A Numerical Study on Motion Responses of a Mat-Support Jack-Up During Positioning

2015 ◽  
Author(s):  
Zhaode Zhang ◽  
Yuhong Wang
Keyword(s):  
Numerical Analysis ◽  
Environmental Conditions ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Analysis Software ◽  
Floating Structure ◽  
Six Degrees Of Freedom ◽  
Motion Responses ◽  
Different Depths ◽  
Jack Up

The motion response of a mat-support jack-up during positioning is studied in this paper using numerical analysis software SESAM. In the process of jack-up positioning, the square bottom mat is gradually lowered and the floating jack-up, secured by anchor chains, moves in six degrees of freedom in response to the dynamic loading of wave, current and wind combined. Numerical simulations are carried out to solve motion responses of the floating structure with mat at different depths. The sensitivity of motion responses to wave periods and directions are analyzed. The maximum motion amplitudes under the design environmental conditions and the risk of the mat crashing with the seafloor are evaluated.

Workspace Optimization of a Six Degrees of Freedom Parallel Manipulator for Micromachining

2010 ◽  
Author(s):  
Ahmet Agaoglu ◽  
Namik Ciblak ◽  
Koray K. Safak
Keyword(s):  
Numerical Analysis ◽  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Base Plane ◽  
Six Degrees Of Freedom ◽  
Moving Platform ◽  
Workspace Optimization ◽  
Kinematic Diagram ◽  
Orientation Workspace

This work addresses the optimization of the workspace of a six degrees of freedom parallel manipulator. In this study, The topology of the manipulator is composed of three xy-tables, symmetrically positioned on a circle on a base plane, connected by three legs to a moving platform. Kinematic composition of the manipulator is introduced and kinematic diagram is illustrated. Orientation workspace is investigated using three different orientation representations. XYZ fixed angles representation is selected considering the benefits of its visualization are considered. By using this representation, the orientation workspace is modeled and kinematic circuits of the manipulator are explored. First, optimization is performed without slider limitations. A result table is obtained based on the user defined parameters. Secondly, optimization is performed under slider limitations. The maximal orientation capability is optimized using numerical analysis. The optimized configuration of the manipulator indicates that a 330% increase in orientation capability is achieved, compared to the old configuration.

Experimental Study the Performance of a Compact Mooring System for a Dual Chamber Floating Oscillating Water Column Device

2020 ◽  
Author(s):  
Sheng Xu ◽  
K. Rezanejad ◽  
Shan Wang ◽  
J. F. M. Gadelho ◽  
C. Guedes Soares
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Degrees Of Freedom ◽  
Wave Energy Converter ◽  
Air Pressure ◽  
Mooring System ◽  
Oscillating Water Column ◽  
Energy Converter ◽  
Six Degrees Of Freedom ◽  
Motion Responses

Abstract A compact mooring system concept is proposed. This novel mooring is composed of submerged buoy and three segments of nylon ropes, which is suitable for the large wave energy converters and wave energy converter array due to its high flexibility and small mooring radius. The performance of this mooring concept was studied experimentally when it was moored to an oscillating water column. The damping of the oscillating water column was modelled by an orifice on top of the chamber. Both regular and irregular head sea wave tests were conducted. In order to study the influence of wave height on system dynamics, two series of regular wave tests with same periods but different wave heights were conducted. An optical tracking system was installed to capture six degrees of freedom motion responses of oscillating water column. The air pressure in the chamber was measured by the air pressure sensor. Two load cells were installed on the top of mooring lines to measure mooring tension time series. Besides, the wave surface elevations inside the chamber were measured by the wave gauges. According to the experimental results, the six degrees of freedom motion responses of floating wave energy converter and mooring tensions are analyzed. Besides, the energy conversion efficiency is evaluated based on the measured data.

