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R. Ajit Shenoi - One of the best experts on this subject based on the ideXlab platform.

  • Feasibility study of a new energy scavenging system for an autonomous underwater vehicle
    Autonomous Robots, 2016
    Co-Authors: N. C. Townsend, R. Ajit Shenoi
    Abstract:

    Autonomous underwater vehicles (AUV) can only operate for hours or days at a time between battery charges. Alternative power systems or in-situ charging strategies are required to extend missions. This paper presents the feasibility of a new gyroscopic wave-energy scavenging system. The energy scavenging system promises to; reduce AUV battery requirements negating the necessity to carry sufficient energy reserves (size and weight) for entire missions, reduce costs by freeing Support Vessel time (a major cost component in AUV deployment) and enable AUVs to be remotely and renewably recharged at sea, indefinitely extending missions. A theoretical description of the system and simulation results for a range of geometrically scaled torpedo style AUVs are presented. The results show that the generated power is sufficient to provide power for a range of AUV sensors and comparable to equivalent solar panel and wind turbine devices.

  • development of a prototype test rig for a cryogenic marine heavy lift buoyancy system
    ASME 2011 30th International Conference on Ocean Offshore and Arctic Engineering, 2011
    Co-Authors: R F Nichollslee, Paul C Mcdonald, S R Turnock, R. Ajit Shenoi
    Abstract:

    There is a continual search for new methods of marine salvage and decommissioning of structures in the open sea in order to improve control and lower operational costs. The concept design of a lightweight, cryogenic, marine, heavy lift, buoyancy system has been investigated. The objective is to be able to raise or lower high mass objects controlled solely from a surface Support Vessel. The overall design concept and associated system development issues have been discussed previously. This work concentrates on the development of a test rig for the cryogenic, marine, heavy lift, buoyancy system and associated test procedures. The main area of concern in the design process is the cryogenic Dewar. This is required to operate at temperatures as low as −196°C but also at pressures exceeding 35bar. A more detailed design of the Dewar, including cryogenic composite materials testing, is considered. The prototype will be assessed through three different testing scenarios; shallow water, open water deep sea, and a hyperbaric chamber for very high pressure testing. The procedures for each of these test scenarios is discussed.Copyright © 2011 by ASME

John J Leonard - One of the best experts on this subject based on the ideXlab platform.

  • efficient auv navigation fusing acoustic ranging and side scan sonar
    International Conference on Robotics and Automation, 2011
    Co-Authors: Maurice Fallon, Michael Kaess, Hordur Johannsson, John J Leonard
    Abstract:

    This paper presents an on-line nonlinear least squares algorithm for multi-sensor autonomous underwater vehicle (AUV) navigation. The approach integrates the global constraints of range to and GPS position of a surface vehicle or buoy communicated via acoustic modems and relative pose constraints arising from targets detected in side-scan sonar images. The approach utilizes an efficient optimization algorithm, iSAM, which allows for consistent on-line estimation of the entire set of trajectory constraints. The optimized trajectory can then be used to more accurately navigate the AUV, to extend mission duration, and to avoid GPS surfacing. As iSAM provides efficient access to the marginal covariances of previously observed features, automatic data association is greatly simplified — particularly in sparse marine environments. A key feature of our approach is its intended scalability to single surface sensor (a vehicle or buoy) broadcasting its GPS position and simultaneous one-way travel time range (OWTT) to multiple AUVs. We discuss why our approach is scalable as well as robust to modem transmission failure. Results are provided for an ocean experiment using a Hydroid REMUS 100 AUV co-operating with one of two craft: an autonomous surface vehicle (ASV) and a manned Support Vessel. During these experiments the ranging portion of the algorithm ran online on-board the AUV. Extension of the paradigm to multiple missions via the optimization of successive survey missions (and the resultant sonar mosaics) is also demonstrated.

Takeshi Nakatani - One of the best experts on this subject based on the ideXlab platform.

