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ABSTRACT: Computerised navigation is a developing technology in a branch of autonomous and intelligent engineering systems. It aims to enhance safety and security at sea and to improve the reliability of ship-to-ship operations and global marine traffic control. A recently standardised automatic identification system (AIS) takes full advantage of GPS based real-time positioning and timing information of ships. The use of the AIS is steadily growing to meet the needs of the merchant shipping and fishing industries. Nevertheless, a significant decrease in the number of ship accidents and hazardous incidents in open waterways has yet to occur. The work gathered in this paper is to establish a proactive means to prevent marine accidents by the use of the full potential of the AIS. Specifically, this paper describes the development of an AIS synthesis capable navigation support system enhanced with a degree of intelligence built from a physical model suitable to capture the dynamics of group based navigation of ocean-going vessels. The system envisioned is to provide adequate decision making support for group shipping, especially during the critical maneuvering in restricted areas such as channel passing and harbour approaches. Foundations for and experimental results of this study, including an analysis with the simulated traffic of Tokyo Uraga Channel route, are presented.
IET Intelligent Transport Systems 10/2009; · 0.51 Impact Factor
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ABSTRACT: This paper proposes a navigation scheme for an AUV to perform large-area imaging of seafloors, especially those of vent fields. The method is based on SLAM (simultaneous localization and mapping) using a profiling sonar and passive acoustic landmarks. Since real-time positioning accuracy of the method is high enough for rough photomosaicing, this method enables an efficient survey with a small overlap and is applicable to seafloors with no visual key for matching. As well as the positioning method, the navigation scheme contains horizontal and vertical path-planning methods, which adapt the vehicle's path to unprescribed landmarks and rough terrains. The method was implemented in the AUV Tri-Dog 1 and a series of sea experiments have been carried out at Tagiri vent field, Kagoshima bay in Japan since 2006. In 2007, the AUV succeeded in imaging around 3,000 m<sup>2</sup> of the seafloor and taking micro bathymetry by light sectioning. The relative accuracy of the navigation scheme is estimated to be 0.5 to 1.0 m by comparing photomosaics between dives.
Autonomous Underwater Vehicles, 2008. AUV 2008. IEEE/OES; 11/2008
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ABSTRACT: Although underwater vent fields are of great scientific interest, accurate visual mapping is difficult because of the presence of bubble plumes that degrade the accuracy of conventional acoustic positioning systems such as long base line (LBL) and super short base line (SSBL). The authors had proposed a visual mapping method of shallow vent fields with an autonomous underwater vehicle (AUV) equipped with a profiling sonar, where positioning is based on vertical rod-shaped acoustic reflectors and bubble plumes. Although performance was verified through a series of experiments, there remain two challenges as follows. Firstly, observation is terminated if the vehicle was surrounded by bubble plumes, since the vehicle tries to avoid collision with not only artificial reflectors but also collision-safe bubble plumes. Secondly, the observation area drifts by disturbance since the waypoints are defined relative to the vehicle's position after descending close to seafloor. This paper proposes a real-time path planning method of an AUV as a part of the proposed observation method. The path of the vehicle is defined based on the types of landmarks as well as the geometric relationship between the vehicle and the landmarks. The vehicle can distinguish landmark types using a sheet laser and a camera. The proposed method was implemented on the AUV Tri-Dog 1 and a series of experiments were carried out in order to verify its performance.
OCEANS 2007; 11/2007
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ABSTRACT: Although underwater vent fields are of great scientific interest, little is understood concerning their influence on the underwater ecosystem due to the great difficulties involved in their underwater survey. The authors propose an underwater survey method using AUVs. In previous works, the authors proposed a practical method to survey the "Tagiri" vent area in Kagoshima, in southern Japan [1] [2], and carried out experiments. The field experiments in Tagiri were at some degree successful, but the system also encountered some difficulties. One of the problems was that the AUV could not identify the type of landmarks used to support accurate positioning. In this paper, we propose an autonomous recognition method of bubble plumes using a sheet laser and a camera by image processing. The performance of the proposed method was verified with data obtained in tank experiments, and then implemented in the AUV Tri-Dog 1. Using the proposed method, Tri-Dog 1 performed seafloor observations of the Tagiri vent area in March 2007. Tri-Dog 1 succeeded in distinguishing between bubble plumes and artificial acoustic reflectors, and localizing itself with sufficient accuracy to create a vast, high resolution visual map of the area.
