• KIEE International Transaction on Systems and Control
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• 제2D권2호
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• pp.97-107
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• 2002

In this paper, we propose the concept of orthonormalized compressed measurement for the stability analysis of discrete linear time-varying Kalman filters. Unlike previous studies that deal with the homogeneous portion of Kalman filters, the proposed Lyapunov method directly deals with the stochastically-driven system. The orthonorrmalized compressed measurement provides information on the a priori state estimate of the Kalman filter at the k-th step that is propagated from the a posteriori state estimate at the previous block of time. Since the complex multiple-step propagations of a candidate Lyapunov function with process and measurement noises can be simplified to a one-step Lyapunov propagation by the orthonormalized compressed measurement, a stochastic radius of attraction can be derived that would be impractically difficult to obtain by the conventional multiple-step Lyapunov method.

• 비파괴검사학회지
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• 제27권6호
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• pp.576-581
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• 2007

Ultrasonic nonlinearity has been considered as a promising method to evaluate the micro damage of material; however, its magnitude is so small that its measurement is not easy. Especially, when we use contact PZT transducer, if the contacting pressure is not kept in constant during the measurement then there exists extraneous fluctuation in the measured nonlinearity caused by the unstable contact condition, In this paper, we developed a pneumatic control system to keep the contacting pressure of transducer in constant during the measurement and analyzed the effect of contacting pressure to the ultrasonic nonlinearity measurement As a result, we found that the pressure of transducer in our measurement system should be greater than 170 kPa to measure the ultrasonic nonlinear parameter in stable with no dependency on the contacting pressure.

• 한국학교보건학회지
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• 제34권1호
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• pp.33-41
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• 2021

Purpose: Exploring the variables that predict teachers' intent when referring students to mental health professionals is important. The Theory of Planned Behavio (TPB) is a theory of predicting people's intentions of performing a particular behavior; the intent to perform a certain behavior is determined by three factors. (1) attitudes toward the behavior, (2) subjective norms, and (3) perceived control. This study aimed to develop a TPB measurement to investigate what variables predict the intentions of teacher's referral behaviors. Methods: A qualitative study following standardized manuals and guidelines for developing a TPB measurement was used. As a qualitative research method, the Consensual Qualitative Research-Modified (CQR-M) was used. According to the findings from the qualitative study, the quantitative measurement to assess teachers' referral intention, attitude, subjective norm, and behavioral control was developed. Results: The reliability and validity of the newly developed measurement were tested and verified. Conclusion: The newly developed measurement would contribute to a future empirical study that will examine predictors of teachers' referral intention.

• 벤처창업연구
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• 제6권2호
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• pp.13-24
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• 2011

우리는 이 논문에서 측정 단위 설정에 대하여 연구하였다. 품질관리는 고객 요구를 관리하는 것이다. 쥬란과 다구찌가 연구한 품질 형태의 측정 단위를 조사하였다. 그리고 품질 형태의 새로운 측정을 제안하였다. 제안한 새로운 품질 측정은 여러 품질 관리 측정을 조합한 것이다. 이러한 측정은 회사의 관리 수준에서 경영 관리에서 사용될 수 있을 것이다. 우리는 제안된 새로운 측정이 실제 사용되고 도움 되기를 기대한다.

• 전자공학회논문지
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• 제52권8호
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• pp.126-131
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• 2015

유도전동기의 고성능 속도 제어를 위해서는 전동기 정수의 정확한 측정이 필요하다. 특히 전동기의 토크 제어를 위해 사용되는 벡터 제어의 경우 회전자 저항과 인덕턴스의 항으로 주어지는 시정수는 제어기의 성능에 큰 영향을 준다. 또한 고정자 저항과 누설 인덕턴스는 전류제어기와 속도 제어기의 이득을 구하고 설계하는 중요한 변수가 된다. 본 논문에서는 기존의 정수 측정 방법을 수정 보완한 새로운 유도 전동기 정수 측정방법을 제시한다.

