• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1979-1983
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• 2011

FRP(Fiber Reinforced Plastic) support insulators for DC(direct current) were developed and their electrical and mechanical characteristics were investigated. Electrical tests were carried out to measure flashover voltages under common use frequency condition. Tensile and bending tests were performed for the mechanical characteristics. The test results showed that FRP support insulators have superior voltage resistances and strengths to porcelain insulators. Field test also is carried out to measure adaptation and to compensate the defect. The test result showed that a new product has no defect in electrical and mechanical.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.72-77
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• 2017

This paper proposes the explicit tuning rule of multi-loop PID controller for brushless direct current motors to predict the system behaviors in time and frequency domains, using properties of the convex combination method. The convex set of the proposed controllers formulates the envelope to satisfy the performances in time and frequency domains. The final control parameters are determined by solving the convex optimization problem subject to the constraints which are represented as convex set of time domain performances. The effectiveness of the proposed control method is shown in the numerical simulation, in which controller tuning algorithm and dynamics of brushless DC motor are well taken into account.

• 한국소음진동공학회논문집
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• 제22권4호
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• pp.365-371
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• 2012

This paper presents robust control performance of a direct current(DC) motor with brake system adopting a giant electrorheological(GER) fluid, whose distinguished feature is an extremely high value of yield stress. As a first step, Bingham characteristics of the GER fluid is experimentally investigated using the Couette type electroviscometer. A cylindrical type of ER brake is then devised based on the Bingham model, and its braking torque is evaluated. Structural analysis of ER break is performed using ANSYS. After formulating the governing equation of motion for the DC motor with ER brake system, a sliding mode control algorithm, which is very robust to external disturbances and parameter uncertainties, is synthesized and experimentally realized in order to achieve desired rotational speed trajectories. The tracking responses of the control system are then evaluated and verified by presenting speed control performance.

• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2249-2255
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• 2015

The use of voltage source converter multi-terminal direct current (VSC-MTDC) systems is anticipated to increase from the introduction of wind farms and super grids in the near future. Effective control of the DC voltage in VSC-MTDC systems is an important research topic. This paper proposes a new dynamic reference-based voltage droop control to control the DC voltage in VSC-MTDC systems more effectively. The main merit of the dynamic reference-based voltage droop control is that it can reduce the steady-state error in conventional voltage droop control by changing references according to the system operating conditions. The performance of the proposed control was tested in a hardware-in-the-loop simulation (HILS) system based on the OPAL-RT real-time digital simulator and four digital signal processing boards.

• Journal of Advanced Marine Engineering and Technology
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• 제31권4호
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• pp.441-447
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• 2007

The speed and torque control performance of the DC motor used in the industrial field is affected by the change of parameters. In particular the change of armature resistance can be greatly originated from various load conditions. Accordingly a large number of studies to estimate those problems in the servo motor control field have already been under way. In this paper, the armature resistance on the DC motor under several load and speed conditions is estimated by the Artificial Neural Network(ANN), and the validity is proven by the speed estimation of sensorless speed control system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1120-1122
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• 2005

인터넷의 급속한 보급으로 인해 데이터 전송 시 발생하는 공간상의 제약을 쉽게 극복 할 수 있게 되어 전 세계 어디서든지 데이터를 주고받을 수 있게 되었다. 이러한 인터넷 웹기반의 장점을 살려서 그동안 실험 연구용으로 사용하던 서보시스템의 PID 제어방법을 인터넷을 기반으로 한 원격제어 시스템으로 구현하였다. 본 논문에서는 DC 서보 모터와 모터 제어 보드, NI사의 DAQ, PC로 시스템을 구현 하였다. UI(User Interface)는 LabVIEW 프로그램을 이용하여 GUI(Graphical User Interface)로 DC 서보 모터의 제어와 작동상태의 모니터링이 용이하도록 하였고, 최적의 PID 이득값을 설정하여 원하는 속도 응답 특성이 양호한 제어를 할 수 있게 하였다. 더 나아가 PID 제어 방법을 원격 실시간의 가상 실습이 가능한 e-Learning에 적용 할 수 있음을 확인하였다.

