Bottom-of-water information collection system with information sharing function and bottom-of-water information collection method involving information sharing

Abstract

To achieve the construction of an information sharing network by multiple observation machines utilizing underwater optical wireless communication, allow bottom-of-water information from the observation machines to be confirmed on board a ship or the like before being retrieved, and reduce the loss of the bottom-of-water information when some of the observation machines are lost.SOLUTION: A bottom-of-water information collection system for collecting bottom-of-water information using multiple observation machines includes a total of three or more underwater vehicles 10 and underwater bottom-landing machines 20. The underwater vehicles 10 periodically approach the underwater bottom-landing machines 20 and perform underwater optical wireless communication with the underwater bottom-landing machines 20, and each time underwater optical wireless communication is performed, the underwater bottom-landing machines 20 store a copy of the bottom-of-water information that the underwater vehicles 10 have acquired by themselves or through underwater optical wireless communication with other observation machines, but that the own machines have not stored, and the underwater vehicles 10 store a copy of the bottom-of-water information that the underwater bottom-landing machines 20 have acquired by themselves or through underwater optical wireless communication with the other observation machines, but that the own vehicles have not stored.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water bottom information collection system with an information sharing function that uses an underwater vehicle that travels near the water bottom and observes the water bottom, and an underwater bottom-landing vehicle that is fixed in position on the water bottom and observes the surrounding water bottom, and a water bottom information collection method that involves information sharing. [Background technology]

[0002] Underwater vehicles such as AUVs (Autonomous Underwater Vehicles), which can navigate underwater without being constrained by a tether cable, are widely used as observation vehicles for detailed and efficient observation and exploration of the bottom of the ocean, etc. Another type of observation vehicle known as an underwater bottom-landing vehicle is one that remains fixed in position on the bottom and observes the surrounding area for a relatively long period of time. Underwater acoustic communication and underwater optical wireless communication are mainly used for underwater wireless communication between observation equipment. Underwater acoustic communication allows for long-distance communication of several hundred meters to several kilometers, but the communication speed is slow, at around several tens of bytes per second. It also has low directivity (highly isotropic). On the other hand, underwater optical wireless communication has a short-distance communication of several meters to several hundred meters, as the communication distance is strongly dependent on the light transmittance of the water near the bottom, but the communication speed is fast, at several megabytes per second. It also has high directivity and requires point-to-point communication. Here, Patent Document 1 discloses an underwater optical wireless communication system that includes a plurality of mobile bodies that can move underwater, each of which includes an optical wireless communication unit that performs two-way communication between the plurality of mobile bodies using communication light of different wavelengths for a plurality of irradiation directions that are opposite to each other, and is configured so that two-way communication is performed between the optical wireless communication unit of one of the plurality of mobile bodies and the optical wireless communication unit of another adjacent mobile body by emitting communication light from the optical wireless communication unit of one mobile body toward the optical wireless communication unit of the other mobile body, and by emitting communication light of a wavelength different from the emitted communication light from the optical wireless communication unit of the other mobile body and receiving it by the optical wireless communication unit of the one mobile body. Patent Document 2 also discloses an underwater power supply device in a charging system that includes an autonomous unmanned underwater vehicle (AUD) that explores the ocean, and an underwater power supply device that is carried to the vicinity of the AUD by another device and supplies power to the AUD, the underwater power supply device comprising: a first power transmission unit that supplies power to the AUD; and a first transceiver unit that transmits to the AUD an action plan that includes commands for the AUD, and receives from the AUD a search result indicating the results of the search performed in accordance with the commands, the first transceiver unit being positioned so that it can communicate with the AUD when the first power transmission unit is able to supply power to the AUD. Patent Document 3 also discloses an underwater visible light communication system in which a wavelength determination unit determines the strongest wavelength of light that reaches a visible light receiving unit of an observation device from among multiple types of visible light wavelengths emitted from a visible light emitting device of an underwater mobile body, the observation device selects the visible light of the wavelength determined by the wavelength determination unit as visible light to be transmitted, and radiates this visible light from the visible light emitting device into the water while incorporating observation data, and the visible light receiving unit of the underwater mobile body demodulates the received visible light to obtain the observation data. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7353610 [Patent Document 2] Japanese Patent Application Publication No. 2019-121167 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-278455 Summary of the Invention [Problem to be solved by the invention]

[0004] In underwater observations using multiple observation vehicles such as AUVs, each vehicle is equipped with a data storage device (memory device) for storing bottom information (observation data). After completing bottom observations, each vehicle is surfaced and retrieved onto a research vessel, where the bottom information stored in the data storage device is recovered. However, even when multiple observation vehicles simultaneously observe the bottom of a single body of water, the bottom information of each vehicle is stored independently, meaning that bottom information acquired by an unrecovered vehicle cannot be confirmed on board the vessel unless that vehicle is retrieved. Furthermore, if one of the observation vehicles is lost due to an accident or malfunction, the bottom information stored on that vehicle is also lost, resulting in a gap in the overall bottom information that was planned to be acquired. To minimize the loss of bottom information due to the loss of an observation device, it is possible to copy and share bottom information acquired by one observation device with other observation devices. In this case, if underwater acoustic communication, which allows long-distance communication, is used, bottom information can be sent and received without the observation devices being in close proximity to each other. However, underwater acoustic communication has a slow communication speed, so transmission takes time. In addition, because underwater acoustic communication has low directionality, underwater acoustic communication conflicts, interference, and signal interception by non-component receivers (other devices) can occur in the water area where communication is taking place. However, managing underwater acoustic communication, which is necessary to prevent these issues, is technically difficult. On the other hand, underwater optical wireless communication has the advantage of being capable of faster communication than underwater acoustic communication, and its high directivity means that it is less susceptible to problems such as interference with other communication devices and signal interception by other devices. The above-mentioned Patent Documents 1 to 3 disclose the use of underwater optical wireless communication for two-way communication underwater. However, Patent Document 1 aims to enable relay-based transmission and reception of control signals even when multiple AUVs are swapped, and does not enable recovery of bottom information from observation vehicles before recovery or prevent loss of bottom information due to loss of some observation vehicles. Patent Document 2 describes recovering bottom information without recovering the AUV by transmitting bottom information (search results) from the AUV to an underwater power supply device that travels between the surface and underwater. However, if the underwater power supply device is lost, all of the bottom information stored in the underwater power supply device will be lost. Patent Document 3 also describes an underwater exploration vehicle collecting bottom information from an observation device installed on the seabed. However, if the underwater exploration vehicle is lost, all of the bottom information stored in the underwater exploration vehicle will be lost. Therefore, the present invention aims to provide a bottom information collection system with an information sharing function that realizes the construction of an information sharing network using multiple observation devices that utilize underwater optical wireless communication, allows the bottom information acquired by the observation devices to be confirmed on board a ship or on land before recovery, and reduces the loss of bottom information when some of the observation devices are lost, as well as a bottom information collection method that involves information sharing. [Means for solving the problem]

[0005] The underwater information collection system with information sharing function according to claim 1 is a system for collecting underwater bottom information using a plurality of observation devices, and the observation devices are an underwater vehicle that acquires underwater bottom information while moving underwater, and an underwater bottom-landing device that is installed on the bottom of the water and acquires information on the surrounding bottom. The underwater vehicle has a vehicle optical communication means used for two-way underwater optical wireless communication, a vehicle observation means used to acquire the bottom information, and a vehicle information recording means that records the bottom information. The underwater bottom-landing device has a bottom-landing device optical communication means used for two-way underwater optical wireless communication, a bottom-landing device observation means used to acquire the bottom information, and a bottom-landing device information recording means that records the bottom information. The underwater vehicle periodically approaches the underwater bottom-reachable device and communicates with the underwater bottom-reachable device through underwater optical wireless communication, and each time underwater optical wireless communication is communicated, the underwater bottom-reachable device copies, to the bottom-reachable device information recording means, the bottom information that the underwater vehicle has acquired through its bottom-reachable device observation means or through underwater optical wireless communication with other observation devices and stored, but that the underwater vehicle has not stored, and the underwater vehicle copies, to the vehicle information recording means, the bottom information that the underwater vehicle has acquired through its bottom-reachable device observation means or through underwater optical wireless communication with other observation devices and stored, but that the vehicle has not stored. According to the present invention as set forth in claim 1, an information sharing network is constructed using multiple observation devices that use underwater optical wireless communication, and the bottom information acquired by each observation device is replicated to the other observation devices, which reduces the loss of bottom information when some observation devices are lost. In addition, by recovering the bottom information from one observation device, it becomes possible to confirm the bottom information acquired by the other observation devices before the device was recovered.

[0006] The present invention described in claim 2 is characterized in that the underwater vehicle further has a vehicle acoustic positioning means used for acoustic positioning using acoustic signals and a vehicle acoustic communication means used for two-way underwater acoustic wireless communication, and the underwater bottom-mounted device further has a bottom-mounted device positioning means that responds to the acoustic signals emitted from the vehicle acoustic positioning means and a bottom-mounted device acoustic communication means used for two-way underwater acoustic wireless communication, the underwater bottom-mounted device transmits the light irradiation direction of the bottom-mounted device optical communication means from the bottom-mounted device acoustic communication means to the underwater vehicle, the underwater vehicle determines a suitable optical communication position where the information communication speed of the underwater optical wireless communication is equal to or greater than a predetermined value based on the light irradiation direction received by the vehicle acoustic communication means, approaches the underwater bottom-mounted device until it reaches a suitable optical communication position while obtaining its relative position with the underwater bottom-mounted device by acoustic positioning using the vehicle acoustic positioning means, and performs underwater optical wireless communication with the underwater bottom-mounted device at the suitable optical communication position. According to the present invention as set forth in claim 2, underwater optical wireless communication between the underwater vehicle and the underwater bottom landing device is performed at an information communication speed equal to or higher than a predetermined value, and transmission and reception of bottom information can be completed in a short time.

[0007] The present invention described in claim 3 is characterized in that, after the underwater vehicle starts moving toward the underwater bottom-reachable device with which it will communicate with the underwater optical wireless communication, when the distance to the underwater bottom-reachable device becomes less than a predetermined value, it transmits a signal from the vehicle acoustic communication means to the underwater bottom-reachable device requesting permission for underwater optical wireless communication, and when the underwater optical wireless communication is permitted by the underwater bottom-reachable device, it transmits a light irradiation start request signal from the vehicle acoustic communication means to the underwater bottom-reachable device, and when the underwater bottom-reachable device receives the light irradiation start request signal, it begins light irradiation from the bottom-reachable device optical communication means and transmits the light irradiation direction from the bottom-reachable device acoustic communication means to the underwater vehicle. According to the present invention as set forth in claim 3, when the distance between the underwater vehicle and the underwater bottom-mounted device becomes close to a certain extent, it is confirmed whether underwater optical wireless communication is possible, and if it is determined that it is possible, light irradiation is started to the underwater bottom-mounted device, and the underwater vehicle can be brought close to a position suitable for optical communication.

[0008] The present invention described in claim 4 is characterized in that the underwater bottom-landing device further has a bottom-landing device imaging means used for photographing, and when it receives a signal from the underwater vehicle requesting permission for underwater optical wireless communication, it photographs the underwater vehicle using the bottom-landing device imaging means, and if the information obtained by the photographing matches the information about the underwater vehicle stored in advance in the device, it transmits a signal permitting underwater optical wireless communication from the bottom-landing device acoustic communication means to the underwater vehicle. According to the present invention as set forth in claim 4, underwater optical wireless communication with other devices that are not the target can be reliably prevented, thereby ensuring the safety of communication.

[0009] The present invention as described in claim 5 is characterized in that the underwater vehicle further has a vehicle imaging means used for photographing, and at a suitable position for optical communication, after the bottom-mounted device optical communication means starts light irradiation, the vehicle imaging means photographs the light irradiation status of the underwater bottom-mounted device, and from the photographed image, determines whether the vehicle optical communication means is facing the bottom-mounted device optical communication means or not, and if it is determined that they are not facing each other, adjusts the orientation of the vehicle so that they are facing each other, and if it is determined that they are facing each other, starts underwater optical wireless communication. According to the present invention as set forth in claim 5, the underwater vehicle's optical communication means is positioned to face the actual light irradiation direction of the underwater bottom-landing device confirmed by photography, so underwater optical wireless communication can be performed reliably.

