• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.8
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• pp.996-1003
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• 1999

This paper propose a position-speed controller with an estimator which can estimate states and disturbance. The overall control system consists of two parts: the position-speed controller and an estimator. The Kalman filter applied as state-feedback controller is an optimal state estimator applied to a dynamic system that involves random perturbations and gives a linear, unbiased and minimum error variance recursive algorithm to optimally estimate the unknown state. Therefore, we consider the error problem about the servo system modeling and the measurement noise as a stochastic system and implement a optimal state observer, and enhance the estimate performance of position and speed using that. Using two-degree-of freedom(TDOF) conception, we design the command input response and the closed loop characteristics independently. The servo system is to improve the closed loop characteristics without affecting the command imput response. The characteristics of the closed loop system is improved by suppressing disturbance torque effectively with the disturbance observer using a inverse-transfer matrix. Therefore, the performance of overall position-speed controller is enhanced. Finally, the performance of the proposed controller is exemplified by some simulations and by applying the real servo system.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.2
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• pp.145-154
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• 2023

In this study, to control the heading angle of a ship, which is constantly subjected to various internal and external disturbances during the voyage, an LADRC (linear active disturbance rejection control) design that focuses more on improving the disturbance removal performance was proposed. The speed rate of change of the ship's heading angle due to the turn of the rudder angle was selected as a significant factor, and the nonlinear model of the ship's maneuvering equation, including the steering gear, was treated as a total disturbance. It is the similar process with an LADRC design for the first-order transfer function model. At this time, the gains of the controller included in LADRC and the gains of the extended state observer were tuned to RCGAs (real-coded genetic algorithms) to minimize the integral time-weighted absolute error as an evaluation function. The simulation was performed by applying the proposed GA-LADRC controller to the heading angle control of the Mariner class vessel. In particular, it was confirmed that the proposed controller satisfactorily maintains and follows the set course even when the disturbances such as nonlinearity, modelling error, uncertainty and noise of the measurement sensor are considered.

• Smart Structures and Systems
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• v.14 no.3
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• pp.327-345
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• 2014

This paper presents a composite control strategy for the active suppression of vibration due to the unknown disturbances, such as external excitation, harmonic effects and control spillover, as well as high-frequency accelerometer measurement noise in the all-clamped stiffened plate. The proposed composite control action based on the modal approach, consists of two contributions including feedback part and feedforward part. The feedback part is the well-known PID controller, which is widely used to increase the structure damping and improve its dynamic performance close to the resonance frequencies. In order to get better performance for vibration suppression, the weight matrixes is optimized by chaos sequence. Then an improved disturbance observer (IDOB) as the feedforward compensation part is developed to enhance the vibration suppression performance of PID under various disturbances and uncertainties. The proposed IDOB can simultaneously estimate the various disturbances dynamically as well as measurement noise acting on the system and suppress them by feedforward compensation design. A rigorous analysis is also given to show why the IDOB can effectively suppress the unknown disturbances and measurement noise. In order to verify the proposed composite control algorithm (IDOB-PID), the dSPACE real-time simulation platform is used and an experimental platform for the all-clamped stiffened plate active vibration control system is set up. The experimental results demonstrate the effectiveness, practicality and strong anti-disturbances ability of the proposed control strategy.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.86.1-86
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• 2001

Combined with a counter, wheel or strip encoders which have equally divided markers are one of frequent measuring choices towards various applications in terms of cost, simplicity, and diversity of measurements, e.g., measuring displacement, velocity, acceleration, and so on. Often, velocity is measured by counting the series of reference clocks for a period of time which sensor-carrying device took for traveling two adjacent encoding markers. Quantizaion error of such that the disturbance caused by quantization error is under control. This paper identifies design issues, developes theory, and proposes a paradigm to design a velocity measurement system such ...

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.453-455
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• 2009

The wind speed measurement is performed using SODAR and LIDAR to evaluate availability of remote sensing in assessment of wind resource. The intercomparison comprises time series, correlation analysis and recovery rate. It shows that LIDAR is more effective than using SODAR to measure wind speed in ambient disturbance.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.356-362
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• 2017

This paper presents a robust position controller for a one degree-of-freedom (DOF) mechanical system using only position measurement. In order to alleviate the performance degradation owing to various uncertainties, a two-stage design method is studied by employing a proportional integral observer (PIO). In the first stage, a baseline backstepping controller is designed for a nominal system without accounting for uncertainties. The PIO is developed for estimating both the velocity information for the backstepping controller and an equivalent input disturbance for a feedforward compensation using the estimated uncertainty. It is shown that the estimation errors with the proposed PIO can be made arbitrarily small in a finite time. If the system suffers from undesirable actuator nonlinearities, however, it might be necessary to estimate the velocity and the disturbance with different rates of convergence. The proposed method combines the predesigned backstepping controller and dual PIOs to reduce mechanical vibrations as well as steady-state errors. The performance of the proposed method is tested through comparative computer simulations and experiments using a laboratory prototype.

