JPS6312544B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for searching for the amount of marine resources that can accurately and quickly determine the amount of marine resources using ultrasonic waves.

In recent years, remote sensing-like resource exploration methods have attracted attention, in which ultrasonic waves are emitted into marine resources, particularly schools of fish, and the amount of fish (resources) is estimated based on the information contained in the reflected signals that return. It's coming.

Based on this background, the present applicant first gave high accuracy to the acoustic and electrical parameters and quantitatively analyzed the reflected signals, thereby making it possible to estimate the amount of resources with high precision, and in the depth direction (in the direction of ultrasonic emission). )
We proposed a device that allows the distribution of the average scattering intensity (described later) to be directly observed.

The purpose of this invention is to provide a highly practical resource quantity searching device that further improves the device and enables continuous grasping of fluctuations in the average distribution of resource quantities as the vessel sails. It is in.

To summarize this invention, the scattering intensity calculation means for calculating the scattering intensity distribution in the emission direction from the received reflected waves calculates the scattering intensity for each ultrasonic emission in the moving range from the reference position as the ultrasonic emitting device moves. By including an average scattering intensity calculation means for calculating the average of the distribution, it is possible to continuously and directly grasp fluctuations in the average distribution of resources as the ultrasonic emitting device moves.

Hereinafter, the case where the device according to the present invention is used as a fish finder will be explained.

Analysis of ultrasonic received signals The scattering intensity of a school of fish refers to the intensity ratio (at unit distance) of the backscattered sound wave to the incident sound wave per unit volume of the school of fish.First, we will explain why this scattering intensity can be determined from the received signal. do.

Reflection signal level from a school of fish Let us now consider a scattering layer in which fish with a reflection coefficient TS are distributed at a density of n fish per unit volume, as shown in Figure 1.
Note that the reflection coefficient TS is expressed as the intensity ratio of the incident and reflected sound waves to a single sphere at a point at a unit distance from the center of the sphere.

Intensity of the sound wave Ii at a point of distance r from the sound source
Ii=Iob(θ,)1/r ² e ^- 〓 ^r ...(3) The reflection intensity Ir from the scatterer with a minute unit volume ΔV is
If the scattering intensity is sv, then Ir＝IisvΔV＝IiTsΔV ……(4) The reflection intensity at the sound source is ΔI＝Irb(θ,)1/r ² e ^- 〓 ^r svΔV ……(5) = Iob ² (θ, ) 1/r ⁴ e ^-2 〓 ^r svΔV ……(6) where Io: Intensity at a point at unit distance from the sound source b: Directional strength β: α/1000r=10Ioge〓 rStereoscopic view of minute volume ^ΔV from the sound source Letting the angle be ΔΩ, the speed of sound C, and the pulse width τ, ΔV=r ² ΔΩcτ/2 ...(7) From equation (6), ΔI = Iob ² (θ,)1/r ² e ^-2 〓 ^r svcτ/2ΔΩ ...(8) Therefore, the reflection intensity from the scatterer included within the directivity angle of the oscillator is: I = ∫Iob ² (θ,)1/r ² e ^-2 〓 ^r svcτ/2dΩ ...(9 ) = Io1/r ² e ^-2 〓 ^r svcτ/2 ⁴ 〓 ₀ ∫b ² (θ,)dΩ
...(10) = Io1/r ² e ^-2 〓 ^r svcτ/2Ψ ...(11) = Io1/r ² e ^-2 〓 ^r ntscτ/2Ψ ...(12) Here, Ψ is the beam width and directivity. It is a sexual constant.

10log I=10log Io−(20logr+2αr/1000) +10log sv+10log(cτ/2Ψ) (13) On the other hand, the transmission strength SL of the sound source is defined as follows.

SL=10logIo/Iref ……(14) where Iref: Reference intensity If the received signal level is EL=10logI/Iref, EL=SL−(20logr+2α/1000r)SV +10log(cτ/2Ψ) ……(15) =SL -(20logr+2α/1000r) +TS+10logn+10log(cτ/2Ψ)...(16) Scattering intensity and fish school density When the ultrasonic transmitter's transducer receiving sensitivity is ER=20log Er, find the output voltage V at the transducer end. .

The received signal output voltage V of the vibrator is proportional to the sound pressure P of the incident sound wave, Here, Po: Sound source sound pressure Pref: Reference sound pressure (1μbar) Equation (19) includes SV as information regarding the amount of fish.
or contains nts. Also, in logarithmic expression, it can be expressed as 20logV=SL+ER...(20log+2α/1000r) +10log(cτ/2Ψ)+SV...(20).