[0010] The present invention as described in claim 6 is characterized in that the underwater vehicle measures the information communication speed of underwater optical wireless communication with the underwater bottom-landing device at a suitable position for optical communication, and if the measurement result is slower than a set value, it moves closer to the underwater bottom-landing device. According to the present invention as set forth in claim 6, it is possible to increase the possibility that the communication conditions of underwater optical wireless communication will be improved.

[0011] The present invention as described in claim 7 is characterized in that it comprises one underwater vehicle and multiple underwater bottom-landing devices, and the underwater vehicle performs underwater optical wireless communication with each of the underwater bottom-landing devices, so that bottom information acquired by one underwater bottom-landing device is copied to the bottom-landing device information recording means of the other underwater bottom-landing devices via the underwater vehicle. According to the present invention as set forth in claim 7, even in the case where there is only one underwater vehicle, the water bottom information acquired by one underwater bottom landing device can be shared with other underwater bottom landing devices.

[0012] The present invention as described in claim 8 is characterized in that it comprises a plurality of underwater vehicles and one underwater bottom-reach device, and each underwater vehicle communicates with the underwater bottom-reach device through underwater optical wireless communication, so that bottom information acquired by one underwater vehicle is copied to the vehicle information recording means of another underwater vehicle via the underwater bottom-reach device. According to the present invention as set forth in claim 8, even in the case where there is only one underwater bottom landing device, the bottom information acquired by one underwater vehicle can be shared with other underwater vehicles.

[0013] The present invention described in claim 9 is characterized in that when the underwater vehicle arrives at a suitable position for optical communication or when the distance to the suitable position for optical communication becomes less than a predetermined value, it measures the turbidity or optical attenuation length at the location, calculates a predetermined SN ratio ensuring distance, which is the distance to the underwater bottom-landing device at which a predetermined SN ratio can be ensured in underwater optical wireless communication, based on the measurement results, and approaches the underwater bottom-landing device until it becomes less than the calculated predetermined SN ratio ensuring distance. According to the present invention as set forth in claim 9, the underwater vehicle approaches the underwater bottom-landing device and performs underwater optical wireless communication until the distance is equal to or less than a predetermined signal-to-noise ratio ensuring distance, so that even if the water around the underwater bottom-landing device is more turbid than usual, the possibility of underwater optical wireless communication failing can be reduced.

[0014] The present invention as described in claim 10 is characterized in that when calculating the distance at which a predetermined signal-to-noise ratio is ensured, the underwater vehicle uses the maximum optical communication distance, which is the longest distance over which underwater optical wireless communication is possible between the vehicle's optical communication means and the bottom-mounted device's optical communication means in transparent water. According to the present invention as set forth in claim 10, the distance for ensuring a predetermined S / N ratio can be determined in consideration of the maximum optical communication distance.

[0015] The present invention as set forth in claim 11 is characterized in that the turbidity or the optical attenuation length is measured by an optical communication means of the vessel. According to the present invention as set forth in claim 11, it is possible to determine the distance ensuring a predetermined signal-to-noise ratio even for an underwater vehicle not equipped with a turbidity meter. Furthermore, by measuring using the same wavelength as that used in underwater optical wireless communication, wavelength conversion is not required when determining the optical attenuation length.

[0016] In a method for collecting information on the bottom of the water that involves information sharing according to claim 12, a method for collecting information on the bottom of the water by a plurality of observation devices, the observation devices include an underwater vehicle having a vehicle optical communication means for two-way underwater optical wireless communication, a vehicle observation means for acquiring the bottom information, and a vehicle information recording means for recording the bottom information, and acquiring the bottom information while moving underwater, and an underwater bottom-contacting device that is installed on the bottom of the water and acquires the bottom information of the surrounding area, and the underwater vehicle has a bottom-contacting device optical communication means for two-way underwater optical wireless communication, a bottom-contacting device observation means for acquiring the bottom information, and a bottom-contacting device information recording means for recording the bottom information, and the underwater vehicle is used in total of three or more observation devices. and a step of periodically approaching the underwater vehicle and the underwater bottom-mounting device that have been brought into close proximity, and causing the underwater vehicle and the underwater bottom-mounting device that have been brought into close proximity to each other to perform underwater optical wireless communication, and each time underwater optical wireless communication is established between the underwater vehicle and the underwater bottom-mounting device, the underwater bottom-mounting device copies, to the bottom-mounting device information recording means, the bottom information that the underwater vehicle has acquired by the bottom-mounting device observation means or acquired by underwater optical wireless communication with other observation devices and stored, but that the underwater vehicle has not stored, and the underwater vehicle copies, to the underwater bottom-mounting device information recording means, the bottom information that the underwater vehicle has acquired by the bottom-mounting device observation means or acquired by underwater optical wireless communication with other observation devices and stored, but that the vehicle has not stored. According to the present invention described in claim 10, an information sharing network is constructed using multiple observation devices that utilize underwater optical wireless communication, and the bottom information acquired by each observation device is replicated to other observation devices, thereby reducing the loss of bottom information when some observation devices are lost.

[0017] The present invention described in claim 13 is characterized in that after a step of having the underwater vehicle and the underwater bottom-landing device perform underwater optical wireless communication, a step is carried out of recovering the underwater vehicle or the underwater bottom-landing device, on board a ship or on land, in which the bottom information acquired by another observation device has been copied to the vehicle information recording means or the bottom-landing device information recording means, and retrieving the bottom information from the recovered underwater vehicle or the underwater bottom-landing device. According to the present invention as set forth in claim 13, by recovering any one of the underwater vehicles or underwater bottom landing devices and collecting bottom information, it is possible to confirm bottom information obtained by other observation devices before they were recovered.

[0018] The present invention described in claim 14 is characterized in that after a step of having the underwater vehicle and the underwater bottom-landing device perform underwater optical wireless communication, the following steps are carried out: floating the underwater vehicle or the underwater bottom-landing device, in which the bottom information acquired by another observation device has been copied to the vehicle information recording means or the bottom-landing device information recording means, until radio wireless communication is possible; and conducting radio wireless communication with the surfaced underwater vehicle or the underwater bottom-landing device from on board a ship or on land to retrieve the bottom information. According to the present invention as set forth in claim 14, by surfacing any one of the underwater vehicles or underwater bottom landing devices to retrieve bottom information, it is possible to also confirm bottom information obtained by other observation devices before they were surfaced.

[0019] The present invention described in claim 15 is characterized in that it has an ROV optical communication means for two-way underwater optical wireless communication and an ROV information recording means for recording bottom information, and after the steps of submerging an ROV (remotely operated underwater vehicle) connected to a ship by a tether cable and having the underwater vehicle and the underwater bottom-attaching device perform underwater optical wireless communication, it carries out the steps of bringing the ROV close to an underwater vehicle or underwater bottom-attaching device in which bottom information acquired by another observation device has been copied in the vehicle information recording means or bottom-attaching device information recording means, making the ROV perform underwater optical wireless communication with the approaching underwater vehicle or underwater bottom-attaching device and copy the bottom information held by the underwater vehicle or underwater bottom-attaching device to the ROV information recording means, and transmitting the bottom information copied by the ROV to the ship via the tether cable for recovery. According to the present invention described in claim 15, the ROV acquires bottom information from each observation device from one of the underwater vehicles or underwater bottom-landing devices and sends it to the ship, so that bottom information can be confirmed on board the ship without having to recover or surface the observation device. [Effects of the Invention]

[0020] According to the present invention, an information sharing network is constructed using multiple observation devices that utilize underwater optical wireless communication, so that the bottom information acquired by the observation devices can be confirmed on board a ship or on land before recovery, and the loss of bottom information can be reduced if some of the observation devices are lost. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 shows an underwater information communication network device according to a first embodiment of the present invention. [Figure 2-1] Flow of the underwater information sharing method [Figure 2-2] Flow of the underwater information sharing method [Figure 3] FIG. 10 is a diagram showing an underwater information communication network device according to a second embodiment of the present invention. [Figure 4-1] Flow of the underwater information sharing method [Figure 4-2] Flow of the underwater information sharing method [Figure 5] FIG. 10 is a diagram showing an underwater information communication network device according to a third embodiment of the present invention. [Figure 6-1] Flow of the underwater information sharing method [Figure 6-2] Flow of the underwater information sharing method [Figure 6-3] Flow of the underwater information sharing method [Figure 6-4] Flow of the underwater information sharing method [Figure 7] A diagram showing the accumulation status of the same bottom information [Figure 8] FIG. 10 is a diagram illustrating control taking into account a predetermined SN ratio ensuring distance for the underwater information communication network device in the first to third embodiments of the present invention. [Figure 9] Diagram of communication distance for underwater optical wireless communication DETAILED DESCRIPTION OF THE INVENTION

[0022] An embodiment of the underwater information communication network device and the underwater information sharing method using the underwater vehicle and the underwater bottom landing device of the present invention will be described. FIG. 1 is a diagram showing an underwater information communication network device in the first embodiment, and FIGS. 2-1 and 2-2 are flowcharts of a method for sharing underwater information in the first embodiment. The underwater information communication network device in the first embodiment is equipped with multiple observation devices that collect various data in observations of the bottom (seabed) 1 of oceans, lakes, and other bodies of water, long-term environmental surveys, etc., and builds a network for sharing underwater information using these observation devices on the bottom. In this embodiment, there are three observation devices in total: one underwater vehicle 10 that acquires bottom information (observation data) by photographing the bottom 1 while moving underwater, and two underwater landing devices 20 that are installed on the bottom 1 and acquire bottom information (observation data) by photographing the surrounding bottom 1. Each observation aircraft acquires information on the bottom of the ocean under the control of a research vessel (support vessel) located on the water. Note that each observation aircraft can also be controlled by an ASV (Autonomous Surface Vehicle) together with or instead of the research vessel.

[0023] The underwater vehicle 10 is a hovering AUV that navigates autonomously underwater without being tethered or manned. The underwater vehicle 10 is equipped with vertical and horizontal thrusters, giving it a high degree of freedom of movement and the ability to maintain its position even in places with water currents, making it ideal for precision observation work near the bottom of the water. The underwater vehicle 10 includes a depth meter / altimeter 101, a vehicle attitude (orientation) measurement means 102, an inertial navigation system (INS) 103 that performs positioning based on the measurement results of various underwater sensors such as an accelerometer and a gyroscope, a vehicle acoustic positioning means 104 that emits acoustic signals for acoustically positioning other observation vehicles, a vehicle acoustic position receiving means 105 such as an acoustic transponder that responds to acoustic signals emitted from a research vessel or the like, a vehicle acoustic communication means 106 that is used for two-way underwater acoustic wireless communication, and a two-way The vessel is equipped with a vessel optical communication means 107 used for underwater optical wireless communication (hereinafter also referred to as "optical communication") in the directional direction, a vessel observation means 108 used to acquire information about the bottom of the water, a vessel information recording means 109 such as a data storage device (memory device) for recording bottom information, a navigation means 110 having vertical and horizontal thrusters, a vessel radio wave wireless communication means 111 such as a wireless LAN antenna used for radio wave wireless communication with research vessels and the like on the water surface, and a vessel control means 112 for controlling each of these means and measuring devices. The vessel observation means 108 includes a vessel imaging means 108A such as an underwater camera, a pH meter 108B, and a turbidity meter 108C. The turbidity meter 108C is, for example, an infrared light backscattering type. The underwater vehicle acoustic positioning means 104 and the underwater vehicle acoustic communication means 106 may be, for example, a small underwater acoustic positioning system "SeaTrack X150" manufactured by Blueprint Subsea, Inc. The underwater vehicle optical communication means 107 may be, for example, an underwater optical wireless communication device "MC100" manufactured by Shimadzu Corporation.

