• Journal of Institute of Control, Robotics and Systems
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• v.17 no.10
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• pp.995-1005
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• 2011

An efficient outdoor local localization method is suggested using multi-sensor fusion with MU-EKF (Multi-Update Extended Kalman Filter) for car-like mobile robots. In outdoor environments, where mobile robots are used for explorations or military services, accurate localization with multiple sensors is indispensable. In this paper, multi-sensor fusion outdoor local localization algorithm is proposed, which fuses sensor data from LRF (Laser Range Finder), Encoder, and GPS. First, encoder data is used for the prediction stage of MU-EKF. Then the LRF data obtained by scanning the environment is used to extract objects, and estimates the robot position and orientation by mapping with map objects, as the first update stage of MU-EKF. This estimation is finally fused with GPS as the second update stage of MU-EKF. This MU-EKF algorithm can also fuse more than three sensor data efficiently even with different sensor data sampling periods, and ensures high accuracy in localization. The validity of the proposed algorithm is revealed via experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.8B
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• pp.1003-1011
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• 2011

In this paper, a real-time multi-source sensor data management system based on wireless sensor network is proposed and implemented. The proposed management system is designed to transmit the wireless data to the server in order to monitor and control the multi-source target's status efficiently by analyzing them. The proposed system is implemented to make it possible to control and transmit the wireless sensor data by classifying them, of which data are issued from the clustered sources composed of a number of the remote multiple sensors. In order to evaluate the performance of the proposed system, we measure and analyze both the transmission delay time according to the distance and the data loss rate issued from multiple data sources. From these results, it is verified that the proposed system has a good performance.

• Journal of KIISE:Databases
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• v.36 no.1
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• pp.8-21
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• 2009

A wireless sensor network is a computer network which consists of spatially distributed devices, called sensor nodes. In wireless sensor networks, energy efficiency is a key issue since sensor nodes must resides upon limited energy. To retrieve sensor information without dealing with the network issues, a sensor network is treated as conceptual database on which query can be requested. When multiple queries are requested for processing in a wireless sensor network, energy consumption can be significantly reduced if common partial results among similar queries can be effectively shared. In this paper, we propose an energy efficient multi-query processing technique based on the coverage relationship between multiple queries. When a new query is requested, our proposed technique derives an equivalent query from queries running at the moment, if it is derivable. Our technique first computes the set of running queries that may derive a partial result of the new query and then test if this set covers all the result of the new query attribute-wise and tuple-wise. If the result of the new query can be derived from the results of executing queries, the new query derives its result at the base station instead of being executed in the sensor network.

• 전자공학회논문지 IE
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• v.48 no.1
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• pp.25-29
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• 2011

Ryu et al. proposed a multiple target angle-tracking algorithm with efficient equation for angular innovation, and Ryu's algorithm has good feature that it has no data association problem. Ryu's algorithm is only applicable to linear sensor array, because its efficient equation for angular innovation is derived in case of using a linear sensor array. In a many fields studying multiple target angle-tracking, the various shapes of sensor array are used. In sonar, a cylindrical sensor array is as much used as a linear sensor array, a example is hull mounted sonar. In this paper, Ryu's algorithm is modified to be applicable to cylindrical sensor array, and the tracking performance of a modified algorithm is verified by various computer simulations.

• Journal of the Korea Society for Simulation
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• v.29 no.3
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• pp.73-82
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• 2020

In the fourth industrial revolution, wireless sensor networks (WSNs) are an important element of collecting and analyzing data in a variety of environments without human intervention. This sensor network is greatly affected by topology and routing protocols. Routing protocols, which affect energy consumption, are executed after deploying sensor nodes. Once built, they are difficult to change. Before the WSN is deployed, a routing protocol is carefully selected in view of various environments and the performance of the protocol is evaluated. In this paper, we propose a model to simulate multiple routing protocols using a discrete event system specification (DEVS). The DEVS-based proposed model simulates various situations without changes and structures of the its model as algorithms of the routing protocols are implemented in its coordinators model. To verify normal behaviors of the proposed model, the number of report delivery and the energy consumption of the sensor network were compared using representative protocols LEACH and Dijkstra. As a result, it was confirmed that the proposed model executes normally in both routing protocols.

