JPS60171472A - Sea bottom discriminating apparatus - Google Patents

Abstract

PURPOSE:To enhance the discrimination capacity of the depth of the sea bottom, by setting a slice level in accordance with the depth of the sea bottom. CONSTITUTION:A wave transmitting receiving apparatus 1 transmits an ultrasonic pulse on the basis of the trigger from a transmission trigger generation circuit 3 for making a cycle variable by data from a range setting circuit 2 and receives reflected waves from a school of fish and the sea bottom. The wave receiving signal is supplied to a depth detection circuit 8 equipped with a counter through an amplifier detector circuit 4 provided with a means (not shown in the drawing) for respectively altering amplification characteristics to 20logr, 30logr when a depth (r) is shown by formulae I , II (wherein 2theta is the directing angle of an ultrasonic pulse, tau is a pulse width and c is a sound speed in water), a gate 5, a sea bottom discriminating slice circuit 6 and a wave shaping circuit 7. The circuit 8 counts a clock pulse on the basis of transmission trigger and the count value is latched by the output of the wave shaping circuit 7 to be outputted to a display device 9 and a control circuit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for determining the seabed in a sonar or sounding device that uses ultrasonic pulses.

In order to prevent malfunctions as much as possible, seabed identification is performed based on the slice level, which is set based on the fact that the reflection level from the seabed is generally relatively higher than the reflection level from schools of fish and other floating objects, and the previous depth if necessary. This is done by both prediction gates that are set.

However, when starting seabed determination, the seabed depth is unknown, so it is necessary to open the gate, but in conventional devices, the slice level is set at a constant level from the sea surface to the seabed, so there are schools of fish near the sea surface. If the level other than the seabed is higher than the slice level, as in the case of Furthermore, since the reflection level differs greatly between a shallow place and a deep place, using only the amplification characteristics of 201ogr, which has been commonly used in the past, there is a risk of erroneous discrimination in such cases as well. Furthermore, the observer is forced to check or change the setting of the pre-z111 gate at the start of discrimination or when the depth change is large.

The present invention has been made in view of the above two points, and focuses on the fact that the received seabed reflection level changes depending on the depth based on predetermined characteristics, and sets a slice level corresponding to the depth. It provides equipment.

The present invention will be explained below with reference to the drawings.

The slice level is determined as follows. In other words, the intensity of ultrasonic waves incident on the seabed at depth r from the sound source is generally: However, ■ is the sound wave intensity at a unit distance.

b(θ, φ) is the directional characteristic of the sound source, θ is half of the directional angle, and β
is the absorption decay constant.

And, if the area average backscattering intensity by the seafloor is Sr, then
The root mean square voltage (2) within all the directivity angles at the sound source is where R is the receiving sensitivity.

It can be expressed as

Now, when it is assumed that the receiving beam has a constant sensitivity within the directivity angle, IbCθ, which is the integral term in equation (2) above,
, φ) The value of dS becomes a problem. This value indicates the seafloor area for which reflected signals can be received simultaneously.

That is, in Fig. 1, when the underwater sound speed is C and the pulse width is τ, Δ1 = −□ cosθ−r (+−canθ) ・
...(3).

This is because the slice level needs to be set taking into account the maximum reflected signal strength, and since the ultrasonic pulse has a certain directivity angle, the reflected signal length will be longer than the above pulse width τ. , Therefore, consider which part of the seabed reflecting part has the maximum reflection intensity depending on whether Δr is positive or negative.

(1) When Δr≧0 In FIG. 3, if L is considered to be the seabed, reflected signals are simultaneously generated from the seabed within all directional angles. (4)
Substituting the formula into formula (2)... (5) Furthermore, if we take 10101o for both sides of formula (5), we get V
= 20Iogv =-201ogr+A (dB)-
...(8) However, A-VR+10101o -2a
r +101101o. 101101o tan2o) Therefore, the amplification characteristic in this case is 201ogr.

(2) In the case of rho In this case, there are two parts where seafloor reflection signals occur simultaneously. Therefore, from Figure 2 l) Directional angle! (However, the sea floor is L) 1 Since this is the case, it can be expressed as 2 2 2 IbCθ, φ) dS= πr tanθ.

