JPH04315079A - Active sonar device for underwater cruiser - Google Patents

Abstract

PURPOSE:To enable exact searching of a target with an active sonar device for an underwater cruiser without being disturbed by the vibration noise generated from an engine. CONSTITUTION:By detecting the revolution speed of an engine 3 with a revolution detector 5, the frequency of the vibration noise and the velocity of the underwater cruiser 1 are calculated with a frequency control circuit 6 using the revolution speed of the engine 3. Based on the calculated data, a transmission frequency to match the vibration noise frequency to the echo frequency from an underwater scatterer 10 is obtained and a transmission circuit 8 transmits a sound wave A1 of this transmission frequency from a transmitter/ accepter 7 into water. The transmitter/accepter 7 receives the echo sound A2 from a sonar target 2. In a band block filter 12 to block the frequency of the echo from the frequency control circuit 6, the echo signal S4R and vibration noise component S4N are eliminated from the received signal S4 to extract echo signal S4E. By comparing the echo signal S4E with a threshold value in a target detection circuit 13, a target detection is judged.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active sonar device for underwater vehicles for detecting targets using sound waves.

0002

2. Description of the Related Art FIG. 3 shows a general configuration of a conventional active sonar device for underwater vehicles. In this figure, a transmission signal s1 output from a transmission circuit 28 of an active sonar device provided in an underwater vehicle 21 is sent to a transducer 27 via a switching circuit 29, and from this transducer 27 to a sonar device. A transmission sound a1 for detecting the target 22 is sent underwater. This transmitted sound a1 hits the sonar target 22 and bounces back, and the echo sound a2 from the target 22 is received by the transducer 27 along with the reverberant sound a3 from the underwater scatterer 30. The received output of the transducer 27 is sent to the amplifier 31 through the switching circuit 29, and the amplified received signal s4 is supplied to the band rejection filter 32.

Here, the frequency of the reverberant sound a3 (reverberation frequency) fRV, the frequency of the echo sound a2 (echo frequency) fE
is given by the following equation, where fTX is the frequency of the transmitted sound a1 (transmission frequency), V0 is the cruising speed of the underwater vehicle 10, VT is the cruising speed of the sonar target 22, and C is the underwater sound speed. fRV=fTX{1+2V0/(C-V0
)}...
(1) fE = fTX[1-2(VT -V0
)/{C+(VT −V0)}] …(2)

0
[004] The rotation speed detector 25 detects the rotation speed of the propulsion engine 23 that drives the propulsion device 24 of the underwater vehicle 21, and the frequency control circuit 26 detects the rotation speed signal sent from the rotation speed detector 25. Speed V0 of the underwater vehicle 21 based on s1
is calculated, and the reverberation frequency f is calculated using equation (1).
RV is required. The obtained reverberation frequency signal s5 is sent to the band rejection filter 32. In this band rejection filter 32, the reverberation frequency fRV from the frequency control circuit 26
is the rejection frequency, the reverberant signal s4R is obtained from the received signal s4.
Signal processing is performed to remove the . 4(a) shows the frequency spectrum of the received signal s4, and FIG. 4(b) shows the frequency spectrum of the received processed signal s6 after the reverberation signal s4R is removed by the band rejection filter 32.

[0005] In the target detection circuit 33 to which the received processed signal s6 is sent, the received processed signal s6 is compared with a certain threshold L, and the echo signal s4E exceeding this threshold L is shown in FIG. 4(c). It is determined that a target is detected,
A target detection signal s7 is output from the output terminal 34.

In the example shown in FIG. 3, the reverberation frequency fRV is calculated by the frequency control circuit 26, but as another method, the rejection frequency of the band rejection filter is fixed, and the transmission frequency fTX is changed to calculate the reverberation frequency fRV from the transmission circuit. We may also send
The same reverberation suppression effect as described above can be obtained.

[0007]

[Problems to be Solved by the Invention] By the way, when the underwater vehicle 21 navigates underwater by rotating the propeller 24 by the propulsion engine 23, the drive system consisting of the motor or engine in the propulsion engine, gears, etc. Mechanical vibration is generated according to the rotation speed, and this vibration noise N (frequency is fN) is transmitted through the outer shell and structures of the vehicle and is received by the transducer 27 like a sound wave from underwater. It will be done. Since this vibration noise component s4N is not removed by the band rejection filter 32, it may be processed as a normal echo sound as shown in FIG. 4, and it may be determined that a target has been detected.