• Journal of information and communication convergence engineering
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• v.20 no.1
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• pp.22-30
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• 2022

The reinforcement learning algorithm has proven its potential in solving sequential decision-making problems under uncertainties, such as finding paths to route data packets in wireless sensor networks. With reinforcement learning, the computation of the optimum path requires careful definition of the so-called reward function, which is defined as a linear function that aggregates multiple objective functions into a single objective to compute a numerical value (reward) to be maximized. In a typical defined linear reward function, the multiple objectives to be optimized are integrated in the form of a weighted sum with fixed weighting factors for all learning agents. This study proposes a reinforcement learning -based routing protocol for wireless sensor network, where different learning agents prioritize different objective goals by assigning weighting factors to the aggregated objectives of the reward function. We assign appropriate weighting factors to the objectives in the reward function of a sensor node according to its hop-count distance to the sink node. We expect this approach to enhance the effectiveness of multi-objective reinforcement learning for wireless sensor networks with a balanced trade-off among competing parameters. Furthermore, we propose SDN (Software Defined Networks) architecture with multiple controllers for constant network monitoring to allow learning agents to adapt according to the dynamics of the network conditions. Simulation results show that our proposed scheme enhances the performance of wireless sensor network under varied conditions, such as the node density and traffic intensity, with a good trade-off among competing performance metrics.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.10
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• pp.3-12
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• 2013

Wireless Sensor Network (WSN) is used in the railway field in terms of efficient management and maintenance. Sensor communication technology based on IEEE 802.15.4/ZigBee is used in low speed train. However, it is difficult to apply in the high speed train that exposed to severe wireless channel environments. In this paper, we propose the sensor communication algorithm for high speed train environment. we improve error rate and throughput using Equalizer, Multiple Input Multiple Output (MIMO), Flexible Spreading Factor (SF) and Modulation. Also, we have analyzed the performance of the IEEE 802.15.4/ZigBee based on the standard of physical layer of 2.4GHz band in each algorithms. Simulation results show that proposed algorithms can improve error rate and throughput of conventional system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3B
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• pp.453-461
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• 2010

A critical issue in wireless sensor networks is an energy-efficiency since the sensor batteries have limited energy power and, in most cases, are not rechargeable. The most practical manner relate to this issue is to use a node wake-up scheduling protocol that some sensor nodes stay active to provide sensing service, while the others are inactive for conserving their energy. Especially, CTC (Connected Target Coverage) problem has been considered as a representative energy-efficiency problem considering connectivity as well as target coverage. In this paper, we propose a new energy consumption model considering multiple-targets and create a new problem, CMTC (Connected Multiple-Target Coverage) problem, of which objective is to maximize the network lifetime based on the energy consumption model. Also, we present SPT (Shortest Path based on Targets)-Greedy algorithm to solve the problem. Our simulation results show that SPT-Greedy algorithm performs much better than previous algorithm in terms of the network lifetime.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.2
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• pp.407-414
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• 2007

A sensor fault detection scheme(SFDS) for a class of nonlinear systems that can be represented by Takagi-Sugeno fuzzy model is proposed. Basically, the SFDS may be considered as a multiple observer scheme(MOS) in which the bank of state observers and the detection & isolation logic are included. However, the proposed scheme has two great differences from the conventional MOSs. First, the proposed scheme includes fuzzy fault detection observers(FFDO) that are constructed based on the T-S fuzzy model that provides very good approximation to nonlinear dynamic systems. Secondly, unlike the conventional MOS, the FFDOS are driven not parallelly but sequentially according to the predetermined sequence to avoid the massive computational burden, which is known to be the biggest obstacle to the practical application of the multiple observer based FDI schemes. During the operating time, each FFDO generates the residuals carrying the information of a specified fault, and the corresponding fault detection logic unit performs the logical operations to detect and isolate the fault of interest. The proposed scheme is applied to an inverted pendulum control system for sensor fault detection/isolation. Simulation study shows the practical feasibility of the proposed scheme.

• Journal of the Korea Society of Computer and Information
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• v.22 no.2
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• pp.37-44
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• 2017

Wireless sensor networks are composed of many wireless sensor nodes that are sensing the environments. These networks have many constraints that are resource constraints, wireless communication, self-construction, etc. But they have many applications that are monitoring environment, tracking the object, etc. In this paper, a mechanism of finding QoS Satisfied multi-path is proposed in wireless sensor networks. In order to satisfy the QoS requirement, the proposed mechanism extends the AODV protocol to find multiple paths from a source node to a destination node by using the additional AODV message types that are proposed. This mechanism will be used to support many QoS applications such as minimum delay time, the better reliability and the better throughput by using the QoS satisfied multi-path. Overheads of the proposed mechanism are evaluated using simulation, and it is showed that QoS satisfied multiple paths are found with a little more overhead than the AODV mechanism.