• 제어로봇시스템학회논문지
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• 제20권10호
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• pp.1023-1029
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• 2014

In this paper, we propose an SPDR (Smith Predictor for Disturbance Reduction) scheme to improve the temperature control by reduction of the disturbance in ROT process with measurement delay. The proposed controller is a combination of Astrom's modified Smith predictor with a disturbance reduction controller and a grey predictor. The grey prediction is used to calculate the inverse of the measurement delay and to predict future variations and tendencies of system output. The simulation results demonstrate the successful performance of the proposed disturbance reduction controller and enhance the robustness of the proposed control scheme.

• 제어로봇시스템학회논문지
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• 제7권2호
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• pp.138-145
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• 2001

Measurement errors in a digital measurement systems are mainly due to the consisting elements accuracies and the circuit parameters changes following the environment variations such as temperature. Further, systems non-linearity makes the measurement accuracy worse, and accordingly a linearization method should be considered to avoid this worsening. In this study, a temperature error-correction method and linearization methods are proposed and a digital temperature measurement system utilizing these methods is realized. And the proposed measurement methods are observed to increase the measurement accuracy of the digital measurement system.

• Journal of Astronomy and Space Sciences
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• 제35권3호
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• pp.163-173
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• 2018

This paper presents relative navigation using intermittent laser-based measurement data for spacecraft flying formation that consist of two spacecrafts; namely, chief and deputy spacecrafts. The measurement data consists of the relative distance measured by a femtosecond laser, and the relative angles between the two spacecrafts. The filtering algorithms used for the relative navigation are the extended Kalman filter (EKF), unscented Kalman filter (UKF), and least squares recursive filter (LSRF). Numerical simulations reveal that the relative navigation performances of the EKF- and UKF-based relative navigation algorithms decrease in accuracy as the measurement outage period increases. However, the relative navigation performance of the UKF-based algorithm is 95 % more accurate than that of the EKF-based algorithm when the measurement outage period is 80 sec. Although the relative navigation performance of the LSRF-based relative navigation algorithm is 94 % and 370 % less accurate than those of the EKF- and UKF-based navigation algorithms, respectively, when the measurement outage period is 5 sec; the navigation error varies within a range of 4 %, even though the measurement outage period is increased. The results of this study can be applied to the design of a relative navigation strategy using the developed algorithms with laser-based measurements for spacecraft formation flying.

• 제어로봇시스템학회논문지
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• 제20권5호
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• pp.563-569
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• 2014

This article focuses on a hemispherical resonator gyro driven by the Coriolis effect. A hemispherical shell, called a resonator, is maintained in the resonance state by amplitude control and phase locking control. Parametric excitation has been used to control the amplitude. For rate measurement mode or FTR mode, nodal points have been kept to an amplitude of zero. Angular rate measurement has been demonstrated by rotating a resonator. Frequency mismatch between two stiffness principal axes is a major cause of low performance: vibrating pattern drift and reduced control effectiveness. This mismatch has been reduced significantly by the addition of small mass. A negative spring effect, which lowers resonance frequencies, has been verified experimentally.

• Journal of Power Electronics
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• 제18권1호
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• pp.147-159
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• 2018

In this paper, the voltage tracking control of a conventional DC-DC boost converter affected by unknown, time-varying circuit parameter perturbations is investigated. Based on the fundamental property of incremental passivity, a passivity based control law is designed. Then, to obtain a better disturbance rejection property, two generalized proportional integral (GPI) observers are employed to estimate the time-varying uncertainties in the output voltage and inductor current channels, and the estimated values are applied as feedforward compensation. Moreover, the global trajectory tracking performance of a system with disturbances is ensured under the composite controller. Finally, simulation and experiment studies are provided to demonstrate the feasibility and effectiveness of the proposed method. The results show that the proposed controller delivers a promising disturbance rejection capability as well as a good nominal tracking performance.