[0024] The underwater bottom-landing device 20 comprises a main body 21 provided with a depth meter 201, a bottom-landing device attitude (orientation) measuring means 202, a bottom-landing device positioning means 203 such as an acoustic transponder that responds to acoustic signals emitted from a research vessel or underwater vehicle 10, etc., a bottom-landing device acoustic communication means 204 used for two-way underwater acoustic wireless communication, a bottom-landing device optical communication means 205 used for two-way underwater optical wireless communication, a bottom-landing device observation means 206 used to acquire bottom information, a bottom-landing device information recording means 207 such as a data storage device (memory device) that records bottom information, a bottom-landing device radio-wave wireless communication means 208 used for radio-wave wireless communication with a research vessel or the like on the water surface, and a bottom-landing device control means 209 that controls each of these means and measuring devices, etc., and a weight 22 that keeps the main body 21 on the bottom 1 of the water. The bottom-landing device observation means 206 includes a bottom-landing device imaging means 206A such as an underwater camera, a salinity meter 206B, and a water temperature meter 206C. When the underwater bottom landing device 20 is dropped onto the water surface from a research vessel, it sinks due to the weight of the sinker 22, and once it reaches the water bottom 1, it acquires bottom information without moving from that position. The sinker 22 is configured to be detached by sending a predetermined sonic signal from the research vessel, and when the sinker 22 is detached, the main body 21 rises to the surface.

[0025] The method for sharing information about the bottom of the water in the first embodiment will be described with reference to FIGS. 2-1 and 2-2. In step S1, a first underwater bottom-landing device 20A, one of two underwater bottom-landing devices 20, is lowered to the water surface using a launching facility from a research vessel that has reached a launching point in the target water area. When the first underwater bottom-landing device 20A is disconnected from the launching facility, it sinks, and when it hits the bottom, it begins acquiring bottom information using the bottom-landing device observation means 206, such as by photographing the nearby bottom 1. The bottom information acquired by the first underwater bottom-landing device 20A, that is, first bottom-landing information, is stored in the bottom-landing device information recording means 207, along with information on the name of the observation device that acquired the bottom information, the time of acquisition, and the location where it was acquired. In step S2, the research vessel has moved to the next deployment point, and another underwater landing device 20, the second underwater landing device 20B, is lowered to the water surface using the deployment equipment. The second underwater landing device 20B sinks when it is disconnected from the deployment equipment, and after it reaches the bottom, it begins acquiring bottom information using the bottom landing device observation means 206, such as by photographing the nearby bottom 1. The bottom information acquired by the second underwater landing device 20B, which is the second bottom landing information, is stored in the bottom landing device information recording means 207, along with information on the name of the observation device that acquired the bottom information, the time of acquisition, and the location where it was acquired. The second underwater landing device 20B is then landed, for example, several kilometers away from the first underwater landing device 20A. In step S3, the underwater vehicle 10 is lowered to the water surface from the research vessel using the launching facility. An observation plan, including the observation route and the timing of optical communication with the underwater bottom-landing device 20, is input into the underwater vehicle 10 before it is launched. When the underwater vehicle 10 is disconnected from the launching facility, it begins submerging and traveling underwater in accordance with the observation plan under the control of the vehicle control means 112, and first moves toward the first underwater bottom-landing device 20A while acquiring its relative position with the first underwater bottom-landing device 20A by acoustic positioning (step S4). The first underwater bottom-landing device 20A, as an underwater acoustic lighthouse, emits a response signal from the bottom-landing device positioning means 203 in response to the acoustic positioning signal from the underwater vehicle 10.

[0026] When the distance to the first underwater bottom-landing device 20A becomes equal to or less than a predetermined value, the underwater vehicle 10 transmits a signal to the first underwater bottom-landing device 20A via the vehicle acoustic communication means 106, requesting permission for optical communication (step S5). If optical communication is not permitted, the underwater vehicle 10 waits at its current position and, after a predetermined time has elapsed, transmits a signal to the first underwater bottom-landing device 20A requesting permission for optical communication again. If optical communication is not permitted even after repeating this process several times, the underwater vehicle 10 may begin moving toward the second underwater bottom-landing device 20B. When optical communication is permitted, the underwater vehicle 10 transmits a light irradiation start request signal to the first underwater bottom-landing device 20A via the vehicle acoustic communication means 106 (step S6). The first underwater bottom-landing device 20A, which has received the light irradiation start request signal via the bottom-landing device acoustic communication means 204, activates the bottom-landing device optical communication means 205 to start emitting light, and transmits the light irradiation direction (light irradiation azimuth) from the bottom-landing device acoustic communication means 204 to the underwater vehicle 10 (step S7). The light irradiation direction (light irradiation azimuth) is determined based on the attitude of the device itself measured by the bottom-landing device attitude (azimuth) measurement means 202. The underwater vehicle 10, having obtained the information on the light irradiation direction, determines a suitable position for optical communication where the information communication speed of optical communication with the first underwater bottom-mounting device 20A is equal to or greater than a predetermined value, approaches the first underwater bottom-mounting device 20A until it reaches the determined suitable position for optical communication, and maintains that position after reaching the suitable position for optical communication (step S8). The suitable position for optical communication depends on the underwater turbidity near the first underwater bottom-mounting device 20A and the performance of the vehicle optical communication means 107 and the bottom-mounting device optical communication means 205, but is expected to be, for example, a position about 5 m away from the first underwater bottom-mounting device 20A in the light irradiation direction. In this way, when the distance between the underwater vehicle 10 and the first underwater bottom-landing device 20A becomes close to a certain extent, it is confirmed whether underwater optical wireless communication is possible, and if it is determined that it is possible, the first underwater bottom-landing device 20A begins irradiating light, and the underwater vehicle 10 approaches to a position suitable for optical communication. The underwater vehicle 10 adjusts its own orientation at the suitable position for optical communication, aligns the light irradiation direction of the vehicle optical communication means 107 with the suitable heading for optical communication, and controls the navigation means 110 so that the light irradiation direction is maintained (step S9). The suitable heading for optical communication here is the direction opposite to the light irradiation direction of the bottom-mounted device optical communication means 205 of the first underwater bottom-mounted device 20A.

[0027] After step S9, the underwater vehicle 10 uses the vehicle imaging means 108A to photograph the shape of the other vehicle with which it has been communicating acoustically, assuming that the other vehicle is the first underwater bottom-landing vehicle 20A, as well as any symbols, numbers, barcodes, or two-dimensional codes attached to the vehicle. The underwater vehicle 10 compares the shape and other information acquired by photographing with information previously stored in the underwater vehicle 10 to determine whether the other vehicle is the first underwater bottom-landing vehicle 20A that it is communicating with (step S10). If the underwater vehicle 10 determines in step S10 that the underwater bottom-landing device is not the first underwater bottom-landing device 20A, it searches for the first underwater bottom-landing device 20A using the vehicle acoustic communication means 106 (step S11) and returns to step S4. This reliably prevents optical communication with other devices that are not the first underwater bottom-landing device 20A, ensuring communication security. Note that if the first underwater bottom-landing device 20A cannot be found even after searching for a predetermined period of time in step S11, the underwater vehicle 10 may proceed to step S15, where it may move to the second underwater bottom-landing device 20B and begin acquiring bottom information by photographing the bottom, for example. On the other hand, if it is determined in step S10 that it is the first underwater bottom-landing device 20A, the underwater vehicle 10 photographs the light irradiation status of the first underwater bottom-landing device 20A using the vehicle imaging means 108A, and determines from the photographed image whether the vehicle optical communication means 107 is facing in a direction suitable for optical communication, i.e., whether the vehicle optical communication means 107 and the bottom-landing device optical communication means 205 are facing each other (step S12). If the underwater vehicle 10 determines in step S12 that the vehicle optical communication means 107 is not facing the preferred orientation for optical communication, it readjusts its own orientation so that the vehicle optical communication means 107 faces the preferred orientation for optical communication (facing the bottom-mounted vehicle optical communication means 205) (step S13), and returns to step S12. On the other hand, if it is determined in step S12 that the underwater vehicle optical communication means 107 is oriented in a direction suitable for optical communication, the underwater vehicle 10 begins optical communication with the first underwater bottom-mounted device 20A (step S14). Because the first underwater bottom-mounted device 20A may be tilted vertically or horizontally due to water currents, as in this embodiment, the actual light irradiation direction of the first underwater bottom-mounted device 20A is confirmed by photographing, and the light irradiation direction of the device itself is adjusted if necessary, thereby enabling optical communication to be performed more stably and reliably.

[0028] In step S14, the underwater vehicle 10 and the first underwater landing device 20A each acquire a copy of the water bottom information not stored in their own device from the other device via optical communication. In the first step S14, the underwater vehicle 10 has not yet acquired the water bottom information, so the water bottom information of the underwater vehicle 10 is not duplicated in the first underwater landing device 20A. Meanwhile, the underwater vehicle 10 receives a copy of the first bottom contact information stored in the bottom contact device information recording means 207 of the first underwater landing device 20A and records it in its own underwater vehicle information recording means 109. This backs up the first bottom contact information to the underwater vehicle 10. Furthermore, in step S14, the underwater vehicle 10 preferably measures the information communication speed of the optical communication before starting to send and receive bottom information, and if the result is slower than a set value, controls to move closer to the first underwater bottom-landing device 20A. This improves the optical communication conditions and increases the possibility of sending and receiving bottom information at high speed. When reapproaching, the underwater vehicle 10 is designed to maintain a distance of at least 2 m from the first underwater bottom-landing device 20A, for example, because getting too close may result in contact. The underwater vehicle 10 stably maintains a suitable position and a suitable orientation for optical communication by acoustic positioning and acoustic communication with the first underwater bottom-landing device 20A until optical communication with the first underwater bottom-landing device 20A is completed. This allows optical communication between the underwater vehicle 10 and the first underwater bottom-landing device 20A to be performed at an information communication speed equal to or higher than a predetermined value, and enables the transmission and reception of bottom information to be completed in a short time. After optical communication is completed, the process proceeds to step S15, where the underwater vehicle 10 starts moving toward the second underwater bottom landing device 20B and starts acquiring bottom information using the vehicle observation means 108. The bottom information acquired by the underwater vehicle 10, i.e., the traveling bottom information, is stored in the vehicle information recording means 109, along with information on the name of the observation device that acquired the bottom information, the time of acquisition, and the location where it was acquired.

[0029] In step S15, the underwater vehicle 10 moves toward the second underwater bottom-landing device 20B while confirming its relative position with the second underwater bottom-landing device 20B by acoustic positioning. The second underwater bottom-landing device 20B, as an underwater acoustic lighthouse, emits a response signal from the bottom-landing device positioning means 203 in response to the acoustic positioning signal from the underwater vehicle 10. When the distance to the second underwater bottom-landing device 20B becomes equal to or less than a predetermined value, the underwater vehicle 10 transmits a signal to the second underwater bottom-landing device 20B via the vehicle acoustic communication means 106, requesting permission for optical communication (step S16). If optical communication is not permitted, the underwater vehicle 10 waits at its current position and, after a predetermined time has elapsed, transmits a signal to the second underwater bottom-landing device 20B again requesting permission for optical communication. If optical communication is not permitted even after repeating this process several times, the underwater vehicle 10 may begin moving toward the first underwater bottom-landing device 20A. When optical communication is permitted, the underwater vehicle 10 transmits a light irradiation start request signal to the second underwater bottom-landing device 20B via the vehicle acoustic communication means 106 (step S17). The second underwater bottom-landing device 20B, which receives the light irradiation start request signal via the bottom-landing device acoustic communication means 204, activates the bottom-landing device optical communication means 205 to start emitting light, and transmits the light irradiation direction (light irradiation azimuth) from the bottom-landing device acoustic communication means 204 to the underwater vehicle 10 (step S18). Having obtained the information on the direction of light irradiation, the underwater vehicle 10 determines a suitable position for optical communication where the information communication speed for optical communication with the second underwater bottom-landing device 20B is equal to or greater than a predetermined value, approaches the second underwater bottom-landing device 20B until it reaches the determined suitable position for optical communication, and maintains that position after reaching the suitable position for optical communication (step S19). The underwater vehicle 10 adjusts its own orientation at the suitable position for optical communication, aligns the light irradiation direction of the vehicle's optical communication means 107 with the suitable orientation for optical communication, and controls the navigation means 110 so that the light irradiation direction is maintained (step S20). The suitable orientation for optical communication here is the direction opposite to the light irradiation direction of the bottom-mounted device optical communication means 205 of the second underwater bottom-mounted device 20B.

