• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.686-689
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• 2005

A numerical simulation method is developed to analyze the dynamic response of a cantilever switch, which is driven by electrostatic force and a basic component of electro-mechanical coupled system. First, point-charges model on conductor is proposed as a lumped parameter of electrical part. Then, this model is easily incorporated into a multi-body dynamics analysis algorithm, the generalized recursive dynamics formula previously developed by our research group. The resulting motion of a coupled overall system is formulated as a differential algebraic equation form including electrical and mechanical variables together. The equation is simultaneously solved in every time step. To implement this approach into the useful dynamics analysis tool, we used multibody dynamics software (RecurDyn) based on the generalized recursive formula using relative coordinate. The developed numerical simulation tool is evaluated by applying to many different driving condition and switch configuration. The final analysis model will be added to RecurDyn as a basic module for dynamics analysis of electro-mechanical coupled system.

• 한국정밀공학회지
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• 제16권2호통권95호
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• pp.218-224
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• 1999

In the feed drive systems of machine tools that consist of many mechanical components such as motor, coupling, ballscrew, nut or table, a torsional vibration is often generated because of its elastic elements in torque transmission. Generally, the accuracy of motion control system is strongly influenced by the dynamic behavior of coupled transmission components. Especially, a torsional vibration caused by the elasticity of mechanical elements might deteriorate the quick movement of system and lead to shorten the life time of the mechanical transmission elements. So, it is necessary to analyze the electromechanical system mathematically to optimize the dynamic characteristics of the feed system. In this paper, the mathematical model of a feed drive system was developed and its mechanical characteristics were analyzed on the basis of the proposed model. The design concepts of speed control loop to stabilize a feed drive system were also proposed.

• International Journal of Fluid Machinery and Systems
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• 제10권1호
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• pp.63-75
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• 2017

Many axial fans have circular arc blades with constant thickness. It is still a challenging task to calculate their performance, i.e. to predict how large their pressure rise and pressure losses are. For this task a need for cascade data exists. Therefore, the designer needs a method which works quickly for design purposes. In the present contribution a design method for such cascades consisting of circular arc blades with constant thickness is described. It is based on a singularity method which is combined with a CFD-data-based flow loss model. The flow loss model uses CFD-data to predict the total pressure losses. An interpolation method for the CFD-data are applied and described in detail. Data of measurements are used to validate the CFD-data and parameter variations are conducted. The parameter variations include the variation of the camber angle, pitch chord ratio and the Reynolds number. Additionally, flow patterns of two dimensional cascades consisting of circular arc blades with constant thickness are shown.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권9호
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• pp.3204-3220
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• 2021

We perform the task of video object segmentation by incorporating a conditional random field (CRF) and convolutional neural networks (CNNs). Most methods employ a CRF to refine a coarse output from fully convolutional networks. Others treat the inference process of the CRF as a recurrent neural network and then combine CNNs and the CRF into an end-to-end model for video object segmentation. In contrast to these methods, we propose a novel higher-order CRF model to solve the problem of video object segmentation. Specifically, we use CNNs to establish a higher-order dependence among pixels, and this dependence can provide critical global information for a segmentation model to enhance the global consistency of segmentation. In general, the optimization of the higher-order energy is extremely difficult. To make the problem tractable, we decompose the higher-order energy into two parts by utilizing auxiliary variables and then solve it by using an iterative process. We conduct quantitative and qualitative analyses on multiple datasets, and the proposed method achieves competitive results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.467-471
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• 2009

In this study a cantilevered carbon nanotube(CNT) switch was investigated with the linear and the nonlinear structural models incorporating the electrostatic force and van der Waals interactions between the CNT and ground surface. Due to the applied voltage and van der Waals interactions the CNT deforms statically and dynamically and finally pull into the surface. When the nonlinear model is considered in case of the relatively large gap between the CNT and the surface, the static pull-in voltage was increased due to the nonlinear hardening effect. Also the dynamic response was investigated with the different external dc and ac voltages. The CNT shows various dynamic behaviors and instabilities including dynamic pull-in. Based on this study, further research on the dynamic and nonlinear stability of CNT nanodevices should be requested to develop the new type of nano switches or nano-memory.

