• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 춘계학술대회
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• pp.152-155
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• 2014

ABS/ESC 기능 통합 SoC에 사용되는 자동차 제동 솔레노이드 밸브 구동용 디지털 PWM 컨트롤러를 설계하였다. 직접 제어와 PI 제어 방식을 지원하도록 설계된 PWM 컨트롤러는 총 12채널로 구성된다. 직접 제어 방식의 6개 채널은 설정된 PWM 듀티값에 따라 일정한 PWM을 출력하며, PI 제어 방식의 6개의 채널은 설정된 전류값을 기준으로 드라이버의 전류 값에 따라 변화하는 PWM을 출력하여 일정한 전류를 갖도록 설계되었다. 또한 솔레노이드 밸브 열림 감지, Dither, PWM 위상 시프트 기능 등을 갖는다. 설계된 PWM 컨트롤러는 44,779 게이트로 구현되었으며, 0.18um CMOS 공정으로 제작된 칩의 측정 결과로부터 기능이 정상적으로 동작하는 것을 확인하였다.

• Journal of Information Display
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• 제10권4호
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• pp.184-187
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• 2009

A liquid crystal device with switchable dynamic and memory modes was investigated and developed. The proposed device reveals the splay, $\pi$-twist, and bend states via selective switching among them. In the dynamic mode, the device is operated in the bend state, which exhibits a wide viewing-angle and a fast-response-time due to its self-compensated bend structure and flow-accelerated fast response time, respectively. In the memory mode, the permanent memory characteristics in the splay and $\pi$-twist sates are obtained, respectively. The switching mechanisms of the tristate device are also proposed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.954-958
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• 2004

본 논문은 부하에 대한 빠른 응답특성을 보이는 새로운 토폴로지를 제안하였다. PI제어기 출력이 포화될 때 windup 현상이 나타나고 그 결과로 성능이 저하된다. 따라서 전동기의 가변속 제어성능을 위해 가속시에는 개선된 Anti-windup PI제어기만을 사용하고, 감속시에는 추가로 부하의 특성을 고려하여 braking 동작을 사용하였다. 시뮬레이션 및 실험결과는 속도성능면에서 제안된 방식이 종래의 다른 제어방식에 비해 우수함을 보여 준다.

• Journal of Magnetics
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• 제12권1호
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• pp.27-30
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• 2007

Experimental evidence suggests that spin pinning conditions for standing spin mode in polycrystalline $Ni_{84}Fe_{16}$ alloy film, is confirmed using the four categories of Camley et al. and the value of q$\bot$ for the pinning conditions, this was achieved by performing Brillouin light scattering measurements. The value of q$\bot$ was observed, in order to increase at a rate of $\pi$/2 with an increasing mode number. With this condition, the coexistence of standing spin wave modes was shown, with intermediate pinning, in addition to free and strong pinning. The values for spin-wave-stiffness constant ($D_B$), g-factor (g), and surface magnetization (4$\pi$M) of the Permalloy film were obtained from the results of BLS, and determined to be $D_B=1.85{\pm}0.05Oecm^2$, $g=2.11{\pm}0.02$, and 4$\pi$M=8.7 kG, respectively.

• 융합신호처리학회 학술대회논문집
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• 한국신호처리시스템학회 2001년도 하계 학술대회 논문집(KISPS SUMMER CONFERENCE 2001
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• pp.105-108
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• 2001

In this paper, we proposed a variable structure controller with fuzzy PI-쇼pe reaching law. we fuzzified as inputs to fuzzy system Rf(representative point's orthogonal distance(rd) to switching surface and RP's distance(r) to the origin of the 2-dimensional space whose coordinates are the error and the error rate. The increments of the coefficients $k_{p}$ and $k_{i}$, of the reaching law are calculated appropriate by the simplified Mamdanl inference. The proposed fuzzy PI-type reaching law makes it reduce the chattering and has no need to tune the PI parameters of reaching law. The effectiveness of the proposed fuzzy PI-type reaching law is shown by the simulation results of the control of a Ball-balance System.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 추계학술대회 논문집
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• pp.67-68
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• 2015

본 논문은 폐루프 고피나스 자속관측기의 P/PI모드를 전환하여 전환점부근 저속에서 모터상수 변동에도 강인한 센서리스 벡터제어가 가능한 전환기법을 제안하였다.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2000년도 춘계학술대회 학술발표 논문집
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• pp.51-54
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• 2000

In variable structure control algorithm, sliding mode makes the closed loop system insensitive to modelling uncertainties and external disturbances. However due to imperfections in switching, the system trajectory chatters, which is very undesirable. And the insensitivity property of a sliding mode controller is present only when the system is in the sliding mode. To overcome these shortcomings, in this paper, new sliding mode control algorithm using time-varying sliding surface and fuzzy PI structrue is proposed.

• Nuclear Engineering and Technology
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• 제31권2호
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• pp.202-213
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• 1999

Effects of the rotary inertia of concentrated masses on the natural vibrations of fluid conveying pipes have been studied by theoretical modeling and computer simulation. For analysis, two boundary conditions for pipe ends, simply supported and clamped-clamped, are assumed and Galerkin's method is used for transformation of the governing equation to the eigenvalues problem and the natural frequencies and mode shapes for the system have been calculated by using the newly developed computer code. Moreover, the critical velocities related to a system instability have been investigated. The main conclusions for the present study are (1) Rotary inertia gives much change on the higher natural frequencies and mode shapes and its effect is visible when it has small value, (2) The number and location of nodes can be changed by rotary inertia, (3) By introducing rotary inertia, the second natural frequency approaches to the first as the location of the concentrated mass approaches to the midspan of the pipe, and (4) The critical fluid velocities to initiate the system unstable are unchanged by introduction of rotary inertia and the first three velocities are $\pi$, 2$\pi$, and 3$\pi$ for the simply supported pipe and 2$\pi$, 8.99, and 12.57 for the clamped-clamped pipe.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권11호
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• pp.538-543
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• 2006

A high-Power continuous-wave (CW) ten-vane double-strapped magnetron oscillator has been investigated using three-dimensional (3D) particle-in-cell (PIC) numerical simulation code, MAGIC3D. The resonant modes and their resonant frequencies of the ten-vane strapped magnetron resonator were obtained to show a large mode separation near the ${\pi}$-mode. An electron cloud formed in an anode-cathode gap, called an interaction space was confined well enough to result in no leakage current. Five spokes were clearly observed in the electron cloud, which definitely ensured the ${\pi}$-mode oscillation in the ten-vane magnetron. Numerical simulations predicted that the saturated microwave output power measured at the coaxial output port was 5.41 kW at the microwave frequency of 893 MHz, corresponding to a power conversion efficiency of 72.6% when the external axial magnetic field was 1150 gauss and the electron beam voltage and current were 6 kV and 1.25 A, respectively.

• 한국산학기술학회논문지
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• 제12권11호
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• pp.5143-5149
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• 2011

본 논문은 슬라이딩 모드 관측기를 이용한 적응 속도 센서리스 벡터제어에 대해 제안한다. 적응 슬라이딩 모드 관측기는 전압식을 이용한 전동기 고정자 기준좌표에 의해 회전자 자속성분이 관측된다. Lyapunov 함수에 의해 얻어지는 추가적인 관계로부터 전동기의 속도가 구해진다. 성능 확인을 위해 전통적인 PI 제어기와 슬라이딩 모드 관측기의 추가적인 특성에 대해 시뮬레이션과 실험을 통해 비교하였다. 분석과 비교에 의한 결과에 의하면 시스템의 유용성을 확인할 수 있었다.