As shown in equation (18), the received signal output voltage of the vibrator is proportional to √ of the scattering intensity SV. Also,
In equation (18), Po/Pref (SL), Er (ER), and c, τ, Ψ are all known system constants. Therefore, by correcting the term 1/re ^- 〓 ^r related to the propagation attenuation of sound waves, by measuring the output voltage V,
SV can be obtained regardless of the distance r.

Furthermore, if this scattering intensity SV can be found, from the relationship SV=nts=nσ/4π...(21) If the reflection coefficient ts or scattering cross section σ per fish is known, from the output voltage V, Fish school density n
You can ask for

Correction of 1/re ^- 〓 ^r can be performed using a variable gain amplifier with a gain characteristic of K・re〓 ^r , like a normal fish finder, and a practical amplifier is equipped with a so-called TVG voltage generator. I have to.

If the gain characteristic of the variable gain amplifier is Eg・re〓 ^r , the output voltage Vo of the amplifier is Therefore, sv=Vo ² / (Eg・Er・Po/Pref)Cτ/2...(23) =Vo ^2/10 {(EG+ER+SL)/10}Cτ/2...(24) Also, the fish school density n (tail /m ³ ) is n=Vo ² /10 {(EG+ER+SL+TS)/10}Cτ/2
...(25) EG: Receiving amplifier gain dB, EG=20logEg ER: Receiving sensitivity dB, odB=1V/1μBar SL: Transmission strength dB, odB=1μBar/1m TS: Reflection coefficient dB τ: Pulse width sec c: Sound speed m/sec Ψ: Directivity constant For example, assume that EG = odB ER = -75 dB SL = 120 dB τ = 3 msec Ψ = 0.062 C = 1500 m/sec, and the transducer received output voltage V = 1 Vrms. If the reflection coefficient TS of a single fish constituting a school of fish is -45 dB, the scattering intensity and density of this school of fish are, from equations (24) and (25), SV = -36.5 dB n = 7.2 fish/m ² is required.

From the above analysis, it can be seen that the scattering intensity or density of a school of fish can be calculated from the received ultrasonic signal.

Calculation and Display of Average Scattered Intensity Incidentally, the scattered intensity obtained as described above is an instantaneous value of the depth r, which is the ultrasonic emission direction, and can be continuously obtained as the depth changes. Therefore, by forming orthogonal coordinates between the depth axis and the scattering intensity axis on a display such as a CRT and plotting the instantaneous scattering intensity, it is possible to directly understand the scattering intensity distribution in the depth direction at the ultrasonic emission position. I can do it.

However, grasping the instantaneous scattering intensity in this way is impractical, at least for fish finders, due to data dispersion, etc. In order to obtain a more practical effect, it is necessary to calculate the horizontal average as follows. It is preferable to determine the scattering intensity.

Now, in Figure 2, if the ship SP sequentially emits ultrasonic waves in the horizontal section L for each section J, the average scattering intensity in the horizontal direction in that section is: = [∫ ^L ₀ sv (x) dx ]/L...(26) =10log...(27)

That is, is the average scattering intensity at depth r in the region to which the ship SP has moved.

By always displaying the distribution of this average scattering intensity in the depth direction on the above-mentioned orthogonal coordinates, it is possible to grasp the average fish mass density from the reference position, that is, the position where the ship SP started moving, to the current position. Become. In this case, if the interval L is the update interval and the average scattering intensity distribution at the end position of the previous interval and the average scattering intensity distribution at the current position are displayed simultaneously on the display,
Changes in fish density can be better understood. Note that in this case, the reference position for determining the latter distribution corresponds to the first position of the currently cruising section.

Next, embodiments of the invention will be described with reference to the drawings.

FIG. 3 shows a block diagram of the main parts of a search device which is an embodiment of the present invention.

In the figure, an ultrasonic transducer 1 is connected to a transmitter 2 and a receiver 3 via a gate, and the receiver 3 is equipped with a TVG voltage generator.
The gain characteristic of re〓 ^r is obtained.

