r are given by the position sensors and velocity sensors of the transmitter 11 and the receiver 10, in equations (18) and (19), there is one equation with the unknown vt cosα and v t This is a two-part equation, cosβ, and in principle it is impossible to find a solution.

[0024] In Patent Document 1, a bistatic active sonar is used in which the transmitter and receiver are located at different positions on the same ship, and the transmitter and receiver are located at the same speed, i.e., v s =v r = v, v t cosα=v t cosβ=m By making this approximation, the unknown variable is reduced to one.

[0025] In Patent Document 1, the target direction from the transmitter is derived using the cosine law for a triangle with the transmitter (transmitting array), receiver (receiving array), and target as vertices. However, the distance from the transmitter to the target and the distance from the target to the receiver are calculated using the distance between the transmitter and receiver, the time it takes for the signal transmitted from the transmitter to pass through the target position and be received by the receiver, the speed of sound in water, and the target direction obtained by the receiver's phaser.

[0026] In Patent Document 1, equation (18) is changed to the following equation (20). TIFF0007749966000030.tif10150…(20)

[0027] From equation (20), the target's line-of-sight velocity m is given by equation (21). TIFF0007749966000031.tif10150…(21)

[0028] In Patent Document 1, m is called "absolute speed," but v is usually called "absolute speed."

[0029] In addition, in equation (18), θr, θ S are the angles formed by the velocity vector 13 of the receiver 10 with respect to the line 17 connecting the target 12 and the receiver 10, and the angles formed by the velocity vector 14 of the transmitter 11 with respect to the line 16 connecting the target 12 and the transmitter 11. In Patent Document 1, θr and θS is the target direction relative to the transmitter and receiver, with the straight line connecting the transmitter and receiver as the reference, and in the equation (5) of Patent Document 1, c-vcosθr, c+vcosθ in the above equation (20) S The + / - are reversed.

[0030] Here, the approximation in Patent Document 1 v t cosα=v t cosβ=m This is what is meant by cosα = cosβ, 1, the angle α formed by the velocity vector 15 of the target 12 with respect to the line 16 connecting the transmitter 11 and the target 12 is equal to the angle β formed by the velocity vector 15 of the target 12 with respect to the line 17 connecting the receiver 10 and the target 12. Therefore, the angle Θ formed by the two lines 16 and 17 is set to 0. This condition is only met when the distance to the target 12 is much greater than the distance between the transmitter 11 and the receiver 10.

[0031] For example, as shown in Figure 2, if the distance between the transmitter 11 and the target 12 is A, the distance between the receiver 10 and the target 12 is B, and the distance between the transmitter 11 and the receiver 10 is C, the following equation (22) holds true from the triangle cosine theorem. TIFF0007749966000032.tif10150…(22)

[0032] If Θ = 0, then cosΘ = 1. For example, in equation (22), if C = 1 kyd (kiloyard) and A = B = 10 kyd, cosΘ=0.995 This appears to be a good approximation to 1, but Θ ≒ 5.73 deg.

[0033] In Figure 1, for example, when α=80deg, β=α+Θ=85.73deg, Then, cosα ≒ 0.174, cosβ ≒ 0.074 and cosα ≠ cosβ This becomes:

[0034] If the distance A between the transmitter 11 and the target 12 and the distance B between the receiver 10 and the target 12 are close to the distance C between the transmitter 11 and the receiver 10, for example, If A=B=C=1kyd, cosΘ=0.5, that is, Θ=60deg. If α=80deg, then β=α+Θ=140deg.

[0035] Then, cosα ≒ 0.174, cosβ ≒ -0.766 Therefore, cosα and cosβ are significantly different.

[0036] At this time, v s =v r =0 knots (knots), α=80deg, β=140deg, v t =10kt Then, m≒-2.97kt and the expected value of receiver 10 is v t This is clearly different from cosβ≒-7.66kt.

[0037] In other words, in Patent Document 1, depending on the conditions, an approximation is used that does not hold true, and there are cases where the correct radial velocity of the target cannot be obtained.

[0038] A method that is not restricted by such conditions is the method described in Non-Patent Document 1. The disclosure of Non-Patent Document 1 will be outlined below. Although the notation is different, the essence is as follows.

[0039] In Non-Patent Document 1, first, the line-of-sight velocity of the target as seen from the transmitter is calculated from the signal received by the sensor (receiving array) on the transmitter side, according to Equation (13) shown below. TIFF0007749966000033.tif10150…(13)

[0040] Next, the Doppler coefficient η of the target 12 as seen from the receiver 10 is calculated from the signal received by the sensor (receiving array) on the receiver 10 side. r Ask for.

[0041] Then, v obtained from the above equation (13) t By substituting cosα into equation (19) derived from equation (18), the line-of-sight velocity v of the target 12 as seen from the receiver 10 side is obtained. t cosβ can be calculated. TIFF0007749966000034.tif10150…(23)

[0042] Here, from Figure 1, α=β-Θ Therefore, TIFF0007749966000035.tif6150…(24)

[0043] v t cosα is calculated using equation (19), and v t cosβ is found using equation (23).

[0044] Θ can be found from equation (22) if distance A to target 12 as seen from transmitter 11, distance B to target 12 as seen from receiver 10, and distance C between transmitter 11 and receiver 10 are known.

[0045] To begin with, active sonar is a device that determines the target distance and the direction of the target 12. Regarding the distance C between the transmitter 11 and the receiver 10, if the transmitter 11 and the receiver 10 are mounted on the same hull, their respective positions can be obtained, for example, from the dimensions at the time of design. Alternatively, even if the transmitter 11 and the receiver 10 are mounted on different hulls and are separated, they can exchange position information with each other, for example, using a GPS (Global Positioning System). If the receiver 10 is towed from the hull on which the transmitter 11 is mounted, the position of the receiver 10 can be known from an attitude sensor or the like on the receiver 10. In this way, v t sinβ is calculated using the following equation (25). TIFF0007749966000036.tif9150…(25)

[0046] From the above, v t cosβ, v t sinβ is obtained. In other words, a 2-D target speed vector 15 is obtained, rather than a scalar, which is the radial velocity (velocity component) of the target 12. Of course, a velocity vector is far more useful than a radial velocity.

