• Journal of IKEEE
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• v.6 no.1 s.10
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• pp.1-9
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• 2002

Converged LAN accepts diverse traffics so that performance analysis is very important for successful development of converged LAN. In this paper, we develop simulation program using SALM II and simulate queue management scheme and scheduling algorithm for converged LAN. The result of simulation shows the effect of performance for cyclic service algorithm larger than priority algorithm using weight. And queue management can be easy by implementation of Back Pressure scheme.

• Journal of Aerospace System Engineering
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• v.15 no.1
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• pp.102-110
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• 2021

Recently, multi-copters equipped with various collision avoidance sensors have been introduced to improve flight stability. LiDAR is used to recognize a three-dimensional position. Multiple cameras and real-time SLAM technology are also used to calculate the relative position to obstacles. A three-dimensional depth sensor with a small process and camera is also used. In this study, a small collision-avoidance multi-copter system capable of in-door flight was developed as a platform for the development of collision avoidance software technology. The multi-copter system was equipped with LiDAR, 3D depth sensor, and small image processing board. Object recognition and collision avoidance functions based on the YOLO algorithm were verified through flight tests. This paper deals with recent trends in drone collision avoidance technology, system design/manufacturing process, and flight test results.

• Journal of the Korea Society for Simulation
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• v.3 no.1
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• pp.89-98
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• 1994

In this paper, a criteria for selecting an appropriate load redistribution algorithm is devised so that a fault-tolerance distributed system can operte at its optimal efficience. To present the guideline for selecting redistributing algorithms, simulation models of fault-tolerant system including redistribution algorithms are developed using SLAM II. The job arrival rate, service rate, failure and repair rate of nodes, and communication delay time due to load migration are used as parameters of simulation. The result of simulation shows that the job arrival rate and the failure rate of nodes are not deciding factors in affecting the relative efficiency of algorithms. Algorithm B shows relatively a consistent performance under various environments, although its performance is between those of other algorithms. If the communication delay time is longer than average job processing time, the performance of algorithm B is better than others. If the repair rate is relatively small or communication delay time is longer than service time, algorithm A leads to good performance. But in opposite environments, algorithm C is superior to other algorithms.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.12
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• pp.1246-1253
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• 2009

To be high efficient for a navigation of unmanned ground vehicle, it must be able to distinguish between safe and hazardous regions in its immediate environment. We present an advanced method using laser range finder for building global 2D digital maps that include environment information. Laser range finder is used for mapping of obstacles and driving environment in the 2D laser plane. Rotary encoders are used for localization of UGV. The main contributions of this research are the development of an algorithm for global 2D map building and it will turn a UGV navigation based on map matching into a possibility. In this paper, a map building algorithm will be introduced and an assessment of algorithm reliability is judged at an each environment.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.8
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• pp.1-10
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• 1994

In this paper load redistribution algorithm to allow fault-tolerance by redistributing the workload of n failure nodes to the remaining good nodes in distributed systems are investigated. To evaluate the efficiency of the algorithms a simulation model of algorithms is developed using SLAM II simulation language. The job arrival rate service rate failure and repair rate of nodes and communication delay time due to load migraion are used as parameters. The result of the simulation shows that the job arrival rate failure and repair rate of nodes do not affected on the relative efficiency of algorithms. If the communication delay time is greater than average job processing time algorithm B is better. Otherwise algorithm C is superior to the others.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.817-820
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• 2014

본 논문에서는 휴대용 카메라를 이용한 3차원 공간 재구성을 위해 카메라의 실시간 포즈를 정확히 추정할 수 있는 카메라 포즈 최적화 시스템을 제안한다. 본 시스템에서는 3차원 공간에서 6차원 자유도를 가지고 움직이는 카메라의 주행 거리와 추정 포즈들 사이의 관계를 3차원 포즈 그래프로 나타냈다. 그리고 이 포즈 그래프에 대표적인 포즈 SLAM 알고리즘인 g2o를 적용함으로써, 최적화된 카메라 포즈들을 계산해낸다. 본 논문에서는 TUM 대학의 벤치마크 데이터 집합을 이용해 다양한 성능 평가 실험들을 수행하였고, 이를 통해 본 논문에서 제안한 카메라 포즈 최적화 시스템의 높은 성능을 확인할 수 있었다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2018.07a
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• pp.389-390
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• 2018

