• Journal of Power Electronics
• /
• v.16 no.2
• /
• pp.399-413
• /
• 2016

This paper presents a topology for a modular power electronic transformer (PET) and a control scheme. The proposed PET consists of a cascaded H-Bridge rectifier on the primary side, a high-frequency DC/DC conversion cell in the center, and a cascaded H-Bridge inverter on the secondary side. It is practical to use PETs in power systems to reduce the cost, weight and size. A detailed analysis of the structure is carried out by using equivalent circuit. An algorithm to control the voltages of each capacitor and to maintain the power flow in the PET is established. The merits are analyzed and verified in theory, including the bi-directional power flow, variable voltage/frequency and high power factor on the primary side. The experimental results validated the propose structure and algorithm.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.31 no.9
• /
• pp.74-81
• /
• 1982

One of the stable thin film transistor fabricated by cadmium suifide with the anodized aluminium oxide as gate material. The principle of the operation for the device is based on the control mechanism of injected majority carricrs to the wide band gap semiconductor, that is cadmium sulfide, by means of the function of the gate control. The fabricated device constructed by evaporating CdS layer in the form of microcrystalline on the oxided thin film characterized by ea, 80 as voltage amplification factor, 1/100 mho as transconductance, 8 kohm as dynamic output resistance, furthermore gain band width products is about 15 MHz.

• Proceedings of the KIEE Conference
• /
• 2002.07c
• /
• pp.1991-1993
• /
• 2002

This paper presents the PDMS surface characteristic change after the plasma process and the electroosmotic flow control technique for the two-dimensional focusing in the micro channels made of PDMS and glass. The channels are fabricated by plastic molding and micromachining technique. To observe the surface characteristic change as time elapses, we measure the contact angle of water on the surface and the velocity of the electroosmotic flow in a channel. The electric field adequate for focusing of a core flow in a confluence channel is obtained by the experiment. The computer simulation is performed to obtain the width and the depth of the core flow for several junction angles of the confluence channel.

• Proceedings of the KIEE Conference
• /
• 2002.07c
• /
• pp.1807-1809
• /
• 2002

In this study, asolid-state laser system adopting a firing time control(FTC) method in which three flashlamps are turned on consecutively was designed and fabricated to examine the pulse width and the pulse shape of the laser beams depending upon the changes in the lamp turn-on time. That is, this study shows a technology that makes it possible to make various pulse shapes by turning on three flashlamps consecutively on a real-time basis with the aid of a PIC one-chip microprocessor With this technique, the lamp turn-on delay time can be varied more diversely from 0 to 10 ms and the real-time control is possible with an external keyboard enabling various pulse shapes. In addition longer pulses can be more widely used for industrial processing and lots of medical purposes.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.140-140
• /
• 2000

Traditional genetic algorithms, though robust, are generally not the most successful optimization algorithm on any particular domain. Hybridizing a genetic algorithm with other algorithms can produce better performance than both the genetic algorithm and the other algorithms. In this paper, we use random process and simulated annealing instead of mutation operator in order to get well tuned fuzzy rules. The key of this approach is to adjust both the width and the center of membership functions so that the tuned rule-based fuzzy controller can generate the desired performance. The effectiveness of the proposed algorithm is verified by computer simulation.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.212-212
• /
• 2000

This study was performed to construct a hot strip speed measuring system and check over whether the measured speed can be used for improving the mass flow of the head-end part of a hot strip in the 7-stand finishing mill. Because the mass flow in hot rolling mill affects the looper operation and the thickness and width control of a strip, accurate measurement of strip speed ie important. The measured speed was compared with the roll speeds of No. 6 and No.7 stand to check the performance of the system and analyzed to find how to apply the speed. As a result, it is shown that the accuracy of the system is enough, strip thickness error can be reduced by -275∼+200$\mu\textrm{m}$ using the measured speed and the existing FSU model has low accuracy for predicting forward slip rate. A neural network was developed to calculate forward slip rate instead of FSU model. The test result of the neural network shows that the neural network is more accurate than the FSU model.

• Transactions of Materials Processing
• /
• v.18 no.5
• /
• pp.377-384
• /
• 2009

The shape of edge cracking in rolling process generally occurred "V" shape. This cracking is successively generated at width edge of strip. The edge cracking is developed to center of strip during rolling process. In the results, the strip is occurred fracture, and the productivity is gone down because of the extensive production time. Accordingly, we need to control crack propagation during rolling process. But, the control of cracking is very difficult in rolling process. Previously the studies of edge cracking were mainly performed on hot rolling process. In this paper, the shape of the edge cracking in rolling was estimated according to process conditions such as initial edge crack size, reduction ratio and tension using FE-simulation and the simplicity experiments on cold rolling process.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.57-58
• /
• 2006

A Simulation model is developed to minimize the path tracking errors when the non-circular cutting is done by a VCM(voice coil motor) driven tool. The relationship between PWM(Pulse Width Modulation) duty ratio and velocity of voice coil motor is theoretically derived from combining the circuit equation for the coils and the motion equation for the magnetic rod of the voice coil motor. The path tracking errors are showed differently according to the rotational speed, the number of segments and the control period in digital control. Given a required accuracy in the non-circular cutting, the optimal values for those parameters are determined based on the developed simulation model.

• Proceedings of the KWS Conference
• /
• 2005.11a
• /
• pp.132-134
• /
• 2005

The friction surfacing system which has been successfully developed in RIST has both position control and force control by using hydraulic cylinder. In friction surfacing process mechtrode rotation speed(N) and feeding speed($V_{z}$), travelling speed($V_{x,y}$) are of critical importance for the width and thickness of the coating. As a result of DOE with developed system, the main effect of coating thickness is a rotation speed of mechtrode.

• Proceedings of the KIEE Conference
• /
• 2002.07d
• /
• pp.2534-2536
• /
• 2002

This paper presents the design of high speed bit and word processor for sequence logic control using a FPGA. This FPGA is able to execute sequence instruction during program fetch cycle, because the program memory was separated from the data memory for high speed execution at 40MHz clock. Also this processor has 274 instructions set with a 32bit fixed width, so instruction decoding time and data memory interface time was reduced. This FPGA was synthesized by V600EHQ240 and Foundation tool of Xilinx company. The final simulation was successfully performed under Foundation tool simulation environment. And the FPGA programmed by VHDL for a 240 pin HQFP package. Finally the benchmark was performed to prove that the designed for bit and word processor has better performance than Q4A of Mitsubishi for the sequence logic control.