• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.11a
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• pp.142-145
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• 2014

동영상에서의 객체 추적 알고리즘에 대한 활발한 연구가 진행되고 있음에도 불구하고 실시간 객체추적을 위해서는 여전히 정확도, 복잡도 등에서의 성능향상이 필요하다. 압축영역 기반 방식에서는 전역 움직임 보상(GMC : Global Motion Compensation)과정을 거쳐 추적하려는 객체와 배경을 구분한다. 전역 움직임 보상방법은 프레임 전 영역을 대상으로 하는 연산으로 전체 추적 시스템에서 차지하는 복잡도가 높다. 본 논문은 관심영역(ROI : Region Of Interest) 기반 전역 움직임 보상방법을 이용한 ST-MRF(Spatio-Temporal Markov Random Field)기반 추적기 고속화 방법을 제안한다. 관심영역을 기반으로 전역 움직임 보상을 적용함으로써 객체와 배경을 분리할 뿐만 아니라 알고리즘의 복잡도를 효과적으로 줄일 수 있다. 제안하는 방법의 추적성능은 평균 precision 87.29%, recall 82.58%, F-measure 83.78%로 기존방법과 비교하여 약 1%의 차이를 유지하였으며 전체 시스템의 수행시간은 평균 29.95ms로 기존방법과 비교하여 1.74배의 속도향상을 보였다.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1016-1026
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• 2017

An adaptive extended Kalman filter based on the maximum likelihood (EKF-ML) is proposed for detecting voltage sag in this paper. Considering that the choice of the process and measurement error covariance matrices affects seriously the performance of the extended Kalman filter (EKF), the EKF-ML method uses the maximum likelihood method to adaptively optimize the error covariance matrices and the initial conditions. This can ensure that the EKF has better accuracy and faster convergence for estimating the voltage amplitude (states). Moreover, without more complexity, the EKF-ML algorithm is almost as simple as the conventional EKF, but it has better anti-disturbance performance and more accuracy in detection of the voltage sag. More importantly, the EKF-ML algorithm is capable of accurately estimating the noise parameters and is robust against various noise levels. Simulation results show that the proposed method performs with a fast dynamic and tracking response, when voltage signals contain harmonics or a pulse and are jointly embedded in an unknown measurement noise.

• Journal of KIISE:Software and Applications
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• v.31 no.4
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• pp.403-410
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• 2004

Bimodal speech recognition systems have been proposed for enhancing recognition rate of ASR under noisy environments. Visual feature extraction is very important to develop these systems. To extract visual features, it is necessary to detect exact lip position. This paper proposed the method that detects a lip position using color similarity model and SVM. Face/Lip color distribution is teamed and the initial lip position is found by using that. The exact lip position is detected by scanning neighbor area with SVM. By experiments, it is shown that this method detects lip position exactly and fast.

• Journal of Power Electronics
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• v.6 no.3
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• pp.226-234
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• 2006

Photovoltaic (PV) generators have nonlinear V-I characteristics and maximum power points which vary with illumination level and temperature. Using a maximum power point tracker (MPPT) with an intermediate converter can increase the system efficiency by matching the PV systems to the load. This paper presents a maximum power point tracker based on fuzzy logic and a control scheme for a single-phase inverter connected to the utility grid. The fuzzy logic controller (FLC) provides an adaptive nature for system performance. Also the FLC provides excellent features such as fast response, good performance and the ability to change the fuzzy parameters to improve the control system. A single-phase AC-DC inverter is used to connect the PV system to the grid utility and local loads. While a control scheme is implemented to inject the PV output power to the utility grid at unity power factor and reduced harmonic level. The simulation results have shown the effectiveness of the proposed scheme.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.4
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• pp.317-325
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• 2011

In this paper a robust voltage controller for a single-phase UPS inverter is newly presented. The voltage controller is designed using ${\mu}$-based robust control scheme to simultaneously guarantee robust stability and robust tracking performance in the presence of load variations. Firstly the robust performance of the resulting controller is theoretically confirmed via ${\mu}$-analysis. Then simulations and experiments for the single-phase inverter system with linear and nonlinear loads demonstrate feasibility of the proposed control method providing improved performance - good regulation and fast dynamic response.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.2073-2082
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• 2010

The 4-th generation of mobile communication aims to realize global, fast and mobile communication service. The satellite communication charges a key role in this field. In this study, an OTM(On-The-Move) antenna which is mounted on ground vehicles and is used for mobile communication between vehicle and satellite was addressed. Since vehicles move during communication, active antenna line-of-sight stabilization is a core technology to guarantee high satellite communication quality. Stabilization of a satellite tracking antenna which consists of 2-DOF gimbals, an elevation gimbal over an azimuth gimbal, was considered in this study. Various disturbance torques such as static and dynamic mass imbalance torques, variation of moment of inertia according to elevation angle, friction torque related to vehicle motion, equivalent disturbance torque due to antenna roll motion, etc. were analyzed. As a robust stabilization control, rate feedback with sliding mode control and position feedback with proportional+integral control was suggested. To compensate antenna roll motion, a supplementary roll rate feed forward control was included beside of the feedback control loop. The feasibility of the analysis and the proposed control design were verified along with some simulation results.

