JPH0125437B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for detecting an underwater object such as a school of fish by transmitting and receiving ultrasonic pulses underwater. prevent it from becoming unidentifiable.

For example, as shown in Figure 1, from ship 1 to seabed 2
When transmitting and receiving ultrasonic pulses in the direction, if the directional direction of the ultrasonic beam 3 is θ and the directional angle is 2α, then
Seabed reflected waves from point A to point C on the seabed 2 are continuously received. Therefore, since the reflected waves from the fish school 4 located near point B on the seabed 2 are included in the seabed reflected waves, it is impossible to distinguish them from the seabed reflected waves unless the level of the reflected waves from the fish school 4 is quite strong.

The present invention realizes an underwater detection device that can clearly distinguish and display waves reflected by fish schools and waves reflected from the seabed in the above-mentioned cases.

In explaining the present invention below, the principle thereof will first be explained.

In FIG. 2, an ultrasonic beam 3 with a directivity angle of 2α
Suppose that the wave is transmitted in the θ ₀ direction and the reflected wave from the water is received.

When the ultrasonic pulse transmitted in the θ ₀ direction is reflected at the seabed 2, the reflected wave from point _P1 returns to the transducer 5 first. At this time, just before the reflected wave from point _P1 returns to the transducer 5, if the directivity angle of the receiving beam 3' is displaced by △θ toward the sea surface with respect to the transmitting beam 3, then the point _P1 Since the reflected wave from the receiving beam 3' is not within the directivity angle of the received beam 3', it is not received.

Similarly, the reflected waves from _two points P are transferred to the transducer 5.
If the direction of the receiving beam 3' is further shifted slightly toward the sea surface immediately before reaching point P, the seafloor reflected wave from point _P2 will not be received either.

Thereafter, if the direction of the receiving beam is gradually shifted toward the sea surface just before the reflected wave from the seabed 2 returns, the reflected wave from the seabed 2 will not be received. Therefore, the reflected waves from the fish school 4 at the point _P3 are not buried in the seabed reflected waves, and only the fish school reflected waves can be clearly extracted.

In the above, the temporal displacement in the pointing direction of the transducer 5 can be determined as follows.

In Fig. 2, when transmitting and receiving an ultrasonic beam with a directivity angle of 2α in the θ ₀ direction, the reflected wave from the point P ₁ on the seabed 2 returns first.
When the distance to _P1 point is L, the time t ₀ for the reflected wave from _P1 point to return is expressed as t ₀ =2L/C (sec) (1). However, C indicates the underwater propagation speed of sound waves.

In equation (1), the distance D to the seabed point P ₀ directly below
is known, the distance L can be found as L=D/cos(90°−θ ₀ −α) …(2), so equation (1) is calculated as t ₀ =2D/C 1/cos(90°−θ ₀ −α) …(3)

Next, if the pointing direction of the ultrasound beam is changed by △θ toward the sea surface and set in the θ ₁ direction, the seafloor reflected wave from point P ₂ will return first, so if that time is t ₁ , then The distance L ₁ to _{the two} points P can be found from L ₁ = 1/2Ct ₁ (4), so the pointing direction θ ₁ is cos(90° - θ ₁ - α) = D/L ₁ = 2D/Ct ₁ …(5), it is expressed as θ ₁ =90°−α−cos ⁻¹ 2D/Ct ₁ …(6).

In equation (6), after the return of the reflected wave from point P _△
Assuming that the reflected wave from point _P2 returns after t seconds, t ₁ = t ₀ + △t...(7), so θ ₁ = 90゜－α－cos ^-1 2D/C(t ₀ +t△) ...(8) It is expressed as follows.

Therefore, as is clear from equation (8), the transducer 5
The directivity direction of the ultrasonic beam may be changed by changing the directivity direction of the ultrasonic beam determined by equation (8) during _Δt seconds after t0 seconds after transmitting the ultrasonic pulse. Strictly speaking, it is preferable to change the pointing direction immediately before t ₀ seconds elapse after transmitting the ultrasonic pulse.

