• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.1029-1034
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• 2004

Linear motion ( LM) guides having rolling elements have been used to position precision machines accurately. For ultra-accurate Positioning control of Precision machines, the understanding of the dynamic behavior of the LM guide at the macro and/or micro scales is most critical, but the research on this subject is rare. The objective of the present research is to investigate the vibration phenomena of the LM guide where balls are used as the rolling elements. Several experiments show the nonlinear characteristics of the LM guide such as hysteresis behavior and force-dependent natural frequencies phenomena.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.4
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• pp.21-28
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• 2014

Daily use characteristics of apparent power supplied to distribution transformer can be separated into two different time zone of waking hours and sleeping hours. In sleeping hours, using amount of power is decreasing. The actual curve of power seemed to be quite similar to this kind of separation. Inserting a condenser into a circuit in each different time zone led to maximize power factor of the transformer. The compensating condenser's on/off time is controlled by hysteresis circuit utilizing op amp and power factor of the transformer was improved from 0.945 to 0.999. As a result, the average of current reduction was 2.53A per hour of transformer.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.9-14
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• 2007

In this paper, a rotating tool clamping device was developed based on a shape memory alloy(SMA) and its feasibility as a tool holder was experimentally explored. The SMA-based device was able to alter clamping to unclamping through temperature control within 1 second. The means and repeatability(${\sigma}$) of the tool clamping force were 185.5N and 6N respectively and its drifts were less than 3% for an hour. Considering the temperature hysteresis of the SMA-based tool clamping device, it is necessary to heat the SMA ring to around $50^{\circ}C$ after tool change to obtain more clamping force.

• Steel and Composite Structures
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• v.18 no.2
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• pp.481-496
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• 2015

A Lead Extrusion Damper (LED) is experimentally studied under various frequencies and displacement amplitudes. Experimental results show that the force-displacement hysteresis loops of the LED are close to rectangular and the force-velocity hysteresis loops exhibit nonlinear hysteretic characteristic. Also, the LED can provide consistent energy dissipation without any stiffness degradation. Based on the experimental results, a mathematical model is then proposed to describe the effects of frequency and displacement on property of LED. It can be proved from the comparison between experimental and numerical results that the mathematical model can accurately describe the mechanical behavior of LED. Subsequently, the seismic responses of the Schwedler reticulated shell structure with LEDs are analyzed by ANSYS software, in which three different installation forms of LEDs are considered. It can be concluded that the LED can effectively reduce the displacement and acceleration responses of this type of structures.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.1
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• pp.1-7
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• 2011

Active power control scheme for distributed generation in microgrid consists of feeder flow control and unit power control. Feeder flow control is more useful than the unit power control for demand-side management, because microgrid can be treated as a dispatchable load at the point of common coupling(PCC). This paper presents detailed descriptions of the feeder flow control scheme for the hybrid system in microgrid. It is divided into three parts, namely, the setting of feeder flow reference range for stable hybrid system operation, feeder flow control algorithm depending on load change in microgrid and hysteresis control. Simulation results using the PSCAD/EMTDC are presented to validate the inverter control method for a feeder flow control mode. As a result, the feeder flow control algorithm for the hybrid system in microgrid is efficient for supplying continuously active power to customers without interruption.

• Journal of Mechanical Science and Technology
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• v.16 no.11
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• pp.1379-1394
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• 2002

In case of a single input single output (SISO) system with a nonlinear term, a signal compression method is useful to identify a system because the equivalent impulse response of linear part from the system can be extracted by the method. However even though the signal compression method is useful to estimate uncertain parameters of the system, the method cannot be directly applied to a unique system with hysteresis characteristics because it cannot estimate all of the two different dynamic properties according to its motion direction. This paper proposes a signal compression method with a pre-processor to identify a unique system with two different dynamics according to its motion direction. The pre-processor plays a role of separating expansion and retraction properties from the system with hysteresis characteristics. For evaluating performance of the proposed approach, a simulation to estimate the assumed unknown parameters for an arbitrary known model is carried out. A motion platform with several single-rod cylinders is a representative unique system with two different dynamics, because each single-rod cylinder has expansion and retraction dynamic properties according to its motion direction. The nominal constant parameters of the motion platform are experimentally identified by using the proposed method. As its application, the identified parameters are applied to a design of a sliding mode controller for the simulator.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.3
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• pp.95-100
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• 2004

A control alogorithm using sliding mode and neural network for Buck type DC-DC converter is presented. Also, we conform a rightness the proposal method by comparing a theoretical values and experimental values obtained from experiment using DSP(digital signal processor). Performance comparisons made with the general hysteresis controller clearly bring out the superior performance of the proposal neural network controller. This paper will be applied to other power conversion system using the proposal neural network controller.

• Structural Engineering and Mechanics
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• v.64 no.2
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• pp.195-204
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• 2017

Analytical and experimental studies of the innovative pipe in pipe damper have been recently investigated by the authors. In this paper, by adding lead or zinc infill or slit diaphragm inside the inner pipe, it is tried to increase the equivalent viscous damping ratio improving the cyclic performance of the recently proposed multi-level control system. The damper consists of three main parts including the outer pipe, inner pipe and added complementary damping part. At first plastic deformations of the external pipe, then the internal pipe and particularly the added core and friction between them make the excellent multi-level damper act as an improved energy dissipation system. Several kinds of added lead or zinc infill and also different shapes of slit diaphragms are modeled inside the inner pipe and their effectiveness on hysteresis curves are investigated with nonlinear static analyses using finite element method by ABAQUS software. Results show that adding lead infill has no major effect on the damper stiffness while zinc infill and slit diaphragm increase damper stiffness sharply up to more than 10 times depending on the plate thickness and pipe diameter. Besides, metal infill increases the viscous damping ratio of dual damper ranging 6-9%. In addition, obtained hysteresis curves show that the multi-level control system as expected can reliably dissipate energy in different imposed energy levels.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.5
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• pp.604-610
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• 2014

In this paper, the analysis and the experiment of independent multi-phase BLDC motor are performed. The back-emf, iron loss analysis are performed by the finite element method and compared with experimental results. The independent multi-phase BLDC motor is manufactured and to measure the efficiency of the motor, evaluation system is also manufactured including the load generator. By comparing the analytic and the experimental results, the effectiveness of the analysis model is verified when calculating the efficiency of the motor.

• Journal of Drive and Control
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• v.9 no.4
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• pp.32-41
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• 2012

Most diagnosis methods for servo valves requires installing spool displacement sensor or flow sensor as well as pressure sensor. The measurement of flow is hard to implement and many kinds of servovalves or proportional direction valves do not have a built-in spool displacement sensor. In this study, static performances of servovalve or proportional-direction-valve are studied theoretically and a diagnosis technique, which uses only load pressure and input current signal, is assessed. An experimental setup was made based upon a personal computer and the LabVIEW graphical language. A series of diagnosis tests were performed and the analysis results showed it possible to measure the pressure gain, hysteresis and null bias in a relatively simple methodology.