Sonar device, homing control method and program

Abstract

To allow for a use of image sonar even at a stage when an underwater vehicle comes close to a target.SOLUTION: A sonar device comprises: an image sonar array that is arranged in an underwater vehicle, in which a center axis of a vertical search range has a prescribed elevation angle or depression angle with respect to an advancing direction of the underwater vehicle; and a search sonar array that is arranged in the underwater vehicle, and sets the center axis of the vertical search range as the advancing direction of the underwater vehicle. In homing using the search sonar array, when detecting satisfying a prescribed condition for transiting to the homing using the image sonar array, the homing is switched from the homing using the search sonar array to the homing using the image sonar array.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a sonar device, a homing control method, and a program.

Background Art

[0002] An image sonar using a cross fan beam method (including sonars called, for example, "image sonar", "imaging sonar", or "multi-beam image sonar") includes a transmission array in which a plurality of transmission elements (acoustic vibrators) that transmit transmission sound waves into water are linearly arranged, and a reception array in which a plurality of reception elements (acoustic vibrators) that receive reflected sound waves reflected from a target in water are orthogonally arranged so as to form a cross with the transmission array (Patent Document 1). Hereinafter, related technologies having a sonar array using a cross fan beam method at the front of an underwater vehicle will be outlined. FIG. 1(A) is a schematic plan view of an underwater vehicle having an image sonar array 30 using a cross fan beam method at its tip, as viewed from the traveling direction (Z-axis direction) of the underwater vehicle. A sonar array used for acquiring an underwater image is referred to as an "image sonar array". The image sonar array 30 includes a transmission array 3 in which a plurality of transmission elements (acoustic vibrators) that convert an electric signal into an acoustic signal are arranged in a row (longitudinal direction: Y direction), and a reception array 4 in which a plurality of reception elements (acoustic vibrators) that convert an acoustic signal into an electric signal are arranged in a row (lateral direction: X direction), and the directivity of the signal of the pixel where the longitudinal transmission beam directivity and the lateral reception beam directivity cross can be obtained. Therefore, there is an advantage that pixel information of the image sonar can be obtained with a small amount of calculation.

[0003] FIG. 1(B) is a diagram schematically showing a transmission beam using a cross fan beam method. Referring to FIG. 1(B), the image sonar array 30 using a cross fan beam method transmits a transmission beam 5 having directivity in the vertical direction (Y direction) from the transmission array 3 in the underwater vehicle 1 for a plurality of pixels in the vertical direction. A plurality of transmission beams 5 from the transmission array 3 are each phase-shifted.

[0004] FIG. 1(C) is a diagram schematically showing a received beam 6 of the cross fan beam method. Referring to FIG. 1(C), in the underwater vehicle 1, a receiving array 4 disposed orthogonally to the transmitting array 3 receives the reflected sound wave of the sound wave transmitted from the transmitting array 3, and generates a plurality of received beams 6 having directivity in the horizontal direction (X direction).

[0005] FIG. 2 is a diagram schematically showing an example of a two-dimensional image obtained by the cross fan beam method. Referring to FIG. 2, it is possible to capture the reflected waves at the crossed portions of a plurality of transmitting beams 5 in the vertical direction and the received beams 6 in the horizontal direction. Thereby, high resolution of the sonar is realized, and the two-dimensional shape and dimensions of an underwater object can be detected.

[0006] Furthermore, by performing horizontal direction directivity synthesis processing (performing phase alignment processing on the received signal to form a directivity beam) by the received beam in a short cycle, the two-dimensional image data is three-dimensionalized as image data in the distance direction, so that the dimensions and three-dimensional shape of a target object on the sea surface or in the sea can be detected in a short time.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In an underwater vehicle, a high frequency is used for an imaging sonar to obtain high-resolution image data. Therefore, the detection distance of underwater targets is short. Thus, after detecting a target with a search sonar, the vehicle approaches the target to a certain extent, and then the imaging sonar is used to detect the size and shape of the target. Thereby, the imaging sonar can be used as a classification sonar for discriminating whether the target is a target to be homed (tracked) or an object that is not a homing target such as an acoustic decoy (a deception device used for confusing the detection and measurement of an opponent's sonar or a torpedo's acoustic homing device).

[0009] However, the imaging sonar cannot be used at the stage when the underwater vehicle is closest to the target. This is because in the imaging sonar array arranged at the front of the underwater vehicle, since the traveling direction of the underwater vehicle and the vertical directivity direction of the imaging sonar are the same direction, when the part where the underwater vehicle is closest to the target is the bottom surface of a ship or the like, at the timing when the underwater vehicle is closest to the target, the target is out of the range of the vertical directivity width of the imaging sonar.

[0010] The present disclosure was conceived in view of the above problems, and one of its purposes is to provide a sonar device, a homing control method, and a program that enable the use of an imaging sonar even when an underwater vehicle is close to a target.

Means for Solving the Problems

[0011] According to the present disclosure, a sonar device includes an imaging sonar array arranged on an underwater vehicle, the central axis of the vertical search range of which forms a predetermined elevation angle or depression angle with respect to the traveling direction of the underwater vehicle; a search sonar array arranged on the underwater vehicle, the central axis of the vertical search range of which is the same as the traveling direction of the underwater vehicle; and a control unit that, when detecting that a predetermined condition for shifting from homing using the search sonar array to homing using the imaging sonar array is satisfied in the homing using the search sonar array, switches from the homing using the search sonar array to the homing using the imaging sonar array.

[0012] According to a method of another aspect of the present disclosure, an image sonar array disposed on an underwater vehicle, the central axis of the vertical search range having a predetermined elevation angle or depression angle with respect to the traveling direction of the underwater vehicle, and an underwater vehicle disposed on the underwater vehicle, and a search sonar array having a central axis of the vertical search range as the traveling direction of the underwater vehicle, a homing control method for a sonar device, comprising: In homing using the search sonar array, when it is detected that a predetermined condition for shifting to homing using the image sonar array is satisfied, the homing using the search sonar array is switched to homing using the image sonar array.

