JP7533973B2 - Imaging sonar device, method and program - Google Patents

Description

The present invention relates to an imaging sonar device, method, and program.

The imaging sonar is configured so that a line array-configured transmitting array is made up of multiple transmitters (acoustic elements) that transmit sound underwater and are arranged in a straight line, and a line array-configured receiving array is made up of multiple receivers that receive sound reflected from underwater targets and are arranged orthogonally to the transmitting array to form a cross (see, for example, Patent Documents 1 and 2).

An acoustic signal is sent out while changing the direction of an acoustic beam (fan beam) that spreads out like a wide fan from top to bottom, for example, and the reflected sound from the target is received by many wide fan beams that are shifted in angle in the horizontal direction. The vertical direction is divided, for example, based on differences in frequency, and the horizontal direction is divided by the angle of the receiving beam, making it possible to obtain highly accurate images. For information on cross-fan beam type imaging sonar, see Patent Documents 1 and 2, etc. Note that sonar that generates two-dimensional/three-dimensional images using the cross-fan beam method is called cross-fan beam type imaging sonar.

The following describes related technology that has a cross-fan beam imaging sonar at the front of an underwater vehicle. As shown in FIG. 1, the cross-fan beam imaging sonar has a transmitting array 3 in which a number of acoustic elements (transmitters) that convert electrical signals into acoustic signals are arranged in a row (vertical direction: Y direction), and a receiving array 4 in which a number of acoustic elements (receivers) that convert acoustic signals into electrical signals are arranged in a row (horizontal direction: X direction), and the directivity of the pixel signal where the vertical transmitting beam directivity and the horizontal receiving beam directivity cross is obtained. This has the advantage that the pixel information of the imaging sonar can be obtained with a small amount of calculation. Note that FIG. 1 is a schematic plan view of the XY plane seen from the Z-axis direction, and the circle surrounding the cross-shaped transmitting array 3 and receiving array 4 may be a schematic representation of the circular outer edge or the inner area of a circle concentric with the outer edge of the cross section (cross section of the front) perpendicular to the longitudinal direction (travel direction) of the underwater vehicle.

Figure 2 shows a transmission beam of the cross fan beam system. As shown in Figure 2, an image sonar using the cross fan beam system transmits multiple transmission beams 5 with directionality in the vertical direction (Y direction) from the transmission array 3 (Figure 1) in an underwater vehicle 1, for m pixels in the vertical direction. Each of the m transmission beams 5 from the transmission array 3 is phase shifted to move in directions θ1 to θm, and each beam is transmitted with a different frequency of sound waves (for example, the beam in direction θ1 is transmitted at frequency F1, and the beam in direction θm is transmitted at frequency Fm).

Figure 3 shows a receiving beam using the cross fan beam method. In the underwater vehicle 1, the receiving array 4 (Figure 1) is arranged perpendicular to the transmitting array 3, and receives the reflected sound of the sound waves transmitted from the transmitting array 3, generating multiple receiving beams 6 with directionality in the horizontal direction (X direction). In Figure 3, there are n receiving beams 6 at angles φ1 to φn in the horizontal direction (X direction).

Figure 4 shows an example of a two-dimensional image obtained using the cross fan beam method. It is possible to capture only the reflected waves from the crossing point between m transmitting beams 5 (Figure 2) in the vertical direction (θ1 to θm) and n receiving beams 6 (Figure 3) in the horizontal direction (φ1 to φn). This allows for high sonar resolution and makes it possible to detect the two-dimensional shape and dimensions of underwater objects.

Furthermore, by performing horizontal directional synthesis processing (performing phasing processing on the received signal to form a directional beam) using the receiving beam at short intervals, the two-dimensional image data is converted into three-dimensional image data in the distance direction, making it possible to detect the three-dimensional shape and dimensions of underwater objects.

However, because cross-fan beam imaging sonar uses a linear array, it is easily affected by the attitude of the underwater vehicle 1.

When a cross-fan beam imaging sonar is installed on an underwater vehicle 1 (which is smaller than a ship) whose attitude is unstable, it is difficult to obtain highly accurate images. In particular, it is easily affected by changes in attitude that occur when the underwater vehicle 1 travels through the water at high speed. The underwater vehicle 1 is generally elongated in the fore-and-aft direction, and in most cases has a circular cross section, and does not have a motion suppression mechanism such as a fin stabilizer or bilge keel that suppresses the rolling of the ship while it is sailing. For this reason, when the underwater vehicle 1 travels at high speed, it can be difficult to stabilize the attitude, especially the roll angle.

Furthermore, if the front of the underwater vehicle 1 is equipped with a transmitting array 3 and a receiving array 4 in an orthogonal line array configuration as a cross-fan beam type imaging sonar, it is difficult to equip the front of the underwater vehicle 1 with an array for another sonar. The example in Figure 1 shows an example in which the front of the underwater vehicle 1 is equipped with a transmitting array 3 and a receiving array 4 of a cross-fan beam type imaging sonar, but because the transmitting array 3 and the receiving array 4 are linear and orthogonal, there tends to be less space for equipping an array for another sonar.

