• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.2
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• pp.215-221
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• 2006

This paper is concerned with the control of multiple nonlinearities included in a humanoid robot system. A humanoid robot has some problems such as the structural instability, which leads to consider the control of multiple nonlinearities caused by driver parts as well as gear reducer. Saturation and backlash are typical examples of nonlinearities in the system. The conventional algorithms of backlash control were fuzzy algorithm, disturbance observer and neural network, etc. However, it is not easy to control the system by employing only single algorithm since the system usually includes multiple nonlinearities. In this paper, a switching Pill is considered for a control of saturation and a dual feedback algorithm is proposed for a backlash control. To implement the above algorithms, the system identification is firstly performed for the minimization of the difference between the results of simulation and experiment, and then the switching Pill gains are determined using genetic algorithm with some heuristic approach. The performance of the switching Pill controller for saturation and the dual feedback for backlash control is investigated through the simulation. Finally, it is shown that the implemented control system has good results and can be applied to the real humanoid robot system ISHURO.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.209-212
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• 2003

This paper proposes a soft-transition control strategy for a three phase ZCS(Zero Current Switching) inverter circuit. Each phase leg of inverter circuit consists of an LC resonant tank, two main switches, and one auxiliary switches. This paper presents design consideration via a study example of a three phase prototype inverter for motor drives. A simple device tester with zero current switching capability is proposed to select eligible auxiliary switches. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 2.2kW 5kHz IGBT based experimental circuit.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.186-189
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• 2002

This paper presents an improved ZVT(Zero Voltage Transition) DC/DC Boost Converter using Active Snubber. The Conventional ZVT PWM Boost Converter is improved to minimize the switching loss of auxiliary switch using the minimum number of the components. In this thesis, advantage and disadvantages of Conventional ZVT Converter using a auxiliary resonant circuit is discussed. Then Improved ZVT soft switching converter will be discussed. In comparison a previous ZVT converter, The proposed converter reduces turn-off switching loss of the auxiliary switch Therefore, the proposed converter has a high efficiency by active snubber. The prototype of 100kHz, 2kW system was implemented to show the improved performance.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.136-139
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• 1997

The active-clamped double forward-flyback converter is studied in this paper. The converter reduces the voltage stress of the switches and decreases switching loss, EMI. The energy stored in the magnetic core is transferred to both the input voltage source and the flyback output. This makes it possible the output circuit of the flyback to operate at CCM without complex control circuit. The MOSFET is used at output stage, which decreases switching loss.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.159-162
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• 2004

The paper proposes the coupled inductor rectifier of Three Level DC/DC converter CICDR-TL(Coupled Inductor Current Doubler Rectifier-Three Level) achieves Zero Voltage Switching (ZVS) for the switches in a wide load range and Zero Current Switching (ZCS) in a light load range. Advantages and disadvantages of this topology compared to the conventional Center Tapped TL Converter are discussed. Experimental evaluation results obtained on a 27V 60A DC/DC converter prototype for the 1.8kW 40kHz IGBT based experimental circuit.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.320-323
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• 2001

A ZVZCS(Zero-Voltage and Zero-Current-Switching) Three Level DC/DC Converter is presented to secondary auxiliary circuit. The converter presented in this paper used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switch. A secondary auxiliary circuit, which consists of one small capacitor and two small diode, is added in the secondary to provides ZVZCS conditions to primary switches, and aids to clamp secondary rectifier voltage. The auxiliary circuit Includes neither lossy component nor addition active switch, which makes the proposed converter efficient and effective. The principle of operation, feature, and design considerations are illustrated and verified through the experiment with a 500W 50kHz prototype converter.

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.200-204
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• 2001

A ZVZCS(Zero Voltage and Zero Current Switching) Three Level DC/DC Converter is presented to secondary auxiliary circuit. The new converter presented in this paper used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switch. A secondary auxiliary circuit, which consists of one small capacitor two small diode and one coupled inductor is added in the secondary to provides ZVZCS conditions to primary switches, ZVS for outer switches and ZCS for inner switches. Many advantages including simple circuit topology high efficiency, and low cost make the new converter attractive for high power applications. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 1kW 50kHz IGBT based experimental circuit.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.4
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• pp.66-73
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• 1997

A capacitor discharge impulse magnetizer using semiconductor switching device is used to produce a high current impulse of short duration in a magnetizing fixture for magnets of the various shapes. The price of today's magnetizer is relatively expensive. This paper described a method for cost estimation of capacitor discharge impulse magnetizer using semiconductor switching device and the economical efficiency analysis. We used a cost structure consisted of five major subsystems. Especially, we estimated the potential for a cost reductions in impulse magnetizer as a function of time using the learning curve, and the potentials of cost by depreciation. The reliable results were obtained by using iron-core fixture coupled to a middle-voltage magnetizer.

• Journal of Electrical Engineering and Technology
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• v.2 no.1
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• pp.98-101
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• 2007

Yttrium(Y)-substituted bismuth titanate $(Bi_{4-x},Y_x)Ti_3O_{12}$ [x=0, 0.25, 0.5, 0.75, 1](BYT) thin films were deposited using an RF sputtering method on the $Pt/TiO_2/SiO_2/Si$ substrates. The structural properties and electrical properties of yttrium-substituted $(Bi_4-xYx)Ti_3O_{12}$ thin films were analyzed. The remanent polarization of $(Bi_4-xYx)Ti_3O_{12}$ films increased with increasing Y-content. The $(Bi_{3.25}Y_{0.75})Ti_3O_{12}$ films fabricated using a top Au electrode showed saturated polarization-electric field(P-E) switching curves with a remanent polarization(Pr) of $8{\mu}C/cm^2$ and coercive field (Ec) of 53 kV/cm at an applied voltage of 7 V. The $(Bi_{3.25}Y_{0.75})Ti_3O_{12}$ films exhibited fatigue-free behavior up to $4.5{\times}10^{11}$ read/write switching cycles at a frequency of 1MHz.

• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.164-167
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• 2005

This paper present ZVS Half-Bridge converter Using IM(Integrated Magnetics). In converter system, magnetic components are important devices used for energy storage, energy transfer, galvanic isolation and filtering. The purposes of IM(Integrated Magnetics) are to reduce the number of magnetic components and voltage/current ripple. This topology is use of three magnetics components thus increasing the cost and size of the system. A prototype featuring 300V input, 15V output, 400kHz switching frequency, and 150W output power.