Supervisory Control of Line Breakage for Thruster-Assisted Position Mooring System

Ren, Zhengru; Skjetne, Roger; Hassani, Vahid

doi:10.1016/j.ifacol.2015.10.286

Cited by 10 publications

(4 citation statements)

References 23 publications

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“…The significant wave height is 2.5 meters. The vessel moves around an equilibrium position by a PID-type DP controller (Ren et al, 2015a). The vessel is heading the waves while moored with 8 mooring cables evenly distributed with 45 deg intervals.…”

Section: Simulationmentioning

confidence: 99%

An On-site Current Profile Estimation Algorithm for a Moored Floating Structure**This work was supported by the Research Council of Norway (RCN) through the Centre for Research-based Innovation on Marine Operations (RCN-project 237929), and partly by the Centre of Excellence AMOS (RCN-project 223254).

Ren

Skjetne

2016

IFAC-PapersOnLine

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Abstract:The current speed influences the safety of subsea and marine operations. This paper proposes an algorithm to estimate the depth-dependent current profile though data from existing commercial sensors, that is the mooring line tension measurements and riser end angle measurements. This will aid prediction of the weather window to enhance the safety during the subsea operations. The influence of various current profile types and the vessel's motion are discussed. A governing equation is proposed for the algorithm. A simulation is conducted to verify the algorithm.

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Section: Simulationmentioning

confidence: 99%

An On-site Current Profile Estimation Algorithm for a Moored Floating Structure**This work was supported by the Research Council of Norway (RCN) through the Centre for Research-based Innovation on Marine Operations (RCN-project 237929), and partly by the Centre of Excellence AMOS (RCN-project 223254).

Ren

Skjetne

2016

IFAC-PapersOnLine

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“…A methodology to detect line breakage and loss of of a buoyancy element in mooring lines was developed in Fang & 105 Blanke (2011); Blanke et al (2012) based on a structure-graph approach Blanke et al (2006). Detection of line breakage was studied in Ren et al (2015) using a supervisory control framework Hespanha (2001).…”

Section: Introductionmentioning

confidence: 99%

“…Common to all of the above-mention methods, except for 110 Ren et al (2015), is the need for measuring the tension of mooring line forces which makes all these techniques susceptible to measurement noise or sensor failure. As a matter of fact, not all the mooring lines are equipped with loadcells and even when they are, it is frequently reported that loadcells do not work…”

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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“…Treated as a backup solution in abnormal conditions, this tension-based localization method can improve redundancy with only software updates. It is a companion paper to Ren et al (2015), which considers the problem of efficient linebreak detection in the case when tension sensors are not available in the TAPM system. Here we consider the converse case when tension sensors are available and can be used as redundancy to the posref systems.…”

Section: Introductionmentioning

confidence: 99%

A Tension-based Position Estimation Approach for Moored Marine Vessels

2015

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This paper presents a novel idea on a tension-based localization approach as a redundancy measure to handle the situation when the position reference (posref) signals are not available or significant GNSS drifts occur, such as sudden ionospheric disturbances, for thruster-assisted moored vessels. The only information needed is the tension measurements from tension cells. This method can improve the redundancy and safety of offshore operation, by detecting and verifying posref failure modes. It can even take over the posref function if one no longer trust the main posref measurements. Based on a residual signal, a fault detection and estimation approach is introduced and verified through simulations.

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Supervisory Control of Line Breakage for Thruster-Assisted Position Mooring System

Cited by 10 publications

References 23 publications

Detection of mooring line failures using Dynamic Hypothesis Testing

A Tension-based Position Estimation Approach for Moored Marine Vessels

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