JP 2004-12237 A JP 2006-64524 A

Below, we will explain the problem that the underwater vehicle 1 is easily affected by changes in attitude that occur when it travels through the water at high speed, which may result in inaccurate measurements of the shape and dimensions of the underwater object.

Figures 5 (A) to (C) are diagrams illustrating the case where a cross-fan beam type imaging sonar transmits a transmission beam 5 when the image sonar is in a position with a roll angle of +10 degrees. As shown in Figure 5 (A), the transmission array 3 is tilted clockwise at a roll angle of +10 degrees. Figure 5 (B) is a diagram illustrating the relationship between the transmission beam 5 transmitted when the underwater vehicle 1 is rolling and the underwater object 2. Figure 5 (C) is a schematic diagram showing an image (image displayed on a display device) obtained when the underwater vehicle 1 is rolling. The underwater object 2, which is originally horizontal, is expected to be detected tilted at about +10 degrees, which corresponds to the roll angle, as shown in Figure 6.

Figures 7 (A) to (C) are diagrams illustrating the case where a cross-fan beam type imaging sonar transmits a transmission beam 5 when the imaging sonar is in a position with a roll angle of -10[deg]. As shown in Figure 7 (A), the transmission array 3 is tilted clockwise at a roll angle of -10[deg]. Figure 7 (B) is a diagram illustrating the relationship between the receiving beam 6 transmitted when the underwater vehicle 1 is rolling and the underwater object 2. Figure 7 (C) is a schematic diagram illustrating an image (image displayed on a display device) obtained when the underwater vehicle 1 is rolling. The underwater object 2, which is originally horizontal, is expected to be detected tilted at about -10[deg], which corresponds to the roll angle, as shown in Figure 8.

When the transmitting beam 5 is tilted at a roll angle of +10[deg] as shown in Figures 5 and 6, and when the receiving beam 6 is tilted at a roll angle of -10[deg] as shown in Figures 7 and 8, the shape of the underwater object 2 detected will be as shown in Figure 9.

As a result of the inclination of the transmitting beam 5 and receiving beam 6, the approximate two-dimensional shape and dimensions of the underwater object 2 obtained by the cross-fan beam imaging sonar are as shown in Figure 10. Figure 10 shows an example of the effect that the roll angle of the underwater vehicle has on the two-dimensional image obtained by the imaging sonar in the cross-fan beam imaging sonar. The underwater object 2 shown in Figure 3 will end up appearing to have an irregular shape (for example, the shape of a sweet potato) as shown in Figure 10.

One example of the use of cross-fan beam imaging sonar is a classification sonar that detects the shape and dimensions of underwater objects and determines whether the underwater object is real or a fake (decoy). However, it is difficult to correctly perform classification from an image such as that shown in Figure 10.

Note that for the cross-fan beam imaging sonar, simulations such as those shown in Figures 5 to 10 were performed when the roll angle of the underwater vehicle 1 changed. However, in an actual underwater vehicle 1, the yaw angle and pitch angle may change while the vehicle is sailing, and the shape and dimensions of the detected underwater object may be even more inaccurate than in the image shown in Figure 10.

As mentioned above, the underwater vehicle 1 is easily affected by changes in attitude that occur when it travels through the water at high speed, which may result in inaccurate measurements of the shape and dimensions of the underwater object.

Furthermore, in the underwater vehicle 1, in addition to the cross-fan beam imaging sonar, a search sonar is also normally used to detect other underwater vehicles. For this reason, it is necessary to secure space in the front of the underwater vehicle 1 to place the search sonar array.

However, if the underwater vehicle 1 is equipped with a transmitting array 3 and a receiving array 4 for a cross-fan beam sonar as shown in Figure 1 at the front, it is difficult to equip it with a search sonar array.

The present invention was devised in consideration of the above problems, and aims to provide an imaging sonar device, method, and program that can suppress the effects of changes in the attitude of the underwater vehicle and ensure space for placing a search sonar array at the front of the underwater vehicle.

According to the present invention, an imaging sonar device is provided with a wave transmitting/receiving array arranged two-dimensionally in a plane perpendicular to the longitudinal direction of an underwater vehicle at the front of the underwater vehicle, the wave transmitting/receiving array being configured with a plurality of transmitters and a plurality of receivers arranged in a hollow ring shape, with the acoustic surfaces of the plurality of transmitters and the plurality of receivers all located on one side of the hollow ring. The sonar device further includes an attitude sensor that detects the attitude of the underwater vehicle, and a directivity synthesis means that performs correction calculations for the directivity synthesis process due to the inclination of the wave transmitting/receiving array based on the detection results of the attitude sensor.

