JP7248262B2 - underwater acoustic communication system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater acoustic communication system that uses acoustic signals to communicate between a ship or the like on or near the surface of the water and an underwater vehicle thrown into the water.

In oceans, lakes, etc., when an underwater vehicle is put into the water to explore the bottom of the water, it is necessary to use equipment placed between a vessel, etc. located on or near the surface of the water and the underwater vehicle, or in the water. Communication with the underwater vehicle is performed using an underwater acoustic communication system using acoustic signals.
For example, in Patent Document 1, an underwater station connected with a cable to a mother ship is arranged in the sea, an acoustic transponder is arranged on the seabed near the survey point, and an unmanned submarine for exploration is used as the underwater station and the acoustic transponder. A technology is disclosed in which ultrasonic signals are used for communication to guide an unmanned underwater vehicle, and if necessary, an unmanned underwater vehicle is docked to an underwater station for charging or battery replacement and exploration data retrieval.
Further, in Patent Document 2, an underwater station equipped with a first transponder, a first wave receiver and a second wave receiver is suspended in the sea from a mother ship, a second transponder is installed on the seabed, and an autonomous type for exploration The unmanned vehicle is equipped with a third transponder and a third wave receiver, and the underwater station attempts to maintain a fixed point by receiving the signal of the second transponder with the first wave receiver. In the middle, self-propelled by receiving the signal of the second transponder with the third receiver, and when the power decreases, it sails towards the underwater station by receiving the signal of the first transponder with the third receiver. , discloses a technique in which an underwater station performs attitude control for accommodating autonomous unmanned navigation by receiving a signal from a third transponder with a second receiver.
Further, Patent Document 3 discloses underwater acoustic communication in which a mother ship located on the water is provided with a transmitter, an unmanned submersible for exploration is provided with a receiver, and a control signal is sent from the mother ship to the unmanned submersible. A technique for correcting transmission errors using the Hough transform of is disclosed.
Further, in Patent Document 4, a self-propelled repeater that relays communication between a mother ship and an underwater vehicle is arranged near the water surface of an observation area, and communication between the self-propelled repeater and the mother ship is radio communication. , and communication between the self-propelled repeater and the underwater vehicle is performed by acoustic communication, thereby improving the communicable distance in the horizontal direction.

JP-A-3-266794 Japanese Patent Application Laid-Open No. 2003-26090 JP-A-5-147583 Japanese Patent Application Laid-Open No. 2001-308766 Japanese Patent Publication No. 2001-500941

When underwater acoustic communication is performed from a ship on or near the surface of the water to an underwater vehicle below the ship, generally due to the influence of sound waves reflected on the water surface, a conical volume with the ship at the apex is generated. is the area where underwater acoustic communication is possible. However, it is conceivable that the underwater vehicle may leave the area where underwater acoustic communication is possible during observation work. When the underwater vehicle exceeds the underwater acoustic communication possible area, the underwater acoustic communication is interrupted.
In the invention described in Patent Document 1, since the mother ship and the underwater station are connected by a cable, movement of the mother ship and the underwater station is restricted. In addition, no consideration is given to the effect on acoustic communication due to reflection of sound waves on the water surface or the bottom of the water.
In the invention described in Patent Document 2, since the underwater station is suspended from the mothership, movement of the mothership and the underwater station is restricted. In addition, no consideration is given to the effect on acoustic communication due to reflection of sound waves on the water surface or the bottom of the water.
The invention described in Patent Document 3 takes into account that underwater acoustic communication is susceptible to reflected sounds from the surface of the water and the seabed. It is intended to prevent falling into However, when the unmanned submersible exceeds the substantially cone-shaped underwater acoustic communication possible area with the mother ship at the apex, the communication is interrupted.
The invention described in Patent Document 4 considers that there are areas where sound waves do not propagate, especially in horizontal communication, because acoustic communication deteriorates due to reflection from the sea surface and seabed. This is intended to extend the horizontal communicable distance by communicating with an underwater vehicle. However, since the self-propelled repeater is placed near the surface of the water, it cannot communicate with the underwater vehicle outside the substantially conical underwater acoustic communication area with the self-propelled repeater at the apex.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an underwater acoustic communication system that expands the underwater acoustic communication range between a ship or the like near the surface of the water and an underwater vehicle in the water.

An underwater acoustic communication system corresponding to claim 1 is used in a sea area having a layer with a low underwater sound velocity of 1490 m/s or less and a high underwater sound velocity layer with an underwater sound velocity of more than 1490 m/s. Underwater communication using acoustic signals between a floating body acoustic communication means that can move on the water surface placed near the In an acoustic communication system, a predetermined area in a substantially conical range below the surface of the water where acoustic signals emitted by the floating body acoustic communication means can easily reach, and the predetermined area is affected by water temperature, salinity, and water depth. Acoustic communication relay means capable of moving in water arranged in a layer with a low underwater sound velocity of 1490 m/s or less among layers classified into a layer with a high underwater sound velocity and a layer with a low underwater sound velocity according to the underwater sound velocity. and moving the acoustic communication relay means so as not to deviate from the predetermined area in the layer where the underwater sound speed is slow following the movement of the floating body acoustic communication means on the water surface, and the underwater vehicle navigates beyond the predetermined area. communication between the acoustic communication relay means and the vehicle acoustic communication means of the underwater vehicle traveling beyond the predetermined area in a layer having a low underwater sound speed in the predetermined area when the underwater vehicle travels. The underwater vehicle is moved to a position where the situation is favorable , and the floating body acoustic communication means and the vehicle acoustic communication means of the underwater vehicle sailing beyond a predetermined area perform acoustic communication via the acoustic communication relay means. .
According to the first aspect of the present invention, the floating body acoustic communication means and the watercraft acoustic communication means can perform acoustic communication via the acoustic communication relay means. Since the sound waves from the acoustic communication relay means arranged in the water are not easily affected by the water surface reflection, they easily reach the vehicle acoustic communication means outside the predetermined area. That is, since the acoustic communication range between the floating body acoustic communication means and the vehicle acoustic communication means is expanded, the activity range of the underwater vehicle is expanded. Further, since the acoustic communication relay means is movable, it is possible to prevent the acoustic communication relay means from deviating from the predetermined area even if the floating acoustic communication means moves by tracking the floating acoustic communication means. Further, since it is possible to move up to a position where acoustic communication with the underwater vehicle is possible within the predetermined area of the substantially conical range, the observation range of the underwater vehicle can be expanded. Further, the acoustic communication relay means is arranged in a layer with a slow underwater sound speed of 1490 m/s or less , and when the underwater vehicle sails beyond a predetermined area, a predetermined Acoustic communication relay means between the floating body acoustic communication means and the vehicle acoustic communication means by operating the underwater vehicle traveling beyond the area at a position where the communication condition with the vehicle acoustic communication means is good. The stability of communication via is further enhanced, and the communication range is further expanded.
"Floating body acoustic communication means placed near the water surface" includes floating body acoustic communication means provided on buoys floating on the water surface, Includes floating acoustic communication means. It also includes the state of being mounted on a floating body such as a ship .