[0047] As described above, Θ can be found from equation (22), or by knowing the angle between the target 12 as seen from the transmitter 11 and the receiver 10, the distance to the target 12 as seen from the transmitter 11, and the distance between the transmitter 11 and the receiver 10. Alternatively, Θ can be found by using the angle between the target 12 as seen from the receiver 10 and the transmitter 11, the distance to the target 12 as seen from the receiver 10, and the distance between the transmitter 11 and the receiver 10. [Prior art documents] [Patent documents]

[0048] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-106748 [Patent Document 2] International Publication No. 2018 / 038128 [Patent Document 3] Japanese Patent Application Publication No. 2019-23577 [Non-patent literature]

[0049] [Non-Patent Document 1] Pascal AM de Theije and Jean-Christophe Sindt, “Single-Ping Target Speed ​​and Course Estimation Using a Bistatic Sonar”, IEEE JOURNAL OF OCEANIC ENGINEERING, VOL. 31, NO. 1, JANUARY 2006 [Non-patent document 2] Shiwa, “A new target Doppler velocity estimation method using integral systems”, Proceedings of the 2020 Research Presentation Meeting of the Society of Marine Acoustics, p.55 [Non-patent document 3] Shiwa, "Target bearing estimation using phase difference and time shift difference between partial arrays", Ultrasonic TECHNO 2020.1-2, VOL32, No.1, pp.28-33. Summary of the Invention [Problem to be solved by the invention]

[0050] Incidentally, Non-Patent Document 1 assumes that the transmitter can also receive signals reflected from a target using a receiving sensor. However, some sonar systems have transmitters that are dedicated to transmission and do not have a receiving function. For example, in a variable depth sonar (VDS) where the transmitter and receiver are towed from a ship, the transmitter is generally dedicated to transmission.

[0051] Furthermore, in the case of CAS (Continuous Active Sonar), which is a sonar that transmits continuously, it transmits constantly. Therefore, even if the transmitter has a receiving function, it cannot receive signals if it uses an acoustic element that can transmit and receive signals. In CAS, the acoustic elements are separate for transmission and reception, and even if reception is possible on the transmitter side, the near-field reverberation is very large and can sometimes even cause saturation. As a result, it is not possible to distinguish echoes from targets in the received signal.

[0052] Therefore, an object of the present invention is to provide a target velocity vector display system, method, and program that can determine and display the velocity vector of a target even when, for example, the transmitter side of a bistatic / multistatic system cannot receive a reflected signal from the target. [Means for solving the problem]

[0053] According to the present invention, there is provided a target velocity vector display system that receives a signal reflected by a target from a transmission signal using a receiving array located at a position different from the transmission source of the transmission signal, and determines and displays the velocity vector of the target, wherein the receiving array is virtually divided into a plurality of partial arrays, and a Doppler coefficient based on the movement of the target is calculated for each of the plurality of partial arrays, and the velocity vector of the target is determined and displayed on a display device based on the Doppler coefficient calculated for each of the plurality of partial arrays.

[0054] According to the present invention, there is provided a target velocity vector display method for receiving a signal reflected by a target using a receiving array at a position different from a transmission source of the transmitted signal, and for determining and displaying a velocity vector of the target, the method comprising: virtually dividing the receiving array into a plurality of partial arrays; calculating a Doppler coefficient based on the movement of the target for each of the plurality of partial arrays; There is provided a target velocity vector display method for determining the velocity vector of the target based on the Doppler coefficient calculated for each of the plurality of partial arrays and displaying it on a display device.

[0055] According to the present invention, there is provided a program for causing a computer to execute a process of receiving a signal resulting from reflection of the transmitted signal by a target using a receiving array at a position different from a transmission source of the transmitted signal, determining a velocity vector of the target, and displaying the velocity vector on a display device, the program including a process of calculating a Doppler coefficient based on the movement of the target for each of a plurality of partial arrays obtained by virtually dividing the receiving array, and determining the velocity vector of the target based on the Doppler coefficient calculated for each of the plurality of partial arrays. Further, according to the present invention, there is provided a computer-readable recording medium (e.g., semiconductor storage such as RAM (Random Access Memory), ROM (Read Only Memory), or EEPROM (Electrically Erasable and Programmable ROM)), HDD (Hard Disk Drive), SSD (Solid State Drive), CD (Compact Disc), or DVD (Digital Versatile Disc) storing the program. [Effects of the Invention]

[0056] According to the present invention, even if the transmitter cannot receive a reflected signal from the target, the velocity vector of the target can be determined and displayed. [Brief explanation of the drawings]

[0057] [Figure 1] FIG. 2 is a diagram illustrating the velocities and Doppler coefficients of a transmitter, a receiver, and a target. [Figure 2] FIG. 2 is a diagram illustrating the velocities and Doppler coefficients of a transmitter, a receiver, and a target. [Figure 3] (A) is a diagram illustrating a transducer array, and (B) and (C) are diagrams illustrating partial arrays. [Figure 4] FIG. 1 is a diagram illustrating a configuration of a first embodiment of the present invention. [Figure 5] FIG. 2 is a diagram illustrating a modified example of the configuration of the first embodiment of the present invention. [Figure 6] FIG. 1 is a diagram illustrating a first embodiment of the present invention. [Figure 7] FIG. 1 is a diagram illustrating a first embodiment of the present invention. [Figure 8] FIG. 10 is a diagram illustrating the configuration of a second embodiment of the present invention. [Figure 9] FIG. 10 is a diagram illustrating the configuration of a second embodiment of the present invention. [Figure 10] FIG. 10 is a diagram illustrating the configuration of a third embodiment of the present invention. [Figure 11] FIG. 10 is a diagram illustrating a third embodiment of the present invention. [Figure 12] FIG. 1 is a diagram illustrating an example of an apparatus configuration according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0058] An embodiment of the present invention will be described. According to the present invention, in a bistatic sonar or multistatic sonar in which the transmission source and receiving sensors are separated, the receiving sensor of one receiver or the receiving sensors of multiple receivers are virtually divided into at least first and second partial arrays, first and second Doppler coefficients are calculated from the received signals received by at least the first and second partial arrays, and for each of the first and second Doppler coefficients, a velocity vector of the target is calculated from simultaneous equations using equations or approximate equations that hold between the Doppler coefficient, signal velocity, the position and velocity of the target, the position and velocity of the transmission source, and the position and velocity of each partial array, and displayed on a display device.

[0059] 4 is a diagram illustrating the configuration of one embodiment of the present invention, in which there are two partial arrays. The system for displaying a target velocity vector includes a first partial array 101-1, a second partial array 101-2, a first beam former 102-1, a second beam former 102-2, a first reception processing device 103-1, a second reception processing device 103-2, a transmission processing device 108, a self-position / velocity sensor 109, a velocity vector calculator 110, and a velocity vector display device 111.

[0060] The first reception processing unit 103-1 is made up of a first Doppler coefficient estimator 104-1, a first direction estimator 105-1, a first reception time estimator 106-1, and a first distance estimator 107-1.

[0061] The second reception processing unit 103-2 is made up of a second Doppler coefficient estimator 104-2, a second direction estimator 105-2, a second reception time estimator 106-2, and a second distance estimator 107-2.

[0062] In Figure 4, the first partial array to first distance estimator are respectively written as partial array 1 to distance estimator 1, and the second partial array to second distance estimator are respectively written as partial array 2 to distance estimator 2.In the following, when it is clear without using reference symbols, partial arrays will be referred to using the notation in the figure, such as partial arrays 1, 2, etc.

