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Suh C.,Center for Intelligent Robotics | Um T.T.,LIG Nex1 | Kim B.,Seoul National University | Noh H.,Center for Intelligent Robotics | And 2 more authors.
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2011

Motion planning for robots subject to holonomic constraints typically involves planning on constraint manifolds. In this paper we present the Tangent Space Rapidly Exploring Random Tree (TS-RRT) algorithm for planning on constraint manifolds. The key idea is to construct random trees not on the constraint manifold itself, but rather on tangent space approximations to the constraint manifold. Curvature-based methods are developed for constructing bounded tangent space approximations, as well as procedures for random node generation and bidirectional tree extension. Extensive numerical experiments suggest that the TS-RRT algorithm, despite its increased preprocessing and bookkeeping, outperforms existing constrained planning algorithms for a wide range of benchmark planning problems. © 2011 IEEE.

Jeong Y.,Sungkonghoe University | Kim J.,LIG Nex1 | Han S.-J.,Yonsei University
Wireless Networks | Year: 2011

Scalability is one of the most important features that future wireless sensor networks (WSNs) should provide, and clustering is widely considered as a viable approach for high scalability. In the cluster-based architecture, the cluster heads play a key role in relaying messages between the sensor nodes and the sink. While the cluster heads are involved in both intra-cluster and inter-cluster communication, the latter typically requires transmission over much longer distance than the former. In this paper, we consider a scenario in which each cluster head is equipped with dual radios: IEEE 802.15.4 and IEEE 802.11 for intra-cluster and inter-cluster communication, respectively. IEEE 802.11 links between the cluster heads and the sink provide a high capacity backbone for large-scale WSNs. IEEE 802.15.4 and IEEE 802.11 share a lot of similarities including CSMA/CA MAC. Their operating spectrum also overlaps at the 2.4 GHz ISM band, and this may cause interference. We first experimentally measure how severe the interference can be, when two radios are concurrently used in a WSN. We, then, propose an interference mitigation solution which relies on adaptive aggregation of packets and adaptive transmission scheduling. Through prototyping and experimental evaluation, we show that the proposed scheme significantly reduces the interferences between the two types of radios. © 2011 Springer Science+Business Media, LLC.

Kim H.,LIG Nex1 | Jung S.,Chungnam National University
Communications in Computer and Information Science | Year: 2012

This paper presents development and control of a personal robotic vehicle for entertainment. The vehicle is designed to carry passengers in urban areas, especially for a touring purpose. The vehicle has a wheel-driven in all texts mobile robot structure such that motions are generated by velocities of two wheels. A physical vehicle system is developed and tested for driving. Although the vehicle is designed to have two driving modes, a mobile robot mode and a balancing mode, here the mobile robot mode is considered only. Experimental studies of driving the vehicle in indoor environment are performed to confirm the feasibility of the personal future vehicle in the urban area. © 2012 Springer-Verlag.

Kim H.,Korea Advanced Institute of Science and Technology | Park J.,Mokwon University | Oh Y.,Korea Advanced Institute of Science and Technology | Kim S.,LIG Nex1 | Kim B.,Agency for Defense Development
Communications in Computer and Information Science | Year: 2012

This research copes with the voice command recognizer for fighter pilots. The voice command is composed of several connected words in the fighter system. And the recognizer automatically separates the command into individual words and implements isolated word recognition for each word. To improve the performance of the command recognizer, the error correction using grammar tree is proposed. The isolated word recognition error is corrected in the error correction process. Our experimental result shows that the grammar tree significantly improved the performance of the command recognizer. © 2012 Springer-Verlag.

Kim T.-H.,Agency for Defense Development | Park B.-G.,LIG Nex1 | Park B.-G.,PGM R and D Laboratory | Tahk M.-J.,Korea Advanced Institute of Science and Technology
Journal of Guidance, Control, and Dynamics | Year: 2013

The proposed suboptimal guidance with a terminal body-attitude constraint for reentry vehicles in appears to be the first attempt to design an impact-angle-constrained guidance. In a modified proportional navigation (PN) guidance with a time-varying bias, which is a function of relative range, was proposed using a nonlinear planar engagement and Lyapunov-like function. Although various guidance laws to control the impact angle have been developed so far, most of these laws are difficult to implement, especially for a passive homing missile equipped with an infrared seeker, because an accurate time-to-go estimation or range information is required. Thereafter, BPN with zero bias is implemented during the remaining flight because the bias is no longer needed. The proposed shaping method provides valuable features. First, the method does not require a time-to-go estimation and range information. Second, the method has a simple and feasible structure for implementation because only the line-of-sight rate information is required.

