• Journal of Positioning, Navigation, and Timing
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• 제9권2호
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• pp.65-70
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• 2020

For a wireless communication system, the angle-of-arrival (AOA) of the signal has a variety of applications. The signal AOA is estimated utilizing various antenna array structure such as Uniform Linear Array (ULA), Uniform Rectangular Array (URA), and Uniform Circular Array (UCA). In this paper, we introduce a cascade AOA estimation algorithm based on the UCA, which is consisted of CAPON and Beamspace MUSIC. CAPON is employed to estimate approximate AOA groups including multiple AOA signals and Beamspace MUSIC is employed to estimate detailed signal AOAs in the estimated AOA groups. In addition, we provide the computer simulation results for verifying and analyzing the performance of the cascade AOA estimator based on UCA.

• 한국생산제조학회지
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• 제22권2호
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• pp.206-215
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• 2013

In this paper, a synchronization control technique of dual-servo motor driven press system is proposed. An independent cascade PID control technique has been applied to the conventional press system for advancement of control stability. However, it is not easy to reduce synchronous error using the independent cascade PID control technique when some different load disturbances are involved in each motor. The eccentric error of the slide caused by the problem degrade the control performance of the BDC(Bottom Dead Center). In order to achieve reduction of the synchronous error between two servo motors and accurate position control simultaneously, a new control scheme comprised with cascade PID control loop and cross-coupling loop is proposed. In simulation using Matlab SIMULINK, the AC servo system is designed. The control performance of proposed technique is compared with conventional control technique to the model of AC servo system. Also, the sub-scale model of dual-servo motor driven press system which can replicate the slide motion is constructed for experimental verification for the performance of the proposed control technique. The cross-coupling control technique reveals more precise and stable performances in the position and synchronization controls.

• 한국통신학회논문지
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• 제39C권10호
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• pp.909-919
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• 2014

License plate (LP) detection is the most imperative part of an automatic LP recognition (LPR) system. Typical LPR contains two steps, namely LP detection (LPD) and character recognition. In this paper, we propose an efficient Vehicle-to-LP detection framework which combines with an adaptive GMM (Gaussian Mixture Model) and a cascade of boosted classifiers to make a faster vehicle LP detector. To develop a background model by using a GMM is possible in the circumstance of a fixed camera and extracts the motions using background subtraction. Firstly, an adaptive GMM is used to find the region of interest (ROI) on which motion detectors are running to detect the vehicle area as blobs ROIs. Secondly, a cascade of boosted classifiers is executed on the blobs ROIs to detect a LP. The experimental results on our test video with the resolution of $720{\times}576$ show that the LPD rate of the proposed system is 99.14% and the average computational time is approximately 42ms.

• 전자공학회논문지SC
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• 제43권1호
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• pp.39-44
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• 2006

델타시그마 변환기에서 limit cycle 에 의한 패턴 노이즈 문제는 오래 동안 설계자들을 괴롭혀 온 문제이다. 델타시그마 변환기의 동작과 출력은 입력과 초기치에 의해 결정된다. 본 논문은 델타시그마 변환기의 구조에 따른 패턴잡음의 발생정도를 널리 쓰이는 네 가지 모델로 비교 하였다. 델타시그마 변환기 중 적분기형 과 공진기형의 차이와 부궤환 방식에 따른 차이를 비교 하였으며 그 결과는 적분기 형식의 증폭단을 사용하는 델타시그마 변환기가 패턴잡음을 적게 발생시키는 것으로 판명되었다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.561-565
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• 2001

This paper proposes a new switching scheme of a static var compensator(SVC) with cascade multilevel inverter which employs H-bridge inverter(HBI). To improve the un­balanced problem of the DC capacitor voltages, the rotated switching scheme of fundamental frequency is newly used. The optimized fundamental switching pattern with low switching frequency is adapted to be suitable for high application. The selective harmonic elimination method(SHEM) allows to keep the total harmonic distortion(THD) low in the output voltage of multilevel inverter. The SVC system is modeled using the d-q transform which calculates the instantaneous reactive power. This model is used to design a controller and analyze the SVC system. Simulated and experimental results are also presented and discussed to validate the proposed schemes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 학술대회 논문집 전문대학교육위원
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• pp.136-141
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• 2000

This paper proposes the novel control of a static synchronous compensator (STATCOM). This STATCOM system consists of cascade multilevel inverter which employs H-bridge inverter(HBI) The STATCOM system is modeled in the d-q transform matrix. This model is used to design a controller. The selective harmonic elimination method(SHEM) allows to keep the total harmonic distortion (THD) low in the output voltage. The switching method produces the staircase type waveform in cascade multilevel inverter. To balance the DC voltages in HBIs capacitor, the rotated switching scheme is newly proposed in this paper. The proposed control scheme is verified in the simulated results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국내학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
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• pp.154-159
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• 1988

In this paper, a hyperstable cascade control scheme for servo drive systems is proposed to reduce the chattering, which is an undesirable property in discontinuously controlled systems. First, a discontinuously controlled hyperstable MRAC scheme is designed with respect to PI speed control system using only output variables, and then a linear position controller is cascaded. It is shown that the above system is asymptotically stable and the chattering is greatly reduced at a constant speed provided that the disturbance torque satisfies a certain condition.

• 제어로봇시스템학회논문지
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• 제7권7호
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• pp.567-573
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• 2001

A real-time HVAC system is proposed which implements real-time control of thermal environment for virtual reality. It consists of a pair of hot and cold loops that serve as thermal reservoirs, and a mixing box to mix hot and cold air streams flowing if from loops. Their flow rates are controlled in real-time to meet a set temperature and flow rate. A cascade control algorithm along with gain scheduling is applied to the system and test results shows that the closed-loop response approached set values within 3 to 4 seconds.

• 대한기계학회논문집
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• 제16권2호
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• pp.313-324
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• 1992

Two-dimensional Navier-Stokes code has been developed for analysis of turbomachinery blade rows and other internal flows. The Navier-Stokes equations are written in a Cartesian coordinate system, then mapped into a generalized body-fitted coordinate system. All direction of viscous terms are incorporated and turbulent effects are modeled using the Baldwin-Lomax algebraic model. Equation are discretized using finite difference method on the C-type grids and solved using implicit LU-ADI decomposition scheme. Calculations are made at a VKI turbine cascade flow in a transonic wind-tunnel and compared to experimental data. Present numerical scheme is shown to be in good agreement with the previous experimental results and simulates the two-dimensional viscous flow phenomena.

• 정보보호학회논문지
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• 제7권3호
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• pp.117-128
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• 1997

다중등급 보안 분산 네트워크 환경에서 MHS(Message Handling System) 보안을 실현하기 위하여 강제적 접근통제(Mandatory Access Control) 정책을 구현한 컴퓨터 시스템들을 상호 연결하였을 때 예기치 않은 캐스케이드 취약성 문제로 인하여 불법적인 정보 흐름이 발생하게 된다 본 논문에서는 이에 대한 해결책으로 캐스케이드 취약성 방지를 위한 새로운 MHS 보안 정책을 제안하고 이를 실현하기 위한 보안 특성 함수를 설계하였다.