• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.77-79
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• 2019

Islanding detection is one of the most important issues for the distributed generation (DG) systems connected to the power grid. The conventional passive islanding detection methods inherently have a non-detection zone (NDZ), and active islanding detection methods may deteriorate the power quality of a power system. This paper proposes a novel hybrid islanding detection method based on Digital Lock-In Amplifier with no NDZ by monitoring the harmonics present in the grid. Proposed method detects islanding by passively monitoring the grid voltage harmonics and verify it by injecting small perturbation for only three-line cycles. Unlike FFT for the harmonic extraction, DLA HC have lower computational burden, moreover, DLA can monitor harmonic in real time, whereas, FFT has certain propagation delay. The simulation results are presented to highlight the effectiveness of the proposed technique. In order to prove the performance of the proposed method it is compared with several passive islanding detection methods. The experimental results confirm that the proposed method exhibits outstanding performance as compared to the conventional methods.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.303-304
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• 2006

This paper proposes detection method of vehicles using camera for auto-vehicle-system. Detection method is based on shadow detection and symmetric feature of vehicle. This method consists of three part. First is lane detection. By lane detection, we can reduce the area for vehicle detection. Second part is shadow detection. Shadow has information of vehicle width and position. Third part is symmetry. This feature is helpful for confirming the vehicle.

• 한국초전도ㆍ저온공학회논문지
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• 제18권3호
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• pp.25-29
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• 2016

A quench detection system of KSTAR Poloidal Field (PF) coils is inevitable for stable operation because normal zone generates overheating during quench occurrence. Recently, new voltage quench detection method, combination of Central Difference Averaging (CDA) and Mutual Inductance Compensation (MIK) for compensating mutual inductive voltage more effectively than conventional voltage detection method, has been suggested and studied. For better performance of mutual induction cancellation by adjacent coils of CDA+MIK method for KSTAR coil system, balance coefficients of CDA must be estimated and adjusted preferentially. In this paper, the balance coefficients of CDA for KSTAR PF coils were numerically estimated. The estimated result was adopted and tested by using simulation. The CDA method adopting balance coefficients effectively eliminated mutual inductive voltage, and also it is expected to improve performance of CDA+MIK method for quench detection of KSTAR PF coils.

• 한국정보통신학회논문지
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• 제13권11호
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• pp.2330-2334
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• 2009

본 논문에서는 기존에 제안되었던 컬러 히스토그램과 $X^2$ 히스토그램을 합성한 방법을 새로운 장면 전환 검출 방법을 제시한다. 이 방법은 차이값 추출 방법들의 단점을 극복하고 장점을 최대한 활용한 방법이다. 또한 급진적 장면 전환 검출에서 점진적 장면 전환 검출까지 모두 검출할 수 있다. 실험을 통해서 기존의 방법보다 제안된 방법이 우수함을 입증하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.1228-1233
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• 1990

This paper proposes a robust on-line fault detection method for uncertain systems. It is based on the fault detection method [10] accounting for modelling errors, which is shown to have superior performance over traditional methods but has some computational problems so that it is hard to be applied to on-line problems. The proposed method in this paper is an on-line version of the fault detection method suggested in [10]. Thus the method has the same detection performance robust to model uncertainties as that of [10]. Moreover, its computational burden is shown to be considerably lessened so that it is applicable to on-line fault detection problems.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권9호
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• pp.445-452
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• 2001

Two switching signal patterns are proposed to prevent short circuit of PWM ac choppers. The voltage detection method and the current detection method are proposed to execute two switching signal patterns. In the voltage detection method, the dead-time has to be inserted to the switching signals after polarity of input voltage is checked by voltage transducer at input side. In the current detection method, the direction of load current is checked by current transducer at output side, and the dead-time delay is not considered. Controlling circuit built by current detection method is simple because the dead-time delay is considered. The experimental results are presented to prevent short circuit of ac chopper safely.