• Journal of ILASS-Korea
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• v.3 no.4
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• pp.1-7
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• 1998

The measurement of breakup length of viscous liquid jet in stagnant air was conducted by a 3CCD digital video camera. The nozzle diameters of 4, 6, 8mm with L/d=50 were selected and the dynamic viscosity of viscous liquid made of glycerine and water was in the range of $1.061\times10^{-6}m^2/s$ to $4.935\times10^{-5}m^2/s$. The critical velocity is decreased and the breakup length is increased with the increase of nozzle diameter at the same dynamic viscosity of liquid. At the same nozzle diameter, the breakup length and the critical velocity are both increased with the increase of dynamic viscosity of liquid. It is found in the theoretical analysis that the initial disturbance level is the main cause of occurrance of critical Reynolds number in the stability curve. The comparison of experimental critical Reynolds number and the empirical correlation by Tanasawa and Toyota reveals the relatively good agreement.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.784-786
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• 1993

Recently, in the industrial applications, the sensorless system is developed, but the sensorless system is required to have robustness for the measurement noise and disturbance. In this paper, for the sensorless system, the method of designing a robust sliding mode observer taking account of the ability of disturbance and noise attenuation is presented. Also, the strategy for the estimation of rotor flux using the sliding mode observer, which is robust to the measurement noise, is described. Robustness are achieved by assigning the pole of the the system during the sliding motion in such a way as to minimize the effects of the disturbances on the rotor flux estimation error. Finally, using worst case desist and LQC(least square error design), the sliding mode absolver is verified by computer simulations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.8
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• pp.877-883
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• 2012

Multipath ultrasonic flowmeters are increasingly being used for the purpose of accurate flow measurement. However, an installation standard has not yet been established for these flowmeters, and this can cause considerable confusion during field installation. There is a need for a minimum straight run to ensure the measurement accuracy of a flowmeter installed upstream and downstream of flow disturbance factors-expansion, contraction, and tee pipes. Experiments were performed by using multipath flowmeters that have less than ${\pm}0.5%$ accuracy-4-paths 1-unit and 2-paths 1-unit are of foreign make, whereas 5-paths 2-units are of domestic make-to determine the straight run under the above conditions. We carried out experiments repeatedly by considering a straight run, velocity, and suggested installation standards for a multipath ultrasonic flowmeter that satisfies the tolerance limits.

• Journal of East-West Nursing Research
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• v.9 no.1
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• pp.35-45
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• 2004

This study as a cross survey study was conducted to provide basic data for more practical approach to nursing the aged, by analyzing the relationship of the loneliness, self-esteem and quality of life on the hearing disturbance aged. This study was based on the survey data from the 90 aged, who are over sity years old and resident in Seoul. In order to measure the general characteristics and subjective audition, Cantril's Ladder Scale Tool was used. For the loneliness, UCLA Loneliness Scale Tool (translated into Korean to suit the Korean environment by Kim's). In order to measure the self-esteem, Rosenberg's Self-esteem Measurement Tool (translated into Korean by Chun) was used. No's Quality of Life Measurement Tool was used to the measure the quality of life. The Data were collected by direct interviewing on the subjects for this study from August 10, 1999 to September 15, 1999. In accordance with each purpose of this study, appropriate analyzing methods such as Descriptive Statistics, T-test, and ANOVA were used in analyzing the collected data. Pearson correlation coefficient was used to test the relationship of the loneliness, self-esteem and quality of life on the hearing disturbance aged. The result of this study is as follows: 1) The average of the degrees of subjective audition was 7.22, The factors that cause the result were sex, religion, the perception of health, the married state. 2) The average of the degrees of loneliness was 55.18, The factor that cause the result was the perception of health. 3) The average of the degrees of self-esteem was 28.42, The factors that cause the result were the number of family, the number of children, the perception of health. 4) The average of the degrees of quality of life was 71.87 the factors that cause the result were age, education, the number of children, the perception of health. 5) Correlation of Loneliness, self-esteem and quality of life is the perception of loneliness showed significant negative correlation with self-esteem (r=-.466, p=.0001) and quality of life (r=-.450, p=.0001). As a result of analysis above: Because of the recognition change of the aged, it seems to them that the subjective audition scale on the hearing disturbance aged is measured by only 10-point ladder scale is inappropriate. Therefore, it is necessary that the physiologic-index can confirm more exactly should be applied to them. It is very important that the social-psychological factor that has influence on the aged should be the self-perception of health. Thus, proper development of nursing intervention should be required to process in the self-perception of health on the aged.