[0013] According to the present disclosure, a computer included in a sonar device including an image sonar array disposed on an underwater vehicle, the central axis of the vertical search range having a predetermined elevation angle or depression angle with respect to the traveling direction of the underwater vehicle, and a search sonar array disposed on the underwater vehicle, the central axis of the vertical search range being the traveling direction of the underwater vehicle, when it is detected that a predetermined condition for shifting to homing using the image sonar array is satisfied in homing using the search sonar array, a program for executing a process of switching from homing using the search sonar array to homing using the image sonar array is disclosed as yet another aspect.

Advantages of the Invention

[0014] According to the present disclosure, it is possible to use an image sonar even when the underwater vehicle approaches a target.

Brief Description of the Drawings

[0015]

Figure 1

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Figure 16

Embodiments for Carrying Out the Invention

[0016] According to the present disclosure, by providing an image sonar array equipped at the front part of an underwater vehicle with a predetermined elevation angle or depression angle with respect to the vertical directivity central axis of the cross fan beam method, an image sonar that can be used for classifying a target is effectively utilized so that it can also be used for tracking a target during homing navigation. In addition, the underwater vehicle can navigate outside the detection range of a passive sonar equipped on a target such as a ship, making it difficult for the target such as a ship to detect the navigation sound of the underwater vehicle.

[0017] Here, the cross fan beam method image sonar array 30 mounted on the underwater vehicle 1 described with reference to FIGS. 1 to 2 will be considered. In the underwater vehicle 1, the cross fan beam method image sonar array 30 is equipped at the front part of the underwater vehicle 1 and detects a target located in the traveling direction of the underwater vehicle 1. The cross fan beam method image sonar array 30 can detect the distance to the target, the shape of the target, the size of the target, and the attitude of the target, but it is not used for the final stage of homing navigation for the underwater vehicle 1 to approach the target to the closest distance. Therefore, the detection of the timing when the underwater vehicle 1 is closest to the target is usually performed using a magnetic sensor or the like mounted on the underwater vehicle 1.

[0018] FIG. 3 is a diagram for explaining an example in which the underwater vehicle 1 approaches the closest to a ship 8 that is a target and the explosive built in the underwater vehicle 1 explodes. FIG. 3(A) schematically shows the case of exploding on the side (side surface) of the ship 8, and FIG. 3(B) schematically shows the case of exploding on the bottom of the ship 8.

[0019] As shown in Fig. 3(A), when the underwater vehicle 1 approaches closest to the side (lateral side) of the ship 8 which is the target object, there is no particular problem even with the cross fan beam type image sonar array 30 described with reference to Figs. 1 and 2. The explosion 9 on the side in Fig. 3(A) indicates that the explosive built into the underwater vehicle 1 explodes on the side of the ship 8. Most of the underwater vehicles 1 during World War II exploded on the side of the ship 8, causing damage to the ship 8 by creating holes below the waterline of the ship 8 and causing flooding. However, when the explosive built into the underwater vehicle 1 is exploded closest to the side (lateral side) of the ship 8 which is the target object (refer to the explosion 9 on the side), most of the energy of the blast generated by the explosion escapes upward. Therefore, it can be said that the energy of the blast generated by the explosion of the explosive does not contribute to the destruction of the ship 8 which is the target object, and the loss is large.

[0020] In order to effectively utilize the energy of the blast generated by the explosion of the explosive built into the underwater vehicle 1 for the purpose of destroying the ship 8 which is the target object, as shown in Fig. 3(B), it is desirable to explode the explosive directly below the ship 8 which is the target object.

[0021] However, it is impossible (extremely difficult) to detect the timing when the image sonar array 30 (Fig. 1(A)) equipped at the front of the underwater vehicle 1 reaches the bottom of the ship 8 which is the target object. In order to detect the timing when it reaches the bottom of the ship 8 which is the target object, sensors such as a magnetic sensor and a water pressure sensor are separately required. Thus, it is difficult to effectively utilize the image sonar array 30 equipped at the front of the underwater vehicle 1.

[0022] When the central axis of the search range of the image sonar array 30 is directed in the traveling direction of the underwater vehicle 1, it is necessary to travel at approximately the same depth as the target ship 8. If the target ship 8 is equipped with a sonar, the traveling sounds such as the engine sound and the rotational sound of the screw propeller of the underwater vehicle 1 will be detected by the sonar equipped on the target ship 8. It is highly likely that the ship 8 (target) that has detected the approach of the underwater vehicle 1 will perform an avoidance action at high speed, or release underwater noise sources or acoustic decoys that interfere with the detection by the image sonar array 30 of the underwater vehicle 1, and take countermeasures to interfere with the detection and homing navigation by the image sonar array 30 of the underwater vehicle 1.

[0023] The explosion 10 at the bottom of the ship in Fig. 3(B) indicates that the explosive built into the underwater vehicle 1 explodes at the bottom of the ship 8. Most modern underwater vehicles 1 since the 1980s explode at the bottom of the ship 8, and the shock wave bubbles (bubble jets) generated by the underwater explosion break the ship or cause holes in the bottom of the ship to cause flooding, thereby damaging the ship 8. In addition, even when the target is a large underwater vehicle instead of a ship, detonating the explosive at the bottom of the large underwater vehicle (the target) has a greater effect of damaging the large underwater vehicle (the target) than detonating the explosive on the side (side surface) of the large underwater vehicle (the target).

[0024] When the underwater vehicle 1 is made to perform homing navigation with respect to the target ship 8, it is desirable that the underwater vehicle 1 is not detected by the sonar of the target ship 8 as much as possible.

[0025] As described above, the cross fan beam type image sonar array 30 is used as a classification sonar that detects the shape and dimensions of a target and determines whether the target is real or fake (acoustic decoy), and has excellent ability to classify the target. However, the detection performance of the shape and dimensions of the target by the image sonar array 30 equipped at the front of the underwater vehicle 1 has no use other than classifying intermediate-stage targets for the purpose of making the underwater vehicle 1 perform homing navigation with respect to the target.

[0026] In the underwater vehicle 1, when the underwater vehicle 1 is in the stage of tracking the target object in the homing run with respect to the target object, the detection performance of the shape and size of the target object by the image sonar array 30 is not effectively utilized.

[0027] In view of the above, in the present disclosure, regarding the image sonar array equipped on the underwater vehicle 1, a structure of the image sonar array is proposed in which the image sonar array is attached so as to have a central axis with a vertical directivity obliquely upward in front of the underwater vehicle 1, enabling the underwater vehicle 1 to approach closest from below the target object.

