• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.149-150
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• 2006

In this paper, design, simulation, fabrication method, and measured results of a digital frequency discriminator(DFD) operating in E, F, and G band are introduced. We describe the direct conversion scheme(DCS) with microwave integrated-circuit(MIC) developed for the small-area and high-speed system. When the input signal is the pulse with a pulse width of 100 ns, accuracy of frequencies measured by the DFD has 1.335 MHz RMS at no noise and 2.64 MHz RMS at signal-to-noise(S/N) ratio within 3 dB in E, F, and G band, which nearly satisfy the specification of 2.5 MHz RMS.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.8
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• pp.577-584
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• 2003

Traditional ankle rehabilitation procedures are tedious, repetitive, and require therapist's help. Therefore, they do not provide patients with good motivation to actively participate in the rehabilitation exercises. In addition, objective diagnosis and evaluation of the treatment progress have been difficult because records of exercise history are made by passive instruments from time to time. The virtual reality technology can make these procedures more fun so that patients can perform everyday rehabilitation exercises more actively. Moreover, haptics technology can give active resistance to the patients ankle motion to improve strength of muscles as well as can record ankle's motion and force histories for objective diagnosis and evaluation. This paper summarizes development of a virtual environment fur reforming the conventional ankle rehabilitation procedures. First of all, conventional rehabilitation procedures have been summarized. Secondly, haptic design and control, user interface design, virtual environment contents design are described. Lastly, mutual cooperation among many developers including medical doctors and therapists and future works are commented.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.5
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• pp.525-529
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• 2009

Most of FLC received input data from error e and change-of-error e' with no relation with system complexity. Basic scheme follows typical PD and PI or PID Controller and that has been developed through fixed ME In this paper, We studied the relationship between MF and system response and system response through changing Fuzzy variable of consequence MF and propose the simple FLC using this relationship. The response of FLC is changed according to the width of Fuzzy variable of consequence MF. As changing the Fuzzy variable of consequence MF shows various nonlinear characteristic, we studied the relation between response and MF using analytical method. We designed the effective FLC using three-variable MF and nine rules and took simulation for verification. In this study, we propose the method to design system with FLC in stability point which is an impotent characteristic of designing system. The circle criterion which is adapted to analysis the nonlinear system is put to use for proposed method. Since SISO FLC has a time-invariant and odd characteristic we can use the critical point not disk which is generally used to determine the stability in the circle criterion, to determine the stability. Using this, we can get the maximum critical point plot of SISO FLC with changing the consequence fuzzy variables. The predetermined critical point plot of FLC can be used to decide the region of the system to be stable. This method is effectively used to design the SISO FLC.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.20 no.1
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• pp.71-78
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• 1990

This research was made to investigate the change of the image layer and of the vertical and horizontal magnification on the Panelipse radiographic image by the control of profile index. Using the Panelipse, a series of 60 exposures were taken with the steel balls placed in the holes of the plastic model plate, and then evaluated by 4 observers. Two points were assigned for a reading of sharp, one for middling sharp, and zero for unsharp. Each ball image then could be given a total reader score of 0 to 8. The author analyzed the image layer as defined by a sharpness score of 6 or more. The results obtained were as follows: As the profile index was increased, the shape of the image layer was not changed, and the width of the image layer was increased, and the position of the layer shifted away from the rotation center. As the profile index was increased, the ranges of vertical and horizontal magnification was increased, especially the ranges of horizontal magnification was greater than that of vertical magnification.

• The Korean Journal of Physiology
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• v.11 no.2
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• pp.67-71
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• 1977

This study was undertaken to investigate the effect of cingulate cortical ablation upon gastric secretion and its components in rats. 23 male rats were divided into the cingulate(N=9) and the operated control(N= 14) groups. Cingulate cortex was ablated through a slit-shaped opening(1 mm in width, 5 mm in length) which was made symmetrically on both sides of, and parallel to, the sagittal suture by removing a bone flap from frontal bone on each side. In the operated control group, the surgical procedure was ended by the removal of the bone flap. Under light ether anesthesia, experimental animals were placed in a restraining jacket of fine mesh wire and gastric juice was collected for 5 hours via a canula which had been inserted through the anterior abdominal wall into the antral portion of the lumen of the stomach. Volume of the gastric juice was measured, and total acid output and free acid output were titrated with 0.04 N NaOH solution by using phenolphthalein and Topfer's reagent at indicator, and chloride ion output was estimated by means of chloridometer. Results obtained were that volume, total acid output, free acid output and chloride ion output of the gastric juice were higher significantly in the cingulate group than in the operated control group. It is inferred from the above results that the cingulate cortex exerts a fascilitatory influence upon gastric secretion and acid output in rats.

