JP2944481B2 - Underwater active sound detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater active acoustic detection apparatus for transmitting an acoustic signal into water, receiving an acoustic signal reflected from a target object, and detecting an underwater object, and more particularly to an active acoustic detection apparatus. Suitable for acoustic homing by underwater vehicles, with means to prevent each transmission sound from affecting the reception of other underwater vehicles when multiple devices are mounted on the underwater vehicle and operated in the same sea area Underwater active sound detector.

[0002]

2. Description of the Related Art Conventionally, an ultrasonic signal is transmitted underwater, an ultrasonic signal reflected from a target object is received, and underwater traveling in the direction of the target object is measured while measuring the distance and direction to the target object. In order to output information for guiding the body, an active sound detection device is mounted on the underwater vehicle as a homing device.

[0003] When a plurality of hulls provided with an active type acoustic homing device are operated in the same sea area, in addition to the sound waves reflected back from the target by the ultrasonic signal transmitted by itself, the sound waves directly return to other objects. The transmitted wave emitted by the underwater vehicle may be received, and its level may be higher than the reflected wave from the target. Serious errors such as incorrect homing of the running body may occur. To avoid this,
It is conceivable to operate the frequency bands apart from each other so as not to interfere with each other, but there is a problem that the homing devices have different basic performances, and the operation is complicated and costly. In order to solve this, there is a method in which each underwater vehicle has FM transmission means of a different code, and by receiving signal processing, it does not detect transmission waves emitted from other underwater vehicles. Proposed. (Japanese Unexamined Patent Publication No.
No. 27687)

[0004]

However, in the prior art, since the FM transmission signal is used as the transmission signal, reliable detection and accuracy of the reflected wave signal from the target object due to the influence of the relative speed with respect to the target object and the like. In some cases it was difficult to detect.

[0005] The reason for this is that if the reception frequency changes due to the Doppler effect due to the speed of the target object or the speed of another underwater vehicle, the FM transmission signal causes a reduction in signal processing gain such as detection processing and high reverberation. This is because, in some cases, it is difficult to detect the reflected sound from the target object, and the transmission signal used for detection of the target object may be inappropriate.

SUMMARY OF THE INVENTION It is an object of the present invention to minimize the influence of Doppler shift due to the relative speed with respect to a moving target object and the influence of other marine vehicles, etc. The present invention provides an underwater active acoustic detection device which can reliably identify a target object, and can sufficiently secure measurement and detection accuracy of a distance, an azimuth, and the like of a target object even in the operation of acoustic homing using a plurality of navigation vehicles. It is in.

[0007]

An underwater active acoustic detection apparatus according to the present invention has a transmitting section for transmitting a sound wave and a receiving section for receiving a reflected wave, and detects a target by comparing a transmitted signal with a received signal. In the underwater active acoustic detection device that performs, the transmission unit transmits a transmission signal of a plurality of different frequencies, the reception unit calculates a difference signal of two different frequencies among the signals of the plurality of frequencies included in the reception signal, The arrival time of the target reflected wave due to the transmission signal is detected by comparing with the corresponding difference signal of the transmission signal of the transmission unit.

Here, the transmitting section can transmit a plurality of frequency signals simultaneously, or can transmit a plurality of frequency signals sequentially.

Further, if the receiving section is configured to extract a reception signal based on a detection result at the arrival time of the target reflected wave and output the target reflected wave, detailed information such as the level of the target reflected wave is obtained. It is suitable for.

Further, the underwater active acoustic detection device of the present invention is preferably mounted on an underwater vehicle and used as an acoustic homing device.

More specifically, ultrasonic transmitting means for transmitting signals of two frequencies (1 to 4 in FIG. 1 and 1, 3 in FIG. 4)
Means for analyzing the frequency of the received signal to detect two frequencies in the received signal (8 in FIG. 1 and 8 in FIG. 4), and a frequency for calculating the difference frequency between the two frequencies in the received signal Difference calculating means (9 in FIG. 1 and 9 in FIG. 4) and frequency difference comparing means for comparing the frequency of the difference between the two frequencies of the transmission signal and the frequency of the difference between the two frequencies of the received signal (FIG. 1
10 and 10) in FIG.

