• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집
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• pp.53-56
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• 2004

This paper describes the method of position error reduction in Linear Pulse Motor (LPM). Though the micro step exiting method is applied, the vibration and position error caused by trust distortion from mechanism still remains. This paper presents the method for reduction of position error on moving the mover at whole cycle, by compensating a scale factor through real-time control of the PWM pulse width corresponding to exiting current command and absolute position error from linear encoder.

• Journal of Power Electronics
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• 제8권4호
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• pp.332-344
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• 2008

High frequency AC (HFAC) power distribution systems delivering power through a high frequency AC link with sinusoidal voltage have the advantages of simple structure and high efficiency. In a multiple module system, where multiple resonant inverters are paralleled to the high frequency AC bus through connection inductors, it is necessary for the output voltage phase angles of the inverters be controlled so that the circulating current among the inverters be minimized. However, the phase angle of the resonant inverters output voltage can not be controlled with conventional phase shift modulation or pulse width modulation. The phase angle is a function of both the phase of the gating signals and the impedance of the resonant tank. In this paper, we proposed a pulse phase modulation (PPM) concept for the resonant inverters, so that the phase angle of the output voltage can be regulated. The PPM can be used to minimize the circulating current between the resonant inverters. The mechanisms of the phase angle control and the PPM were explained. The small signal model of a PPM controlled half-bridge resonant inverter was analyzed. The concept was verified in a half bridge resonant inverter with a series-parallel resonant tank. An HFAC power distribution system with two resonant inverters connected in parallel to a 500kHz, 28V AC bus was presented to demonstrate the applicability of the concept in a high frequency power distribution system.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.672-675
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• 2010

본 연구에서는 저주파영역의 가진분무에 대하여 추가적인 내부가진을 수행함으로써 변조분사되는 분무특성에 대한 연구를 수행하였다. 회전식 가진장치를 사용하여 1차 가진을 생성한 후 2차 가진원인 마그네틱 밸브를 사용하여 변조하였다. 변조분무의 FFT결과와 분무패턴의 가시화를 통하여 관찰한 결과, 2차 가진 제어가 있는 변조분사의 경우 1차 가진만 있는 분사보다 분무의 상하 운동 진폭이 작으며 분무 하단류의 침투깊이가 증가하는 경향성이 발견되었다.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1565-1576
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• 2002

By way of driving a 2-way on/off solenoid hydraulic valve with a pulse width modulation (PWM) signal, control of the pressure in a certain volume is frequently used in various applications. However, the pressure built-up according to the duty ratio and carrier frequency of the PWM signal is not so well understood. In order to clarify the characteristics of 2-way valve hydraulic pressure control systems, in this paper two formula fur the mean and ripple of the load pressure were derived through theoretical analysis. And the accuracy of the derived formula were verified by comparison with the experimental test result. Generally 2-way valve systems are constructed as a bleed-off circuit, while 3-way valves are used as a control element in a meter-in circuit pressure control system. In a bleed-off circuit, the system supply pressure from a hydraulic power pack does not remain constant, but changes according to their external load. In turn, the relief valve in the hydraulic power pack reacts accordingly showing complicated dynamic behavior, which makes an analytical study difficult. In order to resolve the problem, simple but accurate empirical dynamic models fer a bleed-off system were used in the course of formula derivation. As the result, selection criteria for two major control parameters of the driving signal is established and the basic strategy to suppress the unnecessary pressure fluctuation can be provided for a hydraulic pressure control system using a 2-way on/off solenoid valve.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계합동학술대회 논문집
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• pp.168-171
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• 2002

In this study. a solid-state laser system adopting a sequential discharge method in which three flashlamps are turned on sequently 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 sequently with the aid of a PIC one-chip microprocessor. With this technique, the lamp turn-on delay time can be varied more diversely from a to lamp 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.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 추계학술대회
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• pp.325-328
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• 2009

