• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.4
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• pp.244-254
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• 1991

The numerical analysis on tile behaviour of mooring system in the offshore guyed tower is presented. The governing equilibrium equations are derived by the principle of virtual work. The drag and inertia effects of fluid are included in a Morrison type equation. The finite element method is used in the computation. Geometric nonlinearities for the analysis of the mooring line are considered in which both modified Newton-Raphson method and Newmark-$\beta$ method are employed. Numerical experiments show the validity and the capability of the developed mathematical formulation.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.765-767
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• 2001

Linear pulse Motors(LPM) are widely used in fields where smooth linear motion is required, and their position accuracy is higher than other motors. Hybrid linear pulse motors(HLPM) are regarded as an excellent solution to positioning problems that require high accuracy, rapid acceleration and high-speed. The LPM has low mechanical complexity, high reliability, precise open-loop operation and low inertia etc. in many application areas such as factory automation speed positioning, computer peripherals and numerically controlled machine tools. This motor drive system is especially suitable for machine tools the high position accuracy and repeatability. This paper describes about that need of the embroider machine, we want to design position-scanning device for the embroidery machine. At first, to be analysed characteristics of the machine and next designed the LPM. we used the field analysis program, The finite element method(FEM) program tool is employed for calculation the force. The reluctance models will be used the magnetic permeance of air gap by static- conditions. The forces between forcer and platen have been calculated using the virtual work method.

• Journal of Welding and Joining
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• v.21 no.2
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• pp.102-110
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• 2003

A visual sensor consisted of polygonal mirror, laser, and CCD camera was proposed to measure the distance to the weld joint for recognizing the joint shape. To scan the laser beam of the sensor onto an object, 8-facet polygonal mirror was used as the rotating mirror. By locating the laser and the camera at axi-symmetrical positions around the mirror, the synchronized-scan condition could be satisfied even when the mirror was set to rotate through one direction continuously, which could remove the inertia effect of the conventional oscillating-mirror methods. The mathematical modelling of the proposed sensor with the optical triangulation method made it possible to derive the relation between the position of an image on the camera and the one of a laser light on the object. Through the geometrical simulation of the proposed sensor with the principal of reflection and virtual image, the optical path of a laser light could be predicted. The position and direction of the CCD camera were determined based on the Scheimpflug's condition to fit the focus of any image reflected from an object within the field of view. The results of modelling and simulation revealed that the proposed visual sensor could be used to recognize the weld joint and its vicinity located within the range of the field of view and the resolution. (Received February 19, 2003)

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.1
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• pp.11-23
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• 1989

This paper presents the results of the numerical analysis on the behaviour of mooring system of offshore guyed tower. Finite element method is used and geometric nonlinearities are considered in the analysis of mooring line. The governing equilibrium equations are derived by the principle of virtual work, and modified Newton-Raphson method and Newmark-${\beta}$ method are employed in response calculations. The drag and inertia effects of fluid are included using a Morrison type equation. The influences of changing typical parameters like initial inclination and tension of line at the guy attachment point, the length of clump weight, its unit weight and the anchor line length are examined. The effects of idealising the clump weight as a point load(lumped clump weight) on the behaviour of mooring lines are also discussed. Numerical examples demonstrate the validity and capability of the mathematical formulation.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2221-2230
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• 2016

Voltage and frequency stability issues occur in existing centralized power system due to the high penetration of renewable energy sources, which decrease grid absorptive capacity of them. The grid-connected inverter that mimics synchronous generator characteristics with inertia characteristic is beneficial to electric power system stability. This paper proposed a novel three-phase four-wire grid-connected inverter with an independent neutral line module that mimics synchronous generators. A mathematical model of the synchronous generator and operation principles of the synchronverter are introduced. The main circuit and control parameters design procedures are also provided in detail. A 10 kW prototype is built and tested for further verification. The primary frequency modulation and primary voltage regulation characteristics of the synchronous generator are emulated and automatically adjusted by the proposed circuit, which helps to supports the grid.

• Structural Engineering and Mechanics
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• v.42 no.4
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• pp.589-608
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• 2012

In this study, the effect of in-plane deformations on the dynamic behavior of laminated plates is investigated. For this purpose, the displacement-time and strain-time histories obtained from the large deflection analysis of laminated plates are compared for the cases with and without including in-plane deformations. For the first one, in-plane stiffness and inertia effects are considered when formulating the dynamic response of the laminated composite plate subjected to the blast loading. Then, the problem is solved without considering the in-plane deformations. The geometric nonlinearity effects are taken into account by using the von Karman large deflection theory of thin plates and transverse shear stresses are ignored for both cases. The equations of motion for the plate are derived by the use of the virtual work principle. Approximate solution functions are assumed for the space domain and substituted into the equations of motion. Then, the Galerkin method is used to obtain the nonlinear algebraic differential equations in the time domain. The effects of the magnitude of the blast load, the thickness of the plate and boundary conditions on the in-plane deformations are investigated.