[0063] As shown in Figure 3(A), an array in which transducers (acoustic elements that receive transmission signals as electrical signals, convert them into acoustic signals, and transmit the received acoustic signals, and convert the received acoustic signals into electrical signals) are arranged linearly can be virtually divided into two sub-arrays by, for example, dividing the transducers into two separate groups as shown in Figure 3(B), or by making some transducers belong to both groups as shown in Figure 3(C). "Virtual division" means that the transducers are processed as separate arrays in signal processing without physically cutting the array.

[0064] The operation of this embodiment will be described with reference to Figures 6 and 4. Here, a case will be described in which the transmitter 11 and receiver 10 are mounted on the same hull. For example, the transmitter 11 may be a hull sonar or bow sonar (a hull sonar in which the transmitter or receiver is fixedly mounted on the hull) or a towed sound source, and the receiver 10 may be a flank array mounted on the side of the hull or a towed array towed from the stern.

[0065] In this case, as shown in FIG. 6, the velocity vector 14( → v s ) are the velocity vectors 13-1, 13-2 ( → v r ) (the magnitude and direction of the vector are the same).

[0066] Here, the first partial array 101-1 and the second partial array 101-2 in Fig. 4 (corresponding to 10-1: receiver partial array 1 and 10-2: receiver partial array 1 in Fig. 6) are assumed to have a configuration such as that shown in Fig. 3(B) or 3(C). The sound waves received by the first partial array 101-1 are phased by the first beam former 102-1. The sound waves received by the second partial array 101-2 are phased by the second beam former 102-2.

[0067] In FIG. 4, the first Doppler coefficient estimator 104-1 and the second Doppler coefficient estimator 104-2 estimate the first and second Doppler coefficients η r1 , η r2 The first and second Doppler coefficients η are estimated from the signals received by the first and second partial arrays 101-1 and 101-2. r1 , η r2 There is no particular limitation on the method for estimating the received signal waveform S r From (t), in addition to Patent Document 2 and Patent Document 3 which outline an example using the above formula (11) or (12), the method described in Non-Patent Document 2 and the like may also be used.

[0068] The first and second azimuth estimators 105-1 and 105-2 estimate the azimuth of the target as seen from each of the partial arrays.

[0069] One widely used method for estimating the azimuth of the target 12 is, for example, to perform a scan by changing the direction of the beam and determine that the target is in the direction where the reflection intensity is strongest. Alternatively, as shown in Non-Patent Document 3, a method may be used in which the partial arrays 1 and 2 are further divided into a plurality of partial arrays and the target azimuth is estimated from the phase difference between the partial arrays. Alternatively, various commonly used methods exist, such as adaptive beamforming and compressed sensing.

[0070] In FIG. 4, the first reception time estimator 106-1 and the second reception time estimator 106-2 obtain the time from the time when the transmitter 11 transmits a transmission signal to the time when the echo from the target 12 is received at the first and second partial arrays 101-1 and 101-2, respectively. For example, the time when the received sound wave exceeds a threshold during continuous reception is regarded as the reception time and the target sound wave is determined to have arrived. For the transmission time, for example, information on the time when the transmission signal was transmitted from the transmitter is obtained. The reception time is calculated by subtracting the transmission time from the reception time. However, the method is not limited to this, and various known methods may of course be used.

[0071] The first distance estimator 107-1 and the second distance estimator 107-2 estimate the distances (target distances) between the first and second partial arrays 101-1 and 101-2 and the target 12, respectively. In a bi-multistatic sonar, the position of the target 12 at which the reflected sound arrives at a certain time from the transmission time is an ellipse, as shown in FIG.

[0072] In Figure 7, T1 (T3) is the time it takes for the transmitted signal sent from the transmitter 11 to reach the target 12, and T2 (T4) is the time it takes for the sound wave reflected by the target 12 to be received by the receiver 10. In Figure 7, the focus (+f, 0) of the ellipse represents the position of the receiver 10 at time t0 (reception time) when the sound wave reflected by the target 12 is received by the receiver 10, point A on the ellipse represents the position of the target 12 at time t0-T2, and the focus (-f, 0) of the ellipse represents the position of the transmitter 11 at time t0-T2-T1.

[0073] The target distance from the receiver 10 (partial array) to the target 12 cannot be determined based on the reception time of the reflected sound at the receiver 10 (partial array) alone. The target distance can only be determined when the direction (target direction) of the target 12 at the receiver 10 (partial array) is known. The time T0 from when the transmitted signal is sent by the transmitter 11 until the reflected sound arrives at the receiver 10 is T1 + T2, and if the speed of sound is c, the sum of the distances cT1 and cT2 between the target 12 at point A and the transmitter 11 and receiver 10 is the length 2a of the major axis of the ellipse. From TIFF0007749966000037.tif6150, TIFF0007749966000038.tif9150…(26)

[0074] If the distance (spacing) between the transmitter 11 at the position (focal point (-f, 0) of the ellipse) at the time of transmitting the transmitted signal (t0-T2-T1) and the receiver 10 at the position (focal point (+f, 0) of the ellipse) at time t0 is L, then f = L / 2. If the length of the minor axis of the ellipse is 2b, then TIFF0007749966000039.tif14150…(27)

[0075] For example, if the target direction of the target 12 at point A is θ, the target distance R=cT2 from the receiver 10 is calculated by the coordinates of the target 12. TIFF0007749966000040.tif9150…(28) of TIFF0007749966000041.tif10150…(29) In FIG. 7, the target azimuth may be a supplementary angle of θ.

[0076] TIFF0007749966000042.tif15150 TIFF0007749966000043.tif11150…(30)

[0077] The first distance estimator 107-1 (second distance estimator 107-2) estimates, for example, a distance (spacing) L between the transmitter 11 at the time of transmitting a transmitted signal and the first partial array 101-1 (second partial array 101-2) at the position at the time when the transmitted signal is received, a time T0 from when the transmitted signal is received until the first partial array 101-1 (second partial array 101-2) receives the reflected sound, and a target azimuth θ at the first partial array 101-1 (second partial array 101-2). r1 (θ r2 ), the distance R1 (R2) between the first partial array 101-1 and the target 12 is calculated.

[0078] The Doppler coefficient η of the target received by the first partial array 101-1 r1 Using equation (18), TIFF0007749966000044.tif10150…(31) This becomes:

[0079] where: v t is the magnitude of the velocity of target 12, α is the angle between the line 16 connecting the transmitter 11 and the target 12 and the velocity vector 15 of the target 12, β1 is the angle between the line 17 connecting the first partial array 101-1 of the receiver 10 and the target 12 and the velocity vector 15 of the target 12, v s is the magnitude of the velocity of the transmitter 11, θ s is the angle between the line 16 connecting the transmitter 11 and the target 12 and the velocity vector 14 of the transmitter 11, v r is the magnitude of the velocity of the first partial array 101-1, θ r1 is the angle between the line 17 connecting the first partial array 101-1 of the receiver 10 and the target 12 and the velocity vector 13-1 of the first partial array 101-1.