According to the present invention, an imaging sonar method uses a two-dimensionally arranged wave transmitting/receiving array at the front of an underwater vehicle on a plane perpendicular to the longitudinal direction of the underwater vehicle, the wave transmitting/receiving array is configured by arranging multiple transmitters and multiple receivers in a hollow ring shape, and each acoustic surface of the multiple transmitters and multiple receivers is located on one side of the hollow ring, and correction calculations are performed for directional synthesis processing due to the tilt of the wave transmitting/receiving array based on the detection result of the attitude of the underwater vehicle.

According to the present invention, an image sonar device is provided at a front portion of an underwater vehicle, the image sonar device being configured with a wave transmitting/receiving array that is two-dimensionally arranged on a plane perpendicular to the longitudinal direction of the underwater vehicle, the wave transmitting/receiving array being configured with a plurality of wave transmitters and a plurality of wave receivers that are arranged in a hollow ring shape, and each acoustic surface of the plurality of wave transmitters and the plurality of wave receivers is located on one side of the hollow ring.
A program is provided for executing a process of performing a correction calculation for a directivity synthesis process due to the inclination of the wave transmitting/receiving array based on the detection result of the attitude of the underwater vehicle. Furthermore, according to the present invention, a computer-readable recording medium (for example, a semiconductor storage such as a RAM (Random Access Memory), a ROM (Read Only Memory), or an EEPROM (Electrically Erasable and Programmable ROM), a HDD (Hard Disk Drive), a CD (Compact Disc), or a DVD (Digital Versatile Disc)) storing the above program is provided.

The present invention makes it possible to suppress the effects of changes in the attitude of the underwater vehicle, and to secure space for placing a search sonar array at the front of the underwater vehicle.

FIG. 1 is a diagram for explaining a cross-fan beam type wave transmitting/receiving array according to a related art. FIG. 1 is a diagram illustrating a transmission beam according to a related art technique. FIG. 1 is a diagram illustrating a receiving beam according to a related art technique. FIG. 1 is a diagram illustrating an example of a two-dimensional image obtained by a cross fan beam method according to the related art. 1A to 1C are diagrams illustrating an example of a state in which a transmission beam of a cross fan beam type of related art is affected by the roll angle of an underwater vehicle. FIG. 10 is a schematic diagram showing an example of a state in which a transmission beam of a cross fan beam system according to related art is affected by the roll angle of an underwater vehicle and rotates. 1A to 1C are diagrams illustrating examples of states in which a receiving beam of a cross-fan beam system of related art is affected by the roll angle of an underwater vehicle. FIG. 10 is a schematic diagram showing an example of a state in which a receiving beam of a cross fan beam type of related art is affected by the roll angle of an underwater vehicle and rotates. 1 is a schematic diagram showing an example of a state in which the transmitting beam and the receiving beam of a cross fan beam system of related art are affected by the roll angle of an underwater vehicle, causing the transmitting beam and the receiving beam to rotate. FIG. 1 is a schematic diagram showing an example of the effect of the roll angle of an underwater vehicle on a two-dimensional image obtained by an imaging sonar of a cross fan beam type according to related art; 1A is a diagram showing a ring-shaped wave transmitting/receiving array according to an embodiment, and FIG. 1B is a diagram showing a roll angle, a pitch angle, and a yaw angle related to the attitude of an underwater vehicle. 1A and 1B are diagrams showing examples of the arrangement of transducers in a ring-shaped wave transmitting and receiving array for an imaging sonar. 1A is a schematic diagram showing a transmitting and receiving array, and FIG. 1B is a schematic diagram showing a transmitting beam by an imaging sonar device. 1A is a schematic diagram showing a transmitting and receiving array, and FIG. 1B is a schematic diagram showing a receiving beam by an imaging sonar device. 1A and 1B are schematic diagrams showing a transmitting transducer, and FIG. 1C is a schematic diagram showing a transmitting system of an imaging sonar device. 1A and 1B are schematic diagrams showing a receiving transducer, and FIG. 1C is a schematic diagram showing a receiving system of an imaging sonar device. 1A and 1B are diagrams illustrating correction of a roll angle in the image sonar device of the embodiment. 4A to 4C are diagrams illustrating pitch angle correction in the image sonar device of the embodiment. 4A to 4C are diagrams illustrating yaw angle correction in the image sonar device of the embodiment. 4A to 4C are diagrams illustrating correction of the directivity of a receiving beam depending on the attitude of an underwater vehicle in the image sonar device of the embodiment. 4A to 4C are diagrams illustrating correction of the wave receiving directivity of the image sonar in the image sonar device of the embodiment. FIG. 2 is a diagram illustrating a computer constituting the image sonar device according to the embodiment.

