• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.248-253
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• 2013

The maximum speed is one of the most important performance in high speed railway vehicle. The higher the train speed is, the worse the ride comfort is, In order to solve this problem, a semi-active or active suspension can be applied to high speed railway vehicle. The variable damper with hydraulic solenoid valve is used in the semi-active suspension. But the variable damper with hydraulic solenoid valve requires tank for supplying fluid. The MR(Magneto Rheological) damper can be considered instead of hydraulic variable damper which needs additional device, i.e. reserver tank for fluid. In the case of active suspension, hydraulic actuator or electro-mechanical one is used to suppress the carbody vibration in railway vehicle. In this study the MR damper and electro-mechanical actuator was considered in secondary suspension system of high speed railway vehicle. The dynamic analysis was performed by using 10-DOF dynamic equations of railway vehicle. The performance of the semi-active suspension and active suspension system were reviewed by using MATLAB/Simulink S/W. The vibration suppression effect of semi-active and active suspension system were investigated experimentally by using 1/5-scaled railway vehicle model.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.386.1-386.1
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• 2014

The ionic polymer-metal composite (IPMC), a type of electro-active polymer material, has received enormous interest in various fields such as robotics, medical sensors, artificial muscles because it has many advantages of flexibility, light weight, high displacement, and low voltage activation, compare to traditional mechanical actuators. Mostly noble metal materials such as gold or platinum were used to form the electrode of an IPMC by using electroless plating process. Furthermore, carbon-based materials, which are carbon nanotube (CNT) and reduced graphene-CNT composite, were used to alter the electrode of IPMC. To form the electrode of IPMC, we employ the synthesized graphene on copper foil by chemical vapor deposition method and use the transfer process by using a support of PET/silicone film. The properties of graphene were evaluated by Raman spectroscopy, UV/Vis spectroscopy, and 4-point probe. The structure and surface of IPMC were analyzed via field emission scanning electron microscope. The fabricated IPMC performance such as displacement and operating frequency was measured in underwater.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.6
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• pp.264-269
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• 2005

The electrostatic comb drive actuator is one of the main building blocks in the field of micro electro-mechanical systems (MEMS). Most of the comb actuators presented previously have fingers that are rectangular in shape which produce a stable, constant force output during actuation. The use of sawtooth fixed fingers in a comb drive, which were presumed to produce an increasing force output with displacement due to the increased number of regions where fringing force, the driving force of comb actuators, appear. The dimensions of the sawtooth were derived from finite element analysis (FEA) of simplified finger models with sawtooth type fingers of various dimension and were compared to the rectangular finger model that showed that the sawtooth type fingers have $7\~9$ times stronger driving force. Finally, comb drive actuators with sawtooth type and rectangular fingers were fabricated and although the gap was bigger, the comb actuator with sawtooth type fingers showed about 1.7 times greater electrostatic force than the one with rectangular fingers at equal driving voltages. In conclusion, using the proposed sawtooth type comb fingers in a comb drive makes it possible to increase its displacement or reduce the driving voltage.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.943-946
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• 2007

In-plane piezoelectric charge constant of Electro-Active paper (EAPap) was investigated based on direct and converse piezoelectric effects. EAPap samples were made with cellulose film with very thin gold electrode coated on both sides of the film. To characterize direct piezoelectricity of EAPap, induced charge was measured when mechanical stress was applied to EAPap. In-plane piezoelectric charge constant was extracted from the relation between induced charge and applied in-plane normal stress. To investigate converse piezoelectricity, induced in-plane strain was measured when electric field was applied to EAPap. Piezoelectric charge constant was also extracted from the relation of induced in-plane strain and applied electric field. Piezoelectric charge constants obtained from direct and converse piezoelectricity are 31 pC/N and 178 x 10-12m/V for 45 degree sample, respectively. Measured piezoelectric charge constants of EAPap provide promising potential as a piezoelectric material.

