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Search results for: UNDERWATER ACOUSTIC CHANNEL
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Signatures and acoustic images of objects moving in water
PublicationObservation of underwater space is part of a generaltrend, which primary purpose is to protect and increasesafety in the selected area. The basic aim of the paper ispresentation of designated acoustic characteristics typicalfor objects moving on the water surface and under water,which represent some knowledge about detection of theseobjects. Create a catalog of acoustic signature and not onlyacoustic, as well as acoustic images...
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Theoretical Model of Acoustic Wave Propagation in Shallow Water
PublicationThe work is devoted to the propagation of low frequency waves in a shallow sea. As a source of acoustic waves, underwater disturbances generated by ships were adopted. A specific feature of the propagation of acoustic waves in shallow water is the proximity of boundaries of the limiting media characterised by different impedance properties, which affects the acoustic field coming from a source situated in the water layer “ deformed”...
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Some aspects of noise generated by a small ship in the shallow sea
PublicationThe passing and underwater moving objects produce the noises of variable intensity, which significantly increase the overall level of noise in the sea. This applies to both the sonic and ultrasonic range. The excessive levels of underwater noise adversely affects the so-called underwater acoustic climate and is the reason why this phenomenon is intensively investigated from the number of years. The results of experimental work...
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Acoustic emission studies of the 7075 aluminium alloy pitting corrosion process
Open Research DataThe dataset contains the cyclic polarization studies and corresponding acoustic emission measurements, revealing the pitting corrosion process of the passive layer at the surface of the 7075 aluminum alloy in the borate buffer with different chloride ions concentrations, in the range between 0.05 and 25 mM.
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The study of acoustic climate of the Southern Baltic
PublicationThis paper presents the statistical characteristics of seawater properties, which are necessary for predicting the propagation of acoustic waves in selected areas of the Baltic Sea. The statistics were elaborated based on long-term measurements of vertical distributions of sound speed, temperature, and salinity, and the nonlinearity parameter B/A. Nonlinear properties of the environment are considered, in connection...
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Using Fast Frequency Hopping Technique to Improve Reliability of Underwater Communication System
PublicationAcoustic underwater communication systems designed to work reliably in shallow coastal waters must overcome major limitations such as multipath propagation and the Doppler effect. These restrictions are the reason for the complexity of receivers being built, whose task is to decode a symbol on the basis of the received signal. Additional complications are caused by the low propagation speed of the acoustic wave in the water and...
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Identification of hydroacoustic wave sources of ship in motion
PublicationThis paper deals with results of identification tests of acoustic field spectrum of underwater noise generated by ship in motion. The field is connected with acoustic activity of ship mechanisms and devices in operation. Vibration energy generated by the mechanisms and devices is transferred through ship structural elements to surrounding water where it propagates in the form of acoustic waves of a broad band of frequencies. In...
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Underwater Navigation System Based on Doppler Shifts of a Continuous Wave
PublicationThe paper describes a concept of an underwater navigation system designed to determine the location and speed of its ROVs or divers. Conducted by the Department of Marine Electronic Systems at the Gdansk University of Technology for several years, research has focused on navigation systems which determine positions on the basis of Doppler shifts of echo signals reflected from a moving object. This article presents a different version...
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The development of an underwater telephone for digital communication purposes
PublicationThe underwater telephone HTL-10 has been designed to provide voice and data communication between helicopter and submarines using acoustic waves. It works in a half-duplex mode and uses analogue power-efficient modulation in the form of a single side-band, suppressed carrier, in a wide range of frequencies. It generates the transmitted signal, and processes the received signals. It is implemented with the use of digital signal...
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Propagation of Ship-Generated Noise in Shallow Sea
PublicationContamination of sea environment by noise and any energy radiated to water constitutes today a problem to which more and more attention is paid, in view, a.o., of consequences of an impact of these factors onto marine fauna. European Union has introduced a directive by which EU countries are made responsible to undertake efforts aimed at reaching a good envirenmental status of European seas by 2020. A main source of underwater...
