• Journal of Institute of Control, Robotics and Systems
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• v.19 no.12
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• pp.1132-1137
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• 2013

In swarm robot systems, it is vital to maintain network connectivity to ensure cooperative behavior between robots. This paper deals with the behavior control algorithm of the swarm robots for maintaining network connectivity. To do this, we divide swarm robots into search-robots, base-robots, and relay-robots. Using these robots, we propose behavior control algorithm to maintain network connectivity. The behavior control algorithms to maintain network connectivity are proposed for the local path planning using virtual force and global path planning using the Delaunay triangulation, respectively. Finally, we demonstrate the effectiveness and applicability of the proposed method through some simulations.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.5
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• pp.47-53
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• 2007

The purpose of IEEE 802.16j is to extend coverage and to enhance throughput by using relay station additionally to conventional IEEE 802.16e . The cellular system experiences performance degradation at the cell edge due to pathloss, shadow and multipath fading. We can get advantage of spatial diversity gain by using relays more than two cooperatively in the IEEE 802.16j system. Cooperative relaying using space-time code provides better performance under multipath fading and has more robustness against the shadow fading than single relaying. In this paper, we investigate the performance of IEEE 802.16j using cooperative relaying by link level simulation. We also show that the cooperative relaying system achieves better performance than the conventional single relaying system. We apply realistic shadow model considering correlations between shadow fadings of different relaying paths. It is shown that the performance of the system depends highly on the spatial location of relay stations.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.12
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• pp.1122-1131
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• 2012

This paper presents obstacle avoidance method for scout robot or industrial robot in unknown environment by using IR sensor and vision system. In the proposed method, robots share the information where the obstacles are located in real-time, thus the robots can choose the best path for obstacle avoidance. Using IR sensor and vision system, multiple robots efficiently evade the obstacles by the proposed cooperation method. No landmark is used at wall or floor in experiment environment. The obstacles don't have specific color or shape. To get the information of the obstacle, vision system extracts the obstacle coordinate by using an image labeling method. The information obtained by IR sensor is about the obstacle range and the locomotion direction to decide the optimal path for avoiding obstacle. The experiment was conducted in $7m{\times}7m$ indoor environment with two-wheeled mobile robots. It is shown that multiple robots efficiently move along the optimal path in cooperation with each other in the space where obstacles are located.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.6
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• pp.2078-2094
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• 2015

Now a days, Efficient processing of Broadcast Queries is of critical importance with the ever-increasing deployment and use of mobile technologies. BQs have certain unique characteristics that the traditional spatial query processing in centralized databases does not address. In novel query processing technique, by maintaining high scalability and accuracy, latency is reduced considerably in answering BQs. Novel approach is based on peer-to-peer sharing, which enables us to process queries without delay at a mobile host by using query results cached in its neighboring mobile peers. We design and evaluate cooperative caching techniques to efficiently support data access in ad hoc networks. We first propose two schemes: Cache Data, which caches the data, and Cache Path, which caches the data path. After analyzing the performance of those two schemes, we propose a hybrid approach (Hybrid Cache), which can further improve the performance by taking advantage of Cache Data and Cache Path while avoiding their weaknesses. Cache replacement policies are also studied to further improve the performance. Simulation results show that the proposed schemes can significantly reduce the query delay and message complexity when compared to other caching schemes.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.13 no.4
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• pp.307-314
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• 2013

We designed and implemented a fork-type automatic guided vehicle (AGV) with a laser guidance system. Most previous AGVs have used two types of guidance systems: magnetgyro and wire guidance. However, these guidance systems have high costs, are difficult to maintain with changes in the operating environment, and can drive only a pre-determined path with installed sensors. A laser guidance system was developed for addressing these issues, but limitations including slow response time and low accuracy remain. We present a laser guidance system and control system for AGVs with laser navigation. For analyzing the performance of the proposed system, we designed and built a fork-type AGV, and performed repetitions of our experiments under the same working conditions. The results show an average positioning error of 51.76 mm between the simulated driving path and the driving path of the actual fork-type AGV. Consequently, we verified that the proposed method is effective and suitable for use in actual AGVs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.8
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• pp.856-866
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• 1992

