• Journal of the Institute of Electronics Engineers of Korea CI
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• v.37 no.3
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• pp.27-38
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• 2000

This paper proposes how the recurrent neural network controller for a Khepera mobile robot with an obstacle avoiding ability can be determined by co-adaptation of the evolution and learning, The proposed co-adaptation scheme consists of two folds： a population of NN controllers are evolved by the genetic algorithm so that the degree of obstacle avoidance might be reduced through the global searching and each NN controller is trained by CRBP learning so that the running behavior is adapted to its outer environment through the local searching. Experimental results shows that the NN controller coadapted by evolution and learning outperforms its non-learning equivalent evolved by only genetic algorithm in both the ability of obstacle avoidance and the convergence speed reaching to the required running behavior.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1B
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• pp.154-161
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• 2010

In wireless sensor networks, due to the many-to-one convergence of upstream traffic, congestion more probably appears. The existing congestion control protocols avoid congestion by controlling incoming traffic, but the duty-cycle operation of MAC(Medium Access Control) layer has not considered. In this paper, we propose DCA(Duty-cycle Based Congestion Avoidance), an energy efficient congestion control scheme using duty-cycle adjustment for wireless sensor networks. The DCA scheme uses both a resource control approach by increasing the packet reception rate of the receiving node and a traffic control approach by decreasing the packet transmission rate of the sending node for the congestion avoidance. Our results show that the DCA operates energy efficiently and achieves reliability by its congestion control scheme in duty-cycled wireless sensor networks.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.9
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• pp.830-837
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• 2015

Space debris has been a major issue recently for the space-active nations because its growing population is expected to increase the collision risk with operational satellites. Radar and electro-optical system has been used for space debris surveillance, which may cause unnecessary anti-collision manoeuvers due to their low tracking accuracy. So an additional tracking system is required to improve the predicted orbit accuracy and then to jude the anti-collision maneouvers more efficiently. The laser tracking system has been considered as an alternative to decrease these unnecessary manoeuvers. Korea Astronomy and Space Science Institute has been developing a space object laser tracking system which is capable of laser tracking for satellites with retro-reflectors and for space debris using high power laser, and satellite imaging using adaptive optics. In this study, the tracking capability is analyzed for space debris using high power laser based on link budget, false alarm probability and signal detection probability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.279-285
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• 2019

Transverse vibrations of a ship's aft end and deckhouse are mainly induced by transverse exciting forces from the main engine. Resonance should be avoided in the initial design stages when there is a prediction of resonance between the main engine and transverse modes of the deckhouse. Estimates of frequencies for resonance avoidance are possible from the specifications of the main engine and propeller, but the inherent vibration frequency of the structure around the engine room is not easy to estimate due to the variation in the shape. Experience-oriented vibration design is also carried out, which results in many problems, such as process delay, over-injection of on-site personnel, and iterative performance of the design. For the flexible design of 8,600 TEU container vessels, this study addressed the resonance problem caused by the transverse vibration of the main engine when only the main engine was changed from 12 cylinders to 10 cylinders without modification of the hull structure layout. Efficient structural reinforcement design guidelines are presented for avoiding resonances with the main engine lateral vibration and the structure around the engine room. The guidelines are expected to be used as practical design guidelines at design sites.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.1
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• pp.47-54
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• 2011

The remote control mobile robot is the robot accomplishing a task according to the orders giving by a user through departed communication system using a joystick. Basically, to supply a lot of information, as this type of robot uses visual information, the user can check the transmitted information by eyes and give orders to the robot. But the weak point of this type of robot is that it has a possibility to come into a collision with an obstacle not be seen to the user because of the communication delay occurring in a communication system and dead zone happening in visual information. To solve the problem, in this paper, we try to suggest a system applying a fuzzy control system to the robot to avoid collision with an obstacle by an immediate order of the user. The fuzzy control system has better performance than any other existing control methods in the change of noise and parameter. And it is more efficient than any other since it solves easy the complexity of the system analysis occurring because of the nonlinear feature of the mobile robot system. In this paper, we made experiments how the mobile robot controlled by the fuzzy control system avoids an obstacle, tracks the path and avoids the obstacle in the path, to prove the performance and to check the evaluation and the application possibility of the fuzzy control system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.5
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• pp.103-111
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• 2021