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UNDERWATER NOISE GENERATED BY A SMALL SHIP IN THE SHALLOW SEA
PublicationStudy of the sea noise has been a subject of interest for years. The first work of this scope were published at the turn of the twentieth century by Knudsen (KNUDSEN et al., 1948) and G. Wenz (WENZ, 1962). Disturbances called "shipping noise" are one of the important components of the sea noise. In this work the results of an experimental research of underwater noise produced by a small ship of a classic propulsion are...
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POSSIBILITY OF ASSESSMENT OF OPERATION OF SLIDING BEARINGS IN PISTON-CRANK MECHANISMS OF DIESEL ENGINES WITH REGARD TO LOAD AND TIME OF CORRECT WORK OF THE BEARINGS BY APPLYING ACOUSTIC EMISSION AS A DIAGNOSTIC SIGNAL
PublicationAbstract: The paper presents a possibility of determining (assessing) operation of sliding bearings with multilayer bushings in crank-piston mechanisms of diesel engines. Properties of load and wear, particularly fatigue and abrasive, are characterized in general. Acoustic emission as a diagnostic signal was proved to be useful for detection of the wear of sliding and barrier layers. Results of measurements of acoustic emission...
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Modeling of performance of a AUV vehicle towards limiting the hydro-acoustic field.
PublicationSome results of research devoted to the modeling of a AUV-Stealth vehicle performance towards limiting its hydro-acoustic field are presented in the paper. At the beginning the AUV-Stealth autonomous underwater vehicle concept is described. Then the method of research is introduced. Next the key design drivers of the AUV-Stealth vehicle are presented. Between them are the AUV-Stealth hull form, arrangement of internal spaces,...
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Theoretical analysis of a new approach to order determination for a modified Prony method in swath mapping application
PublicationThis article presents a new approach to determine the model order (number of principal components) in the modified Prony method applied to swath acoustic mapping. Determination of the number of principal components is a crucial step in the modified Prony method. In the proposed approach the model order is chosen based on the underlying physical model of the underwater acoustic environment, and utilised signal processing operations....
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Experiment with small objects floating under water in the harbor security aspect.
PublicationObservation of the underwater area is the element of general trend which primary purpose is to protect and enhance the safety of the selected region. The aim of the paper is to present the acoustic characteristics of typical objects floating on the surface or under the water, which constitute some knowledge on how to detect these objects. Create a catalog of acoustic signatures and acoustic images of objects mostly floating under...
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Automatic localization and continous tracking of mobile sound source using passive acoustic radar
PublicationA concept, practical realization and applications of the passive acoustic radar for localization and continuous tracking of fixed and mobile sound sources such as: cars, trucks, aircrafts and sources of shooting, explosions were presented in the paper. The device consists of the new kind of multi-channel miniature three dimensional sound intensity sensors invented by the Microflown company and a group of digital signal processing...
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Mobile inventory system for hydrotechnical objects using data from multiple sensors operating simultaneously
PublicationThe knowledge of the location, shape and other characteristics of spatial objects in the coastal areas has a significant impact on the functioning of ports, shipyards, and other water-infrastructure facilities, both offshore and inland. Therefore, measurements are taken of the underwater part of the waterside zone, which means the bottom of water and other underwater objects (e.g. breakwaters, docks, etc.), and objects above the...
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Multibeam Sonar Data Processing for Seafloor Classification
PublicationDespite many years of the development of methodology for sensing the seafloor by means of underwater acoustics, the currently used techniques are still not mature enough and not ready to be utilised in numerous different (i.e. with respect to a water region character, used equipment type etc.) tasks. Therefore the hydroacoustic methods, both utilising vertical observations (e.g. by singlebeam echosounders), as well as those relying...
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Multisensor System for the Protection of Critical Infrastructure of Seaport
PublicationThere are many separated infrastructural objects within a harbor area that may be considered “critical”, such as gas and oil terminals or anchored naval vessels. Those objects require special protection, including security systems capable of monitoring both surface and underwater areas, because an intrusion into the protected area may be attempted using small surface vehicles (boats, kayaks, rafts, floating devices with weapons...
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RADIATION OF HIGH INTENSITY SOUND BY CIRCULAR DISC BY MEANS OF THE NUMERICAL METHOD
PublicationThe main goal of this paper is to find sound pressure distribution radiated by the circular piezoelectric disc that vibrates with the finite amplitude. There has been presented the pressure distribution close to the radiating surface. Also it is shown the sound pressure distribution in the 3D form. The mathematic modeling was carried out on the base of the nonlinear acoustic equation with the proper boundary condition. The axial...