• Journal of Electrical Engineering and Technology
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• v.7 no.6
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• pp.905-910
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• 2012

This paper reports an investigation of pulse width modulation (PWM) techniques for twophase brushless DC (BLDC) motors fed by a two-phase eight-switch inverter in a fan application. The three-phase BLDC motor is widely applied in industry; however, a lower-cost two-phase BLDC motor and drive circuit has been greatly in demand in recent years. In this paper, we introduce a mathematical model of the two-phase BLDC motor with sinusoidal back electromotive forces (EMFs) based on traditional three-phase BLDC motors. To simplify the drive algorithm and speed up its application, we analyze the principle of block commutation for a two-phase BLDC motor drive in the 180-electricaldegree conduction mode, and we further propose five PWM schemes to improve the commutation performance of the two-phase BLDC drive. The effectiveness of the proposed PWM methods is verified through experiments.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.12
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• pp.592-600
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• 2005

In this paper, a low loss magnetic levitation(Maglev) system is suggested and tested. The suggested Maglev system includes four hybrid magnets which consist of permanent magnet and coil. In the steady state, the levitated module system can be supported by attraction force generated by permanent magnet. The coil current controls only dynamic loads due to external disturbances. The module systems are designed by using finite element method(FEM) software tools such as MAXWELL and ANSYS. Also, digital control systems are designed to keep the magnet airgap at a constant value. The control systems include a VME(versa module europa)-based CPU(central processing unit) board, AD(analog to digital) board, PWM(pulse width modulation) board, 4-quadrant chopper, and sensors. In order to estimate the vertical velocity of the magnet, we use second order state observer with acceleration and gap signals as input and output signals, respectively. The characteristics of the suggested low loss Maglev system are demonstrated by experimental results showing coil current of 0A in the steady state of 3m airgap and performance specifications are satisfied for reference gap and force disturbance.

• Journal of Power Electronics
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• v.12 no.6
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• pp.886-894
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• 2012

This paper presents a secondary-side, dual-mode feedback LLC resonant controller IC with dynamic PWM dimming for LED backlight units. In order to reduce the cost, master and slave outputs can be generated simultaneously with a single LLC resonant core based on dual-mode feedback topologies. Pulse Frequency Modulation (PFM) and Pulse Width Modulation (PWM) schemes are used for the master stage and slave stage, respectively. In order to guarantee the correct dual feedback operation, Phased-Locked Loop (PLL)-based automatic duty control circuit is proposed in this paper. The chip is fabricated using $0.35{\mu}m$ Bipolar-CMOS-DMOS (BCD) technology, and the die size is $2.5mm{\times}2.5mm$. The frequency of the gate driver (GDA/GDB) in the clock generator ranges from 50 to 425 kHz. The current consumption of the LLC resonant controller IC is 40 mA for a 100 kHz operation frequency using a 15 V supply. The duty ratio of the slave stage can be controlled from 40% to 60% independent of the frequency of the master stage.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.4
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• pp.376-382
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• 2014

This paper proposes the pulse width modulation (PWM) control strategy for low-speed operation in the three-level neutral-point-clamped (NPC) inverters based on the bootstrap gate drive circuit. As a purpose of the cost reduction, several papers have paid attention to the bootstrap circuit applied to the three-level NPC inverter. However, the bootstrap gate driver IC cannot generate the gate signal to the IGBT for low-speed operation, because the bootstrap capacitor voltage decreases under the threshold level. For low-speed operation, the dipolar and partial-dipolar modulations can be the effective solution. However, these modulations have drawbacks in terms of the switching loss and THD. Therefore, this paper proposes the PWM control strategy to operate the inverter at low-speed and to minimize the switching loss and harmonics. The experimental results are presented to verify the validity on the proposed method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.325-328
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• 2009

In this study, A Magnetic stimulation Pulse Train control technique is introduced and applied to Flyback converter operating in discontinuous conduction mode. In contrast to the conventional pulse width modulation control scheme, the principal idea of a Magnetic stimulation Pulse Train is to achieve output voltage regulation using high and low power pulses. The proposed technique is applicable to any converter operating in discontinuous conduction. However, this work mainly focuses on Flyback topology. In this paper, the main mathematical concept of the new control algorithm is introduced and simulations as well as experimental results are presented.