Sensitivity and Robustness of Hydrodynamic Mooring Models

Matsuura, Joa ̃o Paulo J.; Bernitsas, Michael M.; Garza-Rios, Luis O.; Nishimoto, Kazuo

doi:10.1115/1.1510873

Cited by 4 publications

(2 citation statements)

References 9 publications

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“…Shenoi et al conducted SA of all hydrodynamic derivatives in a four-DOF of container ship [22]. Matsuura et al performed the sensitivity analysis on a mooring system to optimize the hydrodynamic coefficients [23]. In order to reduce the influence of model complexity on simultaneous drift, Luo and Zou [24] analyzed the sensitivity of a single hydrodynamic derivative on its maneuverability prediction and hydrodynamic modeling.…”

Section: Related Workmentioning

confidence: 99%

A Neural-Network-Based Sensitivity Analysis Approach for Data-Driven Modeling of Ship Motion

Cheng

Skulstad

et al. 2020

IEEE J. Oceanic Eng.

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Researchers have been investigating data-driven modeling as a key way to achieve ship intelligence for years. This paper presents a novel data analysis approach to data-driven modeling of ship motion.We propose a global sensitivity analysis (GSA) approach combining artificial neural network (ANN) and sparse polynomial chaos expansion (SPCE) techniques to accommodate high-dimensional sensor data collected from ship motion. An ANN is constructed as a surrogate model to associate ship sensor data with particular a certain type of ship motion. To account for the computational efficiency of GSA, an SPCE is integrated into the GSA to decrease the need for Monte Carlo (MC) samples generated by the ANN. A probe variable is designed to couple with the MC samples, which plays a role in determining degree of convergence of variable importance. A test on benchmark function demonstrates the efficiency and accuracy of the proposed approach. A case study of ship heading with and without environment effects is conducted. The experimental results show that the proposed approach can identify and rank the most sensitive factors of ship motion. The proposed approach highlights the application of GSA in data-driven modeling for ship intelligence.

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Section: Related Workmentioning

confidence: 99%

A Neural-Network-Based Sensitivity Analysis Approach for Data-Driven Modeling of Ship Motion

Cheng

Skulstad

et al. 2020

IEEE J. Oceanic Eng.

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“…For a discussion of the importance of various model parameters with respect to stability and robustness, see [14].…”

Section: Stability Analysis Model In Sway and Yawmentioning

confidence: 99%

Theoretical and Experimental Study of Heading Stability and Heading Control of a Turret-Moored FPSO

Kaasen

Ludvigsen

Nygaard

et al. 2017

Volume 1: Offshore Technology

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The behaviour and characteristics of a turret-moored FPSO subjected to loading from waves, wind and current are investigated. Of particular importance is to find out if fishtailing instabilities may occur, and if such instability can be disclosed by simple criteria involving basic parameters of the system’s mathematical model. Eight cases from model tests are chosen for theoretical study and time domain simulation. Four of the cases involve heading control with thrusters. For the stability study, a simplified linear model in sway and yaw is formulated. It is shown that the inherent characteristics of the model depend on the strengths and relative directions of the metocean processes. The eigenvalues of the sway-yaw model are computed for the eight selected cases to check the stability. A simple approximate criterion for heading stability is derived from the sway-yaw model. It is assumed, but not proven, that the criterion is a sufficiency criterion for stability. Both the experiments and the simulations show that the eight cases are stable. This is also confirmed by the eigenvalues of the sway-yaw model, while the simple criterion wrongly deems several cases unstable. The simple stability criterion is therefore probably conservative, at least when there is significant damping in the system. In one additional hypothetical case with only wave excitation and weak or lacking stability, the simplified criterion agrees well with the model test and simulation. Heading control is necessary when a heading different from the natural weathervaning heading is wanted. The controller used in the experiments and simulations is of simple SISO PID type. With control, the heading variations are reduced significantly.

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Revealing Nonlinear Dynamics Phenomena in Mooring Due to Slowly-Varying Drift

Bernitsas

Matsuura

2011

Journal of Offshore Mechanics and Arctic Engineering

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The effects of slowly-varying wave drift forces on the nonlinear dynamics of mooring systems have been studied extensively in the past 30 years. It has been concluded that slowly-varying wave drift may resonate with mooring system natural frequencies. In recent work, we have shown that this resonance phenomenon is only one of several possible nonlinear dynamic interactions between slowly-varying wave drifts and mooring systems. We were able to reveal new phenomena, based on the design methodology developed at the University of Michigan for autonomous mooring systems, and treating slowly-varying wave drift as an external time-varying force in systematic simulations. This methodology involves exhaustive search regarding the nonautonomous excitation, however, and approximations in defining response bifurcations. In this paper, a new approach is developed, based on the harmonic balance method, where the response to the slowly-varying wave drift spectrum is modeled by limit cycles of frequency, estimated from a limited number of simulations. Thus, it becomes possible to rewrite the nonautonomous system as autonomous and reveal stability properties of the nonautonomous response. Catastrophe sets of the symmetric principal equilibrium, serving as design charts, define regions in the design space where the trajectories of the mooring system are asymptotically stable, limit cycles, or nonperiodic. This methodology reveals and proves that mooring systems subjected to slowly-varying wave drift exhibit many nonlinear phenomena, which lead to motions with amplitudes two to three orders of magnitude larger than those resulting from linear resonance. A turret mooring system (TMS) is used to demonstrate the harmonic balance methodology developed. The produced catastrophe sets are then compared with numerical results obtained from systematic simulations of the TMS dynamics.

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Sensitivity and Robustness of Hydrodynamic Mooring Models

Cited by 4 publications

References 9 publications

A Neural-Network-Based Sensitivity Analysis Approach for Data-Driven Modeling of Ship Motion

A Neural-Network-Based Sensitivity Analysis Approach for Data-Driven Modeling of Ship Motion

Theoretical and Experimental Study of Heading Stability and Heading Control of a Turret-Moored FPSO

Revealing Nonlinear Dynamics Phenomena in Mooring Due to Slowly-Varying Drift

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