[0030] After step S20, the underwater vehicle 10 uses the vehicle imaging means 108A to photograph the shape of the other vehicle with which acoustic communication has been conducted, assuming it is the second underwater bottom-landing vehicle 20B, as well as any symbols, numbers, barcodes, or two-dimensional codes attached to the vehicle. The underwater vehicle 10 compares the shape and other information acquired by photographing with information previously stored in the underwater vehicle 10 to determine whether the other vehicle is the second underwater bottom-landing vehicle 20B that is the communication target (step S21). If the underwater vehicle 10 determines in step S21 that the underwater vehicle is not the second underwater bottom-landing device 20B, it searches for the second underwater bottom-landing device 20B using the vehicle acoustic communication means 106 (step S22) and returns to step S15. This reliably prevents optical communication with other devices that are not the second underwater bottom-landing device 20B, ensuring communication security. Note that if the second underwater bottom-landing device 20B cannot be found even after searching for a predetermined period of time in step S22, the underwater vehicle 10 may proceed to step S4, where it begins moving toward the first underwater bottom-landing device 20A. On the other hand, if it is determined in step S21 that it is the second underwater bottom-landing device 20B, the underwater vehicle 10 photographs the light irradiation status of the second underwater bottom-landing device 20B using the vehicle imaging means 108A, and determines from the photographed image whether the vehicle optical communication means 107 is facing in a direction suitable for optical communication (step S23). If the underwater vehicle 10 determines in step S23 that the vehicle's optical communication means 107 is not facing the direction suitable for optical communication, it readjusts its own orientation so that the vehicle's optical communication means 107 faces the direction suitable for optical communication (step S24) and returns to step S23. On the other hand, if it is determined in step S23 that the underwater vehicle optical communication means 107 is oriented in a direction suitable for optical communication, the underwater vehicle 10 starts optical communication with the second underwater bottom-landing vehicle 20B (step S25).

[0031] In step S25, the underwater vehicle 10 and the second underwater landing device 20B each acquire a copy of the bottom information not stored in their own device from the other device via optical communication. In the first step S25, the underwater vehicle 10 receives a copy of the second bottom contact information stored in the bottom contact device information recording means 207 of the second underwater landing device 20B and records it in its own underwater vehicle information recording means 109, and the second underwater landing device 20B receives copies of the first bottom contact information and the traveling bottom information stored in the underwater vehicle information recording means 109 of the underwater vehicle 10 and records them in its own bottom contact device information recording means 207. As a result, the second bottom contact information is backed up to the underwater vehicle 10, and the first bottom contact information and the traveling bottom information are backed up to the second underwater landing device 20B. In step S25, as in step S14, it is preferable that the underwater vehicle 10 measures the information communication speed of the optical communication before starting to send and receive bottom information, and if the result is slower than the set value, control is performed to move closer to the second underwater bottom landing device 20B. The underwater vehicle 10 stably maintains a suitable position and orientation for optical communication by acoustic positioning and acoustic communication with the second underwater bottom-landing device 20B until optical communication with the second underwater bottom-landing device 20B is completed. After the optical communication is completed, the process proceeds to step S4, and the underwater vehicle 10 moves again toward the first underwater bottom landing device 20A while acquiring navigation bottom information.

[0032] After proceeding to step S4, the underwater vehicle 10 proceeds to step S14, as in the previous step, and performs optical communication with the first underwater bottom-contacting device 20A. In this second step S14, the underwater vehicle 10 receives a copy of the latest first bottom-contacting information from the first underwater bottom-contacting device 20A and updates the first bottom-contacting information stored in the underwater vehicle 10. This update is preferably performed as a differential backup to reduce time. The first underwater bottom-contacting device 20A also receives copies of the second bottom-contacting information and the traveling bottom information stored in the underwater vehicle 10's vehicle information recording means 109 and records them in its own bottom-contacting device information recording means 207. This updates the first bottom-contacting information backed up in the underwater vehicle 10, and backs up the second bottom-contacting information and the traveling bottom information to the first underwater bottom-contacting device 20A. After the optical communication is completed, the process proceeds to step S15, and the underwater vehicle 10 moves again toward the second underwater bottom landing device 20B while acquiring navigation water bottom information. In the same manner, the underwater vehicle 10 continues to share data by optical communication by traveling back and forth between the first underwater bottom-landing device 20A and the second underwater bottom-landing device 20B until the exploration time or number of explorations reaches a predetermined value. Note that the underwater vehicle 10 does not need to take the same route each time it moves between the underwater bottom-landing devices 20, and can take different routes to expand the observation range.

[0033] Thus, according to this embodiment, a bottom information sharing network is established on the bottom 1 between the underwater vehicle 10 and the underwater bottom landing device 20, with other observation devices as the information sharing destinations, and the underwater vehicle 10, the first underwater bottom landing device 20A, and the second underwater bottom landing device 20B mutually back up navigation bottom information, first bottom landing information, and second bottom landing information, which are updated with each optical communication, increasing the amount of backup. Therefore, if a step of recovering bottom information by recovering at least one observation device on board or on land is performed, bottom information acquired by other observation devices can also be recovered, so that even if one observation device is lost, the amount of bottom information lost can be reduced. Furthermore, if one of the observation instruments is recovered, not only can the bottom information from that instrument be retrieved, but also partial bottom information (backup data) from the other instruments can be retrieved, making it possible to confirm a large amount of bottom information on board or on land without waiting for the other instruments to be recovered.In addition, if the steps of surfacing the observation instrument until radio wireless communication is possible and transmitting bottom information from the surfaced observation instrument to the research vessel or a land base station via radio wireless communication (including satellite communication) using the underwater body radio wireless communication means 111 or the bottom-mounted instrument radio wireless communication means 208 are performed, it will also be possible to confirm a large amount of bottom information on board or on land without waiting for the other instruments to surface, etc.

[0034] The network for sharing information on the bottom of the water by the underwater vehicle 10 and the underwater bottom landing device 20 of this embodiment can be constructed by using at least one wavelength in the optical communication wavelength band and one frequency in the acoustic communication band. It is also easy for new nodes (new observation devices) to join the shared network that has been constructed, and for nodes (observation devices) that were previously in the network to leave. Furthermore, by transmitting bottom information between the underwater vehicle 10 and the underwater landing device 20 using optical communication, large volumes of bottom information can be copied and exchanged more quickly and securely than with acoustic communication. Furthermore, since the underwater vehicle 10 stably maintains the optical communication suitable position and orientation until the optical communication is completed, the possibility of communication being cut off midway can be reduced.

[0035] The observation device may also be a tethered ROV (Remotely Operated Vehicle) connected to the research vessel by a tether cable. The ROV has an ROV optical communication means for two-way underwater optical wireless communication and an ROV information recording means for recording bottom information. When an ROV is used, the system performs the following steps: periodically having the submerged ROV approach one of the underwater vehicles 10 or underwater bottom-landing devices 20; optically communicating with the approaching underwater vehicle 10 or underwater bottom-landing device 20 to copy the bottom information stored in the ROV to the other device; and transmitting the copied bottom information to the research vessel via wired communication via the tether cable for collection. This allows not only the bottom information acquired by the ROV but also the bottom information copied by the ROV from the underwater vehicle 10 or underwater bottom-landing device 20 to be viewed on board the vessel.

[0036] Furthermore, when the underwater bottom-landing device 20 receives a signal requesting permission for optical communication transmitted from the underwater vehicle 10 in step S5 or step S16, it may photograph the underwater vehicle 10 using the bottom-landing device imaging means 206A, and only if the information acquired by the photograph matches information about the underwater vehicle 10 previously stored in the underwater bottom-landing device 20, it may transmit a signal permitting optical communication from the bottom-landing device acoustic communication means 204 to the underwater vehicle 10. This reliably prevents optical communication with other devices that are not the target, ensuring the safety of communication.

[0037] Next, a second embodiment of the present invention will be described. Note that the same components as those in the above embodiment will be denoted by the same reference numerals and the description thereof will be omitted. FIG. 3 is a diagram showing an underwater information communication network device in the second embodiment, and FIGS. 4-1 and 4-2 are flowcharts of a method for sharing underwater information in the second embodiment. The underwater information communication network device in the second embodiment comprises two underwater vehicles 10 and one underwater bottom landing vehicle 20 as observation devices, and constructs a network on the bottom of the sea for sharing information about the bottom using these observation devices.

[0038] In step S101, the underwater bottom landing device 20 is lowered to the water surface using the launching equipment from the research vessel that has arrived at the launching point. The underwater bottom landing device 20 sinks when it is disconnected from the launching equipment, and when it hits the bottom, it starts acquiring bottom information using the bottom landing device observation means 206, such as by taking pictures of the nearby bottom 1. The bottom landing information acquired by the underwater bottom landing device 20 is stored in the bottom landing device information recording means 207, along with information on the name of the observation device that acquired the bottom information, the time of acquisition, and the acquisition location. In step S102, the first underwater vehicle 10A, which is one of the two underwater vehicles 10, is lowered to the water surface from the research vessel using the launching facility. When the first underwater vehicle 10A is disconnected from the launching facility, it begins diving and traveling underwater according to the observation plan under the control of the vehicle control means 112, and first moves toward the underwater bottom-landing vehicle 20 while acquiring its relative position with respect to the underwater bottom-landing vehicle 20 by acoustic positioning (step S103). In step S104, a predetermined time after the first underwater vehicle 10A is launched, a second underwater vehicle 10B, which is another underwater vehicle 10, is lowered to the water surface from the research vessel using the launching facility. When the second underwater vehicle 10B is disconnected from the launching facility, it begins diving and traveling underwater according to the observation plan under the control of the vehicle control means 112, and first moves toward the underwater bottom-landing device 20 while acquiring its relative position with respect to the underwater bottom-landing device 20 by acoustic positioning (step S105).

[0039] When the distance to the underwater bottom-landing device 20 falls below a predetermined value, the first underwater vehicle 10A transmits a signal to the underwater bottom-landing device 20 via the vehicle acoustic communication means 106 requesting permission for optical communication (step S106). If optical communication is not permitted, the first underwater vehicle 10A waits at its position and, after a predetermined time has elapsed, transmits a signal to the underwater bottom-landing device 20 requesting permission for optical communication again. If optical communication is permitted, the first underwater vehicle 10A transmits a light irradiation start request signal from the vehicle acoustic communication means 106 to the underwater bottom-landing device 20 (step S107). When the underwater bottom-landing device 20 receives the light irradiation start request signal via the bottom-landing device acoustic communication means 204, it activates the bottom-landing device optical communication means 205 to start emitting light, and transmits the light irradiation direction (light irradiation orientation) from the bottom-landing device acoustic communication means 204 to the first underwater vehicle 10A (step S108). The first underwater vehicle 10A, having obtained information on the direction of light irradiation, determines a suitable position for optical communication where the information communication speed for optical communication with the underwater bottom-landing device 20 is equal to or greater than a predetermined value, approaches the underwater bottom-landing device 20 until it reaches the determined suitable position for optical communication, and after reaching the suitable position for optical communication, maintains that position (step S109). The first underwater vehicle 10A adjusts its orientation at a suitable position for optical communication, aligns the light irradiation direction of the vehicle's optical communication means 107 with the suitable orientation for optical communication, and controls the navigation means 110 so that the irradiation direction is maintained (step S110).

