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Underwater environment is characterized by harsh conditions and is difficult to monitor. The CADDY project deals with the development of a companion robot devoted to support and to monitor human operations and activities during the dive. In this scenario the communication and correct reception of messages between the diver and the robot are essential for success of the dive goals. However, the underwater...
The WRSC (World Robotic Sailing Championship) / IRSC (International Robotic Sailing Conference) is an international and annual competition and conference that aims at stimulating the development of autonomous marine robotics and its applications. The competition, originally designed for sailboats, is also opened to motorboats as a separate category since 2013. In this paper, we will present the competition...
This paper discusses the problem of passive detection of divers in a shallow water environment. The sound produced due to breathing of the open-circuit divers is prominent in the high frequency range of the data. We formulate a detector to detect the waveforms of a diver's breaths, which occur as periodic bursts of sound. This detector is robust to the presence of other interfering sources. Since...
A real demand for underwater acoustic (UWA) communications exists in oceanography, ocean exploration and undersea navigation. A new Doppler resilient digital communication, based on quadratic frequency modulations (QFM) is presented. The binary information is transmitted using two orthogonal QFM chirps. This signal modulation is suitable for low-data-rate communication such as telemetry. The first...
The adoption of fault detection and isolation (FDI) techniques is fundamental to ensure high levels of safety and productivity, especially in critical and expensive applications like Autonomous Underwater Vehicles (AUV). This paper describes a comparison between different techniques available in the literature, applied to over-actuated AUVs under single fault condition (SFC) and considering only abrupt...
This paper proposes a robust fault tolerant controller design for an underwater hydraulic propulsion system. We design servo-valve controller of hydraulic thruster which is tolerant of faults and robust against disturbances. We assume oil-leakage and contamination faults as parametric variation of the servo-valve and disturbance infow in it. To design the robust fault tolerant controller, we introduce...
Subsea interventions in the oil & gas industry as well as in other domains such as archaeology or geological surveys are demanding and costly activities for which robotic solutions are often deployed in addition or in substitution to human divers — contributing to risks and costs cutting. The operation of ROVs (Remotely Operated Vehicles) nevertheless requires significant off-shore dedicated manpower...
A mathematical model of agent-based decision-making of Autonomous Surface Vehicles (ASVs) is presented with extensive path planning and abstraction capabilities of the environment. The aim is to enable the ASV to pass through heavy harbour traffic to an intended destination safely and efficiently. While predicting the future path of other vehicles and path planning can be carried out by known methods,...
Deep inside the ocean, the earth magnetic signal is one of the merely existing information that tells the heading of robots with very good cost efficiency. Therefore, this paper focuses on the AUV (Autonomous Underwater Vehicle) heading control problem using only one magnetic compass as feedback sensor. In this application, we address AUV modeling and control issues simultaneously. Because of quadratic...
The intersymbol interference (ISI) caused by multipath propagation becomes the major challenge for designing efficient equalization methods for underwater acoustic communications. Even at moderate bit-rates, the computational complexity of adaptive equalizers is high enough to challenge their realtime implementation. Hence, reducing their complexity by either low-complexity algorithms or efficient...
In this paper, we present one underwater image stitching model combined with the Scale Invariant Feature Transform (SIFT) and the wavelet fusion. Poor visibility in the sea and the variations in the illumination, viewpoints, etc., have been comprehensively taken into consideration for image matching. Wavelet fusion is then made full use of to undertake the underwater image mosaic. It is shown in the...
This paper considers the hierarchical control strategy for enhancing the captured and converted powers in heaving wave energy converters. The hierarchical control strategy consists of a higher hierarchical controller (HHC) and a lower hierarchical controller (LHC). The main role of the HHC is to provide the optimum reference for the LHC. The LHC follows the reference despite the existence of perturbations...
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