• International journal of advanced smart convergence
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• 제10권3호
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• pp.81-88
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• 2021

This paper proposes two types of subharmonic RF receiver front-end (called LMV) where, in a single stage, quadrature voltage-controlled oscillator (QVCO) is stacked on top of a low noise amplifier. Since the QVCO itself plays the role of the single-balanced subharmonic mixer with the dc current reuse technique by stacking, the proposed topology can remove the RF mixer component in the RF front-end and thus reduce the chip size and the power consumption. Another advantage of the proposed topologies is that many challenges of the direct conversion receiver can be easily evaded with the subharmonic mixing in the QVCO itself. The intermediate frequency signal can be directly extracted at the center taps of the two inductors of the QVCO. Using a 65 nm complementary metal oxide semiconductor (CMOS) technology, the proposed subharmonic RF front-ends are designed. Oscillating at around 2.4 GHz band, the proposed subharmonic LMVs are compared in terms of phase noise, voltage conversion gain and double sideband noise figure. The subharmonic LMVs consume about 330 ㎼ dc power from a 1-V supply.

• Structural Engineering and Mechanics
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• 제76권5호
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• pp.619-629
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• 2020

In current study, surface/interface effects for pull-in voltage and viscous fluid velocity effects on dimensionless natural frequency (DNF) of fluid-conveying piezoelectric nanosensor (FCPENS) subjected to direct electrostatic voltage DC with nonlinear excitation, harmonic force and also viscoelastic foundation (visco-pasternak medium and structural damping) are investigated using Gurtin-Murdoch surface/interface (GMSIT) theory. For this analysis, Hamilton's principles, the assumed mode method combined with Lagrange-Euler's are used for the governing equations and boundary conditions. The effects of surface/interface parameters of FCPENS such as Lame's constants (λI,S, μI,S), residual stress (τ0I,S), piezoelectric constants (e31psk,e32psk) and mass density (ρI,S) are considered for analysis of dimensionless natural frequency respect to viscous fluid velocity u̅f and pull-in voltage V̅DC.

• 한국표면공학회지
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• 제55권6호
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• pp.308-318
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• 2022

The surface modification and treatment using thermal plasma were reviewed in academic fields. In general, thermal plasma is generated by direct current (DC) and radiofrequency (RF) power sources. Thermal spray coating, a typical commercial process using thermal plasma, is performed by DC thermal plasma, whereas other promising surface modifications have been reported and developed using RF thermal plasma. Beyond the thermal spray coating, physical and chemical surface modifications were attempted widely. Superhydrophobic surface treatment has a very high industrial demand particularly. Besides, RF thermal plasma system for large-area film surface treatment is being developed. Thermal plasma is especially suitable for the surface modification of low-dimensional nanomaterial (e.g., nanotubes) by utilizing high temperature and rapid quenching. It is able to synthesize and modify nanomaterials simultaneously in a one-pot process.

• 지구물리와물리탐사
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• 제24권4호
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• pp.149-157
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• 2021

유도분극 탐사와 전기비저항 탐사는 자료획득이 유사하며, 대부분의 전기비저항 탐사 시스템에는 시간영역 유도분극 탐사 기능이 함께 탑재되어 있다. 또한 시간영역 유도분극 탐사 자료에는 전기비저항 자료가 내포되어 있다. 따라서 유도분극 탐사와 전기비저항 탐사와는 불가분의 관계가 있으며, 유도분극 자료의 역산도 전기비저항 탐사 자료의 역산에 근거한 2단계 역산법이 적용되고 있다. 그러나 유도분극 탐사는 효과적인 해석법의 부재로 인하여 전기비저항 탐사에 비하여 널리 적용되지 못하고 있다. 이 연구에서는 수치 모델링 및 역산실험을 통하여 시간영역 유도분극 자료의 역산해석에 사용되는 역 사상법의 문제점을 분석하였다. 또한 역 사상법 적용시 문제가 되는 역산잡음을 효과적으로 억제할 수 있는 수정된 역 사상법을 제시하였다. 마지막으로 수치자료에 대한 역산실험을 통하여 개발된 역 사상법의 효과를 검증하였다.