[0080] In equation (31), α=β1-Θ (Θ is the angle of intersection between the line 16 connecting the transmitter 11 and the target 12 and the line 17 connecting the receiver 10 and the target 12), and then transform it by substituting cosα=cosβ1cosΘ+sinβ1sinΘ to obtain the component v of the two-dimensional velocity vector of the target 12. t cosβ1, v t Factoring out sinβ1, we get: TIFF0007749966000045.tif6150 TIFF0007749966000046.tif6150

[0081] Here, the magnitude of the velocity of the transmitter 11, v s is the velocity magnitude v of the partial array 1 of the receiver 10 r Since it is identical to v s =v r Then, TIFF0007749966000047.tif6150 TIFF0007749966000048.tif6150…(32)

[0082] Similarly, the Doppler coefficient η of the target received by the second partial array 101-2 is r2 is given by the following equation (33). TIFF0007749966000049.tif10150…(33)

[0083] where v t , α, v s , θ s is the same as equation (31). β2 is the angle between the line 19 connecting the second partial array 101-2 of the receiver 10 and the target 12 and the velocity vector 15 of the target 12, v r is the magnitude of the velocity of the second partial array 101-2, θ r2 is the angle between the line 19 connecting the second partial array 101-2 of the receiver 10 and the target 12 and the velocity vector 13-2 of the first partial array 101-1.

[0084] In equation (33), β2=β1-γ (γ is the intersection angle between the line 17 connecting the first partial array 101-1 and the target 12 and the line 19 connecting the second partial array 101-2 and the target 12), From α=β1-Θ, cosβ2=cosβ1cosγ+sinβ1sinγ, Substituting cosα = cosβ1cosΘ + sinβ1sinΘ, we transform the target 12 into the two-dimensional velocity vector components (x, y) = (v t cosβ1, v t If we factor out sinβ1), we get the following: TIFF0007749966000050.tif6150 TIFF0007749966000051.tif6150 TIFF0007749966000052.tif6150

[0085] Here, the magnitude of the velocity vector of the transmitter 11 is v s is the velocity magnitude v of the partial array 2 of the receiver 10 r Since it is identical to v s =v r Then, TIFF0007749966000053.tif6150 TIFF0007749966000054.tif6150 TIFF0007749966000055.tif6150…(34)

[0086] The self-position / velocity sensor 109 calculates a common velocity v as the velocity vector 14 of the transmitter 11 and the velocity vectors 13-1 and 13-2 of the second partial array. r and supplies it to the velocity vector calculator 110. The self-position / velocity sensor 109 may detect a two-dimensional velocity vector.

[0087] TIFF0007749966000056.tif6150 TIFF0007749966000057.tif6150 TIFF0007749966000058.tif6150 TIFF0007749966000059.tif6150 TIFF0007749966000060.tif6150 If you put TIFF0007749966000061.tif6150, From equations (32) and (34), the following simultaneous equations with two unknowns are obtained: a 11 v t cosβ1+a 12 v t sinβ1=b1 a 21 v t cosβ1+a 22 v t sinβ1=b2 …(35) From the above, the component v of the two-dimensional velocity vector 15 of the target 12 t cosβ1, v t sinβ1 is found.

[0088] That is, a 2x2 matrix A, a 2-dimensional vector → v, → b TIFF0007749966000062.tif8150 TIFF0007749966000063.tif10170…(36)

[0089] TIFF0007749966000064.tif9150…(37)

[0090] TIFF0007749966000065.tif10150…(38) Then, equation (35) can be expressed in matrix form as equation (39). TIFF0007749966000066.tif6150…(39)

[0091] Therefore, TIFF0007749966000067.tif6150…(40)

[0092] That is, TIFF0007749966000068.tif10150…(41)

[0093] The velocity vector calculator 110 calculates the Doppler coefficients η at the first and second partial arrays 101-1 and 101-2 estimated by the first Doppler coefficient estimator 104-1 and the second Doppler coefficient estimator 104-2. r1 , η r2 , An angle θ between a line 17 connecting the first partial array 101-1 and the target 12 and a velocity vector 13-1 of the first partial array 101-1 r1 , An angle θ between a line 19 connecting the second partial array 101-2 and the target 12 and a velocity vector 13-2 of the second partial array 101-2 r2 , The common velocity v of the first and second partial arrays 101-1 and 101-2 r , The angle θs between the line 16 connecting the transmitter 11 and the target 12 and the velocity vector 14 of the transmitter 11 is used to obtain a two-dimensional velocity vector of the target 12, with the direction from the first partial array 101-1 to the target 12 as the first component and the direction perpendicular (orthogonal) to the first component. →> v t =(v t cosβ1,v t sinβ1) can be calculated. The sound speed c can be given in advance or measured on the spot.

[0094] In the velocity vector calculator 110, v r cosθ s ya v r cosθ r1 , v r cosθ r2 may be calculated based on the measurement result of the velocity vector by the self-position / velocity sensor 109 and the position of the target 12. From the measurement result by the self-position / velocity sensor 109, for example, the velocity vectors of the transmitter 11, the first and second partial arrays 101-1 and 101-2 on a two-dimensional plane with the east-west direction as the x-axis and the north-south direction as the y-axis can be calculated. → v s = → v r1 = → v r2 = → v r is derived, and the straight lines 16 and 17 in FIG. 6 are drawn from the position information of the transmitter 11 and the first and second partial arrays 101-1 and 101-2 based on the measurement results of the position sensors and the position of the target 12 (calculated from the target direction and target distance, for example). r cosθ s ya v r cosθ r1 , v r cosθ r2 may be derived.

[0095] Receiver 10 speed v r The speed may be obtained from a speed sensor attached to the hull, or may be calculated from position information obtained by a GPS (Global Positioning System) or the like.

[0096] Θ in the above equation (36) (the intersection angle Θ between the lines 16 and 17 in FIG. 6) can be calculated if the positions of the first partial array 101-1 of the receiver 10, the transmitter 11, and the target 12 are known. If the receiver 10 is mounted on a ship's hull, the position of the first partial array 101-1 can be determined from its structural position. If the receiver 10 is towed, the position can be estimated from the structural length of the towed portion. Alternatively, a position sensor may be mounted on the receiver 10, and the velocity vector calculator 110 may acquire the position of the partial array 101-1 from the position sensor.