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Impact of Spatial Noise Correlation on Bearing Accuracy in DIFAR Systems
PublicationDIFAR type underwater passive systems are one of the more commonly used tools for detecting submarines. At the design stage, which usually uses computer simulations, it is necessary to generate acoustic noise of the sea. It has been shown that correlating noise significantly reduces these errors compared to the assumption that noise is uncorrelated. In addition, bearing errors have been shown to be the same in systems with a commonly...
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Identification of Fast Time-varying Communication Channels Using the Preestimation Technique
PublicationAccurate identification of stochastic systems with fast-varying parameters is a challenging task which cannot be accomplished using model-free estimation methods, such as weighted least squares, which assume only that system coefficients can be regarded as locally constant. The current state-of-the-art solutions are based on the assumption that system parameters can be locally approximated by a linear combination of appropriately...
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The effect of fishing basin construction on the behaviour of a footbrdge over the port channel
PublicationThe paper analyses possible causes of failure of the rotating footbridge over the Ustka port channel. In July, 2015, strange behaviour of this object was observed in the form of excessive vibrations of bridge platform suspension rods, with the accompanying acoustic effects. A preliminary geotechnical analysis has revealed that this destructive effect was caused by the nearby construction works, namely construction of a fishing...
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HYDROACOUSTIC NOISE MEASUREMENTS
PublicationThe paper deals mainly with investigation of underwater noise that propagation is in shallow water. In this paper has been presented the experimental investigation results concerning the distribution of the sound field pressure generated by moving ships in the shallow water at the small distance from the ship. The main acoustical characteristics describing features of the field are spectrograms in pseudo 3D system – distance and frequency...
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A tool for designing water tanks for measuring hydroacoustic transducers
PublicationSpecial water tanks are commonly used to measure the parameters of underwater acoustic systems. They must meet specific requirements, the fulfilment of which ensures very small but acceptable measurement errors. These requirements define the size of the tank and its shape as well as the strong attenuation of reflected waves. At the design stage, it is necessary to determine the impact of the tank structure on the measurement errors...
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Low-Voltage Low-Power Filters with Independent ω0 and Q Tuning for Electronic Cochlea Applications
PublicationAn acoustic second-order low-pass filter is proposed for filter banks emulating the operation of a human cochlea. By using a special filter structure and an innovative quality (Q)-factor tuning technique, an independent change of the cutoff frequency (ω0) and the Q-factor with unchanged gain at low frequencies is achieved in this filter. The techniques applied result in a simple filter design with low Q-factor sensitivity to component...
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A Comparison of Simplified Two-dimensional Flow Models Exemplified by Water Flow in a Cavern
PublicationThe paper shows the results of a comparison of simplified models describing a two-dimensional water flow in the example of a water flow through a straight channel sector with a cavern. The following models were tested: the two-dimensional potential flow model, the Stokes model and the Navier-Stokes model. In order to solve the first two, the boundary element method was employed, whereas to solve the Navier-Stokes equations, the...
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Application of Shape From Shading Technique for Side Scan Sonar Images
PublicationSide scan sonar (SSS) is one of the most widely used imaging systems in the underwater environment. It is relatively cheap and easy to deploy in comparison with more powerful sensors like multibeam echosounder or synthetic aperture sonar. Although, the SSS does not provide directly the seafloor bathymetry measurements. Its outputs are usually in a form of grey level acoustic images of seafloor. However, the analysis of such images...
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Jaroslaw Tegowski prof. dr hab.
PeopleJaroslaw Tegowski was born in Olsztyn, Poland, in 1955. He received the M.S. degree in physics from the University of Gdansk, Gdansk, Poland, in 1981, and the Ph.D. degree in physical oceanography in 1995 and the habilitation degree from the Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland, in 2007. From 1983 to 2008, he was a Research Assistant and a next Associate Professor at the Marine Acoustical Laboratory,...