[0040] After step S110, the first underwater vehicle 10A uses the vehicle imaging means 108A to photograph the shape of the other vehicle with which it has been communicating acoustically, assuming it is an underwater bottom-landing vehicle 20, as well as any symbols, numbers, bar codes, or two-dimensional codes attached to the vehicle. The first underwater vehicle 10A compares the shape and other information acquired by photographing with information previously stored in the first underwater vehicle 10A to determine whether the other vehicle is the underwater bottom-landing vehicle 20 that it is communicating with (step S111). If the first underwater vehicle 10A determines in step S111 that the underwater bottom-landing device 20 is not the underwater bottom-landing device 20, it searches for the underwater bottom-landing device 20 using the underwater vehicle acoustic communication means 106 (step S112) and returns to step S103. This reliably prevents optical communication with other devices that are not underwater bottom-landing devices 20, ensuring the safety of communication. On the other hand, if it is determined in step S111 that the underwater bottom-landing device 20 is the underwater bottom-landing device, the first underwater vehicle 10A photographs the light illumination status of the underwater bottom-landing device 20 using the vehicle imaging means 108A, and determines from the photographed image whether the vehicle optical communication means 107 is facing in a direction suitable for optical communication (step S113). If the first underwater vehicle 10A determines in step S111 that the vehicle's optical communication means 107 is not facing the direction suitable for optical communication, it readjusts its own orientation so that the vehicle's optical communication means 107 faces the direction suitable for optical communication (step S114) and returns to step S113. On the other hand, if it is determined in step S113 that the underwater vehicle optical communication means 107 is oriented in a direction suitable for optical communication, the first underwater vehicle 10A starts optical communication with the underwater bottom landing device 20 (step S115).

[0041] In step S115, the first underwater vehicle 10A and the underwater bottom-contacting device 20 each acquire a copy of the water bottom information not stored in their own vehicle from the other device via optical communication. In the first step S115, the first underwater vehicle 10A has not yet acquired the water bottom information, so the water bottom information of the first underwater vehicle 10A is not duplicated in the underwater bottom-contacting device 20. Meanwhile, the first underwater vehicle 10A receives a copy of the bottom-contacting information stored in the bottom-contacting device information recording means 207 of the underwater bottom-contacting device 20 and records it in its own vehicle information recording means 109. This backs up the bottom-contacting information to the first underwater vehicle 10A. Until optical communication with the underwater bottom-contacting device 20 is completed, the first underwater vehicle 10A stably maintains the optical communication suitable position and optical communication suitable orientation for optical communication by acoustic positioning and acoustic communication with the underwater bottom-contacting device 20. In the second embodiment, as in the first embodiment, it is preferable that the first underwater vehicle 10A measures the information communication speed of the optical communication before starting to send and receive bottom information, and if the result is slower than the set value, control is performed to move closer to the underwater bottom landing device 20. After optical communication is completed, the first underwater vehicle 10A moves away from the underwater bottom landing device 20 and begins acquiring bottom information using the vehicle observation means 108, such as photographing the bottom 1 (step S116). The first underwater bottom information acquired by the first underwater vehicle 10A is stored in the vehicle information recording means 109, along with information on the name of the observation device that acquired the bottom information, the time of acquisition, and the location where it was acquired.

[0042] On the other hand, the second underwater vehicle 10B, which was launched a predetermined time later than the first underwater vehicle 10A, executes steps S117 to S127 after step S105. Steps S117 to S127 are similar to steps S106 to S116 for the first underwater vehicle 10A, and therefore will not be described here. After step S127, the first underwater vehicle 10A and the second underwater vehicle 10B alternately perform optical communication with the underwater bottom landing device 20 at predetermined time intervals. In the second optical communication between the first underwater vehicle 10A and the underwater bottom-landing device 20, the first underwater vehicle 10A receives a copy of the latest bottom-landing information from the underwater bottom-landing device 20 and updates the bottom-landing information stored in the first underwater vehicle 10A. The underwater bottom-landing device 20 also receives a copy of the first underwater bottom information from the first underwater vehicle 10A and records it in its own bottom-landing device information recording means 207. This causes the first underwater bottom information to be backed up in the underwater bottom-landing device 20. In the second optical communication between the second underwater vehicle 10B and the underwater bottom landing device 20, the second underwater vehicle 10B receives a copy of the latest bottom landing information and a copy of the first underwater bottom information from the underwater bottom landing device 20, updates the bottom landing information stored in its own underwater vehicle information recording means 109, and records the first underwater bottom information. As a result, the first underwater bottom information is backed up to the second underwater vehicle 10B. In addition, the underwater bottom landing device 20 receives a copy of the second underwater bottom information, which is the bottom information acquired by the second underwater vehicle 10B, from the second underwater vehicle 10B and records it in its own bottom landing device information recording means 207. As a result, the second underwater bottom information is backed up to the underwater bottom landing device 20. In the third optical communication between the first underwater vehicle 10A and the underwater bottom landing device 20, the first underwater vehicle 10A receives a copy of the latest bottom landing information and a copy of the second underwater bottom information from the underwater bottom landing device 20, updates the bottom landing information stored in its own vehicle information recording means 109, and records the second underwater bottom information. This backs up the second underwater bottom information to the first underwater vehicle 10A. The underwater bottom landing device 20 also receives the latest first underwater bottom information from the first underwater vehicle 10A and updates the first underwater bottom information stored in its own vehicle. In this way, in this embodiment too, a sharing network for bottom information is constructed between the underwater vehicle 10 and the underwater bottom landing device 20, and the first underwater vehicle 10A, the second underwater vehicle 10B, and the underwater bottom landing device 20 mutually back up the first underwater bottom information, the second underwater bottom information, and the bottom landing information, which are updated each time optical communication is performed, increasing the amount of backup information.

[0043] In the second embodiment, the first underwater vehicle 10A and the second underwater vehicle 10B copy each other's bottom information via the underwater landing device 20, but it is also possible to perform optical communication between the first underwater vehicle 10A and the second underwater vehicle 10B and directly copy the bottom information held by each other.

[0044] Next, a third embodiment of the present invention will be described. Note that the same components as those in the above-described embodiment will be denoted by the same reference numerals and the description thereof will be omitted. Figure 5 shows a diagram of an underwater information communication network device in the third embodiment, Figures 6-1 to 6-4 show the flow of the underwater information sharing method in the third embodiment, and Figure 7 shows the accumulation status of underwater information in the third embodiment. The underwater information communication network device in the third embodiment is equipped with two underwater vehicles 10 and two underwater bottom landing vehicles 20 as observation devices, and a network for sharing underwater information by these observation devices is constructed on the bottom of the sea.

[0045] In step S201, a first underwater bottom-landing device 20A, one of two underwater bottom-landing devices 20, is lowered to the water surface using a launching facility from the research vessel that has arrived at the launching point. When the first underwater bottom-landing device 20A is disconnected from the launching facility, it sinks, and when it hits the bottom, it starts acquiring bottom information using the bottom-landing device observation means 206, such as by photographing the nearby bottom 1. The bottom information acquired by the first underwater bottom-landing device 20A, that is, first bottom-landing information, is stored in the bottom-landing device information recording means 207, along with information on the name of the observation device that acquired the bottom information, the time of acquisition, and the location where it was acquired. In step S202, the research vessel has moved to the next deployment point and another underwater bottom-landing device 20, the second underwater bottom-landing device 20B, is lowered to the water surface using the deployment equipment. When the second underwater bottom-landing device 20B is disconnected from the deployment equipment, it sinks, and when it hits the bottom, it starts acquiring bottom information using the bottom-landing device observation means 206, such as by photographing the nearby bottom 1. The bottom information acquired by the second underwater bottom-landing device 20B, that is, the second bottom-landing information, is stored in the bottom-landing device information recording means 207, along with information on the name of the observation device that acquired the bottom information, the time of acquisition, and the location where it was acquired. The distance between the first underwater bottom landing device 20A and the second underwater bottom landing device 20B is set to a distance that the underwater vehicle 10 can travel in just under an hour, and for example, if the movement speed of the underwater vehicle 10 is 0.2 m / s, the distance is within 0.2 m / s * 3600 seconds = 720 m.

[0046] In step S203, the first underwater vehicle 10A, which is one of the two underwater vehicles 10, is lowered to the water surface from the research vessel using the launching facility. When the first underwater vehicle 10A is disconnected from the launching facility, it begins submerging and traveling underwater according to the observation plan under the control of the vehicle control means 112, and first moves toward the first underwater bottom-landing vehicle 20A while acquiring its relative position with the first underwater bottom-landing vehicle 20A by acoustic positioning (step S204). In step S205, a predetermined time after the first underwater vehicle 10A is launched, a second underwater vehicle 10B, another underwater vehicle 10, is lowered to the water surface from the research vessel using the launching facility. When the second underwater vehicle 10B is disconnected from the launching facility, it begins submerging and traveling underwater according to the observation plan under the control of the vehicle control means 112, and first moves toward the first underwater bottom-landing vehicle 20A while acquiring its relative position with respect to the first underwater bottom-landing vehicle 20A by acoustic positioning (step S206).

[0047] The first underwater vehicle 10A, which has started moving to the first underwater landing vehicle 20A in step S204, executes steps S207 to S216. Steps S207 to S216 are substantially the same as steps S5 to S14 in the first embodiment, and therefore a description thereof will be omitted. After step S216, the first underwater vehicle 10A proceeds to step S217, where it leaves the first underwater bottom-reachable device 20A and begins moving toward the second underwater bottom-reachable device 20B and acquiring bottom information. From this point on, the first underwater vehicle 10A travels back and forth between the first underwater bottom-reachable device 20A and the second underwater bottom-reachable device 20B along a survey line approximately every hour, acquiring bottom information during that time. Steps S217 to S227 are substantially similar to steps S15 to S25 in the first embodiment, and therefore will not be described here. After step S227, the first underwater vehicle 10A proceeds to step S204. The second underwater vehicle 10B, which is launched a predetermined time later than the first underwater vehicle 10A and begins moving toward the first underwater landing device 20A in step S206, executes steps S228 to S237. Steps S228 to S237 are substantially the same as steps S117 to S126 in the second embodiment, and therefore will not be described here. After S237, the second underwater vehicle 10B proceeds to step S238, where it leaves the first underwater bottom-reachable device 20A and begins moving toward the second underwater bottom-reachable device 20B and acquiring bottom information. From this point on, the second underwater vehicle 10B travels back and forth along a survey line between the first underwater bottom-reachable device 20A and the second underwater bottom-reachable device 20B approximately every hour, acquiring bottom information during that time. Steps S239 to S248 are substantially similar to steps S117 to S126 in the second embodiment, and therefore will not be described here. After step S248, the second underwater vehicle 10B proceeds to step S206. Thereafter, the first underwater vehicle 10A and the second underwater vehicle 10B alternately perform optical communication with the first underwater bottom landing device 20A and the second underwater bottom landing device 20B at predetermined time intervals.