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.91-93
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• 2001

Linear pulse Motors(LPM) are widely used in fields where smooth linear motion is required, and their position accuracy is higher than other motors. Hybrid linear pulse motors(HLPM) are regarded as an excellent solution to positioning problems that require high accuracy, rapid acceleration and high-speed. The LPM has low mechanical complexity, high reliability, precise open-loop operation and low inertia etc. In many application areas such as factory automation speed positioning, computer peripherals and numerically controlled machine tools, LPM can be used. This motor drive system is especially suitable for machine tools the high position accuracy and repeatability. This paper describes about that need of the embroider machine, we want to design position-scanning device for the embroidery machine. At first, to be analysed characteristics of the machine and next designed the LPM, we used the field analysis program. The finite element method(FEM) program tool is employed for calculation the force. The reluctance models will be used the magnetic permeance of air gap by static-conditions. The forces between forcer and platen have been calculated using the virtual work method. And we used the simulink to know the dynamic characteristics of LPM.

• Steel and Composite Structures
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• v.30 no.6
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• pp.567-576
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• 2019

Time-dependent creep analysis of a rotating functionally graded cantilever beam with trapezoidal longitudinal cross section subjected to thermal and inertia loading is investigated using first-order shear deformation theory (FSDT). The model described in this paper is a simple simulation of a turbine blade working under creep condition. The material is a metal based composite reinforced by a ceramic where the creep properties of which has been described by the Sherby's constitutive model. All mechanical and thermal properties except Poisson's ratio are assumed to be variable longitudinally based on the volume fraction of constituent. The principle of virtual work as well as first order shear deformation theory is used to derive governing equations. Longitudinal distribution of displacements and stresses are investigated for various volume fractions of reinforcement. Method of successive elastic solution is employed to obtain history of stresses and creep deformations. It is found that stresses and displacements approach their steady state values after 40000 hours. The results presented in this paper can be used for selection of appropriate longitudinal distribution of reinforcement to achieve the desired stresses and displacements.

• KIPS Transactions on Software and Data Engineering
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• v.8 no.12
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• pp.491-498
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• 2019

Digital twin is a technology that virtualizes physical objects of the real world on a computer. It is used by collecting sensor data through IoT, and using the collected data to connect physical objects and virtual objects in both directions. It has an advantage of minimizing risk by tuning an operation of virtual model through simulation and responding to varying environment by exploiting experiments in advance. Recently, artificial intelligence and machine learning technologies have been attracting attention, so that tendency to virtualize a behavior of physical objects, observe virtual models, and apply various scenarios is increasing. In particular, recognition of each robot's motion is needed to build digital twin for co-robot which is a heart of industry 4.0 factory automation. Compared with modeling based research for recognizing motion of co-robot, there are few attempts to predict motion based on sensor data. Therefore, in this paper, an experimental environment for collecting current and inertia data in co-robot to detect the motion of the robot is built, and a motion prediction model based on the collected sensor data is proposed. The proposed method classifies the co-robot's motion commands into 9 types based on joint position and uses current and inertial sensor values to predict them by accumulated learning. The data used for accumulating learning is the sensor values that are collected when the co-robot operates with margin in input parameters of the motion commands. Through this, the model is constructed to predict not only the nine movements along the same path but also the movements along the similar path. As a result of learning using SVM, the accuracy, precision, and recall factors of the model were evaluated as 97% on average.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.807-813
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• 2016

The Maritime Traffic Safety Audit Scheme was institutionalized in 2009 to provide for professional surveys, measurement and the evaluation of navigational hazards that might occur in coastal waters in the course of marine work. Related researches that dealt with the reform of the Maritime Traffic Safety Audit Scheme found that there were no rules or regulations for verifying whether marine work conformed to audit results and reviewing the exactitude of ship handling simulations which were a crucial part of the scheme. According to the necessity of adopting an ex post facto management system in the field of maritime traffic, this study analyzed the similar audit acts such as the Natural Environment Impact Audit Scheme and the Road Traffic Safety Audit Scheme, and proposed specific articles for revising Maritime Safety Act in order to break out from the institutional inertia of the current Maritime Traffic Safety Audit Scheme. It is expected that a newly proposed legal system for verifying the performance of audit results and the exactitude of audits will help improve maritime traffic safety by eradicating potentially hidden hazards related to marine work.