• Journal of Astronomy and Space Sciences
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• 제27권2호
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• pp.145-152
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• 2010

In this paper, we developed a local oscillator (LO) system of millimeter wave band receiver for radio astronomy observation. We measured the phase and amplitude drift stability of this LO system. The voltage control oscillator (VCO) of this LO system use the 3 mm band Gunn oscillator. We developed the digital phase locked loop (DPLL) module for the LO PLL function that can be computer-controlled. To verify the performance, we measured the output frequency/power and the phase/amplitude drift stability of the developed module and the commercial PLL module, respectively. We show the good performance of the LO system based on the developed PLL module from the measured data analysis. The test results and discussion will be useful tutorial reference to design the LO system for very long baseline interferometry (VLBI) receiver and single dish radio astronomy receiver at the 3 mm frequency band.

• 천문학회보
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• 제37권2호
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• pp.219.2-219.2
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• 2012

We are developing Adaptive Optics (AO) system for 24 inch telescope at Seoul National University Observatory. It consists of the tip-tilt correction system and the residual wavefront error correction system with a deformable mirror and a wavefront sensor. We present the construction and performance measurements of the tip-tilt correction system. The tip-tilt component is the single largest contributor to wavefront error, especially for small telescope. The tip-tilt correction system consists of a quadrant photodiode, a tip-tilt mirror and a feed back loop. The collimated He-Ne laser beam is used for input light source and is artificially disturbed by air turbulence generated by a heat gun. Most of the turbulence is of low frequency less than 20 Hz, but extends to a few hundreds Hz. It is found that the closed loop system using proportional-integral-derivative (PID) control successfully corrects tip-tilt error at a rate as high as 300~400 Hz.

• 항공우주시스템공학회지
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• 제16권3호
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• pp.93-98
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• 2022

본 논문에서는 풀 브릿지 인버터의 비선형성을 고려한 단상 영구자석 동기 전동기의 오픈 루프 기동성을 개선하기 위한 구형파 전압 주입 기법을 제안한다. 일반적으로 단상 영구자석 동기 전동기는 3상 교류기와 달리 풀 브릿지 인버터를 채택하고 있으며 대칭 공극으로 자기 회로를 설계할 경우, 영토크 지점의 특정 위치에서 기동이 불가능할 수 있기에 비대칭 공극 설계가 요구된다. 이러한 단상 영구자석 동기 전동기의 구동 특성상 센서리스 운전 모드의 오픈 루프 제어시 기동 실패의 가능성이 상당히 높다. 본 논문에서는 이러한 문제를 해결하기 위해 인버터의 비선형성을 고려한 구형파 전압을 인가하여 기동 성능을 개선하는 기법을 제안하고자 한다. 제안한 알고리즘은 다수의 실험을 통해 타당성을 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.1971-1973
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• 1997

Space Vector control of linear induction motor without speed sensor is one of the most up-to-date researching subjects to the engineers in the fields of power electronics and control theory. A conveyance SLIM (Single-sided Linear Induction Motor) has required a stable speed and a soft start/stop when the goods convey. So, the close loop control method to use a speed sensor have been adopted and as the speed sensor, a linear encorder has been used. But when the speed sensor used, the application boundary is limited and the confidence of system is diminished because it is sensitive to external environment variations and its cost is very expensive. So, to solve these problems, this paper deals with speed control of the conveyance SLIM using space vector without speed sensorless.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.587-591
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• 2004

This paper proposes a novel current compensation technique that can eliminate the harmonic currents included in line currents without computation of harmonic current components. A current controller with fast dynamics for an active filter is described. Harmonic currents are directly controlled without the need for sensing and computing the harmonic current of the load current, thus simplifying the control system. Current compensation is done in the time domain, allowing a fast time response. The DC voltage control loop keeps the voltage across the DC capacitor constant. High power factor control by an active filter is described. All control functions are implemented in software using a single-chip microcontroller, thus simplifying the control circuit. Any current-controlled synchronous rectifier can be used as a shunt active filter through only the simple modification of the software and the addition of current sensors. It is shown through experimental results that the proposed controller gives good performance for the shunt active filter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 추계학술대회 논문집
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• pp.105-106
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• 2012

A feedback control algorithm for the input voltage control of boost converter is proposed in this paper. The proposed control system is mathematically formulated such that the state feedback gains. The control algorithm does not rely on manual tuning procedures neither use complex adaptive techniques. For the verification of the proposed control algorithm, simulation results of the proposed algorithm using PSIM 9.0 are given.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.456-460
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• 1996

A nonlinear control scheme for preventing limit cycle due to the nonlinearity of themulti-step bang-bang actuator in mechanical position control systems is proposed. A linearized model, SIDF, fora multi-step bang-bang actuator is introduced to compensate the nonlinearity of the multi-step bang-bang actuator. Using that model, a $H_{\infty}$robust controller for position control systms with a bang-bang actuator is proposed by loop shaping tecniques with normalized coprime factorization stabilization to address the robustness. The proposed scheme needs a smaller deadband as a result of compensating the nonlinearity of the bang-bang actuator. A single-axis servo system is served in order to verify the proposed control scheme experimentally. Experimental results show that the controller can satisfy the special intersts, silent contact switching of the actuator.r.

• Smart Structures and Systems
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• 제5권3호
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• pp.279-290
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• 2009

Two degrees of freedom resonant systems are employed to improve the resonant property of resonant sensor, as compared to a single degree of freedom resonant system. This paper presents design, development and testing of two degrees of freedom resonant sensor. To measure absolute mass, cantilever shaped two different masses (smaller/absorber mass and bigger/drive mass) with identical resonant frequency are mechanically linked to form 2 - Degree-of-Freedom (DOF) resonator which exhibits higher amplitude of displacement at the smaller mass. The same concept is extended for measuring differential quantity, by having two bigger mass and one smaller mass. The main features of this work are the 3 - DOF resonator for differential detection and the microcontroller based closed loop electronics for resonant sensor with piezoelectric sensing and excitation. The advantage of using microcontroller is that the method can be easily extended for any range of measurand.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.126-128
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• 2018

Solar array simulator (SAS) is a special DC power supply that regulates the output voltage or current to emulate characteristics of photovoltaic (PV) panels. Especially, the control of SAS is a challenging task due to the nonlinearity in the output curve, which is dependent on irradiance as well as temperature and is determined by panel materials. Conventionally, both current-mode control and voltage-mode control should be alternated by partitioning the operating curve into multiple sections, which is not only for the measurement noise problem with the feedback sensing but also for the control stability issue near the maximum power point. However, the occurrence of transition among different controllers may deteriorate the overall performance. To eliminate the mode transitions, a novel single controller scheme has been introduced in this paper, where the reference operating projection technique enables simple, smooth and numerically stable control. Theoretical consideration on the loop stability issue is discussed and the performance is verified experimentally for the emulation of a PV panel data in view of stability and response speed.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권1호
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• pp.99-103
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• 2012

This paper presents a new switch-control approach for multiphase interleaved converters. Development of the proposed technique is based on control-signal generation for multi-unit synchronization. Current sharing among the switching cells and voltage regulation are achieved by means of a multi-loop control scheme regardless of changes in input voltage and load. System stability is ensured by single-pole compensation. This proposed technique is straightforward, reliable and inexpensive, and can be applied to any higher number of cells without difficulty.