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Oceanic Engineering, IEEE Journal of

Issue 1 • Date Jan 1995

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Displaying Results 1 - 11 of 11
  • Applying chaos to radar detection in an ocean environment: an experimental study

    Publication Year: 1995 , Page(s): 56 - 64
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    Ship navigation through ice-infested waters is a problem of deep concern to the oil exploration industry of Northern countries. Conventional marine radars do not perform satisfactorily in detecting small targets such as small pieces of iceberg. This paper reports a new method for detection in an ocean environment. The approach is based on the recent observation that sea clutter, radar echoes from the sea surface, can be modeled as a nonlinear deterministic dynamical system which can be used as an alternative to the conventional stochastic process. Based on this model, detection in sea clutter is considered as dynamical system classification instead of statistical hypothesis testing. Two dynamical detection methods are proposed. The first one uses a dynamical invariant called the attractor dimension to distinguish a target from a pure clutter process. The second approach tries to detect the existence of a target by observing the “difference” of the motion of the target and the clutter process. To show the validity of the idea of dynamical detection in sea clutter, real sea clutter, and target data were used in this study View full abstract»

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  • TOBI image processing-the state of the art

    Publication Year: 1995 , Page(s): 85 - 93
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (944 KB)  

    TOBI (Towed Ocean Bottom Instrument) is a deep-tow sidescan sonar vehicle from which sidescan sonar data are now routinely collected and archived. This paper describes the algorithms developed for detailed processing of TOBI data. Sonar imagery has a characteristic set of processing challenges and these are addressed. TOBI provides a very large sonar dataset, and to limit the difficulties of handling and processing these data, the raw data are subjected to a data reduction technique prior to further processing. Slant-range correction is improved by editing vehicle altitude data using a median filter. Noise on TOBI imagery can appear in two main forms; speckle noise and line dropouts. Speckle noise is removed by a small median difference kernel and line dropouts are removed using a ratio of two box-car filters, each with appropriate thresholding techniques. Precise geocoding of the imagery requires an accurate estimate of vehicle location, and a method of calculation is presented. Two optional processing algorithms are also; presented; deblurring of imagery to improve along-track resolution at far range, and the suppression of a surface reflection return which may occur when TOBI is operated in relatively shallow water. Several of the techniques presented can be transcribed and modified to suit other datasets View full abstract»

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  • Design of a high performance variable structure position control of ROVs

    Publication Year: 1995 , Page(s): 42 - 55
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1072 KB)  

    An adaptive control scheme for dynamic positioning (DP) of remotely operated underwater vehicles (ROV) is proposed based on a recently developed output feedback variable structure control (VSC) algorithm named VS-MRAC. Only position measurement is required. Precise modeling of the ROV is not needed and unmodeled perturbations can be effectively rejected. A simple method for discretizing the original continuous-time VS-MRAC is proposed based on dead-beat response. Other important practical implementation issues are considered. The performance is evaluated by simulation with a realistic ROV model and by full-scale experimental pool tests with an actual ROV View full abstract»

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  • Robust regression-based EKF for tracking underwater targets

    Publication Year: 1995 , Page(s): 31 - 41
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    In underwater target tracking applications, measurement uncertainty and inaccuracies are usually modeled as additive Gaussian noise. The Gaussian model of noise may not be appropriate in many practical systems. The non-Gaussian noise and the model non-linearity arising in a tracking system will seriously affect the tracking performance. This paper discusses one way to create a robust version of the extended Kalman filter for enhanced underwater target tracking. State estimation in the filter is done through the robust regression approach and Welsch's proposal is used in the regression process. Monte Carlo simulation results with heavy-tailed contaminated observation noise demonstrate the robustness of the proposed estimation procedure View full abstract»

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  • Propulsion system with flexible/rigid oscillating fin

    Publication Year: 1995 , Page(s): 23 - 30
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    The purpose of this paper is to describe the feasibility research on an oscillating fin propulsion control system as a vehicle actuator. The system is designed and constructed in order to be combined with ship models. Tank cruising tests are conducted to confirm the system's feasibility. As a result, several advantages of the oscillating fin system are found. A neural network is successfully applied for an identification of the ship model with the oscillating fin, and its effectiveness is confirmed View full abstract»

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  • An expert system for monitoring dynamic stability of small craft

    Publication Year: 1995 , Page(s): 13 - 22
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    This paper describes an intelligent monitoring and advisory system for vessel safety. This system uses environmental information obtained from a number of sensors and proposes corrective action based on a rule-base derived from human expertise, experiments, and theoretical research. The architecture of the monitoring and advisory system is described. Capsizing modes of a ship at sea are explained, and the fuzzy expert system used in the decision-making process is detailed. Simulations of various sea conditions leading to capsize are presented, and the vessel response to the corrective action suggested by the advisory system is illustrated View full abstract»

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  • Minimum time-energy trajectory planning for automatic ship berthing