The present invention according to claim 2 is characterized in that the acoustic communication relay means transmits acoustic signals laterally to perform acoustic communication with the vehicle acoustic communication means.
According to the second aspect of the present invention, stable communication can be performed even with a vehicle acoustic communication means that is particularly distant in the horizontal direction.

According to the third aspect of the present invention, when an underwater vehicle exists in a predetermined area, direct communication is performed between the floating body acoustic communication means and the vehicle acoustic communication means.
According to the third aspect of the present invention, the energy consumption and load of the acoustic communication relay means can be reduced, and the communication speed between the floating body acoustic communication means and the ship acoustic communication means can be increased.
Note that "direct communication" refers to communication that does not involve an acoustic communication relay means.

The present invention according to claim 4 is characterized by comprising communication switching means for switching between direct communication between the floating body acoustic communication means and the ship acoustic communication means and indirect communication via the acoustic communication relay means.
According to the fourth aspect of the present invention, direct communication and indirect communication can be switched according to the communication status between the floating body acoustic communication means and the ship acoustic communication means, or as required.

The present invention according to claim 5 is characterized in that the data provided for acoustic communication includes position data.
According to the fifth aspect of the present invention, by including the position data, correction of the position of the floating body acoustic communication means, the acoustic communication relay means, or the underwater vehicle, and correspondence with the data acquired by the underwater vehicle. etc.

The present invention according to claim 6 is characterized in that the position data is data obtained by receiving GNSS signals from GNSS satellites and grasping the self-position of the floating body acoustic communication means.
According to the sixth aspect of the present invention, the position data can be data obtained by receiving GNSS signals and grasping the self-position of the floating body acoustic communication means.

According to a seventh aspect of the present invention, a plurality of floating body acoustic communication means are provided, and each of the plurality of floating body acoustic communication means receives GNSS signals from GNSS satellites and grasps its own position.
According to the seventh aspect of the present invention, the position data can be data obtained by each of the plurality of floating body acoustic communication means receiving GNSS signals and grasping its own position.

According to an eighth aspect of the present invention, the underwater vehicle and/or the acoustic communication relay means has storage means for storing data to be used for acoustic communication.
According to the eighth aspect of the present invention, it is possible to retransmit the data as necessary, and to verify the data after recovering the underwater vehicle or the acoustic communication relay means from the water.

According to a ninth aspect of the present invention, a plurality of underwater vehicles are provided, and the acoustic communication relay means relays acoustic signals from the plurality of underwater vehicles.
According to the ninth aspect of the present invention, it is possible to improve the efficiency of observation work and the like by using a plurality of underwater vehicles.

According to the tenth aspect of the present invention, a plurality of underwater vehicles are each equipped with an acoustic communication relay means, and the underwater vehicles existing in a predetermined area relay the acoustic communication.
According to the tenth aspect of the present invention, the underwater vehicle itself can also serve as an acoustic communication relay function. In addition, by providing a plurality of acoustic communication relay means, indirect communication can be performed using the acoustic communication relay means mounted on other underwater vehicles even if one of them fails.

An eleventh aspect of the present invention is characterized in that the moving speed of the acoustic communication relay means is slower than the running speed of the underwater vehicle.
According to the eleventh aspect of the present invention, by making the moving speed of the acoustic communication relay means slower than the cruising speed of the underwater vehicle, energy consumption of the acoustic communication relay means is saved to prepare for indirect communication. be able to.

According to a twelfth aspect of the present invention, when acoustic communication between the vehicle acoustic communication means and the acoustic communication relay means has become impossible, the underwater vehicle and/or the acoustic communication relay means are allowed to rise to the surface of the water. characterized by
According to the twelfth aspect of the present invention, by surfacing early, the underwater vehicle and/or the acoustic communication relay means can be recovered before they are lost.

According to the thirteenth aspect of the present invention, after the underwater vehicle and/or the acoustic communication relay means have surfaced to the surface of the water, the communication between the floating body acoustic communication means and the underwater vehicle and/or the acoustic communication relay means is performed in space. It is characterized by switching to the wireless communication used.
According to the thirteenth aspect of the present invention, the communication between the floating body acoustic communication means and the surfaced underwater vehicle and/or the acoustic communication relay means can be further increased in the amount of information and can be stably performed over a long horizontal distance. .

According to the underwater acoustic communication system of the present invention, the floating body acoustic communication means and the ship acoustic communication means can perform acoustic communication via the acoustic communication relay means. Since the sound waves from the acoustic communication relay means arranged in the water are not easily affected by the water surface reflection, they easily reach the vehicle acoustic communication means outside the predetermined area. That is, since the acoustic communication range between the floating body acoustic communication means and the vehicle acoustic communication means is expanded, the activity range of the underwater vehicle is expanded. Further, since the acoustic communication relay means is movable, it is possible to prevent the acoustic communication relay means from deviating from the predetermined area even if the floating acoustic communication means moves by tracking the floating acoustic communication means. Further, since it is possible to move up to a position where acoustic communication with the underwater vehicle is possible within the predetermined area of the substantially conical range, the observation range of the underwater vehicle can be expanded. Further, the acoustic communication relay means is arranged in a layer with a slow underwater sound speed of 1490 m/s or less , and when the underwater vehicle sails beyond a predetermined area, a predetermined Acoustic communication relay means between the floating body acoustic communication means and the vehicle acoustic communication means by operating the underwater vehicle traveling beyond the area at a position where the communication condition with the vehicle acoustic communication means is good. The stability of communication via is further enhanced, and the communication range is further expanded .