• Smart Structures and Systems
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• v.15 no.6
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• pp.1601-1623
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• 2015

Electroactive polymers have attracted considerable attention in recent years due to their sensing and actuating properties which make them a material of choice for a wide range of applications including sensors, biomimetic robots, and biomedical micro devices. This paper presents an effective modeling strategy for nonlinear large deformation (small strains and moderate rotations) dynamic analysis of polymer actuators. Considering that the complicated electro-chemo-mechanical dynamics of these actuators is a drawback for their application in functional devices, establishing a mathematical model which can effectively predict the actuator's dynamic behavior can be of paramount importance. To effectively predict the actuator's dynamic behavior, a comprehensive mathematical model is proposed correlating the input voltage and the output bending displacement of polymer actuators. The proposed model, which is based on the rigid finite element (RFE) method, consists of two parts, namely electrical and mechanical models. The former is comprised of a ladder network of discrete resistive-capacitive components similar to the network used to model transmission lines, while the latter describes the actuator as a system of rigid links connected by spring-damping elements (sdes). Both electrical and mechanical components are validated through experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.714-717
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• 2007

In this study, a novel actuator was developed by employing the newly-synthesized ionic networking membrane (INM) of poly (styrene-alt-maleic anhydride) (PSMAn)-incorporated poly (vinylidene fluoride) (PVDF). Based on the same original membrane, various samples of INM actuator were prepared through different reduction times with the electroless-plating technique. The as-prepared INM actuators were tested in terms of surface resistance, platinum morphology, resonance frequency, tip displacement, current and blocked force, and their performance was compared to that of the widely-used traditional Nafion actuator. Scanning electron microscope (SEM) and transmission electron microscopy (TEM) revealed that much smaller and more uniform platinum particles were formed on the surfaces of the INM actuators as well as within their polymer matrix. Although excellent harmonic response was observed for the newly-developed INM actuators, this was found to be sensitive to the applied reduction times during the fabrication. The mechanical displacement of the INM actuator fabricated after optimum reduction times was much larger than that of its Nafion counterpart of comparable thickness under the stimulus of constant and alternating current voltage.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.60-67
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• 2001

As a method of variable valve train(VVT), Electro-Mechanical Valve(EMV) has been studied. Compared with conventional VVT system, the EMV system has a relatively simple structure. The system has two electromagnets, springs and an armature. The system can be operated by reciprocal action between armature and two electromagnets. And, the operating event can be controlled by electrical signal from controller. Therefore, reduction of emission and fuel consumption can be achieved through valve event control at each engine operating condition. In this study, characteristics of EMV system were investigated by simulations and experiments. The results of simulation and experiment show that the core shape and material characteristics are dominant parameters on magnetic force and delay time. In order to apply the system to commercial engine, it has a compact size and high stiffness springs(50N/mm) to increase the valve speed. Because of high valve seating velocity, loud noise and high impact force generated, which can lead to reduction of actuator durability. Therefore, further research is required to reduce valve seating velocity.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.673-675
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• 2002

In this paper. the lumped electrical circuit approach of mass/spring system is used to model the mechanical aspects according to the frequency. Therefore, the mass/spring system can be dealt with here and linked with the equivalent circuit of electric linear oscillatory actuator(LOA). Analysis models are double-coil type linear compressor for stirling refrigerator. The compressor consists of the moving coil LOA, piston, and spring. The electro-mechanical system with mass and spring can be represented using the lumped electrical circuit. We present the system impedance and dynamics of moving coil linear compressor.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.478-481
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• 2004

This study presents the combined effect of electric Held application and mechanical compressive stress loading on deformation in a multilayer ceramic actuator, designed with stacking alternatively 0.2(PbMn$\_$1/3/Nb$\_$2/3/O$_3$)-0.8(PbZr$\_$0.475/Ti$\_$0.525/O$_3$) ceramics and Ag-Pd electrode. The deformation behaviors were thought to be attributed to relative 180$^{\circ}$domain quantities which is determined by pre-loaded stress and electric field. The non-linearity of piezoelectricity and strain are dependent upon the young's modulus resulting from the domain reorientation.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.11
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• pp.1012-1016
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• 2004

In the present paper, equivalent beam and equivalent bimorph beam models for IPMC(ionic Polymer-Metal Composite) actuators are described. Physical properties of an IPMC, such as Young's modulus and electro-mechanical coupling coefficient. are determined from the rule of mixture, bimorph beam equations, and measured force-displacement data of a cantilevered IPMC actuator. By using a beam equation with estimated physical properties, actuation displacements of a cantilevered IPMC actuator was calculated and a good agreement between the computed tip displacements and the measured data was observed. Finite element analysis(FEA) combined with the estimated physical properties was used to reproduce the force-displacement relationship of an IPMC actuator. Results from the FEA agreed well with the measure data. The proposed models might be used for modeling of IPMC actuators with complicated shapes and boundary conditions.