In equation (8), the displacement time Δt in the pointing direction is determined by setting the distance displacement in the two seabed directions. In other words, from the seafloor point P ₀ directly below
Letting the distance to point _P1 be H ₀ and the distance to point P2 be H ₁ , then L ₁ ² = ^{D 2} ₊ H ₁ ² …(9) and L ₁ = L + C/2△t …(10) Therefore, (L+C/2△t) ² = D ² + H ₁ ² Therefore, △t=2/C√ ² + ₁ ² -2/CL...(11) In equation (11), L=D/cos (90°−θ ₀ −α) …(12) Therefore, △t=2/C√ ² + ₁ ² −2/CD/cos(90°−θ ₀ −α) …(13) Also, The distance H ₀ from point P ₀ to point P ₁ is H ₀ = Dtan (90° - θ ₀ - α) ... (14) In equations (13) and (14), D = L cos (90° - θ ₀ - α) ...(15) Therefore, if the distance H ₁ to _{the two} points P is set in advance, the displacement time △t can be calculated based on equations (13) and (14).
can be determined, it is only necessary to displace the pointing direction θ ₁ of the ultrasound beam to the pointing direction determined by equation (8) within that time.

FIG. 3 shows an embodiment based on the above principle, in which the transmission pulses periodically sent out from the transmitter 1 are guided to the transducer 5 via the switch 2, and the ultrasonic pulses are transmitted into the water. . The transducer 5 has a directivity angle of 2α, and the directivity direction is set to θ ₀ when transmitting ultrasonic pulses.

After the ultrasonic pulse is transmitted, the reflected wave from the water is received by the transducer 5 and then guided to the receiver 3 via the switch 2. The receiver 3 amplifies the received reflected wave and sends it to the recorder 4. For example, a sweep type recorder is used as the recorder 4, and at the same time as the transmitter 2 sends out the transmission pulse, the recording pen runs from one end of the recording paper to the other end, and receives the pulse while it travels to the other end. The reflected waves are recorded on recording paper. Therefore,
By setting the time it takes for the recording pen to travel from one end of the recording paper to the other in correspondence with the time required for the ultrasonic pulse transmitted from the transducer 5 to travel back and forth within a predetermined distance, the distance can be adjusted. The reflected waves from the reflector inside the room are recorded on the recording paper.

On the other hand, a part of the transmission pulse sent out from the transmitter 1 is guided to the counter 6. counter 6
counts the pulse train from the clock pulse source 7 at the same time its count value is reset based on the transmitted pulse.

The counted value of the counter 6 is compared with the set value of the distance setting device 9 in the matching circuit 8. Then, when both values match, the matching circuit 8 sends a matching pulse to the depression angle control circuit 10. Depression angle control circuit 10
is for controlling the pointing direction of the transducer 5, and by driving the depression angle control motor 11, the pointing direction is controlled. That is, the pointing direction of the transducer 5 is set in advance in the θ ₀ direction by the depression angle setting device 12, and after the depression angle control circuit 10 is activated, the pointing direction is set based on the set pointing direction θ ₀ . controlled.

Directional direction control of the depression angle control circuit 10 is performed based on equations (8) and (13), as well as equations (14) and (15). That is, the set distance of the distance setting device 9 is
If it is set in advance to 2L, which is twice the straight line distance L from the transducer 5 to the seabed point _P1 , when the coincidence output is sent from the coincidence circuit 8, the depression angle control circuit 10 adjusts the setting of the depression angle setting device 12. Based on the angle θ ₀ and the set distance 2L, the depression angle control motor 1 is operated so that the pointing direction θ ₁ of the transducer 5 changes according to the equation (8) above.
Drive 1. The depression angle control circuit 10 includes the distance D to the seabed point P ₀ directly below the transducer 5, the distance H ₁ from the seabed point P ₀ to the point P ₂ , and the directivity angle of the ultrasonic beam 3.
2α and the underwater propagation velocity C of the sound wave are set in advance.

