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Deep sea survey vehicle ‘OTOHIME’ is one of the underwater vehicle owned in JAMSTEC and its automatic navigation system is developing now. To construct the control system, vehicle motion should be ...

In recent years, unmanned surface vehicles that navigate autonomously have been actively studied. Many of these vehicles are designed to perform unmanned tasks such as observation and transportation. On the other hand, this study uses an unmanned surface vehicle with a moon pool to collect a core sample on the seafloor, which is difficult to be done by an ordinary vehicle. Since the area where the vehicle is used has large disturbance by wind, it is necessary to maintain a fixed point and heading during core sampling. The vehicle is equipped with side thrusters, which enable it to hold a fixed point and heading. In this study, a control method is devised for maintaining the fixed point and heading. The control method is based on the sliding mode control, which is robust against disturbance. The proposed control method was verified by simulations and actual sea tests, and it was confirmed that the desired behavior could be achieved.

Large quantities of volatile radionuclides were released into the atmosphere after the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in March 2011. An inventory of these radionuclides in seafloor sediments is important for evaluating their environmental behavior and effects on aquatic organisms. We developed a dedicated radiation survey device that can be installed on a multipurpose unmanned surface vehicle called the Intelligent Boat for Oceanological Survey from Hama-dori (i-BoSH). Both the i-BoSH and dedicated radiation survey device were developed by a local consortium to survey places of heavy damage from the accident. The radiation survey device can measure radioactivity in-situ and collect eight sediment samples. The device also contains sensors to measure the relative distance between the i-BoSH and the seafloor as well as other fundamental seawater information such as temperature. A comprehensive test that included in-situ radiation measurements in sediment and collection of sediment core samples was conducted offshore from a radiocesium-contaminated fishing port in Fukushima. Consequently, the effectiveness of this device was confirmed via a successful operation at 12 sampling points with two cruises from the fishing port. Good correlations were observed between the laboratory and field measurement results of the sampled sediment cores and the in-situ radiation survey, respectively. Successful application of this device is expected to go beyond environmental surveys around the FDNPS to more general radiation monitoring around nuclear facilities and longer post-accident periods.

This paper describes development of a visible light 4 Pulse position modulation (4PPM) data communication device for underwater swarms using a nonlinear synchronizing system. SWARM—a group robot that uses intelligence as a group—do as ants and bees, is expected to be useful for marine resource exploration. Specifically, numerous SWARMs will be grouped to explore marine resources efficiently. An important difficulty is the change in electronic circuit characteristics because of high water pressure in the deep sea. Development of small and simple underwater SWARM communication devices must eliminate this problem without using large pressure-proof containers. As described herein, we considered nonlinear synchronizing systems as effective because they can be synchronized even if system time constants differ. Such systems resemble the glow mechanism used by fireflies. They have individuality, but they flash synchronously when in a group. We developed a visible light communication device using this nonlinear synchronization system based on the firefly concept. Test results confirmed that they are synchronized even if a time constant difference exists between them. Furthermore, we achieved 4PPM data communication using the nonlinear synchronization signal as a communication clock.

Currently, on the coast of Japan, a sea urchin barren occurred, causing a great deal of damage. Therefore, we constructed a system to conduct sea urchin quantity survey using small ROV. We conducted a survey in Shizugawa bay using the present system. As a result, we found a large amount of large sea urchins near the water depth of 20 m. We also developed a sea urchin survey system using machine learning and conducted experiments.