In addition , when the acoustic communication relay means transmits acoustic signals in the lateral direction to perform acoustic communication with the vehicle acoustic communication means, the acoustic communication relay means is stable especially with the vehicle acoustic communication means distant in the horizontal direction. can communicate.

Further, when an underwater vehicle exists in a predetermined area, direct communication between the floating body acoustic communication means and the vehicle acoustic communication means can reduce energy consumption and load on the acoustic communication relay means, The communication speed between the floating body acoustic communication means and the ship acoustic communication means can be increased.

Further, in the case of providing communication switching means for switching between direct communication between the floating body acoustic communication means and the cruising body acoustic communication means and indirect communication via the acoustic communication relay means, the floating body acoustic communication means and the cruising body acoustic communication means Direct communication and indirect communication can be switched according to the communication status between and as necessary.

In addition, when position data is included as data for acoustic communication, correct the position of the floating body acoustic communication means, acoustic communication relay means, or underwater vehicle, and associate it with the data acquired by the underwater vehicle. be able to.

Further, if the position data is data obtained by receiving GNSS signals from GNSS satellites and ascertaining the self-position of the floating body acoustic communication means, the position data is used to determine the self-position of the floating body acoustic communication means by receiving the GNSS signals. can be used as data that comprehends

Further, when a plurality of floating body acoustic communication means are provided and each of the plurality of floating body acoustic communication means receives GNSS signals from GNSS satellites and grasps its own position, the position data is transmitted to the plurality of floating body acoustic communication means can be data obtained by receiving GNSS signals and grasping their own positions.

In addition, if the underwater vehicle and/or the acoustic communication relay means have storage means for storing data to be used for acoustic communication, the data can be resent as necessary, or the underwater vehicle or the acoustic communication relay means can be used. data can be verified after being recovered from the water.

In addition, when a plurality of underwater vehicles are provided and the acoustic communication relay means relays the acoustic signals of the plurality of underwater vehicles, observation work, etc. can be facilitated by using a plurality of underwater vehicles. Efficiency can be improved.

In addition, when a plurality of underwater vehicles are each equipped with an acoustic communication relay means and an underwater vehicle existing in a predetermined area relays acoustic communication, the underwater vehicle itself carries out the acoustic communication relay function. can serve as In addition, by providing a plurality of acoustic communication relay means, indirect communication can be performed using the acoustic communication relay means mounted on other underwater vehicles even if one of them fails.

If the moving speed of the acoustic communication relay means is slower than the underwater vehicle, the moving speed of the acoustic communication relay means can be made slower than the underwater vehicle. , the energy consumption of the acoustic communication relay means can be saved to prepare for indirect communication.

In addition, when the acoustic communication between the vehicle acoustic communication means and the acoustic communication relay means becomes impossible, the underwater vehicle and/or the acoustic communication relay means should rise to the surface of the water as soon as possible. By doing so, the underwater vehicle and/or the acoustic communication relay means can be recovered before they are lost.

In addition, after the underwater vehicle and/or the acoustic communication relay means rise to the surface of the water, when switching the communication between the floating body acoustic communication means and the underwater vehicle and/or the acoustic communication relay means to wireless communication using space. In addition, communication between the floating body acoustic communication means and the surfaced underwater vehicle and/or the acoustic communication relay means can be further increased in the amount of information and can be carried out stably over a long horizontal distance.

1 is a schematic configuration diagram of an underwater acoustic communication system according to a first embodiment of the present invention; FIG. Diagram showing the relationship between depth and water temperature Diagram showing the relationship between depth and salinity Flow chart showing relay control of acoustic communication relay means Flow diagram showing relay control of acoustic communication relay means Schematic configuration diagram of an underwater acoustic communication system according to a second embodiment of the present invention

Below, an underwater acoustic communication system according to an embodiment of the present invention will be described.

FIG. 1 is a schematic configuration diagram of an underwater acoustic communication system according to a first embodiment of the present invention.
FIG. 2 is a diagram showing the relationship between depth (water depth) and water temperature, with the vertical axis representing depth [m] and the horizontal axis representing water temperature [°C].
FIG. 3 is a diagram showing the relationship between depth (water depth) and salinity, with the vertical axis representing depth [m] and the horizontal axis representing salinity [permil].

FIG. 1 shows a state in which a floating body acoustic communication means 30 is arranged near a water surface A in an ocean, a lake, etc., and a plurality of underwater robots 20 are put in to search for mineral resources, energy resources, etc. on the bottom of the water B. .
A ship 10 floating on a water surface A is equipped with a floating body acoustic communication means 30, communicates with an underwater robot 20 existing underwater where radio waves do not reach, using acoustic signals, and monitors and controls the underwater robot 20. .
The underwater robot 20 is an unmanned autonomous underwater vehicle (AUV: Autonomous Underwater Vehicle) that autonomously navigates underwater without using a cable for connection with the floating body acoustic communication means 30. etc. are observed. By using acoustic communication instead of cable communication for communication between the ship 10 and the underwater robot 20, there is no need to provide equipment for cables on the ship 10, and the movement of the ship 10 is not restricted by the cables getting tangled. I have nothing to do.
The underwater acoustic communication system uses acoustic signals to communicate between the floating body acoustic communication means 30 and the vehicle acoustic communication means 40 provided in the underwater robot 20 .

The floating body acoustic communication means 30 has a wave transmitter that transmits sound waves and a wave receiver that receives sound waves, and is provided in a ship (research mother ship) 10 floating on the water surface A.
A ship 10 can grasp its own position by receiving GNSS signals from a GNSS (Global Navigation Satellite System) satellite 1 .
The ship 10 transmits a search command or the like from the floating body acoustic communication means 30 to the underwater robot 20 , and the floating body acoustic communication means 30 receives observation data or the like transmitted from the underwater robot 20 .