The output of the receiver 3 is squared by the next squaring circuit 4,
Further, the correction circuit 5 calculates the equation (24) to obtain the scattering intensity sv. The horizontal integration circuit 6 integrates the scattering intensity sv from the reference position to the current position, and provides the result to the average scattering intensity calculation circuit 7. In this embodiment, the average scattering intensity calculation circuit 7 is divided into an interval calculation circuit 70 that calculates the average scattering intensity for each section (updated section), and a continuous calculation circuit 71 that continuously calculates the average scattering intensity from the reference position to the current position. It consists of

The CRT 8, which is a display device, is connected to the section calculation circuit 7.
The output of 0 is indicated as a, and the output of the continuous arithmetic circuit 71 is indicated as b on the graph. Note that the fish school image is also drawn on the same screen by a normal received signal processing circuit (not shown). Also,
Ship speed data necessary to determine horizontal integration and transmission timing is provided by a log device 9 and a ship speed correction circuit 10.

To outline the operation of the search device with the above configuration, ultrasonic pulses are emitted from the ultrasonic transducer 1 toward the seabed at intervals of the emission period ΔT, and are received by the same transducer 1. The resulting signal is processed by a receiver 3, a squaring circuit 4, and a correction circuit 5 and converted into a scattering intensity signal. The horizontal integration circuit 6 integrates the obtained scattering intensity from the reference position to the current position for each same depth according to the size of the depth r, and then the continuous calculation circuit 71 calculates the average scattering intensity.
Find the distribution of sv. That is, the average of the scattering intensity distribution for each ultrasonic emission from the reference position to the current position is determined. Then, when the section ends, the section calculating circuit 70 calculates the distribution of the average scattering intensity for that section. The CRT8 displays the two average scattering intensity distributions obtained in this way on the same screen, respectively a and
and b are displayed independently, and the display of a is changed every time the section is updated.

Through the above operations, the average scattering intensity distribution from the reference position to the current position is always displayed on the CRT8 using display b, so it is very easy to understand changes in the fish mass density due to the movement of the boat. I can do it. Furthermore, since the average scattering intensity distribution for each section is also displayed, it becomes possible to better understand changes in fish mass density.

Next, a more detailed example of the above search device is shown in FIG.

In the figure, 20 is a transmitter that periodically generates pulses, and a transmission controller 21 sets the period and pulse width τ of the ultrasonic pulses. Transmission/reception switch 2
2 is a gate means for selectively connecting the ultrasonic transducer 23 and the transmitter 20 or the attenuator 24; it connects the ultrasonic transducer 23 and the transmitter 20 during transmission, and connects the ultrasonic transducer 23 and the transmitter 20 when transmission is finished; 23 and attenuator 24
Connect with. The output of the attenuator 24 is amplified in two stages by amplifiers 25 and 26, and the signal is digitized by an A/D converter 27.

A TVG voltage generator 28 for increasing the gain exponentially is connected to the amplifier 25, and a seabed detector 29 is connected to the amplifier 26 for separating the seabed reflected signal from the received signal.

The received signal digitized by the A/D converter 27 is continuously stored in the memory 30, and the stored data is sequentially read out asynchronously with the write timing and sent to the gate means 31. A signal from the seabed detector 29 is input to this gate means 31, and among the stored data, data after the seafloor signal is cut off. Further, the next-stage saturation detection means 32 detects saturation signals exceeding the dynamic range width of the apparatus, and the slicing means 33 removes signals below the level set by the level setter 34. The lamp 35 is a display means for giving an alarm when the saturation detection means 32 detects a saturation signal.

The output data of the slicing means is subjected to more precise correction by the attenuation correction means 36 in the next stage, in addition to the correction by the TVG voltage generator 28. The details will be described later.

The data corrected by the attenuation correction means 36 is squared by the squaring circuit 37, and at this stage, the right side of equation (24) is
Vo ² will be formed. The adding means 38 corresponds to the previously described horizontal integration circuit 6 (see Fig. 3), which adds the Vo ² data obtained as described above for each same depth, and the addition result is stored in the memory. 3
It is updated every time data is read from 0.

The ship speed signal generator 39 is a means for determining the ship speed v including a log device, etc., and generates a periodic signal that receives this output data and a transmission periodic pulse from the controller 21 and generates a signal according to the ultrasonic emission period. The output data of the device 40 is multiplied by the multiplication means 41 to obtain the distance from the reference position to the current position. The output data of the multiplication means 41 is sent to the comparison means 43 together with the output data of the L setting means 42 which sets the update interval L, and the two output data are compared for coincidence.