This embodiment will be described. Figure 11 (A) is a schematic plan view of the wave transmission and reception array of this embodiment. The wave transmission and reception array 7 for the imaging sonar is arranged two-dimensionally on a plane (X-Y plane) perpendicular to the longitudinal direction (Z-axis direction) of the underwater vehicle 1 at the front of the underwater vehicle 1. The wave transmission and reception array 7 for the imaging sonar has multiple wave transmitting transducers (transmitters) 14 and multiple wave receiving transducers (receivers) 15 arranged in a hollow ring shape.

The acoustic surfaces (surfaces of the acoustic transducers that transmit/receive acoustic signals) of the multiple transmitting transducers 14 and the multiple receiving transducers 15 are arranged facing one side of the hollow ring (same direction (parallel) as the surface of the ring). In other words, the multiple transmitting transducers 14 and the multiple receiving transducers 15 are arranged on the same circumference within an area surrounded by two concentric circles, and transmit signals to the front of the underwater vehicle 1 and receive signals from the front. Figure 11(B) is a diagram showing the roll angle, pitch angle, and yaw angle related to the attitude of the underwater vehicle. In Figure 11(B), 8, 9, 10, 11, 12, and 13 respectively represent the roll angle and roll axis of the underwater vehicle 1, and the pitch angle, pitch axis, yaw angle, and yaw axis of the underwater vehicle 1. Note that when the roll axis, pitch axis, and yaw axis are compared to Figure 11(A), they become the Z axis, X axis, and Y axis.

According to the embodiment, multiple wave-transmitting transducers 14 and multiple wave-receiving transducers 15 are arranged on the same ring, which makes it easier to correct changes in the roll angle 8 of the underwater vehicle 1.

According to the embodiment, by equipping the front of the underwater vehicle 1 with a hollow ring-structured wave transmission/reception array 7 for an imaging sonar, an area in which a search array can be installed, which is a space for arranging a search sonar array, for example, is secured in the hollow portion 71 of the hollow ring-structured wave transmission/reception array 7.

Figure 12 (A) is a schematic plan view showing an example of the configuration of the wave transmission and reception array 7. As shown in Figure 12 (A), in the wave transmission and reception array 7, the first to sixth wave transmission transducers 14-1 to 14-6 are arranged at 60 degree intervals on the same circumference. Furthermore, five wave receiving transducers 15 are arranged adjacent to each other between two adjacent wave transmission transducers 14. That is, 30 wave receiving transducers from the first wave receiving transducer 15-1 to the 30th wave receiving transducer 15-30 are arranged adjacent to each other in groups of five, and a total of 36 wave transmission transducers 14 and wave receiving transducers 15 are arranged at equal intervals (10 [deg]). However, it goes without saying that the number of wave transmission transducers 14 and wave receiving transducers 15 is not limited to the above.

Figure 12 (B) is a side end view of the housing of the wave transmitting and receiving array 7 in Figure 12 (A) as viewed from the X-axis direction. The acoustic surfaces of the transmitting transducer 14 and the receiving transducer 15 are on one side of the circle of the ring structure (the open end side on the left side of the figure). The transmitting transducer 14 and the receiving transducer 15 are fixed on the side opposite the acoustic surface, and the power lines and signal wiring of the transmitting transducer 14 and the receiving transducer 15 may be connected to a substrate (not shown) or the like.

Figure 13 (A) is a diagram showing the arrangement of the transmitting transducers 14 of the transmitting/receiving array 7. Figure 13 (B) is a diagram explaining the transmitting beam 5. By simultaneously transmitting acoustic signals from the first to sixth transmitting transducers 14-1 to 14-6, a transmitting beam 5 (a cone-shaped (unfolded umbrella-shaped) beam) as shown diagrammatically in Figure 13 (B) is formed.

As shown in FIG. 13(B), the transmission beam 5 from the transmission/reception array 7 is a single, wide directional beam, for example 45 degrees, forward (Z-axis direction), eliminating the effects of changes in the roll angle 8 of the underwater vehicle 1.

Fig. 14A is a diagram showing the arrangement of the receiving transducers 15 of the transmitting and receiving array 7. Fig. 14B is a diagram explaining the receiving beam 6 formed from the signal received by the receiving transducer 15.
Sound reflected from a target underwater object 2 is received by a number of narrow directional beams, for example, shifted at angles in the horizontal and vertical directions.

For the imaging sonar receiving beam, a three-dimensional directional beam is generated for each pixel of the imaging sonar, and processing is performed to correct changes in the roll angle, yaw angle, and pitch angle, which are the attitude of the underwater vehicle 1.

According to an embodiment, the transmitting and receiving array mounted on the front of the underwater vehicle employs a ring-structured array that facilitates correction of the effects of changes in the attitude of the underwater vehicle, which is a challenge with the cross-fan beam method, and enables accurate exploration of the dimensions and shape of underwater objects located ahead, even if the attitude of the underwater vehicle 1 changes.

Next, we will explain the configuration and operation of the imaging sonar device.