The underwater robot 20 consists of a single relay 21 and a plurality of underwater vehicles 22 . The relay 21 is equipped with acoustic communication relay means 50 , communication switching means 60 and storage means 70 . Observation of the water bottom B and the like is mainly performed by the underwater vehicle 22, but the intermediary body 21 can also observe the water bottom B and the like.
The vehicle acoustic communication means 40 has a transmitter for transmitting sound waves and a receiver for receiving sound waves. The relay 21 is provided with a relay acoustic communication means 41 as the cruise body acoustic communication means 40, and the underwater cruise body 22 is provided with a cruise body acoustic communication means 42 as the cruise body acoustic communication means 40. ing.
The relay 21 and the underwater vehicle 22 transmit observation data and the like obtained by observation from the relay acoustic communication means 41 and the underwater vehicle acoustic communication means 42 to the vessel 10, and the commands and the like transmitted from the vessel 10 are transmitted. It is received by the relay body acoustic communication means 41 and the vehicle acoustic communication means 42 .
Acoustic communication relay means 50 mounted on relay 21 relays acoustic communication between ship 10 and underwater vehicle 22 . As a result, the ship 10 and the underwater vehicle 22 can perform indirect communication via the acoustic communication relay means 50 of the relay 21 .
As in the present embodiment, a plurality of underwater vehicles 22 are provided, and the relay 21 relays acoustic signals transmitted and received between the plurality of underwater vehicles 22 and the ship 11, thereby efficiently Underwater exploration can be carried out.

In this embodiment, when the underwater vehicle 22 exists in the predetermined area X, the ship 10 and the underwater vehicle 22 existing in the predetermined area X use the acoustic communication relay means 50 of the relay 21. Direct communication without intermediary. This reduces energy consumption and load on the acoustic communication relay means 50 of the relay 22, and improves the communication speed between the ship 10 and the underwater vehicle 22 compared to indirect communication.
In FIG. 1, solid arrows indicate underwater acoustic communication.
The intermediary 21 includes communication switching means 60 for switching between direct communication and indirect communication, and switches between direct communication and indirect communication according to the communication status between the ship 10 and the underwater vehicle 22 or as necessary. You can switch. In addition, when the ship 10 and the underwater vehicle 22 always perform indirect communication, the communication switching means 60 can be omitted.

When acoustic communication is performed between the ship 10 and the underwater robot 20, sound waves transmitted downward are reflected by the water surface A, making it difficult to perform acoustic communication particularly in the horizontal direction and the depression angle direction close thereto. As shown in FIG. 1, the area where the acoustic signal emitted by the ship 10 can easily reach is a predetermined area X, which is a substantially conical range with the floating body acoustic communication means 30 at the apex.
The intermediary body 21 is located below the water surface A in a predetermined area X where acoustic signals from the ship 10 can easily reach, and is controlled so as not to exceed the predetermined area X. By keeping the relay 21 within the predetermined area X, it is possible to prevent interruption of acoustic communication between the ship 10 and the relay 21 .
In addition, the acoustic signal transmitted from the relay 21 placed in the water has a wider horizontal range than the acoustic signal transmitted from the ship 10 because the influence of reflection on the water surface is reduced. Therefore, even when the underwater vehicle 22 is outside the predetermined area X, the relay 21 can easily perform acoustic communication with the underwater vehicle 22 .
Therefore, acoustic communication between the ship 10 and the underwater vehicle 22 can be achieved by the acoustic communication relay means 50 mounted on the relay 21, at least when the underwater vehicle 22 is traveling beyond the predetermined area X. Communication disruption can be avoided by performing indirect communication via As a result, the range in which acoustic communication between the ship 10 and the underwater vehicle 22 is possible is expanded, and the range in which the underwater vehicle 22 can search is expanded.
As the position of the relay 21 becomes deeper, the influence of the water surface reflection on the acoustic signal transmitted from the relay acoustic communication means 41 becomes smaller. It is preferable to consider not only the depth from the water surface A but also the altitude from the water bottom B because the influence of sound waves (bottom reflection) increases. In this case, the shape of the water bottom B is more complicated than that of the water surface A, and the water bottom reflection is also complicated. The horizontal arrival range of the acoustic signal transmitted from the repeater 21 can be estimated from the depth and altitude at which the repeater 21 is located, the incidence/reflection angles of the sound waves toward the water surface A and the water bottom B, and the like.

The relay 21, which is an AUV, can move along with the movement of the ship 10 by means of a vertical thruster or a horizontal thruster, and can hold its position even in a place where there is a water current or the like. Therefore, by mounting the acoustic communication relay means 50 on the relay body 21 as in the present embodiment, that is, by configuring the acoustic communication relay means 50 to be movable, the acoustic communication relay means 50 can be kept within the predetermined area X. can be done. In addition, since the relay 21 can move to a position where acoustic communication with the underwater vehicle 22 is possible as much as possible within the predetermined area X, the observation range of the underwater vehicle 22 can be expanded. can be done.
Since the intermediary body 21 stays in the predetermined area X, the movement range is narrower than that of the underwater vehicle 22 . Therefore, the cruising speed of the intermediary body 21 may be slower than the cruising speed of the underwater cruising body 22 . By suppressing the cruising speed of the relay 21, the energy consumption of the relay 21 can be saved to prepare for indirect communication.