While the depression angle control circuit 10 controls the pointing direction of the transducer 5 as described above, the distance count value of the counter 6 is also sent to another matching circuit 13. The matching circuit 13 compares the set distance of the range setter 14 and the distance count value of the counter 6, and sends out a matching output when the two distances match. Range setting device 14
is used to set the recording range of the recorder 4. Therefore, the recording pen of the recorder 4 is set so that the traveling time on the record matches the time for the sound wave to travel back and forth over the distance set on the range setting device 14. .

When the distances between the range setter 14 and the counter 6 match, the output of the matching circuit 13 is sent to the depression angle control circuit 10. When the output is sent from the matching circuit 13, the depression angle control circuit 10 drives the depression angle control motor 11 to return the pointing direction of the transducer 5 to the initial setting value, that is, the setting pointing direction θ ₀ of the depression angle setting device 12. let Thereafter, when the output is sent again from the coincidence circuit 8, the depression angle control circuit 10 drives the depression angle control motor 11 in the same manner as described above.

FIG. 4 shows an example of electronically controlling the pointing direction of a transducer, and the same numbers as in FIG. 3 indicate the same parts.

In Fig. 4, the transducer includes three oscillators 5A,
5B, 5C, each vibrator 5A, 5B, 5
The transmission output of the transmitter 1 is applied to C through the respective switching devices 2A, 2B, and 2C. At this time, the transmission signal of transmitter 1 is transmitted through phase shifters 17A, 17B, 17C.
After being phase-shifted at , they are guided to their respective oscillators.

The amount of phase shift of the phase shifters 17A, 17B, 17C is determined by the depression angle setter 12,
The respective signals are phase-shifted so that the combined pointing direction of B and 5C becomes the set pointing direction θ ₀ of the depression angle setter 12.

The ultrasonic pulses sent out from each of the transducers 5A, 5B, and 5C are reflected by an underwater target, and then return to each of the transducers 5A, 5B, and 5C again. The received signals of each vibrator 5A, 5B, 5C are transmitted from the respective switching devices 2A, 2B, 2C to the phase shifter 16.
It is guided to each of A, 16B, and 16C.

Each of the phase shifters 16A, 16B, and 16C phase-shifts the received signal of each vibrator 5A, 5B, and 5C, and the amount of each phase shift is determined by the depression angle control circuit 10 and depression angle setting device 12. Ru. The depression angle control circuit 10 uses phase shifters 16A and ₁₆ in a manner similar to that shown in FIG.
Controls each phase shift amount of B and 16C.

Phase shift output of depression angle setter 12 and depression angle control circuit 10
After the phase-shifted outputs are added by an adder 15, they are led to respective phase shifters 16A, 16B, and 16C.
As is clear from equation (8), the depression angle control circuit 10 is
Since the phase shift output is transmitted from t ₀ seconds after the ultrasonic pulse is transmitted, the depression angle setter 12 adjusts the phase shift amounts of the phase shifters 16A, 16B, and 16C for t ₀ seconds after the ultrasonic pulse is transmitted. is determined. The respective phase shift amounts are determined so that the combined receiving direction of the oscillators 5A, 5B, and 5C coincides with the initial direction of direction θ ₀ .
In addition, in the above, the phase shifters 16A, 16B, corresponding to the composite orientation direction of the vibrators 5A, 5B, 5C,
The respective phase shifts of 16C, 17A, 17B, and 17C can be easily determined in a known manner based on the frequency of ultrasonic waves used, the arrangement interval of the transducers, and the like. Further, the recording device 4 is not limited to one in which the recording pen moves mechanically, but a so-called multi-needle electrode pen in which the recording pen moves electronically can also be used. Alternatively, it is also possible to use a display such as a cathode ray tube display. Further, the directivity characteristics during transmission or reception may be set to be asymmetrical with respect to the center line of the beam. In this case, the directional half angles of the transmitted beam are α and β with respect to the reference line, respectively, and α≠β
It becomes a relationship. In Figures 1 and 2, the transmitting beam is symmetrical with respect to the center line, so if the directional half angles are expressed as α and β, respectively, α=
The relationship is β. Further, the distance data sent from the distance setting device 9 may be obtained by measuring the distance D to the seabed point P ₀ directly below (FIG. 2) and using the measured depth value.
That is, the depth D may be measured by transmitting and receiving ultrasonic pulses toward the seabed immediately below, and the distance L from the transducer 5 to the point _P1 may be calculated and used based on the measured depth value.