[0012] It is determined that the reflected wave from the target object by the ultrasonic signal transmitted by itself into the water is the frequency of the difference between the two frequencies in the received signal and the frequency of the corresponding two frequencies in the transmitted signal. Are determined by comparison. For this reason, the Doppler shift based on the relative speed with respect to the target object is always canceled out, and the influence thereof can be ignored. Further, since the transmission signal of another active acoustic detector can be identified by the frequency difference, interference can be eliminated and the timing of the reflected wave itself or the reflected wave itself can be reliably detected.

[0013]

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

Referring to FIG. 1, a first embodiment of the present invention includes two transmitters 1 and 2 and the two transmitters 1 and 2.
A frequency control circuit 3 for controlling the transmission frequency of the transmitter 2 and simultaneously outputting a signal of a transmission frequency difference;
An adding circuit 4 for adding the two output signals;
A transmitter 5 for transmitting the output signal of the underwater into the water, a receiver 6 for receiving the ultrasonic waves in the water, a frequency analysis circuit 7 for performing a frequency analysis of the output signal from the receiver 6, and a result of the frequency analysis A frequency detection circuit 8 for detecting two signal frequencies included in a signal from a received signal, a reception frequency difference calculation circuit 9 for calculating a frequency of a difference between the detected two frequencies, a signal of the transmission frequency difference and the reception frequency A frequency difference comparison circuit 10 that compares the output signals of the difference calculation circuit and outputs an ON signal when the two frequency differences are equal, and outputs an OFF signal when they are not equal, and performs signal processing on an output signal from the receiver 6. A signal processing circuit 11 that outputs a target detection signal, and a gate circuit 12 that is connected to an output of the signal processing circuit 11 and that passes an output signal of the signal processing circuit 11 by an ON signal of the frequency difference comparison circuit 10 You have me.

Next, the operation of the first embodiment of the present invention will be described in detail with reference to FIGS.

FIG. 2 shows a self-propelled underwater vehicle 21 and a target object 2.
2 shows an example of an arrangement diagram of 2 and another underwater vehicle 23. FIG. In FIG. 2, the velocity of the underwater vehicle is V _m , the speed of the target object is V _t , the expected angle of the underwater vehicle with the target object is θ _m , and the expected angle of the target object with the underwater vehicle is θ. _{Let t} . The reception frequency is Doppler-shifted with respect to the transmission frequency according to the equation (1) according to the speed of the underwater vehicle, the speed of the target object, and the relative angle of each other.

[0017]

(Equation 1) Here C: water sound speed V _m: rate of underwater vehicle V _t: velocity of the target object theta _m: visual angle of the target object of the underwater vehicle theta _t: prospects for the underwater vehicle of a target object Angle f _R : Receiving frequency f _T : Transmission frequency When two frequencies of ultrasonic waves are transmitted and the two frequencies to be transmitted are f _T1 and f _T2 , the difference Δf _T between the two frequencies is Δf _T = f _T1 −f _T2. (2) It is shown by.

From equations (1) and (2), the difference Δf _R between the two frequencies of the received signal reflected from the target object by the ultrasonic wave transmitted by itself is given by

[0019]

(Equation 2) Indicated by

The speed of sound C in water is about 1500 m / sec.
Velocity V _m of the underwater vehicle, since the speed V _t of the target object is about 30 m / sec at practically maximum speed of underwater vehicles V
_m, the speed V _t of the target object considering that slow relative water speed of sound C, (3) equation approximately

[0021]

(Equation 3) Becomes

Since the prospective angles θ _m and θ _t are in the range of 0 to ± 180 °, Δf _R is

[0023]

(Equation 4) Is the range calculated by

For reference, the speed of sound in water C = 1500 m /
Second, speed V _m of underwater vehicle, speed V _{t of} target object = 30
When the equation (5) is calculated with m / sec and the transmission frequency difference Δf _T = 2500 Hz, Δf _R falls within the range of 2300 ≦ Δf _R ≦ 2700 (Hz).