The position in the vertical direction of the relay body 21 on which the acoustic communication relay means 50 is mounted is determined so that acoustic communication with the underwater vehicle 22 outside the predetermined area X is possible.
The relay 21 is preferably arranged at an optimum position within the predetermined area X according to the communication status of the underwater acoustic communication ascertained by the relay acoustic communication means 41 . By arranging the relay 21 equipped with the acoustic communication relay means 50 in a position where the communication condition is good even within the predetermined area X, the ship 10 and the underwater vehicle 22 can perform indirect communication via the acoustic communication relay means 50. The stability of communication when performing is further enhanced. The communication status of underwater acoustic communication is grasped by, for example, a signal/noise ratio (S/N ratio).
Although the optimum position may be determined according to the communication status between the relay 21 and the ship 10, the relay 21 is arranged at the optimum position according to the communication status between the relay 21 and the underwater vehicle 22. In this case, the stability of communication is further improved, and the range of acoustic communication with the underwater vehicle 22 can be further expanded.
Further, the intermediary body 21 may be arranged in a low water temperature layer having a low underwater sound velocity in the predetermined area X. In the water temperature range of about 3 to 74 ° C, the lower the water temperature, the slower the underwater sound speed, and the sound wave can reach farther horizontally. 10 and the underwater vehicle 22 through the acoustic communication relay means 50, the acoustic communication possible range is further expanded. Here, FIG. 2 is a diagram showing the relationship between depth and water temperature created based on a survey in a sea area with a water depth of 1700 m or more. From FIG. 2, it can be seen that the water temperature of this sea area is within the range of 3 to 74° C., in which the lower the water temperature, the slower the underwater sound speed, and the further away from the water surface A, the lower the water temperature. Therefore, if only the water depth and water temperature are considered, it is preferable to make the position of the relay 21 deeper in the vertical direction. However, if there is a hydrothermal deposit on the bottom of the water and there is a high water temperature layer where the temperature of the water is higher than the others, the high water temperature layer should be avoided. In this way, by measuring or estimating the change in water temperature due to depth and arranging the relay 21 in a place where the water temperature is lower than the predetermined area X based on the result, the acoustic communication range is further expanded as described above. Expanding.
Further, when the underwater acoustic communication system is used in the ocean, the relay 21 may be arranged in a low-salinity layer of the predetermined area X, which has a lower salinity than the others. The lower the salinity, the slower the underwater sound velocity, and the more likely the sound wave reaches the horizontal distance. Acoustic communication possible range is further expanded. When we investigated the relationship between depth and salinity in sea areas with a depth of 1,700 m or more, we found that the lowest salinity layer is at a depth of about 400 to 600 m, as shown in Fig. 3. In addition, if the water depth is about 400 m or more, the low salinity layer will be at a depth of about 400 to 600 m regardless of the maximum depth. Therefore, when considering only water depth and salinity, it is preferable to arrange the intermediary body 21 at a depth of about 400 to 600 m in the predetermined area X in a sea area with a water depth of about 400 m or more. Also, when both the water temperature and the salinity are low, the underwater sound velocity is further reduced compared to when only one of them is low, so it is more preferable to determine the position of the relay 21 based on both the water temperature and the salinity. Since pressure (depth) also affects the speed of sound in water, the position of the relay 21 may be determined in consideration of this pressure as well.

ここで、
ｃ：音速（m/s）
Ｔ：水温（℃）
Ｓ：塩分（ｐｅｒｍｉｌ）
Ｄ：水深（ｍ）
である。
水温と塩分と水深とを考慮する場合、このMackenzieの式に従って音速を求めることが好ましい。 A method for determining the position of the relay 21 on which the acoustic communication relay means 50 is mounted will be described in further detail.
Mackenzie's equation (Equation 1) is an equation that approximates the relationship between the water temperature, salinity, water depth, and the speed of sound in water.

here,
c: speed of sound (m/s)
T: water temperature (°C)
S: salinity (permil)
D: Water depth (m)
is.
Considering water temperature, salinity, and water depth, it is preferable to obtain the speed of sound according to Mackenzie's formula.

この場合、音速がもっとも小さくなる水深（音速極小点）は１０００ｍであり、水深６００ｍから１４００ｍが、音速が１４９０ｍ／ｓ以下となる音速が遅い層と言える。さらに水深８００ｍから１２００ｍが、音速が１４８６ｍ／ｓ以下となる音速がより遅い音速極小層と言える。
図２に示されるような、水面Ａの水温が３０℃にもなる水温の高い海域においては、音速の変化に与える影響は、水温の変化＞水深の変化＞塩分の変化の順に大きい。水面Ａの水温が低い海域においては、水温の変化よりも水深の変化や塩分の変化の影響が勝ってくる。
音速が遅い層は、水深に対する水温のプロファイル、塩分のプロファイル、及び水深によって異なってくるため、正確を期す場合は、適用海域の水温のプロファイル、塩分のプロファイル、及び水深に応じて、適宜、音速の遅くなる層を、式１等を用いて求めることが好ましい。より正確を期す場合は、水温、塩分、及び水深を例えば音響通信中継手段５０で計測し、式１等に基づいて音速を計算し、音速の遅い層に音響通信中継手段５０を配置することが好ましい。また、音速極小層に音響通信中継手段５０を配置することがさらに好ましい。 Using the relationship between water depth and water temperature shown in FIG. 2 and the relationship between water depth and salinity shown in FIG. The result is

In this case, the water depth at which the speed of sound is the lowest (minimum point of sound speed) is 1000 m, and it can be said that the depth of water from 600 m to 1400 m is the layer where the speed of sound is 1490 m/s or less. Furthermore, it can be said that the water depth of 800 m to 1200 m is the minimum sound velocity layer where the sound velocity is lower than 1486 m/s.
As shown in FIG. 2, in a high water temperature sea area where the water temperature of the water surface A is as high as 30 ° C, the effect on the change in the speed of sound is in the order of change in water temperature > change in water depth > change in salinity. In a sea area where the water temperature of the water surface A is low, the influence of changes in water depth and changes in salinity prevails over changes in water temperature.
Since the layer with slow sound velocity varies depending on the temperature profile, salinity profile, and water depth with respect to the water depth, if accuracy is desired, the sound velocity It is preferable to obtain the layer in which the is slowed down using Equation 1 or the like. If more accuracy is desired, the water temperature, salinity, and water depth can be measured, for example, by the acoustic communication relay means 50, the speed of sound can be calculated based on Equation 1, etc., and the acoustic communication relay means 50 can be placed in a layer where the speed of sound is slow. preferable. Further, it is more preferable to arrange the acoustic communication relay means 50 in the minimum sound velocity layer.