OCEANS 2007; 11/2007
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ABSTRACT: Real-time accurate positioning is a key technology for autonomous underwater vehicles to perform close-range seafloor observations such as photo mosaicing. This paper proposes a real-time positioning method that realizes robust and drift-free positioning in a local area based on a passive acoustic landmarks set in the environment and a profiling sonar (profiler) mounted on the vehicle. The method stochastically updates the vehicle's position based on all the sensory data available. Although the position of landmarks is generally unknown, this paper assumes the position is known without error for simplification. As an observation model of the profiler we propose a radial-angular representation with a non-Gaussian distribution based on experimental data. The performance of the proposed method is verified through tank experiments using the AUV Tri-Dog 1. The effects of the number of landmarks and observation model on the positioning accuracy is discussed. Through comparison with ground truth and off-line estimations based on actual data obtained during the experiments, the positioning accuracy of the proposed method remains within 5 centimeters at all times during the 2 hour duration of the experiment with a traveled distance of 600 meters, with two landmarks at a distance of 10 meters.
OCEANS 2007 - Europe; 07/2007
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ABSTRACT: Although underwater vent areas are scientifically important, precise photo mosaicing of them is for the following reasons still a hard task. Firstly, the visible range is limited by the turbid water and floating particles. Secondly, the conventional acoustic positioning is vulnerable to the bubble plumes of the vent areas. In this paper a navigation method of an autonomous underwater vehicle (AUV) for photo mosaicing of shallow vent areas where bubbles are spouting is proposed. Simultaneously, this method estimates the position of the AUV and the landmarks, such as bubble plumes and artificial sonar reflectors. The simultaneous localization and mapping (SLAM) based approach enables drift free, accurate, real-time and independent navigation in a local area, which is suitable for photo mosaicing. The proposed method has been implemented on the testbed AUV "Tri-Dog 1" and a tank experiment has been carried out to verify its performance.
OCEANS 2006 - Asia Pacific; 06/2007
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ABSTRACT: While visual observation is an ideal method for detailed survey of seafloors, it is still difficult for an autonomous underwater vehicle (AUV) to track rugged terrains at low altitudes of ideal 1 to 2 meters. This paper proposes a real-time navigation architecture for hovering class AUVs equipped with perceptional sensors looking forwards, sideways and downward, to operate under such conditions. The method controls vertical motion while placing almost no restrictions on motion in the horizontal plane, achieving high compatibility with existing navigation scheme. The algorithm is a hybrid of sensor and map based approaches where the vehicle continually updates a local geometrical map of hazard areas using its perceptional measurements while performing conventional auto-altitude tracking. If the vehicle enters any of the hazard areas, sensor based control is invoked with depth as the control reference to elevate the AUV until it passes the hazard area. The method was verified through tank experiments using the AUV Tri-Dog 1. The AUV successfully followed a lawn-mower trajectory over a rugged terrain consisting of knolls and slopes while maintaining an extremely low altitude of 1.2 meters.
Underwater Technology and Workshop on Scientific Use of Submarine Cables and Related Technologies, 2007. Symposium on; 05/2007
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ABSTRACT: This paper proposes a navigation scheme of an Autonomous Underwater Vehicle (AUV) for photo mosaicing of a shallow vent area with bubble plumes. While bubble plumes disturb acoustic positioning systems, they can be detected by sonars. So the method takes advantage of the plumes as landmarks using a profiling sonar. By adopting the concept of Simultaneous Localization and Mapping (SLAM), the method achieves drift-free, accurate and independent positioning without using conventional acoustic transponders. The high positioning accuracy enables complete data acquisition, as well as position based mosaicing without relying on pictorial correlations of the photos. Some artificial acoustic reflectors are also deployed to enhance positioning performance. The scheme was implemented to the testbed AUV "Tri-Dog 1" and the performance was verified through sea experiments at Tagiri vent area, Kagoshima Bay in Japan. The AUV succeeded in fully autonomous observation at the challenging environment, to build photo mosaics of more than 300 m of the floor including a tube-worm colony
OCEANS 2006; 10/2006
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ABSTRACT: This paper proposes a navigation method for an Autonomous underwater vehicle (AUV) operating around structures whose major configuration given in advance. The method consists of a state estimator and a motion controller, enabling localization in the configuration map as well as following pregiven waypoints without any external help. The state estimator is based on a "particle filter" where the vehicle's state, horizontal position and heading, is stochastically updated in real time using multisensor data. This method was implemented on the AUV "Tri-Dog 1" and experiments were carried out around breakwater caissons at the mouth of Kamaishi bay, Iwate Prefecture in Japan. This is the first time a vehicle has succeeded in fully autonomous observation around breakwater caissons. Mosaics of the foot protection blocks, rock mound and caisson's surface are made from the observed images based on the estimated state of the AUV, to verify the performance of the method.