As described above, the present invention is capable of receiving and displaying only the necessary reflected waves from schools of fish near the bottom of the water, without receiving reflected waves from the bottom of the water, when deeply understanding underwater diagonally below the own ship. To provide an underwater detection device capable of

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the detection operation of a conventional underwater detector, Fig. 2 is a diagram for explaining the principle of this invention, Fig. 3 shows an embodiment of this invention, and Fig. 4 is a diagram for explaining the detection operation of a conventional underwater detector. Another example will be shown.

Claims (1)

[Scope of Claims] 1. A transmitting device that transmits ultrasonic pulses in the form of a beam within a predetermined range angle toward the bottom of the water in a diagonal direction; a wave receiving device that receives reflected waves generated by the above-mentioned wave transmitting and receiving beams, a depth measuring means that measures the depth D of the underwater point P ₀ immediately below the wave transmitting and wave receiving device, and the above-mentioned wave transmitting device An output signal is generated at approximately the time when the reflected signal obtained when the ultrasonic pulse emitted from the transmitter is reflected at a point P ₁ on the water bottom within the above range angle, which is the shortest distance from the transmitter, reaches the receiver. the depth D is supplied from the depth measuring means;
When the output signal of the timer is received, the directivity direction θ ₁ of the receiving beam formed by the receiving device is determined based on θ ₁ =90°−α−COS ⁻¹ 2D/C(t ₀ +△t) An underwater detection device characterized in that it is equipped with a directional control device that sequentially changes direction toward the water surface, and receives reflected waves from objects other than the bottom of the water, where: △t=2/C√ ₂ + ₁ ^2-2 /CL C: Propagation speed of sound waves in water H ₁ : Distance from the underwater point (P ₀ ) directly below the wave transmitting/receiving device to the underwater point P ₂ within the above range angle L: From the wave transmitting/receiving device to the above underwater point Distance to P ₁ t ₀ : Time from the time the ultrasonic pulse is emitted from the transmitting device to the time it is reflected at the underwater point P ₁ and reaches the receiving device α : Directional half angle of the transmitted beam from the reference line 2 A transmitting device that transmits ultrasonic pulses within a predetermined range angle toward the bottom of the water diagonally downward; a wave receiving device that receives waves by the receiving beam; a depth measuring means that measures the depth D of the underwater point P ₀ directly below the wave transmitting and wave receiving device; a timer that generates an output signal at approximately the time when a reflected signal obtained by reflection at a point _P1 on the water bottom within the range angle that is the shortest distance from the wave device reaches the wave receiving device; The depth D is supplied;
When the output signal of the timer is received, the directivity direction θ ₁ of the receiving beam formed by the above receiving beam is determined based on θ ₁ =90°−α−COS ⁻¹ 2D/C(t ₀ +△t) An underwater detection device characterized in that it is equipped with a pointing direction control device that sequentially changes in the direction of the water surface, and receives reflected waves from objects other than the bottom of the water, where: △t=2/C√ ² + ₁ ² -2/C ×D/COS (90° - θ ₀ - α) C: Propagation speed of sound waves in water H ₁ : From bottom point P ₀ directly below the wave transmitting/receiving device to bottom point P ₂ within the above range angle distance θ ₀ : Angle of the emission direction of the ultrasonic pulse emitted from the transmitter with respect to the water surface t ₀ : From the time the ultrasonic pulse is emitted from the transmitter, it is emitted from the underwater point P ₁ and reaches the receiver. α: Directional half angle from the reference line of the transmitted beam