Acoustic positioning systems, devices, methods, and programs

Abstract

In an acoustic positioning system that uses a receiver to determine the position of a pinger by receiving an acoustic signal transmitted by the pinger, the system aims to eliminate the deterioration of reception caused by changes in the relative position of the pinger to the receiver due to the pinger's movement, thereby maintaining a good reception environment. [Solution] The distance between the aerial drone 1A and the underwater drone 1B is sufficiently close, allowing the receiver 20 to receive the acoustic signal transmitted by the pinger of the underwater drone 1B well. If, as a result of the underwater drone 1B moving to the next inspection position, the distance between the receiver 20 of the aerial drone 1A and the underwater drone 1B exceeds the receivable distance, the aerial drone 1A moves to the vicinity of the underwater drone 1B's current position by navigating on the water or flying through the air. This brings the distance between the receiver 20 of the aerial drone 1A and the underwater drone 1B close enough that the receiver 20 can continue to receive the acoustic signal transmitted by the pinger 10 well.

Description

Technical Field

[0001] The present invention relates to an acoustic positioning system, apparatus, method, and program for receiving an acoustic signal transmitted by a pinger with a receiver and positioning the position of the pinger. In particular, the present invention relates to an acoustic positioning system, apparatus, method, and program that can eliminate a decrease in the reception state caused by a change in the relative position with the receiver due to the movement of the pinger and continue a good reception state.

Background Art

[0002] Non-Patent Document 1 discloses a "water-air combined drone" in which an aerial drone carries a submersible drone and flies, separates and submerges the submersible drone after landing in the target water area to engage in work, and recovers and takes off from the water after the work is completed, as shown in FIG. 6.

[0003] One feature of the water-air combined drone is that it is equipped with a technology of "acoustic positioning" in which an acoustic signal (acoustic pulse) is transmitted from a transmitter (pinger) attached to the submersible drone, received by an underwater microphone (hydrophone) on the aerial drone side, and then automatically analyzed to calculate the position of the submersible drone. The acoustic positioning technology is disclosed, for example, in P.236-245 of Non-Patent Document 2.

[0004] As shown in FIG. 7, the calculated position information is sent to a land base together with the camera image of the aerial drone [FIG. (a) of the same figure] or the camera image of the submersible drone [FIG. (b) of the same figure], and the position is displayed on the map. In the water-air combined drone, the SSBL (Super Short Base Line) method is adopted for acoustic positioning. First, the time difference of the acoustic pulses received by three or more hydrophones is obtained, and the position of the transmission source is calculated from this.

[0005] Non-patent document 3 discloses an example of an SSBL acoustic positioning system installed on a water-air combined drone. In the SSBL acoustic positioning system, one set of acoustic pulses is emitted within a certain period (for example, 1 second). One set of pulses consists of a fixed number of pulses (for example, 2 pulses), and positioning is performed by receiving these pulses with a hydrophone and processing the signals.

[0006] As a method for simultaneously determining the positions of two pingers, Non-Patent Document 2, pages 125 and 177, discloses a technique in which acoustic pulses are transmitted using an uplink chirp from one pinger and a downlink chirp from the other pinger, thereby separating each acoustic pulse during the calculation of cross-correlation even if the acoustic pulses collide. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent application No. 2022-145518 [Patent Document 2] Patent application No. 2022-195588 [Patent Document 3] Patent application No. 2023-054290 [Non-patent literature]

[0008] [Non-Patent Document 1] KDDI / KDDI Research Institute / ProDrone, News Release: "World's First Aero-Water Combined Drone Successfully Conducts Remote Underwater Photography ~Enables Safe and Efficient Inspection of Offshore Wind Power Generation Facilities Without Launching a Boat~", December 14, 2021 https: / / news.kddi.com / kddi / corporate / newsrelease / 2021 / 12 / 14 / 5593.html [Non-Patent Document 2] The Japan Society for Marine Acoustics, "Fundamentals and Applications of Marine Acoustics," Seizando Shoten, pp. 236-245. [Non-Patent Document 3] Kawada, Nishitani, Kojima: "Acoustic Positioning System for Water-Air Combined Drones," Proceedings of the Japan Society for Marine Acoustics, No. 22-2, pp. 3-4 (2022) [Non-Patent Document 4] Kawada, Nishitani, Kojima: "Acoustic Positioning System for Aquatic-Air Combined Drones," IEICE Technical Report, EA2022-73, pp.72-77 (December 2022) [Overview of the project] [Problems that the invention aims to solve]

[0009] The task of "hull inspection," which involves checking the bottom of anchored vessels for invasive species and other abnormalities, has traditionally been carried out by divers. In recent years, attempts have been made to remotely control these hull inspections using underwater drones, as divers are becoming increasingly scarce. In such cases, knowing the current location of the underwater drone is crucial.