[0097] The position of the transmitter 11 can also be determined from its structural position if the transmitter 11 is attached to the hull. If the transmitter 11 is towed, it can be estimated from the structural length of the towed part. Alternatively, a position sensor may be attached to the transmitter 11, and the velocity vector calculator 110 may acquire the position information from the position sensor. The transmission processing device 108 in FIG. 4 may acquire the position information from the transmitter 11 and supply it to the velocity vector calculator 110.

[0098] The velocity vector calculator 110 can determine the position of the target 12 using the target azimuths θ1 and θ2 obtained by the first and second azimuth estimators 105-1 and 105-2 and the target distances obtained by the first and second distance estimators 107-1 and 107-2.

[0099] γ in equation (36) (the intersection angle between the line 17 connecting the partial array 1 and the target 12 in FIG. 6 and the line 19 connecting the partial array 2 and the target 12) is the difference in target azimuth between the first and second partial arrays 101-1 and 101-2. The velocity vector calculator 110 calculates the velocity vector θ1 and θ2 from the first and second target azimuths θ1 and θ2 obtained by the first and second azimuth estimators 105-1 and 105-2 corresponding to the respective partial arrays 101-1 and 101-2, as follows: TIFF0007749966000069.tif6150…(42) It can be calculated as:

[0100] 6, the target direction θ1 may be set based on a line connecting the first partial array 101-1 of the receiver 10 and the transmitter 11, as shown in FIG. 7, for example, although not limited thereto. The target direction θ2 of the second partial array 101-2 may also be set based on a line parallel to the line connecting the first partial array 101-1 and the transmitter 11.

[0101] In addition, in FIG. 6, since the velocity vectors 13-1 and 13-2 of the first and second partial arrays 101-1 and 101-2 are the same (parallel), the angle θ between the line 17 connecting the first partial array 101-1 and the target 12 and the velocity vector 13-1 of the first partial array 101-1 is r1 , the angle θ between the line 19 connecting the second partial array 101-2 and the target 12 and the velocity vector 13-2 of the second partial array 101-2 r2 Regarding TIFF0007749966000070.tif6150…(43) holds true.

[0102] Alternatively, the velocity vector calculator 110 may calculate and obtain θ1, θ2, and γ using only the distance L between the first and second partial arrays 101-1 and 101-2 and the distances (target distances) R1 and R2 between the first and second partial arrays 101-1 and 101-2 and the target 12, using the law of cosines in triangles, without using the first and second target azimuths θ1, θ2 and γ obtained from equation (42). This is effective when the azimuth accuracy is low.

[0103] The Doppler coefficient η received by the receiver 10 may be based on the approximate equation (19) instead of the equation (18). In this case, the Doppler coefficient η obtained by the partial array 1 r1 is given by the following equation: TIFF0007749966000071.tif9150…(44)

[0104] In equation (44), α = β1 - Θ is substituted with cosα = cosβ1 cosΘ + sinβ1 sinΘ, and the two-dimensional velocity vector component v of target 12 is obtained. t cosβ1, v tFactoring out sinβ1, we get: TIFF0007749966000072.tif6150

[0105] Here, the magnitude of the velocity of the transmitter 11, v s is the velocity magnitude v of the partial array 1 of the receiver 10 r Since it is identical to v s =v r Then, TIFF0007749966000073.tif6150…(45)

[0106] Doppler coefficient η obtained by partial array 2 r2 is given by equation (46). TIFF0007749966000074.tif9150…(46)

[0107] In equation (46), β2=β1-γ, α=β1-Θ, Substituting cosβ2=cosβ1cosγ+sinβ1sinγ and cosα=cosβ1cosΘ+sinβ1sinΘ, we transform the equation to obtain the component v of the two-dimensional velocity vector of target 12. t cosβ1, v t Factoring out sinβ1 gives us the following: TIFF0007749966000075.tif6150

[0108] Here, the magnitude of the velocity of the transmitter 11, v s is the velocity magnitude v of the partial array 2 of the receiver 10 r Since it is identical to v s =v r Then, TIFF0007749966000076.tif6150…(47)

[0109] From the simultaneous equations of (45) and (47), the components of the two-dimensional velocity vector of target 12, v t cosβ1, v tsinβ1 is calculated. That is, the 2 × 2 matrix F and the 2-dimensional vector → v are calculated as in the following equations (48) to (50). t , →g, equation (51) holds. TIFF0007749966000077.tif9150…(48)

[0110] TIFF0007749966000078.tif9150…(49)

[0111] TIFF0007749966000079.tif10150…(50)

[0112] TIFF0007749966000080.tif6150…(51)

[0113] therefore, TIFF0007749966000081.tif6150…(52) 2D velocity vector of target 12 from → v t is obtained.

[0114] The velocity vector display device 111 displays the two-dimensional velocity vector of the target 12 calculated by the velocity vector calculator 110. → v t may be displayed on a display device in association with the distance, direction and time of the target.

[0115] In this embodiment, the case where the array is divided into two partial arrays has been described, but one array may be divided into three or more partial arrays as shown in Fig. 5. In this case, for example, for a combination of any two partial arrays, the Doppler coefficient η obtained for the two partial arrays may be used to calculate the velocity vector of the target, and the arithmetic average of the velocity vectors of the target calculated for each combination may be used as the velocity vector of the target 12.

[0116] In the above embodiment, it is assumed that the transmitter 11 and receiver 10 are mounted on the same hull, or that the receiver 10 is being towed, i.e., the speeds of the transmitter 11 and receiver 10 are the same.

[0117] However, even if the transmitter 11 and receiver 10 are separated and have different velocities, the two-dimensional velocity vector of the target 12 can be determined. This can be the case, for example, when the transmitter 11 is a hull sonar, bow sonar, or towed sound source mounted on a vessel other than the vessel on which the receiver 10 is mounted, and the receiver 10 is a hull sonar or bow sonar mounted on a vessel other than the vessel on which the transmitter 11 is mounted, or a flank array (a sonar in which array elements are integrated into a plate-like form and mounted on the side of a submarine's hull) or a towed array. In this case, as shown in Figure 9, the velocity vectors of the transmitter 11 and receiver 10 (partial array) are different.

[0118] 8 is a diagram showing an example of the configuration of a target velocity vector display system according to a second embodiment of the present invention. This is an example in which a receiver 10 is divided into two partial arrays 1 and 2. Unlike the first embodiment in which the velocity vector 13 of the receiver 10 and the velocity vector 14 of the transmitter 11 are equal, in this embodiment a transmitter position / velocity sensor 112 is added.

[0119] The position and velocity data of the transmitter 11 obtained by the transmitter position and velocity sensor 112 is transmitted from the transmitter 11 to the receiver 10, for example, by communication. The communication method may be a wireless local area network (LAN) or optical communication if the transmitter 11 and receiver 10 are located close to each other. If the distance between the transmitter 11 and receiver 10 is long, wireless communication or satellite communication may be used. Alternatively, the data may be transmitted from the transmitter 11 to the receiver 10 in the form of underwater acoustic communication. Even if the transmitter 11 is a regular sonar without communication capabilities, data can be transmitted by utilizing various modulation methods including frequency modulation and phase modulation.