We have developed a new system for real-time observation of tsunamis and crustal deformation using a seafloor pressure sensor, an array of seafloor transponders and a Precise Point Positioning (PPP ) system on a buoy. The seafloor pressure sensor and the PPP system detect tsunamis, and the pressure sensor and the transponder array measure crustal deformation. The system is designed to be capable of detecting tsunami and vertical crustal deformation of ±8 m with a resolution of less than 5 mm. A noteworthy innovation in our system is its resistance to disturbance by strong ocean currents. Seismogenic zones near Japan lie in areas of strong currents like the Kuroshio, which reaches speeds of approximately 5.5 kt (2.8 m/s) around the Nankai Trough. Our techniques include slack mooring and new acoustic transmission methods using double pulses for sending tsunami data. The slack ratio can be specified for the environment of the deployment location. We can adjust slack ratios, rope lengths, anchor weights and buoy sizes to control the ability of the buoy system to maintain freeboard. The measured pressure data is converted to time difference of a double pulse and this simple method is effective to save battery to transmit data. The time difference of the double pulse has error due to move of the buoy and fluctuation of the seawater environment. We set a wire-end station 1,000 m beneath the buoy to minimize the error. The crustal deformation data is measured by acoustic ranging between the buoy and six transponders on the seafloor. All pressure and crustal deformation data are sent to land station in real-time using iridium communication.

Development of an underwater platform which travels and surveys across entire oceans for the research into the global change, ocean-trench earthquake, and biodiversity is addressed in Japan. The first prototype LCAUV powered by polymer electrolyte membrane fuel cell (PEFC) system named Urashima, which marked the world record of cruising distance of 317 km, had been developed since 1998. Key technology development including a fuel cell system for the second LCAUV started in 2007. A high efficiency PEFC developed by MHI for the LCAUV runs with 60 % of efficiency at an operation point. A function test for a new concept system, which consists of reduced auxiliary devices, using the PEFCs was made. The test results have positive outcomes.

We constructed a buoy system for real-time observations of tsunamis and crustal deformation in collaboration with the Japan Agency for Marine-Earth Science and Technology, Tohoku University, and the Japan Aerospace Exploration Agency. The most important characteristics of our system are resistance to the strong sea currents in the large-earthquake rupture zone around Japan (e.g., the Kuroshio maximum speed > 5 knots), and the capability to transmit data in real-time. Our system has four units: (1) a buoy station with a GPS/Acoustic station serving as a central base, (2) a wire-end station (WES) 1,000 m below the sea surface that serves as a staging base, (3) a pressure seafloor unit (PSU) comprising a pressure sensor, and (4) six GPS/Acoustic transponders to measure crustal deformation. The pressure data used to detect tsunamis and the vertical component of crustal deformation are sent to the land station via the wire-end and buoy stations at intervals of 1 h in normal mode and 15 s in tsunami mode. The data measured between the buoy and six transponders are also sent to the land station at 1-week intervals. The Iridium satellite is used for data transmission of all data to land station. The dynamic range for pressure observations is + ∕− 8 m with a fine resolution of 2 mm, and the accuracy of the crustal deformation measurements is less than 1 m. We tuned the system for an observation period of 5 months and carried out a sea trial. The length of the observation period influences the total system due to the weight of the battery. We rearranged the geometry of the total system to new one with heavier weight and a lot of batteries on the buoy considering long period observation and decided upon a slack ratio of 1.6. In addition, it is important for a long observation period to minimize electrical consumption. We used double pulses for acoustic data transmission between the PSU and WES. The time difference between two pulses indicates the observed pressure value. For the PSU, we designed a tsunami mode on the basis of data from the tsunami generated by the 2011 earthquake off Tohoku, which were recorded by cabled network system data and offline bottom pressure data. The results confirmed that a tsunami can be detected even if the first tsunami signals include strong-motion signals. In this case, the tsunami was detected 10–20 s after the first seismic arrival. During sea trials, we successfully tested the tsunami mode we designed. We succeeded real-time observation of pressure and crustal deformation using buoy system in strong sea current speed area for 5 months. However, there are some issues to be resolved at this moment. For acoustic data transmission, 1 ms step difference of the detection of acoustic signals at the WES, wrong detection of the multiple phases are issues to be resolved. We will consider assigned mapping of transmitted data to the time difference of the double pulses and take measures on the PSU and WES. In addition, we consider strategy to reduce slack ratio in the future. For data transmission from the WES to the buoy station, we experienced electrical unhealthy of the wire rope due to damages by the fisheries activities and the torsion brought by rotation of the buoy. We consider the countermeasure to reduce the rotation.