As described above, the underwater acoustic signal transmitted from the relay 21 placed underwater has a longer reach in the horizontal direction than the underwater acoustic signal transmitted from the ship 10 because the influence of water surface reflection is reduced. . Therefore, when the relay 21 transmits an acoustic signal in the lateral direction (horizontal direction) to perform acoustic communication with the underwater vehicle 22, the underwater vehicle 22, which is particularly distant in the horizontal direction, can be stabilized. can communicate with each other.

The intermediary 21 and the underwater vehicle 22 are provided with storage means 70 such as a hard disk drive or a semiconductor memory for storing data to be used for acoustic communication. 22 or after recovering the acoustic communication relay means 50 from the water, the data can be verified.
The data provided for acoustic communication can include position data such as self position and observed position. By including the position data, it is possible to correct the position of the ship 10, the intermediary body 21, or the underwater vehicle 22, and associate it with the data acquired by the underwater vehicle 22, or the like.

When acoustic communication between the relay acoustic communication means 41 of the relay 21 and the underwater vehicle acoustic communication means 42 of the underwater vehicle 22 becomes impossible, the relay 21 and the underwater vehicle 22 are made to surface on the water surface A. may
By surfacing early, the intermediary body 21 and the underwater vehicle 22 can be recovered before they are lost.
After the relay 21 and the underwater vehicle 22 surface on the water surface A, it is preferable to switch the communication between the ship 10 and the relay 21 and the underwater vehicle 22 to wireless communication using space.
Since sound waves are difficult to reach on water, switching to wireless communication facilitates communication even if the distance between the ship 10 and the floating relay 21 or the underwater vehicle 22 is long. Radio communication, optical communication, acoustic communication, etc. can be used as wireless communication using space.

A plurality of underwater vehicles 22 are each equipped with an acoustic communication relay means 50, and in addition to the relay 21 or instead of the relay 21, the underwater vehicles 22 existing in the predetermined area X communicate with the ship 10 by acoustic communication. Communication may be relayed.
As a result, the underwater vehicle 22 itself can also serve as a relay for acoustic communication. In addition, since each of the plurality of underwater vehicles 22 is provided with the acoustic communication relay means 50, even if one of the underwater vehicles 22 fails, indirect communication can be performed using the acoustic communication relay means 50 mounted on the other underwater vehicles 22. can be done.

Next, an underwater acoustic communication system according to a second embodiment of the present invention will be described. In addition, the same code|symbol is attached|subjected to the same function member as 1st Embodiment, and description is abbreviate|omitted.

FIG. 4 is a schematic configuration diagram of an underwater acoustic communication system according to a second embodiment of the present invention.
In this embodiment, a marine repeater (ASV: Autonomous Surface Vehicle) 11 is provided. This embodiment differs from the first embodiment in that an offshore repeater acoustic communication means 32 is provided as the communication means 30 . Communication between the ship 10 and the marine repeater 11 is performed by wireless communication using radio waves. By using the marine repeater 11, the range of activities of the underwater vehicle 22 can be further expanded.

The ship 10 and the ocean repeater 11 can grasp their positions by receiving GNSS signals from the GNSS satellites 1 .
The marine repeater 11 is used in a semi-submersible state in which the main body 11A is submerged in water at a depth of about 1.5 m and the upper part of the antenna 11B is above the water surface A.
The ship 10 and the marine repeater 11 transmit a search command and the like from the ship acoustic communication means 31 and the marine repeater acoustic communication means 32 to the underwater robot 20, and the observation data and the like transmitted from the underwater robot 20 are transmitted to the ship acoustic communication means. 31, received by the ocean repeater acoustic communication means 32;

The relay 21 and the underwater vehicle 22 transmit observation data and the like obtained by observation from the relay acoustic communication means 41 and the marine vehicle acoustic communication means 42 to the ship 10 and the marine relay 11. Commands and the like transmitted from the repeater 11 are received by the relay acoustic communication means 41 and the vehicle acoustic communication means 42 .
Acoustic communication relay means 50 mounted on relay 21 relays acoustic communication between ship 10 and underwater vehicle 22 . As a result, the ship 10 and the underwater vehicle 22 can perform indirect communication via the acoustic communication relay means 50 of the relay 21 .

The intermediary body 21 is located below the water surface A in a predetermined area X where acoustic signals from the ship 10 can easily reach, and is controlled so as not to exceed the predetermined area X.
The underwater vehicle 22 is located below the water surface A in a predetermined area Y where the acoustic signal from the ocean repeater 11 can easily reach.
Acoustic communication between the ship 10 and the underwater vehicle 22 is performed by acoustic communication relays mounted on the relay 21, at least when the underwater vehicle 22 is sailing beyond the predetermined regions X and Y. By performing indirect communication via means 50, communication interruption can be avoided. As a result, the range in which acoustic communication between the ship 10 and the underwater vehicle 22 is possible is expanded, and the range in which the underwater vehicle 22 can search is expanded.

In addition, the intermediary body 21 may be arranged in a predetermined area Y and controlled so as not to exceed the predetermined area Y. FIG. In this case, since the communication between the relay 21 and the ship 10 is performed via the offshore repeater 11, the ship 10 can omit the ship acoustic communication means 31 and is not affected by the position of the relay 21. can sail.

Next, an example of relay control of the acoustic communication relay means 50 will be described with reference to FIGS. 5 and 6. FIG. Although the first embodiment will be mainly described, the second embodiment is basically the same.