[0008] Therefore, in order to prevent this false detection, it is conceivable to add a band rejection filter that blocks the passage of the vibration noise component s4N, but depending on the relative speed of the underwater vehicle 21 and the sonar target 22, the vibration noise frequency fN
may become equal to the echo frequency fE, resulting in a problem that normal target detection is prevented.

The present invention was proposed in order to solve the problems of the conventional technology, and provides an underwater navigation system that can accurately detect targets without being affected by vibration noise generated by the propulsion engine. The purpose is to provide an active sonar device for traveling objects.

0010

[Means for Solving the Problems] To achieve this object, an active sonar device according to the present invention includes a rotation speed detector that detects the rotation speed of a propulsion engine mounted on an underwater vehicle, and a rotation speed detector that detects the rotation speed of a propulsion engine mounted on an underwater vehicle. A frequency that calculates the vibration noise frequency of the propulsion engine and the speed of the underwater vehicle from the rotation speed detected by A control circuit, a transmission circuit that transmits sound waves from a transmitter at a transmission frequency calculated by this frequency control circuit, and a reception circuit that receives echo sounds from underwater with a receiver and sends the received signal to a band rejection filter. and a reception circuit in which the reverberation frequency is set as a blocking frequency, the blocking frequency can be changed according to a reverberant frequency signal output from the frequency control circuit, and the echo signal is mixed with a reverberant signal due to an underwater scatterer and the vibration noise frequency component. A band-elimination filter extracts an echo signal by suppressing the reverberation signal and vibration noise frequency components from the signal, and the presence or absence of a sonar target is detected by comparing the echo signal output from the band-elimination filter with a threshold value. and a target detection circuit.

[0011]

[Operation] According to the above-described configuration, sound waves can be emitted into the water at a transmission frequency such that the mechanical vibration noise frequency of the propulsion engine and the reverberation frequency of the underwater scatterer match, so that the band rejection filter Reverberation components and vibration noise components can be suppressed simultaneously, and only echo signals can be extracted.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the active sonar device for underwater vehicles according to the present invention will be described in detail below with reference to the drawings. The block diagram of FIG. 1 shows one embodiment of this active sonar device. In this figure, an underwater vehicle 1 detecting a sonar target 2 is navigating underwater with a propulsion device 4 driven by a propulsion engine 3. At this time, the rotation speed detector 5 detects the rotation speed of the propulsion device 4 and sends a rotation speed signal S1 to the frequency control circuit 6. From the drive system consisting of the motor or engine of the propulsion engine 3, gears, etc.
Vibration noise corresponding to the rotational speed of the propulsion engine 3 is generated, and this noise N is transmitted through the outer shell and structures of the underwater vehicle 1 and reaches the transducer 7.

The frequency control circuit 6 contains data of the speed V0 of the underwater vehicle corresponding to the rotational speed of the engine, which is known in advance, and vibration noise frequency fN corresponding to the rotational speed.
The rotation speed signal S from the detector 5 is stored.
When 1 is input, the underwater vehicle speed V0 and the vibration noise frequency fN are calculated in the frequency control circuit 6. Once the underwater vehicle speed V0 and the vibration noise frequency fN are determined, the reverberation frequency fRV and the transmission frequency fT are determined.
X is calculated by the following formula. fRV=fN

...(3)
fTX=fN/{1+2V0/(C-V0)
} (4) The determined transmission frequency signal S2 is input to the transmission circuit 8, and from this transmission circuit 8, the transmission signal S3 of frequency fTX is sent to the transducer 7 via the switching circuit 9. As a result, the transducer 7 transmits the transmission sound A1 of the frequency fTX to the underwater sonar target 2.