Equation (5) indicates that the range of the difference Δf _R between the reception frequencies can be calculated from the difference Δf _T between the transmission frequencies, the speed V _m of the underwater vehicle, and the speed V _{t of the} target object.

When operating a plurality of hulls equipped with the active type acoustic homing device in the same sea area, the difference in transmission frequency between the underwater hulls is determined for each of the plurality of hulls (5).
By setting to be larger than the range shown by the equation, the difference Δf _R between the reception frequencies received by each vehicle is
If it is within the range of Expression (5), it is determined that the reflected wave is from the target object due to the ultrasonic wave transmitted by itself, and if it is out of the range of Expression (5), the ultrasonic wave transmitted by the vehicle other than itself is transmitted. Can be determined.

FIG. 3 is a signal example for explaining the operation of the first embodiment of the present invention. FIG. 3A shows the frequency spectrum of the transmission signal, and the difference between the two frequencies is Δf.
_T. FIG. 3B shows an example of a received signal, in which 31 is a reflected wave from a target object by an ultrasonic wave transmitted by itself, and 32 is an ultrasonic wave transmitted by a vehicle other than itself.
FIG. 3C shows the received signal 31 shown in FIG.
Represents the frequency spectrum output from the reception frequency difference calculation circuit 9 for each of the reception signals 32 in FIG.
FIG. 3E shows an output signal of the frequency difference comparison circuit 10,
The frequency difference Δf _R of the reception signal 31 in FIG.
The ON signal is within the range of the expression, and the frequency difference Δf _R of the received signal 32 is outside the range of the expression (5), and the OFF signal is output. FIG. 3F shows an output example of the signal processing circuit 11, and FIG.
(G) shows a target detection signal output from the gate circuit 12, and the output signal of the frequency difference comparison circuit 10 is O
Only in the case of the N signal, the target detection signal is output.

Further, as a modified example of the first embodiment,
It is also possible to extend the two transmitters to N and prepare a plurality of frequency differences. In this case, the frequency control circuit 3 controls the frequencies of the plurality of oscillators and simultaneously outputs a signal of the transmission frequency difference between the plurality of frequencies and sends out the signal to the frequency difference comparison circuit 10, and the frequency difference comparison circuit 10 Is compared with the signal calculated by the frequency difference calculation circuit 9 to determine the ON state.
It is configured to output a signal or an OFF signal.

Further, in the first embodiment, the gate circuit 12 is connected to the output of the signal processing circuit 11, and the gate circuit 12 is turned on / off by the output signal of the frequency difference comparing circuit 10. However, as a modified example, Alternatively, the signal processing circuit 11 itself may be controlled by the output signal of the frequency difference comparison circuit 10 to stop the processing.

Next, a second embodiment of the present invention will be described with reference to the drawings.

Referring to FIG. 4, according to a second embodiment of the present invention, a transmitter 1 and a transmitter frequency and a transmission timing are simultaneously controlled so that two signals are sequentially transmitted from the transmitter 1 and transmitted. A frequency control circuit 3 for outputting a signal of a frequency difference and a transmission timing, a transmitter 5 for transmitting an output signal of the transmitter 1 underwater, a receiver 6 for receiving underwater ultrasonic waves, A delay circuit 13 for delaying an output signal from the receiver 6, an addition circuit 14 for adding the output signal from the receiver 6 and the output signal of the delay circuit 13, and a frequency analysis of the output signal of the addition circuit 14. A frequency analysis circuit 7, a frequency detection circuit 8 for detecting two signal frequencies included in the signal from the result of the frequency analysis, a reception frequency difference calculation circuit 9 for calculating a frequency of a difference between the detected two frequencies, Said sending A frequency difference comparison circuit 10 for comparing a frequency difference signal with an output signal of the reception frequency difference calculation circuit 9 and outputting an ON signal when both frequency differences are equal; And a signal processing circuit 11 for processing an output signal from the CPU and outputting a target detection signal. An output signal of the signal processing circuit 11 is connected to an output of the signal processing circuit 11 by an ON signal of the frequency difference comparison circuit 10. And a gate circuit 12 through which the signal passes.