[0120] An example of a method for calculating the velocity vector of the target 12 when the velocities of the transmitter 11 and the receiver 10 are different will be shown below. The Doppler coefficient ηr1 of the target received by the first partial array 101-1 of the receiver 10 can be calculated using equation (18) as follows: TIFF0007749966000082.tif10150…(53) This becomes:

[0121] Transforming equation (53) using α=β1-Θ TIFF0007749966000083.tif6150 TIFF0007749966000084.tif6150…(54) This becomes:

[0122] The Doppler coefficient ηr2 of the target received by the subarray 2 is similarly given by the following equation (18): TIFF0007749966000085.tif10150…(55)

[0123] β2 = β1 - γ, α=β1-Θ Therefore, equation (55) can be transformed as follows: TIFF0007749966000086.tif6150 TIFF0007749966000087.tif6150 TIFF0007749966000088.tif6150…(56)

[0124] therefore, TIFF0007749966000089.tif6150 TIFF0007749966000090.tif10170…(57)

[0125] TIFF0007749966000091.tif9150…(58)

[0126] TIFF0007749966000092.tif10150…(59) Then, equations (54) and (56) can be expressed in matrix form as in the following equation (60). TIFF0007749966000093.tif6150…(60)

[0127] Therefore TIFF0007749966000094.tif6150…(61) As v t cosβ1 and v t sinβ1 can be calculated. The magnitude of the velocity v t Since the angle β1 is known, the two-dimensional velocity vector 15 of the target 12 can be obtained. Here, the speed of sound c can be given in advance or measured on the spot. The velocity vector of the receiver 10 → v r may be obtained by a speed sensor attached to the hull, or may be calculated from position information obtained by GPS or the like.

[0128] In equation (57), Θ is the intersection angle between the line 16 connecting the transmitter 11 and the target 12 and the line 17 connecting the receiver 10 and the target 12, and can be calculated if the positions of the partial array 101-1, the transmitter 11, and the target 12 are known. If the receiver 10 is attached to the hull, the position of the partial array 101-1 can be determined from its structural position. If the receiver 10 is towed, the position can be estimated from the structural length of the towed part. A position sensor may be attached to the receiver 10, and the position of the partial array 101-1 may be obtained from the position sensor.

[0129] As described above, the position and velocity of the transmitter 11 may be transmitted to the receiver 10 via communication, for example, by a position / velocity sensor mounted on the transmitter 11. The transmission processing device 108 may receive the position and velocity of the transmitter 11 from the transmitter 11 and supply them to the velocity vector calculator 110.

[0130] The position of the target 12 can be determined using the target direction θ1 obtained by the first direction estimator 105-1 and the target distance R1 obtained by the first distance estimator 107-1.

[0131] Since γ is the azimuth difference between the first and second partial arrays 101-1 and 101-2, it can be calculated from the target azimuths θ1 and θ2 obtained by the first and second azimuth estimators 105-1 and 105-2 corresponding to the respective partial arrays as follows: TIFF0007749966000095.tif6150…(62) It can be calculated as:

[0132] 6, the target direction θ1 may be set based on a straight line connecting the first partial array 101-1 of the receiver 10 and the transmitter 11, as shown in FIG. 7, for example, although not limited thereto. The target direction θ2 of the second partial array 101-2 may also be set based on a straight line parallel to the straight line.

[0133] 9, the angle θ between the line 17 connecting the first partial array 101-1 and the target 12 and the velocity vector 13-1 of the first partial array 101-1 is r1 , the angle θ between the line 19 connecting the second partial array 101-2 and the target 12 and the velocity vector 13-2 of the second partial array 101-2 r2 Regarding TIFF0007749966000096.tif6150…(63) holds true.

[0134] Alternatively, θ1, θ2, and γ may be calculated and used using only the distance R between the first and second partial arrays 101-1 and 101-2 and the target distance from the first and second partial arrays 101-1 and 101-2, without using the target azimuths θ1 and θ2 and γ found from θ1 and θ2. This is effective when the azimuth accuracy is low.

[0135] Note that the equation (19) may be used as an approximation instead of the equation (18). In this case, the Doppler coefficient η obtained by the first partial array 101-1 is r1 teeth, TIFF0007749966000097.tif9150…(64)

[0136] Using α=β1-Θ, equation (64) can be transformed as follows: TIFF0007749966000098.tif6150…(65)

[0137] The Doppler coefficient η obtained by the second partial array 101-2 r2 is given by: TIFF0007749966000099.tif9150…(66)

[0138] β2=β1-γ, α=β1-Θ Therefore, equation (66) can be transformed as follows: TIFF0007749966000100.tif6150…(67)

[0139] where TIFF0007749966000101.tif9150…(68)

[0140] TIFF0007749966000102.tif9150…(69)

[0141] TIFF0007749966000103.tif10150…(70) given that, TIFF0007749966000104.tif6150…(71) and TIFF0007749966000105.tif6150…(72) 2D velocity vector of target 12 from → v t is obtained.

[0142] The velocity vector display device 111 displays the two-dimensional velocity vector of the target 12 calculated by the velocity vector calculator 110. → v t may be displayed on a display device in association with the distance, direction and time of the target.

[0143] Although the case where the array is divided into two partial arrays has been described here, it may be divided into three or more partial arrays, as in the first embodiment. In that case, for example, the velocity vectors obtained by combining any two partial arrays may be averaged between the combinations.

[0144] In the above embodiment, the partial arrays of the receiver 10 are actually virtual divisions of the same sensor, but even if they are physically independent, the velocity vector of the target 12 can be obtained. For example, this is the case when sonars mounted on multiple ships are considered to constitute one array. For example, towed arrays on multiple ships are considered to be partial arrays of one towed array.

[0145] The transmitter 11 may be fixed to a vessel on which any of the receivers 10 is mounted, may be towed, or may be mounted on a vessel dedicated to transmission. The feature of this case is that not only do the velocity vectors differ between the transmitter 11 and the receiver 10, but the velocity vectors may also differ between the partial arrays of the receiver 10, as shown in FIG.

[0146] FIG. 10 is a diagram showing a configuration example of a third embodiment of the present invention. In this embodiment, the receiver 10 is divided into two partial arrays 101-1 and 101-2. Unlike the configuration of the second embodiment in which the velocity vectors between the partial arrays are equal, the first partial array 101-1 and the second partial array 101-2 are provided with self-position / velocity sensors 109-1 and 109-2, respectively. Position and velocity data obtained from one of the self-position / velocity sensors 109-1 and 109-2 of the first partial array 101-1 and the second partial array 101-2 is transmitted to the other partial array by, for example, communication. Communication methods may include wireless LAN or optical communication if the partial arrays are located close to each other, or wireless communication or satellite communication if the partial arrays are located far apart. The position and velocity of the transmitter are the same as those of the second embodiment.

