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Studying fish recognition has important realistic and theoretical significance to aquaculture and marine biology. Fish recognition is challenging problem because of distortion, overlap and occlusion of digital images. Previous researchers have done a lot of work on fish recognition, but the classification accuracy may be not high enough. Classification and recognition methods based on convolutional...
In this paper, the natural supercavitys are studied both experimentally and numerically. A series of supercavitating vehicle water-entry test are carried out at different speeds, where it is found that the minimum pressure in the cavity gradually reduced with the increase of water-entry speed. The cause for the evolution progress of natural supercavitation is difficult to get from the experiment,...
In this paper, we propose a method for cooperative surveys of the seafloor using multiple autonomous underwater vehicles (AUVs) where they detect areas of interest within the survey area in real-time based on a bathymetry map and then details are observed by them. The AUV firstly makes rough observations by mapping using an acoustic sensor and detects areas of interest based on a gradient descent...
An efficient method was developed to compute the pressure field induced on the seafloor by a ship performing maneuvers such as acceleration, deceleration, and turning. Linear, potential flow theory with transient, finite-depth Green function is used to formulate the solution for the velocity potential. To reduce run time, thin-ship approximation is made, and the Green function is evaluated using Chebyshev...
A pressing environmental question facing the ocean is the potential impact of possible deep-sea mining activities. This work presents our initial results in developing an ocean and plume modeling system for the Bismark Sea where deep sea mining operations will probably take place. We employ the MSEAS modeling system to both simulate the ocean and to downscale initial conditions from a global system...
In order to accurately control the portable AUV, a dynamic modeling method based on computational fluid dynamics (CFD) and a improved Generalized Predictive Control (GPC) method were presented. First, the whole modeling process was described from two aspects: dynamic model derivation and model parameter identification. Second, the validity of the model and modeling method were tested by comparing...
A graphical tool to qualitative analysis of underwater unmanned vehicles and cable-like flexible structures is presented. The software provides a realistic virtual environment where the dynamic behavior of different underwater systems can be studied from numerical simulation to generate animations.
The capability of avoiding static obstacles independently is the premise for air cushion vehicle (ACV) operating safely. In this article, an ACV collision avoidance control based on improved artificial potential field method is designed as auxiliary operating system to ensure safe navigation of ACV. It builds mathematical model of the ACV and searches the data of static obstacles. Besides, the collision...
This paper focuses on the problem of seabed survey mission with multiple target points distributed in large scale area. To complete the survey with AUVs in minimum cost, a two-step procedure using greed strategy is presented. In the first step, the locations of so-called anchor points are found by executing k-means algorithm iteratively. In the second step, an ant-cycle system is used to find out...
Deep-sea hydraulic manipulator is an essential operation equipment for scientific investigation and resource exploitation. To improve the efficiency of hydraulic power source for manipulator in the presence of load variations, a pressure control variable displacement pump (PCVDP) is used to respond quickly to dynamic demands of multiple loads. Considering the variations of seawater properties at different...
Closest Point of Approach (CPA) calculations are fundamental calculations for determining the utility and safety of a candidate maneuver of a marine vessel with respect to another vessel, i.e., contact. In certain kinds of path planning, a set of CPA calculations is made for thousands of candidate maneuvers, perhaps several times per second. Furthermore, with multiple contacts, multiple sets need...
The possibility of increasing flight duration, particularly for small and micro fixed-wing Unmanned Aerial Systems (UAS), is typically hindered by the payload and size of the platform. In maritime missions, Atmospheric Energy Harvesting (AEH) near the Marine Atmospheric Boundary Layer (MABL), is a low-cost solution, with very promising results, that may allow drastic increases in flight duration by...
In this paper, we propose a statistical channel model to study the performance of a line-of-sight underwater wireless optical communication (UWOC) link in a data mulling environment. We optimize the range of geometric parameters including detector aperture diameter and field-of-view (FOV) to reduce the effect of excessive scattering on the optical signal. By considering geometric losses, we observe...
During the launching of the AUV especially in air-launching, the water entry problem is inevitable. The AUV will stir the flow field of surrounding fluid during the moving into water, while the fluid will act a strong force on the AUV in return, which may cause trajectory deflection problems or damage to their structure and inner components in severe cases. The water entry experiment of full-size...
This paper introduces an underwater wheeled vehicle towing system which is composed of an anterior traction winch, a posterior brake winch, wire rope and fixed pulleys. Under the coordinate driving of two winches which one draw in the cable while another one let out the cable, the wheeled vehicle can be towed to achieve the accelerating, uniform speed and decelerating movement on the track which is...
This paper aims at investigating the effects of the ocean current in the thrusters closed-loop performance. In particular, the intervention case, and thus the vehicle slowly moving, is of interest. Vehicle controllers are commonly designed without taking into account both the thruster dynamics and the presence of ocean current which, however, influence the closed loop. A fixed gains PID and an adaptive...
Autonomous underwater vehicles (AUVs) are becoming increasingly popular for ocean exploration, military and industrial applications. Motion control of AUV is the key to completing these missions. The classical linear Proportional Integral Derivative (PID) controllers are widely used due to its reliability and simplicity. However, it is difficult to tune the parameters in the classical PID controllers...
Simulation of unmanned underwater vehicles (UUVs) plays an important role in the development of submarine robots. The test of controllers in different simulated scenarios is crucial in order to avoid the lengthy development on the real vehicle. Robot simulators like Gazebo have been extensively used for this purpose, even if off-the-shelf physic engines do not consider one of the main aspects of hydrodynamics:...
In this paper, we employ a dynamics modeling method for investigating a multi-body dynamics system consisting of an unmanned surface vehicle (USV), an umbilical cable (UC), and an autonomous underwater vehicle (ROV). The ROV, which is towed by a UC for the purposes of exploration or mine hunting, is modeled with a Six-Degree-of-Freedom (6-DOF) equation of motion that reflects its hydrodynamics characteristics...
In this study, virtual planar-motion-mechanism (PMM) tests in pure sway motion at constant forward speed are carried out to determine the sway added mass values of a 6:1 prolate spheroid. Added mass values are obtained by solving the Euler equations and the Reynolds Averaged Navier-Stokes (RANS) equations across a range of frequencies and depths. The effect that distance from the surface and radiation...
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