Structural Reliability Criteria for Control of Large-Scale Interconnected Marine Structures

Berntsen, Per Ivar Barth; Leira, Bernt J.; Aamo, Ole Morten; Sørensen, Asgeir J.

doi:10.1115/omae2004-51350

Cited by 7 publications

(2 citation statements)

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“…In order to reduce the possi-bility of mooring line breakage in harsh environmental condi-95 tions, a setpoint chasing algorithm was introduced in Nguyen & Sørensen (2009). A structural reliability index for integrity of the the mooring lines was proposed in Berntsen et al (2004Berntsen et al ( , 2006Berntsen et al ( , 2009 where a new controller was developed to keep the probability of line failure below an acceptable level. A con-100 sistency based diagnosis technique was used to develop fault tolerant control of PM systems in Nguyen et al (2007a) using the methodology developed in Blanke (2005); Blanke et al (2006).…”

Section: Introductionmentioning

confidence: 99%

Detection of mooring line failures using Dynamic Hypothesis Testing

Hassani

Pascoal²,

Sørensen

2018

Ocean Engineering

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This article proposes a novel methodology for the detection of mooring line breakage in thruster assisted position mooring (PM) systems, when no measurements of the tensions on the mooring lines are available. For dynamic positioning (DP) of marine vessels moored to the seabed via a turret-based spread mooring system, the thrusters provide only complementary assistance to the mooring system, which is responsible for a large part of the forces and moments required for station keeping. However, in extreme weather conditions thruster assistance is essential to avoid mooring line failure. Once a mooring line is parted, the remaining lines face an increase in the tension forces due as a means to compensate for the lost tension in the ruptured line. This in turn may lead to a cascade breakage of the mooring lines. Hence, it is of paramount importance to detect any line breakage as soon as it occurs to compensate for the lost tension by proper use of DP thruster assistance. As a contribution to solving this problem, in this paper we propose a methodology that builds on Dynamic Hypothesis Testing (DHT) whereby a set of hypotheses are assessed, at each sampling time, using the measured inputs and outputs of the thruster assisted position mooring system. While the first hypothesis corresponds to the assumption that all mooring lines are intact, the remaining hypotheses are built assuming that a single, or multiple line breakage events have taken place. At each sampling time, the inputs and outputs to the system are used to generate the conditional probability of each hypothesis being true. These conditional probabilities are then used to evaluate which hypothesis is more probable to comply with the collected measurements. In addition, we find conditions for any pair of hypothesis being distinguishable. Numerical simulations, carried out using a high fidelity nonlinear PM simulator illustrate the efficiency of the proposed methodology.

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Section: Introductionmentioning

confidence: 99%

Detection of mooring line failures using Dynamic Hypothesis Testing

Hassani

Pascoal²,

Sørensen

2018

Ocean Engineering

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“…Common for existing PM systems, is that motion is restricted to lie within predefined safety regions, leading to considerable conservativeness with regards to exploiting the capacity of the mooring system. In [16] we proposed a method for taking structural reliability measures of the mooring lines into account when designing PM systems. In the present paper, we strengthen the link between PM systems and structural reliability by designing a controller that employs thruster assistance in a way that operates the vessel and mooring system within acceptable limits in terms of breaking probability of the mooring lines.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Positioning of Moored Vessels Based on Structural Reliability

Berntsen

Aamo

Leira

2006

Proceedings of the 45th IEEE Conference on Decision and Control

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This paper addresses dynamic positioning of surface vessels moored to the seabed via a spread mooring system, referred to as position mooring. In normal weather conditions, the mooring system constrains the vessel and the controller applies thruster force for motion damping and heading control, only. In harsh weather, however, the mooring system becomes inadequate and thruster force is also needed for positioning in order to avoid damage to the mooring lines. While traditional position mooring systems apply thruster force based on constraining the vessel to lie within a predefined geographical region, the controller presented in this paper instead employs structural reliability measures to restrict movement. These structural reliability measures become an intrinsic part of the controller, automatically adjusting the allowed geographical region based on current weather conditions and structural properties of the mooring lines.

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Categories of On-Line Control Schemes Based on Structural Reliability Criteria

Leira

2013

Optimal Stochastic Control Schemes Within a Structural Reliability Framework

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Structural Reliability Criteria for Control of Large-Scale Interconnected Marine Structures

Cited by 7 publications

References 0 publications

Detection of mooring line failures using Dynamic Hypothesis Testing

Detection of mooring line failures using Dynamic Hypothesis Testing

Dynamic Positioning of Moored Vessels Based on Structural Reliability

Categories of On-Line Control Schemes Based on Structural Reliability Criteria

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