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UNDERWATER TECHNOLOGY
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[ITiT] Transmission Channel in Radio Communication Systems
e-Learning Courses{mlang pl} Dyscyplina: informatyka techniczna i telekomunikacja Zajęcia fakultatywne dla doktorantów II roku Prowadzący: dr hab. inż. Sławomir Ambroziak, prof. PG Liczba godzin: 15 Forma zajęć: wykład {mlang} {mlang en} Discipline: technical informatics and telecommunications Elective course for 2nd-year PhD students Academic teachers: dr hab. inż. Sławomir Ambroziak, prof. PG Total hours of training: 15 teaching hours Course...
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Inertial Sensors Applications in Underwater Measurements
PublicationOver the past decades microelectromechanical systems (MEMS) researchers have demonstrated a number of microsensors for almost every possible sensing modality, including attitudes. Current MEMS inertial measurement units (IMU) come in many shapes, sizes, and costs — depending on the application, and performance required. MEMS sensors have proved and demonstrated performance exceeding those of their macroscale counterpart sensors. In...
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Methodology for Processing of 3D Multibeam Sonar Big Data for Comparative Navigation
PublicationAutonomous navigation is an important task for unmanned vehicles operating both on the surface and underwater. A sophisticated solution for autonomous non-global navigational satellite system navigation is comparative (terrain reference) navigation. We present a method for fast processing of 3D multibeam sonar data to make depth area comparable with depth areas from bathymetric electronic navigational charts as source maps during...
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Underwater Welding of Duplex Stainless Steel
PublicationThe present work was conducted to assess the weldability of duplex stainless steel at underwater conditions. Interest of underwater welding of this steel grade is connected with necessity of preparing welding repair technologies for subsea pipelines widely used in offshore oil and gas industry. The GMA local cavity welding method was used in the investigations. Welded beads were performed underwater at 0.5 m depth and in the air....
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Underwater noise recorded in Hornsund Fjord, Spitsbergen, at the front of the Hans Glacier
Open Research DataThe data includes underwater noise recorded in Hornsund Fjord, Spitsbergen at the front of the Hans Glacier between 05/09/2013 and 30/09/2013. A description of the data is in the article
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The Boltzmann sequence-structure channel
PublicationWe rigorously study a channel that maps binary sequences to self-avoiding walks in the two-dimensional grid, inspired by a model of protein statistics. This channel, which we also call the Boltzmann sequence-structure channel, is characterized by a Boltzmann/Gibbs distribution with a free parameter corresponding to temperature. In our previous work, we verified experimentally that the channel capacity has a phase transition for...
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Weldability of S500MC Steel in Underwater Conditions
PublicationWet welding with the use of covered electrodes is one of the methods of underwater welding. This method is the oldest, the most economic and the most versatile. The main difficulties during underwater wet welding are: high cooling rates of the joint, the presence of hydrogen in the arc area and formation of hard martensitic structure in the weld. These phenomena are often accompanied by porosity of welds and large number of spatters,...
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Phase Transition in a Sequence-Structure Channel
PublicationWe study an interesting channel which maps binary sequences to self-avoiding walks in the two-dimensional grid, inspired by a model of protein folding from statistical physics. The channel is characterized by a Boltzmann/Gibbs distribution with a free parameter corresponding to temperature. We estimate the conditional entropy between the input sequence and the output fold, giving an upper bound which exhibits an unusual phase transition...
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[ITiT] Transmission Channel in Radio Communication Systems - 2023/2024
e-Learning Courses{mlang pl} Dyscyplina: informatyka techniczna i telekomunikacja Zajęcia fakultatywne dla doktorantów II roku Prowadzący: dr hab. inż. Sławomir Ambroziak, prof. PG Liczba godzin: 15 Forma zajęć: wykład {mlang} {mlang en} Discipline: technical informatics and telecommunications Elective course for 2nd-year PhD students Academic teachers: dr hab. inż. Sławomir Ambroziak, prof. PG Total hours of training: 15 teaching hours Course...
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RESEARCH ON ORGANIC COATINGS DESIGNED FOR UNDERWATER APPLICATIONS
PublicationUnderwater steel structures require periodic maintenance. In the case of vessels, anti-corrosion works are carried out in the shipyard, where very good conditions for applying organic protective coatings can be provided. Very good surface preparation can be obtained by the use of abrasive blasting. The well-prepared metal surface is free from impurities (particularly inorganic salts). Suitable conditions for the application and...