PubMed | Daegu Gyeongbuk Institute of Science and Technology, Technical University of Delft, University of Ulsan, LIG Nex1 and 2 more.
Type: Journal Article | Journal: Applied ergonomics | Year: 2016

An artificial neural network (ANN) model was developed in the present study to classify the level of a drivers cognitive workload based on electrocardiography (ECG). ECG signals were measured on 15 male participants while they performed a simulated driving task as a primary task with/without an N-back task as a secondary task. Three time-domain ECG measures (mean inter-beat interval (IBI), standard deviation of IBIs, and root mean squared difference of adjacent IBIs) and three frequencydomain ECG measures (power in low frequency, power in high frequency, and ratio of power in low and high frequencies) were calculated. To compensate for individual differences in heart response during the driving tasks, a three-step data processing procedure was performed to ECG signals of each participant: (1) selection of two most sensitive ECG measures, (2) definition of three (low, medium, and high) cognitive workload levels, and (3) normalization of the selected ECG measures. An ANN model was constructed using a feed-forward network and scaled conjugate gradient as a back-propagation learning rule. The accuracy of the ANN classification model was found satisfactory for learning data (95%) and testing data (82%).

Yun J.,LIG Nex1 | Ryoo C.-K.,Inha University
Journal of Guidance, Control, and Dynamics | Year: 2014

This paperpresentsaninteractive multiple-model-based guidance law estimation filter.Anantiship missile's threat index, such as the remaining time of flight and impact angle, can be estimated by using the guidance law estimation filter. The filter bank of the filter was composed of models based on proportional navigation and impact angle control guidance laws. In the guidance law estimation filter, state variables, rather than fixed values of navigation constant or impact angle,are used for estimation.Tothat end, the modified interactive multiple model, which is a modified version of the conventional interactive multiple model method is presented in this paper. The modified interactive multiple model method minimizes the degradation of estimation performance by systematic approach for different state vectors. The effectivenessof the modified interactive multiple model method and the performanceofthe guidance law estimation filter are examined through the numerical simulation of various engagement scenarios. Copyright © 2013 by Joongsup Yun and Chang-Kyung Ryoo.

Yoon H.,LIG Nex1 | Lee J.,Hanyang University
Lecture Notes in Electrical Engineering | Year: 2014

Wireless Sensor Networks(WSN) are used to communicate between Sensor nodes. The ZigBee telecom applications profile specification is announced for a voice communications in the ZigBee networks by the ZigBee Alliance since 2010[1,2], but it has not been considered to interface with the long distance communications. We designed Voice over Sensor Networks(VoSN) considered on long distance communications with each other nodes. © Springer-Verlag Berlin Heidelberg 2014.

Lee H.S.,Yonsei University | Yook J.-G.,Yonsei University | Sim K.,LIG Nex1
2016 Asia-Pacific International Symposium on Electromagnetic Compatibility, APEMC 2016 | Year: 2016

Radiated electromagnetic fields from video display interfaces include display information of electronic devices. This leaked information can be eavesdropped by measuring and analyzing electromagnetic emanations. These compromising electromagnetic emanations of video display interfaces are radiated from the display panel of monitor or video display interconnects such as connector and cable. In this paper, the information of display from radiated electromagnetic fields from display devices is recovered by measuring and analyzing leaked signals. The radiated signals are received by near-field probe connected to the digital oscilloscope. The received signals are reconstructed by applying signal processing algorithm. © 2016 IEEE.

Kim K.,LIG Nex1 | Kong S.-H.,Korea Advanced Institute of Science and Technology | Jeon S.-Y.,Korea Advanced Institute of Science and Technology
IEEE Transactions on Intelligent Transportation Systems | Year: 2015

The position and velocity information of high-speed trains (HSTs) are essential to passenger safety, operational efficiency, and maintenance, for which an accurate navigation system is required. In this paper, we propose a two-stage federated Kalman filter (TS-FKF) for an HST navigation system that uses multi-sensors, such as tachometer, inertial navigation system, differential GPS, and RFID, with a feedback scheme. However, the FKF with a feedback scheme often shows severe performance degradation in the presence of undetected large sensor errors. Tachometers often have large slip or slide errors during the train's acceleration, deceleration, and moving along a curved railway, and there are significant performance differences between different sensors. To make the proposed system robust to these errors, we propose a slip and slide detection algorithm for the tachometer and an adaptive information-sharing algorithm to deal with a large tachometer error and performance difference between sensors. We provide theoretical analysis and simulation results to demonstrate the performance of the proposed navigation system with the proposed algorithms. © 2000-2011 IEEE.

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