2) Directional angle ψ ~ θ (however, the seabed is L) 2
It becomes 2. On the other hand, since , Therefore, (8) Substituting equation (8) into equation (8), that is, equation (7) and equation (10) become equal. From this, since r)Cτ74, 1101 on both sides
Taking o, V= 201ogv=-301ogr+B (dB)
”=(11) Therefore, the amplification characteristic in this case is 30Iog
It becomes r.

By the way, in the above, for example, c = 1500 (m
)3 When τ=10(5), θ=4″, f=50(kH
z), the depth r at which Δr=o is approximately 200(1). Therefore, in this case, if the depth is within 200(1), when amplifying 201ogr+! 1, 200 (1
) or less, ideal seabed detection can be achieved by performing trust processing using the amplification characteristics of 301ogr.

Therefore, FIG. 3 is a circuit diagram showing an example of seabed discrimination using the early amplification characteristics, and l is the signal from the transmission trigger generation circuit 3 whose cycle is varied according to the range data from the range setting circuit 2. It is a transducer that transmits ultrasonic pulses as a sound source based on a transmission trigger, and receives return reflected waves from schools of fish and the seabed. The received signal will be described later in 2.
The signal is guided to an amplification/detection circuit 4 made up of a transistor circuit having a characteristic of 01ogr (where r is depth). That is, the above-mentioned 201ogr characteristic is considered ideal in fish detection.

5 is a gate, 6 is a slice circuit for determining the seabed, and 7 is a shaping circuit. Reference numeral 8 denotes a depth detection circuit having a counter etc. inside, which counts clock pulses (not shown) based on the transmission trigger, and the count value at that time is latched by the output of the shaping circuit 7 and displayed on the display 9 and the control circuit 10. be guided. The depth detection circuit 8 retains the previous depth, and if a new depth cannot be obtained, the previous depth is shown to the display 9, for example.

The control circuit 10 has a built-in computer, etc.
Predetermined data and early amplification characteristics and 201og of the amplification and detection circuit 4 are sent to the gate counter 11 that generates the reference pulse of the prediction gate based on the flowchart shown in FIG.
Predetermined data is sent to a level setting circuit 12 that generates a slice level signal with r characteristics taken into consideration. Reference numeral 13 denotes a prediction gate generation circuit, for example, a 1F flip-flop, which generates a prediction gate using a reference Nockles of a prediction case. The level setting circuit 12 is configured, for example, from a 1fROM and a D/A converter, and is configured to designate the downward depth data sent from the control circuit 1G as a read address, and each address has a corresponding slice level. It is written.

The control circuit 10 mainly performs the following operations and processes.

Figure 4 mainly shows the flow of operation processing at the start of seabed determination. Input 1tlt of range data from the setting port N2 (step S).Next, since the depth is unknown at the start of detection, gates 5 are opened to the entire range (step S2).In addition, the level setting The output level of the circuit lid 2 is set in accordance with the bottom depth of the prediction gate.This is because if it is set to the top or middle depth, the slice level will become too high and there is a risk that the seabed will not be identified. In step S2 above, the set level is such that the seabed is at the deepest part of the detection range.

In step S3, it is determined whether depth data has been obtained by determining the seabed based on the set level, and if depth data has not been obtained, the same operation is repeated. If depth data is obtained, predetermined data for the prediction gate is sent to the gate counter 11 in step S4.

This predetermined data refers to a depth value corresponding to 1, for example, several meters in the vertical direction of the depth based on the obtained depth, and the upper depth value is sent from the U terminal and the lower depth value is sent from the D terminal. . Then, the gate counter 11 counts clock pulses corresponding to the aforementioned depths (not shown) from the time the transmission trigger is generated, and when the count 48 matches both of the above depth values, it generates a reference pulse, and the pulses (two). Based on this, the prediction gate generation circuit 13 generates prediction gates only within both depth ranges.