[0010] The acoustic positioning technology described above is used to determine the location of the underwater drone. The underwater drone is equipped with a pinger or transponder (which immediately returns an ultrasonic signal upon receiving a specific ultrasonic signal), and a receiver (underwater microphone / hydrophone) is fixedly installed on the quay or vessel to measure the drone's position.

[0011] However, when using an underwater drone to inspect the bottom of a ship or quay, the transponder on the underwater drone moves around the bottom of the ship, but the positioning device (receiver) must be fixed in place. Depending on the position of the underwater drone, positioning can be difficult due to sound wave shielding or reflection.

[0012] The object of the present invention is to solve the above technical problems and to provide an acoustic positioning system, apparatus, method, and program that can eliminate the deterioration of reception status caused by changes in the relative position of the pinger with respect to the receiver due to underwater movement, thereby maintaining a good reception environment. [Means for solving the problem]

[0013] In order to achieve the above object, the present invention provides an acoustic positioning system in which an acoustic signal transmitted by an underwater moving object is received by a mother ship capable of moving at least one of on water or in air with a receiver of an acoustic positioning device to position the moving object, and the acoustic positioning device is characterized in having the following configuration.

[0014] (1) Means for determining whether at least one of the position and orientation of the receiver needs to be moved, and means for controlling at least one of the position and orientation of the receiver based on the current position of the moving object in response to the determination result that movement is required are provided.

[0015] (2) The means for control is configured to move the position of the receiver by moving the mother ship on water or in air.

[0016] (3) A first actuator for moving the position of the receiver downward is provided, and the means for control is configured to control the first actuator.

[0017] (4) A second actuator for moving the orientation of the receiver is provided, and the means for control is configured to control the second actuator.

Effect of the Invention

[0018] According to the present invention, since the positional relationship and orientation of a set of an acoustic positioning system (for example, a combination of a pinger and a receiver) can be optimally varied, even if an underwater drone equipped with a pinger moves around over a wide range, its position can be continuously and accurately positioned.

Brief Description of the Drawings

[0019] [Figure 1] It is a perspective view of an aerial-aquatic combined drone to which the present invention is applied. [Figure 2] It is a functional block diagram of an acoustic positioning system and device to which the present invention is applied. [Figure 3] It is a top view schematically showing an example of movement control of an aerial drone. [Figure 4]This is a schematic side view illustrating an example of hydrophone motion control. [Figure 5] This is a schematic side view illustrating an example of attitude control for a hydrophone. [Figure 6] This diagram illustrates examples of applications for aerial-water combined drones. [Figure 7] This figure shows examples of images taken by aerial and underwater drones. [Modes for carrying out the invention]

[0020] Embodiments of the present invention will be described in detail below with reference to the drawings. Figure 1 is a perspective view of a water-air combined drone 1 to which the acoustic positioning system and apparatus of the present invention are applied.

[0021] The combined aquatic and water drone 1 consists of an aerial drone 1A acting as a mother ship and an underwater drone 1B acting as a mobile unit. The underwater drone 1B is docked to the underside of the aerial drone 1A in a manner that allows for easy separation and recombination. The aerial drone 1A and the underwater drone 1B are connected by a sufficiently long signal cable (not shown).

[0022] After the combined water-air drone 1 lands in the target area, the underwater drone 1B separates from the combined water-air drone 1, launches into the water, and submerges. After the work is completed, the signal cable is wound up using a winch or similar device, and the underwater drone 1B reattaches to the combined water-air drone 1.

[0023] The aerial drone 1A is equipped with multiple arms 11 extending radially from its body, and each arm 11 has a rotor 12 and a motor 13 for driving it at its tip. The underside of the aerial drone 1A is equipped with an SSBL receiver 20 housing at least three hydrophones and their signal processing units, as well as a catamaran-type float 15. Each arm 11 also has a float section 14 attached to its underside via a connecting device 16.