[0048] An example of the progress of sharing of bottom information in the third embodiment will be described with reference to FIG. In Figure 7, the first column is the elapsed time [h] from the start of work, the second column is the bottom information stored in the first underwater bottom landing device 20A, the third column is the bottom information stored in the first underwater vehicle 10A, the fourth column is the bottom information stored in the second underwater bottom landing device 20B, the fifth column is the bottom information stored in the second underwater vehicle 10B, and the sixth column is the bottom information stored in the research vessel. [0h] First underwater landing vehicle 20A: After landing from the research vessel, it dives or sinks until it reaches the bottom 1. [1h] First underwater bottom landing device 20A: After landing on the bottom, it starts acquiring bottom information. Second underwater landing vehicle 20B: After landing from the research vessel, it dives or sinks until it reaches the bottom 1. [2h] First underwater bottom landing device 20A: First bottom landing information L1 for approximately 2 hours after starting to acquire bottom information 1-2 is stored in the bottom landing device information recording means 207. Second underwater bottom landing device 20B: After landing on the bottom, starts acquiring bottom information. First Underwater Vehicle 10A: After landing from the research vessel, it will dive and begin moving towards First Underwater Vehicle 10A. [3h] First underwater bottom landing device 20A: First bottom landing information L1 for approximately 3 hours after starting to acquire bottom information 1-3 is stored in the bottom landing device information recording means 207. Second underwater bottom landing device 20B: Second bottom landing information L2 for approximately 2 hours after the start of bottom information acquisition 2-3 is stored in the bottom landing device information recording means 207. First underwater vehicle 10A: Optical communication is performed with first underwater landing device 20A, and first bottom landing information L1 1-3 is copied to the underwater vehicle information recording means 109. Acquisition of water bottom information and movement along the water bottom toward the second underwater vehicle 10B begins. Second underwater vehicle 10B: After landing from the research vessel, it submerges and begins moving towards the first underwater vehicle 10A. [4h] First underwater bottom landing device 20A: First bottom landing information L1 for approximately 4 hours after starting to acquire bottom information 1-4 is stored in the bottom landing device information recording means 207. Second underwater bottom-landing device 20B: Second bottom-landing information L2 for approximately 3 hours after the start of bottom information acquisition 2-4 is stored in the bottom landing device information recording means 207. Optical communication is performed with the first underwater vehicle 10A, and the first bottom landing information L1 1-3 and First Navigation Bottom Information A1 3-4 is copied to the bottom landing device information recording means 207. First underwater vehicle 10A: First underwater bottom information A1 for approximately two hours after the start of bottom information acquisition 3-4 and the replicated first bottom landing information L1 1-3 is stored in the underwater vehicle information recording means 109. Optical communication is performed with the second underwater bottom landing device 20B, and the second bottom landing information L2 2-4 is copied to the underwater vehicle information recording means 109. After the optical communication is completed, the underwater vehicle starts moving toward the first underwater bottom landing vehicle 20A. The second underwater vehicle 10B performs optical communication with the first underwater landing device 20A, and transmits the first bottom landing information L1 1-4 is copied to the underwater vehicle information recording means 109. After the optical communication is completed, the underwater vehicle starts to acquire the water bottom information and move to the water bottom toward the second underwater bottom landing device 20B. [5h] First underwater bottom landing device 20A: First bottom landing information L1 for approximately 5 hours after starting to acquire bottom information 1-5 is stored in the bottom landing device information recording means 207. Optical communication is performed with the first underwater vehicle 10A, and the second bottom landing information L2 2-4 and First Navigation Bottom Information A1 3-5 is copied to the bottom landing device information recording means 207. Second underwater bottom landing device 20B: Second bottom landing information L2 for approximately 4 hours after the start of bottom information acquisition 2-5 and the replicated first bottom landing information L1 1-3 and First Navigation Bottom Information A1 3-4 is stored in the bottom landing device information recording means 207. Optical communication is performed with the second underwater vehicle 10B, and the first bottom landing information in the bottom landing device information recording means 207 is recorded as L11-4 Updated to Second Navigational Bottom Information A2 4-5 is newly replicated. First underwater vehicle 10A: First underwater bottom information A1 for approximately 3 hours after the start of bottom information acquisition 3-5 and the replicated first bottom landing information L1 1-3 and second bottom landing information L2 2-4 is stored in the underwater vehicle information recording means 109. Optical communication is performed with the first underwater bottom landing device 20A, and the first bottom landing information in the underwater vehicle information recording means 109 is recorded as L1 1-5 After the optical communication is completed, the underwater landing device 20B starts moving toward the bottom of the water. Second underwater vehicle 10B: Second underwater bottom information A2 for approximately two hours after the start of bottom information acquisition 4-5 and the replicated first bottom landing information L1 1-4 is stored in the underwater vehicle information recording means 109. Optical communication is performed with the second underwater bottom landing device 20B, and the second bottom landing information L2 2-5 and First Navigation Bottom Information A1 3-4 is copied to the underwater vehicle information recording means 109. After the optical communication is completed, the underwater vehicle starts moving toward the first underwater bottom landing vehicle 20A. [6h] First underwater bottom landing device 20A: First bottom landing information L1 for approximately 6 hours after starting to acquire bottom information 1-6 and the duplicated second bottom landing information L2 2-4 and First Navigation Bottom Information A1 3-5 is stored in the bottom-landing device information recording means 207. Optical communication is performed with the second underwater vehicle 10B, and the second bottom-landing water bottom information stored in the bottom-landing device information recording means 207 is recorded as L2 2-5 Updated to Second Navigational Bottom Information A2 4-6 is newly replicated. Second underwater bottom-landing device 20B: Second bottom-landing information L2 for approximately 5 hours after the start of bottom information acquisition 2-6 and the replicated first bottom landing information L1 1-4 , First navigation bottom information A1 3-4 and second navigation bottom information A2 4-5is stored in the bottom-landing device information recording means 207. Optical communication is performed with the first underwater vehicle 10A, and the first bottom-landing water bottom information stored in the bottom-landing device information recording means 207 is recorded as L1 1-5 The first navigational bottom information is A1 3-6 will be updated to. First underwater vehicle 10A: First underwater bottom information A1 for approximately 4 hours after the start of bottom information acquisition 3-6 and the replicated first bottom landing information L1 1-5 and second bottom landing information L2 2-4 is stored in the underwater vehicle information recording means 109. Optical communication is performed with the second underwater bottom landing device 20B, and the second bottom landing information in the underwater vehicle information recording means 109 is recorded as L2 2-6 Updated to Second Navigational Bottom Information A2 4-5 After the optical communication is completed, the underwater landing device 20A starts moving toward the bottom of the water. Second underwater vehicle 10B: Second underwater bottom information A2 for approximately 3 hours after the start of bottom information acquisition 4-6 and the replicated first bottom landing information L1 1-4 , Second bottom bottom information L2 2-5 and First Navigation Bottom Information A1 3-4 is stored in the underwater vehicle information recording means 109. Optical communication is performed with the first underwater bottom landing device 20A, and the first bottom landing information is stored in the underwater vehicle information recording means 109. 1-6 The first navigational bottom information is A1 3-5 After the optical communication is completed, the underwater landing device 20B starts moving toward the bottom of the water. [7h] First underwater bottom landing device 20A: First bottom landing information L1 for approximately 7 hours after starting to acquire bottom information 1-7 and the duplicated second navigation bottom information A2 4-6 is stored in the bottom-landing device information recording means 207. In addition, optical communication is performed with the first underwater vehicle 10A, and the second bottom-landing water bottom information stored in the bottom-landing device information recording means 207 is recorded as L2 2-5 From L2 2-6 The first navigational bottom information is A1 3-5 From A1 3-7 will be updated to. Second underwater bottom-landing device 20B: Second bottom-landing information L2 for approximately 6 hours after the start of bottom information acquisition 2-7 and the duplicated First Navigation Bottom Information A1 3-6 is stored in the bottom landing device information recording means 207. In addition, optical communication is performed with the second underwater vehicle 10B, and the second underwater traveling information stored in the bottom landing device information recording means 207 is A2 4-5 From A2 4-7 The first bottom contact information is L1 1-5 From L1 1-6 will be updated to. First underwater vehicle 10A: First underwater bottom information A1 for approximately 5 hours after the start of bottom information acquisition 3-7 and the duplicated second bottom landing information L2 2-6 is stored in the underwater vehicle information recording means 109. In addition, optical communication is performed with the first underwater bottom landing device 20A, and the first bottom landing information stored in the underwater vehicle information recording means 109 is recorded as L1 1-5 From L1 1-7 The second navigational bottom information is A2 4-5 From A2 4-6 After the optical communication is completed, the underwater landing device 20B starts moving toward the bottom of the water. Second underwater vehicle 10B: Second underwater bottom information A2 for approximately four hours after the start of bottom information acquisition 4-7 and the replicated first bottom-landing information L1 1-6 is stored in the underwater vehicle information recording means 109. In addition, optical communication is performed with the second underwater bottom landing device 20B, and the second bottom landing information is recorded on L2 2-5 From L2 2-7 The first navigational bottom information is A1 3-5 From A1 3-6 After the optical communication is completed, the underwater landing device 20A starts moving toward the bottom of the water. [8h] First underwater bottom landing device 20A: First bottom landing information L1 for approximately 8 hours after starting to acquire bottom information 1-8 and the duplicated First Navigation Bottom Information A1 3-7 is stored in the bottom landing device information recording means 207. In addition, optical communication is performed with the second underwater vehicle 10B, and the second bottom landing information stored in the bottom landing device information recording means 207 is recorded as L22-6 From L2 2-7 The second navigational bottom information is A2 4-6 From A2 4-8 will be updated to. Second underwater bottom landing device 20B: Second bottom landing information L2 for approximately 7 hours after the start of bottom information acquisition 2-8 and the duplicated second navigation bottom information A2 4-7 is stored in the bottom landing device information recording means 207. In addition, optical communication is performed with the first underwater vehicle 10A, and the first underwater traveling information stored in the bottom landing device information recording means 207 is A1 3-6 From A1 3-8 The first bottom contact information is L1 1-6 From L1 1-7 will be updated to. First underwater vehicle 10A: First underwater bottom information A1 for approximately 6 hours after the start of bottom information acquisition 3-8 and the replicated first bottom-landing information L1 1-7 is stored in the underwater vehicle information recording means 109. In addition, optical communication is performed with the second underwater bottom landing device 20B, and the second bottom landing information stored in the underwater vehicle information recording means 109 is recorded as L2 2-6 From L2 2-8 The second navigational bottom information is A2 4-6 From A2 4-7 After the optical communication is completed, the underwater landing device 20A starts moving toward the bottom of the water. Second underwater vehicle 10B: Second underwater bottom information A2 for approximately 5 hours after the start of bottom information acquisition 4-8 and the duplicated second bottom landing information L2 2-7 is stored in the underwater vehicle information recording means 109. In addition, optical communication is performed with the first underwater bottom landing device 20A, and the first bottom landing information is recorded on L1 1-6 From L1 1-8 The first navigational bottom information is A1 3-6 From A1 3-7 After the optical communication is completed, the underwater landing device 20B starts moving toward the bottom of the water. [9h] First underwater bottom landing device 20A: First bottom landing information L1 for approximately 9 hours after the start of bottom information acquisition 1-9 and the duplicated second navigation bottom information A24-8 is stored in the bottom-landing device information recording means 207. In addition, optical communication is performed with the first underwater vehicle 10A, and the second bottom-landing water bottom information stored in the bottom-landing device information recording means 207 is recorded as L2 2-7 From L2 2-8 The first navigational bottom information is A1 3-7 From A1 3-9 will be updated to. Second underwater bottom landing device 20B: Second bottom landing information L2 for approximately 8 hours after the start of bottom information acquisition 2-9 and the duplicated First Navigation Bottom Information A1 3-8 is stored in the bottom landing device information recording means 207. In addition, optical communication is performed with the second underwater vehicle 10B, and the second underwater traveling information stored in the bottom landing device information recording means 207 is A2 4-7 From A2 4-9 The first bottom contact information is L1 1-7 From L1 1-8 will be updated to. First underwater vehicle 10A: First underwater bottom information A1 for approximately 7 hours after the start of bottom information acquisition 3-9 and the duplicated second bottom landing information L2 2-8 is stored in the underwater vehicle information recording means 109. In addition, optical communication is performed with the first underwater bottom landing device 20A, and the first bottom landing information stored in the underwater vehicle information recording means 109 is recorded as L1 1-7 From L1 1-9 The second navigational bottom information is A2 4-7 From A2 4-8 After the optical communication is completed, the underwater landing device 20B starts moving toward the bottom of the water. Second underwater vehicle 10B: Second underwater bottom information A2 for approximately 6 hours after the start of bottom information acquisition 4-9 and the replicated first bottom landing information L1 1-8 is stored in the underwater vehicle information recording means 109. In addition, optical communication is performed with the second underwater bottom landing device 20B, and the second bottom landing information is recorded on L2 2-7 From L2 2-9 The first navigational bottom information is A1 3-7 From A1 3-8 After the optical communication is completed, the underwater landing device 20A starts moving toward the bottom of the water. [10h] First underwater bottom landing device 20A: First bottom landing information L1 for approximately 10 hours after starting to acquire bottom information 1-10 and the duplicated First Navigation Bottom Information A1 3-9 is stored in the bottom landing device information recording means 207. In addition, optical communication is performed with the second underwater vehicle 10B, and the second bottom landing information stored in the bottom landing device information recording means 207 is recorded as L2 2-8 From L2 2-9 The second navigational bottom information is A2 4-8 From A2 4-10 will be updated to. Second underwater bottom-landing device 20B: Second bottom-landing information L2 for approximately 9 hours after the start of bottom information acquisition 2-10 and the duplicated second navigation bottom information A2 4-9 is stored in the bottom landing device information recording means 207. In addition, optical communication is performed with the first underwater vehicle 10A, and the first underwater traveling information stored in the bottom landing device information recording means 207 is A1 3-8 From A1 3-10 The first bottom contact information is L1 1-8 From L1 1-9 will be updated to. First underwater vehicle 10A: First underwater bottom information A1 for approximately 8 hours after the start of bottom information acquisition 3-10 and the replicated first bottom-landing information L1 1-9 is stored in the underwater vehicle information recording means 109. In addition, optical communication is performed with the second underwater bottom landing device 20B, and the second bottom landing information stored in the underwater vehicle information recording means 109 is recorded as L2 2-8 From L2 2-10 The second navigational bottom information is A2 4-8 From A2 4-9 After the optical communication is completed, it will rise to the surface and be picked up by the research vessel. Second underwater vehicle 10B: Second underwater bottom information A2 for approximately 7 hours after the start of bottom information acquisition 4-10 and the duplicated second bottom landing information L2 2-9 is stored in the underwater vehicle information recording means 109. In addition, optical communication is performed with the first underwater bottom landing device 20A, and the first bottom landing information is recorded on L1 1-8 From L1 1-10 The first navigational bottom information is A1 3-8From A1 3-9 After the optical communication is completed, the underwater landing device 20B starts moving toward the bottom of the water. [11h] First underwater bottom landing device 20A: First bottom landing information L1 for approximately 11 hours since the start of bottom information acquisition 1-11 and the duplicated second bottom landing information L2 2-9 , First navigation bottom information A1 3-9 , and second navigation bottom information A2 4-10 is stored in the bottom landing device information recording means 207. Second underwater bottom-landing device 20B: Second bottom-landing information L2 for approximately 10 hours after the start of bottom information acquisition 2-11 and the duplicated First Navigation Bottom Information A1 3-10 is stored in the bottom landing device information recording means 207. In addition, optical communication is performed with the second underwater vehicle 10B, and the second underwater traveling information stored in the bottom landing device information recording means 207 is A2 4-9 From A2 4-11 The first bottom contact information is L1 1-9 From L1 1-10 will be updated to. First underwater vehicle 10A: First underwater navigation information A1 stored in the vehicle information recording means 109 3-10 , First bottom bottom information L1 1-9 , Second bottom bottom information L2 2-10 , and second navigation bottom information A2 4-9 are copied or transferred to the information recording means on board the research vessel. Second underwater vehicle 10B: Second underwater bottom information A2 for approximately 8 hours after the start of bottom information acquisition 4-11 and the replicated first bottom-landing information L1 1-10 is stored in the underwater vehicle information recording means 109. In addition, optical communication is performed with the second underwater bottom landing device 20B, and the second bottom landing information is recorded on L2 2-9 From L2 2-11 The first navigational bottom information is A1 3-9 From A1 3-10 After the optical communication is completed, it will rise to the surface and be picked up by the research vessel. [12h] First underwater bottom landing device 20A: First bottom landing information L1 for approximately 12 hours after the start of bottom information acquisition 1-12 and the duplicated second bottom landing information L2 2-9 , First navigation bottom information A1 3-9 , and second navigation bottom information A2 4-10 is stored in the bottom landing device information recording means 207. Second underwater bottom landing device 20B: Second bottom landing information L2 for approximately 11 hours after the start of bottom information acquisition 2-12 and the duplicated First Navigation Bottom Information A1 3-10 , Second navigation bottom information A2 4-11 , and first bottom contact information L1 1-10 is stored in the bottom landing device information recording means 207. Second underwater vehicle 10B: Second underwater navigation information A2 stored in the vehicle information recording means 109 4-11 , First navigation bottom information A1 3-10 , First bottom bottom information L1 1-10 , and second bottom landing information L2 2-11 are copied or transferred to the information recording means on board the research vessel.