• Journal of Sensor Science and Technology
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• v.29 no.6
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• pp.440-446
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• 2020

A well-known difficulty in attitude estimation based on inertial measurement unit (IMU) signals is the occurrence of external acceleration under dynamic motion conditions, as the acceleration significantly degrades the estimation accuracy. Lee et al. (2012) designed a Kalman filter (KF) that could effectively deal with the acceleration issue. Ahmed and Tahir (2017) modified this method by adjusting the acceleration-related covariance matrix because they considered covariance modeling as a pivotal factor in the estimation accuracy. This study investigates the effects of covariance modeling on estimation accuracy in an IMU-based attitude estimation KF. The method proposed by Ahmed and Tahir can be divided into two: one uses the covariance including only diagonal components and the other uses the covariance including both diagonal and off-diagonal components. This paper compares these three methods with respect to the motion condition and the window size, which is required for the methods by Ahmed and Tahir. Experimental results showed that the method proposed by Lee et al. performed the best among the three methods under relatively slow motion conditions, whereas the modified method using the diagonal covariance with a high window size performed the best under relatively fast motion conditions.

• International Journal of Automotive Technology
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• v.8 no.5
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• pp.555-562
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• 2007

The Variable Valve Timing(VVT) system for high performance is a key technology used in newly developed engines. The system realizes higher torque, better fuel economy, and lower emissions by allowing an additional degree of freedom in valve timing during engine operation. In this study, a model-based control method is proposed to enable a fast and precise VVT control system that is robust with respect to manufacturing tolerances and aging. The VVT system is modeled by a third-order nonlinear state equation intended to account for nonlinearities of the system. Based on the model, a controller is designed for position control of the VVT system. The sliding mode theory is applied to controller design to overcome model uncertainties and unknown disturbances. The experimental results suggest that the proposed sliding mode controller is capable of improving tracking performance. In addition, the sliding mode controller is robust to battery voltage disturbance.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.102-106
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• 2008

Forensic Marking is the technology that enables the service providers (SP) to identify the illegal digital contents distributors by first inserting markings (data indicating the user information and playback time) in realtime into the digital contents at time of playback of digital contents, and then later by extracting inserted markings from the contents which are illegally captured from the multimedia device such as IPTV STBs and distributed over the Internet. Digital Rights Management (DRM), which is a very popular content protection technology, has the security hole that can be vulnerable because the encrypted digital contents are transformed into their original plaintext forms after the decrypting process on the STBs. Therefore Forensic Marking (FM) has now become a companion content protection solution to DRM. This article describes a new way of tracking up to 4 illegal content users in FM implementation using the blue-difference chroma component of YCbCr color space. This FM technology has many advantages like fast processing time and easy portability to STB devices compared to that of the traditional watermarking processing in the frequency domain.

• Journal of Power Electronics
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• v.15 no.4
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• pp.1093-1104
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• 2015

A standard repetitive controller (RC) is theoretically able to replace a bank of resonant controllers in harmonic signals tracking applications. However, the traditional RC has some drawbacks such as a poor dynamic response and a complex structure to compensate grid frequency deviations for an effective unified power quality conditioner (UPQC) control scheme. In order to solve these problems, an improved RC with an outstanding dynamic response and a simplified grid frequency adaptive scheme is proposed for UPQC control systems in this paper. The control strategy developed for the UPQC has delay time, i.e., one-sixth of a fundamental period (T_p/6), repetitive controllers. As a result, the UPQC system can provide a fast dynamic response along with good compensation performance under both nonlinear and unbalanced loads. Furthermore, to guarantee the excellent performance of the UPQC under grid frequency deviations, a grid frequency adaptive scheme was developed for the RC using a simple first order Padé's approximation. When compared with other approaches, the proposed control method is simpler in structure and requires little computing time. Moreover, the entire control strategy can be easily implemented with a low-cost DSP. The effectiveness of the proposed control method is verified through various experimental tests.