Identification of Influential Parameters in A Ship’s Motion Responses: A Route to Monitoring Dynamic Stability

2012 ◽  
Vol 154 (A1) ◽  
Keyword(s):  
Degrees Of Freedom ◽  
Peak Frequency ◽  
Irregular Waves ◽  
Motion Response ◽  
Six Degrees Of Freedom ◽  
Beam Seas ◽  
Motion Responses ◽  
Frequency Components ◽  
Large Motion ◽  
Influential Parameters

Six degrees of freedom motion response tests of a Ro-Ro model have been carried out in irregular waves under intact conditions. A stationary model was tested in different sea states for following, astern quartering and beam seas. The investigation was limited to the effect of encountered frequency components and associated magnitude of energy of the ship’s motion responses. Analysis of heave, pitch and roll motions confirmed the vulnerability of the model to certain frequency ranges resulting in an adverse effect on the responses, and these were closely related to its natural frequencies. It was confirmed that the roll motion maintains its highest oscillation around the natural frequency in all sea conditions regardless of heading angles. However spectral analysis of the heave and pitch responses revealed the wave peak frequency. Roll is magnified when the peak frequency of wave approaches the natural roll frequency; therefore keeping them apart avoids a large motion response. It was concluded that peak frequency and associated magnitude are two important inherent characteristics of motion responses. Detection of influential parameters of encountered wave through heave and pitch responses could be utilised to limit a large ship’s motion at sea.

Experimental and Numerical Study of the Motions of a Turret Moored FPSO in Waves

2004 ◽  
Vol 127 (3) ◽  
pp. 197-204 ◽  
Author(s):  
C. Guedes Soares ◽  
N. Fonseca ◽  
R. Pascoal
Keyword(s):  
Degrees Of Freedom ◽  
Numerical Study ◽  
Numerical Data ◽  
Irregular Waves ◽  
Experimental Program ◽  
Six Degrees Of Freedom ◽  
Strip Theory ◽  
Wide Range ◽  
Wave Heights ◽  
Mooring Forces

This paper presents the results of an experimental program carried out with a model of a FPSO (Floating Production, Storage and Offloading) unit moored and subjected to incoming waves. In regular waves, a wide range of wavelengths were tested and the effect of the wave amplitude was also investigated. In irregular waves the model was subjected to different sea states, including very severe significant wave heights. The measured responses include the six degrees of freedom absolute motions, relative motions, and the mooring forces. The experimental data of surge, heave, and pitch is compared with calculated results from a Green’s function panel method and a strip theory program. In general, the agreement between experimental and numerical data is very good.

scholarly journals IDENTIFICATION OF INFLUENTIAL PARAMETERS IN A SHIP’S MOTION RESPONSES: A ROUTE TO MONITORING DYNAMIC STABILITY

2021 ◽  
Vol 154 (A1) ◽  
Author(s):  
H Enshaei ◽  
R Birmingham ◽  
E Mesbahi
Keyword(s):  
Degrees Of Freedom ◽  
Peak Frequency ◽  
Irregular Waves ◽  
Motion Response ◽  
Six Degrees Of Freedom ◽  
Beam Seas ◽  
Motion Responses ◽  
Frequency Components ◽  
Large Motion ◽  
Influential Parameters

Six degrees of freedom motion response tests of a Ro-Ro model have been carried out in irregular waves under intact conditions. A stationary model was tested in different sea states for following, astern quartering and beam seas. The investigation was limited to the effect of encountered frequency components and associated magnitude of energy of the ship’s motion responses. Analysis of heave, pitch and roll motions confirmed the vulnerability of the model to certain frequency ranges resulting in an adverse effect on the responses, and these were closely related to its natural frequencies. It was confirmed that the roll motion maintains its highest oscillation around the natural frequency in all sea conditions regardless of heading angles. However spectral analysis of the heave and pitch responses revealed the wave peak frequency. Roll is magnified when the peak frequency of wave approaches the natural roll frequency; therefore keeping them apart avoids a large motion response. It was concluded that peak frequency and associated magnitude are two important inherent characteristics of motion responses. Detection of influential parameters of encountered wave through heave and pitch responses could be utilised to limit a large ship’s motion at sea.