[0049] The first underwater bottom-landing device 20A and the second underwater bottom-landing device 20B continue to observe the bottom even after the first underwater vehicle 10A and the second underwater vehicle 10B are recovered, and after the scheduled observation period is over, the sinker 22 is detached and brought to the surface, and recovered by the research vessel to retrieve the bottom information stored in the bottom-landing device information recording means 207. It is also possible to re-launch the underwater vehicle 10 while the first underwater bottom-landing device 20A and the second underwater bottom-landing device 20B are continuing their observations, and resume sharing of bottom information between the underwater vehicle 10 and the underwater bottom-landing device 20 via optical communication. In the third embodiment, approximately six hours after the start of the survey, each observation aircraft will have copied the bottom information from all the other observation aircraft, so that no matter which of the four observation aircraft is brought to the surface, the bottom information from all aircraft as of at least two hours prior can be recovered on board or on land.

[0050] The number of observation devices is not limited to that in the first to third embodiments. If at least one of the underwater vehicles 10 and the underwater bottom landing devices 20 is three or more, the number of optical communication combinations for transmitting and receiving bottom information increases, but the bottom information can be shared (backed up) by each observation device in the same way.

[0051] Next, modifications of the first to third embodiments will be described. The underwater vehicle 10 determines a suitable position for optical communication where the information communication speed is equal to or greater than a predetermined value, and moves toward that suitable position for optical communication (steps S8 and S19 in the first embodiment, steps S109 and S120 in the second embodiment, and steps S210, S221, S231, and S242 in the third embodiment). However, the signal-to-noise ratio (SN ratio) of optical communication between the underwater vehicle 10 and the underwater landing device 20 at the bottom of the water depends on the underwater turbidity at that time. Because underwater turbidity changes over time, it may not be possible to ensure the minimum SN ratio required for optical communication depending on the turbidity conditions around the suitable position for optical communication when the underwater vehicle 10 arrives. In other words, if the suitable position for optical communication is set based on the maximum optical communication distance between the underwater vehicle 10 and the underwater landing device 20 under highly transparent conditions, if the water near the underwater landing device 20 is more turbid than usual, the underwater vehicle 10 may fail to optically communicate with the underwater landing device 20 from the suitable position for optical communication.

[0052] Therefore, it is preferable to calculate the distance to the underwater bottom-landing device 20 at which the minimum required S / N ratio for optical communication can be ensured (hereinafter also referred to as the "predetermined S / N ratio ensuring distance") according to the underwater turbidity, and to determine whether or not to move the underwater vehicle 10 closer to the underwater bottom-landing device 20 from the optical communication suitable position based on the calculation result. This can reduce the possibility of optical communication failure between the underwater vehicle 10 and the underwater bottom-landing device 20.

[0053] FIG. 8 is a diagram illustrating an example of control in consideration of a predetermined S / N ratio ensuring distance in an underwater information communication network device. The control procedure is as follows: 1) When the underwater vehicle 10 heading toward a suitable position for optical communication arrives at that position or the distance to that position falls below a predetermined value, it uses the onboard turbidity meter 108C to measure the turbidity in the surrounding water and calculates the optical attenuation length in the water area where it is currently located. 2) Next, the underwater vehicle 10 calculates the distance x1 at which a specified signal-to-noise ratio is ensured at that time in the water area based on the optical attenuation length calculated in step 1 and the maximum optical communication distance X0, which is the longest distance over which stable optical communication is possible in the case of high transparency (optical attenuation length L0). 3) Next, the underwater vehicle 10 determines whether the calculated predetermined SN ratio ensuring distance x1 is shorter than the distance from the suitable position for optical communication to the underwater bottom landing device 20, and if it determines that the distance is shorter, the underwater vehicle 10 approaches the underwater bottom landing device 20 until the distance becomes shorter than the predetermined SN ratio ensuring distance x1, and maintains that position after arriving.On the other hand, if it determines that the predetermined SN ratio ensuring distance x1 is longer than the distance from the suitable position for optical communication to the underwater bottom landing device 20, it moves to the suitable position for optical communication as planned and maintains that position. 4) Establish optical communication between the underwater vehicle 10 and the underwater landing vehicle 20.

[0054] In step 1 above, instead of using the turbidity measured by the turbidimeter 108C, the underwater vehicle 10 may obtain the turbidity (optical attenuation length) by measuring the light intensity of scattered light emitted by the light-emitting element of the vehicle optical communication means 107 and receiving the scattered light with the light-receiving element of the same vehicle optical communication means 107. In this case, it is possible to obtain the predetermined S / N ratio ensuring distance x1 even for an underwater vehicle 10 that does not have a turbidimeter 108C. Furthermore, while the wavelength of light used in a typical turbidimeter 108C is around 660 nm (red), the wavelength of light used in optical communication is, for example, 450 nm (blue) or 520 nm (green). Therefore, when obtaining the optical attenuation length from the measured turbidity, wavelength conversion is required to take wavelength dependency into account. However, when the optical attenuation length is obtained by the vehicle optical communication means 107, the same wavelength as that used in communication can be used, making such wavelength conversion unnecessary.

[0055] Regarding the above-mentioned step 2, Fig. 9 is a diagram showing the communication distance of underwater optical wireless communication. In this embodiment, optical communication between the underwater vehicle 10 and the underwater bottom landing device 20, or between the underwater vehicles 10, is in principle bidirectional communication as shown in Fig. 9(b), but Fig. 9(a) shows only unidirectional communication for the sake of explanation. The underwater vehicle 10 and the underwater bottom-landing device 20 perform optical communication with the light-emitting element and light-receiving element of each other's vehicle optical communication means 107 or bottom-landing device optical communication means 205 facing each other. The predetermined S / N ratio ensuring distance x1, taking underwater turbidity into consideration, is calculated using, for example, the following formulas (1) to (3).

number

number

number

[0056] Regarding step 3 above, if the underwater vehicle 10 gets too close to the underwater bottom landing device 20, there is a risk that the two may come into contact, so the limit to which the underwater vehicle 10 can approach in accordance with the specified S / N ratio ensuring distance x1 is set to a distance that will prevent contact with the underwater bottom landing device 20, for example, up to 2 m from the underwater bottom landing device 20. Furthermore, when the calculated specified SN ratio ensuring distance x1 becomes less than the distance that can prevent contact with the underwater bottom landing device 20, such as 1.8 m, the underwater vehicle 10 may wait for a specified period of time and then measure the underwater turbidity again to calculate the specified SN ratio ensuring distance x1, or it may temporarily give up optical communication with the underwater bottom landing device 20 and start moving to another underwater bottom landing device 20.

[0057] In this way, when the underwater vehicle 10 in this example arrives at a suitable position for optical communication or when the distance to the suitable position for optical communication falls below a predetermined value, it measures the underwater turbidity at that location (≒ water transparency, optical attenuation length, optical transmittance), calculates a predetermined S / N ratio ensuring distance x1 based on the measurement results, and if the predetermined S / N ratio ensuring distance x1 is closer to the underwater bottom-landing device 20 than the suitable position for optical communication, approaches the underwater bottom-landing device 20 until it falls below that distance and performs optical communication. This makes it possible to quickly establish stable optical communication between the underwater vehicle 10 and the underwater bottom-landing device 20 even if the water near the underwater bottom-landing device 20 is more turbid than usual. The predetermined SN ratio ensuring distance x1 can also be calculated by the underwater bottom landing device 20 and transmitted to the underwater vehicle 10 by acoustic communication. Furthermore, when optical communication is performed between underwater vehicles 10, the distance between one underwater vehicle 10 and another underwater vehicle 10 can be determined in the same manner, taking into account the predetermined S / N ratio ensuring distance x1.

