• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.80-82
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• 1997

A robust position control system for a BLDC motor using new sliding mode control strategy is presented. Using the new variable structure system, reaching phase problem is eliminated and transient response is largely improved by design of nonlinear sliding surface. The design of the sliding mode position controller is robust in motor parameter, load variations and disturbance. Experiment results show that the proposed approach can achieve accurate position motor tracking in face of large parameter variations and external disturbances, such as a robot arm, etc.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.147-149
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• 2004

This paper presents a new velocity estimation strategy of a non-salient permanent magnet synchronous motor(PMSM) drive without high frequency signal injection or special PWM pattern. This approach is based on the d-axis current regulator output voltage of the drive system which has the information of rotor position error. The rotor velocity can be estimated through a rotor position tracking PI controller that controls the position error to zero. For zero and low speed operation, the PI gains of rotor position tracking controller have a variable structure. The PI tuning formulas are derived by analyzing this control system using the frequency domain specifications such as phase margin and bandwidth assignment.

• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.572-579
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• 2002

The experimental measurements were carried out to examine turbulent disintegration characteristics ejecting from a counter-flowing internal mixing pneumatic nozzle under variable conditions of swirl angles and air pressures. The air injection pressure was varied from 60 kPa to 180 kPa and four counter-flowing internal mixing nozzles with axi-symmetric tangential-drilled holes at swirl angle of 15$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$, and 60$^{\circ}$to the central axis have been specially designed. The experimental results were quantitatively analyzed, focusing mainly on the comparison of turbulent atomization characteristics issuing from an internal mixing swirl nozzle. To illustrate the swirl phenomena, the distributions of mean velocities, turbulence intensities, volume flux, and SMD (Sauter Mean Diameter, or D$\sub$32/) were comparatively analyzed.

• 대한기계학회논문집B
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• 제20권2호
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• pp.649-658
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• 1996

Small-amplitude harmonic oscillations of multi-cylinders are considered both experimentally and theoretically. For the theoretical model, the flow regime is separated into inner and outer regions. In the inner region, the flow is governed by the generalized Stokes boundary layer equation. In the outer region, the full Navier-Stokes equation for the steady streaming flow is solved numerically by using ADI scheme and FVM coupled with the boundary integral method. Flow visualization experiments are conducted by using the Laser Sheet Image Technique. The case of two circular cylinders and square cylinders with variable distances are chosen as a typical example. Although experimental results are based on the flow in the finite domain, both experimental and numerical results agree well qualitatively. As the separation of cylinders is increased, a numerical result shows the asymptotic convergence to a single cylinder case.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 전력전자학술대회 논문집
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• pp.260-264
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• 1998

Three phase Boost/Buck converter which have economical merits and simple control scheme, are analyzed and evaluated through comparative methods and digital simulation for equivalent load. Those play a part of voltage boost/buck as well as power factor correction with single switch. Controller operating in constant and variable frequency is used for rapid output response and stable system condition respectively. Moreover low THD property of single switched converters is available for inverter arc welding machine known as high power and low power factor. So, in this paper a comparison of the characteristics in boost and buck converter is described and then simulation results conforms the merits from point of view of power factor and voltage regulator.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.355-359
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• 2002

Much attention has been given to EMI effects created in variable speed ac drive system. Zero switching states of inverter control invoke large common mode voltage. This paper focuses on the switching techniques to mitigate common mode voltage. This paper proposes a common-mode voltage reduction method based on sinusoidal pulse width modulation in three phase PWM inverter system. By using three carriers wave displaced by 120 degrees, it is possible to eliminate a common mode voltage pulse In one control period. Simulation and experimental results show that common mode voltages In the proposed technique are reduced more than conventional technique.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 추계학술대회 논문집
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• pp.173-177
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• 2003

본 논문에서는 RPWM(Random PWM) 방식을 사용한 3상 유도전동기 구동 시스템의 스위칭 주파수 가변에 따른 구동 특성을 비교 분석하고자 한다. 기존의 RPWM 방식과 본 논문에서 제안한 RPWM 기법을 이용하여 스위칭 주파수 가변에 따른 $M_f$ 변화에 대한 구동특성을 비교 분석하고, 특히 10000[rpm] 이상의 고속운전특성에서의 인버터 출력 전압 및 전류의 고조파 저감효과를 제안된 기법으로부터 확인할 수 있다. 이러한 과정에서는 제안된 RPWM 기법 알고리즘에 대한 타당성 검증을 위해 DSP를 이용한 IGBT 인버터로부터 개별 스위칭 주파수별 실험을 하고, 그 결과의 취득으로부터 스위칭 주파수별 운전 특성을 분석하고자 한다.

• 한국정보처리학회논문지
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• 제7권4호
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• pp.1103-1111
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• 2000

The hyper-geometric distribution software reliability growth model (HGDM) usually assumes that all the software faults detected are perfectly removed without introducing new faults. However, since new faults can be introduced during the test-and-debug phase, the perfect debugging assumption should be relaxed. In this context, Hou, Kuo and Chang [7] developed a modified HGDM for imperfect debugging environment, assuming tat the learning factor is constant. In this paper we extend the existing imperfect debugging HGDM for tow respects: introduction of random sensitivity factor and allowance of variable learning factor. Then the statistical characteristics of he suggested model are studied and its applications to two real data sets are demonstrated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.421-424
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• 1990

In this parer, the parameter for control variable is consist of value that take measured the input line current and input total power-factor, and the compensation susceptance is calculated by its parameters. The compensator can reduce the reactive power generation by the system to zero, thus the input total power-factor is kept on sustaining the unit power- factor.

• The Korean Journal of Pain
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• 제19권2호
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• pp.271-274
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• 2006

Unstable angina is a critical phase of coronary heart disease, with widely variable symptoms and prognoses. Recently, despite the advances in surgical revascularization, catheter-based revascularization and medical treatment, an increasing number of patients with angina pectoris are refractory to medical therapy and; therefore, can not be considered as candidates for coronary artery bypass grafting or interventional angioplasty. These patients are often treated with narcotics for pain relief, and forced to severely reduce their levels of activity and productivity. It has become clear that alleviating the pain caused by myocardial ischemia may be possible by altering the sympathetic afferent nerve fibers. Sympathetic blockade can be produced using high thoracic epidural analgesia. Herein, the case of a patient with intractable angina and poor ventricular function, who received high thoracic epidural analgesia to relieve ischemic chest pain, is reported.