[0028] Regarding the image sonar array equipped on the underwater vehicle 1, for the configuration in which the image sonar array is attached so as to have a central axis with a vertical directivity obliquely upward, the trajectory of the homing run when the underwater vehicle 1 performs homing on the target object is simulated. In this case, when the underwater vehicle 1 approaches closest from below the search range of the vertical directivity of the sonar that would be equipped on the target ship (for example, estimated to be up to a depression angle of about 30 deg (degrees)), detection of the underwater vehicle 1 by the sonar equipped on the ship 8 can be avoided.

[0029] Further, regarding the image sonar array equipped on the underwater vehicle 1, when the configuration is such that the directivity has an elevation angle and searches obliquely upward, by reversing the vertical direction of the underwater vehicle 1 and having the image sonar array search obliquely downward, in shallow sea areas such as the continental shelf, it is also possible to detect a large underwater object 2 sitting on the seabed (for example, there may also be a large underwater vehicle like the seabed target object 25 in FIG. 12 described later). Since the image sonar array equipped on the underwater vehicle 1 can detect the size and shape of the target object, it is considered that it may be used to distinguish between underwater protrusions such as traces of coral reefs during the period when the sea level dropped during the ice age on the seabed in areas with large changes in the seabed topography, such as the seabed of the East China Sea and the South China Sea, and the large underwater object 2 sitting on the seabed.

[0030] FIG. 4 is a diagram schematically illustrating an example of some embodiments of the present disclosure. When the image sonar array equipped at the front of the underwater vehicle 1 has an elevation angle, it schematically shows the state of detecting the target ship 8 by the image sonar array and performing homing navigation with respect to the target ship 8. In FIG. 4, for the image sonar array (not shown) equipped at the front of the underwater vehicle 1, the image sonar vertical directivity central axis 11 is inclined counterclockwise, for example, by 45 deg with respect to the traveling direction 14 of the underwater vehicle 1. The image sonar vertical directivity width 13 is provided on both sides of the image sonar vertical directivity central axis 11. The image sonar vertical directivity width 13 is the range in which the image sonar detects the target object.

[0031] Thus, by providing the image sonar array equipped at the front of the underwater vehicle 1 with an elevation angle (for example, 45 deg), when the underwater vehicle 1 performs homing navigation with respect to the target object by the image sonar array, it becomes possible to perform homing navigation toward the bottom of the target ship 8.

[0032] FIG. 5 is a diagram schematically illustrating an example of some embodiments of the present disclosure. FIG. 5 shows an example of a simulation of the case where the underwater vehicle 1 equipped with an image sonar array having elevation directivity performs homing navigation toward the target ship 8. In FIG. 5, when the underwater vehicle 1 approaches the target ship 8 up to 1 Km (Kilometer), the situation from the timing of switching from homing navigation by the search sonar array to homing navigation by the image sonar array until the underwater vehicle 1 gets closest to the target ship is schematically shown as a side view seen from the side.

[0033] In FIG. 5, the image sonar vertical directivity central axis 11 indicates the central axis of the vertical directivity of the image sonar array having elevation directivity. The image sonar vertical directivity direction 12 indicates the elevation direction of the image sonar vertical directivity central axis. The traveling direction 14 of the underwater vehicle 1 is the vertical traveling direction of the underwater vehicle 1 and is the same as the vertical direction of the central axis of the vertical directivity of the search sonar array (not shown).

[0034] Here, assuming that the direction of the directivity center of the image sonar array of the underwater vehicle 1 (image sonar vertical directivity center axis 11) is at an elevation angle of 45 deg, the speed of the underwater vehicle 1 is 45 kt (knot), the speed of the ship 8 which is the target is 30 kt, and it is so.

[0035] On the track 16 of the underwater vehicle 1, round markers are displayed every 10 seconds. The track 15 of the ship 8 is an example when the ship 8 performs an evasive maneuver at a speed of 30 kt so that the underwater vehicle 1 is directly behind it, and round markers are displayed every 10 seconds.

[0036] Since the vertical directivity center (image sonar vertical directivity center axis 11) of the image sonar array (not shown) of the underwater vehicle 1 is at an elevation angle of 45 deg, at the start of homing navigation, the underwater vehicle 1 starts diving in the direction of a depression angle of 45 deg, and performs homing navigation so as to always look up at the ship 8 which is the target in the direction of an elevation angle of 45 deg (see the traveling direction 14 of the underwater vehicle 1).

[0037] While diving to a maximum depth of about 600 m, the underwater vehicle 1 always approaches the ship 8 which is the target from below at a depression angle of 45 deg as seen from the ship 8 which is the target.

[0038] Therefore, the underwater vehicle 1 performs homing navigation outside the range of the vertical directivity of the sonar equipped on the ship 8 which is the target. The sonar of the ship 8 which is the target cannot detect the underwater vehicle 1 approaching to the closest distance of the ship 8, and loses sight of the position of the underwater vehicle 1. For this reason, the ship 8 which is the target cannot use an effective countermeasure to avoid the homing of the underwater vehicle 1. Thus, since the underwater vehicle 1 approaches from below the ship 8 which is the target, it can make it difficult to detect the traveling sound of the underwater vehicle 1 by the sonar equipped on the ship 8 which is the target.

[0039] The sonar equipped on the target ship 8 has directivity in the vertical direction in order to enhance the detection sensitivity of underwater sound waves arriving from one direction. When viewed from the target ship 8, the downward direction with a large depression angle is outside the range of the vertical directivity of the sonar equipped on the ship 8, resulting in a blind zone.

[0040] The search sonar array equipped at the front of the underwater vehicle 1 detects, for example, as shown in FIG. 9, the distance 24 (L2) from the underwater vehicle 1 to the seabed 23, and in a shallow sea area such as a continental shelf, it prevents the underwater vehicle 1 from diving too deep and colliding with protrusions such as a sunken ship on the seabed or the surface of the seabed.

