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The reliability issue of the mechanical system of Autonomous Underwater Vehicles was analyzed. The system reliability models of the mechanical system of AUV were built under the conditions of random load and ultimate load, respectively. A temporal dynamic model was also built to describe the relationship between reliability and time. Then, the methods of reliability allocation were studied, and an...
An underwater wireless sensor network (UWSN) has multiple functions in ocean survey. A kind of UWSN has been proposed by Zhejiang University. In this paper the CFD method is utilized to verify the ability of a node to adjust its posture in deploying and recovering process. The minimum depth and the minimum time for a node to adjust itself to vertical were obtained in different initial inclined angles...
This paper proposes a method for attitude estimation that utilizes the depth measurement as well as the MEMS-AHRS (Micro-electromechanical systems Attitude Heading Reference System). Estimating attitude in real-time is crucial for navigation of an unmanned underwater vehicle since path planning, trajectory tracking, and collision-avoidance is based on the attitude information. Many of the attitude...
We performed numerical and physical experiment with a marine monostatic electromagnetic (EM) survey system, which is developed primarily for exploration of seafloor mineral deposits. The system is a multi-frequency EM system housed to endure high pressure in deep sea up to 2000 m. To keep stable altitude of the system from the seafloor in rough seafloor topography condition, the system is connected...
Multi-targets tracking has shown great prospects in ocean investigations. In this paper, we apply the adaptive background mixture models to extracts the moving target from the image sequences, and propose a new method which is made use of the EKF and SURF-RANSAC to realize multi-targets tracking via multiple underwater cameras. In this method the centroid coordinate homographic mapping and the Speeded...
A formula is developed in this paper to calculate array gain when the plane-wave assumption is not applied. The formula is developped based on the assumption that the noise in the deep water is Gassian white and isotropic. The performance of a vertical linear is analyzed in the range-independent ocean, and also in a weak range-dependent ocean perturbed by random internal waves. Simulation results...
The majority of port facilities are decreasing in durability such as corrosion due to salt damage of concrete structures. Therefore, the importance of compressive strength management and diagnostic technology of underwater structures is increasing day by day. While the development of high-precision test equipment on land has been quite established, on the other hand the test equipment for underwater...
This paper proposes a novel diving plane control scheme for autonomous underwater vehicle (AUV) based on tracking differentiator (TD) and cascade control (CC). The outer loop controller and inner loop controller adopt PI and P, respectively. Firstly, the mathematical model of AUV is established. The model consists of two parts: one is the depth model, and the other is the pitch model. Then, both controllers...
Damutu Bay in eastern Zhejiang, China has abundant tidal flat resources for years of silt deposition in the wide open seas, making it an ideal place for mudflat reclamation. In this study we set up a two-dimensional hydrodynamic and sediment transport model based on Mike 21 FM to investigate changes in suspended sediment concentration (SSC) after reclaiming to 1 m and 3 m depth contours in the seas...
Under the influence of the sea current, the hydrodynamic performance of the propeller varies with the changing of the incoming flow direction. Aiming to obtain the hydrodynamic performance accurately, the thrust and load characteristic of AUV propeller is investigated under the conditions that different angles incoming flow go through the plane of propeller. First, the visual-physical model is built...
Sediment transport at the Yellow river delta is affected by many different factors, including tide, waves and river flows. With the change of river exit in 1996, a new delta is rapidly growing which leads to a new sediment transport regime. Most existing computer modelling work at the site is yet to take such changes into account. In addition, the wave action at the river mouth is often ignored in...
We develop acoustic communication simulation tools that integrate acoustic wave propagation model with acoustic communication algorithms for the under-ice environment. Our acoustic model uses the BELLHOP ray model augmented with multiple ice layers. Assuming a three-layer model, i.e. seawater/ice/air, we derive matrix expressions for the reflection and transmission coefficients of sound incident from...
Based on the scattering of dual-frequency transmission pulses and frequency-domain data processing, Philip R. Atkins has proposed a new method for standard-target phase calibration of sonar systems. This approach reduces the impact of unknown range and sound speed parameters upon phase calibration accuracy. However, since solutions to the phase of scattering of targets underwater are not offered,...
The aim of this study is to conduct a hydrodynamic analysis of a point absorber-type floating hemisphere with Power take-off(PTO) system for an optimum design of wave energy converter(WEC). In general, to predict the behavior of WEC, the equation of floating body motion can be solved in the frequency-domain analysis. A numerical model of PTO system is usually expressed as a linear damper-spring type...
A novel anchor system which can convert fluid energy into power is designed conceptually in this paper. It combines vortex induced vibration (VIV) and piezoelectric cantilever beam. The transversed motion model of the bluff body established with Sarplaya's lift decomposition model and the bending model of cantilever beam is established with Euler-Bernoulli assumption. With the two separate model the...
Our recent work on Wave Energy Converters (WEC) introduced the ideas of a Linear Sliding WEC (LS-WEC) and an electromechanical spring, or eSpring, to dynamically control system forces and maintain resonance conditions during changing wave conditions. In that work, we assumed that the LS-WEC contained a sliding translator mass that moved on a linear track in response to buoy pitch and roll in a dynamic...
Dynamic behaviors of AUV show a complex six-degrees of freedom (6-DOF) motion. They have great influence on the task precision and are influenced by uncertain marine environment parameters, in which influence of the lateral flow is one of the most significant. In this paper, dynamic behaviors of AUV in lateral flow are investigated using the CFD-based numerical method. Pressure distribution on the...
An adaptive sliding mode heading control approach is proposed for autonomous underwater vehicle (AUV) including the dynamics of rudder in this paper. By the analysis of the driving principle of the rudder, a three-order state equation for AUV heading control system is established, in which the system input is the control voltage of the DC motor. For the problem of the modeling uncertainties, an adaptive...
This paper presents a new type of modular wave energy generation platform model which is based on wave energy conversion system and offshore platform. In this paper, a hydrodynamic analysis commercial software was used to analyze motion responses to different wave conditions at the joints of each two unit modules of this platform in irregular waves. This wave energy generation device mainly has two...
Japan imports more than 94% of its primary energy supply and the import figures reach up to 250 billon US dollars every year. Imported energy resources in the form of crude oil and natural gas are mainly from Middle East Asia and South Asia. The political instability in these region and crude oil scarcity in the future possess a risk of procurement for the energy demands. Improvement of rate of energy...
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