  • Unmanned Seafloor Survey System Without Support Vessel and its Recent Operations in Sea Trials
    2019 IEEE Underwater Technology (UT), 2019
    Co-Authors: Takeshi Ohki, Takeshi Nakatani, Yuya Nishida, Blair Thornton
    Abstract:

    As the future seafloor survey system without a Support Vessel, combinations of autonomous underwater vehicles (AUVs) and autonomous surface vehicles (ASVs) are expected. To realize ship-less operations, we have designed unmanned survey systems which consists of multiple AUVs, AUV towing frames, and an ASV. The ASV of the proposed system works as two roles: transporting AUVs between a shore base and a survey site, and relaying the communication between AUVs and a ground-based mission control. We have developed and tested the two sets of the proposed survey system. The first one is the survey system for 2,000m depth consists of three AUVs supervised by an ASV and the second one was for 4,000m depth consists of two AUVs supervised by the ASV. In this paper, we respectively introduce the two sets of the system design and also report the implementation and results of recent sea-trials in Suruga Bay.

  • fast and ultra wide area bathymetric survey system without Support Vessel
    OCEANS Conference, 2018
    Co-Authors: Takeshi Ohki, Takeshi Nakatani, Yuya Nishida, Lai Thornto
    Abstract:

    Autonomous underwater vehicle (AUV) operations require manned Support Vessel for communication, navigation, deployment, and recovery. Because the number of the Support Vessel is limited, the strong tie between AUV and Support Vessel prevents to operate many AUVs simultaneously. Since this problem has been shared in oceanic markets, we propose a compact and mobile package of multi-robot system to realize fast and ultra-wide area bathymetric survey without Support Vessel. The proposed system consists of several numbers of AUVs, single autonomous surface vehicle (ASV), and ground mission control. The proposed system includes an unmanned deploy and recovery system, which enables towing, deploying and recovering multiple AUVs by an ASV without manned Support Vessel. The three AUVs can equip different payloads and basically follow the order of forming a convoy from the ASV which is also supervised by operators at a remote ground base station. Satellites communications are used between the ground base station and the ASV, and acoustic communications are used between the ASV and the ASVs. The proposed system has been developed and implemented. Several sea-trials had been conducted to confirm the validity of the proposed system. In this paper, we introduce the overall design concept of the proposed system and the recent activities.

  • Development of prototype autonomous surface vehicle
    2016 Techno-Ocean (Techno-Ocean), 2016
    Co-Authors: T. Hyakudome, Takeshi Nakatani, Takao Sawa, Yoshiyuki Nakano, Yoshitaka Watanabe, Tatsuya Fukuda, H. Matsumoto, Ryotaro Suga, Hiroshi Yoshida, Hiroshi Ochi
    Abstract:

    JAMSTEC has operated autonomous underwater vehicles (AUVs) for scientific survey of seabed mineral resources. Conventionally, the number of AUVs the Support Vessel can track is limited to one during operations. However, it takes a long time for one AUV to survey a large target area. To solve this problem, an autonomous surface vehicle (ASV) has been developed. The ASV, instead of the Support Vessel autonomously tracks AUV and monitors its progress, enabling the simultaneous operation of multiple AUVs and thereby the survey of a larger target area within a given period of time.

N. C. Townsend - One of the best experts on this subject based on the ideXlab platform.

  • Feasibility study of a new energy scavenging system for an autonomous underwater vehicle
    Autonomous Robots, 2016
    Co-Authors: N. C. Townsend, R. Ajit Shenoi
    Abstract:

    Autonomous underwater vehicles (AUV) can only operate for hours or days at a time between battery charges. Alternative power systems or in-situ charging strategies are required to extend missions. This paper presents the feasibility of a new gyroscopic wave-energy scavenging system. The energy scavenging system promises to; reduce AUV battery requirements negating the necessity to carry sufficient energy reserves (size and weight) for entire missions, reduce costs by freeing Support Vessel time (a major cost component in AUV deployment) and enable AUVs to be remotely and renewably recharged at sea, indefinitely extending missions. A theoretical description of the system and simulation results for a range of geometrically scaled torpedo style AUVs are presented. The results show that the generated power is sufficient to provide power for a range of AUV sensors and comparable to equivalent solar panel and wind turbine devices.

Junlei Wang - One of the best experts on this subject based on the ideXlab platform.