• Steel and Composite Structures
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• 제19권1호
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• pp.191-208
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• 2015

The sensitivity-based finite element model updating method has received increasing attention in damage detection of structures based on measured modal parameters. Finding an optimization technique with high efficiency and fast convergence is one of the key issues for model updating-based damage detection. A new simple and computationally efficient optimization algorithm is proposed and applied to damage detection by using finite element model updating. The proposed method combines the Gauss-Newton method with region truncation of each iterative step, in which not only the constraints are introduced instead of penalty functions, but also the searching steps are restricted in a controlled region. The developed algorithm is illustrated by a numerically simulated 25-bar truss structure, and the results have been compared and verified with those obtained from the trust region method. In order to investigate the reliability of the proposed method in damage detection of structures, the influence of the uncertainties coming from measured modal parameters on the statistical characteristics of detection result is investigated by Monte-Carlo simulation, and the probability of damage detection is estimated using the probabilistic method.

• 한국위성정보통신학회논문지
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• 제12권4호
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• pp.26-33
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• 2017

드론은 원격 조종 또는 자동 조종을 통해 임무를 수행하는데 이때 무선통신 기술이 사용된다. 최근 무선통신 기술을 사용하여 드론을 악용하는 사례가 증가함에 따라 드론 RF 신호 탐지의 중요성이 증대되고 있다. 본 논문은 ISM(Industry Science Medical) 대역에서 Wi-Fi, Bluetooth 및 전용 드론 통신 방법을 고려한 시뮬레이션을 통해 효율적인 드론 RF 탐지 방식을 제안하였다. 일반 단말기와 드론 신호가 혼재한 환경을 구성한 뒤 드론 움직임에 따른 RF 특성을 이용하여 일반 단말기와 드론 신호를 구별하였다. 제안한 드론 RF 탐지 기법은 WRMD(Windowed RSSI Moving Detection) 연산과 Doppler Frequency 식별 방법이다. 시뮬레이션 환경은 2가지 신호와 4가지 신호가 혼재하는 환경으로 구성하였고 제안한 드론 RF 탐지 기법을 적용하여 드론 탐지율을 통해 성능을 분석하였다.

• Structural Engineering and Mechanics
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• 제30권4호
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• pp.445-466
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• 2008

This paper presents a novel structural damage detection method with a new damage index based on the statistical moments of dynamic responses of a structure under a random excitation. After a brief introduction to statistical moment theory, the principle of the new method is put forward in terms of a single-degree-of-freedom (SDOF) system. The sensitivity of statistical moment to structural damage is discussed for various types of structural responses and different orders of statistical moment. The formulae for statistical moment-based damage detection are derived. The effect of measurement noise on damage detection is ascertained. The new damage index and the proposed statistical moment-based damage detection method are then extended to multi-degree-of-freedom (MDOF) systems with resort to the leastsquares method. As numerical studies, the proposed method is applied to both single and multi-story shear buildings. Numerical results show that the fourth-order statistical moment of story drifts is a more sensitive indicator to structural stiffness reduction than the natural frequencies, the second order moment of story drift, and the fourth-order moments of velocity and acceleration responses of the shear building. The fourth-order statistical moment of story drifts can be used to accurately identify both location and severity of structural stiffness reduction of the shear building. Furthermore, a significant advantage of the proposed damage detection method lies in that it is insensitive to measurement noise.

• Smart Structures and Systems
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• 제28권6호
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• pp.811-825
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• 2021

High-voltage isolating switches play a paramount role in ensuring the safety of power supply systems. However, their exposure to outdoor environmental conditions may cause serious physical defects, which may result in great risk to power supply systems and society. Image processing-based methods have been used for anomaly detection. However, their accuracy is affected by numerous uncertainties due to manually extracted features, which makes the anomaly detection of isolating switches still challenging. In this paper, a vision-based anomaly detection method for isolating switches, which uses the rotational angle of the switch system for more accurate and direct anomaly detection with the help of deep learning (DL) and image processing methods (Single Shot Multibox Detector (SSD), improved frame differencing method, and Hough transform), is proposed. The SSD is a deep learning method for object classification and localization. In addition, an improved frame differencing method is introduced for better feature extraction and a hough transform method is adopted for rotational angle calculation. A number of experiments are conducted for anomaly detection of single and multiple switches using video frames. The results of the experiments demonstrate that the SSD outperforms the You-Only-Look-Once network. The effectiveness and robustness of the proposed method have been proven under various conditions, such as different illumination and camera locations using 96 videos from the experiments.