Oceans 2005 - Europe; 07/2005
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ABSTRACT: It is important to investigate the inside of the hull of a submerged wreck for identifying the accident circumstances and causes. Oil-tanker wrecks usually cause serious damage to natural environment. Periodical inspection is also necessary to protect ocean environment. Although these operations are normally carried out by Remotely Operated Vehicles (ROVs), they require specifically designed support vessels with heavy equipment. Thus, their mobility is inevitably restricted for immediate operation. Therefore, it is expected that the demand for the development of compact and intelligent Autonomous Underwater Vehicles (AUVs) to undertake these complicated missions will increase greatly over the next few years. Since AUV navigation into a semi-closed space is a dangerous operation, the AUV should be aware of its surroundings in real time and make careful path planning based on sensory data. Although acoustic sensors are utilized to survey underwater objects, they are seriously affected by multipath effects in a narrow closed space, and may have poor accuracy and resolution, which are not sufficient for AUV navigation. In this paper, we propose an autonomous navigation and investigation system by stereo vision for surveying closed spaces. The system was implemented in a newly constructed AUV, "Tam-Egg 2", a small size autonomous underwater vehicle, and the vehicle successfully identified the rectangular windows of a model hull placed in an experiment tank, and passed through them without touching the hull.
OCEANS, 2005. Proceedings of MTS/IEEE; 02/2005
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ABSTRACT: Autonomous underwater vehicles (AUVs) are suitable for condition survey of the surface of artificial structures such as pillars and caissons in harbors. This paper introduces a method for AUVs to trace artificial structures using a light-section ranging system. This system acquires the profile of the target objects over a wide area using a sheet laser beam. The vehicle navigates by referencing the principal shape of the structure, and traces its surface while taking video images of it. This ranging system also enables 3D mapping of its surroundings based on high accuracy positioning. The method is implemented on the testbed AUV "Tri-Dog 1" and its performance is verified through tank tests. It is shown that the AUV navigates robustly against small obstacles and floating particles. Precise depth mapping of the tank floor is also carried out using the same system.
Control, Automation, Robotics and Vision Conference, 2004. ICARCV 2004 8th; 01/2005
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ABSTRACT: Autonomous Underwater Vehicles (AUVs) are suitable for ocean observation, since they can swim freely without an umbilical cable. There is a great demand for AUVs not only for wide area surveys, but also for condition surveys of artificial underwater structures. This paper proposes a real-time localization method for navigation that can obtain robust and autonomous observations by fusing data from multiple sensors. This method enables an AUV to localize itself in relation to underwater structures without any support systems except its own sensors. It was actually implemented using the testbed AUV "Tri-Dog 1" and verified by tank tests
OCEANS '04. MTTS/IEEE TECHNO-OCEAN '04; 12/2004
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ABSTRACT: Autonomous Underwater Vehicles (AUVs) are suitable for condition survey of artificial structures such as pillars and caissons in harbors. The authors have developed a method to investigate the structures using AUVs. The method has been successfully demonstrated in tank tests and sea trials as reported in the previous papers. Since the ranging system in this method used an array of pinpoint lasers, it is oversensitive to noise, for example small obstacles and floating particles. This paper describes a method to trace the structure's surface using a sheet laser beam that overcomes the difficulties previously encountered. This ranging system determines the continuous shape of the target objects over a wide area by light-sectioning. The vehicle navigates referencing the principal shape of the structure, tracing its surface while taking video images. The method is implemented using testbed AUV "Tri-Dog 1" and verified by tank tests. It is proved that the new method is more robust against noise and trivial objects than the previous method that used a pinpoint laser ranging system. This ranging system can also be used for 3D mapping of the surface and bottom structure.
Underwater Technology, 2004. UT '04. 2004 International Symposium on; 05/2004
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ABSTRACT: To investigate underwater objects such as piles and caissons in harbors by taking visual images, autonomous under water vehicles (AUVs) have advantages that they have no umbilical cable which may get entangled in the target object and surrounding obstacles. This paper proposes a navigation method for AUVs to observe such objects using a laser range measurement system that consists of a TV camera and laser pointing devices. This ranging system provides precise distance to the target object so that the vehicle can trace the shape of the target object keeping constant distance and attitude. It is assumed that the visibility is adequate for taking visual images of the target. It was implemented in the testbed AUV tri-dog 1, and proved experimentally through tank tests. The vehicle accomplished the observing mission that automatically detects the turn around three pile-objects those are modeled on actual piles in a harbor. This paper also shows the result of sea trials. Based on the proposed method, AUVs will find new practical applications of autonomous observation of underwater objects.
Scientific Use of Submarine Cables and Related Technologies, 2003. The 3rd International Workshop on; 07/2003
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ABSTRACT: To investigate underwater structures such as piles and caissons in harbors, and risers and jackets of deep-sea oilfields by taking visual images, Autonomous Underwater Vehicles (AUV's) have advantages that they have no umbilical cable which may get entangled in the structures and surrounding obstacles. The authors have proposed a navigation method for AUV's to observe such objects using a laser ranging system that consists of TV camera and laser pointing devices in previous papers. This ranging system provides precise distance to the target object so that the vehicle can trace the shape of the target object keeping constant distance and attitude. The method was implemented in the testbed AUV "Tri-Dog 1", and proved experimentally through tank tests in 2001. Following the success of the tank tests, the authors have carried out sea trials in 2002 at the port of Kamaishi, Japan, which has huge breakwaters. This paper describes the result of the sea trials and our perspectives. Based on the proposed system, AUV's will be able to carry out autonomous investigation of underwater structures in the near future.