[0024] The SSBL receiver 20 is connected by a first actuator (not shown) that can be extended and retracted downward, for example, in the vertical direction, by remote control, and a second actuator (not shown) that supports the SSBL receiver 20 in a manner that allows for control of its posture (orientation).

[0025] Figure 2 is a functional block diagram showing the configuration of an acoustic positioning system 1C and device to which the present invention is applied. Its main components are a plurality of pingers 10 that transmit acoustic signals, an SSBL receiver 20 that calculates the position of each pinger 10 based on the acoustic signals, and a movement control unit 30 that controls the movement of the aerial drone 1A based on the acoustic signal reception status and positioning results in the receiver 20. When the present invention is applied to a water-air combined drone 1, the pingers 10 are mounted on the underwater drone 1B, and the receiver 20 and movement control unit 30 are mounted on the aerial drone 1A to realize an acoustic positioning device.

[0026] Each pinger 10 mainly consists of a pressure sensor 101, a depth measurement unit 102, a pulse generation unit 103, and a pulse transmission unit 104, and transmits pulse signals according to the detection and measurement results from the pressure sensor 101 and the depth measurement unit 102 at predetermined time slot periods.

[0027] The receiver 20 primarily consists of a pulse receiving unit 202 equipped with at least three hydrophones 201 and a positioning unit 203. The positioning unit 203 includes a direction calculation unit 203a and a depth calculation unit 203b, which calculate the direction and depth of each pinger 10 based on the delay difference of the acoustic signals received by each hydrophone 201, and position the underwater drone 1B equipped with each pinger 10 based on the calculation results.

[0028] The movement control unit 30 mainly consists of a movement necessity determination unit 301 and a position prediction unit 302. The movement necessity determination unit 301 determines that it is necessary to move the aerial drone 1A to the vicinity of the current position of the underwater drone 1B if the acoustic signal reception state in the pulse receiving unit 202 of the receiver 20, such as reception strength and signal-to-noise ratio, falls below a predetermined threshold that allows for accurate analysis of the acoustic signal.

[0029] When the movement necessity determination unit 301 determines that the aerial drone 1A needs to move, the position prediction unit 302 predicts the current position of the underwater drone 1B based on, for example, the positioning unit 203 of the receiver 20's positioning unit 203 has determined the position of the pinger 10, and instructs the aerial drone 1A to move to that current position.

[0030] Such an acoustic positioning device, with a receiver 20 and a mobile control unit 30 as its main components, can be configured by implementing an application (program) that realizes each of the functions detailed below on a general-purpose computer or server equipped with a CPU, ROM, RAM, bus, interface, etc. Alternatively, it can be configured as a dedicated or single-function device with some of the applications implemented in hardware or software.

[0031] Next, with reference to Figures 3, 4, and 5, the movement control of the aerial drone 1A by the movement control unit 30 and the attitude control of the receiver 20 (hydrophone 201) will be described.

[0032] Figure 3 is a schematic overhead view illustrating an example of movement control of the aerial drone 1A, showing the horizontal relative positions of the underwater drone 1B inspecting the bottom 100a of the vessel 100 under inspection and the aerial drone 1A floating on the water surface and waiting.

[0033] As shown in Figure (a), if the distance between the aerial drone 1A and the underwater drone 1B is sufficiently close, and the receiver 20 of the aerial drone 1A has a clear line of sight to the underwater drone 1B, the receiver 20 can receive the acoustic signal transmitted by the pinger of the underwater drone 1B well. Therefore, the movement control unit 30 determines that movement is unnecessary, and the receiver 20 can accurately determine the current position of the underwater drone 1B based on the positioning pulse of the acoustic signal received at that location.

[0034] Subsequently, when the underwater drone 1B moves to the next inspection position, and the distance between the receiver 20 of the aerial drone 1A and the underwater drone 1B exceeds the receivable distance as shown in Figure (b), the receiver 20's reception of the acoustic signal transmitted by the pinger of the underwater drone 1B deteriorates.