(Transmits underwater sound waves using a transmission beam)
Fig. 15(C) is a diagram showing a schematic configuration of an image sonar device. Fig. 15(A) and (B) are diagrams showing the first and sixth wave transmitting transducers (wave transmitters) 14-1 and 14-6 in the wave transmitting and receiving array 7. In Fig. 15, the second to fifth wave transmitting transducers (wave transmitters) 14-2 to 14-5 are not shown for convenience of drawing. In Fig. 15(C), the circuit group corresponding to the second to fifth wave transmitting transducers (wave transmitters) 14-2 to 14-5 are omitted for convenience of drawing.

The transmission waveform data output unit 25 generates and outputs the waveform data (digital waveform data) to be transmitted. The transmission beams 5 transmitted from the first to sixth transmission transducers 14-1 to 14-6 are wide beams that cover the detection range of the imaging sonar device. As the transmission signal, for example, a single-frequency transmission by a Pulsed Continuous Wave (PCW) in which the carrier signal of the transmission pulse has a constant frequency is used. The acoustic signal waveforms transmitted from the first to sixth transmission transducers 14-1 to 14-6 are the same, and do not change for each transmission transducer.

When the attitude of the underwater vehicle 1 is stable, the transmission waveform data output unit 25 outputs the transmission waveform data to the first through sixth digital to analog converters (DACs) 24-1 through 24-6 corresponding to the first through sixth wave transmitting transducers 14-1 through 14-6.

The first through sixth DA converters 24-1 through 24-6 convert the input transmission waveform data into analog signals of a transmission beam, and the analog signals are passed through the first through sixth band pass filters (BPFs).
The outputs are then sent to the BPFs 23-1 to 23-6.

The first through sixth band pass filters (BPFs) 23-1 through 23-6 remove high-frequency and low-frequency components that are not to be transmitted from the input analog signal, and output the signals to the first through sixth power amplifiers 22-1 through 23-6, respectively.

The first through sixth power amplifiers 22-1 through 22-6 power amplify the input analog signals and output them to the first through sixth wave transmitting transducers 14-1 through 14-6, respectively.

As shown in FIG. 13B, the first to sixth transmitting transducers 14-1 to 14-6 transmit underwater sound waves of a single transmitting beam 5 that covers the detection range of the imaging sonar device only once.

(Receives underwater sound waves using a receiving beam)
Fig. 16C is a diagram showing a schematic configuration of a wave receiving system of an image sonar device. Figs. 16A and 16B are diagrams showing the first and 30th wave receiving transducers (receivers) 15-1 and 15-30 in the wave transmitting and receiving array 7. In Figs. 16A and 16B, the first to sixth wave transmitting transducers 14-1 to 14-6 are not shown for convenience of drawing. In Fig. 16C, the second to 29th wave receiving transducers (receivers) 15-2 to 15-29 and corresponding circuit groups are omitted for convenience of drawing.

After transmitting the transmission beam 5, the receiving system of the imaging sonar device starts the receiving process. The first through thirtieth receiving transducers 15-1 through 15-30 convert the acoustic signal (sound pressure) into an electrical signal (voltage) and output it to the first through thirtieth preamplifiers 26-1 through 26-30, respectively.

The first through thirtieth preamplifiers 26-1 through 26-30 amplify the input weak electrical signals (voltages) and output them to the first through thirtieth bandpass filters (BPFs) 27-1 through 27-30, respectively.

The first through thirtieth band pass filters (BPFs) 27-1 through 27-30 remove high-frequency and low-frequency components that are not treated as received signals from the input analog signal, and output the signal to the first through thirtieth analog-to-digital converters (ADCs) 28-1 through 28-30.

The first through 30th AD converters 28-1 through 28-30 convert the input analog signals into digital waveform data and output them to the first through 30th FFTs (Fast Fourier Transforms) 29-1 through 29-30, respectively.

The first to 30th FFTs 29-1 to 20-30 convert the input waveform data into level data for each frequency component (the square root of the sum of the squares of the real and imaginary parts of the frequency components: also called the amplitude spectrum or signal intensity) and output it to the directivity synthesis processing unit 31.

The attitude sensor 30 is, for example, a gyroscope, and detects the attitude of the underwater vehicle 1 and outputs the detected attitude data, including the roll angle 8, pitch angle 10, and yaw angle 12, to the directivity synthesis processing unit 31 at regular intervals.

The directivity synthesis processing unit 31 corrects the influence of the roll angle, pitch angle, and tilt of the wave transmitting/receiving array 7 due to the roll angle of the underwater vehicle 1 input from the attitude sensor 30 for the level data for each frequency component of each wave receiving transducer input from the first to 30th FFTs 29-1 to 29-30, which corresponds to the frequency of the wave transmitting beam generated by the transmission waveform data output unit 25, and at the same time, performs processing to synthesize the directivity of the pixel direction as shown in Figure 21 as an image sonar, for example, and calculates the value of the level data for each pixel.