Performing oceanographic measurements from the sea surface to the sea bottom is technically challenging under rough or icy sea conditions. In 2011, we tested measures for protecting a buoy under such severe conditions, by incorporating anti-icing and tolerance to high winds and rough seas. Based on the results, we carried out detailed designs of a suitable buoy system. In January 2012, we succeeded in deploying the buoy in the Southern Ocean off the Adelie Coast at 60°S and 140°E. Some of the meteorological and oceanographic data being gathered by the buoy can now be monitored in real time. In this paper, we describe some details concerning the design of the sensor pole and mooring line, in addition to the data already received from the buoy.

JAMSTEC has planned development of a long-rang cruising AUV. This vehicle will enable over 20 days autonomous cruising. To achieve this vehicle, we need various basic technology developments. In this article, a space distributed CPU system development for achieving highly redundant system control and a stationary satellite control system for remote control of the vehicle are described. We carried out sea trial to make sure the each system function using a test bed vehicle. It was shown that the satellite communication system is more effective.

The Japan Agency for Marine-earth Science and Technology is now developing an automatic bottom inspection and sampling mobile, ABISMO, which is a full depth rating remotely operated vehicle for conducting research at the deepest sea bottom, observing the area with a camera, and sampling the bottom layer.

In order to reduce a tension on a cable, a deep sea ROV is designed to minimize the weight. However, the ROV having a lightweight is apt to wheelie when running by means of a crawler system. In order to run stably in counterpoise the combination of the center of gravity and the center of buoyancy should be in an adequate area called “stable area” which can be obtained corresponding to the weight and the buoyancy by the theory described in previous papers. The stable area becomes small as the weight is light. The center of gravity and the center of buoyancy is designed to be in the stable area. However, one of the important matters is that the ROV runs forward and also backward. It results in changing the discrimination of the stable area. And it sometimes makes the center of the gravity and the center of buoyancy sometimes to be outside of stable area. So, it is advantageous to increase the weight only when running by crawler system and to change the center of gravity meaningly. This paper proposes a method to virtually increase the weight and to change the center of gravity by using thrusters. And we conducted preliminary experiments using a small-size ROV having four thrusters and crawler system in a water tank to confirm the advantageous effect.

A deep sea ROV is desired to be light from the viewpoints of reducing a tension on an underwater cable and possessing the adequate movability by thrusters in water. On the other hand, when moving by a crawler system on the seabed, such a lightweight will influence on its movability characteristics. As an initial investigation experiments using an actual ROV were conducted in a water tank. And it was observed that the ROV ran in wheelie in some cases and almost fell down in extreme case in spite of the fact that it could run stably on land. In order to clarify the results fundamental theory of stability of the ROV in steady running is presented. The theory gives the discriminant chart of stable running for the combination of the center of gravity and the center of buoyancy. Experiments using a model were conducted to verify the theory. In order to increase the stable area and also to change meaningly the center of gravity, this paper proposes a method to virtually increase the weight and to change the center of gravity by using thrusters. And preliminary experiments were conducted to confirm its advantageous effect.Copyright © 2009 by ASME

The underwater platform which has enough ability to cruise globally and freely in vast deep sea will allow us to make the survey of entire oceans. We aim to develop an underwater platform which travels and surveys across entire oceans for the research into the global change, ocean-trench earthquake, and biodiversity and so on. We have developed the first prototype underwater platform or the long-range cruising autonomous underwater vehicle (LCAUV) named Urashima since 1998. The vehicle powered by a polymer electrolyte fuel cell system marked the world record of cruising distance of 317 kilometers in 2005. The vehicle has the following specifications: length; 10 m, weight; 10 tons, maximum depth ratings; 3500 m, maximum cruising speed; 3.2 knots, and endurance; 60 hours. This large vehicle has large user payload of a few hundreds kilograms. In 2007, we started research and development of the elemental technologies which will be utilizes for development of the second generation LCAUV to achieve cruising range of over 3000 kilometers. The technologies under research and development are power sources, navigation methods, communication methods, vehicle controllers, materials for body, and advanced sensors for highly resolution survey. The fuel cell and secondary battery hybrid system is had to improve at energy efficiency to generate electricity as possible for long time running with limited energy. A high accuracy inertial navigation system and an underwater positioning system being covered area of over 1000 km are under development. A synthesized aperture sonar is also under development.Copyright © 2009 by ASME