[0014] Echo sound A2 bounced off sonar target 2
The reverberant sound A3 caused by the underwater scatterer 10 is transmitted to the transducer 7.
The signal is received by the receiver, and is sent to the amplifier 11 through the switching circuit 9 together with the mixed vibration noise component, where it is amplified. The received signal S4 output from the amplifier 11 is supplied to a band rejection filter 12. This band rejection filter 1
2 is supplied with a reverberant frequency signal S5 from the frequency control circuit 6. Since the reverberant frequency fRV is controlled in the frequency control circuit 6 to match the vibration noise frequency fN, the rejection frequency in the band rejection filter 12 is has a reverberation frequency fRV equal to the vibration noise frequency fN. Therefore, by passing the received signal S4 through this band rejection filter 12, both the reverberation signal S4R and the vibration noise component S4N are suppressed.

Note that the rejection frequency of the band rejection filter is changed depending on the input reverberation frequency fRV. FIG. 2(a) shows the frequency spectrum of the received signal S4, which includes an echo signal S4E of frequency fE, a reverberation signal S4R of frequency fRV, and a vibration noise component S4N of frequency fN (where fRV=fN), and FIG. ) indicates the frequency spectrum of the received processed signal S6 after passing through the filter.

The received processed signal S6 outputted from the band rejection filter 12 is sent to the target detection circuit 13, where it is compared with a certain threshold value L. If the echo signal S4E exceeds this threshold L, then FIG.
As shown in c), it is determined that the target is detected, and the target detection signal (determination output) S7 is taken out from the output terminal 14.

[0017]

As explained above, according to the present invention, the transmission frequency is adjusted so that the frequency of mechanical vibration noise generated according to the rotation speed of the propulsion engine matches the frequency of reverberation caused by underwater scatterers. Since it can be controlled, a band rejection filter that extracts an echo signal from a received signal can simultaneously suppress reverberation components and vibration noise components. Therefore, the target can be accurately detected without being affected by the vibration noise generated by the propulsion engine as in the past.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an active sonar device for an underwater vehicle according to the present invention.

FIG. 2 is a waveform diagram for explaining processing of received signals in the active sonar device of FIG. 1;

FIG. 3 is a block diagram showing an example of a conventional active sonar device for an underwater vehicle.

FIG. 4 is a waveform diagram for explaining processing of received signals in a conventional active sonar device.

[Explanation of symbols]

1 Underwater vehicle 2 Sonar target 3 Promotion organization 4. Propulsion device 5 Rotation speed detector 6 Frequency control circuit 7 Transducer/receiver 8 Transmission circuit 9 Switching circuit 10　Underwater scatterer 11 Amplifier 12 Bandpass filter 13 Target detection circuit 14 Output terminal A1 Transmission sound A2 Echo sound A3 Reverberation sound N Mechanical vibration noise S1 Rotation speed signal S2 Transmission frequency signal S3 Transmission signal S4 Received signal S4E Echo signal S4R Reverberation signal S4N Vibration noise component S5 Reverberation frequency signal S6 Reception processing signal S7 Target detection signal

Claims (1)

[Claims] [Claim 1] Emitting sound waves into the water from an underwater vehicle,
In an active sonar device for an underwater vehicle that detects a sonar target by detecting the echo sound from the sonar target, there is a rotation speed detector that detects the rotation speed of a propulsion engine mounted on the underwater vehicle, and this rotation speed detection. The vibration noise frequency of the propulsion engine and the speed of the underwater vehicle are calculated from the rotation speed detected by the device, and based on this calculation data, the transmission frequency is calculated so that the vibration noise frequency and the reverberation frequency match. A frequency control circuit, a transmission circuit that transmits sound waves from a transmitter at a transmission frequency calculated by this frequency control circuit, and a receiver that receives echo sounds from underwater and sends the received signal to a band rejection filter. , the reverberation frequency is set as a blocking frequency, the blocking frequency can be changed according to the reverberant frequency signal output from the frequency control circuit, and the received signal is mixed with the reverberant signal due to the underwater scatterer and the vibration noise frequency component in the echo signal. , a band rejection filter that suppresses this reverberation signal and vibration noise frequency components to extract an echo signal, and a target detection circuit that compares the echo signal output from this band rejection filter with a threshold value to detect the presence or absence of a sonar target. An active sonar device for an underwater vehicle, comprising: