• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1065-1066
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• 2011

본 논문에서는 함정의 피탐지 성능 개선을 위한 기초 연구로 dead time 적용시 탈자 프로토콜 변화에 따른 탈자 성능 분석에 관한 연구를 하였다. 함정의 재질은 SM45C로 원통의 형태이다. 자기장 측정에 사용한 자기센서는 영국 Bartington Instruments사의 MAG-03MCB70(Three-Axis Fluxgate Magnetometer)을 사용하였으며, inter-cardinal run 방법을 이용하여 유도자기장과 영구자기장을 분리하였다. Anhyteretic deperm 프로토콜을 적용하여 탈자를 진행하였고 전류의 지속시간이 증가하는 경우에 비하여 dead time을 적용하였을 경우 탈자 성능이 향상된 결과를 얻을 수 있었다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.10a
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• pp.214-219
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• 2001

For navigation of a mobile robot, it is one of the essential tasks of find out its current position. Dead reckoning is the most frequently used method to estimate its position. However conventional dead reckoner is prone to give us false information on the robot position especially when the wheels are slipping. This paper proposes an improved dead reckoning scheme using neural networks. The network detects the instance of wheel slipping and estimates the linear velocity of the wheel ; thus it calculates current position and heading angel of a mobile robot. The structure and variables of the neural network are chosen based on the analysis of slip motion robot. The structure and variables of the neural network are chosen based on the analysis of slip motion characteristics. A series of experiments are performed to investigate the performance of the improved dead reckoning system.

• Journal of Power Electronics
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• v.9 no.3
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• pp.438-446
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• 2009

The performance of direct torque controlled (DTC) interior permanent magnet (IPM) machines is poor at low speeds due to a few reasons, namely limited accuracy of stator voltage acquisition and the presence of offset and drift components in the acquired signals. Due to factors such as forward voltage drop across switching devices in the three phase inverter and dead-time of the devices, the voltage across the machine terminals differ from the reference voltage vector used to estimate stator flux and electromagnetic torque. This can lead to instability of the IPM drive during low speed operation. Compensation schemes for forward voltage drops and dead-time are proposed and implemented in real-time control, resulting in improved performance of the space vector modulated DTC IPM drive, especially at low speeds. No additional hardware is required for these compensators.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.2
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• pp.177-185
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• 2007

Hydraulic efficiency($T_{10}/T$) in clearwell is often estimated by L/W ratio. However, this estimation is not accurate because other factors which give an effect on hydraulic efficiency such as shape of basin, diffuser wall and intra-basin is ignored. Therefore, in this research, hydraulic efficiency is predicted by the quantitative analysis of dead zone using CFD simulation in a pilot scale clearwell. The results show that the reason why higher L/W ratio increase the hydraulic efficiency is to decrease the dead zone of linear region which is located between baffles. Diffuser wall or intra-basin also affects on hydraulic efficiency with this process. Also, we conclude that hydraulic efficiency can not be reached to 0.8 or higher.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.990-993
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• 2005

This paper presents new results on designing a robust adaptive direct controller for a class of non-linear first order systems. The designing method based on the use of dead zone in the parameters' update law. It is shown that the size of the dead zone does not depend on the upper bounds of the disturbances. That means that even if the bounds are large, the tracking error will always converge to a set of the dead zone size. However, in the ideal case, when the exogenous signal functions and the function represents un-modeled dynamics of the systems equal to zero, the proposed controller does nt mean the convergence to zero of the tracking error. Computer simulation results show the effectiveness of the controller in dealing with the stated problems.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2715-2720
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• 1999

To prevent the short circuit of upper and lower arms of bridge type PWM converters as like a voltage source inverter and PWM AC/DC converter, the dead time is inserted in between two switching signals. As a result, unexpected errors are occurred. In this paper, a new dead time minimization method is proposed. According to the proposed method, very short time which is equal to the applied dead time or more short than it, is adopted at the time of current polarity is changing. Moreover, it can be operated with the polarity information of reference current in case of current control. With the experimental results. the varidity of proposed method is verified.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.11
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• pp.120-127
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• 1999

The dead time which is inserted in switching signals of PWM voltage source inverters distorts its output. As a result, the deviations of real fundamental voltage and phase compared with the reference are occurred. And also the harmonics on its output are increased. In this paper, numerical analysis of the distorted voltage on the output of inverter caused by switching dead time is performed. With the calculation results, the fundamental voltage gain and phase deviations according to the modulation index, load displacement factor and dead time are presented.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.250-253
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• 1998

The kinematically admissible velocity field is developed for the shapes of dead metal zone and the curving velocity distribution in the eccentric plane dies extrusion. The shape of dead metal zone is defined as the boundary surface with the maximum friction constant between the deformable zone and the rigid zone. The curving phenomenon in the eccentric plane dies is caused by the eccentricity of plane dies. The axial velocity distribution in the plane dies is divided in to the uniform velocity and the deviated velocity. The deviated velocity is linearly changed with the distance from the center of cross-section of the workpiece. The results show that the curvature of products and the shapes of the dead metal zone are determined by the minimization of the plastic work and that the curvature of the extruded products increases with the eccentricity.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.80-83
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• 1999

Rigid Plasticity Finite Element Analysis is developed for the shapes of dead metal zone and the curving velocity distribution in the eccentric square dies extrusion. The shape of dead metal zone is defined as the boundary surface with the maximum friction constant between the deformable zone and the rigid zone. The curving phenomenon in the eccentric square dies is caused by the eccentricity of square dies. The deviated velocity is changed with the distance form the center of cross-section of the workpiece. The results show that the curving of products and the shapes of the dead metal zone are determined by Rigid Plasticity Finite Element Analysis and that the curvature of the extruded products increases with the eccentricity.

• Transactions of Materials Processing
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• v.10 no.2
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• pp.151-159
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• 2001

Flow defect of a piston-pin for automobile parts is investigated in this study. In combined cold extrusion of piston-pin, lapping defect, which is a kind of flow defect, appears by the dead metal zone. This appearance evidently happens in products with a thin thickness to be pierced for the dimensional accuracy and the decrease of material loss. The flow defect that occurs in piston-pin has bad effects on the strength and the fatigue life of piston-pin. Therefore, it is important to predict and prevent defects in the early stage of process design. The best method that can prevent flow defect is removing or reducing dead metal zone through material flow control. The finite element simulations are applied to analyze the flow defect. This study proposes processes for preventing flow defect by removing dead metal zone. Then the results are compared with the experimental ones for verification. These FE simulation results are in good agreement with the experimental ones.