Step S5 determines whether depth data can be obtained based on the next transmission. That is, if the seabed exists within the previous prediction gate, depth data will be obtained, and then a predetermined prediction gate will be generated to continue seafloor determination. However, as described above, the initial slice level is not set high (prediction gate is opened), so if, for example, a large school of fish near the sea surface is mistakenly judged to be the seabed, depth data cannot be obtained in step S5. do not have. This is because, as a result of the first judgment, it was determined that the seabed depth was shallow (although it was actually an incorrect judgment), so the slice level was set extremely high as described later, and for this reason, the -F enlarged fish school This is because it is thought that it will not be extracted.

In this case, step S6 changes the predicted gate, that is, moves it to the entire depth below the initially set gate range. This is done by changing the upper and lower depth values sent from the U and D terminals of the control circuit 10, as described above.

Furthermore, the presence or absence of depth data is then checked in step S7 based on the transmission. In this case, if depth data is not obtained, it means that no seafloor signal is obtained over the entire detection range, and the same operation process is restarted from the beginning. Conversely, when depth data is obtained, predetermined -L direction and lower depth values are set based on the depth data, and a prediction gate is generated as described above (step S4).

Next, FIG. 5 shows another embodiment of the present invention, in which in addition to the circuit diagram shown in FIG. 3, a level detection circuit 14 and a comparison circuit 15 are shown.
is energized. The operations of the other circuits are the same except that signal processing, which will be described later, is added to the control circuit IO.

Immediately when the depth data is obtained, the control circuit 10 sends a signal to the level detection circuit 14 to detect the level of the signal passing through the gate 5 corresponding to the depth data. This can be easily done, for example, by delaying the input signal to the level detection circuit 14 by a small amount of time.

Therefore, the control circuit 10 transmits the upper and lower depth data for the prediction gate as described above, and based on the obtained depth data, when it is assumed that the force < Wj base, the above-mentioned equation (6) or The level that should be theoretically obtained is calculated based on equation (11). The level of the calculation result and the detected actual level are compared in the comparison circuit 15, and when the Detection III level is high, it is determined that it is the seabed, and conversely, when the detection level is low or the difference is more than a certain value, it is determined that it is the seabed. If it is small, it is assumed that it is not on the ocean floor, and the prediction gate is changed (4th
(see figure). Incidentally, as in the present embodiment, the slice level may be calculated one by one within the control circuit 10 and guided to the slice circuit 6 (FIG. 3) as an analog (digital in some cases) signal. In this case, the level setting circuit 12 consisting of a ROM or the like becomes unnecessary.

As explained above, according to the present invention, the received reflected signal from the seabed is amplified in a nearly ideal state, so that it can be detected accurately, and the slice level corresponding to the depth can be adjusted using the amplification characteristics. By setting , the seabed discrimination ability is improved.

In FIG. 3, since the amplification/detection circuit 4 has a 20Iogr characteristic, the level setting circuit 12 has a constant level when Δr≧0 and a 1101or characteristic when Δr<0. , this is done in consideration of the convenience of switching by changing Δr, and the present invention is not limited to this configuration. Therefore, 1. For example, the amplifier circuit itself is 201og
It also includes those in which the control bias voltage is switched or provided in parallel depending on the depth of the r, 301og r characteristics. Further, in the present invention, gates and circuits therefor are provided as necessary, and basically the slice level may be determined based on the lower depth value.

[Brief explanation of the drawing]

1st. FIG. 2 is a geometric diagram for explaining the amplification characteristics of the present invention. FIG. 3 is a circuit diagram showing an embodiment of the present invention, and FIG. 4 is a flowchart of the control circuit IO. FIG. 5 is a circuit diagram showing another embodiment. Patent applicant Furuno Electric Co., Ltd.

Claims (3)

[Claims] (1) In the seabed identification device HI Kool/X using ultrasonic waves, the directivity angle 2θ of the ultrasonic pulse, Noculus rlτ, water [11 When the sound velocity C1 depth r, the amplification characteristic of 2θlog r, or preferably 301ogr. l@
A detection means for performing bottom inspection ((1) and depth 111e data r obtained based on the output of the detection means
and a changing means for changing the amplification characteristics of the detecting means. (2) The seabed discrimination device according to claim 1, wherein the amplification characteristic of the detection means acts as a signal amplification degree. (3) The seabed discriminating device according to claim 1, wherein the amplification characteristic of the detection means acts as a signal slice level.