How Does Barge-Master Compensate for the Barge Motions: Experimental and Numerical Study

2012 ◽  
Author(s):  
Frederick Jaouen ◽  
Joris van den Berg ◽  
Haite van der Schaaf ◽  
Eelko May ◽  
Jim Koppenol
Keyword(s):  
Time Domain ◽  
Environmental Conditions ◽  
Numerical Study ◽  
Model Tests ◽  
Test Results ◽  
Theoretical Formulation ◽  
Wave Basin ◽  
The Time Domain ◽  
Jack Up ◽  
Economical Alternative

To increase workability and safety in tough environmental conditions, and to create a more economical alternative for jack-up barges, Barge-Master has developed a wave compensating platform for marine and offshore installation barges. To minimize the motions of the crane positioned on top of it, the platform is driven by three hydraulic actuators that compensate for the roll, pitch and heave motions of the barge. To quantify the performance of the platform for different environmental conditions and crane configurations MARIN performed both wave basin model tests and time-domain simulations on the platform. In this paper, the experimental setup is first described and the model test results are presented. Then, the theoretical formulation of the time-domain aNySIM model is described and the numerical results are reported. It is shown that the model tests and time-domain results are in good agreement. The results indicate that the barge motions can be compensated by the platform for more than 90% in 1.2m high sea states. However, it is also shown that the instrumentation, data acquisition and controller system need to be fast and tuned to achieve this optimal compensation.

Clutch micro-slip control in gearshifts for dual clutch transmission

2018 ◽  
Vol 233 (1) ◽  
pp. 43-59
Author(s):  
Tongli Lu ◽  
Bin Zhou ◽  
Jianwu Zhang ◽  
Xiwen Wang
Keyword(s):  
Numerical Analysis ◽  
Dynamic System ◽  
Degrees Of Freedom ◽  
Closed Loop ◽  
Dual Clutch Transmission ◽  
Hydraulic Actuator ◽  
Slip Control ◽  
Six Degrees Of Freedom ◽  
Loop Feedback ◽  
Closed Loop Feedback

Micro-slip control of multi-disc clutches is effective for attenuation of vibration and smooth gearshifts in dual clutch transmission. This paper proposes a method to apply micro-slips on the clutches for gearshift process, which differs from the conventional lockup control. The vehicle powertrain is modelled as a six degrees of freedom dynamic system, including a hydraulic actuator model. Micro-slips of dual clutches are realised by a closed-loop feedback controller according to the control-oriented model. The controller is used to evaluate demands of the clutch torques and transform them to input currents for the hydraulic solenoid valves. Numerical analysis and experiment are preformed, and the results show that the effect of clutch micro-slips is significant in improving the shift smoothness and the drive comfort of the dual clutch transmission during gearshifts.

Mechanisms of Localized Vibration Control in Complex Structures

1996 ◽  
Vol 118 (1) ◽  
pp. 135-139 ◽  
Author(s):  
J. Hannsen Su ◽  
C. E. Ruckman
Keyword(s):  
Vibration Control ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Control Strategies ◽  
Complex Structure ◽  
Element Model ◽  
Property A ◽  
Box Girders ◽  
Six Degrees Of Freedom ◽  
Realistic Structure

This paper describes a numerical study of mechanisms for controlling all six degrees of freedom in localized areas of a complex structure. In localized vibration control, the controller attempts to stabilize one or more localized areas on the structure rather than attempting to stabilize the entire structure. The relative performance levels of different control strategies are evaluated by examining a frequency-dependent disturbance rejection property. A flat plate supported by two box girders is used as an example realistic structure. Plant dynamics from a finite-element model are used to draw general conclusions regarding the mechanisms by which localized vibration control is exerted.

High-Resolution Camera-Space Manipulation

1991 ◽  
Author(s):  
S. B. Skaar ◽  
W. Z. Chen ◽  
R. K. Miller
Keyword(s):  
Degrees Of Freedom ◽  
Task Completion ◽  
Analysis Software ◽  
Position Resolution ◽  
Six Degrees Of Freedom ◽  
Image Analysis Software ◽  
Manufacturing Operations ◽  
Passive Compliance ◽  
Uncalibrated Cameras ◽  
Two Bodies

Abstract The paper presents results from experiments conducted to test the limits on precision and versatility of the method of camera-space manipulation for manufacturing operations. The task used as the basis for the experiment is a close-tolerance rigid-body mating task. The receiving piece is stationary and arbitrarily positioned and oriented. Motion of the inserted piece requires six degrees of freedom for task completion. This is accomplished using the very large GMF S-400 manipulator. The maneuver is guided entirely by information from two uncalibrated cameras. Without the benefit of passive compliance, relative position resolution of the two pieces of about half a millimeter is achieved with considerable reliability. The experiment makes use of newly-developed “ring” cues (and associated image-analysis software) which are painted on the two bodies to be joined.

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