[0035] In this embodiment, when the acoustic signal reception state by the receiver 20 deteriorates as the underwater drone 1B moves, the movement necessity determination unit 301 of the movement control unit 30 determines that movement is necessary, and the position prediction unit 302 predicts the current position of the underwater drone 1B and instructs the aerial drone 1A to move to the vicinity of that position.

[0036] As a result, as shown in Figure (c), the aerial drone 1A moves to the vicinity of the current position of the underwater drone 1B by navigating on the water or flying through the air. This brings the receiver 20 of the aerial drone 1A and the underwater drone 1B close enough that the receiver 20 can continue to receive the acoustic signal transmitted by the pinger 10 well.

[0037] The position prediction unit 302 can predict the current position of the underwater drone 1B using various methods. For example, the aerial drone 1A can track the position of the underwater drone 1B by repeatedly receiving the acoustic signal transmitted by the underwater drone 1B's pinger 10 and continuously determining its position, and can then predict the current position of the underwater drone 1B based on the tracking history.

[0038] Alternatively, if the inspection points on the bottom of the ship 100a are scheduled in advance as location information along with the inspection time, the position of the underwater drone 1B at each time can be predicted based on the relationship between the inspection location and the inspection time.

[0039] Figure 4 is a schematic side view illustrating an example of movement control of the receiver 20 in the aerial drone 1A, showing the relative positional relationship between the underwater drone 1B, which is inspecting the bottom 100a of the vessel 100 under inspection, and the aerial drone 1A, which is floating on the water surface and waiting.

[0040] As shown in Figure (a), when the underwater drone 1B is inspecting a shallow area of ​​the bottom of the ship 100a, the distance between the aerial drone 1A and the underwater drone 1B is sufficiently close, and the receiver 20 of the aerial drone 1A can see the underwater drone 1B clearly, so the receiver 20 can receive the acoustic signal transmitted by the pinger 10 of the underwater drone 1B well.

[0041] Subsequently, as shown in Figure (b), when the underwater drone 1B moves to a deeper position on the bottom of the hull 100a, the curved bottom of the hull 100a becomes an obstruction, preventing the receiver 20 from seeing the underwater drone 1B, which can lead to a decrease in the reception of acoustic signals in the receiver 20.

[0042] In this case, if the aerial drone 1A is far enough away from the ship 100 under inspection, the receiver 20 will be able to see the underwater drone 1B. However, the distance between the two exceeds the reception range, and a decrease in the reception quality of the acoustic signal is unavoidable.

[0043] In contrast, in this embodiment, as shown in Figure (c), the first actuator 20b, which connects the aerial drone 1A and the receiver 20 in a retractable manner, is extended by remote control, causing the receiver 20 to submerge to a position where it can see the underwater drone 1B. As a result, the receiver 20 can continue to receive the acoustic signal transmitted by the pinger 10 with good quality.

[0044] Figure 5 is a schematic side view illustrating an example of attitude control of the receiver 20 in the aerial drone 1A, showing the relative positional relationship between the underwater drone 1B, which is inspecting the bottom 100a of the vessel 100 under inspection, and the aerial drone 1A, which is floating on the water surface and waiting.

[0045] As shown in Figure (a), even if the horizontal distance between the aerial drone 1A and the underwater drone 1B is short, if the water depth of the underwater drone 1B is shallow, the sensor portion located on the bottom of the hydrophone 201 mounted on the receiver 20 may not be able to face the underwater drone 1B directly, resulting in insufficient reception and, consequently, a decrease in the positioning accuracy of the SSBL.

[0046] In such a case, as shown in Figure (b), the attitude of the receiver 20 is controlled by the second actuator so that the sensor portion of the hydrophone 201 faces directly towards the pinger 10 of the underwater drone 1B or in a direction that maintains good reception. This allows the receiver 20 to accurately determine the position of the underwater drone 1B based on the acoustic signal received by the hydrophone 201.

[0047] In the above embodiment, it was explained that a good reception state is maintained by moving the receiver 20 of the aerial drone 1A horizontally or downwards, or by changing its attitude. However, as shown in Figure (c), these controls may be combined to further control the attitude of the receiver 20 so that when the receiver 20 is submerged and the sensor portion of the hydrophone 201 can no longer face the underwater drone 1B directly, the sensor portion of the receiver 20 faces the direction of the underwater drone 1B.