[0041] Figs. 6(A), (B), and (C) are a schematic top view, front view, and side view of the front part of the underwater vehicle 1 of the present disclosure. The image sonar array 18, like the image sonar array 30, has a cross shape where the transmitting array 3 and the receiving array 4 are orthogonal, but it is arranged at an inclination angle of 45 degrees on the inclined part 1C (Fig. 6(C)) of the front surface of the main body 1A of the underwater vehicle 1. The image sonar array 18 is a cross fan beam type image sonar array, and sonar vibrators (for example, electrostrictive vibrators) are arranged so that the transmitting array 3 and the receiving array 4 have vertical directivity in the direction of an elevation angle of 45 degrees.

[0042] The search sonar array 17 is a honeycomb-shaped transmitting array, which is arranged at the front of the underwater vehicle 1 and has a central axis with vertical directivity in the traveling direction of the underwater vehicle 1. Generally, in order to detect a target at a long distance, it is larger in size compared to the image sonar array 18, and electrostrictive vibrators optimized for a lower frequency than the image sonar array 18 are used as the transmitting elements (transducers). Although not particularly limited, in the example of Fig. 6, inside the honeycomb-shaped frame of the search sonar array 17, the search sonar vibrators (electrostrictive vibrators) are arranged in 4, 7, 8, and 9 rows from the left end side to the center side, and 4, 7, 8, and 9 rows from the right end side to the center side.

[0043] The image sonar vibrator 18A (electrostrictive vibrator) incorporated in the cross fan beam type image sonar array 18 has a length in the depth direction. In the array arrangement structure of FIG. 6(C), when the image sonar vibrator 18A (electrostrictive vibrator) mechanically interferes with the search sonar vibrator 17A (electrostrictive vibrator) and makes mounting difficult, for example, as shown in FIG. 7, the arrangement of the transmission array 4 and the reception array 3 of the image sonar array 18 in FIG. 6 is inclined by 45 degrees, for example, to the left or right (clockwise) to avoid mechanical interference. FIGS. 7(A), (B), and (C) are schematic top view, front view, and side view of the front part of the underwater vehicle 1 of the present disclosure. Referring to FIG. 7, the X-type image sonar array 19 has an X shape in which the transmission array (line array) 3 and the reception array (line array) 4 intersect in an X shape. Therefore, in FIG. 7, the image sonar array 19 is referred to as the X-type image sonar array 19. The X-type image sonar array 19 is an image sonar array obtained by rotating the image sonar array 18 in FIG. 6 by 45 degrees, for example, clockwise or counterclockwise to avoid mechanical interference when the image sonar vibrator and the search sonar vibrator mechanically interfere and cannot be mounted.

[0044] Figs. 8(A), (B), and (C) are schematic top, front, and side views of the front part of the underwater vehicle 1 of the present disclosure. The ring-shaped image sonar array 22 is a vibrator array of an image sonar using a non-cross fan beam method (Reference 2). The ring-shaped image sonar array 22 has a ring-shaped transmission array 3 in which a plurality of transmission elements (electrostrictive vibrators) (ring-shaped image sonar vibrators 22A in Fig. 8(C)) are arranged in a ring, and a ring-shaped reception array 4 in which a plurality of reception elements (electrostrictive vibrators) are arranged in a ring, and they are arranged concentrically. In Fig. 8(B), the roll axis, pitch axis, and yaw axis of the posture of the underwater vehicle 1 are the Z-axis, X-axis, and Y-axis, respectively. By simultaneously transmitting acoustic signals from the plurality of vibrators of the ring-shaped transmission array 3, a wide directivity beam with a single width is formed, and the influence of the change in the roll angle of the underwater vehicle 1 can be eliminated. In the reception array 4, the reflected sound from the target is received by a large number of narrow directivity beams whose angles are shifted in the horizontal and vertical directions, for example. Regarding the reception beam of the image sonar, a three-dimensional directivity beam for each pixel of the image sonar is generated, and a process of correcting at least the change in the roll angle among the roll angle, yaw angle, and pitch angle of the posture of the underwater vehicle 1 is performed. The ring-shaped image sonar array 22 equipped at the front part of the underwater vehicle 1 is configured to facilitate correction of the influence of the posture change of the underwater vehicle 1, which is a problem of the cross fan beam method. Even when the posture of the underwater vehicle 1 changes, it is possible to search for the accurate dimensions and shape of the target located in front.

[0045] Fig. 9 schematically shows a situation where the distance to the seabed is detected using a search sonar in order to avoid the underwater vehicle 1 colliding with a protrusion such as a sunken ship existing on the seabed or the surface of the seabed when the underwater vehicle 1 performs homing navigation using the image sonar array according to the present invention. There may be protrusions such as sunken ships on the surface of the seabed 23. The search sonar cannot distinguish between the seabed and the sunken ship, but it is possible to detect them as obstacles in the homing navigation of the underwater vehicle 1. The distance (24) L2 from the underwater vehicle 1 to the seabed 23 is L2 = L0×sinθ0 given by. θ0 is the depression angle of the traveling direction 14 of the underwater vehicle 1, and L0 is the distance to the seabed (target) detected by the search sonar (the distance in the traveling direction 14 of the underwater vehicle 1). The distance 24 (L2) to the seabed is the distance from the underwater vehicle 1 to the seabed 23, and in terms of the seabed surface as a reference, it has the same meaning as the altitude of the underwater vehicle 1.

[0046] FIG. 10(A) is a diagram schematically showing an example of a device configuration for controlling the switching between homing navigation by a search sonar array and homing navigation by an image sonar array. The system of FIG. 10(A) is mounted in the underwater vehicle 1. In the search sonar 51, a transmission waveform output unit 34 generates waveform data (digital waveform data) to be transmitted and outputs it to a DA converter (Digital to Analog Convertor: DAC) 33 under the control of a control unit 60. The DA converter 33 converts the input transmission waveform data into an analog signal of a transmission beam and outputs it to a band pass filter (BPF) 32. The band pass filter (BPF) 32 removes high-frequency components and low-frequency components that are not transmitted from the input analog signal and outputs it to a power amplifier 31. The power amplifier (power amplifier) 31 power-amplifies the input analog signal and outputs it to a search sonar oscillator (e.g., 17A in FIG. 6) of a search sonar array (e.g., 17 in FIG. 6), and the search sonar oscillator outputs an underwater sound wave.