[0058] The underwater vehicle 10 then adjusts its own orientation to align the light irradiation direction of the vehicle's optical communication means 107 with the optical communication suitable orientation and controls the navigation means 110 so that the light irradiation direction is maintained (steps S9 and S20 in the first embodiment, steps S110 and S121 in the second embodiment, steps S211, S222, S232, and S243 in the third embodiment), either within the predetermined S / N ratio ensuring distance x1 if it determines that the predetermined S / N ratio ensuring distance x1 is less than the distance from the optical communication suitable position to the underwater bottom landing device 20, or at the optical communication suitable position if it determines that the predetermined S / N ratio ensuring distance x1 is equal to or greater than the distance from the optical communication suitable position to the underwater bottom landing device 20. Thereafter, the steps of each of the above-described embodiments are executed. [Industrial Applicability]

[0059] The present invention is applicable to long-term seafloor observations using multiple observation devices. By establishing a shared seafloor information network on the seafloor using multiple observation devices, even if some of the observation devices are lost due to an accident or other reason, some of the seafloor information acquired by the lost observation device can be recovered from other observation devices that have been salvaged. Furthermore, when long-term seafloor observations are being conducted using multiple observation devices, simply by bringing one of the observation devices to the surface and accessing its information recording means, it is possible to grasp the status of all the observation devices, such as their locations and the start of observation, and to recover the seafloor information acquired up to that point on board the ship. [Explanation of symbols]

[0060] 1 underwater 10 Underwater vehicle 10A First Underwater Vehicle 10B Second Underwater Vehicle 104 Acoustic positioning means for marine vessels 105 Vehicle acoustic positioning means 106 Acoustic communication means for underwater vehicles 107 Optical communication means for naval vehicles 108 Vehicle Observation Means 108A Vehicle imaging means 108C Turbidity meter 109 Vessel information recording means 110 Means of Navigation 111 Radio wave radio communication means for aircraft 112 Vessel control means 20 Underwater landing machine 20A First Underwater Landing Vehicle 20B Second Underwater Landing Vehicle 202 Bottom landing device attitude (orientation) measurement means 203 Bottom landing vehicle positioning means 204 Acoustic communication means for bottom landing aircraft 205 Bottom-landing optical communication means 206 Bottom-landing observation means 206A Bottom landing vehicle imaging means 207 Bottom landing information recording means 208 Bottom landing aircraft radio communication means 209 Bottom landing machine control means

Claims

1. A bottom information collection system for collecting bottom information using a plurality of observation devices, The observation device comprises a total of three or more underwater vehicles that move underwater to acquire bottom information, and underwater landing devices that are installed on the bottom of the water to acquire information on the surrounding bottom, The underwater vehicle has a vehicle optical communication means for two-way underwater optical wireless communication, a vehicle observation means for acquiring water bottom information, and a vehicle information recording means for recording the water bottom information, The underwater bottom-landing device has a bottom-landing device optical communication means used for two-way underwater optical wireless communication, a bottom-landing device observation means used to acquire bottom information, and a bottom-landing device information recording means for recording the bottom information, the underwater vehicle periodically approaches the underwater bottom-landing device to perform the underwater optical wireless communication with the underwater bottom-landing device; A bottom information collection system with information sharing function, characterized in that each time the underwater optical wireless communication is performed, the underwater bottom-landing device copies to the bottom-landing device information recording means the bottom information that the underwater vehicle has acquired and stored by the bottom-landing device observation means or by underwater optical wireless communication with other observation devices, but that the underwater vehicle has not stored, and the underwater vehicle copies to the bottom-landing device information recording means the bottom information that the underwater vehicle has acquired and stored by the bottom-landing device observation means or by underwater optical wireless communication with other observation devices, but that the vehicle has not stored.

2. the underwater vehicle further comprises a vehicle acoustic positioning means for use in acoustic positioning using acoustic signals, and a vehicle acoustic communication means for use in two-way underwater acoustic wireless communication; The underwater bottom-landing device further includes a bottom-landing device positioning means that responds to an acoustic signal emitted from the underwater vehicle acoustic positioning means, and a bottom-landing device acoustic communication means that is used for two-way underwater acoustic wireless communication, the underwater bottom-landing device transmits the light irradiation direction of the bottom-landing device optical communication means from the bottom-landing device acoustic communication means to the underwater vehicle; The underwater vehicle determines a suitable optical communication position where the information communication speed of the underwater optical wireless communication is equal to or greater than a predetermined value based on the light irradiation direction received by the vehicle acoustic communication means, approaches the underwater bottom-mounting device until it reaches the suitable optical communication position while obtaining its relative position with the underwater bottom-mounting device by acoustic positioning using the vehicle acoustic positioning means, and performs the underwater optical wireless communication with the underwater bottom-mounting device at the suitable optical communication position, as described in claim 1.

3. After the underwater vehicle starts moving toward the underwater bottom-landing device with which the underwater optical wireless communication is to be performed, when the distance to the underwater bottom-landing device becomes equal to or less than a predetermined value, the underwater vehicle transmits a signal from the underwater bottom-landing device's acoustic communication means to the underwater bottom-landing device requesting permission for the underwater optical wireless communication, and when the underwater optical wireless communication is permitted by the underwater bottom-landing device, the underwater vehicle transmits a light irradiation start request signal from the underwater bottom-landing device's acoustic communication means to the underwater bottom-landing device, The underwater bottom information collection system with information sharing function described in claim 2, characterized in that when the underwater bottom-landing device receives the light irradiation start request signal, it starts light irradiation from the bottom-landing device light communication means and transmits the light irradiation direction from the bottom-landing device acoustic communication means to the underwater vehicle.

4. The underwater bottom information collection system with information sharing function described in claim 3, characterized in that the underwater bottom-landing device further has a bottom-landing device imaging means used for photographing, and when it receives a signal from the underwater vehicle requesting permission for the underwater optical wireless communication, it photographs the underwater vehicle using the bottom-landing device imaging means, and if the information obtained by the photographing matches the information of the underwater vehicle that has been stored in the device in advance, it transmits a signal from the bottom-landing device acoustic communication means to the underwater vehicle permitting the underwater optical wireless communication.

5. The underwater vehicle further has a vehicle imaging means for use in photographing, and at the preferred optical communication position, after the bottom-mounted device optical communication means begins light irradiation, the vehicle imaging means photographs the light irradiation status of the underwater bottom-mounted device, and from the photographed image, determines whether the vehicle optical communication means is facing the bottom-mounted device optical communication means.If it is determined that they are not facing each other, it adjusts the orientation of its own vehicle so that they are facing each other, and if it is determined that they are facing each other, it starts the underwater optical wireless communication.The underwater bottom information collection system with information sharing function described in claim 3, characterized in that

6. The underwater vehicle is characterized in that it measures the information communication speed of the underwater optical wireless communication with the underwater bottom-landing device at the suitable optical communication position, and if the measurement result is slower than a set value, it moves closer to the underwater bottom-landing device.

7. The underwater vehicle includes one underwater vehicle and a plurality of underwater landing devices, The underwater vehicle communicates with each of the underwater landing devices via underwater optical wireless communication, A bottom information collection system with information sharing function as described in claim 1, characterized in that bottom information acquired by one of the underwater bottom landing devices is copied to the bottom landing device information recording means of another of the underwater bottom landing devices via the underwater vehicle.

8. The underwater vehicle includes a plurality of the underwater vehicles and one of the underwater landing devices, Each of the underwater vehicles communicates with the underwater bottom landing device through the underwater optical wireless communication. A bottom information collection system with information sharing function as described in claim 1, characterized in that bottom information acquired by one of the underwater vehicles is copied to the vehicle information recording means of another of the underwater vehicles via the underwater bottom landing device.

9. The underwater vehicle measures the turbidity or optical attenuation length at the location when it arrives at the suitable position for optical communication or when the distance to the suitable position for optical communication becomes less than a predetermined value, and based on the measurement results, calculates a predetermined S / N ratio ensuring distance, which is the distance to the underwater bottom-landing device at which a predetermined S / N ratio can be ensured in the underwater optical wireless communication, and approaches the underwater bottom-landing device until it becomes less than the calculated predetermined S / N ratio ensuring distance.

10. The underwater information collection system with information sharing function described in claim 9, characterized in that when calculating the specified S / N ratio ensuring distance, the underwater vehicle uses the maximum optical communication distance, which is the longest distance over which underwater optical wireless communication is possible between the vehicle optical communication means and the bottom-landing device optical communication means in transparent water.

11. 10. The underwater information collection system with information sharing function according to claim 9, wherein the turbidity or the optical attenuation length is measured by the optical communication means of the underwater vehicle.

12. A method for collecting bottom information using a plurality of observation devices, comprising: The observation device comprises three or more underwater vehicles that have a vehicle optical communication means for two-way underwater optical wireless communication, a vehicle observation means for acquiring bottom information, and a vehicle information recording means for recording the bottom information, and acquire bottom information while moving underwater; and an underwater bottom-landing device that is installed on the bottom of the water and acquires bottom information in the surrounding area, and has a bottom-landing device optical communication means for two-way underwater optical wireless communication, a bottom-landing device observation means for acquiring bottom information, and a bottom-landing device information recording means for recording the bottom information, periodically approaching the underwater vehicle to the underwater landing vehicle; and causing the underwater vehicle and the underwater bottom landing device that have been brought close to each other to perform the underwater optical wireless communication; A method for collecting seabed information involving information sharing, characterized in that, each time there is underwater optical wireless communication between the underwater vehicle and the underwater bottom-landing device, the underwater bottom-landing device copies, to the bottom-landing device information recording means, seabed information that the underwater vehicle has acquired by the bottom-landing device observation means or acquired by underwater optical wireless communication with other observation devices and stored, but that the device has not stored, and the underwater vehicle copies, to the bottom-landing device information recording means, seabed information that the underwater vehicle has acquired by the bottom-landing device observation means or acquired by underwater optical wireless communication with other observation devices and stored, but that the device has not stored.

13. A method for collecting seabed information with information sharing as described in claim 12, characterized in that after the step of having the underwater vehicle and the underwater bottom-landing device perform the underwater optical wireless communication, a step is carried out of recovering the underwater vehicle or the underwater bottom-landing device, on board a ship or on land, with the seabed information acquired by the other observation device copied to the vehicle information recording means or the bottom-landing device information recording means, and recovering the seabed information from the recovered underwater vehicle or the underwater bottom-landing device.

14. a step of causing the underwater vehicle and the underwater bottom-landing device to perform the underwater optical wireless communication, followed by a step of causing the underwater vehicle or the underwater bottom-landing device, whose water bottom information acquired by the other observation device has been copied to the underwater vehicle information recording means or the bottom-landing device information recording means, to float until radio wireless communication is possible; A method for collecting bottom information with information sharing as described in claim 12, characterized in that it includes a step of conducting radio wireless communication with the surfaced underwater vehicle or the underwater bottom landing device from a ship or on land to collect bottom information.

15. The ROV (Remotely Operated Underwater Vehicle) has an ROV optical communication means for two-way underwater optical wireless communication and an ROV information recording means for recording bottom information, and is connected to a ship by a tether cable and is submerged. a step of, after the step of causing the underwater vehicle and the underwater bottom-landing vehicle to perform the underwater optical wireless communication, bringing the ROV close to the underwater vehicle or the underwater bottom-landing vehicle, the water bottom information acquired by the other observation vehicle of which has been copied to the underwater vehicle information recording means or the bottom-landing vehicle information recording means; a step of causing the ROV to perform the underwater optical wireless communication with the underwater vehicle or the underwater bottom landing device that has approached, and copying the water bottom information held by the underwater vehicle or the underwater bottom landing device to the ROV information recording means; The method for collecting bottom information with information sharing described in claim 12, characterized in that it also includes a step of transmitting the copied bottom information by the ROV to the ship via the tether cable and collecting it.

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