• Wind and Structures
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• v.16 no.4
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• pp.341-354
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• 2013

This paper presents an experimental investigation concerning the peak amplitudes of oscillation of a square prism due to Vortex-Induced-Vibrations (VIV) as a function of the mass damping parameter $m^*{\zeta}$ (the so called Griffin--plot); $m^*$ and ${\zeta}$ being, respectively, the non-dimensional mass and the mechanical (structural) damping ratio. With this purpose in mind, an electromagnetic actuator has been employed to provide controlled damping. During the experiments the mass--damping parameter was in the range 0.15 < $m^*{\zeta}$ < 2.4. Experiments show that there is a value of $m^*{\zeta}$ below which VIV appears combined with galloping and the prism oscillation increases monotonically with the incoming flow velocity. For $m^*{\zeta}$ >0.3 the present experiments show a well-defined VIV phenomenon and, consequently, a Griffin-plot can be defined.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2392-2394
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• 2005

This paper presents a tuneable bandstop resonator with two possible configurations, it can be used to tune its center frequency, or it can be used to tune its bandwidth. The tuneable bandstop resonator has potential application in microwave communications receivers, where it can be used to tune out interfering signals. The proposed resonator is comb actuated, where the resonator's displacement produces different values of frequency or bandwidth, this is achieved by decoupling electromagnetic energy from a main transmission line. The proposed fabrication process for the resonator is by anodic bonding pyrex glass and tow resistivity silicon, where the comb resonator structure is patterned by deep reactive ion etching (DRIE). This paper presents the resonator and actuator design in both configurations, as well as the fabrication process intended for its development.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2251-2253
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• 2003

This paper is concerned with the active vibration control of flexible cantilever beam system using electromagnetic force actuator. The main objective of this paper is to propose the control algorithms and implement the experimental setups for active vibration control. Several control algorithms are proposed and implemented on the experimental setups to show their efficacy. These include a PID control design, an optimal $H_2$ control design, and a fuzzy PID control design. Effectiveness and performance of the designed controller were verified by both simulation and experiment results.

• Journal of KSNVE
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• v.2 no.4
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• pp.293-304
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• 1992

Active vibration control is presented with simulation and experiment. Dynamic Data System(DDS) method is used for system modeling and this model is combined with an forecasting control technique to derive a control equation. In the experiment, on-line digital computer monitors structural vibration and calculates control input. The control input is sent to an electromagnetic actuator which cancels the structural vibration. Experiment is performed first with a simple beam setup to demonstrate the effetiveness of this method. This method is then applied to a color laser printer to actively modify the structure. The beam experiment showed vibration reduction of over 60% with one-and two-DOF models. In the printer structure experiment, the first mode of 308 Hz was successfully controlled with a one-DOF model.

• Proceedings of the KAIS Fall Conference
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• 2008.05a
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• pp.173-176
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• 2008

The aim of this review is to acquaint a circuit designer with features of piezoelectric ceramic transformers(PT) and to show the general approach to the design of inverters utilizing PT as a circuit element. The description of the piezoelectric effect is not present here and can be easily found in numerous publications as well as complex equations and formulae. What is the most important to understand is that "they are different" - one cannot just change an electromagnetic transformer (EMT) for a piezoelectric one. Several examples of PT-based circuitry will help to start and use PT's advantages most effectively.

• Advances in robotics research
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• v.1 no.1
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• pp.1-19
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• 2014

Microgripper is an essential device in the micro-operation system. It can convert other types of energy into mechanical energy and produce clamp movement with required chucking force, which enables it a broad application prospect in the domain of tiny components' processing and assembly, biomedicine and optics, etc. The performance of a microgripper is dependent on its power supply, type of drive, mechanism structure, sensing components, and controller. This paper presents a state-of-the-art survey of recent development on flexure-based microgrippers. According to the drive type, the existing microgrippers can be mainly classified as electrostatic microgripper, electrothermal microgripper, electromagnetic microgripper, piezoelectric microgripper, and shape memory alloy microgripper. Additionally, some different mechanisms, sensors, and control methods that are used in microgripper system are reviewed. The key issue of how to choose those components in microgripper system design is also addressed.

• Composites Research
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• v.23 no.2
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• pp.24-30
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• 2010

Interfacial evaluation and hydrophobicity of Ni-nanopowder/epoxy composites were investigated for self-sensing and actuation. Contact resistance and resistivity were measured using gradient micro-specimens. The actuation of the composites in the electromagnetic field was studied with three wave functions, i.e., sine, triangle and square functions. Due tothe presence of hydrophobic domains on the heterogeneous surface, the static contact angle of Ni-nanopowder/epoxy nanocomposite wasabout $100^{\circ}$, which was rather lower than that for super-hydrophobicity. The dynamic contact angle showed the similar trend of static contact angle. Ni-nanopowder/epoxy composite was responded wellfor both self-sensing and actuation in electromagnetic field due to the intrinsic metal property of Ni-nanopowder. Displacement of the actuator of Ni-nanopowder/epoxy composite was evaluated to obtain the maximum and the optimum performance using laser displacement sensor as functions of the wave type, frequency, and voltage. Actuation of Ni-nanopowder/epoxy composites also increased as functions of applied frequency and voltage. Actuated strain increased more rapidly at sine wave with increasing voltage compared to those of triangle or rectangular waves.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2320-2323
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• 2014

Piezoelectric inverter for driving CCFL is designed in this study. Of them, CCFL is generally used because it has advantages such as small size, high efficiency and good brightness characteristics. the description of the piezoelectric effect is not present here and can be easily found in numerous publications as well as complex equations and formulae. What is the most important to understand is that "they are different" one cannot just change an electromagnetic transformer(EMT) for a piezoelectric one. The simulation program supports the modeled piezoelectric inverter for this paper and the equivalent circuit. The result of the experiment shows more than 90% improvement in terms of the efficiency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1229-1232
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• 2010

In this study, in order to develop multilayer piezoelectric transformer for high electromechanical coupling factor and mechanical quality factor. and to show the general approach to the design of inverters utilizing PT as a circuit element. The description of the piezoelectric effect is not present here and can be easily found in numerous publications as well as complex equations and formulae. What is the most important to understand is that "they are different" -one cannot just change an electromagnetic transformer (EMT) for a piezoelectric one. Several examples of PT-based circuitry will help to start and use multilayer piezoelectric transformer advantages most effectively.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2809-2811
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• 2005

In this paper, we address an active vibration control system, which suppresses the vibration engaged by magnetically levitated stage. The stage system consists of a levitating platen with four permanent magnetic linear synchronous motors in parallel. Each motor generates vertical force for suspension against gravity and propulsion force horizontally as well. This stage can generate six degrees of freedom motion via the vertical and horizontal forces. In the stage system, which represents the settling-time critical system, the motion of the platen vibrates mechanically. We designed an active vibration control system for suppressing vibration due to the stage moving. The command feedforward with inertial feedback algorithm is used for solving stage system's critical problems. The components of the active vibration control system are accelerometers for detecting stage tables's vibrations, a digital controller with high precise signal converters, and electromagnetic actuators.