[0047] In a cross fan beam type image sonar 52, a transmission waveform output unit 44 generates waveform data (digital waveform data) to be transmitted and outputs it to a DA converter (Digital to Analog Convertor: DAC) 43 under the control of a control unit 60. The DA converter 43 converts the input transmission waveform data into an analog signal of a transmission beam and outputs it to a power amplifier 41 via a band pass filter (BPF) 42. The power amplifier (power amplifier) 41 power-amplifies the input analog signal and outputs it to an image sonar oscillator (e.g., 18A in FIG. 6) of a transmission array 3 of the image sonar array (e.g., 18 in FIG. 6). A plurality of image sonar oscillators 18A of the transmission array 3 output a transmission beam. When a plurality of image sonar oscillators (e.g., 18A in FIG. 6) of a reception array 4 receive an underwater acoustic wave, they convert an acoustic signal (sound pressure) into an electrical signal (voltage) and output it to a preamplifier (pre-amplifier) 45. The preamplifier 45 amplifies the input electrical signal (voltage) and outputs it to an AD converter (ADC) 47 via a band pass filter (BPF) 46. The AD converter 47 converts the input analog signal into waveform data in digital format and outputs it to a reception processing unit 48. The reception processing unit 48 searches for a target under the control of the control unit 60. The reception processing unit 48 performs phase adjustment processing, directivity synthesis processing, etc., and calculates the azimuth of the target, the distance to the target, the shape, the dimensions, etc. In FIG. 10, for simplicity, the signal paths for one of the plurality of search sonar oscillators, one of the plurality of image sonar oscillators of the transmission array, and one of the plurality of image sonar oscillators of the reception array in the search sonar 51 and the image sonar 52 are respectively shown.

[0048] Next, the control operation regarding homing by the image sonar array will be described with reference to FIG. 11. The image sonar array and the search sonar array are assumed to be any of FIGS. 6, 7, and 8 (reference numerals are omitted). The following control operation is performed, for example, by the control unit 60 in FIG. 10.

[0049] The underwater vehicle 1 searches for a target using a search sonar (step S101). When the target is detected by searching for the target using the search sonar (Yes branch in step S102), homing navigation is performed using the search sonar array (step S103). The search sonar array can detect a target at a longer distance (it can detect a target farther away) than the image sonar array. Therefore, until the distance at which the target can be detected by the image sonar array is reached, the underwater vehicle 1 performs homing navigation using the search sonar array so as to approach the target.

[0050] As a result of the homing navigation using the search sonar array, when the underwater vehicle 1 approaches the predicted (estimated, inferred) distance at which the target can be detected by the image sonar array (branch in step S104: within the image sonar detection range), the target is searched for using the image sonar array (step S105). While navigating in the direction of the depression angle corresponding to the vertical directivity direction of the image sonar (12 in FIG. 5) as the traveling direction of the underwater vehicle 1 so that the direction of the vertical directivity center axis of the image sonar becomes the direction of the target, the target is searched for using the image sonar array and an attempt is made to detect the target (step S106). When the target is detected by the image sonar (Yes branch in step S106), homing navigation is performed using the image sonar (step S107). If the target cannot be detected by the image sonar in step S106 (No branch in step S106), the process returns to the homing navigation using the search sonar in step S103.

[0051] In the homing navigation using the image sonar in step S107, the underwater vehicle 1 confirms the azimuth, distance, dimensions, and shape of the target using the image sonar, and determines whether the target is the homing object.

[0052] When the target is determined to be a homing target, similar to the case of searching for the target by the image sonar, while traveling in the direction of the depression angle corresponding to the vertical directivity direction of the image sonar (12 in FIG. 5) as the traveling direction of the underwater vehicle 1 so that the direction of the central axis of the image sonar directivity becomes the direction of the target, it approaches the target. Since the image sonar continuously detects the azimuth and distance of the target, it can calculate the moving direction and moving speed of the target and perform homing navigation toward the predicted meeting point between the target and the underwater vehicle 1.

[0053] By using the image sonar, the dimensions of the target can be detected. By presetting the condition that the dimensions of the target are, for example, 20 m or more in total length, the target and the acoustic decoy can be automatically discriminated. Generally, the size of the acoustic decoy is 10 m or less.

[0054] According to the image sonar, the shape of the target can be detected. Therefore, it is possible to determine which part of the target is closest. Depending on the size of the target and the vertical directivity width of the image sonar, when the distance between the underwater vehicle 1 and the target is shortened to about 100 to 300 m, for example, it is possible to determine whether it is closest to the bottom of the front part, the bottom of the central part, or the bottom of the rear part of the target, and the underwater vehicle 1 can be homing-navigated to aim at an effective part of the target and approach it most closely.

[0055] When the target is equipped with a nuclear reactor, it is theoretically possible to avoid the predicted nuclear reactor mounting part and approach most closely. Generally, the mounting position of the nuclear reactor of the target is slightly behind the center of the hull. If it approaches closest to the front part of the hull, it is considered possible to avoid approaching closest to the mounting position of the nuclear reactor.

[0056] Also, regarding the timing when the underwater vehicle 1 approaches the target most closely, in the related art, explosives were detonated using sensors other than sonar such as magnetic sensors and water pressure sensors. According to this embodiment, by using the image sonar array for homing navigation, the underwater vehicle 1 can detect the closest distance to the bottom of the target.

[0057] Even when the magnetic sensor or the like is interfered with by the target object, the underwater vehicle 1 can surely detect the detonation timing of the explosive closest to the bottom of the target ship.

[0058] During homing navigation using the image sonar, the distance to the seabed is measured by the search sonar (S108).

[0059] When the underwater vehicle 1 performs search for a target object using the image sonar (52 in Fig. 10(A)) and homing navigation using the image sonar, as shown in Fig. 9, the traveling direction of the underwater vehicle 1 is in the direction of the depression angle. In shallow waters of the continental shelf such as the East China Sea and the South China Sea, the underwater vehicle 1 may collide with the seabed. Therefore, the distance from the underwater vehicle 1 to the seabed 23 is measured by the search sonar (51 in Fig. 10(A)) to avoid collision with the seabed 23. Even when the underwater vehicle 1 is performing search for a target object using the image sonar and homing navigation using the image sonar, the search sonar is always operating to detect obstacles ahead.