The system constant is the transmission pulse width τ, (EG,
ER, SL) constants, Ψ, and c are given by τ signal generation means 44, constant signal setting means 45, Ψ setting means 46, and sound speed setting means 47, and the respective data are sent to K calculation means 48. Then, the denominator on the right side of equation (24) is calculated. In this embodiment, since the attenuator 24 is interposed in the path for obtaining the Vo data, the amount of attenuation of the attenuator 24 is actually subtracted from the receiving amplifier gain EG.

On the other hand, Vo ² obtained at the output of the adding means 38
The data is sent to latch means 49 and further to divider means 50. The latch means 49 is connected to the comparison means 4.
When a match signal is received from the adding means 38, the output data of the adding means 38 is latched, and the output data is given to the dividing means 51.

The output data of the K calculation means 48 is given as a dividing value to the division means 50, which always inputs the output data of the addition means 38, and the division means 51, which inputs only the output data of the latch means 49. Calculations are performed on the numerators on the right side of equations (24) and (26). Other dividing means 52 and 53 are means for calculating the average scattering intensity from these results, and the dividing means 52 is given the output data of the multiplying means 41, and the dividing means 53 is given the data of the L setting means 42. It will be done. That is, the output of the dividing means 52 is:
The average distribution of the scattering intensity distribution in the depth direction from the reference position to the current position is obtained, and the output of the dividing means 53 is as follows:
The average distribution of the scattering intensity distribution in the depth direction in the update section L (current) is obtained. Logarithm calculation means 54, 55
converts the average distribution data obtained as described above into logarithmic data and sends it to the display memory 56 separately.

Display memory 56 stores those data along with the reference line, while also storing data from storage 30. The display system including the CRT 57 and the D/A converter 58 uses a raster scan system, and the display position on the screen and the storage position in the memory 56 are geometrically correlated, and their control is performed by scanning. This is done by the controller 59 and the R/W controller 60. Note that the coincidence output data from the comparison means 43 input to the R/W controller 60 is as follows.
It becomes a write synchronization signal when updating the output data of the logarithm calculation means 55.

Next, the details of the correction performed by the attenuation correction means 36 to make the Vo data accurate will be described in detail below.

Generally, the attenuation characteristic TL of ultrasonic waves in water is: TL = 20logr + α / 1000r ... (1) r: distance from the sound source α: absorption attenuation coefficient, which has frequency dependence,
For example, the following empirical formula has been obtained.

α=43.5f ² /7000+f ² +0.00033f ² (dB/Km)...(2) f: Frequency (KHz) The first term in equation (1) indicates attenuation due to diffusion, and the second term indicates attenuation due to absorption.

By the way, the TVG voltage generator 28 outputs an exponential voltage change, and its correction is aimed at diffusion attenuation. Also, the depth is approximately
If the distance exceeds 300m, the correction will generally not be satisfactory.

The attenuation correction means 36 is intended to solve such a drawback, and the correction data is formed by the following means.

First, a correction limit setting means 61 for setting a correction depth limit value is connected to the TVG voltage generator 28, and the correction limit value is generally set at a depth of about 300 m.
Further, in order to obtain the second term of equation (1), a frequency setter 62, an α calculation means 63 for calculating equation (2), and a multiplication means 64 for multiplying α by distance are provided, and the output of the multiplication means 64 is The data is sent to determination means 65.
The determining means 65 determines whether the measured depth is corrected by the correction limit setting means 5.
If it is within the setting range of 0, the output data of the multiplication means 64 is supplied as is to the attenuation correction means 36, but
If the measured depth exceeds the set range, it operates to supply data from the deep depth TVG voltage generation means 66 to the attenuation correction means 36. Note that the deep TVG voltage generating means 66 is
This is a means of calculating X(Δr)i (X: multiplication sign) for .

As a result of the above-described correction being performed continuously, the Vo data output from the attenuation correction means 36 always becomes accurate data regardless of the depth.

Next, the operation of this device will be explained.

The ultrasonic transducer 23 emits ultrasonic pulses toward the ocean floor in response to the pulses generated by the transmitter 20, but the level of the signal received as an echo is controlled by an attenuator 24 and an amplifier 25 that corrects the TVG voltage. ,
It is converted into a digital amount including level information via an amplifier 26 and an A/D converter 27, and is sequentially stored in a memory 3.
It will be stored as 0. The data stored in the storage device 30 is written to the display memory 56 and displayed on the CRT5.
An image C similar to that of a normal fish finder is drawn on the display screen of 7 (see Fig. 5). Further, from the data in the storage device 30, data from the bottom of the ocean is removed by a gate means 31, and low-level data is further removed by a slicing means 33.