본 논문에서는 3차원 복원을 위한 특징점 추출 및 매칭에 대한 보다 정확한 방법을 제안한다. 이 방법은 컴퓨터 비전의 기본이 되는 분야로 복원뿐 만 아니라 SLAM과 같은 지도 작성 및 자율 운행에도 필요한 방법이다. 본 연구는 3차원 물체 복원을 위해서 사용하는 방법 중 하나인 Column space fitting(CSF)을 이용하여 turntable-image data에 적용하여 성능을 평가하여 정확성을 검증을 한다. 오늘날 3D scanner를 이용하여 물체를 3차원 모델을 획득하고 3D프린터를 이용하여 다양한 분야에 적용한다. 그러나 고가의 장비이기 때문에 접근성이 떨어진다. 본 연구는 영상들만을 가지고 기하학적 계산을 통해 3차원 모델을 획득한다. 본 연구결과는 기존의 방법인 KLT 알고리즘과 비교하여 RMSE의 값을 약 5배를 줄이는 성능 향상을 보인다.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.05a
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• pp.481-483
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• 2018

AR은 VR과 달리 실세계 공간의 객체에 대한 서비스를 제공하므로 서비스 개발을 방해하는 많은 요인들이 발생한다. 이를 보완하기위해 비주얼 마커, SLAM, 객체인식 등 여러 AR 기술이 존재한다. 본 논문은 AR 기술 중에서 객체인식의 정확도 향상을 위해 지역가변 이진화(Local variable binarization)와 색상의 군집화를 사용해서 이미지에서 객체를 추출하는 방법을 제안한다. 지역 가변화는 픽셀을 순차적으로 읽어 들이면서 픽셀 주위의 값의 평균을 구하고, 이 값을 해당 픽셀의 임계 값으로 사용하는 알고리즘이다. 픽셀마다 주위 색상 값에 의해 임계 값이 변화되므로 윤곽선 표현이 기존의 이진화보다 뚜렷이 나타난다. 색상의 군집화는 객체의 중요색상과 배경의 중요색상을 중심으로 유사한 색상끼리 군집화 하는 것이다. 객체 내에서 가장 많이 나온 값과 객체 외에 가장 많이 나온 값을 각 각 기준으로 색조와 채도의 값을 Euclidean 거리를 사용해 객체의 색상과 배경 색상을 분리했다.

• The Journal of Korea Robotics Society
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• v.18 no.3
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• pp.337-345
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• 2023

In this paper, we propose a 3D LiDAR sensor-based costmap generation and path planning algorithm using it for reliable autonomous flight in complex indoor environments. 3D path planning is essential for reliable operation of UAVs. However, existing grid search-based or random sampling-based path planning algorithms in 3D space require a large amount of computation, and UAVs with weight constraints require reliable path planning results in real time. To solve this problem, we propose a method that divides a 3D space into several 2D spaces and a path planning algorithm that considers the distance to obstacles within each space. Among the paths generated in each space, the final path (Best path) that the UAV will follow is determined through the proposed objective function, and for this purpose, we consider the rotation angle of the 2D space, the path length, and the previous best path information. The proposed methods have been verified through autonomous flight of UAVs in real environments, and shows reliable obstacle avoidance performance in various complex environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4B
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• pp.675-682
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• 2000

In this paper, we propose a new scheduling algorithm called the Adaptive Weighted Round Robin with Delay Tolerance (AWRR/DT). The proposed scheme is based on the per-class queueing mechanism in which a number of connections of similar characteristics are multiplexed into one class-queue. Traffic classes of the proposed method are classified into a single non-real-time traffic class and other real-time traffic classes. The proposed scheme determines the weights of classes according to the input traffic and delay characteristics of each class at the beginning of every cycle. Furthermore, this scheme incorporates a cell discarding method to reduce the QoS degradation that may be incurred by congestion of networks. We have evaluated the proposed scheme through discrete-event simulation. Simulation results indicate that the proposed scheme can reduce the average delay of non-real-time class while maintaining the QoS of real-timeclasses. The proposed algorithm can be effectively applied to high-speed networks such as ATM networks.