[0060] In the configuration of Fig. 10(A) described above, the search sonar array 17 of the search sonar 51 is composed of a transmitting array (a plurality of transmitting elements). In the distance measurement to the target object by the search sonar 51 (step S104 in Fig. 11) and the distance measurement to the seabed by the search sonar 51 (step S108 in Fig. 11), for example, based on the timing from when the transmission waveform output unit 34 of the search sonar 51 outputs the transmission waveform to the timing when the reflected signal (echo) is received by the image sonar 52, the reception processing unit 48 may perform the operation. Alternatively, as shown in Fig. 10(B), the search sonar array 17 of the search sonar 51 includes a plurality of transmitting and receiving elements (electrostrictive vibrators), and through a switching unit (duplexer) not shown for switching the transmission system and the reception system connected to the transmitting and receiving elements (electrostrictive vibrators), the signal path of the received signal may be configured to include a preamplifier 35, a band-pass filter 36, an AD converter 37, and a reception processing unit 38.

[0061] When the underwater vehicle 1 is performing homing navigation using an image sonar, as shown in FIG. 9, in the first half of the homing navigation, it navigates in the direction of the depression angle. For this reason, the linear distance L0 to the seabed 23 can be detected by the search sonar. Regarding the distance L2 to the seabed 23, even if there are rocky reefs, sunken ships, or large underwater vehicles sitting on the seabed 23, the search sonar will detect them as protrusions on the seabed 23, and it is impossible to determine what the protrusions are. When, during the homing navigation of the underwater vehicle 1 using the image sonar, it is determined that the distance to the seabed 23 is outside the preset collision risk range, the homing navigation using the image sonar is continued as it is.

[0062] When, during the homing navigation of the underwater vehicle 1 using the image sonar, the distance to the seabed 23 is within the preset collision risk range (branch of S109: within the collision risk distance), the process proceeds to the next step S110.

[0063] When the distance to the seabed 23 is outside the preset collision risk range (branch of S109: outside the collision risk distance), the homing navigation using the image sonar is continued as it is, and as shown in FIG. 5, the closest approach occurs at the timing when the track 15 of the ship 8 and the track 16 of the underwater vehicle 1 intersect.

[0064] (Homing navigation while avoiding collision with the seabed) In a shallow sea area such as a continental shelf, when the underwater vehicle 1 continues homing navigation using the image sonar and it is determined by the control unit (60 in FIG. 10) of the underwater vehicle 1 that there will be a collision with the seabed 23, the underwater vehicle 1 is navigated for a predetermined period of time so as to ascend until the distance between the underwater vehicle 1 and the seabed 23 is outside the preset collision risk range.

[0065] For example, in the control unit 60 (Fig. 10), when it is determined that the underwater vehicle 1 is within the collision risk range (branch at S109: within the collision risk distance), the control unit 60 notifies the navigation control unit 70 (Fig. 10) to that effect. The navigation control unit 70 (the controller that controls the navigation of the underwater vehicle 1) controls the navigation so that the underwater vehicle 1 ascends at a pitch angle of 45 deg for a predetermined period of time, and then returns to the homing navigation using the image sonar again. The underwater vehicle 1 sails in the depression angle direction, detects the azimuth, distance, dimensions, shape, course, and speed of the target object using the image sonar, and resumes the homing navigation toward the meeting point with the target object or the closest part to the target object. Note that the underwater vehicle 1 is equipped with a propeller, rudder, propulsion drive unit, steering drive unit, etc., as well as an acceleration sensor, attitude sensor, pressure (water depth) sensor, etc. Based on these measurement results and the information that the distance to the seabed 23 is within the collision risk distance, the navigation control unit 70 controls the propulsion force and rudder angle of the underwater vehicle 1 to enable navigation at a desired depth, course, and speed.

[0066] When the speed of the underwater vehicle 1 is 45 kt and the ascent time at a pitch angle of 45 deg is 2 seconds, after it is determined that the underwater vehicle 1 will collide with the seabed 23, since the underwater vehicle 1 sails at 45 kt = 25.72 m / s, it ascends 36.37 m in 2 seconds at a pitch angle of 45 deg. Then, it returns to the homing navigation using the image sonar in the depression angle direction, re-detects the target object, and performs the homing navigation to approach the target object.

[0067] As illustrated in Fig. 5, a simple homing navigation in which the underwater vehicle 1 looks up at the target object in the pitch angle direction is possible in a sea area deeper than about 600 m. For example, in a shallow sea area such as a continental shelf, the underwater vehicle 1 repeats the descent by homing navigation in the depression angle direction and the ascent in the pitch angle direction to avoid collision with the seabed 23. However, at the stage where the underwater vehicle 1 is closest to the target object, homing navigation using the image sonar is possible unless it is in an extremely shallow harbor or the like. Even in a shallow sea area, if the homing navigation using the image sonar is continued intermittently, the distance between the underwater vehicle 1 and the target object becomes shorter, and as illustrated in Fig. 5, they are closest at the timing when the ship's track 15 and the underwater vehicle's track 16 intersect.

[0068] As described above, according to the present disclosure, for example, the following effects can be achieved (however, it is not limited thereto).

[0069] By arranging the imaging sonar array equipped at the front of the underwater vehicle 1 to have an elevation angle, when the underwater vehicle 1 performs homing navigation so as to be closest to the bottom of the target object, the imaging sonar can detect the azimuth, distance, dimensions and shape to the target object, and the timing of the closest approach can be determined.

[0070] Furthermore, proximity sensors using magnetic sensors and pressure sensors could not bring the underwater vehicle 1 closest to a specific part of the hull of the target object and detect the closest distance. According to the present disclosure, the function of detecting the dimensions and shape of the target object, which is a feature of the imaging sonar, enables the underwater vehicle 1 to be closest to a specific part of the target object and detect the timing of the closest approach as a distance.

[0071] In addition, since the underwater vehicle 1 performs homing navigation approaching from below the target object, it approaches the target object from outside the vertical search range of the sonar equipped on the target object. Therefore, the possibility of being detected by the sonar equipped on the target object is reduced, and there is no room for the target object to perform movements such as avoiding homing navigation by the underwater vehicle 1 or interfering with the homing navigation of the underwater vehicle 1 by acoustic decoys or the like.

