• 항공우주시스템공학회지
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• 제7권4호
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• pp.12-17
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• 2013

Control Moment Gyroscope(CMG) is one of the most efficient momentum exchange devices for satellite attitude control and essential device for agile maneuver system. This paper presents the details of a designed Single Gimbal CMG with a constant speed momentum wheel and single axis attitude control unstable to stable. In order to keep the naturally unstable equivalent point, it should be controlling the gimbal constantly. The experimental data are compared with theoretical result and requirements are used to verify their performance specifications.

• Journal of Electrical Engineering and Technology
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• 제11권1호
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• pp.157-166
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• 2016

In this paper, a new sag and peak voltage detector is proposed for a single-phase inverter using delta square operation. The conventional sag detector is from a single-phase digital phase-locked loop (DPLL) that is based on d-q transformations using an all-pass filter (APF). The d-q transformation is typically used in the three-phase coordinate system. The APF generates a virtual q-axis voltage component with a 90° phase delay, but this virtual phase cannot reflect a sudden change in the grid voltage at the instant the voltage sag occurs. As a result, the peak value is drastically distorted, and it settles down slowly. A modified APF generates the virtual q-axis voltage component from the difference between the current and the previous values of the d-axis voltage component in the stationary reference frame. However, the modified APF cannot detect the voltage sag and peak value when the sag occurs around the zero crossing points such as 0° and 180°, because the difference voltage is not sufficient to detect the voltage sag. The proposed algorithm detects the sag voltage through all regions including the zero crossing voltage. Moreover, the exact voltage drop can be acquired by calculating the q-axis component that is proportional to the d-axis component. To verify the feasibility of the proposed system, the conventional and proposed methods are compared using simulations and experimental results.

• Journal of Power Electronics
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• 제17권2호
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• pp.533-541
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• 2017

This paper presents a novel Parameter-Independent Fictive-Axis (PIFA) approach for the Voltage-Oriented Control (VOC) algorithm used in grid-tied single-phase inverters. VOC is based on the transformation of the single-phase grid current into the synchronous reference frame. As a result, an orthogonal current signal is needed. Traditionally, this signal has been obtained from fixed time delays, digital filters or a Hilbert transformation. Nevertheless, these solutions present stability and transient drawbacks. Recently, the Fictive Axis Emulation (FAE) VOC has emerged as an alternative for the generation of the quadrature current signal. FAE requires detailed information of the grid current filter along with its transfer function for signal creation. When the transfer function is not accurate, the direct and quadrature current components present steady-state oscillations as the fictive two-phase system becomes unbalanced. Moreover, the digital implementation of the transfer function imposes an additional computing burden on the VOC. The PIFA VOC presented in this paper, takes advantage of the reference current to create the required orthogonal current, which effectively eliminates the need for the filter transfer function. Moreover, the fictive signal amplitude and phase do not change with a frequency drift, which results in an increased reliability. This yields a fast, linear and stable system that can be installed without fine tuning. To demonstrate the good performance of the PIFA VOC, simulation and experimental results are presented.

• 한국항공우주학회지
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• 제36권5호
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• pp.514-523
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• 2008

본 논문에서는 한누리 2호의 자세제어 알고리즘 검증을 위해 개발한 KAUSatSIM에 대해서 논의한다. KAUSatSIM은 6개의 에어베어링을 사용하여 무마찰 환경을 모사한 1축 회전 테이블과 한누리 2호에서 사용된 각종 센서 및 모멘텀 휠로 구성되어 있다. 이 시뮬레이터는 한누리 2호의 자세제어 알고리즘에 대한 검증과 새로운 제어 알고리즘 개발, 그리고 그 성능 검증에 사용될 수 있다. 개발된 1축 회전 시뮬레이터를 이용하여 한누리 2호 개발에 이용된 자세제어 알고리즘 검증을 위하여 모멘텀 휠을 이용한 시험을 수행하였다. 비례-미분제어기를 사용한 모멘텀 휠 제어기를 설계하여 좋은 실험 결과를 얻었다. 그리고 더 나아가 추력기 시스템을 추가하여 소형위성에 적용 가능한 새로운 알고리즘 개발 및 검증이 가능하도록 하였다.

• 한국항행학회논문지
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• 제16권1호
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• pp.1-7
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• 2012

본 연구에서는 쿼드로터형 비행체 개발을 위한 선행연구로서 1축 자세 제어장비를 개발하고, 시뮬레이션과 실험을 수행하였다. 두 개의 모터와 프로펠러로 구성된 시소형 1축 자세 제어장비가 제작되었고, 추력 시험을 통해 공력 파라메터를 도출하였다. Matlab/Simulink를 이용하여 시스템의 응답을 추정하였고, 자세 센서와 자세 제어 컴퓨터를 탑재하여 실험을 수행하였다. 시뮬레이션과 실험 데이터를 비교하여 실험 시 발생하는 정상상태 오차에 대한 원인을 파악하고, 사용된 자세알고리즘과 자세 제어 컴퓨터에 대한 성능 검증하였다. 본 과정을 통해, 쿼드로터형 무인항공기 자세 제어를 위한 선행 필수 기초자료를 획득하였다.

• 한국세라믹학회지
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• 제28권3호
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• pp.243-251
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• 1991

High-Tc YBa2Cu3O7-x superconducting thin films have been prepared by single-target off-axis RF magnetron sputtering. Optimal ratio of Y : Ba : Cu of the single-target was determined as 1 : 1.65 : 3.35 in order to obtain the stoichiometric films. Tc, crystalline phase, and microstructures of the surface and cross-section of the ex-situ YBa2Cu3O7-x thin films on MgO(100) had a Tc, zero of 80K, and the films on LaAlO3/Si had a Tc, on-set of 90 K and a Tc, zero of 70 K.

• 한국자동차공학회논문집
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• 제11권1호
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• pp.128-136
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• 2003

In today's design trend of vehicle structure, crush zone is fiequently reinforced by adding a box-shaped sub-frame in order to avoid an excessive deformation against a high-speed offset barrier such as EU Directive 96/97 EC, IIHS offset test. That kind of vehicle structure design results in a relatively monotonic crash pulse for airbag ECU(Electronic Control Unit) located at non-crush zone. As for an angular crash event, the measured crash signal using a single-axis accelerometer in a longitudinal direction is usually weaker than that of frontal barrier crash. Therefore, it is not so easy task to achieve a satisfactory crash discrimination performance for offset and angular crash events. In this paper, we introduce a new crash discrimination algorithm using an electronic X-Y 2-axis accelerometer in order to improve crash discrimination performance especially for those crash events. The proposed method uses a crash signal in lateral direction(Y-axis) as well as in longitudinal direction(X-axis). A crash severity measure obtained from Y-axis acceleration is used to improve the discrimination between fire and no-fire events. The result obtained by the proposed measure is logically ORed with an existing algorithm block using X-axis crash signal. Simulation and pulse injection test have been conducted to verify the performance of proposed algorithm by using real crash data of a 2,000cc passenger vehicle.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2002년도 High Temperature Superconductivity Vol.XII
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• pp.36-36
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• 2002

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제17권4호
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• pp.299-306
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• 2010

In this article we consider axes of a complete embedded minimal surface in $R^3$ of finite total curvature, and then prove that there is no planar ends at which the Gauss map have the minimum branching order if the minimal surface has a single axis.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.346-351
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• 2002

Several algorithm applied to single axis feed system with linear motor has been extensively reviewed in order to check the possible applicability to two axis system Among several factors considered, overshoot of the response was the most important one in minimizing position tracking error. Balance between overshoot and settling time has be adjusted to guarantee to best tracking performance.