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In this paper, the conceptual design with integrating motion control and considering the cross current was applied to establish a submarine motion simulator, where the path motion stability is evaluated. The methods used to construct the simulator include the standard navigation approach by applying the LOS algorithms and PD control Euler-Rodriguez quaternion for conversion between submarines motion...
A numerical method was developed to study vortex-induced vibration (VIV) on free-spanning marine pipelines. The numerical method uses a partitioned fluid-structure interaction solver with implicit coupling. The method was applied to a baseline model of cross flow around a circular cylinder with structure deformation. Further studies would include the effects of sea flow sediment deposition and scour.
This study investigates near-shore circulation and wave characteristics applied to a case-study site in Monterey Bay, California. We integrate physics-based models to resolve wave conditions (based on inputs from a global wave model, wind data from an operational weather platform, and predictions from a regional flow model) together with a linear machine learning algorithm that combines forecasts...
It is known that a dysoxic water mass threatens oyster farming in Dangdong bay. A density current generator is planned to be installed to solve this problem. In this study, we reconstructed the tide level, physical field and dysoxic water mass in Dangdong bay by using numerical simulation and comparing with field measurements and investigated the effect of density current generator by installing it...
This paper presents the motion simulation of an autonomous underwater helicopter (AUH), a new type of underwater vehicle proposed by Zhejiang University. In order to determine whether its controllability meets the design requirements, a singularity-free unit quaternion stable control method is used for simulating the AUH performance in MATLAB, including its force and trajectory under different types...
A novel anomaly detection algorithm is proposed to detect anomalies in trajectory data of autonomous underwater vehicles (AUVs). Compared to existing work, the proposed algorithm estimates vehicle speed (i.e., through-water speed) from trajectory data and detect abnormal motion with estimated vehicle speed by a threshold technique. The influence of ocean flow on AUVs is significant and must disturb...
A set of Matlab tools were developed to create seafloor mosaics from AUV photosurveys. The resulting mosaic products are used to guide instrument placement, ground-truth acoustic backscatter targets, and inspect sensor packages or other targets. Because of the positional sensitivity of these tasks, effort has been made to preserve the geographic distribution of the image content. After initial image...
Autonomous underwater vehicles (AUV) are important resources to be used in the oil exploration industry in deep waters as well as a platform for scanning devices used in open sea regions of difficult human access. This work aims to analyze through computer simulations the influence of marine currents on the maneuverability of a flatfish shaped AUV. The 3D realistic scale simulations were performed...
The National Tsunami Warning Center (NTWC) and the Pacific Tsunami Warning Center (PTWC) collaborate to provide tsunami warning service and mutual backup to tsunami-threatened areas throughout the United States and many other countries throughout the world. With mostly home-grown analysis systems, NTWC staff rapidly locates, sizes, and otherwise characterizes major earthquakes. We determine each earthquake's...
An event-driven positioning control algorithm based active disturbance rejection control (ADRC) method is proposed for dynamic positioning (DP) ship under the influence of external disturbances. The time-driven positioning controller is firstly designed using ADRC method. Then, the event-driven condition is introduced by extending the designed positioning controller, moreover, the trigger decision...
Evaporation duct has strong impacts on the performance of marine radar and communication systems. Evaporation duct channel is a promising channel for marine high capacity data transmission. Wave propagation models and evaporation duct models are well studied, and statistical features of duct channel has been observed. However, the work on the physical model of small-scale characteristics of evaporation...
In order to analyze the dynamic performance of a Remotely Operated Vehicle (ROV) during mission like ship hull inspection, it is necessary to establish the 6 degree-of-freedom equations of motion considering well modeled hydrodynamic force acting on a ROV. Typically, the hydrodynamic force is the model by polynomial functions and those coefficients are obtained by captive model tests or empirical...
Degradation due to wear, chemical deterioration or progressive embrittlement arises frequently in engineering practice. The marine environment is all the more conducive to embrittlement of offshore and subsea structures. Given the stochastic nature of the incremental damage, the important consideration is the distribution of time until the critical limit is reached. The belief that such behavior is...
The paper considers a reference-based control system for heaving wave energy converters. The proposed controller comprises two parts: lower level part (LLP) and higher level part (HLP). The HPL generates the buoy's velocity reference with the objective to maximize the power absorption with the constraints in the maximum control force and the power take-off device's utilization index. The index is...
In this paper we consider the problem of autonomous landing on a horizontally moving platform with vertical unpredictable oscillatory dynamics using a quadrotor system. The quadrotor is equipped with an external Raspberry PI as a companion computer used for communications. The task is divided in two subproblems: tracking and landing. We present the algorithms involved for the entire procedure; a PI...
Cooperative navigation (CN) has been proved to be an efficient method in underwater navigation for multiple Autonomous Underwater Vehicles (multi-AUVs). A new CN algorithm based on optimal weight distribution method (OWDM) is proposed to enhance the performance of multi-AUVs navigation. With the structure of two leaders and one follower, each leader is equipped with high-accuracy navigation system...
A Complex Conjugate (CC) control is implemented with a Proportional-Derivative (PD) controller for WEC devices to improve and optimize power absorbed. Traditionally, CC control has not been realizable due to actual implementation that requires acceleration feedback or exact term cancellation. For the PD implementation, only the stiffness term is employed to modify the impedance and achieve resonance...
This paper addresses the problem of designing a control that maximizes the harvested energy of a wave energy converter, in the presence of displacement constraints. The feasible displacement range is split into two segments. In the first segment (the inner segment), an unconstrained optimal control is used. In the outer segment, a constraint control is used. For the unconstraint control in the inner...
Equipment handling and offshore installations in harsh sea conditions can be a difficult task, and vessel motion always handicaps the operation of marine equipment. Hence, heave compensation system is used to decouple load motion from ship motion when lifting, lowering or holding a load, and reduce variation in cable tension. This paper provides a comprehensive model of an active-passive hybrid heave...
Film-type pressure self-adaptive water-tight junction box (FPSWJB) is a combination of the film-type compensator and water-tight junction box. Taking the advantage of responding rapidly and occupying little volume, the FPSWJB can both separate the sea water from the inside electronic components and keep the inside pressure balanced to the ambient pressure. In this paper, the model of hydraulic oil...
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