[0072] However, in shallow sea areas such as continental shelves where the water depth is shallower than, for example, about 600 m, in order to avoid the underwater vehicle 1 colliding with the seabed, when the distance to the seabed is within the collision risk range, the lower limit of the diving depth of the underwater vehicle 1 is restricted by the water depth, so it may be difficult to approach the target object from outside the vertical search range of the sonar equipped on the target object.

[0073] Regarding an image sonar array arranged to have an elevation angle, when the underwater vehicle 1 is traveling, it is rotated in the 180 deg roll angle direction, and when the depression angle direction is explored by the image sonar as shown in, for example, Fig. 12, it is possible to detect a large underwater vehicle (seabed target 25) sitting on the seabed 23.

[0074] In this case, the distance to the seabed 23 is to detect the dimensions and shape of the protrusion from above the three-dimensional seabed shape in the depression angle direction obtained by the image sonar, and if it is within the range of the dimensions of a large underwater vehicle (seabed target 25) that becomes a homing target, for example, 20 to 200 m, and the shape resembles that of a large underwater vehicle (seabed target 25), it can be determined as a homing target. However, it is expected to be very difficult to distinguish between a sunken ship and an underwater vehicle (seabed target 25) sitting on the seabed by the image sonar.

[0075] The large underwater vehicle (seabed target 25) sitting on the seabed 23 side may sit on the seabed close to a sunken ship whose existence position is known in advance, or may attach a structure that the image sonar misidentifies as a mast or a deck crane for camouflage. In that case, for example, as disclosed in Reference 1, the reverberation sound obtained by the reverberation of the explosion sound emitted from a sound-emitting bomb dropped on the seabed against the seabed protrusion is detected as a signal, and from the result of the frequency analysis of the detected signal, it is determined whether the reverberation sound contains a resonance sound caused by a space filled with gas, so as to determine whether the seabed protrusion is an underwater vehicle. By using this method in combination with distinguishing between a sunken ship and an underwater vehicle sitting on the seabed, it is possible to improve the accuracy of detecting, for example, a large underwater vehicle sitting on the seabed.

[0076] As another example, regarding the operation of the image sonar, as shown in FIG. 13, the homing navigation phase by the search sonar ends, and the conditions for shifting to the target search by the image sonar are reviewed. Instead of whether the distance to the target is within the detection range of the image sonar or outside the detection range of the image sonar, it is also conceivable to change to the condition of whether it is within the image sonar usage range considering the water depth of the sea area where the underwater vehicle 1 is navigating or outside the image sonar usage range. FIG. 13 only differs in that step S104a is different from step S104 in FIG. 11, and the other steps are the same as in FIG. 11. Hereinafter, FIG. 13 will explain step S104a, and the explanation of the other steps will be omitted.

[0077] For example, under the following conditions, as shown in FIG. 5, the depth of the underwater vehicle 1 reaches about 600 m. Therefore, homing navigation will be performed while avoiding collision with the seabed. For example, (a) When the distance to the target at the time of shifting to the image sonar homing phase is 1 Km, as shown in FIG. 5 (b) In the case of a sea area where the water depth is shallower than 600 m (c) When the speed of the target (ship 8) is 30 kt (d) When the speed of the underwater vehicle 1 is 45 kt (e) When the vertical directivity direction of the image sonar is at an elevation angle of 45 deg (f) When the depth of the underwater vehicle 1 at the start of the image sonar homing navigation is 50 m In cases such as these, homing navigation is performed while avoiding collision with the seabed.

[0078] Therefore, regarding the condition for shifting from the search sonar homing phase to the image sonar homing phase, it is conceivable to change to the condition of whether it is within or outside the range of the "image sonar usage range" determined considering the water depth of the sea area, the speed of the target, and the speed of the underwater vehicle 1 (step S104a). As a result of the determination in step S104a, if it is within the image sonar usage range, the target search by the image sonar in step S105 is performed, and if it is outside the image sonar usage range, the homing navigation by the search sonar in step S103 is continued.

[0079] Regarding the distance within the usage range of the image sonar, considering the water depth of the sea area and to avoid the underwater vehicle 1 from colliding with the seabed, the trajectory simulation of the underwater vehicle 1 as shown in Fig. 5 is determined based on the following three conditions. In the calculation of the trajectory simulation of the underwater vehicle 1, since there are multiple changing parameters (conditions) as follows, it cannot be expressed by a simple calculation formula.

[0080] (1) Speed of the target (kt) (2) Speed of the underwater vehicle 1 (kt) (Since it is controllable, it can also be set to a fixed value.) (3) Water depth of the sea area (m) (4) Image sonar vertical directivity direction (deg) (5) Depth of the underwater vehicle 1 at the start of the image sonar homing run (m)

[0081] For example, when the speed of the target is 30 kt, the water depth of the sea area is 100 m, the image sonar vertical directivity direction is an elevation angle of 45 deg, and the depth of the underwater vehicle 1 at the start of the image sonar homing run is 50 m, as illustrated in Fig. 14, by setting the distance within the usage range of the image sonar to 175 m, the maximum depth during the image sonar homing run of the underwater vehicle 1 can be kept within 100 m.

[0082] Also, for example, when the speed of the target is 15 kt, the water depth of the sea area is 100 m, the image sonar vertical directivity direction (12 in Fig. 5) is an elevation angle of 45 deg, and the depth of the underwater vehicle 1 at the start of the image sonar homing run is 50 m, as illustrated in Fig. 15, the distance within the usage range of the image sonar is set to 200 m. Thereby, the maximum depth during the image sonar homing run of the underwater vehicle 1 can be kept within 100 m.

[0083] FIG. 16 is a diagram schematically illustrating a configuration in which a sonar device is implemented in a computer device 100. Referring to FIG. 16, the computer device 100 includes a processor 101, a memory 102 such as a semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory) (or it may be an HDD (Hard Disk Drive) or the like), and an interface 104 connected to the DA converters 33, 43, the AD converters 37, 47, etc. in FIG. 10. By executing the program stored in the memory 102, the processor 101 may execute at least the processes of the transmission waveform output unit 44, the reception processing unit 48, and the control unit 60 in FIG. 10. In the case of a manned vehicle, a display device 103 for displaying an image of an underwater object may be provided based on the processing result of the reception processing unit 48. The processor 101 may be composed of a plurality of processors, and one of them may be a DSP (Digital Signal Processor).

