Kyung-Tae Nam

A novel location finding system for 3GPP LTE

We propose a novel location finding system exploiting the downlink reference signal of the Long Term Evolution (LTE) because of the absence of an efficient location finding system for the LTE. The proposed system is based on the correlation method and Chans method for location sensing and positioning process, respectively. The conventional correlation method, however, is not matched to the LTE since the orthogonal gold sequence used for reference signal is assigned in frequency domain. Therefore, we estimate Time Difference Of Arrival (TDOA) data by cross-correlating the transmitted signal and received signal in the frequency domain. Simulation results show that the proposed system meets the Federal Communication Commission (FCC) requirement for typical Signal-to-Noise Ratio (SNR) region, and the performance can be further improved as more antennas are implemented in transmitter or receiver.

Modeling of a dual actuator system and its control algorithm preventing saturation of fine actuator

This paper discusses the design of control structure of dual actuator system, which is considered as DISO system, for high precision manufacturing stage. It proposes that PA tracks error signal between estimated coarse position and output coarse position at control sample to prevent saturation. Estimators are designed for both fine and coarse actuator plants to derive input signal to PA and state-feedback gain is defined by LQR. Dynamic model is defined by Newtons second law and coupling dynamics is considered for control structure. Experimental results demonstrate that unnecessary movement of PA during the transient response is reduced resulting in enhanced overshoot and settling time of the DSA system.

Position and Velocity Estimation for Two-Inertia System with Nonlinear Stiffness Based on Acceleration Sensor

In this paper, we consider the state estimation problem for flexible joint manipulators that involve nonlinear characteristics in their stiffness. The two key ideas of our design are that (a) an accelerometer is used in order that the estimation error dynamics do not depend on nonlinearities at the link part of the manipulators and (b) the model of the nonlinear stiffness is indeed a Lipschitz function. Based on the measured acceleration, we propose a nonlinear observer under the Lipschitz condition of the nonlinear stiffness. In addition, in order to effectively compensate for the estimation error, the gain of the proposed observer is chosen from the ARE (algebraic Riccati equations) which depend on the Lipschitz constant. Comparative experimental results verify the effectiveness of the proposed method.

Design of a personalized r-learning system for children

This paper introduces the r-learning (robot-learning) system that utilizes robotic interactions to personalize instructions for individual children. A child who is not familiar with using an educational tool to study could learn readily from educational contents through various interactions with a robot which is based on the behavior control. The contents which are chosen according to a childs learning data extracted by analysis from human-robot interaction data could lift the educational effectiveness. An r-learning scenario is designed by using Petri net to handle exception occurred in a learning process. The robot contents maker and the Open API for operating a robot are described as management utilities for a personalized r-learning system.

Low complexity ranging algorithm based on TOA for IEEE 802.15.4a system

A computationally efficient ranging scheme that estimates time of arrival (TOA) by a low complexity minimum mean square error (MMSE) and a matrix pencil techniques is proposed for IEEE 802.15.4a chirp spread spectrum system. In TOA estimation, it is known that accurate channel delay can be estimated by the MMSE technique. However, the major drawback of the MMSE is its high computational complexity, which grows with number of signal samples. In this paper, thus, a computational efficient MMSE technique based on the chirp spectrum characteristic is proposed for a low complexity ranging algorithm. The proposed TOA estimation method consists of two-step signal processing: proposed low complexity MMSE-based channel impulse response (CIR) estimation and the channel delay tracking by matrix pencil algorithm. The proposed TOA estimation method not only has low computational complexity, but also achieves small ranging error. The effectiveness of the proposed algorithm is demonstrated by simulation results.

High Accurate Two-Dimensional Geo-Location System for Social Safety Robot

In this paper, we propose an efficient two-dimensional geo-location system for social safety robot, where its location is obtained by direction of arrival (DOA) and time of arrival (TOA) of the radio signal. The proposed system requires two reference signals while the conventional systems generally deploy more than three reference signals. For estimating TOA and DOA information together, we employ a multiple signal classification (MUSIC) algorithm. The simulation results show that the proposed geo-location system achieves accuracy within 3 meters error in 2 kilo-meters coverage which is constraint for mobile social safety robot.

Design of Nonlinear Observer for Flexible Joint Manipulator with Nonlinear Stiffness Based on Acceleration

Abstract - In this paper, we consider the observer design problem that truly reflects the nonlinear stiffness of the manipulators. The two key ideas of our design are that (a) estimation error dynamics of the manipulator equipped with accelerometer dose not dependent on nonlinearities at the link part, when the measured signals are the motor position and the output of the accelerometer and (b) the nonlinear stiffness is indeed a Lipschitz function. In order to effectively compensate the nonlinear stiffness, the gain of the proposed observer is carefully chosen from the ARE(algebraic Riccati equations) which depend on Lipschitz constant. Comparative simulation result verifies the effectiveness of the proposed solution.Key Words : Flexible Joint Manipulator, Acceleration, Nonlinear Stiffness, Nonlinear Observer, Lipschitz Condition† Corresponding Author : Korean Institute of Industrial Technology, Korea.E-mail: robotnam@kitech.re.kr* Korean Institute of Industrial Technology, Korea.** ASRI, Dept. of Electrical and Computer Engineering, Seoul National University, Korea, and also Korean Institute of Industrial Technology, Korea.*** Dept. of Electronic Eng., Sungkyunkwan Univerity, Korea.Received : November 28, 2014; Accepted : February 27, 2015