[0048] Furthermore, in each of the above embodiments, the position and attitude of the receiver 20 were described as being controlled when the hydrophone 201 can no longer receive the acoustic signal transmitted by the pinger 10 in a position-determining receiving state. However, the present invention is not limited to this, and for example, when a trend of declining reception is detected, the position and attitude of the receiver 20 may be controlled based on the history of the relative positional relationship between the aerial drone 1A and the underwater drone 1B.

[0049] Furthermore, according to each of the above embodiments, accurate acoustic positioning can be achieved between the aerial drone 1A and the underwater drone 1B of the combined aquatic and water drone 1, enabling safe and accurate inspections requiring advanced skills, such as ship bottom inspections and bridge pier inspections, by the aerial drone 1A. Thus, it becomes possible to contribute to United Nations-led Sustainable Development Goals (SDGs) Goal 9, "Build resilient infrastructure and promote inclusive and sustainable industrialization," and Goal 11, "Make cities inclusive, safe, resilient and sustainable." [Explanation of Symbols]

[0050] 1...Water-air combined drone, 1A...Aerial drone, 1B...Underwater drone, 10...Pinger, 11...Arm, 12...Rotor wing, 13...Drive motor, 14...Float section, 15...Catamaran-type float, 16...Connector, 20...Receiver, 30...Movement control unit, 201...Hydrophone

Claims

1. In an acoustic positioning system in which an underwater moving object transmits an acoustic signal, and a mother ship capable of moving on or in the air receives the signal with a receiver of an acoustic positioning device to determine the position of the moving object, The aforementioned acoustic positioning device, Means for determining whether it is necessary to move at least one of the position and orientation of the receiver, An acoustic positioning system characterized by comprising means for controlling at least one of the position and orientation of a receiver based on the current position of a moving object in response to a determination result of a moving object.

2. The acoustic positioning system according to claim 1, characterized in that the control means moves the position of the receiver by moving the mother ship on the water or in the air.

3. The system includes a first actuator that moves the position of the receiver downward, The acoustic positioning system according to claim 1, characterized in that the control means controls the first actuator.

4. The system includes a second actuator for moving the orientation of the receiver, The acoustic positioning system according to claim 1, characterized in that the control means controls the second actuator.

5. The acoustic positioning system according to claim 1, characterized in that the means for determining whether movement is necessary determines whether movement is necessary based on the reception status of an acoustic signal in the receiver.

6. The acoustic positioning system according to claim 1, characterized in that the means for determining whether movement is necessary determines whether movement is necessary based on the relationship between the planned position and time of the moving object.

7. The system further comprises means for predicting the current position of a moving object based on its movement history, The acoustic positioning system according to any one of claims 1 to 6, characterized in that the controlling means controls at least one of the position and orientation of the receiver based on the current position predicted by the moving body.

8. The acoustic positioning system according to claim 7, characterized in that the receiver is an SSBL receiver and incorporates a plurality of hydrophones.

9. The aforementioned acoustic positioning system is a water-air combined drone, The acoustic positioning system according to claim 8, characterized in that the mother ship is an aerial drone and the mobile body is an underwater drone.

10. An acoustic positioning device mounted on a mother ship capable of moving on or in the air, which receives acoustic signals transmitted by a moving object underwater with a receiver to determine the position of the moving object, Means for determining whether it is necessary to move at least one of the position and orientation of the receiver, An acoustic positioning device characterized by comprising means for controlling at least one of the position and orientation of a receiver based on the current position of a moving object in response to a determination result of a moving object.

11. In an acoustic positioning method in which an acoustic signal transmitted by a moving object underwater is received by a mother ship that can move on the water or in the air, at least one of which is received by a receiver, and the position of the moving object is determined by a computer, Determine whether it is necessary to move at least one of the receiver's position and orientation. An acoustic positioning method characterized by controlling at least one of the position and orientation of a receiver based on the current position of a moving object in response to a determination result for movement.

12. In an acoustic positioning program in which an underwater moving object transmits an acoustic signal, and a mother ship capable of moving on or in the air receives the signal with a receiver to determine the position of the moving object, A procedure for determining whether it is necessary to move at least one of the position and orientation of the receiver, An acoustic positioning program characterized by causing a computer to perform a procedure to control at least one of the position and orientation of a receiver based on the current position of a moving object in response to a determination result of a moving object.

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