The purpose of this study is to study a method for preventing collisions of multiple drones in controlled airspace. As a result of the study, it was proved that it is appropriate as a method to control drone collisions after setting accurate information on the ROI (Region of Interest) area estimated based on the expected drone path and time in the control system as a method to avoid drone collision. As a result of the empirical analysis, the diameter of the flight path of the operating drone should be selected to reduce the risk of collision, and the change in the departure time and operating speed of the operating drone did not act as an influencing factor in the collision. In addition, it has been demonstrated that providing flight priority is one of the appropriate methods as a countermeasure to avoid collisions. For collision avoidance methods, not only drone sensor-based collision avoidance, but also collision avoidance can be doubled by monitoring and predicting collisions in the control system and performing real-time control. This study is meaningful in that it provided an idea for a method for preventing collisions of multiple drones in controlled airspace and conducted practical tests. This helps to solve the problem of collisions that occur when multiple drones of different types are operating based on the control system. This study will contribute to the development of related industries by preventing accidents caused by drone collisions and providing a safe drone operation environment.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1810_1811
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• 2009

자율주행 로봇은 자신위치와 장애물의 위치 등 주변 환경을 인지하여 원하는 지점까지 스스로 이동 및 임무 수행이 가능한 로봇 이다. 목표위치를 탐색하기 위하여 GPS 및 초음파 센서를 이용하여 이동 방향 설정 및 주변 장애물 위치를 파악할 수 있도록 하였다. 특히, WLAN을 이용하여 이동 로봇에 대한 위치 정보의 설정 및 위치 데이터의 교신이 가능하도록 하였고 이동로봇을 이용한 실제 실험을 통하여 원하는 위치 탐색과 장애물 회피가 효과적으로 수행됨을 확인한다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2015.01a
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• pp.163-164
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• 2015

최근 로봇 기술은 전자공학, 컴퓨터, 기계공학 등의 비약적인 발전에 힘입어 다양한 용도에 사용되고 있다. 특히 로봇은 극한 환경에서 인간이 실천하기 어려운 작업을 수행할 수가 있으며, 인간과 함께 운용되거나 인간이 로봇을 무선으로 제어하여 현장을 확인을 할 수 있으며 이를 통하여 화재진압 및 인명구조를 수행할 수 있다. 이 때 무선 제어 로봇은 탐사 시 동체가 전복되더라도 지속적인 탐사가 가능해야 한다. 따라서 로봇의 동체보다 바퀴를 크게 하여 동체가 전복해도 동작이 가능하도록 한다. 본 논문에서는 무선 조정 자동차를 사용 하여 차체의 전복에도 충분히 제어 및 탐사가 가능한지 실험하고, 초음파센서로 하여금 능동적으로 장애물 회피를 하는 것을 목적으로 한다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2004.04a
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• pp.555-558
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• 2004

최근 인터넷의 발전으로 디지털 오디오 및 비디오와 같은 멀티미디어 스트림에 대한 요구가 증가하고 있다. 이러한 멀티미디어 스트리밍을 UDP로 전송할 경우 TCP와 같은 혼잡제어를 수행하지 않기 때문에 동일한 전송경로의 TCP 트래픽 궁핍을 일으켜 혼잡붕괴 및 막대한 전송지연을 초래한다. 이러한 문제점으로 인하여 실시간 멀티미디어 스트림의 전송지연과 혼잡제어를 위한 새로운 전송기법과 프로토콜에 대한 다각적인 연구가 수행되고 있다. TCP 친화적 혼잡제어 기법은 크게 일반적인 혼잡윈도우 관리기능을 이용하는 윈도우 기반 혼잡제어와 TCP 모델링 방정식 둥을 이용하여 전송율을 직접 조절하는 율 기반 혼잡제어로 나눌 수 있다. 본 논문은 윈도우 기반과 율 기반을 복합적으로 다룬 하이브리드형 TCP-friendly 혼잡제어 기법에서 Square-root 혼잡회피 알고리즘을 제안하였으며, NS를 사용하여 제안한 TEAR의 성능을 실험하였다. 실험을 통하여 제안한 기법의 적용으로 TEAR의 안정성을 개선함을 알 수 있었다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2017.01a
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• pp.207-208
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• 2017

악성코드는 매년 그 수가 증가하고 있으며, 악성코드의 공격기법이 지능적이고 복합적으로 진화함에 따라 이에 대한 분석과 대응이 요구된다. 하지만 일부 악성코드는 감염여부를 숨기기 위하여 분석에 대한 회피방법으로 루트킷을 통하여 방어자에 의한 악성코드의 코드 분석을 우회함으로써 은폐된 상태로 악의적인 공격을 수행한다. 따라서 본 논문에서는 유저레벨에서 IAT(Import Address Table)의 정보를 후킹하여 악성 행위를 수행하는 루트킷을 탐지하는 대응방안을 제안한다.