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Laser-induced breakdown spectroscopy (LIBS) is a form of chemical analysis that can determine the elemental composition of targets. LIBS has been used for underwater exploration, at over 1000 m depth in active vent fields, and it can potentially form the basis of an efficient screening method prior to detailed sampling or boring surveys. In this study, a method for in-situ chemical classification...
This work describes the development and characterization of a wide beam and wideband ultrasonic transducer, designed as an emitter for underwater communications up to 1.5 MHz. The active element being used is composed of two layers of 110 μm PVDF (Polyvinylidene fluoride) film, with NiCu electrodes. The transducer has a semicircular shape with a diameter of 15 cm. Pool trials show a transmitting voltage...
Underwater gliders are widely used in ocean survey operations due to their unique capability of long-range cruising with low energy consumption. As a critical technique, accurate attitude control is challenging due to the highly nonlinear, heavily coupled system model of an underwater glider with uncertain hydrodynamic parameters and suffering from environmental disturbances. To investigate this problem,...
The main goal of this paper is to study and compare different power distribution alternatives for subsea electrical components for deep-sea mining in the Norwegian Sea. Such application requires power delivery in the multi-MW range at water depth of more than 3000 m. Hence, AC (50Hz), DC, high frequency AC and low frequency AC can be possible options to transfer electrical power to the mining equipment...
An increasingly important of military field and ocean survey is a swarm of AUV working in cooperation in an underwater which can minimizing physical risk to humans and cost. During long range operating task, how to maximum the cooperation efficiency of AUV swarm, to reduce the energy consumption, and to ensure the operating safety, all these are important for AUV community cooperation. This paper...
Underwater imaging has become an active research area in recent years as an effect of increased interest in underwater environments and is getting potential impact on the world economy, in what is called blue growth. Since sound propagates larger distances than electromagnetic waves underwater, sonar is typically used for underwater imaging. One interesting sonar image setting is comprised of using...
This paper describes a method to reconstruct the three-dimensional aspects of underwater objects using side-scan sonar images. The sonar images are segmented into three kinds of regions: echo, shadow and background. A two-dimensional intensity map is estimated from the echoes and a two-dimensional depth map is computed from the shadow information. With the transformation model, the final reconstruction...
Many offshore structures currently in use are supported by piles with large length-to-diameter aspect ratios, because it is well known that such foundations can hold large forces and moments. In environments where long piles are not suitable, structures will use foundations with very low aspect ratios such as skirts and mats. Capacity of long piles has been studied for decades and is well documented,...
Testing is an integral part when developing a highly automated and autonomous safety-critical system. This paper will discuss the current situation of testing of highly automated and autonomous systems in the maritime domain. The development of such systems in the automotive domain is in a more advanced state then in the maritime domain. Due to the highly dynamic market situation much effort is invested,...
A free-fall vertical profiler developed by Ocean University of China had been deployed in the South China Sea with the descend speed of 0.35–0.4 m/s. Both of the fast-response thermistor and shear probes are attached to the turbulence observation instrument, which are used to estimate the turbulence intensity. Throughout the observation period, the profiler succeed to collect time series of turbulence...
In this paper, performance of an underwater acoustic OFDM system is studied for various pilot allocation schemes having different pilot spacings in the frequency and time domain. The underwater OFDM system is first developed to support different pilot allocation schemes, and the experiments is conducted at the western sea near Janggohang, South Korea in July 2016. The system performance is, then,...
The rigid swimming paddle as an auxiliary motive power underwater is modeled and designed as the first attempt for the shoal crab robot Crabot-I. In this work, the hydrodynamics of a swimming paddle is investigated numerically and experimentally. The primary focus of our study is related specifically to the effect of St on hydrodynamic performance of a single swimming paddle in lift-based and drag-based...
A 6-DOF isomorphic master-slave underwater manipulator for deep-water operation is developed. The hydrodynamic model of the manipulator is established. A master — slave controller based on fuzzy PID control is designed for the strong nonlinearity of the master-slave manipulator. The dsPACE semi-physical simulation platform is used to build the two joint test system of the master-slave manipulator...
This paper considers the straight-line trajectory tracking control problem of a class of underactuated underwater vehicles with bounded disturbances and hard input constraints. A constrained robust straight-line tracking controller based on model predictive control (MPC) is designed, and an event-triggered scheduling strategy is incorporated to alleviate the computation load of MPC. Furthermore, sufficient...
In this paper, the influence of delays on the ability of a formation control algorithm to coordinate a group of twelve Biomimetic Autonomous Underwater Vehicles (BAUVs) is investigated. In this study the formation control algorithm is a decentralized methodology based on the behavioural mechanisms of fish within school structures. Incorporated within this algorithm is a representation of the well-known...
The received wind driven noise field can be described as a sum of fields radiated from many random sources on the sea surface. Wind driven noise source levels can be modeled by empirical relationship with local wind speed. A method for modeling wind-driven ambient noise based on ray approach in deep ocean is presented. Simulations are performed to demonstrate the validity of the method. The wind-driven...
This paper proposes a method to build large scale coverage maps of Posidonia Oceanica (P.O.) using the imagery provided by an AUV endowed with a bottom-looking camera. The process begins by detecting the regions containing P.O. in each individual image. Afterwards, the overlap between images is searched and the P.O. detection data in these overlapping regions is fused to build a global detection map...
Communication security is a critical and increasingly challenging issue in wireless networks. Signals have the risk of being intercepted in traditional wireless communication because of the wireless propagation characteristics. There is also the same problem for ship satellite communication. The direct antenna modulation (DAM) is a promising secure communication technique, which scrambles signals...
A method of estimating the source depth of wideband underwater acoustic pulses in deep water is proposed in this paper. The method is based on the characteristic of frequency domain interference oscillation of broadband signals received at a single stationary hydrophone. The oscillation period is related to the Lloyd's Mirror effect (LME) and can be transformed into the information of source depth...
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