• 한국정밀공학회지
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• 제26권4호
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• pp.100-106
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• 2009

The current tendency toward light weight and fast machines has lead to a need to suppress vibration of flexible dynamic systems. Input shaping is an efficient tool to eliminate transient and residual vibration caused by motion of these systems. This paper proposes a new formulation of the design method for multi-mode input shapers to eliminate residual vibration in flexible dynamic systems. The essence of the proposed method is to minimize the number of impulses to be n+1 for n-mode input shapers. This paper also suggests a solution procedure to solve the complex-valued nonlinear matrix equation for the input shapers. The proposed method is applied to two-mode input shapers. This paper discusses characteristics of several input shapers obtained under the same condition. Simulations and experiments show that the proposed method is very useful for designing multi-mode input shapers.

• 한국해안해양공학회지
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• 제8권4호
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• pp.274-286
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• 1996

2차원 유연체해석 이론(수탄성 이론)을 여러개의 단위체 연결로 이루어진 거대 부체구조물의 해석에 적용하였다. 동수역학적 계수를 구하기 위해 경계요소법과 그린함수법이 사용되었으며 부체자체는 연직방향으로 파랑에 반응하는 연체보로 정수역학적 탄성계수에 대한 운동을 고려하여 운동방정식이 유도된다. 두가지 다른 형식의 연결, 즉 회전강성을 가진 것과 강성을 무시한 핀 형식의 연결요소가 고려되며 반잠수한 부체에 대해 해석결과가 제시된다. 해석결과는 거대 부체구조물의 설계에 필요한 변위와 내력에 관한 개념을 제시한다. 또한 수치해석 결과에 따르면 부체의 움직임은 핀연결이 강성체 연결보다 더 크며 부체의 내력휨 응력은 강성체 연결에서 휠씬 더 크게 증가하였다.

• 전기학회논문지
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• 제67권3호
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• pp.413-418
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• 2018

In this paper, we describe the development of a non-enzymatic glucose sensor based on copper nanocubes(Cu NCs) electroplated laser induced graphene(LIG) electrodes which can detect a certain range of glucose concentrations. $CO_2$ laser equipment was used to form LIG electrodes on the PI film. This fabrication method allows easy control of the LIG electrode size and shape. The Cu NCs were electrochemically deposited on the LIG electrodes to improve electron transfer rates and thus enhancing electrocatalytic reaction with glucose. The average sheet resistances before and after electroplating were $15.6{\Omega}/{\Box}$ and $19.6{\Omega}/{\Box}$, respectively, which confirmed that copper nanocubes were formed on the laser induced graphene electrodes. The prepared electrode was used to measure the current according to glucose concentration using an electrochemical method. The LIG electrodes with Cu NCs demonstrated a high degree of sensitivity ($1643.31{\mu}A/mM{\cdot}cm^2$), good stability with a linear response to glucose ranging from 0.05 mM to 1 mM concentration, and a limit of detection of 0.05 mM. In order to verify that these electrodes can be used as flexible devices, the electrodes were bent to $30^{\circ}$, $90^{\circ}$, and $180^{\circ}$ and cyclic voltammetry measurements were taken while the electrodes were bent. The measured data showed that the peak voltage was almost constant at 0.42 V and the signal was stable even in the flexed condition. Therefore, it is concluded that these electrodes can be used in flexible sensors for detecting glucose in the physiological sample like saliva, tear or sweat.

• Wind and Structures
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• 제26권5호
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• pp.279-292
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• 2018

Inspired by the energy harvesting eel, a flexible flag behind a D-shape cylinder in a uniform viscous flow was simulated by using the immersed boundary method (IBM) along with low-speed wind tunnel experimentation. The flag in the wake of the cylinder was strongly influenced by the vortices shed from the upstream cylinder under the vortex-vortex and vortex-body interactions. Geometric and flow parameters were optimized for the flexible flag subjected to passive flapping. The influence of length and bending coefficient of the flexible flag, the diameters (D) of the cylinder and the streamwise spacing between the cylinder and the flag, on the energy generation was examined. Constructive and destructive vortex interaction modes, unidirectional and bidirectional bending and the different flapping frequency were found which explained the variations in the energy of the downstream flag. Voltage output and flapping behavior of the flag were also observed experimentally to find a more direct relationship between the bending of the flag and its power generation.

• Structural Engineering and Mechanics
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• 제62권5호
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• pp.619-629
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• 2017

This paper focuses on the study of complete dynamic modeling and maximum dynamic load carrying capacity computation of N-flexible links and N-flexible joints mobile manipulator undergoing large deformation. Nonlinear dynamic analysis relies on the Timoshenko theory of beams. In order to model the system completely and precisely, structural and joint flexibility, nonlinear strain-displacement relationship, payload, and non-holonomic constraints will be considered to. A finite element solution method based on mixed method is applied to model the shear deformation. This procedure is considerably more involved than displacement based element and shear deformation can be readily included without inducing the shear locking in the element. Another goal of this paper is to present a computational procedure for determination of the maximum dynamic load of geometrically nonlinear manipulators with structural and joint flexibility. An effective measure named as Moment-Height Stability (MHS) measure is applied to consider the dynamic stability of a wheeled mobile manipulator. Simulations are performed for mobile base manipulator with two flexible links and joints. The results represent that dynamic stability constraint is sensitive when calculating the maximum carrying load. Furthermore, by changing the trajectory of end effector, allowable load also changes. The effect of torsional spring parameter on the joint deformation is investigated in a parametric sensitivity study. The findings show that, by the increase of torsional stiffness, the behavior of system approaches to a system with rigid joints and allowable load of robot is also enhanced. A comparison is also made between the results obtained from small and large deformation models. Fluctuation range in obtained figures for angular displacement of links and end effector path is bigger for large deformation model. Experimental results are also provided to validate the theoretical model and these have good agreement with the simulated results.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.311-314
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• 2006

