• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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• pp.19-22
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• 1990

In this paper, in order to reduce the cogging torque in a permanent motor, a method to optimize the shape of permanent magnet and iron pole is presented. Because the cogging torque comes from the irregular system energy variation according to the rotor position, system energy variation is taken as object function and the object function is minimized to optimize the shape. The positions of permanent magnet surface and iron pole surface are chosen as design parameters and sensitivity of object function with respect to design parameter is calculated. The shape is changed according to sensitivity. Sensitivity can be generated by methods that exploit the FEM formulation. A numerical example shows that about 90% of the original cogging torque is reduced.

• 대한전기학회논문지
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• 제39권12호
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• pp.1246-1252
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• 1990

In order to reduce the cogging torque in a permanent magnet motor, a method to optimize the shape of permanent magnet and iron pole is presented. Sine the cogging torque comes from the irregular system energy variation according to the rotor position, system energy variation is taken as object function and the object function is minimized to optimize the shape. The positions of permanent magnet surface and iron pole surface are chosen as design parameters and sensitivity of object function with respect to the design parameter is calculated. The shape is changed according to sensitivity can be generated by methods that exploit the FEM formulation. A numerical example shows that the cogging torque is reduced to about 10% of the original value.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.277-279
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• 1994

In this paper, a novel field weakening scheme for the induction machine by the voltage control strategy is presented. The proposed algorithm ensures producing the maximum torque over the entire field weakening legion. Also by introducing the direct field-oriented control in the field weakening legion with large variation in machine parameters, the drive system can obtain the robustness to machine parameter variation. Moreover, by using estimated speed, sensorless speed control can be possible in very high speed lesion. Experimental results for a laboratory induction motor drive system confirm the validity or the proposed control algorithm.

• 전기학회논문지
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• 제60권10호
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• pp.1865-1874
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• 2011

This paper proposes a novel maximum power point tracking(MPPT) using a new fuzzy control(NFC) algorithm for robust in insolation variation. Maximum power point(MPP) of solar cell has to achieve for improving output efficiency because it is changed with insolation and temperature. Conventional MPPT controller such as constant voltage(CV), perturbation and observation(PO) and incremental conductance(IC) are researched. But these controller have the problem that is failure to MPP with environment changing. The proposed NFC controller is based the fuzzy control algorithm and able to robust control with environment changing. Also the proposed controller of PV system is modeled by PSIM and the response characteristics according to the parameter variation is compared and analyzed. The validity of this controller is proved through response results.

• 대한전자공학회논문지SD
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• 제43권10호
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• pp.61-67
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• 2006

본 논문에서는 Poly-Si의 불규칙한 Grain boundary 분포로 인해 발생하는 문턱전압의 변화에 대해서도 일정한 전류를 흘려줄 수 있는 전류원을 제안하였다. 기존의 문턱전압 보상 전류원에 비해 넓은 입력전압 범위에서도 포화영역의 특성이 매우 향상되었으며 문턱전압의 변화에 따른 전류의 오차를 감소시킬 수 있었다. 마지막으로 HSPICE 시뮬레이션 과정을 통해 Poly-Si TFT의 특성곡선과 제안된 전류원의 특성곡선을 비교하였으며 각각의 입력전압에 대한 문턱전압의 변화에 따른 출력전류의 상대오차를 측정하였다.

• 한국전자통신학회논문지
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• 제11권1호
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• pp.87-92
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• 2016

Van der Pol 발진기는 비선형 제동 현상을 가진 비보존 발진기로서 높은 진폭에서의 에너지는 소산적이며 (dissipative)이고 낮은 진폭들에서는 생성되는 구조를 가진다. 본 논문에서는 Van Der Pol 발진기 모델에서 다른 거동을 확인하기 위하여 주기적 외력을 인가하고 여기에서 파라미터 변화에 따라 어떻게 리미트 사이클이 변화하는지에 대한 패턴을 확인하고자 한다.

• 대한기계학회논문집A
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• 제28권7호
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• pp.970-976
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• 2004

For a long time, design methodologies strive to systematize the design process in order to make the practice more efficient and effective. One of such methodologies is Axiomatic Design. However, this design theory still has some problems and is not completely settled. In this paper, the new issue for the non-linear design in Axiomatic Design is suggested and the representation of system architecture by flow chart is corrected. In the case that the design equation varies as a function of the variation of DP ($\delta$DP), the design should be regarded as the nonlinear design because the design equation is not a constant. When system architectures are represented by a flow chart, all systems could not be independently represented. However, by adding the notation of the end of decoupling to the notations using in flow chart, those can be independently represented.

• 한국세라믹학회지
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• 제33권10호
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• pp.1131-1137
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• 1996

The dielectric properties and phase stabilities of Pb(Zn0.6Mg0.4)1/3Nb2/3O3 [PZMN]system were investigated into substitution of A-site with Ba, Sr and Ca ions. The A-site substitutions led to the complexity of components of perovskite phase and then DPT coefficient increased. The A-site substitutions of Ba or Sr ion perovskite single phase could be easily formed by columbite process due to increase of perovskite phase stability. The variation of lattice parameters in specimen obeyed Vegard's law and curie temperature and dielectric constant of specimen decreased linearly. But Ca substitution led to perovskite phae instability. The lattice parameter dielectric constant and curie temperature of specimens drasticaly decreased with formation of pyrochlore phase.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.25-28
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• 1987

Design procedure of adaptive controller with variable load condition is present and applied to velocity control of small, permanent magnet DC servo motor. The state feedback control scheme is adopted and Recursive Least Squares algorithm is used for parameter estimation. In order to reduce the time consuming. In the procedure of adaptation-gain tuning of state feedback controller, approximate curve fitting technique is applied to the relations between load condition and poles of the system, load condition and feedback gains. With this method, fast adaptation can be accomplished. It is shown that this procedure can be applied not only to variable load condition but also to variation of other system constants, for example variation of resistance and inductance etc.. Simulation results is present for both cases - variable inertia load, variable motor resistance to verify performance improvements. This design procedure produces an adaptive con troller which is feasible for implementation with microprocessor by reducing calculation time.

• 제어로봇시스템학회논문지
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• 제20권4호
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• pp.395-401
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• 2014

Magnetic levitation systems using the attraction force of electromagnets have many constraints according to the variation of air gap and the nonlinearity of electromagnetic force and inductances. As a result of these constraints, the nonlinear control of a magnetic levitation system has been improved by the latest advanced processors and accurate measurement system which can overcome problems such as many constraints and nonlinearity. This paper concentrates on the modeling of a nonlinear magnetic levitation system and an application of an exponential reaching law based sliding mode controller using the exponential reaching law which is one of the most robust controllers against external unexpected disturbances or parameter fluctuations. Controllability of a magnetic levitation system using the sliding mode control algorithm and robustness against parameter fluctuations have been verified through the experimental results.