• Proceedings of the KIEE Conference
• /
• 2001.07b
• /
• pp.986-988
• /
• 2001

This paper presents a digitally speed sensorless control system for induction motor with direct torque control (DTC). Some drawbacks of the classical DTC are the relatively large torque ripple in a low speed range and notable current pulsation during steady state. They are reflected speed response and increased acoustical noise. In this paper, the DTC quick response are preserved at transient state, while better qualify steady state performance is produced by space vector modulation (SVM). The system are closed loop stator flux and torque observer for wide speed range that inputs are currents and voltages sensing of motor terminal, model reference adaptive control (MRAC) with rotor flux linkages for the speed fuming signal at low speed range, two hysteresis controllers and optimal switching look-up table. Simulation results of the suggest system for the 2.2 [kW] general purposed induction motor are presented and discussed.

• Current Optics and Photonics
• /
• v.2 no.1
• /
• pp.1-6
• /
• 2018

Our previous study showed that switching the inhaled gas from hypoxic gas to hyperoxic gas for 10 minutes increased tumor oxygenation and that the magnitude of oxyhemoglobin increase responded earlier than tumor volume change after chemotherapy. During 10 minutes of inhaled-oxygen modulation, oxyhemoglobin concentration first shows a rapid increase and then a slow but gradual increase, which has been fitted with a double-exponential equation in this study. Two amplitude values, amplitudes 1 and 2, respectively represent the magnitudes of rapid and slow increase of oxyhemoglobin. The trends of changes in amplitudes 1 and 2 were different, depending on tumor volume when chemotherapy started. However, both amplitudes 1 and 2 changed earlier than tumor volume, regardless of when chemotherapy was initiated. These results imply that by observing amplitude 1 changes post chemotherapy, we can reduce the time of a respiratory challenge from 10 minutes to less than 2 minutes, to see the chemotherapy response. We believe that by reducing the time of the respiratory challenge, we have taken a step forward to translating our previous study into clinical application.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.3B no.1
• /
• pp.44-51
• /
• 2003

The module UPS can flexibly implement expansion of power system capacities. Further-more, it can be used to build up the parallel redundant system to improve the reliability of power system operation. To realize the module UPS, load sharing without interconnection among parallel connecting modules as well as a small scale and lightweight topology is necessary. In this paper, the three-arm converter/inverter is compared with the general full-bridge and half-bridge topology from a practical point of view and chosen as the module UPS topology. The switching control approaches based on a pulse width modulation of the converter and inverter of the system are presented independently. The frequency and voltage droop method is applied to parallel operation control to achieve load sharing. Two prototype 3㎸A modules are designed and implemented to confirm the effectiveness of the pro-posed approaches. Experimental results show that the three-arm UPS system has a high power factor, a low distortion of output voltage and input current, and good load sharing characteristics.

• Proceedings of the KIEE Conference
• /
• 1999.07f
• /
• pp.2653-2655
• /
• 1999

A technique to suppress the low frequency ripple voltage of the DC output voltage in three-phase buck diode rectifiers is presented. A pulse frequency modulation method is employed to regulate the output voltage of the rectifier and guarantee zero-current switching of the switch over the wide operating range. The pulse frequency control method used in this paper shows generally good performance such as low THD of the input line current and unity power factor. In addition, the pulse frequency method can be effectively used to suppress the low frequency voltage ripple appeared in the dc output voltage. The proposed technique illustrates its validity and effectiveness through the respective simulations and experiments.

• Journal of Institute of Control, Robotics and Systems
• /
• v.20 no.7
• /
• pp.756-759
• /
• 2014

DC/DC converters are commonly used to generate regulated DC output voltages with high-power efficiencies from different DC input sources. The converters can be applied in the regenerative braking of DC motors to return energy back to the supply, resulting in energy savings for the systems at periodic intervals. The fundamental converter studied here consists of an IGBT (Insulated Gate Bipolar mode Transistor), an inductor, a capacitor, a diode, a PWM-IC (Pulse Width Modulation Integrated Circuit) controller with oscillator, amplifier, and comparator. The PWM-IC is a core element and delivers the switching waveform to the gate of the IGBT in a stable manner. Display of the DC/DC converter output depends on the IGBT's changes in the threshold voltage and PWM-IC's pulse width. The simulation was conducted by PSIM software, and the hardware of the DC/DC converter was also implemented. It is necessary to study the fact that the output voltage depends on the duty rate of D, and to compare the output of experimental result with the theory and the simulation.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.04a
• /
• pp.448-455
• /
• 1996

