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이수용,Lee, Sooyong 한국센서학회 2017 센서학회지 Vol.26 No.4
According to recent studies by scientists about how to search for food, homes and the mates, it is found that the gradient information plays a key role. From cells to insects and large animals, they mostly either have special sensing organism or use a strategy to measure the gradient. Use of a perturbation as an additional input is introduced for sensor signal processing in order to get the gradient information. Different from typical approach, which calculates the gradient from differentiation, the proposed processing is done by a form of integration, thus it is very robust to noise. Discrete time domain analyses are given for one, two and three input functions for the estimation of the gradients. The amplitude and the frequency of the perturbation are two important parameters for this approach. A quantitative index to measure the effects of the amplitude is developed based on the linear regression analysis. The frequency of the perturbation is to be selected high enough to finish one period of the perturbation before the property is changed significantly with respect to time. Another quantitative index is proposed for guiding the selection of the frequency.
이수용(Sooyong Lee) 제어로봇시스템학회 2021 제어·로봇·시스템학회 논문지 Vol.27 No.11
Sensor networks are widely used in various environments, especially that that are unreachable for humans, or where long-term monitoring is required. In most of the previously reported sensor network studies, the focus was on energy consumption based on sensing range and communication strength with a large number of sensor nodes deployed a priori. Herein, we describe a sensor node placement that uses a single mobile node or small number of nodes. Initially, a small number of nodes are used under an unknown environment and hence they sparsely distributed. Based on the estimated spatial gradient at each node, extra nodes are added. For a time-varying environment, another sensor placement algorithm based on the heat conductivity theory is introduced. The intermittent sensing schedule requires an efficient node placement such that the distribution of sensor nodes enables an impartial measurement. The quantitative measure, which represents the degree of variance with respect to time, was introduced while estimating the spatial gradient. Thus, using both the algorithms accordingly will enable time-efficient and energy-efficient measurements for unknown environments.
미지 환경 탐색 및 감시를 위한 다개체 로봇의 경로계획
이수용(Sooyong Lee) 제어로봇시스템학회 2012 제어·로봇·시스템학회 논문지 Vol.18 No.5
This paper presents a multi-robot path planner for environment exploration and monitoring. Robotics systems are being widely used as data measurement tools, especially in dangerous environment. For large scale environment monitoring, multiple robots are required in order to save time. The path planner should not only consider the collision avoidance but efficient coordination of robots for optimal measurements. Nonlinear spring force based planning algorithm is integrated with the spatial gradient following path planner. Perturbation/Correlation based estimation of spatial gradient is applied. An algorithm of tuning the stiffness for robot coordination is presented. The performance of the proposed algorithm is discussed with simulation results.
로봇 주행을 위한 세개의 카메라를 사용한 광류 정보 활용
이수용(Sooyong Lee) 제어로봇시스템학회 2012 제어·로봇·시스템학회 논문지 Vol.18 No.2
This paper describes a new design of optical flow estimation system with three cameras. Optical flow provides useful information of camera movement; however a unique solution is not usually available for unknowns including the depth information. A camera and two tilted cameras are used to have different view of angle and direction of movement to the camera axis. Geometric analysis is performed for cases of several independent movements. The ideas of taking advantage of the extra information for robot navigation are discussed with experimental results.
이수용(Sooyong Lee) 제어로봇시스템학회 2011 제어·로봇·시스템학회 논문지 Vol.17 No.9
This paper describes a new method of estimating the gradient of a function with perturbation and correlation. We impose a known periodic perturbation to the input variable and observe the output of the function in order to obtain much richer and more reliable information. By taking the correlation between the input perturbation and the resultant function outputs, we can determine the gradient of the function. The computation of the correlation does not require derivatives; therefore the gradient can be estimated reliably. Robust estimation of the gradient using perturbation/correlation, which is very effective when an analytical solution is not available, is described. To verify the effectiveness of perturbation/correlation based estimation, the results of gradient estimation are compared with the analytical solutions of an example function. The effects of amplitude of the perturbation and number of samplings in a period are investigated. A minimization of a function with the gradient estimation method is performed.
스테레오 적외선 조명 및 단일카메라를 이용한 3차원 환경인지
이수용(Sooyong Lee),송재복(Jae-Bok Song) 제어로봇시스템학회 2009 제어·로봇·시스템학회 논문지 Vol.15 No.5
This paper describes a new sensor system for 3D environment perception using stereo structured infrared light sources and a camera. Environment and obstacle sensing is the key issue for mobile robot localization and navigation. Laser scanners and infrared scanners cover 180° and are accurate but too expensive. Those sensors use rotating light beams so that the range measurements are constrained on a plane. 3D measurements are much more useful in many ways for obstacle detection, map building and localization. Stereo vision is very common way of getting the depth information of 3D environment. However, it requires that the correspondence should be clearly identified and it also heavily depends on the light condition of the environment. Instead of using stereo camera, monocular camera and two projected infrared light sources are used in order to reduce the effects of the ambient light while getting 3D depth map. Modeling of the projected light pattern enabled precise estimation of the range. Two successive captures of the image with left and right infrared light projection provide several benefits, which include wider area of depth measurement, higher spatial resolution and the visibility perception.
무선 메쉬 네트워크에서 H.264 비디오 전송 품질 향상을 위한 Early Drop 기법
이수용(Sooyong Lee),양기원(Giwon Yang),윤요한(Yohaan Yoon),김명철(Myungchul Kim) 한국정보과학회 2011 한국정보과학회 학술발표논문집 Vol.38 No.1D
본 논문에서는 무선 메쉬 네트워크에서 H.264 비디오 코딩을 이용한 대화형 멀티미디어 전송시 서비스 품질을 향상시키기 위한 Early Drop 기법을 제안한다. Early Drop 기법은 비디오 프레임의 재생시간과 H.264로 부호화된 비디오 프레임의 중요도를 고려하여 네트워크 혼잡 시 발생하는 큐잉 지연과 큐 오버플로우로 인한 비디오 서비스 품질 저하를 효과적으로 개선하기 위해 개발되었다. 계층간 최적화(Cross-Layer)기법을 사용하여 각 비디오 패킷 별로 재생시간까지 남은 시간을 의미하는 delay budget을 할당하고 전송 중 재생시간 초과로 인해 목적지 노드에서 재생되지 못하는 비디오 패킷을 전송 초기 손실 시켜 무선대역폭 낭비와 전송 지연을 최소화 한다. 또한, H.264 비디오 프레임 종류별 중요도를 고려하여 차별화 된 delay budget을 할당해 중요도가 높은 비디오 프레임의 전송을 보장하여 비디오 전송 품질을 높인다. 성능 검증을 통해 네트워크 혼잡 시 Early Drop 기법은 기존에 제안된 IEEE 802.11e 기반의 H.264 비디오 전송기법과 비교하여 전송지연과 프레임 손실률을 최소화해 향상된 비디오 품질을 보였다.