OCEANS 2003. Proceedings; 02/2003
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ABSTRACT: To observe underwater structures such as artificial piles in harbors by taking visual images, the autonomous underwater vehicles (AUVs) have advantages that they have no problem related to the umbilical cable which may get entangled with the target object and surrounding obstacles. It is usually difficult to measure the precise configuration of such objects by using acoustic measurement systems because of poor resolution and diffused reflection of sound. This paper proposes sensing and navigation methods to observe such objects based on images by a CCD camera with laser pointers, on the assumption that the visibility is enough for taking their visual images. The navigation system cannot provide accurate enough position. Thus, AUVs change over their navigation basis from navigation system to relative position to the target so as to trace the shape of that. The proposed method was implemented in the testbed AUV Tri-Dog 1 and proved experimentally through tank tests. The vehicle accomplished the mission that autonomously detects 3 piles of 1 meter in diameter that are modeled on actual piles in a harbor, and turns around them. Based on the proposed system, AUVs will be able to carry out surveys of the target object without any help from outside.
Underwater Technology, 2002. Proceedings of the 2002 International Symposium on; 02/2002
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ABSTRACT: To observe underwater objects such as artificial piles and natural chimneys by taking visual images, autonomous underwater vehicles (AUVs) have advantages that they have no problem related to the umbilical cable which may get entangled with the target and surrounding obstacles. This paper proposes a navigation method for AUVs to observe such objects based on images by a CCD camera with simple laser pointers, on the assumption that the visibility is enough for taking their visual images. It includes a localization method under a distorted magnetic field. The proposed method was implemented in the developed testbed AUV "Tri-Dog 1", and proved experimentally through tank tests. The vehicle accomplished the observing mission that automatically detects three pile-objects and turns around them which were modeled on actual piles in a harbor. Based on the proposed method, AUVs are able to carry out a survey of the target object in detail without any help from outside.
Robotics and Automation, 2002. Proceedings. ICRA '02. IEEE International Conference on; 02/2002
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ABSTRACT: Near underwater structures or the surface of shallow water,
acoustic sensing based navigation of autonomous underwater vehicles
(AUVs) suffers from inaccurate positioning which is caused by acoustic
sensing such as multi-pass and noisy data. In the paper a new underwater
navigation method for AUVs is proposed based on artificial underwater
landmarks which are recognized by a vision system implemented in the
robot. An underwater image processing strategy and an underwater vision
environment analysis method are introduced to improve reliability of the
underwater vision system. Experiments were carried out to demonstrate
the efficiency of the proposed navigation method of AUVs
OCEANS, 2001. MTS/IEEE Conference and Exhibition; 02/2001
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ABSTRACT: AUV (autonomous underwater vehicles) can be used to observe and
get video images of underwater structures. This paper proposes a
navigation method of AUV for observing large objects which disturb
magnetic fields, based on images by a CCD camera, assuming that
visibility is good enough. The AUV uses dead reckoning navigation until
it comes near to the object. For detecting and observing the object, it
uses two laser pointers, which are mounted in parallel on the head of
the AUV, and a CCD camera. Through visual processing, the AUV calculates
distances to two reflected points of laser beams, then determines angle
between the object and the AUV. The AUV can then turn around the object
keeping constant distance and angle. The proposed algorithm was
implemented in the developed test bed AUV "Tri-Dog 1" and tested through
tank tests. The vehicle successfully traced a straight wall and a curved
wall, detected piles of 1 meter in diameter, and turned around them. It
finds the precise distance to an object. An AUV will thus be able to
carry out a survey of a target object in detail without any help from
outside
OCEANS, 2001. MTS/IEEE Conference and Exhibition; 02/2001
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ABSTRACT: Autonomous underwater vehicles (AUV) are suitable for condition survey of artificial structures such as pillars and caissons in harbors. This paper describes a method to trace the structure's surface using a light-section profiling system. This profiling system determines the continuous shape of the target objects over a wide area by the light sectioning method. The vehicle navigates referencing the principal shape of the structure, tracing its surface while taking video images. This method also enables three-dimensional mapping of traced structures and the seabed. The method is implemented using testbed AUV "Tri-Dog 1" and verified by tank tests. The AUV navigates robustly against trivial objects such as small obstacles and floating particles. Precise depth mapping of the tank bottom is carried out.
Intelligent Robots and Systems, 2004. (IROS 2004). Proceedings. 2004 IEEE/RSJ International Conference on;