    Publication Year: 1995 , Page(s): 4 - 12
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    A ship optimal trajectory planning method based on the dynamic model of the ship is presented. First a mathematical modular model is introduced for describing the non-linear dynamics of the ship. Then the problem of optimal trajectory planning is discussed. The trajectory is obtained through the optimization of a time-energy criterion, taking into account constraints on the steering system, environment, non-linearities, and non-convexity of the state space equations. The discrete augmented Lagrangian approach is used to compute the optimal constrained controller. The method was programmed on a HP700 workstation. This approach was applied to automatic ship berthing maneuver View full abstract»

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  • A techno-economic comparison of power systems for autonomous underwater vehicles

    Publication Year: 1995 , Page(s): 94 - 100
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    This paper compares lead-acid batteries, sodium-sulfur batteries, solid polymer fuel cells and closed-cycle diesel engines for autonomous underwater vehicle (AUV) applications. The service is described in terms of a parametric mission and life cycle. A generic AUV is used as a basis for comparison. Power systems are evaluated by two criteria: (1) submerged endurance capability and (2) life cycle cost. This study determines categories of service for which each power system is preferred. The solid polymer fuel cell can provide greater submerged endurance than other power systems examined. For extremely long duration AUV missions, the fuel cell is the required system, indicating a possible market niche for today's fuel cell technology. Considering cost projections for each power system, the results also show that the SPFC can become cost-competitive with conventional technologies, particularly for services characterized by high levels of utilization View full abstract»

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  • The use of artificial neural networks for the intelligent optimal control of surface ships

    Publication Year: 1995 , Page(s): 65 - 72
    Cited by:  Papers (8)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    Many conventional ship autopilots use proportional integral and derivative (PID) control algorithms to guide a ship on a fixed heading (course-keeping) or a new heading (course-changing). Such systems usually have a gyrocompass as a single sensory input. Modern sea going vessels have a range of navigation aids most of which may be interconnected to form integrated systems. It is possible to employ the navigational data to provide best estimates of state vectors (Kalman filter) and optimal guidance strategies. Such techniques require powerful computing facilities, particularly if the dynamic characteristics of the vessel are changing, as may be the case in a maneuvering situation or changes in forward speed. This paper investigates the possibility of training a neural network to behave in the same manner as an optimal ship guidance system, the objective being to provide a system that can adapt its parameters so that it provides optimal performance over a range of conditions, without incurring a large computational penalty. A series of simulation studies have been undertaken to compare the performance of a trained neural network with that of the original optimal guidance system over a range of forward speeds. It is demonstrated that a single network has comparable performance to a set of optimal guidance control laws, each computed for different forward speeds View full abstract»

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  • Performance analysis of the incoherent and skewness matched filter detectors in multipath environments

    Publication Year: 1995 , Page(s): 80 - 84
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    For cases in which a received signal is known exactly and the additive noise is white and Gaussian, the optimal detector can be implemented as a matched filter followed by a threshold comparator. However, the performance of this detector is sensitive to signal shifts and mismatch between the assumed and the actual structure of the received signal. As such, the use of a matched filter detector in a multipath environment can result in substantially poorer performance than expected. Here, it is shown that the use of the incoherent (or sliding) matched filter can also result in a substantial performance loss if the signal autocorrelation function is narrow relative to the interarrival times of the pulses. In contrast, a detector that compares the zero-zero lag of the matched filter cumulant sequence to a threshold has a performance that is relatively insensitive to multipath channels View full abstract»

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  • Adaptive separation of mixed broadband sound sources with delays by a beamforming Herault-Jutten network

    Publication Year: 1995 , Page(s): 73 - 79
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    The Herault-Jutten network has been used to separate independent sound sources that have been linearly mixed. The problem of separating a mixture of several independent signals in free-field conditions or a signal and echoes in confined spaces is compounded by propagation time delays between the source(s) and the microphones because the conventional Herault-Jutten network cannot tolerate time delays. In this paper, we combine a symmetrically balanced beamforming array with the conventional Herault-Jutten network. The resulting system can adaptively separate signals that include delays introduced by the propagation medium. The proposed algorithm has been simulated in digital communication multipath channels where intersymbol interference exists. The simulation results show two clear advantages of the proposed method over the conventional adaptive equalization: (1) there is no penalty for very long impulse responses caused by long delays, and (2) no training signals are needed for equalization. The design of a multibeamformer to handle the source separation of multiple broad-band signals is also presented View full abstract»

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Aims & Scope

The IEEE Journal of Oceanic Engineering (ISSN 0364-9059) is published quarterly by the IEEE Oceanic Engineering Society (IEEE OES). The scope of the Journal is the field of interest of the IEEE OES, which encompasses all aspects of science, engineering, and technology that address research, development, and operations pertaining to all bodies of water. This includes the creation of new capabilities and technologies from concept design through prototypes, testing, and operational systems to sense, explore, understand, develop, use, and responsibly manage natural resources.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
N. Ross Chapman
School of Earth & Ocean Sciences
University of Victoria
3800 Finnerty Road
Victoria, BC V8P 5C2 Canada
chapman@uvic.ca