Next, the operation of the embodiment of the present invention will be described in detail with reference to FIG.

FIG. 5A shows an example of a transmission signal.
Is a first transmission signal, and 52 is a second transmission signal.
The difference between the frequencies of the transmission signals 51 and 52 is Δf _T , and the transmission time difference is T. FIG. 5B shows an example of the received signal. Reference numeral 53 denotes a first reception signal based on its own transmission signal, and its frequency is f _R1 . 54 is 2 based on its own transmission signal
This is the second received signal, and the frequency is f _R2 . Received signal 5
The frequency difference between 3 and 54 is Δf _R , and the reception time difference is Tf
It is. Reference numeral 55 denotes a first reception signal based on a transmission signal of another vehicle, and has a frequency of f _R1 ′. Reference numeral 56 denotes a second reception signal based on a transmission signal of another vehicle, and the frequency is f _R2 ′. The difference between the frequencies of the received signals 55 and 56 is Δf
_R ′ and the reception time difference is T. FIG. 5C shows an output signal of the delay circuit 13. Reference numeral 57 denotes a first reception signal based on the own transmission signal, and reference numeral 58 denotes a second reception signal based on the own transmission signal. Reference numeral 59 denotes a first received signal based on a transmission signal of another vehicle, and reference numeral 60 denotes a second received signal based on a transmission signal of another vehicle. FIG. 5D shows the addition circuit 14.
Is the output signal. The frequency of 61 is f _R1 , and the frequency of 62 is f _R1 and f _R2 . The frequency of 63 is f _R2 . Similarly, the frequency of 64 is f _{R1 ′} , and the frequency of 65 is f _R1 ′ and f _R2 ′. The frequency of 66 is f _R2 '. The frequency detection circuit 8 analyzes the frequency of the signal shown in FIG. 5D, calculates the difference between the two frequencies included in the reception signal 58 by the reception frequency difference calculation circuit 9, and outputs it to the frequency difference comparison circuit 10. The frequency difference comparison circuit 10 determines that the output signal Δf _{R of the} reception frequency difference calculation circuit 9 can be calculated from the transmission frequency difference Δf _T , the speed V _m of the underwater vehicle, and the speed V _t of the target object. An ON signal is output when there is, and an OFF signal is output when it is out of the range. 5D, the received signal 62 includes a signal of two frequencies and a difference between the two frequencies is within a specified range. 5E shows an output signal of the frequency difference comparison circuit 10, FIG. 5F shows an output example of the signal processing circuit 11, and FIG. 5G shows a gate output signal.
The gate output signal is output only when the output signal is ON.

Further, as a modified example of the second embodiment,
Two transmission signals transmitted from the transmitter 1 are extended to N,
A plurality of delay circuits can be prepared. In this case, the frequency control circuit 3 controls the frequencies of the plurality of transmitters and outputs a signal of a mutual frequency difference between the plurality of transmission frequencies and a transmission timing, and the frequency difference comparison circuit 10 It is configured to perform a comparison with an output signal and output an ON signal or an OFF signal in accordance with, for example, all or a large number of matches or mismatches.

Further, in the second embodiment, the gate circuit 12 is connected to the output of the signal processing circuit 11 and is turned on / off by the output signal of the frequency difference comparison circuit 10, but as a modified example, the frequency difference The signal processing circuit 11 may be controlled by the output signal of the comparison circuit 10 to stop the processing.

[0036]

According to the present invention, even in an environment where transmission signals are complicated or reverberation is likely to occur, such as when acoustic homing is performed by a plurality of hulls equipped with an active acoustic detection device in the same sea area. It is possible to reliably identify the arrival time of the target reflected wave signal and the reflected wave signal itself by the ultrasonic signal transmitted by itself. For this reason, it is possible to prevent erroneous operation of measurement and detection of the distance, direction, and the like of the target object without receiving interference or the like due to a sound wave signal transmitted from another navigation body, and to improve the accuracy of measurement and detection.