(Posture correction process)
The directivity synthesis processing unit 31 performs correction calculations for directivity synthesis processing due to the inclination of the wave transmitting and receiving array 7 from data on the roll angle, pitch angle, and yaw angle that indicate the attitude of the underwater vehicle 1. First, the displacement of the wave receiving transducer 15 due to the roll angle is calculated.

As shown in Figure 17, the three-dimensional position coordinates of the center of the receiving transducer 15-k, which is positioned at an angle A [deg] from directly above (Y axis) the transmitting and receiving array 7, are (X0, Y0, Z0), the separation distance between the center of the receiving transducer 15-k and the center (0,0,0) of the transmitting and receiving array 7 is R0, and the roll angle is aR.

(X0,Y0,Z0)=(R0sin(aR), R0cos(aR), 0)
…(1)

Due to the inclination of the roll angle aR, the position of the receiving transducer 15-k changes from (X0, Y0, Z0) to (X1, Y1, Z1). In other words, the rotation matrix R _Z (ψ) that rotates the transducer counterclockwise around the Z axis by an angle ψ is given by the following equation (2).

…(2)

…(2)

…(3) therefore,

…(3)

X1=R0*{cos(aR)sin(A)+ sin(aR) cos(A)}=R0*sin(A+aR)
Y1=R0*{-sin(aR)sin(A)+ cos(aR) cos(A)}=R0*cos(A+aR)
Z1＝0
…(4)

Next, the directivity synthesis processing unit 31 calculates the displacement due to the pitch angle for the receiving transducer 15-k in FIG. 17. For any receiving transducer 15-k (three-dimensional position coordinates: (X1, Y1, Z1)) shown in FIG. 18, the pitch angle is aP. The position (X1, Y1, Z1) of the receiving transducer 15-k changes to (X2, Y2, Z2) as shown below.

The rotation matrix R _X (φ) for rotating an image counterclockwise around the X axis by an angle φ is given by the following equation (5).

…(5)

…(5)

…(6) therefore,

…(6)

X2 = X1
Y2 = cos(aP)*Y1
Z2 = sin(aP)*Y1
…(7)

The directivity synthesis processing unit 31 further calculates the displacement due to the yaw angle for the receiving transducer 15-k in FIG. 18. For an arbitrary receiving transducer 15-k (three-dimensional position coordinates: (X2, Y2, Z2)) shown in FIG. 19, if the yaw angle is aY, the position of the receiving transducer 15-k changes to (X3, Y3, Z3) as shown below.

That is, the rotation matrix R _Y (θ) for rotating an angle θ counterclockwise around the Y axis is given by the following equation (8).

…(8)

…(8)

…(9) therefore,

…(9)

X3 = cos(aY)*X2
Y3 = Y2
Z3 = sin(aY)*X2
…(10)

Next, the directivity synthesis processing unit 31 calculates the displacement D of the receiving transducer 15-N displaced by the roll angle aR, pitch angle aP, and yaw angle aY. As described above, the receiving transducer 15-k has displaced from its original position (X0, Y0, Z0) (Figure 17) to (X3, Y3, Z3). As shown in Figure 20 (A), the original position (X0, Y0, Z0) and the displaced position (X3, Y3, Z3) are projected onto the XY plane as (X0, Y0) and (X3, Y3), respectively, and the displacement distance R3 is given by the following equation (11).

…(11)

…(11)

…(12) The distance R0 from the origin of the original position on the XY plane is given by the following equation (12).

…(12)

The difference between the position after displacement and the original position projected onto the Z axis (Z3-Z0) and the difference between the distance R3 after displacement on the XY plane and the distance R0 from the origin of the original position (R3-R0) give the distance D (amount of displacement) between the position after displacement and the original position, given by the following equation (13).

…(13)

…(13)

Next, the directivity synthesis processing unit 31 calculates the angle at which the phase of the underwater sound wave changes while the underwater sound wave travels the distance D. If the speed of sound in water is approximately 1500 m/s and the frequency of the underwater sound wave of the transmission beam is C Hz, then the wavelength λ of the underwater sound wave of the transmission beam is:

…(14)
である。

…(14)
It is.

The frequency of the receiving underwater sound beam, which is the underwater sound wave of the transmitting underwater sound beam reflected by the underwater object 2, is considered to be approximately the same frequency, although there is a Doppler effect due to the movement of the underwater object 2.

As the receiving transducer 15-N travels through a displacement D [m], the underwater sound waves of the receiving beam change phase by an angle E [deg] given by the following equation (15).

…(15)

…(15)

Therefore, in order to cancel the phenomenon in which any receiving transducer 15-N (N=1 to 30) changes its attitude due to the roll angle, pitch angle, and yaw angle of the underwater vehicle 1, the receiving signal of the receiving transducer 15-N is multiplied by a trigonometric function (complex number, COS for real numbers, -SIN for imaginary numbers) of the angle at which the phase of the underwater sound wave changes as it travels the distance D, as a phase phasing coefficient.