[0147] In this embodiment, when the velocities of the transmitter 11 and the partial arrays 101-1 and 101-2 are different, the velocity vector of the target 12 is → v t An example of how to calculate is described below.

[0148] The Doppler coefficient η of the target received by the first partial array 101-1 r1 From the above equation (18), TIFF0007749966000106.tif10150…(73) This becomes:

[0149] Using α=β1-Θ, we transform equation (73) TIFF0007749966000107.tif6150 TIFF0007749966000108.tif6150…(74) This becomes:

[0150] The Doppler coefficient η of the target 12 received by the second partial array 101-2 r2 Also from equation (18), TIFF0007749966000109.tif10150…(75) This becomes:

[0151] β2=β1-γ Since α=β1-Θ, equation (75) can be transformed as follows: TIFF0007749966000110.tif6150 TIFF0007749966000111.tif11150…(76)

[0152] therefore, TIFF0007749966000112.tif6150 TIFF0007749966000113.tif9170…(77)

[0153] TIFF0007749966000114.tif9150…(78)

[0154] TIFF0007749966000115.tif10150…(79) Then, equations (74) and (76) can be expressed in the matrix form of equation (80).

[0155] TIFF0007749966000116.tif6150…(80)

[0156] Therefore TIFF0007749966000117.tif6150…(81) From the velocity vector of target 12 → v t =(v_ t cosβ1, v_ t sinβ1) can be calculated. Here, the sound velocity c can be given in advance or measured on the spot. r1 , v r2 may be obtained by the self-position / velocity sensors 109-1 and 109-2 attached to the hull, or may be calculated from position information obtained by GPS or the like.

[0157] In equations (77) and (79), θ r1 and θ r2 is the angle formed by the velocity vectors 13-1 and 13-2 of the first and second partial arrays 101-1 and 101-2 and the lines 17 and 19 connecting the first and second partial arrays 101-1 and 101-2 and the target 12. Θ is the intersection angle between the lines 16 and 17, and can be calculated if the positions of the first partial array 101-1, the transmitter 11, and the target 12 are known. If the receiver 10 is mounted on the hull, the position of the first partial array 101-1 can be determined from its structural position. Alternatively, if the receiver 10 is towed, the position of the first partial array 101-1 can be estimated from the structural length of the towed part. Alternatively, a position sensor may be mounted on the receiver 10 and the position may be obtained from the position sensor.

[0158] As for the position and speed of the transmitter 11, data from a mounted position and speed sensor may be transmitted to the receiver side by communication, as in the previous embodiment.

[0159] The position of the target 12 can be found using the target direction obtained by the direction estimator 105 and the target distance obtained by the distance estimator 107. Since γ is the target direction difference between the first and second partial arrays 101-1 and 101-2, it can be calculated from the target directions θ1 and θ2 obtained by the first and second direction estimators 105-1 and 105-2 corresponding to the first and second partial arrays 101-1 and 101-2 as follows: TIFF0007749966000118.tif6150…(82) It can be calculated as:

[0160] Alternatively, instead of using the azimuths θ1, θ2 and γ obtained from θ1 and θ2, θ1, θ2, and γ may be calculated using only the distance between the first and second partial arrays 101-1, 101-2 and the target distance from each of the partial arrays 101-1, 101-2, and these may be used. This is effective when the azimuth accuracy is low.

[0161] It should be noted that the equation (19) may be used as the basis instead of the equation (18). In this case, the Doppler coefficient η obtained by the first partial array 101-1 is r1 is given by the following equation (83). TIFF0007749966000119.tif9150…(83)

[0162] α=β1-Θ Using this, equation (83) can be transformed as follows: TIFF0007749966000120.tif6150…(84)

[0163] The Doppler coefficient η obtained by the second partial array 101-2 r2 is given by the following equation (85). TIFF0007749966000121.tif9150…(85)

[0164] β2 = β1 - γ, α=β1-Θ Using this, equation (85) can be transformed into the following: TIFF0007749966000122.tif6150…(86)

[0165] where TIFF0007749966000123.tif9150…(87) TIFF0007749966000124.tif9150…(88) TIFF0007749966000125.tif10150 …(89) given that, TIFF0007749966000126.tif6150…(90) and TIFF0007749966000127.tif6150…(91) from the velocity vector of target 12 → v t is obtained.

[0166] Although the description here is of the case where the array has two partial arrays, it may have three or more partial arrays, as in the first embodiment. In that case, for example, the velocity vectors obtained by combining any two partial arrays may be averaged between the combinations. Note that the calculation of the velocity vector described in the embodiment is just an example, and other methods of calculation may also be used.

[0167] FIG. 12 is a diagram illustrating an embodiment of the present invention, illustrating a configuration in which a direction estimation apparatus is implemented in a computer device 200. Referring to FIG. 12, the computer device 200 includes a processor 201, a memory 202 such as a semiconductor memory (e.g., a random access memory (RAM), a read-only memory (ROM), or an electrically erasable programmable read-only memory (EEPROM)) (or a hard disk drive (HDD)), a display device 203, and an interface 204 (bus interface). The processor 201 may be a digital signal processor (DSP). By executing a program 205 stored in the memory 202, the processor 201 performs the processing of at least the reception processing devices 103-1 and 103-2 and the velocity vector calculator 110 shown in FIG. 4. The display device 203 constitutes the velocity vector display device 111 shown in FIG. 4.

[0168] In the above embodiment, sonar has been described as an example, but the present invention can also be applied to radar, LiDAR (Light Detection And Ranging), and the like.