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Acoustic streaming caused by some types of aperiodic sound. Buildup of acoustic streaming
PublicationThe analysis of streaming caused by aperiodic sound of different types (switched on at transducer sound or sound determined by initial conditions) is undertaken. The analysis bases on analytical governing equation for streaming Eulerian velocity, which is a result of decomposition of the hydrodynamic equations into acoustic and non-acoustic parts. Its driving force (of acoustic nature) represents a sum of two terms; one is the...
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A simplified channel estimation procedure for NB-IoT downlink
PublicationThis paper presents a low-complexity channel estimation procedure which is suitable for use in energy-efficient NB-IoT user equipment devices. The procedure is based on the well-established least squares scheme, followed by linear interpolation in the time domain and averaging in the frequency domain. The quality of channel estimation vs. signal-to-noise ratio is evaluated for two channel models and compared with the performance...
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Interaction between acoustic and non-acoustic mode in bubbly liquid
PublicationThe nonlinear interaction of acoustic and entropy modes in a bubbly liquid is the subject of investigation. Thedynamic equation governing an excess density of the entropy mode is derived. Nonlinearity and dispersion are the reasons forexcitation of the entropy mode. The nonlinear interaction of modes as a reason for bubble to grow due to sound, is discovered.Some numerical examples of the modes interactions are made.
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A simple test for quantum channel capacity
PublicationBased on state and channel isomorphism we point out that semidefiniteprogramming can be used as a quick test for nonzero one-way quantum channelcapacity. This can be achieved by searching for symmetric extensions of statesisomorphic to a given quantum channel. With this method we provide examplesof quantum channels that can lead to high entanglement transmission but stillhave zero one-way capacity, in particular, regions of symmetric...
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Smart acoustic band structures
PublicationSmart acoustic band structures exhibit very interesting and non-standard physical properties due to the periodic nature of their certain characteristic on different scale levels. They manifest mostly in their frequency spectra as socalled frequency band-gaps or stop-bands, what has a great impact on the behaviour of these structures in relation to the propagation of vibro-acoustic signals that can be transmitted through the structures...
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A Simplistic Downlink Channel Estimation Method for NB-IoT
PublicationThis paper presents a downlink channel estimation method intended for a Narrowband Internet of Things (NB-IoT) access link. Due to its low computational complexity, this method is well suited for energy-efficient IoT devices, still providing acceptable reception quality in terms of signal-to-noise (SNR) performance. This paper describes the physical layer of NB-IoT within the scope of channel estimation, and also reviews existing...
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Interaction of Acoustic and Thermal Modes in the Vibrationally Relaxing Gases. Acoustic Cooling
PublicationThe dynamic equation which governs an excess temperature associated with the thermal mode in vibrationally relaxing gas is derived. The nonlinear transfer of acoustic energy to the energy of the thermal mode in a relaxing gas causes slow variation of temperature with time. The nal dynamic equation is instantaneous. All types of sound, including aperiodic, may be considered as an acoustic source of corresponding heating or cooling....
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Integration of inertial sensors and GPS system data for underwater navigation
PublicationThe Inertial Navigation System (INS) is usually employed to determine the position of an underwater vehicles, like Remotely Operated Vehicles (ROV) and, more recently, Autonomous Underwater Vehicle (AUV). The accuracy of the position provided by the INS, which uses accelerometers and gyroscopes, deteriorates with time. An external aiding sources such as the Global Positioning System (GPS) can be employed to reduce the error growth...
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On the Characteristic Graph of a Discrete Symmetric Channel
PublicationWe present some characterizations of characteristic graphs of row and/or column symmetric channels. We also give a polynomial-time algorithm that decides whether there exists a discrete symmetric channel whose characteristic graph is equal to a given input graph. In addition, we show several applications of our results.
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Small rov to detection and identification of dangerous underwater objects
PublicationA small unmanned underwater vehicle (UUV) to inspection of an undersea space is presented in the paper. Its behavior is controlled by a trained pilot. Correct detection and identification of targets depends on vehicle'sprecise displacement along a predefined route. Nowadays, the UUVs are equipped with an automatic control system to execute some basic maneuvers without constant human interventions. Hence, in the paper, an autopilot...