(Image sonar directional synthesis processing)
The imaging sonar device needs to have lattice-like directivity in the left-right and up-down directions, as shown in Fig. 21 for example. With respect to the two-dimensional directivity of the imaging sonar, the left-right direction (X-axis) corresponds to the yaw angle for the underwater vehicle 1, and the up-down direction corresponds to the pitch angle for the underwater vehicle 1. Thus, in the above-mentioned attitude correction process, the directivity synthesis processor 31 can perform attitude correction and directivity synthesis process for the imaging sonar at the same time by adding the desired yaw angle and pitch angle of the two-dimensional directivity of the imaging sonar.

For example, in the case of the imaging sonar shown in Figure 21, where i varies from -16 to +16 and j varies from -16 to +16, and i and j are in units of 1 degree, it is necessary to perform directivity synthesis of 33 ² = 1089 receiving beams.
Pitch angle is the attitude pitch angle aP＋j,
The yaw angle is the attitude yaw angle aY+i
As,
By calculating the directional synthesis of 1,089 receiving beams of the imaging sonar pixels (X(-i), Y(-j)) to (X(+i), Y(+j)) (i = -16 to +16, j = -16 to +16), it is possible to obtain an image of the underwater object 2 while correcting the attitude of the underwater vehicle 1.

Note that a known method is used for directional synthesis processing by phasing the underwater sound waves, so a description of this method is omitted.

As described above, the present embodiment provides the following advantages.
By equipping the front of the underwater vehicle 1 with a transmitter-receiver array 7 for an imaging sonar, which has transmitters and receivers arranged in a ring shape, it becomes easier to correct any changes in the attitude (roll angle, pitch angle, and yaw angle) of the underwater vehicle 1.

In addition, according to the embodiment, a ring-shaped wave transmission/reception array 7 for an imaging sonar is provided at the front of the underwater vehicle 1, so that space can be secured inside the ring-shaped wave transmission/reception array to place a search sonar array, as shown in FIG. 10. The wave transmission/reception array of the embodiment is mounted on the front of the underwater vehicle 1 and can be used as an imaging sonar device that detects the dimensions and shape of underwater objects. Note that in the embodiment, the underwater vehicle 1 may be an unmanned underwater vehicle, and it is of course applicable to manned underwater vehicles as well.

FIG. 22 is a diagram for explaining a configuration in which a sonar device is implemented in a computer device 100. Referring to FIG. 22, the computer device 100 includes a processor 101, a memory 102 such as a semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), or an EEPROM (Electrically Erasable Programmable Read-Only Memory) (or a HDD (Hard Disk Drive)), a display device 103, and an interface 104 that connects to the DA converters 24-1 to 24-6 in FIG. 15 and the FFTs 29-1 to 29-30 in FIG. 16. By executing a program stored in the memory 102, the processor 101 may execute at least the processing of the transmission waveform data output unit 25 in FIG. 15 and the directivity synthesis processing unit 31 in FIG. 16. The display device 103 displays an image of the underwater object 2 based on the processing result of the directivity synthesis processing unit 31. The processor 101 may be a DSP (Digital Signal Processor). In this case, the interface 104 may be connected to the AD converters 28-1 to 28-30 in FIG. 16, and the processor 101 (DSP) may execute the FFTs 29-1 to 29-30.

The disclosures of Patent Documents 1 and 2 are incorporated herein by reference. Modifications and adjustments of the embodiments and examples are possible within the scope of the entire disclosure of the present invention (including the scope of the claims), and further based on the basic technical ideas. Furthermore, various combinations and selections of the various disclosed elements (including each element of each claim, each element of each example, each element of each drawing, etc.) are possible within the scope of the claims of the present invention. In other words, the present invention naturally includes various modifications and alterations that a person skilled in the art would be able to make in accordance with the entire disclosure, including the scope of the claims, and the technical ideas.

1 Underwater vehicle 2 Underwater object 3 Transmitting array 4 Receiving array 5 Transmitting beam 6 Receiving beam 7 Transmitting and receiving array 8 Roll angle 9 Roll axis 10 Pitch angle 11 Pitch axis 12 Yaw angle 13 Yaw axis 14, 14-1 to 14-6 Transmitting transducer (transmitter)
15, 15-1 to 15-30 Receiving transducer (receiver)
22-1 to 22-6 Power amplifier 23-1 to 23-6 Band pass filter (BPF)
24-1 to 24-6 Digital to analog converter (DAC)
25 Transmission waveform data output section 26-1 to 26-30 Preamplifier 27-1 to 27-30 Band pass filter (BPF)
28-1 to 28-30 Analog-to-digital converter (ADC)
29-1 to 29-30 FFT
30 Attitude sensor 31 Directivity synthesis processing unit 71 Hollow section (search sonar array equipment area)
100 Computer device 101 Processor 102 Memory 103 Display device 104 Interface