This paper concerns about total dynamic analysis of integrated mining system. This system consists of vertical steel pipe, intermediate buffer station, flexible pipe and self-propelled miner. The self-propelled miner and buffer are assumed as rigid-body of 6-dof. Discrete models of vertical steel pipe and flexible pipe are adopted, which are obtained by means of lumped-parameter method. The motion of mining vessel is not considered. Instead, the motion of mining vessel is taken into account in form of various boundary conditions (e.g. forced excitation in slow motion and/or fast oscillation and so on). A terramechanics model of extremely soft cohesive soil is applied to the self-propelled miner. The hydrodynamic forces and moments are included in the dynamic models of vehicle and lifting pipe system. Hinged and fixed constraints are used to define the connections between sub-systems (vertical steel pipe, buffer, flexible pipe, miner). Equations of motion of the coupled model are derived with respect to the each local coordinates system. Four Euler parameters are used to express the orientations of the sub-systems. To solve the equations of motion of the total dynamic model, an incremental-iterative formulation is employed. Newmark-b method is used for time-domain integration. The total dynamic responses of integrated mining system are investigated.

• 한국해안·해양공학회논문집
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• 제24권2호
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• pp.89-96
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• 2012

유탄성이론과 고유함수전개법에 기초하여 규칙파중 유연한 그물망의 동적거동과 파랑하중을 살펴보았다. 그물망은 일정한 잠긴깊이를 가지고 수직으로 설치되어 있으며, 상단 끝은 수면에 고정되어 있고 하단 끝은 추에 연결되어 있다. 초기장력이 충분히 크다고 가정하여 장력의 동적 성분을 무시하였다. 유연한 그물망에서의 경계조건식은 투과효과를 나타내는 Darcy의 법칙과 유연성을 나타내는 물체 경계조건식이 결합된 형태이다. 개발된 해석모델은 불투과성/투과성 수직판과 유연막 모델로 확장이 가능하다. 해석모델을 이용하여 여러 설계변수(파랑특성, 공극율, 잠긴깊이, 초기장력)들의 변화가 그물망의 파랑하중과 거동특성에 미치는 영향을 살펴보았다.

• 한국재료학회지
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• 제21권2호
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• pp.115-119
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• 2011

Si Nanowire (NW) field effect transistors (FETs) were fabricated on hard Si and flexible polyimide (PI) substrates, and their electrical characteristics were compared. Si NWs used as channels were synthesized by electroless etching method at low temperature, and these NWs were refined using a centrifugation method to get the NWs to have an optimal diameter and length for FETs. The gate insulator was poly(4-vinylphenol) (PVP), prepared using a spin-coating method on the PI substrate. Gold was used as electrodes whose gap was 8 ${\mu}m$. These gold electrodes were deposited using a thermal evaporator. Current-voltage (I-V) characteristics of the device were measured using a semiconductor analyzer, HP-4145B. The electrical properties of the device were characterized through hole mobility, $I_{on}/I_{off}$ ratio and threshold voltage. The results showed that the electrical properties of the TFTs on PVP were similar to those of TFTs on $SiO_2$. The bending durability of SiNWs TFTs on PI substrate was also studied with increasing bending times. The results showed that the electrical properties were maintained until the sample was folded about 500 times. But, after more than 1000 bending tests, drain current showed a rapid decrease due to the defects caused by the roughness of the surface of the Si NWs and mismatches of the Si NWs with electrodes.

• 한국자동차공학회논문집
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• 제22권5호
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• pp.66-72
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• 2014

A kinematic analysis method has been used as analysis method for dynamic behavior of moving parts of vehicle, especially hood part. Such analysis method, however, has its limitations in terms of design technology, including, over travel of hood that occurs due to lack of considerations of compliance characteristics, such as flexible components of hood's weather strip and over slam bumper. Therefore, it is necessary to develop a modeling which reflects compliance of flexible components of hood and elastic characteristics of panel for improvement of design process. In this thesis, a finite element method as mentioned earlier, is developed to represent over travel of hood. Also optimization process applying sequential approximate optimization is suggested to prevent over travel. The over travel analysis method and optimization process, which are developed through the research, would make it possible to design with high quality and credibility. Furthermore, it is expected that the time for design would be reduced and the design quality also improved.

• 대한기계학회논문집
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• 제18권2호
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• pp.339-350
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• 1994

This paper presents a method for automatic generation of line balanced assembly sequences based on disassemblability and proposes a method of evaluating an assembly work time using neural networks. Since a line balancing problem in flexible assembly system requires a sophisticated planning method, reasoning about line balanced assembly sequences is an important field of concern for planning assembly lay-out. For the efficient inference of line balanced assembly sequences, many works have been reported on how to evaluate an assembly work time at each work station. However, most of them have some limitations in that they use cumbersome user query or approximated assembly work time data without considering assembly conditions. To overcome such criticism, this paper proposes a new approach to mathematically verify assembly conditions based on disassemblability. Based upon the results, we present a method of evaluating assembly work time using neural networks. The proposed method provides an effective means of solving the line balancing problem and gives a design guidance of planning assembly lay-out in flexible assembly application. An example study is given to illustrate the concepts and procedure of the proposed scheme.