[0169] The disclosures of Patent Documents 1-3 and Non-Patent Documents 1-3 are incorporated herein by reference. Modifications and adjustments of the embodiments and examples are possible within the scope of the entire disclosure of the present invention (including the scope of the claims), and further based on the basic technical ideas thereof. Furthermore, various combinations and selections of the various disclosed elements (including each element of each claim, each element of each example, each element of each drawing, etc.) are possible within the scope of the claims of the present invention. In other words, the present invention naturally includes various modifications and alterations that would be possible for a person skilled in the art based on the entire disclosure, including the scope of the claims, and the technical ideas thereof. [Explanation of symbols]

[0170] 10 Receiver 11 Transmitter 12 Goals 13 Receiver velocity vector 13-1 Velocity vector of the first subarray 13-2 Velocity vector of the second subarray 14 Transmitter velocity vector 15 Target velocity vector 16 Straight line connecting the target and transmitter 17 Line connecting the target and receiver (partial array 1) 18 Straight line connecting transmitter and receiver 19 Line connecting the target and receiver (partial array 2) 20, 21 Same direction as the velocity vector of the receiver (partial array 1) 101-1 First subarray (subarray 1) 101-2 Second subarray (subarray 2) 101-N Nth partial array (partial array N) 102-1 First beam generator (Beam generator 1) 102-2 Second Beam Generator (Beam Generator 2) 102-N Nth Beam Generator (Beam Generator N) 103-1 First reception processing device (reception processing device 1) 103-2 Second reception processing device (reception processing device 2) 103-N Nth receiving processing device (receiving processing device N) 104-1 First Doppler Coefficient Estimator (Doppler Coefficient Estimator 1) 104-2 Second Doppler Coefficient Estimator (Doppler Coefficient Estimator 2) 105-1 First bearing estimator (bearing estimator 1) 105-2 Second bearing estimator (bearing estimator 2) 106-1 First reception time estimator (reception time estimator 1) 106-2 Second Reception Time Estimator (Reception Time Estimator 2) 107-1 First distance estimator (distance estimator 1) 107-2 Second distance estimator (distance estimator 2) 108 Transmission processing device 109 Self-position and speed sensor 109-1 First self-position / speed sensor (self-position / speed sensor 1) 109-2 Second self-position / speed sensor (self-position / speed sensor 2) 110 Velocity Vector Calculator 111 Velocity Vector Display 112 Transmitter position and speed sensor 200 Computer Equipment 201 processor 202 memory 203 Display device 204 Interface 205 Programs

Claims

1. A target velocity vector display system that receives a signal reflected from a target by a receiving array at a position different from a transmission source of the transmission signal, and determines and displays a velocity vector of the target, calculating a Doppler coefficient based on the movement of the target for each of a plurality of partial arrays obtained by virtually dividing the receiving array; a target velocity vector display system that calculates a velocity vector of the target using the Doppler coefficients for each of the plurality of partial arrays and displays the calculated velocity vector on a display device;

2. the plurality of sub-arrays comprises at least first and second sub-arrays, each of which constitutes a part of the receive array; first and second Doppler coefficient calculation means provided corresponding to the first and second partial arrays, for calculating first and second Doppler coefficients based on movement of the target from the signals received by the first and second partial arrays, respectively; the first and second Doppler coefficients; The signal speed and a velocity component of the transmitting source relative to a direction from the transmitting source to the target; a velocity component of the target relative to a direction from the target to the transmitting source; velocity components of the first and second subarrays relative to the target heading from the first and second subarrays; a velocity component of the target relative to the orientation of the first and second sub-arrays from the target; a velocity vector calculation means for calculating a velocity vector of the target based on a simultaneous equation derived from an approximation of the equation or an equation that holds between the above equations; a velocity vector display means for displaying the velocity vector of the target on the display device; 2. The target velocity vector display system according to claim 1, comprising:

3. The velocity vector calculation means A velocity vector of the target having a first component that is a projection of the target onto a straight line connecting the first partial array and the target, and a second component that is a projection onto a direction perpendicular to the direction of the straight line is calculated from the simultaneous equations as follows: the first and second Doppler coefficients; the signal rate; and a projection of the velocity vector of the transmitting source onto a line connecting the transmitting source and the target; projection of the velocity vectors of the first and second partial arrays onto a line connecting the first and second partial arrays and the target; an intersection angle between a line connecting the transmitting source and the target and a line connecting the first partial array and the target; 3. The target velocity vector display system according to claim 2, wherein the target velocity vector is calculated by performing a calculation on an intersection angle between a line connecting said first partial array and said target and a line connecting said second partial array and said target.

4. 4. The target velocity vector display system according to claim 2, wherein the velocity vector calculation means averages the velocity vectors of the target calculated from the Doppler coefficients of the partial array pairs for a combination of the first and second partial arrays that is a predetermined partial array pair among the plurality of partial arrays, and sets the average velocity vector of the target to the velocity vector of the target.

5. A target velocity vector display system that receives a signal reflected by a target from a transmission signal using a receiving array located at a position different from a transmission source of the transmission signal, and determines and displays a velocity vector of the target, A receiving array of a plurality of receivers is regarded as one receiving array, and the receiving array of the plurality of receivers is regarded as a plurality of partial arrays; determining a Doppler coefficient based on the movement of the target for each of the plurality of partial arrays; a target velocity vector display system that calculates a velocity vector of the target using the Doppler coefficients for each of the plurality of partial arrays and displays the calculated velocity vector on a display device;

6. A target velocity vector display method for determining and displaying a velocity vector of a target by receiving a signal reflected from a target by a receiving array at a position different from a transmission source of the transmission signal, the method comprising: The receiving array is virtually divided into a plurality of sub-arrays; determining a Doppler coefficient based on the movement of the target for each of the plurality of partial arrays; a target velocity vector display method, which calculates a velocity vector of the target using the Doppler coefficients for each of the plurality of partial arrays and displays the calculated velocity vector on a display device;

7. calculating first and second Doppler coefficients based on the movement of the target from the received signals received by at least first and second partial arrays that constitute a part of the receiving array; the first and second Doppler coefficients; The signal speed and a velocity component of the transmitting source relative to a direction from the transmitting source to the target; a velocity component of the target relative to a direction from the target to the transmitting source; velocity components of the first and second subarrays relative to the target heading from the first and second subarrays; a velocity component of the target relative to the orientation of the first and second sub-arrays from the target; calculating a velocity vector of the target based on an equation that holds between the vectors or a simultaneous equation derived from an approximation of the equation; 7. The method for displaying a target velocity vector according to claim 6, further comprising displaying the target velocity vector on the display device.

8. A program that causes a computer to execute a process of receiving a signal that is a transmission signal reflected by a target using a receiving array at a position different from a transmission source of the transmission signal, and determining a velocity vector of the target and displaying the velocity vector on a display device, calculating a Doppler coefficient based on the movement of the target for each of a plurality of partial arrays obtained by virtually dividing the receiving array; a program including a process for calculating a velocity vector of the target using the Doppler coefficients for each of the plurality of partial arrays.

9. a process of calculating first and second Doppler coefficients based on the movement of the target from each of the received signals received by at least first and second partial arrays that constitute a part of the receiving array; the first and second Doppler coefficients; The signal speed and a velocity component of the transmitting source relative to a direction from the transmitting source to the target; a velocity component of the target relative to a direction from the target to the transmitting source; velocity components of the first and second subarrays relative to the target heading from the first and second subarrays; a velocity component of the target relative to the orientation of the first and second sub-arrays from the target; a process of calculating a velocity vector of the target based on an equation that holds between the above equations or a simultaneous equation derived from an approximation of the above equation; displaying the velocity vector of the target on the display device; The program according to claim 8, which causes the computer to execute the steps of:

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