In this method, a transmission signal of a plurality of frequencies is transmitted from a transmission unit, and a frequency difference between two frequencies in the reception signal is calculated by analyzing the frequency of the reception signal from the reception unit. This is because, by comparing with a difference frequency of a plurality of corresponding frequencies, it is determined whether a reflected wave signal of the own transmission signal or another transmission signal or the like.
The influence of the Doppler shift due to the movement of the target object or the like can be minimized, and the own reflected wave signal can be detected without interference due to the identification of the frequency difference with respect to the transmission signal of another active acoustic detection device. Because.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of an underwater active acoustic detection device according to the present invention.

FIG. 2 is a layout diagram illustrating an example of a positional relationship between a self-propelled underwater vehicle, a target object, and another underwater vehicle.

FIG. 3 is a signal example for explaining the operation of FIG. 1;
(A) is a transmission signal frequency according to an embodiment of the present invention;
(B) is a received signal example, (c) is a received signal frequency reflected from a target by an ultrasonic signal transmitted by itself,
(D) is a reception signal frequency of a transmission signal of another vehicle, (e) is an output example of a frequency difference comparison circuit, (f) is an output example of a signal processing circuit, and (g) is an output example of a gate circuit. It is.

FIG. 4 is a system diagram showing another embodiment of the underwater active acoustic detection device of the present invention.

FIG. 5 is a signal example for explaining the operation of another embodiment of the present invention. (A) is a transmission signal example of another embodiment of the present invention, (b) is a reception signal example, (c) is a delay circuit output example, (d) is an addition circuit output example, (e) Is an output example of the frequency difference comparison circuit, (f) is an output example of the signal processing circuit,
(G) is an example of a gate circuit output.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Oscillator 2 Oscillator 3 Frequency control circuit 4 Addition circuit 5 Transmitter 6 Receiver 7 Frequency analysis circuit 8 Frequency detection circuit 9 Reception frequency difference calculation circuit 10 Frequency difference comparison circuit 11 Signal processing circuit 12 Gate circuit 13 Delay circuit 14 Addition circuit 21 Own underwater vehicle 22 Target object 23 Other underwater vehicle 31 Reception waveform of reflected wave from target object by ultrasonic wave transmitted by itself 32 Ultrasonic wave transmitted by vehicle other than own Received waveform 51 First transmitted signal 52 Second transmitted signal 53 First received signal due to own transmitted signal 54 Second received signal due to own transmitted signal 55 First received due to transmitted signal of other marine vehicle Signal 56 Second received signal based on transmission signal of another vehicle 57-60 Received signal 61-66 Adder circuit output signal

────────────────────────────────────────────────── ─── Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01S 3/80-3/86 G01S 5/18-5/30 G01S 7/52-7/64 G01S 15 / 00-15/96

Claims (5)

(57) [Claims] 1. An underwater active acoustic detection device that has a transmitting unit that transmits a sound wave and a receiving unit that receives a reflected wave and compares a transmitted signal with a received signal to detect a target, Transmit transmission signals of different frequencies,
The receiving unit calculates a difference signal of two different frequencies among signals of a plurality of frequencies included in the reception signal, and compares the difference signal with a difference signal of a corresponding frequency of the transmission signal of the transmission unit to obtain a target reflected wave by the transmission signal. An underwater active acoustic detection device, which detects the arrival time of a vehicle. 2. The underwater active acoustic detection device according to claim 1, wherein the transmitting unit transmits a plurality of frequency signals simultaneously. 3. The underwater active acoustic detection device according to claim 1, wherein the transmitting unit sequentially transmits a plurality of frequency signals. 4. The underwater active acoustic detection device according to claim 1, wherein the receiving unit extracts a reception signal based on a detection result of a target reflected wave arrival time and outputs a target reflected wave. . 5. The underwater active acoustic detection device according to claim 1, which is used for acoustic homing of an underwater vehicle.