In this study, to reduce vibration of step motor we use Microstep control. Microstep control of stepmotor is usually thought of as an extension of conventional stepmotor control technology. The essence ofmicro stepping is that we divide the full step of a stepmotor into a number of substep called microstep and cause the stepmotor to move through a substep per input pulse. In ideal case, bycontrolling the individual phase currents of a two-phase step motor sinusoidally we can get uniform torque and step angles. But due to the monlinear characteristics of the step motor, we need to compensate current waveform to improve the overall smoothness of the conventional micro stepping system. We implement digital Pulse Width Modulation(PWM) driver to drive step motor and microphone was used for detecting vibration. Driver enables speed change automatically byincreasing or decreasing micro stepping ratio which we call Automatic Switching on the Fly. To compensate the torque harmonics, Neural Networks is applied to the system and we foundcompensated optimal input current waveform. Finally we can get smooth motion of step motor in a wide range of motor speed.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.24 no.5
• /
• pp.583-587
• /
• 2015

In this study, a half-duplex mutual communication device via human skin was developed. Frequency-shift keying (FSK) digital modulation and demodulation control were used to transmit and receive data. Data communication through the human body is an effective communication technique and has high-grade security characteristics. In addition, making contact is a natural instinct of humans. Transmitting data through the human body is currently a highly conspicuous technology, because recently a lot of commercial sensors for humans have been developed. A body area network (BAN) can be easily constructed by this communication method on human skin. In this study, a half-duplex FSK mutual communication device was developed using a commercial FSK modulator and demodulator. A special control switching circuit and communication sequence were developed for mutual communication through human skin.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.19 no.3
• /
• pp.17-26
• /
• 2005

The random pulse width modulation(RPWM) in inverter-fed induction motor drive is presented. This paper describes a RPWM method based on space vector PWM strategy for shaping the switching noise spectrum in such a way it can merge with the natural system noise. To verify the validity of the proposed RPWM scheme, the experiment based on the DSP56F803 microprocessor was executed finally, the simulation and experimental results will be given to demonstrate the effectiveness of the unposed RPWM scheme.

• 한국정보통신설비학회:학술대회논문집
• /
• 2006.08a
• /
• pp.57-61
• /
• 2006

As high speed internet users are tremendously increasing, three are keenly in need of development of high speed portable internet technology which can provide high quality wireless internet service cheaply even in the mobile. Unlike the FDD-CDMA, TDD-OFDMA has relatively poor wave environment with inducing interference, fading and delay because it agrees to multi-carrier modulation method and time-division radio telecommunication system. To solve this problem, it is necessary to develop repeater operating by digital signal processing method which have more strict wireless channel control and wave signal processing technology over TDD telecommunication equipments. This thesis is dealing with design and implementation of Digital RF Repeater which implemented 'Synchronization Acquisition Unit', 'TDD signal switching Unit', 'Feedback Signal Cancellation Unit'. Over this argument, we will develop digital RF repeater with more cheap, more adaptive in wave environment like oscillation control, adaptive wave monitoring and output increasing and having control function as a result it will be helpful for success in high speed portable internet service business.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.5 no.6
• /
• pp.632-637
• /
• 2000

In this paper, to control with light dimming levels of the fluorescent lamps, we have used the power line instead of the signal line to transmit the control signals. To reduce the BER(Bit Error Rate) on the power line communication with the serious noise interferences. We have adapted the FSK(Frequency Shift Keying) modulation and demodulation technique. Since the electronic ballast produced the EMI(ElctroMagnetic Interference) noise in some frequency bands, we have reduced the EMI levels in the band below -50dB. By varying the switching frequency of the ballast for the FL032/T8 from 18kHz to 25kHz, it is possible that the dimming levels are controled with the range of 5∼100%