• 한국세라믹학회지
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• 제24권5호
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• pp.470-476
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• 1987

The system of 0.1Pb(Mg1/3N2/3)O3-yPbTiO3-zPbZrO3 piezoelectric ceramics was made in the radial model disk and ring dot type filter. The resonant frequency(fr) variations were investigated for 100 hours and the temperature range from 20$^{\circ}C$ to 100$^{\circ}C$. As the results, the morphotropic phase boundary was supposed to be the composition of 45 y 50 and 40 z 45. The best characteristic of againg effect, after 10-hours, was composed of y, z=45. The stabilized characteristic of temperature varition, to become 0.1% up to 100$^{\circ}C$, was composed of y=50 and z=40. The bandwidth was broadened with increasing the electromechanical coefficient(kp), and the filter characteristics was approached ideal mode with increasing mechanical quality factor(Qm). Kp and Qm affected combinationally on filter characteristics.

• 한국생산제조학회지
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• 제8권2호
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• pp.44-49
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• 1999

This paper is concerned with the theoretical and experimental study on the force conrtrol of a miniature robotic gripper. The gripper is an uniform flexible cantilever equipped with a distributed set of compact force sensor. As an actuator piezoelectric acturator, piezoelectric acturator is fixed with cupper plate at which the beam is clamped. The mathematical model of the assembled electro-mechaincal system is developed. The force sensor is described by a set of concentrated mass-spring system. The formulated equations of motion are applied to he study of a control problem where the gripper is commanded to grip an object The usefulness of the PID control technique is verified by experiment.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.487-495
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• 2015

This paper proposes a new robust decentralized power oscillation dampers (POD) design of doubly-fed induction generator (DFIG) wind turbine for damping of low frequency electromechanical oscillations in an interconnected power system. The POD structure is based on the practical $2^{nd}$-order lead/lag compensator with single input. Without exact mathematical model, the inverse output multiplicative perturbation is applied to represent system uncertainties such as system parameters variation, various loading conditions etc. The parameters optimization of decentralized PODs is carried out so that the stabilizing performance and robust stability margin against system uncertainties are guaranteed. The improved firefly algorithm is applied to tune the optimal POD parameters automatically. Simulation study in two-area four-machine interconnected system shows that the proposed robust POD is much superior to the conventional POD in terms of stabilizing effect and robustness.

• Journal of Electrical Engineering and Technology
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• 제3권3호
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• pp.401-407
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• 2008

The dynamic model and displacement control of piezoelectric actuators, which are commercially available materials for managing extremely small displacements in the range of sub-nanometers, are presented. Piezoceramics have electromechanical characteristics that transduce energy between the electrical and mechanical domains. However, they have hysteresis between the input voltage and output displacement, and this behavior is very demanding and complicated. In this paper, we propose a method of designing the control algorithm, and present the dynamic modeling equations that represent the hysteretic behavior between input voltage and output displacement. For this process, the piezoelectric actuator is treated as a second-order linear dynamic system and system constants are determined by the system identification method. Also, a classical PID controller is designed and used to regulate the output displacement of the actuator. To evaluate the performance of the proposed method, numerical simulation results are presented.

• Smart Structures and Systems
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• 제4권1호
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• pp.35-46
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• 2008

In this paper the authors address the problem of comparing two different smart damping techniques using the numerical modelling of the electro-mechanical impedance for plate structures partially treated with active constrained layer damping treatments. The paper summarizes the modelling procedures including a finite element formulation capable of accounting for the observed behaviour. The example used is a smart cantilever plate structure containing a viscoelastic material (VEM) layer sandwiched between a piezoelectric constrained layer and the host vibrating plate. Comparisons are made between active constrained layer and active damping only and based on the resonance frequency amplitudes of the electrical admittance numerically evaluated at the surface of the piezoelectric model of the vibrating structure.