Recently, a number of bacteria including new one have been found from mud samples of Challenger Deep in the Mariana Trench. In order to get those samples or the sediment core in there, an underwater vehicle, which can dive to the deepest ocean and carry out the task, is needed, however, currently, there is no such vehicle in the world. So Japan Agency for Marine-Earth Science and Technology (JAMSTEC) began developing a new ROV for the deepest ocean use in 2005, it is "ABISMO". In this paper, several main systems of ABISMO and results of sea trials carried out before now are shown, and the operation support system is described.

JAMSTEC (Japan Agency for Marine-Earth Science and Technology) has been developing the deep sea ROV ABISMO (Automatic Bottom Inspection and Sampling Mobile) having the capability to dive to the deepest sea. The purposes of ABISMO are to inspect on the seabed in the deep sea and to obtain sediment samples from there. ABISMO consists of a launcher and a vehicle which is launched from the launcher and surveys on the seabed to determine the place for sampling. Core sampling system, which is exchangeable with a gravity piston type or a grab type, is equipped in the launcher. The both of the launcher and the vehicle have cameras to observe. One of the features of ABISMO is that the vehicle has crawlers in addition to thrusters in order to advance mobility. ABISMO is operated with the support ship KAIREI and dived by means of its onboard equipment including a primary cable. We conducted sea trials in January and September 2007 at the areas with the water depths up to 1,300m in Sagami Bay as primary function tests. And we conducted the third sea trial at Izu-Ogasawara trench in December 2007 and made the successful results of diving to the depths up to 9707 m and obtaining a sediment sample from the seabed in 9760 m water depth. This paper describes the features and the outline of ABISMO as well as the sea trial results.Copyright © 2008 by ASME

In order to reduce a tension on a cable, a deep sea ROV is designed to minimize the weight. However, such a light weight will influence on the movability of crawlers. As an initial investigation experiments were conducted in a water tank using a vehicle of ROV "ABISMO" changing the weight, the buoyancy, the center of gravity and the center of buoyancy. It was observed that the ROV ran unstably in some cases in spite of the fact that the ROV could run stably on land. Especially when the weight in water of was less, the stability of the ROV got worse. It seemed that the ROV could not run on the sea floor in such cases. On the other hand, the ROV ran stably when the ROV had an adequate weight in water and adequate center of gravity as well as center of buoyancy. This paper describes the experiment results of motion of the ROV running in water by means of crawler system. This paper also describes a fundamental theoretical investigation for ROV running in water. A discrimination chart of stable running is presented for the center of gravity and the center of buoyancy. The discrimination line is obtained with the weight and the buoyancy of ROV, the water residence, the point of its application and the dimension of crawlers.

An autonomous underwater vehicle (AUV) is equipped with an inertial navigation system (INS) in order to understand its own position in real time while it cruises without the communication with the external environment such as a support ship and GPS. Japan Agency for Marine-Earth Science and Technology has the cruising AUV URASHIMA, and it is also equipped with the INS. However the INS outputs its own absolute position containing the error that increases with time. It means, it is very difficult for URASHIMA to cruise dependent only on the position data outputted by the INS for a long time. So we have proposed the method to improve the performance of the INS, and its effect was confirmed in experiments. In the method, it was put on a turntable with assumption that it is fixed inside URASHIAM and the INS has been rotated by it around one rotation axis according to some rules. Consequently, the INS's position error was decreased by the rotational motion. In order to cause this effect, a precondition had to be met. It was that URASHIMA keeps its own posture to near-horizontal while cruising. However URASHIMA usually cruises with the roll motion which is caused by its shape. So the roll motion such as URASHIMA's one in a sea trial was applied to the turntable, and the INS was rotated in the situation. As the result, the INS's position error was decreased about half of the original one.