Next, the output data of the slicing means 33 is precisely corrected by the attenuation correction means 36 and converted into Vo ² data by the squaring circuit 37. this
The Vo ² data is added for each depth by the adding means 38 each time the ship sails and an ultrasonic pulse is emitted, and the average scattered intensity distribution data is continuously divided by the dividing means 50 and 52. is formed. Furthermore, when the ship navigates the update section L, the data of the adding means 38 at that time is latched by the latch means 49, and the average scattered intensity distribution data of the section L is formed by the dividing means 51 and 53. Ru.

The two average scattering intensity distribution data obtained in this way are one that is updated continuously and the other that is updated in the interval L.
The images are written into the display memory 56 while being updated each time, and the former is displayed as image b and the latter as image a at the center and left side of the screen, respectively (see FIG. 5). These images a and b are
In both cases, the height relative to the reference lines d ₁ and d ₂ is expressed as the average scattering intensity at that depth. Therefore, if the height of the distribution curve at a certain depth is high, the average scattering intensity at that depth, in other words, the fish mass density. can be judged to be large.

As described above, in this embodiment, in addition to the advantage of being able to continuously grasp the average scattering intensity distribution in the depth direction in the range moved from the reference position to the current position, the average scattering intensity distribution in the depth direction in the previous update section L is Since the distribution is also displayed on the same screen, it has the advantage of being able to grasp changes in fish mass density over a wide range.

Although the apparatus shown in FIG. 4 performs correction processing and arithmetic processing by separate means, these processing can also be performed by a microcomputer system. FIG. 6 is a block diagram of a search device in which correction, arithmetic processing, etc. are performed by a microcomputer system.

In the figure, an ultrasonic transducer 80, a receiver 8
1. The operation contents of each element of the transmitter 82 and TVG voltage generator 83 are general and similar to the above example, but they are controlled by the microcomputer 85.
It is carried out by. microcomputer 85
is equipped with an integration memory 86 for executing horizontal integration peculiar to this device, and input data includes received data via an A/D converter 84,
There are constant data from a setting means 87 that generates various constants, and ship speed data from a ship speed detection device 88. In addition, microcomputer 85
A display unit is placed on the output side of the display unit, and this display unit also employs the general raster scan method as in the previous example. The display section is display memory 89, CRT
90, a D/A converter 91, a scanning circuit 92, and a read control circuit 93.

In addition, as shown in Figure 5, if the magnitude of the average scattering intensity at a certain depth is expressed numerically,
The value as fish quantity information is further increased. In this example, the average scattering intensity values corresponding to image a are displayed at three positions on the left end of the screen, but the average scattering intensity values corresponding to image b may also be displayed.

As described in detail above, according to the present invention, it is possible to continuously grasp the fluctuations in the average distribution of resource amount as the voyage progresses, making it possible to replenish resources efficiently, with high precision and high A search device with practicality can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between a school of fish and an ultrasonic transducer, and FIG. 2 is a diagram showing an ultrasonic emission section.
Furthermore, FIG. 3 shows a block diagram of the main parts of a search device which is an embodiment of the present invention, FIG. 4 shows a more detailed example of the same device, and FIG. 6 shows a concrete example of the same device using a microcomputer system. Each example is shown as a block diagram. Furthermore, FIG. 5 shows an example of a display on a CRT used in the above search device. 1,23,80...Ultrasonic transducer, 2,20,
82...Transmitter, 3,81...Receiver, 4,37...2
Multiplication circuit, 6...Horizontal integration circuit, 7...Average scattered intensity calculation circuit, 8, 57, 90...CRT.

Claims (1)

[Claims] 1. An ultrasonic emitting device that sequentially emits an ultrasonic search wave while moving, a scattering intensity calculation means that calculates the scattering intensity distribution in the emission direction from the received reflected waves, and displays the obtained scattering intensity distribution. In the resource quantity search device, the scattering intensity calculation means calculates an average scattering intensity distribution for each ultrasonic emission in a movement range from a reference position to a minute depth as the ultrasonic emission device moves. It includes an average scattering intensity calculation means calculated for each range, and the display means sequentially displays the average scattering intensity in the minute depth range calculated by the average scattering intensity calculation means as a distribution curve in correspondence with the height from the reference line. A resource quantity search device comprising a resource quantity distribution display control means.