Motion Control System Design for a Barge Type Vessel Moored by Ropes
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BARGE
Mooring
Dynamic positioning
Position (finance)
The mixing of dynamic positioning and mooring would be used simultaneously for semi-submersible drilling rig under requirement.The analysis of rig movement under positioning mode of mixing dynamic positioning and mooring is complex,it is almost impossible to analyze the capability of the mixing positioning if rig.According to the positioning characteristic of dynamic positioning and mooring,the static method was used firstly to analyze the external force of rig,and then the dynamic method was used to analyze the capability of mooring.At last,the capability of mixing was obtained.
Mooring
Dynamic positioning
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ABSTRACT This paper deals with the concept of and a system for complete control of the slowly varying bow motion of a bow-moored ship using dynamic positioning. System performance is shown by simulated case studies with an offshore 1oading tanker. Significant improvements of motion behaviour and mooring force performance are demonstrated. A complete positioning system is presently runn1ng successfully onboard a 125000 dwt tanker in the North Sea. Some preliminary results are shown. INTRODUCTION Mooring of large ships at offshore terminals are done by single-point mooring. The ship is connected to the terminal through a single mooring line, or hawser, which allows H to position itself according to the preventing weather and sea conditions, like a weather-vane, and thereby to remain moored with a minimum mooring force when the direction of forces changes. A major problem faced by single-p01nt mooring In hostel areas is due to the motion of the ship and the terminal. The ship tends to oscillate slowly relative to its mooring point with a following oscillatory behaviour of the mooring stresses, and with the effects of wave following motions superimposed. When the mooring force exceeds a prescribed value, loading must be stopped and mooring abandoned. The low frequency ship motionstems from unstable ship mooring configuration and/or dynamic force excitations from wind and wavesl. From practical experience a certain amount of astern thrust is found to have a favorable effect on the slow motion, but it is questionable as a remedy for reducing peak hawser tension. Dynamic positioning (dp) has been applied with great success to freely moving ships and moored vessels for more than ten years. While keeping the ship In a fixed position is typical to most dp system applications, the desirable objective in single-point mooring is to keep the distance between the mooring terminal and the ship's bow as nearly constant as possible, while maintaining the overall weather-vane capability. In this paper a review of the essential slow motion behaviour of a bow moored tanker 1s presented with emphasis on stability and mode dynam1cs. The des1gn and the theoretical performance of a dp-system to meet the single-point mooring positioning objective Is presented and, finally, results from full scale tests with a 125000 dwt tanker during offshore loading are shown. ANALYSIS OF SLOW MOTIONS IN SINGLE-POINT MOORING Only static (elastic) properties of the mooring terminal affects the slow motion behaviour, while the high frequency (wave following) propert1es are reflected in the mooring force. Hence, the terminal is left out in the following analysis. Governing equations The governing equations describing the slow motion of a bow moored ship In wind, waves and current are reasonably well establ1shed. A detailed description is presented In1. Applying some symmetry assumptions, the equations of motion In moored ship coordinates.
Mooring
Dynamic positioning
Tension (geology)
Position (finance)
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Most of the derrick pipe laying vessels are dumb barges with mooring systems. It is flexible,cost-effective,safe and reliable if the barge is outfitted with good mooring system. Therefore mooring system is important for lifting,pipe laying and survival.Research on mooring position installation scheme of derrick lay barge is introduced in this paper combing with codes and practice.
BARGE
Mooring
Position (finance)
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Turret
Mooring
Dynamic positioning
Line (geometry)
Position (finance)
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The mooring position control systems are used to maintain a position ofthe marine plant, and be helped to keep position to not drift by external forces like as waves, currents and winds. It is necessary to know how to be evaluated for the motion characteristics at mooring condition, variation of mooring tension in positioning mooring floating offshore facilities. A numerical procedure is described for predicting the motion of barge ship in regular waves. The numerical approach is based on a combination of the three-dimensional source distribution method and the finite element method. is presented for the prediction of motions of barge ship in regular waves.
BARGE
Mooring
Position (finance)
Response amplitude operator
Tension (geology)
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This paper presents some experimental results about Position Mooring (PM) system applied to the barge ship. In PM operation, the station keeping in surge, sway of vessel is provided by the mooring system. In this paper, a system, consisting of a barge vessel and mooring lines, is mathematically modeled. The position and orientation of vessel is controlled by changing the tensions in the mooring lines. The PID control strategy is applied to evaluate the efficiency of proposed system. Experimental result which corresponds to the applied control strategy is presented and discussed.
BARGE
Mooring
Position (finance)
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Structural modifications of a ship may cause a fatal accident such as sinking and wrecking of ship. Especially, barge ship can be easily reconstructed to load more bulk cargo. In this study, for a real accident case, change of mooring force due to structural modification was analyzed to evaluate accident risk. A two dimensional dynamic model for the barge ship was constructed to compute mooring forces with related to floating motion. The equation of motion was established in Matlab code and buoyancy was calculated by using direct integration of submerged volume. The results showed that wind force, current force, and mooring force after rebuilding was approximately 4.3 kN, 14 kN, 1,561 kN respectively. The maximum force of mooring force according to the length of mooring cable were 1,614 kN at 30 m of mooring cable. Thus, an arbitrary modification of ship lead instability and unreliable result so that illegal rebuilding of ship should be avoided.
BARGE
Mooring
Fictitious force
Wind force
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Semi-submersible Ferry-type Landing is built up by docking barge,double block roll off platform and assembled mooring system which installed special upright anchor device.The design of docking barge model and the analogue of anchor cable was comparatively introduced,the mooring system′s status in different assembled modes was analyzed,based on the analysis,the mechanical attribute and response regulation when the docking barge under the multiple term in which storm waves and shedding were assembled.
BARGE
Mooring
Docking (animal)
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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. When environmental loads due to wind, waves, and current increase, thruster assistance is required also 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 designed in this paper instead employs structural reliability measures for the mooring lines to restrict movement. These structural reliability measures become an intrinsic part of the controller, enabling it to automatically adjust the admissible region for the vessel in the presence of changing winds, currents, and waves.
Mooring
Dynamic positioning
Position (finance)
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