FIG. 5 is a flowchart showing relay control of the acoustic communication relay means when requesting establishment of acoustic communication from the ship to the underwater vehicle.
When the vessel 10 requests the underwater vehicle 22 to establish acoustic communication, the floating body acoustic communication means 30 transmits a first acoustic signal requesting the underwater vehicle 22 to reply. Since sound waves are non-directional, the first acoustic signal transmitted by the floating body acoustic communication means 30 is also received by the relay body acoustic communication means 41 of the relay body 21 located in the predetermined area X. When the relay acoustic communication means 41 receives the first acoustic signal, the relay control of the acoustic communication relay means 50 is started (step 1). In the second embodiment, the ship 10 transmits a signal requesting a response from the underwater vehicle 22 to the offshore repeater 11 by wireless communication, and the ship's acoustic signal is used as the first acoustic signal. Send from the communication means 31 . A signal by radio communication is converted into an acoustic signal by the ocean repeater 11 and transmitted from the ocean repeater acoustic communication means 32 as a first acoustic signal.
When the vehicle acoustic communication means 42 receives the first acoustic signal transmitted in step 1, the underwater vehicle 22 transmits a second acoustic signal notifying that the first acoustic signal has been received. It is transmitted from the acoustic communication means 42 . After receiving the first acoustic signal transmitted in step 1, the acoustic communication relay means 50 determines whether the relay body acoustic communication means 41 has received the second acoustic signal that should be transmitted from the underwater vehicle 22. Determine whether or not (step 2).
If it is determined in step 2 that the relay acoustic communication means 41 has received the second acoustic signal, the acoustic communication relay means 50 ends the relay control (step 3). This is because it can be determined that direct communication is possible between the ship 10 and the underwater vehicle 22 . In this case, acoustic communication between the ship 10 and the underwater vehicle 22 is performed by direct communication without the intermediary of the relay 21 .
If it is determined in step 2 that the relay acoustic communication means 41 has not received the second acoustic signal, the acoustic communication relay means 50 transmits the first acoustic signal received in step 1 to the relay acoustic communication. A call is sent from the means 41 (step 4). This is because it can be determined that the first acoustic signal transmitted in step 1 has not reached the vehicle acoustic communication means 42 .
When the vehicle acoustic communication means 42 receives the first acoustic signal transmitted in step 4, the underwater vehicle 22 transmits a second acoustic signal notifying that the first acoustic signal has been received. It is transmitted from the acoustic communication means 42 . After transmitting the first acoustic signal in step 4, the acoustic communication relay means 50 checks whether or not the relay body acoustic communication means 41 has received the second acoustic signal that should be transmitted from the underwater vehicle 22. Judge (step 5).
When it is determined in step 5 that the relay acoustic communication means 41 has received the second acoustic signal, the acoustic communication relay means 50 switches to indirect communication by the communication switching means 60 (step 6). This is because it can be determined that indirect communication is possible between the ship 10 and the underwater vehicle 22 . In this case, acoustic communication between the ship 10 and the underwater vehicle 22 is performed by indirect communication via the relay 21 .
If it is determined in step 5 that the relay acoustic communication means 41 has not received the second acoustic signal, the acoustic communication relay means 50 ends the relay control (step 7). This is because it can be determined that indirect communication between the ship 10 and the underwater vehicle 22 is also impossible. The intermediary body 21 may be floated and recovered. In the second embodiment, even in this case, there is a possibility that communication between the ship 10 and the underwater vehicle 22 is established via the ocean repeater 11 . Therefore, an acoustic signal indicating whether or not the ship 10 has received the second acoustic signal converted into radio waves by the marine repeater 11 may be transmitted from the ship acoustic communication means 31 to the relay 21. good.

In the ship 10, when the floating body acoustic communication means 30 does not receive the second acoustic signal, the floating body sends an acoustic signal asking whether or not the first acoustic signal has been transmitted (whether the operation of step 4 has been performed). The first acoustic signal transmitted from the acoustic communication means 30 to the relay 21 or transmitted from the relay acoustic communication means 41 in step 4 may be received by the floating body acoustic communication means 30 .

FIG. 6 is a flowchart for explaining the relay control of the acoustic communication relay means when requesting establishment of acoustic communication from the underwater vehicle to the ship.
When the underwater vehicle 22 requests the vessel 10 to establish acoustic communication, the underwater vehicle 22 transmits a third acoustic signal requesting the vessel 10 to reply from the vehicle acoustic communication means 42 . There is a possibility that the non-directional third acoustic signal transmitted by the vehicle acoustic communication means 42 can also be received by the relay acoustic communication means 41 . When the relay acoustic communication means 41 receives the third acoustic signal, the relay control of the acoustic communication relay means 50 is started (step 11). In addition, in the second embodiment, the third acoustic signal that has reached the marine repeater 11 is converted into radio waves and transmitted to the ship 10 by wireless communication.
When the floating body acoustic communication means 30 receives the third acoustic signal transmitted in step 11, the ship 10 transmits from the floating body acoustic communication means 30 a fourth acoustic signal notifying that the third acoustic signal has been received. . After receiving the third acoustic signal transmitted in step 11, the acoustic communication relay means 50 checks whether the relay body acoustic communication means 41 has received the fourth acoustic signal that should be transmitted from the ship 10. Make a decision (step 12). In the second embodiment, the ship 10 transmits a signal notifying that it has received the third acoustic signal to the marine repeater 11 by wireless communication, and the fourth acoustic signal is the ship acoustic signal. Send from the communication means 31 . A signal by wireless communication is converted into an acoustic signal by the ocean repeater 11 and transmitted from the ocean repeater acoustic communication means 32 as a fourth acoustic signal.
If it is determined in step 12 that the relay acoustic communication means 41 has received the fourth acoustic signal, the acoustic communication relay means 50 ends the relay control (step 13). This is because it can be determined that direct communication is possible between the ship 10 and the underwater vehicle 22 . In this case, acoustic communication between the ship 10 and the underwater vehicle 22 is performed by direct communication without the intermediary of the relay 21 .
If it is determined in step 12 that the relay acoustic communication means 41 has not received the fourth acoustic signal, the acoustic communication relay means 50 transmits the third acoustic signal received in step 11 to the relay acoustic communication. A call is sent from the means 41 (step 14). This is because it can be determined that the third acoustic signal transmitted in step 11 has not reached the floating body acoustic communication means 30 .
When the floating body acoustic communication means 30 receives the third acoustic signal transmitted in step 14, the ship 10 transmits from the floating body acoustic communication means 30 a fourth acoustic signal notifying that the third acoustic signal has been received. . After transmitting the third acoustic signal in step 14, the acoustic communication relay means 50 determines whether or not the relay body acoustic communication means 41 has received the fourth acoustic signal that should be transmitted from the ship 10 ( step 15). In the second embodiment, the ship 10 transmits a signal notifying that it has received the third acoustic signal to the marine repeater 11 by wireless communication, and the fourth acoustic signal is the ship acoustic signal. Send from the communication means 31 . A signal by wireless communication is converted into an acoustic signal by the ocean repeater 11 and transmitted from the ocean repeater acoustic communication means 32 as a fourth acoustic signal.
In step 15, when it is determined that the relay acoustic communication means 41 has received the fourth acoustic signal, the acoustic communication relay means 50 transmits the received fourth acoustic signal from the relay acoustic communication means 41. At the same time, switching to indirect communication is performed by the communication switching means 60 (step 16). This is because it can be determined that indirect communication is possible between the ship 10 and the underwater vehicle 22 . In this case, acoustic communication between the ship 10 and the underwater vehicle 22 is performed by indirect communication via the relay 21 .
If it is determined in step 15 that the relay acoustic communication means 41 has not received the fourth acoustic signal, the acoustic communication relay means 50 ends the relay control (step 17). This is because it can be determined that indirect communication between the ship 10 and the underwater vehicle 22 is also impossible. The intermediary body 21 may be floated and recovered. In this case, since the fourth acoustic signal does not reach the vehicle acoustic communication means 42, the underwater vehicle 22 is commanded to surface if it does not receive the fourth acoustic signal for a predetermined time. By providing it in advance, the underwater vehicle 22 can be surfaced and recovered. In the second embodiment, even in this case, there is a possibility that the ship 10 and the underwater vehicle 22 are able to communicate via the ocean repeater 11 . Therefore, an acoustic signal indicating whether or not the ship 10 has received the third acoustic signal converted into radio waves by the marine repeater 11 may be transmitted from the ship acoustic communication means 31 to the relay 21. good.

