• Journal of Astronomy and Space Sciences
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• 제28권4호
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• pp.311-317
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• 2011

Momentum changing actuators like reaction wheels and control moment gyros are generally used for spacecraft attitude control. This type of actuators produces force and torque disturbances. These disturbances must be reduced since they degrade the quality of spacecraft attitude control. Major disturbances are mainly due to static and dynamic imbalances. This paper gives attention to the reduction of the static and dynamic imbalance. Force/torque measurement system is used to measure the disturbance of the test reaction wheel. An identification method for the location and magnitude of the imbalance is suggested, and the corrections of the imbalance are performed using balancing method. Through balancing, the static and dynamic imbalance is remarkably reduced.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2087-2092
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• 2005

Using disturbance observer (DOB) is effective in enhancing the performance of dynamic system in the presence of disturbances. Recently the definition of disturbance has been expanded to modeling uncertainty including parameter variation, internal disturbance. Various structures of DOB have been proposed to improve sensitivity of system for better disturbance rejection performance. However in the case of improvement of sensitivity function, it tends to bring poor transient response due to cross-coupling and phase lag. Furthermore it could be very sensitive to measurement noise due to increased peak of complementary sensitivity function. In this paper, a dual disturbance observer (Dual-DOB) is proposed to reduce the effect of such cross-coupling. It is possible for us to improve the sensitivity function with additional external DOB with hardly affecting complementary sensitivity function. Thus it is able to have robustness against measurement noise. Since we are able to design DOBs of internal and external loop independently, we could prevent transient response quality from degrading while improving the sensitivity function. The proposed Dual-DOB is applied to a commercial optical disk drive tracking servo system. The experimental result shows that the Dual-DOB is an effective method in rejecting the disturbance as well as improving the tracking performance.

• 한국산업정보학회:학술대회논문집
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• 한국산업정보학회 2001년도 춘계학술대회논문집:21세기 신지식정보의 창출
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• pp.145-151
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• 2001

An extension of interaction matrix formulation to the problem of system and disturbance identification for a plant that is corrupter by both process and output disturbances is presented. With only an assumed upper bound on the order of the system and an assumed upper bound on the number of disturbance frequencies, it is shown that both the disturbance-free model and disturbance effect can be recovered exactly from disturbance-corrupted input-output data without direct measurement of the periodic disturbances. The rich information returned by the identification can be used by a performance-oriented model-based loaming or repetitive control system to eliminate unwanted periodic disturbances.

• 제어로봇시스템학회논문지
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• 제9권6호
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• pp.425-434
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• 2003

The disturbance observer(DOB) has been widely used in high speed and high precision motion control applications and the characteristics of DOB have been investigated in depth. Though most of DOB's have been implemented as the discrete-time form in digital devices, we are still short of the researches on discrete-time DOB (DDOB) in spite of rich references on continuous-time DOB. In this paper, we discuss about the disturbance rejection property and measurement noise effect of discrete-time DOB. Especially, we will focus on revealing the role of sampling time in designing the discrete-time DOB and show the validity of analysis through simulations and experiments for optical disk drive systems.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2005년도 한국우주과학회보 제14권1호
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• pp.138-142
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• 2005

위성자세제어용 구동기 인 반작용 휠은 축 방향 토크뿐만 아니 라 횡 축 방향 외 란 토크와 힘을 발생시켜 위성의 정밀 지향 안정성에 영향을 미치게 된다. 이를 위해서는 반작용 휠 구동시의 발생 외란을 정밀하게 측정할 필요가 있다. 그러나 반작용 휠의 구동은 측정테이블의 진동을 야기 시키고 테이블의 공진 주파수 영역에서 큰 측정 오차를 유발한다. 본 논문은 이러한 진동오차들을 줄이기 위하여 주파수 보정법에 의한 사후처리 과정을 제시하고, 이 보정법으로 얻어진 데이터들로부터 외란 파라미터를 결정함으로써 구동기 외란의 보다 정밀한 측정을 가능케 하기 위함이다. 이 보정법을 적용함으로써 구동기 외란 측정 주파수범위를 넓힐 수 있다.

• Communications for Statistical Applications and Methods
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• 제17권3호
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• pp.349-356
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• 2010

The ordinary least squares based estimator of the disturbance variance in a regression model for spatial panel data is shown to be asymptotically unbiased and weakly consistent in the context of SAR(1), SMA(1) and SARMA(1,1)-disturbances when there is measurement error in the regressor matrix.

• 한국전자파학회논문지
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• 제24권8호
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• pp.772-780
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• 2013

고고도 핵폭발로 생성되는 고출력 전자기 펄스(HEMP)에 의해 복사성 방해 환경과 케이블 커플링에 의한 전도성 방해 환경이 조성된다. IEC 61000-2-10은 HEMP의 전도성 방해 환경에 대하여 정의한다. IEC 61000-5-5에는 HEMP 전도성 방해에 대한 보호 장치의 특성이 규정되어 있다. IEC 61000-4-24는 보호 장치에 대한 특성 측정 방법을 다루고 있다. IEC 61000-4-24:1997은 소형 보호 소자에 대한 측정 방법을 기술하고 있으나, 최근 많이 사용되고 있는 보호 소자와 필터가 결합된 형태의 조합형 필터에 대한 측정 방법은 미비한 상태이다. HEMP 전도성 방해 신호는 50 MHz 이하의 주파수 스펙트럼을 포함하고 있으므로 측정 셋업을 구성하는데 있어서 케이블의 굵기, 길이, 접지평면으로부터의 높이 등의 측정 셋업 파라미터의 특성을 파악하는 것이 중요하다. 본 논문에서는 HEMP 전도성 방해 전류 파형의 주파수 스펙트럼을 고려하고, 측정셋업에서 존재하는 케이블 파라미터의 영향을 분석하여 최적의 PCI 측정 방법을 도출하고자 한다.

• 전기학회논문지
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• 제59권5호
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• pp.966-971
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• 2010

An adaptive state observer is presented for a class of LTI systems that have a sinusoidal disturbance in the measurement output. Adaptation rules are developed for identifying the unknown sinusoidal disturbance signal from the system output. For the application of the identification result to the state estimation problem, the sinusoidal signal with arbitrary initial phase has been considered in this paper. In order to test the performance of proposed algorithm, comparative computer simulations have been carried out with an existing robust observer. The simulation results show the effectiveness of the proposed method.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1209-1212
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• 1996

In this paper, we design a stabilizing controller with disturbance rejection properties for multirate sampled-data systems which have periodic output measurement scheme. We assume that the plant is open-loop unstable and the disturbance consists of a sum of finite number of sine waves with different frequencies. A sufficient condition for maintaining observability in multirate sampled-data systems is derived. The proposed controller has an IMC structure and can be decomposed into the filtered-disturbance estimator and the inverse of the fast uniform sampled model of the pre-stabilized plant. An example is presented for illustrations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.241-244
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• 2002

Using disturbance observers is effective in enhancing the performance of systems in presence of disturbances. In this paper, we present a novel design of disturbance observers to achieve enhanced robust performance. In addition, we propose a new method of reducing the effect of measurement noise via modification of plant modeling in disturbance observer.