JAMSTEC has developed the two types of underwater vehicle since 2005: an ROV to the oceans' deepest depth called ASSS11k (advanced sediment sampling system to 11,000 meter) and a hybrid underwater vehicle for use in shallow-water to mid-depth zones named PICASSO (Plankton Investigatory Collaborating Autonomous Survey System Operon). The most important purpose of the ASSS11k is to get a lot of mud sample of challenger deep in the Mariana Trench, because a number of bacteria have been found there. Scientist wants to continuously explore the deepest parts of the oceans with a vehicle equipped with sediment samplers. ASSS11k consists of a sampling station and a sediment probe. The station contains two types of bottom samplers. One launches the probe to make a preliminary survey, launching the sampler to obtain a sample. We carried out the first sea trial using support vessel of "KAIREI" in January 2007. We tested every functions of the system and achieved sediment sampling at Sagami bay. PICASSO (2 times 0.8 times 0.8 m, 200 kg) is designed for biological and oceanographic observations in depths of up to 1,000 m. This small, light vehicle can be handled and operated by a team of only a few people. The easy-to-use vehicle does not need a dedicated support ship. The vehicle can be used either as untethered remotely operated vehicle (UROV) or autonomous underwater vehicle (AUV). In order to develop these vehicles, we used some new technologies and then developed new original devices: a small electrical-optical hybrid communication system, an HDTV optical communication system with Ethernet interface, synthetic designed pressure vessel-chassis-inner circuit boards, buoyancy material for deepest depth, a thin cable with high-tensile strength, a core sampler launcher, crawlers, compact winch motor drivers, a USBL system, a ballast controller, a friendly-user-interface program for operator, a high capacity lithium ion battery, a down sizing optical fiber spooler, and a prototype of underwater electromagnetic communication system.

An Autonomous Underwater Vehicle (AUV) is equipped with an Inertial Navigation System (INS) in order to detect its own current position for the autonomous cruise. It has a sensor part and an arithmetical part. The sensor part is composed of three gyros and three accelerometers, and the three-dimensional coordinate system (INS coordinate system) is defined in the arithmetical part. And an accelerometer and a gyro are set on each axis in the coordinate system. The INS calculates AUV's position using outputs of the sensors. So the position accuracy of it depends strongly on the precision of the sensors. However they have drift-bias errors which increase with the passage of the time. So, a method, which applies the rotational motion to the INS, is proposed in order to reduce the errors. In this method, the INS is put on the turntable and the INS is rotated by it around an axis of the INS coordinate system. And the errors of sensors, which are set on non-rotation axis, were reduced on average. This causes the position accuracy improvement. As the experimental results, the position error of the INS is reduced up to four times if suitable methods are given to it.

Recently, a number of bacteria have been found from a mud sample of Challenger Deep in the Mariana Trench. Sampling those sediment samples, an ROV to the oceans' deepest depth is needed. But no vehicle gets to the deepest depth in the world. Scientists want to continuously explore the deepest parts of the oceans with a vehicle equipped with sediment samplers. JAMSTEC started developing a sediment sampling system from April 2005. The system consists of a sampling station and a sediment probe. The station contains two types of bottom samplers. One launches the probe to make a preliminary survey, launching the sampler to obtain a sample. We carried out a sea trial on January 5-7, 2007 in Sagami Bay and was successfully completed. The ROV took a mud sample by using the gravity core sampler.

JAMSTEC has been developing the remotely operated vehicle system having a limited role to explore the deepest parts of the oceans since April 2005. This ROV system's main mission is to survey sediments in sea bottoms. This system consists of a launcher and a small vehicle. The launcher carries two types of bottom samplers as well as the vehicle. One launches the small vehicle to make a preliminary survey, launching the sampler to obtain a sample. The samplers can be changed a gravity core sampler for a grabber. The system assembly will be completed by the spring of 2006 and then its sea trials will be started.