INDUSTRIAL APPLICABILITY The underwater acoustic communication system of the present invention can expand the range in which acoustic communication can be performed between a ship or the like near the surface of the water and an underwater robot during underwater exploration in the ocean, lakes, or the like. Exploration can be done.

22 Underwater Vehicle 30 Floating Body Acoustic Communication Means 40, 42 Vehicle Acoustic Communication Means 50 Acoustic Communication Relay Means 60 Communication Switching Means 70 Storage Means A Water Surface X Predetermined Area

Claims (13)

It is used in a sea area having a layer with a low underwater sound velocity of 1490 m/s or less and a high underwater layer with an underwater sound velocity of more than 1490 m/s, and can move on the water surface placed near the water surface. In an underwater acoustic communication system in which communication is performed using acoustic signals between a floating body acoustic communication means and a vehicle acoustic communication means provided on an underwater vehicle that travels in the water, below the water surface A predetermined area in a substantially conical range where the acoustic signal transmitted by the floating body acoustic communication means can easily reach, and the predetermined area is determined according to the underwater sound speed affected by water temperature, salinity, and water depth , an acoustic communication relay means capable of moving in the water, which is arranged in the layer with the slow underwater sound velocity of 1490 m/s or less among the layers with the high underwater sound velocity and the layers with the slow underwater sound velocity. and moving the acoustic communication relay means so as not to deviate from the predetermined area in the layer where the speed of sound in water is slow , following the movement of the floating body acoustic communication means on the water surface, and When sailing over the predetermined area, the acoustic communication relay means is placed in a layer of the predetermined area where the speed of sound in water is slow , and the water sails over the predetermined area with the acoustic communication relay means. Said underwater cruising , in which the intermediate cruising body is moved to a position where communication with the cruising body acoustic communication means is favorable , and the floating body acoustic communication means and the floating body acoustic communication means travel beyond the predetermined area via the acoustic communication relay means. An underwater acoustic communication system, wherein said vehicle acoustic communication means of a body performs acoustic communication. 2. An underwater acoustic communication system according to claim 1 , wherein said acoustic communication relay means transmits said acoustic signal laterally to perform said acoustic communication with said vehicle acoustic communication means. 3. The underwater acoustics according to claim 1 , wherein when the underwater vehicle exists in the predetermined area, direct communication is performed by the floating body acoustic communication means and the vehicle acoustic communication means . Communications system. 4. Underwater acoustics according to claim 3 , further comprising communication switching means for switching between said direct communication between said floating body acoustic communication means and said ship acoustic communication means, and indirect communication via said acoustic communication relay means. Communications system. 5. The underwater acoustic communication system according to claim 1 , wherein position data is included as data provided for said acoustic communication. 6. The underwater acoustic communication system according to claim 5 , wherein said position data is data obtained by receiving GNSS signals from GNSS satellites and grasping the self-position of said floating body acoustic communication means. 7. The floating body acoustic communication means according to claim 6 , wherein each of the plurality of floating body acoustic communication means receives the GNSS signals from the GNSS satellites and grasps the self position of each of the floating body acoustic communication means. Underwater acoustic communication system. 8. The underwater acoustic according to any one of claims 1 to 7 , wherein the underwater vehicle and/or the acoustic communication relay means has storage means for storing data to be used for the acoustic communication. Communications system. The apparatus according to any one of claims 1 to 8 , wherein a plurality of underwater vehicles are provided, and the acoustic communication relay means relays the acoustic signals of the plurality of underwater vehicles. An underwater acoustic communication system as described. 10. The underwater vehicle according to claim 9 , wherein a plurality of said underwater vehicles are each equipped with said acoustic communication relay means, and said underwater vehicle existing in said predetermined area relays said acoustic communication. Acoustic communication system. 10. An underwater acoustic communication system according to claim 1, wherein the moving speed of said acoustic communication relay means is slower than the running speed of said underwater vehicle. When the acoustic communication between the vehicle acoustic communication means and the acoustic communication relay means is disabled, the underwater vehicle and/or the acoustic communication relay means are floated to the surface of the water. An underwater acoustic communication system according to any one of claims 1 to 11 . After the underwater vehicle and/or the acoustic communication relay means rises to the surface of the water, the communication between the floating body acoustic communication means and the underwater vehicle and/or the acoustic communication relay means is performed wirelessly using space. 13. An underwater acoustic communication system according to claim 12 , characterized by switching to communication.

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