Claims (10)

An image sonar device comprising a wave transmitting/receiving array arranged two-dimensionally on a plane perpendicular to a longitudinal direction of an underwater vehicle at a front portion of the underwater vehicle,
The wave transmitting/receiving array is configured such that a plurality of wave transmitters and a plurality of wave receivers are arranged in a hollow annular shape,
each acoustic surface of the plurality of transducers and the plurality of transducers is located on an open end side of a hollow ring;
moreover,
an attitude sensor for detecting the attitude of the underwater vehicle;
an imaging sonar device comprising: a directivity synthesis means for performing a correction calculation for a directivity synthesis process caused by the inclination of the transmitting and receiving array based on the detection result of the attitude sensor; The wave transmitting/receiving array has the wave receivers arranged adjacent to each other on the same circumference in a predetermined number of units,
2. The imaging sonar device according to claim 1, wherein the wave transmitter is provided between the predetermined number of adjacently arranged groups of the wave receivers. a transmission waveform data output unit for generating transmission waveform data to be transmitted from the plurality of transducers of the transmission/reception array,
The directivity synthesis means outputs, for data for each frequency component of the received signal at the plurality of receivers of the wave transmitting/receiving array, data corresponding to the frequency of the transmitted wave beam generated by the transmitted waveform data output means,
3. The imaging sonar device according to claim 1 or 2, which corrects for the effect of tilting the receiver of the transmitting and receiving array due to the roll angle, pitch angle, and yaw angle of the underwater vehicle detected by the attitude sensor, performs processing to synthesize the directivity of the pixel directions of the imaging sonar, and calculates a level value for each pixel. The image sonar device according to claim 3, wherein the transmission waveform data output means transmits the same transmission acoustic signal covering a detection range from the multiple transmitters of the transmission/reception array. The directivity synthesis means performs the correction calculation as follows:
For each of the plurality of receivers arranged in the hollow annular shape,
A separation distance between the center of the receiver of the transducer array and the center of the transducer array;
A roll angle detected by the attitude sensor;
Based on
Calculating the displacement of the three-dimensional coordinate position of the receiver;
Regarding the pitch angle and the yaw angle detected by the attitude sensor,
4. The imaging sonar device according to claim 3, wherein displacement of the three-dimensional coordinate position of said receiver is calculated. The imaging sonar device according to claim 5, wherein the directivity synthesis means performs directivity synthesis processing of the imaging sonar simultaneously with attitude correction of the underwater vehicle by adding the yaw angle and the pitch angle of the underwater vehicle, which are set as a first axis direction and a second axis direction orthogonal to the first axis direction, respectively, for two-dimensional directivity in a plane perpendicular to the traveling direction of the underwater vehicle. 1. An image sonar method using a wave transmitting/receiving array arranged two-dimensionally on a plane perpendicular to a longitudinal direction of an underwater vehicle at a front portion of the underwater vehicle, comprising:
The wave transmitting/receiving array is configured by arranging a plurality of wave transmitters and a plurality of wave receivers in a hollow circular ring shape,
each acoustic surface of the plurality of transducers and the plurality of transducers is located on an open end side of a hollow ring;
An imaging sonar method comprising: performing a correction calculation for a directivity synthesis process caused by the inclination of the wave transmitting and receiving array based on the detection result of the attitude of the underwater vehicle. The wave transmitting/receiving array has the wave receivers arranged adjacent to each other on the same circumference in a predetermined number of units,
8. The imaging sonar method according to claim 7, wherein said wave transmitters are arranged between said predetermined number of said adjacently arranged wave receiver groups. For data for each frequency component of the received signal at the plurality of receivers of the transmitting/receiving array, data corresponding to the frequency of the transmitting beam transmitted from the plurality of transmitters is
9. The imaging sonar method according to claim 7 or 8, further comprising the steps of: correcting for the influence of the inclination of the receivers of the transducer array due to the roll angle, pitch angle, and roll angle of the underwater vehicle; synthesizing the directivity of the directions of the pixels of the imaging sonar; and calculating a level value for each pixel. a wave transmitting/receiving array disposed two-dimensionally on a plane perpendicular to a longitudinal direction of the underwater vehicle at a front portion of the underwater vehicle;
a computer that configures an image sonar device in which the wave transmitting and receiving array is configured with a plurality of wave transmitters and a plurality of wave receivers arranged in a hollow annular shape, and each acoustic surface of the plurality of wave transmitters and the plurality of wave receivers is located on an open end side of the hollow annular shape;
A program for executing a process of performing a correction calculation for the directivity synthesis process due to the inclination of the wave transmitting and receiving array based on the detection result of the attitude of the underwater vehicle.

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