On-line identification and convergence analysis of excitation-force and drag-force models for moored floating structures

Jordan, M.A.

doi:10.1016/j.oceaneng.2005.05.016

Cited by 1 publication

(2 citation statements)

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“…Using Fig. 6 and putting Equation (13) into Equation (12), the impulse-response function is numerically found. Figure 7 shows different impulseresponse functions for a set of values of D and d. One concludes the importance of the response for low depths and relatively large diameters.…”

Section: Equations Of Motion: Modelmentioning

confidence: 99%

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Numerical stability analysis and control of umbilical–ROV systems in one-degree-of-freedom taut–slack condition

Jordan

Bustamante

2006

Nonlinear Dyn

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In this paper, the stability of an umbilical-ROV system under nonlinear oscillations in heave motion is analyzed using numerical methods for the uncontrolled and controlled cases comparatively. Mainly the appearance of the so-called taut-slack phenomenon on the umbilical cable produced by interactions of monochromatic waves and an operated ROV is specially focused. Nonlinear elements were considered as nonlinear drag damping, bilinear restoring force and saturation of the actuators. Free-of-taut/slack stability regions are investigated in a space of physical bifurcation parameters involving a set of both operation and design parameters. They indicate a wide diversity in qualitative behaviors, both in the periodicity and possible routes to chaos from the stability regions to outside. For detection of periodicity of the nonlinear oscillations inside and outside the stability regions, a method based on Cauchy series is developed. The first part of the results is dedicated to the stability of the uncontrolled dynamics. These results suggest the design of a control system that is able to counteract hefty hauls of the cable during the sinking/lifting operation under perturbation. A combination of a force and cinematic controller based on nonlinear model-reference control is proposed. Through a comparative study of the stability regions for uncontrolled and controlled dynamics, it is shown that the control system can extend considerably these regions without appearance of the taut-slack phenomenon despite the presence of wave perturbations. The limits between the taut and taut-slack zones are defined by the wave steepness and the available energy of the actuators.

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Section: Equations Of Motion: Modelmentioning

confidence: 99%

“…Fortunately, the evanescence of κ(τ ) for τ → ∞ and the passivity of system (17) and (18) indicate that the fact of supposing f 0 = 0 has no effect on the accuracy of the solution d(t) at steady state (see [12]). So, for the following studies in steady state, it is assumed null.…”

Section: Equations Of Motion: Modelmentioning

confidence: 99%