[0084] The underwater vehicle 1 is an unmanned underwater vehicle intended for an explosion at the bottom of the hull in FIG. 3(B). However, the homing control of the present disclosure is applicable to a manned underwater vehicle when the self-destruction at the bottom of the hull is not the purpose. In the case of a manned underwater vehicle, it goes without saying that the navigation control such as collision avoidance and the attitude control of the underwater vehicle 1 may be manual operations. The sonar device of the present disclosure is equipped on the underwater vehicle 1 performing homing navigation and can be used as an image sonar device for detecting the dimensions and shape of a target object on the sea surface or in the sea.

[0085] [Reference 1] Japanese Patent Application Laid-Open No. 2016-188840 [Reference 2] Japanese Patent Application Laid-Open No. 2023-146347

[0086] The disclosures of Patent Document 1 and References 1 and 2 mentioned above are hereby incorporated by reference into this specification. Within the scope of the entire disclosure of the present invention (including the claims), modifications and adjustments of the embodiments or examples can be made based on the basic technical idea. Also, within the scope of the claims of the present invention, various combinations or selections of various disclosure elements (including each element of each claim, each element of each embodiment, each element of each drawing, etc.) are possible. That is, the present invention naturally includes all the disclosures including the claims and various modifications and corrections that could be made by those skilled in the art according to the technical idea.

Explanation of Reference Signs

[0087] 1 Underwater vehicle 1A Main body 1B Tip (front surface) 1C Inclined portion 2 Underwater object 3 Transmitting array 4 Receiving array 5 Transmitting beam 6 Receiving beam 7 Sea surface 8 Ship 9 Explosion on the side 10 Explosion at the bottom 11 Image sonar vertical directivity central axis 12 Image sonar vertical directivity direction 13 Image sonar vertical directivity width 14 Traveling direction of the underwater vehicle 15 Ship's track 16 Underwater vehicle's track 17 Search sonar array 17A Search sonar oscillator 18 Image sonar array 18A Image sonar oscillator 19 X-type image sonar array 20 X-type image sonar oscillator 21 Search sonar oscillator 22 Ring-type image sonar array 22A Ring-type image sonar oscillator 23 Seabed 24 Distance to the seabed 25 Underwater target 30 Image sonar array 31, 41 Power amplifier 32, 36, 42, 46 Band-pass filter (BPF) 33, 43 Digital-to-analog converter (DAC) 34, 44 Transmission waveform output section 35, 45 Preamplifier 37, 47 Analog-to-digital converter (ADC) 38, 48 Reception processing section 51 Search sonar 52 Image sonar 60 Control section (control device) 70 Navigation control section 100 Computer device 101 Processor 102 Memory 103 Display device 104 Interface

Claims

1. An imaging sonar array disposed in an underwater vehicle, wherein a central axis of a vertical search range forms a predetermined elevation angle or depression angle with respect to a traveling direction of the underwater vehicle; A search sonar array disposed in the underwater vehicle, wherein a central axis of a vertical search range is the same as the traveling direction of the underwater vehicle; In homing using the search sonar array, When it is detected that a predetermined condition for shifting to homing using the imaging sonar array is satisfied, a control unit for switching from homing using the search sonar array to homing using the imaging sonar array; A sonar device comprising:

2. The predetermined condition is that the distance to the target object reaches a predetermined distance, or the sonar device according to claim 1, which is within a usage range of the imaging sonar array.

3. In homing using the imaging sonar array, when the distance to the seabed by the search sonar array is within a predetermined distance, the control unit controls to change the traveling direction of the underwater vehicle. The sonar device according to claim 1.

4. The imaging sonar array is disposed in an inclined portion between a region including the center of the front portion of the underwater vehicle and an outer edge, The search sonar array is disposed in a region including the center of the front portion of the underwater vehicle in the underwater vehicle. The sonar device according to claim 1.

5. The imaging sonar array has a configuration in which a transmitting array in which a plurality of transmitting oscillators are linearly arranged and a receiving array in which a plurality of receiving oscillators are linearly arranged are arranged in a cross shape; has a configuration in which a transmitting array in which a plurality of transmitting oscillators are linearly arranged and a receiving array in which a plurality of receiving oscillators are linearly arranged cross in an X shape; has a configuration in which a transmitting array and a receiving array, each having a plurality of transmitting oscillators arranged in a ring shape, are arranged concentrically; The sonar device according to claim 1, including any one of the above.

6. An imaging sonar array disposed in an underwater vehicle, wherein a central axis of a vertical search range forms a predetermined elevation angle or depression angle with respect to a traveling direction of the underwater vehicle; A search sonar array disposed in the underwater vehicle, wherein a central axis of a vertical search range is the same as the traveling direction of the underwater vehicle; A homing control method for a sonar device comprising: In homing using the search sonar array, When it is detected that a predetermined condition for shifting to homing using the image sonar array is satisfied, a homing control method for switching from homing using the search sonar array to homing using the image sonar array.

7. The predetermined condition is whether the distance to the target object becomes a predetermined distance, The homing control method according to claim 6, which is within the usage range of the image sonar array.

8. When the distance to the seabed by the search sonar array is within a predetermined distance during the execution of homing using the image sonar array, the homing control method according to claim 6, which controls to change the traveling direction of the underwater vehicle.

9. An image sonar array disposed on the underwater vehicle, the central axis of the vertical search range having a predetermined elevation angle or depression angle with respect to the traveling direction of the underwater vehicle, A search sonar array disposed on the underwater vehicle, the central axis of the vertical search range being the traveling direction of the underwater vehicle, In a computer included in a sonar device including In the homing using the search sonar array, When it is detected that a predetermined condition for shifting to homing using the image sonar array is satisfied, a program for executing a process of switching from homing using the search sonar array to homing using the image sonar array.

10. The predetermined condition is whether the distance to the target object becomes a predetermined distance, The program according to claim 9, which is within the usage range of the image sonar array.

Images