• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.85-86
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• 2006

In this paper, a nonlinear controller based on adaptive sliding-mode method which has a sliding surface vector including new boundary function is proposed and applied to a two-wheeled voiding mobile robot (WMR). This controller makes the welding point of WMR achieve tracking a reference point which is moving on a smooth curved welding path with a desired constant velocity. The mobile robot is considered in view of a kinematic model and a dynamic model in Cartesian coordinates. The proposed controller can overcome uncertainties and external disturbances by adaptive sliding-mode technique. To design the controller, the tracking error vector is defined, and then the new sliding is proposed to guarantee that the error vector converges to zero asymptotically. The stability of the dynamic system will be shown through the Lyapunov method. The simulations is shown to prove the effectiveness of the proposed controller.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.8
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• pp.367-375
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• 2001

In Underwater Flight Vehicle depth control system, the followings must be required. First, it needs robust performance which can get over modeling error, parameter variation and disturbance. Second, it needs accurate performance which have small overshoot phenomenon and steady state error to avoid colliding with ground surface or obstacles. Third, it needs continuous control input to reduce the acoustic noise and propulsion energy consumption. Finally, it needs interpolation method which can sole the speed dependency problem of controller parameters. To solve these problems, we propose a depth control method using Fuzzy Sliding Mode Controller with feedforward control-plane bias term and Neural Network Interpolator. Simulation results show the proposed method has robust and accurate control performance by the continuous control input and has no speed dependency problem.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.175-180
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• 2005

Incorrections between model and plant are parameter, system order uncertainties and modeling error due to disturbance like friction. Therefore to achieve a good tracking performance, adaptive discrete time sliding mode tracking controller is used under time-varying desired position. Based on the diophantine equation, a new discrete time sliding function is defined and utilized for the control law. Robustness is increased by using both a recursive least-square method and a sliding function-based nonlinear feedback. The effectiveness of the proposed control algorithm is proved by the results of simulation and experiment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1776-1784
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• 2003

In this paper, we propose the architecture of stream producer for MPEG­4 Video encoding. This module receives the quantized coefficient from DCT and Quantization module in macroblock unit and performs the VLC coding according to the encoding mode, and supports the error concealment mode of MPEG­4 and data partitioning mode. Using the VHDL, we designed the module using this architecture and performed the evaluations of this module by performing the post­-simulation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.3
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• pp.89-95
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• 2016

In this paper, we propose a dual-mode blind equalization algorithm that two of the blind equalization algorithm using the size of the decision-directed error signal is automatically switched. The proposed algorithm has a faster convergence speed due to operation of the MSAGF-SMMA with large fixed step-size mainly in the initial equalization. After the equalization has been made to some extent, the proposed algorithm has a smaller residual error in the steady- state by operation of the MSAGF-SMMA with a variable step-size mainly. The variable step-size is determined by multiplying the size of the decision-directed error signal of a fixed step-size. In this paper, we analyze the performance of the proposed algorithm. The computer simulation results demonstrate that the proposed algorithm has a significantly improved performance in terms of a residual inter-symbol interference and residual error in the steady-state compared with the MMA, SMMA, and MSAGF-SMMA.

• The Journal of the Acoustical Society of Korea
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• v.31 no.1
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• pp.1-10
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• 2012

The linear and decision-feedback equalization can mitigate time-varying intersymbol interference (ISI) caused by time-varying multipath propagation for underwater acoustic channels. The perfect elimination of interference components, however, is difficult using the linear equalization and the decision feedback equalizer has an error propagation problem. To overcome these shortcomings, this paper proposes an equalizer mode selection method using training sequences. The proposed method selects an equalization mode corresponding to the signal-to-noise ratio (SNR). If the SNR is low, the proposed system operates the linear equalizer for preventing the error propagation and if the SNR is high, the decision feedback equalizer for eliminating the residual ISI. Therefore, the proposed method can improve the error performance compared to the conventional equalizers. The computer simulation shows the proposed method improves the bit error performance using practical underwater channels responses acquired from the sea experiment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2C
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• pp.49-58
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• 2005

For the improvement of coding efficiency, the H.264 standard uses new coding tools. Using these coding tools, H.264 has achieved significant improvements from rate-distortion point of view. The adoption of these tools enables a macroblock in H.264 to have more information, sixteen motion vectors, four reference frames and a macroblock mode. In this paper, we present an efficient temporal error concealment algorithm by using not only motion vectors and reference frames but also macroblock mode of neighbor macroblocks. Our algorithm conceals the macroblock error with variable sizes, $16{\times}16,\;16{\times}8,\;8{\times}16,\;8{\times}8$ depending on the macroblock modes of neighbor macroblocks. Simulation results show that the proposed method increase the objective quality regardless of bit-rate and block error rate.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.5
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• pp.1036-1042
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• 2011

This paper presents an algorithm that conducts automatic memory scrubbing operated by dedicated hardwares. The proposed algorithm is designed so that it can scrub entire memory in a given scrub period, while minimally affecting the execution of flight softwares. The scrub controller is constructed in a form of state machines, which have two execution modes - normal mode and burst mode. The deadline event generator and period tick generator are designed in a separate way to support the behavior of the scrub controller. The proposed controller is implemented in VHDL code to validate its applicability. A simple version of the controller is also applied to mass memory modules used in STSAT-3.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.632-634
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• 1998

This paper presents experimental results of the fuzzy controller for DC servo motor. The fuzzy controller consists of 9 quantized levels and 25 fuzzy rules. The fine Controller is employed in the fine control mode when the value of error is between -0.03 and +0.03, whereas the coarse controller is used in the coarse control mode when the value of error is in the outside range of -0.03 and +0.03. The experimental results show that the fuzzy controller provides a better performance (lower overshoot and error) than the PID controller regardless of the load applied.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.3
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• pp.245-248
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• 2010

Almost all of control schemes proposed so far have been designed in the continuous-time domain theoretically. Actual systems, however, have been implemented in the discrete-time domain since Micro Control Unit(MCU) and/or microprocessors have been used for the controllers. Thus, the overall system turned to be a sampled-data system, and generally speaking, the ultimate error cannot converge to zero in the actual system even though the proposed control algorithm showed the asymptotic stability in the continuous-time domain. In this paper, therefore, the ultimate error bound of a sampled data system with a short sampling period has been investigated. The ultimate error is shown to be related in the sampling period.