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For Unmanned Underwater Vehicles (UUV), the problem of position estimation is crucial for many different aspects ranging from good navigation performance to suitable geo-referencing capabilities of the payload data. The possibility of accurately estimating the UUV orientation has a positive impact on it, as the most of position estimation algorithms rely on the orientation signal. Among the orientation...
Autonomous underwater vehicles (AUVs) are increasingly being used to perform search operations but its capabilities are limited by the efficiency of the planning process. The objective of the paper is to propose new survey planning methods for AUVs. In particular, the problem of multi-objective search mission planning with an AUV navigating in known or unknown 3D environments is studied. The vehicle...
This paper proposes a non-stationary time-continuous simulation model for wideband shallow underwater acoustic (UWA) channels based on measured Doppler power spectrums (DPSs). Measurement-based channel simulators are essential for the test, optimization, and performance analysis of UWA communication systems. The aim is to fit the DPS of the simulation model to that of the measured UWA channel. The...
This paper describes how to automatically identify Posidonea Oceanica (P.O.) from seabed images gathered by a bottom-looking camera. Different methods based on machine learning and deep learning algorithms are presented and compared. On the one hand, texture descriptors and co-occurrence matrices are used to characterize the images and classify the P.O. regions by means of Support Vector Machine and...
The detection of dissolved carbon dioxide (dCO2) is made possible through a colorimetric effect that occurs in a sensitive membrane. The reaction with dCO2 changes the pH of the membrane causing a small difference in its colour which results in a characteristic absorbance spectrum band near 435 nm. A sensing platform based on this effect was developed and tested in gaseous and in aqueous environments...
Analysis of the dynamics of coastal relief during long time scales allows us to define differences and general trends in the evolution of different coastal types. Long-term dynamics of various coastal profiles was explored on the basis of cartographic data and individual field measurements for different types of sandy beaches located in the northern and northwestern coasts of the Black Sea. The variability...
Tidal stream energy is a reliable and predictable low-carbon energy source. Over the next few years the first arrays of multiple tidal stream turbines will be deployed mostly in UK, French and Canadian waters. The potential environmental effects should first be examined, in order to scale and site them appropriately. Large theoretical arrays of tidal stream turbines were designed for Scottish Waters...
There is significant evidence that the low-frequency mean acoustic noise pressure level in the ocean has been constantly increasing in the last decades. The main noise sources responsible for this increase were identified as ship traffic, offshore construction and oil & gas surveying. The Portuguese Navy funded SUBECO project aims at deploying a network of multiparametric offshore buoys for environmental...
The autonomous underwater vehicle (AUV) Guanay II was designed to navigate on the surface of the sea, and to realize a vertical immersion in specific points. This vehicle has three thrusters located on stern, oriented to provide propulsion and yaw control on the horizontal plane. On the other hand, the immersion system used in the Guanay II is based in the change of the buoyancy of the vehicle, by...
Biofouling represents a real technical challenge in the marine environment. Current antifouling strategies offer insufficient protection from biofouling for many applications, e.g. water sensing technologies, and effective novel methods of antifouling are required to support technology developments in the marine. Non-toxic approaches to antifouling are desirable; however, further development of effective...
An experimental work has been devised to investigate the bore height and velocity on a dry flatbed as well as the impingement forces acting on a vertical structure subjected to both Newtonian (water) and non-Newtonian (kaolin clay at 20% concentration) fluids using physical modelling. Rheological analysis has shown that within the observed shear rate range (10 to 500 1/s), the kaolin mixture exhibits...
This paper investigates trajectory tracking control problem for Autonomous Underwater Vehicles (AUVs) in presence of actuator dynamics constraints and a large initial tracking error or a sudden change in the desired trajectory. A new tracking control algorithm is developed by re-planning a new local trajectory. Based on the AUV's current position and the desired position after a certain interval,...
Laser ranging in a water medium is always challenging owing to the attenuation and scattering of the laser. This paper presents a correction method for laser ranging based on a laser ranging experiment in different turbidities of water. First, this paper examines the influence of water on the dynamic range and accuracy of laser ranging. Then, the effects of attenuation and scattering are eliminated...
Underwater vision has specific characteristics such as high attenuation of lights, severe noise and haze in the images. For real-time fish detection using underwater vision, this paper proposes convolutional neural network based techniques based on You Only Look Once algorithm. Actual fish video images were used to evaluate the reliability and accuracy of the proposed method. As a result, the network...
During the engineering feasibility study period of circular synthetic aperture sonar (CSAS) design, it is necessary to establish the computer simulation model of the CSAS imaging with various sonar parameters and underwater extended targets. In this work, the TriKirch scattering model also known as the Planar elements method, which is based on the Kirchhoff approximation and triangulation of target's...
The presence of a huge amount unexploded ordnance devices (UXO) on the sea floor is one of the major problems during installation and maintenance of offshore wind farms and other offshore structures. To identify all targets, time and cost consuming campaigns are necessary. The clearance of UXO is often limited by time due to the idea that UXO can migrate on the sea floor. Therefore the UXO-measure...
Mechanical devices operating in noisy environments lead to low signal-to-noise-ratios creating a challenging signal processing problem to monitor the device in real-time. To detect/classify a particular type of device from noisy vibration data, it is necessary to identify signatures that make it unique. Resonant (modal) frequencies emitted offer a signature characterizing its operation. The monitoring...
This paper presents a method of direction-of-arrival estimation using the high-order superdirective beamforming for a circular hydrophone array. The weighting vectors with different orders used for DOA estimation can be obtained using the previously proposed eigenbeam decomposition and synthesis theory, which can provide frequency-invariant beampatterns in a wide frequency band. The DOA estimation...
The current evolution of unmanned systems has unlocked a valuable opportunity to extend military operational capabilities in maritime environments, through the performance of missions such as: maritime reconnaissance, surveillance, patrolling, and search and rescue. To further develop this potential, the implementation of an interoperable structure that contains several unmanned vehicles cooperating...
There is an urgent need among the scientific community for a better understanding of the air-sea interactions that occur during typhoons and improved accuracy in typhoon forecasting. To this end, the Institute of Oceanography at the National Taiwan University (IONTU) has developed a buoy that can measure meteorological and hydrographic conditions, and transmit the high-precision data in near real-time...
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