In this paper, the graphic simulation system Is presented which supports the determination of efficient multi-robot motions during cooperation. For the construction of the simulation software for multi robot motions, two problems are described. First problem is that all the robot motions must be determined using both the desired object motions and the holonomic constraints with the object. To find the robot motions combined with the various object motion path, the robot motions are derived from the desired object path instead of a master robot path. There ore, robot motions can be easily modifiable with #he various object motions. This type of motion determination Is different from that of the master-slaves method using the master robot motions.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.196-198
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• 2014

Wireless Sensor Networks(WSN) 기반의 Border Surveillance Networks(BSN)는 다양한 제한조건을 동반하며 침입 혹은 환경 등을 감시함을 목적으로 하고 있기 때문에 이벤트 발생시 신뢰적인 데이터 전송은 매우 중요한 부분을 차치하게 된다. 본 논문에서 적용한 대표적인 요구기반 라우팅 방법인 Ad hoc On-demand Distance Vector Routing(AODV)는 BSN 에 적용하였을 경우 홉 수(Hop Count)를 메트릭으로 최적의 경로를 계산하고 선택하여 Uni-Path 로 데이터를 전송하게 된다. 이때 AODV 는 Uni-path 로 데이터 전송을 진행하게 되며 링크의 단절이 빈번히 발생하는 BSN 의 환경적 요인으로 데이터 전송의 신뢰성이 감소하게 될 것이며 이는 비효과적인 데이터 전송을 야기하게 된다. 따라서 본 논문에서는 Multi-path 개념을 도입하여 데이터 전송 시 링크단절에 의해 발생하는 시간의 지연을 줄이고 더욱 신뢰성 있게 데이터를 전송할 수 있는 방법을 제안한다. 제안하는 방법은 송, 수신하는 두 노드의 전송범위에 공통으로 속한 노드들이 전송되는 데이터를 중복 전송하게 된다. 그리하여 링크의 단절이 일어날 경우 발생하는 경로 재 탐색 및 경로복구의 발생 빈도를 줄이고 동시에 데이터 전송률을 증가시켜 신뢰적인 데이터 전송을 하게 된다.

• Journal of Internet Computing and Services
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• v.23 no.5
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• pp.1-7
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• 2022

IoT technology that utilizes wireless body area networks (WBAN) and biosensors is an important field in the health industry to minimize resources and monitor patients. In order to integrate IoT and WBAN, a cooperative protocol that constitutes WBAN's limited sensor nodes and rapid routing for efficient data transmission is required. In this paper we propose an we propose an energy efficient and cooperative link energy-efficient routing strategy(LEERS) to solve the problems of redundant data transmission detection and limited network sensor lifetime extention. The proposed scheme considers the hop count node congestion level towards the residual energy sink and bandwidth and parameters. In addition, by determining the path cost function and providing effective multi-hop routing, it is shown that the existing method is improved in terms of residual energy and throughput

• ETRI Journal
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• v.34 no.6
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• pp.858-868
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• 2012

In this paper, stochastic models for the cross-correlation of multiple channels are established based on measurement data collected using a wideband multiple-input multiple-output relay Band Exploration and Channel Sounder system at 3.7 GHz. We propose models for the cross-correlation characteristics of large-scale parameters (LSPs) between two links, that is, the base station and mobile station (MS) link and the relay station and MS link. The LSPs include shadow fading, Rician K-factor, delay spread, angle spread of arrival, and angle spread of departure. Furthermore, models are established for the cross-correlation of the small-scale fading in the impulse responses of two links. The statistics of these model parameters are investigated as functions of geometrical features of the multilink. They are extracted from a large amount of cross-correlation observations, which are obtained in three measurement sites along more than one hundred measurement routes. These models can be used together with the standard single-link channel models for the generation of correlated components, for example, path clusters, in two separate channels.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.5
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• pp.423-428
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• 2013

This paper investigates a boundary tracking problem using multiple quadrotor UAVs to detect and track the boundary of physical events. We set the boundary estimation problem as a classification problem of the region in which the physical events occur, and employ SVL (Support Vector Learning). We also demonstrate a velocity vector field which is globally attractive to a desired closed path with circulation at the desired speed and a virtual phase for stabilizing the collective configuration of the multiple quadrotors. Experimental results with multiple quadrotors show that this study provides good performance of the collective boundary tracking.