자기 자극장치 펄스트레인 기술이 비연속 전도모드에서 플라이백 컨버터로 응용되는 방식을 제안 하고자 한다. 전통적인 펄스폭 제어 방식과는 달리, 자기 자극 펄스 트레인의 주요한 방식은 저전력과 고전력에서 출력전압조절로 구할 수가 있다. 제안한 기술은 불연속 유도에 있는 어떤 변환기에도 적용 가능하다. 그러나, 본 연구에서는 Flyback 연구에 주로 초점을 맞추었다. 본 논문에서, 새로운 제어 연산 논리의 주요 수학 개념은 실험적인 결과가 산출되어 소개 하고자 한다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.401-401
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• 2009

Recently, demands for the development of compact, lightweight power supplies with higher power density and higher efficiency have been increased. Since Piezoelectric Transformer (PT) was emerged in device and material industry, it has been suggested as a viable alternative to the magnetic transformer in some applications. PT has some advantages such as low profile and mechanical energy transfer with little electromagnetic interface (EMI). Also, PT can provide high voltage stepping ratio with good isolation and requires no copper windings saving copper usage especially for large voltage conversion differences. Conventional control of PT converter has mainly two-way. One is the pulse frequency modulation (PFM) control method and the other is the pulse width modulation (PWM) control with frequency fixed method. It is known that the maximum PT efficiency can be obtained when it operates near the resonant frequency of the PT. And, also PT's resonant frequency moves according to the load condition. Therefore, selection of PT converter control method is very difficult. This paper analyzes general piezo-electric converter modeling and proposes a guide-line to selection of control method and stabilization control.

• Journal of Astronomy and Space Sciences
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• 제26권1호
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• pp.47-58
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• 2009

In this study, a Hardware-In-the-Loop (HIL) simulator using thrusters is developed to validate the spacecraft attitude system. To control the attitude of the simulator, eight cold gas thrusters are aligned with roll, pitch and yaw axis. Also linear actuators are applied to the HIL simulator for automatic mass balancing to compensate the center of mass offset from the center of rotation. The HIL simulator consists of an embedded computer (Onboard PC) for simulator system control, a wireless adapter for wireless network, a rate gyro sensor to measure 3-axis attitude of the simulator, an inclinometer to measure horizontal attitude, and a battery set to supply power for the simulator independently. For the performance test of the HIL simulator, a bang-bang controller and Pulse-Width Pulse-Frequency (PWPF) modulator are evaluated successfully. The maneuver of 68 deg. in yaw axis is tested for the comparison of the both controllers. The settling time of the bang -bang controller is faster than that of the PWPF modulator by six seconds in the experiment. The required fuel of the PWPF modulator is used as much as 51% of bang-bang controller in the experiment. Overall, the HIL simulator is appropriately developed to validate the control algorithms using thrusters.

• Journal of Power Electronics
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• 제18권5호
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• pp.1347-1356
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• 2018

In a three-phase system, three-phase AC signals can be translated into two-phase DC signals through a coordinate transformation. Thus, the PI regulator can realize a zero steady-state error for the DC signals. In the control of a three-phase grid-connected inverter, the phase angle of grid is normally detected by a phase-locked loop (PLL) and takes part in a coordinate transformation. A novel control strategy for a three-phase grid-connected inverter with a frequency-locked loop (FLL) based on coordinate transformation is proposed in this paper. The inverter is controlled as a current supply. The grid angle, which takes part in the coordinate transformation, is replaced by a periodic linear changing angle from $-{\pi}$ to ${\pi}$. The changing angle has the same frequency but a different phase than the grid angle. The frequency of the changing angle tracks the grid frequency by the negative feedback of the reactive power, which forms a FLL. The control strategy applies to non-ideal grids and it is a lot simpler than the control strategies with a PLL that are applied to non-ideal grids. The structure of the FLL is established. The principle and advantages of the proposed control strategy are discussed. The theoretical analysis is confirmed by experimental results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.432-435
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• 1997

This Paper proposes a novel sinusoidal converter which improves input power factor and input current waveform without any complicated switching modulation such as a pulse width modulation or a complicated feed-back control. It is composed of a full bridge diode, a pair of capacitors, a pair of inductors and a pair of switching devices. The configuration and control strategy are both simple however, the sinusoidal converter effectively reduces reactive power and hamonics included in a input line current. Excellent behavior of the proposed converter is verified by theoretical analysis and experimental results.